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we consider a rather special class of translation surfaces ( called m - origamis in this work ) that are obtained from dessins by a construction introduced by martin m \ " oller. we give a new proof with a more combinatorial flavour of m \ " oller ' s theorem that $ \ mathrm { gal } ( \ overline { \ mathbb { q } } / \ mathbb { q } ) $ acts faithfully on the teichm \ " uller curves of m - origamis and extend his result by investigating the galois action in greater detail. we determine the strebel directions and corresponding cylinder decompositions of an m - origami, as well as its veech group, which contains the modular group $ \ gamma ( 2 ) $ and is closely connected to a certain group of symmetries of the underlying dessin. finally, our calculations allow us to give explicit examples of galois orbits of m - origamis and their teichm \ " uller curves. | arxiv:1408.6769 |
background. the excess mortality rate in aotearoa new zealand during the covid - 19 pandemic is frequently estimated to be among the lowest in the world. however, to facilitate international comparisons, many of the methods that have been used to estimate excess mortality do not use age - stratified data on deaths and population size, which may compromise their accuracy. methods. we used a quasi - poisson regression model for monthly all - cause deaths among new zealand residents, controlling for age, sex and seasonality. we fitted the model to deaths data for 2014 - 19. we estimated monthly excess mortality for 2020 - 23 as the difference between actual deaths and projected deaths according to the model. we conducted sensitivity analysis on the length of the pre - pandemic period used to fit the model. we benchmarked our results against a simple linear regression on the standardised annual mortality rate. results. we estimated cumulative excess mortality in new zealand in 2020 - 23 was 1040 ( 95 % confidence interval [ - 1134, 2927 ] ), equivalent to 0. 7 % [ - 0. 8 %, 2. 0 % ] of expected mortality. excess mortality was negative in 2020 - 21. the magnitude, timing and age - distribution of the positive excess mortality in 2022 - 23 were closely matched with confirmed covid - 19 deaths. conclusions. negative excess mortality in 2020 - 21 reflects very low levels of covid - 19 and major reductions in seasonal respiratory diseases during this period. in 2022 - 23, covid - 19 deaths were the main contributor to excess mortality and there was little or no net non - covid - 19 excess. overall, new zealand experienced one of the lowest rates of pandemic excess mortality in the world. | arxiv:2412.08927 |
we have measured the x - ray absorption ( xas ) and x - ray magnetic circular dichroism ( xmcd ) at the mn l3, 2 edges in ferromagnetic ga1 - xmnxp films for 0. 018 < x < 0. 042. large xmcd asymmetries at the l3 edge indicate significant spin - polarization of the density of states at the fermi energy. the spectral shapes of the xas and xmcd are nearly identical with those for ga1 - xmnxas indicating that the hybridization of mn d states and anion p states is similar in the two materials. finally, compensation with sulfur donors not only lowers the ferromagnetic curie temperature but also reduces the spin polarization of the hole states. | arxiv:cond-mat/0607393 |
we report the application of evaporative cooling to clouds of trapped antiprotons, resulting in plasmas with measured temperature as low as 9 ~ k. we have modeled the evaporation process for charged particles using appropriate rate equations. good agreement between experiment and theory is observed, permitting prediction of cooling efficiency in future experiments. the technique opens up new possibilities for cooling of trapped ions and is of particular interest in antiproton physics, where a precise \ emph { cpt } test on trapped antihydrogen is a long - standing goal. | arxiv:1009.4687 |
we propose an algorithm for tracing polylines on a triangle mesh such that : they are aligned with a n - symmetry direction field, and two such polylines cannot cross or merge. this property is fundamental for mesh segmentation and is very difficult to enforce with numerical integration of vector fields. we propose an alternative solution based on " stream - mesh ", a new combinatorial data structure that defines, for each point of a triangle edge, where the corresponding polyline leaves the triangle. it makes it possible to trace polylines by iteratively crossing triangles. vector field singularities and polyline / vertex crossing are characterized and consistently handled. the polylines inherits the cross - free property of the stream - mesh, except inside triangles where avoiding local overlaps would require higher order polycurves. | arxiv:1306.0706 |
sequential change point tests aim at giving an alarm as soon as possible after a structural break occurs while controlling the asymptotic false alarm error. for such tests it is of particular importance to understand how quickly a break is detected. while this is often assessed by simulations only, in this paper, we derive the asymptotic distribution of the delay time for sequential change point procedures based on u - statistics. this includes the difference - of - means ( dom ) sequential test, that has been discussed previously, but also a new robust wilcoxon sequential change point test. similar to asymptotic relative efficiency in an a - posteriori setting, the results allow us to compare the detection delay of the two procedures. it is shown that the wilcoxon sequential procedure has a smaller detection delay for heavier tailed distributions which is also confirmed by simulations. while the previous literature only derives results for early change points, we obtain the asymptotic distribution of the delay time for both early as well as late change points. finally, we evaluate how well the asymptotic distribution approximates the actual stopping times for finite samples via a simulation study. | arxiv:2003.08847 |
dynamic full - field optical coherence tomography ( dffoct ) has recently emerged as an invaluable label - free microscopy technique, owing to its sensitivity to cell activity, as well as speed and sectioning ability. however, the quality of dffoct images are often degraded due to phase noise and fringe artifacts. in this work, we present a new implementation named rolling - phase ( rp ) dffoct, in which the reference arm is slowly scanned over magnitudes exceeding 2 $ \ pi $. we demonstrate mathematically and experimentally that it shows superior image quality while enabling to extract both static and dynamic contrast simultaneously. we showcase rp dffoct on monkey retinal explant, and demonstrate its ability to better resolve subcellular structures, including intranuclear activity. | arxiv:2501.08359 |
monte carlo techniques are used to investigate the equilibrium threshold concentration, xe, in the dilute anisotropic antiferromagnet fe ( x ) zn ( 1 - x ) f2 in an applied magnetic field, considered to be an ideal random - field ising model system. above xe equilibrium behavior is observed whereas below xe metastability and domain formation dominate. monte carlo results agree very well with experimental data obtained using this system. | arxiv:cond-mat/0009049 |
online free - viewpoint video ( fvv ) streaming is a challenging problem, which is relatively under - explored. it requires incremental on - the - fly updates to a volumetric representation, fast training and rendering to satisfy real - time constraints and a small memory footprint for efficient transmission. if achieved, it can enhance user experience by enabling novel applications, e. g., 3d video conferencing and live volumetric video broadcast, among others. in this work, we propose a novel framework for quantized and efficient encoding ( queen ) for streaming fvv using 3d gaussian splatting ( 3d - gs ). queen directly learns gaussian attribute residuals between consecutive frames at each time - step without imposing any structural constraints on them, allowing for high quality reconstruction and generalizability. to efficiently store the residuals, we further propose a quantization - sparsity framework, which contains a learned latent - decoder for effectively quantizing attribute residuals other than gaussian positions and a learned gating module to sparsify position residuals. we propose to use the gaussian viewspace gradient difference vector as a signal to separate the static and dynamic content of the scene. it acts as a guide for effective sparsity learning and speeds up training. on diverse fvv benchmarks, queen outperforms the state - of - the - art online fvv methods on all metrics. notably, for several highly dynamic scenes, it reduces the model size to just 0. 7 mb per frame while training in under 5 sec and rendering at 350 fps. project website is at https : / / research. nvidia. com / labs / amri / projects / queen | arxiv:2412.04469 |
we use replicator dynamics to study an iterated prisoners ' dilemma game with memory. in this study, we investigate the characteristics of all 32 possible strategies with a single - step memory by observing the results when each strategy encounters another one. based on these results, we define similarity measures between the 32 strategies and perform a network analysis of the relationship between the strategies by constructing a strategies network. interestingly, we find that a win - lose circulation, like rock - paper - scissors, exists between strategies and that the circulation results from one unusual strategy. | arxiv:1403.1048 |
in rational verification, the aim is to verify which temporal logic properties will obtain in a multi - agent system, under the assumption that agents ( " players " ) in the system choose strategies for acting that form a game theoretic equilibrium. preferences are typically defined by assuming that agents act in pursuit of individual goals, specified as temporal logic formulae. to date, rational verification has been studied using non - cooperative solution concepts - nash equilibrium and refinements thereof. such non - cooperative solution concepts assume that there is no possibility of agents forming binding agreements to cooperate, and as such they are restricted in their applicability. in this article, we extend rational verification to cooperative solution concepts, as studied in the field of cooperative game theory. we focus on the core, as this is the most fundamental ( and most widely studied ) cooperative solution concept. we begin by presenting a variant of the core that seems well - suited to the concurrent game setting, and we show that this version of the core can be characterised using atl *. we then study the computational complexity of key decision problems associated with the core, which range from problems in pspace to problems in 3exptime. we also investigate conditions that are sufficient to ensure that the core is non - empty, and explore when it is invariant under bisimilarity. we then introduce and study a number of variants of the main definition of the core, leading to the issue of credible deviations, and to stronger notions of collective stable behaviour. finally, we study cooperative rational verification using an alternative model of preferences, in which players seek to maximise the mean - payoff they obtain over an infinite play in games where quantitative information is allowed. | arxiv:2301.06157 |
in this paper, we study the problem of multi - view sketch correspondence, where we take as input multiple freehand sketches with different views of the same object and predict as output the semantic correspondence among the sketches. this problem is challenging since the visual features of corresponding points at different views can be very different. to this end, we take a deep learning approach and learn a novel local sketch descriptor from data. we contribute a training dataset by generating the pixel - level correspondence for the multi - view line drawings synthesized from 3d shapes. to handle the sparsity and ambiguity of sketches, we design a novel multi - branch neural network that integrates a patch - based representation and a multi - scale strategy to learn the pixel - level correspondence among multi - view sketches. we demonstrate the effectiveness of our proposed approach with extensive experiments on hand - drawn sketches and multi - view line drawings rendered from multiple 3d shape datasets. | arxiv:2001.05744 |
