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multimodal large language models ( mllms ), built upon llms, have recently gained attention for their capabilities in image recognition and understanding. however, while mllms are vulnerable to adversarial attacks, the transferability of these attacks across different models remains limited, especially under targeted attack setting. existing methods primarily focus on vision - specific perturbations but struggle with the complex nature of vision - language modality alignment. in this work, we introduce the dynamic vision - language alignment ( dynvla ) attack, a novel approach that injects dynamic perturbations into the vision - language connector to enhance generalization across diverse vision - language alignment of different models. our experimental results show that dynvla significantly improves the transferability of adversarial examples across various mllms, including blip2, instructblip, minigpt4, llava, and closed - source models such as gemini. | arxiv:2502.19672 |
we study the correlation function between one single - trace scalar operator and a circular wilson loop in the $ 4d $ $ \ mathcal { n } = 2 $ superconformal field theory with gauge group $ su ( n ) $ and matter transforming in the symmetric and anti - symmetric representations. by exploiting supersymmetric localization, we resum the perturbative expansion of this correlator in the large - $ n $ ' t hooft limit. furthermore, using both analytical and numerical techniques, we provide a prediction for the leading term of its strong coupling expansion and we compare this prediction to numerical pad \ ' e resummations of the perturbative series. | arxiv:2303.08210 |
the effect of spin - orbit interaction was studied in a high - quality $ p $ - algaas / gaas / algaas structure with a square quantum well using acoustic methods. the structure grown on a gaas ( 100 ) substrate was symmetrically doped with carbon on both sides of the quantum well. shubnikov - de haas - type oscillations of the ac conductance of two - dimensional holes were measured. at a low magnetic field $ b < $ 2 t conductance oscillations undergo beating induced by a spin - orbit interaction. analysis of the beating character made it possible to separate the conductance contributions from the two heavy holes subbands split by the spin - orbit interaction. for each of the subbands the values of the effective masses and quantum relaxation times have been determined, and then the energy of the spin - orbit interaction was obtained. the quantum well profile, as well as the small magnitude of the spin - orbit interaction, allowed us to conclude that the spin - orbit splitting is governed by the dresselhaus mechanism. | arxiv:2110.07302 |
transportation problem is an important aspect which has been widely studied in operations research domain. it has been studied to simulate different real life problems. in particular, application of this problem in np - hard problems has a remarkable significance. in this paper, we present a comparative study of transportation problem through probabilistic and fuzzy uncertainties. fuzzy logic is a computational paradigm that generalizes classical two - valued logic for reasoning under uncertainty. in order to achieve this, the notation of membership in a set needs to become a matter of degree. by doing this we accomplish two things viz., ( i ) ease of describing human knowledge involving vague concepts and ( ii ) enhanced ability to develop cost - effective solution to real - world problem. the multi - valued nature of fuzzy sets allows handling uncertain and vague information. it is a model - less approach and a clever disguise of probability theory. we give comparative simulation results of both approaches and discuss the computational complexity. to the best of our knowledge, this is the first work on comparative study of transportation problem using probabilistic and fuzzy uncertainties. | arxiv:1307.1891 |
besides serving as prediction models, classification trees are useful for finding important predictor variables and identifying interesting subgroups in the data. these functions can be compromised by weak split selection algorithms that have variable selection biases or that fail to search beyond local main effects at each node of the tree. the resulting models may include many irrelevant variables or select too few of the important ones. either eventuality can lead to erroneous conclusions. four techniques to improve the precision of the models are proposed and their effectiveness compared with that of other algorithms, including tree ensembles, on real and simulated data sets. | arxiv:1011.0608 |
liquid democracy is the principle of making collective decisions by letting agents transitively delegate their votes. despite its significant appeal, it has become apparent that a weakness of liquid democracy is that a small subset of agents may gain massive influence. to address this, we propose to change the current practice by allowing agents to specify multiple delegation options instead of just one. much like in nature, where - - - fluid mechanics teaches us - - - liquid maintains an equal level in connected vessels, so do we seek to control the flow of votes in a way that balances influence as much as possible. specifically, we analyze the problem of choosing delegations to approximately minimize the maximum number of votes entrusted to any agent, by drawing connections to the literature on confluent flow. we also introduce a random graph model for liquid democracy, and use it to demonstrate the benefits of our approach both theoretically and empirically. | arxiv:1808.01906 |
during the first three years of low luminosity operation, the lhc will facilitate a number of precision tests of the electroweak sector of the standard model. the prospects for measuring the w boson and top quark masses and for probing the charged triple gauge boson couplings at atlas are presented here. in each case the most likely analysis methods are described and the statistical and systematic uncertainties which can be expected are reported. | arxiv:hep-ex/0405015 |
while right - censored time - to - event outcomes have been studied for decades, handling time - to - event covariates, also known as right - censored covariates, is now of growing interest. so far, the literature has treated right - censored covariates as distinct from missing covariates, overlooking the potential applicability of estimators to both scenarios. we bridge this gap by establishing connections between right - censored and missing covariates under various assumptions about censoring and missingness, allowing us to identify parallels and differences to determine when estimators can be used in both contexts. these connections reveal adaptations to five estimators for right - censored covariates in the unexplored area of informative covariate right - censoring and to formulate a new estimator for this setting, where the event time depends on the censoring time. we establish the asymptotic properties of the six estimators, evaluate their robustness under incorrect distributional assumptions, and establish their comparative efficiency. we conducted a simulation study to confirm our theoretical results, and then applied all estimators to a huntington disease observational study to analyze cognitive impairments as a function of time to clinical diagnosis. | arxiv:2409.04684 |
methods for finding the optimal choices of the applied remote loads - - the applied normal force, moment, shear force and remote bulk stresses - - needed to solve frictional contact problems in partial - slip using half - plane theory are derived by using data from contacts analysed by the finite element method. while the normal and shear forces and moment are readily found from equilibrium considerations, in order to determine the bulk stresses we must exploit details of the traction ratio and the direct strain within the contact, both of which are readily extracted from simulations. these contact loads enable the formulation of an equivalent half - plane problem for the contact, which can be used to determine much more precise estimates of the slip - zone sizes than are obtainable from direct use of frictional finite element analysis, as aggregated data from the finite element output is employed, and the half - plane analysis will add precision in terms of satisfaction of the laws of frictional slip and stick. | arxiv:2103.15802 |
we characterize semigroups $ x $ whose semigroups of filters $ \ varphi ( x ) $, maximal linked systems $ \ lambda ( x ) $, linked upfamilies $ n _ 2 ( x ) $, and upfamilies $ \ upsilon ( x ) $ are commutative. | arxiv:1303.4606 |
this paper investigates the interplay between information diffusion in social networks and its impact on financial markets with an agent - based model ( abm ). agents receive and exchange information about an observable stochastic component of the dividend process of a risky asset \ ` a la grossman and stiglitz. a small proportion of the network has access to a private signal about the component, which can be clean ( information ) or distorted ( misinformation ). other agents are uninformed and can receive information only from their peers. all agents are bayesian, adjusting their beliefs according to the confidence they have in the source of information. we examine, by means of simulations, how information diffuses in the network and provide a framework to account for delayed absorption of shocks, that are not immediately priced as predicted by classical financial models. we investigate the effect of the network topology on the resulting asset price and evaluate under which condition misinformation diffusion can make the market more inefficient. | arxiv:2412.16269 |
in complex inferential tasks like question answering, machine learning models must confront two challenges : the need to implement a compositional reasoning process, and, in many applications, the need for this reasoning process to be interpretable to assist users in both development and prediction. existing models designed to produce interpretable traces of their decision - making process typically require these traces to be supervised at training time. in this paper, we present a novel neural modular approach that performs compositional reasoning by automatically inducing a desired sub - task decomposition without relying on strong supervision. our model allows linking different reasoning tasks though shared modules that handle common routines across tasks. experiments show that the model is more interpretable to human evaluators compared to other state - of - the - art models : users can better understand the model ' s underlying reasoning procedure and predict when it will succeed or fail based on observing its intermediate outputs. | arxiv:1807.08556 |
we calculate the ordered k _ 0 - group of a graph c * - algebra and mention applications of this result to af - algebras, states on the k _ 0 - group of a graph algebra, and tracial states of graph algebras. | arxiv:math/0204095 |
##urologist known as the father of psychoanalysis. jerome isaac friedman ( 1930 – ) : american physicist who won the 1990 nobel prize in physics along with henry kendall and richard taylor, for work showing an internal structure for protons later known to be quarks. christer fuglesang ( 1957 – ) : swedish astronaut and physicist. = = g = = george gamow ( 1904 – 1968 ) : russian - born theoretical physicist and cosmologist. an early advocate and developer of lemaitre ' s big bang theory. joseph louis gay - lussac ( 1772 – 1850 ) : french chemist and physicist. he is known mostly for two laws related to gases. ivar giaever ( 1929 – ) : norwegian - american physicist who shared the nobel prize in physics in 1973 with leo esaki and brian josephson " for their discoveries regarding tunnelling phenomena in solids ". giaever is an institute professor emeritus at the rensselaer polytechnic institute, a professor - at - large at the university of oslo, and the president of applied biophysics. sheldon glashow ( 1932 – ) : american theoretical physicist. he shared the 1979 nobel prize in physics with steven weinberg and abdus salam for his contribution to the electroweak unification theory. camillo golgi ( 1843 – 1926 ) : italian physician, biologist, pathologist, scientist, and nobel laureate. several structures and phenomena in anatomy and physiology are named for him, including the golgi apparatus, the golgi tendon organ and the golgi tendon reflex. he is recognized as the greatest neuroscientist and biologist of his time. herb grosch ( 1918 – 2010 ) : canadian - american computer scientist, perhaps best known for grosch ' s law, which he formulated in 1950. david gross ( 1941 – ) : american theoretical physicist and string theorist who was awarded a nobel prize in physics for his co - discovery of asymptotic freedom. = = h = = jacques hadamard ( 1865 – 1963 ) : french mathematician who made major contributions in number theory, complex function theory, differential geometry and partial differential equations. jonathan haidt ( c. 1964 – ) : associate professor of psychology at the university of virginia, focusing on the psychological bases of morality across different cultures, and author of the happiness hypothesis. j. b. s. haldane ( 1892 – 1964 ) : british polymath well known for his works in physiology, genetics and evolutionary biology. he was also a mathematician making | https://en.wikipedia.org/wiki/List_of_atheists_in_science_and_technology |
