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the millimeter wave ( mmwave ) frequencies are likely to play a significant role in fifth - generation ( 5g ) cellular systems. a key challenge in developing systems in these bands is the potential for rapid channel dynamics : since mmwave signals are blocked by many materials, small changes in the position or orientation of the handset relative to objects in the environment can cause large swings in the channel quality. this paper addresses the issue of tracking the signal to noise ratio ( snr ), which is an essential procedure for rate prediction, handover and radio link failure detection. a simple method for estimating the snr from periodic synchronization signals is considered. the method is then evaluated using real experiments in common blockage scenarios combined with outdoor statistical models. | arxiv:1604.05623 |
surface quality inspection of optical components is critical in optical and electronic industries. structured - light modulation analysis technique ( smat ) is a novel method recently proposed for the contaminant and defect detection of specular surfaces and transparent objects, and this approach was verified to be effective in eliminating ambient light. the mechanisms and mathematical models of smat were analyzed and established based on the theory of photometry and the optical characteristics of contaminants and defects. however, there are still some phenomena exist as conundrums in actual detection process, which cannot be well explained. in order to better analyze the phenomena in practical circumstances, improved mathematical models of smat are constructed based on the surface topography of contaminants and defects in this paper. these mathematical models can be used as tools for analyzing various contaminants and defects in different systems, and provide effective instruction for subsequent work. simulations and experiments on the modulation and the luminous flux of fringe patterns have been implemented to verify the validity of these mathematical models. in adddition, by using the fringe patterns with mutually perpendicular sinusoidal directions, two obtained modulation images can be merged to solve the incomplete information acquisition issue caused by the differentiated response of modulation. | arxiv:2005.04026 |
the influence that the atmosphere ( n _ 2 or ar ) and sintering time have on microstructure evolution in liquid - phase - sintered alpha - sic and on its mechanical properties at high temperature was investigated. the microstructure of the samples sintered in n2 was equiaxed with a grain size of 0. 70 { \ mu } m and a density of 98 % of the theoretical value regardless of the sintering time. in contrast, samples sintered in ar had an elongated - grain microstructure with a density decreasing from 99 % to 95 % and a grain size increasing from 0. 64 to 1. 61 { \ mu } m as the sintering time increased from 1 to 7 hours. the mechanical behaviour at 1450 { \ deg } c showed the samples sintered in nitrogen to be brittle and fail at very low strains, with a fracture stress increasing from 400 to 800 mpa as the sintering time increased. in contrast, the samples sintered in ar were quasi - ductile with increasing strain to failure as the sintering time increased, and a fracture stress strongly linked to the form and size of the grains. these differences in the mechanical properties of the two materials are discussed in the text. during mechanical tests, a loss of intergranular phase takes place in a region, between 50 and 150 { \ mu } m thick, close to the surface of the samples - - the effect being more important in the samples sintered in ar | arxiv:2402.02436 |
we refute the so - called one - line proof of the infinitude of primes in [ 1 ]. | arxiv:1710.07633 |
current machine learning models have shown high efficiency in solving a wide variety of real - world problems. however, their black box character poses a major challenge for the understanding and traceability of the underlying decision - making strategies. as a remedy, many post - hoc explanation and self - explanatory methods have been developed to interpret the models ' behavior. these methods, in addition, enable the identification of artifacts that can be learned by the model as class - relevant features. in this work, we provide a detailed case study of the self - explaining network, protopnet, in the presence of a spectrum of artifacts. accordingly, we identify the main drawbacks of protopnet, especially, its coarse and spatially imprecise explanations. we address these limitations by introducing prototypical relevance propagation ( prp ), a novel method for generating more precise model - aware explanations. furthermore, in order to obtain a clean dataset, we propose to use multi - view clustering strategies for segregating the artifact images using the prp explanations, thereby suppressing the potential artifact learning in the models. | arxiv:2108.12204 |
the wiener index of a graph, which is the sum of the distances between all pairs of vertices, has been well studied. recently, sills and wang in 2012 proposed two conjectures on the maximal wiener index of trees with a given degree sequence. this note proves one of the two conjectures and disproves the other. | arxiv:1304.0873 |
in this note we explore the variation of hodge structures associated to the orbifold landau - ginzburg b - model whose superpotential has two variables. we extend the getzler - gauss - manin connection to hochschild chains twisted by group action. as an application, we provide explicit computations for the getzler - gauss - manin connection on the universal ( noncommutative ) unfolding of $ \ mathbb { z } _ 2 $ - orbifolding of a - type singularities. the result verifies an example of deformed version of mckay correspondence. | arxiv:1904.09426 |
wavelets are a new and powerful mathematical tool, whose most celebrated applications are data compression and de - noising. in paper i ( romeo, horellou & bergh 2003, astro - ph / 0302343 ), we have shown that wavelets can be used for removing noise efficiently from cosmological, galaxy and plasma n - body simulations. the expected two - orders - of - magnitude higher performance means, in terms of the well - known moore ' s law, an advance of more than one decade in the future. in this paper, we describe a wavelet add - on code designed for such an application. our code can be included in common grid - based n - body codes, is written in fortran, is portable and available on request from the first author. the code can also be applied for removing noise from standard data, such as signals and images. | arxiv:astro-ph/0408181 |
underwater image enhancement ( uie ) has attracted much attention owing to its importance for underwater operation and marine engineering. motivated by the recent advance in generative models, we propose a novel uie method based on image - conditional diffusion transformer ( icdt ). our method takes the degraded underwater image as the conditional input and converts it into latent space where icdt is applied. icdt replaces the conventional u - net backbone in a denoising diffusion probabilistic model ( ddpm ) with a transformer, and thus inherits favorable properties such as scalability from transformers. furthermore, we train icdt with a hybrid loss function involving variances to achieve better log - likelihoods, which meanwhile significantly accelerates the sampling process. we experimentally assess the scalability of icdts and compare with prior works in uie on the underwater imagenet dataset. besides good scaling properties, our largest model, icdt - xl / 2, outperforms all comparison methods, achieving state - of - the - art ( sota ) quality of image enhancement. | arxiv:2407.05389 |
this study investigates whether physically recurrent neural networks ( prnns ), a recent surrogate model for heterogeneous materials, trained on a micromodel with fixed material parameters, can maintain accuracy for varying material properties without retraining, and propagate uncertainty in a multiscale framework. unlike conventional rnns, where parameter changes require training or explicit inclusion of material properties as extra input features, prnns embeds material models in their material layer that allow for modification of material parameters after training. when adjusting material properties dynamically according to the input during testing, prnn shows high accuracy across a wide range of parameters. therefore the surrogate can be applied to multiscale uncertainty quantification ( uq ). compared to the full - order simulations on an overly coarse mesh, the prnn - driven model reduces simulation time by over 7000 times while accurately capturing highly nonlinear evolution of the probability density for the macroscopic response as a result of a given distribution for microscale material parameters. a prnn - driven uq is demonstrated on a more accurate finer mesh that would be computationally infeasible with the full - order model. | arxiv:2504.11625 |
we consider the framework of convex high dimensional stochastic control problems, in which the controls are aggregated in the cost function. as first contribution, we introduce a modified problem, whose optimal control is under some reasonable assumptions an $ \ varepsilon $ - optimal solution of the original problem. as second contribution, we present a decentralized algorithm whose convergence to the solution of the modified problem is established. finally, we study the application of the developed tools in an engineering context, studying a coordination problem for large populations of domestic thermostatically controlled loads ( tcls ) | arxiv:2008.09827 |
we study a natural generalization of covering projections defined in terms of unique lifting properties. a map $ p : e \ to x $ has the " continuous path - covering property " if all paths in $ x $ lift uniquely and continuously ( rel. basepoint ) with respect to the compact - open topology. we show that maps with this property are closely related to fibrations with totally path - disconnected fibers and to the natural quotient topology on the homotopy groups. in particular, the class of maps with the continuous path - covering property lies properly between hurewicz fibrations and serre fibrations with totally path - disconnected fibers. we extend the usual classification of covering projections to a classification of maps with the continuous path - covering property in terms of topological $ \ pi _ 1 $ : for any path - connected hausdorff space $ x $, maps $ e \ to x $ with the continuous path - covering property are classified up to weak equivalence by subgroups $ h \ leq \ pi _ 1 ( x, x _ 0 ) $ with totally path - disconnected coset space $ \ pi _ 1 ( x, x _ 0 ) / h $. here, " weak equivalence " refers to an equivalence relation generated by formally inverting bijective weak homotopy equivalences. | arxiv:2006.03667 |
a simple proof is given that the probabilities of observations in a large universe are not given directly by born ' s rule as the expectation values of projection operators in a global quantum state of the entire universe. an alternative procedure is proposed for constructing an averaged density matrix for a random small region of the universe and then calculating observational probabilities indirectly by born ' s rule as conditional probabilities, conditioned upon the existence of an observation. | arxiv:0907.4152 |
we describe and compute the homotopy of spectra of topological modular forms of level 3. we give some computations related to the " building complex " associated to level 3 structures at the prime 2. finally, we note the existence of a number of connective models of the spectrum tmf ( gamma _ 0 ( 3 ) ). | arxiv:0812.2009 |
this paper presents an investigation on the four open clusters czernik 14, haffner 14, haffner 17 and king 10 located near the perseus arm of milky way galaxy using gaia dr2, 2mass, wise, apass and pan - starrs1 data sets. we find normal interstellar extinction in twelve photometric bands for these clusters. likely cluster members are identified as 225, 353, 350 and 395 for czernik 14, haffner 14, haffner 17 and king 10, respectively by using gaia dr2 proper motion data. radii are determined as 3. 5, 3. 7, 6. 2 and 5. 7 arcmin for czernik 14, haffner 14, haffner 17 and king 10 respectively. mean proper motions in ra and dec are estimated as ( - 0. 42 \ pm 0. 02, - 0. 38 \ pm 0. 01 ), ( - 1. 82 \ pm 0. 009, 1. 73 \ pm 0. 008 ), ( - 1. 17 \ pm 0. 007, 1. 88 \ pm 0. 006 ) and ( - 2. 75 \ pm 0. 008, - 2. 04 \ pm 0. 006 ) mas / yr for czernik 14, haffner 14, haffner 17 and king 10, respectively. the comparison of observed cmds with solar metallicity isochrones leads to an age of 570 \ pm 60, 320 \ pm 35, 90 \ pm 10 and 45 \ pm 5 myr for these clusters. the distances 2. 9 \ pm 0. 1, 4. 8 \ pm 0. 4, 3. 6 \ pm 0. 1 and 3. 8 \ pm 0. 1 kpc determined using parallax are comparable with the values derived by the isochrone fitting method. mass function slopes are found to be in good agreement with the salpeter value. the total masses are derived as 348, 595, 763 and 1088 solar mass for the clusters czernik 14, haffner 14, haffner 17 and king 10, respectively. evidence for the existence of mass - segregation effect is observed in each cluster. using the galactic potential model, galactic orbits are derived for the clusters. the present study indicates that all clusters under study fallow a circular path around the galactic center. | arxiv:2003.02448 |
