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satterthwaite and toepke ( 1970 phys. rev. lett. 25 741 ) predicted high - temperature superconductivity in hydrogen - rich metallic alloys, based on an idea that these compounds should exhibit high debye frequency of the proton lattice, which boosts the superconducting transition temperature, tc. the idea has got full confirmation more than four decades later when drozdov et al ( 2015 nature 525 73 ) experimentally discovered near - room - temperature superconductivity in highly - compressed sulphur superhydride, h3s. to date, more than a dozen of high - temperature hydrogen - rich superconducting phases in ba - h, pr - h, p - h, pt - h, ce - h, th - h, s - h, y - h, la - h, and ( la, y ) - h systems have been synthesized and, recently, hong et al ( 2021 arxiv : 2101. 02846 ) reported on the discovery of c2 / m - snh12 phase with superconducting transition temperature of tc ~ 70 k. here we analyse the magnetoresistance data, r ( t, b ), of c2 / m - snh12 phase and report that this superhydride exhibits the ground state superconducting gap of $ \ delta $ ( 0 ) = 9. 2 mev, the ratio of 2 $ \ delta $ ( 0 ) / k $ _ b $ tc = 3. 3, and 0. 010 < tc / tf < 0. 014 ( where tf is the fermi temperature ) and, thus, c2 / m - snh12 falls into unconventional superconductors band in the uemura plot. | arxiv:2104.07364 |
many authors noted that the principle of relativity, together with space - time symmetries, suffices to derive lorentz - like coordinate transformations between inertial frames. these contain a free parameter, $ k $, ( equal to $ c ^ { - 2 } $ in special relativity ) which is usually claimed to be empirically determinable, so that special relativity does not need the postulate of constancy of the speed of light. i analyze this claim and find that all methods destined to measure $ k $ fail without further assumptions, similar to the second postulate. specifically, measuring $ k $ requires a signal that travels identically in opposite directions ( this is unrelated to the conventionality of synchronization, as the one - postulate program implicitly selects the standard synchronization convention ). positing such a property about light is logically weaker than einstein ' s second postulate but suffices to recover special relativity in full. | arxiv:1408.3142 |
production cross sections of charged pions, kaons and antikaons have been measured in c + c and c + au collisions at beam energies of 1. 0 and 1. 8 agev for different polar emission angles. the kaon and antikaon energy spectra can be described by boltzmann distributions whereas the pion spectra exhibit an additional enhancement at low energies. the pion multiplicity per participating nucleon m ( pi + ) / a _ part is a factor of about 3 smaller in c + au than in c + c collisions at 1. 0 agev whereas it differs only little for the c and the au target at a beam energy of 1. 8 agev. the k + multiplicities per participating nucleon m ( k + ) / a _ part are independent of the target size at 1 agev and at 1. 8 agev. the k - multiplicity per participating nucleon m ( k - ) / a _ part is reduced by a factor of about 2 in c + au as compared to c + c collisions at 1. 8 agev. this effect might be caused by the absorption of antikaons in the heavy target nucleus. transport model calculations underestimate the k - / k + ratio for c + c collisions at 1. 8 agev by a factor of about 4 if in - medium modifications of k mesons are neglected. | arxiv:nucl-ex/0011010 |
this paper investigates the use of extended kalman filtering to train recurrent neural networks with rather general convex loss functions and regularization terms on the network parameters, including $ \ ell _ 1 $ - regularization. we show that the learning method is competitive with respect to stochastic gradient descent in a nonlinear system identification benchmark and in training a linear system with binary outputs. we also explore the use of the algorithm in data - driven nonlinear model predictive control and its relation with disturbance models for offset - free closed - loop tracking. | arxiv:2111.02673 |
social dilemmas, where mutual cooperation can lead to high payoffs but participants face incentives to cheat, are ubiquitous in multi - agent interaction. we wish to construct agents that cooperate with pure cooperators, avoid exploitation by pure defectors, and incentivize cooperation from the rest. however, often the actions taken by a partner are ( partially ) unobserved or the consequences of individual actions are hard to predict. we show that in a large class of games good strategies can be constructed by conditioning one ' s behavior solely on outcomes ( ie. one ' s past rewards ). we call this consequentialist conditional cooperation. we show how to construct such strategies using deep reinforcement learning techniques and demonstrate, both analytically and experimentally, that they are effective in social dilemmas beyond simple matrix games. we also show the limitations of relying purely on consequences and discuss the need for understanding both the consequences of and the intentions behind an action. | arxiv:1710.06975 |
addressing subwavelength object and displacement is crucial in optical nanometrology. we show in this letter that nano antennas with subwavelength structures can be addressed precisely by incident beams with singularity. this accurate feeding beyond the diffraction limit can lead to dynamic control of the unidirectional scattering in the far field. the combination of polarization discontinuity of the incoming singular beam, along with the rapid phase variation near the antenna leads to remarkable sensitivity of the far field scattering to displacement at deep subwavelength scale. this opens a far field deep subwavelength postion detection method based on the interaction of singular optics with nano antennas. | arxiv:1603.06606 |
we report the first measurement of the transverse momentum dependence of double spin asymmetries in semi - inclusive production of pions in deep inelastic scattering off the longitudinally polarized proton. data have been obtained using a polarized electron beam of 5. 7 gev with the clas detector at the thomas jefferson national accelerator facility ( jlab ). a significant non - zero $ \ sin2 \ phi $ single spin asymmetry was also observed for the first time indicating strong spin - orbit correlations for transversely polarized quarks in the longitudinally polarized proton. the azimuthal modulations of single spin asymmetries have been measured over a wide kinematic range. | arxiv:1003.4549 |
we study the ground - state phase diagram of a spin - 1 / 2 xxz model with a chirality - chirality interaction ( cci ) on a two - leg ladder. this model offers a minimal setup to study an interplay between spin and chirality degrees of freedom. the spin - chirality duality transformation allows us to relate the regimes of weak and strong ccis. by applying the abelian bosonization and the duality, we obtain a rich phase diagram that contains distinct gapped featureless and ordered phases. in particular, neel and vector chiral orders appear for easy - axis anisotropy, while two distinct symmetry protected topological ( spt ) phases appear for easy - plane anisotropy. the two spt phases can be viewed as twisted variants of the haldane phase. we also present an effective description in terms of ( spinor ) hard - core bosons, which reveals critical behavior on the self - dual line in the easy - axis and easy - plane regimes. we perform numerical simulations to confirm the predicted phase structure and critical properties. we further demonstrate that the two spt phases and a trivial phase are distinguished by topological indices in the presence of certain symmetries. a similar phase structure is expected in a spin - 1 / 2 xxz ladder with four - spin ring exchange. | arxiv:2311.07053 |
nrel ' s computational sciences center hosts the largest high - performance computing ( hpc ) capabilities dedicated to energy research while functioning as a living laboratory for energy - efficient computing. nrel ' s hpc capabilities support the research needs of the department of energy ' s office of energy efficiency and renewable energy ( eere ). in ten years of operation, hpc use in eere - sponsored research has grown by a factor of 30, including work in electricity generation, energy efficiency, transportation, and energy system modeling. this paper analyzes this research portfolio, providing examples of individual use cases. the paper documents nrel ' s history of operating one of the world ' s most energy - efficient data centers while examining pathways to reduce economic and environmental impact beyond reduction of power usage efficiency ( pue ). this paper concludes by examining the unique opportunities created for accelerating improvements in data center efficiency created by combining an hpc system dedicated to energy research and a research program in energy - efficient computing. | arxiv:2412.12355 |
we present a complete and independent set of dimension - 7 operators in the low energy effective field theory ( left ) where the dynamical degrees of freedom are the standard model five quarks and all of the neutral and charged leptons. all operators are non - hermitian and are classified according to their baryon ( $ \ delta b $ ) and lepton ( $ \ delta l $ ) numbers violated. including hermitian - conjugated operators, there are in total $ 3168 $, $ 750 $, $ 588 $, $ 712 $ operators with $ ( \ delta b, \ delta l ) = ( 0, 0 ) $, $ ( 0, \ pm 2 ) $, $ ( \ pm 1, \ mp 1 ) $, $ ( \ pm 1, \ pm 1 ) $ respectively. we perform the tree - level matching with the standard model effective field theory ( smeft ) up to dimension - 7 ( dim - 7 ) operators in both left and smeft. as a phenomenological application we study the effective neutrino - photon interactions due to dim - 7 lepton number violating operators that are induced and much enhanced at one loop from dim - 6 operators that in turn are matched from dim - 7 smeft operators. we compare the cross sections of various neutrino - photon scattering with their counterparts in the standard model and highlight the new features. finally we illustrate how these effective interactions could arise from ultraviolet completion. | arxiv:2005.08013 |
we construct and study a triangulated category of motives with modulus $ \ mathbf { mdm } _ { \ mathrm { gm } } ^ { \ mathrm { eff } } $ over a field $ k $ that extends voevodsky ' s category $ \ mathbf { dm } _ { \ mathrm { gm } } ^ { \ mathrm { eff } } $ in such a way as to encompass non - homotopy invariant phenomena. in a similar way as $ \ mathbf { dm } _ { \ mathrm { gm } } ^ { \ mathrm { eff } } $ is constructed out of smooth $ k $ - varieties, $ \ mathbf { mdm } _ { \ mathrm { gm } } ^ { \ mathrm { eff } } $ is constructed out of proper modulus pairs, introduced in part i of this work. to such a modulus pair we associate its motive in $ \ mathbf { mdm } _ { \ mathrm { gm } } ^ { \ mathrm { eff } } $. in some cases the $ \ mathrm { hom } $ group in $ \ mathbf { mdm } _ { \ mathrm { gm } } ^ { \ mathrm { eff } } $ between the motives of two modulus pairs can be described in terms of bloch ' s higher chow groups. | arxiv:2011.11859 |
coarse - graining is a powerful tool for extending the reach of dynamic models of proteins and other biological macromolecules. topological coarse - graining, in which biomolecules or sets thereof are represented via graph structures, is a particularly useful way of obtaining highly compressed representations of molecular structure, and simulations operating via such representations can achieve substantial computational savings. a drawback of coarse - graining, however, is the loss of atomistic detail - an effect that is especially acute for topological representations such as protein structure networks ( psns ). here, we introduce an approach based on a combination of machine learning and physically - guided refinement for inferring atomic coordinates from psns. this " neural upscaling " procedure exploits the constraints implied by psns on possible configurations, as well as differences in the likelihood of observing different configurations with the same psn. using a 1 $ \ mu $ s atomistic molecular dynamics trajectory of a $ \ beta _ { 1 - 40 } $, we show that neural upscaling is able to effectively recapitulate detailed structural information for intrinsically disordered proteins, being particularly successful in recovering features such as transient secondary structure. these results suggest that scalable network - based models for protein structure and dynamics may be used in settings where atomistic detail is desired, with upscaling employed to impute atomic coordinates from psns. | arxiv:2109.06700 |
a dual quaternion - based control strategy for formation flying of small uav groups is proposed. through the definition of a virtual structure, the coordinated control of formation ' s position, orientation, and shape parameters is enabled. this abstraction simplifies formation management, allowing a low - level controller to compute commands for individual uavs. the controller is divided into a pose control module and a geometry - based adaptive strategy, providing efficient and precise task execution. simulation and experimental results validate the approach. | arxiv:2504.05560 |
we analytically calculate the spin - dependent electronic conductance through a one - dimensional ballistic ring in the presence of an inhomogeneous magnetic field and identify signatures of geometric and berry phases in the general non - adiabatic situation. for an in - plane magnetic field, we rigorously prove the spin - flip effect presented in frustaglia et al., phys. rev. lett. 87, 256602 ( 2001 ), which allows to control and switch the polarization of outgoing electrons by means of an aharonov - bohm flux, and derive analytical expressions for the energy - averaged magneto - conductance. our results support numerical calculations for two - dimensional ballistic rings presented in the second paper ( frustaglia et al., submitted to phys. rev. b ) of this series. | arxiv:cond-mat/0402165 |
