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we study tree approximations to classical two - body partition functions on sparse and loopy graphs via the brydges - kennedy - abdessalam - rivasseau forest expansion. we show that for sparse graphs ( with large cycles ), the partition function above a certain temperature $ t ^ * $ can be approximated by a graph polynomial expansion over forests of the interaction graph. within this " forest phase ", we show that the approximation can be written in terms of a reference tree $ \ mathcal t $ on the interaction graph, with corrections due to cycles. from this point of view, this implies that high - temperature models are easy to solve on sparse graphs, as one can evaluate the partition function using belief propagation. we also show that there exists a high - and low - temperature regime, in which $ \ mathcal t $ can be obtained via a maximal spanning tree algorithm on a ( given ) weighted graph. we study the algebra of these corrections and provide first - and second - order approximation to the tree ansatz, and give explicit examples for the first - order approximation.
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arxiv:2009.00113
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we study evolution of a flat friedmann - robertson walker universe filled with a bulk viscous cosmological fluid in a higher derivative theory of gravity in the presence of time varying gravitational and cosmological constant. cosmological models admitting both power - law and exponential expansions are explored here in the presence of imperfect fluid described by full israel and stewart theory. we note some new and interesting cosmological solutions relevant for model building including present accelerating phase. in the case of power law, it is found that gravitational constant increases as the time evolves for a positive cosmological constant whereas it decreases for a negative cosmological constant. the evolution of temperature of a viscous universe is also determined.
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arxiv:1105.3307
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the delaunay tessellation of a locally finite subset of hyperbolic space is constructed using convex hulls in euclidean space of one higher dimension. for finite and lattice - invariant sets it is proven to be a polyhedral decomposition, and versions ( necessarily modified from the euclidean setting ) of the empty circumspheres condition and geometric duality with the voronoi tessellation are proved. some pathological examples of infinite, non lattice - invariant sets are exhibited.
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arxiv:1308.4899
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this paper addresses a mathematically tractable model of the prisoner ' s dilemma using the framework of active inference. in this work, we design pairs of bayesian agents that are tracking the joint game state of their and their opponent ' s choices in an iterated prisoner ' s dilemma game. the specification of the agents ' belief architecture in the form of a partially - observed markov decision process allows careful and rigourous investigation into the dynamics of two - player gameplay, including the derivation of optimal conditions for phase transitions that are required to achieve certain game - theoretic steady states. we show that the critical time points governing the phase transition are linearly related to each other as a function of learning rate and the reward function. we then investigate the patterns that emerge when varying the agents ' learning rates, as well as the relationship between the stochastic and deterministic solutions to the two - agent system.
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arxiv:2306.15494
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in this article we review four - dimensional string vacua with n = 2 space - time supersymmetry. in particular, we will discuss several aspects of the string - string duality between the heterotic string, compactified on $ k3 \ times t ^ 2 $, and the type ii superstring compactified on a calabi - yau three - fold. we investigate the massless supersymmetric spectra, showing agreement for a large class of dual heterotic / type ii string pairs. some emphasis is given to non - perturbative heterotic phenomena, such as non - perturbative transitions among different vacua and strong coupling singularities, and to their geometric calabi - yau description on the type ii side. we compare the effective n = 2 supergravity actions of dual heterotic / type ii string compactifications, and show that the n = 2 prepotentials and also higher order gravitational couplings nicely agree in the weak heterotic coupling limit. finally we consider extremal black hole solutions of n = 2 supergravity which arise in the context of heterotic or type ii n = 2 compactifications. for the type ii backgrounds we show how the entropies of these black holes depend on the topological data of the underlying calabi - yau spaces ; we also construct massless black holes which are relevant for the conifold transition among different calabi - yau vacua.
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arxiv:hep-th/9803072
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we verify functional a posteriori error estimate for obstacle problem proposed by repin. simplification into 1d allows for the construction of a nonlinear benchmark for which an exact solution of the obstacle problem can be derived. quality of a numerical approximation obtained by the finite element method is compared with the exact solution and the error of approximation is bounded from above by a majorant error estimate. the sharpness of the majorant error estimate is discussed.
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arxiv:1301.5923
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there has been substantial interest in obtaining a quantum - gravitational description of de sitter space. however, any such attempts have encountered formidable obstacles, and new philosophical directions may be in order. one possibility, although somewhat speculative, would be to view the physical universe as a timelike hypersurface evolving in a higher - dimensional bulk spacetime ; that is, the renowned brane - world scenario. in this paper, we extend some recent studies along this line, and consider a non - critical 3 - brane moving in the background of an anti - de sitter reissner - nordstrom - like black hole. interestingly, even an arbitrarily small electrostatic charge in the bulk can induce a singularity - free ` ` bounce ' ' universe on the brane, whereas a vanishing charge typically implies a singular cosmology. however, under closer examination, from a holographic ( ds / cft ) perspective, we demonstrate that the charge - induced bounce cosmologies are not physically viable. this implies the necessity for censoring against charge in a bulk black hole.
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arxiv:hep-th/0205251
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in this paper we develop a theory of linear differential systems analogous to the classical one for odes, including the obtaining of fundamental matrices, the development of a variation of parameters formula and the expression of the green ' s functions. we also derive interesting results in the case of differential equations with reflection and generalize the hyperbolic phasor addition formula to the case of matrices.
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arxiv:1707.00839
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in the standard model ( sm ), the $ \ rho $ parameter is equal to 1 and the ratio $ \ lambda _ { wz } $ of higgs $ \ to zz $ and higgs $ \ to ww $ is also equal to 1 at the tree level. when going beyond the sm with more than one types of higgs representations these quantities may be different from the sm predictions which can provide crucial information about new physics. there may also exist a certain charged higgs $ h ^ + $ decays into a $ w ^ + $ and a $ z $. imposing a custodial symmetry can force the parameter $ \ rho $ to be equal to 1 with certain predictions for $ \ lambda _ { wz } $ and $ h ^ + \ to w ^ + z $. however, imposing $ \ rho = 1 $ without custodial symmetry may have different predictions. we show how differences arise and how to use experimental data to obtain information about the underlying physics in a model with the sm plus a real and a complex $ su ( 2 ) _ l $ triplets.
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arxiv:1803.05254
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we show that the aharonov - bohm effect finds a natural description in the setting of qft on curved spacetimes in terms of superselection sectors of local observables. the extension of the analysis of superselection sectors from minkowski spacetime to an arbitrary globally hyperbolic spacetime unveils the presence of a new quantum number labeling charged superselection sectors. in the present paper we show that this " topological " quantum number amounts to the presence of a background flat potential which rules the behaviour of charges when transported along paths as in the aharonov - bohm effect. to confirm these abstract results we quantize the dirac field in presence of a background flat potential and show that the aharonov - bohm phase gives an irreducible representation of the fundamental group of the spacetime labeling the charged sectors of the dirac field. we also show that non - abelian generalizations of this effect are possible only on space - times with a non - abelian fundamental group.
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arxiv:1912.05297
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generalized mode - coupling theory ( gmct ) constitutes a systematically correctable, first - principles theory to study the dynamics of supercooled liquids and the glass transition. it is a hierarchical framework that, through the incorporation of increasingly many particle density correlations, can remedy some of the inherent limitations of the ideal mode - coupling theory ( mct ). however, despite mct ' s limitations, the ideal theory also enjoys several remarkable successes, notably including the analytical scaling laws for the $ \ alpha $ - and $ \ beta $ - relaxation dynamics. here we mathematically derive similar scaling laws for arbitrary - order multi - point density correlation functions obtained from gmct under arbitrary mean - field closure levels. more specifically, we analytically derive the asymptotic and preasymptotic solutions for the long - time limits of multi - point density correlators, the critical dynamics with two power - law decays, the factorization scaling laws in the $ \ beta $ - relaxation regime, and the time - density superposition principle in the $ \ alpha $ - relaxation regime. the two characteristic power - law - divergent relaxation times for the two - step decay and the non - trivial relation between their exponents are also obtained. the validity ranges of the leading - order scaling laws are also provided by considering the leading preasymptotic corrections. furthermore, we test these solutions for the percus - yevick hard - sphere system. we demonstrate that gmct preserves all the celebrated scaling laws of mct while quantitatively improving the exponents, rendering the theory a promising candidate for an ultimately quantitative first - principles theory of glassy dynamics.
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arxiv:2008.10550
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we present 168 arcmin ^ 2 spectral images of the sgr b2 complex taken with herschel / spire - fts. we detect ubiquitous emission from co ( up to j = 12 - 11 ), h2o, [ ci ] 492, 809 ghz, and [ nii ] 205 um lines. we also present maps of the sio, n2h +, hcn, and hco + emission obtained with the iram30m telescope. the cloud environment dominates the emitted fir ( 80 % ), h2o 752 ghz ( 60 % ) mid - j co ( 91 % ), and [ ci ] ( 93 % ) luminosity. the region shows very extended [ nii ] emission ( spatially correlated with the 24 and 70 um dust emission ). the observed fir luminosities imply g _ 0 ~ 10 ^ 3. the extended [ ci ] emission arises from a pervasive component of neutral gas with n _ h ~ 10 ^ 3 cm - 3. the high ionization rates, produced by enhanced cosmic - ray ( cr ) fluxes, drive the gas heating to tk ~ 40 - 60 k. the mid - j co emission arises from a similarly extended but more pressurized gas component ( p _ th ~ 10 ^ 7 k cm - 3 ). specific regions of enhanced sio emission and high co - to - fir intensity ratios ( > 10 ^ - 3 ) show mid - j co emission compatible with shock models. a major difference compared to more quiescent star - forming clouds in the disk of our galaxy is the extended nature of the sio and n2h + emission in sgr b2. this can be explained by the presence of cloud - scale shocks, induced by cloud - cloud collisions and stellar feedback, and the much higher cr ionization rate ( > 10 ^ - 15 s - 1 ) leading to overabundant h3 + and n2h +. hence, sgr b2 hosts a more extreme environment than star - forming regions in the disk of the galaxy. as a usual template for extragalactic comparisons, sgr b2 shows more similarities to ultra luminous infrared galaxies such as arp 220, including a " deficit " in the [ ci ] / fir and [ nii ] / fir intensity ratios, than to pure starburst galaxies such as m82. however, it is the extended cloud environment, rather than the cores, that serves as a useful template when telescopes do not resolve such extended regions
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arxiv:2103.17177
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we establish lower bounds for all weighted even moments of primes up to $ x $ in intervals which are in agreement with a conjecture of montgomery and soundararajan. our bounds hold unconditionally for an unbounded set of values of $ x $, and hold for all $ x $ under the riemann hypothesis. we also deduce new unconditional $ \ omega $ - results for the classical prime counting function.