a u - net is trained to recover acoustic interference striations ( aiss ) from distorted ones. a random mode - coupling matrix model is introduced to generate a large number of training data quickly, which are used to train the u - net. the performance of ais recovery of the u - net is tested in range - dependent waveguides with nonlinear internal waves ( nliws ). although the random mode - coupling matrix model is not an accurate physical model, the test results show that the u - net successfully recovers aiss under different signal - to - noise ratios ( snrs ) and different amplitudes and widths of nliws for different shapes. | arxiv:2003.10661 |
in many applications, it is of interest to assess the dependence structure in multivariate longitudinal data. discovering such dependence is challenging due to the dimensionality involved. by concatenating the random effects from component models for each response, dependence within and across longitudinal responses can be characterized through a large random effects covariance matrix. motivated by the common problems in estimating this matrix, especially the off - diagonal elements, we propose a bayesian approach that relies on shrinkage priors for parameters in a modified cholesky decomposition. without adjustment, such priors and previous related approaches are order - dependent and tend to shrink strongly toward an artype structure. we propose moment - matching ( mm ) priors to mitigate such problems. efficient gibbs samplers are developed for posterior computation. the methods are illustrated through simulated examples and are applied to a longitudinal epidemiologic study of hormones and oxidative stress. | arxiv:1208.2977 |
we propose a framework for optimizing a planar parallel - jaw gripper for use with multiple objects. while optimizing general - purpose grippers and contact locations for grasps are both well studied, co - optimizing grasps and the gripper geometry to execute them receives less attention. as such, our framework synthesizes grippers optimized to stably grasp sets of polygonal objects. given a fixed number of contacts and their assignments to object faces and gripper jaws, our framework optimizes contact locations along these faces, gripper pose for each grasp, and gripper shape. our key insights are to pose shape and contact constraints in frames fixed to the gripper jaws, and to leverage the linearity of constraints in our grasp stability and gripper shape models via an augmented lagrangian formulation. together, these enable a tractable nonlinear program implementation. we apply our method to several examples. the first illustrative problem shows the discovery of a geometrically simple solution where possible. in another, space is constrained, forcing multiple objects to be contacted by the same features as each other. finally a toolset - grasping example shows that our framework applies to complex, real - world objects. we provide a physical experiment of the toolset grasps. | arxiv:2310.18425 |
the status of solutions to the ultra - high energy cosmic ray puzzle that involve particle physics beyond the standard model is reviewed. signatures and experimental constraints are discussed for most proposals like the z burst model and topological defects ( both allowed only as subdominant contribution ), supermassive dark matter ( no positive evidence from its key signatures galactic anisotropy and photon dominance ), strongly interacting neutrinos or new primaries ( no viable models known ), and violation of lorentz invariance ( possible ). | arxiv:hep-ph/0406174 |
understanding the equation of state of dense qcd matter remains a major challenge in both nuclear physics and astrophysics. neutron star observations from electromagnetic and gravitational wave spectra provide critical insights into the behavior of dense neutron - rich matter. the next generation of telescopes and gravitational wave observatories will offer even more detailed observations of neutron stars. utilizing deep learning techniques to map neutron star mass and radius observations to the equation of state allows for its accurate and reliable determination. this work demonstrates the feasibility of using deep learning to extract the equation of state directly from neutron star observational data, and to also obtain related nuclear matter properties such as the slope, curvature, and skewness of the nuclear symmetry energy at saturation density. most importantly, we show that this deep learning approach is able to reconstruct \ textit { realistic } equations of state, and deduce \ textit { realistic } nuclear matter properties. this highlights the potential of artificial neural networks in providing a reliable and efficient means to extract crucial information about the equation of state and related properties of dense neutron - rich matter in the era of multi - messenger astrophysics. | arxiv:2303.17146 |
we provide introductory explanations and illustrations of the $ n $ - body hydrodynamics code charm n - body gravity solver ( changa ). changa simulates the gravitational motion and gas dynamics of matter in space, with the goal of modeling galactic and / or cosmological structure and evolution. we discuss the algorithm for leapfrog integration and smoothed particle hydrodynamics and computer science concepts used by the program, including the binary data structure for the particle positions. our presentation borrows from the doctoral dissertation of j. \ g. \ stadel. problems are provided in order to use changa to learn or solidify some cosmological concepts. | arxiv:2302.01895 |
we analyze the sources of free electrons that produce the large dispersion measures, dm $ \ approx 300 - 1600 $ ( in units cm $ ^ { - 3 } $ pc ), observed toward fast radio bursts ( frbs ). individual galaxies typically produce dm $ \ sim 25 - 60 $ cm $ ^ { - 3 } $ pc from ionized gas in their disk, disk - halo interface, and circumgalactic medium. toward an frb source at redshift $ z $, a homogeneous igm containing a fraction $ f _ { \ rm igm } $ of cosmological baryons will produce dm $ = ( 935 ~ { \ rm cm } ^ { - 3 } ~ { \ rm pc } ) f _ { \ rm igm } \, h _ { 70 } ^ { - 1 } i ( z ) $, where $ i ( z ) = ( 2 / 3 \ omega _ m ) [ \ { \ omega _ m ( 1 + z ) ^ 3 + \ omega _ { \ lambda } \ } ^ { 1 / 2 } - 1 ] $. a structured igm of photoionized ly - alpha absorbers in the cosmic web produces similar dispersion, modeled from the observed distribution, $ f _ b ( n, z ) $, of h i ( lya - forest ) absorbers in column density and redshift with ionization corrections and scaling relations from cosmological simulations. an analytic formula for dm ( $ z $ ) applied to observed frb dispersions suggests that $ z _ { \ rm frb } \ approx 0. 2 - 1. 5 $ for an igm containing a significant baryon fraction, $ f _ { \ rm igm } = 0. 6 \ pm0. 1 $. future surveys of the statistical distribution, dm ( $ z ) $, of frbs identified with specific galaxies and redshifts, can be used to calibrate the igm baryon fraction and distribution of ly - alpha absorbers. fluctuations in dm at the level $ \ pm10 $ cm $ ^ { - 3 } $ pc will arise from filaments and voids in the cosmic web. | arxiv:1712.01280 |
the swimming of a two - sphere system and of a three - sphere chain in an incompressible viscous fluid is studied on the basis of simplified equations of motion which take account of both stokes friction and added mass effects. the analysis is based on an explicit expression for the asymptotic periodic swimming velocity and a corresponding evaluation of the mean rate of dissipation. the mean swimming velocity of the two - sphere system is found to be non - vanishing provided that the two spheres are not identical. the swimming of a comparable chain of three identical spheres is much more efficient. | arxiv:1606.02400 |
the coupling between ricci scalar curvature and the baryon number current dynamically breaks cpt in an expanding universe and leads to baryon asymmetry. we study the effect of time dependence of equation of state parameter of the frw universe on this asymmetry. | arxiv:0709.0697 |
the search for one - dimensional ( 1d ) topologically - protected electronic states has become an important research goal for condensed matter physics owing to their potential use in spintronic devices or as a building block for topologically non - trivial electronic states. using low temperature scanning tunneling microscopy, we demonstrate the formation of 1d electronic states at twin boundaries at the surface of the noncentrosymmetric material bipd. these twin boundaries are topological defects which separate regions with antiparallel orientations of the crystallographic \ textit { b } axis. we demonstrate that the formation of the 1d electronic states can be rationalized by a change in effective mass of two - dimensional surface states across the twin boundary. our work therefore reveals a novel route towards designing 1d electronic states with strong spin - orbit coupling. | arxiv:1811.02832 |
in several image acquisition and processing steps of x - ray radiography, knowledge of the existence of metal implants and their exact position is highly beneficial ( e. g. dose regulation, image contrast adjustment ). another application which would benefit from an accurate metal segmentation is cone beam computed tomography ( cbct ) which is based on 2d x - ray projections. due to the high attenuation of metals, severe artifacts occur in the 3d x - ray acquisitions. the metal segmentation in cbct projections usually serves as a prerequisite for metal artifact avoidance and reduction algorithms. since the generation of high quality clinical training is a constant challenge, this study proposes to generate simulated x - ray images based on ct data sets combined with self - designed computer aided design ( cad ) implants and make use of convolutional neural network ( cnn ) and vision transformer ( vit ) for metal segmentation. model test is performed on accurately labeled x - ray test datasets obtained from specimen scans. the cnn encoder - based network like u - net has limited performance on cadaver test data with an average dice score below 0. 30, while the metal segmentation transformer with dual decoder ( mst - dd ) shows high robustness and generalization on the segmentation task, with an average dice score of 0. 90. our study indicates that the cad model - based data generation has high flexibility and could be a way to overcome the problem of shortage in clinical data sampling and labelling. furthermore, the mst - dd approach generates a more reliable neural network in case of training on simulated data. | arxiv:2203.09207 |
a semiclassical thomas - fermi method, including a weizs \ " acker gradient term, is implemented to describe ground states of two dimensional nanostructures of arbitrary shape. time dependent density oscillations are addressed in the same spirit using the corresponding semiclassical time - dependent equations. the validity of the approximations is tested, both for ground state and density oscillations, comparing with the available microscopic kohn - sham solutions. | arxiv:cond-mat/9910324 |
we consider a scalar field theory in ads _ { d + 1 }, and introduce a formalism on surfaces at equal values of the radial coordinate. in particular, we define the corresponding conjugate momentum. we compute the noether currents for isometries in the bulk, and perform the asymptotic limit on the corresponding charges. we then introduce poisson brackets at the border, and show that the asymptotic values of the bulk scalar field and the conjugate momentum transform as conformal fields of scaling dimensions \ delta _ { - } and \ delta _ { + }, respectively, where \ delta _ { \ pm } are the standard parameters giving the asymptotic behavior of the scalar field in ads. then we consider the case d = 2, where we obtain two copies of the virasoro algebra, with vanishing central charge at the classical level. an ads _ 3 / cft _ 2 prescription, giving the commutators of the boundary cft in terms of the poisson brackets at the border, arises in a natural way. we find that the boundary cft is similar to a generalized ghost system. we introduce two different ground states, and then compute the normal ordering constants and quantum central charges, which depend on the mass of the scalar field and the ads radius. we discuss certain implications of the results. | arxiv:0902.3835 |
