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this study concerns the security challenges that the people face in the usage and implementation of cloud computing. despite its growth in the past few decades, this platform has experienced different challenges. they all arise from the concern of data safety that the nature of sharing in the cloud presents. this paper looks to identify the benefits of using a cloud computing platform and the issue of information security. the paper also reviews the concept of information hiding and its relevance to the cloud. this technique has two ways about it that impact how people use cloud computing in their organizations and even for personal implementations. first it presents the potential to circulate harmful information and files that can adversely affect the data those users upload on those platforms. it is also the basis of the strategies such as steganalysis and cryptographic storage architecture that are essential for data security. | arxiv:1610.03179 |
an algebraic integer ( ai ) based time - multiplexed row - parallel architecture and two final - reconstruction step ( frs ) algorithms are proposed for the implementation of bivariate ai - encoded 2 - d discrete cosine transform ( dct ). the architecture directly realizes an error - free 2 - d dct without using frss between row - column transforms, leading to an 8 $ \ times $ 8 2 - d dct which is entirely free of quantization errors in ai basis. as a result, the user - selectable accuracy for each of the coefficients in the frs facilitates each of the 64 coefficients to have its precision set independently of others, avoiding the leakage of quantization noise between channels as is the case for published dct designs. the proposed frs uses two approaches based on ( i ) optimized dempster - macleod multipliers and ( ii ) expansion factor scaling. this architecture enables low - noise high - dynamic range applications in digital video processing that requires full control of the finite - precision computation of the 2 - d dct. the proposed architectures and frs techniques are experimentally verified and validated using hardware implementations that are physically realized and verified on fpga chip. six designs, for 4 - and 8 - bit input word sizes, using the two proposed frs schemes, have been designed, simulated, physically implemented and measured. the maximum clock rate and block - rate achieved among 8 - bit input designs are 307. 787 mhz and 38. 47 mhz, respectively, implying a pixel rate of 8 $ \ times $ 307. 787 $ \ approx $ 2. 462 ghz if eventually embedded in a real - time video - processing system. the equivalent frame rate is about 1187. 35 hz for the image size of 1920 $ \ times $ 1080. all implementations are functional on a xilinx virtex - 6 xc6vlx240t fpga device. | arxiv:1502.04221 |
we explore fitting gamma - ray burst spectra with three physically - motivated models, and thus revisit the viability of synchrotron radiation as the primary source of grb prompt emission. we pick a sample of 100 bright grbs observed by the fermi gamma - ray burst monitor ( gbm ), based on their energy flux values. in addition to the standard empirical spectral models used in previous gbm spectroscopy catalogs, we also consider three physically - motivated models ; ( a ) a thermal synchrotron model, ( b ) a band model with a high - energy cutoff, and ( c ) a smoothly broken power law ( sbpl ) model with a multiplicative broken power law ( mbpl ). we then adopt the bayesian information criterion ( bic ) to compare the fits obtained and choose the best model. we find that 42 % of the grbs from the fluence spectra and 23 % of grbs from the peak - flux spectra have one of the three physically - motivated models as their preferred one. from the peak - flux spectral fits, we find that the low - energy index distributions from the empirical model fits for long grbs peak around the synchrotron value of - 2 / 3, while the two low - energy indices from the sbpl + mbpl fits of long grbs peak close to the - 2 / 3 and - 3 / 2 values expected for a synchrotron spectrum below and above the cooling frequency. | arxiv:2311.13566 |
we present a measurement of the branching fraction for the doubly - cabibbo - suppressed decay d + to k + pi0, using 281 pb - 1 of data accumulated with the cleo - c detector on the psi ( 3770 ) resonance. we find b ( d + to k + pi0 ) = ( 2. 25 + - 0. 36 + - 0. 15 + - 0. 07 ) times 10 ^ { - 4 }, where the first uncertainty is statistical, the second is systematic, and the last error is due to the uncertainty in the reference mode. the results presented in this document are preliminary. | arxiv:hep-ex/0607075 |
the tiled convolutional neural network ( tiled cnn ) has been applied only to computer vision for learning invariances. we adjust its architecture to nlp to improve the extraction of the most salient features for sentiment analysis. knowing that the major drawback of the tiled cnn in the nlp field is its inflexible filter structure, we propose a novel architecture called hybrid tiled cnn that applies a filter only on the words that appear in the similar contexts and on their neighbor words ( a necessary step for preventing the loss of some n - grams ). the experiments on the datasets of imdb movie reviews and semeval 2017 demonstrate the efficiency of the hybrid tiled cnn that performs better than both cnn and tiled cnn. | arxiv:2001.11857 |
in the first part of this talk i discuss two somewhat different supergravity approaches to calculating correlation functions in strongly coupled yang - mills theory. the older approach relates two - point functions to cross - sections for absorption of certain incident quanta by threebranes. in this approach the normalization of operators corresponding to the incident particles is fixed unambiguously by the d3 - brane dbi action. by calculating absorption cross - sections of all partial waves of the dilaton we find corresponding two - point functions at strong ` t hooft coupling and show that they are identical to the weak coupling results. the newer approach to correlation functions relates them to boundary conditions in ads space. using this method we show that for a certain range of negative mass - squared there are two possible operator dimensions corresponding to a given scalar field in ads, and indicate how to calculate correlation functions for either of these choices. in the second part of the talk i discuss an example of ads / cft duality which arises in the context of type 0 string theory. the cft on n coincident electric and magnetic d3 - branes is argued to be stable for sufficiently weak ` t hooft coupling. it is suggested that its transition to instability at a critical coupling is related to singularity of planar diagrams. | arxiv:hep-th/9908165 |
two dimensional su ( n ) yang - mills theory is known to be equivalent to a string theory, as found by gross in the large n limit, using the 1 / n expansion. later it was found that even a generalized ym theory leads to a string theory of the gross type. in the standard ym theory case, douglas and others found the string hamiltonian describing the propagation and the interactions of states made of strings winding on a cylindrical space - time. we address the problem of finding a similar hamiltonian for the generalized ym theory. as in the standard case we start by writing the theory as a theory of free fermions. performing a bosonization, we express the hamiltonian in terms of the modes of a bosonic field, that are interpreted as in the standard case as creation and destruction operators for states of strings winding around the cylindrical space - time. the result is similar to the standard hamiltonian, but with new kinds of interaction vertices. | arxiv:hep-th/0211133 |
computed tomography ( ct ) is an important imaging technique used in medical analysis of the internal structure of the human body. previously, image segmentation methods were required after acquiring reconstructed ct images to obtain segmented ct images which made it susceptible to errors from both reconstruction and segmentation algorithms. however, this paper introduces a new approach using an advanced quantum optimization algorithm called quadratic unconstrained binary optimization ( qubo ). this algorithm enables acquisition of segmented ct images from x - ray projection data with minimized discrepancies between experimentally obtained sinograms and quantized sinograms derived from quantized segmented ct images using the radon transform. this study utilized d - wave ' s hybrid solver system for verification on real - world x - ray data. | arxiv:2306.05522 |
previous studies have demonstrated the effectiveness of point - based neural models on the point cloud analysis task. however, there remains a crucial issue on producing the efficient input embedding for raw point coordinates. moreover, another issue lies in the limited efficiency of neighboring aggregations, which is a critical component in the network stem. in this paper, we propose a global attention - guided dual - domain feature learning network ( gad ) to address the above - mentioned issues. we first devise the contextual position - enhanced transformer ( cpt ) module, which is armed with an improved global attention mechanism, to produce a global - aware input embedding that serves as the guidance to subsequent aggregations. then, the dual - domain k - nearest neighbor feature fusion ( dkff ) is cascaded to conduct effective feature aggregation through novel dual - domain feature learning which appreciates both local geometric relations and long - distance semantic connections. extensive experiments on multiple point cloud analysis tasks ( e. g., classification, part segmentation, and scene semantic segmentation ) demonstrate the superior performance of the proposed method and the efficacy of the devised modules. | arxiv:2407.08994 |
in $ \ mathcal { n } = 1 $ supersymmetric yang - mills theory, regularised on a space - time lattice, in addition to the breaking by the gluino mass term, supersymmetry is broken explicitly by the lattice regulator. in addition to the parameter tuning in the theory, the supersymmetric ward identities can be used as a tool to investigate lattice artefacts as well as to check whether supersymmetry can be recovered in the chiral and continuum limits. in this paper we present the numerical results of an analysis of the supersymmetric ward identities for our available gauge ensembles at different values of the inverse gauge coupling $ \ beta $ and of the hopping parameter $ \ kappa $. the results clearly indicate that the lattice artefacts vanish in the continuum limit, confirming the restoration of supersymmetry. | arxiv:2003.04110 |
learned image compression ( lic ) has achieved dramatic progress regarding objective and subjective metrics. mse - based models aim to improve objective metrics while generative models are leveraged to improve visual quality measured by subjective metrics. however, they all suffer from blurring or deformation at low bit rates, especially at below $ 0. 2bpp $. besides, deformation on human faces and text is unacceptable for visual quality assessment, and the problem becomes more prominent on small faces and text. to solve this problem, we combine the advantage of mse - based models and generative models by utilizing region of interest ( roi ). we propose hierarchical - roi ( h - roi ), to split images into several foreground regions and one background region to improve the reconstruction of regions containing faces, text, and complex textures. further, we propose adaptive quantization by non - linear mapping within the channel dimension to constrain the bit rate while maintaining the visual quality. exhaustive experiments demonstrate that our methods achieve better visual quality on small faces and text with lower bit rates, e. g., $ 0. 7x $ bits of hific and $ 0. 5x $ bits of bpg. | arxiv:2403.13030 |
we solve the boltzmann equation for cosmological neutrinos around the epoch of the electron - positron annihilation in order to verify the freeze - out approximation and to compute accurately the cosmological neutrino distribution function. we find the radiation energy density to be about 0. 3 % higher than the one predicted by the freeze - out approximation. as a result, the spectrum of the cosmic microwave background anisotropies changes by 0. 3 - 05 %, depending on the angular scale, and the amplitude of the mass fluctuations on scales below about 100 h ^ { - 1 } mpc decreases by about 0. 2 - 0. 3 %. | arxiv:astro-ph/9712199 |