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arxiv:2009.05760
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in three dimensions, dipole - dipole interactions which alter atomic level shifts and spontaneous decay rates only persist over distances comparable to the wavelength of the emitted light. in this paper we show that it is possible to significantly extend the range of these interactions with the help of a partially transparent asymmetric mirror interface. suppose two two - level atoms are placed on opposite sides of the interface, each at the position of the mirror image of the other. in this case, their emitted light interferes almost exactly as it would when the atoms are right next to each other. hence their dipole - dipole interaction assumes an additional maximum, even when the actual distance of the atoms is several orders of magnitude larger than the transition wavelength. although the resulting ultralong - range interactions are in general relatively weak, we expect them to find applications in quantum technology, like non - invasive quantum sensing.
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arxiv:2305.18826
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this paper presents the analysis of a deep near - infrared j, h, ks - imaging survey ( 37. 5 sq deg ) aimed at tracing the galaxy distribution of the great attractor ( ga ) in the zone of avoidance along the so - called norma wall. the resulting galaxy catalog is complete to extinction - corrected magnitudes ks ^ o = 14. 8 mag for extinctions less than a _ k = 1. 0 mag and star densities below log n ( ks < 14. 0 ) < 4. 72. of the 4360 cataloged galaxies, 99. 2 % lie in the hereby constrained 89. 5 % of the survey area. although the analyzed galaxy distribution reveals no new major galaxy clusters at the ga distance ( albeit some more distant ones ), the overall number counts and luminosity density indicate a clear and surprisingly smooth overdensity at the ga distance that extends over the whole surveyed region. a mass estimate of the norma wall overdensity derived from ( a ) galaxy number counts and ( b ) photometric redshift distribution gives a lower value compared to the original prediction by lynden - bell et al. 1988 ( ~ 14 % ), but is consistent with more recent independent assessments.
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arxiv:1107.1069
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discussion of ` ` equi - energy sampler ' ' by kou, zhou and wong [ math. st / 0507080 ]
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arxiv:math/0611219
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the recurrent activity of radio agn, with phases of activity alternating with periods of quiescence, has been known since the early studies of these objects. the full relevance of this cycle is emphasised by the requirement, from the agn feedback scenario, of a recurrent impact of the energy released by the smbh during the lifetime of the host galaxy : only in this way can agn feedback influence galaxy evolution. radio agn in different evolutionary phases can be identified by their properties, like morphology and spectral indices. dying / remnant and restarted sources have been the most elusive to select and characterise, but they are crucial to quantify the full life cycle. thanks to the availability of new, large radio surveys ( particularly at low frequencies ), it is finally possible to make a more complete census of these rare sources and start building larger samples. this paper gives an overview of the recent work conducted using a variety of radio telescopes and surveys, highlighting some of the new results characterising the properties of dying / remnant and restarted radio sources and what has been learned about the life cycle of radio agn. the comparison with the predictions from numerical simulations is also discussed. the results so far show that remnant and restarted radio agn have a variety of properties which make these objects more complex than previously thought.
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arxiv:2403.13329
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spiking neural network ( snn ) has attracted much attention due to their powerful spatio - temporal information representation ability. capsule neural network ( capsnet ) does well in assembling and coupling features at different levels. here, we propose spiking capsnet by introducing the capsules into the modelling of spiking neural networks. in addition, we propose a more biologically plausible spike timing dependent plasticity routing mechanism. by fully considering the spatio - temporal relationship between the low - level spiking capsules and the high - level spiking capsules, the coupling ability between them is further improved. we have verified experiments on the mnist and fashionmnist datasets. compared with other excellent snn models, our algorithm still achieves high performance. our spiking capsnet fully combines the strengthens of snn and capsnet, and shows strong robustness to noise and affine transformation. by adding different salt - pepper and gaussian noise to the test dataset, the experimental results demonstrate that our spiking capsnet shows a more robust performance when there is more noise, while the artificial neural network can not correctly clarify. as well, our spiking capsnet shows strong generalization to affine transformation on the affnist dataset.
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arxiv:2111.07785
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in this paper, we propose and analyze a new matrix - free primal - dual algorithm, called restarted halpern primal - dual hybrid gradient ( rhpdhg ), for solving linear programming ( lp ). we show that rhpdhg can achieve optimal accelerated linear convergence on feasible and bounded lp. furthermore, we present a refined analysis that demonstrates an accelerated two - stage convergence of rhpdhg over the vanilla pdhg with an improved complexity for identification and an accelerated eventual linear convergence that does not depend on the conservative global hoffman constant. regarding infeasible lp, we show that rhpdhg can recover infeasibility certificates with an accelerated linear rate, improving the previous convergence rates. furthermore, we discuss an extension of rhpdhg by adding reflection operation ( which is dubbed as $ \ mathrm { r ^ 2hpdhg } $ ), and demonstrate that it shares all theoretical guarantees of rhpdhg with an additional factor of 2 speedup in the complexity bound. lastly, we build up a gpu - based lp solver using rhpdhg / $ \ mathrm { r ^ 2hpdhg } $, and the experiments on 383 miplib instances showcase an improved numerical performance compared cupdlp. jl.
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arxiv:2407.16144
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the pattern of a large approximate degeneracy of the excited hadron spectra ( larger than the chiral restoration degeneracy ) is present in the recent experimental report of bugg. here we try to model this degeneracy with state of the art quark models. we review how the coulomb gauge chiral invariant and confining bethe - salpeter equation simplifies in the case of very excited quark - antiquark mesons, including angular or radial excitations, to a salpeter equation with an ultrarelativistic kinetic energy with the spin - independent part of the potential. the resulting meson spectrum is solved, and the excited chiral restoration is recovered, for all mesons with j > 0. applying the ultrarelativistic simplification to a linear equal - time potential, linear regge trajectories are obtained, for both angular and radial xcitations. the spectrum is also compared with the semi - classical bohr - sommerfeld quantization relation. however the excited angular and radial spectra do not coincide exactly. we then search, with the classical bertrand theorem, for central potentials producing always classical closed orbits with the ultrarelativistic kinetic energy. we find that no such potential exists, and this implies that no exact larger degeneracy can be obtained in our equal - time framework, with a single principal quantum number comparable to the non - relativistic coulomb or harmonic oscillator potentials. nevertheless we find plausible that the large experimental approximate degeneracy will be modelled in the future by quark models beyond the present state of the art.
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arxiv:hep-ph/0703114
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the pure spinor formulation of superstring theory includes an interacting sector of central charge $ c _ { \ lambda } = 22 $, which can be realized as a curved $ \ beta \ gamma $ system on the cone over the orthogonal grassmannian $ \ text { og } ^ { + } ( 5, 10 ) $. we find that the spectrum of the $ \ beta \ gamma $ system organizes into representations of the $ \ mathfrak { g } = \ mathfrak { e } _ 6 $ affine algebra at level $ - 3 $, whose $ \ mathfrak { so } ( 10 ) _ { - 3 } \ oplus { \ mathfrak u } ( 1 ) _ { - 4 } $ subalgebra encodes the rotational and ghost symmetries of the system. as a consequence, the pure spinor partition function decomposes as a sum of affine $ \ mathfrak { e } _ 6 $ characters. we interpret this as an instance of a more general pattern of enhancements in curved $ \ beta \ gamma $ systems, which also includes the cases $ \ mathfrak { g } = \ mathfrak { so } ( 8 ) $ and $ \ mathfrak { e } _ 7 $, corresponding to target spaces that are cones over the complex grassmannian $ \ text { gr } ( 2, 4 ) $ and the complex cayley plane $ \ mathbb { op } ^ 2 $. we identify these curved $ \ beta \ gamma $ systems with the chiral algebras of certain $ 2d $ $ ( 0, 2 ) $ cfts arising from twisted compactification of 4d $ \ mathcal { n } = 2 $ scfts on $ s ^ 2 $.
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arxiv:1902.09504
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then be compared to the us community colleges. since the implementation of bologna process in portugal in 2007, the polytechnics offer the 1st cycle ( licentiate degree ) and 2nd cycle ( master ' s degree ) of higher studies. until 1998, the polytechnics only awarded bachelor ( portuguese : bacharelato ) degrees ( three - year short - cycle degrees ) and were not authorized to award higher degrees. they however granted post - bachelor diplomas in specialized higher studies ( dese, diploma de estudos superiores especializados ), that could be obtained after the conclusion of a two - year second cycle of studies and were academical equivalent to the university ' s licentiate degrees ( licenciatura ). after 1998, they started to be allowed to confer their own licentiate degrees, which replaced the dese diplomas. = = = romania = = = politehnica university of bucharest, 1864 polytechnic university of timisoara, 1920 gheorghe asachi technical university of iasi, 1937 technical university of cluj - napoca, 1948 technical university of civil engineering of bucharest, 1948 oil & gas university of ploiesti, 1948 university of petrosani, 1948 technical military academy of bucharest, 1949 = = = russia = = = bauman moscow state technical university saint petersburg polytechnical university novosibirsk state technical university tomsk polytechnic university moscow polytechnic university = = = singapore = = = polytechnics in singapore do not offer bachelor ' s, master ' s degrees or doctorate. however, polytechnics in singapore offer three - year diploma courses in fields ranging from applied sciences to business, information technology, humanities, social sciences, and other vocational fields such as engineering and nursing. there are five polytechnics in singapore : singapore polytechnic, ngee ann polytechnic, temasek polytechnic, nanyang polytechnic and republic polytechnic. the polytechnic diploma certification in singapore is equivalent to an associate degree obtainable at the community colleges in the united states. a polytechnic diploma in singapore is also known to be parallel and sometimes equivalent to the first years at a bachelor ' s degree - granting institution, thus, polytechnic graduates in singapore have the privilege of being granted transfer credits or module exemptions when they apply to a local or overseas universities, depending on the university ' s policies on transfer credits. the only university in singapore with the term " institute of technology ", most notably the singapore institute of technology were developed in 2009 as an option for polytechnic graduates who desire to pursue a bachelor ' s degree. other technological
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https://en.wikipedia.org/wiki/Institute_of_technology
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in this paper, we use the inverse curvature flow to prove a sharp geometric inequality on star - shaped and two - convex hypersurface in hyperbolic space.
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arxiv:1211.4109
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we consider a chain of anharmonic oscillators with local mean field interaction and long - range stochastic exchanges of velocity. even if the particles are not exchangeable, we prove the convergence of the empirical measure associated with this chain to a solution of a vlasov - type equation. we then use this convergence to prove energy diffusion for a restricted class of anharmonic potentials.
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arxiv:2010.02531
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we solve the general problem of determining, through imaging, the three - dimensional positions of $ n $ weak incoherent point - like emitters in an arbitrary spatial configuration. we show that a structured measurement strategy in which a linear interferometer feeds into an array of photo - detectors is always optimal for this estimation problem, in the sense that it saturates the quantum cram \ ' er - rao bound. we provide a method for the explicit construction of the optimal interferometer. further explicit results for the quantum fisher information and the optimal interferometer design that attains it are obtained for the case of one and two incoherent emitters in the paraxial regime. this work provides insights into the phenomenon of super - resolution through incoherent imaging that has attracted much attention recently. our results will find a wide range of applications over a broad spectrum of frequencies, from fluorescence microscopy to stellar interferometry.
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arxiv:1909.09581
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hpc systems used for research run a wide variety of software and workflows. this software is often written or modified by users to meet the needs of their research projects, and rarely is built with security in mind. in this paper we explore several of the key techniques that mit lincoln laboratory supercomputing center has deployed on its systems to manage the security implications of these workflows by providing enforced separation for processes, filesystem access, network traffic, and accelerators to make every user feel like they are running on a personal hpc.
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arxiv:2409.10770
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witnessing entanglement is crucial in quantum information processing. with properly preparing ancillary states, it has been shown previously that genuine entanglement can be witnessed without trusting measurement devices. in this work, we generalize the scenario and show that generic multipartite entanglement structures, including entanglement of subsystems and entanglement depth, can be witnessed via measurement - device - independent means. as the original measurement - device - independent entanglement witness scheme exploits only one out of four bell measurement outcomes for each party, a direct generalization to multipartite quantum states will inevitably cause inefficiency in entanglement detection after taking account of statistical fluctuations. to resolve this problem, we also present a way to utilize all the measurement outcomes. the scheme is efficient for multipartite entanglement detection and can be realized with state - of - the - art technologies.
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arxiv:1607.08002
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the high production rate and $ \ langle x _ { f } \ rangle > 0. 33 $ of the doubly charmed baryons measured by the selex experiment is not amenable to perturbative qcd analysis. in this paper we calculate the production of the doubly heavy baryons with the double intrinsic charm fock states whose existence is rigorously predicted by qcd. the production rate and the longitudinal momentum distribution are both reproduced. we also show that the production rates of the doubly charmed baryons and double $ j / \ psi $ production observed by na3 collaboration are comparable. recent experimental results are reviewed. the production cross section of the doubly charmed baryons at a fixed - target experiment at the lhc is presented.
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arxiv:1605.03070
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we present a simple paradigm for detection of an immobile target by a space - time coupled random walker with a finite lifetime. the motion of the walker is characterized by linear displacements at a fixed speed and exponentially distributed duration, interrupted by random changes in the direction of motion and resumption of motion in the new direction with the same speed. we call these walkers " mortal creepers ". a mortal creeper may die at any time during its motion according to an exponential decay law characterized by a finite mean death rate $ \ omega _ m $. while still alive, the creeper has a finite mean frequency $ \ omega $ of change of the direction of motion. in particular, we consider the efficiency of the target search process, characterized by the probability that the creeper will eventually detect the target. analytic results confirmed by numerical results show that there is an $ \ omega _ m $ - dependent optimal frequency $ \ omega = \ omega _ { opt } $ that maximizes the probability of eventual target detection. we work primarily in one - dimensional ( $ d = 1 $ ) domains and examine the role of initial conditions and of finite domain sizes. numerical results in $ d = 2 $ domains confirm the existence of an optimal frequency of change of direction, thereby suggesting that the observed effects are robust to changes in dimensionality. in the $ d = 1 $ case, explicit expressions for the probability of target detection in the long time limit are given. in the case of an infinite domain, we compute the detection probability for arbitrary times and study its early - and late - time behavior. we further consider the survival probability of the target in the presence of many independent creepers beginning their motion at the same location and at the same time. we also consider a version of the standard " target problem " in which many creepers start at random locations at the same time.
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arxiv:1503.02013
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we study computational methods for the approximation of special functions recurrent in geometric function theory and quasiconformal mapping theory. the functions studied can be expressed as quotients of complete elliptic integrals and as inverses of such quotients. in particular, we consider the distortion function $ \ varphi _ k ( r ) $ which gives a majorant for $ | f ( x ) | $ when $ f : \ mathbb { b } ^ 2 \ to \ mathbb { b } ^ 2, f ( 0 ) = 0, $ is a quasiconformal mapping of the unit disk $ \ mathbb { b } ^ 2. $ it turns out that the approximation method is very simple : five steps of landen iteration is enough to achieve machine precision.
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arxiv:2212.09336
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training advanced ai models requires large investments in computational resources, or compute. yet, as hardware innovation reduces the price of compute and algorithmic advances make its use more efficient, the cost of training an ai model to a given performance falls over time - a concept we describe as increasing compute efficiency. we find that while an access effect increases the number of actors who can train models to a given performance over time, a performance effect simultaneously increases the performance available to each actor. this potentially enables large compute investors to pioneer new capabilities, maintaining a performance advantage even as capabilities diffuse. since large compute investors tend to develop new capabilities first, it will be particularly important that they share information about their ai models, evaluate them for emerging risks, and, more generally, make responsible development and release decisions. further, as compute efficiency increases, governments will need to prepare for a world where dangerous ai capabilities are widely available - for instance, by developing defenses against harmful ai models or by actively intervening in the diffusion of particularly dangerous capabilities.
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arxiv:2311.15377
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we have surveyed 84 class 0, class i, and flat - spectrum protostars in mid - infrared [ si ii ], [ fe ii ] and [ s i ] line emission, and 11 of these in far - infrared [ o i ] emission. we use the results to derive their mass outflow rates. thereby we observe a strong correlation of mass outflow rates with bolometric luminosity, and with the inferred mass accretion rates of the central objects, which continues through the class 0 range the trend observed in class ii young stellar objects. along this trend from large to small mass - flow rates, the different classes of young stellar objects lie in the sequence class 0 - - class i / flat - spectrum - - class ii, indicating that the trend is an evolutionary sequence in which mass outflow and accretion rates decrease together with increasing age, while maintaining rough proportionality. the survey results include two which are key tests of magnetocentrifugal outflow - acceleration mechanisms : the distribution of the outflow / accretion branching ratio b, and limits on the distribution of outflow speeds. neither rule out any of the three leading outflow - acceleration, angular - momentum - ejection mechanisms, but they provide some evidence that disk winds and accretion - powered stellar winds ( apsws ) operate in many protostars. an upper edge observed in the branching - ratio distribution is consistent with the upper bound of b = 0. 6 found in models of apsws, and a large fraction ( 0. 31 ) of the sample have branching ratio sufficiently small that only disk winds, launched on scales as large as several au, have been demonstrated to account for them.
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arxiv:1511.04787
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we study two models describing the interaction of a two - level system with two quantum field modes. the first one is equivalent to a dissipative two - state system with just two boson fields in the absence of tunneling. the second describes two orthogonal fields interacting with the corresponding orthogonal dipoles of a two - level system. we show that both models present a partial two - mode $ su ( 2 ) $ symmetry and that they can be solved in the exceptional case of resonant fields. we study their ground state configurations, that is, we find the quantum precursors of the corresponding semi - classical phase transitions, as well as their whole spectra to infer their integrability. we show that the first model in the exceptional case is isomorphic with the quantum rabi model and allows just two ground state configurations, vacuum and non - vacuum. the second model allows four ground state configurations, one vacuum, two non - vacuum single mode and one non - vacuum dual mode, and give analytic and numerical pointers that may suggest its integrability. we also show that in the single excitation subspace these models can serve as a fast $ su ( 2 ) $ beam splitter even in the ultra - strong coupling regime.
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arxiv:1504.02748
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we show that excitability is generic in systems displaying dissipative solitons when spatial inhomogeneities and drift are present. thus, dissipative solitons in systems which do not have oscillatory states, such as the prototypical swift - hohenberg equation, display oscillations and type i and ii excitability when adding inhomogeneities and drift to the system. this rich dynamical behavior arises from the interplay between the pinning to the inhomogeneity and the pulling of the drift. the scenario presented here provides a general theoretical understanding of oscillatory regimes of dissipative solitons reported in semiconductor microresonators. our results open also the possibility to observe this phenomenon in a wide variety of physical systems.
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arxiv:1302.3536
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multi - view unsupervised feature selection ( mufs ) has been demonstrated as an effective technique to reduce the dimensionality of multi - view unlabeled data. the existing methods assume that all of views are complete. however, multi - view data are usually incomplete, i. e., a part of instances are presented on some views but not all views. besides, learning the complete similarity graph, as an important promising technology in existing mufs methods, cannot achieve due to the missing views. in this paper, we propose a complementary and consensus learning - based incomplete multi - view unsupervised feature selection method ( c $ ^ { 2 } $ imufs ) to address the aforementioned issues. concretely, c $ ^ { 2 } $ imufs integrates feature selection into an extended weighted non - negative matrix factorization model equipped with adaptive learning of view - weights and a sparse $ \ ell _ { 2, p } $ - norm, which can offer better adaptability and flexibility. by the sparse linear combinations of multiple similarity matrices derived from different views, a complementary learning - guided similarity matrix reconstruction model is presented to obtain the complete similarity graph in each view. furthermore, c $ ^ { 2 } $ imufs learns a consensus clustering indicator matrix across different views and embeds it into a spectral graph term to preserve the local geometric structure. comprehensive experimental results on real - world datasets demonstrate the effectiveness of c $ ^ { 2 } $ imufs compared with state - of - the - art methods.
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arxiv:2208.09736
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this paper extends the work of a previous paper [ arxiv : 1208. 2611 ] on the flow of time, to consider the origin of the arrow of time. it proposes that a ` past condition ' cascades down from cosmological to micro scales, being realized in many microstructures and setting the arrow of time at the quantum level by top - down causation. this physics arrow of time then propagates up, through underlying emergence of higher level structures, to geology, astronomy, engineering, and biology. the appropriate space - time picture to view all this is an emergent block universe ( ` ebu ' ), that recognizes the way the present is different from both the past and the future. this essential difference is the ultimate reason the arrow of time has to be the way it is.
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arxiv:1302.7291
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the possibility of distinguishing dirac and majorana fermions by cosmic torsion in the spatial - flat frw spacetime is discussed. the scattering amplitudes of two types of fermions deviate from each other by the vector part of torsion in non - minimal coupling case. the scattering of massive fermions by cosmic torsion leads to a shift of final state energy distribution. the difference between shift values of two types of fermions can be used to distinguish fermion types of neutrinos.
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arxiv:2304.00475
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we apply a functional - integral formalism for markovian birth and death processes to determine asymptotic corrections to mean - field theory in the malthus - verhulst process ( mvp ). expanding about the stationary mean - field solution, we identify an expansion parameter that is small in the limit of large mean population, and derive a diagrammatic expansion in powers of this parameter. the series is evaluated to fifth order using computational enumeration of diagrams. although the mvp has no stationary state, we obtain good agreement with the associated { \ it quasi - stationary } values for the moments of the population size, provided the mean population size is not small. we compare our results with those of van kampen ' s $ \ omega $ - expansion, and apply our method to the mvp with input, for which a stationary state does exist.
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arxiv:cond-mat/0507576
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cost savings attributed to developing and testing for quality code as soon as possible in the process, particularly before release. = = = professions = = = a person with a profession in computer engineering is called a computer engineer. = = applications and practice = = there are two major focuses in computer engineering : hardware and software. = = = computer hardware engineering = = = according to the united states bls, job outlook employment for computer hardware engineers, the expected ten - year growth from 2019 to 2029 for computer hardware engineering was an estimated 2 % and a total of 71, 100 jobs. ( " slower than average " in their own words when compared to other occupations ) ". this is a decrease from the 2014 to 2024 bls computer hardware engineering estimate of 3 % and a total of 77, 700 jobs ; " and is down from 7 % for the 2012 to 2022 bls estimate and is further down from 9 % in the bls 2010 to 2020 estimate. " today, computer hardware is somewhat equal to electronic and computer engineering ( ece ) and has been divided into many subcategories, the most significant being embedded system design. = = = computer software engineering = = = according to the u. s. bureau of labor statistics ( bls ), " computer applications software engineers and computer systems software engineers are projected to be among the faster than average growing occupations " the expected ten - year growth as of 2014 for computer software engineering was an estimated seventeen percent and there was a total of 1, 114, 000 jobs that same year. this is down from the 2012 to 2022 bls estimate of 22 % for software developers. and, further down from the 30 % 2010 to 2020 bls estimate. in addition, growing concerns over cybersecurity add up to put computer software engineering high above the average rate of increase for all fields. however, some of the work will be outsourced in foreign countries. due to this, job growth will not be as fast as during the last decade, as jobs that would have gone to computer software engineers in the united states would instead go to computer software engineers in countries such as india. in addition, the bls job outlook for computer programmers, 2014 – 24 has an −8 % ( a decline, in their words ), then a job outlook, 2019 - 29 of - 9 % ( decline ), then a 10 % decline for 2021 - 2031 and now an 11 % decline for 2022 - 2032 for those who program computers ( i. e. embedded systems
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https://en.wikipedia.org/wiki/Computer_engineering
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recent years have seen embodied visual navigation advance in two distinct directions : ( i ) in equipping the ai agent to follow natural language instructions, and ( ii ) in making the navigable world multimodal, e. g., audio - visual navigation. however, the real world is not only multimodal, but also often complex, and thus in spite of these advances, agents still need to understand the uncertainty in their actions and seek instructions to navigate. to this end, we present avlen ~ - - an interactive agent for audio - visual - language embodied navigation. similar to audio - visual navigation tasks, the goal of our embodied agent is to localize an audio event via navigating the 3d visual world ; however, the agent may also seek help from a human ( oracle ), where the assistance is provided in free - form natural language. to realize these abilities, avlen uses a multimodal hierarchical reinforcement learning backbone that learns : ( a ) high - level policies to choose either audio - cues for navigation or to query the oracle, and ( b ) lower - level policies to select navigation actions based on its audio - visual and language inputs. the policies are trained via rewarding for the success on the navigation task while minimizing the number of queries to the oracle. to empirically evaluate avlen, we present experiments on the soundspaces framework for semantic audio - visual navigation tasks. our results show that equipping the agent to ask for help leads to a clear improvement in performance, especially in challenging cases, e. g., when the sound is unheard during training or in the presence of distractor sounds.
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arxiv:2210.07940
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food engineering is a scientific, academic, and professional field that interprets and applies principles of engineering, science, and mathematics to food manufacturing and operations, including the processing, production, handling, storage, conservation, control, packaging and distribution of food products. given its reliance on food science and broader engineering disciplines such as electrical, mechanical, civil, chemical, industrial and agricultural engineering, food engineering is considered a multidisciplinary and narrow field. due to the complex nature of food materials, food engineering also combines the study of more specific chemical and physical concepts such as biochemistry, microbiology, food chemistry, thermodynamics, transport phenomena, rheology, and heat transfer. food engineers apply this knowledge to the cost - effective design, production, and commercialization of sustainable, safe, nutritious, healthy, appealing, affordable and high - quality ingredients and foods, as well as to the development of food systems, machinery, and instrumentation. = = history = = although food engineering is a relatively recent and evolving field of study, it is based on long - established concepts and activities. the traditional focus of food engineering was preservation, which involved stabilizing and sterilizing foods, preventing spoilage, and preserving nutrients in food for prolonged periods of time. more specific traditional activities include food dehydration and concentration, protective packaging, canning and freeze - drying. the development of food technologies were greatly influenced and urged by wars and long voyages, including space missions, where long - lasting and nutritious foods were essential for survival. other ancient activities include milling, storage, and fermentation processes. although several traditional activities remain of concern and form the basis of today ’ s technologies and innovations, the focus of food engineering has recently shifted to food quality, safety, taste, health and sustainability. = = application and practices = = the following are some of the applications and practices used in food engineering to produce safe, healthy, tasty, and sustainable food : = = = refrigeration and freezing = = = the main objective of food refrigeration and / or freezing is to preserve the quality and safety of food materials. refrigeration and freezing contribute to the preservation of perishable foods, and to the conservation some food quality factors such as visual appearance, texture, taste, flavor and nutritional content. freezing food slows the growth of bacteria that could potentially harm consumers. = = = evaporation = = = evaporation is used to pre - concentrate, increase the solid content, change
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https://en.wikipedia.org/wiki/Food_engineering
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unscheduled maintenance has contributed to longer downtime for vehicles and increased costs for logistic readiness squadrons ( lrss ) in the air force. when vehicles are in need of repair outside of their scheduled time, depending on their priority level, the entire squadron ' s slated repair schedule is transformed negatively. the repercussions of unscheduled maintenance are specifically seen in the increase of man hours required to maintain vehicles that should have been working well : this can include more man hours spent on maintenance itself, waiting for parts to arrive, hours spent re - organizing the repair schedule, and more. the dominant trend in the current maintenance system at lrss is that they do not have predictive maintenance infrastructure to counteract the influx of unscheduled repairs they experience currently, and as a result, their readiness and performance levels are lower than desired. we use data pulled from the defense property and accountability system ( dpas ), that the lrss currently use to store their vehicle maintenance information. using historical vehicle maintenance data we receive from dpas, we apply three different algorithms independently to construct an accurate predictive system to optimize maintenance schedules at any given time. through the application of logistics regression, random forest, and gradient boosted trees algorithms, we found that a logistic regression algorithm, fitted to our data, produced the most accurate results. our findings indicate that not only would continuing the use of logistic regression be prudent for our research purposes, but that there is opportunity to further tune and optimize our logistic regression model for higher accuracy.
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arxiv:2112.13922
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we introduce a scheme for remote entanglement generation for the photon polarization. the technique is based on transferring the initial frequency correlations to specific polarization - frequency correlations by local dephasing and their subsequent removal by frequency up - conversion. on fundamental level, our theoretical results show how to create and transfer entanglement, to particles which never interact, by means of local operations. this possibility stems from the multi - path interference and its control in frequency space. for applications, the developed techniques and results allow for the remote generation of entanglement with distant parties without bell state measurements and opens the perspective to probe frequency - frequency entanglement by measuring the polarization state of the photons.
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arxiv:1705.01713
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recent research shows that hawking radiation can be treated as a quantum tunnelling process, and hawking temperature of dirac particles across the horizon of a black hole can be correctly recovered via fermions tunnelling method. in this paper, motivated by fermions tunnelling method, we attempt to apply the analysis to derive hawking radiation of dirac particles via tunnelling from black ring solutions of 5 - dimensional einstein - maxwell - dilaton gravity theory. finally, it is interesting to find as in black hole cases, fermions tunnelling can also result in correct hawking temperatures for the rotating neutral, dipole and charged black rings.
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arxiv:0807.1358
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the homogeneous and isotropic cosmological model in the weyl conformal geometry is considered. we showed that, despite the conformal invariance, the dust matter is allowed in such a universe. it is shown that the number of dust particles is not conserved, i. e., they are continuously produced. the general form of the law for their creation is found.
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arxiv:2203.04257
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we provide explicit expression of squeezing function for infinitely connected planar domain obtained by removing a convergent sequence of points from the unit disk converging to the boundary of unit disk. we also discuss fridman invariant associated with this domain as well as some examples of squezzing functions corresponding to polydisk.
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arxiv:2210.08593
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the conformity effect, indicating the evolution of a galaxy is related to its surrounding neighbour galaxies as far as a few mpc, is an interesting phenomenon in the modeling of galaxy and evolution. here we study the conformity effect of hi galaxies in a matched galaxy sample between sdss dr7 and alfalfa surveys. by checking the probability difference for the detected hi galaxies as a function of distance around a normal or an hi galaxy, we find that this effect is significant out to 5 mpc. it also shows a dependence on the stellar mass of galaxies, with the strength the strongest in the stellar mass range of 10 ^ 10 ~ 10 ^ 10. 5. however, when the sample is confined to central galaxies in groups with virial radii smaller than 1 mpc, the 1 - halo conformity signal is still evident, while the 2 - halo conformity signal is reduced to a very weak amplitude. our results confirm the previous study in the optical band that the 2 - halo term is possibly caused by the bias effect in the sample selection. furthermore, we confirm the existence of the 1 - halo conformity discovered in the optical and radio band in previous lectures. our results provide another viewpoint of the conformity effect and hope to shed the light on the co - evolution of the galaxies and their neighbours in the current galaxy formation models.
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arxiv:2008.05682
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typescript is a quickly evolving superset of javascript with active development of new features. our paper seeks to understand how quickly these features are adopted by the developer community. existing work in javascript shows the adoption of dynamic language features can be a major hindrance to static analysis. as typescript evolves the addition of features makes the underlying standard more and more difficult to keep up with. in our work we present an analysis of 454 open source typescript repositories and study the adoption of 13 language features over the past three years. we show that while new versions of the typescript compiler are aggressively adopted by the community, the same cannot be said for language features. while some experience strong growth others are rarely adopted by projects. our work serves as a starting point for future study of the adoption of features in typescript. we also release our analysis and data gathering software as open source in the hope it helps the programming languages community.
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arxiv:2303.09802
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the submillimeter array ( sma ), a collaboration between the smithsonian astrophysical observatory and the academica sinica institute for astronomy and astrophysics of taiwan, is an eight - element radio - interferometer designed to operate throughout the major atmospheric windows from about 180 to 900 ghz. in an effort to mitigate the effects of atmospheric instabilities which limit the phase coherence of the array especially in the higher frequency bands, the array was designed to allow simultaneous operation of a low frequency receiver ( < 350 ghz ) with a high frequency receiver ( > 330 ghz ). the overlap region of 330 - 350 ghz was included to facilitate dual polarization measurements in the frequency range considered to offer the highest sensitivity for continuum observations with the array. so far, the array is equipped with working sis receivers covering the frequency ranges 176 - 256 ghz, 260 - 350 ghz, and 600 - 700 ghz, and single frequency operation has been routine in the lower two frequency bands for the past year. more recently, with the completion of if hardware required to make full use of the sma cross - correlator, dual receiver operation became possible. we have since made a number of galactic and extra - galactic astronomical observations in dual - band mode with the hopes of using the 230 ghz receiver as a phase reference to enable improved interferometry in the 650 ghz band. we will present the current antenna and receiver performance, some of the first interferometric images in the 650 ghz receiver band, and our initial attempts at phase transfer.
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arxiv:astro-ph/0509467
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we investigate the possibility of band structure engineering in the recently predicted 2d layered form of blue phosphorus via an electric field ( e $ _ z $ ) applied perpendicular to the layer ( s ). using density functional theory, we study the effect of a transverse electric field in monolayer, as well as three differently stacked bilayer structures of blue phosphorus. we find that, for e $ _ z > 0. 2 $ v / \ aa the direct energy gap at the $ \ gamma $ point, which is much larger than the default indirect band gap of mono - and bilayer blue phosphorus, decreases linearly with the increasing electric field ; becomes comparable to the default indirect band gap at e $ _ z \ approx 0. 45 ( 0. 35 ) $ v / \ aa for monolayer ( bilayers ) and decreases further until the semiconductor to metal transition of 2d blue phosphorus takes place at e $ _ z \ approx 0. 7 ( 0. 5 ) $ v / \ aa for monolayer ( bilayers ). calculated values of the electron and hole effective masses along various high symmetry directions in the reciprocal lattice suggests that the mobility of charge carriers is also influenced by the applied electric field.
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arxiv:1412.0858
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for a stable process, we give an explicit formula for the potential measure of the process killed outside a bounded interval and the joint law of the overshoot, undershoot and undershoot from the maximum at exit from a bounded interval. we obtain the equivalent quantities for a stable process reflected in its infimum. the results are obtained by exploiting a simple connection with the lamperti representation and exit problems of stable processes.
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arxiv:1312.1222
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in this paper we construct a pseudorandom multisequence $ ( x _ { n _ 1,..., n _ r } ) $ based on $ k $ th - order linear recurrences modulo $ p $, such that the discrepancy of the $ s $ - dimensional multisequence $ ( x _ { n _ 1 + i _ 1,..., n _ r + i _ r } ) _ { 1 \ leq i _ j \ leq s _ j, 1 \ leq j \ leq r } $ $ 1 \ leq n _ j \ leq n _ j, 1 \ leq j \ leq r $ is equal to $ o ( ( n _ 1... n _ r ) ^ { - 1 / 2 } \ ln ^ { s + 3r } ( n _ 1... n _ r ) ) $, where $ s = s _ 1... s _ r $, for all $ n _ 1,..., n _ r $ with $ 1 < n _ 1... n _ r \ leq p ^ k
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arxiv:1106.5860
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in december 2015, a bounty emerged to establish both reliable communication and secure transfer of value between the dogecoin and ethereum blockchains. this prized " dogethereum bridge " would allow parties to " lock " a doge coin on dogecoin and in exchange receive a newly minted wow token in ethereum. any subsequent owner of the wow token could burn it and, in exchange, earn the right to " unlock " a doge on dogecoin. we describe an efficient, trustless, and retrofitting dogethereum construction which requires no fork but rather employs economic collateral to achieve a " lock " operation in dogecoin. the protocol relies on bulletproofs, truebit, and parametrized tokens to efficiently and trustlessly relay events from the " true " dogecoin blockchain into ethereum. the present construction not only enables cross - platform exchange but also allows ethereum smart contracts to trustlessly access dogecoin. a similar technique adds ethereum - based smart contracts to bitcoin and bitcoin data to ethereum smart contracts.
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arxiv:1908.03999
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we begin with giving some motivation for the study of charm semileptonic and fully leptonic decays. we turn next to a discussion of semileptonic absolution branching fraction results form cleo - c. two exciting high statistics results on fully leptonic decays of the d + - > mu + nu and ds + - > mu + nu from cleo - c and babar are reviewed. we turn next to a discussion of recent results on charm meson decay to pseudo - scalar l nu decays from focus, babar, and cleo - c. we conclude with a review of charm meson decay into vector l nu.
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arxiv:hep-ex/0605030
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existing protocols for multilateral negotiation require a full consensus among the negotiating parties. in contrast, we propose a protocol for multilateral negotiation that allows partial consensus, wherein only a subset of the negotiating parties can reach an agreement. we motivate problems that require such a protocol and describe the protocol formally.
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arxiv:2205.06678
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this paper analyzes the performance of multicell massive multiple - input and multiple - output ( mimo ) systems with variable - resolution analog - to - digital converters ( adcs ). in such an architecture, each adc uses arbitrary quantization resolution to save power and hardware cost. along this direction, we first introduce a quantization - aware channel estimator based on additive quantization noise model ( aqnm ) and linear minimum mean - squared error ( lmmse ) estimate theory. afterwards, by leveraging on the estimated channel state information ( csi ), we derive the asymptotic expressions of achievable uplink spectral efficiency ( se ) over spatially correlated rayleigh fading channels for maximal ratio combining ( mrc ), quantization - aware multicell minimum mean - squared error ( qa - m - mmse ) combining, and quantization - aware single - cell mmse ( qa - s - mmse ) combining, respectively. during the derivations, we consider the effect of quantization errors and resort to random matrix theory to achieve the asymptotic results. finally, simulation results demonstrate that our theoretical analyses are correct and that the proposed quantization - aware estimator and combiners are more beneficial than the quantization - unaware counterparts. besides, based on a generic power consumption model, it is shown that low - resolution adcs can obtain the best tradeoff between se and energy efficiency ( ee ) under multicell scenarios.
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arxiv:2109.09335
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biomedical engineering = = = ebme technicians and engineers in the uk work in the nhs and private sector. they are part of the clinical engineering familiar in the uk. their role is to manage and maintain medical equipment assets in nhs and private healthcare organizations. they are professionally registered with the engineering council as chartered engineers, incorporated engineers, or engineering technicians. the ebme community share their knowledge on the ebme forums. there is also an annual 2 - day national exhibition and conference, wherein engineers meet to learn about the latest medical products and to attend the 500 - seat conference where academic and business leaders share their expertise. the conference was founded in 2009 as a way of improving healthcare through sharing knowledge from experienced professionals involved in medical equipment management. = = in india = = healthcare has increasingly become technology - driven and requires trained manpower to keep pace with the growing demand for professionals in the field. an m - tech clinical engineering course was initiated by indian institute of technology madras, sree chitra thirunal institute of medical sciences and technology, trivandrum and christian medical college, vellore, to address the country ' s need for human resource development. this was aimed at indigenous biomedical device development as well as technology management in order to contribute to the overall development of healthcare delivery in the country. during the course, students of engineering are given an insight into biology, medicine, relevant electronic background, clinical practices, device development, and even management aspects. students are paired with clinical doctors from cmc and sctimst to get hands - on experience during internships. an important aspect of this training is simultaneous, long - term, and detailed exposure to the clinical environment as well as to medical device development activity. this will help students understand how to recognize unmet clinical needs and contribute to the creation of future medical devices. engineers will be trained to handle and oversee the safe and effective use of technology in healthcare delivery sites as part of the program. the minimum qualification for joining this course is a bachelor ' s degree in any discipline of engineering, technology, or architecture, and a valid gate score with an interview process in that field. = = see also = = biomedical engineering = = references = = = = further reading = = villafane, carlos, cbet. ( june 2009 ). biomed : from the student ' s perspective, first edition. [ techniciansfriend. com ]. isbn 978 - 1 - 61539 - 663 - 4. { { cite book } } : cs1 maint : multiple
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https://en.wikipedia.org/wiki/Clinical_engineering
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the neutrino oscillations in vacuum are derived in a manifestly coherent scheme. the mechanism is operative in a quantum field theoretical framework, justifying nevertheless a formal analogy with quantum mechanical two - ( or more ) level systems and their oscillatory behaviour. both the flavour states and the massive states are eigenstates of certain hamiltonians which, in special conditions, can be argued to share the same hilbert space. in this scheme, flavour neutrinos are massless and play the role of asymptotic states for any interactions, including the weak interactions, while massive neutrinos are effective propagation states. the vacuum is interpreted as a medium, where the flavour neutrinos undergo coherent forward scatterings which modify their energy and mix their flavour. the treatment of matter conversion and msw effect fits in naturally ; the extension to other neutral particle oscillations, like $ k _ 0 - \ bar k _ 0 $, is straightforward. the scheme is eclectic insofar as it combines seamlessly quantum field theory and quantum mechanics.
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arxiv:2304.13491
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recent large language models ( llms ) have revealed strong abilities to understand natural language. since most of them share the same basic structure, i. e. the transformer block, possible contributors to their success in the training process are scaling and instruction tuning. however, how these factors affect the models ' language perception is unclear. this work compares the self - attention of several existing llms ( llama, alpaca and vicuna ) in different sizes ( 7b, 13b, 30b, 65b ), together with eye saccade, an aspect of human reading attention, to assess the effect of scaling and instruction tuning on language perception. results show that scaling enhances the human resemblance and improves the effective attention by reducing the trivial pattern reliance, while instruction tuning does not. however, instruction tuning significantly enhances the models ' sensitivity to instructions. we also find that current llms are consistently closer to non - native than native speakers in attention, suggesting a sub - optimal language perception of all models. our code and data used in the analysis is available on github.
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arxiv:2310.19084
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we discuss elementary entwiners that cross - weave the variables of certain integrable models : liouville, sine - gordon, and sinh - gordon field theories in two - dimensional spacetime, and their quantum mechanical reductions. first we define a complex time parameter that varies from one energy - shell to another. then we explain how field propagators can be simply expressed in terms of elementary functions through the combination of an evolution in this complex time and a duality transformation.
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arxiv:quant-ph/0011101
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we consider systems $ ( m, \ omega, g ) $ with $ m $ a closed smooth manifold, $ \ omega $ a real valued closed one form and $ g $ a riemannian metric, so that $ ( \ omega, g ) $ is a morse - smale pair, definition ~ 2. we introduce a numerical invariant $ \ rho ( \ omega, g ) \ in [ 0, \ infty ] $ and improve morse - novikov theory by showing that the novikov complex comes from a cochain complex of free modules over a subring $ \ lambda ' _ { [ \ omega ], \ rho } $ of the novikov ring $ \ lambda _ { [ \ omega ] } $ which admits surjective ring homomorphisms $ \ ev _ s : \ lambda ' _ { [ \ omega ], \ rho } \ to \ c $ for any complex number $ s $ whose real part is larger than $ \ rho $. we extend witten - helffer - sj \ " ostrand results from a pair $ ( h, g ) $ where $ h $ is a morse function to a pair $ ( \ omega, g ) $ where $ \ omega $ is a morse one form. as a consequence we show that if $ \ rho < \ infty $ the novikov complex can be entirely recovered from the spectral geometry of $ ( m, \ omega, g ) $.
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arxiv:math/0101043
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consider the following interacting particle system on the $ d $ - ary tree, known as the frog model : initially, one particle is awake at the root and i. i. d. poisson many particles are sleeping at every other vertex. particles that are awake perform simple random walks, awakening any sleeping particles they encounter. we prove that there is a phase transition between transience and recurrence as the initial density of particles increases, and we give the order of the transition up to a logarithmic factor.
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arxiv:1501.05874
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the conformable time fractional jimbo - miwa and zakharov - kuznetsov equations are solved by the generalized form of the kudryashov method. a simple compatible wave transformation is employed to reduce the dimension of the equations to one. the predicted solution is of the form of a rational expression of two finite series at both the numerator and the denominator. the terms of both series are of the powers of some functions having exponential expressions satisfying a particular ode. the exact solutions are expressed explicitly in terms of powers of some exponential functions in form of rational expressions.
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arxiv:1706.00349
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suppose m is a noncompact connected pl 2 - manifold. in this paper we study the topological property of the triple ( h ( m ) _ 0, h ^ pl ( m ) _ 0, h ^ pl, c ( m ) _ 0 ), where h ( m ) _ 0 is the identity component of the homeomorphism group { \ cal h } ( m ) of m with the compact - open topology, and h ^ pl ( m ) _ 0 and h ^ pl, c ( m ) _ 0 are the identity components of the subgroups consisting of pl - homeomorphisms of m and ones with compact supports. we show that this triple is a ( s ^ infty, sigma ^ infty, sigma ^ infty _ f ) - manifold and determine its topological type. we also study the subgroups of lipschitz homeomorphisms.
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arxiv:math/0010224
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we propose a spreading model in multilayer networks and study the nature of nonequilibrium phase transition in the model. the model integrates the susceptible - infected - susceptible ( or susceptible - infected - recovered ) spreading dynamics with a biased diffusion process among different layers. a parameter $ \ alpha $ is introduced to control the bias of the diffusion process, such that each individual prefers to move to one layer with more infected ( or recovered ) neighbors for larger values of $ \ alpha $. using stochastic simulations and mean - field theory, we show that the type of phase transition from a disease - free phase to an endemic phase depends on the value of $ \ alpha $. when $ \ alpha $ is small enough, the system undergoes a usual continuous phase transition as an effective spreading rate $ \ beta $ increases, as in single - layer networks. interestingly, when $ \ alpha $ exceeds a critical value the system shows either a hybrid two - step phase transition or a one - step discontinuous phase transition as $ \ beta $ increases. the former contains a continuous transition between the disease - free phase and a low - prevalence endemic phase, and a discontinuous transition between the low - prevalence endemic phase and a high - prevalence endemic phase. for the latter, only a discontinuous transition occurs from the disease - free phase directly to the high - prevalence endemic phase. moreover, we show that the discontinuous transition is always accompanied by a spontaneous symmetry breaking in occupation probabilities of individuals in each layer.
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arxiv:1907.13364
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we describe the orbit structure for the action of the centralizer group of a linear operator on a finite - dimensional complex vector space. the main application is to the classification of solutions to a system of first - order odes with constant coefficients. we completely describe the lattice structure on the set of orbits and provide a generating function for the number of orbits in each dimension.
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arxiv:1110.4899
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synthetic spectra generated with the parameterized supernova synthetic - spectrum code synow are compared to observed photospheric - phase spectra of the type ic supernova 1994i. the observed optical spectra can be well matched by synthetic spectra that are based on the assumption of spherical symmetry. we consider the identification of the infrared absorption feature observed near 10, 250 \ aa, which previously has been attributed to he i $ \ lambda10830 $ and regarded as strong evidence that sn 1994i ejected some helium. we have difficulty accounting for the infrared absorption with he i alone. it could be a blend of he i and c i lines. alternatively, we find that it can be fit by si i lines without compromising the fit in the optical region. in synthetic spectra that match the observed spectra, from 4 days before to 26 days after the time of maximum brightness, the adopted velocity at the photosphere decreases from 17, 500 to 7000 \ kms. simple estimates of the kinetic energy carried by the ejected mass give values that are near the canonical supernova energy of $ 10 ^ { 51 } $ ergs. the velocities and kinetic energies that we find for sn 1994i in this way are much lower than those that we find elsewhere for the peculiar type ic sne 1997ef and 1998bw, which therefore appear to have been hyper - energetic.
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arxiv:astro-ph/9906496
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aperiodic point sets ( or tilings ) which can be obtained by the method of cut and projection from higher dimensional periodic sets play an important role for the description of quasicrystals. their topological invariants can be computed using the higher dimensional periodic structure. we report on the results obtained for the cohomology groups of projection point patterns supplemented by explicit calculations made by f. gaehler for many well - known icosahedral tilings.
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arxiv:math-ph/0010050
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imaging through dense fog presents unique challenges, with essential visual information crucial for applications like object detection and recognition obscured, thereby hindering conventional image processing methods. despite improvements through neural network - based approaches, these techniques falter under extremely low visibility conditions exacerbated by inhomogeneous illumination, which degrades deep learning performance due to inconsistent signal intensities. we introduce in this paper a novel method that adaptively filters background illumination based on structural differential and integral filtering ( sdif ) to enhance only vital signal information. the grayscale banding is eliminated by incorporating a visual optimization strategy based on image gradients. maximum histogram equalization ( mhe ) is used to achieve high contrast while maintaining fidelity to the original content. we evaluated our algorithm using data collected from both a fog chamber and outdoor environments, and performed comparative analyses with existing methods. our findings demonstrate that our proposed method significantly enhances signal clarity under extremely low visibility conditions and out - performs existing techniques, offering substantial improvements for deep fog imaging applications.
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arxiv:2404.17503
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we have searched 4. 5 square degrees of archival hst / acs images for cosmic strings, identifying close pairs of similar, faint galaxies and selecting groups whose alignment is consistent with gravitational lensing by a long, straight string. we find no evidence for cosmic strings in five large - area hst treasury surveys ( covering a total of 2. 22 square degrees ), or in any of 346 multi - filter guest observer images ( 1. 18 square degrees ). assuming that simulations ccurately predict the number of cosmic strings in the universe, this non - detection allows us to place upper limits on the unitless universal cosmic string tension of g mu / c ^ 2 < 2. 3 x 10 ^ - 6, and cosmic string density of omega _ s < 2. 1 x 10 ^ - 5 at the 95 % confidence level ( marginalising over the other parameter in each case ). we find four dubious cosmic string candidates in 318 single filter guest observer images ( 1. 08 square degrees ), which we are unable to conclusively eliminate with existing data. the confirmation of any one of these candidates as cosmic strings would imply g mu / c ^ 2 ~ 10 ^ - 6 and omega _ s ~ 10 ^ - 5. however, we estimate that there is at least a 92 % chance that these string candidates are random alignments of galaxies. if we assume that these candidates are indeed false detections, our final limits on g mu / c ^ 2 and omega _ s fall to 6. 5 x 10 ^ - 7 and 7. 3 x 10 ^ - 6. due to the extensive sky coverage of the hst / acs image archive, the above limits are universal. they are quite sensitive to the number of fields being searched, and could be further reduced by more than a factor of two using forthcoming hst data.
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arxiv:0908.0602
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a string $ w $ is called a minimal absent word ( maw ) for another string $ t $ if $ w $ does not occur in $ t $ but the proper substrings of $ w $ occur in $ t $. for example, let $ \ sigma = \ { \ mathtt { a, b, c } \ } $ be the alphabet. then, the set of maws for string $ w = \ mathtt { abaab } $ is $ \ { \ mathtt { aaa, aaba, bab, bb, c } \ } $. in this paper, we study combinatorial properties of maws in the sliding window model, namely, how the set of maws changes when a sliding window of fixed length $ d $ is shifted over the input string $ t $ of length $ n $, where $ 1 \ leq d < n $. we present \ emph { tight } upper and lower bounds on the maximum number of changes in the set of maws for a sliding window over $ t $, both in the cases of general alphabets and binary alphabets. our bounds improve on the previously known best bounds [ crochemore et al., 2020 ].
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arxiv:2105.08496
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we provide a lowerbound on the sample complexity of distribution - free parity learning in the realizable case in the shuffle model of differential privacy. namely, we show that the sample complexity of learning $ d $ - bit parity functions is $ \ omega ( 2 ^ { d / 2 } ) $. our result extends a recent similar lowerbound on the sample complexity of private agnostic learning of parity functions in the shuffle model by cheu and ullman. we also sketch a simple shuffle model protocol demonstrating that our results are tight up to $ poly ( d ) $ factors.
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arxiv:2103.15690
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measuring the similarities between objects in information networks has fundamental importance in recommendation systems, clustering and web search. the existing metrics depend on the meta path or meta structure specified by users. in this paper, we propose a stratified meta structure based similarity $ smss $ in heterogeneous information networks. the stratified meta structure can be constructed automatically and capture rich semantics. then, we define the commuting matrix of the stratified meta structure by virtue of the commuting matrices of meta paths and meta structures. as a result, $ smss $ is defined by virtue of these commuting matrices. experimental evaluations show that the proposed $ smss $ on the whole outperforms the state - of - the - art metrics in terms of ranking and clustering.
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arxiv:1801.00783
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a deep neural network has been successfully applied to an electroencephalogram ( eeg ) - based brain - computer interface. however, in most studies, the correlation between eeg channels and inter - region relationships are not well utilized, resulting in sub - optimized spatial feature extraction. in this study, we propose an attention - based dual - stream 3d - convolutional neural network that can enhance spatial feature extraction by emphasizing the relationship between channels with dot product - based channel attention and 3d convolution. the proposed method showed superior performance than the comparative models by achieving an accuracy of 0. 58 for 4 - class visual imagery ( vi ) eeg classification. through statistical and neurophysiological analysis, visual motion imagery showed higher alpha - power spectral density ( psd ) over the visual cortex than static vi. also, the vi of swarm dispersion showed higher beta - psd over the pre - frontal cortex than the vi of swarm aggregation.