machine learning is rapidly becoming one of the most important technology for malware traffic detection, since the continuous evolution of malware requires a constant adaptation and the ability to generalize. however, network traffic datasets are usually oversized and contain redundant and irrelevant information, and this may dramatically increase the computational cost and decrease the accuracy of most classifiers, with the risk to introduce further noise. we propose two novel dataset optimization strategies which exploit and combine several state - of - the - art approaches in order to achieve an effective optimization of the network traffic datasets used to train malware detectors. the first approach is a feature selection technique based on mutual information measures and sensibility enhancement. the second is a dimensional reduction technique based autoencoders. both these approaches have been experimentally applied on the mta - kdd ' 19 dataset, and the optimized results evaluated and compared using a multi layer perceptron as machine learning model for malware detection. | arxiv:2009.11347 |
in recent years planck - scale modifications of the dispersion relation have been attracting increasing interest also from the viewpoint of possible applications in astrophysics and cosmology, where spacetime curvature cannot be neglected. nonetheless the interplay between planck - scale effects and spacetime curvature is still poorly understood, particularly in cases where curvature is not constant. these challenges have been so far postponed by relying on an ansatz, first introduced by jacob and piran. we here propose a general strategy of analysis of the effects of modifications of dispersion relation in frw spacetimes, applicable both to cases where the relativistic equivalence of frames is spoiled ( " preferred - frame scenarios " ) and to the alternative possibility of " dsr - relativistic theories ", theories that are fully relativistic but with relativistic laws deformed so that the modified dispersion relation is observer independent. we show that the jacob - piran ansatz implicitly assumes that spacetime translations are not affected by the planck - scale, while under rather general conditions the same planck - scale quantum - spacetime structures producing modifications of the dispersion relation also affect translations. through the explicit analysis of one of the effects produced by modifications of the dispersion relation, an effect amounting to planck - scale corrections to travel times, we show that our concerns are not merely conceptual but rather can have significant quantitative implications. | arxiv:1507.02056 |
the carbon - nitrogen - oxygen ( cno ) cycle is fundamental to the process of hydrogen burning in stars, serving as a pivotal mechanism. at its core, the primary reaction involves the radiative capture of a proton by $ ^ { 12 } $ c, crucially influencing the isotopic ratio of $ ^ { 12 } $ c to $ ^ { 13 } $ c observed in celestial bodies, including our solar system. we have addressed this reaction mechanism by extrapolating to low - energy cross sections and s - factors with the aid of astrophysical r - matrix. our investigation aims to shed light on its implications for nuclear reaction rates, thus influencing the abundance ratio of $ ^ { 12 } $ c to $ ^ { 13 } $ c in the cosmic environment. | arxiv:2405.20223 |
in the face of mounting numerical evidence, metlitski and grover [ arxiv : 1112. 5166 ] have given compelling analytical arguments that systems with spontaneous broken continuous symmetry contain a sub - leading contribution to the entanglement entropy that diverges logarithmically with system size. they predict that the coefficient of this log is a universal quantity that depends on the number of goldstone modes. in this paper, we confirm the presence of this log term through quantum monte carlo calculations of the second r \ ' enyi entropy on the spin 1 / 2 xy model. devising an algorithm to facilitate convergence of entropy data at extremely low temperatures, we demonstrate that the single goldstone mode in the ground state can be identified through the coefficient of the log term. furthermore, our simulation accuracy allows us to obtain an additional geometric constant additive to the r \ ' enyi entropy, that matches a predicted fully - universal form obtained from a free bosonic field theory with no adjustable parameters. | arxiv:1502.01722 |
it is well known that temperature variations and acoustic noise affect ultrastable frequency dissemination along optical fiber. active stabilization techniques are in general adopted to compensate for the fiber - induced phase noise. however, despite this compensation, the ultimate link performances remain limited by the so called delay - unsuppressed fiber noise that is related to the propagation delay of the light in the fiber. in this paper, we demonstrate a data post - processing approach which enables us to overcome this limit. we implement a subtraction algorithm between the optical signal delivered at the remote link end and the round - trip signal. in this way, a 6 db improvement beyond the fundamental limit imposed by delay - unsuppressed noise is obtained. this result enhances the resolution of possible comparisons between remote optical clocks by a factor of 2. we confirm the theoretical prediction with experimental data obtained on a 47 km metropolitan fiber link, and propose how to extend this method for frequency dissemination purposes as well. | arxiv:1405.5895 |
mixed halide perovskites undergo phase segregation, manifested as spectral red - shifting of photoluminescence spectra under illumination. in the iodine - bromide mixed perovskites, the origin of the low - energy luminescence is related to iodine - enriched domains formation. such domains create favorable bands for the induced carrier funneling into them. despite the phase segregation process is crucial for mixed halide perovskite - based optoelectronics, numerous gaps exist within the understanding of this phenomenon. one such gap pertains to the emergence of temporary and intermediate photoluminescence peaks during the initial stages of phase segregation. however, these peaks appear only within the first few seconds of illumination. nevertheless, the decreasing temperature may prolong these initial stages. in this work, we carry out a detailed study of the temperature dependence of anion segregation in mapbbr _ 2i and mapbbr2. 5i0. 5 halide perovskites, to obtain a deeper comprehension of segregation processes, particularly during their initial stages. the temporal evolution of low - temperature photoluminescence reveals the undergoing of the intermediate stage during the segregation process and temperature - related phase transition from orthorhombic to tetragonal phase. to complement the phase segregation study, the temperature dependence of time - resolved photoluminescence spectroscopy is provided, allowing us to estimate the change in the photoluminescence lifetimes for the initial and segregated peaks with temperature. | arxiv:2307.08392 |
we consider a 3rd - order generalized monge - ampere equation u _ yyy - u _ xxy ^ 2 + u _ xxx u _ xyy = 0 ( which is closely related to the associativity equation in the 2 - d topological field theory ) and describe all integrable structures related to it ( i. e., hamiltonian, symplectic, and recursion operators ). infinite hierarchies of symmetries and conservation laws are constructed as well. | arxiv:1104.0258 |
we report near - infrared integral field spectroscopic observations of the active galactic nucleus ngc 4151 with archive data from the nifs - gemini north telescope. we have selected best - seeing observations ( $ \ lesssim $ 0. 3 arcsec ) that, allied to our methodology of image processing techniques, show structures with spatial resolution comparable to those of the hst. the intricate outflow of ngc 4151 is revisited in light of the results found for ngc 1068, in a previous work, and a very similar dynamic is found : the low - velocity [ fe ii ] emission depicts the glowing walls of an hourglass structure, while the high - velocity gas fills its volume. from this finding, we show that the misalignment between the jet and the nlr is not a projection effect, as previously thought. a molecular outflow is detected for the first time in this galaxy and, just like in ngc 1068, the transition between the molecular and the ionized gas phases comes from the fragmentation of molecular cavity walls into bullets of ionized gas exposed to the central source. furthermore, it is suggestive that the same geometrical dichotomy between the cones seen in ngc 1068 is found here, with one side, where the cavity is disrupted by the agn, being more extended than the other. finally, a new spatial correlation between the high - velocity [ fe ii ] and the soft x - ray emission of [ ne ix ] is found, which is unexpected given the difference between their ionization potentials. | arxiv:2007.07374 |
in the pioneering work by r. a. marcus, the solvation effect on electron transfer ( et ) processes was investigated, giving rise to the celebrated nonadiabatic et rate formula. in this work, on the basis of the thermodynamic solvation potentials analysis, we reexamine marcus ' formula with respect to the rice - ramsperger - kassel - marcus ( rrkm ) theory. interestingly, the obtained rrkm analogue, which recovers the original marcus ' rate that is in a linear solvation scenario, is also applicable to the nonlinear solvation scenarios, where the multiple curve { crossing of solvation potentials exists. parallelly, we revisit the corresponding fermi ' s golden rule results, with some critical comments against the rrkm analogue proposed in this work. for illustration, we consider the quadratic solvation scenarios, on the basis of physically well - supported descriptors. | arxiv:2012.12699 |
electrodeposition is a fundamental process in electrochemistry, and has applications in numerous industries, such as corrosion protection, decorative finishing, energy storage, catalysis, and electronics. while there is a long history of using electrodeposition, its application for controlled nanostructure growth is limited. the establishment of an atomic - scale understanding of the electrodeposition process and dynamics is crucial to enable the controlled fabrication of metal nanoparticles and other nanostructures. significant advancements in molecular simulation capabilities and the electronic structure theory of electrified solid - liquid interfaces bring theory closer to realistic applications, but a gap remains between realistic applications, theoretical understanding of dynamics, and atomistic simulation. in this review we briefly summarize the current state - of - the - art computational techniques available for the simulation of electrodeposition and electrochemical growth on surfaces, and identify the remaining open challenges. | arxiv:2409.16704 |
we extend the study of the light hadron spectrum and the quark mass in two - flavor qcd to smaller sea quark mass, corresponding to $ m _ { ps } / m _ { v } = 0. 60 $ - - 0. 35. numerical simulations are carried out using the rg - improved gauge action and the meanfield - improved clover quark action at $ \ beta = 1. 8 $ ( $ a = 0. 2 $ fm from $ \ rho $ meson mass ). we observe that the light hadron spectrum for small sea quark mass does not follow the expectation from chiral extrapolations with quadratic functions made from the region of $ m _ { ps } / m _ { v } = 0. 80 $ - - 0. 55. whereas fits with either polynomial or continuum chiral perturbation theory ( chpt ) fails, the wilson chpt ( wchpt ) that includes $ a ^ 2 $ effects associated with explicit chiral symmetry breaking successfully fits the whole data : in particular, wchpt correctly predicts the light quark mass spectrum from simulations for medium heavy quark mass, such as $ m _ { ps } / m _ v \ simgt 0. 5 $. reanalyzing the previous data % at $ m _ { ps } / m _ { v } = 0. 80 $ - - 0. 55 with the use of wchpt, we find the mean up and down quark mass being smaller than the previous result from quadratic chiral extrapolation by approximately 10 %, $ m _ { ud } ^ { \ bar { \ rm ms } } ( \ mu = 2 { gev } ) = 3. 11 ( 17 ) $ [ mev ] in the continuum limit. | arxiv:hep-lat/0404014 |