some significant medical research. notable islamic medical pioneers include the persian polymath, avicenna, who, along with imhotep and hippocrates, has also been called the " father of medicine ". he wrote the canon of medicine which became a standard medical text at many medieval european universities, considered one of the most famous books in the history of medicine. others include abulcasis, avenzoar, ibn al - nafis, and averroes. persian physician rhazes was one of the first to question the greek theory of humorism, which nevertheless remained influential in both medieval western and medieval islamic medicine. some volumes of rhazes ' s work al - mansuri, namely " on surgery " and " a general book on therapy ", became part of the medical curriculum in european universities. additionally, he has been described as a doctor ' s doctor, the father of pediatrics, and a pioneer of ophthalmology. for example, he was the first to recognize the reaction of the eye ' s pupil to light. the persian bimaristan hospitals were an early example of public hospitals. in europe, charlemagne decreed that a hospital should be attached to each cathedral and monastery and the historian geoffrey blainey likened the activities of the catholic church in health care during the middle ages to an early version of a welfare state : " it conducted hospitals for the old and orphanages for the young ; hospices for the sick of all ages ; places for the lepers ; and hostels or inns where pilgrims could buy a cheap bed and meal ". it supplied food to the population during famine and distributed food to the poor. this welfare system the church funded through collecting taxes on a large scale and possessing large farmlands and estates. the benedictine order was noted for setting up hospitals and infirmaries in their monasteries, growing medical herbs and becoming the chief medical care givers of their districts, as at the great abbey of cluny. the church also established a network of cathedral schools and universities where medicine was studied. the schola medica salernitana in salerno, looking to the learning of greek and arab physicians, grew to be the finest medical school in medieval europe. however, the fourteenth and fifteenth century black death devastated both the middle east and europe, and it has even been argued that western europe was generally more effective in recovering from the pandemic than the middle east. in the early modern period, important early figures in medicine and anatomy emerged in europe, including gabriele | https://en.wikipedia.org/wiki/Medicine |
the introduction of the spatial lambda - fleming - viot model ( lv ) in population genetics was mainly driven by the pioneering work of alison etheridge, in collaboration with nick barton and amandine v \ ' eber about ten years ago ( 1, 2 ). the lv model provides a sound mathematical framework for describing the evolution of a population of related individuals along a spatial continuum. it alleviates the " pain in the torus " issue with wright and mal \ ' ecot ' s isolation by distance model and is sampling consistent, making it a tool of choice for statistical inference. yet, little is known about the potential connections between the lv and other stochastic processes generating trees and the spatial coordinates along the corresponding lineages. this work focuses on a version of the lv whereby lineages move infinitely rapidly over infinitely small distances. using simulations, we show that the induced lv tree - generating process is well approximated by a birth - death model. our results also indicate that brownian motions modelling the movements of lineages along birth - death trees do not generally provide a good approximation of the lv due to habitat boundaries effects that play an increasingly important role in the long run. finally, we describe efficient algorithms for fast simulation of the backward and forward in time versions of the lv model. | arxiv:2307.02431 |
in this work, we present an efficient rank - compression approach for the classical simulation of kraus decoherence channels in noisy quantum circuits. the approximation is achieved through iterative compression of the density matrix based on its leading eigenbasis during each simulation step without the need to store, manipulate, or diagonalize the full matrix. we implement this algorithm in an in - house simulator, and show that the low rank algorithm speeds up simulations by more than two orders of magnitude over an existing implementation of full rank simulator, and with negligible error in the target noise and final observables. finally, we demonstrate the utility of the low rank method as applied to representative problems of interest by using the algorithm to speed - up noisy simulations of grover ' s search algorithm and quantum chemistry solvers. | arxiv:2009.06657 |
it is shown in this paper that for open systems, states which are localized in space, discrete in energy, and embedded in the continuum of extended states, can be sustained by low - dimensional and channeled leads. these states have an origin different from that of analogous states discussed by j. von neumann and e. wigner [ phys. z., vol. 30, 465 ( 1929 ) ]. a few representative systems are discussed. these states cause, for example, infinitely sharp fano resonance in transport when they are marginally destroyed. | arxiv:cond-mat/0609214 |
unlike standard quantum mechanics, dynamical reduction models assign no particular a priori status to ` measurement processes ', ` apparata ', and ` observables ', nor self - adjoint operators and positive operator valued measures enter the postulates defining these models. in this paper, we show why and how the hilbert - space operator formalism, which standard quantum mechanics postulates, can be derived from the fundamental evolution equation of dynamical reduction models. far from having any special ontological meaning, we show that within the dynamical reduction context the operator formalism is just a compact and convenient way to express the statistical properties of the outcomes of experiments. | arxiv:0707.2940 |
a necessary and sufficient condition for existence of a banach space with a finite dimensional decomposition but without the $ \ pi $ - property in terms of norms of compositions of projections is found. | arxiv:0811.1763 |
scaling sequence length has become a critical demand in the era of large language models. however, existing methods struggle with either computational complexity or model expressivity, rendering the maximum sequence length restricted. to address this issue, we introduce longnet, a transformer variant that can scale sequence length to more than 1 billion tokens, without sacrificing the performance on shorter sequences. specifically, we propose dilated attention, which expands the attentive field exponentially as the distance grows. longnet has significant advantages : 1 ) it has a linear computation complexity and a logarithm dependency between any two tokens in a sequence ; 2 ) it can be served as a distributed trainer for extremely long sequences ; 3 ) its dilated attention is a drop - in replacement for standard attention, which can be seamlessly integrated with the existing transformer - based optimization. experiments results demonstrate that longnet yields strong performance on both long - sequence modeling and general language tasks. our work opens up new possibilities for modeling very long sequences, e. g., treating a whole corpus or even the entire internet as a sequence. | arxiv:2307.02486 |
a transverse zeeman slower composed of an array of compact discrete neodymium magnets is considered. a simple and precise model of such a slower based on magnetic dipoles is developed. the theory of a general zeeman slower is modified to include spatial nonuniformity of the slowing laser beam intensity due to its convergence and absorption by slowed atoms. the slower needs no high currents or water cooling and the spatial distribution of its magnetic field can be adjusted. in addition the slower provides a possibility to cool the slowed atoms transversally along the whole length of the slower. such a slower would be ideal for transportable optical atomic clocks and their future applications in space physics. | arxiv:physics/0702074 |
e661 in the enestrom index. this was originally published as " variae considerationes circa series hypergeometricas " ( 1776 ). in this paper euler is looking at the asymptotic behavior of infinite products that are similar to the gamma function. he looks at the relations between some infinite products and integrals. he takes the logarithm of these infinite products, and expands these using the euler - maclaurin summation formula. in section 14, euler seems to be rederiving some of the results he already proved in the paper. however i do not see how these derivations are different. if any readers think they understand please i would appreciate it if you could email me. i am presently examining euler ' s work on analytic number theory. the two main topics i want to understand are the analytic continuation of analytic functions and the connection to divergent series, and the asymptotic behavior of the gamma function. | arxiv:0804.1981 |
we study the approximate and mean approximate controllability properties of fractional partial differential equations associated with the so - called hilfer type time - fractional derivative and a non - negative selfadjoint operator $ a _ b $ with a compact resolvent on $ l ^ 2 ( \ omega ) $, where $ \ omega \ subset \ mathbb { r } ^ n $ ( $ n \ ge 1 $ ) is a bounded open set. more precisely, we show that if $ 0 \ le \ nu \ le 1 $, $ 0 < \ mu \ le 1 $ and $ \ omega \ subset \ mathbb r ^ n $ is a bounded open set, then the system $ $ \ mathbb d _ t ^ { \ mu, \ nu } u + a _ bu = f | _ { \ omega } \ ; \ ; \ mbox { in } \ ; \ omega \ times ( 0, t ), \, \, ( \ mathbb i _ t ^ { ( 1 - \ nu ) ( 1 - \ mu ) } u ) ( \ cdot, 0 ) = u _ 0 \ mbox { in } \ ; \ omega, $ $ is approximately controllable for any $ t > 0 $, $ u _ 0 \ in l ^ 2 ( \ omega ) $ and any non - empty open set $ \ omega \ subset \ omega $. in addition, if the operator $ a _ b $ has the unique continuation property, then the system is also mean approximately controllable. the operator $ a _ b $ can be the realization in $ l ^ 2 ( \ omega ) $ of a symmetric, non - negative uniformly elliptic second order operator with dirichlet or robin boundary conditions, or the realization in $ l ^ 2 ( \ omega ) $ of the fractional laplace operator $ ( - \ delta ) ^ s $ ( $ 0 < s < 1 $ ) with the dirichlet exterior condition, $ u = 0 $ in $ \ mathbb r ^ n \ setminus \ omega $, or the nonlocal robin exterior condition, $ \ mathcal n ^ su + \ beta u = 0 $ in $ \ mathbb r ^ n \ setminus \ overline { \ omega } $. | arxiv:2003.08188 |
nitrogen reduction reaction ( nrr ) which converts nitrogen ( n2 ) to ammonia ( nh3 ) normally requires harsh conditions to break the bound nitrogen bond. herein, via first - principles calculation we reveal that a superior nrr catalytic activity could be obtained through anchoring atomic catalyst above a phosphorene - like puckering surface of germanium selenide ( gese ). through examining the single - and double - atoms ( b, fe, w, mo and ru ) decorated on gese, we find that its rippled structure allows an intimate contact between the deposited species and the gese which significantly promotes the states hybridization. amongst the various atomic catalyst, we predict that the ru dimer decorated gese monolayer ( ru2 @ gese ) has superior catalytic activity for the n2 fixation and reduction. through examining the three nrr pathways ( distal, alternating and enzymatic ), the distal and enzymatic pathway is both the thermodynamically favorable with the maximum gibbs free energy change ( { \ delta } gmax ) of 0. 25 and 0. 26 ev, respectively. such a superior activity could be attributed to the filtered states of gese by ru dimer which leads to the effective activation of the adsorbed n2 bond. as an efficient near - infrared absorber of gese, the ru mediated hybridization of gese - ru - n2 complex enables an in - gap state which further broadens the absorbing window, rendering for a broadband solar absorption and possible photocatalysis. | arxiv:2201.11892 |
we report several results concerning $ w ( \ lambda, q ) = \ exp ( s _ 0 / k _ b ) $, the exponent of the ground state entropy of the potts antiferromagnet on a lattice $ \ lambda $. first, we improve our previous rigorous lower bound on $ w ( hc, q ) $ for the honeycomb ( hc ) lattice and find that it is extremely accurate ; it agrees to the first eleven terms with the large - $ q $ series for $ w ( hc, q ) $. second, we investigate the heteropolygonal archimedean $ 4 \ cdot 8 ^ 2 $ lattice, derive a rigorous lower bound, on $ w ( 4 \ cdot 8 ^ 2, q ) $, and calculate the large - $ q $ series for this function to $ o ( y ^ { 12 } ) $ where $ y = 1 / ( q - 1 ) $. remarkably, these agree exactly to all thirteen terms calculated. we also report monte carlo measurements, and find that these are very close to our lower bound and series. third, we study the effect of non - nearest - neighbor couplings, focusing on the square lattice with next - nearest - neighbor bonds. | arxiv:cond-mat/9706162 |
we consider the semilinear wave equation $ $ \ partial _ t ^ 2 u - \ delta u = f ( u ), \ quad ( x, t ) \ in \ mathbb r ^ n \ times [ 0, t ), \ qquad ( 1 ) $ $ with $ f ( u ) = | u | ^ { p - 1 } u \ log ^ a ( 2 + u ^ 2 ) $, where $ p > 1 $ and $ a \ in \ mathbb r $, with subconformal power nonlinearity. we will show that the blow - up rate of any singular solution of ( 1 ) is given by the ode solution associated with $ ( 1 ) $, the result in one space dimension, has been proved in \ cite { hzjmaa2020 }. our goal here is to extend this result to higher dimensions. | arxiv:2012.05374 |