deep learning approaches for marine fog detection and forecasting have outperformed traditional methods, demonstrating significant scientific and practical importance. however, the limited availability of open - source datasets remains a major challenge. existing datasets, often focused on a single region or satellite, restrict the ability to evaluate model performance across diverse conditions and hinder the exploration of intrinsic marine fog characteristics. to address these limitations, we introduce \ textbf { mfoghub }, the first multi - regional and multi - satellite dataset to integrate annotated marine fog observations from 15 coastal fog - prone regions and six geostationary satellites, comprising over 68, 000 high - resolution samples. by encompassing diverse regions and satellite perspectives, mfoghub facilitates rigorous evaluation of both detection and forecasting methods under varying conditions. extensive experiments with 16 baseline models demonstrate that mfoghub can reveal generalization fluctuations due to regional and satellite discrepancy, while also serving as a valuable resource for the development of targeted and scalable fog prediction techniques. through mfoghub, we aim to advance both the practical monitoring and scientific understanding of marine fog dynamics on a global scale. the dataset and code are at \ href { https : / / github. com / kaka0910 / mfoghub } { https : / / github. com / kaka0910 / mfoghub }. | arxiv:2505.10281 |
it is shown that observers in the standard adm 3 + 1 treatment of matter are the same as the observers used in the matter treatment of bondi : they are comoving and local minkowskian. bondi ' s observers are the basis of the post - - quasitatic approximation ( pqsa ) to study a contracting distribution of matter. this correspondence suggests the possibility of using the pqsa as a test bed for numerical relativity. the treatment of matter by the pqsa and its connection with the adm 3 + 1 treatment are presented, for its practical use as a calibration tool and as a test bed for numerical relativistic hydrodynamic codes. | arxiv:0905.3362 |
we reconsider the dispersive evaluation of the weak matrix elements < 2pi _ { i = 2 } | q _ { 7, 8 } | k0 > in the chiral limit. the perturbative matching is accomplished fully within the scheme dependence used in the two loop weak ope calculations. the effects of dimension eight ( and higher dimension ) operators are fully accounted for. we perform a numerical determination of the weak matrix elements using our dispersive sum rules fortified by constraints from the classical chiral sum rules. a careful assessment of the attendant uncertainties is given. | arxiv:hep-ph/0109113 |
we provide a rigorous calculation of the free energy of a non - metallic crystal containing a small concentration of defects. the low - temperature leading contribution is found to be $ \ propto t ^ 2 $. this further gives a linear - in - $ t $ low - temperature specific heat as that exhibited by glasses. these results also show that, similarly to what happens in glasses, the long - wavelength spectrum of a nearly perfect crystal does not suffice to determine its low - temperature behavior. | arxiv:0710.1837 |
we study the diameter of lps ramanujan graphs $ x _ { p, q } $. we show that the diameter of the bipartite ramanujan graphs is greater than $ ( 4 / 3 ) \ log _ { p } ( n ) + o ( 1 ) $ where $ n $ is the number of vertices of $ x _ { p, q } $. we also construct an infinite family of $ ( p + 1 ) $ - regular lps ramanujan graphs $ x _ { p, m } $ such that the diameter of these graphs is greater than or equal to $ \ lfloor ( 4 / 3 ) \ log _ { p } ( n ) \ rfloor $. on the other hand, for any $ k $ - regular ramanujan graph we show that the distance of only a tiny fraction of all pairs of vertices is greater than $ ( 1 + \ epsilon ) \ log _ { k - 1 } ( n ) $. we also have some numerical experiments for lps ramanujan graphs and random cayley graphs which suggest that the diameters are asymptotically $ ( 4 / 3 ) \ log _ { k - 1 } ( n ) $ and $ \ log _ { k - 1 } ( n ) $, respectively. | arxiv:1511.09340 |
we study the impact of explicit chiral symmetry breaking of lattice wilson fermions on mesonic correlators in the epsilon - regime using wilson chiral perturbation theory. we generalize the epsilon - expansion of continuum chiral perturbation theory to nonzero lattice spacing a and distinguish various regimes. it turnes out that lattice corrections are highly suppressed, as long as quark masses are of the order a \ lambda ^ 2 _ qcd. the lattice spacing effects become more pronounced for smaller quark masses and may lead to non - trivial corrections of the continuum results at next - to - leading order. we compute these corrections for standard current and density correlation functions. a fit to lattice data shows that these corrections are small, as expected. | arxiv:0904.4407 |
we formulate a method to find the meromorphic solutions of higher - order recurrence relations in the form of the sum over poles with coefficients defined recursively. several explicit examples of the application of this technique are given. the main advantage of the described approach is that the analytical properties of the solutions are very clear ( the position of poles is explicit, the behavior at infinity can be easily determined ). these are exactly the properties that are required for the application of the multiloop calculation method based on dimensional recurrence relations and analyticity ( the dra method ). | arxiv:1712.05166 |
a mid - infrared atlas of part of the galactic plane ( $ 75 ^ \ circ < l < 148 ^ \ circ, b = \ pm6 ^ \ circ $ ) has been constructed using hires processed infrared data to provide a mid - infrared data set for the canadian galactic plane survey ( cgps ). the addition of this data set to the cgps will enable the study of the emission from the smallest components of interstellar dust at an angular resolution comparable to that of the radio, millimetre, and far - infrared data in the cgps. the mid - infrared galaxy atlas ( miga ) is a mid - infrared ( 12 $ \ mu $ m and 25 $ \ mu $ m ) counterpart to the far - infrared iras galaxy atlas ( iga ), and consists of resolution enhanced ( $ \ sim 0. 5 ' $ resolution ) hires images along with ancillary maps. this paper describes the processing and characteristics of the atlas, the cross - beam simulation technique used to obtain high - resolution ratio maps, and future plans to extend both the iga and miga. | arxiv:astro-ph/9904380 |
pulsars show two classes of rotational irregularities that can be used to understand neutron - star interiors and magnetospheres : glitches and timing noise. here we present an analysis of the vela pulsar spanning nearly 21 yr of observation and including 8 glitches. we identify the relative pulse number of all of the observations between glitches, with the only pulse - number ambiguities existing over glitch events. we use the phase coherence of the timing solution to simultaneously model the timing noise and glitches in a bayesian framework, allowing us to select preferred models for both. we find the glitches can be described using only permanent and transient changes in spin frequency, i. e., no step changes in frequency derivative. for all of the glitches, we only need two exponentially decaying changes in spin frequency to model the transient components. in contrast to previous studies, we find that the dominant transient components decay on a common $ \ approx $ 1300 d time scale, and that a larger fraction ( $ \ gtrsim 25 \ % $ ) of glitch amplitudes are associated with these transient components. we also detect shorter - duration transient components of $ \ approx $ 25 d, as previously observed, but are limited in sensitivity to events with shorter durations by the cadence of our observations. the timing noise is well described by a steep power - law process that is independent of the glitches and subdominant to the glitch recovery. the braking index is constrained to be $ < $ 8 with 95 % confidence. this methodology can be used to robustly measure the properties of glitches and timing noise in other pulsars. | arxiv:1604.02661 |
we use monte carlo simulations of the 2d one component coulomb gas on a triangular lattice, to study the depinning transition of a 2d vortex lattice in a commensurate periodic potential. a detailed finite size scaling analysis indicates this transition to be first order. no significant changes in behavior were found as vortex density was varied over a wide range. | arxiv:cond-mat/0007110 |
by constructing the configuration of d3 - branes with d ( - 1 ) - branes as d - instantons, we study the three - dimensional yang - mills chern - simons theory in holography. due to the presence of the d - instantons, the d7 - branes with discrepant embedding functions are able to be introduced in order to include the fundamental fermions ( as flavors ) and the chern - simons term ( at very low energy ) in the dual theory. the vacuum structure at zero temperature is studied in the soliton background and it illustrates the topological phase transition in the presence of instantons. moreover, since the confinement / deconfinement phase transition could be holographically identified as the hawking - page transition in the bulk, we accordingly calculate the critical temperature of the deconfinement phase transition by collecting the bulk onshell action as the thermodynamical free energy. on the other hand, we evaluate the difference of the entanglement entropy in slab configuration by using the rt formula since the confinement may also be characterized by the entanglement entropy. altogether we find the behavior of the critical temperature is in qualitative agreement with the behavior of the critical length determined by the entanglement entropy which implies the entanglement entropy could indeed be a character of the confinement in our setup and the d3 - d ( - 1 ) system would be a remarkable approach to study the three - dimensional gauge theory. | arxiv:2106.04038 |
the paper revisits the robust $ s $ - $ t $ path problem, one of the most fundamental problems in robust optimization. in the problem, we are given a directed graph with $ n $ vertices and $ k $ distinct cost functions ( scenarios ) defined over edges, and aim to choose an $ s $ - $ t $ path such that the total cost of the path is always provable no matter which scenario is realized. with the view of each cost function being associated with an agent, our goal is to find a common $ s $ - $ t $ path minimizing the maximum objective among all agents, and thus create a fair solution for them. the problem is hard to approximate within $ o ( \ log k ) $ by any quasi - polynomial time algorithm unless $ \ mathrm { np } \ subseteq \ mathrm { dtime } ( n ^ { \ mathrm { poly } \ log n } ) $, and the best approximation ratio known to date is $ \ widetilde { o } ( \ sqrt { n } ) $ which is based on the natural flow linear program. a longstanding open question is whether we can achieve a polylogarithmic approximation even when a quasi - polynomial running time is allowed. we give the first polylogarithmic approximation for robust $ s $ - $ t $ path since the problem was proposed more than two decades ago. in particular, we introduce a $ o ( \ log n \ log k ) $ - approximate algorithm running in quasi - polynomial time. the algorithm is built on a novel linear program formulation for a decision - tree - type structure which enables us to get rid of the $ \ omega ( \ max \ { k, \ sqrt { n } \ } ) $ integrality gap of the natural flow lp. further, we also consider some well - known graph classes, e. g., graphs with bounded treewidth, and show that the polylogarithmic approximation can be achieved polynomially on these graphs. we hope the new proposed techniques in the paper can offer new insights into the robust $ s $ - $ t $ path problem and related problems in robust optimization. | arxiv:2305.16439 |
in the paper, with the aid of the fa \ ` a di bruno formula, in terms of central factorial numbers of the second kind, and with the terminology of the stirling numbers of the second kind, the authors derive several series expansions for any positive integer powers of the sinc and sinhc functions, discover several closed - form formulas for partial bell polynomials of all derivatives of the sinc function, establish several series expansions for any real powers of the sinc and sinhc functions, and present several identities for central factorial numbers of the second kind and for the stirling numbers of the second kind. | arxiv:2204.05612 |