we study the persistence of warps in galactic discs in the presence of massive halos. a disc is approximated by a set of massive rings, while a halo is represented by a conventional n - body simulation. we confirm the conclusion of nelson & tremaine ( 1995 ) that a halo responds strongly to an embedded precessing disc. this response invalidates the approximations made by in the derivation of classical ` modified tilt ' modes. we show that the response of the halo causes the line of nodes of a disc that starts from a modified tilt mode to wind up within a few dynamical times. we explain this finding in terms of the probable spectrum of true normal modes of a combined disc - halo system. | arxiv:astro-ph/9708024 |
the paper presents a new state estimation algorithm for a bilinear equation representing the fourier - galerkin ( fg ) approximation of the navier - stokes ( ns ) equations on a torus in r2. this state equation is subject to uncertain but bounded noise in the input ( kolmogorov forcing ) and initial conditions, and its output is incomplete and contains bounded noise. the algorithm designs a time - dependent gain such that the estimation error converges to zero exponentially. the sufficient condition for the existence of the gain are formulated in the form of algebraic riccati equations. to demonstrate the results we apply the proposed algorithm to the reconstruction a chaotic fluid flow from incomplete and noisy data. | arxiv:1712.08833 |
the goal of a learner, in standard online learning, is to have the cumulative loss not much larger compared with the best - performing function from some fixed class. numerous algorithms were shown to have this gap arbitrarily close to zero, compared with the best function that is chosen off - line. nevertheless, many real - world applications, such as adaptive filtering, are non - stationary in nature, and the best prediction function may drift over time. we introduce two novel algorithms for online regression, designed to work well in non - stationary environment. our first algorithm performs adaptive resets to forget the history, while the second is last - step min - max optimal in context of a drift. we analyze both algorithms in the worst - case regret framework and show that they maintain an average loss close to that of the best slowly changing sequence of linear functions, as long as the cumulative drift is sublinear. in addition, in the stationary case, when no drift occurs, our algorithms suffer logarithmic regret, as for previous algorithms. our bounds improve over the existing ones, and simulations demonstrate the usefulness of these algorithms compared with other state - of - the - art approaches. | arxiv:1303.0140 |
for the hypoelliptic differential operators $ p = { \ partial ^ 2 _ x } + ( x ^ k \ partial _ y - x ^ l { \ partial _ t } ) ^ 2 $ introduced by t. hoshiro, generalizing a class of m. christ, in the cases of $ k $ and $ l $ left open in the analysis, the operators $ p $ also fail to be { \ em { analytic } } hypoelliptic ( except for $ ( k, l ) = ( 0, 1 ) $ ), in accordance with treves ' conjecture. the proof is constructive, suitable for generalization, and relies on evaluating a family of eigenvalues of a non - self - adjoint operator. | arxiv:math/0212167 |
we report on our theoretical study of the magnetoresistance in spin polarized transport through a finite carbon nanotube ( cnt ). varying the fermi energy of a cnt and the relative strength of couplings to two ferromagnetic ( fm ) electrodes, we studied the conductance as well as the magnetoresistance ( mr ). due to resonant transport through discrete energy levels in a finite cnt, the conductance and mr are oscillating as a function of the cnt fermi energy. the mr is peaked at the conductance valleys and dipped close to the conductance peaks. when couplings to two fm electrodes are asymmetric, the mr dips become negative under a rather strong asymmetry. when couplings are more or less symmetric, the mr dips remain positive except for a very strong coupling case. under strong coupling case, the line broadening is significant and transport channels through neighboring energy levels in a cnt interfere with each other, leading to the negative mr. | arxiv:0810.5719 |
survival analysis is a critical tool for the modelling of time - to - event data, such as life expectancy after a cancer diagnosis or optimal maintenance scheduling for complex machinery. however, current neural network models provide an imperfect solution for survival analysis as they either restrict the shape of the target probability distribution or restrict the estimation to pre - determined times. as a consequence, current survival neural networks lack the ability to estimate a generic function without prior knowledge of its structure. in this article, we present the metaparametric neural network framework that encompasses existing survival analysis methods and enables their extension to solve the aforementioned issues. this framework allows survival neural networks to satisfy the same independence of generic function estimation from the underlying data structure that characterizes their regression and classification counterparts. further, we demonstrate the application of the metaparametric framework using both simulated and large real - world datasets and show that it outperforms the current state - of - the - art methods in ( i ) capturing nonlinearities, and ( ii ) identifying temporal patterns, leading to more accurate overall estimations whilst placing no restrictions on the underlying function structure. | arxiv:2110.06610 |
we propose a novel multi - source direction of arrival ( doa ) estimation technique using a convolutional neural network algorithm which learns the modal coherence patterns of an incident soundfield through measured spherical harmonic coefficients. we train our model for individual time - frequency bins in the short - time fourier transform spectrum by analyzing the unique snapshot of modal coherence for each desired direction. the proposed method is capable of estimating simultaneously active multiple sound sources on a $ 3 $ d space using a single - source training scheme. this single - source training scheme reduces the training time and resource requirements as well as allows the reuse of the same trained model for different multi - source combinations. the method is evaluated against various simulated and practical noisy and reverberant environments with varying acoustic criteria and found to outperform the baseline methods in terms of doa estimation accuracy. furthermore, the proposed algorithm allows independent training of azimuth and elevation during a full doa estimation over $ 3 $ d space which significantly improves its training efficiency without affecting the overall estimation accuracy. | arxiv:2003.08050 |
we report the detection of thermal sunyaev - zeldovich effect ( sz ) fluctuations in the intracluster medium ( icm ) of coma cluster observed with $ { \ it planck } $. the sz data links the maximum observable x - ray scale to the large mpc scale, extending our knowledge of the power spectrum of icm fluctuations. deprojecting the 2 - d sz perturbations into 3 - d pressure fluctuations, we find an amplitude spectrum which peaks at $ \ delta p / p = 33 \ pm 12 \ % $ and $ 74 \ pm19 \ % $ in the $ 15 ' $ and $ 40 ' $ radius region, respectively. we perform tests to ensure fluctuations are intrinsic to the cluster and not due to noise contamination. by using high - resolution hydrodynamical models, we improve the icm turbulence constraints in coma, finding 3 - d mach number $ { \ rm ma _ { 3d } } = 0. 8 \ pm0. 3 $ ( 15 ' region ), increasing to supersonic values at larger radii ( 40 ' ), and an injection scale $ l _ { \ rm inj } \ approx 500 $ kpc. such properties are consistent with driving due to mergers, in particular tied to internal galaxy groups. the large pressure fluctuations show that coma is in adiabatic mode ( mediated by sound waves ), rather than isobaric mode ( mediated by buoyancy waves ). as predicted by turbulence models, the distribution of sz fluctuations is log - normal with mild non - gaussianities ( heavy tails ). the substantial non - thermal pressure support implies hydrostatic mass bias $ b _ m = - 15 \ % $ to $ - 45 \ % $ from the core to the outskirt region, respectively. while total sz power probes the thermal energy content, the sz fluctuations constrain the non - thermal deviations important for precision cosmology. the proposed, novel approach can be exploited by multifrequency observations using ground based interferometers and future space cmb missions. | arxiv:1604.03106 |
frame theory has been a popular subject in the design of structured signals and codes in recent years, with applications ranging from the design of measurement matrices in compressive sensing, to spherical codes for data compression and data transmission, to spacetime codes for mimo communications, and to measurement operators in quantum sensing. high - performance codes usually arise from designing frames whose elements have mutually low coherence. building off the original " group frame " design of slepian which has since been elaborated in the works of vale and waldron, we present several new frame constructions based on cyclic and generalized dihedral groups. slepian ' s original construction was based on the premise that group structure allows one to reduce the number of distinct inner pairwise inner products in a frame with $ n $ elements from $ \ frac { n ( n - 1 ) } { 2 } $ to $ n - 1 $. all of our constructions further utilize the group structure to produce tight frames with even fewer distinct inner product values between the frame elements. when $ n $ is prime, for example, we use cyclic groups to construct $ m $ - dimensional frame vectors with at most $ \ frac { n - 1 } { m } $ distinct inner products. we use this behavior to bound the coherence of our frames via arguments based on the frame potential, and derive even tighter bounds from combinatorial and algebraic arguments using the group structure alone. in certain cases, we recover well - known welch bound achieving frames. in cases where the welch bound has not been achieved, and is not known to be achievable, we obtain frames with close to welch bound performance. | arxiv:1509.05087 |
photon - induced nuclear excitation ( i. e. photo - excitation ) can be used for production of nuclear isomers, which have potential applications in astrophysics, energy storing, and medical diagnosis and treatment. this paper presents a feasibility study on production of four nuclear isomers ( { 99m } ^ tc, { 103m } ^ rh and { 113m, 115m } ^ in ) using high - intensity { \ gamma } - ray source based on laser - electron compton scattering ( lcs ), for use in the medical diagnosis and treatment. the decay properties and the medical applications of these nuclear isomers were reviewed. the cross - section curves, simulated yields and activity of product of each photo - excitation process were calculated. the cutoff energy of lcs { \ gamma } - ray beam is optimized by adjusting the electron energy in order to maximize the yields as well as the activities of photo - excitation products. it is found that the achievable activity of above - mentioned isomers can exceed 10 mci for 6 - hour target irradiation at an intensity of the order of 10 ^ { 13 } { \ gamma } / s. such magnitude of activity satisfies the dose requirement of medical diagnosis. our simulation results suggest the prospect of producing medically interesting isomers with photo - excitation using the state - of - art lcs { \ gamma } - ray beam facility. | arxiv:2007.02659 |
recently, tool learning with large language models ( llms ) has emerged as a promising paradigm for augmenting the capabilities of llms to tackle highly complex problems. despite growing attention and rapid advancements in this field, the existing literature remains fragmented and lacks systematic organization, posing barriers to entry for newcomers. this gap motivates us to conduct a comprehensive survey of existing works on tool learning with llms. in this survey, we focus on reviewing existing literature from the two primary aspects ( 1 ) why tool learning is beneficial and ( 2 ) how tool learning is implemented, enabling a comprehensive understanding of tool learning with llms. we first explore the " why " by reviewing both the benefits of tool integration and the inherent benefits of the tool learning paradigm from six specific aspects. in terms of " how ", we systematically review the literature according to a taxonomy of four key stages in the tool learning workflow : task planning, tool selection, tool calling, and response generation. additionally, we provide a detailed summary of existing benchmarks and evaluation methods, categorizing them according to their relevance to different stages. finally, we discuss current challenges and outline potential future directions, aiming to inspire both researchers and industrial developers to further explore this emerging and promising area. we also maintain a github repository to continually keep track of the relevant papers and resources in this rising area at https : / / github. com / quchangle1 / llm - tool - survey. | arxiv:2405.17935 |
