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We present a unified picture of outflowing gas from the X-ray binary system Hercules X-1/HZ Herculis. We suggest that the outflowing gas (a wind) causes UV emission seen in mid-eclipse, narrow UV absorption lines, and broad UV P Cygni lines. Observations with the FOS and STIS spectrographs on the Hubble Space Telescope (HST) show UV emission lines in the middle of X-ray eclipse, when the X-ray heated atmosphere of the normal star and accretion disk should be entirely hidden from view. Narrow absorption lines (FWHM~50 km/s) blueshifted by 500 km/s during observations in 1998 and by 400 km/s during observations in 1999 were seen from phi=0.0-0.3. The line velocity was constant to within 20 km/s. The P Cygni profiles from Hercules~X-1 have optical depths tau<1 with a maximum expansion velocity of 600 km/s, and are seen in the resonance lines N V 1238.8,1242.8, Si IV 1393.7,1402.8, and C IV 1548.2, 1550.8. We discuss whether this wind originates in the accretion disk or on the companion star, and how the relevant ions can survive X-ray ionization by the neutron star.
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X線連星系ヘルクレスX-1／HZヘルクリスからの流出ガスについて統一的な描像を提示する。我々は、この流出ガス（風）が、皆食の中間段階に観測される紫外線（UV）輝線、狭いUV吸収線、および広いUV P・セイギニー線を引き起こしていると提唱する。ハッブル宇宙望遠鏡（HST）に搭載されたFOSおよびSTIS分光器による観測では、X線皆食の真っ只中にUV輝線が検出された。この時期には、通常星のX線加熱大気および降着円盤が完全に視界から隠れているはずである。1998年の観測では位相φ=0.0–0.3の間に、500 km/sの青方偏移を示す狭い吸収線（半値幅～50 km/s）が、1999年の観測では400 km/sの青方偏移がそれぞれ観測された。これらの吸収線の速度は20 km/s以内で一定であった。ヘルクレスX-1のP・セイギニー型プロファイルは光学的深度τ＜1であり、最大膨張速度は600 km/sで、共鳴線N V 1238.8、1242.8、Si IV 1393.7、1402.8、およびC IV 1548.2、1550.8に現れる。本研究では、この風が降着円盤から生じているのか、あるいは伴星から生じているのか、また関連するイオンが中性子星からのX線電離に対してどのようにして生き残り得るのかについて議論する。
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ja
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We investigate the propagation of locally plane, small-amplitude, monochromatic gravitational waves through cold compressible interstellar gas in order to provide a more accurate picture of expected waveforms for direct detection. The quasi-isothermal gas is concentrated in a spherical symmetric cloud held together by self-gravitation. Gravitational waves can be treated as linearized perturbations on the background inner Schwarzschild spacetime. The perturbed quantities lead to the field equations governing the gas dynamics and describe the interaction of gravitational waves with matter. The resulted field equations decouple asymptotically for slowly varying short waves to a set of three PDEs of different orders of magnitude. A second-order WKB method provides transport equations for the wave amplitudes. The influence of background curvature already appears in the first-order amplitudes, which gives rise to diffraction. We have shown that the transport equation of these amplitudes provides numerical solutions for the frequency-alteration. The energy dissipating process is responsible for decreasing frequency. The decrease is significantly smaller than the magnitude of the original frequency and exhibits a power-law relationship between original and decreased frequencies. The frequency deviation was examined particularly for the transient signal GW150914. Considering AGNs as larger background structures and high-frequency signals emitted by BNS mergers, the frequency-deviation grows large enough to be relevant in future GW-observations with increased sensitivity.
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局所的に平面波であり、振幅が小さく、単色の重力波が冷たい圧縮性の星間ガス中を伝播する様子を調査し、直接検出における期待される波形のより正確な描像を得る。準等温のガスは、自己重力によって束縛された球対称の雲に集中している。重力波は、背景となる内部シュワルツシルト時空上の線形摂動として扱うことができる。摂動量は、ガスの力学を支配する場の方程式を導き、重力波と物質との相互作用を記述する。得られた場の方程式は、ゆっくりと変化する短波長の波に対して漸近的に分離され、異なるオーダーの大きさを持つ3つの偏微分方程式の系となる。2次精度のWKB法を用いることで、波の振幅に対する輸送方程式が得られる。背景の曲率の影響はすでに1次振幅に現れ、回折を引き起こす。これらの振幅の輸送方程式を用いて、周波数変化の数値解が得られることを示した。エネルギー散逸過程が周波数の低下を引き起こす。この低下は元の周波数の大きさに比べて著しく小さく、元の周波数と低下した周波数の間にべき乗則的な関係が見られる。周波数のずれは特に、過渡信号GW150914について検討された。活動的銀河核（AGN）をより大きな背景構造とし、連星中性子星（BNS）合体から放出される高周波信号を想定すると、周波数ずれは、感度が向上する将来の重力波観測において無視できなくなるほど大きくなる。
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ja
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We present a theoretical study of the spin transport properties of mono-atomic magnetic chains with a focus on the spectroscopical features of the I-V curve associated to spin-flip processes. Our calculations are based on the s-d model for magnetism with the electron transport treated at the level of the non-equilibrium Green's function formalism. Inelastic spin-flip scattering processes are introduced perturbatively via the first Born approximation and an expression for the associated self-energy is derived. The computational method is then applied to describe the I-V characteristics and its derivatives of one dimensional chains of Mn atoms and the results are then compared to available experimental data. We find a qualitative and quantitative agreement between the calculated and the experimental conductance spectra. Significantly we are able to describe the relative intensities of the spin excitation features in the I-V curve, by means of a careful analysis of the spin transition selection rules associated to the atomic chains.
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Spin devrilme süreçlerine ilişkin I-V eğrisinin spektroskopik özelliklerine odaklanarak, tek atomlu manyetik zincirlerin spin taşıma özelliklerinin teorik bir incelemesini sunuyoruz. Hesaplamalarımız, elektron taşımasının dengesiz Green fonksiyonu formalizminin düzeyinde ele alındığı s-d modeline dayanmaktadır. Esnek olmayan spin devrilme saçılma süreçleri, ilk Born yaklaşımı yoluyla pertürbatif olarak tanıtılmış ve ilişkili özyüzdeşlik ifadesi türetilmiştir. Daha sonra hesaplama yöntemi, Mn atomlarının bir boyutlu zincirlerinin I-V karakteristiklerini ve türevlerini tanımlamak için uygulanmış ve sonuçlar mevcut deneysel verilerle karşılaştırılmıştır. Hesaplanan ve deneysel iletkenlik spektrumları arasında nitel ve nicel bir uyum bulduk. Önemli olan, atomik zincirlerle ilişkili spin geçiş seçme kurallarının dikkatli bir analizi aracılığıyla, I-V eğrisindeki spin uyarım özelliklerinin göreli şiddetlerini tanımlayabilmemizdir.
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tr
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The deep reinforcement learning method usually requires a large number of training images and executing actions to obtain sufficient results. When it is extended a real-task in the real environment with an actual robot, the method will be required more training images due to complexities or noises of the input images, and executing a lot of actions on the real robot also becomes a serious problem. Therefore, we propose an extended deep reinforcement learning method that is applied a generative model to initialize the network for reducing the number of training trials. In this paper, we used a deep q-network method as the deep reinforcement learning method and a deep auto-encoder as the generative model. We conducted experiments on three different tasks: a cart-pole game, an atari game, and a real-game with an actual robot. The proposed method trained efficiently on all tasks than the previous method, especially 2.5 times faster on a task with real environment images.
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تتطلب طريقة التعلم المعزز العميق عادةً عددًا كبيرًا من صور التدريب وتنفيذ العديد من الإجراءات للحصول على نتائج كافية. وعند توسيعها لتطبيقها على مهمة حقيقية في بيئة فعلية باستخدام روبوت فعلي، تصبح الحاجة إلى عدد أكبر من صور التدريب أمراً ضرورياً نظراً لتعقيدات أو الضوضاء الموجودة في صور المدخلات، كما يصبح تنفيذ عدد كبير من الإجراءات على الروبوت الفعلي مشكلة جسيمة. لذلك، نقترح طريقة موسعة للتعلم المعزز العميق يتم فيها تطبيق نموذج توليدي لتهيئة الشبكة بهدف تقليل عدد محاولات التدريب. في هذا البحث، استخدمنا طريقة الشبكة-Q العميقة كطريقة للتعلم المعزز العميق، واستخدمنا المشفر الذاتي العميق كنموذج توليدي. وقد أجرينا تجارب على ثلاث مهام مختلفة: لعبة العربة والقضيب، ولعبة أتاري، ولعبة حقيقية باستخدام روبوت فعلي. أظهرت الطريقة المقترحة تدريباً فعالاً في جميع المهام مقارنة بالطريقة السابقة، وبخاصة أنها كانت أسرع بـ 2.5 مرة في المهمة التي تستخدم صور بيئة حقيقية.
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ar
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The oversampling multiscale finite element method (MsFEM) is one of the most popular methods for simulating composite materials and flows in porous media which may have many scales. But the method may be inapplicable or inefficient in some portions of the computational domain, e.g., near the domain boundary or near long narrow channels inside the domain due to the lack of permeability information outside of the domain or the fact that the high-conductivity features cannot be localized within a coarse-grid block. In this paper we develop a combined finite element and multiscale finite element method (FE-MsFEM), which deals with such portions by using the standard finite element method on a fine mesh and the other portions by the oversampling MsFEM. The transmission conditions across the FE-MSFE interface is treated by the penalty technique. A rigorous convergence analysis for this special FE-MsFEM is given under the assumption that the diffusion coefficient is periodic. Numerical experiments are carried out for the elliptic equations with periodic and random highly oscillating coefficients, as well as multiscale problems with high contrast channels, to demonstrate the accuracy and efficiency of the proposed method.
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La méthode d'éléments finis multi-échelles avec suréchantillonnage (MsFEM) est l'une des méthodes les plus populaires pour simuler les matériaux composites et les écoulements en milieux poreux pouvant comporter de nombreuses échelles. Toutefois, cette méthode peut être inapplicable ou inefficace dans certaines parties du domaine de calcul, par exemple près de la frontière du domaine ou près de canaux longs et étroits à l'intérieur du domaine, en raison du manque d'informations sur la perméabilité à l'extérieur du domaine ou du fait que les caractéristiques à haute conductivité ne peuvent pas être localisées au sein d'un bloc de maillage grossier. Dans cet article, nous développons une méthode combinée d'éléments finis et d'éléments finis multi-échelles (FE-MsFEM), qui traite ces régions en utilisant la méthode classique des éléments finis sur un maillage fin, tandis que les autres régions sont traitées par la MsFEM avec suréchantillonnage. Les conditions de transmission à l'interface entre la zone EF et la zone MsFE sont traitées à l'aide d'une technique de pénalisation. Une analyse rigoureuse de convergence pour cette FE-MsFEM particulière est fournie sous l'hypothèse que le coefficient de diffusion est périodique. Des expériences numériques sont menées sur des équations elliptiques à coefficients fortement oscillants, périodiques ou aléatoires, ainsi que sur des problèmes multi-échelles comportant des canaux à fort contraste, afin de démontrer la précision et l'efficacité de la méthode proposée.
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fr
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Among the combinations $L_e-L_\mu$, $L_e-L_\tau$ and $L_\mu-L_\tau$ any one can be gauged in anomaly free way with the standard model gauge group. The masses of these gauge bosons can be so light that it can induce long-range forces on the Earth due to the electrons in the Sun. This type of forces can be constrained significantly from neutrino oscillation. As the sign of the potential is opposite for neutrinos and antineutrinos, a magnetized iron calorimeter detector (ICAL) would be able to produce strong constraint on it. We have made conservative studies of these long-range forces with atmospheric neutrinos at ICAL considering only the muons of charge current interactions. We find stringent bounds on the couplings $ \alpha_{e\mu, e\tau} \lapp 1.65 \times 10^{-53}$ at 3$\sigma$ CL with an exposure of 1 Mton$\cdot$yr if there is no such force. For nonzero input values of the couplings we find that the potential $V_{e\mu}$ opposes and $V_{e\tau}$ helps to discriminate the mass hierarchy. However, both potentials help significantly to discriminate the octant of $\theta_{23}$. The explanation of the anomaly in recent MINOS data (the difference of $\Delta m^2_{32}$ for neutrinos and antineutrinos), using long-range force originated from the mixing of the gauge boson $Z^\prime$ of $L_\mu-L_\tau$ with the standard model gauge boson $Z$, can be tested at ICAL at more than 5$\sigma$ CL. We have also discussed how to disentangle this from the solution with CPT violation using the seasonal change of the distance between the Earth and the Sun.
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Parmi les combinaisons $L_e-L_\mu$, $L_e-L_\tau$ et $L_\mu-L_\tau$, l'une quelconque peut être associée à un groupe de jauge sans anomalies avec le groupe de jauge du modèle standard. Les masses de ces bosons de jauge peuvent être suffisamment faibles pour induire des forces à longue portée sur Terre dues aux électrons du Soleil. Ce type de forces peut être fortement contraint par les oscillations de neutrinos. Étant donné que le signe du potentiel est opposé pour les neutrinos et les antineutrinos, un détecteur calorimétrique à fer magnétisé (ICAL) serait capable d'apporter une contrainte forte sur celles-ci. Nous avons effectué des études prudentes de ces forces à longue portée avec les neutrinos atmosphériques à ICAL, en considérant uniquement les muons provenant des interactions en courant chargé. Nous obtenons des limites strictes sur les couplages $ \alpha_{e\mu, e\tau} \lapp 1{,}65 \times 10^{-53}$ au niveau de confiance 3$\sigma$, avec une exposition de 1 Mton$\cdot$an, en l'absence d'une telle force. Pour des valeurs d'entrée non nulles des couplages, nous constatons que le potentiel $V_{e\mu}$ s'oppose, tandis que $V_{e\tau}$ favorise la discrimination de la hiérarchie de masse. Toutefois, les deux potentiels contribuent fortement à discriminer l'octant de $\theta_{23}$. L'explication de l'anomalie observée récemment dans les données de MINOS (la différence de $\Delta m^2_{32}$ entre neutrinos et antineutrinos), à l'aide d'une force à longue portée provenant du mélange du boson de jauge $Z^\prime$ associé à $L_\mu-L_\tau$ avec le boson de jauge $Z$ du modèle standard, peut être testée à ICAL à plus de 5$\sigma$ de niveau de confiance. Nous avons également discuté la manière de distinguer cette explication de celle impliquant une violation de la symétrie CPT, en utilisant la variation saisonnière de la distance entre la Terre et le Soleil.
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fr
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Multisensory object-centric perception, reasoning, and interaction have been a key research topic in recent years. However, the progress in these directions is limited by the small set of objects available -- synthetic objects are not realistic enough and are mostly centered around geometry, while real object datasets such as YCB are often practically challenging and unstable to acquire due to international shipping, inventory, and financial cost. We present ObjectFolder, a dataset of 100 virtualized objects that addresses both challenges with two key innovations. First, ObjectFolder encodes the visual, auditory, and tactile sensory data for all objects, enabling a number of multisensory object recognition tasks, beyond existing datasets that focus purely on object geometry. Second, ObjectFolder employs a uniform, object-centric, and implicit representation for each object's visual textures, acoustic simulations, and tactile readings, making the dataset flexible to use and easy to share. We demonstrate the usefulness of our dataset as a testbed for multisensory perception and control by evaluating it on a variety of benchmark tasks, including instance recognition, cross-sensory retrieval, 3D reconstruction, and robotic grasping.
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Pemersepsi, penaakulan, dan interaksi berpusat objek pelbagai deria telah menjadi topik penyelidikan utama dalam beberapa tahun kebelakangan ini. Namun begitu, kemajuan dalam arah ini terbatas oleh set objek yang kecil tersedia—objek sintetik tidak cukup realistik dan kebanyakannya berfokus pada geometri semata-mata, manakala set data objek sebenar seperti YCB sering kali sukar dan tidak stabil untuk diperoleh disebabkan oleh penghantaran antarabangsa, inventori, dan kos kewangan. Kami mempersembahkan ObjectFolder, satu set data yang terdiri daripada 100 objek maya yang menangani kedua-dua cabaran tersebut melalui dua inovasi utama. Pertama, ObjectFolder menyandarkan data deria visual, pendengaran, dan sentuhan bagi semua objek, membolehkan pelbagai tugas pengenalan objek pelbagai deria, melebihi set data sedia ada yang hanya berfokus pada geometri objek. Kedua, ObjectFolder menggunakan perwakilan tersirat, berpusat objek, dan seragam bagi tekstur visual, simulasi akustik, dan bacaan sentuhan setiap objek, menjadikan set data ini fleksibel untuk digunakan dan mudah dikongsi. Kami menunjukkan kegunaan set data kami sebagai tapak uji untuk pemersepsi dan kawalan pelbagai deria dengan menilainya melalui pelbagai tugas rujukan, termasuk pengenalan instans, pengambilan merentas deria, pembinaan semula 3D, dan pencengkaman robotik.
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ms
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We study theoretically the low-energy hole states in Si, Ge, and Ge/Si core/shell nanowires (NWs). The NW core in our model has a rectangular cross section, the results for a square cross section are presented in detail. In the case of Ge and Ge/Si core/shell NWs, we obtain very good agreement with previous theoretical results for cylindrically symmetric NWs. In particular, the NWs allow for an unusually strong and electrically controllable spin-orbit interaction (SOI) of Rashba type. We find that the dominant contribution to the SOI is the "direct Rashba spin-orbit interaction" (DRSOI), which is an important mechanism for systems with heavy-hole-light-hole mixing. Our results for Si NWs depend significantly on the orientation of the crystallographic axes. The numerically observed dependence on the growth direction is consistent with analytical results from a simple model, and we identify a setup where the DRSOI enables spin-orbit energies of the order of millielectronvolts in Si NWs. Furthermore, we analyze the dependence of the SOI on the electric field and the cross section of the Ge or Si core. A helical gap in the spectrum can be opened with a magnetic field. We obtain the largest g factors with magnetic fields applied perpendicularly to the NWs.
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Estudamos teoricamente os estados de buraco de baixa energia em nanofios (NWs) de Si, Ge e Ge/Si núcleo/casca. O núcleo do NW em nosso modelo possui uma seção transversal retangular, sendo apresentados em detalhe os resultados para uma seção transversal quadrada. No caso dos NWs de Ge e Ge/Si núcleo/casca, obtemos uma concordância muito boa com resultados teóricos anteriores para NWs com simetria cilíndrica. Em particular, os NWs permitem uma interação spin-órbita (SOI) do tipo Rashba incomumente forte e eletricamente controlável. Descobrimos que a contribuição dominante para a SOI é a "interação spin-órbita Rashba direta" (DRSOI), que constitui um mecanismo importante em sistemas com mistura entre buracos pesados e buracos leves. Nossos resultados para NWs de Si dependem significativamente da orientação dos eixos cristalográficos. A dependência observada numericamente em relação à direção de crescimento é consistente com resultados analíticos obtidos a partir de um modelo simples, e identificamos uma configuração na qual a DRSOI possibilita energias de spin-órbita da ordem de milielétron-volts em NWs de Si. Além disso, analisamos a dependência da SOI em relação ao campo elétrico e à seção transversal do núcleo de Ge ou Si. Um gap helicoidal no espectro pode ser aberto com a aplicação de um campo magnético. Obtemos os maiores fatores g com campos magnéticos aplicados perpendicularmente aos NWs.
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pt
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We study effects of pinning on the dynamics of a vortex lattice in a type II superconductor in the strong-pinning situation and determine the force--velocity (or current--voltage) characteristic combining analytical and numerical methods. Our analysis deals with a small density $n_p$ of defects that act with a large force $f_p$ on the vortices, thereby inducing bistable configurations that are a characteristic feature of strong pinning theory. We determine the velocity-dependent average pinning-force density $\langle F_p(v)\rangle$ and find that it changes on the velocity scale $v_p \sim f_p/\eta a_0^3$, where $\eta$ is the viscosity of vortex motion and $a_0$ the distance between vortices. In the small pin-density limit, this velocity is much larger than the typical flow velocity $v_c \sim F_c/\eta$ of the free vortex system at drives near the critical force-density $F_c = \langle F_p(v=0)\rangle \propto n_p f_p$. As a result, we find a generic excess-force characteristic, a nearly linear force--velocity characteristic shifted by the critical force-density $F_c$; the linear flux-flow regime is approached only at large drives. Our analysis provides a derivation of Coulomb's law of dry friction for the case of strong vortex pinning.