we propose a methodology that allows communication with piping and instrumentation diagrams ( p & ids ) using natural language. in particular, we represent p & ids through the dexpi data model as labeled property graphs and integrate them with large language models ( llms ). the approach consists of three main parts : 1 ) p & ids are cast into a graph representation from the dexpi format using our pydexpi python package. 2 ) a tool for generating p & id knowledge graphs from pydexpi. 3 ) integration of the p & id knowledge graph to llms using graph - based retrieval augmented generation ( graph - rag ). this approach allows users to communicate with p & ids using natural language. it extends llm ' s ability to retrieve contextual data from p & ids and mitigate hallucinations. leveraging the llm ' s large corpus, the model is also able to interpret process information in pids, which could help engineers in their daily tasks. in the future, this work will also open up opportunities in the context of other generative artificial intelligence ( genai ) solutions on p & ids, and ai - assisted hazop studies. | arxiv:2502.18928 |
the determination of transport coefficients plays a central role in characterizing hot and dense nuclear matter. currently, there are significant discrepancies between various calculations of the electric conductivity of hot hadronic matter. in the present work we calculate the electric conductivity of hot pion matter by extracting it from the electromagnetic spectral function, via its zero energy limit at vanishing 3 - momentum, within the vector dominance model ( vdm ). since within the vdm the photon couples to the hadronic currents primarily through the $ \ rho $ meson, we use hadronic many - body theory to calculate the $ \ rho $ - meson ' s self - energy in hot pion matter, by dressing its pion cloud with thermal $ \ pi $ - $ \ rho $ and $ \ pi $ - $ \ sigma $ loops including vertex corrections to maintain gauge invariance. in particular, we analyze the low - energy transport peak of the spectral function, extract its behavior with temperature and compare to ( the results of ) existing approaches in the literature. | arxiv:2211.08713 |
in recent developments, a general approach for solving riemann - - hilbert problems numerically has been developed. we review this numerical framework, and apply it to the calculation of orthogonal polynomials on the real line. combining this numerical algorithm with an approach to compute fredholm determinants, we are able to calculate level densities and gap statistics for general finite - dimensional unitary ensembles. we also include a description of how to compute the hastings - - mcleod solution of the homogeneous painlev \ ' e ii equation. | arxiv:1210.2199 |
training - free metrics ( a. k. a. zero - cost proxies ) are widely used to avoid resource - intensive neural network training, especially in neural architecture search ( nas ). recent studies show that existing training - free metrics have several limitations, such as limited correlation and poor generalisation across different search spaces and tasks. hence, we propose sample - wise activation patterns and its derivative, swap - score, a novel high - performance training - free metric. it measures the expressivity of networks over a batch of input samples. the swap - score is strongly correlated with ground - truth performance across various search spaces and tasks, outperforming 15 existing training - free metrics on nas - bench - 101 / 201 / 301 and transnas - bench - 101. the swap - score can be further enhanced by regularisation, which leads to even higher correlations in cell - based search space and enables model size control during the search. for example, spearman ' s rank correlation coefficient between regularised swap - score and cifar - 100 validation accuracies on nas - bench - 201 networks is 0. 90, significantly higher than 0. 80 from the second - best metric, nwot. when integrated with an evolutionary algorithm for nas, our swap - nas achieves competitive performance on cifar - 10 and imagenet in approximately 6 minutes and 9 minutes of gpu time respectively. | arxiv:2403.04161 |
we revisit the issue of causality violations in g \ " { o } del ' s universe, restricting to geodesic motions. it is well - known that while there are closed timelike curves in this spacetime, there are no closed causal geodesics. we show further that no observer can communicate directly ( i. e. \ using a single causal geodesic ) with their own past. however, we show that this type of causality violation can be achieved by a system of relays : we prove that from any event $ p $ in g \ " { o } del ' s universe, there is a future - directed lightlike path - a sequence of future - directed null geodesic segments, laid end to end - which has $ p $ as its past and future endpoints. by analysing the envelope of the family of future directed null geodesics emanating from a point of the spacetime, we show that this lightlike path must contain a minimum of eight geodesic segments, and show further that this bound is attained. we prove a related general result, that events of a time orientable spacetime are connected by a ( closed ) timelike curve if and only if they are connected by a ( closed ) lightlike path. this suggests a means of violating causality in g \ " { o } del ' s universe without the need for unfeasibly large accelerations, using instead a sequence of light signals reflected by a suitably located system of mirrors. | arxiv:1911.08602 |
let $ n $ be a positive integer and $ q $ a prime power. we prove that a refined version of brou \ ' { e } ' s abelian defect group conjecture holds for unipotent $ \ ell $ - blocks of $ { \ rm gl } _ n ( q ) $, where $ \ ell \ nmid q $. we also give a sufficient condition on general $ \ ell $ - blocks of $ { \ rm gl } _ n ( q ) $ to satisfy the refined abelian defect group conjecture. we explain by an example that this sufficient condition does not hold in general. | arxiv:2302.12129 |
& = b \ cdot e & & { \ text { ( } } e { \ text { is the identity element ) } } \ \ & = b \ cdot ( a \ cdot c ) & & { \ text { ( } } c { \ text { and } } a { \ text { are inverses of each other ) } } \ \ & = ( b \ cdot a ) \ cdot c & & { \ text { ( associativity ) } } \ \ & = e \ cdot c & & { \ text { ( } } b { \ text { is an inverse of } } a { \ text { ) } } \ \ & = c & & { \ text { ( } } e { \ text { is the identity element and } } b = c { \ text { ) } } \ end { aligned } } } therefore, it is customary to speak of the inverse of an element. = = = division = = = given elements a { \ displaystyle a } and b { \ displaystyle b } of a group g { \ displaystyle g }, there is a unique solution x { \ displaystyle x } in g { \ displaystyle g } to the equation a ⋅ x = b { \ displaystyle a \ cdot x = b }, namely a − 1 ⋅ b { \ displaystyle a ^ { - 1 } \ cdot b }. it follows that for each a { \ displaystyle a } in g { \ displaystyle g }, the function g → g { \ displaystyle g \ to g } that maps each x { \ displaystyle x } to a ⋅ x { \ displaystyle a \ cdot x } is a bijection ; it is called left multiplication by a { \ displaystyle a } or left translation by a { \ displaystyle a }. similarly, given a { \ displaystyle a } and b { \ displaystyle b }, the unique solution to x ⋅ a = b { \ displaystyle x \ cdot a = b } is b ⋅ a − 1 { \ displaystyle b \ cdot a ^ { - 1 } }. for each a { \ displaystyle a }, the function g → g { \ displaystyle g \ to g } that maps each x { \ displaystyle x } to x ⋅ a { \ displaystyle x \ cdot a } is a bijection called right multiplication by a { \ displaystyle a } | https://en.wikipedia.org/wiki/Group_(mathematics) |
we calculate the ohmic and hall conductivities from linear response theory in a system consisting of the intersection of nc dp - branes and nf < < n _ c dq - branes. agreement is found between previous results found in a macroscopic approach comparing induced currents with external electric fields. the issue of how to deal with mixed operators is raised. the retarded green ' s function is given by a matrix that can be computed from the boundary action similarly to the green ' s function for uncoupled operators. | arxiv:0911.4976 |
investigation of dynamical excitations is difficult but crucial to the understanding of many exotic quantum phenomena discovered in quantum materials. this is particularly true for highly frustrated quantum antiferromagnets whose dynamical properties deviate strongly from theoretical predictions made based on the spin - wave or other approximations. here we present a large - scale numerical calculation on the dynamical correlation functions of spin - $ 1 / 2 $ triangular heisenberg model using a state - of - the - art tensor network renormalization group method. the calculated results allow us to gain for the first time a comprehensive picture on the nature of spin excitation spectra in this highly frustrated quantum system. it provides a quantitative account for all the key features of the dynamical spectra disclosed by inelastic neutron scattering measurements for $ \ rm ba _ 3cosb _ 2o _ 9 $, revealing the importance of the interplay between low - and high - energy excitations and its renormalization effect to the low - energy magnon bands and high - energy continuums. we identify the longitudinal higgs modes in the intermediate - energy scale and predict the energy and momentum dependence of spectral functions along the three principal axes that can be verified by polarized neutron scattering experiments. furthermore, we find that the spin excitation spectra weakly depend on the anisotropic ratio of the antiferromagnetic interaction. | arxiv:2201.12121 |
wi - fi ( ) is a family of wireless network protocols based on the ieee 802. 11 family of standards, which are commonly used for local area networking of devices and internet access, allowing nearby digital devices to exchange data by radio waves. these are the most widely used computer networks, used globally in home and small office networks to link devices and to provide internet access with wireless routers and wireless access points in public places such as coffee shops, restaurants, hotels, libraries, and airports. wi - fi is a trademark of the wi - fi alliance, which restricts the use of the term " wi - fi certified " to products that successfully complete interoperability certification testing. non - compliant hardware is simply referred to as wlan, and it may or may not work with " wi - fi certified " devices. as of 2017, the wi - fi alliance consisted of more than 800 companies from around the world. as of 2019, over 3. 05 billion wi - fi - enabled devices are shipped globally each year. wi - fi uses multiple parts of the ieee 802 protocol family and is designed to work well with its wired sibling, ethernet. compatible devices can network through wireless access points with each other as well as with wired devices and the internet. different versions of wi - fi are specified by various ieee 802. 11 protocol standards, with different radio technologies determining radio bands, maximum ranges, and speeds that may be achieved. wi - fi most commonly uses the 2. 4 gigahertz ( 120 mm ) uhf and 5 gigahertz ( 60 mm ) shf radio bands, with the 6 gigahertz shf band used in newer generations of the standard ; these bands are subdivided into multiple channels. channels can be shared between networks, but, within range, only one transmitter can transmit on a channel at a time. wi - fi ' s radio bands work best for line - of - sight use. common obstructions, such as walls, pillars, home appliances, etc., may greatly reduce range, but this also helps minimize interference between different networks in crowded environments. the range of an access point is about 20 m ( 66 ft ) indoors, while some access points claim up to a 150 m ( 490 ft ) range outdoors. hotspot coverage can be as small as a single room with walls that block radio waves or as large as many square kilometers using multiple overlapping access points with roaming permitted between them. over time, the speed and spectral efficiency of wi - fi has increased. as of 2019, some versions of | https://en.wikipedia.org/wiki/Wi-Fi |
