text stringlengths 1 3.65k | source stringlengths 15 79 |
|---|---|
we introduce and study level - planar straight - line drawings with a fixed number $ \ lambda $ of slopes. for proper level graphs, we give an $ o ( n \ log ^ 2 n / \ log \ log n ) $ - time algorithm that either finds such a drawing or determines that no such drawing exists. moreover, we consider the partial drawing extension problem, where we seek to extend an immutable drawing of a subgraph to a drawing of the whole graph, and the simultaneous drawing problem, which asks about the existence of drawings of two graphs whose restrictions to their shared subgraph coincide. we present $ o ( n ^ { 4 / 3 } \ log n ) $ - time and $ o ( { \ lambda } n ^ { 10 / 3 } \ log n ) $ - time algorithms for these respective problems on proper level - planar graphs. we complement these positive results by showing that testing whether non - proper level graphs admit level - planar drawings with $ \ lambda $ slopes is $ \ textsf { np } $ - hard even in restricted cases. | arxiv:1907.13558 |
we present a description of saturation in small $ x $ deep inelastic scattering from power counting in a top - down effective theory derived from qcd. a factorization formula isolates the universal physics of the nucleus at leading power in $ x $. the onset of saturation is then understood as a breakdown in the expansion in an emergent power counting parameter, which is defined by the matrix element of a gauge invariant operator. we identify a new radiation mode, which enables us to extend previous literature by distinguishing the appearance of the saturation scale from the transition to non - linear evolution. | arxiv:2305.16393 |
in this work we study the solutions to some fractional higher - order equations. special cases in which time - fractional derivatives take integer values are also examined and the explicit solutions are presented. such solutions can be expressed by means of the transition laws of stable subordinators and their inverse processes. in particular we establish connections between fractional and higher - order equations. | arxiv:1106.1906 |
this paper is a continuation of the paper [ v. s. mashkevich, gr - qc / 9409010 ]. indeterministic quantum gravity is a theory that unifies general relativity and quantum theory involving indeterministic conception, i. e., quantum jumps. by the same token the theory claims to describe all the universe. spacetime is the direct product of cosmic time and space. the state of the universe is given by metric, its derivative with respect to cosmic time, and the number of an energy level. a quantum jump occurs at the tangency of two levels. equations of motion are the restricted einstein equation ( the cosmic space part thereof ) and a probability rule for the quantum jump. keywords : indeterminism, quantum jumps, state vector reduction, cosmology, cosmic spacetime | arxiv:gr-qc/9505034 |
curricula for goal - conditioned reinforcement learning agents typically rely on poor estimates of the agent ' s epistemic uncertainty or fail to consider the agents ' epistemic uncertainty altogether, resulting in poor sample efficiency. we propose a novel algorithm, query the agent ( qta ), which significantly improves sample efficiency by estimating the agent ' s epistemic uncertainty throughout the state space and setting goals in highly uncertain areas. encouraging the agent to collect data in highly uncertain states allows the agent to improve its estimation of the value function rapidly. qta utilizes a novel technique for estimating epistemic uncertainty, predictive uncertainty networks ( pun ), to allow qta to assess the agent ' s uncertainty in all previously observed states. we demonstrate that qta offers decisive sample efficiency improvements over preexisting methods. | arxiv:2210.02585 |
by a symmetry argument, a synethic aperture radar collection along a linear path does not collect three - dimensional information about the scene. however, it is known that vertical curvature can be used to derive some vertical position information. this paper approaches the problem from a monopulse perspective, resulting in a non - iterative computation that commutes with efficient image formation algorithms. | arxiv:2211.17127 |
in this paper we study duality for evaluation codes on intersections of d hypersurfaces with given d - dimensional newton polytopes, so called toric complete intersection codes. in particular, we give a condition for such a code to be quasi - self - dual. in the case of d = 2 it reduces to a combinatorial condition on the newton polygons. this allows us to give an explicit construction of dual and quasi - self - dual toric complete intersection codes. we provide a list of examples over the field of 16 elements. | arxiv:1310.5061 |
i give explicit fromulae for full propagators of vector and scalar fields in a generic spin - 1 gauge model quantized in an arbitrary linear covariant gauge. the propagators, expressed in terms of all - order one - particle - irreducible correlation functions, have a remarkably simple form because of constraints originating from slavnov - taylor identities of becchi - rouet - stora symmetry. i also determine the behavior of the propagators in the neighborhood of the poles, and give a simple prescription for the coefficients that generalize ( to the case with an arbitrary vector - scalar mixing ) the standard $ \ sqrt { \ mathcal { z } } $ factors of lehmann, symanzik and zimmermann. so obtained generalized $ \ sqrt { \ mathcal { z } } $ factors, are indispensable to the correct extraction of physical amplitudes from the amputated correlation functions in the presence of mixing. the standard $ r _ \ xi $ guauges form a particularly important subclass of gauges considered in this paper. while the tree - level vector - scalar mixing is, by construction, absent in $ r _ \ xi $ gauges, it unavoidably reappears at higher orders. therefore the prescription for the generalized $ \ sqrt { \ mathcal { z } } $ factors given in this paper is directly relevant for the extraction of amplitudes in $ r _ \ xi $ gauges. | arxiv:1903.09670 |
we consider online scheduling for an energy harvesting communication system where a sensor node collects samples from a gaussian source and sends them to a destination node over a gaussian channel. the sensor is equipped with a finite - sized battery that is recharged by an independent and identically distributed ( i. i. d. ) energy harvesting process over time. the goal is to minimize the long term average distortion of the source samples received at the destination. we study two problems : the first is when sampling is cost - free, and the second is when there is a sampling cost incurred whenever samples are collected. we show that fixed fraction policies [ shaviv - ozgur ], in which a fixed fraction of the battery state is consumed in each time slot, are near - optimal in the sense that they achieve a long term average distortion that lies within a constant additive gap from the optimal solution for all energy arrivals and battery sizes. for the problem with sampling costs, the transmission policy is bursty ; the sensor can collect samples and transmit for only a portion of the time. | arxiv:1705.10305 |
the eigenstate thermalization hypothesis ( eth ) underpins much of our modern understanding of the thermalization of closed quantum many - body systems. here, we investigate the statistical properties of observables in the eigenbasis of the lindbladian operator of a markovian open quantum system. we demonstrate the validity of a lindbladian eth ansatz through extensive numerical simulations of several physical models. to highlight the robustness of lindbladian eth, we consider what we dub the dilute - click regime of the model, in which one postselects only quantum trajectories with a finite fraction of quantum jumps. the average dynamics are generated by a non - trace - preserving liouvillian, and we show that the lindbladian eth ansatz still holds in this case. on the other hand, the no - click limit is a singular point at which the lindbladian reduces to a doubled non - hermitian hamiltonian and lindbladian eth breaks down. | arxiv:2504.10261 |
we introduce the liquid bin model as a continuous - time deterministic dynamics, arising as the hydrodynamic limit of a discrete - time stochastic interacting particle system called the infinite bin model. for the liquid bin model, we prove the existence and uniqueness of a stationary evolution, to which the dynamics converges exponentially fast. the speed of the front of the system is explicitly computed as a continuous piecewise rational function of the parameters of the model, revealing an underlying wall - crossing phenomenon. we show that the regions on which the speed is rational are of non - empty interior and are naturally indexed by dyck paths. we provide a complete description of the adjacency structure of these regions, which generalizes the stanley lattice for dyck paths. finally we point out an intriguing connection to the topic of extensions of partial cyclic orders to total cyclic orders. | arxiv:2504.00301 |
a digital quantum simulator is an envisioned quantum device that can be pro - grammed to efficiently simulate any other local system. we demonstrate and investigate the digital approach to quantum simulation in a system of trapped ions. using sequences of up to 100 gates and 6 qubits, the full time dynamics of a range of spin systems are digitally simulated. interactions beyond those naturally present in our simulator are accurately reproduced and quantitative bounds are provided for the overall simulation quality. our results demon - strate the key principles of digital quantum simulation and provide evidence that the level of control required for a full - scale device is within reach. | arxiv:1109.1512 |
two initially correlated coherent states, each interacting with its own independent dissipative environment exhibit a sudden transition from classical to quantum decoherence. this change in the dynamics is a turning point in the decoherence, in the sense that depending on the average number of photons of each cavity, decoherence can even be suppressed. indeed, the quantum state is time - independent for a time span in the mesoscopic regime, revealing a decoherence - free subspace. furthermore, the absence of decoherence is manifested in the apparition of a metastable pointer state basis. | arxiv:1801.09310 |
reconstructions of past climates are based on the calibration of available proxy data. this calibration is usually achieved by means of linear regression models. in the recent paleo - climate literature there is an ongoing discussion on the validity of highly resolved climate reconstructions. the reason for this is that the proxy data are noisy, i. e. in addition to the variability that is related to the climate variable of interest, they contain other sources of variability. inadequate treatment of such noise leads to a biased estimation of regression slopes, resulting in a wrong representation of the real amplitude of past climate variations. methods to overcome this problem have had a limited success so far. here, we present a new approach - sinoma - for noisy serial data streams that are characterized by different spectral characteristics of signal and noise. sinoma makes use of specific properties of the data streams temporal or spatial structure and by this is able to deliver a precise estimate of the true regression slope and, simultaneously, of the ratio of noise variances present in the predictor and predictand. the paper introduces the underlying mathematics as well as a general description of the presented algorithm. the validity of sinoma is illustrated with two test data - sets. finally we address methodological limitations and further potential applications. | arxiv:1604.00823 |
interactions and relations between objects may be pairwise or higher - order in nature, and so network - valued data are ubiquitous in the real world. the " space of networks ", however, has a complex structure that cannot be adequately described using conventional statistical tools. we introduce a measure - theoretic formalism for modeling generalized network structures such as graphs, hypergraphs, or graphs whose nodes come with a partition into categorical classes. we then propose a metric that extends the gromov - wasserstein distance between graphs and the co - optimal transport distance between hypergraphs. we characterize the geometry of this space, thereby providing a unified theoretical treatment of generalized networks that encompasses the cases of pairwise, as well as higher - order, relations. in particular, we show that our metric is an alexandrov space of non - negative curvature, and leverage this structure to define gradients for certain functionals commonly arising in geometric data analysis tasks. we extend our analysis to the setting where vertices have additional label information, and derive efficient computational schemes to use in practice. equipped with these theoretical and computational tools, we demonstrate the utility of our framework in a suite of applications, including hypergraph alignment, clustering and dictionary learning from ensemble data, multi - omics alignment, as well as multiscale network alignment. | arxiv:2409.06302 |