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arxiv:2112.07148
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we propose a general framework to study language emergence through signaling games with neural agents. using a continuous latent space, we are able to ( i ) train using backpropagation, ( ii ) show that discrete messages nonetheless naturally emerge. we explore whether categorical perception effects follow and show that the messages are not compositional.
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arxiv:2005.00110
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in this paper, we present a comprehensive uav system design to perform the highly complex task of off - centered aerial grasping. this task has several interdisciplinary research challenges which need to be addressed at once. the main design challenges are gps - denied functionality, solely onboard computing, and avoiding off - the - shelf costly positioning systems. while in terms of algorithms, visual perception, localization, control, and grasping are the leading research problems. hence in this paper, we make interdisciplinary contributions : ( i ) a detailed description of the fundamental challenges in indoor aerial grasping, ( ii ) a novel lightweight gripper design, ( iii ) a complete aerial platform design and in - lab fabrication, and ( iv ) localization, perception, control, grasping systems, and an end - to - end flight autonomy state - machine. finally, we demonstrate the resulting aerial grasping system drone - bee achieving a high grasping rate for a highly challenging agricultural task of apple - like fruit harvesting, indoors in a vertical farming setting ( fig. 1 ). to our knowledge, such a system has not been previously discussed in the literature, and with its capabilities, this system pushes aerial manipulation towards 4th generation.
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arxiv:2410.05738
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we introduce a novel measure to quantify the non - gaussian character of a quantum state : the quantum relative entropy between the state under examination and a reference gaussian state. we analyze in details the properties of our measure and illustrate its relationships with relevant quantities in quantum information as the holevo bound and the conditional entropy ; in particular a necessary condition for the gaussian character of a quantum channel is also derived. the evolution of non - gaussianity ( nong ) is analyzedfor quantum states undergoing conditional gaussification towards twin - beam and de - gaussification driven by kerr interaction. our analysis allows to assess nong as a resource for quantum information and, in turn, to evaluate the performances of gaussification and de - gaussification protocols.
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arxiv:0805.1645
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in this work we deal with the funding costs rising from hedging the risky securities underlying a target volatility strategy ( tvs ), a portfolio of risky assets and a risk - free one dynamically rebalanced in order to keep the realized volatility of the portfolio on a certain level. the uncertainty in the tvs risky portfolio composition along with the difference in hedging costs for each component requires to solve a control problem to evaluate the option prices. we derive an analytical solution of the problem in the black and scholes ( bs ) scenario. then we use reinforcement learning ( rl ) techniques to determine the fund composition leading to the most conservative price under the local volatility ( lv ) model, for which an a priori solution is not available. we show how the performances of the rl agents are compatible with those obtained by applying path - wise the bs analytical strategy to the tvs dynamics, which therefore appears competitive also in the lv scenario.
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arxiv:2112.01841
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this is an " essay - review " of a book with the same title, by jeffrey bub ( cambridge university press, 1997 ).
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arxiv:quant-ph/9711003
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cloud computing is a cost - effective way for start - up life sciences laboratories to store and manage their data. however, in many instances the data stored over the cloud could be redundant which makes cloud - based data management inefficient and costly because one has to pay for every byte of data stored over the cloud. here, we tested efficient management of data generated by an electron cryo microscopy ( cryoem ) lab on a cloud - based environment. the test data was obtained from cryoem repository empiar. all the images were subjected to an in - house parallelized version of principal component analysis. an efficient cloud - based mapreduce modality was used for parallelization. we showed that large data in order of terabytes could be efficiently reduced to its minimal essential self in a cost - effective scalable manner. furthermore, on - spot instance on amazon ec2 was shown to reduce costs by a margin of about 27 percent. this approach could be scaled to data of any large volume and type.
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arxiv:1703.10105
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the generalized degrees of freedom ( gdof ) of the symmetric two - user gaussian interference relay channel ( irc ) is studied. while it is known that the relay does not increase the dof of the ic, this is not known for the more general gdof. for the characterization of the gdof, new sum - capacity upper bounds and lower bounds are derived. the lower bounds are obtained by a new scheme, which is based on functional decode - and - forward ( fdf ). the gdof is characterized for the regime in which the source - relay link is weaker than the interference link, which constitutes half the overall space of channel parameters. it is shown that the relay can indeed increase the gdof of the irc and that it is achieved by fdf.
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arxiv:1207.0335
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the origin of the narrow optical emission bands seen toward the red rectangle is not yet understood. in this paper we investigate further the proposal that these are due to luminescence of large carbonaceous molecules. polarised signals of several percent could be expected from certain asymmetric molecular rotators. the espadons echelle spectrograph mounted at the cfht was used to obtain high - resolution optical spectropolarimetric data of the red rectangle nebular emission. the rrbs at 5800, 5850, and 6615 angstrom are detected in spectra of the nebular emission 7 " and 13 " north - east from the central star. the 5826 and 6635 angstrom rrb are detected only at the position nearest to the central star. for both positions the stokes q and u spectra show no unambiguous polarisation signal in any of the rrbs. we derive an upper limit of 0. 02 % line polarisation for these rrbs. a tentative feature with peak polarisation of 0. 05 % is seen for the 5800 rrb at 7 " offset. however, the null spectra suggest that this may be an instrumental artifact. the lack of a clear polarisation signal for the five detected rrbs implies that, if the emission is due to luminescence of complex organics, these gas - phase molecular carriers are likely to have a high degree of symmetry, as they do not exhibit a q - branch in their rotational profile, although this may be modified by statistical effects.
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arxiv:1105.4795
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theoretical models of populations and swarms typically start with the assumption that the motion of agents is governed by the local stimuli. however, an intelligent agent, with some understanding of the laws that govern its habitat, can anticipate the future, and make predictions to gather resources more efficiently. here we study a specific model of this kind, where agents aim to maximize their consumption of a diffusing resource, by attempting to predict the future of a resource field and the actions of other agents. once the agents make a prediction, they are attracted to move towards regions that have, and will have, denser resources. we find that the further the agents attempt to see into the future, the more their attempts at prediction fail, and the less resources they consume. we also study the case where predictive agents compete against non - predictive agents and find the predictors perform better than the non - predictors only when their relative numbers are very small. we conclude that predictivity pays off either when the predictors do not see too far into the future or the number of predictors is small.
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arxiv:1611.09687
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the cosmological solutions of horava - witten theory discovered by lukas, ovrut and waldram are generalized to allow non vanishing spatial curvature. the solution with closed spatial sections has initial and final curvature singularities. we find two solutions with open spatial sections, both of which evolve from an initial curvature singularity to the supersymmetric domain wall solution at late times. we also present a solution with open spatial sections and a non - zero ramond - ramond scalar. the behaviour of the solutions in eleven dimensions is discussed.
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arxiv:hep-th/9809195
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nanodiamond reinforced silver matrix nanocomposites with different nanodiamond content are produced from pure silver and nanodiamond powders by a combination of two severe plastic deformation methods, ball - milling and high - pressure torsion ( hpt ). the ball milling parameters are varied to improve the distribution of the nanodiamonds in the powder blends. an optimized processing route combining both processes has been developed to achieve a homogenous dispersion of small nanodiamond particles in a nanocrystalline silver matrix. the microstructure of these nanocomposites was characterized by scanning and transmission electron microscopy. the mechanical properties were characterized by microhardness measurements and tensile tests. an increasing amount of nanodiamonds ( up to 5 wt % and 15 vol %, respectively ) can raise the microhardness by up to 70 % and the tensile strength by up to 60 % of the values achieved in hpt deformed pure silver. the microhardness and tensile strength is about 5 times higher than microcrystalline pure silver.
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arxiv:2003.10759
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quantum error - correcting codes ( qeccs ) and decoherence - free subspace ( dfs ) codes provide active and passive means, respectively, to address certain types of errors that arise during quantum computation. the latter technique is suitable to correct correlated errors with certain symmetries and the former to correct independent errors. the concatenation of a qecc and a dfs code results in a degenerate code that splits into actively and passively correcting parts, with the degeneracy impacting either part, leading to degenerate errors as well as degenerate stabilizer operators. the concatenation of the two types of code can aid universal fault - tolerant quantum computation when a mix of correlated and independent errors is encountered. in particular, we show that for sufficiently strongly correlated errors, the concatenation with the dfs as the inner code provides better entanglement fidelity, whereas for sufficiently independent errors, the concatenation with the qecc as the inner code is preferable. as illustrative examples, we examine in detail the concatenation of a two - qubit dfs code and a three - qubit repetition code or five - qubit knill - laflamme code, under independent and correlated errors.
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arxiv:2312.08322
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over the past years a lot of progress has been made in the understanding of single spin asymmetries in hard scattering processes. we briefly review this subject, covering the non - vanishing of time - reversal odd parton distributions, universality of fragmentation functions, and the discovery of previously unknown time - reversal odd parton distributions at subleading twist. interestingly enough, all these developments were initiated by simple model calculations.
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arxiv:hep-ph/0411118
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we have selected a sample of 80 candidates for obscured radio - loud active galactic nuclei and presented their basic optical / near - infrared ( nir ) properties in paper 1. in this paper, we present both high - resolution radio continuum images for all of these sources and hi 21cm absorption spectroscopy for a few selected sources in this sample. a - configuration 4. 9 and 8. 5 ghz vla continuum observations find that 52 sources are compact or have substantial compact components with size < 0. 5 " and flux density > 0. 1 jy at 4. 9 ghz. the most compact 36 sources were then observed with the vlba at 1. 4 ghz. one definite and 10 candidate compact symmetric objects ( csos ) are newly identified, a detection rate of csos ~ 3 times higher than the detection rate previously found in purely flux - limited samples. based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption - line searches. twenty seven sources were observed for hi 21cm absorption at their photometric or spectroscopic redshifts with only 6 detections made ( one detection is tentative ). however, five of these were from a small subset of six csos with pure galaxy optical / nir spectra and for which accurate spectroscopic redshifts place the redshifted 21cm line in a rfi - free spectral window. it is likely that the presence of ubiquitous rfi and the absence of accurate spectroscopic redshifts preclude hi detections in similar sources ( only one detection out of the remaining 22 sources observed, 14 of which have only photometric redshifts ). future searches for highly - redshifted hi and molecular absorption can easily find more distant csos among bright, blank field ' radio sources but will be severely hampered by an inability to determine accurate spectroscopic redshifts for them due to their lack of rest - frame uv continuum.
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arxiv:1512.07707
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given a finite, simple, connected graph $ g = ( v, e ) $ with $ | v | = n $, we consider the associated graph laplacian matrix $ l = d - a $ with eigenvalues $ 0 = \ lambda _ 1 < \ lambda _ 2 \ leq \ dots \ leq \ lambda _ n $. one can also consider the same graph equipped with positive edge weights $ w : e \ rightarrow \ mathbb { r } _ { > 0 } $ normalized to $ \ sum _ { e \ in e } w _ e = | e | $ and the associated weighted laplacian matrix $ l _ w $. we say that $ g $ is conformally rigid if constant edge - weights maximize the second eigenvalue $ \ lambda _ 2 ( w ) $ of $ l _ w $ over all $ w $, and minimize $ \ lambda _ n ( w ' ) $ of $ l _ { w ' } $ over all $ w ' $, i. e., for all $ w, w ' $, $ $ \ lambda _ 2 ( w ) \ leq \ lambda _ 2 ( 1 ) \ leq \ lambda _ n ( 1 ) \ leq \ lambda _ n ( w ' ). $ $ conformal rigidity requires an extraordinary amount of symmetry in $ g $. every edge - transitive graph is conformally rigid. we prove that every distance - regular graph, and hence every strongly - regular graph, is conformally rigid. certain special graph embeddings can be used to characterize conformal rigidity. cayley graphs can be conformally rigid but need not be, we prove a sufficient criterion. we also find a small set of conformally rigid graphs that do not belong into any of the above categories ; these include the hoffman graph, the crossing number graph 6b and others. conformal rigidity can be certified via semidefinite programming, we provide explicit examples.
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arxiv:2402.11758
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this paper presents a comparison of two reduced - order, sequential and variational data assimilation methods : the seek filter and the r - 4d - var. a hybridization of the two, combining the variational framework and the sequential evolution of covariance matrices, is also preliminarily investigated and assessed in the same experimental conditions. the comparison is performed using the twin - experiment approach on a model of the tropical pacific domain. the assimilated data are simulated temperature profiles at the locations of the tao / triton array moorings. it is shown that, in a quasi - linear regime, both methods produce similarly good results. however the hybrid approach provides slightly better results and thus appears as potentially fruitful. in a more non - linear regime, when tropical instability waves develop, the global nature of the variational approach helps control model dynamics better than the sequential approach of the seek filter. this aspect is probably enhanced by the context of the experiments in that there is a limited amount of assimilated data and no model error.
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arxiv:0709.2808
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analyzing large datasets requires responsive query execution, but executing sql queries on massive datasets can be slow. this paper explores whether query execution can begin even before the user has finished typing, allowing results to appear almost instantly. we propose speql, a system that leverages large language models ( llms ) to predict likely queries based on the database schema, the user ' s past queries, and their incomplete query. since exact query prediction is infeasible, speql speculates on partial queries in two ways : 1 ) it predicts the query structure to compile and plan queries in advance, and 2 ) it precomputes smaller temporary tables that are much smaller than the original database, but are still predicted to contain all information necessary to answer the user ' s final query. additionally, speql continuously displays results for speculated queries and subqueries in real time, aiding exploratory analysis. a utility / user study showed that speql improved task completion time, and participants reported that its speculative display of results helped them discover patterns in the data more quickly. in the study, speql improves user ' s query latency by up to $ 289 \ times $ and kept the overhead reasonable, at $ \ $ 4 $ per hour.
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arxiv:2503.00714
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the fairness and trustworthiness of large language models ( llms ) are receiving increasing attention. implicit hate speech, which employs indirect language to convey hateful intentions, occupies a significant portion of practice. however, the extent to which llms effectively address this issue remains insufficiently examined. this paper delves into the capability of llms to detect implicit hate speech ( classification task ) and express confidence in their responses ( calibration task ). our evaluation meticulously considers various prompt patterns and mainstream uncertainty estimation methods. our findings highlight that llms exhibit two extremes : ( 1 ) llms display excessive sensitivity towards groups or topics that may cause fairness issues, resulting in misclassifying benign statements as hate speech. ( 2 ) llms ' confidence scores for each method excessively concentrate on a fixed range, remaining unchanged regardless of the dataset ' s complexity. consequently, the calibration performance is heavily reliant on primary classification accuracy. these discoveries unveil new limitations of llms, underscoring the need for caution when optimizing models to ensure they do not veer towards extremes. this serves as a reminder to carefully consider sensitivity and confidence in the pursuit of model fairness.
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arxiv:2402.11406
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independent sociological polls are forbidden in belarus. online polls performed without sound scientific rigour do not yield representative results. yet, both inside and outside belarus it is of great importance to obtain precise estimates of the ratings of all candidates. these ratings could function as reliable proxies for the election ' s outcomes. we conduct an independent poll based on the combination of the data collected via viber and on the streets of belarus. the viber and the street data samples consist of almost 45000 and 1150 unique observations respectively. bayesian regressions with poststratification were build to estimate ratings of the candidates and rates of early voting turnout for the population as a whole and within various focus subgroups. we show that both the officially announced results of the election and early voting rates are highly improbable. with a probability of at least 95 %, sviatlana tikhanouskaya ' s rating lies between 75 % and 80 %, whereas aliaksandr lukashenka ' s rating lies between 13 % and 18 % and early voting rate predicted by the method ranges from 9 % to 13 % of those who took part in the election. these results contradict the officially announced outcomes, which are 10. 12 %, 80. 11 %, and 49. 54 % respectively and lie far outside even the 99. 9 % credible intervals predicted by our model. the only marginal groups of people where the upper bounds of the 99. 9 % credible intervals of the rating of lukashenka are above 50 % are people older than 60 and uneducated people. for all other marginal subgroups, including rural residents, even the upper bounds of 99. 9 % credible intervals for lukashenka are far below 50 %. the same is true for the population as a whole. thus, with a probability of at least 99. 9 % lukashenka could not have had enough electoral support to win the 2020 presidential election in belarus.
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arxiv:2009.06615
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we demonstrate that a weak disorder in atomic positions introduces spatially localized optical modes in a dense three - dimensional ensemble of immobile two - level atoms arranged in a diamond lattice and coupled by the electromagnetic field. the frequencies of the localized modes concentrate near band edges of the unperturbed lattice. finite - size scaling analysis of the percentiles of thouless conductance reveals two mobility edges and yields an estimation $ \ nu = 0. 8 $ - - 1. 1 for the critical exponent of the localization length. the localized modes disappear when the disorder becomes too strong and the system starts to resemble a fully disordered one where all modes are extended.
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arxiv:2007.10648
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in this paper we introduce a novel neural networks - based approach for approximating solutions to the ( 2d ) incompressible navier - - stokes equations, which is an extension of so called deep random vortex methods ( drvm ), that does not require the knowledge of the biot - - savart kernel associated to the computational domain. our algorithm uses a neural network ( nn ), that approximates the vorticity based on a loss function that uses a computationally efficient formulation of the random vortex dynamics. the neural vorticity estimator is then combined with traditional numerical pde - solvers, which can be considered as a final implicit linear layer of the network, for the poisson equation to compute the velocity field. the main advantage of our method compared to the standard drvm and other nn - based numerical algorithms is that it strictly enforces physical properties, such as incompressibility or ( no slip ) boundary conditions, which might be hard to guarantee otherwise. the approximation abilities of our algorithm, and its capability for incorporating measurement data, are validated by several numerical experiments.
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arxiv:2405.13691
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in this work, we present a software package in python for high - throughput first - principles calculations of thermodynamic properties at finite temperatures, which we refer to as dfttk ( density functional theory tool kit ). dfttk is based on the atomate package and integrates our experiences in the last decades on the development of theoretical methods and computational software. it includes task submissions on all major operating systems and task execution on high - performance computing environments. the distribution of the dfttk package comes with examples of calculations of phonon density of states, heat capacity, entropy, enthalpy, and free energy under the quasi - harmonic phonon scheme for the stoichiometric phases of al, ni, al3ni, alni, alni3, al3ni4, and al3ni5, and the fcc solution phases treated using the special quasirandom structures at the compositions of al3ni, alni, and alni3.
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arxiv:2107.03966
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there is a relation between the generalized property r conjecture and the schoenflies conjecture that suggests a new line of attack on the latter. the approach gives a quick proof of the genus 2 schoenflies conjecture and suffices to prove the genus 3 case, even in the absence of new progress on the generalized property r conjecture.
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arxiv:math/0603511
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in a low - statistics pet imaging context, the positive bias in regions of low activity is a burning issue. to overcome this problem, algorithms without the built - in non - negativity constraint may be used. they allow negative voxels in the image to reduce, or even to cancel the bias. however, such algorithms increase the variance and are difficult to interpret, since negative radioactive concentrations have no physical meaning. here, we propose a post - processing strategy to remove negative intensities while preserving the local mean activities. our idea is to transfer the negative intensities to neighboring voxels, so that the mean of the image is preserved. the proposed post - processing algorithm solves a linear programming problem with a specific symmetric structure, and the solution can be computed in a very efficient way. acquired data from an yttrium - 90 phantom show that on images produced by a non - constrained algorithm, a much lower variance in the cold area is obtained after the post - processing step.
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arxiv:2012.06432
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in a combined analysis of the experimental data on the coupled processes $ \ pi \ pi \ to \ pi \ pi, k \ bar { k } $ in the channel with $ i ^ gj ^ { pc } = 0 ^ + 0 ^ { + + } $, the various scenarios of these reactions ( with different numbers of resonances ) are considered. in a model - independent approach, based only on analyticity and unitarity, a resonance is represented by of a pole cluster ( poles on the riemann surface ) of the definite type that is defined by the state nature. the best scenario contains the resonances $ f _ 0 ( 665 ) $ ( with properties of the $ \ sigma $ - meson ), $ { f _ 0 } ( 980 ) $ ( with a dominant $ s { \ bar s } $ component ), $ f _ 0 ( 1500 ) $ ( with a dominant flavour - singlet, { \ it e. g. }, glueball component ) and the $ { f _ 0 } ( 1710 ) $ ( with a considerable $ s { \ bar s } $ component ). if the $ { f _ 0 } ( 1370 ) $ exists, it has a dominant $ s { \ bar s } $ component. the coupling constants of observed states with the considered channels and the $ \ pi \ pi $ and $ k \ bar { k } $ scattering lengths are obtained. the conclusion on the linear realization of chiral symmetry is drawn.
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arxiv:hep-ph/0204007
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effective charged neutrons involved in one - and two - nucleon tunneling processes in heavy ion collisions between superfluid nuclei are expected to emit photons. although the centroid, width and integrated energy area characterizing the associated gamma - strength functions are rather similar, the corresponding line shapes reflect the thermal equilibrated - like character of the quasiparticle transfer ( 1n - channel, blackbody spectral functional dependence ), and the quantal coherent character of the cooper pair transfer ( 2n - channel, gaussian functional dependence ) respectively. the predicted angular distributions, polarizations and analyzing power provide further insight into the profoundly different physics to be found at the basis of what can be considered a transient joule - like and a ( ac ) josephson - like nuclear processes
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arxiv:2202.13193
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