March 2001 arXiv papers — page 24

Markus Demleitner, Burkhard Fuchs

We examine the modes admitted by the Mestel disk, a disk with a globally flat rotation curve. In contrast to previous analyses of this problem by Zang (\cite{1976PhDT........26Z}) and Evans & Read (\cite{1998MNRAS.300...83E}, \cite{1998MNRAS.300..106E}), we approximate the orbits to obtain almost closed expressions for the kernel of the integral equation gov

T. Ekholm, Yu. Baryshev, P. Teerikorpi, M. O. Hanski

Cepheid distances of local galaxies (<7 Mpc) are used to study the very nearby velocity field, as pioneered by Sandage (Sandage 1986) who also pointed out its remarkable properties: linearity and quietness. The new data show that the velocity dispersion in the distance range as seen from the barycentre of the Local Group 1-8 Mpc is as low as 38 km/sec. The l

E. Giacani, D. A. Frail, W. M. Goss, M. Vieytes

We present high resolution VLA images taken at the wavelengths of lambda 20 cm, lambda 6 cm, and lambda 3.6 cm in the vicinity of the pulsars PSR B1706-44 (PSR J1709-4428) and PSR B1643-43 (PSR J1646-4346). Both of these pulsars are young (<30,000 yrs) and have large spin-down luminosities (e+35 erg/sec) and hence are good candidates to search for extended s

Harald Dimmelmeier, Jose A. Font, Ewald Mueller

We present results from simulations of axisymmetric relativistic rotational core collapse. The general relativistic hydrodynamic equations are formulated in flux-conservative form and solved using a high-resolution shock-capturing scheme. The Einstein equations are approximated with a conformally flat 3-metric. We use the quadrupole formula to extract wavefo

M. Lacy, S. A. Laurent-Muehleisen, S. E. Ridgway, R. H. Becker

Several independent lines of evidence now point to a correlation between black hole mass, M_bh, and radio-luminosity. In this paper we discuss the correlation for quasars from the FIRST Bright Quasar Survey (FBQS), using black hole mass estimates from Hbeta linewidths. The FBQS objects fill in the gap between the radio-loud and radio-quiet quasars in the rad

Michael Dahlem, Matthias Ehle, Stuart Ryder

Australia Telescope Compact Array HI observations reveal the existence of 5.8x10^8 M_sun of HI gas in the central 7 kpc of the edge-on spiral galaxy NGC 3175. The detected HI and CO gas can explain why star formation, as traced by other emission processes, is going on in the inner part of its disk. On the other hand, the entire outer disk, beyond 3.5 kpc rad

A. Roberge, A. Lecavelier des Etangs, C. A. Grady, A. Vidal-Madjar

We present the first observations of a Herbig Ae star with a circumstellar disk by the Far Ultraviolet Spectroscopic Explorer (FUSE), as well as a simultaneous observation of the star obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS). The spectra of AB Aurigae show emission and absorption features arising from gasses that h

Brian D. Fields, James W. Truran, John J. Cowan

Recent observations of heavy elements produced by rapid neutron capture (r-process) in the halo have shown a striking and unexpected behavior: within a single star, the relative abundances of r-process elements heavier than Eu are the same as the same as those of solar system matter, while across stars with similar metallicity Fe/H, the r/Fe ratio varies ove

Rafael I. Nepomechie

We argue that, contrary to previous claims, the supersymmetric sine-Gordon model with boundary has a two-parameter family of boundary interactions which preserves both integrability and supersymmetry. We also propose the corresponding boundary S matrix for the first supermultiplet of breathers.

P. P. Avelino, J. P. M. de Carvalho, C. J. A. P. Martins

We consider a very simple toy model for a spatially varying `cosmological constant&#39;, where we are inside a spherical bubble (with a given set of cosmological parameters) that is surrounded by a larger region where these parameters are different. This model includes essential features of more realistic scenarios with a minimum number of parameters. We cal

R. G. Sharp, R. G. McMahon, M. J. Irwin, S. T. Hodgkin

We report the first results of an observational program designed to determine the luminosity density of high redshift quasars (z > 5 quasars) using deep multi-colour CCD data. We report the discovery and spectra of 3 i < 21.5 high redshift (z > 4.4) quasars, including one with z > 5. At z=5.17, this is the fourth highest redshift quasar currently published.