it is shown in the paper " variational properties of the gauss - bonnet curvatures " of m. l. labbi, that metrics with constant 2k - gauss - bonnet curvature on a closed n - dimensional manifold, 1 < 2k < n, are critical points for a certain hilbert type functional with respect to volume preserving conformal variations. this motivates the corresponding yamabe problem : is it true that any metric on a closed manifold is conformal to a metric with constant 2k - gauss - bonnet curvature? using perturbative methods we affirmatively answer this question for small perturbations of certain space forms. more precisely, if ( x, g ) is a non - flat closed space form not isometric to a round sphere, we show the existence of a neighborhood u, of g, in the space of metrics such that any g ' in u is conformal to a metric whose 2k - gauss - bonnet curvature is constant. | arxiv:1005.0584 |
in this paper, we study analytically the impact of an inhibitory autapse on neuronal activity. in order to do this, we formulate conditions on a set of non - adaptive spiking neuron models with delayed feedback inhibition, instead of considering a particular neuronal model. the neuron is stimulated with a stochastic point renewal process of excitatory impulses. probability density function ( pdf ) $ p ( t ) $ of output interspike intervals ( isis ) of such a neuron is found exactly without any approximations made. it is expressed in terms of isis pdf for the input renewal stream and isis pdf for that same neuron without any feedback. obtained results are applied to a subset of neuronal models with threshold 2 when the time intervals between input impulses are distributed according to the erlang - 2 distribution. in that case we have found explicitly the model - independent initial part of isis pdf $ p ( t ) $ defined at some initial interval $ [ 0 ; t _ 2 ] $ of isi values. | arxiv:2110.11161 |
we present an analytic derivation of the full four - loop cusp anomalous dimension of $ \ mathcal { n } = 4 $ supersymmetric yang - mills theory from the sudakov form factor. to extract the cusp anomalous dimension, we calculate the $ \ epsilon ^ { - 2 } $ pole of the form factor using parametric integrations of finite integrals. we provide uniformly transcendental results for the master integrals through to weight six and confirm a very recent independent analytic result for the full four - loop cusp anomalous dimension of the $ \ mathcal { n } = 4 $ model. | arxiv:1912.13459 |
the physics of kinetic mixing between ordinary and mirror photons is discussed. an important role is played by four linear combinations we dub the physical photon, the sterile photon, the physical mirror photon, and the sterile mirror photon. because of the mass degeneracy between the two gauge bosons, quantum coherence effects are important. the physical photon becomes a certain coherent superposition of the bare ordinary photon and the bare mirror photon. similarly, the physical mirror photon is another, but { \ it not orthogonal }, coherent superposition. we discuss the physics of the interaction between physical mirror photons and ordinary matter. observational signatures for some hybrid ordinary / mirror binary astrophysical systems are qualitatively discussed. we show that a small amount of ordinary matter at the center of a mirror star may make the mirror star observable. we speculate that the recently reported halo white dwarfs might actually be mirror halo stars. | arxiv:astro-ph/0011156 |
we perform a statistical analysis of strong gravitational lensing by quasar hosts of background galaxies, in the two competing models of dark matter halos of quasars, hod and cs models. utilizing the bolshoip simulation we demonstrate that strong gravitational lensing provides a potentially very powerful test of models of quasar hosting halos. for quasars at $ z = 0. 5 $, the lensing probability by quasars of background galaxies in the hod model is higher than that of the cs model by two orders of magnitude or more for lensing image separations in the range of $ \ theta \ sim 1. 2 - 12 ~ $ arcsec. to observationally test this, we show that, as an example, at the depth of the candels wide field survey and with a quasar sample of $ 1000 $ at $ z = 0. 5 $, the two models can be differentiated at $ 3 - 4 \ sigma $ confidence level. | arxiv:1604.06473 |
recent laboratory efforts ( fu et al., 2014 ) have constrained the remanent magnetizations of chondrules and the magnetic field strengths at which the chondrules were exposed to as they cooled below their curie points. an outstanding question is whether the inferred paleofields represent the background magnetic field of the solar nebula or were unique to the chondrule - forming environment. we investigate the amplification of the magnetic field above background values for two proposed chondrule formation mechanisms, large - scale nebular shocks and planetary bow shocks. behind large - scale shocks, the magnetic field parallel to the shock front is amplified by factors $ \ sim 10 - 30 $, regardless of the magnetic diffusivity. therefore, chondrules melted in these shocks probably recorded an amplified magnetic field. behind planetary bow shocks, the field amplification is sensitive to the magnetic diffusivity. we compute the gas properties behind a bow shock around a 3000 km - radius planetary embryo, with and without atmospheres, using hydrodynamics models. we calculate the ionization state of the hot, shocked gas, including thermionic emission from dust, and thermal ionization of gas - phase potassium atoms, and the magnetic diffusivity due to ohmic dissipation and ambipolar diffusion. we find that the diffusivity is sufficiently large that magnetic fields have already relaxed to background values in the shock downstream where chondrules acquire magnetizations, and that these locations are sufficiently far from the planetary embryos that chondrules should not have recorded a significant putative dynamo field generated on these bodies. we conclude that, if melted in planetary bow shocks, chondrules probably recorded the background nebular field. | arxiv:1803.05055 |
monolayer transition - metal dichalcogenides ( tmdcs ) present high second - order optical nonlinearity, which is extremely desirable for, e. g., frequency conversion in nonlinear photonic devices. on the other hand, the atomic thickness of 2d materials naturally leads to low frequency converted intensities, highlighting the importance to design structures that enhance the nonlinear response for practical applications. a number of methods to increase the pump electric field at the 2d material has been reported, relying on complex plasmonic and / or metasurface structures. here, we take advantage of the fact that unstructured substrates with a low refractive index naturally maximize the pump field at a dielectric interface, offering a simple means to promote enhanced nonlinear optical effects. in particular, we measured second harmonic generation ( shg ) in mos2 and ws2 on fluorine tin oxide ( fto ), which presents an epsilon - near - zero point near our 1550 - nm pump wavelength. polarized shg measurements reveal an shg intensity that is one order of magnitude higher on fto than on a glass substrate. | arxiv:2011.08000 |
optimal power flow ( opf ) is a key tool for planning and operations in energy grids. the line - flow constraints, generator loading effect, piece - wise cost functions, emission, and voltage quality cost make the optimization model non - convex and computationally cumbersome to solve. metaheuristic techniques for solving the problem have emerged as a promising solution to solve the complex opf problem. recently, the water cycle algorithm ( wca ), a method inspired by the observation of the water cycle process and the surface run - off model was proposed for solving optimization problems. this paper proposes an improved version of wca that uses the concept of sharing global and local information among individuals to improve the exploitation ability compared with the standard wca. the so called fully informed wca ( fiwca ) is tested against standard wca and other metaheuristic techniques studied in the literature on ieee 30 and 57 bus systems for various scenarios. comparison and discussion regarding the performance and reliability of the metaheuristics approaches studied in literature are discussed. the obtained optimization results show that the better performance of proposed fiwca comparing with the wca and other algorithms especially in term of stability performance over replications. consequently, it emerges as a tool for solving opf in a reliable and efficient manner. | arxiv:1909.08800 |
in this work, we review the figures used to characterize an epidemic outbreak most. particular attention is drawn to epidemic spreading at time - varying transition rates. a time - varying sir - like model is used to describe the epidemic dynamics, from which closed equations relating parameters and key quantities like reproduction ratio and doubling time are derived. the definition and computation of these metrics are revisited in the context of the general solution to the time - varying model dynamics, focusing on the similarities and differences with the time - invariant case. further, the prediction of these metrics, that is of the disease evolution, as response to different scenarios is also investigated. | arxiv:2011.02516 |
the daya bay neutrino experiment is proposed to measure sin ^ 2 ( 2 \ theta _ { 13 } ) to better than 0. 01 at 90 % c. l. in a three - year run. the experimental site, detector design, and background estimation are presented. | arxiv:hep-ex/0509041 |
we present estimates for the accretion rates in 13 x - - ray bursting sources which exhibit photospheric expansion, basing on theoretical models of stationary, radiatively driven winds from neutron stars. the relatively high values obtained, $ \ mdot _ { acc } \ magcir 10 ^ { - 9 } \ ms $, are in accordance with theoretical limits for unstable helium burning, and, at the same time, almost never exceed the ` ` dynamical ' ' limit for stationary accretion, $ \ sim 10 \ mdot _ { edd } $. the only exceptions are 1820 - 30, already known to be a very peculiar object, and 1608 - 522 ; there are indications, however, that in both sources, accretion could be non - - stationary. | arxiv:astro-ph/9405066 |
adversarial attacks have become a major threat for machine learning applications. there is a growing interest in studying these attacks in the audio domain, e. g, speech and speaker recognition ; and find defenses against them. in this work, we focus on using representation learning to classify / detect attacks w. r. t. the attack algorithm, threat model or signal - to - adversarial - noise ratio. we found that common attacks in the literature can be classified with accuracies as high as 90 %. also, representations trained to classify attacks against speaker identification can be used also to classify attacks against speaker verification and speech recognition. we also tested an attack verification task, where we need to decide whether two speech utterances contain the same attack. we observed that our models did not generalize well to attack algorithms not included in the attack representation model training. motivated by this, we evaluated an unknown attack detection task. we were able to detect unknown attacks with equal error rates of about 19 %, which is promising. | arxiv:2107.04448 |
the effective field theory likelihood for the density field of biased tracers allows for cosmology inference from the clustering of galaxies that consistently uses all available information at a given order in perturbation theory. this paper presents results and implementation details on the real - space ( as opposed to fourier - space ) formulation of the likelihood, which allows for the incorporation of survey window functions. the implementation further uses a lagrangian forward model for biased tracers which automatically accounts for all relevant contributions up to any desired order. unbiased inference of $ \ sigma _ 8 $ is demonstrated at the 2 % level for cutoff values $ \ lambda \ leq 0. 14h \, { \ rm mpc } ^ { - 1 } $ for halo samples over a range of masses and redshifts. the inferred value shows the expected convergence to the ground truth in the low - cutoff limit. apart from the possibility of including observational effects, this represents further substantial improvement over previous results based on the eft likelihood. | arxiv:2009.14176 |