solutions of the cauchy problem for the wave equation on a non - globally hyperbolic spacetime, which contains closed timelike curves ( time machines ) are considered. it is proved, that there exists a solution of the cauchy problem, it is discontinuous and in some sense unique for arbitrary initial conditions, which are given on a hypersurface at time, that precedes the formation of closed timelike curves ( ctc ). if the hypersurface of initial conditions intersects the region containing ctc, then the solution of the cauchy problem exists only for such initial conditions, that satisfy a certain requirement of self - consistency. | arxiv:0903.0567 |
motivated by various kinds of new physics models, a new light neutral vector boson ( the dark photon ) connected to the standard model of particle physics only through the kinetic mixing with the u ( 1 ) _ y factor has been studied extensively. various kinds of experiments are proposed to detect it. for the dark photon with a mass smaller than 10 kev, it can be copiously produced inside the sun, and then be detected by the detectors on the earth. we show that with the s2 only analysis, the result from xenon10 experiment provides the up - to - date most stringent limit on the region 10 ^ { - 5 } ev < m _ v < 10 ^ 3 ev : kappa m _ v < 3 times 10 ^ { - 12 } ev for the stueckelberg dark photon model, where kappa is the kinetic mixing and m _ v is the mass of the dark photon. if there is a light higgs boson accompanied with the dark photon, the sensitivity of xenon10 experiment is kappa times e ' < 10 ^ { - 13 }, which is still second to the constraints from the lifetime of horizontal branch starts which dictates kappa times e ' < 3 times10 ^ { - 14 }. | arxiv:1401.8287 |
we propose an approximation for the first return time distribution of random walks on undirected networks. we combine a message - passing solution with a mean - field approximation, to account for the short - and long - term behaviours respectively. we test this approximation on several classes of large graphs and find excellent agreement between our approximations and the true distributions. while the statistical properties of a random walk will depend on the structure of the network, the observed agreement between our approximations and numerical calculations implies that while local structure is clearly very influential, global structure is only important in a relatively superficial way, namely through the total number of edges. | arxiv:2405.20166 |
the formation of massive black hole binaries ( mbhbs ) is an unavoidable outcome of galaxy evolution via successive mergers. however, the mechanism that drives their orbital evolution from parsec separations down to the gravitational wave ( gw ) dominated regime is poorly understood, and their final fate is still unclear. if such binaries are embedded in gas - rich and turbulent environments, as observed in remnants of galaxy mergers, the interaction with gas clumps ( such as molecular clouds ) may efficiently drive their orbital evolution. using numerical simulations, we test this hypothesis by studying the dynamical evolution of an equal - mass, circular mbhb accreting infalling molecular clouds. we investigate different orbital configurations, modelling a total of 13 systems to explore different possible impact parameters and relative inclinations of the cloud - binary encounter. we focus our study on the prompt, transient phase during the first few orbits when the dynamical evolution of the binary is fastest, finding that this evolution is dominated by the exchange of angular momentum through gas capture by the individual black holes and accretion. building on these results, we construct a simple model for evolving a mbhb interacting with a sequence of clouds, which are randomly drawn from reasonable populations with different levels of anisotropy in their angular momenta distributions. we show that the binary efficiently evolves down to the gw emission regime within a few hundred million years, overcoming the ' final parsec ' problem regardless of the stellar distribution. | arxiv:1602.01966 |
diffusion models have been successfully adapted to text generation tasks by mapping the discrete text into the continuous space. however, there exist nonnegligible gaps between training and inference, owing to the absence of the forward process during inference. thus, the model only predicts based on the previously generated reverse noise rather than the noise computed by the forward process. besides, the widely - used downsampling strategy in speeding up the inference will cause the mismatch of diffusion trajectories between training and inference. to understand and mitigate the above two types of training - inference discrepancies, we launch a thorough preliminary study. based on our observations, we propose two simple yet effective methods to bridge the gaps mentioned above, named distance penalty and adaptive decay sampling. extensive experiments on \ textbf { 6 } generation tasks confirm the superiority of our methods, which can achieve $ 100 \ times \ rightarrow 200 \ times $ speedup with better performance. | arxiv:2305.04465 |
we address the separability problem for straight - line string constraints. the separability problem for languages of a class c by a class s asks : given two languages a and b in c, does there exist a language i in s separating a and b ( i. e., i is a superset of a and disjoint from b )? the separability of string constraints is the same as the fundamental problem of interpolation for string constraints. we first show that regular separability of straight line string constraints is undecidable. our second result is the decidability of the separability problem for straight - line string constraints by piece - wise testable languages, though the precise complexity is open. in our third result, we consider the positive fragment of piece - wise testable languages as a separator, and obtain an expspace algorithm for the separability of a useful class of straight - line string constraints, and a pspace - hardness result. | arxiv:2005.09489 |
the ginzburg - landau theory is used for the superconducting structures free energy fluctuations study. on its basis, we have defined the value of the heat capacity jump in the macroscopic zero - dimensional sample and in the zero - dimensional microstructures ensemble of the total volume equal to the macroscopic sample volume. the inference is made that in the ginzburg - landau methodology frameworks, it is essential to take into account the superconducting clean sample effective dimensionality only on the last stage of its thermodynamical characteristics calculation. | arxiv:0910.4641 |
in this paper, we propose a fourth order pde model for image inpainting based on a variant of the famous mumford - shah ( ms ) image segmentation model. convexity splitting is used to discrtised the time and we replace the laplacian by its fractional counterpart in the time discretised scheme. fourier spectral method is used for space discretization. consistency, stability and convergence of the time discretised model has been carried out. the model is tested on some standard test images and compared them with the result of some models existed in the literature. | arxiv:2208.01887 |
we report the first detections of so _ 2, ns and no in an extragalactic source, the nucleus of the starburst galaxy ngc 253. five so _ 2 transitions, three groups of hyperfine components of no and five of ns were detected. all three species show large abundances averaged over the inner 200 pc of ngc 253. with a relative abundance of a few 10 ^ - 7, the emission of the no molecule is similar or even larger than that found in galactic star forming regions. the derived relative molecular abundances for each molecule have been compared with those of prototypical galactic molecular clouds. these results seem to confirm that large scale shocks dominate the chemistry of these molecules in the nucleus of ngc 253, ruling out a chemistry dominated by pdrs for the bulk of the gas. | arxiv:astro-ph/0309663 |
electromagnetic modeling provides an interesting context to present a link between physical phenomena and homology and cohomology theories. over the past twenty - five years, a considerable effort has been invested by the computational electromagnetics community to develop fast and general techniques for potential design. when magneto - quasi - static discrete formulations based on magnetic scalar potential are employed in problems which involve conductive regions with holes, \ textit { cuts } are needed to make the boundary value problem well defined. while an intimate connection with homology theory has been quickly recognized, heuristic definitions of cuts are surprisingly still dominant in the literature. the aim of this paper is first to survey several definitions of cuts together with their shortcomings. then, cuts are defined as generators of the first cohomology group over integers of a finite cw - complex. this provably general definition has also the virtue of providing an automatic, general and efficient algorithm for the computation of cuts. some counter - examples show that heuristic definitions of cuts should be abandoned. the use of cohomology theory is not an option but the invaluable tool expressly needed to solve this problem. | arxiv:1111.2374 |
we analyse the kinematic properties of a plasma electron hole : a non - linear self - sustained localized positive electric potential perturbation, trapping electrons, that behaves as a coherent entity. when a hole accelerates or grows in depth, ion and electron plasma momentum is changed both within the hole and outside it, by an energization process we call jetting. we present a comprehensive analytic calculation of the momentum changes of an isolated general one - dimensional hole. the conservation of the total momentum gives the hole ' s kinematics, determining its velocity evolution. our results explain many features of the behavior of hole speed observed in numerical simulations, including self - acceleration at formation, and hole pushing and trapping by ion streams. | arxiv:1605.06520 |
stellar streams from globular clusters ( gcs ) offer constraints on the nature of dark matter and have been used to explore the dark matter halo structure and substructure of our galaxy. detection of gc streams in other galaxies would broaden this endeavor to a cosmological context, yet no such streams have been detected to date. to enable such exploration, we develop the hough stream spotter ( hss ), and apply it to the pan - andromeda archaeological survey ( pandas ) photometric data of resolved stars in m31 ' s stellar halo. we first demonstrate that our code can re - discover known dwarf streams in m31. we then use the hss to blindly identify 27 linear gc stream - like structures in the pandas data. for each hss gc stream candidate, we investigate the morphologies of the streams and the colors and magnitudes of all stars in the candidate streams. we find that the five most significant detections show a stronger signal along the red giant branch in color - magnitude diagrams ( cmds ) than spurious non - stream detections. lastly, we demonstrate that the hss will easily detect globular cluster streams in future nancy grace roman space telescope data of nearby galaxies. this has the potential to open up a new discovery space for gc stream studies, gc stream gap searches, and for gc stream - based constraints on the nature of dark matter. | arxiv:2107.00017 |
we introduce and investigate a series of models for an infection of a diplodiploid host species by the bacterial endosymbiont \ textit { wolbachia }. the continuous models are characterized by partial vertical transmission, cytoplasmic incompatibility and fitness costs associated with the infection. a particular aspect of interest is competitions between mutually incompatible strains. we further introduce an age - structured model that takes into account different fertility and mortality rates at different stages of the life cycle of the individuals. with only a few parameters, the ordinary differential equation models exhibit already interesting dynamics and can be used to predict criteria under which a strain of bacteria is able to invade a population. interestingly, but not surprisingly, the age - structured model shows significant differences concerning the existence and stability of equilibrium solutions compared to the unstructured model. | arxiv:0906.1676 |
nowadays, indoor localization has received extensive research interest due to more and more applications ' needs for location information to provide a more precise and effective service [ 1 ], [ 2 ]. there are various wireless techniques and mechanisms that have been proposed ; some of them have been studied in depth and come into use, such as wi - fi, rfid, and sensor networks. in comparison, the development of bluetooth location technology is slow and there are not many papers and surveys in this field, although the performance and market value of bluetooth are increasing steadily. in this paper, we aim to provide a detailed survey of various indoor localization systems with bluetooth. in contrast with the existing surveys, we categorize the exciting localization techniques that have been proposed in the literature in order to sketch the development of bluetooth location compared to other technologies. we also evaluate different systems from the perspective of availability, cost, scalability, and accuracy. we also discuss remaining problems and challenges to accurate bluetooth localization. | arxiv:2404.12529 |