spontaneous breaking of global symmetries can produce ` ` alice ' ' strings : line defects which make unbroken symmetries multivalued, induce apparent charge violation via aharonov - bohm interactions, and form point defects when twisted into loops. we demonstrate this behavior for both divergent and textured global alice strings. both adiabatically scatter charged particles via effective wilson lines. for textured alice strings, such wilson lines occur at all radii, and are multivalued only inside the string. this produces measurable effects, including path - dependent charge violation. | arxiv:hep-th/0103238 |
we study the formation of molecules and dust clusters in the ejecta of solar metallicity, type ii - p supernovae using a chemical kinetic approach. we follow the evolution of molecules and small dust cluster masses from day 100 to day 1500 after explosion. we consider stellar progenitors with initial mass of 12, 15, 19 and 25 msun that explode as supernovae with stratified ejecta. the molecular precursors to dust grains comprise molecular chains, rings and small clusters of silica, silicates, metal oxides, sulphides and carbides, pure metals, and carbon, where the nucleation of silicate clusters is described by a two - step process of metal and oxygen addition. we study the impact of the 56ni mass on the type and amount of synthesised dust. we predict that large masses of molecules including co, sio, sis, o2, and so form in the ejecta. we show that the discrepancy between the small dust masses detected at infrared wavelengths some 500 days post - explosion and the larger amounts of dust recently detected with herschel in supernova remnants can be explained by the non - equilibrium chemistry linked to the formation of molecules and dust clusters in the ejected material. dust gradually builds up from small ( ~ 10 ^ { - 5 } msun ) to large masses ( ~ 5x 10 ^ { - 2 } msun ) over a 5 yr period after explosion. subsequent dust formation and / or growth is hampered by the shortage of chemical agents participating in the dust nucleation and the long time scale for accretion. the results highlight the dependence of the dust chemical composition and mass on the amount of 56ni synthesised during the explosion. this dependence may partly explain the diversity of epochs at which dust forms in supernovae. more generally, our results indicate that type ii - p supernovae are efficient but moderate dust producers with an upper limit on the mass of synthesised dust ranging from ~ 0. 03 to 0. 09 msun. | arxiv:1309.5887 |
we prove that the teichm \ " { u } ller space $ \ mathscr { t } $ of a closed surface of genus $ g \ ge 2 $ cannot be biholomorphic to any domain which is locally strictly convex at some boundary point. | arxiv:1701.06860 |
the transformation behaviour of the vector valued theta function of a positive - definite even lattice under the metaplectic group $ \ mathrm { mp } _ 2 ( \ mathbb { z } ) $ is described by the weil representation. we show that the invariants of this representation are induced from $ 5 $ fundamental invariants. as an application we give simple generating sets for jacobi forms of singular weight. | arxiv:2208.01921 |
this paper presents a general formulation of equations of motion of a pendulum with n point mass by use of two different methods. the first one is obtained by using lagrange mechanics and mathematical induction ( inspection ), and the second one is derived by defining a vector. today, these equations can be obtained by employing numerous programs ; however, this study gives a very compact form of these equations that is more efficient than solving euler - lagrange equations for every pendulum with more complex structures than simple or double pendulum. additionally, we investigate what will happen to our n - point mass system when we take limit as number of point masses goes infinity under well - defined assumptions. we find out that it converges to hanging rope system. | arxiv:1910.12610 |
the main objective of this article is to study the three - dimensional rayleigh - benard convection in a rectangular domain from a pattern formation perspective. it is well known that as the rayleigh number crosses a critical threshold, the system undergoes a type - i transition, characterized by an attractor bifurcation. the bifurcated attractor is an ( m - 1 ) - dimensional homological sphere where m is the multiplicity of the first critical eigenvalue. when m = 1, the structure of this attractor is trivial. when m = 2, it is known that the bifurcated attractor consists of steady states and their connecting heteroclinic orbits. the main focus of this article is then on the pattern selection mechanism and stability of rolls, rectangles and mixed modes ( including hexagons ) for the case where m = 2. we derive in particular a complete classification of all transition scenarios, determining the patterns of the bifurcated steady states, their stabilities and the basin of attraction of the stable ones. the theoretical results lead to interesting physical conclusions, which are in agreement with known experimental results. for example, it is shown in this article that only the pure modes are stable whereas the mixed modes are unstable. | arxiv:1109.5655 |
knowledge graph ( kg ) representation learning aims to encode entities and relations into dense continuous vector spaces such that knowledge contained in a dataset could be consistently represented. dense embeddings trained from kg datasets benefit a variety of downstream tasks such as kg completion and link prediction. however, existing kg embedding methods fell short to provide a systematic solution for the global consistency of knowledge representation. we developed a mathematical language for kg based on an observation of their inherent algebraic structure, which we termed as knowledgebra. by analyzing five distinct algebraic properties, we proved that the semigroup is the most reasonable algebraic structure for the relation embedding of a general knowledge graph. we implemented an instantiation model, seme, using simple matrix semigroups, which exhibits state - of - the - art performance on standard datasets. moreover, we proposed a regularization - based method to integrate chain - like logic rules derived from human knowledge into embedding training, which further demonstrates the power of the developed language. as far as we know, by applying abstract algebra in statistical learning, this work develops the first formal language for general knowledge graphs, and also sheds light on the problem of neural - symbolic integration from an algebraic perspective. | arxiv:2204.07328 |
this paper introduces a novel architecture for a distributed ledger, commonly referred to as a " blockchain ", which is organized in the form of directed acyclic graph ( dag ) with utxo transactions as vertices, rather than as a chain of blocks. consensus on the state of ledger assets is achieved through the cooperative consensus : a profit - driven behavior of token holders themselves, which is viable only when they cooperate by following the " biggest ledger coverage rule ", akin the " longest chain rule " of bitcoin. the cooperative behavior is facilitated by enforcing purposefully designed utxo transaction validity constraints. token holders are the sole category of participants authorized to make amendments to the ledger, making participation completely permissionless - without miners, validators, committees or staking - and without any need of knowledge about the composition of the set of all participants in the consensus. the setup allows to achieve high throughput and scalability alongside with low transaction costs, while preserving key aspects of high decentralization, open participation, and asynchronicity found in bitcoin and other proof - of - work blockchains, but without unreasonable energy consumption. sybil protection is achieved similarly to proof - of - stake blockchains, using tokens native to the ledger, yet the architecture operates in a leaderless manner without block proposers and committee selection. | arxiv:2411.16456 |
a review is made of recent efforts to find relations between the commutation relations which define a noncommutative geometry and the gravitational field which remains as a shadow in the commutative limit. | arxiv:gr-qc/9611026 |
dark matter ( dm ) with self - interactions is a promising solution for the small - scale problems of the standard cosmological model. here we perform the first cosmological simulation of frequent dm self - interactions, corresponding to small - angle dm scatterings. the focus of our analysis lies in finding and understanding differences to the traditionally assumed rare dm ( large - angle ) self scatterings. for this purpose, we compute the distribution of dm densities, the matter power spectrum, the two - point correlation function and the halo and subhalo mass functions. furthermore, we investigate the density profiles of the dm haloes and their shapes. we find that overall large - angle and small - angle scatterings behave fairly similarly with a few exceptions. in particular, the number of satellites is considerably suppressed for frequent compared to rare self - interactions with the same cross - section. overall we observe that while differences between the two cases may be difficult to establish using a single measure, the degeneracy may be broken through a combination of multiple ones. for instance, the combination of satellite counts with halo density or shape profiles could allow discriminating between rare and frequent self - interactions. as a by - product of our analysis, we provide - for the first time - upper limits on the cross - section for frequent self - interactions. | arxiv:2205.02243 |
an experiment is described that confirms the security of a well - studied class of cryptographic protocols ( dolev - yao intruder model ) can be verified by two - way nondeterministic pushdown automata ( 2npda ). a nondeterministic pushdown program checks whether the intersection of a regular language ( the protocol to verify ) and a given dyck language containing all canceling words is empty. if it is not, an intruder can reveal secret messages sent between trusted users. the verification is guaranteed to terminate in cubic time at most on a 2npda - simulator. the interpretive approach used in this experiment simplifies the verification, by separating the nondeterministic pushdown logic and program control, and makes it more predictable. we describe the interpretive approach and the known transformational solutions, and show they share interesting features. also noteworthy is how abstract results from automata theory can solve practical problems by programming language means. | arxiv:1803.10327 |
a new development of the ` ` monodromy transform ' ' method for analysis of hyperbolic as well as elliptic integrable reductions of einstein equations is presented. compatibility conditions for some alternative representations of the fundamental solutions of associated linear systems with spectral parameter in terms of a pair of dressing ( ` ` scattering ' ' ) matrices give rise to a new set of linear ( quasi - fredholm ) integral equations equivalent to the symmetry reduced einstein equations. unlike previously derived singular integral equations constructed with the use of conserved ( nonevolving ) monodromy data on the spectral plane for the fundamental solutions of associated linear systems, the scalar kernels of the new equations include another kind of functional parameters - - the evolving ( ` ` dynamical ' ' ) monodromy data for the scattering matrices. for hyperbolic reductions, in the context of characteristic initial value problem these data are determined completely by the characteristic initial data for the fields. in terms of solutions of the new integral equations the field components are expressed in quadratures. | arxiv:gr-qc/0105111 |