we report a comprehensive study on the elastic properties of a hexanary high - entropy alloy superconductor ( sczrnbta ) $ _ { 0. 685 } $ [ rhpd ] $ _ { 0. 315 } $ at room and cryogenic temperatures, by resonant ultrasound spectroscopy experiments. the derived elastic constants are bulk modulus $ k = 132. 7 $ gpa, young ' s modulus $ e = 121. 0 $ gpa, shear modulus $ g = 44. 9 $ gpa, and poisson ' s ratio $ \ nu $ = 0. 348 for room temperature. the young ' s and shear moduli are $ \ sim 10 \ % $ larger than those in nbti superconductor with similar $ t _ c $, while the ductility is comparable. moreover, the mechanical performance is further enhanced at cryogenic temperature. our work confirms the advantageous mechanical properties of high - entropy alloy superconductors and suggests the application prospects. | arxiv:2204.07993 |
a new method for the optimal solutions is proposed. originating from the continuous - time dynamics stability theory in the control field, the optimal solution is anticipated to be obtained in an asymptotically evolving way. by introducing a virtual dimension, the variation time, a dynamic system that describes the variation motion is deduced from the optimal control problem ( ocp ), and the optimal solution is its equilibrium point. through this method, the intractable ocp is transformed to the initial - value problem ( ivp ) and it may be solved with mature ordinary differential equation ( ode ) numerical integration methods. especially, the deduced dynamic system is globally stable, so any initial value will evolve to the extremal solution ultimately. | arxiv:1703.10263 |
we provide a set of exact solutions in field theory of scalar fields with $ z _ 2 $ symmetry that involve jacobi elliptic functions. these solutions have the interesting property to provide massive waves even if one starts from a massless equation. we analyze them classically providing also exact solutions to the corresponding equations for the green functions needed to completely solve them in a strong coupling limit. this is accomplished using a functional expansion into powers of the current. it is shown that the spontaneous breaking of the $ z _ 2 $ symmetry is due to the existence of a zero mode that persists also in the case of the higgs mechanism. in this latter case, the zero mode seems to play a role similar to the goldstone boson in the breaking of a continuous symmetry and so, it should be important at lower momenta as a long range excitation. | arxiv:1310.6630 |
the dark matter particle explorer ( dampe ) is one of the four satellites within the strategic pioneer research program in space science of the chinese academy of science ( cas ). the silicon - tungsten tracker ( stk ), which is composed of 768 singled - sided silicon microstrip detectors, is one of the four subdetectors in dampe, providing track reconstruction and charge identification for relativistic charged particles. the charge response of dampe silicon microstrip detectors is complicated, depending on the incident angle and impact position. a new charge reconstruction algorithm for the dampe silicon microstrip detector is introduced in this paper. this algorithm can correct the complicated charge response, and was proved applicable by the ion test beam. | arxiv:1712.08011 |
do not adhere to the substrate. = = see also = = energetically modified cement – class of cements, mechanically processed to transform reactivity surface finishing – range of processes that alter the surface of an item to achieve a certain property surface science – study of physical and chemical phenomena that occur at the interface of two phases surface metrology – measurement of small - scale features on surfaces tribology – science of rubbing surfaces = = references = = r. chattopadhyay, ’ advanced thermally assisted surface engineering processes ’ kluwer academic publishers, ma, us ( now springer, ny ), 2004, isbn 1 - 4020 - 7696 - 7, e - isbn 1 - 4020 - 7764 - 5. r. chattopadhyay, ’ surface wear - analysis, treatment, & prevention ’, asm - international, materials park, oh, us, 2001, isbn 0 - 87170 - 702 - 0. sanjay kumar thakur and r. gopal krishnan, ’ advances in applied surface engineering ’, research publishing services, singapore, 2011, isbn 978 - 981 - 08 - 7922 - 8. = = external links = = institute of surface chemistry and catalysis ulm university | https://en.wikipedia.org/wiki/Surface_engineering |
exploration is a key challenge in reinforcement learning, especially in long - horizon, deceptive and sparse - reward environments. for such applications, population - based approaches have proven effective. methods such as quality - diversity deals with this by encouraging novel solutions and producing a diversity of behaviours. however, these methods are driven by either undirected sampling ( i. e. mutations ) or use approximated gradients ( i. e. evolution strategies ) in the parameter space, which makes them highly sample - inefficient. in this paper, we propose a model - based quality - diversity approach. it extends existing qd methods to use gradients for efficient exploitation and leverage perturbations in imagination for efficient exploration. our approach optimizes all members of a population simultaneously to maintain both performance and diversity efficiently by leveraging the effectiveness of qd algorithms as good data generators to train deep models. we demonstrate that it maintains the divergent search capabilities of population - based approaches on tasks with deceptive rewards while significantly improving their sample efficiency and quality of solutions. | arxiv:2211.12610 |
an extended version of the ads / qcd soft - wall model that incorporates qcd - like anomalous contributions to the dimensions of gauge theory operators is proposed. this exploratory approach leads to a relation between scalar glueball masses and beta functions. using this relation, properties of the glueball mass spectroscopy that emerge from phenomenological beta functions proposed in the literature are investigated. the reverse problem is also considered : starting from a linear regge trajectory which fits the lattice glueball masses, beta functions with different asymptotic infrared behaviours are found. remarkably, some of them present a fixed point at finite coupling. | arxiv:1208.2291 |
virtual reality and augmented reality ( xr ) bring increasing demand for 3d content. however, creating high - quality 3d content requires tedious work that a human expert must do. in this work, we study the challenging task of lifting a single image to a 3d object and, for the first time, demonstrate the ability to generate a plausible 3d object with 360 { \ deg } views that correspond well with the given reference image. by conditioning on the reference image, our model can fulfill the everlasting curiosity for synthesizing novel views of objects from images. our technique sheds light on a promising direction of easing the workflows for 3d artists and xr designers. we propose a novel framework, dubbed neurallift - 360, that utilizes a depth - aware neural radiance representation ( nerf ) and learns to craft the scene guided by denoising diffusion models. by introducing a ranking loss, our neurallift - 360 can be guided with rough depth estimation in the wild. we also adopt a clip - guided sampling strategy for the diffusion prior to provide coherent guidance. extensive experiments demonstrate that our neurallift - 360 significantly outperforms existing state - of - the - art baselines. project page : https : / / vita - group. github. io / neurallift - 360 / | arxiv:2211.16431 |
the mass loss rates of red supergiants ( rsgs ) govern their evolution towards supernova and dictate the appearance of the resulting explosion. to study how mass - loss rates change with evolution we measure the mass - loss rates ( \ mdot ) and extinctions of 19 red supergiants in the young massive cluster ngc2100 in the large magellanic cloud. by targeting stars in a coeval cluster we can study the mass - loss rate evolution whilst keeping the variables of mass and metallicity fixed. mass - loss rates were determined by fitting dusty models to mid - ir photometry from wise and spitzer / irac. we find that the \ mdot \ in red supergiants increases as the star evolves, and is well described by \ mdot \ prescription of de jager, used widely in stellar evolution calculations. we find the extinction caused by the warm dust is negligible, meaning the warm circumstellar material of the inner wind cannot explain the higher levels of extinction found in the rsgs compared to other cluster stars. we discuss the implications of this work in terms of supernova progenitors and stellar evolution theory. we argue there is little justification for substantially increasing the \ mdot \ during the rsg phase, as has been suggested recently in order to explain the absence of high mass type iip supernova progenitors. we also argue that an increase in reddening towards the end of the rsg phase, as observed for the two most evolved cluster stars, may provide a solution to the red supergiant problem. | arxiv:1608.03895 |
we prove consistency of four different approaches to formalizing the idea of minimum average edge - length in a path linking some infinite subset of points of a poisson process. the approaches are ( i ) shortest path from origin through some $ m $ distinct points ; ( ii ) shortest average edge - length in paths across the diagonal of a large cube ; ( iii ) shortest path through some specified proportion $ \ delta $ of points in a large cube ; ( iv ) translation - invariant measures on paths in $ \ reals ^ d $ which contain a proportion $ \ delta $ of the poisson points. we develop basic properties of a normalized average length function $ c ( \ delta ) $ and pose challenging open problem | arxiv:math/0509492 |
in this paper, we analyze the performance of an electro - optic modulator based on a single quantum dot strongly coupled to a nano - resonator, where electrical control of the quantum dot frequency is achieved via quantum confined stark effect. using realistic system parameters, we show that modulation speeds of a few tens of ghz are achievable with this system, while the energy per switching operation can be as small as 0. 5 fj. in addition, we study the non - linear distortion, and the effect of pure quantum dot dephasing on the performance of the modulator. | arxiv:0911.5207 |
we report the finding of unidirectional electronic properties, analogous to a semiconductor diode, in two - dimensional artificial permalloy honeycomb lattice of ultra - small bond, with a typical length of ~ 12 nm. the unidirectional transport behavior, characterized by the asymmetric colossal enhancement in differential conductivity at a modest current application of ~ 10 - 15 $ \ mu $ a, persists to t = 300 k in honeycomb lattice of thickness ~ 6 nm. the asymmetric behavior arises without the application of magnetic field. a qualitative analysis of experimental data suggests the role of magnetic charge or monopoles in the unusual observations with strong implication for spintronics. | arxiv:1701.08455 |
we present a theoretical study of the phase diagram of a frustrated ising model with nearest - neighbor ferromagnetic interactions and long - range ( coulombic ) antiferromagnetic interactions. for nonzero frustration, long - range ferromagnetic order is forbidden, and the ground - state of the system consists of phases characterized by periodically modulated structures. at finite temperatures, the phase diagram is calculated within the mean - field approximation. below the transition line that separates the disordered and the ordered phases, the frustration - temperature phase diagram displays an infinite number of ` ` flowers ' ', each flower being made by an infinite number of modulated phases generated by structure combination branching processes. the specificities introduced by the long - range nature of the frustrating interaction and the limitation of the mean - field approach are finally discussed. | arxiv:cond-mat/0006262 |
we consider a distributed learning problem, where agents minimize a global objective function by exchanging information over a network. our approach has two distinct features : ( i ) it substantially reduces communication by triggering communication only when necessary, and ( ii ) it is agnostic to the data - distribution among the different agents. we therefore guarantee convergence even if the local data - distributions of the agents are arbitrarily distinct. we analyze the convergence rate of the algorithm both in convex and nonconvex settings and derive accelerated convergence rates for the convex case. we also characterize the effect of communication failures and demonstrate that our algorithm is robust to these. the article concludes by presenting numerical results from distributed learning tasks on the mnist and cifar - 10 datasets. the experiments underline communication savings of 35 % or more due to the event - based communication strategy, show resilience towards heterogeneous data - distributions, and highlight that our approach outperforms common baselines such as fedavg, fedprox, scaffold and fedadmm. | arxiv:2405.10618 |
the subclass of magnetic cataclysmic variables ( cv ), known as asynchronous polars, are still relatively poorly understood. an asynchronous polar is a polar in which the spin period of the white dwarf is either shorter or longer than the binary orbital period ( typically within a few percent ). the asynchronous polars have been disproportionately detected in soft gamma - ray observations, leading us to consider the possibility that they have intrinsically harder x - ray spectra. we compared standard and asynchronous polars in order to examine the relationship between a cv ' s synchronization status and its spectral shape. using the entire sample of asynchronous polars, we find that the asynchronous polars may, indeed, have harder spectra, but that the result is not statistically significant. | arxiv:2107.03328 |
this dissertation considers new constructions and decoding approaches for error - correcting codes based on non - conventional polynomials, with the objective of providing new coding solutions to the applications mentioned above. with skew polynomials, we construct codes that are dual - containing, which is a desired property of quantum error - correcting codes. by considering evaluation codes based on skew polynomials, a condition on the existence of optimal support - constrained codes is derived and an application of such codes in the distributed multi - source networks is proposed. for a class of multicast networks, the advantage of vector network coding compared to scalar network coding is investigated. multivariate polynomials have been attracting increasing interest in constructing codes with repair capabilities by accessing only a small amount of available symbols, which is required to build failure - resistant distributed storage systems. a new class of bivariate evaluation codes and their local recovery capability are studied. interestingly, the well - known reed - solomon codes are used in a class of locally recoverable codes with availability ( multiple disjoint recovery sets ) via subspace design. aside from new constructions, decoding approaches are considered in order to increase the error correction capability in the case where the code is fixed. in particular, new lower and upper bounds on the success probability of joint decoding interleaved alternant codes by a syndrome - based decoder are derived, where alternant codes are an important class of algebraic codes containing goppa codes, bch codes, and reed - muller codes as sub - classes. | arxiv:2501.03961 |
a defect density which quantifies the deviation from the spin ground state characterizes non - equilibrium dynamics during phase transitions. the widely recognized kibble - zurek scaling predicts how the defect density evolves during phase transitions. however, it can be perturbed by a noise, leading to the anti - kibble - zurek scaling. in this research, we analytically investigate the effect of gaussian white noise on the transition probabilities of the landau - zener model. we apply this analysis to the one - dimensional transverse field ising model and obtain an analytical approximate solution of the defect density. our analysis reveals that when the introduced noise is small, the model follows the previously known anti - kibble - zurek scaling. conversely, when the noise increases, the scaling can be obtained by using the adiabatic approximation. this result indicates that deriving the anti - kibble - zurek scaling does not require solving differential equations, instead, it can be achieved simply by applying the adiabatic approximation. furthermore, we identify the parameter that minimizes the defect density based on the new scaling, which allows us to verify how effective the already known scaling of the optimized parameter is. | arxiv:2404.17247 |
the gauss - bonnet topological scalar is presented in metric - teleparallel formalism as well as in the symmetric and general teleparallel formulations. in all of the aforementioned frameworks, the full expressions are provided explicitly in terms of torsion, non - metricity and levi - civita covariant derivative. the number of invariant terms of this form is counted and compared with the number which can appear in the corresponding effective field theory. although the difference in this number is not very large, it is found that the gauss - bonnet invariant excludes some of the effective field theory terms. this result sheds new light on how general relativity symmetries can be maintained at higher order in teleparallel theories : this fact appears to be highly nontrivial in the teleparallel formulation. the importance of the so - called ` ` pseudo - invariant ' ' theories like $ f ( t ) $ - and $ f ( t, t _ \ mathcal { g } ) $ - gravity is further discussed in the context of teleparallel gauss - bonnet gravity. | arxiv:2308.03632 |
we give a direct analytic proof of the classical boundary harnack inequality for solutions to linear uniformly elliptic equations in either divergence or non - divergence form. | arxiv:1909.00062 |
nuclear structure and reaction theory is undergoing a major renaissance with advances in many - body methods, strong interactions with greatly improved links to quantum chromodynamics ( qcd ), the advent of high performance computing, and improved computational algorithms. predictive power, with well - quantified uncertainty, is emerging from non - perturbative approaches along with the potential for guiding experiments to new discoveries. we present an overview of some of our recent developments and discuss challenges that lie ahead. our foci include : ( 1 ) strong interactions derived from chiral effective field theory ; ( 2 ) advances in solving the large sparse matrix eigenvalue problem on leadership - class supercomputers ; ( 3 ) selected observables in light nuclei with the jisp16 interaction ; ( 4 ) effective electroweak operators consistent with the hamiltonian ; and, ( 5 ) discussion of a = 48 system as an opportunity for the no - core approach with the reintroduction of the core. | arxiv:1803.04101 |
we propose an end - to - end attribute compression method for dense point clouds. the proposed method combines a frequency sampling module, an adaptive scale feature extraction module with geometry assistance, and a global hyperprior entropy model. the frequency sampling module uses a hamming window and the fast fourier transform to extract high - frequency components of the point cloud. the difference between the original point cloud and the sampled point cloud is divided into multiple sub - point clouds. these sub - point clouds are then partitioned using an octree, providing a structured input for feature extraction. the feature extraction module integrates adaptive convolutional layers and uses offset - attention to capture both local and global features. then, a geometry - assisted attribute feature refinement module is used to refine the extracted attribute features. finally, a global hyperprior model is introduced for entropy encoding. this model propagates hyperprior parameters from the deepest ( base ) layer to the other layers, further enhancing the encoding efficiency. at the decoder, a mirrored network is used to progressively restore features and reconstruct the color attribute through transposed convolutional layers. the proposed method encodes base layer information at a low bitrate and progressively adds enhancement layer information to improve reconstruction accuracy. compared to the latest g - pcc test model ( tmc13v23 ) under the mpeg common test conditions ( ctcs ), the proposed method achieved an average bjontegaard delta bitrate reduction of 24. 58 % for the y component ( 21. 23 % for yuv combined ) on the mpeg category solid dataset and 22. 48 % for the y component ( 17. 19 % for yuv combined ) on the mpeg category dense dataset. this is the first instance of a learning - based codec outperforming the g - pcc standard on these datasets under the mpeg ctcs. | arxiv:2409.10293 |
we consider the extremal limit of a black hole geometry of the reissner - nordstrom type and compute the quantum corrections to its entropy. universally, the limiting geometry is the direct product of two 2 - dimensional spaces and is characterized by just a few parameters. we argue that the quantum corrections to the entropy of such extremal black holes due to a massless scalar field have a universal behavior. we obtain explicitly the form of the quantum entropy in this extremal limit as function of the parameters of the limiting geometry. we generalize these results to black holes with toroidal or higher genus horizon topologies. in general, the extreme quantum entropy is completely determined by the spectral geometry of the horizon and in the ultra - extreme case it is just a determinant of the 2 - dimensional laplacian. as a byproduct of our considerations we obtain expressions for the quantum entropy of black holes which are not of the reissner - nordstrom type : the extreme dilaton and extreme kerr - newman black holes. in both cases the classical bekenstein - hawking entropy is modified by logarithmic corrections. | arxiv:hep-th/9709064 |
silicon is vital to the computing industry due to the high quality of its native oxide and well - established doping technologies. isotopic purification has enabled quantum coherence times on the order of seconds, thereby placing silicon at the forefront of efforts to create a solid state quantum processor. we demonstrate strong coupling of a single electron in a silicon double quantum dot to the photonic field of a microwave cavity, as shown by the observation of vacuum rabi splitting. strong coupling of a quantum dot electron to a cavity photon would allow for long - range qubit coupling and the long - range entanglement of electrons in semiconductor quantum dots. | arxiv:1703.03047 |
federated self - supervised learning ( fssl ) has recently emerged as a promising paradigm that enables the exploitation of clients ' vast amounts of unlabeled data while preserving data privacy. while fssl offers advantages, its susceptibility to backdoor attacks, a concern identified in traditional federated supervised learning ( fsl ), has not been investigated. to fill the research gap, we undertake a comprehensive investigation into a backdoor attack paradigm, where unscrupulous clients conspire to manipulate the global model, revealing the vulnerability of fssl to such attacks. in fsl, backdoor attacks typically build a direct association between the backdoor trigger and the target label. in contrast, in fssl, backdoor attacks aim to alter the global model ' s representation for images containing the attacker ' s specified trigger pattern in favor of the attacker ' s intended target class, which is less straightforward. in this sense, we demonstrate that existing defenses are insufficient to mitigate the investigated backdoor attacks in fssl, thus finding an effective defense mechanism is urgent. to tackle this issue, we dive into the fundamental mechanism of backdoor attacks on fssl, proposing the embedding inspector ( eminspector ) that detects malicious clients by inspecting the embedding space of local models. in particular, eminspector assesses the similarity of embeddings from different local models using a small set of inspection images ( e. g., ten images of cifar100 ) without specific requirements on sample distribution or labels. we discover that embeddings from backdoored models tend to cluster together in the embedding space for a given inspection image. evaluation results show that eminspector can effectively mitigate backdoor attacks on fssl across various adversary settings. our code is avaliable at https : / / github. com / shuchiwu / eminspector. | arxiv:2405.13080 |
recently, ieee 802. 11ax task group has adapted ofdma as a new technique for enabling multi - user transmission. it has been also decided that the scheduling duration should be same for all the users in a multi - user ofdma so that the transmission of the users should end at the same time. in order to realize that condition, the users with insufficient data should transmit null data ( i. e. padding ) to fill the duration. while this scheme offers strong features such as resilience to overlapping basic service set ( obss ) interference and ease of synchronization, it also poses major side issues of degraded throughput performance and waste of devices ' energy. in this work, for ofdma based 802. 11 wlans we first propose practical algorithm in which the scheduling duration is fixed and does not change from time to time. in the second algorithm the scheduling duration is dynamically determined in a resource allocation framework by taking into account the padding overhead, airtime fairness and energy consumption of the users. we analytically investigate our resource allocation problems through lyapunov optimization techniques and show that our algorithms are arbitrarily close to the optimal performance at the price of reduced convergence rate. we also calculate the overhead of our algorithms in a realistic set - up and propose solutions for the implementation issues. | arxiv:1602.07104 |
the development of high - resolution imaging methods such as electron and scanning probe microscopy and atomic probe tomography have provided a wealth of information on structure and functionalities of solids. the availability of this data in turn necessitates development of approaches to derive quantitative physical information, much like the development of scattering methods in the early xx century which have given one of the most powerful tools in condensed matter physics arsenal. here, we argue that this transition requires adapting classical macroscopic definitions, that can in turn enable fundamentally new opportunities in understanding physics and chemistry. for example, many macroscopic definitions such as symmetry can be introduced locally only in a bayesian sense, balancing the prior knowledge of materials ' physics and experimental data to yield posterior probability distributions. at the same time, a wealth of local data allows fundamentally new approaches for the description of solids based on construction of statistical and physical generative models, akin to ginzburg - landau thermodynamic models. finally, we note that availability of observational data opens pathways towards exploring causal mechanisms underpinning solid structure and functionality. | arxiv:2109.07350 |
let $ f $ be a fixed self - contragradient hecke - maass form for $ sl ( 3, \ mathbb z ) $, and $ u $ an even hecke - maass form for $ sl ( 2, \ mathbb z ) $ with laplace eigenvalue $ 1 / 4 + k ^ 2 $, $ k > 0 $. a subconvexity bound $ o \ big ( k ^ { 4 / 3 + \ varepsilon } \ big ) $ in the eigenvalue aspect is proved for the central value at $ s = 1 / 2 $ of the rankin - selberg $ l $ - function $ l ( s, f \ times u ) $. meanwhile, a subconvexity bound $ o \ big ( ( 1 + | t | ) ^ { 2 / 3 + \ varepsilon } \ big ) $ in the $ t $ aspect is proved for $ l ( 1 / 2 + it, f ) $. these bounds improved corresponding subconvexity bounds proved by xiaoqing li ( annals of mathematics, 2011 ). the main technique in the proof, other than those used by li, is an $ n $ th - order asymptotic expansion of a weighted stationary phase integral, for arbitrary $ n \ geq1 $. this asymptotic expansion sharpened the classical result for $ n = 1 $ by huxley. | arxiv:1510.01219 |
we present results of tensor - network simulations of the three - dimensional $ o ( 2 ) $ model at non - zero chemical potential and temperature, which were computed using the higher - order tensor - renormalization - group method ( hotrg ). this necessitated enhancements to the hotrg blocking procedure to reduce the truncation error in the case of anisotropic tensors. moreover, the construction of the truncated vector spaces was adapted to strongly reduce the effect of systematic errors in the computation of observables using the finite - difference method. our ( improved ) hotrg results for the evolution of the number density with the chemical potential are in agreement with results obtained with the worm algorithm, and both the silver blaze phenomenon at zero temperature and the temperature dependence of the number density can be adequately reproduced. | arxiv:2112.01414 |
for an odd prime p and a number field f containing a primitive p - th root of unity, we describe the kummer radical a _ f of the first layers of all the z _ p - extensions of f in terms of universal norms of p - units along the cyclotomic tower of f. we also study " twisted " radicals related to af. | arxiv:1303.0176 |
we report the first systematic analysis of single exposures of all optical and ultraviolet ( uv ) observations performed by the ultraviolet and optical telescope ( uvot ) on board the { \ em neil gehrels swift observatory } satellite available up to 2019 april of six $ \ gamma $ - ray - emitting narrow - line seyfert 1 galaxies ( nlsy1 ). rapid variability has been significantly detected on hours time - scale for 1h 0323 + 342, sbs 0846 + 513, pmn j0948 + 0022, and pks 2004 - 447 in 18 observations for a total of 34 events. in particular, we report the first detection of significant variability on short time - scale ( 3 - 6 ks ) in optical for pks 2004 - 447, and uv for 1h 0323 + 342 and pmn j0948 + 0022. the shortest variability time - scale observed for 1h 0323 + 342, sbs 0846 + 513, pmn j0948 + 0022, and pks 2004 - 447 ( assuming a doppler factor delta = 10 ) gives a lower limit on the size of emission region between 9. 7 $ \ times $ 10 $ ^ { 14 } $ ( for sbs 0846 + 513 ) and 1. 6 $ \ times $ 10 $ ^ { 15 } $ cm ( for 1h 0323 + 342 ), suggesting that the optical and uv emission during these events is produced in compact regions within the jet. these observations provide unambiguous evidence about the relativistically beamed synchrotron emission in these sources, similar to blazars. a remarkable variability has been observed for pmn j0948 + 0022 on 2009 june 23 with an increase from $ \ sim $ 1. 1 to 0. 4 mag going from v to w2 filter in $ \ sim $ 1. 6 h and a decrease at the initial level in a comparable time. the higher fractional flux change observed for this and other events at lower frequencies suggests that the synchrotron emission is more contaminated by thermal emission from accretion disc at higher frequencies. | arxiv:2009.00630 |
two common definitions of the spatially local rate of kinetic energy cascade at some scale $ \ ell $ in turbulent flows are ( i ) the cubic velocity difference term appearing in the generalized kolmogorov - hill equation ( gkhe ) ( structure function approach ), and ( ii ) the subfilter - scale energy flux term in the transport equation for subgrid - scale kinetic energy ( filtering approach ). we perform a comparative study of both quantities based on direct numerical simulation data of isotropic turbulence at taylor - scale reynolds number of 1250. while observations of negative subfilter - scale energy flux ( backscatter ) have in the past led to debates regarding interpretation and relevance of such observations, we argue that the interpretation of the local structure function - based cascade rate definition is unambiguous since it arises from a divergence term in scale space. conditional averaging is used to explore the relationship between the local cascade rate and the local filtered viscous dissipation rate as well as filtered velocity gradient tensor properties such as its invariants. we find statistically robust evidence of inverse cascade when both the large - scale rotation rate is strong and the large - scale strain rate is weak. even stronger net inverse cascading is observed in the ` ` vortex compression ' ' $ r > 0 $, $ q > 0 $ quadrant where $ r $ and $ q $ are velocity gradient invariants. qualitatively similar, but quantitatively much weaker trends are observed for the conditionally averaged subfilter scale energy flux. flow visualizations show consistent trends, namely that spatially the inverse cascade events appear to be located within large - scale vortices, specifically in subregions when $ r $ is large. | arxiv:2307.10568 |
the large time behavior of non - negative solutions to the viscous hamilton - jacobi equation $ u _ t - \ delta u + | \ nabla u | ^ q = 0 $ in the whole space $ r ^ n $ is investigated for the critical exponent $ q = ( n + 2 ) / ( n + 1 ) $. convergence towards a rescaled self - similar solution of the linear heat equation is shown, the rescaling factor being $ ( \ log ( t ) ) ^ { - ( n + 1 ) } $. the proof relies on the construction of a one - dimensional invariant manifold for a suitable truncation of the equation written in self - similar variables. | arxiv:math/0609750 |
tidal interactions have a significant influence on the late dynamics of compact binary systems, which constitute the prime targets of the upcoming network of gravitational - wave detectors. we refine the theoretical description of tidal interactions ( hitherto known only to the second post - newtonian level ) by extending our recently developed analytic self - force formalism, for extreme mass - ratio binary systems, to the computation of several tidal invariants. specifically, we compute, to linear order in the mass ratio and to the 7. 5 $ ^ { \ rm th } $ post - newtonian order, the following tidal invariants : the square and the cube of the gravitoelectric quadrupolar tidal tensor, the square of the gravitomagnetic quadrupolar tidal tensor, and the square of the gravitoelectric octupolar tidal tensor. our high - accuracy analytic results are compared to recent numerical self - force tidal data by dolan et al. \ cite { dolan : 2014pja }, and, notably, provide an analytic understanding of the light ring asymptotic behavior found by them. we transcribe our kinematical tidal - invariant results in the more dynamically significant effective one - body description of the tidal interaction energy. by combining, in a synergetic manner, analytical and numerical results, we provide simple, accurate analytic representations of the global, strong - field behavior of the gravitoelectric quadrupolar tidal factor. a striking finding is that the linear - in - mass - ratio piece in the latter tidal factor changes sign in the strong - field domain, to become negative ( while its previously known second post - newtonian approximant was always positive ). we, however, argue that this will be more than compensated by a probable fast growth, in the strong - field domain, of the nonlinear - in - mass - ratio contributions in the tidal factor. | arxiv:1409.6933 |
differential force measurements between spheres coated with either nickel or gold and rotating disks with periodic distributions of nickel and gold are reported. the rotating samples are covered by a thin layer of titanium and a layer of gold. while titanium is used for fabrication purposes, the gold layer ( nominal thicknesses of 21, 37, 47 and 87 nm ) provides an isoelectronic environment, and is used to nullify the electrostatic contribution but allow the passage of long wavelength casimir photons. a direct comparison between the experimental results and predictions from drude and plasma models for the electrical permittivity is carried out. in the models the magnetic permeability of nickel is allowed to change to investigate its effects. possible sources of errors, both in the experimental and theoretical sides, are taken into account. it is found that a drude response with magnetic properties of nickel taken into account is unequivocally ruled out. the full analysis of the data indicates that a dielectric plasma response with magnetic properties of ni included shows good agreement with the data. neither a drude nor a plasma dielectric response provide a satisfactory description if the magnetic properties of nickel are disregarded. | arxiv:1509.05349 |
we report a search for a heavy neutral lepton ( hnl ) that mixes predominantly with $ \ nu _ \ tau $. the search utilizes data collected with the belle detector at the kekb asymmetric energy $ e ^ + e ^ - $ collider. the data sample was collected at and just below the center - of - mass energies of the $ \ upsilon ( 4s ) $ and $ \ upsilon ( 5s ) $ resonances and has an integrated luminosity of $ 915 ~ \ textrm { fb } ^ { - 1 } $, corresponding to $ ( 836 \ pm 12 ) \ times 10 ^ 6 $ $ e ^ + e ^ \ to \ tau ^ + \ tau ^ - $ events. we search for production of the hnl ( denoted $ n $ ) in the decay $ \ tau ^ - \ to \ pi ^ - n $ followed by its decay via $ n \ to \ mu ^ + \ mu ^ - \ nu _ \ tau $. the search focuses on the parameter - space region in which the hnl is long lived, so that the $ \ mu ^ + \ mu ^ - $ originate from a common vertex that is significantly displaced from the collision point of the kekb beams. consistent with the expected background yield, one event is observed in the data sample after application of all the event - selection criteria. we report limits on the mixing parameter of the hnl with the $ \ tau $ neutrino as a function of the hnl mass. | arxiv:2402.02580 |
the quasi - normal modes for black holes are the resonances for the scattering of incoming waves by black holes. here we consider scattering of massless uncharged dirac fields propagating in the outer region of de sitter - reissner - nordstr { \ " o } m black hole, which is spherically symmetric charged exact solution of the einstein - maxwell equations. using the spherical symmetry of the equation and restricting to a fixed harmonic the problem is reduced to a scattering problem for the 1d massless dirac operator on the line. the resonances for the problem are related to the resonances for a certain semiclassical schr { \ " o } dinger operator with exponentially decreasing positive potential. we give exact relation between the sets of dirac and schr { \ " o } dinger resonances. the asymptotic distribution of the resonances is close to the lattice of pseudopoles associated to the non - degenerate maxima of the potentials. using the techniques of quantum birkhoff normal form we give the complete asymptotic formulas for the resonances. in particular, we calculate the first three leading terms in the expansion. moreover, similar results are obtained for the de sitter - schwarzschild quasi - normal modes, thus improving the result of s \ ' a barreto and zworski from 1997. | arxiv:1407.3654 |
the correlation of particular fourier components of the light curves of rr lyrae variables with metallicity, discovered by simon and later by kovacs and his coworkers, is shown to have the same explanation as the period ratios ( period shifts in log p ) between rrab lyrae variables that have the same colors, amplitudes, and light - curve shapes but different metallicities. a purpose of this paper is to demonstrate that the model which predicts the period - metallicity relations is the mediating parameters of colors, amplitudes, and light - curve shapes also explains the simon / kovacs et al. correlation between period, phi _ 31, and metallicity. the proof is made by demonstrating that the combination of the first and third phase terms in a fourier decomposition of rrab light curves, called phi _ 31 by simon and lee, varies monotonically across the rr lyrae instability strip in the same way that amplitude, color, and rise time vary with period within the strip. the premise of the model is that if horizontal branches at the rr lyrae strip are stacked in luminosity according to the metallicity, then there necessarily must be a log period shift between rr lyraes with different metallicities at the same phi _ 31 values. however, there are exceptions to the model. (... ) | arxiv:astro-ph/0405480 |
we present an approach to compute the monetary value of individual data points, in context of an automated decision system. the proposed method enables us to explore and implement a paradigm of data minimalism for large - scale machine learning systems. data minimalistic implementations enhance scalability, while maintaining or even optimizing a system ' s performance. using two types of recommender systems, we first demonstrate how much data is ineffective in both settings. we then present a general account of computing data value via sensitivity analysis, and how, in theory, individual data points can be priced according to their informational contribution to automated decisions. we further exemplify this method to lab - scale recommender systems and outline further steps towards commercial data - minimalistic applications. | arxiv:1907.12404 |
blazars are known to emit a broad band emission from radio to gamma - rays with rapid time variations, particularly, in x - and gamma - rays. synchrotron radiation and inverse compton scattering are thought to play an important role in emission and the time variations are likely related to the acceleration of nonthermal electrons. as simultaneous multiwavelength observations with continuous time spans are recently available, some characteristics of electron acceleration are possibly inferred from the spectral changes of high energy emission. in order to make such inferences, we solve the time - dependent kinetic equations of electrons and photons simultaneously using a simple model for electron acceleration. we then show how the time variations of emission are dependent on electron acceleration. we also present a simple model for a flare in x - rays and tev gamma - rays by temporarily changing the acceleration timescale. our model will be used, in future, to analyze observed data in detail to obtain information on electron acceleration in blazars. | arxiv:astro-ph/0002137 |
a cluster growth model is proposed to study chiral symmetry breaking in stirred crystallization from an achiral element. achiral monomers are assumed to coagulate to form chiral clusters from dimers to hexamers. due to the stirring, the hexamers break into dimers. the coagulation of two dimers into a tetramer also occurs. the fixed point analysis of coupled rate equations of cluster densities and their numerical integrations show that the chiral symmetry becomes broken if dimers are critical and able to dissociate back to achiral monomers. the chirality selection is understood by showing that, in a quasi - steady approximation, the rate equations reduce to those of dimers with nonlinear autocatalysis and decomposition. | arxiv:cond-mat/0412216 |
determining which between projected local density and distance from the cluster center plays a major role in regulating morphological fractions in clusters is a longstanding debate. reaching a definitive answer will shed light on the main physical mechanisms at play in the most extreme environments. here we make use of the data from the omegawings survey, currently the largest survey of clusters in the local universe extending beyond 2 virial radii from the cluster cores, to extend previous analysis outside the virial radius. local density and clustercentric distance seems to play different roles for galaxies of different morphology : the fraction of elliptical galaxies mainly depends on local density, suggesting that their formation was linked to the primordial densities, which now correspond to the cluster cores. only the fraction of low mass ellipticals shows an anticorrelation with clustercentric distance, suggesting a different origin for these objects. excluding elliptical galaxies, the relative fraction of s0s and spirals instead depends on local density only far from the cluster cores, while within the virial radius their proportion is regulated by distance, suggesting that cluster specific processes halt the star formation and transform sp galaxies into s0s. this interpretation is supported by literature results on the kinematical analysis of early and late type galaxies, according to which fast and slow rotators have distinct dependencies on halo mass and local density. | arxiv:2302.02376 |
sleep condition is closely related to an individual ' s health. poor sleep conditions such as sleep disorder and sleep deprivation affect one ' s daily performance, and may also cause many chronic diseases. many efforts have been devoted to monitoring people ' s sleep conditions. however, traditional methodologies require sophisticated equipment and consume a significant amount of time. in this paper, we attempt to develop a novel way to predict individual ' s sleep condition via scrutinizing facial cues as doctors would. rather than measuring the sleep condition directly, we measure the sleep - deprived fatigue which indirectly reflects the sleep condition. our method can predict a sleep - deprived fatigue rate based on a selfie provided by a subject. this rate is used to indicate the sleep condition. to gain deeper insights of human sleep conditions, we collected around 100, 000 faces from selfies posted on twitter and instagram, and identified their age, gender, and race using automatic algorithms. next, we investigated the sleep condition distributions with respect to age, gender, and race. our study suggests among the age groups, fatigue percentage of the 0 - 20 youth and adolescent group is the highest, implying that poor sleep condition is more prevalent in this age group. for gender, the fatigue percentage of females is higher than that of males, implying that more females are suffering from sleep issues than males. among ethnic groups, the fatigue percentage in caucasian is the highest followed by asian and african american. | arxiv:1704.06853 |
let $ k $ be the cantor set. we prove that arbitrarily close to a homeomorphism $ t : k \ rightarrow k $ there exists a homeomorphism $ \ widetilde t : k \ rightarrow k $ such that the $ \ alpha $ - limit and the $ \ omega $ - limit of every orbit is a periodic orbit. we also prove that arbitrarily close to an endomorphism $ t : k \ rightarrow k $ there exists an endomorphism $ \ widetilde t : k \ rightarrow k $ close to $ t $ such that every orbit is finally periodic. | arxiv:1410.5857 |
we study a certain cycle map defined on finite dimensional modules for the w - algebra with regular integral central character. via comparison with the theory in postive characteristic, we show that this map injects into the top borel - moore homology group of a springer fibre. this is the first result in a larger program to completely desribe the finite dimensional modules for the w algebras. | arxiv:1009.2456 |
in their study of cyclic pattern containment, domagalski et al. conjecture differential equations for the generating functions of circular permutations avoiding consecutive patterns of length 3. in this note, we prove and significantly generalize these conjectures. we show that, for every consecutive pattern $ \ sigma $ beginning with 1, the bivariate generating function counting occurrences of $ \ sigma $ in circular permutations can be obtained from the generating function counting occurrences of $ \ sigma $ in ( linear ) permutations. this includes all the patterns for which the latter generating function is known. | arxiv:2107.04717 |
we present a derivation of an exact high temperature expansion for a one - loop thermodynamic potential $ \ omega ( \ tilde { \ mu } ) $ with complex chemical potential $ \ tilde { \ mu } $. the result is given in terms of a single sum the coefficients of which are analytical functions of $ \ tilde { \ mu } $ consisting of polynomials and polygamma functions, decoupled from the physical expansion parameter $ \ beta m $. the analytic structure of the coefficients permits us to explicitly calculate the thermodynamic potential for the imaginary chemical potential and analytically continue the domain to the complex $ \ tilde { \ mu } $ plane. furthermore, our representation of $ \ omega ( \ tilde { \ mu } ) $ is particularly well suited for the landau - - ginzburg - type of phase transition analysis. this fact, along with the possibility of interpreting the imaginary chemical potential as an effective generalized - statistics phase, allows us to investigate the singular origin of the $ m ^ 3 $ term appearing only in the bosonic thermodynamic potential. | arxiv:1311.2512 |
in this paper the phonon self energy produced by anharmonicity is calculated using second order many body perturbation theory for all bcc, fcc and hcp transition metals. the symmetry properties of the phonon interactions are used to obtain an expression for the self energy as a sum over irreducible triplets, very similar to integration in the irreducible part of the brillouin zone for one particle properties. the results obtained for transition metals shows that the lifetime is on the order of 10 ^ 10 s. moreover the peierls approximation for the imaginary part of the self energy is shown to be reasonable for bcc and fcc metals. for hcp metals we show that the raman active mode decays into a pair of acoustic phonons, their wave vector being located on a surface defined by conservation laws. | arxiv:1103.0137 |
let a - > b be a homomorphism of commutative rings. the squaring operation is a functor sq _ { b / a } from the derived category d ( b ) of complexes b - modules into itself. the squaring operation is needed for the definition of rigid complexes ( in the sense of van den bergh ), that in turn leads to a new approach to grothendieck duality for rings, schemes and even dm stacks. in our paper with j. j. zhang from 2008 we introduced the squaring operation, and explored some of its properties. unfortunately some of the proofs in that paper had severe gaps in them. in the present paper we reproduce the construction of the squaring operation. this is done in a somewhat more general context than in the first paper : here we consider a homomorphism a - > b of commutative dg rings. our first main result is that the square sq _ { b / a } ( m ) of a dg b - module m is independent of the resolutions used to present it. our second main result is on the trace functoriality of the squaring operation. we give precise statements and complete correct proofs. in a subsequent paper we will reproduce the remaining parts of the 2008 paper that require fixing. this will allow us to proceed with the other papers, mentioned in the bibliography, on the rigid approach to grothendieck duality. the proofs of the main results require a substantial amount of foundational work on commutative and noncommutative dg rings, including a study of semi - free dg rings, their lifting properties, and their homotopies. this part of the paper could be of independent interest. | arxiv:1412.4229 |
the simplest unified extension of the minimal supersymmetric standard model with bi - linear r - parity violation naturally predicts a hierarchical neutrino mass spectrum, suitable to explain atmospheric and solar neutrino fluxes. we study whether the individual violation of the lepton numbers l _ { e, mu, tau } in the charged sector can lead to measurable rates for br ( mu - > e gamma ) and $ br ( tau - > mu gamma ). we find that some of the r - parity violating terms that are compatible with the observed atmospheric neutrino oscillations could lead to rates for mu - > e gamma measurable in projected experiments. however, the delta m ^ 2 _ { 12 } obtained for those parameters is too high to be compatible with the solar neutrino data, excluding therefore the possibility of having measurable rates for mu - > e gamma in the model. | arxiv:hep-ph/0202054 |
a new - type structural transition has been found in li2ruo3 with honeycomb lattice of edge - sharing ruo6 - octahedra. with decreasing temperature t, the electrical resistivity exhibits an anomalous increase at t = tc ~ 540 k, suggesting the ( metal to insulator ) - like transition and the magnetic susceptibility also shows a sharp decrease. detailed structure analyses have revealed that the high temperature space group c2 / m changes to p21 / m at tc. the most striking fact is that a significant reduction of the bond lengths is found between two of six ru - ru pairs of the hexagon in the low temperature phase, indicating a new type phase transition by the mechanism of the formation of molecular orbits of these ru - ru pairs. | arxiv:cond-mat/0612026 |
we discuss chiral perturbation theory for two and three quark flavors in the epsilon expansion at next - to - next - to - leading order ( nnlo ) including a small imaginary chemical potential. we calculate finite - volume corrections to the low - energy constants $ \ sigma $ and $ f $ and determine the non - universal modifications of the theory, i. e., modifications that cannot be mapped to random matrix theory ( rmt ). in the special case of two quark flavors in an asymmetric box we discuss how to minimize the finite - volume corrections and non - universal modifications by an optimal choice of the lattice geometry. furthermore we provide a detailed calculation of a special version of the massless sunset diagram at finite volume. | arxiv:1004.5584 |
" overlearning " means that a model trained for a seemingly simple objective implicitly learns to recognize attributes and concepts that are ( 1 ) not part of the learning objective, and ( 2 ) sensitive from a privacy or bias perspective. for example, a binary gender classifier of facial images also learns to recognize races \ textemdash even races that are not represented in the training data \ textemdash and identities. we demonstrate overlearning in several vision and nlp models and analyze its harmful consequences. first, inference - time representations of an overlearned model reveal sensitive attributes of the input, breaking privacy protections such as model partitioning. second, an overlearned model can be " re - purposed " for a different, privacy - violating task even in the absence of the original training data. we show that overlearning is intrinsic for some tasks and cannot be prevented by censoring unwanted attributes. finally, we investigate where, when, and why overlearning happens during model training. | arxiv:1905.11742 |
computational intelligence in finance has been a very popular topic for both academia and financial industry in the last few decades. numerous studies have been published resulting in various models. meanwhile, within the machine learning ( ml ) field, deep learning ( dl ) started getting a lot of attention recently, mostly due to its outperformance over the classical models. lots of different implementations of dl exist today, and the broad interest is continuing. finance is one particular area where dl models started getting traction, however, the playfield is wide open, a lot of research opportunities still exist. in this paper, we tried to provide a state - of - the - art snapshot of the developed dl models for financial applications, as of today. we not only categorized the works according to their intended subfield in finance but also analyzed them based on their dl models. in addition, we also aimed at identifying possible future implementations and highlighted the pathway for the ongoing research within the field. | arxiv:2002.05786 |
variational data assimilation in ocean models depends on the ability to model general correlation operators in the presence of coastlines. grid - point filters based on diffusion operators are widely used for this purpose, but come with a computational bottleneck - the costly estimation of normalization factors for every model grid point. in this paper, we show that a simple convolutional neural network can effectively learn these normalization factors with better accuracy than the current operational methods. our network is tested with a two - dimensional diffusion operator from the nemovar ocean data assimilation system, applied to a global ocean grid with approximately one degree horizontal resolution. the network is trained on exact normalization factors estimated by a brute - force method. knowing that convolutional networks can only model translation - equivariant functions, we ensure that the normalization estimation problem is indeed translation - equivariant. specifically, we show how the number of inputs of this problem can be reduced while preserving translation equivariance. adding the distance to the coastline as an input channel is found to improve the performance of the network around coastlines. extensions to three - dimensional diffusion and to higher horizontal resolutions are discussed. removing the computational bottleneck associated with normalization opens the way to using adaptive correlation models for operational ocean data assimilation. the code for this work is publicly available at https : / / github. com / folkeks / dl - normalization / tree / core - features | arxiv:2312.05068 |
transfer learning has become the dominant paradigm for many natural language processing tasks. in addition to models being pretrained on large datasets, they can be further trained on intermediate ( supervised ) tasks that are similar to the target task. for small natural language inference ( nli ) datasets, language modelling is typically followed by pretraining on a large ( labelled ) nli dataset before fine - tuning with each nli subtask. in this work, we explore gradient boosted decision trees ( gbdts ) as an alternative to the commonly used multi - layer perceptron ( mlp ) classification head. gbdts have desirable properties such as good performance on dense, numerical features and are effective where the ratio of the number of samples w. r. t the number of features is low. we then introduce freegbdt, a method of fitting a gbdt head on the features computed during fine - tuning to increase performance without additional computation by the neural network. we demonstrate the effectiveness of our method on several nli datasets using a strong baseline model ( roberta - large with mnli pretraining ). the freegbdt shows a consistent improvement over the mlp classification head. | arxiv:2105.03791 |
this scoping review assesses the current use of simulation - based design optimization ( sbdo ) in marine engineering, focusing on identifying research trends, methodologies, and application areas. analyzing 277 studies from scopus and web of science, the review finds that sbdo is predominantly applied to optimizing marine vessel hulls, including both surface and underwater types, and extends to key components like bows, sterns, propellers, and fins. it also covers marine structures and renewable energy systems. a notable trend is the preference for deterministic single - objective optimization methods, indicating potential growth areas in multi - objective and stochastic approaches. the review points out the necessity of integrating more comprehensive multidisciplinary optimization methods to address the complex challenges in marine environments. despite the extensive application of sbdo in marine engineering, there remains a need for enhancing the methodologies ' efficiency and robustness. this review offers a critical overview of sbdo ' s role in marine engineering and highlights opportunities for future research to advance the field. | arxiv:2404.18654 |
we demonstrate efficient pulse - energy extraction from a partly - quenched erbium - doped aluminosilicate fiber amplifier. this has a high erbium - concentration, which allows for short devices with reduced nonlinear distortions, but which also results in partial quenching and thus significant unsaturable absorption, even though the fiber is still able to amplify. although the quenching degrades the average - power efficiency, the pulse energy remains high, and our results point to an increasingly promising outcome for short pulses. furthermore, unlike unquenched fibers, the conversion efficiency improves at low repetition rates, which we attribute to smaller relative energy loss to quenched ions at higher pulse energy. a short ( 2. 6 m ) cladding - pumped partly - quenched er - doped - fiber with 95 - db / m 1530 - nm peak absorption and saturation energy estimated to 85 { \ mu } j, reached 0. 8 mj of output energy when seeded by 0. 2 - { \ mu } s, 23 - { \ mu } j pulses. thus, according to our results, pulses can be amplified to high energy in short highly - er - doped fibers designed to reduce nonlinear distortions, at the expense of average - power efficiency | arxiv:2002.04356 |
the electronic structure of the ferroelectric crystal, nano $ _ 2 $, is studied by means of first - principles, local density calculations. our ab - initio, non - relativistic calculations employed a local density functional approximation ( lda ) potential and the linear combination of atomic orbitals ( lcao ). following the bagayoko, zhao, williams, method, as enhanced by ekuma, and franklin ( bzw - ef ), we solved self - consistently both the kohn - sham equation and the equation giving the ground state charge density in terms of the wave functions of the occupied states. we found an indirect band gap of 2. 83 ev, from w to r. our calculated direct gaps are 2. 90, 2. 98, 3. 02, 3. 22, and 3. 51 ev at r, w, x, { \ gamma }, and t, respectively. the band structure and density of states show high localization, typical of a molecular solid. the partial density of states shows that the valence bands are formed only by complex anionic states. these results are in excellent agreement with experiment. so are the calculated densities of states. our calculated electron effective masses of 1. 18, 0. 63, and 0. 73 mo in the { \ gamma } - x, { \ gamma } - r, and { \ gamma } - w directions, respectively, show the highly anisotropic nature of this material. | arxiv:1208.5710 |
this paper summarizes recent ( as of ssi - 02, in some cases updated in november, 2002 ) results from the super - kamiokande and k2k experiments. the interpretation of super - kamiokande results on atmospheric and solar neutrinos provides strong evidence for neutrino oscillations, hence non - zero neutrino mass. while statistics are still limited, k2k data are consistent with super - kamiokande results on neutrino oscillations. the effort to reconstruct super - kamiokande following a cascade of phototube implosions in november, 2001 is described. plans for the future are also discussed. | arxiv:hep-ex/0212035 |
the aim of this paper is to introduce a new incremental procedure that can be used for numerical evaluation of the limit load. existing incremental type methods are based on parametrization of the energy by the loading parameter $ \ zeta \ in [ 0, \ zeta _ { lim } ) $, where $ \ zeta _ { lim } $ is generally unknown. in the new method, the incremental procedure is operated in terms of an inverse mapping and the respective parameter $ \ alpha $ is changing in the interval $ ( 0, + \ infty ) $. theoretically, in each step of this algorithm, we obtain a guaranteed lower bound of $ \ zeta _ { lim } $. reduction of the problem to a finite element subspace associated with a mesh $ \ mathcal t _ h $ generates computable bound $ \ zeta _ { lim, h } $. under certain assumptions, we prove that $ \ zeta _ { lim, h } $ tends to $ \ zeta _ { lim } $ as $ h \ rightarrow0 _ + $. numerical tests confirm practical efficiency of the suggested method. | arxiv:1511.02681 |
we construct all six - particle helicity amplitude integrands in color - dressed, maximally supersymmetric yang - mills theory at two loops in a single prescriptive basis of master integrands. | arxiv:2112.06934 |
we present the first evidence of multiple populations in the galactic globular cluster ngc 6362. we used optical and near - uv hubble space telescope and ground based photometry, finding that both the sub giant and red giant branches are split in two parallel sequences in all color magnitude diagrams where the f336w filter ( or u band ) is used. this cluster is one of the least massive globulars ( m _ tot ~ 5x10 ^ 4 m _ sun ) where multiple populations have been detected so far. even more interestingly and at odds with any previous finding, we observe that the two identified populations share the same radial distribution all over the cluster extension. ngc 6362 is the first system where stars from different populations are found to be completely spatially mixed. based on n - body and hydrodynamical simulations of multiple stellar generations, we argue that, to reproduce these findings, ngc 6362 should have lost up to the 80 % of its original mass | arxiv:1407.0484 |