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강한 못 박기 상황에서 제2종 초전도체 내의 와동 격자의 동역학에 대한 못 박기의 영향을 연구하고, 해석적 방법과 수치적 방법을 결합하여 힘-속도(또는 전류-전압) 특성을 결정한다. 우리의 분석은 와동에 대해 큰 힘 $f_p$를 작용시키는 결함의 낮은 밀도 $n_p$를 다루며, 이는 강한 못 박기 이론의 특징적인 특징인 이중안정 상태를 유도한다. 우리는 속도에 따라 변하는 평균 못 박기 힘 밀도 $\langle F_p(v)\rangle$를 결정하였으며, 이 값이 속도 척도 $v_p \sim f_p/\eta a_0^3$에서 변화함을 발견하였다. 여기서 $\eta$는 와동 운동의 점성이며, $a_0$는 와동 사이의 거리이다. 낮은 못 박기 밀도 극한에서 이 속도는 임계 힘 밀도 $F_c = \langle F_p(v=0)\rangle \propto n_p f_p$ 근처의 구동에서 자유 와동계의 전형적인 흐름 속도 $v_c \sim F_c/\eta$보다 훨씬 크다. 그 결과, 우리는 일반적인 과잉 힘 특성을 발견하였으며, 이는 임계 힘 밀도 $F_c$만큼 이동된 거의 선형적인 힘-속도 특성이며, 선형적인 플럭스 흐름 영역은 오직 큰 구동에서만 접근된다. 우리의 분석은 강한 와동 못 박기 경우에 대한 건조 마찰의 쿨롱 법칙을 유도해 준다.
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ko
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A general framework for the study of regular variation (RV) is that of Polish star-shaped metric spaces, while recent developments in [1] have discussed RV with respect to some properly localised boundedness $\mathcal{B}$ imposing weak assumptions on the structure of Polish space. Along the lines of the latter approach, we discuss the RV of Borel measures and random processes on general Polish metric spaces. Tail measures introduced in [2] appear naturally as limiting measures of regularly varying time series. We define tail measures on a measurable space indexed by $\mathcal{H}(D)$, a countable family of homogeneous coordinate maps, and show some tractable instances for the investigation of RV when $\mathcal{B}$ is determined by $\mathcal{H}(D)$. This allows us to study the regular variation of cadlag processes on $D(R^l, R^d)$ retrieving in particular results obtained in [1] for RV of stationary cadlag processes on the real line removing $l=1$ therein. Further, we discuss potential applications and open questions.
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Obecný rámec pro studium pravidelné variability (RV) tvoří polské hvězdicové metrické prostory, zatímco nedávné vývoje v [1] diskutovaly RV vzhledem k nějaké vhodně lokalizované omezenosti $\mathcal{B}$, přičemž kladou slabé požadavky na strukturu polského prostoru. V duchu tohoto posledně zmíněného přístupu rozebíráme RV borelovských měr a náhodných procesů na obecných polských metrických prostorech. Chvostové míry zavedené v [2] přirozeně vystupují jako limitní míry pravidelně se měnících časových řad. Definujeme chvostové míry na měřitelném prostoru indexovaném $\mathcal{H}(D)$, spočetnou rodinou homogenních souřadnicových zobrazení, a ukazujeme některé zvládnutelné případy pro zkoumání RV, když je $\mathcal{B}$ určeno pomocí $\mathcal{H}(D)$. To nám umožňuje studovat pravidelnou variabilitu cadlag procesů na $D(R^l, R^d)$ a zejména rekonstruovat výsledky získané v [1] pro RV stacionárních cadlag procesů na reálné ose po odstranění předpokladu $l=1$. Dále rozebíráme potenciální aplikace a otevřené otázky.
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cs
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A recent ALMA observation of the Elias 2-27 system revealed a two-armed structure extending out to ~300 au in radius. The protostellar disc surrounding the central star is unusually massive, raising the possibility that the system is gravitationally unstable. Recent work has shown that the observed morphology of the system can be explained by disc self-gravity, so we examine the physical properties of the disc necessary to detect self-gravitating spiral waves. Using three-dimensional Smoothed Particle Hydrodynamics, coupled with radiative transfer and synthetic ALMA imaging, we find that observable spiral structure can only be explained by self-gravity if the disc has a low opacity (and therefore efficient cooling), and is minimally supported by external irradiation. This corresponds to a very narrow region of parameter space, suggesting that, although it is possible for the spiral structure to be due to disc self-gravity, other explanations, such as an external perturbation, may be preferred.
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エリヤス2-27系の最近のALMA観測により、半径約300auまで及ぶ二重腕構造が明らかになった。中心星を取り巻く原始星円盤は異常に質量が大きく、この系が重力的に不安定である可能性を示唆している。最近の研究では、この系で観測された形態が円盤の自己重力によって説明できることが示されているため、自己重力による渦巻き波動を検出するために必要な円盤の物理的性質を検討した。三次元スムーズド粒子ハイドロダイナミクス法を用い、放射伝達および合成ALMA画像を組み合わせて解析した結果、観測される渦巻き構造が自己重力によって説明されるのは、円盤の不透明度が低く（したがって冷却効率が高く）、外部からの放射照の影響が最小限に抑えられている場合に限られることがわかった。これはパラメータ空間のごく狭い領域に対応しており、渦巻き構造が円盤の自己重力に起因する可能性はあるものの、外部摂動などの他の説明の方が好ましい可能性を示唆している。
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ja
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Semi-competing risks refer to the setting where primary scientific interest lies in estimation and inference with respect to a non-terminal event, the occurrence of which is subject to a terminal event. In this paper, we present the R package SemiCompRisks that provides functions to perform the analysis of independent/clustered semi-competing risks data under the illness-death multi-state model. The package allows the user to choose the specification for model components from a range of options giving users substantial flexibility, including: accelerated failure time or proportional hazards regression models; parametric or non-parametric specifications for baseline survival functions; parametric or non-parametric specifications for random effects distributions when the data are cluster-correlated; and, a Markov or semi-Markov specification for terminal event following non-terminal event. While estimation is mainly performed within the Bayesian paradigm, the package also provides the maximum likelihood estimation for select parametric models. The package also includes functions for univariate survival analysis as complementary analysis tools.
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Semi-kompetierende Risiken beziehen sich auf einen Kontext, bei dem das primäre wissenschaftliche Interesse auf der Schätzung und Inferenz bezüglich eines nicht-terminalen Ereignisses liegt, dessen Eintreten von einem terminalen Ereignis abhängig ist. In dieser Arbeit stellen wir das R-Paket SemiCompRisks vor, das Funktionen zur Analyse unabhängiger bzw. gruppiert vorliegender Daten mit semi-kompetierenden Risiken im Rahmen des Krankheits-Todes-Multi-State-Modells bereitstellt. Das Paket ermöglicht es dem Anwender, die Modellkomponenten aus einer Reihe von Optionen auszuwählen, wodurch eine erhebliche Flexibilität gegeben ist, einschließlich: Accelerated-Failure-Time- oder proportionale Hazards-Regressionsmodelle; parametrische oder nichtparametrische Spezifikationen der Baseline-Überlebensfunktionen; parametrische oder nichtparametrische Spezifikationen der Verteilungen zufälliger Effekte, wenn die Daten gruppenkorreliert sind; sowie eine Markov- oder semi-Markov-Spezifikation für das terminale Ereignis nach dem nicht-terminalen Ereignis. Während die Schätzung hauptsächlich im bayesschen Paradigma erfolgt, stellt das Paket auch die Maximum-Likelihood-Schätzung für ausgewählte parametrische Modelle bereit. Das Paket enthält außerdem Funktionen zur univariaten Überlebenszeitanalyse als ergänzende Analysewerkzeuge.
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de
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The mixing of the quasifission component to the fissionlike cross section causes ambiguity in the quantitative estimation of the complete fusion cross section from the observed angular and mass distributions of the binary products. We show that the partial cross section of quasifission component of binary fragments covers the whole range of the angular momentum values leading to capture. The calculated angular momentum distributions for the compound nucleus and dinuclear system going to quasifission may overlap: competition between complete fusion and quasifission takes place at all values of initial orbital angular momentum. Quasifission components formed at large angular momentum of the dinuclear system can show isotropic angular distribution and their mass distribution can be in mass symmetric region similar to the characteristics of fusion-fission components. As result the unintentional inclusion of the quasifission contribution into the fusion-fission fragment yields can lead to overestimation of the probability of the compound nucleus formation.
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La mezcla del componente de cuasifisión a la sección eficaz de tipo fisión provoca ambigüedad en la estimación cuantitativa de la sección eficaz de fusión completa a partir de las distribuciones angulares y de masas observadas de los productos binarios. Mostramos que la sección eficaz parcial del componente de cuasifisión de los fragmentos binarios abarca todo el rango de valores del momento angular que conducen a la captura. Las distribuciones calculadas del momento angular para el núcleo compuesto y para el sistema dinuclear que evoluciona hacia cuasifisión pueden solaparse: la competencia entre fusión completa y cuasifisión tiene lugar en todos los valores del momento angular orbital inicial. Los componentes de cuasifisión formados con un momento angular grande del sistema dinuclear pueden presentar una distribución angular isotrópica y su distribución de masas puede estar en la región de simetría de masa, similar a las características de los componentes de fisión por fusión. Como resultado, la inclusión involuntaria de la contribución de cuasifisión en los rendimientos de fragmentos de fisión por fusión puede llevar a una sobreestimación de la probabilidad de formación del núcleo compuesto.
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es
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For several decades, the interest of the scientific community in aneutronic fusion reactions such as proton-Boron fusion has grown because of potential applications in different fields. Recently, many scientific teams in the world have worked experimentally on the possibility to trigger proton-Boron fusion using intense lasers demonstrating an important renewal of interest of this field. It is now possible to generate ultra-short high intensity laser pulses at high repetition rate. These pulses also have unique properties that can be leveraged to produce proton-Boron fusion reactions. In this article, we investigate the interaction of a high energy attosecond pulse with a solid proton-Boron target and the associated ion acceleration supported by numerical simulations. We demonstrate the efficiency of single-cycle attosecond pulses in comparison to multi-cycle attosecond pulses in ion acceleration and magnetic field generation. Using these results we also propose a path to proton-Boron fusion using high energy attosecond pulses.
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Depuis plusieurs décennies, l'intérêt de la communauté scientifique pour les réactions de fusion aneutronique, telles que la fusion proton-bore, n'a cessé de croître en raison de leurs applications potentielles dans divers domaines. Récemment, de nombreuses équipes scientifiques à travers le monde ont travaillé expérimentalement sur la possibilité d'initier la fusion proton-bore à l'aide de lasers intenses, démontrant ainsi un regain d'intérêt marqué pour ce domaine. Il est désormais possible de générer des impulsions laser ultracourtes de haute intensité à haut taux de répétition. Ces impulsions possèdent également des propriétés uniques qui peuvent être exploitées pour produire des réactions de fusion proton-bore. Dans cet article, nous étudions l'interaction d'une impulsion attoseconde de haute énergie avec une cible solide de proton-bore et l'accélération ionique associée, à l'aide de simulations numériques. Nous démontrons l'efficacité des impulsions attosecondes monocyclus par rapport aux impulsions attosecondes multicycles en matière d'accélération ionique et de génération de champ magnétique. À partir de ces résultats, nous proposons également une voie vers la fusion proton-bore utilisant des impulsions attosecondes de haute énergie.
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fr
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Robots which interact with the physical world will benefit from a fine-grained tactile understanding of objects and surfaces. Additionally, for certain tasks, robots may need to know the haptic properties of an object before touching it. To enable better tactile understanding for robots, we propose a method of classifying surfaces with haptic adjectives (e.g., compressible or smooth) from both visual and physical interaction data. Humans typically combine visual predictions and feedback from physical interactions to accurately predict haptic properties and interact with the world. Inspired by this cognitive pattern, we propose and explore a purely visual haptic prediction model. Purely visual models enable a robot to "feel" without physical interaction. Furthermore, we demonstrate that using both visual and physical interaction signals together yields more accurate haptic classification. Our models take advantage of recent advances in deep neural networks by employing a unified approach to learning features for physical interaction and visual observations. Even though we employ little domain specific knowledge, our model still achieves better results than methods based on hand-designed features.
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الروبوتات التي تتفاعل مع العالم المادي ستستفيد من فهم دقيق وتفصيلي للخصائص اللمسية للأشياء والأسطح. بالإضافة إلى ذلك، قد تحتاج الروبوتات في بعض المهام إلى معرفة الخصائص الحسية اللمسية لجسم ما قبل لمسه. لتمكين الروبوتات من فهم أفضل للخصائص اللمسية، نقترح طريقة لتصنيف الأسطح باستخدام صفات لمسية (مثل "قابل للانضغاط" أو "أملس") استنادًا إلى بيانات التفاعل البصري والفيزيائي معًا. عادةً ما يجمع البشر بين التنبؤات البصرية والتغذية الراجعة الناتجة عن التفاعلات المادية للتنبؤ بدقة بالخصائص اللمسية والتفاعل مع العالم. مستوحين من هذا النمط المعرفي، نقترح ونستكشف نموذجًا للتنبؤ بالخصائص اللمسية يعتمد على الإدراك البصري فقط. تتيح النماذج البصرية البحتة للروبوت أن "يشعر" دون الحاجة إلى تفاعل مادي. علاوة على ذلك، نُظهر أن استخدام إشارات التفاعل البصري والفيزيائي معًا يؤدي إلى تصنيف أكثر دقة للخصائص اللمسية. تستفيد نماذجنا من التطورات الحديثة في الشبكات العصبية العميقة من خلال تبني نهج موحد لتعلم السمات الخاصة بالتفاعل المادي والملاحظات البصرية. وعلى الرغم من استخدامنا القليل من المعرفة الخاصة بالنطاق، فإن نموذجنا لا يزال يحقق نتائج أفضل من الطرق القائمة على سمات تم تصميمها يدويًا.
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ar
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Data on the photoproduction of $\omega$ mesons on nuclei have been re-analyzed in a search for in-medium modifications. The data were taken with the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in Bonn. First results from the analysis of the data set were published by D. Trnka et al. in Phys. Rev. Lett 94 (2005) 192303 \cite{david}, claiming a lowering of the $\omega$ mass in the nuclear medium by 14$%$ at normal nuclear matter density. The extracted $\omega$ line shape was found to be sensitive to the background subtraction. For this reason a re-analysis of the same data set has been initiated and a new method has been developed to reduce the background and to determine the shape and absolute magnitude of the background directly from the data. Details of the re-analysis and of the background determination are described. The $\omega$ signal on the $Nb$ target, extracted in the re-analysis, does not show a deviation from the corresponding line shape on a $LH_2$ target, measured as reference. The earlier claim of an in-medium mass shift is thus not confirmed. The sensitivity of the $\omega$ line shape to different in-medium modification scenarios is discussed.
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Dữ liệu về quá trình tạo thành các meson $\omega$ dưới tác dụng của photon trên các hạt nhân đã được phân tích lại nhằm tìm kiếm các hiệu chỉnh trong môi trường trung gian. Dữ liệu được thu thập bằng hệ thống detector Crystal Barrel (CB)/TAPS tại cơ sở gia tốc ELSA ở Bonn. Những kết quả đầu tiên từ việc phân tích bộ dữ liệu này đã được D. Trnka và cộng sự công bố trên Phys. Rev. Lett 94 (2005) 192303 \cite{david}, trong đó khẳng định khối lượng của $\omega$ bị giảm đi 14$%$ trong môi trường hạt nhân ở mật độ vật chất hạt nhân thông thường. Hình dạng phổ của $\omega$ thu được cho thấy nhạy cảm với việc trừ nền. Vì lý do này, một cuộc phân tích lại cùng bộ dữ liệu đã được tiến hành và một phương pháp mới đã được phát triển nhằm giảm thiểu nền và xác định hình dạng cũng như độ lớn tuyệt đối của nền trực tiếp từ dữ liệu. Các chi tiết về việc phân tích lại và xác định nền được trình bày. Tín hiệu $\omega$ trên bia $Nb$, thu được từ phân tích lại, không cho thấy sự sai lệch nào so với hình dạng phổ tương ứng trên bia $LH_2$, vốn được đo làm chuẩn. Do đó, khẳng định trước đây về sự dịch chuyển khối lượng trong môi trường trung gian không được khẳng định lại. Mức độ nhạy của hình dạng phổ $\omega$ đối với các kịch bản hiệu chỉnh khác nhau trong môi trường trung gian cũng được thảo luận.
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vi
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The gaussian damping factor (g.d.f.) and the new interaction vertex with the symplectic tensor are the characteristic properties of the N-point scalar-vector scattering amplitudes of the p-p' (p < p') open string system which realizes noncommutative geometry. The g.d.f. is here interpreted as a form factor of the Dp-brane by noncommutative U(1) current. Observing that the g.d.f. is in fact equal to the Fourier transform of the noncommutative projector soliton introduced by Gopakumar, Minwalla and Strominger, we further identify the Dp-brane in the zero slope limit with the noncommutative soliton state. It is shown that the g.d.f. depends only on the total momentum of N-2 incoming/outgoing photons in the zero slope limit. In the description of the low-energy effective action (LEEA) proposed before, this is shown to follow from the delta function propagator and the form of the initial/final wave functions in the soliton sector which resides in x^{m} m= p+1, ...p' dependent part of the scalar field \Phi(x^\mu, x^m). The three and four point amplitudes computed from LEEA agree with string calculation. We discuss related issues which are resummation/lifting of infinite degeneracy and conservation of momentum transverse to the Dp-brane.
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Ang gaussian damping factor (g.d.f.) at ang bagong interaction vertex na may symplectic tensor ay ang mga katangian ng N-point scalar-vector scattering amplitudes ng p-p' (p < p') na bukas na sistema ng string na nagpapakita ng di-nagkakasunduang heometriya. Ang g.d.f. ay ipinapakahulugan dito bilang isang form factor ng Dp-brane sa pamamagitan ng di-nagkakasunduang U(1) na kuryente. Sa pagmamasid na ang g.d.f. ay talagang katumbas ng Fourier transform ng di-nagkakasunduang projector soliton na ipinakilala ni Gopakumar, Minwalla, at Strominger, karagdagang nailalarawan natin ang Dp-brane sa zero slope limit bilang di-nagkakasunduang soliton na kalagayan. Ipinapakita na ang g.d.f. ay nakadepende lamang sa kabuuang momentum ng N-2 na papasok/labas na mga photon sa zero slope limit. Sa paglalarawan ng dating iminungkahing low-energy effective action (LEEA), ipinapakita na ito ay nagmumula sa delta function propagator at sa anyo ng paunang/pangwakas na wave function sa loob ng soliton sector na matatagpuan sa x^{m}, m= p+1, ...p' na bahaging nakadepende sa scalar field na \Phi(x^\mu, x^m). Ang mga amplitude ng tatlo at apat na punto na kinompyut mula sa LEEA ay tugma sa resulta ng kalkulasyon sa string. Talakayin din ang mga kaugnay na isyu tulad ng resummation/lifting ng walang hanggang pagkakapareho at ang pag-iingat ng momentum na nakatayo sa Dp-brane.
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tl
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Among the combinations $L_e-L_\mu$, $L_e-L_\tau$ and $L_\mu-L_\tau$ any one can be gauged in anomaly free way with the standard model gauge group. The masses of these gauge bosons can be so light that it can induce long-range forces on the Earth due to the electrons in the Sun. This type of forces can be constrained significantly from neutrino oscillation. As the sign of the potential is opposite for neutrinos and antineutrinos, a magnetized iron calorimeter detector (ICAL) would be able to produce strong constraint on it. We have made conservative studies of these long-range forces with atmospheric neutrinos at ICAL considering only the muons of charge current interactions. We find stringent bounds on the couplings $ \alpha_{e\mu, e\tau} \lapp 1.65 \times 10^{-53}$ at 3$\sigma$ CL with an exposure of 1 Mton$\cdot$yr if there is no such force. For nonzero input values of the couplings we find that the potential $V_{e\mu}$ opposes and $V_{e\tau}$ helps to discriminate the mass hierarchy. However, both potentials help significantly to discriminate the octant of $\theta_{23}$. The explanation of the anomaly in recent MINOS data (the difference of $\Delta m^2_{32}$ for neutrinos and antineutrinos), using long-range force originated from the mixing of the gauge boson $Z^\prime$ of $L_\mu-L_\tau$ with the standard model gauge boson $Z$, can be tested at ICAL at more than 5$\sigma$ CL. We have also discussed how to disentangle this from the solution with CPT violation using the seasonal change of the distance between the Earth and the Sun.