D. Mateos, P. K. Townsend

It is shown that a IIA superstring carrying D0-brane charge can be `blown-up&#39;, in a {\it Minkowski vacuum} background, to a (1/4)-supersymmetric tubular D2-brane, supported against collapse by the angular momentum generated by crossed electric and magnetic Born-Infeld fields. This `supertube&#39; can be viewed as a worldvolume realization of the sigma-mo

Jürgen König, Tomas Jungwirth, A. H. MacDonald

We present a microscopic theory of the long-wavelength magnetic properties of the ferromagnetic diluted magnetic semiconductor (Ga,Mn)As. Details of the host semiconductor band structure, described by a six-band Kohn-Luttinger Hamiltonian, are taken into account. We relate our quantum-mechanical calculation to the classical micromagnetic energy functional an

J. Camacho, R. Guimera, L. A. N. Amaral

We analyze the properties of seven community food webs from a variety of environments--including freshwater, marine-freshwater interfaces and terrestrial environments. We uncover quantitative unifying patterns that describe the properties of the diverse trophic webs considered and suggest that statistical physics concepts such as scaling and universality may

S. N. Molotkov, S. S. Nazin

We analyze the restrictions on the distinguishability of quantum states imposed by special relativity. An explicit expression relating the error probability for distinguishing between two orthogonal single-photon states with the time $T$ elapsed from the start of the measurement procedure until the measurement result is obtained by the observer.

H. Jirari, H. Kröger, X. Q. Luo, G. Melkonyan

We study a recently proposed quantum action depending on temperature. We construct a renormalisation group equation describing the flow of action parameters with temperature. At zero temperature the quantum action is obtained analytically and is found free of higher time derivatives. It makes the quantum action an ideal tool to investigate quantum chaos and

Roberto Gomez

A partially first-order form of the characteristic formulation is introduced to control the accuracy in the computation of gravitational waveforms produced by highly distorted single black hole spacetimes. Our approach is to reduce the system of equations to first-order differential form on the angular derivatives, while retaining the proven radial and time

G. Aarts, J. Berges

Transport or kinetic equations are often derived assuming a quasi-particle (on-shell) representation of the spectral function. We investigate this assumption using a three-loop approximation of the 2PI effective action in real time, without a gradient expansion or on-shell approximation. For a scalar field in 1+1 dimensions the nonlinear evolution, including

S. Arnouts, B. Vandame, C. Benoist, M. A. T. Groenewegen

This paper presents multi-passband optical data obtained from observations of the Chandra Deep Field South (CDF-S), located at alpha ~ 3h 32m, delta ~ -27d 48m. The observations were conducted at the ESO/MPG 2.2m telescope at La Silla using the 8kx8k Wide-Field Imager (WFI). This data set, taken over a period of one year, represents the first field to be com

Dinesh Kumar Srivastava, Bikash Sinha, Ioulia Kvasnikova, Charles Gale

The production of single photons in $Pb+Pb$ collisions at the CERN SPS as measured by the WA98 experiment is analysed. A quark gluon plasma is assumed to be formed initially, which expands, cools, hadronizes, and undergoes freeze-out. A rich hadronic equation of state is used and the transverse expansion of the interacting system is taken into account. The r

H. Hofmann, F. A. Ivanyuk, C. Rummel, S. Yamaji

Semi-analytical expressions are suggested for the temperature dependence of those combinations of transport coefficients which govern the fission process. This is based on experience with numerical calculations within the linear response approach and the locally harmonic approximation. A reduced version of the latter is seen to comply with Kramers&#39; simpl

Kiwoon Choi, Kyuwan Hwang, Sin Kyu Kang, Kang Young Lee

Motivated by the recently measured muon&#39;s anomalous magnetic moment $a_μ$, we examine the supersymmetry contribution to $a_μ$ in various mediation models of supersymmetry breaking which lead to predictive flavor conserving soft parameters at high energy scale. The studied models include dilaton/modulus-mediated models in heterotic string/$M$ theory, gaug

Domingos Soares

Astronomy is not in the list of natural sciences aimed at by the Nobel awards. In spite of that, there were, throughout the 1930s until the early 1950s, effective moves by important scientists to distinguish Hubble with the Prize. A short report on these attempts is made as well as speculation on what would be the citation for the prize in view of the broad