we investigate the spectrum and eigenstates of ultracold fermionic atoms in the bilayer honeycomb optical lattice. in the low energy approximation, the dispersion relation has parabolic form and the quasiparticles are chiral. in the presence of the effective magnetic field, which is created for the system with optical means, the energy spectrum shows an unconventional landau level structure. furthermore, the experimental detection of the spectrum is proposed with the bragg scattering techniques. | arxiv:0905.3035 |
an emerging optimisation problem from the real - world applications, named the multi - point dynamic aggregation ( mpda ) problem, has become one of the active research topics of the multi - robot system. this paper focuses on a multi - objective mpda problem which is to design an execution plan of the robots to minimise the number of robots and the maximal completion time of all the tasks. the strongly - coupled relationships among robots and tasks, the redundancy of the mpda encoding, and the variable - size decision space of the mo - mpda problem posed extra challenges for addressing the problem effectively. to address the above issues, we develop a hybrid decomposition - based multi - objective evolutionary algorithm ( hdmoea ) using $ \ varepsilon $ - constraint method. it selects the maximal completion time of all tasks as the main objective, and converted the other objective into constraints. hdmoea decomposes a mo - mpda problem into a series of scalar constrained optimization subproblems by assigning each subproblem with an upper bound robot number. all the subproblems are optimized simultaneously with the transferring knowledge from other subproblems. besides, we develop a hybrid population initialisation mechanism to enhance the quality of initial solutions, and a reproduction mechanism to transmit effective information and tackle the encoding redundancy. experimental results show that the proposed hdmoea method significantly outperforms the state - of - the - art methods in terms of several most - used metrics. | arxiv:2105.04934 |
since their discovery, the infinite - layer nickelates have been regarded as an appealing system for gaining deeper insights into high temperature superconductivity ( htsc ). however, the synthesis of superconducting samples has been proved to be challenging. here, we develop an ultrahigh vacuum ( uhv ) $ { \ mathrm { \ textit { in situ } } } $ reduction method using atomic hydrogen as reducing agent and apply it in lanthanum nickelate system. the reduction parameters, including the reduction temperature ( $ { \ mathrm { \ textit { t } _ { r } } } $ ) and hydrogen pressure ( $ { \ mathrm { \ textit { p } _ { h } } } $ ), are systematically explored. we found that the reduction window for achieving superconducting transition is quite wide, reaching nearly 80 $ ^ \ circ $ c in $ { \ mathrm { \ textit { t } _ { r } } } $ and 3 orders of magnitude in $ { \ mathrm { \ textit { p } _ { h } } } $ when the reduction time is set to 30 mins. and there exists an optimal $ { \ mathrm { \ textit { p } _ { h } } } $ for achieving the highest $ { \ mathrm { \ textit { t } _ { c } } } $ if both $ { \ mathrm { \ textit { t } _ { r } } } $ and reduction time are fixed. more prominently, as confirmed by atomic force microscopy and scanning transmission electron microscopy, the atomically flat surface can be preserved during the $ { \ mathrm { \ textit { in situ } } } $ reduction process, providing advantages over the $ { \ mathrm { \ textit { ex situ } } } $ cah $ _ 2 $ method for surface - sensitive experiments. | arxiv:2401.15979 |
in 5g networks, a radio over fiber architecture utilizing multicore fibers can be adopted for the transmission of mmwave signals feeding phased array antennas. the mmwave signals undergo phase shifts imposed by optical true time delay networks, to provide squint free beams. multicore fibers are used to transfer the phase shifted optical signals. however, the intercore static skew of these fibers, if not compensated, distorts the radiation pattern. we propose an efficient method to compensate the differential delays, without full equalization of the transmission path lengths, reducing the power loss and complexity. statistical analysis shows that regardless of the skew distribution, the frequency response can be estimated with respect to the rms skew delays. simulation analysis of the complete radio over fiber and rf link validates the method. | arxiv:2102.04813 |
we investigate non - equilibrium turbulence where the non - dimensionalised dissipation coefficient $ c _ { \ varepsilon } $ scales as $ c _ { \ varepsilon } \ sim re _ { m } ^ { m } / re _ { \ ell } ^ { n } $ with $ m \ approx 1 \ approx n $ ( $ re _ m $ and $ re _ { \ ell } $ are global / inlet and local reynolds numbers respectively ) by measuring the downstream evolution of the scale - by - scale energy transfer, dissipation, advection, production and transport in the lee of a square - mesh grid and compare with a region of equilibrium turbulence ( i. e. where $ c _ { \ varepsilon } \ approx \ mathrm { constant } $ ). these are the main terms of the inhomogeneous, anisotropic version of the von k \ ' { a } rm \ ' { a } n - howarth - monin equation. it is shown in the grid - generated turbulence studied here that, even in the presence of non - negligible turbulence production and transport, production and transport are large - scale phenomena that do not contribute to the scale - by - scale balance for scales smaller than about a third of the integral - length scale, $ \ ell $, and therefore do not affect the energy transfer to the small - scales. in both the non - equilibrium and the equilibrium decay regions, the peak of the scale - by - scale energy transfer scales as $ ( \ overline { u ^ 2 } ) ^ { 3 / 2 } / \ ell $ ( $ \ overline { u ^ 2 } $ is the variance of the longitudinal fluctuating velocity ). in the non - equilibrium case this scaling implies an imbalance between the energy transfer to the small scales and the dissipation. this imbalance is reflected on the small - scale advection which becomes larger in proportion to the maximum energy transfer as the turbulence decays whereas it stays proportionally constant in the further downstream equilibrium region where $ c _ { \ varepsilon } \ approx \ mathrm { constant } $ even though $ re _ { \ ell } $ is lower. | arxiv:1307.5901 |
we derive a bound on the precision of state estimation for finite dimensional quantum systems and prove its attainability in the generic case where the spectrum is non - degenerate. our results hold under an assumption called local asymptotic covariance, which is weaker than unbiasedness or local unbiasedness. the derivation is based on an analysis of the limiting distribution of the estimator ' s deviation from the true value of the parameter, and takes advantage of quantum local asymptotic normality, a useful asymptotic characterization of identically prepared states in terms of gaussian states. we first prove our results for the mean square error of a special class of models, called d - invariant, and then extend the results to arbitrary models, generic cost functions, and global state estimation, where the unknown parameter is not restricted to a local neighbourhood of the true value. the extension includes a treatment of nuisance parameters, i. e. parameters that are not of interest to the experimenter but nevertheless affect the precision of the estimation. as an illustration of the general approach, we provide the optimal estimation strategies for the joint measurement of two qubit observables, for the estimation of qubit states in the presence of amplitude damping noise, and for noisy multiphase estimation. | arxiv:1802.07587 |
in this paper we present a pipeline using stereo images in order to automatically identify, track in 3d fish, and measure fish population. | arxiv:2312.07357 |
we study $ u ( n ) _ k $ chern - simons theory coupled to fundamental fermions and scalars in a large $ n $ ` t hooft limit. we compute the thermal free energy at high temperature, as well as two - and three - point functions of simple gauge - invariant operators. our findings support various dualities between chern - simons - matter theories with $ \ mathcal { n } = 0, 1, $ and $ 2 $ supersymmetry. | arxiv:1910.07484 |
cyberbullying is a pervasive problem in online communities. to identify cyberbullying cases in large - scale social networks, content moderators depend on machine learning classifiers for automatic cyberbullying detection. however, existing models remain unfit for real - world applications, largely due to a shortage of publicly available training data and a lack of standard criteria for assigning ground truth labels. in this study, we address the need for reliable data using an original annotation framework. inspired by social sciences research into bullying behavior, we characterize the nuanced problem of cyberbullying using five explicit factors to represent its social and linguistic aspects. we model this behavior using social network and language - based features, which improve classifier performance. these results demonstrate the importance of representing and modeling cyberbullying as a social phenomenon. | arxiv:2004.01820 |
data silos, mainly caused by privacy and interoperability, significantly constrain collaborations among different organizations with similar data for the same purpose. distributed learning based on divide - and - conquer provides a promising way to settle the data silos, but it suffers from several challenges, including autonomy, privacy guarantees, and the necessity of collaborations. this paper focuses on developing an adaptive distributed kernel ridge regression ( adadkrr ) by taking autonomy in parameter selection, privacy in communicating non - sensitive information, and the necessity of collaborations in performance improvement into account. we provide both solid theoretical verification and comprehensive experiments for adadkrr to demonstrate its feasibility and effectiveness. theoretically, we prove that under some mild conditions, adadkrr performs similarly to running the optimal learning algorithms on the whole data, verifying the necessity of collaborations and showing that no other distributed learning scheme can essentially beat adadkrr under the same conditions. numerically, we test adadkrr on both toy simulations and two real - world applications to show that adadkrr is superior to other existing distributed learning schemes. all these results show that adadkrr is a feasible scheme to defend against data silos, which are highly desired in numerous application regions such as intelligent decision - making, pricing forecasting, and performance prediction for products. | arxiv:2309.04236 |
we study the nucleon matrix elements of the quark scalar - density operator using maximally twisted mass fermions with dynamical light ( $ u $, $ d $ ), strange and charm degrees of freedom. we demonstrate that in this setup the nucleon matrix elements of the light and strange quark densities can be obtained with good statistical accuracy, while for the charm quark counterpart only a bound can be provided. the present calculation which is performed at only one value of the lattice spacing and pion mass serves as a benchmark for a future more systematic computation of the scalar quark content of the nucleon. | arxiv:1202.1480 |
copulas. we study the model risk of multivariate risk models in a comprehensive empirical study on copula - garch models used for forecasting value - at - risk and expected shortfall. to determine whether model risk inherent in the forecasting of portfolio risk is caused by the candidate marginal or copula models, we analyze different groups of models in which we fix either the marginals, the copula, or neither. model risk is economically significant, is especially high during periods of crisis, and is almost completely due to the choice of the copula. we then propose the use of the model confidence set procedure to narrow down the set of available models and reduce model risk for copula - garch risk models. our proposed approach leads to a significant improvement in the mean absolute deviation of one day ahead forecasts by our various candidate risk models. | arxiv:2109.10946 |