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Trong số các tổ hợp $L_e-L_\mu$, $L_e-L_\tau$ và $L_\mu-L_\tau$, bất kỳ tổ hợp nào cũng có thể được lượng tử hóa theo cách không có dị thường cùng với nhóm chuẩn của mô hình chuẩn. Khối lượng của các boson gauge này có thể nhẹ đến mức gây ra các lực tầm xa trên Trái Đất do các electron trong Mặt Trời. Loại lực này có thể bị ràng buộc mạnh mẽ thông qua hiện tượng dao động neutrino. Vì dấu của thế năng ngược nhau đối với neutrino và phản neutrino, một detector calorimeter sắt từ hóa (ICAL) sẽ có khả năng đặt ra ràng buộc mạnh đối với lực này. Chúng tôi đã thực hiện các nghiên cứu thận trọng về các lực tầm xa này bằng neutrino khí quyển tại ICAL, chỉ xét các muon từ các tương tác dòng điện tích. Chúng tôi tìm thấy các giới hạn chặt chẽ đối với các hằng số liên kết $ \alpha_{e\mu, e\tau} \lapp 1.65 \times 10^{-53}$ ở độ tin cậy 3$\sigma$ với thời gian phơi sáng 1 Mton$\cdot$yr nếu không tồn tại lực như vậy. Đối với các giá trị đầu vào khác không của hằng số liên kết, chúng tôi thấy rằng thế năng $V_{e\mu}$ cản trở và $V_{e\tau}$ hỗ trợ việc phân biệt bậc phân cấp khối lượng. Tuy nhiên, cả hai thế năng đều hỗ trợ đáng kể việc phân biệt phần tám của $\theta_{23}$. Việc giải thích dị thường trong dữ liệu gần đây của MINOS (sự khác biệt của $\Delta m^2_{32}$ đối với neutrino và phản neutrino), bằng lực tầm xa bắt nguồn từ sự trộn lẫn giữa boson gauge $Z^\prime$ của $L_\mu-L_\tau$ với boson gauge $Z$ của mô hình chuẩn, có thể được kiểm chứng tại ICAL ở mức độ tin cậy hơn 5$\sigma$. Chúng tôi cũng đã thảo luận cách tách biệt trường hợp này khỏi lời giải dựa trên sự vi phạm CPT bằng cách sử dụng sự thay đổi theo mùa của khoảng cách giữa Trái Đất và Mặt Trời.
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vi
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En este trabajo, se obtiene una expresi\'on num\'erica para calcular el espectro de emisi\'on de un sistema microcavidad-punto cu\'antico usando una teor\'ia de campo medio en el formalismo de la matriz densidad. El sistema modelado es un micropilar semiconductor que contiene un \'unico punto cu\'antico en el interior de la microcavidad, este sistema presenta p\'erdida de fotones a trav\'es de los espejos de la cavidad y bombeo de excitones al punto cu\'antico. Obtenemos una ecuaci\'on maestra de campo medio no lineal que nos permite calcular el espectro de emisi\'on. In this work, we deduce a numerical expression to calculate the emission spectrum for a quantum dot-microcavity system, using a mean field theory in the density matrix formalism. The open system modeled, is a typical semiconductor micropillar that contains a single quantum dot inside a microcavity, this system presents leakage of photons through cavity mirrors and pumping of excitons to the quantum dot. We obtain a mean field nonlinear master equation that allow us calculate the emission spectrum.
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Dalam karya ini, kami memperoleh ekspresi numerik untuk menghitung spektrum emisi suatu sistem titik kuantum-mikrokavitas, menggunakan teori medan rata-rata dalam formalisme matriks densitas. Sistem terbuka yang dimodelkan adalah mikropilar semikonduktor khas yang mengandung satu titik kuantum tunggal di dalam mikrokavitas, sistem ini menunjukkan kebocoran foton melalui cermin rongga dan pemompaan eksiton ke titik kuantum. Kami memperoleh persamaan master nonlinier medan rata-rata yang memungkinkan kami menghitung spektrum emisi.
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id
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A general framework for the study of regular variation (RV) is that of Polish star-shaped metric spaces, while recent developments in [1] have discussed RV with respect to some properly localised boundedness $\mathcal{B}$ imposing weak assumptions on the structure of Polish space. Along the lines of the latter approach, we discuss the RV of Borel measures and random processes on general Polish metric spaces. Tail measures introduced in [2] appear naturally as limiting measures of regularly varying time series. We define tail measures on a measurable space indexed by $\mathcal{H}(D)$, a countable family of homogeneous coordinate maps, and show some tractable instances for the investigation of RV when $\mathcal{B}$ is determined by $\mathcal{H}(D)$. This allows us to study the regular variation of cadlag processes on $D(R^l, R^d)$ retrieving in particular results obtained in [1] for RV of stationary cadlag processes on the real line removing $l=1$ therein. Further, we discuss potential applications and open questions.
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Un cadre général pour l'étude de la variation régulière (VR) est celui des espaces métriques polonais étoilés, tandis que des développements récents dans [1] ont abordé la VR par rapport à une bornitude $\mathcal{B}$ convenablement localisée, en imposant des hypothèses faibles sur la structure de l'espace polonais. Dans la lignée de cette dernière approche, nous étudions la variation régulière de mesures de Borel et de processus aléatoires sur des espaces métriques polonais généraux. Les mesures de queue introduites dans [2] apparaissent naturellement comme mesures limites de séries chronologiques à variation régulière. Nous définissons des mesures de queue sur un espace mesurable indexé par $\mathcal{H}(D)$, une famille dénombrable d'applications coordonnées homogènes, et nous mettons en évidence certains cas particuliers exploitables pour l'étude de la VR lorsque $\mathcal{B}$ est déterminé par $\mathcal{H}(D)$. Cela nous permet d'analyser la variation régulière de processus càdlàg sur $D(R^l, R^d)$, retrouvant en particulier les résultats obtenus dans [1] pour la VR de processus càdlàg stationnaires sur la droite réelle en supprimant ici la condition $l=1$. En outre, nous discutons des applications potentielles et de questions ouvertes.
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fr
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We study effects of pinning on the dynamics of a vortex lattice in a type II superconductor in the strong-pinning situation and determine the force--velocity (or current--voltage) characteristic combining analytical and numerical methods. Our analysis deals with a small density $n_p$ of defects that act with a large force $f_p$ on the vortices, thereby inducing bistable configurations that are a characteristic feature of strong pinning theory. We determine the velocity-dependent average pinning-force density $\langle F_p(v)\rangle$ and find that it changes on the velocity scale $v_p \sim f_p/\eta a_0^3$, where $\eta$ is the viscosity of vortex motion and $a_0$ the distance between vortices. In the small pin-density limit, this velocity is much larger than the typical flow velocity $v_c \sim F_c/\eta$ of the free vortex system at drives near the critical force-density $F_c = \langle F_p(v=0)\rangle \propto n_p f_p$. As a result, we find a generic excess-force characteristic, a nearly linear force--velocity characteristic shifted by the critical force-density $F_c$; the linear flux-flow regime is approached only at large drives. Our analysis provides a derivation of Coulomb's law of dry friction for the case of strong vortex pinning.
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Nous étudions les effets de l'ancrage sur la dynamique d'un réseau de vortex dans un supraconducteur de type II en situation d'ancrage fort, et déterminons la caractéristique force-vitesse (ou courant-tension) en combinant des méthodes analytiques et numériques. Notre analyse porte sur une faible densité $n_p$ de défauts exerçant sur les vortex une force importante $f_p$, induisant ainsi des configurations bistables qui constituent une caractéristique essentielle de la théorie de l'ancrage fort. Nous déterminons la densité moyenne de force d'ancrage dépendant de la vitesse $\langle F_p(v)\rangle$ et constatons qu'elle varie à l'échelle de vitesse $v_p \sim f_p/\eta a_0^3$, où $\eta$ est la viscosité du mouvement des vortex et $a_0$ la distance entre vortex. Dans la limite d'une faible densité d'ancrage, cette vitesse est beaucoup plus grande que la vitesse d'écoulement typique $v_c \sim F_c/\eta$ du système de vortex libre soumis à des forces proches de la densité de force critique $F_c = \langle F_p(v=0)\rangle \propto n_p f_p$. En conséquence, nous obtenons une caractéristique générique de force excédentaire, une relation quasi linéaire entre force et vitesse décalée par la densité de force critique $F_c$ ; le régime linéaire d'écoulement du flux n'est atteint que pour de fortes excitations. Notre analyse fournit une dérivation de la loi de Coulomb du frottement sec dans le cas de l'ancrage fort des vortex.
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Charginos $\tilde{\chi}^\pm$ and neutralinos $\tilde{\chi}^0$ in supersymmetric theories can be produced copiously at $e^+e^-$ colliders and their properties can be measured with high accuracy. Consecutively to the chargino system, in which the SU(2) gaugino parameter $M_2$, the higgsino mass parameter $\mu$ and $\tan\beta$ can be determined, the remaining fundamental supersymmetry parameter in the gaugino/higgsino sector of the minimal supersymmetric extension of the Standard Model, the U(1) gaugino mass $M_1$, can be analyzed in the neutralino system, including its modulus and its phase in CP-noninvariant theories. The CP properties of the neutralino system are characterized by unitarity quadrangles. Analytical solutions for the neutralino mass eigenvalues and for the mixing matrix are presented for CP-noninvariant theories in general. They can be written in compact form for large supersymmetric mass parameters. The closure of the neutralino and chargino systems can be studied by exploiting sum rules for the pair-production processes in $e^+e^-$ collisions. Thus the picture of the non-colored gaugino and higgsino complex in supersymmetric theories can comprehensively be reconstructed in these experiments.
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Dalam teori supersimetri, chargino $\tilde{\chi}^\pm$ dan neutralino $\tilde{\chi}^0$ boleh dihasilkan dengan banyak di penggalak $e^+e^-$ dan sifat-sifat mereka boleh diukur dengan ketepatan tinggi. Secara berterusan daripada sistem chargino, di mana parameter gaugino SU(2) $M_2$, parameter jisim higgsino $\mu$ dan $\tan\beta$ boleh ditentukan, parameter asas supersimetri yang tinggal dalam sektor gaugino/higgsino pelanjutan minimal supersimetri Model Piawai, iaitu jisim gaugino U(1) $M_1$, boleh dianalisis dalam sistem neutralino, termasuk modulus dan fasa dalam teori yang tidak invariant CP. Sifat CP sistem neutralino dicirikan oleh segi empat unitari. Penyelesaian analitikal bagi nilai eigen jisim neutralino dan matriks pencampuran dibentangkan secara umum untuk teori yang tidak invariant CP. Penyelesaian ini boleh ditulis dalam bentuk padat untuk parameter jisim supersimetri yang besar. Penutupan sistem neutralino dan chargino boleh dikaji dengan memanfaatkan peraturan jumlah bagi proses pengeluaran pasangan dalam perlanggaran $e^+e^-$. Dengan itu, gambaran lengkap kompleks gaugino dan higgsino yang tidak berwarna dalam teori supersimetri boleh dibina semula secara menyeluruh dalam eksperimen ini.
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A new kind of quantum indeterminacy of transverse position is shown to arise from quantum degrees of freedom of spacetime, based on the assumption that classical trajectories can be defined no better than the diffraction limit of Planck scale waves. Indeterminacy of the angular orientation of particle trajectories due to wave/particle duality at the Planck scale leads to indeterminacy of a nearly-flat spacetime metric, described as a small nonvanishing quantum commutation relation between transverse position operators at different events along a null trajectory. An independent derivation of the same effect is presented based on the requirement of unitarity in black hole evaporation. The indeterminacy is interpreted as a universal holographic quantum spacetime noise, with a frequency-independent spectrum of metric perturbation amplitude, h_H^2^{1/2} \simeq \sqrt{l_P}=2.3 \times 10^{-22} /\sqrt{Hz}, where l_P denotes the Planck length. The effect is estimated to be directly measurable using current interferometer technology similar to LIGO and LISA.
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Se demuestra que surge una nueva clase de indeterminación cuántica de la posición transversal a partir de los grados de libertad cuánticos del espacio-tiempo, basada en el supuesto de que las trayectorias clásicas no pueden definirse con mayor precisión que el límite de difracción de ondas a escala de Planck. La indeterminación en la orientación angular de las trayectorias de partículas debida a la dualidad onda/partícula a la escala de Planck conduce a una indeterminación en la métrica de un espacio-tiempo casi plano, descrita como una pequeña relación de conmutación cuántica no nula entre operadores de posición transversal en diferentes sucesos a lo largo de una trayectoria nula. Se presenta una derivación independiente del mismo efecto basada en el requisito de unitariedad en la evaporación de agujeros negros. La indeterminación se interpreta como un ruido cuántico universal de espacio-tiempo holográfico, con un espectro independiente de la frecuencia en la amplitud de las perturbaciones métricas, h_H^2^{1/2} \simeq \sqrt{l_P}=2.3 \times 10^{-22} /\sqrt{Hz}, donde l_P denota la longitud de Planck. Se estima que el efecto puede medirse directamente utilizando tecnología actual de interferómetros similar a LIGO y LISA.
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es
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Graphene nanoribbons (GNRs) synthesized using a bottom-up technique potentially enable future electronic devices owing to the tunable electronic structures depending on the well-defined width and edge geometry. For instance, armchair-edged GNRs (AGNRs) exhibit width-dependent bandgaps. However, the bandgaps of AGNRs synthesized experimentally thus far are relatively large, well above 1 eV. Such a large bandgap may deteriorate device performances due to large Schottky barriers and carrier effective masses. We describe the bottom-up synthesis of AGNRs with a smaller bandgap using dibromobenzene-based precursors. Two types of AGNRs with different widths of 17 and 13 carbon atoms were synthesized on Au(111), and their atomic and electronic structures were investigated by scanning probe microscopy and spectroscopy. We reveal that the 17-AGNRs has the smallest bandgap as well as the smallest electron/hole effective mass among bottom-up AGNRs reported thus far. The successful synthesis of 17-AGNRs is a significant step toward the development of GNR-based electronic devices.
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采用自下而上方法合成的石墨烯纳米带（GNRs）因其电子结构可调，且取决于明确定义的宽度和边缘几何结构，有望用于未来的电子器件。例如，扶手椅型边缘石墨烯纳米带（AGNRs）表现出与宽度相关的带隙。然而，迄今为止实验合成的AGNRs带隙相对较大，远超过1 eV。如此大的带隙可能因产生较大的肖特基势垒和载流子有效质量而恶化器件性能。本文报道了使用二溴苯类前驱体自下而上合成具有较小带隙的AGNRs。在Au(111)表面合成了两种不同宽度（分别为17个和13个碳原子）的AGNRs，并利用扫描探针显微镜和谱学技术对其原子结构和电子结构进行了研究。研究发现，17-AGNRs是迄今为止报道的自下而上合成的AGNRs中带隙最小、电子/空穴有效质量最小的材料。17-AGNRs的成功合成是迈向发展基于GNR电子器件的重要一步。
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Data on the photoproduction of $\omega$ mesons on nuclei have been re-analyzed in a search for in-medium modifications. The data were taken with the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in Bonn. First results from the analysis of the data set were published by D. Trnka et al. in Phys. Rev. Lett 94 (2005) 192303 \cite{david}, claiming a lowering of the $\omega$ mass in the nuclear medium by 14$%$ at normal nuclear matter density. The extracted $\omega$ line shape was found to be sensitive to the background subtraction. For this reason a re-analysis of the same data set has been initiated and a new method has been developed to reduce the background and to determine the shape and absolute magnitude of the background directly from the data. Details of the re-analysis and of the background determination are described. The $\omega$ signal on the $Nb$ target, extracted in the re-analysis, does not show a deviation from the corresponding line shape on a $LH_2$ target, measured as reference. The earlier claim of an in-medium mass shift is thus not confirmed. The sensitivity of the $\omega$ line shape to different in-medium modification scenarios is discussed.
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Data mengenai fotopenghasilan meson $\omega$ pada nuklei telah dianalisis semula dalam pencarian pengubahsuaian di dalam medium. Data tersebut diambil menggunakan sistem pengesan Crystal Barrel (CB)/TAPS di kemudahan akselerator ELSA di Bonn. Keputusan awal daripada analisis set data telah diterbitkan oleh D. Trnka et al. dalam Phys. Rev. Lett 94 (2005) 192303 \cite{david}, yang mendakwa penurunan jisim $\omega$ di dalam medium nuklear sebanyak 14$%$ pada ketumpatan jirim nuklear normal. Bentuk garis $\omega$ yang diperoleh didapati sensitif terhadap penolakan latar belakang. Oleh sebab itu, satu analisis semula terhadap set data yang sama telah dijalankan dan satu kaedah baharu telah dibangunkan untuk mengurangkan latar belakang serta menentukan bentuk dan magnitud mutlak latar belakang secara langsung daripada data. Butiran mengenai analisis semula dan penentuan latar belakang diterangkan. Isyarat $\omega$ pada sasaran $Nb$, yang diperoleh daripada analisis semula, tidak menunjukkan sebarang penyimpangan daripada bentuk garis sepadan pada sasaran $LH_2$, yang diukur sebagai rujukan. Tuntutan terdahulu mengenai anjakan jisim di dalam medium dengan itu tidak disahkan. Kepekaan bentuk garis $\omega$ terhadap pelbagai senario pengubahsuaian di dalam medium dibincangkan.
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ms
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En este trabajo, se obtiene una expresi\'on num\'erica para calcular el espectro de emisi\'on de un sistema microcavidad-punto cu\'antico usando una teor\'ia de campo medio en el formalismo de la matriz densidad. El sistema modelado es un micropilar semiconductor que contiene un \'unico punto cu\'antico en el interior de la microcavidad, este sistema presenta p\'erdida de fotones a trav\'es de los espejos de la cavidad y bombeo de excitones al punto cu\'antico. Obtenemos una ecuaci\'on maestra de campo medio no lineal que nos permite calcular el espectro de emisi\'on. In this work, we deduce a numerical expression to calculate the emission spectrum for a quantum dot-microcavity system, using a mean field theory in the density matrix formalism. The open system modeled, is a typical semiconductor micropillar that contains a single quantum dot inside a microcavity, this system presents leakage of photons through cavity mirrors and pumping of excitons to the quantum dot. We obtain a mean field nonlinear master equation that allow us calculate the emission spectrum.
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Dans ce travail, on obtient une expression numérique permettant de calculer le spectre d'émission d'un système microcavité-point quantique en utilisant une théorie de champ moyen dans le formalisme de la matrice densité. Le système ouvert modélisé est un micropilier semi-conducteur typique contenant un unique point quantique à l'intérieur d'une microcavité ; ce système présente une fuite de photons à travers les miroirs de la cavité et un pompage d'excitons vers le point quantique. Nous obtenons une équation maîtresse non linéaire de champ moyen qui nous permet de calculer le spectre d'émission.
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fr
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For several decades, the interest of the scientific community in aneutronic fusion reactions such as proton-Boron fusion has grown because of potential applications in different fields. Recently, many scientific teams in the world have worked experimentally on the possibility to trigger proton-Boron fusion using intense lasers demonstrating an important renewal of interest of this field. It is now possible to generate ultra-short high intensity laser pulses at high repetition rate. These pulses also have unique properties that can be leveraged to produce proton-Boron fusion reactions. In this article, we investigate the interaction of a high energy attosecond pulse with a solid proton-Boron target and the associated ion acceleration supported by numerical simulations. We demonstrate the efficiency of single-cycle attosecond pulses in comparison to multi-cycle attosecond pulses in ion acceleration and magnetic field generation. Using these results we also propose a path to proton-Boron fusion using high energy attosecond pulses.
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Po několik desetiletí roste zájem vědecké komunity o aneutronické fúzní reakce, jako je fúze proton-boron, kvůli potenciálnímu využití v různých oblastech. V poslední době pracovalo mnoho vědeckých týmů na celém světě experimentálně na možnosti vyvolání fúze proton-boron pomocí intenzivních laserů, což svědčí o významném oživení zájmu o tento obor. Nyní je možné generovat ultra-krátké laserové pulzy vysoké intenzity s vysokou frekvencí opakování. Tyto pulzy mají také jedinečné vlastnosti, které lze využít k produkci fúzních reakcí proton-boron. V tomto článku zkoumáme interakci vysoce energetického atosekundového pulzu s pevným terčem proton-boron a související urychlování iontů podpořené numerickými simulacemi. Ukazujeme efektivitu jedno-periodických atosekundových pulzů ve srovnání s mnoho-periodickými atosekundovými pulzy při urychlování iontů a generování magnetického pole. Na základě těchto výsledků navrhujeme také cestu k fúzi proton-boron pomocí vysoce energetických atosekundových pulzů.
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cs
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In 1978, Schaefer proved his famous dichotomy theorem for generalized satisfiability problems. He defined an infinite number of propositional satisfiability problems, showed that all these problems are either in P or NP-complete, and gave a simple criterion to determine which of the two cases holds. This result is surprising in light of Ladner's theorem, which implies that there are an infinite number of complexity classes between P and NP-complete (under the assumption that P is not equal to NP). Schaefer also stated a dichotomy theorem for quantified generalized Boolean formulas, but this theorem was only recently proven by Creignou, Khanna, and Sudan, and independently by Dalmau: Determining truth of quantified Boolean formulas is either PSPACE-complete or in P. This paper looks at alternation-bounded quantified generalized Boolean formulas. In their unrestricted forms, these problems are the canonical problems complete for the levels of the polynomial hierarchy. In this paper, we prove dichotomy theorems for alternation-bounded quantified generalized Boolean formulas, by showing that these problems are either $\Sigma_i^p$-complete or in P, and we give a simple criterion to determine which of the two cases holds. This is the first result that obtains dichotomy for an infinite number of classes at once.