in many real - world scenarios, decision makers seek to efficiently optimize multiple competing objectives in a sample - efficient fashion. multi - objective bayesian optimization ( bo ) is a common approach, but many of the best - performing acquisition functions do not have known analytic gradients and suffer from high computational overhead. we leverage recent advances in programming models and hardware acceleration for multi - objective bo using expected hypervolume improvement ( ehvi ) - - - an algorithm notorious for its high computational complexity. we derive a novel formulation of q - expected hypervolume improvement ( qehvi ), an acquisition function that extends ehvi to the parallel, constrained evaluation setting. qehvi is an exact computation of the joint ehvi of q new candidate points ( up to monte - carlo ( mc ) integration error ). whereas previous ehvi formulations rely on gradient - free acquisition optimization or approximated gradients, we compute exact gradients of the mc estimator via auto - differentiation, thereby enabling efficient and effective optimization using first - order and quasi - second - order methods. our empirical evaluation demonstrates that qehvi is computationally tractable in many practical scenarios and outperforms state - of - the - art multi - objective bo algorithms at a fraction of their wall time. | arxiv:2006.05078 |
the monty hal problem is an attractive puzzle. it combines simple statement with answers that seem surprising to most audiences. the problem was thoroughly solved over two decades ago. yet, more recent discussions indicate that the solution is incompletely understood. here, we review the solution and discuss pitfalls and other aspects that make the problem interesting. | arxiv:1808.05150 |
we study random surfaces constructed by glueing together $ n / k $ filled $ k $ - gons along their edges, with all $ ( n - 1 )!! = ( n - 1 ) ( n - 3 )... 3 \ cdot 1 $ pairings of the edges being equally likely. ( we assume that lcm $ \ { 2, k \ } $ divides $ n $. ) the euler characteristic of the resulting surface is related to the number of cycles in a certain random permutation of $ \ { 1,..., n \ } $. gamburd has shown that when 2 lcm $ \ { 2, k \ } $ divides $ n $, the distribution of this random permutation converges to that of the uniform distribution on the alternating group $ a _ n $ in the total - variation distance as $ n \ to \ infty $. we obtain large - deviations bounds for the number of cycles that, together with gamburd ' s result, allow us to derive sharp estimates for the moments of the number of cycles. these estimates allow us to confirm certain cases of conjectures made by pippenger and schleich. | arxiv:0902.3646 |
fitting ' s heyting - valued logic and heyting - valued modal logic have already been studied from an algebraic viewpoint. in addition to algebraic axiomatizations with the completeness of fitting ' s heyting - valued logic and heyting - valued modal logic, both topological and coalgebraic dualities have also been developed for algebras of fitting ' s heyting - valued modal logic. bitopological methods have recently been employed to investigate duality for fitting ' s heyting - valued logic. however, the concepts of bitopology and bivietoris coalgebras are conspicuously absent from the development of dualities for fitting ' s many - valued modal logic. with this study, we try to bridge that gap. we develop a bitopological duality for algebras of fitting ' s heyting - valued modal logic. we construct a bi - vietoris functor on the category $ pbs _ { \ mathcal { l } } $ of $ \ mathcal { l } $ - valued ( $ \ mathcal { l } $ is a heyting algebra ) pairwise boolean spaces. finally, we obtain a dual equivalence between categories of bivietoris coalgebras and algebras of fitting ' s heyting - valued modal logic. as a result, we conclude that fitting ' s many - valued modal logic is sound and complete with respect to the coalgebras of a bivietoris functor. we discuss the application of this coalgebraic approach to bitopological duality. | arxiv:2312.16276 |
we discuss an interesting feature of the distribution of luminous blue variables on the h - r diagram, and we propose a connection with the bistability jump in the winds of early - type supergiants. there appears to be a deficiency of quiescent lbvs on the s dor instability strip at luminosities between log l / lsun = 5. 6 and 5. 8. the upper boundary, is also where the temperature - dependent s dor instability strip intersects the bistability jump at about 21, 000 k. due to increased opacity, winds of early - type supergiants are slower and denser on the cool side of the bistability jump, and we postulate that this may trigger optically - thick winds that inhibit quiescent lbvs from residing there. we conduct numerical simulations of radiation - driven winds for a range of temperatures, masses, and velocity laws at log l / lsun = 5. 7 to see what effect the bistability jump should have. we find that for relatively low stellar masses the increase in wind density at the bistability jump leads to the formation of a modest to strong pseudo photosphere - - enough to make an early b - type star appear as a yellow hypergiant. thus, the proposed mechanism will be most relevant for lbvs that are post - red supergiants. yellow hypergiants like irc + 10420 and rho cas occupy the same luminosity range as the ` ` missing ' ' lbvs, and show apparent temperature variations at constant luminosity. if these yellow hypergiants do eventually become wolf - rayet stars, we speculate that they may skip the normal lbv phase, at least as far as their apparent positions on the hr diagram are concerned. | arxiv:astro-ph/0407202 |
the ability to read, write, and speak mathematics is critical to students becoming comfortable with statistical models and skills. faster development of those skills may act as encouragement to further engage with the discipline. vocabulary has been the focus of scholarship in existing literature on the linguistics of mathematics and statistics but there are structures such as grammar that go beyond the content of words and symbols. here i introduce ideas for grammar structures through a sequence of examples. | arxiv:2410.07569 |
in this paper, the finite element method is combined with the brownian configuration field ( bfc ) method to simulate the fibre suspension flow in axisymmetric contraction and expansion passages. in order to solve for the high stress at high concentration, the discrete adaptive viscoelastic stress splitting ( davss ) method is employed. for the axisymmetric contraction and expansion passages with different geometry ratios, the results obtained are compared to available constitutive models and experiments. the predicted vortex length for dilute suspensions agrees well with experimental data in literature. our numerical results show clearly the effect on vortex enhancement with increase of the volume fractions and the aspect ratios. effect of aspect ratio of fibres on the vortex length is also studied. it is found that for the lower expansion ratio flows the vortex dimension in the corner region is fairly independent of fibre concentration and aspect ratio of fibres while the said vortex dimension increases with the increase of fibre concentration for contraction flows. the finding suggests that the aligned fibre approximation traditionally employed in previous work does not exactly describe the effect of fibre motion, and the present bfc method is deemed more suitable for the flow of dilute fibre suspensions. in terms of numerics, the employment of davss enhances numerical stability in the presence of high concentration of fibre in the flow. | arxiv:0811.1413 |
the spectra from fe - peak elements may be used to determine the temperature and density of various astrophysical objects. determination of these quantities is underpinned by the accuracy and the comprehensiveness of the underlying atomic structure and collisional calculations. in the following paper, we shall focus specifically on ni iv lines associated with transitions amongst several low - lying levels. we shall employ modified versions of the parallel dirac r - matrix codes, considering both electron - impact excitation of ni $ ^ { 3 + } $ and the photoionisation of both the ground and excited states of ni $ ^ { 2 + } $. we produce high - quality data sets for both processes, and using these data, we calculate line ratios relevant for plasma diagnostics of temperature and density. | arxiv:1809.05472 |
recently, the two dimensional ( 2d ) materials have become a potential candidates for various technological applications in spintronics and optoelectronics. in the present study, the structural, electronic, and phase stability of 2d layered znsb compounds of four different phases viz. wurzite ( w ), tetragonal ( t ), hexagonal ( h ), and orthorhombic ( o ) have been tuned using the first principle calculations based on density functional theory ( dft ). we invoked the perdew - burke - ernzerhof ( pbe ) functional and the projected augmented wave ( paw ) method during all the calculations. based on our numerical results, we predicted the novel tetragonal phase as stable phase of znsb next to existing orthorhombic structure. we reported the pressure induced phase transition between orthorhombic to tetragonal phase at 12. 48 gpa / atom. the projected density of states indicates the strong p - d hybridization between sb - 5p and zn - 3d states confirming the nature of strong covalent bonding between them. the electronic band structures suggest that t - znsb, w - znsb, and h - znsb are metallic in nature whereas o - znsb is semiconducting with narrow band gap of 0. 03 ev using pbe. we predicted the possibility of extracting the two dimensional ( 2d ) monolayer sheet in t - znsb and o - znsb according to the exfoliation energy criterion. in addition, the 2d monolayer ( ml ) of o - znsb has been predicted to be dynamically stable but that of t - znsb is not stable as manifested in phonon dispersion bands. surprisingly, the semiconducting band gap nature of o - znsb changes from indirect and narrow to direct and sizable while going from 3d bulk to 2d ml structure. further, we estimated the value of work functions for the surfaces of t - znsb and o - znsb as 4. 61 ev and 4. 04 ev respectively. such materials can find the niche applications in next generation electronic devices utilizing 2d hetero - structures. | arxiv:2106.10757 |
a numerical model of interacting nanomagnetic elements is used to demonstrate active inference with a three dimensional artificial spin ice structure. it is shown that thermal fluctuations can drive this magnetic spin system to evolve under dynamic constraints imposed through interactions with an external environment as predicted by the neurological free energy principle and active inference. the structure is defined by two layers of magnetic nanoelements where one layer is a square artificial spin ice geometry. the other magnetic layer functions as a sensory filter that mediates interaction between the external environment and the hidden artificial spin ice layer. spin dynamics displayed by the bilayer structure are shown to be well described using a continuous form of a neurological free energy principle that has been previously proposed as a high level description of certain biological neural processes. numerical simulations demonstrate that this proposed bilayer geometry is able to reproduce theoretical results derived previously for examples of active inference in neurological contexts. | arxiv:2401.12211 |
when applied to stiff, linear differential equations with time - dependent forcing, runge - kutta methods can exhibit convergence rates lower than predicted by the classical order condition theory. commonly, this order reduction phenomenon is addressed by using an expensive, fully implicit runge - kutta method with high stage order or a specialized scheme satisfying additional order conditions. this work develops a flexible approach of augmenting an arbitrary runge - kutta method with a fully implicit method used to treat the forcing such as to maintain the classical order of the base scheme. our methods and analyses are based on the general - structure additive runge - kutta framework. numerical experiments using diagonally implicit, fully implicit, and even explicit runge - kutta methods confirm that the new approach eliminates order reduction for the class of problems under consideration, and the base methods achieve their theoretical orders of convergence. | arxiv:2201.07940 |