broadcasting systems such as p2p streaming systems represent important network applications that support up to millions of online users. an efficient broadcasting mechanism is at the core of the system design. despite substantial efforts on developing efficient broadcasting algorithms, the following important question remains open : how to achieve the maximum broadcast rate in a distributed manner with each user maintaining information queues only for its direct neighbors? in this work, we first derive an innovative formulation of the problem over acyclic overlay networks with arbitrary underlay capacity constraints. then, based on the formulation, we develop a distributed algorithm to achieve the maximum broadcast rate and every user only maintains one queue per - neighbor. due to its lightweight nature, our algorithm scales very well with the network size and remains robust against high system dynamics. finally, by conducting simulations we validate the optimality of our algorithm under different network capacity models. simulation results further indicate that the convergence time of our algorithm grows linearly with the network size, which suggests an interesting direction for future investigation. | arxiv:1301.5107 |
we analyze star formation ( sf ) as a function of stellar mass ( m _ * ) and redshift z in the all wavelength extended groth strip international survey ( aegis ), for star - forming field galaxies with m _ * > ~ 10 ^ 10 m _ sun out to z = 1. 1. the data indicate that the high specific sf rates ( sfr ) of many less massive galaxies do not represent late, irregular or recurrent, starbursts in evolved galaxies. they rather seem to reflect the onset ( initial burst ) of the dominant sf episode of galaxies, after which sf gradually declines on gyr timescales to z = 0 and forms the bulk of a galaxy ' s m _ *. with decreasing mass, this onset of major sf shifts to decreasing z for an increasing fraction of galaxies ( staged galaxy formation ). this process may be an important component of the ` ` downsizing ' ' phenomenon. we find that the predominantly gradual decline of sfr ( noeske et al. 2007, this volume ) can be reproduced by exponential sf histories ( tau models ), if less massive galaxies have systematically longer e - folding times tau, and a later onset of sf ( z _ f ). our model can provide a first parametrization of sfr as a function of m _ * and z, and quantify mass - dependences of tau and z _ f, from direct observations of m _ * and sfr up to z > 1. the observed evolution of sf in galaxies can plausibly reflect the dominance of gradual gas exhaustion. the data are also consistent with the history of cosmological accretion onto dark matter halos. | arxiv:astro-ph/0703056 |
a high degree of chaos synchronization among transverse mode pairs with parity - symmetric polarizations was demonstrated in a laser - diode pumped thin - slice c - cut nd : gdvo4 laser. the amplitude correlation coefficient greater than r > 0. 994 resulted from a non - reversing mirror symmetric - polarization - dependent structural change in the modal patterns, where chaotic dynamics of the whole system consisting of qualitatively different dynamics, which depend on the polarization crossing angle, resembled that of a chaotic single mode laser. a self - organized sender - receiver type of chaos synchronization of a single pair of modes among an infinite number of parity - symmetric polarizations and the associated chaotic camouflaging as well as extracting experiment of a self - mixing solid - state laser doppler velocimetry signal were demonstrated. | arxiv:2008.10229 |
we introduce the notion of relative averaging operators on hom - associative algebras with a representation. relative averaging operators are twisted generalizations of relative averaging operators on associative algebras. we give two characterizations of relative averaging operators of hom - associative algebras via graphs and nijenhuis operators. a ( homomorphic ) relative averaging operator of hom - associative algebras with respect to a given representation gives rise to hom - associative ( tri ) dialgebras. by admissibility, a hom - jordan ( tri ) dialgebra and a hom - ( tri ) leibniz algebra can be obtained from hom - associative ( tri ) dialgebra. | arxiv:2311.08407 |
the rasch model is the most prominent member of the class of latent trait models that are in common use. the main reason is that it can be considered as a measurement model that allows to separate person and item parameters, a feature that is referred to as invariance of comparisons or specific objectivity. it is shown that the property is not an exclusive trait of rasch type models but is also found in alternative latent trait models. it is distinguished between separability in the theoretical measurement model and empirical separability with empirical separability meaning that parameters can be estimated without reference to the other group of parameters. a new type of pairwise estimator with this property is proposed that can be used also in alternative models. separability is considered in binary models as well as in polytomous models. | arxiv:2301.03048 |
we study a generalized distributionally robust chance - constrained set covering problem ( drc ) with a wasserstein ambiguity set, where both decisions and uncertainty are binary - valued. we establish the np - hardness of drc and recast it as a two - stage stochastic program, which facilitates decomposition algorithms. furthermore, we derive two families of valid inequalities. the first family targets the hypograph of a " shifted " submodular function, which is associated with each scenario of the two - stage reformulation. we show that the valid inequalities give a complete description of the convex hull of the hypograph. the second family mixes inequalities across multiple scenarios and gains further strength via lifting. our numerical experiments demonstrate the reliability of the drc model and the effectiveness of our proposed reformulation and valid inequalities. | arxiv:2010.05671 |
in this paper, we present some necessary and sufficient conditions for semi - compact operators being almost l - weakly compact ( resp. almost m - weakly compact ) and the converse. mainly, we prove that if $ x $ is a nonzero banach space, then every semi - compact operator $ t : x \ rightarrow e $ is almost l - weakly compact if and only if the norm of $ e $ is order continuous. and every positive semi - compact operator $ t : e \ rightarrow f $ is almost m - weakly compact if and only if the norm of $ e ' $ is order continuous. moreover, we investigate the relationships between almost l - weakly compact operators and dunford - pettis ( resp. almost dunford - pettis ) operators. | arxiv:1904.08116 |
a buyer wishes to purchase a durable good from a seller who in each period chooses a mechanism under limited commitment. the buyer ' s valuation is binary and fully persistent. we show that posted prices implement all equilibrium outcomes of an infinite - horizon, mechanism selection game. despite being able to choose mechanisms, the seller can do no better and no worse than if he chose prices in each period, so that he is subject to coase ' s conjecture. our analysis marries insights from information and mechanism design with those from the literature on durable goods. we do so by relying on the revelation principle in doval and skreta ( 2020 ). | arxiv:1904.07456 |
bayesian optimization ( bo ) is an integral part of automated scientific discovery - - the so - called self - driving lab - - where human inputs are ideally minimal or at least non - blocking. however, scientists often have strong intuition, and thus human feedback is still useful. nevertheless, prior works in enhancing bo with expert feedback, such as by incorporating it in an offline or online but blocking ( arrives at each bo iteration ) manner, are incompatible with the spirit of self - driving labs. in this work, we study whether a small amount of randomly arriving expert feedback that is being incorporated in a non - blocking manner can improve a bo campaign. to this end, we run an additional, independent computing thread on top of the bo loop to handle the feedback - gathering process. the gathered feedback is used to learn a bayesian preference model that can readily be incorporated into the bo thread, to steer its exploration - exploitation process. experiments on toy and chemistry datasets suggest that even just a few intermittent, asynchronous expert feedback can be useful for improving or constraining bo. this can especially be useful for its implication in improving self - driving labs, e. g. making them more data - efficient and less costly. | arxiv:2406.06459 |
the objective of this paper is to introduce and demonstrate a robust method for multi - constrained topology optimization. the method is derived by combining the topological sensitivity with the classic augmented lagrangian formulation. the primary advantages of the proposed method are : ( 1 ) it rests on well - established augmented lagrangian formulation for constrained optimization, ( 2 ) the augmented topological level - set can be derived systematically for an arbitrary set of loads and constraints, and ( 3 ) the level - set can be updated efficiently. the method is illustrated through numerical experiments. | arxiv:2203.15111 |
a cayley graph cay $ ( g ; s ) $ has the ci ( cayley isomorphism ) property if for every isomorphic graph cay $ ( g ; t ) $, there is a group automorphism $ \ alpha $ of $ g $ such that $ s ^ \ alpha = t $. the dci ( directed cayley isomorphism ) property is defined analogously on digraphs. a group $ g $ is a ci - group if every cayley graph on $ g $ has the ci property, and is a dci - group if every cayley digraph on $ g $ has the dci property. since a graph is a special type of digraph, this means that every dci - group is a ci - group, and if a group is not a ci - group then it is not a dci - group, but there are well - known examples of groups that are ci - groups but not dci - groups. in 2009, spiga showed that $ \ mathbb z _ 3 ^ 8 $ is not a dci - group, by producing a digraph that does not have the dci property. he also showed that $ \ mathbb z _ 3 ^ 5 $ is a dci - group ( and therefore also a ci - group ). until recently the question of whether there are elementary abelian $ 3 $ - groups that are not ci - groups remained open. in a recent preprint with dave witte morris, we showed that $ \ mathbb z _ 3 ^ { 10 } $ is not a ci - group. in this paper we show that with slight modifications, the underlying undirected graph of order $ 3 ^ 8 $ described by spiga is does not have the ci property, so $ \ mathbb z _ 3 ^ 8 $ is not a ci - group. | arxiv:2303.08742 |
the morphology and stellar content of the cygnus ob2 association has been determined using 2mass infrared observations in the j, h, and k bands. the analysis reveals a spherically symmetric association of 2 deg in diameter with a half light radius of 13 ', corresponding to rh = 6. 4 pc at an assumed distance of 1. 7 kpc. the interstellar extinction for member stars ranges from av = 5m to 20m, which led to a considerable underestimation of the association size and richness in former optical studies. from the infrared colour - magnitude diagram, the number of ob member stars is estimated to 2600 + / - 400, while the number of o stars amounts to 120 + / - 20. this is the largest number of o stars ever found in a galactic massive star association. the slope of the initial mass function has been determined from the colour - magnitude diagram to gamma = - 1. 6 + / - 0. 1. the total mass of cyg ob2 is estimated to ( 4 - 10 ) * 10 ^ 4 msol, where the primary uncertainty comes from the unknown lower mass cut - off. using the radial density profile of the association, the central mass density is determined to rho0 = 40 - 150 msol pc ^ - 3. considering the mass, density, and size of cyg ob2 it seems untenable to classify this object still as ob association. cygnus ob2 more closely resembles a young globular cluster like those observed in the large magellanic cloud or in extragalactic star forming regions. it is therefore suggested to re - classify cygnus ob2 as young globular cluster - an idea which goes back to reddish et al. ( 1966 ). cygnus ob2 would then be the first object of this class in the milky way. | arxiv:astro-ph/0007442 |
count data with excessive zeros are often encountered when modelling infectious disease occurrence. the degree of zero inflation can vary over time due to non - epidemic periods as well as by age group or region. the existing endemic - epidemic modelling framework ( aka hhh ) lacks a proper treatment for surveillance data with excessive zeros as it is limited to poisson and negative binomial distributions. in this paper, we propose a multivariate zero - inflated endemic - epidemic model with random effects to extend hhh. parameters of the new zero - inflation and the hhh part of the model can be estimated jointly and efficiently via ( penalized ) maximum likelihood inference using analytical derivatives. a simulation study confirms proper convergence and coverage probabilities of confidence intervals. applying the model to measles counts in the 16 german states, 2005 - - 2018, shows that the added zero - inflation improves probabilistic forecasts. | arxiv:2201.07285 |