we study the cascading traffic jamming on a two - dimensional random geometric graph using the motter and lai model. the traffic jam is caused by a localized attack incapacitating circular region or a line of a certain size, as well as a dispersed attack on an equal number of randomly selected nodes. we investigate if there is a critical size of the attack above which the network becomes completely jammed due to cascading jamming, and how this critical size depends on the average degree $ \ langle k \ rangle $ of the graph, on the number of nodes $ n $ in the system, and the tolerance parameter $ \ alpha $ of the motter and lai model. | arxiv:2204.09011 |
vector format has been popular for representing icons and sketches. it has also been famous for design purposes. regarding image editing, research on vector graphics editing rarely exists in contrast with the raster counterpart. we considered the reason to be the lack of datasets and benchmarks. thus, we propose svgeditbench v2, a benchmark dataset for instruction - based svg editing. svgeditbench v2 comprises triplets of an original image, a ground truth image, and the editing prompt. we built the dataset by first extracting image pairs from various svg emoji datasets. then, we had gpt - 4o to create the prompt. we found that triplets gained by this simple pipeline contain varying sorts of editing tasks. additionally, we performed the editing tasks with existing llms and investigated how those current methods can perform svg editing. although there were some successful cases, we found that there is a massive room for improvement. | arxiv:2502.19453 |
we use a natural generalization of the discrete fourier transform to define transition maps between hilbert subspaces and the global transport operator $ z $. by using these transition maps as kraus ( or noise ) operators, an extension of the quantum energy transport model of 10. 1142 / s0219025718500182 describing the dynamics of an open quantum system of $ n $ - levels is presented. we deduce the structure of the invariant states which can be recovered by transporting states supported on the first level. | arxiv:2008.05008 |
lower bounds for the first and the second eigenvalue of uniform hypergraphs which are regular and linear are obtained. one of these bounds is a generalization of the alon - boppana theorem to hypergraphs. | arxiv:1512.02710 |
we consider the problem of active learning for single neuron models, also sometimes called ` ` ridge functions ' ', in the agnostic setting ( under adversarial label noise ). such models have been shown to be broadly effective in modeling physical phenomena, and for constructing surrogate data - driven models for partial differential equations. surprisingly, we show that for a single neuron model with any lipschitz non - linearity ( such as the relu, sigmoid, absolute value, low - degree polynomial, among others ), strong provable approximation guarantees can be obtained using a well - known active learning strategy for fitting \ emph { linear functions } in the agnostic setting. % - - i. e. for the case when there is no non - linearity. namely, we can collect samples via statistical \ emph { leverage score sampling }, which has been shown to be near - optimal in other active learning scenarios. we support our theoretical results with empirical simulations showing that our proposed active learning strategy based on leverage score sampling outperforms ( ordinary ) uniform sampling when fitting single neuron models. | arxiv:2210.13601 |
with the complication of future communication scenarios, most conventional signal processing technologies of multi - user multiple - input multiple - output ( mu - mimo ) become unreliable, which are designed based on ideal assumptions, such as gaussian signaling and independent identically distributed ( iid ) channel matrices. as a result, this paper considers a generalized mu - mimo ( gmu - mimo ) system with more general assumptions, i. e., arbitrarily fixed input distributions, and general unitarily - invariant channel matrices. however, there is still no accurate capacity analysis and capacity optimal transceiver with practical complexity for gmu - mimo under the constraint of coding. to address these issues, inspired by the replica method, the constrained sum capacity of coded gmu - mimo with fixed input distribution is calculated by using the celebrated mutual information and minimum mean - square error ( mmse ) lemma and the mmse optimality of orthogonal / vector approximate message passing ( oamp / vamp ). then, a capacity optimal multiuser oamp / vamp receiver is proposed, whose achievable rate is proved to be equal to the constrained sum capacity. moreover, a design principle of multi - user codes is presented for the multiuser oamp / vamp, based on which a kind of practical multi - user low - density parity - check ( mu - ldpc ) code is designed. numerical results show that finite - length performances of the proposed mu - ldpc codes with multi - user oamp / vamp are about 2 db away from the constrained sum capacity and outperform those of the existing state - of - art methods. | arxiv:2206.12134 |
merging black holes produce the loudest signal in the detectors. however, this is the most difficult signal to accurately predict with analytical techniques. only computer simulations can account for the nonlinear physics during the collision, but they are inherently complex, costly, and affected by numerical errors. in order to bypass this problem, two analytical models for the merger have been developed : the implicit rotating source ( irs ) and the newer backwards one body ( bob ). in this work, we assess the performance of the bob model by comparing it with the older irs model and with the numerical data, identifying its strengths and weaknesses. our main finding reveals discrepancies in amplitude, but overall excellent accord in frequency. the bob model is comparable with the irs and nr simulations, having the added advantage that it depends only indirectly on numerical data, it accounts for spin, and it offers a seamless fit with the analytical formalisms for the inspiral. by independently evaluating and testing those models, we bring evidence of their reproducibility, thus upholding high scientific standards, and make available our implementation, enabling readers to evaluate our results themselves. | arxiv:2205.14742 |
the problem of proximity full - text search is considered. if a search query contains high - frequently occurring words, then multi - component key indexes deliver an improvement in the search speed compared with ordinary inverted indexes. it was shown that we can increase the search speed by up to 130 times in cases when queries consist of high - frequently occurring words. in this paper, we investigate how the multi - component key index architecture affects the quality of the search. we consider several well - known methods of relevance ranking, where these methods are of different authors. using these methods, we perform the search in the ordinary inverted index and then in an index enhanced with multi - component key indexes. the results show that with multi - component key indexes we obtain search results that are very close, in terms of relevance ranking, to the search results that are obtained by means of ordinary inverted indexes. | arxiv:2108.00410 |
we study l ^ 2 - betti numbers for von neumann algebras, as defined by d. shlyakhtenko and a. connes, in the presence of a bi - finite correspondence and prove a proportionality formula. | arxiv:math/0601408 |
the presentation of supergravity theories of our previous paper " super - poincare ' algebras, space - times and supergravities ( i ) " is re - formulated in the language of berezin - leites - kostant theory of supermanifolds. it is also shown that the equations of cremmer, julia and scherk ' s theory of 11d - supergravity are equivalent to manifestly covariant equations on a supermanifold. | arxiv:1108.6314 |
based on the degenerate darboux transformation, the $ n $ - order smooth positon solutions for the derivative nonlinear schr \ " { o } dinger equation are generated by means of the general determinant expression of the $ n $ - soliton solution, and interesting dynamic behaviors of the smooth positons are shown by the corresponding three dimensional plots in this paper. furthermore, the decomposition process, bent trajectory and the change of the phase shift for the positon solutions are discussed in detail. additional, three kinds of mixed solutions, namely ( 1 ) the hybrid of one - positon and two - positon solutions, ( 2 ) the hybrid of two - positon and two - positon solutions, and ( 3 ) the hybrid of one - soliton and three - positon solutions are presented and their rather complicated dynamics are revealed. | arxiv:1904.09277 |
we present resistivity and thermal conductivity measurements on bulk samples, prepared either by a standard method or by a one - step technique. the latter samples, due to their high density and purity, show residual resistivity values as low as 0. 5 mw cm and thermal conductivity values as high as 215 w / mk, higher than the single crystal ones. thermal and electrical data of all the samples are analysed in the framework of the bloch - gruneisen equation giving reliable parameter values. in particular the temperature resitivity coefficient, obtained both from resistivity and thermal conductivity, in the dirty sample comes out ten time larger than in the clean ones. this result supports the hypothesis of ref. [ 1 ] that p and s bands conduct in parallel, prevailing p conduction in clean samples and s conduction in dirty samples. | arxiv:cond-mat/0210047 |
more than two hundred classical cepheids were measured by the hipparcos astrometric satellite, making possible a geometrical calibration of the cepheid distance scale. however, the large average distance of even the nearest cepheids measured by hipparcos implies trigonometric parallaxes of at most a few mas. determining unbiased distances and absolute magnitudes from such high relative error parallax data is not a trivial problem. in 1997, feast & catchpole announced that hipparcos cepheid parallaxes indicated a period - luminosity scale 0. 2 mag brighter than previous calibrations, with important consequences on the whole cosmic distance scale. in the wake of this initial study, several authors have reconsidered the question, and favour fainter calibrations of cepheid luminositites, compatible with pre - hipparcos values. all authors used equivalent data sets, and the bulk of the difference in the results arises from the statistical treatment of the parallax data. we have attempted to repeat the analyses of all these studies and test them with monte carlo simulations and synthetic samples. we conclude that the initial feast & catchpole study is sound, and that the subsequent studies are subjected in several different ways to biases involved in the treatment of high relative error parallax data. we consider the source of these biases in some detail. we also propose a reappraisal of the error budget in the final hipparcos cepheid result, leading to a pl relation - - adapted from feast & catchpole - - of m _ v = - 2. 81 ( assumed ) log p - 1. 43 + - 0. 16 ( stat ) + 0 - 0. 03 ( syst ). we compare this calibration to recent values from cluster cepheids or the surface brightness method, and find that the overall agreement is good within the uncertainties. | arxiv:astro-ph/9812074 |
change points in real - world systems mark significant regime shifts in system dynamics, possibly triggered by exogenous or endogenous factors. these points define regimes for the time evolution of the system and are crucial for understanding transitions in financial, economic, social, environmental, and technological contexts. building upon the bayesian approach introduced in \ cite { c : 07 }, we devise a new method for online change point detection in the mean of a univariate time series, which is well suited for real - time applications and is able to handle the general temporal patterns displayed by data in many empirical contexts. we first describe time series as an autoregressive process of an arbitrary order. second, the variance and correlation of the data are allowed to vary within each regime driven by a scoring rule that updates the value of the parameters for a better fit of the observations. finally, a change point is detected in a probabilistic framework via the posterior distribution of the current regime length. by modeling temporal dependencies and time - varying parameters, the proposed approach enhances both the estimate accuracy and the forecasting power. empirical validations using various datasets demonstrate the method ' s effectiveness in capturing memory and dynamic patterns, offering deeper insights into the non - stationary dynamics of real - world systems. | arxiv:2407.16376 |