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1978年，Schaefer证明了关于广义可满足性问题的著名二分定理。他定义了一类无限的命题可满足性问题，证明所有这些问题要么属于P类，要么是NP完全的，并给出了一个简单的判据来确定属于哪一种情况。考虑到Ladner定理的结论，这一结果令人惊讶，因为Ladner定理表明，在P与NP完全之间存在无限多个复杂性类（假设P不等于NP）。Schaefer还提出了关于量化广义布尔公式的二分定理，但该定理直到最近才由Creignou、Khanna和Sudan，以及独立地由Dalmau所证明：判断量化布尔公式的真值问题要么是PSPACE完全的，要么属于P类。本文研究了交替量词层数受限的量化广义布尔公式。在不受限制的情况下，这些问题分别是多项式层次各级别的完全问题。在本文中，我们证明了交替层数受限的量化广义布尔公式的二分定理，即这些问题要么是$\Sigma_i^p$-完全的，要么属于P类，并给出了一个简单的判据来确定属于哪一种情况。这是首次同时对无限多个复杂性类获得二分性结果。
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High-contrast coronagraphy will be needed to image and characterize faint extra-solar planetary systems. Coronagraphy is a rapidly evolving field, and many enhanced alternatives to the classical Lyot coronagraph have been proposed in the past ten years. Here, we discuss the operation of the vector vortex coronagraph, which is one of the most efficient possible coronagraphs. We first present recent laboratory results, and then first light observations at the Palomar observatory. Our near-infrared H-band (centered at ~ 1.65 microns) and K-band (centered at ~ 2.2 microns) vector vortex devices demonstrated excellent contrast results in the lab, down to ~ 1e-6 at an angular separation of 3 lb/d. On sky, we detected a brown dwarf companion 3000 times fainter than its host star (HR 7672) in the Ks band (centered at ~2.15 microns), at an angular separation of ~ 2.5 lb/d. Current and next-generation high-contrast instruments can directly benefit from the demonstrated capabilities of such a vector vortex: simplicity, small inner working angle, high optical throughput (>90%), and maximal off-axis discovery space.
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La coronografia ad alto contrasto sarà necessaria per immaginare e caratterizzare deboli sistemi planetari extrasolari. La coronografia è un campo in rapida evoluzione e negli ultimi dieci anni sono state proposte numerose alternative migliorative rispetto al classico coronografo di Lyot. In questo lavoro discutiamo il funzionamento del coronografo a vortice vettoriale, che è uno dei coronografi più efficienti possibili. Presentiamo innanzitutto recenti risultati sperimentali ottenuti in laboratorio, seguiti dalle prime osservazioni effettuate all'osservatorio di Palomar. I nostri dispositivi a vortice vettoriale nel vicino infrarosso, nella banda H (centrata a circa 1,65 micron) e nella banda K (centrata a circa 2,2 micron), hanno dimostrato eccellenti risultati in termini di contrasto in laboratorio, fino a circa 1e-6 a una separazione angolare di 3 λ/D. In osservazione astronomica, abbiamo rilevato un compagno nana bruna 3000 volte più debole della sua stella ospite (HR 7672) nella banda Ks (centrata a circa 2,15 micron), a una separazione angolare di circa 2,5 λ/D. Gli strumenti attuali e di prossima generazione per l'alta contrastografia possono trarre diretto vantaggio dalle capacità dimostrate di questo tipo di coronografo a vortice vettoriale: semplicità, piccolo angolo interno di funzionamento, elevata trasmissione ottica (>90%) e massimo spazio di scoperta per oggetti fuori asse.
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it
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The generalized belief propagation (GBP), introduced by Yedidia et al., is an extension of the belief propagation (BP) algorithm, which is widely used in different problems involved in calculating exact or approximate marginals of probability distributions. In many problems, it has been observed that the accuracy of GBP considerably outperforms that of BP. However, because in general the computational complexity of GBP is higher than BP, its application is limited in practice. In this paper, we introduce a stochastic version of GBP called stochastic generalized belief propagation (SGBP) that can be considered as an extension to the stochastic BP (SBP) algorithm introduced by Noorshams et al. They have shown that SBP reduces the complexity per iteration of BP by an order of magnitude in alphabet size. In contrast to SBP, SGBP can reduce the computation complexity if certain topological conditions are met by the region graph associated to a graphical model. However, this reduction can be larger than only one order of magnitude in alphabet size. In this paper, we characterize these conditions and the amount of computation gain that we can obtain by using SGBP. Finally, using similar proof techniques employed by Noorshams et al., for general graphical models satisfy contraction conditions, we prove the asymptotic convergence of SGBP to the unique GBP fixed point, as well as providing non-asymptotic upper bounds on the mean square error and on the high probability error.
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La propagación de creencias generalizada (GBP), introducida por Yedidia et al., es una extensión del algoritmo de propagación de creencias (BP), que se utiliza ampliamente en diversos problemas relacionados con el cálculo de marginales exactos o aproximados de distribuciones de probabilidad. En muchos problemas se ha observado que la precisión de GBP supera considerablemente a la de BP. Sin embargo, debido a que en general la complejidad computacional de GBP es mayor que la de BP, su aplicación está limitada en la práctica. En este artículo, introducimos una versión estocástica de GBP denominada propagación de creencias generalizada estocástica (SGBP), que puede considerarse como una extensión del algoritmo de propagación de creencias estocástica (SBP) introducido por Noorshams et al. Ellos han demostrado que SBP reduce la complejidad por iteración de BP en un orden de magnitud respecto al tamaño del alfabeto. En contraste con SBP, SGBP puede reducir la complejidad computacional si se cumplen ciertas condiciones topológicas en el grafo de regiones asociado a un modelo gráfico. Sin embargo, esta reducción puede ser mayor que un solo orden de magnitud en el tamaño del alfabeto. En este artículo, caracterizamos estas condiciones y la cantidad de ganancia computacional que podemos obtener al usar SGBP. Finalmente, empleando técnicas de demostración similares a las utilizadas por Noorshams et al. para modelos gráficos generales que satisfacen condiciones de contracción, demostramos la convergencia asintótica de SGBP al punto fijo único de GBP, así como proporcionamos cotas superiores no asintóticas para el error cuadrático medio y para el error con alta probabilidad.
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es
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We study effects of pinning on the dynamics of a vortex lattice in a type II superconductor in the strong-pinning situation and determine the force--velocity (or current--voltage) characteristic combining analytical and numerical methods. Our analysis deals with a small density $n_p$ of defects that act with a large force $f_p$ on the vortices, thereby inducing bistable configurations that are a characteristic feature of strong pinning theory. We determine the velocity-dependent average pinning-force density $\langle F_p(v)\rangle$ and find that it changes on the velocity scale $v_p \sim f_p/\eta a_0^3$, where $\eta$ is the viscosity of vortex motion and $a_0$ the distance between vortices. In the small pin-density limit, this velocity is much larger than the typical flow velocity $v_c \sim F_c/\eta$ of the free vortex system at drives near the critical force-density $F_c = \langle F_p(v=0)\rangle \propto n_p f_p$. As a result, we find a generic excess-force characteristic, a nearly linear force--velocity characteristic shifted by the critical force-density $F_c$; the linear flux-flow regime is approached only at large drives. Our analysis provides a derivation of Coulomb's law of dry friction for the case of strong vortex pinning.
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Estudamos os efeitos da fixação (pinning) na dinâmica de um reticulado de vórtices em um supercondutor do tipo II na situação de fixação forte e determinamos a característica força--velocidade (ou corrente--tensão) combinando métodos analíticos e numéricos. Nossa análise trata de uma baixa densidade $n_p$ de defeitos que atuam sobre os vórtices com uma força elevada $f_p$, induzindo assim configurações bistáveis que são uma característica marcante da teoria da fixação forte. Determinamos a densidade média da força de fixação dependente da velocidade $\langle F_p(v)\rangle$ e verificamos que ela varia na escala de velocidade $v_p \sim f_p/\eta a_0^3$, onde $\eta$ é a viscosidade do movimento dos vórtices e $a_0$ a distância entre vórtices. No limite de baixa densidade de fixação, essa velocidade é muito maior do que a velocidade de escoamento típica $v_c \sim F_c/\eta$ do sistema de vórtices livres para forças próximas da densidade de força crítica $F_c = \langle F_p(v=0)\rangle \propto n_p f_p$. Como resultado, encontramos uma característica genérica de força em excesso, uma relação quase linear entre força e velocidade deslocada pela densidade de força crítica $F_c$; o regime linear de escoamento do fluxo é alcançado apenas para forças elevadas. Nossa análise fornece uma derivação da lei de Coulomb de atrito seco para o caso da fixação forte de vórtices.
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pt
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High-contrast coronagraphy will be needed to image and characterize faint extra-solar planetary systems. Coronagraphy is a rapidly evolving field, and many enhanced alternatives to the classical Lyot coronagraph have been proposed in the past ten years. Here, we discuss the operation of the vector vortex coronagraph, which is one of the most efficient possible coronagraphs. We first present recent laboratory results, and then first light observations at the Palomar observatory. Our near-infrared H-band (centered at ~ 1.65 microns) and K-band (centered at ~ 2.2 microns) vector vortex devices demonstrated excellent contrast results in the lab, down to ~ 1e-6 at an angular separation of 3 lb/d. On sky, we detected a brown dwarf companion 3000 times fainter than its host star (HR 7672) in the Ks band (centered at ~2.15 microns), at an angular separation of ~ 2.5 lb/d. Current and next-generation high-contrast instruments can directly benefit from the demonstrated capabilities of such a vector vortex: simplicity, small inner working angle, high optical throughput (>90%), and maximal off-axis discovery space.
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Koronagrafi berkontras tinggi diperlukan untuk mengimej dan mencirikan sistem planet luar suria yang malap. Koronagrafi merupakan bidang yang berkembang dengan pesat, dan banyak alternatif peningkatan terhadap koronagraf Lyot klasik telah dicadangkan dalam sepuluh tahun kebelakangan ini. Di sini, kami membincangkan operasi koronagraf vorteks vektor, yang merupakan salah satu koronagraf yang paling cekap. Kami terlebih dahulu mempersembahkan keputusan makmal terkini, kemudian pemerhatian cahaya pertama di observatori Palomar. Peranti vorteks vektor kami dalam jalur H inframerah dekat (berpusat pada ~1.65 mikron) dan jalur K (berpusat pada ~2.2 mikron) menunjukkan keputusan kontras yang sangat baik di makmal, hingga ~1e-6 pada pemisahan sudut 3 λ/D. Di langit, kami mengesan rakan bintang kerdil perang yang 3000 kali lebih malap daripada bintang induknya (HR 7672) dalam jalur Ks (berpusat pada ~2.15 mikron), pada pemisahan sudut ~2.5 λ/D. Instrumen berkontras tinggi generasi semasa dan akan datang boleh mendapat manfaat secara langsung daripada keupayaan yang telah terbukti bagi koronagraf vorteks vektor sebegini: kesederhanaan, sudut kerja dalaman yang kecil, kecekapan optik yang tinggi (>90%), dan ruang penemuan maksimum bagi objek luar paksi.
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ms
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En este trabajo, se obtiene una expresi\'on num\'erica para calcular el espectro de emisi\'on de un sistema microcavidad-punto cu\'antico usando una teor\'ia de campo medio en el formalismo de la matriz densidad. El sistema modelado es un micropilar semiconductor que contiene un \'unico punto cu\'antico en el interior de la microcavidad, este sistema presenta p\'erdida de fotones a trav\'es de los espejos de la cavidad y bombeo de excitones al punto cu\'antico. Obtenemos una ecuaci\'on maestra de campo medio no lineal que nos permite calcular el espectro de emisi\'on. In this work, we deduce a numerical expression to calculate the emission spectrum for a quantum dot-microcavity system, using a mean field theory in the density matrix formalism. The open system modeled, is a typical semiconductor micropillar that contains a single quantum dot inside a microcavity, this system presents leakage of photons through cavity mirrors and pumping of excitons to the quantum dot. We obtain a mean field nonlinear master equation that allow us calculate the emission spectrum.
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Бұл жұмыста тығыздық матрицасының формализмінде орташа өріс теориясын қолдана отырып, кванттық нүкте-микросаңылау жүйесі үшін шығарылым спектрін есептеуге мүмкіндік беретін сандық өрнек алынады. Моделденген ашық жүйе – микросаңылаудың ішінде жалғыз кванттық нүктені қамтитын типтік жартылай өткізгіш микротіреңкі болып табылады, бұл жүйеде фотондардың саңылау айнасы арқылы шығып кетуі және кванттық нүктеге экситондардың сорғылануы байқалады. Біз шығарылым спектрін есептеуге мүмкіндік беретін орташа өрістің сызықтық емес бас теңдеуін аламыз.
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kk
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We use the Kubo-Landauer formalism to compute the longitudinal (two-terminal) conductance of a two dimensional electron system placed in a strong perpendicular magnetic field, and subjected to periodic modulations and/or disorder potentials. The scattering problem is recast as a set of inhomogeneous, coupled linear equations, allowing us to find the transmission probabilities from a finite-size system computation; the results are exact for non-interacting electrons. Our method fully accounts for the effects of the disorder and the periodic modulation, irrespective of their relative strength, as long as Landau level mixing is negligible. In particular, we focus on the interplay between the effects of the periodic modulation and those of the disorder. This appears to be the relevant regime to understand recent experiments [S. Melinte {\em et al}, Phys. Rev. Lett. {\bf 92}, 036802 (2004)], and our numerical results are in qualitative agreement with these experimental results. The numerical techniques we develop can be generalized straightforwardly to many-terminal geometries, as well as other multi-channel scattering problems.
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Nous utilisons le formalisme de Kubo-Landauer pour calculer la conductance longitudinale (à deux bornes) d'un système bidimensionnel d'électrons placé dans un champ magnétique perpendiculaire intense, et soumis à des potentiels de modulation périodique et/ou de désordre. Le problème de diffusion est reformulé sous la forme d'un ensemble d'équations linéaires couplées non homogènes, ce qui nous permet de déterminer les probabilités de transmission à partir d'un calcul sur un système de taille finie ; les résultats sont exacts dans le cas d'électrons non corrélés. Notre méthode prend intégralement en compte les effets du désordre et de la modulation périodique, quelle que soit leur intensité relative, tant que le mélange des niveaux de Landau reste négligeable. En particulier, nous nous concentrons sur l'interaction entre les effets de la modulation périodique et ceux du désordre. Ce régime semble pertinent pour comprendre des expériences récentes [S. Melinte {\em et al}, Phys. Rev. Lett. {\bf 92}, 036802 (2004)], et nos résultats numériques sont en accord qualitatif avec ces résultats expérimentaux. Les techniques numériques que nous développons peuvent être généralisées sans difficulté à des géométries à plusieurs bornes, ainsi qu'à d'autres problèmes de diffusion multicanal.
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fr
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The evolution of a walker in standard "Discrete-time Quantum Walk (DTQW)" is determined by coin and shift unitary operators. The conditional shift operator shifts the position of the walker to right or left by unit step size while the direction of motion is specified by the coin operator. This scenario can be generalized by choosing the step size randomly at each step in some specific interval. For example, the value of the roll of a dice can be used to specify the step size after throwing the coin. Let us call such a quantum walk "Discrete-time Random Step Quantum Walk (DTRSQW)". A completely random probability distribution is obtained whenever the walker follows the DTRSQW. We have also analyzed two more types of quantum walks, the "Discrete-time Un-biased Quantum Walk (DTUBQW)" and the "Discrete-time Biased Quantum Walk (DTBQW)". In the first type, the step size is kept different than unit size but the same for left and right shifts, whereas in the second type left and right shifts can also be different. The probability distribution in DTUBQW is found to follow a certain rule. The standard deviation ($\sigma$) of DTRSQW is higher than DTQW and hence DTRSQW spreads faster. The $\sigma$ of DTUBQW shows sawtooth behavior with faster spread than DTQW for some specific values of rotation angles and steps.
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A evolução de um andador em um "Passeio Quântico em Tempo Discreto (DTQW)" padrão é determinada por operadores unitários de moeda e de deslocamento. O operador de deslocamento condicional move a posição do andador para a direita ou para a esquerda em um passo unitário, enquanto a direção do movimento é especificada pelo operador de moeda. Esse cenário pode ser generalizado escolhendo-se aleatoriamente o tamanho do passo a cada etapa dentro de um intervalo específico. Por exemplo, o valor obtido no lançamento de um dado pode ser usado para especificar o tamanho do passo após o lançamento da moeda. Vamos chamar esse tipo de passeio quântico de "Passeio Quântico em Tempo Discreto com Passo Aleatório (DTRSQW)". Uma distribuição de probabilidade completamente aleatória é obtida sempre que o andador segue o DTRSQW. Também analisamos dois outros tipos de passeios quânticos: o "Passeio Quântico em Tempo Discreto Não-Viciado (DTUBQW)" e o "Passeio Quântico em Tempo Discreto Viciado (DTBQW)". No primeiro tipo, o tamanho do passo é mantido diferente do tamanho unitário, mas igual para os deslocamentos à esquerda e à direita; já no segundo tipo, os deslocamentos para a esquerda e para a direita também podem ser diferentes. A distribuição de probabilidade no DTUBQW mostra seguir uma certa regra. O desvio padrão ($\sigma$) do DTRSQW é maior do que o do DTQW, e portanto o DTRSQW se espalha mais rapidamente. O $\sigma$ do DTUBQW exibe um comportamento em forma de serra, com uma propagação mais rápida do que a do DTQW para certos valores específicos de ângulos de rotação e número de passos.
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pt
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Crystals arise as the result of the breaking of a spatial translation symmetry. Similarly, translation symmetries can also be broken in time so that discrete time crystals appear. Here, we introduce a method to describe, characterize, and explore the physical phenomena related to this phase of matter using tools from graph theory. The analysis of the graphs allows to visualizing time-crystalline order and to analyze features of the quantum system. For example, we explore in detail the melting process of a minimal model of a period-2 discrete time crystal and describe it in terms of the evolution of the associated graph structure. We show that during the melting process, the network evolution exhibits an emergent preferential attachment mechanism, directly associated with the existence of scale-free networks. Thus, our strategy allows us to propose a previously unexplored far-reaching application of time crystals as a quantum simulator of complex quantum networks.
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ผลึกเกิดขึ้นจากการที่ความสมมาตรของการเลื่อนตำแหน่งในเชิงพื้นที่ถูกละเมิด ในทำนองเดียวกัน ความสมมาตรของการเลื่อนตำแหน่งยังสามารถถูกละเมิดในมิติเวลาได้ ทำให้เกิดผลึกเวลาแบบไม่ต่อเนื่อง (discrete time crystals) ที่นี่ เราได้นำเสนอวิธีการอธิบาย จำแนก และศึกษาปรากฏการณ์ทางกายภาพที่เกี่ยวข้องกับสถานะของสสารชนิดนี้ โดยใช้เครื่องมือจากทฤษฎีกราฟ การวิเคราะห์กราฟทำให้สามารถแสดงภาพระเบียบของผลึกเวลา และวิเคราะห์คุณลักษณะของระบบควอนตัมได้ ตัวอย่างเช่น เราได้ศึกษาอย่างละเอียดถี่ถ้วนเกี่ยวกับกระบวนการละลายของแบบจำลองที่เล็กที่สุดของผลึกเวลาแบบไม่ต่อเนื่องที่มีคาบเป็น 2 และอธิบายกระบวนการนี้ในรูปแบบของวิวัฒนาการของโครงสร้างกราฟที่เกี่ยวข้อง เราแสดงให้เห็นว่าระหว่างกระบวนการละลาย วิวัฒนาการของเครือข่ายแสดงกลไกการยึดติดแบบมีลำดับความสำคัญที่เกิดขึ้นใหม่ (emergent preferential attachment mechanism) ซึ่งสัมพันธ์โดยตรงกับการมีอยู่ของเครือข่ายที่ไม่มีสเกล (scale-free networks) ดังนั้น กลยุทธ์ของเราจึงทำให้เราสามารถเสนอการประยุกต์ใช้ผลึกเวลาในด้านใหม่ที่ยังไม่เคยมีการสำรวจมาก่อน นั่นคือ การใช้เป็นตัวจำลองควอนตัมสำหรับเครือข่ายควอนตัมซับซ้อน
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th
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Integrating sensing into standardized communication systems can potentially benefit many consumer applications that require both radio frequency functions. However, without an effective sensing method, such integration may not achieve the expected gains of cost and energy efficiency. Existing sensing methods, which use communication payload signals, either have limited sensing performance or suffer from high complexity. In this paper, we develop a novel and flexible sensing framework which has a complexity only dominated by a Fourier transform and also provides the flexibility in adapting for different sensing needs. We propose to segment a whole block of echo signal evenly into sub-blocks; adjacent ones are allowed to overlap. We design a virtual cyclic prefix (VCP) for each sub-block that allows us to employ two common ways of removing communication data symbols and generate two types of range-Doppler maps (RDMs) for sensing. We perform a comprehensive analysis of the signal components in the RDMs, proving that their interference-plus-noise (IN) terms are approximately Gaussian distributed. The statistical properties of the distributions are derived, which leads to the analytical comparisons between the two RDMs as well as between the prior and our sensing methods. Moreover, the impact of the lengths of sub-block, VCP and overlapping signal on sensing performance is analyzed. Criteria for designing these lengths for better sensing performance are also provided. Extensive simulations validate the superiority of the proposed sensing framework over prior methods in terms of signal-to-IN ratios in RDMs, detecting performance and flexibility.
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L'integrazione della rilevazione nei sistemi di comunicazione standardizzati può potenzialmente beneficiare numerose applicazioni consumer che richiedono funzionalità in radiofrequenza. Tuttavia, in assenza di un metodo efficace di rilevazione, tale integrazione potrebbe non raggiungere i guadagni attesi in termini di efficienza economica ed energetica. I metodi di rilevazione esistenti, che utilizzano segnali utile delle comunicazioni, presentano prestazioni limitate oppure soffrono di elevata complessità. In questo articolo, proponiamo un nuovo framework flessibile per la rilevazione la cui complessità è dominata soltanto da una trasformata di Fourier e che offre flessibilità nell'adattamento a diverse esigenze di rilevazione. Proponiamo di suddividere uniformemente un intero blocco di segnale eco in sottoblocchi; coppie adiacenti possono sovrapporsi. Progettiamo un prefisso ciclico virtuale (VCP) per ciascun sottoblocco, che ci consente di impiegare due metodi comuni per rimuovere i simboli dati delle comunicazioni e generare due tipi di mappe range-Doppler (RDM) per la rilevazione. Effettuiamo un'analisi completa dei componenti del segnale nelle RDM, dimostrando che i termini di interferenza più rumore (IN) sono approssimativamente distribuiti secondo una distribuzione gaussiana. Ne deriviamo le proprietà statistiche, ottenendo confronti analitici tra le due RDM e tra i metodi di rilevazione esistenti e il nostro. Inoltre, analizziamo l'impatto delle lunghezze del sottoblocco, del VCP e del segnale sovrapposto sulle prestazioni di rilevazione. Forniamo anche criteri per la progettazione di queste lunghezze al fine di migliorare le prestazioni di rilevazione. Simulazioni estese confermano la superiorità del framework proposto rispetto ai metodi precedenti in termini di rapporto segnale-IN nelle RDM, prestazioni di rilevamento e flessibilità.
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it
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Crystals arise as the result of the breaking of a spatial translation symmetry. Similarly, translation symmetries can also be broken in time so that discrete time crystals appear. Here, we introduce a method to describe, characterize, and explore the physical phenomena related to this phase of matter using tools from graph theory. The analysis of the graphs allows to visualizing time-crystalline order and to analyze features of the quantum system. For example, we explore in detail the melting process of a minimal model of a period-2 discrete time crystal and describe it in terms of the evolution of the associated graph structure. We show that during the melting process, the network evolution exhibits an emergent preferential attachment mechanism, directly associated with the existence of scale-free networks. Thus, our strategy allows us to propose a previously unexplored far-reaching application of time crystals as a quantum simulator of complex quantum networks.
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Кристаллы возникают в результате нарушения симметрии пространственных трансляций. Аналогичным образом симметрии трансляций могут нарушаться и во времени, в результате чего появляются дискретные временные кристаллы. В данной работе мы предлагаем метод описания, характеризации и исследования физических явлений, связанных с этим состоянием вещества, с использованием инструментов теории графов. Анализ графов позволяет визуализировать временно-кристаллический порядок и исследовать особенности квантовой системы. Например, мы подробно изучаем процесс плавления минимальной модели дискретного временного кристалла с периодом 2 и описываем его в терминах эволюции соответствующей графовой структуры. Мы показываем, что в ходе процесса плавления эволюция сети демонстрирует возникающий механизм предпочтительного присоединения, непосредственно связанный с существованием масштабно-инвариантных сетей. Таким образом, наш подход позволяет предложить ранее неизвестное и перспективное применение временных кристаллов в качестве квантового симулятора сложных квантовых сетей.
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ru
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A new kind of quantum indeterminacy of transverse position is shown to arise from quantum degrees of freedom of spacetime, based on the assumption that classical trajectories can be defined no better than the diffraction limit of Planck scale waves. Indeterminacy of the angular orientation of particle trajectories due to wave/particle duality at the Planck scale leads to indeterminacy of a nearly-flat spacetime metric, described as a small nonvanishing quantum commutation relation between transverse position operators at different events along a null trajectory. An independent derivation of the same effect is presented based on the requirement of unitarity in black hole evaporation. The indeterminacy is interpreted as a universal holographic quantum spacetime noise, with a frequency-independent spectrum of metric perturbation amplitude, h_H^2^{1/2} \simeq \sqrt{l_P}=2.3 \times 10^{-22} /\sqrt{Hz}, where l_P denotes the Planck length. The effect is estimated to be directly measurable using current interferometer technology similar to LIGO and LISA.
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Một dạng mới của sự bất định lượng tử về vị trí ngang được chỉ ra là phát sinh từ các bậc tự do lượng tử của không-thời gian, dựa trên giả định rằng các quỹ đạo cổ điển không thể được xác định chính xác hơn giới hạn nhiễu xạ của các sóng cỡ Planck. Sự bất định về hướng góc của các quỹ đạo hạt do lưỡng tính sóng/hạt ở thang Planck dẫn đến sự bất định của mêtric không-thời gian gần phẳng, được mô tả bằng một quan hệ giao hoán lượng tử nhỏ khác không giữa các toán tử vị trí ngang tại các sự kiện khác nhau dọc theo một quỹ đạo null. Một cách dẫn ra độc lập cùng hiệu ứng này được trình bày dựa trên yêu cầu tính đơn vị trong quá trình bốc hơi hố đen. Sự bất định này được diễn giải như một tiếng ồn lượng tử không-thời gian toàn ảnh phổ quát, với phổ biên độ nhiễu loạn mêtric không phụ thuộc tần số, h_H^2^{1/2} \simeq \sqrt{l_P}=2,3 \times 10^{-22} /\sqrt{Hz}, trong đó l_P ký hiệu chiều dài Planck. Hiệu ứng này được ước tính có thể đo trực tiếp bằng công nghệ giao thoa kế hiện tại tương tự như LIGO và LISA.
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vi
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We study the thermal transport properties of three CaF$_{2}$ polymorphs up to a pressure of 30 GPa using first-principle calculations and an interatomic potential based on machine learning. The lattice thermal conductivity $\kappa$ is computed by iteratively solving the linearized Boltzmann transport equation (BTE) and by taking into account three-phonon scattering. Overall, $\kappa$ increases nearly linearly with pressure, and we show that the recently discovered $\delta$-phase with $P\bar{6}2m$ symmetry and the previously known $\gamma$-CaF$_{2}$ high-pressure phase have significantly lower lattice thermal conductivities than the ambient-thermodynamic cubic fluorite ($Fm\bar{3}m$) structure. We argue that the lower $\kappa$ of these two high-pressure phases stems mainly due to a lower contribution of acoustic modes to $\kappa$ as a result of their small group velocities. We further show that the phonon mean free paths are very short for the $P\bar{6}2m$ and $Pnma$ structures at high temperatures, and resort to the Cahill-Pohl model to assess the lower limit of thermal conductivity in these domains.
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Estudiamos las propiedades de transporte térmico de tres polimorfos de CaF$_{2}$ hasta una presión de 30 GPa utilizando cálculos de primeros principios y un potencial interatómico basado en aprendizaje automático. La conductividad térmica reticular $\kappa$ se calcula resolviendo iterativamente la ecuación linealizada de Boltzmann para el transporte (BTE) y considerando la dispersión de fonones de tres cuerpos. En general, $\kappa$ aumenta casi linealmente con la presión, y mostramos que la fase recientemente descubierta $\delta$, con simetría $P\bar{6}2m$, y la fase de alta presión $\gamma$-CaF$_{2}$ previamente conocida tienen conductividades térmicas reticulares significativamente más bajas que la estructura cúbica de fluorita ($Fm\bar{3}m$) estable en condiciones ambientales. Argumentamos que la menor $\kappa$ de estas dos fases de alta presión se debe principalmente a una contribución más baja de los modos acústicos a $\kappa$, como consecuencia de sus bajas velocidades grupales. Además, mostramos que las longitudes medias de libre camino de los fonones son muy cortas para las estructuras $P\bar{6}2m$ y $Pnma$ a altas temperaturas, y recurrimos al modelo de Cahill-Pohl para evaluar el límite inferior de la conductividad térmica en estos dominios.
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es
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We propose Otiy, a node-centric location service that limits the impact of location updates generate by mobile nodes in IEEE802.11-based wireless mesh networks. Existing location services use node identifiers to determine the locator (aka anchor) that is responsible for keeping track of a node's location. Such a strategy can be inefficient because: (i) identifiers give no clue on the node's mobility and (ii) locators can be far from the source/destination shortest path, which increases both location delays and bandwidth consumption. To solve these issues, Otiy introduces a new strategy that identifies nodes to play the role of locators based on the likelihood of a destination to be close to these nodes- i.e., locators are identified depending on the mobility pattern of nodes. Otiy relies on the cyclic mobility patterns of nodes and creates a slotted agenda composed of a set of predicted locations, defined according to the past and present patterns of mobility. Correspondent nodes fetch this agenda only once and use it as a reference for identifying which locators are responsible for the node at different points in time. Over a period of about one year, the weekly proportion of nodes having at least 50% of exact location predictions is in average about 75%. This proportion increases by 10% when nodes also consider their closeness to the locator from only what they know about the network.
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Wir schlagen Otiy vor, einen knotenzentrierten Ortungsdienst, der die Auswirkungen von Positionsaktualisierungen, die von mobilen Knoten in drahtlosen Mesh-Netzwerken auf Basis von IEEE802.11 erzeugt werden, begrenzt. Bestehende Ortungsdienste verwenden Knotenidentifikatoren, um den Locator (auch bekannt als Anker) zu bestimmen, der dafür verantwortlich ist, die Position eines Knotens zu verfolgen. Eine solche Strategie kann ineffizient sein, da: (i) Identifikatoren keinen Hinweis auf die Mobilität des Knotens geben und (ii) die Locatoren weit vom kürzesten Pfad zwischen Quelle und Ziel liegen können, was sowohl die Ortungsverzögerung als auch den Bandbreitenverbrauch erhöht. Um diese Probleme zu lösen, führt Otiy eine neue Strategie ein, die Knoten basierend auf der Wahrscheinlichkeit auswählt, dass ein Ziel nahe bei diesen Knoten liegt – das heißt, Locatoren werden abhängig vom Mobilitätsmuster der Knoten bestimmt. Otiy stützt sich auf die zyklischen Mobilitätsmuster der Knoten und erstellt einen getakteten Plan, der aus einer Reihe vorhergesagter Positionen besteht, die anhand der vergangenen und gegenwärtigen Mobilitätsmuster definiert werden. Kommunikationspartner laden diesen Plan nur einmal herunter und verwenden ihn als Referenz, um zu ermitteln, welche Locatoren zu verschiedenen Zeitpunkten für den Knoten zuständig sind. Über einen Zeitraum von etwa einem Jahr lag der wöchentliche Anteil der Knoten, bei denen mindestens 50 % der Positionsprognosen exakt waren, im Durchschnitt bei etwa 75 %. Dieser Anteil steigt um 10 %, wenn die Knoten zusätzlich ihre Nähe zum Locator unter Berücksichtigung ihres Wissens über das Netzwerk bewerten.
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de
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We consider an unmanned aerial vehicle enabled (UAV-enabled) fog-radio access network (F-RAN) in which UAVs are considered as flying remote radio heads (RRH) equipped with caching and cooperative communications capabilities. We are mainly focus on probabilistic/randomized content placement strategy, and accordingly formulate the content placement as an optimization problem. We then study the efficiency of the proposed content placement by evaluating the average system capacity and its energy-efficiency. Our results indicate that cooperative communication plays an essential role in UAVenabled edge communications as it effectively curbs the impact of dominant Line-of-Sight (LOS) received interference. It is also seen that cooperative cache-enabled UAV F-RAN performs better in high-rise environments than dense urban and sub-urban environments. This is due to a significant reduction of the received LOS interference because of blockage by the high-rise buildings, and the performance gain of cooperative communication on the attending signal. Comparing the performances of the developed content placement strategy and conventional caching techniques shows that our proposed probabilistic/randomized caching outperforms the others in most of the practical cases.
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Consideramos una red de acceso radio con niebla habilitada por vehículos aéreos no tripulados (UAV-enabled F-RAN), en la que los UAV se consideran cabezas de radio remotas voladoras (RRH) equipadas con capacidades de almacenamiento en caché y comunicaciones cooperativas. Principalmente nos centramos en una estrategia de ubicación de contenido probabilística/aleatoria, y en consecuencia formulamos la colocación de contenido como un problema de optimización. Luego estudiamos la eficiencia de la colocación de contenido propuesta evaluando la capacidad promedio del sistema y su eficiencia energética. Nuestros resultados indican que la comunicación cooperativa desempeña un papel esencial en las comunicaciones periféricas habilitadas por UAV, ya que reduce eficazmente el impacto de la interferencia dominante recibida en línea de vista (LOS). También se observa que la red F-RAN con UAV con caché y comunicación cooperativa funciona mejor en entornos de edificios altos que en entornos urbanos densos y suburbanos. Esto se debe a una reducción significativa de la interferencia recibida en línea de vista (LOS) provocada por el bloqueo de los edificios altos, así como a la mejora del rendimiento de la comunicación cooperativa en la señal recibida. La comparación del rendimiento de la estrategia de colocación de contenido desarrollada con las técnicas convencionales de almacenamiento en caché muestra que nuestro método propuesto de almacenamiento probabilístico/aleatorio supera a los demás en la mayoría de los casos prácticos.
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es
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To realize efficient computational fluid dynamics (CFD) prediction of two-phase flow, a multi-scale framework was proposed in this paper by applying a physics-guided data-driven approach. Instrumental to this framework, Feature Similarity Measurement (FSM) technique was developed for error estimation in two-phase flow simulation using coarse-mesh CFD, to achieve a comparable accuracy as fine-mesh simulations with fast-running feature. By defining physics-guided parameters and variable gradients as physical features, FSM has the capability to capture the underlying local patterns in the coarse-mesh CFD simulation. Massive low-fidelity data and respective high-fidelity data are used to explore the underlying information relevant to the main simulation errors and the effects of phenomenological scaling. By learning from previous simulation data, a surrogate model using deep feedforward neural network (DFNN) can be developed and trained to estimate the simulation error of coarse-mesh CFD. The research documented supports the feasibility of the physics-guided deep learning methods for coarse mesh CFD simulations which has a potential for the efficient industrial design.
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Per realizzare una previsione efficiente della dinamica dei fluidi computazionale (CFD) per flussi bifase, in questo articolo è stato proposto un approccio basato su un framework multiscala che applica un metodo guidato dalla fisica e basato sui dati. Fondamentale per questo framework, è stata sviluppata la tecnica di Misurazione della Similarità delle Caratteristiche (Feature Similarity Measurement, FSM) per la stima degli errori nella simulazione di flussi bifase mediante CFD con griglia grossolana, al fine di ottenere un'accuratezza paragonabile a quella delle simulazioni con griglia fine mantenendo un tempo di esecuzione ridotto. Definendo parametri guidati dalla fisica e gradienti delle variabili come caratteristiche fisiche, la FSM è in grado di catturare i modelli locali sottostanti nella simulazione CFD con griglia grossolana. Vengono utilizzati grandi volumi di dati a bassa fedeltà e i corrispondenti dati ad alta fedeltà per esplorare le informazioni sottostanti relative agli errori principali della simulazione e agli effetti della scala fenomenologica. Attraverso l'apprendimento dai dati di simulazione precedenti, può essere sviluppato e addestrato un modello surrogato basato su una rete neurale profonda feedforward (DFNN) per stimare l'errore di simulazione del CFD con griglia grossolana. La ricerca documentata supporta la fattibilità di metodi di apprendimento profondo guidati dalla fisica per simulazioni CFD con griglia grossolana, i quali mostrano un potenziale per una progettazione industriale efficiente.
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it
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Within the framework of classical field theory, the connection between the Dirac field as the field of matter and the spacetime metric is discussed. Polarization structure of the Dirac field is shown to be rich enough to determine the spacetime metric locally and to explain the emergence of observed matter as localized waveforms. The localization of the waveforms is explained as the result of the local time slowdown and the Lorentz contraction as a dynamic re-shaping of the waveforms in the course of their acceleration. A definition of mass as a limiting curvature of the spinor-induced metric is proposed. A view of the vacuum as a uniformly distributed unit invariant density of the Dirac field with an explicitly preserved invariance of the light cone is brought forward. Qualitative explanation of the observed charge asymmetry as the consequence of the dynamics of localization is given. The classical pion field is obtained as a manifestation of stresses, mass and charge flux in localized waveforms of the Dirac field. Some implications of the finite size of colliding objects for high-energy processes are discussed. A hypothesis that known internal degrees of freedom are the local spacetime (angular) coordinates that have no precise counterparts in Riemannian geometry is proposed.
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Dans le cadre de la théorie classique des champs, on examine la relation entre le champ de Dirac en tant que champ de matière et la métrique de l'espace-temps. On montre que la structure de polarisation du champ de Dirac est suffisamment riche pour déterminer localement la métrique de l'espace-temps et expliquer l'apparition de la matière observée sous forme d'ondes localisées. La localisation de ces formes d'onde est expliquée comme résultant du ralentissement local du temps et de la contraction de Lorentz, interprétée comme une remise en forme dynamique des ondes lors de leur accélération. Une définition de la masse comme courbure limite de la métrique induite par le spineur est proposée. Une conception du vide comme une densité invariante unitaire uniformément répartie du champ de Dirac, avec une invariance explicite du cône de lumière préservée, est avancée. Une explication qualitative de l'asymétrie de charge observée, en tant que conséquence de la dynamique de la localisation, est fournie. Le champ classique du pion est obtenu comme manifestation des contraintes, du flux de masse et du flux de charge dans les formes d'onde localisées du champ de Dirac. Certaines implications de la taille finie des objets en collision pour les processus à haute énergie sont discutées. Une hypothèse selon laquelle les degrés de liberté internes connus seraient des coordonnées locales de l'espace-temps (angulaires) n'ayant pas de correspondants précis en géométrie riemannienne est proposée.
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fr
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The deep reinforcement learning method usually requires a large number of training images and executing actions to obtain sufficient results. When it is extended a real-task in the real environment with an actual robot, the method will be required more training images due to complexities or noises of the input images, and executing a lot of actions on the real robot also becomes a serious problem. Therefore, we propose an extended deep reinforcement learning method that is applied a generative model to initialize the network for reducing the number of training trials. In this paper, we used a deep q-network method as the deep reinforcement learning method and a deep auto-encoder as the generative model. We conducted experiments on three different tasks: a cart-pole game, an atari game, and a real-game with an actual robot. The proposed method trained efficiently on all tasks than the previous method, especially 2.5 times faster on a task with real environment images.
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Die Methode des tiefen Verstärkungslernens erfordert gewöhnlich eine große Anzahl von Trainingsbildern und ausgeführten Aktionen, um ausreichende Ergebnisse zu erzielen. Wenn sie auf eine reale Aufgabe in einer echten Umgebung mit einem physischen Roboter erweitert wird, sind aufgrund der Komplexität oder der Rauschanteile in den Eingangsbildern noch mehr Trainingsbilder nötig, und das Ausführen vieler Aktionen am realen Roboter wird ebenfalls zu einem ernsthaften Problem. Daher schlagen wir eine erweiterte Methode des tiefen Verstärkungslernens vor, bei der ein generatives Modell verwendet wird, um das Netzwerk zu initialisieren und so die Anzahl der Trainingsschritte zu reduzieren. In dieser Arbeit verwendeten wir die Deep-Q-Network-Methode als tiefes Verstärkungslernen und einen tiefen Auto-Encoder als generatives Modell. Wir führten Experimente zu drei verschiedenen Aufgaben durch: ein Cart-Pole-Spiel, ein Atari-Spiel und ein reales Spiel mit einem physischen Roboter. Die vorgeschlagene Methode wurde bei allen Aufgaben effizienter trainiert als die vorherige Methode, insbesondere war sie bei einer Aufgabe mit Bildern aus der realen Umgebung 2,5-mal schneller.
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de
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Multistage stochastic programs can be approximated by restricting policies to follow decision rules. Directly applying this idea to problems with integer decisions is difficult because of the need for decision rules that lead to integral decisions. In this work, we introduce Lagrangian dual decision rules (LDDRs) for multistage stochastic mixed integer programming (MSMIP) which overcome this difficulty by applying decision rules in a Lagrangian dual of the MSMIP. We propose two new bounding techniques based on stagewise (SW) and nonanticipative (NA) Lagrangian duals where the Lagrangian multiplier policies are restricted by LDDRs. We demonstrate how the solutions from these duals can be used to drive primal policies. Our proposal requires fewer assumptions than most existing MSMIP methods. We compare the theoretical strength of the restricted duals and show that the restricted NA dual can provide relaxation bounds at least as good as the ones obtained by the restricted SW dual. In our numerical study, we observe that the proposed LDDR approaches yield significant optimality gap reductions compared to existing general-purpose bounding methods for MSMIP problems.
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Многоэтапные стохастические программы могут быть аппроксимированы путем ограничения политик следованию правилам принятия решений. Прямое применение этой идеи к задачам с целочисленными решениями затруднительно из-за необходимости в правилах принятия решений, приводящих к целочисленным решениям. В данной работе мы вводим двойственные правила принятия решений по Лагранжу (LDDR) для многоэтапного стохастического смешанного целочисленного программирования (MSMIP), которые преодолевают эту трудность за счет применения правил принятия решений в лагранжевой двойственной задаче MSMIP. Мы предлагаем два новых метода построения оценок, основанных на поэтапной (SW) и непрерывной (NA) лагранжевой двойственности, где политики множителей Лагранжа ограничены с помощью LDDR. Мы демонстрируем, как решения из этих двойственных задач могут использоваться для построения прямых политик. Наш подход требует меньше предположений, чем большинство существующих методов MSMIP. Мы сравниваем теоретическую силу ограниченных двойственных задач и показываем, что ограниченная NA-двойственная задача может давать оценки релаксации, по крайней мере, не хуже, чем полученные с помощью ограниченной SW-двойственной задачи. В нашем численном исследовании мы наблюдаем, что предлагаемые подходы LDDR обеспечивают значительное сокращение зазоров оптимальности по сравнению с существующими общими методами построения оценок для задач MSMIP.
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ru
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In 1978, Schaefer proved his famous dichotomy theorem for generalized satisfiability problems. He defined an infinite number of propositional satisfiability problems, showed that all these problems are either in P or NP-complete, and gave a simple criterion to determine which of the two cases holds. This result is surprising in light of Ladner's theorem, which implies that there are an infinite number of complexity classes between P and NP-complete (under the assumption that P is not equal to NP). Schaefer also stated a dichotomy theorem for quantified generalized Boolean formulas, but this theorem was only recently proven by Creignou, Khanna, and Sudan, and independently by Dalmau: Determining truth of quantified Boolean formulas is either PSPACE-complete or in P. This paper looks at alternation-bounded quantified generalized Boolean formulas. In their unrestricted forms, these problems are the canonical problems complete for the levels of the polynomial hierarchy. In this paper, we prove dichotomy theorems for alternation-bounded quantified generalized Boolean formulas, by showing that these problems are either $\Sigma_i^p$-complete or in P, and we give a simple criterion to determine which of the two cases holds. This is the first result that obtains dichotomy for an infinite number of classes at once.
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En 1978, Schaefer a démontré son célèbre théorème de dichotomie pour les problèmes de satisfiabilité généralisés. Il a défini un nombre infini de problèmes de satisfiabilité propositionnelle, montré que tous ces problèmes sont soit dans P, soit NP-complets, et donné un critère simple permettant de déterminer dans quel cas on se trouve. Ce résultat est surprenant au vu du théorème de Ladner, qui implique qu'il existe une infinité de classes de complexité entre P et NP-complet (sous l'hypothèse que P n'est pas égal à NP). Schaefer a également énoncé un théorème de dichotomie pour les formules booléennes généralisées quantifiées, mais ce théorème n'a été démontré que récemment par Creignou, Khanna et Sudan, et indépendamment par Dalmau : la détermination de la vérité des formules booléennes quantifiées est soit PSPACE-complète, soit dans P. Cet article étudie les formules booléennes généralisées quantifiées à alternance bornée. Sous leur forme non restreinte, ces problèmes sont les problèmes canoniques complets pour les niveaux de la hiérarchie polynomiale. Dans cet article, nous démontrons des théorèmes de dichotomie pour les formules booléennes généralisées quantifiées à alternance bornée, en montrant que ces problèmes sont soit $\Sigma_i^p$-complets, soit dans P, et nous donnons un critère simple permettant de déterminer dans quel cas on se trouve. Il s'agit du premier résultat établissant une dichotomie pour une infinité de classes simultanément.
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fr
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Privacy has become a major concern in Online Social Networks (OSNs) due to threats such as advertising spam, online stalking and identity theft. Although many users hide or do not fill out their private attributes in OSNs, prior studies point out that the hidden attributes may be inferred from some other public information. Thus, users' private information could still be at stake to be exposed. Hitherto, little work helps users to assess the exposure probability/risk that the hidden attributes can be correctly predicted, let alone provides them with pointed countermeasures. In this article, we focus our study on the exposure risk assessment by a particular privacy-sensitive attribute - current city - in Facebook. Specifically, we first design a novel current city prediction approach that discloses users' hidden `current city' from their self-exposed information. Based on 371,913 Facebook users' data, we verify that our proposed prediction approach can predict users' current city more accurately than state-of-the-art approaches. Furthermore, we inspect the prediction results and model the current city exposure probability via some measurable characteristics of the self-exposed information. Finally, we construct an exposure estimator to assess the current city exposure risk for individual users, given their self-exposed information. Several case studies are presented to illustrate how to use our proposed estimator for privacy protection.
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Privasi telah menjadi satu kebimbangan utama dalam Rangkaian Sosial Dalam Talian (OSN) disebabkan oleh ancaman seperti spam pengiklanan, penguntitan dalam talian dan pencurian identiti. Walaupun ramai pengguna menyembunyikan atau tidak mengisi atribut peribadi mereka dalam OSN, kajian terdahulu menunjukkan bahawa atribut tersembunyi tersebut boleh disimpulkan daripada maklumat awam yang lain. Oleh itu, maklumat peribadi pengguna masih berisiko untuk didedahkan. Sehingga kini, hanya sedikit kajian yang membantu pengguna menilai kebarangkalian/risiko pendedahan atribut tersembunyi tersebut, apatah lagi memberikan langkah-langkah penangkisan yang spesifik. Dalam artikel ini, kami memfokuskan kajian kami kepada penilaian risiko pendedahan terhadap satu atribut yang sensitif dari segi privasi—iaitu bandar semasa—di Facebook. Secara khususnya, kami terlebih dahulu mereka bentuk satu pendekatan baharu untuk meramal bandar semasa yang mendedahkan bandar semasa pengguna yang tersembunyi berdasarkan maklumat yang mereka dedahkan sendiri. Berdasarkan data 371,913 pengguna Facebook, kami mengesahkan bahawa pendekatan ramalan yang dicadangkan ini dapat meramal bandar semasa pengguna dengan lebih tepat berbanding pendekatan terkini. Selanjutnya, kami menganalisis keputusan ramalan dan memodelkan kebarangkalian pendedahan bandar semasa melalui beberapa ciri yang boleh diukur daripada maklumat yang didedahkan sendiri. Akhirnya, kami membina satu penganggar pendedahan untuk menilai risiko pendedahan bandar semasa bagi setiap pengguna secara individu, berdasarkan maklumat yang mereka dedahkan sendiri. Beberapa kajian kes dibentangkan untuk menunjukkan bagaimana menggunakan penganggar yang dicadangkan ini bagi tujuan perlindungan privasi.
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ms
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In the present paper, we propose Krylov-based methods for solving large-scale differential Sylvester matrix equations having a low rank constant term. We present two new approaches for solving such differential matrix equations. The first approach is based on the integral expression of the exact solution and a Krylov method for the computation of the exponential of a matrix times a block of vectors. In the second approach, we first project the initial problem onto a block (or extended block) Krylov subspace and get a low-dimensional differential Sylvester matrix equation. The latter problem is then solved by some integration numerical methods such as BDF or Rosenbrock method and the obtained solution is used to build the low rank approximate solution of the original problem. We give some new theoretical results such as a simple expression of the residual norm and upper bounds for the norm of the error. Some numerical experiments are given in order to compare the two approaches.
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In der vorliegenden Arbeit schlagen wir Krylov-basierte Verfahren zur Lösung von großskaligen differentiellen Sylvester-Matrixgleichungen mit einem konstanten Term von niedrigem Rang vor. Wir stellen zwei neue Ansätze zur Lösung solcher differentieller Matrixgleichungen vor. Der erste Ansatz basiert auf der Integraldarstellung der exakten Lösung und einem Krylov-Verfahren zur Berechnung des Exponentials einer Matrix multipliziert mit einem Block von Vektoren. Bei dem zweiten Ansatz projizieren wir zunächst das ursprüngliche Problem auf einen Block- (oder erweiterten Block-) Krylov-Unterraum und erhalten so eine differentialgleichung mit niedriger Dimension vom Sylvester-Typ. Letzteres Problem wird dann mit numerischen Integrationsverfahren wie BDF oder dem Rosenbrock-Verfahren gelöst, und die erhaltene Lösung wird verwendet, um die Näherungslösung mit niedrigem Rang für das ursprüngliche Problem aufzubauen. Wir geben einige neue theoretische Ergebnisse an, wie etwa einen einfachen Ausdruck für die Norm des Residuums sowie obere Schranken für die Norm des Fehlers. Um die beiden Ansätze miteinander zu vergleichen, werden einige numerische Experimente durchgeführt.
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de
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The oversampling multiscale finite element method (MsFEM) is one of the most popular methods for simulating composite materials and flows in porous media which may have many scales. But the method may be inapplicable or inefficient in some portions of the computational domain, e.g., near the domain boundary or near long narrow channels inside the domain due to the lack of permeability information outside of the domain or the fact that the high-conductivity features cannot be localized within a coarse-grid block. In this paper we develop a combined finite element and multiscale finite element method (FE-MsFEM), which deals with such portions by using the standard finite element method on a fine mesh and the other portions by the oversampling MsFEM. The transmission conditions across the FE-MSFE interface is treated by the penalty technique. A rigorous convergence analysis for this special FE-MsFEM is given under the assumption that the diffusion coefficient is periodic. Numerical experiments are carried out for the elliptic equations with periodic and random highly oscillating coefficients, as well as multiscale problems with high contrast channels, to demonstrate the accuracy and efficiency of the proposed method.
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Метод многомасштабных конечных элементов с апсемплированием (MsFEM) является одним из наиболее популярных методов моделирования композиционных материалов и течений в пористых средах, которые могут содержать множество масштабов. Однако данный метод может оказаться неприменимым или неэффективным в некоторых частях расчётной области, например, вблизи границы области или вблизи узких протяжённых каналов внутри области из-за отсутствия информации о проницаемости за пределами области или из-за того, что высокопроводящие особенности невозможно локализовать в пределах одного блока крупной сетки. В данной работе разработан комбинированный метод конечных элементов и многомасштабных конечных элементов (FE-MsFEM), в котором такие участки обрабатываются с помощью стандартного метода конечных элементов на мелкой сетке, а остальные участки — с помощью MsFEM с апсемплированием. Условия передачи на границе между FE и MsFE обрабатываются с использованием метода штрафа. Под строгим предположением о периодичности коэффициента диффузии дан анализ сходимости для этого специального FE-MsFEM. Проведены численные эксперименты для эллиптических уравнений с периодическими и случайными сильно осциллирующими коэффициентами, а также для многомасштабных задач с каналами высокой контрастности, подтверждающие точность и эффективность предложенного метода.
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ru
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The Fredholm determinants of a special class of integral operators K supported on the union of m curve segments in the complex plane are shown to be the tau-functions of an isomonodromic family of meromorphic covariant derivative operators D_l. These have regular singular points at the 2m endpoints of the curve segments and a singular point of Poincare index 1 at infinity. The rank r of the vector bundle over the Riemann sphere on which they act equals the number of distinct terms in the exponential sums entering in the numerator of the integral kernels. The deformation equations may be viewed as nonautonomous Hamiltonian systems on an auxiliary symplectic vector space M, whose Poisson quotient, under a parametric family of Hamiltonian group actions, is identified with a Poisson submanifold of the loop algebra Lgl_R(r) with respect to the rational R-matrix structure. The matrix Riemann-Hilbert problem method is used to identify the auxiliary space M with the data defining the integral kernel of the resolvent operator at the endpoints of the curve segments. A second associated isomonodromic family of covariant derivative operators D_z is derived, having rank n=2m, and r finite regular singular points at the values of the exponents defining the kernel of K. This family is similarly embedded into the algebra Lgl_R(n) through a dual parametric family of Poisson quotients of M. The operators D_z are shown to be analogously associated to the integral operator obtained from K through a Fourier-Laplace transform.
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Se demuestra que los determinantes de Fredholm de una clase especial de operadores integrales K, soportados en la unión de m segmentos de curva en el plano complejo, son funciones tau de una familia isomonodrómica de operadores meromorfos de derivación covariante D_l. Estos poseen puntos singulares regulares en los 2m extremos de los segmentos de curva y un punto singular de índice de Poincaré 1 en el infinito. El rango r del fibrado vectorial sobre la esfera de Riemann sobre el que actúan coincide con el número de términos distintos en las sumas exponenciales que aparecen en el numerador de los núcleos integrales. Las ecuaciones de deformación pueden verse como sistemas hamiltonianos no autónomos sobre un espacio vectorial simpléctico auxiliar M, cuyo cociente de Poisson, bajo una familia paramétrica de acciones hamiltonianas de grupo, se identifica con una subvariedad de Poisson del álgebra de bucles Lgl_R(r) respecto a la estructura racional de matriz R. Se utiliza el método del problema matricial de Riemann-Hilbert para identificar el espacio auxiliar M con los datos que definen el núcleo integral del operador resolvente en los extremos de los segmentos de curva. Se deriva una segunda familia isomonodrómica asociada de operadores de derivación covariante D_z, de rango n=2m y r puntos singulares regulares finitos en los valores de los exponentes que definen el núcleo de K. Esta familia se incrusta de manera análoga en el álgebra Lgl_R(n) mediante una familia paramétrica dual de cocientes de Poisson de M. Se demuestra que los operadores D_z están análogamente asociados al operador integral obtenido a partir de K mediante una transformada de Fourier-Laplace.
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es
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Robots which interact with the physical world will benefit from a fine-grained tactile understanding of objects and surfaces. Additionally, for certain tasks, robots may need to know the haptic properties of an object before touching it. To enable better tactile understanding for robots, we propose a method of classifying surfaces with haptic adjectives (e.g., compressible or smooth) from both visual and physical interaction data. Humans typically combine visual predictions and feedback from physical interactions to accurately predict haptic properties and interact with the world. Inspired by this cognitive pattern, we propose and explore a purely visual haptic prediction model. Purely visual models enable a robot to "feel" without physical interaction. Furthermore, we demonstrate that using both visual and physical interaction signals together yields more accurate haptic classification. Our models take advantage of recent advances in deep neural networks by employing a unified approach to learning features for physical interaction and visual observations. Even though we employ little domain specific knowledge, our model still achieves better results than methods based on hand-designed features.
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Các robot tương tác với thế giới vật lý sẽ được hưởng lợi từ việc hiểu biết chi tiết về cảm giác xúc giác đối với các vật thể và bề mặt. Ngoài ra, đối với một số nhiệm vụ nhất định, robot có thể cần biết các thuộc tính xúc giác của một vật thể trước khi chạm vào nó. Để nâng cao khả năng hiểu biết xúc giác cho robot, chúng tôi đề xuất một phương pháp phân loại các bề mặt theo các tính từ mô tả xúc giác (ví dụ: mềm nén được hoặc nhẵn) dựa trên cả dữ liệu hình ảnh và dữ liệu từ tương tác vật lý. Con người thường kết hợp dự đoán hình ảnh với phản hồi từ các tương tác vật lý để dự đoán chính xác các thuộc tính xúc giác và tương tác với thế giới. Lấy cảm hứng từ mô hình nhận thức này, chúng tôi đề xuất và nghiên cứu một mô hình dự đoán xúc giác hoàn toàn dựa trên thị giác. Các mô hình hoàn toàn dựa trên thị giác cho phép robot "cảm nhận" mà không cần tương tác vật lý. Hơn nữa, chúng tôi chứng minh rằng việc sử dụng đồng thời các tín hiệu thị giác và tương tác vật lý sẽ mang lại kết quả phân loại xúc giác chính xác hơn. Các mô hình của chúng tôi tận dụng những tiến bộ gần đây trong mạng nơ-ron sâu bằng cách áp dụng một phương pháp thống nhất để học các đặc trưng từ cả tương tác vật lý và quan sát hình ảnh. Mặc dù sử dụng rất ít kiến thức chuyên biệt về lĩnh vực cụ thể, mô hình của chúng tôi vẫn đạt được kết quả tốt hơn so với các phương pháp dựa trên các đặc trưng được thiết kế thủ công.
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vi
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There has never been a more exciting time in the overlapping areas of nuclear physics, particle physics and relativistic astrophysics than today. Orbiting observatories such as the Hubble Space Telescope, Rossi X-ray Timing Explorer (RXTE), Chandra X-ray satellite, and the X-ray Multi Mirror Mission (XMM) have extended our vision tremendously, allowing us to see vistas with an unprecedented clarity and angular resolution that previously were only imagined, enabling astrophysicists for the first time ever to perform detailed studies of large samples of galactic and extragalactic objects. On the Earth, radio telescopes (e.g., Arecibo, Green Bank, Parkes, VLA) and instruments using adaptive optics and other revolutionary techniques have exceeded previous expectations of what can be accomplished from the ground. The gravitational wave detectors LIGO, LISA VIRGO, and Geo-600 are opening up a window for the detection of gravitational waves emitted from compact stellar objects such as neutron stars and black holes. Together with new experimental forefront facilities like ISAC, ORLaND and RIA, these detectors provide direct, quantitative physical insight into nucleosynthesis, supernova dynamics, accreting compact objects, cosmic-ray acceleration, and pair-production in high energy sources which reinforce the urgent need for a strong and continuous feedback from nuclear and particle theory and theoretical astrophysics. In my lectures, I shall concentrate on three selected topics, which range from the behavior of superdense stellar matter, to general relativistic stellar models, to strange quark stars and possible signals of quark matter in neutron stars.
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Nunca ha habido un momento más emocionante en las áreas superpuestas de la física nuclear, la física de partículas y la astrofísica relativista que el actual. Observatorios en órbita como el Telescopio Espacial Hubble, el Explorador de Rayos X de Tiempo-Rápido Rossi (RXTE), el satélite de rayos X Chandra y la Misión de Múltiples Espejos de Rayos X (XMM) han ampliado enormemente nuestra visión, permitiéndonos observar panoramas con una claridad y resolución angular sin precedentes que anteriormente solo se habían imaginado, posibilitando que los astrofísicos realicen por primera vez estudios detallados de grandes muestras de objetos galácticos y extragalácticos. En la Tierra, radiotelescopios (por ejemplo, Arecibo, Green Bank, Parkes, VLA) e instrumentos que utilizan óptica adaptativa y otras técnicas revolucionarias han superado las expectativas anteriores sobre lo que se puede lograr desde el suelo. Los detectores de ondas gravitacionales LIGO, LISA, VIRGO y Geo-600 están abriendo una ventana para la detección de ondas gravitacionales emitidas por objetos estelares compactos como estrellas de neutrones y agujeros negros. Junto con nuevas instalaciones experimentales de vanguardia como ISAC, ORLaND y RIA, estos detectores proporcionan una visión física directa y cuantitativa sobre la nucleosíntesis, la dinámica de supernovas, objetos compactos con acreción, la aceleración de rayos cósmicos y la producción de pares en fuentes de alta energía, lo cual refuerza la necesidad urgente de una retroalimentación constante y sólida por parte de la teoría nuclear y de partículas y de la astrofísica teórica. En mis conferencias, me concentraré en tres temas seleccionados, que van desde el comportamiento de la materia estelar superdensa, hasta modelos estelares en relatividad general, pasando por estrellas extrañas de quarks y posibles señales de materia de quarks en estrellas de neutrones.
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es
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We present optical photopolarimetric observations of the BL Lac object S4 0954+658 obtained with the 70-cm telescope in Crimea, 40-cm telescope in St.Petersburg, and 1.8-m Perkins telescope at Lowell Observatory (Flagstaff, Az). After a faint state with a brightness level R ~17.6 mag registered in the first half of January 2011, the optical brightness of the source started to rise and reached ~14.8 mag during the middle of March, showing flare-like behavior. The most spectacular case of intranight variability was observed during the night of 2011 March 9, when the blazar brightened by ~0.7 mag within ~7 hours. During the rise of the flux the position angle of optical polarization rotated smoothly over more than 200 degrees. S4 0954+658 is a gamma-ray blazar with gamma-ray flux of (5{\pm}3)x10^{-10} phot/cm^2/s according to the Fermi 11-month Catalog Extragalactic Sources. Our analysis of contemporaneous Fermi LAT data does not show any sign of increased gamma-ray activity above the detection threshold except for an elevated flux on 2011 March 5, JD2455626, coincident with the local optical maximum.