we investigate an extension of a lower bound on the waring ( cactus ) rank of homogeneous forms due to ranestad and schreyer. we show that for particular classes of homogeneous forms, for which a generalization of this method applies, the lower bound extends to the level of border ( cactus ) rank. the approach is based on recent results on tensor asymptotic rank. | arxiv:1907.03487 |
characterizing the elastic properties of soft materials through bulge testing relies on accurate measurement of deformation, which is experimentally challenging. to avoid measuring deformation, we propose a hydrodynamic bulge test for characterizing the material properties of thick, pre - stressed elastic sheets via their fluid - - structure interaction with a steady viscous fluid flow. specifically, the hydrodynamic bulge test relies on a pressure drop measurement across a rectangular microchannel with a deformable top wall. we develop a mathematical model using first - order shear - deformation theory of plates with stretching, and the lubrication approximation for newtonian fluid flow. specifically, a relationship is derived between the imposed flow rate and the total pressure drop. then, this relationship is inverted numerically to yield estimates of the young ' s modulus ( given the poisson ratio ), if the pressure drop is measured ( given the steady flow rate ). direct numerical simulations of two - way - coupled fluid - - structure interaction are carried out in ansys to determine the cross - sectional membrane deformation and the hydrodynamic pressure distribution. taking the simulations as ` ` ground truth, ' ' a hydrodynamic bulge test is performed using the simulation data to ascertain the accuracy and validity of the proposed methodology for estimating material properties. an error propagation analysis is performed via monte carlo simulation to characterize the susceptibility of the hydrodynamic bulge test estimates to noise. we find that, while a hydrodynamic bulge test is less accurate in characterizing material properties, it is less susceptible to noise, in the input ( measured ) variable, than a hydrostatic bulge test. | arxiv:1910.03513 |
we present a necessary and sufficient condition on nonnegative radon measures $ \ mu $ and $ \ nu $ for the existence of a positive continuous solution of the dirichlet problem for the sublinear elliptic equation $ - \ delta u = \ mu u ^ q + \ nu $ with prescribed nonnegative continuous boundary data in a general domain. moreover, two - sided pointwise estimates of brezis - kamin type for positive bounded solutions and the uniqueness of a positive continuous $ l ^ q $ - solution are investigated. | arxiv:2009.06939 |
we investigate nitrogen isotope fractionation in forming and evolving molecular clouds using gas - ice astrochemical simulations. we find that the bulk gas can become depleted in heavy nitrogen ( 15n ) due to the formation of 15n - enriched ices. around the chemical transition from atomic nitrogen to n2, n15n is selectively photodissociated, which results in the enrichment of 15n in atomic nitrogen. as 15n - enriched atomic nitrogen is converted to ammonia ice via grain surface reactions, the bulk gas is depleted in 15n. the level of 15n depletion in the bulk gas can be up to a factor of two compared to the elemental nitrogen isotope ratio, depending on the photodesorption yield of ammonia ice. once the nitrogen isotopes are differentially partitioned between gas and solids in a molecular cloud, it should remain in the later stages of star formation ( e. g., prestellar core ) as long as the sublimation of ammonia ice is inefficient. our model suggests that all the n - bearing molecules in the cold gas of star - forming regions can be depleted in 15n, which is at least qualitatively consistent with the observations toward prestellar core l1544. in our models, icy species show both 15n and deuterium fractionation. the fractionation pattern within ice mantles is different between 15n and deuterium, reflecting their fractionation mechanisms ; while the concentration of deuterium almost monotonically increases from the lower layers of the ice mantles to the upper layers, the concentration of 15n reaches the maximum at a certain depth and declines towards the surface. | arxiv:1803.06787 |
like a black hat hacker, but is specifically someone who is very skilled and tries via hacking to make profits or to benefit, not just to vandalize. crackers find exploits for system vulnerabilities and often use them to their advantage by either selling the fix to the system owner or selling the exploit to other black hat hackers, who in turn use it to steal information or gain royalties. grey hat computer security experts who may sometimes violate laws or typical ethical standards, but do not have the malicious intent typical of a black hat hacker. = = = hacker culture = = = hacker culture is an idea derived from a community of enthusiast computer programmers and systems designers in the 1960s around the massachusetts institute of technology ' s ( mit ' s ) tech model railroad club ( tmrc ) and the mit artificial intelligence laboratory. the concept expanded to the hobbyist home computing community, focusing on hardware in the late 1970s ( e. g. the homebrew computer club ) and on software ( video games, software cracking, the demoscene ) in the 1980s / 1990s. later, this would go on to encompass many new definitions such as art, and life hacking. = = motives = = four primary motives have been proposed as possibilities for why hackers attempt to break into computers and networks. first, there is a criminal financial gain to be had when hacking systems with the specific purpose of stealing credit card numbers or manipulating banking systems. second, many hackers thrive off of increasing their reputation within the hacker subculture and will leave their handles on websites they defaced or leave some other evidence as proof that they were involved in a specific hack. third, corporate espionage allows companies to acquire information on products or services that can be stolen or used as leverage within the marketplace. lastly, state - sponsored attacks provide nation states with both wartime and intelligence collection options conducted on, in, or through cyberspace. = = overlaps and differences = = the main basic difference between programmer subculture and computer security hacker is their mostly separate historical origin and development. however, the jargon file reports that considerable overlap existed for the early phreaking at the beginning of the 1970s. an article from mit ' s student paper the tech used the term hacker in this context already in 1963 in its pejorative meaning for someone messing with the phone system. the overlap quickly started to break when people joined in the activity who did it in a less responsible way. this was the case after the publication of an article exposing the activities of draper and engressia. according to | https://en.wikipedia.org/wiki/Hacker |
we consider the moduli space of log smooth pairs formed by a cubic surface and an anticanonical divisor. we describe all compactifications of this moduli space which are constructed using geometric invariant theory and the anticanonical polarization. the construction depends on a weight on the divisor. for smaller weights the stable pairs consist of mildly singular surfaces and very singular divisors. conversely, a larger weight allows more singular surfaces, but it restricts the singularities on the divisor. the one - dimensional space of stability conditions decomposes in a wall - chamber structure. we describe all the walls and relate their value to the worst singularities appearing in the compactification locus. furthermore, we give a complete characterization of stable and polystable pairs in terms of their singularities for each of the compactifications considered. | arxiv:1607.03697 |
we study two - color qcd in an external magnetic backround at finite temperature using the polyakov - loop extended two - flavor two - color njl model. at t = 0, the chiral condensate is calculated and it is found to increase as a function of the magnetic field $ b $. in the chiral limit the deconfinement transition lies below the chiral transition for nonzero magnetic fields $ b $. at the physical point, the two transitions seem to coincide for field strengths up to $ | qb | \ approx 5m _ { \ pi } ^ 2 $ whereafter they split. the splitting between the two increases as a function of $ b $ in both the chiral limit and at the physical point. in the range from zero magnetic field and $ | qb | = 20 m _ { \ pi } ^ 2 $, the transition temperature for the chiral transition increases by approximately 35 mev, while the transition temperature for deconfinement is essentially constant. | arxiv:1211.7293 |
in this paper, we will derive the cross section formula for the higgs pair production at a linear $ e ^ + e ^ - $ collider in models with large extra dimensions and study the feasibility of its measurement through realistic monte carlo simulations. since the process has essentially no standard model background, once produced, it will provide us with a very clean signature of physics beyond the standard model. moreover, since the final state particles are spinless, the spin 2 of the intermediate virtual kk gravitons has to be conserved by the orbital angular momentum of the higgs pair. this results in a very characteristic angular distribution of the final states. taking into account finite detector acceptance and resolutions as well as initial state radiation and beamstrahlung, we demonstrate in this paper that, given a sufficiently high center of mass energy, the angular distribution of the higgs pair is indeed measurable at the linear collider and will allow us to prove the spin 2 nature of the kk gravitons exchanged in the s - channel. | arxiv:hep-ex/0403029 |
we present new kinematic measurements and modeling of a sample of 116 young stars in the central parsec of the galaxy in order to investigate the properties of the young stellar disk. the measurements were derived from a combination of speckle and laser guide star adaptive optics imaging and integral field spectroscopy from the keck telescopes. compared to earlier disk studies, the most important kinematic measurement improvement is in the precision of the accelerations in the plane of the sky, which have a factor of six smaller uncertainties ( ~ 10 uas / yr / yr ). we have also added the first radial velocity measurements for 8 young stars, increasing the sample at the largest radii ( 6 " - 12 " ) by 25 %. we derive the ensemble properties of the observed stars using monte - carlo simulations of mock data. there is one highly significant kinematic feature ( ~ 20 sigma ), corresponding to the well - known clockwise disk, and no significant feature is detected at the location of the previously claimed counterclockwise disk. the true disk fraction is estimated to be ~ 20 %, a factor of ~ 2. 5 lower than previous claims, suggesting that we may be observing the remnant of what used to be a more densely populated stellar disk. the similarity in the kinematic properties of the b stars and the o / wr stars suggests a common star formation event. the intrinsic eccentricity distribution of the disk stars is unimodal, with an average value of < e > = 0. 27 + / - 0. 07, which we show can be achieved through dynamical relaxation in an initially circular disk with a moderately top - heavy mass function. | arxiv:1401.7354 |
this is a preliminary report on the contou - carrere symbol for surfaces. it consists of two parts. in the first part, we recall technical results needed to define the symbol. the second part is where we compute all components of the coutou - carrere symbol for surfaces, using iterated integrals over membranes. | arxiv:1310.7065 |
the kissing number of $ \ mathbb { r } ^ n $ is the maximum number of pairwise - nonoverlapping unit spheres that can simultaneously touch a central unit sphere. mittelmann and vallentin ( 2010 ), based on the semidefinite programming bound of bachoc and vallentin ( 2008 ), computed the best known upper bounds for the kissing number for several values of $ n \ leq 23 $. in this paper, we exploit the symmetry present in the semidefinite programming bound to provide improved upper bounds for $ n = 9, \ ldots, 23 $. | arxiv:1609.05167 |
quantum simulation is one of the key applications of quantum computing, which accelerates research and development in the fields such as chemistry and material science. the recent development of noisy intermediate - scale quantum ( nisq ) devices urges the exploration of applications without the necessity of quantum error correction. in this paper, we propose an efficient method to simulate quantum dynamics driven by a static hamiltonian on nisq devices, named subspace variational quantum simulator ( svqs ). svqs employs the subspace - search variational quantum eigensolver ( ssvqe ) to find a low - lying eigensubspace and extends it to simulate dynamics within the subspace with lower overhead compared to the existing schemes. we experimentally simulate the time - evolution operator in a low - lying eigensubspace of a hydrogen molecule. we also define the subspace process fidelity as a measure between two quantum processes in a subspace. the subspace time evolution mimicked by svqs shows the subspace process fidelity of $ 0. 88 $ - $ 0. 98 $. | arxiv:1904.08566 |