in this paper we prove local existence of a ricci de turck flow starting at a space with incomplete edge singularities and flowing for a short time within a class of incomplete edge manifolds. we derive regularity properties for the corresponding family of riemannian metrics and discuss boundedness of the ricci curvature along the flow. for riemannian metrics that are sufficiently close to a flat incomplete edge metric, we prove long time existence of the ricci de turck flow. under certain conditions, our results yield existence of ricci flow on spaces with incomplete edge singularities. the proof works by a careful analysis of the lichnerowicz laplacian and the ricci de turck flow equation. | arxiv:1603.06545 |
fe $ _ 5 $ gete $ _ 2 $ ( n = 3, 4, 5 ) have recently attracted increasing attention due to their two - dimensional van der waals characteristic and high temperature ferromagnetism, which make promises for spintronic devices. the fe ( 1 ) split site is one important structural characteristic of fe $ _ 5 $ gete $ _ 2 $ which makes it very different from other fe $ _ 5 $ gete $ _ 2 $ ( n = 3, 4 ) systems. the local atomic disorder and short - range order can be induced by the split site. in this work, the high - quality van der waals ferromagnet fe $ _ 5 $ gete $ _ 2 $ were grown to study the low - temperature transport properties. we found a resistivity upturn below 10 k. the temperature and magnetic field dependence of the resistivity are in good agreement with a combination of the theory of disorder - enhanced three - dimensional electron - electron and single - channel kondo effect. the kondo effect exists only at low magnetic field b < 3 t, while electron - electron dominates the appearance for the low - temperature resistivity upturn. we believe that the enhanced three - dimensional electron - electron interaction in this system is induced by the local atomic structural disorder due to the split site of fe ( 1 ). our results indicate that the split site of fe plays an important role for the exceptional transport properties. | arxiv:2207.11383 |
quantum dot ( qd ) solids are promising optoelectronic materials ; further advancing their device functionality depends on understanding their energy transport mechanisms. the commonly invoked near - field f \ " orster resonance energy transfer ( fret ) theory often underestimates the exciton hopping rate in qd solids, yet no consensus exists on the underlying cause. in response, we use time - resolved ultrafast stimulated emission depletion ( trusted ) microscopy, an ultrafast transformation of stimulated emission depletion ( sted ) microscopy to spatiotemporally resolve exciton diffusion in tellurium - doped cdse - core / cds - shell qd superlattices. we measure the concomitant time - resolved exciton energy decay due to excitons sampling a heterogeneous energetic landscape within the superlattice. the heterogeneity is quantified by single - particle emission spectroscopy. this powerful multimodal set of observables provides sufficient constraints on a kinetic monte carlo simulation of exciton transport to elucidate a composite transport mechanism that includes both near - field fret and previously - neglected far - field emission / reabsorption contributions. uncovering this mechanism offers a much - needed unified framework in which to characterize transport in qd solids and additional principles for device design. | arxiv:2302.10453 |
the study of meteorites and their microstructures is a topic which spans multiple fields of research, such as meteoritics and materials science. for materials scientists and engineers, the extreme and unusual conditions which these microstructures form allow for insight into materials which would exist at the edge of our thermomechanical processing abilities. one such microstructure found in low - shock event iron meteorites is neumann bands. these bands are an array of lenticular deformation twins that form throughout the fe - ni matrix with numerous intersections, resulting in many high stress and strain regions within the material ' s surface. the existence of these regions and the shocks that formed them encourage atypical strain accommodating mechanisms and structural changes of the material. however, direct investigation of the deformation twin intersections and the microstructural behaviour in and around these regions has been limited. in this work, investigation of these regions in a campo del cielo meteorite fragment, with electron backscatter diffraction ( ebsd ) and forescatter electron ( fse ) imaging, revealed two primary findings : high - intensity pattern doubling mirrored across the { 110 } band at twin - twin intersection and microband formation across the sample surface, which suggest multilayer twinning and constraint of the crystal structure at points of twin - twin intersection. microbands were found to form along the { 110 } plane and in regions near neumann bands. the simultaneous existence of neumann bands ( microtwins ) and microbands is presented here for a bcc material, and it is believed the neumann band and microbands formed during different types and / or shock events. the presence of both neumann bands and microbands within a bcc iron meteorite is previously unreported and may be valuable in furthering our understanding of shock deformation within iron - based materials. | arxiv:2408.16901 |
let $ k $ be a field and $ s = k [ x _ 1,..., x _ n ] $. in 1982, stanley defined what is now called the stanley depth of an $ s $ - module $ m $, denoted $ \ sdepth ( m ) $, and conjectured that $ \ depth ( m ) \ le \ sdepth ( m ) $ for all finitely generated $ s $ - modules $ m $. this conjecture remains open for most cases. however, herzog, vladoiu and zheng recently proposed a method of attack in the case when $ m = i / j $ with $ j \ subset i $ being monomial $ s $ - ideals. specifically, their method associates $ m $ with a partially ordered set. in this paper we take advantage of this association by using combinatorial tools to analyze squarefree veronese ideals in $ s $. in particular, if $ i _ { n, d } $ is the squarefree veronese ideal generated by all squarefree monomials of degree $ d $, we show that if $ 1 \ le d \ le n < 5d + 4 $, then $ \ sdepth ( i _ { n, d } ) = \ floor { \ binom { n } { d + 1 } \ big / \ binom { n } { d } } + d $, and if $ d \ geq 1 $ and $ n \ ge 5d + 4 $, then $ d + 3 \ le \ sdepth ( i _ { n, d } ) \ le \ floor { \ binom { n } { d + 1 } \ big / \ binom { n } { d } } + d $. | arxiv:0910.4645 |
the distributed subgraph detection asks, for a fixed graph $ h $, whether the $ n $ - node input graph contains $ h $ as a subgraph or not. in the standard congest model of distributed computing, the complexity of clique / cycle detection and listing has received a lot of attention recently. in this paper we consider the induced variant of subgraph detection, where the goal is to decide whether the $ n $ - node input graph contains $ h $ as an \ emph { induced } subgraph or not. we first show a $ \ tilde { \ omega } ( n ) $ lower bound for detecting the existence of an induced $ k $ - cycle for any $ k \ geq 4 $ in the congest model. this lower bound is tight for $ k = 4 $, and shows that the induced variant of $ k $ - cycle detection is much harder than the non - induced version. this lower bound is proved via a reduction from two - party communication complexity. we complement this result by showing that for $ 5 \ leq k \ leq 7 $, this $ \ tilde { \ omega } ( n ) $ lower bound cannot be improved via the two - party communication framework. we then show how to prove stronger lower bounds for larger values of $ k $. more precisely, we show that detecting an induced $ k $ - cycle for any $ k \ geq 8 $ requires $ \ tilde { \ omega } ( n ^ { 2 - \ theta { ( 1 / k ) } } ) $ rounds in the congest model, nearly matching the known upper bound $ \ tilde { o } ( n ^ { 2 - \ theta { ( 1 / k ) } } ) $ of the general $ k $ - node subgraph detection ( which also applies to the induced version ) by eden, fiat, fischer, kuhn, and oshman ~ [ disc 2019 ]. finally, we investigate the case where $ h $ is the diamond ( the diamond is obtained by adding an edge to a 4 - cycle, or equivalently removing an edge from a 4 - clique ), and show non - trivial upper and lower bounds on the complexity of the induced version of diamond detecting and listing. | arxiv:2110.00741 |
. | arxiv:1510.06286 |
this article introduces a novel dynamic framework to bayesian model averaging for time - varying parameter quantile regressions. by employing sequential markov chain monte carlo, we combine empirical estimates derived from dynamically chosen quantile regressions, thereby facilitating a comprehensive understanding of the quantile model instabilities. the effectiveness of our methodology is initially validated through the examination of simulated datasets and, subsequently, by two applications to the us inflation rates and to the us real estate market. our empirical findings suggest that a more intricate and nuanced analysis is needed when examining different sub - period regimes, since the determinants of inflation and real estate prices are clearly shown to be time - varying. in conclusion, we suggest that our proposed approach could offer valuable insights to aid decision making in a rapidly changing environment. | arxiv:1602.00856 |
in this paper, we are concerned with the bicomplex analog of the well - known result asserting that real - valued harmonic functions, on simply connected domains, are the real parts of holomorphic functions. we show that this assertion, word for word, fails for bc - harmonic functions and we provide a complete characterization of bc - harmonic functions that are the hyperbolic real parts of a specific kind of bc - holomorphic functions. moreover, we extend the result to bicomplex polyharmonic functions, which implies the introduction of specific classes of bc - polyholomorphic functions. | arxiv:2012.00126 |
we propose a novel approach to designing rdf - stores with the goal of improving the consistency and predictability of query performance. when designing these systems, three properties are commonly desired : support for the full range of sparql query features ( q ), support for widely varying rdf datasets in terms of structuredness and size ( s ), and high performance ( p ). we develop the empirical spq conjecture which states that it may be impossible to achieve all the three desiderata simultaneously. we present a strong case for its plausibility based on our experimental results. the tradeoffs among the three and design guidelines based on the spq conjecture are also discussed. | arxiv:2209.04593 |
reinforcement learning has shown great promise in robotics thanks to its ability to develop efficient robotic control procedures through self - training. in particular, reinforcement learning has been successfully applied to solving the reaching task with robotic arms. in this paper, we define a robust, reproducible and systematic experimental procedure to compare the performance of various model - free algorithms at solving this task. the policies are trained in simulation and are then transferred to a physical robotic manipulator. it is shown that augmenting the reward signal with the hindsight experience replay exploration technique increases the average return of off - policy agents between 7 and 9 folds when the target position is initialised randomly at the beginning of each episode. | arxiv:2011.05782 |
we prove that for all but a measure zero set of local hamiltonians, starting from random product states at sufficiently high but finite temperature, with overwhelming probability expectation values of observables equilibrate such that at sufficiently long times, fluctuations around the stationary value are exponentially small in the system size. | arxiv:2409.08436 |