air pollution by nitrogen oxides ( nox ) is a major concern in large cities as it has severe adverse health effects. however, the statistical properties of air pollutants are not fully understood. here, we use methods borrowed from nonequilibrium statistical mechanics to construct suitable superstatistical models for air pollution statistics. in particular, we analyze time series of nitritic oxide ( $ no $ ) and nitrogen dioxide ( $ no _ 2 $ ) concentrations recorded at several locations throughout greater london. we find that the probability distributions of concentrations have heavy tails and that the dynamics is well - described by $ \ chi ^ 2 $ superstatistics for $ no $ and inverse $ \ chi ^ 2 $ superstatistics for $ no _ 2 $. our results can be used to give precise risk estimates of high - pollution situations and pave the way to mitigation strategies. | arxiv:1909.10433 |
gravitational waves from a phase transition associated with the generation of the masses of elementary particles are within the reach of future space - based detectors such as lisa. a key determinant of the resulting power spectrum, not previously studied, is the lifetime of the acoustic turbulence which follows. we study decaying acoustic turbulence using numerical simulations of a relativistic fluid in two dimensions. working in the limit of non - relativistic bulk velocities, with an ultra - relativistic equation of state, we find that the energy spectrum evolves towards a self - similar broken power law, with a high - wavenumber behaviour of $ k ^ { - 2. 08 \ pm 0. 08 } $, cut off at very high $ k $ by the inverse width of the shock waves. our model for the decay of acoustic turbulence can be extended to three dimensions using the universality of the high - $ k $ power law and the evolution laws for the kinetic energy and the integral length scale. it is used to build an estimate for the gravitational wave power spectrum resulting from a collection of shock waves, as might be found in the aftermath of a strong first order phase transition in the early universe. the power spectrum has a peak wavenumber set by the initial length scale of the acoustic waves, and a new secondary scale at a lower wavenumber set by the integral scale after a hubble time. between these scales a distinctive new power law appears. our results allow more accurate predictions of the gravitational wave power spectrum for a wide range of early universe phase transition scenarios. | arxiv:2112.12013 |
in this work, the spin wave calculations were carried out using the heisenberg hamiltonian to study the allowed spin waves of zigzag and armchair edged stripes for ferromagnetic nanodots arrayed in a 2d honeycomb lattice \ cite { selim2011 }. the hamiltonian is used to construct the $ \ mathbf { e } $ matrix which encodes the exchange flow of magnons in the stripes. it is found that the allowed spin wave modes are the eigenvalues of the $ \ mathbf { e } $ matrix and therefore it is used to study the effects of the stripe width, edge exchange, the edge uniaxial anisotropy, and impurities on the allowed spin waves of stripes. the obtained results almost coincide with the results of graphene nanoribbons described by tight binding hamiltonian for electronic excitations. therefore, we suggest the fabrication of the magnetic counterpart to graphene as a new technology in the field of spintronic devices and magnetic applications. | arxiv:1110.5716 |
an adaptive finite element method is presented for the elastic scattering of a time - harmonic plane wave by a periodic surface. first, the unbounded physical domain is truncated into a bounded computational domain by introducing the perfectly matched layer ( pml ) technique. the well - posedness and exponential convergence of the solution are established for the truncated pml problem by developing an equivalent transparent boundary condition. second, an a posteriori error estimate is deduced for the discrete problem and is used to determine the finite elements for refinements and to determine the pml parameters. numerical experiments are included to demonstrate the competitive behavior of the proposed adaptive method. | arxiv:1605.08746 |
let x be a smooth separated geometrically connected variety over f _ q and f : y - > x a smooth projective morphism. we compare the invariant dimensions of the l - adic representation v _ l and the f _ l - representation \ bar v _ l of the geometric \ ' etale fundamental group of x arising from the sheaves r ^ wf _ * q _ l and r ^ wf _ * z / lz respectively. these invariant dimension data is used to deduce a maximality result of the geometric monodromy action on v _ l whenever \ bar v _ l is semisimple and l is sufficiently large. we also provide examples for \ bar v _ l to be semisimple for l > > 0. | arxiv:1508.07499 |
cp violation in the charm sector is highly sensitive to new physics due to its small predicted value within the standard model. by this work, we investigated the cp violation in the cascade decay process $ d ^ 0 ( t _ 1 ) \ to \ pi ^ 0 k ( t _ 2 ) \ to \ pi ^ 0 ( \ pi ^ \ pm \ ell ^ \ mp \ nu ) $. our results indicate that the cp violation induced by the interference of unmixed $ d $ - meson decay amplitudes dominates, with a peak value reaching $ 5 \ times 10 ^ { - 3 } $. this is one order of magnitude larger than the sub - leading contribution, namely the double - mixing cp violation. furthermore, the cp violation in the decay channel with the semileptonic final state $ \ pi ^ - \ ell ^ + \ nu _ \ ell $ is one to two orders of magnitude larger than that in the channel with $ \ pi ^ + \ ell ^ - \ bar { \ nu } _ \ ell $. we propose that the cp asymmetry of the combined two decay channels can be measured experimentally. the resulting value is approximately half of the cp violation observed in the $ \ pi ^ - \ ell ^ + \ nu _ \ ell $ channel, with the dominant contribution still reaching the order of $ 10 ^ { - 3 } $. this approach offers the advantage of eliminating the need for flavor tagging of the initial $ d $ meson, thereby avoiding associated efficiency losses. | arxiv:2501.05689 |
in this paper we construct massive supermultiplets out of appropriate set of massless ones in the same way as massive spin s particle could be constructed out of massless spin s, s - 1,... ones leading to gauge invariant description of massive particle. mainly we consider massive spin 3 / 2 supermultiplets in a flat d = 4 minkowski space both without central charge for n = 1, 2, 3 as well as with central charge for n = 2, 4. besides, we give two examples of massive n = 1 supermultiplets with spin 3 / 2 and 2 in ads _ 4 space. | arxiv:hep-th/0703118 |
star formation is known to occur more readily where more raw materials are available. this is often expressed by a ' kennicutt - schmidt ' relation where the surface density of young stellar objects ( ysos ) is proportional to column density to some power, $ \ mu $. the aim of this work was to determine if column density alone is sufficient to explain the locations of class 0 / i ysos within serpens south, serpens core, ophiuchus, ngc1333 and ic348, or if there is clumping or avoidance that would point to additional influences on the star formation. using the o - ring test as a summary statistic, 95 per cent confidence envelopes were produced for different values of $ \ mu $ from probability models made using the herschel column density maps. the ysos were tested against four distribution models : the best - estimate of $ \ mu $ for the region, $ \ mu = 0 $ above a minimum column density threshold and zero probability elsewhere, $ \ mu = 1 $, and the power - law that best represents the five regions as a collective, $ \ mu = 2. 05 \ pm 0. 20 $. results showed that $ \ mu = 2. 05 $ model was consistent with the majority of regions and, for those regions, the spatial distribution of ysos at a given column density is consistent with being random. serpens south and ngc1333 rejected the $ \ mu = 2. 05 $ model on small scales of $ \ sim 0. 15 \ mathrm { pc } $ which implies that small - scale interactions may be necessary to improve the model. on scales above 0. 15 pc, the positions of ysos in all five regions can be well described using column density alone. | arxiv:2108.02466 |
preceding the current interest in layered materials for electronic applications, research in the 1960 ' s found that black phosphorus combines high carrier mobility with a fundamental band gap. we introduce its counterpart, dubbed few - layer phosphorene, as a new 2d p - type material. same as graphene and mos2, phosphorene is flexible and can be mechanically exfoliated. we find phosphorene to be stable and, unlike graphene, to have an inherent, direct and appreciable band - gap that depends on the number of layers. our transport studies indicate a carrier mobility that reflects its structural anisotropy and is superior to mos2. at room temperature, our phosphorene field - effect transistors with 1. 0 um channel length display a high on - current of 194 ma / mm, a high hole field - effect mobility of 286 cm2 / vs, and an on / off ratio up to 1e4. we demonstrate the possibility of phosphorene integration by constructing the first 2d cmos inverter of phosphorene pmos and mos2 nmos transistors. | arxiv:1401.4133 |
the purpose of this paper is to present the first continuous families of riemannian manifolds isospectral on functions but not on 1 - forms, and simultaneously, the first continuous families of riemannian manifolds with the same marked length spectrum but not the same 1 - form spectrum. the examples presented here are riemannian three - step nilmanifolds and thus provide a counterexample to the ouyang - pesce conjecture for higher - step nilmanifolds. ouyang and pesce independently showed that all isospectral deformations of two - step nilmanifolds must arise from the gordon - wilson method for constructing isospectral nilmanifolds. in particular, all continuous families of riemannian two - step nilmanifolds that are isospectral on functions must also be isospectral on p - forms for all p. they conjectured that all isospectral deformations of nilmanifolds must arise in this manner. these examples arise from a general method for constructing isospectral riemannian nilmanifolds previously introduced by the author. | arxiv:dg-ga/9702010 |
we study condensation in one - dimensional transport models with a kinetic constraint. the kinetic constraint results in clustering of immobile vehicles ; these clusters can grow to macroscopic condensates, indicating the onset of dynamic phase separation between free flowing and arrested traffic. we investigate analytically the conditions under which this occurs, and derive a necessary and sufficient criterion for phase separation. this criterion is applied to the well - known nagel - schreckenberg model of traffic flow to analytically investigate the existence of dynamic condensates. we find that true condensates occur only when acceleration out of jammed traffic happens in a single time step, in the limit of strong overbraking. our predictions are further verified with simulation results on the growth of arrested clusters. these results provide analytic understanding of dynamic arrest and dynamic phase separation in one - dimensional traffic and transport models. | arxiv:1402.6220 |
graphene bilayers with layer antisymmetric strains are studied using the dirac - harper model for a pair of single layer dirac hamiltonians coupled by a one - dimensional moir \ ' e - periodic interlayer tunneling amplitude. this model hosts low energy, nearly dispersionless bands near charge neutrality that support anomalous polarizations of its charge multipole distributions. these are analyzed introducing a generalized berry curvature that encodes the field - induced dynamics of multipole fields allowed in a chiral medium with time reversal symmetry. the formulation identifies a reciprocity relation between responses to layer - symmetric and layer - antisymmetric in - plane electric fields and reveals momentum - space quantum oscillations produced by a spatial pattern of band inversions on the moir \ ' e scale. | arxiv:2102.11850 |
precise management of patients with cerebral diseases often requires intracranial pressure ( icp ) monitoring, which is highly invasive and requires a specialized icu setting. the ability to noninvasively estimate icp is highly compelling as an alternative to, or screening for, invasive icp measurement. most existing approaches for noninvasive icp estimation aim to build a regression function that maps noninvasive measurements to an icp estimate using statistical learning techniques. these data - based approaches have met limited success, likely because the amount of training data needed is onerous for this complex applications. in this work, we discuss an alternative strategy that aims to better utilize noninvasive measurement data by leveraging mechanistic understanding of physiology. specifically, we developed a bayesian framework that combines a multiscale model of intracranial physiology with noninvasive measurements of cerebral blood flow using transcranial doppler. virtual experiments with synthetic data are conducted to verify and analyze the proposed framework. a preliminary clinical application study on two patients is also performed in which we demonstrate the ability of this method to improve icp prediction. | arxiv:1807.10345 |
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