R. Chary, D. Elbaz

We present a detailed interpretation of the spectrum of the cosmic infrared background longwards of 5 microns and of galaxy counts from various surveys at mid-infrared, far-infrared and submillimeter wavelengths by evolving the mid-infrared local luminosity function with redshift. We find that all evolutionary models that fit the counts require a flattening

Youichi Yamada

It was recently pointed out that the on-shell renormalization of the Cabibbo-Kobayashi-Maskawa (CKM) matrix in the method by Denner and Sack causes a gauge parameter dependence of the amplitudes. We analyze the gauge dependence of the on-shell renormalization of the mixing matrices both for fermions and scalars in general cases, at the one-loop level. We the

S. A. Zaitsev, E. I. Kramar

An approximate inverse scattering method [7,8] has been used to construct separable potentials with the Laguerre form factors. As an application, we invert the phase shifts of proton-proton in the $^1S_0$ and $^3P_2-^3F_2$ channels and neutron-proton in the $^3S_1-^3D_1$ channel elastic scattering. In the latter case the deuteron wave function of a realistic

Pei-Ming Ho

Based on results about open string correlation functions, a nonassociative algebra was proposed in a recent paper for D-branes in a background with nonvanishing $H$. We show that our associative algebra obtained by quantizing the endpoints of an open string in an earlier work can also be used to reproduce the same correlation functions. The novelty of this a

Masahide Yamaguchi

We propose a natural double inflation model in supergravity. In this model, chaotic inflation first takes place by virtue of the Nambu-Goldstone-like shift symmetry, which guarantees the absence of the exponential factor in the potential for the inflaton field. During chaotic inflation, an initial value of the second inflation (new inflation) is set. In this

G. Alexanian, A. P. Balachandran, G. Immirzi, B. Ydri

Regularization of quantum field theories (QFT&#39;s) can be achieved by quantizing the underlying manifold (spacetime or spatial slice) thereby replacing it by a non-commutative matrix model or a ``fuzzy manifold&#39;&#39;. Such discretization by quantization is remarkably successful in preserving symmetries and topological features, and altogether overcomin

Vania E. Barlette, Marcelo M. Leite, Sadhan K. Adhikari

A self-contained discussion of integral equations of scattering is presented in the case of centrally-symmetric potentials in one dimension, which will facilitate the understanding of more complex scattering integral equations in two and three dimensions. The present discussion illustrates in a simple fashion the concept of partial-wave decomposition, Green&

Mingjun Shi, Jiangfeng Du

The set of all separable quantum states is compact and convex. We focus on the two-qubit quanum system and study the boundary of the set. Then we give the criterion to determine whether a separable state is on the boundary. Some straightforward geometrical interpretations for entanglement are based on the concept and presented subsequently.

S. -K. Yip

We discuss the line shape for an internal state transition for bosonic atoms confined as a one-dimensional gas. Typical line shape is an edge singularity due to the absence of Bose-Einstein Condensation in such systems.

Jorge Piekarewicz

Isoscalar monopole and dipole compressional modes are computed for a variety of closed-shell nuclei in a relativistic random-phase approximation to three different parametrizations of the Walecka model with scalar self-interactions. Particular emphasis is placed on the role of self-consistency which by itself, and with little else, guarantees the decoupling

Miloslav Znojil, Milos Tater

A new exactly solvable alternative to the Calogero three-particle model is proposed. Sharing its confining long-range part, it contains the mere zero-range two-particle barriers. Their penetrability gives rise to a tunneling, tunable via their three independent strengths. Their variability can control the removal of the degeneracy of the energy levels in an

F. Simkovic, M. Smotlak, A. A. Raduta

A new Quasiparticle Random Phase Approximation approach is presented. The corresponding ground state is variationally determined and exhibits a minimum energy. New solutions for the ground state, some with spontaneously broken symmetry, of a solvable Hamiltonian are found. A non-iterative procedure to solve the non-linear QRPA equations is used and thus all

Amruta Mishra, P. K. Panda, W. Greiner

We derive the equation of state for hot nuclear matter using Walecka model in a nonperturbative formalism. We include here the vacuum polarisation effects arising from the nucleon and scalar mesons through a realignment of the vacuum. A ground state structure with baryon-antibaryon condensates yields the results obtained through the relativistic Hartree appr