image fusion typically employs non - invertible neural networks to merge multiple source images into a single fused image. however, for clinical experts, solely relying on fused images may be insufficient for making diagnostic decisions, as the fusion mechanism blends features from source images, thereby making it difficult to interpret the underlying tumor pathology. we introduce fusioninn, a novel decomposable image fusion framework, capable of efficiently generating fused images and also decomposing them back to the source images. fusioninn is designed to be bijective by including a latent image alongside the fused image, while ensuring minimal transfer of information from the source images to the latent representation. to the best of our knowledge, we are the first to investigate the decomposability of fused images, which is particularly crucial for life - sensitive applications such as medical image fusion compared to other tasks like multi - focus or multi - exposure image fusion. our extensive experimentation validates fusioninn over existing discriminative and generative fusion methods, both subjectively and objectively. moreover, compared to a recent denoising diffusion - based fusion model, our approach offers faster and qualitatively better fusion results. | arxiv:2403.15769 |
we reminisce on the first steps of the cosmology community in portugal, which can be traced back to about 20 years ago, and discuss its achievements and current specificities. we also reflect on the aspirations, hopes and challenges for the future. | arxiv:physics/0612066 |
delay - coupled networks are investigated with nonidentical delay times and the effects of such heterogeneity on the emergent dynamics of complex systems are characterized. a simple decomposition method is presented that decouples the dynamics of the network into node - size modal equations in the vicinity of equilibria. the resulting independent components contain distributed delays that map the spatiotemporal complexity of the system to the time domain. we demonstrate that this new approach can be used to reveal new physical phenomena in heterogenous vehicular traffic when vehicles are linked via vehicle - to - vehicle ( v2v ) communication. | arxiv:1305.6771 |
in 1938, morse and hedlund proved that the subword complexity function of an infinite word is either bounded or at least linearly growing. in 1982, ehrenfeucht and rozenberg proved that this gap property holds for the subword complexity function of any language. the aim of the present paper is to present a self - contained, compact proof of ehrenfeucht and rozenberg ' s result. | arxiv:0903.1627 |
pagedattention is a popular approach for dynamic memory allocation in llm serving systems. it enables on - demand allocation of gpu memory to mitigate kv cache fragmentation - - a phenomenon that crippled the batch size ( and consequently throughput ) in prior systems. however, in trying to allocate physical memory at runtime, pagedattention ends up changing the virtual memory layout of the kv cache from contiguous to non - contiguous. such a design leads to non - trivial programming and performance overheads. we present vattention - - an approach that mitigates fragmentation in physical memory while retaining the contiguity of kv cache in virtual memory. we achieve this by decoupling the allocation of virtual and physical memory using cuda virtual memory management apis. we also introduce various llm - specific optimizations to address the limitations of cuda virtual memory support. overall, vattention is a simpler, portable, and performant alternative to pagedattention : it supports various attention kernels out - of - the - box and improves llm serving throughput by up to 1. 23x compared to the use of pagedattention - based kernels of flashattention and flashinfer. | arxiv:2405.04437 |
an important problem in fiber - optic communications is to invert the nonlinear schr \ " odinger equation in real time to reverse the deterministic effects of the channel. interestingly, the popular split - step fourier method ( ssfm ) leads to a computation graph that is reminiscent of a deep neural network. this observation allows one to leverage tools from machine learning to reduce complexity. in particular, the main disadvantage of the ssfm is that its complexity using m steps is at least m times larger than a linear equalizer. this is because the linear ssfm operator is a dense matrix. in previous work, truncation methods such as frequency sampling, wavelets, or least - squares have been used to obtain " cheaper " operators that can be implemented using filters. however, a large number of filter taps are typically required to limit truncation errors. for example, ip and kahn showed that for a 10 gbaud signal and 2000 km optical link, a truncated ssfm with 25 steps would require 70 - tap filters in each step and 100 times more operations than linear equalization. we find that, by jointly optimizing all filters with deep learning, the complexity can be reduced significantly for similar accuracy. using optimized 5 - tap and 3 - tap filters in an alternating fashion, one requires only around 2 - 6 times the complexity of linear equalization, depending on the implementation. | arxiv:1804.02799 |
these are the proceedings of the second international workshop on safe control of autonomous vehicles, which took place on the 10th of april 2018 in porto, portugal as an affiliated workshop of cspweek. the task of this workshop is to identify open research problems, discuss recent achievements, bring together researchers in, e. g., control theory, adaptive systems, machine self - organization and autonomy, mobile intelligent robotics, transportation, traffic control, machine learning, software verification, and dependability and security engineering. | arxiv:1804.03406 |
we prove the 3 - fold dt / pt correspondence for k - theoretic vertices via wall - crossing techniques. we provide two different setups, following mochizuki and following joyce ; both reduce the problem to q - combinatorial identities on word rearrangements. an important technical step is the construction of symmetric almost - perfect obstruction theories ( apots ) on auxiliary moduli stacks, e. g. master spaces, from the symmetric dt or pt obstruction theory. for this, we introduce symmetrized pullbacks of symmetric obstruction theories along smooth morphisms of artin stacks. | arxiv:2311.15697 |
we investigate the temporal evolution of the electronic states at the bismuth ( 111 ) surface by means of time and angle resolved photoelectron spectroscopy. the binding energy of bulk - like bands oscillates with the frequency of the $ a _ { 1g } $ phonon mode whereas surface states are insensitive to the coherent displacement of the lattice. a strong dependence of the oscillation amplitude on the electronic wavevector is correctly reproduced by \ textit { ab initio } calculations of electron - phonon coupling. besides these oscillations, all the electronic states also display a photoinduced shift towards higher binding energy whose dynamics follows the evolution of the electronic temperature. | arxiv:1112.3949 |
we propose a new method for projective dependency parsing based on headed spans. in a projective dependency tree, the largest subtree rooted at each word covers a contiguous sequence ( i. e., a span ) in the surface order. we call such a span marked by a root word \ textit { headed span }. a projective dependency tree can be represented as a collection of headed spans. we decompose the score of a dependency tree into the scores of the headed spans and design a novel $ o ( n ^ 3 ) $ dynamic programming algorithm to enable global training and exact inference. our model achieves state - of - the - art or competitive results on ptb, ctb, and ud. our code is publicly available at \ url { https : / / github. com / sustcsonglin / span - based - dependency - parsing }. | arxiv:2108.04750 |
because of the herschel and planck satellite missions, there is strong interest in the interpretation the sub - millimetre dust spectra from interstellar clouds. much work has been done to understand the dependence between the spectral index beta _ obs and the colour temperature t _ c that is partly caused by the noise. the ( t _ c, beta _ obs ) confidence regions are elongated, banana - shaped structures. we studied under which conditions these exhibit anomalous, strongly non - gaussian behaviour that could affect the interpretation of the observed ( t _ c, beta _ obs ) relations. we examined modified black body spectra and spectra calculated from radiative transfer models of filamentary clouds at wavelengths 100um - 850um. we performed modified black body fits and examined the structure of the chi ^ 2 ( t _, beta _ obs ) function. we show cases where, when the signal - to - noise ratio is low, the chi ^ 2 has multiple local minima in the ( t _ c, beta _ obs ) plane. a small change in the weighting of the data points can cause the solution to jump to completely different values. in particular, noise can lead to the appearance of a separate population of solutions with low colour temperatures and high spectral indices. the anomalies are caused by the noise but the tendency to show multiple chi ^ 2 minima depends on the model and the wavelengths analysed. deviations from the assumed single modified black body spectrum are not important. the presence of local minima implies that the results obtained from the chi ^ 2 minimisation depend on the starting point of the optimisation and may correspond to non - global minima. the ( t _ c, beta _ obs ) distributions may be contaminated by a few solutions with unrealistically low colour temperatures and high spectral indices. proper weighting must be applied to avoid the determination of the beta _ obs ( t _ c ) relation to be unduly affected by these measurements. | arxiv:1203.2263 |
shokurov ' s acc conjecture says that the set of all log canonical thresholds on varieties of bounded dimension satisfies the ascending chain condition. this conjecture was proved for log canonical thresholds on smooth varieties in [ em1 ]. here we use this result and inversion of adjunction to establish the conjecture for locally complete intersection varieties. | arxiv:0811.4642 |
we carried out a systematic study of full - orbit phase curves for known transiting systems in the northern ecliptic sky that were observed during year 2 of the tess primary mission. we applied the same methodology for target selection, data processing, and light - curve fitting as we did in our year 1 study. out of the 15 transiting systems selected for analysis, seven - hat - p - 7, kelt - 1, kelt - 9, kelt - 16, kelt - 20, kepler - 13a, and wasp - 12 - show statistically significant secondary eclipses and day - night atmospheric brightness modulations. small eastward dayside hotspot offsets were measured for kelt - 9b and wasp - 12b. kelt - 1, kepler - 13a, and wasp - 12 show additional phase - curve variability attributed to the tidal distortion of the host star ; the amplitudes of these signals are consistent with theoretical predictions. we combined occultation measurements from tess and spitzer to compute dayside brightness temperatures, tess - band geometric albedos, bond albedos, and phase integrals for several systems. the new albedo values solidify the previously reported trend between dayside temperature and geometric albedo for planets with $ 1500 < t _ { \ mathrm { day } } < 3000 $ k. for kepler - 13ab, we carried out an atmospheric retrieval of the full secondary eclipse spectrum, which revealed a non - inverted temperature - pressure profile, significant h $ _ { 2 } $ o and k absorption in the near - infrared, evidence for strong optical atmospheric opacity due to sodium, and a confirmation of the high geometric albedo inferred from our simpler analysis. we explore the implications of the phase integrals ( ratios of bond to geometric albedos ) for understanding exoplanet clouds. we also report updated transit ephemerides for all of the systems studied in this work. | arxiv:2106.02610 |
the mathematical structure of realist quantum theories has given rise to a debate about how our ordinary 3 - dimensional space is related to the 3n - dimensional configuration space on which the wave function is defined. which of the two spaces is our ( more ) fundamental physical space? i review the debate between 3n - fundamentalists and 3d - fundamentalists and evaluate it based on three criteria. i argue that when we consider which view leads to a deeper understanding of the physical world, especially given the deeper topological explanation from the unordered configurations to the symmetrization postulate, we have strong reasons in favor of 3d - fundamentalism. i conclude that our evidence favors the view that our fundamental physical space in a quantum world is 3 - dimensional rather than 3n - dimensional. i outline lines of future research where the evidential balance can be restored or reversed. finally, i draw lessons from this case study to the debate about theoretical equivalence. | arxiv:2110.14531 |