despite the chiral topological semimetal cosi is known as bulk diamagnetic, it shows unusual surface ferromagnetism of debatable origin. the ferromagnetic ordering has been attributed to the distorted bonds, the superlattice of ordered vacancies, or even to topological surface textures due to the spin polarization in the neighboring fermi arcs. we experimentally compare magnetization reversal curves for initially oxidized cosi single crystals and cleaved samples with a fresh, oxide - free surface. while the oxidized cosi samples do not show sizable ferromagnetism, the fresh cosi surface gives a strong ferromagnetic response, which is accompanied by the pronounced modulation of the angle dependence of magnetization, as it can be expected for easy and hard axes in a ferromagnet. in addition to the first order reversal curves analysis, this observation allows us to distinguish between different mechanisms of the ferromagnetic ordering in cosi single crystals. we conclude that the surface states - induced rkky interaction between distorted bonds near the sample surface is responsible for the strong ferromagnetic multi - domain behavior for freshly cleaved samples. | arxiv:2212.12383 |
we present spatially resolved gas - phase metallicity for a system of three galaxies at z = 1. 85 detected in the grism lens - amplified survey from space ( glass ). the combination of hst ' s diffraction limit and strong gravitational lensing by the cluster macs j0717 + 3745 results in a spatial resolution of ~ 200 - 300 pc, enabling good spatial sampling despite the intrinsically small galaxy sizes. the galaxies in this system are separated by 50 - 200 kpc in projection and are likely in an early stage of interaction, evidenced by relatively high specific star formation rates. their gas - phase metallicities are consistent with larger samples at similar redshift, star formation rate, and stellar mass. we obtain a precise measurement of the metallicity gradient for one galaxy and find a shallow slope compared to isolated galaxies at high redshift, consistent with a flattening of the gradient due to gravitational interaction. an alternative explanation for the shallow metallicity gradient and elevated star formation rate is rapid recycling of metal - enriched gas, but we find no evidence for enhanced gas - phase metallicities which should result from this effect. notably, the measured stellar masses log ( m / msun ) = 7. 2 - 9. 1 probe to an order of magnitude below previous mass - metallicity studies at this redshift. the lowest mass galaxy has properties similar to those expected for fornax at this redshift, indicating that glass is able to directly study the progenitors of local group dwarf galaxies on spatially resolved scales. larger samples from the full glass survey will be ideal for studying the effects of feedback, and the time evolution of metallicity gradients. these initial results demonstrate the utility of hst spectroscopy combined with gravitational lensing for characterizing resolved physical properties of galaxies at high redshift. | arxiv:1410.0967 |
the debris disk known as " the moth " is named after its unusually asymmetric surface brightness distribution. it is located around the ~ 90 myr old g8v star hd 61005 at 34. 5 pc and has previously been imaged by the hst at 1. 1 and 0. 6 microns. polarimetric observations suggested that the circumstellar material consists of two distinct components, a nearly edge - on disk or ring, and a swept - back feature, the result of interaction with the interstellar medium. we resolve both components at unprecedented resolution with vlt / naco h - band imaging. using optimized angular differential imaging techniques to remove the light of the star, we reveal the disk component as a distinct narrow ring at inclination i = 84. 3 \ pm 1. 0 { \ deg }. we determine a semi - major axis of a = 61. 25 \ pm 0. 85 au and an eccentricity of e = 0. 045 \ pm 0. 015, assuming that periastron is located along the apparent disk major axis. therefore, the ring center is offset from the star by at least 2. 75 \ pm 0. 85 au. the offset, together with a relatively steep inner rim, could indicate a planetary companion that perturbs the remnant planetesimal belt. from our imaging data we set upper mass limits for companions that exclude any object above the deuterium - burning limit for separations down to 0. 3 ". the ring shows a strong brightness asymmetry along both the major and minor axis. a brighter front side could indicate forward - scattering grains, while the brightness difference between the ne and sw components can be only partly explained by the ring center offset, suggesting additional density enhancements on one side of the ring. the swept - back component appears as two streamers originating near the ne and sw edges of the debris ring. | arxiv:1011.2496 |
considering trajectory curves, integral of n - dimensional dynamical systems, within the framework of differential geometry as curves in euclidean n - space, it will be established in this article that the curvature of the flow, i. e. the curvature of the trajectory curves of any n - dimensional dynamical system directly provides its slow manifold analytical equation the invariance of which will be then proved according to darboux theory. thus, it will be stated that the flow curvature method, which uses neither eigenvectors nor asymptotic expansions but only involves time derivatives of the velocity vector field, constitutes a general method simplifying and improving the slow invariant manifold analytical equation determination of high - dimensional dynamical systems. moreover, it will be shown that this method generalizes the tangent linear system approximation and encompasses the so - called geometric singular perturbation theory. then, slow invariant manifolds analytical equation of paradigmatic chua ' s piecewise linear and cubic models of dimensions three, four and five will be provided as tutorial examples exemplifying this method as well as those of high - dimensional dynamical systems. | arxiv:1408.1712 |
the open radio access network ( o - ran ) architecture supports intelligent network control algorithms as one of its core capabilities. data - driven applications incorporate such algorithms to optimize radio access network ( ran ) functions via ran intelligent controllers ( rics ). deep reinforcement learning ( drl ) algorithms are among the main approaches adopted in the o - ran literature to solve dynamic radio resource management problems. however, despite the benefits introduced by the o - ran rics, the practical adoption of drl algorithms in real network deployments falls behind. this is primarily due to the slow convergence and unstable performance exhibited by drl agents upon deployment and when encountering previously unseen network conditions. in this paper, we address these challenges by proposing transfer learning ( tl ) as a core component of the training and deployment workflows for the drl - based closed - loop control of o - ran functionalities. to this end, we propose and design a hybrid tl - aided approach that leverages the advantages of both policy reuse and distillation tl methods to provide safe and accelerated convergence in drl - based o - ran slicing. we conduct a thorough experiment that accommodates multiple services, including real vr gaming traffic to reflect practical scenarios of o - ran slicing. we also propose and implement policy reuse and distillation - aided drl and non - tl - aided drl as three separate baselines. the proposed hybrid approach shows at least : 7. 7 % and 20. 7 % improvements in the average initial reward value and the percentage of converged scenarios, and a 64. 6 % decrease in reward variance while maintaining fast convergence and enhancing the generalizability compared with the baselines. | arxiv:2309.07265 |
we investigate uncertainty estimation and multimodality via the non - deterministic predictions of bayesian neural networks ( bnns ) in fluid simulations. to this end, we deploy bnns in three challenging experimental test - cases of increasing complexity : we show that bnns, when used as surrogate models for steady - state fluid flow predictions, provide accurate physical predictions together with sensible estimates of uncertainty. further, we experiment with perturbed temporal sequences from navier - stokes simulations and evaluate the capabilities of bnns to capture multimodal evolutions. while our findings indicate that this is problematic for large perturbations, our results show that the networks learn to correctly predict high uncertainties in such situations. finally, we study bnns in the context of solver interactions with turbulent plasma flows. we find that bnn - based corrector networks can stabilize coarse - grained simulations and successfully create multimodal trajectories. | arxiv:2205.01222 |
differentiable simulators promise faster computation time for reinforcement learning by replacing zeroth - order gradient estimates of a stochastic objective with an estimate based on first - order gradients. however, it is yet unclear what factors decide the performance of the two estimators on complex landscapes that involve long - horizon planning and control on physical systems, despite the crucial relevance of this question for the utility of differentiable simulators. we show that characteristics of certain physical systems, such as stiffness or discontinuities, may compromise the efficacy of the first - order estimator, and analyze this phenomenon through the lens of bias and variance. we additionally propose an $ \ alpha $ - order gradient estimator, with $ \ alpha \ in [ 0, 1 ] $, which correctly utilizes exact gradients to combine the efficiency of first - order estimates with the robustness of zero - order methods. we demonstrate the pitfalls of traditional estimators and the advantages of the $ \ alpha $ - order estimator on some numerical examples. | arxiv:2202.00817 |
hitherto, six p - type planets are found around five binary systems, i. e. kepler - 16 b, 34 b, 35 b, 38 b, 47 b, c, which are all neptune or jupiter - like planets. the stability of planets and the habitable zones are influenced by the gravitational and radiative perturbations of binary companions. in this letter, we check the stability of an additional habitable earth - mass planet in each system. based on our simulations in 10 myr, a habitable " earth " is hardly stable in kepler - 16 while a stable " earth " in kepler - 47 close to the boundaries of the habitable zone is possible. in contrast, kepler - 34, 35 and 38 seem to have high probabilities of being able to tolerate a stable " earth " in their habitable zones. the affects of transit time variations are quite small due to the small mass of an undetected " earth ", except that of kepler - 16 b. with a time precision of 0. 001 day ( ~ 88 s ), an " earth " in the corotational resonance with kepler - 16 b can be detected in 3 years, while habitable " earths " in kepler - 34 and 38 systems can be detected in 10 years. habitable " earths " in kepler - 35 and 47 are not likely to be detected in 10 years under this precision. | arxiv:1304.2895 |
in a transformation method, the numerical solution of a given boundary value problem is obtained by solving one or more related initial value problems. therefore, a transformation method, like a shooting method, is an initial value method. the main difference between a transformation and a shooting method is that the former is conceived and derive its formulation from the scaling invariance theory. this paper is concerned with the application of the iterative transformation method to several problems in the boundary layer theory. the iterative method is an extension of the t { \ " o } pfer ' s non - iterative algorithm developed as a simple way to solve the celebrated blasius problem. this iterative method provides a simple numerical test for the existence and uniqueness of solutions. here we show how the method can be applied to problems with a homogeneous boundary conditions at infinity and in particular we solve the sakiadis problem of boundary layer theory. moreover, we show how to couple our method with newton ' s root - finder. the obtained numerical results compare well with those available in the literature. the main aim here is that any method developed for the blasius, or the sakiadis, problem might be extended to more challenging or interesting problems. in this context, the iterative transformation method has been recently applied to compute the normal and reverse flow solutions of stewartson for the falkner - skan model [ comput. \ & fluids, { \ bf 73 } ( 2013 ) pp. 202 - 209 ]. | arxiv:2003.07971 |
this paper investigates the application of consensus clustering and meta - clustering to the set of all possible partitions of a data set. we show that when using a " complement " of rand index as a measure of cluster similarity, the total - separation partition, putting each element in a separate set, is chosen. | arxiv:1702.03724 |
