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optimizing amino - acid mutations has been a most challenging task in modern bio - industrial enzyme designing. it is well known that many successful designs often hinge on extensive correlations among mutations at different sites within the enzyme, however, the underpinning mechanism for these correlations is far from clear. here, we present a topology - based model to quantitively characterize correlation effects between mutations. the method is based on the molecular dynamic simulations and the amino - acid network clique analysis that simply examines if two single mutation sites belong to some 3 - clique. we analyzed 13 dual mutations of t4 phage lysozyme and found that the clique - based model successfully distinguishes highly correlated or non - additive double - site mutations from those with less correlation or additive mutations. we also applied the model to the protein eglin c whose topology is significantly distinct from that of t4 phage lysozyme, and found that the model can, to some extension, still identify non - additive mutations from additive ones. our calculations showed that mutation correlation effects may heavily depend on topology relationship among mutation sites, which can be quantitatively characterized using amino - acid network k - cliques. we also showed that double - site mutation correlations can be significantly altered by exerting a third mutation, indicating that more detailed physico - chemistry interactions might be considered with the network model for better understanding of the elusive mutation - correlation principle. | arxiv:1804.05175 |
we study the thermal conductivity in disordered $ s $ - wave superconductors. expanding on previous works for normal metals, we develop a formalism that tackles particle diffusion as well as the weak localization ( wl ) and weak anti - localization ( wal ) effects. using a green ' s functions diagrammatic technique, which takes into account the superconducting nature of the system by working in nambu space, we identify the system ' s low - energy modes, the diffuson and the cooperon. the time scales that characterize the diffusive regime are energy dependent ; this is in contrast with the the normal state, where the relevant time scale is the mean free time $ \ tau _ e $, independent of energy. the energy dependence introduces a novel energy scale $ \ varepsilon _ * $, which in disordered superconductors ( $ \ tau _ e \ delta \ ll 1 $, with $ \ delta $ the gap ) is given by $ \ varepsilon _ * = \ sqrt { \ delta / \ tau _ e } $. from the diffusive behavior of the low - energy modes, we obtain the wl correction to the thermal conductivity. we give explicitly expressions in two dimensions. we determine the regimes in which the correction depends explicitly on $ \ varepsilon _ * $ and propose an optimal regime to verify our results in an experiment. | arxiv:2002.05590 |
annotation of discourse relations is a known difficult task, especially for non - expert annotators. in this paper, we investigate novice annotators ' uncertainty on the annotation of discourse relations on spoken conversational data. we find that dialogue context ( single turn, pair of turns within speaker, and pair of turns across speakers ) is a significant predictor of confidence scores. we compute distributed representations of discourse relations from co - occurrence statistics that incorporate information about confidence scores and dialogue context. we perform a hierarchical clustering analysis using these representations and show that weighting discourse relation representations with information about confidence and dialogue context coherently models our annotators ' uncertainty about discourse relation labels. | arxiv:2308.07179 |
in the quest to realize a quantum spin liquid ( qsl ), magnetic long - range order is hardly welcome. yet it can offer deep insights into a complex world of strong correlations and fluctuations. much hope was placed in the cubic pyrochlore yb $ _ 2 $ ti $ _ 2 $ o $ _ 7 $ as a putative u ( 1 ) qsl but a new class of ultra - pure single crystals make it abundantly clear the stoichiometric compound is a ferromagnet. here we present a detailed experimental and theoretical study of the corresponding field - temperature phase diagram. we find it to be richly anisotropic with a critical endpoint for $ \ vec { b } \, \ parallel \, \ langle 100 \ rangle $, while field parallel to $ \ langle 110 \ rangle $ and $ \ langle 111 \ rangle $ enhances the critical temperature by up to a factor of two and shifts the onset of the field - polarized state to finite fields. landau theory shows that yb $ _ 2 $ ti $ _ 2 $ o $ _ 7 $ in some ways is remarkably similar to pure iron. however, it also pinpoints anomalies that cannot be accounted for at the classical mean - field level including a dramatic enhancement of $ t _ { \ mathrm { c } } $ and reentrant phase boundary by fields with a component transverse to the easy axes, as well as the anisotropy of the upper critical field in the quantum limit. | arxiv:1912.11058 |
we analyze the stellar initial mass functions ( imf ) of a large sample of early type galaxies ( etgs ) provided by manga. the large number of ifu spectra of individual galaxies provide high signal - to - noise composite spectra that are essential for constraining imf and to investigate possible radial gradients of the imf within individual galaxies. the large sample of etgs also make it possible to study how the imf shape depends on various properties of galaxies. we adopt a novel approach to study imf variations in etgs, use bayesian inferences based on full spectrum fitting. the bayesian method provides a statistically rigorous way to explore potential degeneracy in spectrum fitting, and to distinguish different imf models with bayesian evidence. we find that the imf slope depends systematically on galaxy velocity dispersion, in that galaxies of higher velocity dispersion prefer a more bottom - heavy imf, but the dependence is almost entirely due to the change of metallicity, $ z $, with velocity dispersion. the imf shape also depends on stellar age, $ a $, but the dependence is completely degenerate with that on metallicity through a combination $ az ^ { - 1. 42 } $. using independent age and metallicity estimates we find that the imf variation is produced by metallicity instead of age. the imf near the centers of massive etgs appears more bottom - heavy than that in the outer parts, while a weak opposite trend is seen for low - mass etgs. uncertainties produced by star formation history, dust extinction, $ \ alpha $ - element abundance enhancement and noise in the spectra are tested. | arxiv:1811.09799 |
a stochastic gravitational - wave background ( sgwb ) is expected to arise from the superposition of many independent and unresolved gravitational - wave signals, of either cosmological or astrophysical origin. some cosmological models ( characterized, for instance, by a pseudo - scalar inflaton, or by some modification of gravity ) break parity, leading to a polarized sgwb. we present a new technique to measure this parity violation, which we then apply to the recent results from ligo to produce the first upper limit on parity violation in the sgwb, assuming a generic power - law sgwb spectrum across the ligo sensitive frequency region. we also estimate sensitivity to parity violation of the future generations of gravitational - wave detectors, both for a power - law spectrum and for a model of axion inflation. this technique offers a new way of differentiating between the cosmological and astrophysical sources of the isotropic sgwb, as astrophysical sources are not expected to produce a polarized sgwb. | arxiv:1212.4165 |
in this work, we study the thermodynamics of a two - level system ( qubit ) embedded in a finite - temperature structured - bath under periodical measurements. the system under measurements will reach a quasi - steady state, whose effective temperature can be maintained lower than that of the surrounding environment. to study the influence of the environmental oscillators from different regimes of frequency on the qubit, the spectrum of the bath consisting of a large number of bosonic harmonic oscillators can be approximately divided into three parts according to their effects of cooling or heating. due to the spectral analysis over the structured - bath based on the non - markovian master equation beyond the rotating - wave approximation, we propose a sufficient cooling condition for the bath in the context of quantum non - selective measurement. it is consisted of two items : ( i ) the logarithmic derivative of the spectrum around the system transition frequency is large enough, at least larger than one half of the inverse temperature of the bath ; ( ii ) the spectrum should have a sharp high - frequency cutoff that is not far - detuning from the system transition frequency. from this condition, we find that two popular types of spectra, i. e., the modified lorentzian models and the super - ohmic models, are available environments for cooling the open quantum system. | arxiv:1901.09667 |
we study the dynamics of clusters of active brownian disks generated by motility - induced phase separation, by applying an algorithm that we devised to track cluster trajectories. we identify an aggregation mechanism that goes beyond ostwald ripening but also yields $ z = 3 $. active clusters of mass $ m $ self - propel with enhanced diffusivity $ d \ sim $ pe $ ^ 2 / \ sqrt { m } $. their fast motion drives aggregation into large fractal structures, which are patchworks of diverse hexatic orders, and coexist with regular, orientationally uniform, smaller ones. to bring out the impact of activity, we perform a comparative study of a passive system that evidences major differences with the active case. | arxiv:2211.12361 |
we introduce the concept of tied links in the solid torus, which generalize naturally the concept of tied links in $ s ^ 3 $ previously introduced by aicardi and juyumaya. we also define an invariant of these tied links by using skein relations, and subsequently we recover this invariant by using jones ' method over the bt - algebra of type $ \ mathtt { b } $ and the markov trace defined on this. | arxiv:1910.10778 |
a method for extracting finite - dimensional hamiltonian systems from a class of 2 + 1 hamiltonian mean field theories is presented. these theories possess noncanonical poisson brackets, which normally resist hamiltonian truncation, but a process of beatification by coordinate transformation near a reference state is described in order to perturbatively overcome this difficulty. two examples of four - wave truncation of euler ' s equation for scalar vortex dynamics are given and compared : one a direct non - hamiltonian truncation of the equations of motion, the other obtained by beatifying the poisson bracket and then truncating. | arxiv:1509.09247 |
this paper derives a discrete dual problem for a prototypical hybrid high - order method for convex minimization problems. the discrete primal and dual problem satisfy a weak convex duality that leads to a priori error estimates with convergence rates under additional smoothness assumptions. this duality holds for general polyhedral meshes and arbitrary polynomial degrees of the discretization. a novel postprocessing is proposed and allows for a ~ posteriori error estimates on regular triangulations into simplices using primal - dual techniques. this motivates an adaptive mesh - refining algorithm, which performs superiorly compared to uniform mesh refinements. | arxiv:2308.03223 |
the increasing use of heterogeneous embedded systems with multi - core cpus and graphics processing units ( gpus ) presents important challenges in effectively exploiting pipeline, task and data - level parallelism to meet throughput requirements of digital signal processing ( dsp ) applications. moreover, in the presence of system - level memory constraints, hand optimization of code to satisfy these requirements is inefficient and error - prone, and can therefore, greatly slow down development time or result in highly underutilized processing resources. in this paper, we present vectorization and scheduling methods to effectively exploit multiple forms of parallelism for throughput optimization on hybrid cpu - gpu platforms, while conforming to system - level memory constraints. the methods operate on synchronous dataflow representations, which are widely used in the design of embedded systems for signal and information processing. we show that our novel methods can significantly improve system throughput compared to previous vectorization and scheduling approaches under the same memory constraints. in addition, we present a practical case - study of applying our methods to significantly improve the throughput of an orthogonal frequency division multiplexing ( ofdm ) receiver system for wireless communications. | arxiv:1711.11154 |
sound is assumed to be the primary modality of communication among marine mammal species. analyzing acoustic recordings helps to understand the function of the acoustic signals as well as the possible impact of anthropogenic noise on acoustic behavior. motivated by a dataset from a network of hydrophones in cape cod bay, massachusetts, utilizing automatically detected calls in recordings, we study the communication process of the endangered north atlantic right whale. for right whales an " up - call " is known as a contact call, and ensuing counter - calling between individuals is presumed to facilitate group cohesion. we present novel spatiotemporal excitement modeling consisting of a background process and a counter - call process. the background process intensity incorporates the influences of diel patterns and ambient noise on occurrence. the counter - call intensity captures potential excitement, that calling elicits calling behavior. call incidence is found to be clustered in space and time ; a call seems to excite more calls nearer to it in time and space. we find evidence that whales make more calls during twilight hours, respond to other whales nearby, and are likely to remain quiet in the presence of increased ambient noise. | arxiv:2404.12583 |