a mechanism of controlling the degree of strain relaxation in gesn epilayers, grown by molecular beam epitaxy on ge / si ( 001 ) substrates, is reported in this work. it is demonstrated that by suitably controlling the thickness and the growth recipe of the underlying ge buffer layer, both fully - strained and highly - relaxed gesn epilayers can be obtained, without significant sn segregation. the strain relaxation of the gesn epilayer is mediated by threading dislocations of the ge buffer layer, propagating across the ge - gesn interface. systematic estimation of the threading dislocation density in both the alloy epilayer and the ge buffer layer, by the approach developed by benediktovich et al. [ a. benediktovitch, a. zhylik, t. ulyanenkova, m. myronov, a. ulyanenkov ( 2015 ), j. appl. cryst. 48, 655 - 665 ] supports this observation, and also reveals that no additional dislocations are generated at the ge - gesn interface. together with recently reported techniques to arrest dislocation propagation in gesn epilayers, these results bode extremely well for realization of highly - relaxed gesn epilayers, much coveted for development of gesn - based emitters. | arxiv:1807.09718 |
image fusion is famous as an alternative solution to generate one high - quality image from multiple images in addition to image restoration from a single degraded image. the essence of image fusion is to integrate complementary information from source images. existing fusion methods struggle with generalization across various tasks and often require labor - intensive designs, in which it is difficult to identify and extract useful information from source images due to the diverse requirements of each fusion task. additionally, these methods develop highly specialized features for different downstream applications, hindering the adaptation to new and diverse downstream tasks. to address these limitations, we introduce defusion + +, a novel framework that leverages self - supervised learning ( ssl ) to enhance the versatility of feature representation for different image fusion tasks. defusion + + captures the image fusion task - friendly representations from large - scale data in a self - supervised way, overcoming the constraints of limited fusion datasets. specifically, we introduce two innovative pretext tasks : common and unique decomposition ( cud ) and masked feature modeling ( mfm ). cud decomposes source images into abstract common and unique components, while mfm refines these components into robust fused features. jointly training of these tasks enables defusion + + to produce adaptable representations that can effectively extract useful information from various source images, regardless of the fusion task. the resulting fused representations are also highly adaptable for a wide range of downstream tasks, including image segmentation and object detection. defusion + + stands out by producing versatile fused representations that can enhance both the quality of image fusion and the effectiveness of downstream high - level vision tasks, simplifying the process with the elegant fusion framework. | arxiv:2410.12274 |
researchers are constantly leveraging new forms of data with the goal of understanding how people perceive the built environment and build the collective place identity of cities. latest advancements in generative artificial intelligence ( ai ) models have enabled the production of realistic representations learned from vast amounts of data. in this study, we aim to test the potential of generative ai as the source of textual and visual information in capturing the place identity of cities assessed by filtered descriptions and images. we asked questions on the place identity of a set of 31 global cities to two generative ai models, chatgpt and dall - e2. since generative ai has raised ethical concerns regarding its trustworthiness, we performed cross - validation to examine whether the results show similar patterns to real urban settings. in particular, we compared the outputs with wikipedia data for text and images searched from google for image. our results indicate that generative ai models have the potential to capture the collective image of cities that can make them distinguishable. this study is among the first attempts to explore the capabilities of generative ai in understanding human perceptions of the built environment. it contributes to urban design literature by discussing future research opportunities and potential limitations. | arxiv:2306.04662 |
different spacetime regions separated by horizons are not related to each other. we know that this statement holds for classical spacetimes. in this paper we carry out a canonical quantization of a kantowski - sachs minisuperspace model whose classical solutions exhibit both an event horizon and a cosmological horizon in order to check whether the above statement also holds from the quantum gravitational point of view. our analysis shows that in fact this is not the case : quantum gravitational states with support in spacetime configurations that exclusively describe either the region between horizons or outside them are not consistent in the sense that there exist unitary operators describing a natural notion of evolution that connect them. in other words, unitarity is only preserved in this quantization when dealing with the whole spacetime and not in each region separately. | arxiv:1410.2543 |
given c $ ^ * $ - algebras $ a $ and $ b $ and a $ ^ * $ - homomorphism $ \ phi : a \ rightarrow b $, we adopt the portrait of the relative $ k $ - theory $ k _ * ( \ phi ) $ due to karoubi using banach categories and banach functors. we show that the elements of the relative groups may be represented in a simple form. we prove the existence of two six - term exact sequences, and we use these sequences to deduce the fact that the relative theory is isomorphic, in a natural way, to the $ k $ - theory of the mapping cone. | arxiv:2106.02620 |
the nonlinear effects of environmental variability on species abundance plays an important role in the maintenance of ecological diversity. nonetheless, many common models use parametric nonlinear terms pre - determining ecological conclusions. motivated by this concern, we study the estimate of the second derivative ( curvature ) of the link function g in a functional single index model. since the coefficient function and the link function are both unknown, the estimate is expressed as a nested optimization. for a fixed and unknown coefficient function, the link function and its second derivative are estimated by local quadratic approximation, then the coefficient function is estimated by minimizing the mse of the model. in this paper, we derive the rate of convergence of the estimation. in addition, we prove that the argument of g, can be estimated root - n consistently. however, practical implementation of the method requires solving a nonlinear optimization problem, and our results show that the estimates of the link function and the coefficient function are quite sensitive to the choices of starting values. | arxiv:1803.09321 |
how is knowledge of position - role mappings in natural language learned? we explore this question in a computational setting, testing whether a variety of well - performing pertained language models ( bert, roberta, and distilbert ) exhibit knowledge of these mappings, and whether this knowledge persists across alternations in syntactic, structural, and lexical alternations. in experiment 1, we show that these neural models do indeed recognize distinctions between theme and recipient roles in ditransitive constructions, and that these distinct patterns are shared across construction type. we strengthen this finding in experiment 2 by showing that fine - tuning these language models on novel theme - and recipient - like tokens in one paradigm allows the models to make correct predictions about their placement in other paradigms, suggesting that the knowledge of these mappings is shared rather than independently learned. we do, however, observe some limitations of this generalization when tasks involve constructions with novel ditransitive verbs, hinting at a degree of lexical specificity which underlies model performance. | arxiv:2202.03611 |
we report on the status of efforts to improve the reinterpretation of searches and measurements at the lhc in terms of models for new physics, in the context of the lhc reinterpretation forum. we detail current experimental offerings in direct searches for new particles, measurements, technical implementations and open data, and provide a set of recommendations for further improving the presentation of lhc results in order to better enable reinterpretation in the future. we also provide a brief description of existing software reinterpretation frameworks and recent global analyses of new physics that make use of the current data. | arxiv:2003.07868 |
we prove, when $ s $ is a $ 2 $ - group of order at most $ 2 ^ 9 $, that each reduced fusion system over $ s $ is the fusion system of a finite simple group and is tame. it then follows that each saturated fusion system over a $ 2 $ - group of order at most $ 2 ^ 9 $ is realizable. what is most interesting about this result is the method of proof : we show that among $ 2 $ - groups with order in this range, the ones which can be sylow $ 2 $ - subgroups of finite simple groups are almost completely determined by criteria based on bender ' s classification of groups with strongly $ 2 $ - embedded subgroups. | arxiv:1606.05059 |
rr fields in string backgrounds including orientifold planes and branes on top of them are classified by k - theory. following the idea introduced in hep - th / 0103183, we also classify such fluxes by cohomology. both of them are compared through the atiyah - hirzebruch spectral sequence. some new correlations between branes on orientifold planes $ op ^ \ pm $ and obstructions to the existence of some branes are found. finally, we find a topological condition that avoid the presence of global gauge anomalies in lower dimensional systems. | arxiv:hep-th/0206183 |
nonlinear negative imaginary ( ni ) systems arise in various engineering applications, such as controlling flexible structures and air vehicles. however, unlike linear ni systems, their theory is not well - developed. in this paper, we propose a data - driven method for learning a lifted linear ni dynamics that approximates a nonlinear dynamical system using the koopman theory, which is an operator that captures the evolution of nonlinear systems in a lifted high - dimensional space. the linear matrix inequality that characterizes the ni property is embedded in the koopman framework, which results in a non - convex optimization problem. to overcome the numerical challenges of solving a non - convex optimization problem with nonlinear constraints, the optimization variables are reformatted in order to convert the optimization problem into a convex one with the new variables. we compare our method with local linearization techniques and show that our method can accurately capture the nonlinear dynamics and achieve better control performance. our method provides a numerically tractable solution for learning the koopman operator under ni constraints for nonlinear ni systems and opens up new possibilities for applying linear control techniques to nonlinear ni systems without linearization approximations | arxiv:2305.04191 |
we consider a minimal go - or - grow model of cell invasion, whereby cells can either proliferate, following logistic growth, or move, via linear diffusion, and phenotypic switching between these two states is density - dependent. formal analysis in the fast switching regime shows that the total cell density in the two - population go - or - grow model can be described in terms of a single reaction - diffusion equation with density - dependent diffusion and proliferation. using the connection to single - population models, we study travelling wave solutions, showing that the wave speed in the go - or - grow model is always bounded by the wave speed corresponding to the well - known fisher - kpp equation. | arxiv:2404.11251 |
it is proved that for integers $ b, r $ such that $ 3 \ leq b < r \ leq \ binom { b + 1 } { 2 } - 1 $, there exists a red / blue edge - colored graph such that the red degree of every vertex is $ r $, the blue degree of every vertex is $ b $, yet in the closed neighborhood of every vertex there are more blue edges than red edges. the upper bound $ r \ le \ binom { b + 1 } { 2 } - 1 $ is best possible for any $ b \ ge 3 $. we further extend this theorem to more than two colours, and to larger neighbourhoods. a useful result required in some of our proofs, of independent interest, is that for integers $ r, t $ such that $ 0 \ leq t \ le \ frac { r ^ 2 } { 2 } - 5r ^ { 3 / 2 } $, there exists an $ r $ - regular graph in which each open neighborhood induces precisely $ t $ edges. several explicit constructions are introduced and relationships with constant linked graphs, $ ( r, b ) $ - regular graphs and vertex transitive graphs are revealed. | arxiv:2312.08777 |
spectrophotometric observations of the coma of the comets c / 2000 wm1 ( linear ) and c / 2002 c1 ( ikeya - zhang ) were taken during nov, dec 2001 and mar, apr 2002 respectively with 104 - cm telescope of the state observatory, nainital. cn ( $ \ lambda $ 3883 \ aa ) and c $ _ { 2 } $ swan bands ( $ \ lambda $ 4695, $ \ lambda $ 5165 and $ \ lambda $ 5538 \ aa ) have been identified in both the comets. na i emission was detected in comet ikeya - zhang. an estimate of cn and c $ _ { 2 } $ abundances and their production rates have been derived. dust production rates have also been determined. | arxiv:astro-ph/0211143 |
we demonstrate that the gibbs - shannon entropy is applicable to non - equilibrium systems of any size and boundary conditions. the change in microscopic entropy can be attributed to the stochastic nature of dynamic processes and to the inherent uncertainties of thermodynamic systems. the latter predicts that entropy production is nonnegative on average and varies with different trajectories according to the fluctuation theorem. by contrast, heat is affiliated with stochastic processes underlying particle motions and the ensemble average over all possible trajectories leads to the clausius inequality. the jarzynski / crooks equations can be readily derived by applying the fluctuation theorem to heat variation over different trajectories linking equilibrium states. | arxiv:2010.04648 |
the problem of data synchronization arises in networked applications that require some measure of consistency. indeed data synchronization approaches have demonstrated a significant potential for improving performance in various applications ranging from distributed ledgers to fog - enabled storage offloading for iot. although several protocols for data sets synchronization have been proposed over the years, there is currently no widespread utility implementing them, unlike the popular rsync utility available for file synchronization. to that end, we describe a new middleware called gensync that abstracts the subtleties of the state - of - the - art data synchronization protocols, allows users to choose protocols based on a comparative evaluation under realistic system conditions, and seamlessly integrate protocols in existing applications through a public api. we showcase gensync through a case study, in which we integrate it into one of the world ' s largest wireless emulators and compare the performance of its included protocols. | arxiv:2303.17530 |
this paper analyzes the fundamental limit of the strategic semantic communication problem in which a transmitter obtains a limited number of indirect observation of an intrinsic semantic information source and can then influence the receiver ' s decoding by sending a limited number of messages to an imperfect channel. the transmitter and the receiver can have different distortion measures and can make rational decision about their encoding and decoding strategies, respectively. the decoder can also have some side information ( e. g., background knowledge and / or information obtained from previous communications ) about the semantic source to assist its interpretation of the semantic information. we focus particularly on the case that the transmitter can commit to an encoding strategy and study the impact of the strategic decision making on the rate distortion of semantic communication. three equilibrium solutions including the strong stackelberg equilibrium, weak stackelberg equilibrium, as well as nash equilibrium have been studied and compared. the optimal encoding and decoding strategy profiles under various equilibrium solutions have been derived. we prove that committing to an encoding strategy cannot always bring benefit to the encoder. we therefore propose a feasible condition under which committing to an encoding strategy can always reduce the distortion performance of semantic communication. | arxiv:2202.03711 |
the t = 0 dynamical properties of the one - dimensional ( 1d ) $ s = 1 / 2 $ heisenberg antiferromagnet in a uniform magnetic field are studied via bethe ansatz for cyclic chains of $ n $ sites. the ground state at magnetization $ 0 < m _ z < n / 2 $, which can be interpreted as a state with $ 2m _ z $ spinons or as a state of $ m _ z $ magnons, is reconfigured here as the vacuum for a different species of quasiparticles, the { \ em psinons } and { \ em antipsinons }. we investigate three kinds of quantum fluctuations, namely the spin fluctuations parallel and perpendicular to the direction of the applied magnetic field and the dimer fluctuations. the dynamically dominant excitation spectra are found to be sets of collective excitations composed of two quasiparticles excited from the psinon vacuum in different configurations. the bethe ansatz provides a framework for ( i ) the characterization of the new quasiparticles in relation to the more familiar spinons and magnons, ( ii ) the calculation of spectral boundaries and densities of states for each continuum, ( iii ) the calculation of transition rates between the ground state and the dynamically dominant collective excitations, ( iv ) the prediction of lineshapes for dynamic structure factors relevant for experiments performed on a variety of quasi - 1d antiferromagnetic compounds, including kcuf $ _ 3 $, cu ( c $ _ 4 $ h $ _ 4 $ n $ _ 2 ) ( no _ 3 ) _ 2 $, and cugeo $ _ 3 $. | arxiv:cond-mat/0205142 |
in this paper, we study forward - backward doubly stochastic differential equations driven by brownian motions and poisson process ( fbdsdep in short ). both the probabilistic interpretation for the solutions to a class of quasilinear stochastic partial differential - integral equations ( spdies in short ) and stochastic hamiltonian systems arising in stochastic optimal control problems with random jumps are treated with fbdsdep. under some monotonicity assumptions, the existence and uniqueness results for measurable solutions of fbdsdep are established via a method of continuation. furthermore, the continuity and differentiability of the solutions of fbdsdep depending on parameters is discussed. finally, the probabilistic interpretation for the solutions to a class of quasilinear spdies is given. | arxiv:1005.2494 |
the observed neutrino oscillation data might be explained by new physics at a tev scale, which is testable in the future experiments. among various possibilities, the low - energy higgs triplet model is a prime candidate of such new physics since it predicts clean signatures of lepton flavor violating processes directly related to the neutrino masses and mixing. it is discussed how various neutrino mass patterns can be discriminated by examining the lepton flavor violating decays of charged leptons as well as the collider signatures of a doubly charged higgs boson in the model. | arxiv:hep-ph/0304069 |
young giant planets, which are embedded in a circumstellar disk, will significantly perturb the disk density distribution. this effect can potentially be used as an indirect tracer for planets. we investigate the feasibility of observing planet - induced gaps in circumstellar disks in scattered light. we perform 3d hydrodynamical disk simulations combined with subsequent radiative transfer calculations in scattered light for different star, disk, and planet configurations. the results are compared to those of a corresponding study for the ( sub ) mm thermal re - emission. the feasibility of detecting planet - induced gaps in scattered light is mainly influenced by the optical depth of the disk and therefore by the disk size and mass. planet - induced gaps are in general only detectable if the photosphere of the disks is sufficiently disturbed. within the limitations given by the parameter space here considered, we find that gap detection is possible in the case of disks with masses below $ \ sim 10 ^ { - 4 \ dots - 3 } \, \ rm m _ \ odot $. compared to the disk mass that marks the lower atacama large ( sub ) millimeter array ( alma ) detection limit for the thermal radiation re - emitted by the disk, it is possible to detect the same gap both in re - emission and scattered light only in a narrow range of disk masses around $ \ sim 10 ^ { - 4 } \, \ rm m _ \ odot $, corresponding to $ 16 \ % $ of cases considered in our study. | arxiv:1411.2735 |
how to detect spacetime torsion? in this essay we provide the theoretical basis for an answer to this question. multipolar equations of motion for a very general class of gravitational theories with nonminimal coupling in spacetimes admitting torsion are given. our findings provide a framework for the systematic testing of whole classes of theories with the help of extended test bodies. one surprising feature of nonminimal theories turns out to be their potential sensitivity to torsion of spacetime even in experiments with ordinary ( not microstructured ) test matter. | arxiv:1405.4137 |
transferring knowledge across domains is one of the most fundamental problems in machine learning, but doing so effectively in the context of reinforcement learning remains largely an open problem. current methods make strong assumptions on the specifics of the task, often lack principled objectives, and - - crucially - - modify individual policies, which might be sub - optimal when the domains differ due to a drift in the state space, i. e., it is intrinsic to the environment and therefore affects every agent interacting with it. to address these drawbacks, we propose tvd : transfer via distribution matching, a framework to transfer knowledge across interactive domains. we approach the problem from a data - centric perspective, characterizing the discrepancy in environments by means of ( potentially complex ) transformation between their state spaces, and thus posing the problem of transfer as learning to undo this transformation. to accomplish this, we introduce a novel optimization objective based on an optimal transport distance between two distributions over trajectories - - those generated by an already - learned policy in the source domain and a learnable pushforward policy in the target domain. we show this objective leads to a policy update scheme reminiscent of imitation learning, and derive an efficient algorithm to implement it. our experiments in simple gridworlds show that this method yields successful transfer learning across a wide range of environment transformations. | arxiv:2211.14469 |
round robin, considered as the most widely adopted cpu scheduling algorithm, undergoes severe problems directly related to quantum size. if time quantum chosen is too large, the response time of the processes is considered too high. on the other hand, if this quantum is too small, it increases the overhead of the cpu. in this paper, we propose a new algorithm, called an, based on a new approach called dynamic - time - quantum ; the idea of this approach is to make the operating systems adjusts the time quantum according to the burst time of the set of waiting processes in the ready queue. based on the simulations and experiments, we show that the new proposed algorithm solves the fixed time quantum problem and increases the performance of round robin. | arxiv:1111.5348 |
single - cell studies often show significant phenotypic variability due to the stochastic nature of intra - cellular biochemical reactions. when the numbers of molecules, e. g., transcription factors and regulatory enzymes, are in low abundance, fluctuations in biochemical activities become significant and such " noise " can propagate through regulatory cascades in terms of biochemical reaction networks. here we develop an intuitive, yet fully quantitative method for analyzing how noise affects cellular phenotypes based on identifying a system ' s nonlinearities and noise propagations. we observe that such noise can simultaneously enhance sensitivities in one behavioral region while reducing sensitivities in another. employing this novel phenomenon we designed three biochemical signal processing modules : ( a ) a gene regulatory network that acts as a concentration detector with both enhanced amplitude and sensitivity. ( b ) a non - cooperative positive feedback system, with a graded dose - response in the deterministic case, that serves as a bistable switch due to noise - induced bimodality. ( c ) a noise - induced linear amplifier for gene regulation that requires no feedback. the methods developed in the present work allow one to understand and engineer nonlinear biochemical signal processors based on fluctuation - induced phenotypes. | arxiv:1309.2588 |
we present the first large sample of accurate iron abundances and temperatures for clusters at redshifts greater than 0. 14. we find that the fe abundance shows little or no evolution out to redshift 0. 3. this and the early formation epoch of elliptical galaxies in clusters indicate that most of the enrichment of the intracluster medium occurred at redshifts greater than 1. if clusters represent fair samples of the universe, then global metal production is 2 - 5 times greater than is inferred from recent studies of galaxies at low and high redshifts. | arxiv:astro-ph/9702149 |