let $ f $ be an $ ( r + 1 ) $ - color critical graph with $ r \ geq 2 $, that is, $ \ chi ( f ) = r + 1 $ and there is an edge $ e $ in $ f $ such that $ \ chi ( f - e ) = r $. gerbner recently conjectured that every $ n $ - vertex maximal $ f $ - free graph with at least $ ( 1 - \ frac { 1 } { r } ) \ frac { n ^ 2 } { 2 } - o ( n ^ { \ frac { r + 1 } { r } } ) $ edges contains an induced complete $ r $ - partite graph on $ n - o ( n ) $ vertices. let $ f _ { s, k } $ be a graph obtained from $ s $ copies of $ c _ { 2k + 1 } $ by sharing a common edge. in this paper, we show that for all $ k \ geq 2 $ if $ g $ is an $ n $ - vertex maximal $ f _ { s, k } $ - free graph with at least $ n ^ { 2 } / 4 - o ( n ^ { \ frac { s + 2 } { s + 1 } } ) $ edges, then $ g $ contains an induced complete bipartite graph on $ n - o ( n ) $ vertices. we also show that it is best possible. this disproves gerbner ' s conjecture for $ r = 2 $. | arxiv:2205.00426 |
in this paper, we develop a novel dynamic distributed optimal safe consensus protocol to simultaneously achieve safety requirements and output optimal consensus. specifically, we construct a distributed projection optimization algorithm with an expanding constraint set in the decision - making layer, while we propose a reference tracking safety controller to ensure that each agent ' s output remains within a shrinking safety set in the control layer. we also establish the convergence and safety analysis of the closed - loop system using the small - gain theorem and time - varying control barrier function ( cbf ) theory, respectively. besides, unlike previous works on distributed optimal consensus, our approach does not require prior knowledge of the local objective or gradient function and adopts a mild assumption on the dynamics of multiagent systems ( mass ) by using the transmission zeros condition. | arxiv:2401.06245 |
we prove that a 1 - dimnl family of abelian varieties with an ample sheaf defining principal polarization can be canonically compactified ( after a finite base change ) to a projective family with an ample sheaf. we show that the central fiber ( p, l ), which we call an sqav, has a canonical cartier theta divisor. we give a combinatorial definition for sqavs and describe their geometrical properties, in particular compute cohomologies of l ^ n, n \ ge0. | arxiv:alg-geom/9608014 |
for each configuration of rational points on the affine line, we define an operation on the group of unstable a1 motivic homotopy classes of endomorphisms of the projective line. we also derive an algebraic formula for the image of such an operation under cazanave and morel ' s unstable degree map, which is valued in an extension of the grothendieck - - witt group. in contrast to the topological setting, these operations depend on the choice of configuration of points via a discriminant. we prove this by first showing a local - to - global formula for the global unstable degree as a modified sum of local terms. we then use an anabelian argument to generalize from the case of local degrees of a global rational function to the case of an arbitrary collection of endomorphisms of the projective line. | arxiv:2411.15347 |
in this thesis, we take a journey through two different but not dissimilar stories with an underlying theme of combinatorics emerging from scattering amplitudes in quantum field theories. the first part tells the tale of the $ c _ 2 $ - invariant, an arithmetic invariant related to the feynman integral in $ \ phi ^ 4 $ - theory, which studies the zeros of the kirchoff polynomial and related graph polynomials. through reformulating the $ c _ 2 $ - invariant as a purely combinatorial problem, we show how enumerating certain edge bipartitions through fixed - point free involutions can complete a special case of the long sought after $ c _ 2 $ completion conjecture. the second part tells the tale of the positive grassmannian and a combinatorial t - duality map on its cells, as related to scattering amplitudes in planar $ \ mathcal { n } = 4 $ sym theory. in particular, t - duality is a bridge between triangulations of the hypersimplex and triangulations of the amplituhedron, two objects that appear as images of the positive grassmannian. we give an algorithm for viewing t - duality as a map on le diagrams and characterize a nice structure to the le diagrams ( which can then be used in lieu of the algorithm ). through this le diagram perspective on t - duality, we show how the dimensional relationship between the positroid cells on either side of the map can be directly explained. | arxiv:2206.04749 |
lane - keeping assistance system ( lkas ) is convenient and widely available today, but also extremely security and safety critical. in this work, we design and implement the first systematic approach to attack real - world dnn - based lkases. we identify dirty road patches as a novel and domain - specific threat model for practicality and stealthiness. we formulate the attack as an optimization problem, and address the challenge from the inter - dependencies among attacks on consecutive camera frames. we evaluate our approach on a state - of - the - art lkas and our preliminary results show that our attack can successfully cause it to drive off lane boundaries within as short as 1. 3 seconds. | arxiv:2003.01782 |
rgb - thermal video object detection ( rgbt vod ) can address the limitation of traditional rgb - based vod in challenging lighting conditions, making it more practical and effective in many applications. however, similar to most rgbt fusion tasks, it still mainly relies on manually aligned multimodal image pairs. in this paper, we propose a novel multimodal spatio - temporal graph learning network ( msgnet ) for alignment - free rgbt vod problem by leveraging the robust graph representation learning model. specifically, we first design an adaptive partitioning layer ( apl ) to estimate the corresponding regions of the thermal image within the rgb image ( high - resolution ), achieving a preliminary inexact alignment. then, we introduce the spatial sparse graph learning module ( s - sglm ) which employs a sparse information passing mechanism on the estimated inexact alignment to achieve reliable information interaction between different modalities. moreover, to fully exploit the temporal cues for rgbt vod problem, we introduce hybrid structured temporal modeling ( hstm ), which involves a temporal sparse graph learning module ( t - sglm ) and temporal star block ( tsb ). t - sglm aims to filter out some redundant information between adjacent frames by employing the sparse aggregation mechanism on the temporal graph. meanwhile, tsb is dedicated to achieving the complementary learning of local spatial relationships. extensive comparative experiments conducted on both the aligned dataset vt - vod50 and the unaligned dataset uvt - vod2024 demonstrate the effectiveness and superiority of our proposed method. our project will be made available on our website for free public access. | arxiv:2504.11779 |
we study the volume - limited and nearly mass selected ( stellar mass m > 6 * 10 ^ 9 msun ) atlas3d sample of 260 early - type galaxies. we construct detailed axisymmetric dynamical models ( jam ), which allow for orbital anisotropy, include a dark matter halo, and reproduce in detail both the galaxy images and the high - quality integral - field stellar kinematics. we derive accurate total m / l and dark matter fractions f _ dm, within a sphere of radius r = re. we also measure the stellar m / l and derive a median dark matter fraction f _ dm = 13 %. we find that the thin two - dimensional subset spanned by galaxies in the ( m _ jam, sigma _ e, r _ e ) coordinates system, which we call the mass plane ( mp ) has an observed rms scatter of 19 % and an intrinsic one of 11 %. the mp satisfies the scalar virial relation m _ jam sigma _ e ^ 2 r _ e within our tight errors. however, the details of how both re and sigma _ e are determined are critical in defining the precise deviation from the virial exponents. we revisit the ( m / l ) - sigma _ e relation, which describes most of the deviations between the mp and the fp. the best - fitting relation is ( m / l ) sigma _ e ^ 0. 72 ( r - band ). it provides an upper limit to any systematic increase of the imf mass normalization with sigma _ e. we study of the link between sigma _ e and the galaxies circular velocity v _ circ within 1re ( where stars dominate ) and find the relation max ( v _ circ ) ~ 1. 76 * sigma _ e, which has an observed scatter of 7 %. the accurate parameters described in this paper are used in the companion paper xx of this series to explore the variation of global galaxy properties, including the imf, on the projections of the mp. [ abridged ] | arxiv:1208.3522 |
we present a direct measurement of the width of the w boson using the shape of the transverse mass distribution of w - > enu candidates selected in 1 fb - 1 of data collected with the d0 detector at the fermilab tevatron collider in ppbar collisions at sqrt { s } = 1. 96 tev. we use the same methods and data sample that were used for our recently published w boson mass measurement, except for the modeling of the recoil, which is done with a new method based on a recoil library. our result, 2. 028 + - 0. 072 gev, is in agreement with the predictions of the standard model. | arxiv:0909.4814 |
let $ \ sigma $ be a $ c ^ 3 $ compact symmetric convex hypersurface in $ \ mathbf { r } ^ { 8 } $. for some special cases, we prove that when $ \ sigma $ carries exactly four geometrically distinct closed characteristics, then all of them must be symmetric. | arxiv:1309.3398 |
nearly all statistical inference methods were developed for the regime where the number $ n $ of data samples is much larger than the data dimension $ p $. inference protocols such as maximum likelihood ( ml ) or maximum a posteriori probability ( map ) are unreliable if $ p = o ( n ) $, due to overfitting. this limitation has for many disciplines with increasingly high - dimensional data become a serious bottleneck. we recently showed that in cox regression for time - to - event data the overfitting errors are not just noise but take mostly the form of a bias, and how with the replica method from statistical physics once can model and predict this bias and the noise statistics. here we extend our approach to arbitrary generalized linear regression models ( glm ), with possibly correlated covariates. we analyse overfitting in ml / map inference without having to specify data types or regression models, relying only on the glm form, and derive generic order parameter equations for the case of $ l2 $ priors. second, we derive the probabilistic relationship between true and inferred regression coefficients in glms, and show that, for the relevant hyperparameter scaling and correlated covariates, the $ l2 $ regularization causes a predictable direction change of the coefficient vector. our results, illustrated by application to linear, logistic, and cox regression, enable one to correct ml and map inferences in glms systematically for overfitting bias, and thus extend their applicability into the hitherto forbidden regime $ p = o ( n ) $. | arxiv:2004.06329 |
available works addressing multi - label classification in a data stream environment focus on proposing accurate models ; however, these models often exhibit inefficiency and cannot balance effectiveness and efficiency. in this work, we propose a neural network - based approach that tackles this issue and is suitable for high - dimensional multi - label classification. our model uses a selective concept drift adaptation mechanism that makes it suitable for a non - stationary environment. additionally, we adapt our model to an environment with missing labels using a simple yet effective imputation strategy and demonstrate that it outperforms a vast majority of the state - of - the - art supervised models. to achieve our purposes, we introduce a weighted binary relevance - based approach named ml - bels using the broad ensemble learning system ( bels ) as its base classifier. instead of a chain of stacked classifiers, our model employs independent weighted ensembles, with the weights generated by the predictions of a bels classifier. we show that using the weighting strategy on datasets with low label cardinality negatively impacts the accuracy of the model ; with this in mind, we use the label cardinality as a trigger for applying the weights. we present an extensive assessment of our model using 11 state - of - the - art baselines, five synthetics, and 13 real - world datasets, all with different characteristics. our results demonstrate that the proposed approach ml - bels is successful in balancing effectiveness and efficiency, and is robust to missing labels and concept drift. | arxiv:2310.00665 |
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