collaborative perception is essential for networks of agents with limited sensing capabilities, enabling them to work together by exchanging information to achieve a robust and comprehensive understanding of their environment. however, localization inaccuracies often lead to significant spatial message displacement, which undermines the effectiveness of these collaborative efforts. to tackle this challenge, we introduce feakm, a novel method that employs feature - level keypoints matching to effectively correct pose discrepancies among collaborating agents. our approach begins by utilizing a confidence map to identify and extract salient points from intermediate feature representations, allowing for the computation of their descriptors. this step ensures that the system can focus on the most relevant information, enhancing the matching process. we then implement a target - matching strategy that generates an assignment matrix, correlating the keypoints identified by different agents. this is critical for establishing accurate correspondences, which are essential for effective collaboration. finally, we employ a fine - grained transformation matrix to synchronize the features of all agents and ascertain their relative statuses, ensuring coherent communication among them. our experimental results demonstrate that feakm significantly outperforms existing methods on the dair - v2x dataset, confirming its robustness even under severe noise conditions. the code and implementation details are available at https : / / github. com / uestchjw / feakm. | arxiv:2502.11003 |
explainable ai ( xai ) has gained significant attention for providing insights into the decision - making processes of deep learning models, particularly for image classification tasks through visual explanations visualized by saliency maps. despite their success, challenges remain due to the lack of annotated datasets and standardized evaluation pipelines. in this paper, we introduce saliency - bench, a novel benchmark suite designed to evaluate visual explanations generated by saliency methods across multiple datasets. we curated, constructed, and annotated eight datasets, each covering diverse tasks such as scene classification, cancer diagnosis, object classification, and action classification, with corresponding ground - truth explanations. the benchmark includes a standardized and unified evaluation pipeline for assessing faithfulness and alignment of the visual explanation, providing a holistic visual explanation performance assessment. we benchmark these eight datasets with widely used saliency methods on different image classifier architectures to evaluate explanation quality. additionally, we developed an easy - to - use api for automating the evaluation pipeline, from data accessing, and data loading, to result evaluation. the benchmark is available via our website : https : / / xaidataset. github. io. | arxiv:2310.08537 |
we report bose - einstein condensation of $ ^ { 88 } $ sr, which has a small, negative s - wave scattering length ( $ a _ { 88 } = - 2 $ \, $ a _ 0 $ ). we overcome the poor evaporative cooling characteristics of this isotope by sympathetic cooling with $ ^ { 87 } $ sr atoms. $ ^ { 87 } $ sr is effective in this role in spite of the fact that it is a fermion because of the large ground state degeneracy arising from a nuclear spin of $ i = 9 / 2 $, which reduces the impact of pauli blocking of collisions. we observe a limited number of atoms in the condensate ( $ n _ { max } \ approx 10 ^ 4 $ ) that is consistent with the value of $ a _ { 88 } $ and the optical dipole trap parameters. | arxiv:1003.3867 |
let g be a plane graph with exactly one triangle t and all other cycles of length at least 5, and let c be a facial cycle of g of length at most six. we prove that a 3 - coloring of c does not extend to a 3 - coloring of g if and only if c has length exactly six and there is a color x such that either g has an edge joining two vertices of c colored x, or t is disjoint from c and every vertex of t is adjacent to a vertex of c colored x. this is a lemma to be used in a future paper of this series. | arxiv:1010.2472 |
it follows from oseledec multiplicative ergodic theorem ( or kingmans subadditional ergodic theorem ) that the lyapunov - irregular set of points for which the oseledec averages of a given continuous cocycle diverge has zero measure with respect to any invariant probability measure. in strong contrast, for any dynamical system f with exponential specification property and a holder continuous matrix cocycle a, we show here that if there exist ergodic measures with different lyapunov spectrum, then the lyapunov - irregular set of a displays distributional chaos of type 1. | arxiv:1907.09400 |
grease ice is an agglomeration of disc - shaped ice crystals, named frazil ice, which forms in turbulent waters of the polar oceans and in rivers as well. it has been recognized that the properties of grease ice to damp surface gravity waves could be explained in terms of the effective viscosity of the ice slurry. this paper is devoted to the study of the dynamics of a suspension of disc - shaped particles in a gravity wave field. for dilute suspensions, depending on the strength and frequency of the external wave flow, two orientation regimes of the particles are predicted : a preferential orientation regime with the particles rotating in coherent fashion with the wave field, and a random orientation regime in which the particles oscillate around their initial orientation while diffusing under the effect of brownian motion. for both motion regimes, the effective viscosity has been derived as a function of the wave frequency, wave amplitude and aspect ratio of the particles. model predictions have been compared with wave attenuation data in frazil ice layers grown in wave tanks. | arxiv:physics/0402047 |
pedestrian route choice is a complex, situation - and population - dependent issue. in this contribution an example is presented, where pedestrians can choose among two seemingly similar alternatives. the choice ratio is not even close to being balanced, but almost all pedestrians choose the same alternative. a number of possible causes for this are given. | arxiv:1001.4047 |
quantum chaos is one of the distinctive features of the sachdev - ye - kitaev ( syk ) model, $ n $ majorana fermions in $ 0 + 1 $ dimensions with infinite - range two - body interactions, which is attracting a lot of interest as a toy model for holography. here we show analytically and numerically that a generalized syk model with an additional one - body infinite - range random interaction, which is a relevant perturbation in the infrared, is still quantum chaotic and retains most of its holographic features for a fixed value of the perturbation and sufficiently high temperature. however a chaotic - integrable transition, characterized by the vanishing of the lyapunov exponent and spectral correlations given by poisson statistics, occurs at a temperature that depends on the strength of the perturbation. we speculate about the gravity dual of this transition. | arxiv:1707.02197 |
computer programming was once thought of as a skill required only by professional software developers. but today, given the ubiquitous nature of computation and data science it is quickly becoming necessary for all scientists and engineers to have at least a basic knowledge of how to program. teaching how to program, particularly to those students with little or no computing background, is well - known to be a difficult task. however, there is also a wealth of evidence - based teaching practices for teaching programming skills which can be applied to greatly improve learning outcomes and the student experience. adopting these practices naturally gives rise to greater learning efficiency - this is critical if programming is to be integrated into an already busy geoscience curriculum. this paper considers an undergraduate computer programming course, run during the last 5 years in the department of earth science and engineering at imperial college london. the teaching methodologies that were used each year are discussed alongside the challenges that were encountered, and how the methodologies affected student performance. anonymised student marks and feedback are used to highlight this, and also how the adjustments made to the course eventually resulted in a highly effective learning environment. | arxiv:1505.05425 |
scientific misconduct is the violation of the standard codes of scholarly conduct and ethical behavior in the publication of professional scientific research. it is the violation of scientific integrity : violation of the scientific method and of research ethics in science, including in the design, conduct, and reporting of research. a lancet review on handling of scientific misconduct in scandinavian countries provides the following sample definitions, reproduced in the cope report 1999 : danish definition : " intention or gross negligence leading to fabrication of the scientific message or a false credit or emphasis given to a scientist " swedish definition : " intention [ al ] distortion of the research process by fabrication of data, text, hypothesis, or methods from another researcher ' s manuscript form or publication ; or distortion of the research process in other ways. " the consequences of scientific misconduct can be damaging for perpetrators and journal audiences and for any individual who exposes it. in addition there are public health implications attached to the promotion of medical or other interventions based on false or fabricated research findings. scientific misconduct can result in loss of public trust in the integrity of science. three percent of the 3, 475 research institutions that report to the us department of health and human services ' office of research integrity indicate some form of scientific misconduct. however the ori will only investigate allegations of impropriety where research was funded by federal grants. they routinely monitor such research publications for red flags and their investigation is subject to a statute of limitations. other private organizations like the committee of medical journal editors ( coje ) can only police their own members. = = motivation = = according to david goodstein of caltech, there are motivators for scientists to commit misconduct, which are briefly summarised here. career pressure science is still a very strongly career - driven discipline. scientists depend on a good reputation to receive ongoing support and funding, and a good reputation relies largely on the publication of high - profile scientific papers. hence, there is a strong imperative to " publish or perish ". this pressure is stronger in some research settings than others, contributing to the impression that misconduct may be more prevalent in some parts of the world than others. this may motivate desperate ( or fame - hungry ) scientists to fabricate results. ease of fabrication in many scientific fields, results are often difficult to reproduce accurately, being obscured by noise, artifacts, and other extraneous data. that means that even if a scientist does falsify data, they can expect to get away with it – or at least claim innocence if their results conflict with others in the same field. there | https://en.wikipedia.org/wiki/Scientific_misconduct |
the vertex - edge marking game is played between two players on a graph, $ g = ( v, e ) $, with one player marking vertices and the other marking edges. the players want to minimize / maximize, respectively, the number of marked edges incident to an unmarked vertex. the vertex - edge coloring number for $ g $ is the maximum score achievable with perfect play. bre \ v { s } ar et al., [ 4 ], give an upper bound of $ 5 $ for the vertex - edge coloring number for finite planar graphs. it is not known whether the bound is tight. in this paper, in response to questions in [ 4 ], we show that the vertex - edge coloring number for the infinite regular triangularization of the plane is 4. we also give two general techniques that allow us to calculate the vertex - edge coloring number in many related triangularizations of the plane. | arxiv:2201.03633 |
the critical buckling characteristics of hydrostatically pressurized complete spherical shells filled with an elastic medium are demonstrated. a model based on small deflection thin shell theory, the equations of which are solved in conjunction with variational principles, is presented. in the exact formulation, axisymmetric and inextensional assumptions are not used initially and the elastic medium is modelled as a winkler foundation, i. e., using uncoupled radial springs with a constant foundation modulus that is independent of wave numbers of shell buckling modes. simplified approximations based on a rayleigh - ritz approach are also introduced for critical buckling pressure and mode number with a considerable degree of accuracy. characteristic modal shapes are demonstrated for a wide range of material and geometric parameters. a phase diagram is established to obtain the requisite thickness to radius, and stiffness ratios for a desired mode profile. the present exact formulation can be readily extended to apply to more general cases of non - axisymmetric buckling problems. | arxiv:1103.2179 |