Wieslaw Krolikowski, Ole Bang, Jens Juul Rasmuss, John Wyller

We study modulational instability (MI) of plane waves in nonlocal nonlinear Kerr media. For a focusing nonlinearity we show that, although the nonlocality tends to suppress MI, it can never remove it completely, irrespectively of the particular profile of the nonlocal response function. For a defocusing nonlinearity the stability properties depend sensitivel

A. B. Aleksandrov, S. Janson, V. V. Peller, R. Rochberg

We consider the class of integral operators $Q_\f$ on $L^2(\R_+)$ of the form $(Q_\f f)(x)=\int_0^\be\f (\max\{x,y\})f(y)dy$. We discuss necessary and sufficient conditions on $ϕ$ to insure that $Q_ϕ$ is bounded, compact, or in the Schatten-von Neumann class $\bS_p$, $1<p<\infty$. We also give necessary and sufficient conditions for $Q_ϕ$ to be a finite rank

Olivier Garet

We consider a generalization of the so-called divide and color model recently introduced by Haggstrom. We investigate the behaviour of the magnetization in large boxes and its fluctuations. Thus, laws of large numbers and Central Limit theorems are proved, both quenched and annealed. We show that the properties of the underlying percolation process roughly i

Michael Schlosser

We give an r-dimensional generalization of H. S. Shukla&#39;s very-well-poised 8-psi-8 summation formula. We work in the setting of multiple basic hypergeometric series very-well-poised over the root system A_{r-1}, or equivalently, the unitary group U(r). Our proof, which is already new in the one-dimensional case, utilizes an A_{r-1} nonterminating very-we

Ichiro Torisu

In this article, we consider the maximal value of the Thurston--Bennequin invariant of Legendrian knots which topologically represent a fixed knot type in the standard contact 3-space and we prove a formula of the value under the connected sum operation of knots.

Stéphane Gaussent

Following Contou-Carrere [CC], we consider the Bott-Samelson resolution of a Schubert variety as a variety of galleries in the Tits building associated to the situation. We prove that the rational smoothness of a Schubert variety can be expressed in terms of a subspace of the Zariski tangent space called, the combinatorial tangent space. For this, we use a c

Toshiki Nakashima

Specializing properly the parameters contained in the maximal cyclic representation of the non-restricted A-type quantum algebra at roots of unity, we find the unique primitive vector in it. We show that the submodule generated by the primitive vector can be identified with an irreducble highest weight module of the finite dimensional A-type quantum algebra

Lars Kadison, A. A. Stolin

We study a Hopf algebra $H$, which is finitely generated and projective over a commutative ring $k$, as a $P$-Frobenius algebra. We define modular functions in this setting, and provide a complete proof of Radford&#39;s formula for the fourth power of the antipode, using Frobenius algebraic techniques. As further applications, we extend Etingof and Gelaki&#3

Lars Kadison, A. A. Stolin

In Section 1 we introduce Frobenius coordinates in the general setting that includes Hopf subalgebras. In Sections 2 and 3 we review briefly the theories of Frobenius algebras and augmented Frobenius algebras with some new material in Section 3. In Section 4 we study the Frobenius structure of an FH-algebra H \cite{Par72} and extend two recent theorems in \c

Matti Pitkanen

A strategy for proving (not a proof of, as was the first over-optimistic belief) the Riemann hypothesis is suggested. The vanishing of Riemann Zeta reduces to an orthogonality condition for the eigenfunctions of a non-Hermitian operator D^+ having the zeros of Riemann Zeta as its eigenvalues. The construction of D^+ is inspired by the conviction that Riemann

Georges Racinet

We describe in this note a torsor structure arising on the affine scheme defined by a system of rationnal algebraic relations between polyzetas at roots of unity (values of hyperlogarithmic functions on a fixed finite group of complex roots of unity). When this group is reduced to 1, we call these numbers the polyzetas. They generalize the values of the Riem

Lucia Caporaso, Edoardo Sernesi

We show that a general plane curve of degree at least 4 is uniquely determined by the full set of its bitangent lines. This problem has an elementary solution for degree at least 5, and the paper is almost entirely devoted to curves of degree 4, where we generalize the result to nodal quartics. In other words, we show that a general curve of genus 3 can be r

Robert L. Bryant

I use local differential geometric techniques to prove that the algebraic cycles in certain extremal homology classes in Hermitian symmetric spaces are either rigid (i.e., deformable only by ambient motions) or quasi-rigid (roughly speaking, foliated by rigid subvarieties in a nontrivial way). These rigidity results have a number of applications: First, they

Arkady Yu. Segal

An action describing the dynamics of an infinite collection of massless integer spin fields with spin s=0,1,2,3, ...$\infty$ corresponding to totally symmetric Young tableaux representations of Poincare and anti-de Sitter groups is constructed, in any dimension d, in terms of two functions on a 2d-dimensional manifold. The action is represented by an integra

Richard Battye, Paul Sutcliffe

We apply two very different approaches to calculate Skyrmions with baryon number B less than 23. The first employs the rational map ansatz, where approximate charge B Skyrmions are constructed from a degree B rational map between Riemann spheres. We use a simulated annealing algorithm to search for the minimal energy rational map of a given degree B. The sec

Sayan Kar

Renormalisation Group (RG) flows in theory space (the space of couplings) are generated by a vector field -- the $β$ function. Using a specific metric ansatz in theory space and certain methods employed largely in the context of General Relativity, we examine the nature of the expansion, shear and rotation of geodesic RG flows. The expansion turns out to be

Guang-jiong Ni, Tsao Chang

Based on the experimental discovery that the mass-square of neutrino is negative, a quantum theory for superluminal neutrino is proposed. Two Weyl equations coupled together via a mass term respecting the maximum parity violation lead to a new equation which describes the superluminal motion of neutrino with permanent helicity. Various strange features of su

Rodolfo A. Diaz, R. Martinez, J. -Alexis Rodriguez

Current muon anomalous magnetic moment data have challenged the SM, and seems to open a window to new Physics. Since the difference between SM and experimental predictions is approximately $2.6σ$. In the framework of the General Two Higgs Doublet Model (2HDM), we calculate the muon anomalous magnetic moment to get lower and upper bounds for the Flavor Changi

S. Groote, A. A. Pivovarov

We calculate a correction to the electromagnetic current induced by a heavy quark loop. The contribution of this correction to the vacuum polarization function appears at the O(alpha_s^3) order of perturbation theory and has a qualitatively new feature -- its absorptive part starts at zero energy in contrast to other contributions where the absorptive parts

Adriano Di Giacomo

An updated review is presented of our understanding of color confinement. Lattice results on condensation of magnetic charges are discussed. The role of vortices is analysed.

Thomas DeGrand, Anna Hasenfratz

We comment on the recent paper (hep-lat/0102003) by Horvath, Isgur, McCune, and Thacker, which concludes that the local chiral structure of fermionic eigenmodes is not consistent with instanton dominance. Our calculations, done with an overlap action, suggest the opposite conclusion.

The DELPHI Collaboration, P. Abreu

Searches for pair production of supersymmetric particles under the assumption that R-parity is not conserved are presented, based on data recorded by the DELPHI detector in 1998 from e+e- collisions at a centre-of-mass energy of 189 GeV. Only one R-parity violating LL\bar{E} term (i.e. one lambda coupling), which couples scalar leptons to leptons, is conside

The DELPHI Collaboration, P. Abreu

A test of the QED process e+e- -> gamma gamma (gamma) is reported. The data analysed were collected with the DELPHI detector in 1998 and 1999 at the highest energies achieved at LEP, reaching 202 GeV in the centre-of-mass. The total integrated luminosity amounts to 375.7 pb^{-1}. The differential and total cross-sections for the process e+e- -> gamma gamma w

The DELPHI Collaboration, P. Abreu

Measurements of on-shell ZZ production are described, using data collected by DELPHI in 1997 and 1998, at centre-of-mass energies sqrt(s) = 182.6 GeV and 188.6 GeV respectively. Results obtained in each of the final states q qbar q qbar, mu+mu- q qbar, e+e- q qbar, nu nubar q qbar, l+l-l+l-, and nu nubar l+l- are presented. The measured cross-sections for on

J. Bagger

Several proposals are being developed around the world for an e+e- linear collider with an initial center of mass energy of 500 GeV. In this paper, we will discuss why a project of this type deserves priority as the next major initiative in high energy physics.