lyman - alpha ( ly $ \ alpha $ ) emission from galaxies can be used to trace neutral hydrogen in the epoch of reionization, however, there is a degeneracy between the attenuation of ly $ \ alpha $ in the intergalactic medium ( igm ) and the line profile emitted from the galaxy. large shifts of ly $ \ alpha $ redward of systemic due to scattering in the interstellar medium can boost ly $ \ alpha $ transmission in the igm during reionization. the relationship between ly $ \ alpha $ velocity offset from systemic and other galaxy properties is not well - established at high - redshift or low luminosities, due to the difficulty of observing emission lines which trace systemic redshift. rest - frame optical spectroscopy with jwst / nirspec has opened a new window into understanding of ly $ \ alpha $ at z > 3. we present a sample of 12 uv - faint galaxies ( $ - 20 \ lesssim $ muv $ \ lesssim - 16 $ ) at $ 3 \ lesssim z \ lesssim 6 $, with ly $ \ alpha $ velocity offsets, $ \ delta v _ { \ mathrm { ly } \ alpha } $, measured from vlt / muse and jwst / nirspec from the glass - jwst early release program. we find median $ \ delta v _ { \ mathrm { ly } \ alpha } $ of 205 km s $ ^ { - 1 } $ and standard deviation 75 km s $ ^ { - 1 } $, compared to 320 and 170km s $ ^ { - 1 } $ for muv < - 20 galaxies in the literature. our new sample demonstrates the previously observed trend of decreasing ly $ \ alpha $ velocity offset with decreasing uv luminosity and optical line velocity dispersion, extends to muv $ \ gtrsim $ - 20, consistent with a picture where the ly $ \ alpha $ profile is shaped by gas close to the systemic redshift. our results imply that during reionization ly $ \ alpha $ from uv - faint galaxies will be preferentially attenuated, but that detecting ly $ \ alpha $ with low $ \ delta v _ { \ mathrm { ly } \ alpha } $ can be an indicator of large ionized bubbles. | arxiv:2304.02666 |
in this paper we present the first results of a detailed spectroscopic and photometric analysis of the v = 11. 7m eclipsing binary asas j052821 + 0338. 5. with the fies spectrograph at the nordic optical telescope we have obtained a series of high - resolution spectra ( r = 47000 ) covering the entire orbit of the system. in addition we obtained simultaneous broadband photometry from three small aperture telescopes. from these spectroscopic and photometric data we have derived the system ' s orbital parameters and determined the fundamental stellar parameters of the two components. our results indicate that asas j052821 + 0338. 5 is a k1 / k3 pre - main - sequence eclipsing binary, with component masses of 1. 38 m _ sun and 1. 33 m _ sun and a period of 3. 87 days, located at a distance of 280 + / - 30 pc. the kinematics, physical location and the evolutionary status of the two stars suggest that asas j052821 + 0338. 5 is a member of the approximately 11 myr old orion ob1a subassociation. the systems also exhibits smooth 0. 15m out - of - eclipse variations that are similar to those found in rs cvn binaries. furthermore the parameters we derived are consistent with the 10 - 13 myr isochrones of the popular baraffe stellar evolutionary models. | arxiv:0801.3927 |
within the framework of a relativistic transport model ( art ) for heavy - ion collisions at ags energies, we examine the effects of kaon dispersion relation on the transverse flow of kaons and their transverse momentum and azimuthal angle distributions. we find that the transverse flow is the most sensitive observable for studying the kaon dispersion relation in dense medium. | arxiv:nucl-th/9609019 |
we improve and generalize some operator inequalities for positive linear maps. it is shown, among other inequalities, that if $ 0 < m \ le b \ le m ' < m ' \ le a \ le m $ or $ 0 < m \ le a \ le m ' < m ' \ le b \ le m $, then for each $ 2 \ le p < \ infty $ and $ \ nu \ in \ left [ 0, 1 \ right ] $, \ begin { equation * } { { \ phi } ^ { p } } \ left ( a { { \ nabla } _ { \ nu } } b \ right ) \ le { { \ left ( \ frac { k \ left ( h \ right ) } { { { 4 } ^ { \ frac { 2 } { p } - 1 } } { { k } ^ { r } } \ left ( h ' \ right ) } \ right ) } ^ { p } } { { \ phi } ^ { p } } \ left ( a { { \ # } _ { \ nu } } b \ right ), \ end { equation * } and \ begin { equation * } { { \ phi } ^ { p } } \ left ( a { { \ nabla } _ { \ nu } } b \ right ) \ le { { \ left ( \ frac { k \ left ( h \ right ) } { { { 4 } ^ { \ frac { 2 } { p } - 1 } } { { k } ^ { r } } \ left ( h ' \ right ) } \ right ) } ^ { p } } { { \ left ( \ phi \ left ( a \ right ) { { \ # } _ { \ nu } } \ phi \ left ( b \ right ) \ right ) } ^ { p } }, \ end { equation * } where $ r = \ min \ left \ { \ nu, 1 - \ nu \ right \ } $, $ h = \ frac { m } { m } $ and $ h ' = \ frac { m ' } { m ' } $. we also obtain an improvement of operator p \ ' olya - szeg \ " o inequality. | arxiv:1701.03428 |
training a personalized dialogue system requires a lot of data, and the data collected for a single user is usually insufficient. one common practice for this problem is to share training dialogues between different users and train multiple sequence - to - sequence dialogue models together with transfer learning. however, current sequence - to - sequence transfer learning models operate on the entire sentence, which might cause negative transfer if different personal information from different users is mixed up. we propose a personalized decoder model to transfer finer granularity phrase - level knowledge between different users while keeping personal preferences of each user intact. a novel personal control gate is introduced, enabling the personalized decoder to switch between generating personalized phrases and shared phrases. the proposed personalized decoder model can be easily combined with various deep models and can be trained with reinforcement learning. real - world experimental results demonstrate that the phrase - level personalized decoder improves the bleu over multiple sentence - level transfer baseline models by as much as 7. 5 %. | arxiv:1711.04079 |
a significant challenge for predictive maintenance in the pulp - and - paper industry is the infrequency of paper breaks during the production process. in this article, operational data is analyzed from a paper manufacturing machine in which paper breaks are relatively rare but have a high economic impact. utilizing a dataset comprising 18, 398 instances derived from a quality assurance protocol, we address the scarcity of break events ( 124 cases ) that pose a challenge for machine learning predictive models. with the help of conditional generative adversarial networks ( ctgan ) and synthetic minority oversampling technique ( smote ), we implement a novel data augmentation framework. this method ensures that the synthetic data mirrors the distribution of the real operational data but also seeks to enhance the performance metrics of predictive modeling. before and after the data augmentation, we evaluate three different machine learning algorithms - decision trees ( dt ), random forest ( rf ), and logistic regression ( lr ). utilizing the ctgan - enhanced dataset, our study achieved significant improvements in predictive maintenance performance metrics. the efficacy of ctgan in addressing data scarcity was evident, with the models ' detection of machine breaks ( class 1 ) improving by over 30 % for decision trees, 20 % for random forest, and nearly 90 % for logistic regression. with this methodological advancement, this study contributes to industrial quality control and maintenance scheduling by addressing rare event prediction in manufacturing processes. | arxiv:2311.09333 |
this is the introductory part of my ph. d thesis, defended at the faculty of science and technology, ntnu on december 10, 2012. | arxiv:1304.2941 |
we study the schwinger mechanism in qcd in the presence of an arbitrary time - dependent chromo - electric background field $ e ^ a ( t ) $ with arbitrary color index $ a $ = 1, 2,... 8 in su ( 3 ). we obtain an exact result for the non - perturbative quark ( antiquark ) production from an arbitrary $ e ^ a ( t ) $ by directly evaluating the path integral. we find that the exact result is independent of all the time derivatives $ \ frac { d ^ ne ^ a ( t ) } { dt ^ n } $ where $ n = 1, 2,... \ infty $. this result has the same functional dependence on two casimir invariants $ [ e ^ a ( t ) e ^ a ( t ) ] $ and $ [ d _ { abc } e ^ a ( t ) e ^ b ( t ) e ^ c ( t ) ] ^ 2 $ as the constant chromo - electric field $ e ^ a $ result with the replacement : $ e ^ a \ rightarrow e ^ a ( t ) $. this result relies crucially on the validity of the shift conjecture, which has not yet been established. | arxiv:0705.2770 |
we propose a new method to define anomaly scores and apply this to particle physics collider events. anomalies can be either rare, meaning that these events are a minority in the normal dataset, or different, meaning they have values that are not inside the dataset. we quantify these two properties using an ensemble of one - class deep support vector data description models, which quantifies differentness, and an autoregressive flow model, which quantifies rareness. these two parameters are then combined into a single anomaly score using different combination algorithms. we train the models using a dataset containing only simulated collisions from the standard model of particle physics and test it using various hypothetical signals in four different channels and a secret dataset where the signals are unknown to us. the anomaly detection method described here has been evaluated in a summary paper [ 1 ] where it performed very well compared to a large number of other methods. the method is simple to implement and is applicable to other datasets in other fields as well. | arxiv:2106.10164 |
spin alignments of vector mesons and hyperons in relativistic heavy - ion collisions have been proposed as signals of the global polarization. the star experiment first observed the $ \ rm \ lambda $ polarization. recently, the alice collaboration measured the transverse momentum ( $ p _ t $ ) and the collision centrality dependence of $ k ^ * $ and $ \ phi $ spin alignments in pb - pb collisions at $ \ rm \ sqrt { s _ { nn } } $ = 2. 76 tev. a large signal is observed in the low $ p _ t $ region of mid - central collisions for $ k ^ * $ while the signal is much smaller for $ \ phi $, and these have not been understood yet. since vector mesons have different lifetimes and their decay products have different scattering cross sections, they suffer from different hadronic effects. in this paper, we study the effect of hadronic interactions on the spin alignment of $ k ^ * $, $ \ phi $ and $ \ rho $ mesons in relativistic heavy - ion collisions with a multi - phase transport model. we find that hadronic scatterings lead to a deviation of the observed spin alignment matrix element $ \ rho _ { 00 } $ away from the true value for $ \ rho $ and $ k ^ * $ mesons ( with a bigger effect on $ \ rho $ ) while the effect is negligible for the $ \ phi $ meson. the effect depends on the kinematic acceptance : the observed $ \ rho _ { 00 } $ value is lower than the true value when the pseudorapidity ( $ \ eta $ ) coverage is small while there is little effect when the $ \ eta $ coverage is big. our study thus provides valuable information to understand the vector meson spin alignment signals observed in the experiments. | arxiv:2102.05266 |
this paper explores the behaviour of malicious hacker groups operating in cyberspace and how they organize themselves in structured networks. to better understand these groups, the paper uses social network analysis ( sna ) to analyse the interactions and relationships among several malicious hacker groups. the study uses a tested dataset as its primary source, providing an empirical analysis of the cooperative behaviours exhibited by these groups. the study found that malicious hacker groups tend to form close - knit networks where they consult, coordinate with, and assist each other in carrying out their attacks. the study also identified a " small world " phenomenon within the population of malicious actors, which suggests that these groups establish interconnected relationships to facilitate their malicious operations. the small world phenomenon indicates that the actor - groups are densely connected, but they also have a small number of connections to other groups, allowing for efficient communication and coordination of their activities. | arxiv:2309.16442 |
the explosive wireless data service requirement accompanied with carbon dioxide emission and consumption of traditional energy has put pressure on both industry and academia. wireless networks powered with the uneven and intermittent generated renewable energy have been widely researched and lead to a new research paradigm called green communication. in this paper, we comprehensively consider the total generated renewable energy, qos requirement and channel quality, then propose a utility based renewable energy allocation policy. the utility here means the satisfaction degree of users with a certain amount allocated renewable energy. the energy allocation problem is formulated as a constraint optimization problem and a heuristic algorithm with low complexity is derived to solve the raised problem. numerical results show that the renewable energy allocation policy is applicable for any situation. when the renewable energy is very scarce, only users with good channel quality can achieve allocated energy. | arxiv:1612.03452 |
partial f } { \ partial z } } \ end { bmatrix } } = { \ begin { bmatrix } 4x ^ { 3 } & 4y ^ { 3 } & 4z ^ { 3 } \ end { bmatrix } }. } this has maximal rank at every point except for ( 0, 0, 0 ) { \ displaystyle ( 0, 0, 0 ) }. also, the fibers f − 1 ( { t } ) = { ( a, b, c ) ∈ r 3 : a 4 + b 4 + c 4 = t } { \ displaystyle f ^ { - 1 } ( \ { t \ } ) = \ left \ { ( a, b, c ) \ in \ mathbb { r } ^ { 3 } : a ^ { 4 } + b ^ { 4 } + c ^ { 4 } = t \ right \ } } are empty for t < 0 { \ displaystyle t < 0 }, and equal to a point when t = 0 { \ displaystyle t = 0 }. hence, we only have a smooth submersion f : r 3 ( 0, 0, 0 ) → r > 0, { \ displaystyle f \ colon \ mathbb { r } ^ { 3 } \ setminus { ( 0, 0, 0 ) } \ to \ mathbb { r } _ { > 0 }, } and the subsets m t = { ( a, b, c ) ∈ r 3 : a 4 + b 4 + c 4 = t } { \ displaystyle m _ { t } = \ left \ { ( a, b, c ) \ in \ mathbb { r } ^ { 3 } : a ^ { 4 } + b ^ { 4 } + c ^ { 4 } = t \ right \ } } are two - dimensional smooth manifolds for t > 0 { \ displaystyle t > 0 }. = = examples = = any projection π : r m + n → r n ⊂ r m + n { \ displaystyle \ pi \ colon \ mathbb { r } ^ { m + n } \ rightarrow \ mathbb { r } ^ { n } \ subset \ mathbb { r } ^ { m + n } } local diffeomorphisms riemannian submersions the projection in a smooth vector bundle or a more general smooth fibration. the surjectivity of the differential is a necessary condition for the | https://en.wikipedia.org/wiki/Submersion_(mathematics) |