the astrophysical multimessenger observatory network ( amon ) has been built with the purpose of enabling near real - time coincidence searches using data from leading multimessenger observatories and astronomical facilities. its mission is to evoke discovery of multimessenger astrophysical sources, exploit these sources for purposes of astrophysics and fundamental physics, and explore multimessenger datasets for evidence of multimessenger source population amon aims to promote the advancement of multimessenger astrophysics by allowing its participants to study the most energetic phenomena in the universe and to help answer some of the outstanding enigmas in astrophysics, fundamental physics, and cosmology. the main strength of amon is its ability to combine and analyze sub - threshold data from different facilities. such data cannot generally be used stand - alone to identify astrophysical sources. the analyses algorithms used by amon can identify statistically significant coincidence candidates of multimessenger events, leading to the distribution of amon alerts used by partner observatories for real - time follow - up that may identify and, potentially, confirm the reality of the multimessenger association. we present the science motivation, partner observatories, implementation and summary of the current status of the amon project. | arxiv:1903.08714 |
we study perturbations of massive and massless vector fields on a schwarzschild black - hole background, including a non - minimal coupling between the vector field and the curvature. the coupling is given by the horndeski vector - tensor operator, which we show to be unique, also when the field is massive, provided that the vector has a vanishing background value. we determine the quasi - normal mode spectrum of the vector field, focusing on the fundamental mode of monopolar and dipolar perturbations of both even and odd parity, as a function of the mass of the field and the coupling constant controlling the non - minimal interaction. in the massless case, we also provide results for the first two overtones, showing in particular that the isospectrality between even and odd modes is broken by the non - minimal gravitational coupling. we also consider solutions to the mode equations corresponding to quasi - bound states and static configurations. our results for quasi - bound states provide strong evidence for the stability of the spectrum, indicating the impossibility of a vectorization mechanism within our set - up. for static solutions, we analytically and numerically derive results for the electromagnetic susceptibilities ( the spin - 1 analogs of the tidal love numbers ), which we show to be non - zero in the presence of the non - minimal coupling. | arxiv:2202.07131 |
upper main sequence stars, white dwarfs and neutron stars are known to possess stable, large - scale magnetic fields. numerical works have confirmed that stable mhd equilibria can exist in non - barotropic, stably stratified stars. on the other hand, it is unclear whether stable equilibria are possible in barotropic stars, although the existing evidence suggests that they are all unstable. this work aims to construct barotropic equilibria in order to study their properties, as a first step to test their stability. we have assumed that the star is a perfectly conducting, axially symmetric fluid, allowing for both poloidal and toroidal components of the magnetic field. in addition, we made the astrophysically justified assumption that the magnetic force has a negligible influence on the fluid structure, in which case the equilibrium is governed by the grad - shafranov equation, involving two arbitrary functions of the poloidal flux. we built a numerical code to solve this equation, allowing for an arbitrary prescription for these functions. taking particularly simple, but physically reasonable choices for these functions with a couple of adjustable parameters, all of the equilibria found present only a small ( $ \ lesssim 10 \ % { } $ ) fraction of the magnetic energy stored in the toroidal component, confirming previous results. we developed an analytical model in order to study in more detail the behavior of the magnetic energy over the full range of parameters. the model confirms that the toroidal fraction of the energy and the ratio of toroidal to poloidal flux are bounded from above for the whole range of parameters. | arxiv:1412.1524 |
in this thesis we use the language of sheaf theory in order to develop a deeper understanding of some of the fundamental differences - such as entanglement, contextuality and non - locality - between quantum and classical physics. we first present, based on the work of abramsky and brandenburger, how sheaves, defined over certain posets of physically meaningful contexts, give a natural setting for capturing and analysing important quantum mechanical phenomena, such as quantum non - locality and contextuality. we also describe how this setting naturally leads to a three level hierarchy of quantum contextuality : weak contextuality, logical non - locality and strong contextuality. we use these insights in order to classify certain multipartite entangled states. almost all of these turn out to be at least logically non - local, and a number of them even turn out to be strongly contextual. we further extend this result by showing that all n - qubit entangled states, with the exception of tensor products of single - qubit and bipartite maximally - entangled states, are logically non - local. our proof is constructive : given any n - qubit state, we present an algorithm which produces n + 2 local observables witnessing its logical non - locality. in the second half of the thesis we use the same basic principle of sheaves defined over physically meaningful contexts, in order to present an elegant mathematical language, known under the name of the topos approach, in which many quantum mechanical concepts, such as states, observables, and propositions about these, can be expressed. we then show that the language of the topos approach is as least as expressive, in logical terms, as traditional quantum logic. finally, starting from a topos - theoretic perspective, we develop the construction of contextual entropy in order to give a unified treatment of classical and quantum notions of information theoretic entropy. | arxiv:1510.02561 |
the mu2e experiment at fermilab is being designed to study the coherent neutrino - less conversion of a negative muon into an electron in the field of a nucleus. this process has an extremely low probability in the standard model, and its observation would provide unambiguous evidence for beyond the standard model physics. the mu2e design aims to reach a single - event - sensitivity of about $ 2. 5 \ times 10 ^ { - 17 } $ and will probe effective new physics mass scales in the 103 - 104 tev range, well beyond the reach of the lhc. this work will examine the maximum beam power that can be tolerated for beam energies in the 0. 5 - 8 gev range. this has implications for how the sensitivity might be further improved with a second generation experiment using an upgraded proton beam from the pip - ii project, which will be capable of providing mw beams to fermilab experiments later in the next decade. | arxiv:1612.08931 |
we investigate radio - mode agn activity among post - starburst galaxies from the sloan digital sky survey to determine whether agn feedback may be responsible for the cessation of star formation. based on radio morphology and radio - loudness from the first and nvss data, we separate objects with radio activity due to an agn from ongoing residual star formation. of 513 sdss galaxies with strong a - star spectra, 12 objects have 21 - cm flux density above 1 mjy. these galaxies do not show optical agn emission lines. considering that the lifetime of radio emission is much shorter than the typical time - scale of the spectroscopic features of post - starburst galaxies, we conclude that the radio - emitting agn activity in these objects was triggered after the end of the recent starburst, and thus cannot be an important feedback process to explain the post - starburst phase. the radio luminosities show a positive correlation with total galaxy stellar mass, but not with the mass of recently formed stars. thus the mechanical power of agn feedback derived from the radio luminosity is related to old stellar populations dominating the stellar mass, which in turn are related to the masses of central supermassive black holes. | arxiv:1008.2774 |
let l be the manifold of all ( unparametrized ) oriented lines of r ^ 3. we study the controllability of the control system in l given by the condition that a curve in l describes at each instant, at the infinitesimal level, an helicoid with prescribed angular speed alpha. actually, we pose the analogous more general problem by means of a control system on the manifold g _ kappa of all the oriented complete geodesics of the three dimensional space form of curvature kappa : r ^ 3 for kappa = 0, s ^ 3 for kappa = 1 and hyperbolic 3 - space for kappa = - 1. we obtain that the system is controllable if and only if alpha ^ 2 not equal kappa. in the spherical case with alpha = ( + / - ) 1, an admissible curve remains in the set of fibers of a fixed hopf fibration of s ^ 3. we also address and solve a sort of kendall ' s ( aka oxford ) problem in this setting : finding the minimum number of switches of piecewise continuous curves joininig two arbitrary oriented lines, with pieces in some distinguished families of admissible curves. | arxiv:2208.13010 |
we prove that if $ g = g _ 1 \ times \ dots \ times g _ n $ acts essentially, properly and cocompactly on a cat ( 0 ) cube complex x, then the cube complex splits as a product. we use this theorem to give various examples of groups for which the minimal dimension of a cube complex the group acts on is strictly larger than that of the minimal dimension of a cat ( 0 ) space upon which the group acts. | arxiv:1912.05055 |
load balancing plays a crucial role in many large scale systems. several different load balancing principles have been proposed in the literature, such as join - shortest - queue ( jsq ) and its variations, or join - below - threshold. we provide a high level mathematical framework to examine heterogeneous server clusters in the mean - field limit as the system load and the number of servers scale proportionally. we aim to identify both the transient mean - field limit and the stationary mean - field limit for various choices of load balancing principles, compute relevant performance measures such as the distribution and mean of the system time of jobs, and conduct a comparison from a performance point of view. | arxiv:2307.04360 |
a search for the pair - production of heavy leptons ( $ n ^ 0, l ^ { \ pm } $ ) predicted by the type - iii seesaw theory formulated to explain the origin of small neutrino masses is presented. the decay channels $ n ^ 0 \ rightarrow w ^ { \ pm } l ^ { \ mp } $ ( $ \ ell = e, \ mu, \ tau $ ) and $ l ^ { \ pm } \ rightarrow w ^ \ pm \ nu $ ( $ \ nu = \ nu _ e, \ nu _ \ mu, \ nu _ \ tau $ ) are considered. the analysis is performed using the final state that contains two leptons ( electrons or muons ), two jets from a hadronically decaying $ w $ boson, and large missing transverse momentum. the data used in the measurement correspond to an integrated luminosity of $ 20. 3 \, fb ^ { - 1 } $ of $ pp $ collisions at $ \ sqrt { s } = 8 $ tev collected by the atlas detector at the lhc. no evidence of heavy lepton pair - production is observed. heavy leptons with masses below 325 - - 540 gev are excluded at the 95 % confidence level, depending on the theoretical scenario considered. | arxiv:1506.01839 |
we study metastability and nucleation in a kinetic two - dimensional ising model which is driven out of equilibrium by a small random perturbation of the usual dynamics at temperature t. we show that, at a mesoscopic / cluster level, a nonequilibrium potential describes in a simple way metastable states and their decay. we thus predict noise - enhanced stability of the metastable phase and resonant propagation of domain walls at low t. this follows from the nonlinear interplay between thermal and nonequilibrium fluctuations, which induces reentrant behavior of the surface tension as a function of t. our results, which are confirmed by monte carlo simulations, can be also understood in terms of a langevin equation with competing additive and multiplicative noises. | arxiv:cond-mat/0604556 |
we describe the strong dual space $ ( { \ mathcal o } ( d ) ) ^ * $ for the space $ { \ mathcal o } ( d ) $ of holomorphic functions of several complex variables over a bounded lipschitz domain $ d $ with connected boundary $ \ partial d $ ( as usual, $ { \ mathcal o } ( d ) $ is endowed with the topology of the uniform convergence on the compact subsets of $ d $ ). we identify the dual space with a closed subspace of the space of harmonic functions on the closed set $ { \ mathbb c } ^ n \ setminus d $, $ n > 1 $, with elements vanishing at the infinity and satisfying the tangential cauchy - riemann equations on $ \ partial d $. in particular, we extend in a way the classical grothendieck - k { \ " o } the - sebasti \ ~ { a } o e silva duality for the space of holomorphic functions of one complex variable to the multi - dimensional situation. we use the bochner - martinelli kernel $ { \ mathfrak u } _ n $ in $ { \ mathbb c } ^ n $, $ n > 1 $, instead of the cauchy kernel over the complex plane $ { \ mathbb c } $ and we prove that the duality holds true if and only if the space $ { \ mathcal o } ( d ) \ cap h ^ 1 ( d ) $ of the sobolev holomorphic functions over $ d $ is dense in $ { \ mathcal o } ( d ) $. | arxiv:2303.07656 |
in this work we propose a new orbital architecture for the two proposed circumbinary planets around the polar eclipsing binary hu aquarii. we base the new two - planet, light - travel time model on the result of a monte carlo simulation driving a least - squares levenberg - marquardt minimisation algorithm on the observed eclipse egress times. our best - fitting model with $ \ chi _ { r } ^ 2 = 1. 43 $ resulted in high final eccentricities for the two companions leading to an unstable orbital configuration. from a large ensemble of initial guesses we examined the distribution of final eccentricities and semi - major axes for different $ \ chi _ { r } ^ 2 $ parameter intervals and encountered qualitatively a second population of best - fitting parameters. the main characteristic of this population is described by low - eccentric orbits favouring long - term orbital stability of the system. we present our best - fitting model candidate for the proposed two - planet system and demonstrate orbital stability over one million years using numerical integrations. | arxiv:1112.0066 |
there are many results on the minimum distance of a cyclic code of the form that if a certain set t is a subset of the defining set of the code, then the minimum distance of the code is greater than some integer t. this includes the bch, hartmann - tzeng, roos, and shift bounds and generalizations of these. in this paper we define certain projective varieties v ( t, t ) whose properties determine whether, if t is in the defining set, the code has minimum distance exceeding t. thus our attention shifts to the study of these varieties. by investigating them using class field theory and arithmetical geometry, we will prove various new bounds. it is interesting, however, to note that there are cases that existing methods handle, that our methods do not, and vice versa. we end with a number of conjectures. | arxiv:math/0009257 |
we introduce a new type of binary magnonic crystal, where ni $ _ { 80 } $ fe $ _ { 20 } $ nanodots of two different sizes are diagonally connected forming a unit and those units are arranged in a square lattice. the magnetization dynamics of the sample is measured by using time - resolved magneto - optical kerr effect microscope with varying magnitude and in - plane orientation ( $ \ phi $ ) of the bias magnetic field. interestingly, at $ \ phi = 0 ^ { \ circ } $, the spin - wave mode profiles show frequency selective spatial localization of spin - wave power within the array. with the variation of $ \ phi $ in the range $ 0 ^ { \ circ } < \ phi \ leq 45 ^ { \ circ } $, we observe band narrowing due to localized to extended spin - wave mode conversion. upon further increase of $ \ phi $, the spin - wave modes slowly lose the extended nature and become fully localized again at 90 $ ^ { \ circ } $. we have extensively demonstrated the role of magnetostatic stray field distribution on the rotational symmetries obtained for the spin - wave modes. from micromagnetic simulations, we find that the dipole - exchange coupling between the nano - dots leads to remarkable modifications of the spin - wave mode profiles when compared with arrays of individual small and large dots. numerically, we also show that the physical connection between the nano - dots provides more control points over the spin - wave propagation in the lattice at different orientations of bias magnetic field. this new type of binary magnonic crystal may find potential applications in magnonic devices such as spin - wave waveguide, filter, coupler, and other on - chip microwave communication devices. | arxiv:1901.09325 |
in order to gain a mechanistic understanding of how tinnitus emerges in the brain, we must build biologically plausible computational models that mimic both tinnitus development and perception, and test the tentative models with brain and behavioral experiments. with a special focus on tinnitus research, we review recent work at the intersection of artificial intelligence, psychology and neuroscience, indicating a new research agenda that follows the idea that experiments will yield theoretical insight only when employed to test brain - computational models. this view challenges the popular belief, that tinnitus research is primarily data limited, and that producing large, multi - modal, and complex datasets, analyzed with advanced data analysis algorithms, will finally lead to fundamental insights into how tinnitus emerges. however, there is converging evidence that although modern technologies allow assessing neural activity in unprecedentedly rich ways in both, animals and humans, empirical testing one verbally defined hypothesis about tinnitus after another, will never lead to a mechanistic understanding. instead, hypothesis testing needs to be complemented with the construction of computational models that generate verifiable predictions. we argue, that even though, contemporary artificial intelligence and machine learning approaches largely lack biological plausibility, the models to be constructed will have to draw on concepts from these fields, since they have already proven to do well in modeling brain function. nevertheless, biological fidelity will have to be increased successively, leading to ever better and fine - grained models, allowing at the end for even testing possible treatment strategies in silico, before application in animal or patient studies. | arxiv:2010.01914 |
the hot jupiter hd 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known ( v - mag = 7. 65 ; k - mag = 6. 308 ) and has a large planet - to - star contrast ratio. hd 209458b is predicted to be in synchronous rotation about its host star with a hot spot that is shifted eastward of the substellar point by superrotating equatorial winds. here we present the first full - orbit observations of hd 209458b, in which its 4. 5 $ \ mu $ m emission was recorded with $ spitzer $ / irac. our study revises the previous 4. 5 $ \ mu $ m measurement of hd 209458b ' s secondary eclipse emission downward by $ \ sim $ 35 % to $ 0. 1391 % ^ { + 0. 0072 % } _ { - 0. 0069 % } $, changing our interpretation of the properties of its dayside atmosphere. we find that the hot spot on the planet ' s dayside is shifted eastward of the substellar point by $ 40. 9 ^ { \ circ } \ pm { 6. 0 ^ { \ circ } } $, in agreement with circulation models predicting equatorial superrotation. hd 209458b ' s dayside ( t $ _ { bright } $ = 1499 $ \ pm $ 15 k ) and nightside ( t $ _ { bright } $ = 972 $ \ pm $ 44 k ) emission indicates a day - to - night brightness temperature contrast smaller than that observed for more highly irradiated exoplanets, suggesting that the day - to - night temperature contrast may be partially a function of the incident stellar radiation. the observed phase curve shape deviates modestly from global circulation model predictions potentially due to disequilibrium chemistry or deficiencies in the current hot ch $ _ { 4 } $ line lists used in these models. observations of the phase curve at additional wavelengths are needed in order to determine the possible presence and spatial extent of a dayside temperature inversion, as well as to improve our overall understanding of this planet ' s atmospheric circulation. | arxiv:1405.5923 |
in this paper we present a novel inference methodology to perform bayesian inference for spatiotemporal cox processes where the intensity function depends on a multivariate gaussian process. dynamic gaussian processes are introduced to allow for evolution of the intensity function over discrete time. the novelty of the method lies on the fact that no discretisation error is involved despite the non - tractability of the likelihood function and infinite dimensionality of the problem. the method is based on a markov chain monte carlo algorithm that samples from the joint posterior distribution of the parameters and latent variables of the model. the models are defined in a general and flexible way but they are amenable to direct sampling from the relevant distributions, due to careful characterisation of its components. the models also allow for the inclusion of regression covariates and / or temporal components to explain the variability of the intensity function. these components may be subject to relevant interaction with space and / or time. real and simulated examples illustrate the methodology, followed by concluding remarks. | arxiv:1504.06638 |
quantum computing offers a promising route for tackling hard optimization problems by encoding them as ising models. however, sparse qubit connectivity requires the use of minor - embedding, mapping logical qubits onto chains of physical qubits, which necessitates stronger intra - chain coupling to maintain consistency. this elevated coupling strength forces a rescaling of the hamiltonian due to hardware - imposed limits on the allowable ranges of coupling strengths, reducing the energy gaps between competing states, thus, degrading the solver ' s performance. here, we introduce a theoretical model that quantifies this degradation. we show that as the connectivity degree increases, the effective temperature rises as a polynomial function, resulting in a success probability that decays exponentially. our analysis further establishes worst - case bounds on the energy scale degradation based on the inverse conductance of chain subgraphs, revealing two most important drivers of chain strength, \ textit { chain volume } and \ textit { chain connectivity }. our findings indicate that achieving quantum advantage is inherently challenging. experiments on d - wave quantum annealers validate these findings, highlighting the need for hardware with improved connectivity and optimized scale - aware embedding algorithms. | arxiv:2503.08303 |
we analyze the effect of adding, removing, and moving basepoints on link floer homology. we prove that adding or removing basepoints via a procedure called quasi - stabilization is a natural operation on a certain version of link floer homology, which we call $ cfl _ { uv } ^ \ infty $. we consider the effect on the full link floer complex of moving basepoints, and develop a simple calculus for moving basepoints on the link floer complexes. we apply it to compute the effect of several diffeomorphisms corresponding to moving basepoints. using these techniques we prove a conjecture of sarkar about the map on the full link floer complex induced by a finger move along a link component. | arxiv:1604.04316 |
for a graph g, we construct two algebras, whose dimensions are both equal to the number of spanning trees of g. one of these algebras is the quotient of the polynomial ring modulo certain monomial ideal, while the other is the quotient of the polynomial ring modulo certain powers of linear forms. we describe the set of monomials that forms a linear basis in each of these two algebras. the basis elements correspond to g - parking functions that naturally came up in the abelian sandpile model. these ideals are instances of the general class of monotone monomial ideals and their deformations. we show that the hilbert series of a monotone monomial ideal is always bounded by the hilbert series of its deformation. then we define an even more general class of monomial ideals associated with posets and construct free resolutions for these ideals. in some cases these resolutions coincide with scarf resolutions. we prove several formulas for hilbert series of monotone monomial ideals and investigate when they are equal to hilbert series of deformations. in the appendix we discuss the sandpile model. | arxiv:math/0301110 |
the high computation complexity of nonlinear adaptive filtering algorithms poses significant challenges at the hardware implementation level. in order to tackle the computational complexity problem, this paper proposes a novel block - oriented functional link adaptive filter ( bo - flaf ) to model memoryless nonlinear systems. through theoretical complexity analysis, we show that the proposed hammerstein bo trigonometric flaf ( hbo - tflaf ) has 47 % lesser multiplications than the original tflaf for a filter order of 1024. moreover, the hbo - tflaf exhibits a faster convergence rate and achieved 3 - 5 db lesser steady - state mean square error ( mse ) compared to the original tflaf for a memoryless nonlinear system identification task. | arxiv:2310.10276 |
we propose a quantum algorithm to solve systems of nonlinear differential equations. using a quantum feature map encoding, we define functions as expectation values of parametrized quantum circuits. we use automatic differentiation to represent function derivatives in an analytical form as differentiable quantum circuits ( dqcs ), thus avoiding inaccurate finite difference procedures for calculating gradients. we describe a hybrid quantum - classical workflow where dqcs are trained to satisfy differential equations and specified boundary conditions. as a particular example setting, we show how this approach can implement a spectral method for solving differential equations in a high - dimensional feature space. from a technical perspective, we design a chebyshev quantum feature map that offers a powerful basis set of fitting polynomials and possesses rich expressivity. we simulate the algorithm to solve an instance of navier - stokes equations, and compute density, temperature and velocity profiles for the fluid flow in a convergent - divergent nozzle. | arxiv:2011.10395 |
in this article we consider the spectrum of a laplacian matrix, also known as the markov matrix, under the independence assumption. we assume that the entries have a variance profile. motivated by recent works on generalized wigner matrices we assume that variance profile gives rise to a sequence of graphons. under the assumption that these graphons converge, we show that the limiting spectral distribution of the scaled laplacian converge. we give an expression for the moments of the limiting measure in terms of graph homomorphisms. in some special cases we identify the limit explicitly. we also study the spectral norm and derive the order of the maximum eigenvalue. we show that our results cover laplacian of various random graphs include inhomogeneous erd \ h { o } s - r \ ' enyi random graph, sparse w - random graphs, stochastic block matrices and constrained random graphs. | arxiv:2011.07912 |
we study sequential coding of markov sources under an error propagation constraint. an encoder sequentially compresses a sequence of vector - sources that are spatially i. i. d. but temporally correlated according to a first - order markov process. the channel erases up to b packets in a single burst, but reveals all other packets to the destination. the destination is required to reproduce all the source - vectors instantaneously and in a lossless manner, except those sequences that occur in an error propagation window of length b + w following the start of the erasure burst. we define the rate - recovery function r ( b, w ) - the minimum achievable compression rate per source sample in this framework - and develop upper and lower bounds on this function. our upper bound is obtained using a random binning technique, whereas our lower bound is obtained by drawing connections to multi - terminal source coding. our upper and lower bounds coincide, yielding r ( b, w ), in some special cases. more generally, both the upper and lower bounds equal the rate for predictive coding plus a term that decreases as 1 / ( w + 1 ), thus establishing a scaling behaviour of the rate - recovery function. for a special class of semi - deterministic markov sources we propose a new optimal coding scheme : prospicient coding. an extension of this coding technique to gaussian sources is also developed. for the class of symmetric markov sources and memoryless encoders, we establish the optimality of random binning. when the destination is required to reproduce each source sequence with a fixed delay and when w = 0 we also establish the optimality of binning. | arxiv:1202.5259 |
motivated by the recent discoveries of binary black - hole mergers by the advanced laser interferometer gravitational - wave observatory ( advanced ligo ), we investigate the prospects of ground - based detectors to perform a spectroscopic analysis of signals emitted during the ringdown of the final kerr black - hole formed by a stellar mass binary black - hole merger. if we assume an optimistic rate of 240 gpc $ ^ { - 3 } $ yr $ ^ { - 1 } $, about 3 events per year can be measured by advanced ligo. further, upgrades to the existing ligo detectors will increase the odds of measuring multiple ringdown modes significantly. new ground - based facilities such as einstein telescope or cosmic explorer could measure multiple ringdown modes in about thousand events per year. we perform monte - carlo injections of $ 10 ^ { 6 } $ binary black - hole mergers in a search volume defined by a sphere of radius 1500 mpc centered at the detector, for various proposed ground - based detector models. we assume a uniform random distribution in component masses of the progenitor binaries, sky positions and orientations to investigate the fraction of the population that satisfy our criteria for detectability and resolvability of multiple ringdown modes. we investigate the detectability and resolvability of the sub - dominant modes $ l = m = 3 $, $ l = m = 4 $ and $ l = 2, m = 1 $. our results indicate that the modes with $ l = m = 3 $ and $ l = 2, m = 1 $ are the most promising candidates for sub - dominant mode measurability. we find that for stellar mass black - hole mergers, resolvability is not a limiting criteria for these modes. we emphasize that the measurability of the $ l = 2, m = 1 $ mode is not impeded by the resolvability criterion. | arxiv:1607.07845 |
path integral monte carlo simulation of the dipositronium " molecule " ps $ _ 2 $ reveals its surprising thermal instability. although, the binding energy is $ \ sim 0. 4 $ ev, due to the strong temperature dependence of its free energy ps $ _ 2 $ dissociates, or does not form, above $ \ sim 1000 $ k, except for high densities where a small fraction of molecules are in equilibrium with ps atoms. this prediction is consistent with the recently reported first observation of stable ps $ _ 2 $ molecules by cassidy & mills jr., nature { \ bf 449 }, 195 ( 07 ), and phys. rev. lett. { \ bf 100 }, 013401 ( 08 ) ; at temperatures below 1000 k. the relatively sharp transition from molecular to atomic equilibrium, that we find, remains to be experimentally verified. to shed light on the origin of the large entropy factor in free energy we analyze the nature of interatomic interactions of these strongly correlated quantum particles. the conventional diatomic potential curve is given by the van der waals interaction at large distances, but due to the correlations and high delocalization of constituent particles the concept of potential curve becomes ambiguous at short atomic distances. | arxiv:0812.4900 |
consider a text $ t [ 1.. n ] $ prefixed by a reference sequence $ r = t [ 1.. \ ell ] $. we show how, given $ r $ and the $ z ' $ - phrase relative lempel - ziv parse of $ t [ \ ell + 1.. n ] $ with respect to $ r $, we can build the lz77 parse of $ t $ in $ n \, \ mathrm { polylog } ( n ) $ time and $ o ( \ ell + z ' ) $ total space. | arxiv:2211.13254 |
double perovskite bi $ _ 2 $ fecro $ _ 6 $, related with bifeo $ _ 3 $, is very interesting because strong ferroelectricity and high magnetic curie temperature beyond room temperature are observed in it. however, existing density - functional - theory ( dft ) studies, using pseudo - potentials, produce metallic ground state under the local density approximation ( lda ) and need lda + u method to yield needed nonmetallic ground state, resulting in low magnetic curie temperature ( below 130 k ). here, we optimize its crystal structure and then investigate its electronic structure and magnetic and optical properties by combining the full - potential augmented plane wave method with monte carlo simulation. our optimized structure is a robust ferrimagnetic semiconductor. this nonmetallic phase is formed due to crystal field splitting and spin exchange splitting, in contrast to mott - hubbard states in previous dft studies. spin exchange constants and optical properties are calculated. our ab initio magnetic curie temperature is 450 k, much higher than previous dft - based value and consistent with experimental results. our study and analysis reveals that the main magnetic mechanism is an antiferromagnetic superexchange between fe and cr over the intermediate o atom. these results are useful to understanding such perovskite materials and exploring their potential applications. | arxiv:1210.5981 |
we present a theory of magnon - polaritons in quantum ising materials, and develop a formalism describing the coupling between light and matter as an ising system is tuned through its quantum critical point. the theory is applied to ising materials having multilevel single - site hamiltonians, in which multiple magnon modes are present, such as the insulating ising magnet lihof $ _ 4 $. we find that the magnon - photon coupling strengths may be tuned by the applied transverse field, with the coupling between the soft mode present in the quantum ising material and a photonic resonator mode diverging at the quantum critical point of the material. a fixed system of spins will not exhibit the diamagnetic response expected when light is coupled to mobile spins or atoms. without the diamagnetic response, one expects a divergent magnon - photon coupling strength to lead to a superradiant quantum phase transition. however, this neglects the effects of damping and decoherence present in any real system. we show that damping and decoherence may block the superradiant quantum phase transition, and lead to weak coupling between the soft magnon mode and the resonator mode. the results of the theory are applied to experimental data on the model system lihof $ _ 4 $ in a microwave resonator. | arxiv:2209.08674 |
by addressing a long - standing open problem, listed in a highly regarded collection of open questions in the field and described as a " worthwhile research project ", this note extends markov ' s theorem ( markoff, math. ann., 27 : 177 - 182, 1886 ) on the variation of zeros of orthogonal polynomials on the real line to the setting of multiple orthogonal polynomials on angelesco sets. the analysis reveals that the only distinction from the classical 1886 result lies in establishing sufficient conditions for a given $ \ mathcal { z } $ - matrix - - which, in the markov case, is the identity matrix - - to be an $ \ mathcal { m } $ - matrix. in contrast to most existing studies, which often present highly technical proofs for specific results, this note seeks to provide a simple proof of a general result without imposing restrictions on the weight functions ( such as their potential " classical " nature ), the number of intervals, or the structure of the partition. | arxiv:2502.04992 |
a comprehensive study of the electronic states at the 4s + 5s asymptote in krb is presented. abundant spectroscopic data on the \ astate state were collected by fourier - transform spectroscopy which allow to determine an accurate experimental potential energy curve up to 14. 8 \ aa. the existing data set ( c. amiot et al. j. chem. phys. 112, 7068 ( 2000 ) ) on the ground state \ xstate was extended by several additional levels lying close to the atomic asymptote. in a coupled channels fitting routine complete molecular potentials for both electronic states were fitted. along with the line frequencies of the molecular transitions, recently published positions of feshbach resonances in $ ^ { 40 } $ k and $ ^ { 87 } $ rb mixtures ( f. ferlaino et al. phys. rev. a 74, 039903 ( 2006 ) ) were included in the fit. this makes the derived potential curves capable for an accurate description of observed cold collision features so far. predictions of scattering lengths and feshbach resonances in other isotopic combinations are reported. | arxiv:0706.2849 |
the oldest, most metal - poor stars in the galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical conditions of the earliest star forming environments in the universe. we review the fields of stellar archaeology and dwarf galaxy archaeology by examining the chemical abundance measurements of various elements in extremely metal - poor stars. focus on the carbon - rich and carbon - normal halo star populations illustrates how these provide insight into the population iii star progenitors responsible for the first metal enrichment events. we extend the discussion to near - field cosmology, which is concerned with the formation of the first stars and galaxies and how metal - poor stars can be used to constrain these processes. complementary abundance measurements in high - redshift gas clouds further help to establish the early chemical evolution of the universe. the data appear consistent with the existence of two distinct channels of star formation at the earliest times. | arxiv:1501.06921 |
the origin of the correlation between surface reactivity and quantum - size effects, observed in recent experiments on the oxidation of ultrathin magnesium films, is addressed by means of ab - initio calculations and model predictions. we show that the decay length in vacuum of the electronic local density of states at the fermi energy exhibits systematic oscillations with film thickness, with local maxima induced when a quantum well state at k / / = 0 crosses the fermi energy. the predicted changes in the decay length are expected to have a major impact on the electron transfer rate by tunneling, which has been proposed to control the initial sticking of o2 in the oxidation process. | arxiv:cond-mat/0601364 |
all indian institutes of technology ( iits ) was slightly over ₹70 billion ( us $ 830 million ). however, the aggregate money spent by indian students for tertiary education in the united states was about six times more than what the central government spends on all iits. in june 2023, education officials of india and tanzania announced that the first foreign iit campus would be established on the tanzanian autonomous territory of zanzibar, as a satellite campus of iit madras. the campus is scheduled to begin offering classes in october 2023. = = organisational structure = = the president of india is the ex officio visitor, and has residual powers. directly under the president is the iit council, comprising minister - in - charge of technical education in the union government, the chairmen of all iits, the directors of all iits, the chairman of the university grants commission, the director general of csir, the chairman of iisc, the director of iisc, three members of parliament, the joint council secretary of ministry of education, and three appointees each of the union government, aicte, and the visitor. under the iit council is the board of governors of each iit. under the board of governors is the director, who is the chief academic and executive officer of the iit. under the director, in the organisational structure, comes the deputy director. under the director and the deputy director, come the deans, heads of departments, registrar, president of the students ' council, and chairman of the hall management committee. the registrar is the chief administrative officer of the iit and overviews the day - to - day operations. below the heads of department ( hod ) are the faculty members ( professors, associate professors, and assistant professors ). the wardens come under the chairman of the hall management committee. = = = the institutes of technology act = = = the institute of technology act ( parliamentary legislation ) gives legal status, including degree - granting powers, to the indian institutes of technology ( iits ). it was notified in the gazette as act number 59 of 1961 on 20 december 1961 and came into effect on 1 april 1962. the act also declares these institutes as institutes of national importance. = = academics = = the iits receive comparatively higher grants than other engineering colleges in india. while the total government funding to most other engineering colleges is around ₹ 100 – 200 million ( $ 2 – 4 million ) per year, the amount varies between ₹ 900 – 1300 million ( $ 19 | https://en.wikipedia.org/wiki/Indian_Institutes_of_Technology |
given integers $ 2 \ leq p \ leq c \ leq q $, we construct a finite simple graph $ g $ with $ \ nu _ 1 ( g ) = p $ and $ \ nu ( g ) = q $ for which the squarefree power $ i ( g ) ^ { [ k ] } $ of the edge ideal $ i ( g ) $ of $ g $ has linear quotients for each $ c \ leq k \ leq q $ and is not linearly related for each $ 1 \ leq k < c $, where $ \ nu _ 1 ( g ) $ is the induced matching number of $ g $ and $ \ nu ( g ) $ is the matching number of $ g $. | arxiv:2503.21008 |
for high - dimensional omics data, sparsity - inducing regularization methods such as the lasso are widely used and often yield strong predictive performance, even in settings when the assumption of sparsity is likely violated. we demonstrate that under a specific dense model, namely the high - dimensional joint latent variable model, the lasso produces sparse prediction rules with favorable prediction error bounds, even when the underlying regression coefficient vector is not sparse at all. we further argue that this model better represents many types of omics data than sparse linear regression models. we prove that the prediction bound under this model in fact decreases with increasing number of predictors, and confirm this through simulation examples. these results highlight the need for caution when interpreting sparse prediction rules, as strong prediction accuracy of a sparse prediction rule may not imply underlying biological significance of the individual predictors. | arxiv:2502.07959 |
supervised machine learning and predictive models have achieved an impressive standard today, enabling us to answer questions that were inconceivable a few years ago. besides these successes, it becomes clear, that beyond pure prediction, which is the primary strength of most supervised machine learning algorithms, the quantification of uncertainty is relevant and necessary as well. however, before quantification is possible, types and sources of uncertainty need to be defined precisely. while first concepts and ideas in this direction have emerged in recent years, this paper adopts a conceptual, basic science perspective and examines possible sources of uncertainty. by adopting the viewpoint of a statistician, we discuss the concepts of aleatoric and epistemic uncertainty, which are more commonly associated with machine learning. the paper aims to formalize the two types of uncertainty and demonstrates that sources of uncertainty are miscellaneous and can not always be decomposed into aleatoric and epistemic. drawing parallels between statistical concepts and uncertainty in machine learning, we emphasise the role of data and their influence on uncertainty. | arxiv:2305.16703 |
for integrated sensing and communications, an intriguing question is whether information - bearing channel - coded signals can be reused for sensing - specifically ranging. this question forces the hitherto non - overlapping fields of channel coding ( communications ) and sequence design ( sensing ) to intersect by motivating the design of error - correcting codes that have good autocorrelation properties. in this letter, we demonstrate how machine learning ( ml ) is well - suited for designing such codes, especially for short block lengths. as an example, for rate 1 / 2 and block length 32, we show that even an unsophisticated ml code has a bit - error rate performance similar to a polar code with the same parameters, but with autocorrelation sidelobes 24db lower. while a length - 32 zadoff - chu ( zc ) sequence has zero autocorrelation sidelobes, there are only 16 such sequences and hence, a 1 / 2 code rate cannot be realized by using zc sequences as codewords. hence, ml bridges channel coding and sequence design by trading off an ideal autocorrelation function for a large ( i. e., rate - dependent ) codebook size. | arxiv:2503.23119 |
we prove that the cohomology groups of a definably compact set over an o - minimal expansion of a group are finitely generated and invariant under elementary extensions and expansions of the language. we also study the cohomology of the intersection of a definable decreas - ing family of definably compact sets, under the additional assumption that the o - minimal structure expands a field. | arxiv:0705.3425 |
ramanujan ' s religious belief had been romanticised by westerners and overstated — in reference to his belief, not practice — by indian biographers. at the same time, he remarked on ramanujan ' s strict vegetarianism. similarly, in an interview with frontline, berndt said, " many people falsely promulgate mystical powers to ramanujan ' s mathematical thinking. it is not true. he has meticulously recorded every result in his three notebooks, " further speculating that ramanujan worked out intermediate results on slate that he could not afford the paper to record more permanently. berndt reported that janaki said in 1984 that ramanujan spent so much of his time on mathematics that he did not go to the temple, that she and her mother often fed him because he had no time to eat, and that most of the religious stories attributed to him originated with others. however, his orthopraxy was not in doubt. = = mathematical achievements = = in mathematics, there is a distinction between insight and formulating or working through a proof. ramanujan proposed an abundance of formulae that could be investigated later in depth. g. h. hardy said that ramanujan ' s discoveries are unusually rich and that there is often more to them than initially meets the eye. as a byproduct of his work, new directions of research were opened up. examples of the most intriguing of these formulae include infinite series for π, one of which is given below : 1 π = 2 2 9801 k = 0 ∞ ( 4 k )! ( 1103 + 26390 k ) ( k! ) 4 396 4 k. { \ displaystyle { \ frac { 1 } { \ pi } } = { \ frac { 2 { \ sqrt { 2 } } } { 9801 } } \ sum _ { k = 0 } ^ { \ infty } { \ frac { ( 4k )! ( 1103 + 26390k ) } { ( k! ) ^ { 4 } 396 ^ { 4k } } }. } this result is based on the negative fundamental discriminant d = −4 × 58 = −232 with class number h ( d ) = 2. further, 26390 = 5 × 7 × 13 × 58 and 16 × 9801 = 3962, which is related to the fact that e π 58 = 396 4 − 104. 000000177 … | https://en.wikipedia.org/wiki/Srinivasa_Ramanujan |
the search for room temperature superconductivity has accelerated dramatically in the last few years driven largely by theoretical predictions that first indicated alloying dense hydrogen with other elements could produce conventional phonon - mediated superconductivity at very high temperatures and at accessible pressures, and more recently, with the success of structure search methods that have identified specific candidates and pressure - temperature ( p - t ) conditions for synthesis. these theoretical advances have prompted improvements in experimental techniques to test these predictions. as a result, experimental studies of simple binary hydrides under pressure have yielded high critical superconducting transition temperatures ( tc ), of 260 k in lah10, close to the commonly accepted threshold for room temperature, 293 k, at pressures near 180 gpa. we successfully synthesized a metallic la - based superhydride from la metal and ammonia borane, nh3bh3, and find a multi - step transition with a tc of 294 k for the highest onset. when subjected to subsequent thermal excursions to higher temperatures that promoted a chemical reaction to what we believe is a ternary or higher order system, the transition temperature was driven to higher temperatures. although the reaction does not appear to be complete, the onset temperature was pushed from 294 k to 556 k before the experiments had to be terminated. the results provide evidence for hot superconductivity well above room temperature, in line with recent predictions for a higher order hydride under pressure. | arxiv:2006.03004 |
this paper presents a study of brane formation in six - dimensional space. there is no a priori assumption of the brane ( s ) existence. however, the analysis of the generalized einstein equations reveals that there are a set of metrics describing two static branes even in the absence of matter fields. the trapping of massive particles on branes is a consequence of the metric structure, which prevents these particles from moving between branes. it is shown that the communication between charged particles located on different branes provides by photons. such positron - electron annihilation could be experimentaly study at the lhc collider. the higgs field is distributed between the branes in such a way that it can serve as a higgs portal connecting two worlds located on different branes. the values of the 4d physical parameters depend on the extra metric structure near the branes. a particular metric of the extra space was found to provide the observed value of the higgs vacuum average. we also found a non - trivial effect of decompactification of the extra space when the hubble parameter is varied. | arxiv:2408.14692 |
normalized compression distance ( ncd ) is a popular tool that uses compression algorithms to cluster and classify data in a wide range of applications. existing discussions of ncd ' s theoretical merit rely on certain theoretical properties of compression algorithms. however, we demonstrate that many popular compression algorithms don ' t seem to satisfy these theoretical properties. we explore the relationship between some of these properties and file size, demonstrating that this theoretical problem is actually a practical problem for classifying malware with large file sizes, and we then introduce some variants of ncd that mitigate this problem. | arxiv:1509.00689 |
a fundamental problem in manifold learning is to approximate a functional relationship in a data chosen randomly from a probability distribution supported on a low dimensional sub - manifold of a high dimensional ambient euclidean space. the manifold is essentially defined by the data set itself and, typically, designed so that the data is dense on the manifold in some sense. the notion of a data space is an abstraction of a manifold encapsulating the essential properties that allow for function approximation. the problem of transfer learning ( meta - learning ) is to use the learning of a function on one data set to learn a similar function on a new data set. in terms of function approximation, this means lifting a function on one data space ( the base data space ) to another ( the target data space ). this viewpoint enables us to connect some inverse problems in applied mathematics ( such as inverse radon transform ) with transfer learning. in this paper we examine the question of such lifting when the data is assumed to be known only on a part of the base data space. we are interested in determining subsets of the target data space on which the lifting can be defined, and how the local smoothness of the function and its lifting are related. | arxiv:2302.00160 |
we report a coherent layer - by - layer high - order harmonic generation ( hhg ) build - up in artificially stacked transition metal dichalcogenides ( tmdc ) crystals in their various stacking configurations. in the experiments, millimeter - sized single crystalline monolayers are synthesized using the gold foil - exfoliation method, followed by artificially stacking on a transparent substrate. high - order harmonics up to the 19th order are generated by the interaction with an ultrafast mid - infrared ( mir ) driving laser. we find that the generation is sensitive to the number of layers and their relative orientation. for aaaa stacking configuration, both odd - and even - orders exhibit a quadratic increase in intensity as a function of the number of layers, which is a signature of constructive interference of high - harmonic emission from successive layers. particularly, we observe some deviations from this scaling at photon energies above the bandgap, which is explained by self - absorption effects. for ab and abab stacking, even - order harmonics remain below the detection level, consistent with the presence of inversion symmetry. our study confirms the capability of producing non - perturbative high - order harmonics from stacked layered materials subjected to intense mir fields without damaging samples. it has implications for optimizing solid - state hhg sources at the nano - scale and developing high - harmonics as an ultrafast probe of artificially stacked layered materials. because the hhg process is a strong - field driven process, it has the potential to probe high - momentum and energy states in the bandstructure combined with atomic - scale sensitivity in real space, making it an attractive probe of novel material structures such as the moir \ ' e pattern. | arxiv:2212.02354 |