Daniel Muller, Helio V. Fagundes, Reuven Opher

A few years ago, Cornish, Spergel and Starkman (CSS), suggested that a multiply connected ``small&#39;&#39; Universe could allow for classical chaotic mixing as a pre-inflationary homogenization process. The smaller the volume, the more important the process. Also, a smaller Universe has a greater probability of being spontaneously created. Previously DeWitt

A. Miyazaki

The Machian cosmological solution satisfying $ϕ=O(ρ/ω)$ in the generalized scalar-tensor theory of gravitation with the varying cosmological constant is summarized. The scalar field $ϕ$ with the exponential potential is introduced as dark matter and the barotropic evolution of matter in the universe is discussed. As the universe expands, the coefficient $γ$

Amos Ori

We calculate the asymptotic behavior of the curvature scalar $(Riemann)^2$ near the null weak singularity at the inner horizon of a generic spinning black hole, and show that this scalar oscillates infinite number of times while diverging. The dominant parallelly-propagated Riemann components oscillate in a similar manner. This oscillatory behavior, which is

Miroslav Pardy

Strictly respecting the Einstein equations and supposing space-time is a medium, we derive the deformation of this medium by gravity. We derive the deformation in case of infinite plane, Robertson-Walker manifold, Schwarzschild manifold and gravitational waves. Some singularities are removed or changed. We call this procedure renormalization of gravity. We s

Ilia Bisnovatyi

Modal synthesis is an important area of physical modeling whose exploration in the past has been held back by a large number of control parameters, the scarcity of general-purpose design tools and the difficulty of obtaining the computational power required for real-time synthesis. This paper presents an overview of a flexible software framework facilitating

Ilia Bisnovatyi, Michael J. O&#39;Donnell

This paper describes a method for decomposing steady-state instrument data into excitation and formant filter components. The input data, taken from several series of recordings of acoustical instruments is analyzed in the frequency domain, and for each series a model is built, which most accurately represents the data as a source-filter system. The source p

Yosef Ashkenazy, Jeffrey M. Hausdorff, Plamen Ch. Ivanov, Ary L. Goldberger

We present a stochastic model of gait rhythm dynamics, based on transitions between different ``neural centers&#39;&#39;, that reproduces distinctive statistical properties of normal human walking. By tuning one model parameter, the hopping range, the model can describe alterations in gait dynamics from childhood to adulthood --- including a decrease in the

H. O. Jeschke, M. E. Garcia, K. H. Bennemann

The physical mechanisms for damage formation in graphite films induced by femtosecond laser pulses are analyzed using a microscopic electronic theory. We describe the nonequilibrium dynamics of electrons and lattice by performing molecular dynamics simulations on time-dependent potential energy surfaces. We show that graphite has the unique property of exhib

M. Dzugutov

It is demonstrated that a straightforward extension of the Arrhenius law accurately describes diffusion in the thermodynamically stable liquid of hard spheres. A sharp negative deviation from this behaviour is observed as the liquid is compressed beyond its stability limit, which can be compared with super-Arrhenius slowing down in supercooled liquids. It is

H. P. Ying, B. Zheng, Y. Yu, S. Trimper

With large-scale Monte Carlo simulations, we confirm that for the two-dimensional XY model, there is a logarithmic correction to scaling in the dynamic relaxation starting from a completely disordered state, while only an inverse power law correction in the case of starting from an ordered state. The dynamic exponent $z$ is $z=2.04(1)$.

H. Schomerus

We investigate the effects of wave localization on the delay time tau (frequency sensitivity of the scattering phase shift) of a wave transmitted through a disordered wave guide. Localization results in a separation tau=chi+chi&#39; of the delay time into two independent but equivalent contributions, associated to the left and right end of the wave guide. Fo

R. Guimera, A. Arenas, A. Diaz-Guilera

We study a general and simple model for communication processes. In the model, agents in a network (in particular, an organization) interchange information packets following simple rules that take into account the limited capability of the agents to deal with packets and the cost associated to the existence of open communication channels. Due to the limitati

A. Andreone, A. Cassinese, L. Gianni, M. Iavarone

Surface impedance measurements of LuNi2B2C superconducting thin films as a function of temperature have been performed down to 1.5 K and at 20 GHz using a dielectric resonator technique. The magnetic penetration depth closely reproduces the standard B.C.S. result, but with a reduced value of the energy gap at low temperature. These data provide evidence for

David Katz, Oded Millo, Shi-Hai Kan, Uri Banin

Tunneling spectroscopy of InAs nanocrystals deposited on graphite was measured using scanning tunneling microscopy, in a double-barrier tunnel-junction configuration. The effect of the junction symmetry on the tunneling spectra is studied experimentally and modeled theoretically. When the tip is retracted, we observe resonant tunneling through the nanocrysta

Z. Burda, J. Jurkiewicz, M. A. Nowak, G. Papp

We consider a covariance matrix composed of asymmetric and free random Levy matrices. We use the results of free random variables to derive an algebraic equation for the resolvent and solve it to extract the spectral density. For an appropriate choice of asymmetry and Levy index ($α/2=3/4$) the free eigenvalue spectrum is in remarkable agreement with the one

Z. Burda, J. Jurkiewicz, M. A. Nowak, G. Papp

In a given market, financial covariances capture the intra-stock correlations and can be used to address statistically the bulk nature of the market as a complex system. We provide a statistical analysis of three SP500 covariances with evidence for raw tail distributions. We study the stability of these tails against reshuffling for the SP500 data and show t

Szilard Pafka, Imre Kondor

We analyze the performance of RiskMetrics, a widely used methodology for measuring market risk. Based on the assumption of normally distributed returns, the RiskMetrics model completely ignores the presence of fat tails in the distribution function, which is an important feature of financial data. Nevertheless, it was commonly found that RiskMetrics performs

Lorenzo Matassini, Fabio Franci

Simulation of the trading activity based on the implementation of the book.

C. Reichhardt, C. J. Olson

We examine the dynamics of an elastic string interacting with quenched disorder driven perpendicular and parallel to the string. We show that the string is the most disordered at the depinning transition but with increasing drive partial ordering is regained. For low drives the noise power is high and we observe a 1/f^2 noise signature crossing over to a whi

J. Farago, C. Van den Broeck

We calculate analytically the phase boundary for a nonequilibrium phase transition in a one-dimensional array of coupled, overdamped parametric harmonic oscillators in the limit of strong and weak spatial coupling. Our results show that the transition is reentrant with respect to the spatial coupling in agreement with the prediction of the mean field theory.

E. G. Timoshenko, R. Basovsky, Yu. A. Kuznetsov

In recent experiments involving PNIPAM copolymers it has been observed that stable spherical nanoparticles are being formed by association of several chains in poor aqueous solution instead of aggregation. This type of mesoscopic structures called mesoglobules has an extremely monodispersed size distribution. Previously we have studied theoretically formatio

E. G. Timoshenko, Yu. A. Kuznetsov

By means of continuous space Monte Carlo simulation we study conformational structures formed by star and comb heteropolymers during kinetics of folding from the coil to the globule, as well as the corresponding equilibrium states on going from the good to the poor solution. Particular examples of combs with hydrophobic backbone and hydrophilic side-groups (

William Barford, Robert J. Bursill, Mikhail Yu Lavrentiev

We present density matrix renormalisation group calculations of the Pariser- Parr-Pople-Peierls model of linear polyenes within the adiabatic approximation. We calculate the vertical and relaxed transition energies, and relaxed geometries for various excitations on long chains. The triplet (3Bu+) and even- parity singlet (2Ag+) states have a 2-soliton and 4-

V. N. Bogomolov

A possibility of explaining the light absorption observed to occur under pressure-induced xenon metallization as due to the transition to the superconducting state is analyzed. The mechanism of the van der Waals bonding is discussed.

Denis Ullmo, Harold U. Baranger

We use random matrix models to investigate the ground state energy of electrons confined to a nanoparticle. Our expression for the energy includes the charging effect, the single-particle energies, and the residual screened interactions treated in Hartree-Fock. This model is applicable to chaotic quantum dots or nanoparticles--in these systems the single-par

F. Scheffold, S. E. Skipetrov, S. Romer, P. Schurtenberger

We introduce an elegant method which allows the application of diffusing-wave spectroscopy (DWS) to nonergodic, solid-like samples. The method is based on the idea that light transmitted through a sandwich of two turbid cells can be considered ergodic even though only the second cell is ergodic. If absorption and/or leakage of light take place at the interfa