we have developed a quantitative model for the creation of cytoplasmic ca2 + gradients near the inner surface of the plasma membrane ( pm ). in particular we simulated the refilling of the sarcoplasmic reticulum ( sr ) via pm - sr junctions during asynchronous [ ca2 + ] oscillations in smooth muscle cells of the rabbit inferior vena cava. we have combined confocal microscopy data on the [ ca2 + ] oscillations, force transduction data from cell contraction studies and electron microscopic images to build a basis for computational simulations that model the transport of calcium ions from na + / ca2 + exchangers ( ncx ) on the pm to sarcoplasmic / endoplasmic reticulum ca2 + atpase ( serca ) pumps on the sr as a three - dimensional random walk through the pm - sr junctional cytoplasmic spaces. electron microscopic ultrastructural images of the smooth muscle cells were elaborated with software algorithms to produce a very clear and dimensionally accurate picture of the pm - sr junctions. from this study, we conclude that it is plausible and possible for enough ca2 + to pass through the pm - sr junctions to replete the sr during the regenerative ca2 + release, which underlies agonist induced asynchronous ca2 + oscillations in vascular smooth muscle. | arxiv:q-bio/0603001 |
this study presents constructions of the space - time conservation element and solution element ( cese ) methods to accommodate adaptive unstructured quadrilateral meshes. subsequently, a novel algorithm is devised to effectively manage the mesh adaptation process for staggered schemes, leveraging a unique cell - tree - vertex data structure that expedites the construction of conservation elements and simplifies the interconnection among computational cells. the integration of second - order a - { \ alpha }, courant number - insensitive, and upwind cese schemes with this adaptation algorithm is demonstrated. numerical simulations focusing on compressible inviscid flows are carried out to validate the effectiveness of the extended schemes and the adaptation algorithm. | arxiv:2409.01562 |
based on definitions, two joint - criteria, namely, the optical - thin constraint and the energy budget constraint, are proposed to judge whether the emission nature of radio pulsars is incoherent or obligatory to be coherent. we find that the widely accepted criterion, $ kt _ b \ le \ epsilon $, is not a rational criterion to describe the optical - thin condition, even for the simplest case. the energy budget constraint could be released by introducing a certain efficient radiation mechanism ( e. g. the inverse compton scattering, ql98 ) with emission power of a single particle as high as a critical value $ p _ { sing, c } \ sim 10 ^ { - 4 } - 10 ^ { - 3 } { erg s } ^ { - 1 } $. this in principle poses the possibilities to interpret high luminosities of pulsars in terms of incoherent emission mechanisms, if the optical - thin constraint could be released by certain mechanism as well. coherence may not be an essential condition to account for pulsar radio emission. | arxiv:astro-ph/9902072 |
we present the study of a quantum controlled - controlled - not gate, implemented in a chain of three nuclear spins weakly ising interacting between all of them, that is, taking into account first and second neighbor spin interactions. this implementation is done using a single resonant $ \ pi $ - pulse on the initial state of the system ( digital and superposition ). the fidelity parameter is used to determine the behavior of the ccn quantum gate as a function of the ratio of the second neighbor interaction coupling constant to the first neighbor interaction coupling constant ( $ j ' / j $ ). we found that for $ j ' / j \ ge 0. 02 $ we can have a well defined ccn quantum gate. | arxiv:quant-ph/0608147 |
we study the elastic wave system in three spatial dimensions. for admissible harmonic elastic materials, we prove a desired low - regularity local well - posedness result for the corresponding elastic wave equations. for such materials, we can split the dynamics into the divergence - part and the curl - part, and each part satisfies a distinct coupled quasilinear wave system with respect to different acoustical metrics. our main result is that the sobolev norm $ h ^ { 3 + } $ of the divergence - part ( the faster - wave part ) and the $ h ^ { 4 + } $ of the curl - part ( the slower - wave part ) can be controlled in terms of initial data for short times. we note that the sobolev norm assumption $ h ^ { 3 + } $ is optimal for the divergence - part. this marks the first favorable low - regularity local well - posedness result for a wave system with multiple wave speeds. | arxiv:2411.15886 |
we apply geometric arbitrage theory to obtain results in mathematical finance, which do not need stochastic differential geometry in their formulation. first, for a generic market dynamics given by a multidimensional it \ ^ o ' s process we specify and prove the equivalence between ( nflvr ) and expected utility maximization. as a by - product we provide a geometric characterization of the ( nupbr ) condition given by the zero curvature ( zc ) condition. finally, we extend the black - scholes pde to markets allowing arbitrage. | arxiv:1904.11565 |
low - dimensional materials are susceptible to electronic instabilities such as charge density waves ( cdws ), originating from a divergence in the lindhard electron response function, combined with a finite electron - phonon coupling strength. in this report, we present a detailed characterisation of the cdw in the quasi - one - dimensional material cute, including ( 1 ) direct visualization of lattice distortion seen with non - contact atomic force microscopy in real space, ( 2 ) the out - of - plane momentum dependency of the cdw gap size of the quasi - 1 - dimensional bands, by angle - resolved photoemission spectroscopy, ( 3 ) coherent dynamics of a photoexcited phonon mode seen by time - and angle - resolved photoemission spectroscopy, with frequency and wavevector q _ cdw corresponding to the soft phonon modes predicted by theory. furthermore, we find that the cdw gap closes through a transient band renormalisation. we thus confirm that, despite the quasi - 1d characteristics of cute, it hosts inherently 3 - dimensional cdws. | arxiv:2405.09461 |
the hermitian veronesean in $ pg ( 3, q ^ 2 ) $, given by $ \ mathcal { v } : = \ { ( 1, x, x ^ q, x ^ { q + 1 } ) : x \ in \ mathbb { f } _ q \ } \ cup \ { ( 0, 0, 0, 1 ) \ } $, is a well - studied rational curve, and forms a { \ em special } set of the hermitian surface $ h ( 3, q ^ 2 ) $. in this paper, we give two local characterisations of the hermitian veronesean, based on sublines and triples of points in perspective. | arxiv:2505.05827 |
in this paper, we consider the maximization of a probability $ \ mathbb { p } \ { \ zeta \ mid \ zeta \ in \ mathbf { k } ( \ mathbf x ) \ } $ over a closed and convex set $ \ mathcal x $, a special case of the chance - constrained optimization problem. we define $ \ mathbf { k } ( \ mathbf x ) $ as $ \ mathbf { k } ( \ mathbf x ) \ triangleq \ { \ zeta \ in \ mathcal { k } \ mid c ( \ mathbf { x }, \ zeta ) \ geq 0 \ } $ where $ \ zeta $ is uniformly distributed on a convex and compact set $ \ mathcal { k } $ and $ c ( \ mathbf { x }, \ zeta ) $ is defined as either { $ c ( \ mathbf { x }, \ zeta ) \ triangleq 1 - | \ zeta ^ t \ mathbf { x } | ^ m $, $ m \ geq 0 $ } ( setting a ) or $ c ( \ mathbf { x }, \ zeta ) \ triangleq t \ mathbf { x } - \ zeta $ ( setting b ). we show that in either setting, $ \ mathbb { p } \ { \ zeta \ mid \ zeta \ in \ mathbf { k ( x ) } \ } $ can be expressed as the expectation of a suitably defined function $ f ( \ mathbf { x }, \ xi ) $ with respect to an appropriately defined gaussian density ( or its variant ), i. e. $ \ mathbb { e } _ { \ tilde p } [ f ( \ mathbf x, \ xi ) ] $. we then develop a convex representation of the original problem requiring the minimization of $ { g ( \ mathbb { e } [ f ( \ mathbf { x }, \ xi ) ] ) } $ over $ \ mathcal x $ where $ g $ is an appropriately defined smooth convex function. traditional stochastic approximation schemes cannot contend with the minimization of $ { g ( \ mathbb { e } [ f ( \ cdot, \ xi ) ] ) } $ over $ \ mathcal x $, since conditionally unbiased sampled gradients are unavailable. we then develop a regularized variance - reduced stochastic approximation ( r - vrsa ) scheme that obviates the need for | arxiv:1802.09682 |
we provide a way for embedding a 4 - dimensional geometry corresponding to the simpson visser ( sv ) spacetime which is capable of representing a traversable wormhole, a one - way wormhole, or a regular black hole into a randall - sundrum setup. to achieve this, we linearly deform the bulk geometry and the bulk matter distribution concerning a coupling constant. these deformations induce a transition from a $ 5d $ vacuum ads state to an anisotropic matter distribution. the latter results in the induced geometry on the brane transitioning from a singular schwarzschild spacetime to a regularized sv spacetime. since there are no sources or matter fields on the brane, we can assert that the induced sv geometry on the brane arises from the influence of geometrical and matter deformations in the bulk. thus, the central singularity is suppressed. we determine the cases where the energy conditions are either satisfied or violated. our spacetime is asymptotically radial ads, which is intriguing given the absence of a global ads box that would prevent instability under larger wavelength perturbations. therefore, it is no longer appropriate to claim that instability exists for very small perturbations near the ads horizon. thus, we propose that the stability of the solution can be analyzed by examining the speed of sound due to the presence of matter fields in the energy momentum tensor. | arxiv:2405.08048 |
we demonstrate a method for preparing and detecting all eigenstates of a three - level microwave dressed system with a single trapped ion. the method significantly reduces the experimental complexity of gate operations with dressed - state qubits, as well as allowing all three of the dressed - states to be prepared and detected, thereby providing access to a qutrit that is well protected from magnetic field noise. in addition, we demonstrate individual addressing of the clock transitions in two ions using a strong static magnetic field gradient, showing that our method can be used to prepare and detect microwave dressed - states in a string of ions when performing multi - ion quantum operations with microwave and radio frequency fields. the individual addressability of clock transitions could also allow for the control of pairwise interaction strengths between arbitrary ions in a string using lasers. | arxiv:1409.1696 |
this paper introduces a cost - efficient active learning ( al ) framework for classification, featuring a novel query design called candidate set query. unlike traditional al queries requiring the oracle to examine all possible classes, our method narrows down the set of candidate classes likely to include the ground - truth class, significantly reducing the search space and labeling cost. moreover, we leverage conformal prediction to dynamically generate small yet reliable candidate sets, adapting to model enhancement over successive al rounds. to this end, we introduce an acquisition function designed to prioritize data points that offer high information gain at lower cost. empirical evaluations on cifar - 10, cifar - 100, and imagenet64x64 demonstrate the effectiveness and scalability of our framework. notably, it reduces labeling cost by 42 % on imagenet64x64. | arxiv:2502.06209 |
we give an introduction to the theory of initial ideals and initial algebras with emphasis on the transfer of structural properties. | arxiv:math/0308102 |