we study the problem of testing whether a matrix $ \ mathbf { a } \ in \ mathbb { r } ^ { n \ times n } $ with bounded entries ( $ \ | \ mathbf { a } \ | _ \ infty \ leq 1 $ ) is positive semi - definite ( psd ), or $ \ epsilon $ - far in euclidean distance from the psd cone, meaning that $ \ min _ { \ mathbf { b } \ succeq 0 } \ | \ mathbf { a } - \ mathbf { b } \ | _ f ^ 2 > \ epsilon n ^ 2 $, where $ \ mathbf { b } \ succeq 0 $ denotes that $ \ mathbf { b } $ is psd. our main algorithmic contribution is a non - adaptive tester which distinguishes between these cases using only $ \ tilde { o } ( 1 / \ epsilon ^ 4 ) $ queries to the entries of $ \ mathbf { a } $. if instead of the euclidean norm we considered the distance in spectral norm, we obtain the " $ \ ell _ \ infty $ - gap problem ", where $ \ mathbf { a } $ is either psd or satisfies $ \ min _ { \ mathbf { b } \ succeq 0 } \ | \ mathbf { a } - \ mathbf { b } \ | _ 2 > \ epsilon n $. for this related problem, we give a $ \ tilde { o } ( 1 / \ epsilon ^ 2 ) $ query tester, which we show is optimal up to $ \ log ( 1 / \ epsilon ) $ factors. our testers randomly sample a collection of principal submatrices and check whether these submatrices are psd. consequentially, our algorithms achieve one - sided error : whenever they output that $ \ mathbf { a } $ is not psd, they return a certificate that $ \ mathbf { a } $ has negative eigenvalues. we complement our upper bound for psd testing with euclidean norm distance by giving a $ \ tilde { \ omega } ( 1 / \ epsilon ^ 2 ) $ lower bound for any non - adaptive algorithm. our lower bound construction is general, and can be used to derive lower bounds for a number of spectral testing problems. as an example of the applicability of our construction, we obtain a new $ \ til | arxiv:2005.06441 |
this paper describes " variable zo, " a novel and proprietary approach to antenna design and optimization. the new methodology is illustrated by applying it to the design of a resistively - loaded bowtie antenna and to two broadband yagi - uda arrays. variable zo is applicable to any antenna design or optimization methodology. using it will result in generally better antenna designs across any user - specified set of performance objectives. | arxiv:1107.1437 |
a micro - ring - resonator ( mrr ) optical biosensor based on the evanescent field sensing mechanism has been extensively studied due to its high sensitivity and compact device size. however, a suitable on - chip integrated spectrometer device has to be demonstrated for the lab - on - a - chip applications, which can read the resonance wavelength shift from mrr biosensors based on minuscule changes in refractive index. in this paper, we demonstrated the design and experimental results of the near - infrared lab - on - a - chip optical biosensor platform that monolithically integrates the mrr and the on - chip spectrometer on the silicon - on - insulator ( soi ) wafer, which can eliminate the external optical spectrum analyzer for scanning the wavelength spectrum. the symmetric add - drop mrr biosensor is designed to have a free spectral range ( fsr ) of ~ 19 nm, and a bulk sensitivity of ~ 73 nm / riu ; then the drop - port output resonance peaks are reconstructed from the integrated spatial - heterodyne fourier transform spectrometer ( shfts ) with the spectral resolution of ~ 3. 1 nm and bandwidth of ~ 50 nm, which results in the limit of detection of 0. 042 riu. the mrr output spectrum with air - and water - claddings are measured and reconstructed from the mrr - shfts integrated device experimentally to validate the wavelength shifting measurement. | arxiv:2207.07754 |
we present preliminary results of an extensive study of the fundamental properties of dwarf elliptical galaxies ( des ) in the coma cluster. our study will combine hst surface photometry with ground - based ubrijk photometry and optical spectroscopy. the combined data set will be used to investigate the intrinsic correlations among global parameters in cluster des, including the fundamental plane, the color - magnitude relation, the faber - jackson and kormendy relation, and velocity dispersion versus line strength indices. these empirical correlations have provided important constraints to theoretical models of galaxy formation and evolution for " normal " elliptical galaxies. although des are the most abundant galaxy population in clusters their properties remain, however, largely unknown. our study aims to provide an essential reference for testing current theories on the formation and evolution of des in clusters, and understanding their relation to more massive elliptical galaxies. | arxiv:astro-ph/0303390 |
we introduce a data capture system and a new dataset, ho - cap, for 3d reconstruction and pose tracking of hands and objects in videos. the system leverages multiple rgbd cameras and a hololens headset for data collection, avoiding the use of expensive 3d scanners or mocap systems. we propose a semi - automatic method for annotating the shape and pose of hands and objects in the collected videos, significantly reducing the annotation time compared to manual labeling. with this system, we captured a video dataset of humans interacting with objects to perform various tasks, including simple pick - and - place actions, handovers between hands, and using objects according to their affordance, which can serve as human demonstrations for research in embodied ai and robot manipulation. our data capture setup and annotation framework will be available for the community to use in reconstructing 3d shapes of objects and human hands and tracking their poses in videos. | arxiv:2406.06843 |
recent studies reveal that a well - trained deep reinforcement learning ( rl ) policy can be particularly vulnerable to adversarial perturbations on input observations. therefore, it is crucial to train rl agents that are robust against any attacks with a bounded budget. existing robust training methods in deep rl either treat correlated steps separately, ignoring the robustness of long - term rewards, or train the agents and rl - based attacker together, doubling the computational burden and sample complexity of the training process. in this work, we propose a strong and efficient robust training framework for rl, named worst - case - aware robust rl ( wocar - rl ) that directly estimates and optimizes the worst - case reward of a policy under bounded l _ p attacks without requiring extra samples for learning an attacker. experiments on multiple environments show that wocar - rl achieves state - of - the - art performance under various strong attacks, and obtains significantly higher training efficiency than prior state - of - the - art robust training methods. the code of this work is available at https : / / github. com / umd - huang - lab / wocar - rl. | arxiv:2210.05927 |
we prove that there is no genus - 2 curve over f _ q whose jacobian has characteristic polynomial of frobenius equal to x ^ 4 + ( 1 - 2q ) x ^ 2 + q ^ 2. maisner and nart had observed ( by direct computation ) that this was true for all q less than 65. | arxiv:math/0111006 |
the decays of psi ( 2s ) into gamma p bar { p }, pi ^ 0 p bar { p } and eta p bar { p } have been studied with the cleo - c detector using a sample of 24. 5 million psi ( 2s ) events obtained from e ^ + e ^ - annihilations at sqrt { s } = 3686 mev. the data show evidence for the excitation of several n ^ * resonances in p pi ^ 0 and p eta channels in pi ^ 0 p bar { p } and eta p bar { p } decays, and f _ 2 states in gamma p bar { p } decay. branching fractions for decays of psi ( 2s ) to gamma p bar { p }, pi ^ 0 p bar { p } and eta p bar { p } have been determined. no evidence for p bar { p } threshold enhancements was found in the reactions psi ( 2s ) - > x p bar { p }, where x = gamma, pi ^ 0, eta. we do, however, find confirming evidence for a p bar { p } threshold enhancement in j / psi - > gamma p bar { p } as previously reported by bes. | arxiv:1007.2886 |
preserving data analyses produced by the collaborations at lhc in a parametrized fashion is crucial in order to maintain reproducibility and re - usability. we argue for a declarative description in terms of individual processing steps - packtivities - linked through a dynamic directed acyclic graph ( dag ) and present an initial set of json schemas for such a description and an implementation - yadage - capable of executing workflows of analysis preserved via linux containers. | arxiv:1706.01878 |
although deep learning algorithms have been intensively developed for computer - aided tuberculosis diagnosis ( ctd ), they mainly depend on carefully annotated datasets, leading to much time and resource consumption. weakly supervised learning ( wsl ), which leverages coarse - grained labels to accomplish fine - grained tasks, has the potential to solve this problem. in this paper, we first propose a new large - scale tuberculosis ( tb ) chest x - ray dataset, namely the tuberculosis chest x - ray attribute dataset ( tbx - att ), and then establish an attribute - assisted weakly - supervised framework to classify and localize tb by leveraging the attribute information to overcome the insufficiency of supervision in wsl scenarios. specifically, first, the tbx - att dataset contains 2000 x - ray images with seven kinds of attributes for tb relational reasoning, which are annotated by experienced radiologists. it also includes the public tbx11k dataset with 11200 x - ray images to facilitate weakly supervised detection. second, we exploit a multi - scale feature interaction model for tb area classification and detection with attribute relational reasoning. the proposed model is evaluated on the tbx - att dataset and will serve as a solid baseline for future research. the code and data will be available at https : / / github. com / gangmingzhao / tb - attribute - weak - localization. | arxiv:2207.00251 |
we use deep panchromatic datasets in the goods - n field, from galex to the deepest herschel far - infrared and vla radio continuum imaging, to explore, using mass - complete samples, the evolution of the star formation activity and dust attenuation of star - forming galaxies to z ~ 4. our main results can be summarized as follows : i ) the slope of the sfr - m correlation is consistent with being constant, and equal to ~ 0. 8 at least up to z ~ 1. 5, while its normalization keeps increasing with redshift ; ii ) for the first time here we are able to explore the fir - radio correlation for a mass - selected sample of star - forming galaxies : the correlation does not evolve up to z ~ 4 ; iii ) we confirm that galaxy stellar mass is a robust proxy for uv dust attenuation in star - forming galaxies, with more massive galaxies being more dust attenuated, strikingly we find that this attenuation relation evolves very weakly with redshift, the amount of dust attenuation increasing by less than 0. 3 magnitudes over the redshift range [ 0. 5 - 4 ] for a fixed stellar mass, as opposed to a tenfold increase of star formation rate ; iv ) the correlation between dust attenuation and the uv spectral slope evolves in redshift, with the median uv spectral slope of star - forming galaxies becoming bluer with redshift. by z ~ 3, typical uv slopes are inconsistent, given the measured dust attenuation, with the predictions of commonly used empirical laws. finally, building on existing results, we show that gas reddening is marginally larger ( by a factor of around 1. 3 ) than stellar reddening at all redshifts probed, and also that the amount of dust attenuation at a fixed ism metallicity increases with redshift. we speculate that our results support evolving ism conditions of typical star - forming galaxies such that at z ~ 1. 5 main sequence galaxies have ism conditions getting closer to those of local starbursts. | arxiv:1407.5072 |
we calculate the current noise power spectrum in a nanoscopic interferometer consisting of a majorana bound state ( mbs ) and a localized spin. we show that for large voltage ( though less than the superconducting gap ) several strong resonance peaks appear at frequencies that depend on the zeeman splitting of the localized spin and on its tunneling to the localized spin. we also evaluate the differential conductance and find the unitary limit peak $ 2e ^ 2 / h $ at zero voltage as well as peaks at voltages corresponding to the resonances. we propose that detection of the resonances and related peaks in the differential conductance provide a strong support for the presence of an mbs. | arxiv:1407.5179 |
response surface methodology ( rsm ) and desirability functions were employed in a case study to optimize the thermal and daylight performance of a computational model of a tropical housing typology. specifically, this approach simultaneously optimized indoor overheating hours ( ioh ) and useful daylight illuminance ( udi ) metrics through an overall desirability ( d ). the lack of significant association between ioh and other annual daylight metrics enabled a focused optimization of ioh and udi. each response required only 138 simulation runs ( ~ 30 hours for 276 runs ) to determine the optimal values for passive strategies : window - to - wall ratio ( wwr ) and roof overhang depth across four orientations, totalling eight factors. first, initial screening based on $ 2 _ v ^ { 8 - 2 } $ fractional factorial design, identified four key factors using stepwise and lasso regression, narrowed down to three : roof overhang depth on the south and west, wwr on the west, and wwr on the south. then, rsm optimization yielded an optimal solution ( roof overhang : 3. 78 meters, west wwr : 3. 76 %, south wwr : 29. 3 % ) with a d of 0. 625 ( ioh : 8. 33 %, udi : 79. 67 % ). finally, robustness analysis with 1, 000 bootstrap replications provided 95 % confidence intervals for the optimal values. this study optimally balances thermal comfort and daylight with few experiments using a computationally - efficient multi - objective approach. | arxiv:2409.09093 |
a dielectric nonlinear response in model two - phase composites, prepared from a displacive ferroelectric material with a dominant dielectric response due to a single oscillator ferroelectric mode and a dielectric material, is characterized by the existence of new modes due to geometric resonances below the percolation threshold in the ferroelectric matrix. the geometric nature of oscilations depends on composition and geometric properties of the mixture. generation of higher frequency modes is studied within our model and discussed for displacive ferroelectric materials of the $ batio _ { 3 } $ type. the bergman representation of the effective dielectric function together with our model for spectral function recently introduced are used simultaneously with theory of absorption in finite displacive ferroelectric crystals in quasistatic approximation to describe the physics of the composite. the boundaries of the present study are within this quasistatic approximation. new ways how to optimize material properties for nonlinear optics is outlined. | arxiv:1806.09118 |
the evolution and distribution of species body sizes for terrestrial mammals is well - explained by a macroevolutionary tradeoff between short - term selective advantages and long - term extinction risks from increased species body size, unfolding above the 2g minimum size induced by thermoregulation in air. here, we consider whether this same tradeoff, formalized as a constrained convection - reaction - diffusion system, can also explain the sizes of fully aquatic mammals, which have not previously been considered. by replacing the terrestrial minimum with a pelagic one, at roughly 7000g, the terrestrial mammal tradeoff model accurately predicts, with no tunable parameters, the observed body masses of all extant cetacean species, including the 175, 000, 000g blue whale. this strong agreement between theory and data suggests that a universal macroevolutionary tradeoff governs body size evolution for all mammals, regardless of their habitat. the dramatic sizes of cetaceans can thus be attributed mainly to the increased convective heat loss is water, which shifts the species size distribution upward and pushes its right tail into ranges inaccessible to terrestrial mammals. under this macroevolutionary tradeoff, the largest expected species occurs where the rate at which smaller - bodied species move up into large - bodied niches approximately equals the rate at which extinction removes them. | arxiv:1207.1478 |
we review the status of an ongoing long - term lattice investigation of the spectrum and structure of tetraquark candidates. we focus on the light scalar meson $ a _ 0 ( 980 ) $. first steps regarding the study of a possibly existing $ c c \ bar { c } \ bar { c } $ tetraquark are also outlined. | arxiv:1310.6905 |
the infrared structure of quantum gravity is explored by solving a lattice version of the wheeler - dewitt equations. in the present paper only the case of 2 + 1 dimensions is considered. the nature of the wavefunction solutions is such that a finite correlation length emerges and naturally cuts off any infrared divergences. properties of the lattice vacuum are consistent with the existence of an ultraviolet fixed point in $ g $ located at the origin, thus precluding the existence of a weak coupling perturbative phase. the correlation length exponent is determined exactly and found to be $ \ nu = 6 / 11 $. the results obtained so far lend support to the claim that the lorentzian and euclidean formulations belong to the same field - theoretic universality class. | arxiv:1207.3759 |
we construct a kodaira - spencer map from the big quantum cohomology of a sphere with three orbifold points to the jacobian ring of the mirror landau - ginzburg potential function. this is constructed via the lagrangian floer theory of the seidel lagrangian and we show that kodaira - spencer map is a ring isomorphism. | arxiv:2002.11180 |
the main intention of the paper is to investigate an osculating curve under the conformal map. we obtain a sufficient condition for the conformal invariance of an osculating curve. we also find an equivalent system of a geodesic curve under the conformal transformation ( motion ) and show its invariance under isometry and homothetic motion. | arxiv:1907.03597 |
electric dipole moments of atoms can arise from p - odd and t - odd electron - - nucleon couplings. this work studies a general class of dimension - six electron - - nucleon interactions mediated by lorentz - violating tensors of ranks ranging from $ 1 $ to $ 4 $. the possible couplings are listed as well as their behavior under c, p, and t, allowing us to select the couplings compatible with electric - dipole - moment physics. the unsuppressed contributions of these couplings to the atom ' s hamiltonian can be read as equivalent to an electric dipole moment. the lorentz - violating coefficients ' magnitudes are limited using electric - dipole - moment measurements at the levels of $ 3. 2 \ times10 ^ { - 31 } \ text { ( ev ) } ^ { - 2 } $ or $ 1. 6 \ times10 ^ { - 33 } \ text { ( ev ) } ^ { - 2 } $. | arxiv:1907.10538 |
by juxtaposing ideas from fractal geometry and dynamical systems, furstenberg proposed a series of conjectures in the late 1960 ' s that explore the relationship between digit expansions with respect to multiplicatively independent bases. in this work, we introduce and study - in the discrete context of the integers - analogues of some of the notions and results surrounding furstenberg ' s work. in particular, we define a new class of fractal sets of integers that parallels the notion of $ \ times r $ - invariant sets on the 1 - torus and investigate the additive and geometric independence between two such fractal sets when they are structured with respect to multiplicatively independent bases. our main results in this direction parallel the works of furstenberg, hochman - shmerkin, shmerkin, wu, and lindenstrauss - meiri - peres and include : - a classification of all subsets of the positive integers that are simultaneously $ \ times r $ - and $ \ times s $ - invariant ; - integer analogues of two of furstenberg ' s transversality conjectures pertaining to the dimensions of the intersection $ a \ cap b $ and the sumset $ a + b $ of $ \ times r $ - and $ \ times s $ - invariant sets $ a $ and $ b $ when $ r $ and $ s $ are multiplicatively independent ; and - a description of the dimension of iterated sumsets $ a + a + \ cdots + a $ for any $ \ times r $ - invariant set $ a $. we achieve these results by combining ideas from fractal geometry and ergodic theory to build a bridge between the continuous and discrete regimes. for the transversality results, we rely heavily on quantitative bounds on the $ l ^ q $ - dimensions of projections of restricted digit cantor measures obtained recently by shmerkin. we end by outlining a number of open questions and directions regarding fractal subsets of the integers. | arxiv:2007.05480 |
the difference graph $ d ( g ) $ of a finite group $ g $ is the difference of enhanced power graph of $ g $ and power graph of $ g $, with all isolated vertices are removed. in this paper we study the connectedness and perfectness of $ d ( g ) $ with respect to various properties of the underlying group $ g $. we also find several connection between the difference graph of $ g $ and the gruenberg - kegel graph of $ g $. | arxiv:2206.12422 |
we summarize the state of the art of the ` ` close approximation ' ' to black hole collisions. we discuss results to first and second order in perturbation theory for head - on collisions of momentarily - stationary and non - stationary black holes and discuss the near - future prospect of non - axisymmetric collisions. | arxiv:gr-qc/9803005 |
we construct the holographic dual for $ \ mathcal n = 4 $ sym on $ \ rm s ^ 4 $ and $ \ rm ads _ 4 $ coupled to massive $ \ mathcal n = 2 $ supersymmetric quenched flavor fields on a codimension - 1 defect, which is $ \ rm s ^ 3 $ and $ \ rm ads _ 3 $, respectively. the holographic description is in terms of a d3 / probe d5 brane system. we set up and reduce the bps equations for d5 - brane embeddings with arbitrary supersymmetric deformations and partly solve them at the non - linear level. the remaining equations are solved explicitly in a small - mass expansion. we compute the contribution of the defect fields to the partition function on s $ ^ 4 $ and compare to a field theory computation using supersymmetric localization, for which we set up the matrix model. both computations agree, lending strong support to holographic probe brane constructions using d3 / d5 configurations in general. | arxiv:1709.08650 |
we show that a domain wall separating single layer graphene ( slg ) and aa - stacked bilayer graphene ( aa - blg ) can be used to generate highly collimated electron beams which can be steered by a magnetic field. such system exists in two distinct configurations, namely, locally delaminated aa - blg and terminated aa - blg whose terminal edge - type can be either zigzag or armchair. we investigate the electron scattering using semi - classical dynamics and verify the results independently with wave - packed dynamics simulations. we find that the proposed system supports two distinct types of collimated beams that correspond to the lower and upper cones in aa - blg. our computational results also reveal that collimation is robust against the number of layers connected to aa - blg and terminal edges. | arxiv:1907.06827 |
in parts i [ 6 ] and ii [ 7 ] we studied how metrics $ g _ { ij } $ on $ \ mathfrak { su } ( n ) $ may spontaneously break symmetry and $ \ textit { crystallize } $ into a form which is kaq, $ \ textit { knows about qubits } $. we did this for $ n = 2 ^ n $ and then away from powers of 2. here we address the fermionic version and find kam metrics, these $ \ textit { know about majoranas } $. that is, there is a basis of principal axes $ \ { h _ k \ } $ of which is of homogeneous majorana degree. in part i, we searched unsuccessfully for functional minima representing crystallized metrics exhibiting the brown - susskind penalty schedule, motivated by their study of black hole scrambling time. here, by segueing to the fermionic setting we find, to good approximation, kam metrics adhering to this schedule on both $ \ mathfrak { su } ( 4 ) $ and $ \ mathfrak { su } ( 8 ) $. thus, with this preliminary finding, our toy model exhibits two of the three features required for the spontaneous emergence of spatial structure : 1. localized degrees of freedom and, 2. a preference for low body - number ( or low majorana number ) interactions. the final feature, 3. constraints on who may interact with whom, i. e. a neighborhood structure, must await an effective analytic technique, being entirely beyond what we can approach with classical numerics. | arxiv:2112.08613 |
recent experimental data on space - and time - like form factors of the nucleon are analyzed in terms of a two - component model with a quark - like intrinsics structure and a meson cloud. a good overall agreement is found for all electromagnetic form factors with the exception of the neutron magnetic form factor in the time - like region. | arxiv:nucl-th/0502050 |
assuming that the near horizon geometry of the black hole solution of the gravity dual to the abjm model, in the presence of a coupling between the weyl tensor and the field strength, is $ ads _ { 2 } \ times s ^ { 2 } $, we compute sen ' s entropy function for this theory. by extremizing the entropy function we write a formula for the entropy of the black hole, and then we compute the same entropy using wald ' s formula and show that the results are the same. in this way we generalize the calculation of black hole entropy to cases of curvature coupling to the field strength, including at first order, and we also show how to calculate the black hole entropy when the black hole solution is unknown, from just a few simple assumptions about the horizon. | arxiv:1502.05949 |
the imaginary poynting momentum ( ipm ) of light has been captivated an unusual origin of optomechanical effects on dipolar magnetoelectric particles, but yet observed in experiments. here, we report, for the very first time, a whole family of high - order ipm forces for not only magnetoelectric but also generic mie particles, assisted with their excited higher multipoles within. such optomechanical phenomena derive from a nonlinear contribution of the ipm to the optical force, and can be remarkable even when the incident ipm is small. we observe the high - order optomechanics in a structured light beam with vortex - like ipm streamlines, which allows the low - order dipolar contribution to be suppressed. our results provide the first unambiguous evidence of the ponderomotive nature of the ipm, expand the classification of optical forces and open new possibilities for optical forces and micromanipulations. | arxiv:2206.03153 |
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