I. P. McCulloch, A. R. Bishop, M. Gulacsi

We describe in detail the application of the recent non-Abelian Density Matrix Renormalization Group (DMRG) algorithm to the two dimensional t-J model. This extension of the DMRG algorithm allows us to keep the equivalent of twice as many basis states as the conventional DMRG algorithm for the same amount of computational effort, which permits a deeper under

Y. G. Zhao, Eric Li, Tom Wu, S. B. Ogale

The photon energy dependence of optical Cooper pair breaking rate (CPBR) is studied for compressibly strained La1.85Sr0.15CuO4 (LSCO) films and YBa2Cu2.92Zn0.08O7-delta (YBCZO) thin films, and compared to that in YBa2Cu3O7-delta (YBCO). Unlike in the case of YBCO, the CPBR for LSCO does not show obvious photon energy dependence. In YBCZO the CPBR shows stron

Koichi Kusakabe

By introducing a set of auxiliary equations representing a many-body system, we have derived an extension of the Kohn-Sham scheme for the density functional theory. These equations consist of a Kohn-Sham-type equation determining single-particle orbitals and an eigen-value equation for an effective many-body problem. A variational method similar to the Kohn-

Tomosuke Aono, Mikio Eto

The Kondo effect in coupled quantum dots is investigated from the viewpoint of transmission spectroscopy using the slave-boson formalism of the Anderson model. The antiferromagnetic spin-spin coupling $J$ between the dots is taken into account. Conductance $G$ through the dots connected in a series is characterized by the competition between the dot-dot tunn

A. V. Panov

A computer model of the feed-forward neural network with the hidden layer is developed to reconstruct physical field investigated by the fiber-optic measuring system. The Gaussian distributions of some physical quantity are selected as learning patterns. Neural network is learned by error back-propagation using the conjugate gradient and coordinate descent m

S. F. Edwards, M. Schwartz

We consider the exactly soluble Edwards-Wilkinson Model in one dimension and demonstrate explicitly, that it is possible to construct a field, that does not depend explicitly on time, such that the corresponding time dependent correlation function,, is dominated at long times by a stretched exponential decay. The difference between this and the stretched exp

K. Voelker, V. I. Anisimov, T. M. Rice

We present strong evidence for the existence of an acoustic plasmon mode, that is, a quadrupolar charge collective mode with linear dispersion, in MgB2. This mode may be responsible for the anomalously small value of the Coulomb pseudopotential required to explain the high superconducting transition temperature of 40K.

E. Aurell, K. Sneppen

We develop a framework to discuss stability of epigenetic states as first exit problems in dynamical systems with noise. We consider in particular the stability of the lysogenic state of the lambda prophage, which is known to exhibit exceptionally large stability. The formalism defines a quantative measure of robustness of inherited states. In contrast to Kr

M. Ausloos

A few characteristic exponents describing power law behaviors of roughness, coherence and persistence in stochastic time series are compared to each other. Relevant techniques for analyzing such time series are recalled in order to distinguish how the various exponents are measured, and what basic differences exist between each one. Financial time series, li

Ivana Mrkonjic, Slaven Barisic

The three band structure of the extended Emery model for the copper-oxide layered materials is analyzed for all the values of the effective tight-binding parameters. The model is characterized by the Cu-O site energy splitting, the Cu-O first neighbor hopping and the O-O second neighbor hopping. For the sufficiently large O-O hoppings, two bands can come tog

T. Okabe

This paper has been withdrawn.

V. S. Geroyannis

The white dwarf in AE Aqr is observed to spin down at a steady time rate ~ 5.64*10^{-14} s s^{-1}, while at the same time its UV and X-ray accretion luminosities remain almost unchanged. This is a contradiction, however, since the classicaly estimated spin-down power ~ -10^{34} erg s^{-1} exceeds the accretion luminosity of the primary by a factor ~ 10^2 and

L. Cambresy, W. T. Reach, C. A. Beichman, T. H. Jarrett

Using the 2MASS 2nd Incremental Data Release and the Zodiacal-Subtracted Mission Average maps of COBE/DIRBE, we estimate the cosmic background in the J (1.25 micron) and K (2.2 microns) bands using selected areas representing 550 square degrees of sky. We find a J background of 22.9 \pm 7.0 kJy/sr (54.0 \pm 16.8 nW/m2/sr) and a K background of 20.4 \pm 4.9 k