this paper presents the first results of comparison of planck along with iras data with green bank telescope 21 - cm observations in 14 fields covering more than 800 square degrees at high galactic latitude. galactic dust emission for fields with average hi column density lower than 2 x 10 ^ 20 cm ^ - 2 is well correlated with 21 - cm emission. the residual emission in these fields, once the hi - correlated emission is removed, is consistent with the expected statistical properties of the cosmic infrared background fluctuations. fields with larger column densities show significant excess dust emission compared to the hi column density. regions of excess lie in organized structures that suggest the presence of hydrogen in molecular form, though they are not always correlated with co emission. dust emission from intermediate - velocity clouds is detected with high significance. its spectral properties are consistent with, compared to the local ism values, significantly hotter dust ( t ~ 20 k ), lower sub - millimeter dust opacity, and a relative abundance of very small grains to large grains about four times higher. these results are compatible with expectations for clouds that are part of the galactic fountain in which there is dust shattering and fragmentation. correlated dust emission in hvcs is not detected ; the average of the 99. 9 % confidence upper limits to the emissivity is 0. 15 times the local ism value at 857 and 3000 ghz, in accordance with gas phase evidence for lower metallicity and depletion in these clouds. unexpected anti - correlated variations of the dust temperature and emission cross - section per h atom are identified in the local ism and ivcs, a trend that continues into molecular environments. this suggests that dust growth through aggregation, seen in molecular clouds, is active much earlier in the cloud condensation and star formation processes. | arxiv:1101.2036 |
wolpert ' s cosine formula on teichm \ " uller space gives the weil - petersson poisson bracket $ \ { l _ \ alpha, l _ \ beta \ } $ for geodesic length functions $ l _ \ alpha, l _ \ beta $ of closed curves $ \ alpha, \ beta $ as the sum of the cosines of the angle of intersection of the associated geodesics. this was recently generalized to hitchin representations by labourie. in this paper, we give a short proof of this generalization using goldman ' s formula for the poisson bracket on representation varieties of surface groups into reductive lie groups. | arxiv:1502.05975 |
in recent years, deep learning based object detection methods have achieved promising performance in controlled environments. however, these methods lack sufficient capabilities to handle underwater object detection due to these challenges : ( 1 ) images in the underwater datasets and real applications are blurry whilst accompanying severe noise that confuses the detectors and ( 2 ) objects in real applications are usually small. in this paper, we propose a novel sample - weighted hyper network ( swipenet ), and a robust training paradigm named curriculum multi - class adaboost ( cma ), to address these two problems at the same time. firstly, the backbone of swipenet produces multiple high resolution and semantic - rich hyper feature maps, which significantly improve small object detection. secondly, a novel sample - weighted detection loss function is designed for swipenet, which focuses on learning high weight samples and ignore learning low weight samples. moreover, inspired by the human education process that drives the learning from easy to hard concepts, we here propose the cma training paradigm that first trains a clean detector which is free from the influence of noisy data. then, based on the clean detector, multiple detectors focusing on learning diverse noisy data are trained and incorporated into a unified deep ensemble of strong noise immunity. experiments on two underwater robot picking contest datasets ( urpc2017 and urpc2018 ) show that the proposed swipenet + cma framework achieves better accuracy in object detection against several state - of - the - art approaches. | arxiv:2010.10006 |
it is well known that if $ g $ is a group and $ h $ is a normal subgroup of $ g $ of finite index $ k $, then $ x ^ k \ in h $ for every $ x \ in g $. we examine finite groups $ g $ with the property that $ x ^ k \ in h $ for every subgroup $ h $ of $ g $, where $ k $ is the index of $ h $ in $ g $. we prove that a finite group $ g $ satisfies this property if and only if $ g $ is nilpotent. | arxiv:2407.05498 |
it is generally believed that the de broglie - bohm model does not admit a particle interpretation for massive relativistic spin - 0 particles, on the basis that particle trajectories cannot be defined. we show this situation is due to the fact that in the standard ( canonical ) representation of the klein - gordon equation the wavefunction systematically contains superpositions of particle and anti - particle contributions. \ we argue that by working in a foldy - wouthuysen type representation uncoupling the particle from the anti - particle evolutions, a positive conserved density for a particle and associated density current can be defined. \ for the free klein - gordon equation the velocity field obtained from this current density appears to be well - behaved and sub - luminal in typical instances. as an illustration, bohmian trajectories for a spin - 0 boson distribution are computed numerically for free propagation in situations in which the standard velocity field would take arbitrarily high positive and negative values. | arxiv:2207.14646 |
we report the direct comparison between the stabilities of two mobile absolute gravimeters of different technology : the lne - syrte cold atom gravimeter and fg5x \ # 216 of the universit \ ' e du luxembourg. these instruments rely on two different principles of operation : atomic and optical interferometry. the comparison took place in the walferdange underground laboratory for geodynamics in luxembourg, at the beginning of the last international comparison of absolute gravimeters, icag - 2013. we analyse a 2h10 duration common measurement, and find that the cag shows better immunity with respect to changes in the level of vibration noise, as well as a slightly better short term stability. | arxiv:1406.5134 |
it is well known that hyperspectral images ( hsi ) contain rich spatial - spectral contextual information, and how to effectively combine both spectral and spatial information using dnn for hsi classification has become a new research hotspot. compared with cnn with square kernels, gcn have exhibited exciting potential to model spatial contextual structure and conduct flexible convolution on arbitrarily irregular image regions. however, current gcn only using first - order spectral - spatial signatures can result in boundary blurring and isolated misclassification. to address these, we first designed the graph - based second - order pooling ( gsop ) operation to obtain contextual nodes information in non - euclidean space for gcn. further, we proposed a novel multi - stream hybridized convolutional network ( mshcnet ) with combination of first and second order statistics in euclidean / non - euclidean spaces to learn and fuse multi - view complementary information to segment hsis. specifically, our mshcnet adopted four parallel streams, which contained g - stream, utilizing the irregular correlation between adjacent land covers in terms of first - order graph in non - euclidean space ; c - stream, adopting convolution operator to learn regular spatial - spectral features in euclidean space ; n - stream, combining first and second order features to learn representative and discriminative regular spatial - spectral features of euclidean space ; s - stream, using gsop to capture boundary correlations and obtain graph representations from all nodes in graphs of non - euclidean space. besides, these feature representations learned from four different streams were fused to integrate the multi - view complementary information for hsi classification. finally, we evaluated our proposed mshcnet on three hyperspectral datasets, and experimental results demonstrated that our method significantly outperformed state - of - the - art eight methods. | arxiv:2110.03346 |
in carbon capture and sequestration, building an effective monitoring method is a crucial step to detect and respond to co2 leakage. co2 leakage detection methods rely on geophysical observations and monitoring sensor network. however, traditional methods usually require physical models to be interpreted by experts, and the accuracy of these methods will be restricted by different application conditions. in this paper, we develop a novel data - driven detection method based on densely connected convolutional networks. our detection method learns a mapping relation between seismic data and the co2 leakage mass. to account for the spatial and temporal characteristics of seismic data, we design a novel network architecture by combining 1 - d and 2 - d convolutional neural networks together. to overcome the expensive computational cost, we further apply a densely - connecting policy to our network architecture to reduce the network parameters. we employ our detection method to synthetic seismic datasets using kimberlina model. the numerical results show that our leakage detection method accurately detects the leakage mass. therefore, our novel co2 leakage detection method has great potential for monitoring co2 storage. | arxiv:1810.05932 |
we study the stable norm on the first homology of a closed, non - orientable surface equipped with a riemannian metric. we prove that in every conformal class there exists a metric whose stable norm is polyhedral. furthermore the stable norm is never strictly convex if the first betti number of the surface is greater than two. | arxiv:math/0703667 |
the null geodesics of the regular and rotating magnetically charged black hole in a non - minimally coupled einstein - yang - mills theory surrounded by a plasma medium is studied. the effect of magnetic charge and yang - mills parameter on the effective potential and radius of photon orbits has investigated. we then study the shadow of a regular and rotating magnetically charged black hole along with the observables in presence of the plasma medium. the presence of plasma medium affects the apparent size of the shadow of a regular rotating black hole in comparison to vacuum case. variation of shadow radius and deformation parameter with yang - mills and plasma parameter has examined. furthermore, the deflection angle of the massless test particles in weak field approximation around this black hole spacetime in presence of homogeneous plasma medium is also investigated. finally, we have compared the obtained results with kerr - newman and schwarzschild black hole solutions in general relativity ( gr ). | arxiv:2207.10717 |
in this work, we study the pseudo - riemannian submanifolds of a pseudo - sphere with 1 - type pseudo - spherical gauss map. first, we classify the lorentzian surfaces in a 4 - dimensional pseudo - sphere $ \ mathbb { s } ^ 4 _ s ( 1 ) $ with index s, $ s = 1, 2 $, and having harmonic pseudo - spherical gauss map. then we give a characterization theorem for pseudo - riemannian submanifolds of a pseudo - sphere $ \ mathbb { s } ^ { m - 1 } _ s ( 1 ) \ subset \ mathbb { e } ^ m _ s $ with 1 - type pseudo - spherical gauss map, and we classify spacelike surfaces and lorentzian surfaces in the de sitter space $ \ mathbb { s } ^ 4 _ 1 ( 1 ) \ subset \ mathbb { e } ^ 5 _ 1 $ with 1 - type pseudo - spherical gauss map. finally, according to the causal character of the mean curvature vector we obtain the classification of submanifolds of a pseudo - sphere having 1 - type pseudo - spherical gauss map with nonzero constant component in its spectral decomposition. | arxiv:1510.08399 |
we report magnetization, heat capacity and electrical resistivity for a newly discovered heavy fermion ( hf ) compound $ \ mathrm { ybv _ 6sn _ 6 } $ which is crystallized in a hexagonal $ \ mathrm { hffe _ 6ge _ 6 } $ - type structure, highlighted by the stacking of triangular ytterbium sublattice and kagome vanadium sublattice. above 2 k, $ \ mathrm { ybv _ 6sn _ 6 } $ shows typical hf properties due to the kondo effect on the kramers doublet of $ \ mathrm { yb ^ { 3 + } } $ ions in crystal electric field. a remarkable magnetic ordering occurs at $ t _ { \ mathrm { n } } $ = 0. 40 k in zero field while a weak external field suppresses the ordering and induces non - fermi liquid ( nfl ) behavior. in strong magnetic field the compound shows a heavy fermi liquid state. $ \ mathrm { ybv _ 6sn _ 6 } $ presents as one of the few examples of yb - based hf compounds hosting triangular kondo lattice on which a magnetic field induces quantum criticality near zero temperature. | arxiv:2210.12117 |