we present a mass profile for a1689 from 0. 13 h ^ { - 1 } mpc < r < 2 h ^ { - 1 } mpc from a weak lensing analysis of a 34 ' x34 ' r - band image from the eso / mpg wide field imager. we detect the gravitational shearing of a 23 < r < 25. 5 background galaxy population even at the edge of the image with a 4 - sigma significance, and find a two - dimensional mass reconstruction has a 13. 4 - sigma significance mass peak centered on the brightest cluster galaxy. this peak is well fit by both a 1028 + - 35 km / s singular isothermal sphere and a r200 = 1. 28 mpc, c = 6 universal cdm profile, although the universal cdm profile provides a better fit with 95. 5 % confidence. these mass measurements are lower than most of those derived by other means and we discuss possible reasons for weak lensing providing an underestimate of the true mass of the cluster. we find that the correction factors needed to reconcile the weak lensing mass models with the strong lensing einstein radius would result is a much larger fraction of faint stars and foreground and cluster dwarf galaxies in the 23 < r < 25. 5 object catalog than is seen in other fields. | arxiv:astro-ph/0107433 |
of these cellular components. the different stages of mitosis all together define the mitotic phase of an animal cell cycle — the division of the mother cell into two genetically identical daughter cells. the cell cycle is a vital process by which a single - celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. after cell division, each of the daughter cells begin the interphase of a new cycle. in contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of dna replication followed by two divisions. homologous chromosomes are separated in the first division ( meiosis i ), and sister chromatids are separated in the second division ( meiosis ii ). both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. both are believed to be present in the last eukaryotic common ancestor. prokaryotes ( i. e., archaea and bacteria ) can also undergo cell division ( or binary fission ). unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. before binary fission, dna in the bacterium is tightly coiled. after it has uncoiled and duplicated, it is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. growth of a new cell wall begins to separate the bacterium ( triggered by ftsz polymerization and " z - ring " formation ). the new cell wall ( septum ) fully develops, resulting in the complete split of the bacterium. the new daughter cells have tightly coiled dna rods, ribosomes, and plasmids. = = = sexual reproduction and meiosis = = = meiosis is a central feature of sexual reproduction in eukaryotes, and the most fundamental function of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. two aspects of sexual reproduction, meiotic recombination and outcrossing, are likely maintained respectively by the adaptive advantages of recombinational repair of genomic dna damage and genetic complementation which masks the expression of deleterious recessive mutations. the beneficial effect of genetic complementation, derived from outcrossing ( cross - fertilization ) is also referred to as hybrid vigor or heterosis. charles | https://en.wikipedia.org/wiki/Biology |
an algorithm for simulating self - gravitating cosmological astrophysical fluids is presented. the advantages include a large dynamic range, parallelizability, high resolution per grid element and fast execution speed. the code is based on a finite volume flux conservative total - variation - diminishing ( tvd ) scheme for the shock capturing hydro, and an iterative multigrid solver for the gravity. the grid is a time dependent field, whose motion is described by a generalized potential flow. approximately constant mass per cell can be obtained, providing all the advantages of a lagrangian scheme. the grid deformation combined with appropriate limiting and smoothing schemes guarantees a regular and well behaved grid geometry, where nearest neighbor relationships remain constant. the full hydrodynamic fluid equations are implemented in the curvilinear moving grid, allowing for arbitrary fluid flow relative to the grid geometry. this combination retains all the advantages of the grid based schemes including high speed per fluid element and a rapid gravity solver. the current implementation is described, and empirical simulation results are presented. accurate execution speed calculations are given in terms of floating point operations per time step per grid cell. this code is freely available to the community. | arxiv:astro-ph/9704258 |
vector and vortex laser beams are desired in many applications and are usually created by manipulating the laser output or by inserting optical components in the laser cavity. distinctly, inserting liquid crystals into the laser cavity allows for extensive control over the emitted light due to their high susceptibility to external fields and birefringent nature. in this work we demonstrate diverse optical modes for lasing as enabled and stablised by topological birefringent soft matter structures using numerical modelling. we show diverse structuring of light - - with different 3d intensity and polarization profiles - - as realised by topological soft matter structures in radial nematic droplet, in 2d nematic cavities of different geometry and including topological defects with different charges and winding numbers, in arbitrary varying birefringence fields with topological defects and in pixelated birefringent profiles. we use custom written fdfd code to calculate emergent electromagnetic eigenmodes. control over lasing is of a particular interest aiming towards the creation of general intensity, polarization and topologically shaped laser beams. | arxiv:2211.06158 |
in this paper, a class of semilinear fractional elliptic equations associated to the spectral fractional dirichlet laplace operator is considered. we establish the existence of optimal solutions as well as a minimum principle of pontryagin type and the first order necessary optimality conditions of associated optimal control problems. second order conditions for optimality are also obtained for $ l ^ { \ infty } $ and $ l ^ 2 - $ local solutions under some structural assumptions. | arxiv:2304.13853 |
we performed extensive molecular dynamics simulations to obtain pressure - density phase diagram, orientational order parameter, pair correlation functions and translational diffusion coefficients of gay - berne fluids. different sets of parameters were employed for the gay - berne potential, in particular we studied the cases $ \ kappa ' = 5, 10, 15, 20 $ and $ \ kappa = 3 $, $ \ mu = 2 $, $ \ nu = 1 $ at different conditions of density and temperature. the structure was analyzed in terms of the order parameter and the pair correlation functions. we found that for the highest value $ \ kappa ' = 20 $ the region where pressure increases with density is significantly reduced at low temperatures ; additionally the pressure shows several decays with density as an indicative that several structural phases can take place. these effects are discussed in terms of the pair correlation functions. for higher temperatures the pressure shows only two decays for all $ \ kappa ' $ ' s studied. as this parameter increases its value those decays are shifted to lower densities. | arxiv:1911.07366 |
passive acoustic mapping ( pam ) is a promising tool for monitoring acoustic cavitation activities in the applications of ultrasound therapy. data - adaptive beamformers for pam have better image quality compared to the time exposure acoustics ( tea ) algorithms. however, the computational cost of data - adaptive beamformers is considerably expensive. in this work, we develop a deep beamformer based on a generative adversarial network, which can switch between different transducer arrays and reconstruct high - quality pam images directly from radio frequency ultrasound signals with low computational cost. the deep beamformer was trained on the dataset consisting of simulated and experimental cavitation signals of single and multiple microbubble clouds measured by different ( linear and phased ) arrays covering 1 - 15 mhz. we compared the performance of the deep beamformer to tea and three different data - adaptive beamformers using the simulated and experimental test dataset. compared with tea, the deep beamformer reduced the energy spread area by 18. 9 % - 65. 0 % and improved the image signal - to - noise ratio by 9. 3 - 22. 9 db in average for the different arrays in our data. compared to the data - adaptive beamformers, the deep beamformer reduced the computational cost by three orders of magnitude achieving 10. 5 ms image reconstruction speed in our data, while the image quality was as good as that of the data - adaptive beamformers. these results demonstrated the potential of the deep beamformer for high - resolution monitoring of microbubble cavitation activities for ultrasound therapy. | arxiv:2412.02327 |
we present the first systematic study of the stability of the structure and electrical properties of fecl $ _ 3 $ intercalated few - layer graphene to high levels of humidity and high temperature. complementary experimental techniques such as electrical transport, high resolution transmission electron microscopy and raman spectroscopy conclusively demonstrate the unforeseen stability of this transparent conductor to a relative humidity up to $ 100 \ % $ at room temperature for 25 days, to a temperature up to $ 150 \, ^ \ circ $ c in atmosphere and up to a temperature as high as $ 620 \, ^ \ circ $ c in vacuum, that is more than twice higher than the temperature at which the intercalation is conducted. the stability of fecl $ _ 3 $ intercalated few - layer graphene together with its unique values of low square resistance and high optical transparency, makes this material an attractive transparent conductor in future flexible electronic applications. | arxiv:1506.04907 |
this work proposes an extension of the 1 - d hilbert huang transform for the analysis of images. the proposed method consists in ( i ) adaptively decomposing an image into oscillating parts called intrinsic mode functions ( imfs ) using a mode decomposition procedure, and ( ii ) providing a local spectral analysis of the obtained imfs in order to get the local amplitudes, frequencies, and orientations. for the decomposition step, we propose two robust 2 - d mode decompositions based on non - smooth convex optimization : a " genuine 2 - d " approach, that constrains the local extrema of the imfs, and a " pseudo 2 - d " approach, which constrains separately the extrema of lines, columns, and diagonals. the spectral analysis step is based on prony annihilation property that is applied on small square patches of the imfs. the resulting 2 - d prony - huang transform is validated on simulated and real data. | arxiv:1404.7680 |
we introduce omnisource, a novel framework for leveraging web data to train video recognition models. omnisource overcomes the barriers between data formats, such as images, short videos, and long untrimmed videos for webly - supervised learning. first, data samples with multiple formats, curated by task - specific data collection and automatically filtered by a teacher model, are transformed into a unified form. then a joint - training strategy is proposed to deal with the domain gaps between multiple data sources and formats in webly - supervised learning. several good practices, including data balancing, resampling, and cross - dataset mixup are adopted in joint training. experiments show that by utilizing data from multiple sources and formats, omnisource is more data - efficient in training. with only 3. 5m images and 800k minutes videos crawled from the internet without human labeling ( less than 2 % of prior works ), our models learned with omnisource improve top - 1 accuracy of 2d - and 3d - convnet baseline models by 3. 0 % and 3. 9 %, respectively, on the kinetics - 400 benchmark. with omnisource, we establish new records with different pretraining strategies for video recognition. our best models achieve 80. 4 %, 80. 5 %, and 83. 6 top - 1 accuracies on the kinetics - 400 benchmark respectively for training - from - scratch, imagenet pre - training and ig - 65m pre - training. | arxiv:2003.13042 |
in nanomechanical photothermal absorption spectroscopy and microscopy, the measured substance becomes a part of the detection system itself, inducing a nanomechanical resonance frequency shift upon thermal relaxation. suspended, nanometer - thin ceramic or 2d material resonators are innately highly - sensitive thermal detectors of localized heat exchanges from substances on their surface or integrated into the resonator itself. consequently, the combined nanoresonator - analyte system is a self - measuring spectrometer and microscope : responding to a substances transfer of heat over the entire spectrum for which it absorbs, according to the intensity it experiences. limited by their own thermostatistical fluctuation phenomena, nanoresonators have demonstrated sufficient sensitivity for measuring trace analyte as well as single particles and molecules with incoherent light or focused and unfocused coherent light. they are versatile in their design, support various sampling methods and hyphenation with other spectroscopic methods, and are capable in a wide range of applications including fingerprinting, separation science, and surface sciences. | arxiv:2306.16057 |