we study large random matrices with i. i. d. entries conditioned to have prescribed row and column sums ( margin ). this problem has rich connections to relative entropy minimization, schr \ " { o } dinger bridge, the enumeration of contingency tables, and random graphs with given degree sequences. we show that such margin - constrained random matrix is sharply concentrated around a certain deterministic matrix, which we call the \ textit { typical table }. typical tables have dual characterizations : ( 1 ) the expectation of the random matrix ensemble with minimum relative entropy from the base model constrained to have the expected target margin, and ( 2 ) the expectation of the maximum likelihood model obtained by rank - one exponential tilting of the base model. the structure of the typical table is dictated by two dual variables, which give the maximum likelihood estimates of the tilting parameters. based on these results, for a sequence of " tame " margins that converges in \ ( l ^ { 1 } \ ) to a limiting continuum margin as the size of the matrix diverges, we show that the sequence of margin - constrained random matrices converges in cut norm to a limiting kernel, which is the $ l ^ { 2 } $ - limit of the corresponding rescaled typical tables. the rate of convergence is controlled by how fast the margins converge in $ l ^ { 1 } $. we derive several new results for random contingency tables from our general framework. | arxiv:2407.14942 |
relay - aided transmission is envisioned as a key strategy to combat severe path loss and link blockages emerging as unique challenges in millimeter - wave ( mmwave ) communications. this work considers a relay - aided multiuser mmwave communications scenario aiming at maximizing the sum rate through optimal transmit and relay precoder design. we propose a novel joint precoder design strategy, which exploits weighted minimum mean - square error ( wmmse ) using its equivalency to sum - rate maximization. we obtain closed form expressions of transmit and relay precoders, and propose to compute them through alternating - optimization iterations without having to resort to complicated numerical optimization techniques. numerical results verify the superiority of the proposed precoding strategy as compared to conventional precoding schemes. | arxiv:2003.03140 |
sea quark contents of the octet baryons are investigated by employing an extended chiral constituent quark approach, which embodies higher fock five - quark components in the baryons wave - functions. the well - known flavor asymmetry of the nucleon sea $ \ bar { d } - \ bar { u } $, is used as input to predict the probabilities of $ \ bar { u } $, $ \ bar { d } $ and $ \ bar { s } $ in the nucleon, $ \ lambda $, $ \ sigma $ and $ \ xi $ baryons, due to the intrinsic five - quark components in the baryons wave functions. | arxiv:1204.0300 |
the paper presents a novel approach for unsupervised techniques in the field of clustering. a new method is proposed to enhance existing literature models using the proper bayesian bootstrap to improve results in terms of robustness and interpretability. our approach is organized in two steps : k - means clustering is used for prior elicitation, then proper bayesian bootstrap is applied as resampling method in an ensemble clustering approach. results are analyzed introducing measures of uncertainty based on shannon entropy. the proposal provides clear indication on the optimal number of clusters, as well as a better representation of the clustered data. empirical results are provided on simulated data showing the methodological and empirical advances obtained. | arxiv:2409.08954 |
we look for a non - gaussian signal in the wmap 5 - year temperature anisotropy maps by performing a needlet - based data analysis. we use the foreground - reduced maps obtained by the wmap team through the optimal combination of the w, v and q channels, and perform realistic non - gaussian simulations in order to constrain the non - linear coupling parameter $ \ fnl $. we apply a third - order estimator of the needlet coefficients skewness and compute the $ \ chi ^ 2 $ statistics of its distribution. we obtain $ - 80 < \ fnl < 120 $ at 95 % confidence level, which is consistent with a gaussian distribution and comparable to previous constraints on the non - linear coupling. we then develop an estimator of $ \ fnl $ based on the same simulations and we find consistent constraints on primordial non - gaussianity. we finally compute the three point correlation function in needlet space : the constraints on $ \ fnl $ improve to $ - 50 < \ fnl < 110 $ at 95 % confidence level. | arxiv:0812.2478 |
we show that group algebras kg of polycyclic - by - finite groups g, where k is a field, are catenary : given prime ideals p and p ' of kg, with p contained in p ', all saturated chains of primes between p and p ' have the same length. | arxiv:math/9808123 |
steganography and steganalysis are two important branches of the information hiding field of research. steganography methods consist in hiding information in such a way that the secret message is undetectable for the uninitiated. steganalyzis encompasses all the techniques that attempt to detect the presence of such hidden information. this latter is usually designed by making classifiers able to separate innocent images from steganographied ones according to their differences on well - selected features. we wonder, in this article whether it is possible to construct a kind of universal steganalyzer without any knowledge regarding the steganographier side. the effects on the classification score of a modification of either parameters or methods between the learning and testing stages are then evaluated, while the possibility to improve the separation score by merging many methods during learning stage is deeper investigated. | arxiv:1608.05850 |
medicine is the science and practice of caring for patients, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. medicine encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness. contemporary medicine applies biomedical sciences, biomedical research, genetics, and medical technology to diagnose, treat, and prevent injury and disease, typically through pharmaceuticals or surgery, but also through therapies as diverse as psychotherapy, external splints and traction, medical devices, biologics, and ionizing radiation, amongst others. medicine has been practiced since prehistoric times, and for most of this time it was an art ( an area of creativity and skill ), frequently having connections to the religious and philosophical beliefs of local culture. for example, a medicine man would apply herbs and say prayers for healing, or an ancient philosopher and physician would apply bloodletting according to the theories of humorism. in recent centuries, since the advent of modern science, most medicine has become a combination of art and science ( both basic and applied, under the umbrella of medical science ). for example, while stitching technique for sutures is an art learned through practice, knowledge of what happens at the cellular and molecular level in the tissues being stitched arises through science. prescientific forms of medicine, now known as traditional medicine or folk medicine, remain commonly used in the absence of scientific medicine and are thus called alternative medicine. alternative treatments outside of scientific medicine with ethical, safety and efficacy concerns are termed quackery. = = etymology = = medicine ( uk :, us : ) is the science and practice of the diagnosis, prognosis, treatment, and prevention of disease. the word " medicine " is derived from latin medicus, meaning " a physician ". the word " physic " itself, from which " physician " derives, was the old word for what is now called a medicine, and also the field of medicine. = = clinical practice = = medical availability and clinical practice vary across the world due to regional differences in culture and technology. modern scientific medicine is highly developed in the western world, while in developing countries such as parts of africa or asia, the population may rely more heavily on traditional medicine with limited evidence and efficacy and no required formal training for practitioners. in the developed world, evidence - based medicine is not universally used in clinical practice ; for example, a 2007 survey of literature reviews found that about 49 % of the | https://en.wikipedia.org/wiki/Medicine |
we present the results of four three - dimensional radiation magnetohydrodynamic simulations of accretion disks around a $ 10 ^ 8 $ solar mass black hole, which produce the far ultraviolet spectrum peak and demonstrate a robust physical mechanism to produce the extreme ultraviolet to soft x - ray power - law continuum component. the disks are fed from rotating tori and reach accretion rates ranging from $ 0. 03 $ to $ 4 $ times the eddington value. the disks become radiation pressure or magnetic pressure dominated depending on the relative timescales of radiative cooling and gas inflow. magnetic pressure supported disks can form with or without net poloidal magnetic fields as long as the inflowing gas can cool quickly enough, which can typically happen when the accretion rate is low. we calculate the emerging spectra from these disks using multi - group radiation transport with realistic opacities and find that they typically peak around $ 10 $ ev. at accretion rates close to or above the eddington limit, a power - law component can appear for photon energies between $ 10 $ ev and 1 kev with a spectral slope varying between $ l _ \ nu \ propto \ nu ^ { - 1 } $ and $ \ nu ^ { - 2 } $, comparable to what is observed in radio quiet quasars. the disk with $ 3 \ % $ eddington accretion rate does not exhibit this component. these high energy photons are produced in an optically thick region $ \ approx 30 ^ { \ circ } - 45 ^ { \ circ } $ from the disk midplane by compressible bulk comptonization within the converging accretion flow. strongly magnetized disks that have a very small surface density will produce a spectrum that is very different from what is observed. | arxiv:2505.09671 |
recent studies indicate that the progenitors of merging black hole ( bh ) binaries from young star clusters can undergo a common envelope phase just like isolated binaries. if the stars emerge from the common envelope as naked cores, tidal interactions can efficiently synchronize their spins before they collapse into bhs. contrary to the isolated case, these binary bhs can also undergo dynamical interactions with other bhs in the cluster before merging. the interactions can tilt the binary orbital plane, leading to spin - orbit misalignment. we estimate the spin properties of merging binary bhs undergoing this scenario by combining up - to - date binary population synthesis and accurate few - body simulations. we show that post - common envelope binary bhs are likely to undergo only a single encounter, due to the high binary recoil velocity and short coalescence times. adopting conservative limits on the binary - single encounter rates, we obtain a local bh merger rate density of ~ 6. 6 yr ^ - 1 gpc ^ - 3. assuming low ( < 0. 2 ) natal bh spins, this scenario reproduces the trends in the distributions of effective spin xeff and precession parameters xp inferred from gwtc - 2, including the peaks at ( xeff, xp ) ~ ( 0. 1, 0. 2 ) and the tail at negative xeff values. | arxiv:2102.01689 |
over the past three years we have built a practice - oriented, bachelor level, educational programme for software engineers to specialize as ai engineers. the experience with this programme and the practical assignments our students execute in industry has given us valuable insights on the profession of ai engineer. in this paper we discuss our programme and the lessons learned for industry and research. | arxiv:2103.10703 |
with the expansion in tenders on the internet and social media, arabic sentiment analysis ( asa ) has assumed a significant position in the field of text mining study and has since remained used to explore the sentiments of users about services, various products or topics conversed over the internet. this mapping paper designs to comprehensively investigate the papers demographics, fertility, and directions of the asa research domain. furthermore, plans to analyze current asa techniques and find movements in the research. this paper describes a systematic mapping study ( sms ) of 51 primary selected studies ( pss ) is handled with the approval of an evidence - based systematic method to ensure handling of all related papers. the analyzed results showed the increase of both the asa research area and numbers of publications per year since 2015. three main research facets were found, i. e. validation, solution, and evaluation research, with solution research becoming more treatment than another research type. therefore numerous contribution facets were singled out. in totality, the general demographics of the asa research field were highlighted and discussed | arxiv:1911.05483 |
let $ t \ colon l ^ p ( { \ mathcal m } ) \ to l ^ p ( { \ mathcal n } ) $ be a bounded operator between two noncommutative $ l ^ p $ - spaces, $ 1 \ leq p < \ infty $. we say that $ t $ is $ \ ell ^ 1 $ - bounded ( resp. $ \ ell ^ 1 $ - contractive ) if $ t \ otimes i _ { \ ell ^ 1 } $ extends to a bounded ( resp. contractive ) map from $ l ^ p ( { \ mathcal m } ; \ ell ^ 1 ) $ into $ l ^ p ( { \ mathcal n } ; \ ell ^ 1 ) $. we show that yeadon ' s factorization theorem for $ l ^ p $ - isometries, $ 1 \ leq p \ not = 2 < \ infty $, applies to an isometry $ t \ colon l ^ 2 ( { \ mathcal m } ) \ to l ^ 2 ( { \ mathcal n } ) $ if and only if $ t $ is $ \ ell ^ 1 $ - contractive. we also show that a contractive operator $ t \ colon l ^ p ( { \ mathcal m } ) \ to l ^ p ( { \ mathcal n } ) $ is automatically $ \ ell ^ 1 $ - contractive if it satisfies one of the following two conditions : either $ t $ is $ 2 $ - positive ; or $ t $ is separating, that is, for any disjoint $ a, b \ in l ^ p ( { \ mathcal m } ) $ ( i. e. $ a ^ * b = ab ^ * = 0 ) $, the images $ t ( a ), t ( b ) $ are disjoint as well. | arxiv:1907.03995 |
we consider spherical averages of the fourier transform of fractal measures and improve both the upper and lower bounds on the rate of decay. maximal estimates with respect to fractal measures are deduced for the schr \ " odinger and wave equations. this refines the almost everywhere convergence of the solution to its initial datum as time tends to zero. a consequence is that the solution to the wave equation cannot diverge on a $ ( d - 1 ) $ - dimensional manifold if the data belongs to the energy space $ \ dot { h } ^ 1 ( \ mathbb { r } ^ d ) \ times l ^ 2 ( \ mathbb { r } ^ d ) $. | arxiv:1503.00105 |
pull - based id / loc split protocols, such as lisp ( rfc6830 ), retrieve mappings from a mapping system to encapsulate and forward packets. this is done by means of a control - plane channel. in this short paper we describe three attacks against this channel ( denial - of - service and overflowing ) as well as the against the local cache used to store such mappings. we also provide a solution against such attacks that implements a per - source rate - limiter using a count - min sketch data - structure. | arxiv:1803.08568 |
a new nonparametric model of maximum - entropy ( maxent ) copula density function is proposed, which offers the following advantages : ( i ) it is valid for mixed random vector. by ` mixed ' we mean the method works for any combination of discrete or continuous variables in a fully automated manner ; ( ii ) it yields a bonafide density estimate with intepretable parameters. by ` bonafide ' we mean the estimate guarantees to be a non - negative function, integrates to 1 ; and ( iii ) it plays a unifying role in our understanding of a large class of statistical methods. our approach utilizes modern machinery of nonparametric statistics to represent and approximate log - copula density function via lp - fourier transform. several real - data examples are also provided to explore the key theoretical and practical implications of the theory. | arxiv:2108.09438 |
the exponential increase of multimedia services by the mobile users requires seamless connectivity with cost effective quality of service qos provisioning. for providing such on - demand qos, the network needs to utilize the radio channels among the mobile hosts ( mhs ) effectively. we use vector genetic algorithm vga for temporal imploration of sharable channel ( s ) from the neighbouring cells to fulfill the needs of a cell. we propose a new micro - level temporal channel imploration mechanism mici, which promptly allocates available borrowing channel s of the neighbouring cell ( s ) to the needy cell. the novelty of mici is scalability, high availability, and on demand allocation of the channels to the desired cells. the performance of our model has been tested by simulation against a standard fca scheme as well as a greedy borrowing heuristic. in all the test cases mici shows promising results in comparison to both the schemes. | arxiv:1104.4204 |
we review recent developments in two - dimensional $ \ mathcal { n } = ( 2, 2 ) $ supersymmetric gauge theories focusing on the implementation and applications of localization techniques. | arxiv:1608.03607 |
this paper is concerned with the design of a non - intrusive model order reduction ( mor ) for the system of parametric time - domain maxwell equations. a time - and parameter - independent reduced basis ( rb ) is constructed by using a two - step proper orthogonal decomposition ( pod ) technique from a collection of full - order electromagnetic field solutions, which are generated via a discontinuous galerkin time - domain ( dgtd ) solver. the mapping between the time / parameter values and the projection coefficients onto the rb space is approximated by a gaussian process regression ( gpr ). based on the data characteristics of electromagnetic field solutions, the singular value decomposition ( svd ) is applied to extract the principal components of the training data of each projection coefficient, and the gpr models are trained for time - and parameter - modes respectively, by which the final global regression function can be represented as a linear combination of these time - and parameter - gaussian processes. the extraction of the rb and the training of gpr surrogate models are both completed in the offline stage. then the field solution at any new input time / parameter point can be directly recovered in the online stage as a linear combination of the rb with the regression outputs as the coefficients. in virtue of its non - intrusive nature, the proposed pod - gpr framework, which is equation - free, decouples the offline and online stages completely, and hence can predict the electromagnetic solution fields at unseen parameter locations quickly and effectively. the performance of our method is illustrated by a scattering problem of a multi - layer dielectric cylinder. | arxiv:2103.12472 |
fourier feature approximations have been successfully applied in the literature for scalable gaussian process ( gp ) regression. in particular, quadrature fourier features ( qff ) derived from gaussian quadrature rules have gained popularity in recent years due to their improved approximation accuracy and better calibrated uncertainty estimates compared to random fourier feature ( rff ) methods. however, a key limitation of qff is that its performance can suffer from well - known pathologies related to highly oscillatory quadrature, resulting in mediocre approximation with limited features. we address this critical issue via a new trigonometric quadrature fourier feature ( tqff ) method, which uses a novel non - gaussian quadrature rule specifically tailored for the desired fourier transform. we derive an exact quadrature rule for tqff, along with kernel approximation error bounds for the resulting feature map. we then demonstrate the improved performance of our method over rff and gaussian qff in a suite of numerical experiments and applications, and show the tqff enjoys accurate gp approximations over a broad range of length - scales using fewer features. | arxiv:2310.14544 |
we use numerical simulations to explore whether direct collapse can lead to the formation of smbh seeds at high - z. we follow the evolution of gas within dm halos of 2 x 10 ^ 8 mo and 1 kpc. we adopt cosmological density profiles and j - distributions. our goal is to understand how the collapsing flow overcomes the centrifugal barrier and whether it is subject to fragmentation. we find that the collapse leads either to a central runaway or to off - center fragmentation. a disk - like configuration is formed inside the centrifugal barrier. for more cuspy dm distribution, the gas collapses more and experiences a bar - like perturbation and a central runaway. we have followed this inflow down to ~ 10 ^ { - 4 } pc. the flow remains isothermal and the specific angular momentum is efficiently transferred by gravitational torques in a cascade of nested bars. this cascade supports a self - similar, disk - like collapse. in the collapsing phase, virial supersonic turbulence develops and fragmentation is damped. for larger initial dm cores the timescales become longer. in models with more organized initial rotation, a torus forms and appears to be supported by turbulent motions. the evolution depends on the competition between two timescales, corresponding to the onset of the central runaway and off - center fragmentation. for less organized rotation, the torus is greatly weakened, the central accretion timescale is shortened, and off - center fragmentation is suppressed - - - triggering the central runaway even in previously ` stable ' models. the resulting smbh masses lie in the range 2 x 10 ^ 4 mo - 2 x 10 ^ 6 mo, much higher than for population iii remnants. we argue that the above upper limit appears to be more realistic mass. corollaries of this model include a possible correlation between smbh and dm halo masses, and similarity between the smbh and halo mass functions, at time of formation. | arxiv:1304.1369 |
we study the thermodynamic properties of four - component fermionic mixtures described by the hubbard model using the dynamical mean - field - theory approach. special attention is given to the system with su ( 4 ) - symmetric interactions at half filling, where we analyze equilibrium many - body phases and their coexistence regions at nonzero temperature for the case of simple cubic lattice geometry. we also determine the evolution of observables in low - temperature phases while lowering the symmetry of the hamiltonian towards the two - band hubbard model. this is achieved by varying interflavor interactions or by introducing the spin - flip term ( hund ' s coupling ). by calculating the entropy for different symmetries of the model, we determine the optimal regimes for approaching the studied phases in experiments with ultracold alkali and alkaline - earth - like atoms in optical lattices. | arxiv:1612.06258 |
if $ g $ is a countable, discrete group generated by two finite subgroups $ h $ and $ k $ and $ p $ is a ii $ _ 1 $ factor with an outer g - action, one can construct the group - type subfactor $ p ^ h \ subset p \ rtimes k $ introduced in \ cite { bh }. this construction was used in \ cite { bh } to obtain numerous examples of infinite depth subfactors whose standard invariant has exotic growth properties. we compute the planar algebra ( in the sense of jones \ cite { j2 } ) of this subfactor and prove that any subfactor with an abstract planar algebra of " group type " arises from such a subfactor. the action of jones ' planar operad is determined explicitly. | arxiv:0807.4134 |
we study the problem of lossless feature selection for a $ d $ - dimensional feature vector $ x = ( x ^ { ( 1 ) }, \ dots, x ^ { ( d ) } ) $ and label $ y $ for binary classification as well as nonparametric regression. for an index set $ s \ subset \ { 1, \ dots, d \ } $, consider the selected $ | s | $ - dimensional feature subvector $ x _ s = ( x ^ { ( i ) }, i \ in s ) $. if $ l ^ * $ and $ l ^ * ( s ) $ stand for the minimum risk based on $ x $ and $ x _ s $, respectively, then $ x _ s $ is called lossless if $ l ^ * = l ^ * ( s ) $. for classification, the minimum risk is the bayes error probability, while in regression, the minimum risk is the residual variance. we introduce nearest - neighbor based test statistics to test the hypothesis that $ x _ s $ is lossless. this test statistic is an estimate of the excess risk $ l ^ * ( s ) - l ^ * $. surprisingly, estimating this excess risk turns out to be a functional estimation problem that does not suffer from the curse of dimensionality in the sense that the convergence rate does not depend on the dimension $ d $. for the threshold $ a _ n = \ log n / \ sqrt { n } $, the corresponding tests are proved to be consistent under conditions on the distribution of $ ( x, y ) $ that are significantly milder than in previous work. also, our threshold is universal ( dimension independent ), in contrast to earlier methods where for large $ d $ the threshold becomes too large to be useful in practice. | arxiv:2311.05033 |
by work of farinati, solberg, and taillefer, it is known that the hopf algebra cohomology of a quasi - triangular hopf algebra, as a graded lie algebra under the gerstenhaber bracket, is abelian. motivated by the question of whether this holds for nonquasi - triangular hopf algebras, we show that gerstenhaber brackets on hopf algebra cohomology can be expressed via an arbitrary projective resolution using volkov ' s homotopy liftings as generalized to some exact monoidal categories. this is a special case of our more general result that a bracket operation on cohomology is preserved under exact monoidal functors - one such functor is an embedding of hopf algebra cohomology into hochschild cohomology. as a consequence, we show that this lie structure on hopf algebra cohomology is abelian in positive degrees for all quantum elementary abelian groups, most of which are nonquasi - triangular. | arxiv:2101.09805 |
three - dimensional layered mg $ _ 3 $ bi $ _ 2 $ has emerged as thermoelectric material due to its high cooling performance at ambient temperature, which benefits from its low lattice thermal conductivity and semimetal character. however, the semimetal character of mg $ _ 3 $ bi $ _ 2 $ is sensitive to spin - orbit coupling ( soc ). thus, the underlying origin of low lattice thermal conductivity needs to be clarified in the presence of the soc. in this work, the first - principles calculations within the two - channel model are employed to investigate the effects of the soc on the phonon - phonon scattering on the phonon transport of mg $ _ 3 $ bi $ _ 2 $. our results show that the soc strongly reduces the lattice thermal conductivity ( up to $ \ sim 35 $ % ). this reduction originates from the influence of the soc on the transverse acoustic modes involving interlayer shearing, leading to weak interlayer bonding and enhancement anharmonicity around 50 cm $ ^ { - 1 } $. our results clarify the mechanism of low thermal conductivity in mg $ _ 3 $ bi $ _ 2 $ and support the design of mg $ _ 3 $ bi $ _ 2 $ - based materials for thermoelectric applications. | arxiv:2310.14639 |
using ideas from light front holography, we discuss the calculation of hadronic properties. in this talk i will pay special attention to hadronic masses and the nucleon helicity - independent generalized parton distributions of quarks in the zero skewness case | arxiv:1107.5553 |
we investigate local fractional nonlinear riccati differential equations ( lfnrde ) by transforming them into local fractional linear ordinary differential equations. the case of lfnrde with constant coefficients is considered and non - differentiable solutions for special cases obtained. | arxiv:1612.02280 |
we study the unintegrated, or transverse momentum dependent ( tmd ) gluon distribution obtained from the best description of the lhc data on the inclusive spectra of hadrons produced in the mid - rapidity region and low transverse momenta at starting scale q0 ^ 2 = 1 gev ^ 2. to extend this gluon density at higher q ^ 2 we apply the catani - ciafoloni - fiorani - marchesini ( ccfm ) evolution equation. the influence of the initial ( starting ) non - perturbative gluon distribution is studied. the application of the obtained gluon density to the analysis of the ep deep inelastic scattering allows us to get the results which describe reasonably well the h1 and zeus data on the longitudinal proton structure function fl ( x, q ^ 2 ). so, the connection between the soft processes at lhc and small x physics at hera has been confirmed and extended to a wide kinematical region. | arxiv:1310.7893 |
energy conservation of sensor nodes for increasing the network life is the most crucial design goal while developing efficient routing protocol for wireless sensor networks. recent technological advances help in the development of wide variety of sensor nodes. heterogeneity takes the advantage of different types of sensor nodes and improves the energy efficiency and network life. generally sensors are deployed randomly and densely in a sensing region so short distance multihop communication reduces the long distance transmission in the sensor network. in this research paper meep ( multihop energy efficient protocol for heterogeneous sensor network ) is proposed. the proposed protocol combines the idea of clustering and multihop communication. heterogeneity is created in the network by using some nodes of high energy. low energy nodes use a residual energy based scheme to become a cluster head. high energy nodes act as the relay nodes for low energy cluster head when they are not performing the duty of a cluster head to save their energy further. protocol also suggests a sleep state for nodes in the cluster formation process for saving energy and increasing the life of sensor network. simulation result shows that the proposed scheme is better than other two level heterogeneous sensor network protocol like sep in energy efficiency and network life. | arxiv:1409.1412 |
we study the ensemble x - ray variability properties of active galactic nuclei ( agn ) over a large range of timescales ( 20 ks $ \ leq t \ leq $ 14 yrs ), redshift ( $ 0 \ leq z \ lesssim 3 $ ), luminosities ( $ 10 ^ { 40 } $ erg s $ ^ { - 1 } \ leq l _ x \ leq 10 ^ { 46 } $ erg s $ ^ { - 1 } $ ) and black hole ( bh ) masses ( $ 10 ^ 6 \ leq $ m $ _ \ odot \ leq 10 ^ 9 $ ). we propose the use of the variance - frequency diagram, as a viable alternative to the study of the power spectral density ( psd ), which is not yet accessible for distant, faint and / or sparsely sampled agn. we show that the data collected from archival observations and previous literature studies are fully consistent with a universal psd form which does not show any evidence for systematic evolution of shape or amplitude with redshift or luminosity, even if there may be differences between individual agn at a given redshift or luminosity. we find new evidence that the psd bend frequency depends on bh mass and, possibly, on accretion rate. we finally discuss the implications for current and future agn population and cosmological studies. | arxiv:2302.08524 |
we propose a highly efficient " worm " like cluster monte carlo algorithm for the quantum rotor model in the link - current representation. we explicitly prove detailed balance for the new algorithm even in the presence of disorder. for the pure quantum rotor model with $ \ mu = 0 $ the new algorithm yields high precision estimates for the critical point $ k _ c = 0. 33305 ( 5 ) $ and the correlation length exponent $ \ nu = 0. 670 ( 3 ) $. for the disordered case, $ \ mu = 1 / 2 \ pm 1 / 2 $, we find $ \ nu = 1. 15 ( 10 ) $. | arxiv:cond-mat/0211262 |
identifying a reasonably small hilbert space that completely describes an unknown quantum state is crucial for efficient quantum information processing. we introduce a general dimension - certification protocol for both discrete and continuous variables that is fully evidence - based, relying solely on the experimental data collected and no other unjustified assumptions whatsoever. using the bayesian concept of relative belief, we take the effective dimension of the state as the smallest one such that the posterior probability is larger than the prior, as dictated by the data. the posterior probabilities associated with the relative - belief ratios measure the strength of the evidence provide by these ratios so that we can assess whether there is weak or strong evidence in favor or against a particular dimension. using experimental data from spectral - temporal and polarimetry measurements, we demonstrate how to correctly assign bayesian plausible error bars for the obtained effective dimensions. this makes relative belief a conservative and easy - to - use model - selection method for any experiment. | arxiv:2401.01562 |
the quantum nature of photonic systems is reflected in the photon statistics of the light they emit. therefore, the development of quantum optics tools with single photon sensitivity and excellent temporal resolution is paramount to the development of exotic sources, and is particularly challenging in the thz range where photon energies approach kbt at t = 300 k. here, we report on the first room temperature measurement of field g1 ( { \ tau } ) and intensity correlations g2 ( { \ tau } ) in the thz range with sub - cycle temporal resolution ( 146 fs ) over the bandwidth 0. 3 - 3 thz, based on electro - optic sampling. with this system, we are able to measure the photon statistics at threshold of a thz quantum cascade laser. | arxiv:1611.09562 |
structure from motion ( sfm ) using imagery that involves extreme appearance changes is yet a challenging task due to a loss of feature repeatability. using feature correspondences obtained by matching densely extracted convolutional neural network ( cnn ) features significantly improves the sfm reconstruction capability. however, the reconstruction accuracy is limited by the spatial resolution of the extracted cnn features which is not even pixel - level accuracy in the existing approach. providing dense feature matches with precise keypoint positions is not trivial because of memory limitation and computational burden of dense features. to achieve accurate sfm reconstruction with highly repeatable dense features, we propose an sfm pipeline that uses dense cnn features with relocalization of keypoint position that can efficiently and accurately provide pixel - level feature correspondences. then, we demonstrate on the aachen day - night dataset that the proposed sfm using dense cnn features with the keypoint relocalization outperforms a state - of - the - art sfm ( colmap using rootsift ) by a large margin. | arxiv:1805.03879 |
we prove that it is relatively consistent with the usual axioms of mathematics that all automorphisms of the calkin algebra are inner. together with a 2006 phillips - - weaver construction of an outer automorphism using the continuum hypothesis, this gives a complete solution to a 1977 problem of brown - douglas - fillmore. we also give a simpler and self - contained proof of the phillips - - weaver result. | arxiv:0705.3085 |
we report the recent discovery of two new eruptions of the recurrent nova m31n 2017 - 01e in the andromeda galaxy. the latest eruption, m31n 2024 - 08c, reached $ r = 17. 8 $ on 2024 august 06. 85 ut, $ \ sim2 $ months earlier than predicted. in addition to this recent eruption, a search of archival ptf data has revealed a previously unreported eruption on 2014 june 18. 46 ut that reached a peak brightness of $ r \ sim17. 9 $ approximately a day later. the addition of these two eruption timings has allowed us to update the mean recurrence time of the nova. we find $ \ langle t _ \ mathrm { rec } \ rangle = 924. 0 \ pm7. 0 $ days ( $ 2. 53 \ pm0. 02 $ yr ), which is slightly shorter than our previous determination. thus, m31n 2017 - 01e remains the nova with the second shortest recurrence time known, with only m31n 2008 - 12a being shorter. we also present a low - resolution spectrum of the likely quiescent counterpart of the nova, a $ \ sim20. 5 $ mag evolved b star displaying an $ \ sim14. 3 $ d photometric modulation. | arxiv:2410.07105 |
we address the question of whether a reflecting stationary set may be partitioned into two or more reflecting stationary subsets, providing various affirmative answers in zfc. as an application to singular cardinals combinatorics, we infer that it is never the case that there exists a singular cardinal all of whose scales are very good. | arxiv:1907.08581 |
establishing the stellar masses ( m * ), and hence specific star - formation rates ( ssfrs ) of submillimetre galaxies ( smgs ) is crucial for determining their role in the cosmic galaxy / star formation. however, there is as yet no consensus over the typical m * of smgs. specifically, even for the same set of smgs, the reported average m * have ranged over an order of magnitude, from ~ 5x10 ^ 10 mo to ~ 5x10 ^ 11 mo. here we study how different methods of analysis can lead to such widely varying results. we find that, contrary to recent claims in the literature, potential contamination of irac 3 - 8 um photometry from hot dust associated with an active nucleus is not the origin of the published discrepancies in derived m *. instead, we expose in detail how inferred m * depends on assumptions made in the photometric fitting, and quantify the individual and cumulative effects of different choices of initial mass function, different brands of evolutionary synthesis models, and different forms of assumed star - formation history. we review current observational evidence for and against these alternatives as well as clues from the hydrodynamical simulations, and conclude that, for the most justifiable choices of these model inputs, the average m * of smgs is ~ 2x10 ^ 11 mo. we also confirm that this number is perfectly reasonable in the light of the latest measurements of their dynamical masses, and the evolving m * function of the overall galaxy population. m * of this order imply that the average ssfr of smgs is comparable to that of other star - forming galaxies at z > 2, at 2 - 3 gyr ^ - 1. this supports the view that, while rare outliers may be found at any m *, most smgs simply form the top end of the main - sequence of star - forming galaxies at these redshifts. conversely, this argues strongly against the viewpoint that smgs are extreme pathological objects, of little relevance in the cosmic history of star - formation. | arxiv:1108.6058 |
cooke, roger ( 2005 ), the history of mathematics : a brief course, new york : wiley - interscience, 632 pages, isbn 978 - 0 - 471 - 44459 - 6. dani, s. g. ( 25 july 2003 ), " on the pythagorean triples in the sulvasutras " ( pdf ), current science, 85 ( 2 ) : 219 – 224, archived from the original ( pdf ) on 4 august 2003. datta, bibhutibhusan ( december 1931 ), " early literary evidence of the use of the zero in india ", the american mathematical monthly, 38 ( 10 ) : 566 – 572, doi : 10. 2307 / 2301384, jstor 2301384. datta, bibhutibhusan ; singh, avadesh narayan ( 1962 ), history of hindu mathematics : a source book, bombay : asia publishing house { { citation } } : cs1 maint : publisher location ( link ). de young, gregg ( 1995 ), " euclidean geometry in the mathematical tradition of islamic india ", historia mathematica, 22 ( 2 ) : 138 – 153, doi : 10. 1006 / hmat. 1995. 1014. kim plofker ( 2007 ), " mathematics, south asian ", encyclopaedia britannica online, pp. 1 – 12, retrieved 18 may 2007. filliozat, pierre - sylvain ( 2004 ), " ancient sanskrit mathematics : an oral tradition and a written literature ", in chemla, karine ; cohen, robert s. ; renn, jurgen ; et al. ( eds. ), history of science, history of text ( boston series in the philosophy of science ), dordrecht : springer netherlands, 254 pages, pp. 137 – 157, pp. 360 – 375, doi : 10. 1007 / 1 - 4020 - 2321 - 9 _ 7, isbn 978 - 1 - 4020 - 2320 - 0. fowler, david ( 1996 ), " binomial coefficient function ", the american mathematical monthly, 103 ( 1 ) : 1 – 17, doi : 10. 2307 / 2975209, jstor 2975209. hayashi, takao ( 1995 ), the bakhshali manuscript, an ancient indian mathematical treatise, groningen : egbert forsten, 596 pages, isbn 978 - 90 | https://en.wikipedia.org/wiki/Indian_mathematics |
the a - hypergeometric system was introduced by gel ' fand, kapranov and zelevinsky in the 1980 ' s. among several classes of a - hypergeometric functions, those for 1 - simplex $ \ times $ ( n - 1 ) - simplex are known to be a very nice class. we will study an incomplete analog of this class. | arxiv:1012.3826 |
deep residual networks ( resnets ) made a recent breakthrough in deep learning. the core idea of resnets is to have shortcut connections between layers that allow the network to be much deeper while still being easy to optimize avoiding vanishing gradients. these shortcut connections have interesting side - effects that make resnets behave differently from other typical network architectures. in this work we use these properties to design a network based on a resnet but with parameter sharing and with adaptive computation time. the resulting network is much smaller than the original network and can adapt the computational cost to the complexity of the input image. | arxiv:1804.10123 |
a medium - sized schwarzchild - couder telescope ( sct ) is being developed as a possible extension for the cherenkov telescope array ( cta ). the cherenkov camera of the telescope is designed to have 11328 silicon photomultiplier pixels capable of capturing high - resolution images of air showers in the atmosphere. the combination of the large number of pixels and the high trigger rate ( > 5 khz ) expected for this telescope results in a multi - gbps data throughput. this sets challenging requirements on the design and performance of a data acquisition system for processing and storing this data. a prototype sct ( psct ) with a partial camera containing 1600 pixels, covering a field of view of 2. 5 x 2. 5 square degrees, is being assembled at the f. l. whipple observatory. we present the design and current status of the sct data acquisition system. | arxiv:1509.00710 |
renewable energy source such as photovoltaic ( pv ) cell generates power from the sun light by converting solar power to electrical power with no moving parts and less maintenance. a single photovoltaic cell produces voltage of low level. in order to boost up the voltage, a dc - dc boost converter is used. in order to use this dc - dc converter for high voltage and high frequency applications, silicon carbide ( sic ) device is most preferred because of larger current carrying capability, higher voltage blocking capability, high operating temperature and less static and dynamic losses than the traditional silicon ( si ) power switches. in the proposed work, the static and dynamic characteristics of sic mosfet for different temperatures are observed. a sic mosfet based boost converter is investigated which is powered by pv source. this dc - dc converter is controlled using a pulse - width method ( pwm ) and the duty cycle d is calculated for tracking the maximum power point using incremental conductance algorithm of the pv systems implemented in fpga. simulation studies are carried out in matlab / simulink. a prototype of the sic converter is built and the results are verified experimentally. the performance parameters of the proposed converter such as output voltage ripple input current ripple and losses are computed and it is compared with the classical silicon ( si ) mosfet converter. | arxiv:1810.11452 |
we present the results of a combined metadynamics - umbrella sampling investigation of the puckered conformers of pyranoses described using the gromos 45a4 force field. the free energy landscape of cremer - pople puckering coordinates has been calculated for the whole series of alpha and beta aldohexoses. we show that the 45a4 force field parameters fail in reproducing proper free energy differences between chair conformers for many of the inspected monosaccharides. in the extreme cases of galactose, mannose and allose, the experimentally non - detectable inverted chair conformers become even substantially populated. the opposite behavior is observed in the case of idose, which is the only experimentally known aldohexose that shows equilibrium between chair and inverted chair. we suggest a modification to the gromos 45a4 parameter set, which improves considerably the accordance of simulation results with theoretical and experimental estimates of puckering free energies. | arxiv:1001.3667 |
it is the purpose of the present manuscript to emphasize those aspects that make the scalar sector with vacuum quantum numbers rather unique. chiral symmetry is the basic tool for our study together with a resummation of chiral perturbation theory ( chpt ) that stresses the role of unitarity but also allows one to include explicit resonance fields and to match with the chpt expansion at low energies. | arxiv:hep-ph/0007349 |
the complex transverse water proton magnetization subject to diffusion - encoding magnetic field gradient pulses in a heterogeneous medium such as brain tissue can be modeled by the bloch - torrey partial differential equation. the spatial integral of the solution of this equation in realistic geometry provides a gold - standard reference model for the diffusion mri signal arising from different tissue micro - structures of interest. a closed form representation of this reference diffusion mri signal has been derived twenty years ago, called matrix formalism that makes explicit the link between the laplace eigenvalues and eigenfunctions of the biological cell and its diffusion mri signal. in addition, once the laplace eigendecomposition has been computed and saved, the diffusion mri signal can be calculated for arbitrary diffusion - encoding sequences and b - values at negligible additional cost. up to now, this representation, though mathematically elegant, has not been often used as a practical model of the diffusion mri signal, due to the difficulties of calculating the laplace eigendecomposition in complicated geometries. in this paper, we present a simulation framework that we have implemented inside the matlab - based diffusion mri simulator spindoctor that efficiently computes the matrix formalism representation for realistic neurons using the finite elements method. we show the matrix formalism representation requires around a few hundred eigenmodes to match the reference signal computed by solving the bloch - torrey equation when the cell geometry comes from realistic neurons. as expected, the number of required eigenmodes to match the reference signal increases with smaller diffusion time and higher b - values. we gave the transformation that links the laplace eigenfunctions to the eigenfunctions of the bloch - torrey operator and computed the bloch - torrey eigenfunctions and eigenvalues. | arxiv:1911.07165 |
we investigate how the complexity of euclidean tsp for point sets $ p $ inside the strip $ ( - \ infty, + \ infty ) \ times [ 0, \ delta ] $ depends on the strip width $ \ delta $. we obtain two main results. first, for the case where the points have distinct integer $ x $ - coordinates, we prove that a shortest bitonic tour ( which can be computed in $ o ( n \ log ^ 2 n ) $ time using an existing algorithm ) is guaranteed to be a shortest tour overall when $ \ delta \ leq 2 \ sqrt { 2 } $, a bound which is best possible. second, we present an algorithm that is fixed - parameter tractable with respect to $ \ delta $. our algorithm has running time $ 2 ^ { o ( \ sqrt { \ delta } ) } n + o ( \ delta ^ 2 n ^ 2 ) $ for sparse point sets, where each $ 1 \ times \ delta $ rectangle inside the strip contains $ o ( 1 ) $ points. for random point sets, where the points are chosen uniformly at random from the rectangle $ [ 0, n ] \ times [ 0, \ delta ] $, it has an expected running time of $ 2 ^ { o ( \ sqrt { \ delta } ) } n $. these results generalise to point sets $ p $ inside a hypercylinder of width $ \ delta $. in this case, the factors $ 2 ^ { o ( \ sqrt { \ delta } ) } $ become $ 2 ^ { o ( \ delta ^ { 1 - 1 / d } ) } $. | arxiv:2003.09948 |
in this paper we present a classical construction of the hyperbolic structure of the complement of a link in the sense of thurston for the particular case of the borromean rings link. as this is nothing new, the aim of this paper is to complete the literature about this topic in the particular case of the borromean rings complement. | arxiv:2104.00516 |
during the conference on ulam ' s type stability ( rytro, poland, 2014 ), ioan rasa recalled his 25 - years - old problem concerning some inequality involving the bernstein polynomials. we offer the complete solution ( in positive ). as a ~ tool we use stochastic orderings ( which we prove for binomial distributions ) as well as so - called concentration inequality. our methods allow us to pose ( and solve ) the extended version of the problem in question. | arxiv:1604.07381 |
understanding the thermalization dynamics of quantum many - body systems at the microscopic level is among the central challenges of modern statistical physics. here we experimentally investigate individual spin dynamics in a two - dimensional ensemble of electron spins on the surface of a diamond crystal. we use a near - surface nv center as a nanoscale magnetic sensor to probe correlation dynamics of individual spins in a dipolar interacting surface spin ensemble. we observe that the relaxation rate for each spin is significantly slower than the naive expectation based on independently estimated dipolar interaction strengths with nearest neighbors and is strongly correlated with the timescale of the local magnetic field fluctuation. we show that this anomalously slow relaxation rate is due to the presence of strong dynamical disorder and present a quantitative explanation based on dynamic resonance counting. finally, we use resonant spin - lock driving to control the effective strength of the local magnetic fields and reveal the role of the dynamical disorder in different regimes. our work paves the way towards microscopic study and control of quantum thermalization in strongly interacting disordered spin ensembles. | arxiv:2207.10688 |
in this work, we have performed numerical simulations of primordial black hole ( pbh ) formation in the friedman - lema \ ^ itre - robertson - walker universe filled by radiation fluid, introducing the local - type non - gaussianity to the primordial curvature fluctuation. we have compared the numerical results from simulations with previous analytical estimations on the threshold value for pbh formation done in the previous paper arxiv : 2109. 00791, particularly for negative values of the non - linearity parameter $ f _ { \ rm nl } $. our numerical results show the existence of pbh formation of ( the so - called ) type i also in the case $ f _ { \ rm nl } \ lesssim - 0. 336 $, which was not found in the previous analytical expectations using the critical averaged compaction function. in particular, although the universal value for the averaged critical compaction function $ \ bar { \ mathcal { c } } _ { c } = 2 / 5 $ found previously in the literature is not satisfied for all the profiles considered in this work, an alternative direct analytical estimate has been found to be roughly accurate to estimate the thresholds, which gives the value of the critical averaged density with a few $ \ % $ deviation from the numerical one for $ f _ { \ rm nl } \ gtrsim - 1 $. | arxiv:2202.01028 |
use less energy than conventional thermal separation processes such as distillation, sublimation or crystallization. the separation process is purely physical and both fractions ( permeate and retentate ) can be obtained as useful products. cold separation using membrane technology is widely used in the food technology, biotechnology and pharmaceutical industries. furthermore, using membranes enables separations to take place that would be impossible using thermal separation methods. for example, it is impossible to separate the constituents of azeotropic liquids or solutes which form isomorphic crystals by distillation or recrystallization but such separations can be achieved using membrane technology. depending on the type of membrane, the selective separation of certain individual substances or substance mixtures is possible. important technical applications include the production of drinking water by reverse osmosis. in waste water treatment, membrane technology is becoming increasingly important. ultra / microfiltration can be very effective in removing colloids and macromolecules from wastewater. this is needed if wastewater is discharged into sensitive waters especially those designated for contact water sports and recreation. about half of the market is in medical applications such as artificial kidneys to remove toxic substances by hemodialysis and as artificial lung for bubble - free supply of oxygen in the blood. the importance of membrane technology is growing in the field of environmental protection ( nano - mem - pro ippc database ). even in modern energy recovery techniques, membranes are increasingly used, for example in fuel cells and in osmotic power plants. = = mass transfer = = two basic models can be distinguished for mass transfer through the membrane : the solution - diffusion model and the hydrodynamic model. in real membranes, these two transport mechanisms certainly occur side by side, especially during ultra - filtration. = = = solution - diffusion model = = = in the solution - diffusion model, transport occurs only by diffusion. the component that needs to be transported must first be dissolved in the membrane. the general approach of the solution - diffusion model is to assume that the chemical potential of the feed and permeate fluids are in equilibrium with the adjacent membrane surfaces such that appropriate expressions for the chemical potential in the fluid and membrane phases can be equated at the solution - membrane interface. this principle is more important for dense membranes without natural pores such as those used for reverse osmosis and in fuel cells. during the filtration process a boundary layer forms on the membrane. this concentration gradient is created by molecules which cannot pass through the membrane. the | https://en.wikipedia.org/wiki/Membrane_technology |
in this paper, we apply star - digital gabor transform in analysis compressed sensing and speech denoising. based on assumptions on the ambient dimension, we produce a window vector that generates a spark deficient gabor frame with many linear dependencies among its elements. we conduct computational experiments on both synthetic and real - world signals, using as baseline three gabor transforms generated by state - of - the - art window vectors and compare their performance to star - gabor transform. results show that the proposed star - gabor transform outperforms all others in all signal cases. | arxiv:2110.09296 |
we study a class of entangling gates for trapped atomic ions and demonstrate the use of numeric optimization techniques to create a wide range of fast, error - robust gate constructions. our approach introduces a framework for numeric optimization using individually addressed, amplitude and phase modulated controls targeting maximally and partially entangling operations on ion pairs, complete multi - ion registers, multi - ion subsets of large registers, and parallel operations within a single register. our calculations and simulations demonstrate that the inclusion of modulation of the difference phase for the bichromatic drive used in the m \ o lmer - s \ o rensen gate permits approximately time - optimal control across a range of gate configurations, and when suitably combined with analytic constraints can also provide robustness against key experimental sources of error. we further demonstrate the impact of experimental constraints such as bounds on coupling rates or modulation band - limits on achievable performance. using a custom optimization engine based on tensorflow we also demonstrate time - to - solution for optimizations on ion registers up to 20 ions of order tens of minutes using a local - instance laptop, allowing computational access to system - scales relevant to near - term trapped - ion devices. | arxiv:2005.00366 |
the propagator which evolves the wave - function in nrqm, can be expressed as a matrix element of a time evolution operator : i. e $ g _ { \ rm nr } ( x ) = \ langle { \ mathbf { x } _ 2 } | { u _ { \ rm nr } ( t ) } | { \ mathbf { x } _ 1 } \ rangle $ in terms of the orthonormal eigenkets $ | { \ mathbf { x } } \ rangle $ of the position operator. in qft, it is not possible to define a conceptually useful single - particle position operator or its eigenkets. it is also not possible to interpret the relativistic ( feynman ) propagator $ g _ r ( x ) $ as evolving any kind of single - particle wave - functions. in spite of all these, it is indeed possible to express the propagator of a free spinless particle, in qft, as a matrix element $ \ langle { \ mathbf { x } _ 2 } | { u _ { \ rm r } ( t ) } | { \ mathbf { x } _ 1 } \ rangle $ for a suitably defined time evolution operator and ( non - orthonormal ) kets $ | { \ mathbf { x } } \ rangle $ labeled by spatial coordinates. at mesoscopic scales, which are close but not too close to planck scale, one can incorporate quantum gravitational corrections to the propagator by introducing a zero - point - length. it turns out that even this qg corrected propagator can be expressed as a matrix element $ \ langle { \ mathbf { x } _ 2 } | { u _ { \ rm qg } ( t ) } | { \ mathbf { x } _ 1 } \ rangle $. i describe these results and explore several consequences. it turns out that the evolution operator $ u _ { \ rm qg } ( t ) $ becomes non - unitary for sub - planckian time intervals while remaining unitary for time interval is larger than planck time. the results can be generalised to any ultrastatic curved spacetime. | arxiv:2006.06701 |
the quantum brst charge for the most general, two - dimensional, non - linear, $ n = 4 $ quasi - superconformal algebra $ \ hat { d } ( 1, 2 ; \ a ) $, whose linearisation is the so - called ` large ' $ n = 4 $ superconformal algebra, is constructed. the $ \ hat { d } ( 1, 2 ; \ a ) $ algebra has $ \ hat { su ( 2 ) } _ { k ^ + } \ oplus \ hat { su ( 2 ) } _ { k ^ - } \ oplus \ hat { u ( 1 ) } $ ka \ v { c } - moody component, and $ \ a = k ^ - / k ^ + $. as a pre - requisite to our construction, we check the $ \ hat { d } ( 1, 2 ; \ a ) $ jacobi identities and construct a classical brst charge. then, we analyse the quantum brst charge nilpotency conditions and find the only solution, $ k ^ + = k ^ - = - 2 $. the $ \ hat { d } ( 1, 2 ; 1 ) $ algebra is actually isomorphic to the $ so ( 4 ) $ - based bershadsky - knizhnik non - linear quasi - superconformal algebra. we argue about the existence of a new string theory with ( i ) the non - linearly realised $ n = 4 $ world - sheet supersymmetry, ( ii ) non - unitary matter in a $ \ hat { d } ( 1, 2 ; \ a ) $ representation of $ k = - 2 $ and $ c = - 6 $, and ( iii ) negative ` critical dimension '. | arxiv:hep-th/9409017 |
the gauss map ( or continued fraction map ) is an important dissipative one - dimensional discrete - time dynamical system that exhibits chaotic behaviour and which generates a symbolic dynamics consisting of infinitely many different symbols. here we introduce a generalization of the gauss map which is given by $ x _ { t + 1 } = \ frac { 1 } { x _ t ^ \ alpha } - \ bigl [ \ frac { 1 } { x _ t ^ \ alpha } \ bigr ] $ where $ \ alpha \ geq 0 $ is a parameter and $ x _ t \ in [ 0, 1 ] $ ( $ t = 0, 1, 2, 3, \ ldots $ ). the symbol $ [ \ dots ] $ denotes the integer part. this map reduces to the ordinary gauss map for $ \ alpha = 1 $. the system exhibits a sudden ` jump into chaos ' at the critical parameter value $ \ alpha = \ alpha _ c \ equiv 0. 241485141808811 \ dots $ which we analyse in detail in this paper. several analytical and numerical results are established for this new map as a function of the parameter $ \ alpha $. in particular, we show that, at the critical point, the invariant density approaches a $ q $ - gaussian with $ q = 2 $ ( i. e., the cauchy distribution ), which becomes infinitely narrow as $ \ alpha \ to \ alpha _ c ^ + $. moreover, in the chaotic region for large values of the parameter $ \ alpha $ we analytically derive approximate formulas for the invariant density, by solving the corresponding perron - frobenius equation. for $ \ alpha \ to \ infty $ the uniform density is approached. we provide arguments that some features of this transition scenario are universal and are relevant for other, more general systems as well. | arxiv:2411.13629 |
satellite communication systems are the means of realizing a global broadband integrated services digital network. due to the statistical nature of the integrated services traffic, the resulting rate fluctuations and burstiness render congestion control a complicated, yet indispensable function. the long propagation delay of the earth - satellite link further imposes severe demands and constraints on the congestion control schemes, as well as the media access control techniques and retransmission protocols that can be employed in a satellite network. the problems in designing satellite network protocols, as well as some of the solutions proposed to tackle these problems, will be the primary focus of this survey. | arxiv:cs/9809076 |
social gaming is today a pervasive phenomenon. driven by the advent of social networks and the digitization of game distribution. in this paper the impact of digitization and so - cial networks such as facebook on digital games is de - scribed and evaluated. this impact follows several vectors, including the introduction of new game formats and extend - ing the traditional audiences for games, which in turn has increased industrial revenue. the industry is in turn shaped by new business model such as free - to - play, digital distri - bution and the use of viral social features. these changes do not only appear irreversible, but more importantly, play a part in shaping the future of digital game design, notably for mobile devices. the paper presents new knowledge from controlled live experiments from a casual social game across facebook and mobile platforms, finding positive re - turns by adding social gameplay features. this suggests that not only social network games, but also casual mobile games can benefit from deeper social gameplay mechanics. given the impact of social features on gameplay, game an - alytics will need to evolve to be able to handle requirements that arise from the introduction of social features, e. g. how to measure engagement against social features and shaping organic and viral spreading of a game. | arxiv:1612.02172 |
in this paper we propose a general framework to characterize and solve the stochastic optimization problems with multiple objectives underlying many real world learning applications. we first propose a projection based algorithm which attains an $ o ( t ^ { - 1 / 3 } ) $ convergence rate. then, by leveraging on the theory of lagrangian in constrained optimization, we devise a novel primal - dual stochastic approximation algorithm which attains the optimal convergence rate of $ o ( t ^ { - 1 / 2 } ) $ for general lipschitz continuous objectives. | arxiv:1211.6013 |
the quark propagator is at the core of lattice hadron spectrum calculations as well as studies in other nonperturbative schemes. we investigate the quark propagator with an improved staggered action ( asqtad ) and an improved gluon action, which provides good quality data down to small quark masses. this is used to construct ans \ " { a } tze suitable for model hadron calculations as well as adding to our intuitive understanding of qcd. | arxiv:hep-lat/0209129 |
this paper presents a simplified model - based trajectory optimization ( to ) formulation for motion planning on quadruped mobile manipulators that carry heavy payload of known mass. the proposed payload - aware formulation simultaneously plans locomotion, payload manipulation and considers both robot and payload model dynamics while remaining computationally efficient. at the presence of heavy payload, the approach exhibits reduced leg outstretching ( thus increased manipulability ) in kinematically demanding motions due to the contribution of payload manipulation in the optimization. the framework ' s computational efficiency and performance is validated through a number of simulation and experimental studies with the bi - manual quadruped centauro robot carrying on its arms a payload that exceeds 15 % of its mass and traversing non - flat terrain. | arxiv:2210.06803 |
we investigate the effects of user cooperation on the secrecy of broadcast channels by considering a cooperative relay broadcast channel. we show that user cooperation can increase the achievable secrecy region. we propose an achievable scheme that combines marton ' s coding scheme for broadcast channels and cover and el gamal ' s compress - and - forward scheme for relay channels. we derive outer bounds for the rate - equivocation region using auxiliary random variables for single - letterization. finally, we consider a gaussian channel and show that both users can have positive secrecy rates, which is not possible for scalar gaussian broadcast channels without cooperation. | arxiv:0811.1317 |
we study the universal characteristics of the shape of a polymer chain in an environment with correlated structural obstacles, applying the field - theoretical renormalization group approach. our results qualitatively indicate an increase of the asymmetry of the polymer shape in crowded environment comparing with the pure solution case. | arxiv:1003.1856 |
this study presents the design of four $ 178 \ times178 $ $ ( mm ) ^ { 2 } $ wideband, high gain, highly efficient metasurface - based 4t4r mimo ( multiple - input multiple - output ) antennas with highly isolated ports, covering the middle and a portion of the upper bands of the sub 6 ghz 5g frequency spectrum for 5g - based systems, such as iot ( internet of things ) applications, vehicular communications ( e. g., rooftop antennas of cars or trains ), smart industries ( e. g., farms and factories ). the radiating elements of these antennas use the aperture - coupled feeding technique with a dumbbell - shaped slot, a truncated square patch with two u - shaped slots, and a metasurface layer. the proposed mimo structures place four identical radiating elements like a $ 2 \ times2 $ matrix with $ 90 ^ \ circ $ successive rotations to produce orthogonal electromagnetic waves, improving the isolation between ports. six - millimeter spaces are added between these elements, and two vertical and horizontal strip slots are carved on the ground as the decoupling structure to decrease the mutual coupling. simulation results show that antenna \ _ { 1 }, antenna \ _ { 2 }, and antenna \ _ { 3 } achieve gain values of 6. 2 to 9. 4 dbi, 8. 2 to 11. 6 dbi, 6. 2 to 9. 5 dbi, below - 35, - 25, and - 33 isolation and almost 10 db diversity gain from 2. 8 to 4. 7 ghz, 2. 8 to 4. 5 ghz, and 2. 7 to 4. 9 ghz, respectively. as a prototype, antenna \ _ { 4 } is manufactured, and measurements are performed. it achieves 6. 28 to 10. 45 dbi gain values, below - 23 db isolation, and 0. 001 envelope correlation coefficient over 2. 7 to 4. 3 ghz. the results confirm that the proposed mimo antennas are compatible with the 5g essential requisites. | arxiv:2309.07131 |
we apply the symanzik improvement programme to the 4 + 1 - dimensional local re - formulation of the gradient flow in pure $ su ( n ) $ lattice gauge theories. we show that the classical nature of the flow equation allows to eliminate all cutoff effects at $ \ mathcal o ( a ^ 2 ) $ which originate either from the discretized gradient flow equation or from the gradient flow observable. all the remaining $ \ mathcal o ( a ^ 2 ) $ effects can be understood in terms of local counterterms at the zero flow time boundary. we classify these counterterms and provide a complete set as required for on - shell improvement. compared to the 4 - dimensional pure gauge theory only a single additional counterterm is required, which corresponds to a modified initial condition for the flow equation. a consistency test in perturbation theory is passed and allows to determine all counterterm coefficients to lowest non - trivial order in the coupling. | arxiv:1508.05552 |
pure mathematics is the study of mathematical concepts independently of any application outside mathematics. these concepts may originate in real - world concerns, and the results obtained may later turn out to be useful for practical applications, but pure mathematicians are not primarily motivated by such applications. instead, the appeal is attributed to the intellectual challenge and aesthetic beauty of working out the logical consequences of basic principles. while pure mathematics has existed as an activity since at least ancient greece, the concept was elaborated upon around the year 1900, after the introduction of theories with counter - intuitive properties ( such as non - euclidean geometries and cantor ' s theory of infinite sets ), and the discovery of apparent paradoxes ( such as continuous functions that are nowhere differentiable, and russell ' s paradox ). this introduced the need to renew the concept of mathematical rigor and rewrite all mathematics accordingly, with a systematic use of axiomatic methods. this led many mathematicians to focus on mathematics for its own sake, that is, pure mathematics. nevertheless, almost all mathematical theories remained motivated by problems coming from the real world or from less abstract mathematical theories. also, many mathematical theories, which had seemed to be totally pure mathematics, were eventually used in applied areas, mainly physics and computer science. a famous early example is isaac newton ' s demonstration that his law of universal gravitation implied that planets move in orbits that are conic sections, geometrical curves that had been studied in antiquity by apollonius. another example is the problem of factoring large integers, which is the basis of the rsa cryptosystem, widely used to secure internet communications. it follows that, currently, the distinction between pure and applied mathematics is more a philosophical point of view or a mathematician ' s preference rather than a rigid subdivision of mathematics. = = history = = = = = ancient greece = = = ancient greek mathematicians were among the earliest to make a distinction between pure and applied mathematics. plato helped to create the gap between " arithmetic ", now called number theory, and " logistic ", now called arithmetic. plato regarded logistic ( arithmetic ) as appropriate for businessmen and men of war who " must learn the art of numbers or [ they ] will not know how to array [ their ] troops " and arithmetic ( number theory ) as appropriate for philosophers " because [ they have ] to arise out of the sea of change and lay hold of true being. " euclid of alexandria, when asked by one of his students of what use was the study of geometry, asked his slave to give the | https://en.wikipedia.org/wiki/Pure_mathematics |
surpassing the individual characteristics of the non - hermitian skin effect ( nhse ) and the scale - free ( sf ) effect observed recently, we systematically exploit the exponential decay behavior of bulk eigenstates via the transfer matrix approach in non - hermitian systems. we concentrate on one - dimensional ( 1d ) finite - size non - hermitian systems with 2 * 2 transfer matrices in either the absence or presence of the boundary impurity. we analytically unveil that the unidirectional sf effect emerges with the singular transfer matrices, while the hybrid scale - free skin ( sfs ) effect appears with the nonsingular transfer matrices even when an open boundary condition ( obc ) is imposed. the unidirectional sf effect exceeds the scope of the sf effect in previous works, while the hybrid sfs effect is an interesting interplay between the skin effect and the sf effect in finite - size systems. our results reveal that the skin effect under the obc prevails when it coexists with the sf effect as the system approaches the thermodynamic limit in the presence of the hybrid sfs effect. our approach paves the way for rigorous and unified explorations of the skin and sf effects in both hermitian and non - hermitian systems with generic boundary conditions. | arxiv:2307.16632 |
this paper describes the architecture and performance of oracle, an approach for detecting a unique radio from a large pool of bit - similar devices ( same hardware, protocol, physical address, mac id ) using only iq samples at the physical layer. oracle trains a convolutional neural network ( cnn ) that balances computational time and accuracy, showing 99 \ % classification accuracy for a 16 - node usrp x310 sdr testbed and an external database of $ > $ 100 cots wifi devices. our work makes the following contributions : ( i ) it studies the hardware - centric features within the transmitter chain that causes iq sample variations ; ( ii ) for an idealized static channel environment, it proposes a cnn architecture requiring only raw iq samples accessible at the front - end, without channel estimation or prior knowledge of the communication protocol ; ( iii ) for dynamic channels, it demonstrates a principled method of feedback - driven transmitter - side modifications that uses channel estimation at the receiver to increase differentiability for the cnn classifier. the key innovation here is to intentionally introduce controlled imperfections on the transmitter side through software directives, while minimizing the change in bit error rate. unlike previous work that imposes constant environmental conditions, oracle adopts the ` train once deploy anywhere ' paradigm with near - perfect device classification accuracy. | arxiv:1812.01124 |
we present a yolov3 - cnn pipeline for detecting vehicles, segregation of number plates, and local storage of final recognized characters. vehicle identification is performed under various image correction schemes to determine the effect of environmental factors ( angle of perception, luminosity, motion - blurring, and multi - line custom font etc. ). a yolov3 object detection model was trained to identify vehicles from a dataset of traffic images. a second yolov3 layer was trained to identify number plates from vehicle images. based upon correction schemes, individual characters were segregated and verified against real - time data to calculate accuracy of this approach. while characters under direct view were recognized accurately, some numberplates affected by environmental factors had reduced levels of accuracy. we summarize the results under various environmental factors against real - time data and produce an overall accuracy of the pipeline model. | arxiv:2211.05229 |
for a knot $ k $ the cube number is a knot invariant defined to be the smallest $ n $ for which there is a cube diagram of size $ n $ for $ k $. there is also a legendrian version of this invariant called the \ emph { legendrian cube number }. we will show that the legendrian cube number distinguishes the legendrian left hand torus knots with maximal thurston - bennequin number and maximal rotation number from the legendrian left hand torus knots with maximal thurston - bennequin number and minimal rotation number. | arxiv:1012.4482 |
we analyze the temporal structure of long ( ( t _ { 90 } > 2sec ) ) and short ( ( t _ { 90 } < 2sec ) ) batse bursts. we find that : ( i ) in many short bursts ( \ delta t _ { min } / t \ ll 1 ) ( where ( \ delta t _ { min } ) is the shortest pulse ). this indicates that short bursts arise, like long ones, in internal shocks. ( ii ) in long bursts there is an excess of long intervals between pulses ( relative to a lognormal distribution ). this excess can be explained by the existence of \ emph { quiescent times }, long periods with no signal above the background that arise, most likely, from periods with no source activity. the lognormal distribution of the intervals ( excluding the \ emph { quiescent times } ) is similar and correlated with the distribution of the pulses width, in agreement with the predictions of the internal shock model. | arxiv:astro-ph/0103011 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.