we introduce an analog of part of the langlands - shahidi method to the p - adic setting, constructing reciprocals of certain p - adic l - functions using the nonconstant terms of the fourier expansions of eisenstein series. we carry out the method for the group sl ( 2 ), and give explicit p - adic measures whose mellin transforms are reciprocals of dirichlet l - functions. | arxiv:1001.1913 |
the nonlinear dynamics of resistive flow with a chemical reaction is studied. proceeding from the lagrangian description, the influence of a chemical reaction on the development of fluid singularities is considered. | arxiv:1504.04205 |
despite strong evidence for the existence of large amounts of dark matter ( dm ) in our universe, there is no direct indication of its presence in our own solar system. all estimates of the local dm density rely on extrapolating results on much larger scales. we demonstrate for the first time the possibility of simultaneously measuring the local dm density and interaction cross - section with a direct detection experiment. it relies on the assumption that incoming dm particles frequently scatter on terrestrial nuclei prior to detection, inducing an additional time - dependence of the signal. we show that for sub - gev dm, with a large spin - independent dm - proton cross section, future direct detection experiments should be able to reconstruct the local dm density with smaller than 50 % uncertainty. | arxiv:2004.01621 |
this review presents an overview of the current research in kinetic exchange models for opinion formation in a society. the review begins with a brief introduction to previous models and subsequently provides an in - depth discussion of the progress achieved in the biswas - chatterjee - sen model proposed in 2012, also known as the bchs model in some later research publications. the unique feature of the model is its inclusion of negative interaction between agents. the review covers various topics, including phase transitions between different opinion states, critical behavior dependent on various parameters, and applications in realistic scenarios such as the united states presidential election and brexit. | arxiv:2304.03575 |
the way theorem establishes an important constraint that conservation laws impose on quantum mechanical measurements. we formulate the way theorem in the broader context of resource theories, where one is constrained to a subset of quantum mechanical operations described by a symmetry group. establishing connections with the theory of quantum state discrimination we obtain optimal unitaries describing the measurement of arbitrary observables, explain how prior information can permit perfect measurements that circumvent the way constraint, and provide a framework that establishes a natural ordering on measurement apparatuses through a decomposition into asymmetry and charge subsystems. | arxiv:1209.0921 |
cosmic variance is the intrinsic scatter in the number density of galaxies due to fluctuations in the large - scale dark matter density field. in this work, we present a simple analytic model of cosmic variance in the high redshift universe ( $ z \ sim5 - 15 $ ). we assume that galaxies grow according to the evolution of the halo mass function, which we allow to vary with large - scale environment. our model produces a reasonable match to the observed ultraviolet luminosity functions in this era by regulating star formation through stellar feedback and assuming that the uv luminosity function is dominated by recent star formation. we find that cosmic variance in the uvlf is dominated by the variance in the underlying dark matter halo population, and not by differences in halo accretion or the specifics of our stellar feedback model. we also find that cosmic variance dominates over poisson noise for future high - $ z $ surveys except for the brightest sources or at very high redshifts ( $ z \ gtrsim 12 $ ). we provide a linear approximation of cosmic variance for a variety of redshifts, magnitudes, and survey areas through the public python package galcv. finally, we introduce a new method for incorporating priors on cosmic variance into estimates of the galaxy luminosity function and demonstrate that it significantly improves constraints on that important observable. | arxiv:2009.05059 |
it has been proposed that interactions lead to ferromagnetism on a zigzag edge of a graphene sheet. while not yet directly studied experimentally, dramatically improving techniques for making and studying clean zigzag edges may soon make this possible. so far, most theoretical investigations of this claim have been based on mean field theories or more exact calculations using the hubbard model. but long - range coulomb interactions are unscreened in graphene so it is important to consider their effects. we study rather general non - local interactions, including of coulomb $ 1 / r $ form, using the technique of projection to a strongly interacting edge hamiltonian, valid at first order in the interactions. the ground states as well as electron / hole and exciton excitations are studied in this model. our results indicate that ferromagnetism survives with unscreened coulomb interactions. | arxiv:1702.00452 |
we present preliminary results of numerical simulations of dissipationless merging of stellar systems, aimed at exploring the consequences of merging between gas free, spheroidal systems. in particular, we study the dynamical and structural characteristics of hierarchical merging between equal mass stellar systems, and we compare the properties of the end - products with the most important structural and dynamical scaling relations obeyed by spheroids. in the explored hierarchy of four successive mergings we find that the fp tilt is marginally conserved, but both the faber - jackson and kormendy relations are not conserved. | arxiv:astro-ph/0112133 |
we investigate the mechanical stability of bose - fermi mixtures at zero temperature in the presence of a tunable feshbach resonance, which induces a competition between boson condensation and boson - fermion pairing when the boson density is smaller than the fermion density. using a many - body diagrammatic approach validated by fixed - node quantum monte carlo calculations and supported by recent experimental observations, we determine the minimal amount of boson - boson repulsion required to guarantee the stability of the mixture across the entire range of boson - fermion interactions from weak to strong coupling. our stability phase diagrams indicate that mixtures with boson - to - fermion mass ratios near two, such as the $ ^ { 87 } $ rb - $ ^ { 40 } $ k system, exhibit optimal stability conditions. moreover, by applying our results to a recent experiment with a $ ^ { 23 } $ na - $ ^ { 40 } $ k mixture, we find that the boson - boson repulsion was insufficient to ensure stability, suggesting that the experimental timescale was short enough to avoid mechanical collapse. on the other hand, we also show that even in the absence of boson - boson repulsion, bose - fermi mixtures become intrinsically stable beyond a certain coupling strength, preceding the quantum phase transition associated with the vanishing of the bosonic condensate. we thus propose an experimental protocol for observing this quantum phase transition in a mechanically stable configuration. | arxiv:2504.06681 |
we propose the quantum simulation of a fermion and an antifermion field modes interacting via a bosonic field mode, and present a possible implementation with two trapped ions. this quantum platform allows for the scalable add - up of bosonic and fermionic modes, and represents an avenue towards quantum simulations of quantum field theories in perturbative and nonperturbative regimes. | arxiv:1107.5233 |
neutrinos can undergo fast flavor conversions ( ffcs ) within extremely dense astrophysical environments such as core - collapse supernovae ( ccsne ) and neutron star mergers ( nsms ). in this study, we explore ffcs in a \ emph { multi - energy } neutrino gas, revealing that when the ffc growth rate significantly exceeds that of the vacuum hamiltonian, all neutrinos ( regardless of energy ) share a common survival probability dictated by the energy - integrated neutrino spectrum. we then employ physics - informed neural networks ( pinns ) to predict the asymptotic outcomes of ffcs within such a multi - energy neutrino gas. these predictions are based on the first two moments of neutrino angular distributions for each energy bin, typically available in state - of - the - art ccsn and nsm simulations. our pinns achieve errors as low as $ \ lesssim6 \ % $ and $ \ lesssim 18 \ % $ for predicting the number of neutrinos in the electron channel and the relative absolute error in the neutrino moments, respectively. | arxiv:2401.17424 |
stepped - wedge cluster randomized trials ( sw - crts ) are traditionally analyzed with models that assume an immediate and sustained treatment effect. previous work has shown that making such an assumption in the analysis of sw - crts when the true underlying treatment effect varies by exposure time can produce severely misleading estimates. alternatively, the true underlying treatment effect might vary by calendar time. comparatively less work has examined treatment effect structure misspecification in this setting. here, we evaluate the behavior of the mixed effects model - based immediate treatment effect, exposure time - averaged treatment effect, and calendar time - averaged treatment effect estimators in different scenarios where they are misspecified for the true underlying treatment effect structure. we show that the immediate treatment effect estimator is relatively robust to bias when estimating a true underlying calendar time - averaged treatment effect estimand. however, when there is a true underlying calendar ( exposure ) time - varying treatment effect, misspecifying an analysis with an exposure ( calendar ) time - averaged treatment effect estimator can yield severely misleading estimates and even converge to a value of the opposite sign of the true calendar ( exposure ) time - averaged treatment effect estimand. in this article, we highlight the two different time scales on which treatment effects can vary in sw - crts and clarify potential vulnerabilities that may arise when considering different types of time - varying treatment effects in a sw design. accordingly, we emphasize the need for researchers to carefully consider whether the treatment effect may vary as a function of exposure time and / or calendar time in the analysis of sw - crts. | arxiv:2409.14706 |
geo - reactor models suggest the existence of natural nuclear reactors at different deep - earth locations with loosely defined output power. reactor fission products undergo beta decay with the emission of electron antineutrinos, which routinely escape the earth. neutrino mixing distorts the energy spectrum of the electron antineutrinos. characteristics of the distorted spectrum observed at the earth ' s surface could specify the location of a geo - reactor, discriminating the models and facilitating more precise power measurement. the existence of a geo - reactor with known position could enable a precision measurement of the neutrino oscillation parameter delta - mass - squared. | arxiv:0905.0523 |
modeling distributions that depend on external control parameters is a common scenario in diverse applications like molecular simulations, where system properties like temperature affect molecular configurations. despite the relevance of these applications, existing solutions are unsatisfactory as they require severely restricted model architectures or rely on energy - based training, which is prone to instability. we introduce trade, which overcomes these limitations by formulating the learning process as a boundary value problem. by initially training the model for a specific condition using either i. i. d. ~ samples or backward kl training, we establish a boundary distribution. we then propagate this information across other conditions using the gradient of the unnormalized density with respect to the external parameter. this formulation, akin to the principles of physics - informed neural networks, allows us to efficiently learn parameter - dependent distributions without restrictive assumptions. experimentally, we demonstrate that trade achieves excellent results in a wide range of applications, ranging from bayesian inference and molecular simulations to physical lattice models. | arxiv:2410.19492 |
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