clinical guidelines recommend maintaining serum potassium levels between 4. 0 and 5. 0 meq / l in patients with acute myocardial infarction ( mi ). these guidelines are based on recent studies that found significant associations between crossing of absolute potassium limits ( by in - hospital mean or by min / max values ) and mortality. this paper investigates a different approach : we hypothesized that a change in the potassium level may be a harbinger of short survivability, rather than crossing of absolute boundaries. our objectives were : ( 1 ) to examine if a " change in mean " indicator has the ability to distinguish between survivors and non - survivors of mi hospitalization, and if so, ( 2 ) to formulate a framework for detecting life - threatening changes in potassium level of patients hospitalized with mi. the study included 195 patients who were hospitalized for mi from 2002 to 2014, with at least 40 potassium measurements ( i. e., severely ill ). in a retrospective analysis we found evidence that the " change in mean " criterion significantly discriminated between survivors and non - survivors. a threshold for raising an alarm was specified by plotting an roc curve and choosing the value that yields the best combination of sensitivity and specificity. in this case, the method detected ~ 80 % of the patients that eventually died, while wrongly alerting for only ~ 40 % of the survivors. the proposed approach is not intended for replacing the absolute - level protocols but to add valuable knowledge to cardiologists. | arxiv:1602.06717 |
in this paper we study the representation theory of three monoids of partial functions on an $ n $ - set. the monoid of all order - preserving functions ( i. e., functions satisfying $ f ( x ) \ leq f ( y ) $ if $ x \ leq y $ ) the monoid of all order - decreasing functions ( i. e. functions satisfying $ f ( x ) \ leq x $ ) and their intersection ( also known as the partial catalan monoid ). we use an isomorphism between the algebras of these monoids and the algebras of some corresponding locally trivial categories. we obtain an explicit description of a quiver presentation for each algebra. moreover, we describe other invariants such as the cartan matrix and the loewy length. | arxiv:1812.01300 |
this report discusses a recently developed concept of limiting phase trajectories ( lpts ) providing a unified description of resonant energy transport in a wide range of classical and quantum dynamical systems with constant and time - varying parameters. it is shown that strongly modulated non - stationary processes occurring in a nonlinear oscillator array under certain initial conditions may characterize either maximum possible energy exchange between the clusters of oscillators ( effective particles ) or maximum energy transfer from an external source of energy to the system. the trajectories corresponding to these processes are referred to as lpts. the development and the use of the lpt concept are motivated by the fact that highly non - stationary resonance processes occurring in a broad variety of finite - dimensional physical models are beyond the well - known paradigm of the nonlinear normal modes ( nnms ), fully justified only for stationary processes, their stability and bifurcations, as well as for non - stationary processes described approximately by some combinations of non - resonating normal modes. thus, the role of lpts in understanding and description of non - stationary energy transfer is similar to the role of nnms for the stationary processes. several applications of the lpt concept to significant nonlinear problems and a scenario of the transition from regular to chaotic behavior with the lpts implication are presented. in order to highlight the novelty and perspectives of the developed approach, we place the lpt concept into the context of complex dynamical phenomena related to energy transfer problems. | arxiv:1605.09264 |
based on classical transport theory, we present a general set of covariant equations describing the dynamics of mean fields and their statistical fluctuations in a non - abelian plasma in or out - of - equilibrium. a procedure to obtain the collision integrals for the boltzmann equation from the microscopic theory is described. as an application, we study a hot non - abelian plasma close to equilibrium, where the fluctuations are integrated out explicitly. for soft fields, and at logarithmic accuracy, we obtain b \ " odeker ' s effective theory. | arxiv:hep-ph/9902430 |
we concentrate on several relatively new aspects of the study of fast electron scattering by atoms and atom - like objects, namely endohedral atoms and fullerenes. we show that the corresponding cross sections, being expressed via so - called generalized oscillator strengths ( gos ), give information on the electronic structure of the target and on the role of electron correlations in it. we consider what sort of information became available when analyzing the dependence of gos upon their multipolarity, transferred momentum and energy. we demonstrate the role of nondipole corrections in the small - angle fast - electron inelastic scattering. there dipole contribution dominates while non - dipole corrections can be considerably and controllably enhanced as compared to the case of low and medium energy photoionization. we show also that analyses of gos for discrete level excitations permit to clarify their multipolarity. the results of calculations of compton excitation and ionization cross - sections for noble gas atoms are presented. attention is given to cooperative effects in inelastic fast electron - atom scattering that results in directed motion of the secondary electrons, a phenomenon that is similar to drag currents in photoionization. we demonstrate how one should derive gos for endohedral atoms, e. g. a @ c60 and what is the additional information that can be obtained from corresponding gos. most of discussions are illustrated by the results of concrete calculations. | arxiv:physics/0611218 |
we prove the existence of local - in - time smooth solutions of the incompressible semi - geostrophic equations expressed in eulerian co - ordinates in 3 - dimensional smooth bounded simply - connected domains. our solutions adhere to cullen ' s stability principle in that the geopotential is guaranteed to be a convex map for all times of its existence. we achieve our results by appealing to the theory of so - called div - curl systems ( or hodge systems ), making use of recent results of wang, which yield useful estimates on the ageostrophic velocity field. to our knowledge, this work constitutes the first time that any notion of bounded solution of the semi - geostrophic equations in eulerian co - ordinates has been constructed on a bounded domain. indeed, our work solves an open problem as highlighted by, among others, a. figalli in his cime lectures on the semi - geostrophic equations. our methods are largely elementary. we discuss the application of the novel ideas in this work to the case of variable coriolis force in the final section of the article. | arxiv:1807.01006 |
when obtaining visual illustrations from text descriptions, today ' s methods take a description with - a single text context caption, or an action description - and retrieve or generate the matching visual context. however, prior work does not permit visual illustration of multistep descriptions, e. g. a cooking recipe composed of multiple steps. furthermore, simply handling each step description in isolation would result in an incoherent demonstration. we propose stitch - a - recipe, a novel retrieval - based method to assemble a video demonstration from a multistep description. the resulting video contains clips, possibly from different sources, that accurately reflect all the step descriptions, while being visually coherent. we formulate a training pipeline that creates large - scale weakly supervised data containing diverse and novel recipes and injects hard negatives that promote both correctness and coherence. validated on in - the - wild instructional videos, stitch - a - recipe achieves state - of - the - art performance, with quantitative gains up to 24 % as well as dramatic wins in a human preference study. | arxiv:2503.13821 |
bismuth - gallium co - doped silica glass fiber preform was prepared from nano - porous silica xerogels using a conventional solution doping technique with a heterotrinuclear complex and subsequent sintering. ga - connected optical bismuth active center ( bac ) was identified as the analogue of al - connected bac. visible and infrared photoluminescence ( pl ) were investigated in a wide temperature range of 1. 46 - 300 k. based on the results of the continuous wave ( cw ) and time resolved spectroscopy we identify the centers emitting in the spectral region of 480 - 820 nm as bi $ ^ + $ ions. the near infrared ( nir ) pl around 1100 nm consists of two bands. while the first one can be ascribed to the transition in bi $ ^ + $ ion, the second band is presumably associated to defects. we put in evidence the energy transfer between bi $ ^ + $ ions and the second nir emitting center via quadrupole - quadrupole and dipole - quadrupole mechanisms of interactions. finally, we propose the energy level diagram of bi $ ^ + $ ion interacting with this defect. | arxiv:1305.3428 |
let $ \ g $ be a finite dimensional lie algebra over a field $ k $ of characteristic zero. an element $ x $ of $ \ g $ is said to have an \ emph { abstract jordan - chevalley decomposition } if there exist unique $ s, n \ in \ g $ such that $ x = s + n $, $ [ s, n ] = 0 $ and given any finite dimensional representation $ \ pi : \ g \ to \ gl ( v ) $ the jordan - chevalley decomposition of $ \ pi ( x ) $ in $ \ gl ( v ) $ is $ \ pi ( x ) = \ pi ( s ) + \ pi ( n ) $. in this paper we prove that $ x \ in \ g $ has an abstract jordan - chevalley decomposition if and only if $ x \ in [ \ g, \ g ] $, in which case its semisimple and nilpotent parts are also in $ [ \ g, \ g ] $ and are explicitly determined. we derive two immediate consequences : ( 1 ) every element of $ \ g $ has an abstract jordan - chevalley decomposition if and only if $ \ g $ is perfect ; ( 2 ) if $ \ g $ is a lie subalgebra of $ \ gl ( n, k ) $ then $ [ \ g, \ g ] $ contains the semisimple and nilpotent parts of all its elements. the last result was first proved by bourbaki using different methods. our proof only uses elementary linear algebra and basic results on the representation theory of lie algebras, such as the invariance lemma and lie ' s theorem, in addition to the fundamental theorems of ado and levi. | arxiv:1008.1217 |
we apply general difference calculus in order to obtain solutions to the functional equations of the second order. we show that factorization method can be successfully applied to the functional case. this method is equivariant under the change of variables. some examples of applications are presented. | arxiv:math-ph/0208006 |
the pluripolar hull of a pluripolar set e in $ \ mathbb { p } ^ n $ is the intersection of all complete pluripolar sets in $ \ mathbb { p } ^ n $ that contain $ e $. we prove that the pluripolar hull of each compact pluripolar set in $ \ mathbb { p } ^ n $ is $ f _ \ sigma $. the convergence set of a divergent formal power series $ f ( z _ { 0 }, \ dots, z _ { n } ) $ is the set of all " directions " $ \ xi \ in \ mathbb { p } ^ { n } $ along which $ f $ is convergent. we prove that the union of the pluripolar hulls of a countable collection of compact pluripolar sets in $ \ mathbb { p } ^ n $ is the convergence set of some divergent series $ f $. the convergence sets on $ \ gamma : = \ { [ 1 : z : \ psi ( z ) ] : z \ in \ mathbb { c } \ } \ subset \ mathbb { c } ^ 2 \ subset \ mathbb { p } ^ 2 $, where $ \ psi $ is a transcendental entire holomorphic function, are also studied and we obtain that a subset on $ \ gamma $ is a convergence set in $ \ mathbb { p } ^ 2 $ if and only if it is a countable union of compact projectively convex sets, and hence the union of a countable collection of convergence sets on $ \ gamma $ is a convergence set. | arxiv:1710.08827 |
inspired by a width invariant on permutations defined by guillemot and marx, bonnet, kim, thomass \ ' e, and watrigant introduced the twin - width of graphs, which is a parameter describing its structural complexity. this invariant has been further extended to binary structures, in several ( basically equivalent ) ways. we prove that a class of binary relational structures ( that is : edge - colored partially directed graphs ) has bounded twin - width if and only if it is a first - order transduction of a ~ proper permutation class. as a by - product, we show that every class with bounded twin - width contains at most $ 2 ^ { o ( n ) } $ pairwise non - isomorphic $ n $ - vertex graphs. | arxiv:2102.06880 |
in inverse rendering, accurately modeling visibility and indirect radiance for incident light is essential for capturing secondary effects. due to the absence of a powerful gaussian ray tracer, previous 3dgs - based methods have either adopted a simplified rendering equation or used learnable parameters to approximate incident light, resulting in inaccurate material and lighting estimations. to this end, we introduce inter - reflective gaussian splatting ( irgs ) for inverse rendering. to capture inter - reflection, we apply the full rendering equation without simplification and compute incident radiance on the fly using the proposed differentiable 2d gaussian ray tracing. additionally, we present an efficient optimization scheme to handle the computational demands of monte carlo sampling for rendering equation evaluation. furthermore, we introduce a novel strategy for querying the indirect radiance of incident light when relighting the optimized scenes. extensive experiments on multiple standard benchmarks validate the effectiveness of irgs, demonstrating its capability to accurately model complex inter - reflection effects. | arxiv:2412.15867 |