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Presentamos observaciones fotopolarimétricas ópticas del objeto BL Lac S4 0954+658 obtenidas con el telescopio de 70 cm en Crimea, el telescopio de 40 cm en San Petersburgo y el telescopio Perkins de 1,8 m en el Observatorio Lowell (Flagstaff, AZ). Tras un estado tenue con un nivel de brillo R ~17,6 mag registrado en la primera mitad de enero de 2011, el brillo óptico de la fuente comenzó a aumentar y alcanzó ~14,8 mag a mediados de marzo, mostrando un comportamiento tipo erupción. El caso más espectacular de variabilidad intranocturna se observó durante la noche del 9 de marzo de 2011, cuando el blazar aumentó su brillo en ~0,7 mag en aproximadamente 7 horas. Durante el incremento del flujo, el ángulo de posición de la polarización óptica rotó suavemente más de 200 grados. S4 0954+658 es un blazar de rayos gamma con un flujo de rayos gamma de (5±3)x10^{-10} fot/cm^2/s según el Catálogo de Fuentes Extragalácticas de 11 meses de Fermi. Nuestro análisis de datos simultáneos del LAT de Fermi no muestra ninguna señal de actividad aumentada en rayos gamma por encima del umbral de detección, excepto por un flujo elevado el 5 de marzo de 2011, JD2455626, coincidente con el máximo óptico local.
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es
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Within the framework of classical field theory, the connection between the Dirac field as the field of matter and the spacetime metric is discussed. Polarization structure of the Dirac field is shown to be rich enough to determine the spacetime metric locally and to explain the emergence of observed matter as localized waveforms. The localization of the waveforms is explained as the result of the local time slowdown and the Lorentz contraction as a dynamic re-shaping of the waveforms in the course of their acceleration. A definition of mass as a limiting curvature of the spinor-induced metric is proposed. A view of the vacuum as a uniformly distributed unit invariant density of the Dirac field with an explicitly preserved invariance of the light cone is brought forward. Qualitative explanation of the observed charge asymmetry as the consequence of the dynamics of localization is given. The classical pion field is obtained as a manifestation of stresses, mass and charge flux in localized waveforms of the Dirac field. Some implications of the finite size of colliding objects for high-energy processes are discussed. A hypothesis that known internal degrees of freedom are the local spacetime (angular) coordinates that have no precise counterparts in Riemannian geometry is proposed.
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No âmbito da teoria clássica de campos, discute-se a conexão entre o campo de Dirac, enquanto campo da matéria, e a métrica do espaço-tempo. Mostra-se que a estrutura de polarização do campo de Dirac é suficientemente rica para determinar localmente a métrica do espaço-tempo e explicar o surgimento da matéria observada como formas de onda localizadas. A localização das formas de onda é explicada como resultado da desaceleração local do tempo e da contração de Lorentz como uma reconfiguração dinâmica das formas de onda durante sua aceleração. Propõe-se uma definição de massa como curvatura limite da métrica induzida pelo espinor. Apresenta-se uma visão do vácuo como uma densidade invariante unitária uniformemente distribuída do campo de Dirac, com invariância do cone de luz explicitamente preservada. Oferece-se uma explicação qualitativa da assimetria de carga observada como consequência da dinâmica da localização. O campo clássico do píon é obtido como manifestação das tensões, bem como do fluxo de massa e carga em formas de onda localizadas do campo de Dirac. Discutem-se algumas implicações do tamanho finito de objetos colidentes para processos de alta energia. Propõe-se a hipótese de que os graus de liberdade internos conhecidos são coordenadas locais do espaço-tempo (angulares) que não possuem contrapartes precisas na geometria riemanniana.
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pt
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A new kind of quantum indeterminacy of transverse position is shown to arise from quantum degrees of freedom of spacetime, based on the assumption that classical trajectories can be defined no better than the diffraction limit of Planck scale waves. Indeterminacy of the angular orientation of particle trajectories due to wave/particle duality at the Planck scale leads to indeterminacy of a nearly-flat spacetime metric, described as a small nonvanishing quantum commutation relation between transverse position operators at different events along a null trajectory. An independent derivation of the same effect is presented based on the requirement of unitarity in black hole evaporation. The indeterminacy is interpreted as a universal holographic quantum spacetime noise, with a frequency-independent spectrum of metric perturbation amplitude, h_H^2^{1/2} \simeq \sqrt{l_P}=2.3 \times 10^{-22} /\sqrt{Hz}, where l_P denotes the Planck length. The effect is estimated to be directly measurable using current interferometer technology similar to LIGO and LISA.
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Jenis baru ketidakpastian kuantum dari posisi transversal ditunjukkan muncul dari derajat kebebasan kuantum ruangwaktu, berdasarkan asumsi bahwa lintasan klasik tidak dapat didefinisikan lebih baik daripada batas difraksi gelombang skala Planck. Ketidakpastian orientasi sudut lintasan partikel akibat dualitas gelombang/partikel pada skala Planck menghasilkan ketidakpastian metrik ruangwaktu yang hampir datar, yang digambarkan sebagai relasi komutasi kuantum kecil yang tidak nol antara operator posisi transversal pada peristiwa-peristiwa berbeda sepanjang lintasan nol. Suatu penurunan independen dari efek yang sama disajikan berdasarkan syarat unitaritas dalam penguapan lubang hitam. Ketidakpastian tersebut ditafsirkan sebagai gangguan kuantum ruangwaktu holografik universal, dengan spektrum amplitudo gangguan metrik yang bebas frekuensi, h_H^2^{1/2} \simeq \sqrt{l_P}=2,3 \times 10^{-22} /\sqrt{Hz}, di mana l_P menyatakan panjang Planck. Diperkirakan efek ini dapat diukur secara langsung menggunakan teknologi interferometer saat ini yang mirip dengan LIGO dan LISA.
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id
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Within the framework of classical field theory, the connection between the Dirac field as the field of matter and the spacetime metric is discussed. Polarization structure of the Dirac field is shown to be rich enough to determine the spacetime metric locally and to explain the emergence of observed matter as localized waveforms. The localization of the waveforms is explained as the result of the local time slowdown and the Lorentz contraction as a dynamic re-shaping of the waveforms in the course of their acceleration. A definition of mass as a limiting curvature of the spinor-induced metric is proposed. A view of the vacuum as a uniformly distributed unit invariant density of the Dirac field with an explicitly preserved invariance of the light cone is brought forward. Qualitative explanation of the observed charge asymmetry as the consequence of the dynamics of localization is given. The classical pion field is obtained as a manifestation of stresses, mass and charge flux in localized waveforms of the Dirac field. Some implications of the finite size of colliding objects for high-energy processes are discussed. A hypothesis that known internal degrees of freedom are the local spacetime (angular) coordinates that have no precise counterparts in Riemannian geometry is proposed.
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Sa loob ng balangkas ng klasikong teorya ng field, tinalakay ang ugnayan sa pagitan ng Dirac field bilang field ng materia at ng spacetime metric. Ipinakita na sapat na mayaman ang estruktura ng polarisasyon ng Dirac field upang matukoy nang lokal ang spacetime metric at upang ipaliwanag ang paglitaw ng obserbadong materia bilang lokal na mga hugis-bagyo. Ang lokal na pagbagal ng oras at ang Lorentz contraction ay ipinaliwanag bilang resulta ng dinamikong pagbabago ng hugis ng mga bagyo habang ito ay pinapabilis. Iminungkahi ang kahulugan ng masa bilang limitadong kurba ng spinor-induced metric. Ipinanukala ang ideya ng bakuum bilang isang unipormeng ipinamahaging yunit na hindi nagbabagong densidad ng Dirac field na may malinaw na pagpapanatili sa invariance ng light cone. Ibinigay ang kwalitatibong paliwanag sa obserbadong charge asymmetry bilang kahihinatnan ng dinamika ng lokalidad. Ang klasikong pion field ay natamo bilang pagpapahayag ng mga stress, masa, at daloy ng singa sa lokal na mga hugis-bagyo ng Dirac field. Tinalakay ang ilang mga implikasyon ng hangganan ng sukat ng mga nagbangganan na bagay sa mga prosesong may mataas na enerhiya. Iminungkahi ang hipotesis na ang kilalang mga antas ng panloob na kalayaan ay mga lokal na spacetime (angular) na koordinado na walang tiyak na katumbas sa Riemannian geometry.
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tl
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We describe the construction of a database of extremely metal-poor (EMP) stars in the Galactic halo whose elemental abundances have been determined. Our database contains detailed elemental abundances, reported equivalent widths, atmospheric parameters, photometry, and binarity status, compiled from papers in the recent literature that report studies of EMP halo stars with [Fe/H] < -2.5. The compilation procedures for this database have been designed to assemble the data effectively from electronic tables available from online journals. We have also developed a data retrieval system that enables data searches by various criteria, and permits the user to explore relationships between the stored variables graphically. Currently, our sample includes 1212 unique stars (many of which are studied by more than one group) with more than 15000 individual reported elemental abundances, covering all of the relevant papers published by December 2007. We discuss the global characteristics of the present database, as revealed by the EMP stars observed to date. For stars with [Fe/H] < -2.5, the number of giants with reported abundances is larger than that of dwarfs by a factor of two. The fraction of carbon-rich stars (among the sample for which the carbon abundance is reported) amount to ~30 % for [Fe/H] < -2.5. We find that known binaries exhibit different distributions of orbital period, according to whether they are giants or dwarfs, and also as a function of metallicity, although the total sample of such stars is still quite small.
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은하 헤일로 내에서 원소 조성이 측정된 극도로 금속 농도가 낮은(EMP) 별들의 데이터베이스를 구축한 과정을 설명한다. 본 데이터베이스는 [Fe/H] < -2.5인 EMP 헤일로 별들을 연구한 최근 문헌의 논문들로부터 취합한 상세한 원소 조성, 보고된 동등폭, 대기 파라미터, 광도 측정값, 그리고 이중성 여부를 포함한다. 이 데이터베이스의 취합 절차는 온라인 저널에서 제공하는 전자 테이블 형태의 자료를 효율적으로 수집할 수 있도록 설계되었다. 또한 다양한 기준에 따라 자료를 검색할 수 있고 저장된 변수들 간의 관계를 그래픽적으로 탐색할 수 있는 자료 검색 시스템도 개발하였다. 현재 본 표본에는 2007년 12월까지 출간된 관련 논문들에 포함된 1,212개의 고유한 별들(많은 경우 여러 연구팀에 의해 중복 연구됨)이 포함되어 있으며, 15,000건이 넘는 개별 원소 조성 값이 수록되어 있다. 본 연구에서는 지금까지 관측된 EMP 별들을 통해 드러난 현재 데이터베이스의 전반적인 특성들을 논의한다. [Fe/H] < -2.5인 별들에 대해서는 조사된 왜성보다 거성의 수가 두 배 이상 많다. 탄소 풍부한 별의 비율은(탄소 조성이 보고된 표본 내에서) [Fe/H] < -2.5 구간에서 약 30%에 달한다. 또한 알려진 이중성 별들이 거성과 왜성에 따라, 그리고 금속량에 따라 서로 다른 궤도 주기 분포를 보임을 발견하였으나, 이러한 별들의 전체 표본 수는 여전히 매우 적다.
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ko
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We present optical photopolarimetric observations of the BL Lac object S4 0954+658 obtained with the 70-cm telescope in Crimea, 40-cm telescope in St.Petersburg, and 1.8-m Perkins telescope at Lowell Observatory (Flagstaff, Az). After a faint state with a brightness level R ~17.6 mag registered in the first half of January 2011, the optical brightness of the source started to rise and reached ~14.8 mag during the middle of March, showing flare-like behavior. The most spectacular case of intranight variability was observed during the night of 2011 March 9, when the blazar brightened by ~0.7 mag within ~7 hours. During the rise of the flux the position angle of optical polarization rotated smoothly over more than 200 degrees. S4 0954+658 is a gamma-ray blazar with gamma-ray flux of (5{\pm}3)x10^{-10} phot/cm^2/s according to the Fermi 11-month Catalog Extragalactic Sources. Our analysis of contemporaneous Fermi LAT data does not show any sign of increased gamma-ray activity above the detection threshold except for an elevated flux on 2011 March 5, JD2455626, coincident with the local optical maximum.
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Apresentamos observações fotopolarimétricas ópticas do objeto BL Lac S4 0954+658 obtidas com o telescópio de 70 cm na Criméia, o telescópio de 40 cm em São Petersburgo e o telescópio Perkins de 1,8 m no Observatório Lowell (Flagstaff, AZ). Após um estado fraco com nível de brilho R ~17,6 mag registrado na primeira metade de janeiro de 2011, o brilho óptico da fonte começou a aumentar e atingiu ~14,8 mag por volta de meados de março, exibindo comportamento semelhante a uma explosão. O caso mais impressionante de variabilidade intra-noturna foi observado na noite de 9 de março de 2011, quando o blazar aumentou seu brilho em ~0,7 mag em cerca de 7 horas. Durante o aumento do fluxo, o ângulo de posição da polarização óptica girou suavemente por mais de 200 graus. S4 0954+658 é um blazar de raios gama com fluxo de raios gama de (5±3)x10^{-10} fot/cm^2/s de acordo com o Catálogo de Fontes Extragalácticas de 11 meses do Fermi. Nossa análise de dados simultâneos do LAT do Fermi não mostra nenhum sinal de atividade aumentada em raios gama acima do limite de detecção, exceto por um fluxo elevado em 5 de março de 2011, JD2455626, coincidente com o máximo óptico local.
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pt
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Multisensory object-centric perception, reasoning, and interaction have been a key research topic in recent years. However, the progress in these directions is limited by the small set of objects available -- synthetic objects are not realistic enough and are mostly centered around geometry, while real object datasets such as YCB are often practically challenging and unstable to acquire due to international shipping, inventory, and financial cost. We present ObjectFolder, a dataset of 100 virtualized objects that addresses both challenges with two key innovations. First, ObjectFolder encodes the visual, auditory, and tactile sensory data for all objects, enabling a number of multisensory object recognition tasks, beyond existing datasets that focus purely on object geometry. Second, ObjectFolder employs a uniform, object-centric, and implicit representation for each object's visual textures, acoustic simulations, and tactile readings, making the dataset flexible to use and easy to share. We demonstrate the usefulness of our dataset as a testbed for multisensory perception and control by evaluating it on a variety of benchmark tasks, including instance recognition, cross-sensory retrieval, 3D reconstruction, and robotic grasping.
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Çok duyulu nesne merkezli algılama, akıl yürütme ve etkileşim son yıllarda önemli bir araştırma konusu olmuştur. Ancak bu alanlardaki ilerleme mevcut nesne sayısının az olmasıyla sınırlıdır—sentetik nesneler yeterince gerçekçi değildir ve çoğunlukla geometriye odaklanır, gerçek nesne veri kümeleri ise YCB gibi uluslararası kargo, envanter ve maliyet nedeniyle pratikte elde etmesi zor ve kararsızdır. Bu iki zorluğun üstesinden gelen iki temel yenilikle ObjectFolder adlı 100 sanallaştırılmış nesneden oluşan bir veri kümesi sunuyoruz. Birincisi, ObjectFolder tüm nesneler için görsel, işitsel ve dokunsal duyusal verileri kodlayarak sadece nesne geometrisine odaklanan mevcut veri kümelerinin ötesinde, çok duyulu nesne tanıma görevlerinin bir dizi için olanak sağlar. İkincisi, ObjectFolder her bir nesnenin görsel dokuları, akustik simülasyonları ve dokunsal ölçümleri için birim, nesne merkezli ve örtük bir temsil kullanır ve böylece veri kümesinin kullanımı esnek ve paylaşımı kolay hale gelir. Nesne tanıma, çapraz duyusal geri çağırma, 3B yeniden yapılandırma ve robotik kavrama da dahil olmak üzere çeşitli kıyaslama görevlerinde değerlendirmeler yaparak veri kümemizin çok duyulu algılama ve kontrol için bir deneme ortamı olarak faydalılığını gösteriyoruz.
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tr
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We present a unified picture of outflowing gas from the X-ray binary system Hercules X-1/HZ Herculis. We suggest that the outflowing gas (a wind) causes UV emission seen in mid-eclipse, narrow UV absorption lines, and broad UV P Cygni lines. Observations with the FOS and STIS spectrographs on the Hubble Space Telescope (HST) show UV emission lines in the middle of X-ray eclipse, when the X-ray heated atmosphere of the normal star and accretion disk should be entirely hidden from view. Narrow absorption lines (FWHM~50 km/s) blueshifted by 500 km/s during observations in 1998 and by 400 km/s during observations in 1999 were seen from phi=0.0-0.3. The line velocity was constant to within 20 km/s. The P Cygni profiles from Hercules~X-1 have optical depths tau<1 with a maximum expansion velocity of 600 km/s, and are seen in the resonance lines N V 1238.8,1242.8, Si IV 1393.7,1402.8, and C IV 1548.2, 1550.8. We discuss whether this wind originates in the accretion disk or on the companion star, and how the relevant ions can survive X-ray ionization by the neutron star.
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Presentiamo un quadro unificato del gas in fuoriuscita dal sistema binario a raggi X Hercules X-1/HZ Herculis. Proponiamo che il gas in fuoriuscita (un vento) sia responsabile dell'emissione ultravioletta (UV) osservata a metà eclissi, delle righe di assorbimento UV strette e delle righe ampie di tipo P Cygni nell'ultravioletto. Osservazioni effettuate con gli spettrografi FOS e STIS a bordo del Telescopio Spaziale Hubble (HST) mostrano righe di emissione UV nel mezzo dell'eclissi a raggi X, quando l'atmosfera riscaldata dai raggi X della stella normale e del disco di accrescimento dovrebbe essere completamente nascosta alla vista. Righe di assorbimento strette (FWHM~50 km/s), spostate verso il blu di 500 km/s durante osservazioni nel 1998 e di 400 km/s durante osservazioni nel 1999, sono state osservate nell'intervallo di fase phi=0,0-0,3. La velocità delle righe è rimasta costante entro 20 km/s. I profili di tipo P Cygni di Hercules~X-1 presentano profondità ottiche tau<1 con una velocità massima di espansione di 600 km/s, e sono osservati nelle righe di risonanza N V 1238,8,1242,8, Si IV 1393,7,1402,8 e C IV 1548,2, 1550,8. Discutiamo se questo vento abbia origine nel disco di accrescimento o sulla stella compagna, e come gli ioni coinvolti possano sopravvivere all'ionizzazione da raggi X proveniente dalla stella di neutroni.
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it
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We propose Otiy, a node-centric location service that limits the impact of location updates generate by mobile nodes in IEEE802.11-based wireless mesh networks. Existing location services use node identifiers to determine the locator (aka anchor) that is responsible for keeping track of a node's location. Such a strategy can be inefficient because: (i) identifiers give no clue on the node's mobility and (ii) locators can be far from the source/destination shortest path, which increases both location delays and bandwidth consumption. To solve these issues, Otiy introduces a new strategy that identifies nodes to play the role of locators based on the likelihood of a destination to be close to these nodes- i.e., locators are identified depending on the mobility pattern of nodes. Otiy relies on the cyclic mobility patterns of nodes and creates a slotted agenda composed of a set of predicted locations, defined according to the past and present patterns of mobility. Correspondent nodes fetch this agenda only once and use it as a reference for identifying which locators are responsible for the node at different points in time. Over a period of about one year, the weekly proportion of nodes having at least 50% of exact location predictions is in average about 75%. This proportion increases by 10% when nodes also consider their closeness to the locator from only what they know about the network.
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Nous proposons Otiy, un service de localisation centré sur les nœuds qui limite l'impact des mises à jour de localisation générées par les nœuds mobiles dans les réseaux maillés sans fil basés sur IEEE802.11. Les services de localisation existants utilisent les identifiants des nœuds pour déterminer le localisateur (appelé aussi ancre) chargé de suivre la position d'un nœud. Une telle stratégie peut être inefficace car : (i) les identifiants ne donnent aucune indication sur la mobilité du nœud et (ii) les localisateurs peuvent se trouver éloignés du chemin le plus court entre la source et la destination, ce qui augmente à la fois les délais de localisation et la consommation de bande passante. Pour résoudre ces problèmes, Otiy introduit une nouvelle stratégie qui identifie les nœuds devant jouer le rôle de localisateurs en fonction de la probabilité qu'une destination se trouve proche de ces nœuds, c'est-à-dire que les localisateurs sont choisis selon le modèle de mobilité des nœuds. Otiy s'appuie sur les motifs cycliques de mobilité des nœuds et crée un agenda fractionné en créneaux, composé d'un ensemble de localisations prédites, définies selon les motifs passés et présents de mobilité. Les nœuds correspondants récupèrent cet agenda une seule fois et l'utilisent comme référence pour identifier quels localisateurs sont responsables du nœud à différents moments. Sur une période d'environ un an, la proportion hebdomadaire de nœuds ayant au moins 50 % de prédictions exactes de localisation est en moyenne d'environ 75 %. Cette proportion augmente de 10 % lorsque les nœuds prennent également en compte leur proximité avec le localisateur, uniquement à partir des informations qu'ils possèdent sur le réseau.