we present our results of the spectroscopic study of the lenticular galaxy ngc 4143 - an outskirt member of the ursa major cluster. using the observations at the 6 - m sao ras telescope with the scorpio - 2 spectrograph and also the archive data of panoramic spectroscopy with the sauron ifu at the wht, we have detected an extended inclined gaseous disk which is traced up to a distance of about 3. 5 kpc from the center, with a spin approximately opposite to the spin of the stellar disk. the galaxy images in the h - alpha and [ nii ] 6583 emission lines obtained at the 2. 5 - m cmo sai msu telescope with the mangal instrument have shown that the emission lines are excited by a shock wave. a spiral structure that is absent in the stellar disk of the galaxy is clearly seen in the brightness distribution of ionized - gas lines ( h - alpha and [ nii ] from the mangal data and [ oiii ] from the sauron data ). a complex analysis of both the lick index distribution along the radius and of the integrated colors, including the ultraviolet measurements with the galex space telescope and the near - infrared measurements with the wise space telescope, has shown that there has been no star formation in the galaxy, perhaps, for the last 10 gyr. thus, the recent external - gas accretion detected in ngc 4143 from its kinematics, was not accompanied by star formation, probably, due to an inclined direction of the gas inflow onto the disk. | arxiv:2009.00126 |
we obtained a second chandra timing measurement of the 3. 82 s pulsar cxou j171405. 7 - 381031 in the supernova remnant ( snr ) ctb 37b, which shows that it is spinning down rapidly. the average period derivative of ( 5. 88 + / - 0. 08 ) e - 11 over the 1 year time span corresponds to a dipole magnetic field strength b = 4. 8e14 g, well into the magnetar range. the spin - down power e - dot = 4. 2e34 erg / s is among the largest for magnetars, and the corresponding characteristic age tau = p / 2p - dot = 1030 years is comparable to estimates of the age of the snr. the period derivative enables us to recover probable pulsations in an asca observation taken in 1996, which yields a mean characteristic age of 860 years over the longer 13 year time span. the source is well detected up to 10 kev, and its composite spectrum is typical of a magnetar. ctb 37b hosts hess j1713 - 381, the first tev source that is coincident with a magnetar. while the tev emission has been attributed to the snr shell, it is possibly centrally peaked, and we hypothesize that this particularly young, energetic magnetar may contribute to the hess source. we also searched for pulsations from another source in a hess snr, xmmu j173203. 3 - 344518 in hess j1731 - 347 / g353. 6 - 0. 7 but could not confirm pulsations or long - term flux variability, making it more likely that this source is a weakly magnetized central compact object. | arxiv:1008.2558 |
we prove that the only bott manifolds such that the futaki invariant vanishes for any k \ " ahler class are isomorphic to the products of the projective lines. | arxiv:2305.05924 |
introduction : substance use disorders ( suds ) have emerged as a pressing public health crisis in the united states, with adolescent substance use often leading to suds in adulthood. effective strategies are needed to prevent this progression. to help in filling this need, we develop a novel and the first - ever absolute risk prediction model for cannabis use disorder ( cud ) for adolescent or young adult cannabis users. methods : we train a bayesian machine learning model that provides a personalized cud absolute risk for adolescent or young adult cannabis users using data from the national longitudinal study of adolescent to adult health. model performance is assessed using 5 - fold cross - validation ( cv ) with area under the curve ( auc ) and ratio of the expected to observed number of cases ( e / o ). external validation of the final model is conducted using two independent datasets. results : the proposed model has five risk factors : biological sex, delinquency, and scores on personality traits of conscientiousness, neuroticism, and openness. for predicting cud risk within five years of first cannabis use, auc and e / o, computed via 5 - fold cv, were 0. 68 and 0. 95, respectively. for the same type of prediction in external validation, auc values were 0. 64 and 0. 75, with e / o values of 0. 98 and 1, indicating good discrimination and calibration performances of the model. discussion and conclusion : the proposed model is the first absolute risk prediction model for an sud. it can aid clinicians in identifying adolescent / youth substance users at a high risk of developing cud in future for clinically appropriate interventions. | arxiv:2501.09156 |
i analyze cutoff effects of the gradient flow for wilson - type fermions. i show that with a proper choice of the higher dimensional fields in the symanzik effective theory, o ( $ a $ ) improvement of the action is achieved changing the initial conditions of the gradient flow equation. | arxiv:2301.08591 |
low - field ( < 1t ) magnetic resonance imaging ( mri ) scanners remain in widespread use in low - and middle - income countries ( lmics ) and are commonly used for some applications in higher income countries e. g. for small child patients with obesity, claustrophobia, implants, or tattoos. however, low - field mr images commonly have lower resolution and poorer contrast than images from high field ( 1. 5t, 3t, and above ). here, we present image quality transfer ( iqt ) to enhance low - field structural mri by estimating from a low - field image the image we would have obtained from the same subject at high field. our approach uses ( i ) a stochastic low - field image simulator as the forward model to capture uncertainty and variation in the contrast of low - field images corresponding to a particular high - field image, and ( ii ) an anisotropic u - net variant specifically designed for the iqt inverse problem. we evaluate the proposed algorithm both in simulation and using multi - contrast ( t1 - weighted, t2 - weighted, and fluid attenuated inversion recovery ( flair ) ) clinical low - field mri data from an lmic hospital. we show the efficacy of iqt in improving contrast and resolution of low - field mr images. we demonstrate that iqt - enhanced images have potential for enhancing visualisation of anatomical structures and pathological lesions of clinical relevance from the perspective of radiologists. iqt is proved to have capability of boosting the diagnostic value of low - field mri, especially in low - resource settings. | arxiv:2304.13385 |
##electronics and mems in particular. silicon nanowires, fabricated through the thermal oxidation of silicon, are of further interest in electrochemical conversion and storage, including nanowire batteries and photovoltaic systems. polymers even though the electronics industry provides an economy of scale for the silicon industry, crystalline silicon is still a complex and relatively expensive material to produce. polymers on the other hand can be produced in huge volumes, with a great variety of material characteristics. mems devices can be made from polymers by processes such as injection molding, embossing or stereolithography and are especially well suited to microfluidic applications such as disposable blood testing cartridges. metals metals can also be used to create mems elements. while metals do not have some of the advantages displayed by silicon in terms of mechanical properties, when used within their limitations, metals can exhibit very high degrees of reliability. metals can be deposited by electroplating, evaporation, and sputtering processes. commonly used metals include gold, nickel, aluminium, copper, chromium, titanium, tungsten, platinum, and silver. ceramics the nitrides of silicon, aluminium and titanium as well as silicon carbide and other ceramics are increasingly applied in mems fabrication due to advantageous combinations of material properties. aln crystallizes in the wurtzite structure and thus shows pyroelectric and piezoelectric properties enabling sensors, for instance, with sensitivity to normal and shear forces. tin, on the other hand, exhibits a high electrical conductivity and large elastic modulus, making it possible to implement electrostatic mems actuation schemes with ultrathin beams. moreover, the high resistance of tin against biocorrosion qualifies the material for applications in biogenic environments. the figure shows an electron - microscopic picture of a mems biosensor with a 50 nm thin bendable tin beam above a tin ground plate. both can be driven as opposite electrodes of a capacitor, since the beam is fixed in electrically isolating side walls. when a fluid is suspended in the cavity its viscosity may be derived from bending the beam by electrical attraction to the ground plate and measuring the bending velocity. = = basic processes = = = = = deposition processes = = = one of the basic building blocks in mems processing is the ability to deposit thin films of material with a thickness anywhere from one micrometre to about 100 micrometres. the nems process is the same, | https://en.wikipedia.org/wiki/MEMS |
magnetic flux rope ( mfr ) plays an important role in solar activities. a quantitative assessment of the topology of an mfr and its evolution is crucial for a better understanding of the relationship between the mfr and the associated activities. in this paper, we investigate the magnetic field of active region 12017 from 2014 march 28 to 29, where 12 flares were triggered by the intermittent eruptions of a filament ( either successful or confined ). using the vector magnetic field data from the helioseismic and magnetic imager on board the \ textit { solar dynamics observatory }, we calculate the magnetic energy and helicity injection in the active region, and extrapolate the 3d magnetic field with a nonlinear force - free field model. from the extrapolations, we find an mfr that is cospatial with the filament. we further determine the configuration of this mfr by a closed quasi - separatrix layer ( qsl ) around it. then, we calculate the twist number and the magnetic helicity for the field lines composing the mfr. the results show that the closed qsl structure surrounding the mfr gets smaller as a consequence of the flare occurrence. we also find that the flares in our sample are mainly triggered by kink instability. moreover, the twist number varies more sensitively than other parameters to the occurrence of flares. | arxiv:1604.07502 |
the prevalence of covid - 19 has been the most serious health challenge of the 21th century to date, concerning national health systems on a daily basis, since december 2019 when it appeared in wuhan city. nevertheless, most of the proposed mathematical methodologies aiming to describe the dynamics of an epidemic, rely on deterministic models that are not able to reflect the true nature of its spread. in this paper, we propose a seihcrdv model - an extension / improvement of the classic sir compartmental model - which also takes into consideration the populations of exposed, hospitalized, admitted in intensive care units ( icu ), deceased and vaccinated cases, in combination with an unscented kalman filter ( ukf ), providing a dynamic estimation of the time dependent system ' s parameters. the stochastic approach is considered necessary, as both observations and system equations are characterized by uncertainties. apparently, this new consideration is useful for examining various pandemics more effectively. the reliability of the model is examined on the daily recordings of covid - 19 in france, over a long period of 265 days. two major waves of infection are observed, starting in january 2021, which signified the start of vaccinations in europe providing quite encouraging predictive performance, based on the produced nrmse values. special emphasis is placed on proving the non - negativity of seihcrdv model, achieving a representative basic reproductive number r0 and demonstrating the existence and stability of disease equilibria according to the formula produced to estimate r0. the model outperforms in predictive ability not only deterministic approaches but also state - of - the - art stochastic models that employ kalman filters. | arxiv:2207.05011 |
we have constructed a sequence of solutions of the helmholtz equation forming an orthogonal sequence on a given surface. coefficients of these functions depend on an explicit algebraic formulae from the coefficient of the surface. moreover, for exterior helmholtz equation we have constructed an explicit normal derivative of the dirichlet green function. in the same way the dirichlet - to - neumann operator is constructed. we proved that normalized coefficients are uniformly bounded from zero. | arxiv:0709.1929 |
when a binary of early - type stars from the young stellar populations in the galactic center ( gc ) region is scattered to the vicinity of the supermassive black hole ( smbh ) sgr ~ $ \ rm { a } ^ { * } $, one of the components would be tidally ejected as an early - type hypervelocity star ( hvs ) and the counterpart would be captured on a tight orbit around sgr ~ $ \ rm { a } ^ { * } $. dozens of b - type hvss moving faster than the galactic escape speed have been discovered in the galactic halo and are produced most likely by the smbh sgr ~ $ \ rm { a } ^ { * } $. however, the velocity distribution and in particular the deficit of the hvss above $ 700 \, \ rm { km \, s ^ { - 1 } } $ is seriously inconsistent with the expectations of the present models. here we show that the high - velocity deficit is due to the deficiency in close interactions of stars with the smbh sgr ~ $ \ rm { a } ^ { * } $, because an orbiting intermediate - mass black hole ( imbh ) of about 15, 000 solar mass kicked away slowly approaching stars 50 - - 250 million years ago. the smbh - imbh binary formed probably after the merger of the milky way with the gaia - sausage - enceladus dwarf galaxy, and coalesced about 10 million years ago, leading to a gravitational recoil of sgr ~ $ \ rm { a } ^ { * } $ at a velocity of 0. 3 - - 0. 5 $ \, \ rm { km \, s ^ { - 1 } } $ and to a change of the hvs ejection scenarios. the smbh - imbh binary scenario predicts the formation of the s - star cluster at the gc with the distribution of the orbital size and stellar ages that are well consistent with the observations. | arxiv:2411.09278 |
time - resolved pump - probe measurements of xe, pumped at 133 ~ nm and probed at 266 ~ nm, are presented. the pump pulse prepared a long - lived hyperfine wavepacket, in the xe $ 5p ^ 5 ( ^ 2p ^ { \ circ } _ { 1 / 2 } ) 6s ~ ^ 2 [ 1 / 2 ] ^ { \ circ } _ 1 $ manifold ( $ e = $ 77185 cm $ ^ { - 1 } = $ 9. 57 ev ). the wavepacket was monitored via single - photon ionization, and photoelectron images measured. the images provide angle - and time - resolved data which, when obtained over a large time - window ( 900 ~ ps ), constitute a precision quantum beat spectroscopy measurement of the hyperfine state splittings. additionally, analysis of the full photoelectron image stack provides a quantum beat imaging modality, in which the fourier components of the photoelectron images correlated with specific beat components can be obtained. this may also permit the extraction of isotope - resolved photoelectron images in the frequency domain, in cases where nuclear spins ( hence beat components ) can be uniquely assigned to specific isotopes ( as herein ), and also provides phase information. the information content of both raw, and inverted, image stacks is investigated, suggesting the utility of the fourier analysis methodology in cases where images cannot be inverted. | arxiv:1803.01081 |
we use published measurements of the transmission power spectrum of the lyman alpha forest to constrain several parameters that describe cosmology and thermal properties of the intergalactic medium ( igm ). a 6 parameter grid is constructed using particle - mesh dark matter simulations together with scaling relations to make predictions for the gas properties. we fit for all parameters simultaneously and identify several degeneracies. we find that the temperature of the igm can be well determined from the fall - off of the power spectrum at small scales. we find a temperature around 20. 000 k, dependent on the slope of the gas equation of state. we see no evidence for evolution in the igm temperature. we place constraints on the amplitude of the dark matter fluctuations. however, contrary to previous results, the slope of the dark matter power spectrum is poorly constrained. this is due to uncertainty in the effective jeans smoothing scale, which depends on the temperature as well as the thermal history of the gas. | arxiv:astro-ph/0011559 |
in the last years the direct measurement of cosmic rays received a push forward by the possibility of conducting experiments on board long duration balloon flights, satellites and on the international space station. the increase in the collected statistics and the technical improvements in the construction of the detectors permit the fluxes measurement to be performed at higher energies with a reduced discrepancy among different experiments respect to the past. however, high statistical precision is not always associated to the needed precision in the estimation of systematics ; features in the particle spectra can be erroneously introduced or hidden. a review and a comparison of the latest experimental results on direct cosmic rays measurements will be presented with particular emphasis on their similarities and discrepancies. | arxiv:1407.1143 |
we propose a novel approach, sequential lasso, for feature selection in linear regression models with ultra - high dimensional feature spaces. we investigate in this article the asymptotic properties of sequential lasso and establish its selection consistency. like other sequential methods, the implementation of sequential lasso is not limited by the dimensionality of the feature space. it has advantages over other sequential methods. the simulation studies comparing sequential lasso with other sequential methods are reported. | arxiv:1107.2734 |
consider a random graph, having a pre - specified degree distribution f but other than that being uniformly distributed, describing the social structure ( friendship ) in a large community. suppose one individual in the community is externally infected by an infectious disease and that the disease has its course by assuming that infected individuals infect their not yet infected friends independently with probability p. for this situation the paper determines r _ 0 and tau _ 0, the basic reproduction number and the asymptotic final size in case of a major outbreak. further, the paper looks at some different local vaccination strategies where individuals are chosen randomly and vaccinated, or friends of the selected individuals are vaccinated, prior to the introduction of the disease. for the studied vaccination strategies the paper determines r _ v : the reproduction number, and tau _ v : the asymptotic final proportion infected in case of a major outbreak, after vaccinating a fraction v. | arxiv:math/0702021 |
even though dyadic regressions are widely used in empirical applications, the ( asymptotic ) properties of estimation methods only began to be studied recently in the literature. this paper aims to provide in a step - by - step manner how u - statistics tools can be applied to obtain the asymptotic properties of pairwise differences estimators for a two - way fixed effects model of dyadic interactions. more specifically, we first propose an estimator for the model that relies on pairwise differencing such that the fixed effects are differenced out. as a result, the summands of the influence function will not be independent anymore, showing dependence on the individual level and translating to the fact that the usual law of large numbers and central limit theorems do not straightforwardly apply. to overcome such obstacles, we show how to generalize tools of u - statistics for single - index variables to the double - indices context of dyadic datasets. a key result is that there can be different ways of defining the hajek projection for a directed dyadic structure, which will lead to distinct, but equivalent, consistent estimators for the asymptotic variances. the results presented in this paper are easily extended to non - linear models. | arxiv:2309.02089 |
we study the boundary behavior of the kobayashi - royden metric and the kobayashi hyperbolicity of domains in riemannian manifolds. as an application, we prove a fatou type theorem on the existence, almost everywhere, of non tangential limits for bounded conformal harmonic immersed discs. we also prove a picard theorem for conformal harmonic discs and give some examples of kobayashi hyperbolic riemannian manifolds. | arxiv:2407.15976 |
the recently emerged symbol - level precoding ( slp ) technique has been regarded as a promising solution in multi - user wireless communication systems, since it can convert harmful multi - user interference ( mui ) into beneficial signals for enhancing system performance. however, the tremendous computational complexity of conventional symbol - level precoding designs severely hinders the practical implementations. in order to tackle this difficulty, we propose a novel deep learning ( dl ) based approach to efficiently design the symbol - level precoders. particularly, in this correspondence, we consider a multi - user multi - input single - output ( mu - miso ) downlink system. an efficient precoding neural network ( epnn ) is introduced to optimize the symbol - level precoders for maximizing the minimum quality - of - service ( qos ) of all users under the power constraint. simulation results demonstrate that the proposed epnn based slp design can dramatically reduce the computing time at the price of slight performance loss compared with the conventional convex optimization based slp design. | arxiv:2104.09799 |
let $ m _ \ sigma $ be an $ n $ - dimensional thom - mather stratified space of depth $ 1 $. we denote by $ \ beta m $ the singular locus and by $ l $ the associated link. in this paper we study the problem of when such a space can be endowed with a wedge metric of positive scalar curvature. we relate this problem to recent work on index theory on stratified spaces, giving first an obstruction to the existence of such a metric in terms of a wedge $ \ alpha $ - class $ \ alpha _ w ( m _ \ sigma ) \ in ko _ n $. in order to establish a sufficient condition we need to assume additional structure : we assume that the link of $ m _ \ sigma $ is a homogeneous space of positive scalar curvature, $ l = g / k $, where the semisimple compact lie group $ g $ acts transitively on $ l $ by isometries. examples of such manifolds include compact semisimple lie groups and riemannian symmetric spaces of compact type. under these assumptions, when $ m _ \ sigma $ and $ \ beta m $ are spin, we reinterpret our obstruction in terms of two $ \ alpha $ - classes associated to the resolution of $ m _ \ sigma $, $ m $, and to the singular locus $ \ beta m $. finally, when $ m _ \ sigma $, $ \ beta m $, $ l $, and $ g $ are simply connected and $ \ dim m $ is big enough, and when some other conditions on $ l $ ( satisfied in a large number of cases ) hold, we establish the main result of this article, showing that the vanishing of these two $ \ alpha $ - classes is also sufficient for the existence of a well - adapted wedge metric of positive scalar curvature. | arxiv:1908.04420 |
the riemann curvature correction to the type ii supergravity at eight - derivative level is given schematically as $ ( t _ 8t _ 8 + { 1 } { 8 } \ eps _ { 10 } \ eps _ { 10 } ) r ^ 4 $ at tree - level. the replacement of the generalized riemann curvature in $ t _ 8t _ 8r ^ 4 $, proposed by gross and sloan, produces various ns - ns couplings which are invariant under t - duality. recently, using the combination of s - duality and t - duality transformations on these couplings, we have found groups of couplings which are invariant under the s - duality transformation. in this paper, we have examined the couplings involving the dilaton with direct scattering amplitude calculations of four ns - ns vertex operators in the superstring theory and found exact agreement. the coupling $ \ eps _ { 10 } \ eps _ { 10 } r ^ 4 $ is a total derivative term at four - field level. the $ \ sigma $ - model beta function approach implies the presence of this term at the tree - level. by examining the sphere - level scattering amplitude of five gravitons, we have also confirmed the presence of this term in the tree - level effective action. | arxiv:1306.6851 |
we use idealised n - body simulations of equilibrium discs in live and static haloes to study how dark matter co - evolution impacts the assembly of stellar particles into a bar and the halo response. initial conditions correspond to a marginally unstable disc according to commonly used disc stability criteria, and are evolved for the equivalent of about 150 disc dynamical times ( 10gyr ). an extensive convergence study ensures accurate modelling of the bar formation process. live haloes lead to the formation of a strong bar, but the same disc remains unbarred when evolved in a static halo. neither seeded disc instabilities, nor longer ( 60gyr ) simulations result in the formation of a bar when the halo is static. when the live halo is replaced with a static analogue at later times the previously robust bar slowly dissipates, suggesting : ( 1 ) the co - evolution of the disc and halo is critical for the assembly and long - term survival of bars in marginally unstable discs ; and ( 2 ) global disc stability criteria must be modified for discs in the presence of live haloes. in our live halo runs, a " dark bar " grows synchronously with the stellar bar. processes that inhibit the transfer of angular momentum between the halo and disc may stabilise a galaxy against bar formation, and can lead to the dissolution of the bar itself. this raises further questions about the puzzling stability of observed discs that are marginally unstable, but unbarred. | arxiv:2408.03375 |
in this article a complete set of invariants for ordinary quartic curves in characteristic 2 is computed. | arxiv:math/0405052 |
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