learning sophisticated feature interactions behind user behaviors is critical in maximizing ctr for recommender systems. despite great progress, existing methods seem to have a strong bias towards low - or high - order interactions, or require expertise feature engineering. in this paper, we show that it is possible to derive an end - to - end learning model that emphasizes both low - and high - order feature interactions. the proposed model, deepfm, combines the power of factorization machines for recommendation and deep learning for feature learning in a new neural network architecture. compared to the latest wide \ & deep model from google, deepfm has a shared input to its " wide " and " deep " parts, with no need of feature engineering besides raw features. comprehensive experiments are conducted to demonstrate the effectiveness and efficiency of deepfm over the existing models for ctr prediction, on both benchmark data and commercial data. | arxiv:1703.04247 |
this paper aims to characterize rank - one arithmetic and locally symmetric metrics in the coarsely geometric setting using coarse - geometric commensurators. we provide a positive answer in general under the hilbert - smith conjecture and unconditionally for finite volume negatively curved manifolds with finitely many cusps. | arxiv:2412.07614 |
in this paper, we propose a deep multimodal fusion network to fuse multiple modalities ( face, iris, and fingerprint ) for person identification. the proposed deep multimodal fusion algorithm consists of multiple streams of modality - specific convolutional neural networks ( cnns ), which are jointly optimized at multiple feature abstraction levels. multiple features are extracted at several different convolutional layers from each modality - specific cnn for joint feature fusion, optimization, and classification. features extracted at different convolutional layers of a modality - specific cnn represent the input at several different levels of abstract representations. we demonstrate that an efficient multimodal classification can be accomplished with a significant reduction in the number of network parameters by exploiting these multi - level abstract representations extracted from all the modality - specific cnns. we demonstrate an increase in multimodal person identification performance by utilizing the proposed multi - level feature abstract representations in our multimodal fusion, rather than using only the features from the last layer of each modality - specific cnns. we show that our deep multi - modal cnns with multimodal fusion at several different feature level abstraction can significantly outperform the unimodal representation accuracy. we also demonstrate that the joint optimization of all the modality - specific cnns excels the score and decision level fusions of independently optimized cnns. | arxiv:1807.01332 |
collisionless space plasma environments are typically characterised by distinct particle populations. although moments of their velocity distribution functions help in distinguishing different plasma regimes, the distribution functions themselves provide more comprehensive information about the plasma state, especially at times when the distribution function includes non - thermal effects. unlike moments, however, distribution functions are not easily characterised by a small number of parameters, making their classification more difficult to achieve. in order to perform this classification, we propose to distinguish between the different plasma regions by applying dimensionality reduction and clustering methods to electron distributions in pitch angle and energy space. we utilise four separate algorithms to achieve our plasma classifications : autoencoders, principal component analysis, mean shift, and agglomerative clustering. we test our classification algorithms by applying our scheme to data from the cluster - peace instrument measured in the earth ' s magnetotail. traditionally, it is thought that the earth ' s magnetotail is split into three different regions ( the plasma sheet, the plasma sheet boundary layer, and the lobes ), that are primarily defined by their plasma characteristics. starting with the eclat database with associated classifications based on the plasma parameters, we identify 8 distinct groups of distributions, that are dependent upon significantly more complex plasma and field dynamics. by comparing the average distributions as well as the plasma and magnetic field parameters for each region, we relate several of the groups to different plasma sheet populations, and the rest we attribute to the plasma sheet boundary layer and the lobes. we find clear distinctions between each of our classified regions and the eclat results. | arxiv:2009.10466 |
we study the eta - invariant, defined by atiyah - patodi - singer a real valued invariant of an oriented odd - dimensional riemannian manifold equipped with a unitary representation of its fundamental group. when the representation varies analytically, the corresponding eta - invariant may have an integral jump, known also as the spectral flow. the main result of the paper establishes a formula for this spectral jump in terms of the signatures of some homological forms, defined naturally by the path of representations. these signatures may also be computed by means of a spectral sequence of hermitian forms, defined by the deformation data. our theorem on the spectral jump has a generalization to arbitrary analytic families of self - adjoint elliptic operators. as an application we consider the problem of homotopy invariance of the rho - invariant. we give an intrinsic homotopy theoretic definition of the rho - invariant, up to indeterminacy in the form of a locally constant function on the space of unitary representations. in an appendix, written by s. weinberger, it is shown ( using the results of this paper ) that the difference in the rho - invariants of homotopy - equivalent manifolds is always rational. | arxiv:dg-ga/9407008 |
the anomalous low energy behaviour observed in metals with strong electron correlation, such as in the heavy fermion materials, is believed to arise from the scattering of the itinerant electrons with low energy spin fluctuations. in systems with magnetic impurities this scattering leads to the kondo effect and a low energy renormalized energy scale, the kondo temperature $ t _ { \ rm k } $. it has been generally assumed that these low energy scales can only be accessed by a non - perturbative approach due to the strength of the local inter - electron interactions. here we show that it is possible to circumvent this difficulty by first suppressing the spin fluctuations with a large magnetic field. as a first step field - dependent renormalized parameters are calculated using standard perturbation theory. a renormalized perturbation theory is then used to calculate the renormalized parameters for a reduced magnetic field strength. the process can be repeated and the flow of the renormalized parameters continued to zero magnetic field. we illustrate the viability of this approach for the single impurity anderson model. the results for the renormalized parameters, which flow as a function of magnetic field, can be checked with those from numerical renormalization group and bethe ansatz calculations. | arxiv:1101.2840 |
an upper bound for the number of hamiltonian cycles of symmetric diagraphs is established first in this paper, which is tighter than the famous minc ' s bound and the br $ \ acute { e } $ gman ' s bound. a transformation on graphs is proposed, so that counting the number of hamiltonian cycles of an undirected graph can be done by counting the number of hamiltonian cycles of its corresponding symmetric directed graph. in this way, an upper bound for the number of hamiltonian cycles of undirected graphs is also obtained. | arxiv:0712.0616 |
the method of multidimensional susy quantum mechanics is applied to the investigation of supersymmetrical n - particle systems on a line for the case of separable center - of - mass motion. new decompositions of the superhamiltonian into block - diagonal form with elementary matrix components are constructed. matrices of coefficients of these minimal blocks are shown to coincide with matrices of irreducible representations of permutations group s _ n, which correspond to the young tableaux ( n - m, 1 ^ m ). the connections with known generalizations of n - particle calogero and sutherland models are established. | arxiv:quant-ph/0001063 |
congenital anomalies arising as a result of a defect in the structure of the heart and great vessels are known as congenital heart diseases or chds. a pcg can provide essential details about the mechanical conduction system of the heart and point out specific patterns linked to different kinds of chd. this study aims to investigate the minimum signal duration required for the automatic classification of heart sounds. this study also investigated the optimum signal quality assessment indicator ( root mean square of successive differences ) rmssd and ( zero crossings rate ) zcr value. mel - frequency cepstral coefficients ( mfccs ) based feature is used as an input to build a transformer - based residual one - dimensional convolutional neural network, which is then used for classifying the heart sound. the study showed that 0. 4 is the ideal threshold for getting suitable signals for the rmssd and zcr indicators. moreover, a minimum signal length of 5s is required for effective heart sound classification. it also shows that a shorter signal ( 3 s heart sound ) does not have enough information to categorize heart sounds accurately, and the longer signal ( 15 s heart sound ) may contain more noise. the best accuracy, 93. 69 %, is obtained for the 5s signal to distinguish the heart sound. | arxiv:2404.00470 |
we experimentally demonstrate novel structures for the realisation of registers of atomic qubits : we trap neutral atoms in one and two - dimensional arrays of far - detuned dipole traps obtained by focusing a red - detuned laser beam with a microfabricated array of microlenses. we are able to selectively address individual trap sites due to their large lateral separation of 125 mu m. we initialize and read out different internal states for the individual sites. we also create two interleaved sets of trap arrays with adjustable separation, as required for many proposed implementations of quantum gate operations. | arxiv:quant-ph/0110140 |
we study single - qutrit gates composed of clifford and $ t $ gates, using the qutrit version of the $ t $ gate proposed by howard and vala. we propose a normal form for single - qutrit gates analogous to the matsumoto - amano normal form for qubits. we prove that the normal form is optimal with respect to the number of $ t $ gates used and that any string of qutrit clifford + $ t $ operators can be put into this normal form in polynomial time. we also prove that this form is unique and provide an algorithm for exact synthesis of any single qutrit clifford + $ t $ operator. | arxiv:1803.03228 |
deep neural networks ( dnn ) have an impressive ability to invert very complex models, i. e. to learn the generative parameters from a model ' s output. once trained, the forward pass of a dnn is often much faster than traditional, optimization - based methods used to solve inverse problems. this is however done at the cost of lower interpretability, a fundamental limitation in most medical applications. we propose an approach for solving general inverse problems which combines the efficiency of dnn and the interpretability of traditional analytical methods. the measurements are first projected onto a dense dictionary of model - based responses. the resulting sparse representation is then fed to a dnn with an architecture driven by the problem ' s physics for fast parameter learning. our method can handle generative forward models that are costly to evaluate and exhibits similar performance in accuracy and computation time as a fully - learned dnn, while maintaining high interpretability and being easier to train. concrete results are shown on an example of model - based brain parameter estimation from magnetic resonance imaging ( mri ). | arxiv:2107.10657 |
wide field planetary camera 2 ( wfpc2 ) exposures are already some 20 years older than gaia epoch observations, or future jwst observations. as such, they offer an unprecedented time baseline for high - precision proper - motion studies, provided the full astrometric potential of these exposures is reached. we have started such a project with the work presented here being its first step. we explore geometric distortions beyond the well - known ones published in the early 2000s. this task is accomplished by using the entire database of wfpc2 exposures in filters f555w, f606w and f814w and three standard astrometric catalogs : gaia edr3, 47 tuc and $ \ omega $ cen. the latter two were constructed using hst observations made with cameras other than wfpc2. we explore a suite of centering algorithms, and various distortion maps in order to understand and quantify their performance. we find no high - frequency systematics beyond the 34th - row correction, down to a resolution of 10 pixels. low - frequency systematics starting at a resolution of 50 - pixels are present at a level of 30 - 50 millipix ( 1. 4 - 2. 3 mas ) for the pc and 20 - 30 millipix ( 2 - 3 mas ) for the wf chips. we characterize these low - frequency systematics by providing correction maps and updated cubic - distortion coefficients for each filter. | arxiv:2105.02330 |