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fr
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The evolution of a walker in standard "Discrete-time Quantum Walk (DTQW)" is determined by coin and shift unitary operators. The conditional shift operator shifts the position of the walker to right or left by unit step size while the direction of motion is specified by the coin operator. This scenario can be generalized by choosing the step size randomly at each step in some specific interval. For example, the value of the roll of a dice can be used to specify the step size after throwing the coin. Let us call such a quantum walk "Discrete-time Random Step Quantum Walk (DTRSQW)". A completely random probability distribution is obtained whenever the walker follows the DTRSQW. We have also analyzed two more types of quantum walks, the "Discrete-time Un-biased Quantum Walk (DTUBQW)" and the "Discrete-time Biased Quantum Walk (DTBQW)". In the first type, the step size is kept different than unit size but the same for left and right shifts, whereas in the second type left and right shifts can also be different. The probability distribution in DTUBQW is found to follow a certain rule. The standard deviation ($\sigma$) of DTRSQW is higher than DTQW and hence DTRSQW spreads faster. The $\sigma$ of DTUBQW shows sawtooth behavior with faster spread than DTQW for some specific values of rotation angles and steps.
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Ang pagbabago ng isang tagalakad sa karaniwang "Discrete-time Quantum Walk (DTQW)" ay tinutukoy ng mga unitary na operador na barya at paglipat. Ang kondisyonal na operador ng paglipat ay naglilipat ng posisyon ng tagalakad pakanan o pakaliwa ng isang yunit na sukat ng hakbang, kung saan ang direksyon ng paggalaw ay tinutukoy ng operador ng barya. Maaaring palawigin ang senaryong ito sa pamamagitan ng pagpili ng sukat ng hakbang nang buong pagkakataon sa bawat hakbang sa loob ng isang tiyak na saklaw. Halimbawa, maaaring gamitin ang resulta ng paghagis ng isang dice upang tukuyin ang sukat ng hakbang pagkatapos ihagis ang barya. Tawagin natin ang ganitong uri ng quantum walk na "Discrete-time Random Step Quantum Walk (DTRSQW)". Isang ganap na random na distribusyon ng probabilidad ang nakukuha tuwing sinusundan ng tagalakad ang DTRSQW. Sinuri rin namin ang dalawa pang uri ng quantum walk, ang "Discrete-time Un-biased Quantum Walk (DTUBQW)" at ang "Discrete-time Biased Quantum Walk (DTBQW)". Sa unang uri, ang sukat ng hakbang ay pinapanatiling hindi katumbas ng yunit na sukat ngunit pareho para sa kaliwa at kanang paglipat, samantalang sa ikalawang uri, ang kaliwa at kanang paglipat ay maaari ring magkaiba. Natuklasan na ang distribusyon ng probabilidad sa DTUBQW ay sumusunod sa isang tiyak na tuntunin. Ang standard deviation ($\sigma$) ng DTRSQW ay mas mataas kaysa DTQW at kaya't mas mabilis kumalat ang DTRSQW. Ang $\sigma$ ng DTUBQW ay nagpapakita ng sawtooth na pag-uugali na may mas mabilis na pagkalat kaysa DTQW para sa ilang tiyak na halaga ng mga anggulo ng pag-ikot at mga hakbang.
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tl
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The generalized belief propagation (GBP), introduced by Yedidia et al., is an extension of the belief propagation (BP) algorithm, which is widely used in different problems involved in calculating exact or approximate marginals of probability distributions. In many problems, it has been observed that the accuracy of GBP considerably outperforms that of BP. However, because in general the computational complexity of GBP is higher than BP, its application is limited in practice. In this paper, we introduce a stochastic version of GBP called stochastic generalized belief propagation (SGBP) that can be considered as an extension to the stochastic BP (SBP) algorithm introduced by Noorshams et al. They have shown that SBP reduces the complexity per iteration of BP by an order of magnitude in alphabet size. In contrast to SBP, SGBP can reduce the computation complexity if certain topological conditions are met by the region graph associated to a graphical model. However, this reduction can be larger than only one order of magnitude in alphabet size. In this paper, we characterize these conditions and the amount of computation gain that we can obtain by using SGBP. Finally, using similar proof techniques employed by Noorshams et al., for general graphical models satisfy contraction conditions, we prove the asymptotic convergence of SGBP to the unique GBP fixed point, as well as providing non-asymptotic upper bounds on the mean square error and on the high probability error.
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Обобщённое распространение доверия (GBP), введённое Иедидией и др., представляет собой расширение алгоритма распространения доверия (BP), который широко используется в различных задачах, связанных с вычислением точных или приближённых маргиналов вероятностных распределений. Во многих задачах было замечено, что точность GBP значительно превосходит точность BP. Однако, поскольку в общем случае вычислительная сложность GBP выше, чем у BP, её применение на практике ограничено. В данной статье мы вводим стохастическую версию GBP, называемую стохастическим обобщённым распространением доверия (SGBP), которую можно рассматривать как расширение стохастического алгоритма BP (SBP), предложенного Нооршамсом и др. Они показали, что SBP снижает вычислительную сложность на одну итерацию BP на порядок по размеру алфавита. В отличие от SBP, SGBP может снизить вычислительную сложность, если для графа областей, соответствующего графической модели, выполняются определённые топологические условия. При этом снижение может быть больше, чем на один порядок по размеру алфавита. В данной статье мы характеризуем эти условия и величину выигрыша в вычислениях, который можно получить при использовании SGBP. Наконец, используя аналогичные методы доказательства, применённые Нооршамсом и др. для общих графических моделей, удовлетворяющих условиям сжатия, мы доказываем асимптотическую сходимость SGBP к единственной неподвижной точке GBP, а также приводим неасимптотические верхние оценки среднеквадратичной ошибки и ошибки с высокой вероятностью.
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ru
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Transportation systems often rely on understanding the flow of vehicles or pedestrian. From traffic monitoring at the city scale, to commuters in train terminals, recent progress in sensing technology make it possible to use cameras to better understand the demand, i.e., better track moving agents (e.g., vehicles and pedestrians). Whether the cameras are mounted on drones, vehicles, or fixed in the built environments, they inevitably remain scatter. We need to develop the technology to re-identify the same agents across images captured from non-overlapping field-of-views, referred to as the visual re-identification task. State-of-the-art methods learn a neural network based representation trained with the cross-entropy loss function. We argue that such loss function is not suited for the visual re-identification task hence propose to model confidence in the representation learning framework. We show the impact of our confidence-based learning framework with three methods: label smoothing, confidence penalty, and deep variational information bottleneck. They all show a boost in performance validating our claim. Our contribution is generic to any agent of interest, i.e., vehicles or pedestrians, and outperform highly specialized state-of-the-art methods across 5 datasets. The source code and models are shared towards an open science mission.
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교통 시스템은 종종 차량이나 보행자의 흐름을 이해하는 데 의존한다. 도시 규모의 교통 모니터링부터 철도역사 내 통근자에 이르기까지, 최근 센서 기술의 발전으로 카메라를 활용해 수요를 더 잘 이해하고, 즉 움직이는 개체(예: 차량 및 보행자)를 더 정확하게 추적하는 것이 가능해졌다. 드론, 차량, 또는 건축 환경에 고정된 형태로 카메라가 설치되든 간에, 그들은 필연적으로 산발적으로 존재하게 된다. 우리는 서로 겹치지 않는 시야 영역에서 촬영된 이미지들 간에 동일한 개체를 재식별하는 기술을 개발해야 한다. 이를 시각적 재식별 과제라 한다. 최신 기법들은 크로스엔트로피 손실 함수를 사용하여 훈련된 신경망 기반 표현을 학습한다. 우리는 이러한 손실 함수가 시각적 재식별 과제에 적합하지 않다고 주장하며, 표현 학습 프레임워크 내에서 신뢰도를 모델링할 것을 제안한다. 우리는 라벨 스무딩, 신뢰도 페널티, 딥 변분 정보 병목의 세 가지 방법을 통해 신뢰도 기반 학습 프레임워크의 효과를 보여준다. 이 모든 방법은 성능 향상을 나타내며 우리의 주장을 입증한다. 우리의 기여는 차량이나 보행자 등 관심 대상 개체에 관계없이 일반적으로 적용 가능하며, 5개의 데이터셋에서 고도로 특화된 최신 기법들을 능가한다. 소스 코드와 모델은 오픈 사이언스 목표를 위해 공개된다.
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ko
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The mixing of the quasifission component to the fissionlike cross section causes ambiguity in the quantitative estimation of the complete fusion cross section from the observed angular and mass distributions of the binary products. We show that the partial cross section of quasifission component of binary fragments covers the whole range of the angular momentum values leading to capture. The calculated angular momentum distributions for the compound nucleus and dinuclear system going to quasifission may overlap: competition between complete fusion and quasifission takes place at all values of initial orbital angular momentum. Quasifission components formed at large angular momentum of the dinuclear system can show isotropic angular distribution and their mass distribution can be in mass symmetric region similar to the characteristics of fusion-fission components. As result the unintentional inclusion of the quasifission contribution into the fusion-fission fragment yields can lead to overestimation of the probability of the compound nucleus formation.
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Smíchání kvazíštěpné složky do průřezu podobného štěpení způsobuje nejednoznačnost při kvantitativním odhadu průřezu úplného fúzního procesu z pozorovaných úhlových a hmotnostních rozdělení binárních produktů. Ukazujeme, že parciální průřez kvazíštěpné složky binárních fragmentů pokrývá celý rozsah hodnot úhlového momentu vedoucích ke zachycení. Vypočítaná rozdělení úhlového momentu pro složené jádro a dvojjaderný systém přecházející do kvazíštěpení se mohou překrývat: soutěž mezi úplnou fúzí a kvazíštěpením probíhá při všech hodnotách počátečního orbitálního úhlového momentu. Kvazíštěpné složky vznikající při velkém úhlovém momentu dvojjaderného systému mohou vykazovat izotropní úhlové rozdělení a jejich hmotnostní rozdělení může být v oblasti hmotnostní symetrie podobně jako charakteristiky složek fúze-štěpení. V důsledku toho může neúmyslné zahrnutí příspěvku kvazíštěpení do výtěžků fragmentů fúze-štěpení vést k nadhodnocení pravděpodobnosti vzniku složeného jádra.
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cs
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Permutation entropy techniques can be useful in identifying anomalies in paleoclimate data records, including noise, outliers, and post-processing issues. We demonstrate this using weighted and unweighted permutation entropy of water-isotope records in a deep polar ice core. In one region of these isotope records, our previous calculations revealed an abrupt change in the complexity of the traces: specifically, in the amount of new information that appeared at every time step. We conjectured that this effect was due to noise introduced by an older laboratory instrument. In this paper, we validate that conjecture by re-analyzing a section of the ice core using a more-advanced version of the laboratory instrument. The anomalous noise levels are absent from the permutation entropy traces of the new data. In other sections of the core, we show that permutation entropy techniques can be used to identify anomalies in the raw data that are not associated with climatic or glaciological processes, but rather effects occurring during field work, laboratory analysis, or data post-processing. These examples make it clear that permutation entropy is a useful forensic tool for identifying sections of data that require targeted re-analysis---and can even be useful in guiding that analysis.
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Técnicas de entropia de permutação podem ser úteis na identificação de anomalias em registros de dados paleoclimáticos, incluindo ruído, valores atípicos e problemas decorrentes do pós-processamento. Demonstramos isso utilizando entropia de permutação ponderada e não ponderada de registros de isótopos de água em um testemunho de gelo polar profundo. Em uma região desses registros isotópicos, nossos cálculos anteriores revelaram uma mudança abrupta na complexidade dos traços: especificamente, na quantidade de nova informação que aparecia a cada passo de tempo. Conjecturamos que esse efeito era devido ao ruído introduzido por um instrumento laboratorial mais antigo. Neste artigo, validamos essa conjectura ao reanalisar uma seção do testemunho de gelo utilizando uma versão mais avançada do instrumento laboratorial. Os níveis anômalos de ruído estão ausentes nos traços de entropia de permutação dos novos dados. Em outras seções do testemunho, mostramos que as técnicas de entropia de permutação podem ser usadas para identificar anomalias nos dados brutos que não estão associadas a processos climáticos ou glaciológicos, mas sim a efeitos ocorridos durante trabalhos de campo, análises laboratoriais ou pós-processamento dos dados. Esses exemplos deixam claro que a entropia de permutação é uma ferramenta forense útil para identificar seções de dados que exigem reanálise direcionada — e pode até mesmo ser útil para orientar essa análise.
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pt
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Privacy has become a major concern in Online Social Networks (OSNs) due to threats such as advertising spam, online stalking and identity theft. Although many users hide or do not fill out their private attributes in OSNs, prior studies point out that the hidden attributes may be inferred from some other public information. Thus, users' private information could still be at stake to be exposed. Hitherto, little work helps users to assess the exposure probability/risk that the hidden attributes can be correctly predicted, let alone provides them with pointed countermeasures. In this article, we focus our study on the exposure risk assessment by a particular privacy-sensitive attribute - current city - in Facebook. Specifically, we first design a novel current city prediction approach that discloses users' hidden `current city' from their self-exposed information. Based on 371,913 Facebook users' data, we verify that our proposed prediction approach can predict users' current city more accurately than state-of-the-art approaches. Furthermore, we inspect the prediction results and model the current city exposure probability via some measurable characteristics of the self-exposed information. Finally, we construct an exposure estimator to assess the current city exposure risk for individual users, given their self-exposed information. Several case studies are presented to illustrate how to use our proposed estimator for privacy protection.
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La privacy è diventata una questione fondamentale nei Social Network Online (OSN) a causa di minacce come lo spam pubblicitario, lo stalking online e il furto di identità. Sebbene molti utenti nascondano o non inseriscano nei loro profili gli attributi privati, studi precedenti indicano che tali attributi nascosti potrebbero essere dedotti a partire da altre informazioni pubbliche. Di conseguenza, le informazioni private degli utenti potrebbero comunque essere esposte. Finora, pochi studi aiutano gli utenti a valutare la probabilità/rischio che i loro attributi nascosti possano essere correttamente predetti, tantomeno forniscono contromisure mirate. In questo articolo, concentriamo il nostro studio sulla valutazione del rischio di esposizione di un attributo particolarmente sensibile dal punto di vista della privacy: la città attuale su Facebook. In particolare, progettiamo innanzitutto un nuovo approccio per la previsione della città attuale, che rivela la "città attuale" nascosta dagli utenti a partire dalle informazioni da loro stessi rese pubbliche. Sulla base dei dati di 371.913 utenti Facebook, verifichiamo che il nostro approccio proposto permette di predire la città attuale degli utenti con maggiore accuratezza rispetto agli approcci all'avanguardia. Inoltre, analizziamo i risultati della previsione e modelliamo la probabilità di esposizione della città attuale attraverso alcune caratteristiche misurabili delle informazioni rese pubbliche dagli utenti. Infine, costruiamo un estimatore di esposizione per valutare il rischio di esposizione della città attuale per ciascun utente, sulla base delle informazioni da lui pubblicate. Vengono presentati diversi casi di studio per illustrare come utilizzare il nostro estimatore proposto ai fini della protezione della privacy.
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it
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Self-supervised methods play an increasingly important role in monocular depth estimation due to their great potential and low annotation cost. To close the gap with supervised methods, recent works take advantage of extra constraints, e.g., semantic segmentation. However, these methods will inevitably increase the burden on the model. In this paper, we show theoretical and empirical evidence that the potential capacity of self-supervised monocular depth estimation can be excavated without increasing this cost. In particular, we propose (1) a novel data augmentation approach called data grafting, which forces the model to explore more cues to infer depth besides the vertical image position, (2) an exploratory self-distillation loss, which is supervised by the self-distillation label generated by our new post-processing method - selective post-processing, and (3) the full-scale network, designed to endow the encoder with the specialization of depth estimation task and enhance the representational power of the model. Extensive experiments show that our contributions can bring significant performance improvement to the baseline with even less computational overhead, and our model, named EPCDepth, surpasses the previous state-of-the-art methods even those supervised by additional constraints.
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Les méthodes auto-supervisées jouent un rôle de plus en plus important dans l'estimation de la profondeur monoculaire en raison de leur grand potentiel et de leur faible coût d'annotation. Pour combler l'écart avec les méthodes supervisées, les travaux récents exploitent des contraintes supplémentaires, par exemple la segmentation sémantique. Toutefois, ces méthodes augmentent inévitablement la charge du modèle. Dans cet article, nous présentons des preuves théoriques et empiriques que la capacité potentielle de l'estimation de profondeur monoculaire auto-supervisée peut être exploitée sans accroître ce coût. En particulier, nous proposons (1) une nouvelle approche d'augmentation des données appelée greffage de données, qui oblige le modèle à exploiter davantage d'indices pour inférer la profondeur en dehors de la position verticale dans l'image, (2) une perte d'auto-distillation exploratoire, supervisée par une étiquette d'auto-distillation générée par notre nouvelle méthode de post-traitement – le post-traitement sélectif, et (3) le réseau à échelle complète, conçu pour doter l'encodeur d'une spécialisation dans la tâche d'estimation de profondeur et renforcer la puissance de représentation du modèle. De nombreuses expériences montrent que nos contributions permettent d'améliorer significativement les performances par rapport à la ligne de base, avec même une surcharge calculatoire réduite, et que notre modèle, nommé EPCDepth, surpasse les méthodes précédentes à l'état de l'art, y compris celles supervisées par des contraintes supplémentaires.
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fr
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We study the Wouthuysen-Field coupling at early universe with numerical solutions of the integrodifferential equation describing the kinetics of photons undergoing resonant scattering. The numerical solver is developed based on the weighted essentially non-oscillatory (WENO) scheme for the Boltzmann-like integrodifferential equation. We focus on the time evolution of the Wouthuysen-Field (W-F) coupling in relation to the 21 cm emission and absorption at the epoch of reionization. We show that a local Boltzmann distribution will be formed if photons with frequency \sim \nu_0 have undergone a ten thousand or more times of scattering, which corresponds to the order of 10^3 yrs for neutral hydrogen density of the concordance \Lambda CDM model. The time evolution of the shape and width of the local Boltzmann distribution actually doesn't dependent on the details of atomic recoil, photon sources, or initial conditions very much. However, the intensity of photon flux at the local Boltzmann distribution is substantially time-dependent. The time scale of approaching the saturated intensity can be as long as 10^5-10^6 yrs for typical parameters of the \Lambda CDM model. The intensity of the local Boltzmann distribution at time less than 10^5 yrs is significantly lower than that of the saturation state. Therefore, it may not be always reasonable to assume that the deviation of the spin temperature of 21 cm energy states from cosmic background temperature is mainly due to the W-F coupling if first stars or their emission/absorption regions evolved with a time scale equal to or less than Myrs.
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Sinusuri namin ang Wouthuysen-Field coupling sa maagang uniberso gamit ang mga numerikal na solusyon ng integrodyferensyal na ekwasyon na naglalarawan sa kilusan ng mga photon na sumasailalim sa resonant scattering. Ang numerikal na solver ay binuo batay sa weighted essentially non-oscillatory (WENO) scheme para sa Boltzmann-tulad na integrodyferensyal na ekwasyon. Tinutuon namin ang pansin sa pagbabago sa paglipas ng panahon ng Wouthuysen-Field (W-F) coupling kaugnay ng 21 cm emission at absorption sa panahon ng reionization. Ipinapakita namin na ang lokal na Boltzmann distribution ay bubuo kung ang mga photon na may dalas na ~ \nu_0 ay nakaranas ng sampung libo o higit pang beses na scattering, na tumutugma sa kahit umabot sa 10^3 taon para sa densidad ng neutral na hydrogen sa sumasang-ayon na \Lambda CDM model. Ang pagbabago sa hugis at lapad ng lokal na Boltzmann distribution sa paglipas ng panahon ay hindi gaanong nakadepende sa mga detalye ng atomic recoil, pinagmulan ng photon, o paunang kondisyon. Gayunpaman, ang intensity ng photon flux sa lokal na Boltzmann distribution ay malaki ang pagbabago batay sa panahon. Ang tagal ng panahon upang umabot sa saturated intensity ay maaaring umabot sa 10^5–10^6 taon para sa karaniwang mga parameter ng \Lambda CDM model. Ang intensity ng lokal na Boltzmann distribution sa panahon na mas maikli kaysa 10^5 taon ay makabuluhang mas mababa kaysa sa saturation state. Kaya, maaaring hindi laging makatuwiran na ipagpalagay na ang paglihis ng spin temperature ng 21 cm energy states mula sa cosmic background temperature ay pangunahing dahil sa W-F coupling kung ang mga unang bituin o ang kanilang mga rehiyon ng emission/absorption ay umunlad sa isang panahon na katumbas o mas maikli kaysa Myrs.
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