May 2002 arXiv papers — page 2

Axel Krause

We study the thermodynamic consequences of a recently proposed description for a Schwarzschild black hole based on Euclidean (D3,D3)+(\bar{D3},\bar{D3}) brane pairs described in terms of chain-like excitations. A discrete mass-spectrum of Bekenstein-type is inferred and upon identification of the black hole mass with the chain's energy the leading correc

C. Ciuti, J. P. McGuire, L. J. Sham

A theoretical prediction of the spin-dependent electron self-energy and in-plane transport of a two-dimensional electron gas in proximity with a ferromagnetic gate is presented. The application of the predicted spin-dependent properties is illustrated by the proposal of a device configuration with two neighboring ferromagnetic gates which produces a magnetor

Johan Bijnens, Pierre Dhonte, Fredrik Persson

The CP conserving amplitudes for the decays $K\to3π$ are calculated in Chiral Perturbation Theory at the next-to-leading order. We present the expressions in a compact form with single parameter functions only. These expressions are then fitted to all available $K\to2π$ and $K\to3π$ data to obtain a fit of the parameters that occur. We compare with the work

Angus MacKinnon

The quantum mechanics of a simple mechanical system is considered. A group of gears can serve as a model for several different systems such as an artifically constructed nanomechanical device or a group of ring molecules. It is shown that the classical motion of the gears in which the angular velocities are locked together does not correspond to a solution o

H. W. Braden, A. Marshakov

We discuss the associativity or WDVV equations and demonstrate that they can be rewritten as certain functional relations between the {\it second} derivatives of a single function, similar to the dispersionless Hirota equations. The properties of these functional relations are further discussed.

Geza Odor

This work is designed to overview our present knowledge about universality classes occurring in nonequilibrium systems defined on regular lattices. In the first section I summarize the most important critical exponents, relations and the field theoretical formalism used in the text. In the second section I briefly address the question of scaling behavior at

N. S. Manton, J. M. Speight

At critical coupling, the interactions of Ginzburg-Landau vortices are determined by the metric on the moduli space of static solutions. The asymptotic form of the metric for two well separated vortices is shown here to be expressible in terms of a Bessel function. A straightforward extension gives the metric for N vortices. The asymptotic metric is also sho

David Chavalarias

We propose a model of emergence of cooperation in evolutionary games that high- lights the role of network formation and effect of network structure. In line with empirical data, the model proposes a mechanism that explains the persistence of heterogeneous types (heterogeneity in rules for changing behavior) within a population, and in particular the sustain

Victor A. Gopar, K. A. Muttalib, P. Wölfle

We calculate the distribution of the conductance P(g) for a quasi-one-dimensional system in the metal to insulator crossover regime, based on a recent analytical method valid for all strengths of disorder. We show the evolution of P(g) as a function of the disorder parameter from a insulator to a metal. Our results agree with numerical studies reported on th

A. