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Flooved
by David Lippman;Jeff Eldridge;Mike Kenyon;Lawrence Morales;Melonie Rasmussen
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Topics: Maths, Mathematics
Source: http://www.flooved.com/reader/3501
Flooved
by Peter M. Neumann
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These notes are intended as a rough guide to the eight-lecture course Introduction to Pure Mathematics which is a part of the Oxford 1st-year undergraduate course for the Preliminary Examination in Mathematics. Please do not expect a polished account. They are my personal lecture notes, not a carefully checked textbook. Nevertheless, I hope they may be of some help.
Topic: Maths
Source: http://www.flooved.com/reader/1056
Arxiv.org
by Zbigniew Koza; Maciej Matyka; Sebastian Szkoda; Łukasz Mirosław
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A new format for storing sparse matrices is proposed for efficient sparse matrix-vector (SpMV) product calculation on modern throughput-oriented computer architectures. This format extends the standard compressed row storage (CRS) format and is easily convertible to and from it without any memory overhead. Computational performance of an SpMV kernel for the new format is determined for over 140 sparse matrices on two Fermi-class graphics processing units (GPUs) and the efficiency of the kernel,...
Source: http://arxiv.org/abs/1203.2946v1
Arxiv.org
by Ankur Sinha; Pekka Malo; Timo Kuosmanen
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Variable selection is recognized as one of the most critical steps in statistical modeling. The problems encountered in engineering and social sciences are commonly characterized by over-abundance of explanatory variables, non-linearities and unknown interdependencies between the regressors. An added difficulty is that the analysts may have little or no prior knowledge on the relative importance of the variables. To provide a robust method for model selection, this paper introduces a technique...
Source: http://arxiv.org/abs/1203.6276v2
Arxiv.org
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In a seminal paper of 2005, Nualart and Peccati discovered a surprising central limit theorem (called the "Fourth Moment Theorem" in the sequel) for sequences of multiple stochastic integrals of a fixed order: in this context, convergence in distribution to the standard normal law is equivalent to convergence of just the fourth moment. Shortly afterwards, Peccati and Tudor gave a multidimensional version of this characterization. Since the publication of these two beautiful papers,...
Source: http://arxiv.org/abs/1203.4147v3
Flooved
by Peter Ouwehand
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These notes are for a short course in set theory at the undergraduate level at Stellenbosch University. No pretense at orignality is claimed. Though ampli�ed by material from a number of additional sources, the debt to the �rst few chapters of the book Set Theory, by Thomas Jech, Springer 2003, should be easily discernible.
Topics: Maths, Logic, Numbers and Set Theory, Set Theory, Mathematics
Source: http://www.flooved.com/reader/3368
Arxiv.org
by Benoit Carry
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A considerable amount of information regarding the processes that occurred during the accretion of the early planetesimals is still present among the small bodies of our solar system. A review of our current knowledge of the density of small bodies is presented here. Intrinsic physical properties of small bodies are sought by searching for relationships between the dynamical and taxonomic classes, size, and density. Mass and volume estimates for 287 small bodies are collected from the...
Source: http://arxiv.org/abs/1203.4336v1
Arxiv.org
by Yongji Wang; Xiaofeng Liao; Hu Wu; Jingzheng Wu
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Recommender systems require their recommendation algorithms to be accurate, scalable and should handle very sparse training data which keep changing over time. Inspired by ant colony optimization, we propose a novel collaborative filtering scheme: Ant Collaborative Filtering that enjoys those favorable characteristics above mentioned. With the mechanism of pheromone transmission between users and items, our method can pinpoint most relative users and items even in face of the sparsity problem....
Source: http://arxiv.org/abs/1203.5415v1
Arxiv.org
by Jim Fowler; Andrew Groot; Deven Pandya; Bart Snapp
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Let $T(\Z_m \times \Z_n)$ denote the maximal number of points that can be placed on an $m \times n$ discrete torus with "no three in a line," meaning no three in a coset of a cyclic subgroup of $\Z_m \times \Z_n$. By proving upper bounds and providing explicit constructions, for distinct primes $p$ and $q$, we show that $T(\Z_p \times \Z_{p^2}) = 2p$ and $T(\Z_p \times \Z_{pq}) = p+1$. Via Gr\"obner bases, we compute $T(\Z_m \times \Z_n)$ for $2 \leq m \leq 7$ and $2 \leq n \leq...
Source: http://arxiv.org/abs/1203.6604v1
Arxiv.org
by Hiroshi Miki; Satoshi Tsujimoto; Luc Vinet; Alexei Zhedanov
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Quantum state transfer in a triangular domain of a two-dimensional, equally-spaced, spin lat- tice with non-homogeneous nearest-neighbor couplings is analyzed. An exact solution of the one- excitation dynamics is provided in terms of 2-variable Krawtchouk orthogonal polynomials that have been recently defined. The probability amplitude for an excitation to transit from one site to another is given. For some values of the parameters, perfect transfer is shown to take place from the apex of the...
Source: http://arxiv.org/abs/1203.2128v2
Arxiv.org
by K. S. Babu; R. N. Mohapatra
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We show that grand unified theories based on SO(10) generate naturally the next-to-leading baryon number violating operators of dimension seven. These operators, which violate B-L, lead to unconventional decays of the nucleon such as n -> e^-K^+, e^- \pi^+ and p -> \nu \pi^+. In two-step breaking schemes of non-supersymmetric SO(10), nucleon lifetime for decays into these modes is found to be within reach of experiments. We also identify supersymmetric scenarios where these decays may be...
Source: http://arxiv.org/abs/1203.5544v1
The collisional rates associated with the isotropic velocity moments $$ and the anisotropic moments $$ and $$ are exactly derived in the case of the inelastic Maxwell model as functions of the exponent $r$, the coefficient of restitution $\alpha$, and the dimensionality $d$. The results are applied to the evolution of the moments in the homogeneous free cooling state. It is found that, at a given value of $\alpha$, not only the isotropic moments of a degree higher than a certain value diverge...
Source: http://arxiv.org/abs/1107.0280v3
Arxiv.org
by J. Fischmann; W. Bruzda; B. A. Khoruzhenko; H. -J. Sommers; K. Zyczkowski
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A generalisation of the Ginibre ensemble of non-Hermitian random square matrices is introduced. The corresponding probability measure is induced by the ensemble of rectangular Gaussian matrices via a quadratisation procedure. We derive the joint probability density of eigenvalues for such induced Ginibre ensemble and study various spectral correlation functions for complex and real matrices, and analyse universal behaviour in the limit of large dimensions. In this limit the eigenvalues of the...
Source: http://arxiv.org/abs/1107.5019v2
Arxiv.org
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In this work we construct an infinite class of four-point functions for massless higher-spin fields in flat space that are consistent with the gauge symmetry. In the Lagrangian picture, these reflect themselves in a peculiar non-local nature of the corresponding non-abelian higher-spin couplings implied by the Noether procedure that starts from the fourth order. We also comment on the nature of the colored spin-2 excitation present both in the open string spectrum and in the Vasiliev system,...
Source: http://arxiv.org/abs/1107.5843v2
Arxiv.org
by Andreas U. Schmidt; Andreas Leicher; Yogendra Shah; Inhyok Cha
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The establishment of trust relationships to a computing platform relies on validation processes. Validation allows an external entity to build trust in the expected behaviour of the platform based on provided evidence of the platform's configuration. In a process like remote attestation, the 'trusted' platform submits verification data created during a start up process. These data consist of hardware-protected values of platform configuration registers, containing nested measurement values,...
Source: http://arxiv.org/abs/1007.0642v4
Arxiv.org
by Axel Brandenburg; Koen Kemel; Nathan Kleeorin; Igor Rogachevskii
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To understand the basic mechanism of the formation of magnetic flux concentrations, we determine by direct numerical simulations the turbulence contributions to the mean magnetic pressure in a strongly stratified isothermal layer with large plasma beta, where a weak uniform horizontal mean magnetic field is applied. The negative contribution of turbulence to the effective mean magnetic pressure is determined for strongly stratified forced turbulence over a range of values of magnetic Reynolds...
Source: http://arxiv.org/abs/1005.5700v4
Arxiv.org
by Ibrahima Bah; Christopher Beem; Nikolay Bobev; Brian Wecht
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We engineer a large new set of four-dimensional N=1 superconformal field theories by wrapping M5-branes on complex curves. We present new supersymmetric AdS_5 M-theory backgrounds which describe these fixed points at large N, and then directly construct the dual four-dimensional CFTs for a certain subset of these solutions. Additionally, we provide a direct check of the central charges of these theories by using the M5-brane anomaly polynomial. This is a companion paper which elaborates upon...
Source: http://arxiv.org/abs/1203.0303v1
Arxiv.org
by L. Jilkova; G. Carraro; B. Jungwiert; I. Minchev
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NGC 6791 is a unique stellar system among Galactic open clusters being at the same time one of the oldest open clusters and the most metal rich. Combination of its properties is puzzling and poses question of its origin. One possible scenario is that the cluster formed close to the Galactic Center and later migrated outwards to its current location. In this work we study the cluster's orbit and investigate the possible migration processes which might have displaced NGC 6791 to its present-day...
Source: http://arxiv.org/abs/1203.0546v2
Arxiv.org
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Motivated by recent observations of non-zero $\theta_{13}$ from the Daya Bay and RENO experiments, we propose a renormalizable neutrino model with $A_4$ discrete symmetry accounting for deviations from the tri-bimaximal mixing pattern of neutrino mixing matrix indicated by neutrino oscillation data. In the model, the light neutrino masses can be generated by radiative corrections, and we show how the light neutrino mass matrix can be diagonalized by the Pontecorvo-Maki-Nakagawa-Sakata mixing...
Source: http://arxiv.org/abs/1203.4185v3
Arxiv.org
by Florian Pop
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In this note we show that a special case of a recent result by Obus-Wewers (used as a black box) together with a deformation argument in characteristic $p$ leads to a proof of the Oort Conjecture in the general case. A boundedness result is given as well.
Source: http://arxiv.org/abs/1203.1867v1
Arxiv.org
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We study the asymptotic behavior of a diffusion process with small diffusion in a domain $D$. This process is reflected at $\partial D$ with respect to a co-normal direction pointing inside $D$. Our asymptotic result is used to study the long time behavior of the solution of the corresponding parabolic PDE with Neumann boundary condition.
Source: http://arxiv.org/abs/1203.5092v2
Arxiv.org
by Tanmoy Bhattacharya; Rajan Gupta; Anosh Joseph; Huey-Wen Lin; Saul D. Cohen
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The standard model weak interactions can be described by four-fermion V-A operators at low energies. New physics at the TeV scale can, however, generate the other Lorentz structures. In this talk, we review the constraints on such interactions from nuclear and hadronic decays, as well as from collider searches. Currently the most stringent bounds come from the analysis of the 0+ to 0+ nuclear and the pi to e nu gamma radiative pion decays. In the near future, the ultracold neutron beta decay...
Source: http://arxiv.org/abs/1203.6843v1
Arxiv.org
by Pierre-Emmanuel Caprace; Nicolas Monod
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Consider a proper cocompact CAT(0) space X. We give a complete algebraic characterisation of amenable groups of isometries of X. For amenable discrete subgroups, an even narrower description is derived, implying Q-linearity in the torsion-free case. We establish Levi decompositions for stabilisers of points at infinity of X, generalising the case of linear algebraic groups to Is(X). A geometric counterpart of this sheds light on the refined bordification of X (\`a la Karpelevich) and leads to a...
Source: http://arxiv.org/abs/1203.1058v1
Arxiv.org
by Xi Dong; Bart Horn; Eva Silverstein; Gonzalo Torroba
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We generalize unitarity bounds on operator dimensions in conformal field theory to field theories with spacetime dependent couplings. Below the energy scale of spacetime variation of the couplings, their evolution can strongly affect the physics, effectively shifting the infrared operator scaling and unitarity bounds determined from correlation functions in the theory. We analyze this explicitly for large-$N$ double-trace flows, and connect these to UV complete field theories. One motivating...
Source: http://arxiv.org/abs/1203.1680v1
Arxiv.org
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High-resolution Brillouin scattering is used to achieve 3-dimensional maps of the longitudinal acoustic mode frequency shift in soda-lime silicate glasses subject to Vickers indentations. Assuming that residual stress-induced effects are simply proportional to density changes, residual densification fields are obtained. The density gradient is nearly isotropic, confirming earlier optical observations made on a similar glass. The results show that Brillouin micro-spectroscopy opens the way to a...
Source: http://arxiv.org/abs/1203.3046v2
Arxiv.org
by Simon Barthelmé; Nicolas Chopin
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Many models of interest in the natural and social sciences have no closed-form likelihood function, which means that they cannot be treated using the usual techniques of statistical inference. In the case where such models can be efficiently simulated, Bayesian inference is still possible thanks to the Approximate Bayesian Computation (ABC) algorithm. Although many refinements have been suggested, ABC inference is still far from routine. ABC is often excruciatingly slow due to very low...
Source: http://arxiv.org/abs/1107.5959v2
Flooved
by Barbara Illowsky;Susan Dean
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The textbook was developed over several years and has been used in regular and honors-level classroom settings and in distance learning classes. This textbook is intended for introductory statistics courses being taken by students at two� and four�year colleges who are majoring in fields other than math or engineering. Intermediate algebra is the only prerequisite. The book focuses on applications of statistical knowledge rather than the theory behind it.
Topics: Maths, Mathematics
Source: http://www.flooved.com/reader/3483
Arxiv.org
by Vitaly Skachek; Olgica Milenkovic; Angelia Nedic
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We describe a novel extension of subspace codes for noncoherent networks, suitable for use when the network is viewed as a communication system that introduces both dimension and symbol errors. We show that when symbol erasures occur in a significantly large number of different basis vectors transmitted through the network and when the min-cut of the networks is much smaller then the length of the transmitted codewords, the new family of codes outperforms their subspace code counterparts. For...
Source: http://arxiv.org/abs/1107.4581v3
Arxiv.org
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We study C*-algebras associated with subsemigroups of groups. For a large class of such semigroups including positive cones in quasi-lattice ordered groups and left Ore semigroups, we describe the corresponding semigroup C*-algebras as C*-algebras of inverse semigroups, groupoid C*-algebras and full corners in associated group crossed products. These descriptions allow us to characterize nuclearity of semigroup C*-algebras in terms of faithfulness of left regular representations and amenability...
Source: http://arxiv.org/abs/1203.0021v2
Arxiv.org
by JunYan Luo; Lun-Wu Zhu; Xiao-Ling He; Bensheng Yun; Shiping Ruan
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Continuous measurement of a quantum two-level system (qubit) by mesoscopic charge detectors has attracted wide attention in the community of solid-state quantum computation. In this work, we revisit the measurement of a charge qubit by a quantum point contact, with particular attention paid to the unique non-Markovian measurement characteristics. The finite-frequency-support feature due to non-Markovian correlation leads to a remarkable suppression of the pedestal in noise spectrum, which...
Source: http://arxiv.org/abs/1203.2233v1
Arxiv.org
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If $A$ is a $\sigma$-unital $C^*$-algebra and $a$ is a strictly positive element of $A$ then for every compact subset $K$ of the complete regularization $\mathrm{Glimm}(A)$ of $\mathrm{Prim}(A)$ there exists $\alpha > 0$ such that $K\subset \{G\in \mathrm{Glimm}(A) \mid \|a + G\|\geq \alpha\}$. This extends a 1974 result of J. Dauns to all $\sigma$-unital $C^*$-algebras. However, there is a $C^*$-algebra $A$ and a compact subset of $\mathrm{Glimm}(A)$ that is not contained in any set of the...
Source: http://arxiv.org/abs/1203.3350v1
Arxiv.org
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In this paper, an analytical method that solves the forward displacement problem of several common spherical parallel manipulators (SPMs) is presented. The method uses the the quaternion algebra to restate the problem as a system of four quadrics in four variables and uses an algebraic geometry result by Dixon from 1908 to solve. In addition, a case study is presented for a specific SPM.
Source: http://arxiv.org/abs/1203.6023v1
Arxiv.org
by Arash Azarfar; Jean-François Frigon; Brunilde Sansò
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The popularity of opportunistic spectrum access (OSA), implemented by cognitive radios (CRs), necessitates that these networks should be able to provide service differentiation for different classes of traffic. One of the classic schemes for such a goal is through priority queueing. As link interruptions in OSA networks are frequent, we discuss in this paper four priority queueing disciplines in the presence of interruptions: preemptive-resume, non-preemptive, exceptional non-preemptive and...
Source: http://arxiv.org/abs/1203.6413v1
Arxiv.org
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Graphene can at present be grown at large quantities only by the chemical vapor deposition method, which produces polycrystalline samples. Here, we describe a method for constructing realistic polycrystalline graphene samples for atomistic simulations, and apply it for studying their mechanical properties. We show that cracks initiate at points where grain boundaries meet and then propagate through grains predominantly in zigzag or armchair directions, in agreement with recent experimental...
Source: http://arxiv.org/abs/1203.4196v3
Arxiv.org
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The state space of a polymer molecule is analysed. We show how the size of the state space can be reduced on the basis of symmetry. In the reduced state space, the probability of a new state (termed below as class) is equal to the number of old states represented by the new state multiplied by the probability of each old state. As an application, the electrophoretic motion of the molecule in gel is considered. We discuss the influence of the gel medium and of external field on the molecule...
Source: http://arxiv.org/abs/1203.6540v1
Arxiv.org
by Hao Wang; Jerome P. Reiter
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When releasing data to the public, data stewards are ethically and often legally obligated to protect the confidentiality of data subjects' identities and sensitive attributes. They also strive to release data that are informative for a wide range of secondary analyses. Achieving both objectives is particularly challenging when data stewards seek to release highly resolved geographical information. We present an approach for protecting the confidentiality of data with geographic identifiers...
Source: http://arxiv.org/abs/1203.4122v1
Flooved
by Prof. Joseph Fields
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f(x). However, many of the functions of importance both within mathematics itself as
Topics: Maths, Mathematics
Source: http://www.flooved.com/reader/3477
We study two initial value problems of the linear diffusion equation and a nonlinear diffusion equation, when Cauchy data are bounded and oscillate mildly. The latter nonlinear heat equation is the equation of the curvature flow, when the moving curves are represented by graphs. By using an elementary scaling technique, we show some formulas for space-time behavior of the solution. Keywords: scaling argument, self-similar solution, nonstabilizing solution, nontrivial dynamics, nontrivial...
Source: http://arxiv.org/abs/1203.4315v1
Arxiv.org
by Karen L. Collins; Ann Trenk
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Nordhaus and Gaddum proved, for any graph G, that the chromatic number of G plus the chromatic number of G complement is less than or equal to the number of vertices in G plus 1. Finck characterized the class of graphs that satisfy equality in this bound. In this paper, we provide a new characterization of this class of graphs, based on vertex degrees, which yields a new polynomial-time recognition algorithm and efficient computation of the chromatic number of graphs in this class. Our...
Source: http://arxiv.org/abs/1203.5765v1
Arxiv.org
by Slawomir Rams; Matthias Schuett
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This paper investigates a specific smooth quintic surface suggested by Barth for it contains the current record of 75 lines over the complex numbers. Our main incentive is to prove that the complex quintic has Picard number 41, and to compute the Neron-Severi group up to a 2-power index. We also compute Picard numbers for reductions to positive characteristic and verify the Tate conjecture.
Source: http://arxiv.org/abs/1107.2210v2
Arxiv.org
by Paul Gassiat; Fausto Gozzi; Huyên Pham
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We consider an illiquid financial market with different regimes modeled by a continuous-time finite-state Markov chain. The investor can trade a stock only at the discrete arrival times of a Cox process with intensity depending on the market regime. Moreover, the risky asset price is subject to liquidity shocks, which change its rate of return and volatility, and induce jumps on its dynamics. In this setting, we study the problem of an economic agent optimizing her expected utility from...
Source: http://arxiv.org/abs/1107.4210v2
Arxiv.org
by D. J. Eden; T. J. T. Moore; R. Plume; L. K. Morgan
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By positional matching to the catalogue of Galactic Ring Survey molecular clouds, we have derived distances to 793 Bolocam Galactic Plane Survey (BGPS) sources out of a possible 806 located within the region defined by Galactic longitudes l = 28.5 degr to 31.5 degr and latitudes |b| < 1 degr. This section of the Galactic Plane contains several major features of Galactic structure at different distances, mainly mid-arm sections of the Perseus and Sagittarius spiral arms and the tangent of the...
Source: http://arxiv.org/abs/1203.0295v1
Arxiv.org
by Serge F. Timashev; Oleg Yu. Panischev; Yuriy S. Polyakov; Sergey A. Demin; Alexander Ya. Kaplan
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We apply flicker-noise spectroscopy (FNS), a time series analysis method operating on structure functions and power spectrum estimates, to study the clinical electroencephalogram (EEG) signals recorded in children/adolescents (11 to 14 years of age) with diagnosed schizophrenia-spectrum symptoms at the National Center for Psychiatric Health (NCPH) of the Russian Academy of Medical Sciences. The EEG signals for these subjects were compared with the signals for a control sample of chronically...
Source: http://arxiv.org/abs/1107.1884v3
Arxiv.org
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The Caccetta-Haggkvist conjecture made in 1978 asserts that every orgraph on n vertices without oriented cycles of length
Source: http://arxiv.org/abs/1107.2247v2
Arxiv.org
by Alexandre Janon; Maëlle Nodet; Clémentine Prieur
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Global sensitivity analysis of a numerical code, more specifically estimation of Sobol indices associated with input variables, generally requires a large number of model runs. When those demand too much computation time, it is necessary to use a reduced model (metamodel) to perform sensitivity analysis, whose outputs are numerically close to the ones of the original model, while being much faster to run. In this case, estimated indices are subject to two kinds of errors: sampling error, caused...
Source: http://arxiv.org/abs/1107.3542v2
Arxiv.org
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Numerical integration of ODEs by standard numerical methods reduces a continuous time problems to discrete time problems. Discrete time problems have intrinsic properties that are absent in continuous time problems. As a result, numerical solution of an ODE may demonstrate dynamical phenomena that are absent in the original ODE. We show that numerical integration of system with one fast rotating phase lead to a situation of such kind: numerical solution demonstrate phenomenon of scattering on...
Source: http://arxiv.org/abs/1203.4113v1
Arxiv.org
by Alexander Petrov; Eite Tiesinga; Svetlana Kotochigova
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We explore the anisotropic nature of Feshbach resonances in the collision between ultracold magnetic submerged-shell dysprosium atoms, which can only occur due to couplings to rotating bound states. This is in contrast to well-studied alkali-metal atom collisions, where most Feshbach resonances are hyperfine induced and due to rotation-less bound states. Our novel first-principle coupled-channel calculation of the collisions between open-4f-shell spin-polarized bosonic dysprosium reveals a...
Source: http://arxiv.org/abs/1203.4172v1
Arxiv.org
by Ben Barber
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For a left-compressed intersecting family \A contained in [n]^(r) and a set X contained in [n], let \A(X) = {A in \A : A intersect X is non-empty}. Borg asked: for which X is |\A(X)| maximised by taking \A to be all r-sets containing the element 1? We determine exactly which X have this property, for n sufficiently large depending on r.
Source: http://arxiv.org/abs/1203.4188v2
Arxiv.org
by Kevin G. Hare; Michael J. Mossinghoff
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Let $n$ be a positive integer, not a power of two. A \textit{Reinhardt polygon} is a convex $n$-gon that is optimal in three different geometric optimization problems: it has maximal perimeter relative to its diameter, maximal width relative to its diameter, and maximal width relative to its perimeter. For almost all $n$, there are many Reinhardt polygons with $n$ sides, and many of them exhibit a particular periodic structure. While these periodic polygons are well understood, for certain...
Source: http://arxiv.org/abs/1203.4107v2
Arxiv.org
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Gaussian mixtures are a common density representation in nonlinear, non-Gaussian Bayesian state estimation. Selecting an appropriate number of Gaussian components, however, is difficult as one has to trade of computational complexity against estimation accuracy. In this paper, an adaptive Gaussian mixture filter based on statistical linearization is proposed. Depending on the nonlinearity of the considered estimation problem, this filter dynamically increases the number of components via...
Source: http://arxiv.org/abs/1203.6750v1
Arxiv.org
by Koji Hashimoto; Norihiro Iizuka
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Robustness of the Luttinger theorem for fermionic liquids is examined in holography. The statement of the Luttinger theorem, the equality between the fermion charge density and the volume enclosed by the Fermi surface, can be mapped to a Gauss's law in the gravity dual, a la Sachdev. We show that various deformations in the gravity dual, such as inclusion of magnetic fields, a parity-violating theta-term, dilatonic deformations, and higher-derivative corrections, do not violate the holographic...
Source: http://arxiv.org/abs/1203.5388v2
Arxiv.org
by Giuseppe Durisi; Veniamin I. Morgenshtern; Helmut Bölcskei
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The noncoherent capacity of stationary discrete-time fading channels is known to be very sensitive to the fine details of the channel model. More specifically, the measure of the support of the fading-process power spectral density (PSD) determines if noncoherent capacity grows logarithmically in SNR or slower than logarithmically. Such a result is unsatisfactory from an engineering point of view, as the support of the PSD cannot be determined through measurements. The aim of this paper is to...
Source: http://arxiv.org/abs/1107.2527v2
Arxiv.org
by Pascal O. Vontobel
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It has recently been observed that the permanent of a non-negative square matrix, i.e., of a square matrix containing only non-negative real entries, can very well be approximated by solving a certain Bethe free energy function minimization problem with the help of the sum-product algorithm. We call the resulting approximation of the permanent the Bethe permanent. In this paper we give reasons why this approach to approximating the permanent works well. Namely, we show that the Bethe free...
Source: http://arxiv.org/abs/1107.4196v3
Arxiv.org
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We study transport of fermions in a system composed of a short optical lattice connecting two finite atomic reservoirs at different filling levels. The average equilibration current through the optical lattice, for strong lattice-reservoir coupling and finite temperatures, is calculated within the Landauer formalism using a nonequilibrium Green's functions approach. We moreover determine quantum and thermal fluctuations in the transport and find significant shot-to-shot deviations from the...
Source: http://arxiv.org/abs/1107.4792v2
Arxiv.org
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We prove a structure theorem for topologically recurrent real skew product extensions of distal minimal compact metric flows with a compactly generated Abelian acting group (e.g. $\Z^d$-flows and $\R^d$-flows). The main result states that every such extension apart from a coboundary can be represented by a perturbation of a so-called Rokhlin skew product. We obtain as a corollary that the topological ergodic decomposition of the skew product extension into prolongations is continuous and...
Source: http://arxiv.org/abs/1005.1221v2
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Given a divisor $D$ on a tropical curve $\Gamma$, we show that reduced divisors define an integral affine map from the tropical curve to the complete linear system $|D|$. This is done by providing an explicit description of the behavior of reduced divisors under infinitesimal modifications of the base point. We consider the cases where the reduced-divisor map defines an embedding of the curve into the linear system, and in this way, classify all the tropical curves with a very ample canonical...
Source: http://arxiv.org/abs/1007.5364v2
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by T. Le Bertre; L. D. Matthews; E. Gérard; Y. Libert
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We report the detection of the HI line at 21 cm in the direction of alpha Ori with the Nancay Radiotelescope and with the Very Large Array. The observations confirm the previous detection of HI emission centered on alpha Ori, but additionally reveal for the first time a quasi-stationary detached shell of neutral atomic hydrogen ~4 arcmin. in diameter (0.24 pc at a distance of 200 pc). The detached shell appears elongated in a direction opposite to the star's space motion. A simple model shows...
Source: http://arxiv.org/abs/1203.0255v1
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by Frederico Durao; Peter Dolog
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Tagging activity has been recently identified as a potential source of knowledge about personal interests, preferences, goals, and other attributes known from user models. Tags themselves can be therefore used for finding personalized recommendations of items. In this paper, we present a tag-based recommender system which suggests similar Web pages based on the similarity of their tags from a Web 2.0 tagging application. The proposed approach extends the basic similarity calculus with external...
Source: http://arxiv.org/abs/1203.0332v1
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by Patricia Gonçalves
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We consider the one-dimensional asymmetric zero-range process starting from a step decreasing profile. In the hydrodynamic limit this initial condition leads to the rarefaction fan of the associated hydrodynamic equation. Under this initial condition and for totally asymmetric jumps, we show that the weighted sum of joint probabilities for second class particles sharing the same site is convergent and we compute its limit. For partially asymmetric jumps we derive the Law of Large Numbers for...
Source: http://arxiv.org/abs/1203.0287v1
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by E. Chmielewska; M. Tomczak
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We present the results of the first attempt of statistical research devoted to the association between X-ray Plasma Ejections (XPEs) and prominences. For this aim, we compared contents of a catalogue of XPEs, observed by the Soft X-ray Telescope onboard Yohkoh, to H$\alpha$ reports from the Solar-Geophysical Data. We found that only less than one third of XPEs shows a low-temperature counterpart. A modest connection between hot and cool plasma motions in the corona is also supported by by a...
Source: http://arxiv.org/abs/1203.0783v1
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by Eliyahu Osherovich; Michael Zibulevsky; Irad Yavneh
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In this work we develop an algorithm for signal reconstruction from the magnitude of its Fourier transform in a situation where some (non-zero) parts of the sought signal are known. Although our method does not assume that the known part comprises the boundary of the sought signal, this is often the case in microscopy: a specimen is placed inside a known mask, which can be thought of as a known light source that surrounds the unknown signal. Therefore, in the past, several algorithms were...
Source: http://arxiv.org/abs/1203.0879v1
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by Yuka K. Uchimoto; Toru Yamada; Masaru Kajisawa; Mariko Kubo; Takashi Ichikawa; Yuichi Matsuda; Masayuki Akiyama; Tomoki Hayashino; Masahiro Konishi; Tetsuo Nishimura; Koji Omata; Ryuji Suzuki; Ichi Tanaka; Chihiro Tokoku; Tomohiro Yoshikawa
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We present the results of wide-field deep JHK imaging of the SSA22 field using MOIRCS instrument equipped with Subaru telescope. The observed field is 112 arcmin^2 in area, which covers the z=3.1 protocluster characterized by the overdensities of Ly Alpha emitters (LAEs) and Ly Alpha Blobs (LABs). The 5 sigma limiting magnitude is K_{AB} = 24.3. We extract the potential protocluster members from the K-selected sample by using the multi-band photometric-redshift selection as well as the simple...
Source: http://arxiv.org/abs/1203.0814v2
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by A. A. Grinyuk; H. Jung; G. I. Lykasov; A. V. Lipatov; N. P. Zotov
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We found the parameterization of the unintegrated gluon distribution from the best description of the LHC data on the inclusive spectra of hadrons produced in $pp$ collisions at the mid-rapidity region and small transverse momenta. It is different from the one obtained within perturbative QCD only at low intrinsic transverse momenta $k_t$. The application of this distribution to analysis of the $e-p$ DIS allows us to get the results which do not contradict the H1 and ZEUS data on the structure...
Source: http://arxiv.org/abs/1203.0939v1
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This paper is dedicated to the proof of new maximal regularity results involving Besov spaces for the heat equation in the half-space or in bounded or exterior domains of R^n. We strive for time independent a priori estimates in regularity spaces of type L^1(0,T;X) where X stands for some homogeneous Besov space. In the case of bounded domains, the results that we get are similar to those of the whole space or of the half-space. For exterior domains, we need to use mixed Besov norms in order to...
Source: http://arxiv.org/abs/1203.1129v1
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An abstract chordal metric is defined on linear control systems described by their transfer functions. Analogous to a previous result due to Jonathan Partington ("Robust control and approximation in the chordal metric", in Robust Control, LNCIS 183, Springer, 1992) for H^infty, it is shown that strong stabilizability is a robust property in this metric.
Source: http://arxiv.org/abs/1203.1214v1
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by David Ariza-Ruiz; Laurentiu Leustean; Genaro Lopez-Acedo
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Firmly nonexpansive mappings play an important role in metric fixed point theory and optimization due to their correspondence with maximal monotone operators. In this paper we do a thorough study of fixed point theory and the asymptotic behaviour of Picard iterates of these mappings in different classes of geodesic spaces, as (uniformly convex) $W$-hyperbolic spaces, Busemann spaces and CAT(0) spaces. Furthermore, we apply methods of proof mining to obtain effective rates of asymptotic...
Source: http://arxiv.org/abs/1203.1432v3
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We study the magnetic properties of topological insulators doped with isoelectronic magnetic impurities. We obtain that at zero temperature the impurities order ferromagnetically, but when raising the temperature the topological insulator undergoes a first order phase transition to a spin density wave phase before the system reaches the paramagnetic phase. The origin of this phase is the non-trivial dependence of the topological insulator spin susceptibility on the momentum. We analyze the...
Source: http://arxiv.org/abs/1203.1436v2
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The observed prevalence of oscillatory signals in the spectroscopy of biological light-harvesting complexes at ambient temperatures has led to a search for mechanisms supporting coherent transport through larger molecules in noisy environments. We demonstrate a generic mechanism supporting long-lasting electronic coherence up to 0.3 ps at a temperature of 277 K. The mechanism relies on two properties of the spectral density: (i) a large dissipative coupling to a continuum of higher-frequency...
Source: http://arxiv.org/abs/1203.1485v3
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by S. Dev; Sanjeev Kumar; Surender Verma; Shivani Gupta; R. R. Gautam
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We attempt the integration of the phenomenologically successful four zero texture of fermion mass matrices with the renormalizable SO(10) GUT. The resulting scenario is found to be highly predictive. Firstly, we examine the phenomenological implications of a class of the lepton mass matrices with parallel texture structures and obtain interesting constraints on the parameters of the charged lepton and the neutrino mass matrices. We combine these phenomenological constraints with the constraints...
Source: http://arxiv.org/abs/1203.1403v2
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by Pedram Hekmati; Varghese Mathai
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In this paper we show that the T-duality transform of Bouwknegt, Evslin and Mathai applies to determine isomorphisms of certain current algebras and their associated vertex algebras on topologically distinct T-dual spacetimes compactified to circle bundles with $H$-flux.
Source: http://arxiv.org/abs/1203.1709v3
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In this paper, coordinated beamforming based on relaxed zero forcing (RZF) for K transmitter-receiver pair multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) interference channels is considered. In the RZF coordinated beamforming, conventional zero-forcing interference leakage constraints are relaxed so that some predetermined interference leakage to undesired receivers is allowed in order to increase the beam design space for larger rates than those of the...
Source: http://arxiv.org/abs/1203.1758v2
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by Abner J. Salgado; Johnny Guzman; Francisco-Javier Sayas
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The analysis of finite-element-like Galerkin discretization techniques for the stationary Stokes problem relies on the so-called LBB condition. In this work we discuss equivalent formulations of the LBB condition.
Source: http://arxiv.org/abs/1203.1870v1
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by Di Zhou; Gregorio D'Agostino; Antonio Scala; H. Eugene Stanley
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It was recently recognized that interdependencies among different networks can play a crucial role in triggering cascading failures and hence system-wide disasters. A recent model shows how pairs of interdependent networks can exhibit an abrupt percolation transition as failures accumulate. We report on the effects of topology on failure propagation for a model system consisting of two interdependent networks. We find that the internal node correlations in each of the two interdependent...
Source: http://arxiv.org/abs/1203.0029v2
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Exponential families are a particular class of statistical manifolds which are particularly important in statistical inference, and which appear very frequently in statistics. For example, the set of normal distributions, with mean {\mu} and deviation {\sigma}, form a 2-dimensional exponential family. In this paper, we show that the tangent bundle of an exponential family is naturally a Kahler manifold. This simple but crucial observation leads to the formalism of quantum mechanics in its...
Source: http://arxiv.org/abs/1203.2056v1
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by Roger Casals; Dishant M. Pancholi; Francisco Presas
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We prove that every homotopy class of almost contact structures on a closed 5-dimensional manifold admits a contact structure.
Source: http://arxiv.org/abs/1203.2166v3
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by Risheng Liu; Zhouchen Lin; Fernando De la Torre; Zhixun Su
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Subspace clustering and feature extraction are two of the most commonly used unsupervised learning techniques in computer vision and pattern recognition. State-of-the-art techniques for subspace clustering make use of recent advances in sparsity and rank minimization. However, existing techniques are computationally expensive and may result in degenerate solutions that degrade clustering performance in the case of insufficient data sampling. To partially solve these problems, and inspired by...
Source: http://arxiv.org/abs/1203.2210v2
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by Miguel Moscoso; Alexei Novikov; George Papanicolaou; Lenya Ryzhik
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We present an ordinary differential equations approach to the analysis of algorithms for constructing $l_1$ minimizing solutions to underdetermined linear systems of full rank. It involves a relaxed minimization problem whose minimum is independent of the relaxation parameter. An advantage of using the ordinary differential equations is that energy methods can be used to prove convergence. The connection to the discrete algorithms is provided by the Crandall-Liggett theory of monotone nonlinear...
Source: http://arxiv.org/abs/1203.2309v1
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by Rodrigo de Abreu; Vasco Guerra
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A simple and effective approach to thermodynamics is suggested, which solves the major difficulties in the traditional presentation of the subject. The internal energy is introduced from the behavior of deformable bodies, whereas the importance of keeping in mind the microscopic picture is emphasized. A straightforward model is used to show that the internal energy depends on the volume and entropy, from where the relationship between mechanics and thermodynamics is immediate, mechanics...
Source: http://arxiv.org/abs/1203.2294v1
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by Anna Ferré-Mateu; Alexandre Vazdekis; Ignacio Trujillo; Patricia Sánchez-Blázquez; Elena Ricciardelli; Ignacio G. de la Rosa
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We characterize the kinematics, morphology, stellar populations and star formation histories of a sample of massive compact galaxies in the nearby Universe, which might provide a closer look to the nature of their high redshift (z > 1.0) massive counterparts. We find that nearby compact massive objects show elongated morphologies and are fast rotators. New high-quality long-slit spectra show that they have young mean luminosity-weighted ages ( < 2Gyr) and solar metallicities or above...
Source: http://arxiv.org/abs/1203.2623v1
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by Eun Jung Kim; Daniel Goncalves
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In the Permutation Constraint Satisfaction Problem (Permutation CSP) we are given a set of variables $V$ and a set of constraints C, in which constraints are tuples of elements of V. The goal is to find a total ordering of the variables, $\pi\ : V \rightarrow [1,...,|V|]$, which satisfies as many constraints as possible. A constraint $(v_1,v_2,...,v_k)$ is satisfied by an ordering $\pi$ when $\pi(v_1)
Source: http://arxiv.org/abs/1203.2801v1
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by M. V. Ioffe; E. V. Krupitskaya; D. N. Nishnianidze
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Recently, a new quantum model - two-dimensional generalization of the Scarf II - was completely solved analytically by SUSY method for the integer values of parameter. Now, the same integrable model, but with arbitrary values of parameter, will be studied by means of supersymmetrical intertwining relations. The Hamiltonian does not allow the conventional separation of variables, but the supercharge operator does allow, leading to the partial solvability of the model. This approach, which can be...
Source: http://arxiv.org/abs/1203.3076v1
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by Michael McQuillan; Daniel Panazzolo
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We investigate the structure of fully non-linear P.D.E.'s in holomorphic functions, with emphasis on the functorial generalisation of so called "irregular" O.D.E.'s. Highlights are an implicit function theorem removing the perturbation conditions of Nash-Moser type, best possible existence results when the singularity of the linearised P.D.E. is at worst bi-dimensional, and various, again optimal, corollaries on existence of centre manifolds and conjugation to normal form of...
Source: http://arxiv.org/abs/1203.3045v1
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by Manish Dev Shrimali; Subhashish Banerjee
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The delay logistic map with two types of q-deformations: Tsallis and Quantum-group type are studied. The stability of the map and its bifurcation scheme is analyzed as a function of the deformation and delay feedback parameters. Chaos is suppressed in a certain region of deformation and feedback parameter space. The steady state obtained by delay feedback is maintained in one type of deformation while chaotic behavior is recovered in another type with increasing delay.
Source: http://arxiv.org/abs/1203.3137v1
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In this paper, some new inequalities of the Hermite-Hadamard type for h-convex functions via Riemann-Liouville fractional integral are given.
Source: http://arxiv.org/abs/1203.3318v1
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In this note, we study the Martin boundary of the simple random walk on an example of directed graph. More precisely, the Martin boundary is shown to be trivial, i.e. there is no non-constant positive harmonic functions. The proof involves fine estimates of the Green function which are summarized in this note.
Source: http://arxiv.org/abs/1203.3314v1
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Let $S$ be a polynomial algebra over a field. We study classes of monomial ideals (as for example lexsegment ideals) of $S$ having minimal depth. In particular, Stanley's conjecture holds for these ideals. Also we show that if Stanley's conjecture holds for a square free monomial ideal then it holds for all its trivial modifications.
Source: http://arxiv.org/abs/1203.3319v1
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Interval translation maps (ITMs) are non-invertible generalizations of interval exchanges (IETs). The dynamics of finite type ITMs is similar to IETs, while infinite type ITMs are known to exhibit new interesting effects. In this paper, we prove the finiteness conjecture for the ITMs of three intervals. Namely, the subset of ITMs of finite type is open, dense, and has full Lebesgue measure. For this, we show that any ITM of three intervals can be reduced either to a rotation or to a double...
Source: http://arxiv.org/abs/1203.3405v3
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by Evan Ranken; Parampreet Singh
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We investigate the dynamics of single and multiple scalar fields with exponential potentials, leading to power-law and assisted inflation, in loop quantum cosmology. Unlike in the classical theory, dynamical trajectories in loop quantum cosmology are generically non-singular, with a big bounce replacing classical big bang in the Planck regime. Post bounce, after a phase of super-inflation, dynamical trajectories evolve towards the classical attractor in the inflationary scenarios. Depending on...
Source: http://arxiv.org/abs/1203.3449v2
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by William Detmold; C. -J. David Lin; Stefan Meinel
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We calculate matrix elements of the axial current for static-light mesons and baryons in lattice QCD with dynamical domain wall fermions. We use partially quenched heavy hadron chiral perturbation theory in a finite volume to extract the axial couplings g_1, g_2, and g_3 from the data. These axial couplings allow the prediction of strong decay rates and enter chiral extrapolations of most lattice results in the b sector. Our calculations are performed with two lattice spacings and with pion...
Source: http://arxiv.org/abs/1203.3600v1
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by Peiji Chen; Wenjing Ma; Srinath Mandalapu; Chandrashekhar Nagarajan; Jayavel Shanmugasundaram; Sergei Vassilvitskii; Erik Vee; Manfai Yu; Jason Zien
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A large fraction of online display advertising is sold via guaranteed contracts: a publisher guarantees to the advertiser a certain number of user visits satisfying the targeting predicates of the contract. The publisher is then tasked with solving the ad serving problem - given a user visit, which of the thousands of matching contracts should be displayed, so that by the expiration time every contract has obtained the requisite number of user visits. The challenges of the problem come from (1)...
Source: http://arxiv.org/abs/1203.3593v1
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by Martin R. Hediger; Luca De Vico; Allan Svendsen; Werner Besenmatter; Jan H. Jensen
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We present a fast computational method to efficiently screen enzyme activity. In the presented method, the effect of mutations on the barrier height of an enzyme-catalysed reaction can be computed within 24 hours on roughly 10 processors. The methodology is based on the PM6 and MOZYME methods as implemented in MOPAC2009, and is tested on the first step of the amide hydrolysis reaction catalyzed by Candida Antarctica lipase B (CalB) enzyme. The barrier heights are estimated using adiabatic...
Source: http://arxiv.org/abs/1203.2950v3
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by Itai Benjamini; Nicolas Curien; Agelos Georgakopoulos
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It is shown that if a planar graph admits no non-constant bounded harmonic functions then the trajectories of two independent simple random walks intersect almost surely.
Source: http://arxiv.org/abs/1203.4002v2
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by Michael Menzel; Rajiv Ranjan
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Cloud computing is the latest computing paradigm that delivers hardware and software resources as virtualized services in which users are free from the burden of worrying about the low-level system administration details. Migrating Web applications to Cloud services and integrating Cloud services into existing computing infrastructures is non-trivial. It leads to new challenges that often require innovation of paradigms and practices at all levels: technical, cultural, legal, regulatory, and...
Source: http://arxiv.org/abs/1203.3997v1
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by Mark Hindmarsh; Ippocratis D. Saltas
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We explore the cosmological dynamics of an effective f(R) model constructed from a renormalisation group (RG) improvement of the Einstein--Hilbert action, using the non-perturbative beta functions of the exact renormalisation group equation. The resulting f(R) model has some remarkable properties. It naturally exhibits an unstable de Sitter era in the ultraviolet (UV), dynamically connected to a stable de Sitter era in the IR, via a period of radiation and matter domination, thereby describing...
Source: http://arxiv.org/abs/1203.3957v1
The first measurement of neutron emission in electromagnetic dissociation of $^{208}$Pb nuclei at the LHC is presented. The measurement is performed using the neutron Zero Degree Calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with neutron emission are $\sigma_{\rm single\ EMD} = 187.4\pm0.2$ (stat.) $^{+13.2}_{-11.2}$ (syst.)...
Source: http://arxiv.org/abs/1203.2436v2
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by Jiankui Li; Qihua Shen; Jianbin Guo
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Let $\mathcal{A}$ be a unital algebra, $\delta$ be a linear mapping from $\mathcal{A}$ into itself and $m$, $n$ be fixed integers. We call $\delta$ an (\textit{m, n})-derivable mapping at $Z$, if $m\delta(AB)+n\delta(BA)=m\delta(A)B+mA\delta(B)+n\delta(B)A+nB\delta(A)$ for all $A, B\in \mathcal{A}$ with $AB=Z$. In this paper, (\textit{m, n})-derivable mappings at 0 (resp. $I_\mathcal{A}\oplus0$, $I$) on generalized matrix algebras are characterized. We also study (\textit{m, n})-derivable...
Source: http://arxiv.org/abs/1203.2497v1
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by Shuang Wang; Wei Chen; Zhen-Qiang Yin; Yang Zhang; Tao Zhang; Hong-Wei Li; Fang-Xing Xu; Zheng Zhou; Yang Yang; Da-Jun Huang; Li-Jun Zhang; Fang-Yi Li; Dong Liu; Yong-Gang Wang; Guang-Can Guo; Zheng-Fu Han
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We propose a wavelength-saving topology of quantum key distribution(QKD) network based on passive optical elements, and report the field test of this network on the commercial telecom optical fiber. In this network, 5 nodes are supported with 2 wavelengths, and every two nodes can share secure keys directly at the same time. All QKD links in the network operate at the frequency of 20 MHz. We also characterized the insertion loss and crosstalk effects on the point-to-point QKD system after...
Source: http://arxiv.org/abs/1203.4321v1
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by Yeow-Khiang Chia; Rajiv Soundararajan; Tsachy Weissman
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We consider the problem of estimating a signal corrupted by independent interference with the assistance of a cost-constrained helper who knows the interference causally or noncausally. When the interference is known causally, we characterize the minimum distortion incurred in estimating the desired signal. In the noncausal case, we present a general achievable scheme for discrete memoryless systems and novel lower bounds on the distortion for the binary and Gaussian settings. Our Gaussian...
Source: http://arxiv.org/abs/1203.4311v1
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by K. Miyamoto; A. Kimura; T. Okuda; H. Miyahara; K. Kuroda; H. Namatame; M. Taniguchi; S. V. Eremeev; T. V. Menshchikova; E. V. Chulkov; K. A. Kokh; O. E. Tereshchenko
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Helical spin textures with the marked spin polarizations of topological surface states have been firstly unveiled by the state-of-the-art spin- and angle-resolved photoemission spectroscopy for two promising topological insulators Bi$_2$Te$_2$Se and Bi$_2$Se$_2$Te. The highly spin-polarized natures are found to be persistent across the Dirac point in both compounds. This novel finding paves a pathway to extending their utilization of topological surface state for future spintronic applications.
Source: http://arxiv.org/abs/1203.4439v1
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by N. Xu; T. Qian; P. Richard; Y. -B. Shi; X. -P. Wang; P. Zhang; Y. -B. Huang; Y. -M. Xu; H. Miao; G. Xu; G. -F. Xuan; W. -H. Jiao; Z. -A. Xu; G. -H. Cao; H. Ding
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We report a systematic angle-resolved photoemission spectroscopy study on Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ for a wide range of Ru concentrations (0.15 $\leq$ \emph{x} $\leq$ 0.74). We observed a crossover from two-dimension to three-dimension for some of the hole-like Fermi surfaces with Ru substitution and a large reduction in the mass renormalization close to optimal doping. These results suggest that isovalent Ru substitution has remarkable effects on the low-energy electron excitations, which...
Source: http://arxiv.org/abs/1203.4699v1