multiple scattering of waves in disordered media is a nightmare whether it be for detection or imaging purposes. the best approach so far to get rid of multiple scattering is optical coherence tomography. it basically combines confocal microscopy and coherence time - gating to discriminate ballistic photons from a predominant multiple scattering background. nevertheless, the imaging depth range remains limited to 1 mm at best in human soft tissues. here we propose a matrix approach of optical imaging to push back this fundamental limit. by combining a matrix discrimination of ballistic waves and iterative time - reversal, we show both theoretically and experimentally an extension of the imaging - depth limit by at least a factor two compared to optical coherence tomography. in particular, the reported experiment demonstrates imaging through a strongly scattering layer from which only one reflected photon over 1000 billion is ballistic. this approach opens a new route towards ultra - deep tissue imaging. | arxiv:1510.08613 |
robots are becoming increasingly essential for traversing complex environments such as disaster areas, extraterrestrial terrains, and marine environments. yet, their potential is often limited by mobility and adaptability constraints. in nature, various animals have evolved finely tuned designs and anatomical features that enable efficient locomotion in diverse environments. sea turtles, for instance, possess specialized flippers that facilitate both long - distance underwater travel and adept maneuvers across a range of coastal terrains. building on the principles of embodied intelligence and drawing inspiration from sea turtle hatchings, this paper examines the critical interplay between a robot ' s physical form and its environmental interactions, focusing on how morphological traits and locomotive behaviors affect terrestrial navigation. we present a bio - inspired robotic system and study the impacts of flipper / body morphology and gait patterns on its terrestrial mobility across diverse terrains ranging from sand to rocks. evaluating key performance metrics such as speed and cost of transport, our experimental results highlight adaptive designs as crucial for multi - terrain robotic mobility to achieve not only speed and efficiency but also the versatility needed to tackle the varied and complex terrains encountered in real - world applications. | arxiv:2405.13948 |
a geometric approach to the friction phenomena is presented. it is based on the holographic view which has recently been popular in the theoretical physics community. we see the system in one - dimension - higher space. the heat - producing phenomena are most widely treated by using the non - equilibrium statistical physics. we take 2 models of the earthquake. the dissipative systems are here formulated from the geometric standpoint. the statistical fluctuation is taken into account by using the ( generalized ) feynman ' s path - integral. | arxiv:1404.6627 |
we study the effect of a chern - simons term in a theory with discrete gauge group h, which in ( 2 + 1 ) - dimensional space time describes ( non - abelian ) anyons. as in a previous paper, we emphasize the underlying algebraic structure, namely the hopf algebra d ( h ). we argue on physical grounds that the addition of a chern - simons term in the action leads to a non - trivial 3 - cocycle on d ( h ). accordingly, the physically inequivalent models are labelled by the elements of the cohomology group h ^ 3 ( h, u ( 1 ) ). it depends periodically on the coefficient of the chern - simons term which model is realized. this establishes a relation with the discrete topological field theories of dijkgraaf and witten. some representative examples are worked out explicitly. | arxiv:hep-th/9203047 |
detection of the radiation emitted from some of the earliest galaxies will be made possible in the next decade, with the launch of the james webb space telescope ( jwst ). a significant fraction of these galaxies may host population ( pop ) iii star clusters. the detection of the recombination radiation emitted by such clusters would provide an important new constraint on the initial mass function ( imf ) of primordial stars. here i review the expected recombination line signature of pop iii stars, and present the results of cosmological radiation hydrodynamics simulations of the initial stages of pop iii starbursts in a first galaxy at z ~ 12, from which the time - dependent luminosities and equivalent widths of imf - sensitive recombination lines are calculated. while it may be unfeasible to detect the emission from pop iii star clusters in the first galaxies at z > 10, even with next generation telescopes, pop iii star clusters which form at lower redshifts ( i. e. at z < 6 ) may be detectable in deep surveys by the jwst. | arxiv:1003.5311 |
the discovery of large number of cepheid variables in far - off galaxies offers a unique opportunity to determine the accurate distance of the host galaxy through their period - luminosity relation. the main aim of the present study is to identify short - period and relatively faint cepheids in the crowded field of m31 disk which was observed as part of the nainital microlensing survey. the cousins r and i - band photometric observations were obtained with a 1 - m telescope on more than 150 nights over the period between november 1998 to january 2002. the data was analysed using the pixel technique and the mean magnitudes of the cepheids were determined by correlating their pixel fluxes with the corresponding psf - fitted photometric magnitudes. here, we report identification of 39 short - period cepheid variables in the m31 disk. most of the cepheids are found with r ( mean ) ~ 20 - 21 mag and the dense phase coverage of our observations enabled us to identify cepheids with periods as short as 3. 4 days the frequency - period distribution of these cepheids peaks at logp ~ 0. 9 and 1. 1 days. | arxiv:0912.5415 |
a city under french control. in 1912, ramanujan moved with his wife and mother to a house in saiva muthaiah mudali street, george town, madras, where they lived for a few months. in may 1913, upon securing a research position at madras university, ramanujan moved with his family to triplicane. = = = pursuit of career in mathematics = = = in 1910, ramanujan met deputy collector v. ramaswamy aiyer, who founded the indian mathematical society. wishing for a job at the revenue department where aiyer worked, ramanujan showed him his mathematics notebooks. as aiyer later recalled : i was struck by the extraordinary mathematical results contained in [ the notebooks ]. i had no mind to smother his genius by an appointment in the lowest rungs of the revenue department. aiyer sent ramanujan, with letters of introduction, to his mathematician friends in madras. some of them looked at his work and gave him letters of introduction to r. ramachandra rao, the district collector for nellore and the secretary of the indian mathematical society. rao was impressed by ramanujan ' s research but doubted that it was his own work. ramanujan mentioned a correspondence he had with professor saldhana, a notable bombay mathematician, in which saldhana expressed a lack of understanding of his work but concluded that he was not a fraud. ramanujan ' s friend c. v. rajagopalachari tried to quell rao ' s doubts about ramanujan ' s academic integrity. rao agreed to give him another chance, and listened as ramanujan discussed elliptic integrals, hypergeometric series, and his theory of divergent series, which rao said ultimately convinced him of ramanujan ' s brilliance. when rao asked him what he wanted, ramanujan replied that he needed work and financial support. rao consented and sent him to madras. he continued his research with rao ' s financial aid. with aiyer ' s help, ramanujan had his work published in the journal of the indian mathematical society. one of the first problems he posed in the journal was to find the value of : 1 + 2 1 + 3 1 + { \ displaystyle { \ sqrt { 1 + 2 { \ sqrt { 1 + 3 { \ sqrt { 1 + \ cdots } } } } } } } he waited for a solution to be offered in three issues, over six months, but failed to receive any | https://en.wikipedia.org/wiki/Srinivasa_Ramanujan |
we construct here the parametric representation of a translation - invariant renormalizable scalar model on the noncommutative moyal space of even dimension $ d $. this representation of the feynman amplitudes is based on some integral form of the noncommutative propagator. all types of graphs ( planar and non - planar ) are analyzed. the r \ ^ ole played by noncommutativity is explicitly shown. this parametric representation established allows to calculate the power counting of the model. furthermore, the space dimension $ d $ is just a parameter in the formulas obtained. this paves the road for the dimensional regularization of this noncommutative model. | arxiv:0807.2779 |
we show how quantum many - body systems on hyperbolic lattices with nearest - neighbor hopping and local interactions can be mapped onto quantum field theories in continuous negatively curved space. the underlying lattices have recently been realized experimentally with superconducting resonators and therefore allow for a table - top quantum simulation of quantum physics in curved background. our mapping provides a computational tool to determine observables of the discrete system even for large lattices, where exact diagonalization fails. as an application and proof of principle we quantitatively reproduce the ground state energy, spectral gap, and correlation functions of the noninteracting lattice system by means of analytic formulas on the poincar \ ' { e } disk, and show how conformal symmetry emerges for large lattices. this sets the stage for studying interactions and disorder on hyperbolic graphs in the future. importantly, our analysis reveals that even relatively small discrete hyperbolic lattices emulate the continuous geometry of negatively curved space, and thus can be used to experimentally resolve fundamental open problems at the interface of interacting many - body systems, quantum field theory in curved space, and quantum gravity. | arxiv:1910.12318 |
atmospheric parameters and oxygen abundances of 825 nearby fgk stars are derived using high - quality spectra and a non - lte analysis of the 777 nm o i triplet lines. we assign a kinematic probability for the stars to be thin - disk ( p1 ), thick - disk ( p2 ), and halo ( p3 ) members. we confirm previous findings of enhanced [ o / fe ] in thick - disk ( p2 > 0. 5 ) relative to thin - disk ( p1 > 0. 5 ) stars with [ fe / h ] < - 0. 2, as well as a " knee " that connects the mean [ o / fe ] - [ fe / h ] trend of thick - disk stars with that of thin - disk members at [ fe / h ] > - 0. 2. nevertheless, we find that the kinematic membership criterion fails at separating perfectly the stars in the [ o / fe ] - [ fe / h ] plane, even when a very restrictive kinematic separation is employed. stars with " intermediate " kinematics ( p1 < 0. 7, p2 < 0. 7 ) do not all populate the region of the [ o / fe ] - [ fe / h ] plane intermediate between the mean thin - disk and thick - disk trends, but their distribution is not necessarily bimodal. halo stars ( p3 > 0. 5 ) show a large star - to - star scatter in [ o / fe ] - [ fe / h ], but most of it is due to stars with galactocentric rotational velocity v < - 200 km / s ; halo stars with v > - 200 km / s follow an [ o / fe ] - [ fe / h ] relation with almost no star - to - star scatter. early mergers with satellite galaxies explain most of our observations, but the significant fraction of disk stars with " ambiguous " kinematics and abundances suggests that scattering by molecular clouds and radial migration have both played an important role in determining the kinematic and chemical properties of solar neighborhood stars. | arxiv:1301.1582 |
for each $ 1 \ leq n \ leq6 $ we present formulas for the number of $ n - $ nodal curves in an $ n - $ dimensional linear system on a smooth, projective surface. this yields in particular the numbers of rational curves in the system of hyperplane sections of a generic $ k3 - $ surface imbedded in \ p { n } by a complete system of curves of genus $ n $ as well as the number { \ bf17, 601, 000 } of rational ( { \ em singular } ) plane quintic curves in a generic quintic threefold. | arxiv:alg-geom/9312012 |
archaeology has long faced fundamental issues of sampling and scalar representation. traditionally, the local - to - regional - scale views of settlement patterns are produced through systematic pedestrian surveys. recently, systematic manual survey of satellite and aerial imagery has enabled continuous distributional views of archaeological phenomena at interregional scales. however, such ' brute force ' manual imagery survey methods are both time - and labor - intensive, as well as prone to inter - observer differences in sensitivity and specificity. the development of self - supervised learning methods offers a scalable learning scheme for locating archaeological features using unlabeled satellite and historical aerial images. however, archaeological features are generally only visible in a very small proportion relative to the landscape, while the modern contrastive - supervised learning approach typically yields an inferior performance on highly imbalanced datasets. in this work, we propose a framework to address this long - tail problem. as opposed to the existing contrastive learning approaches that treat the labelled and unlabeled data separately, our proposed method reforms the learning paradigm under a semi - supervised setting in order to utilize the precious annotated data ( < 7 % in our setting ). specifically, the highly unbalanced nature of the data is employed as the prior knowledge in order to form pseudo negative pairs by ranking the similarities between unannotated image patches and annotated anchor images. in this study, we used 95, 358 unlabeled images and 5, 830 labelled images in order to solve the issues associated with detecting ancient buildings from a long - tailed satellite image dataset. from the results, our semi - supervised contrastive learning model achieved a promising testing balanced accuracy of 79. 0 %, which is a 3. 8 % improvement as compared to other state - of - the - art approaches. | arxiv:2112.06437 |
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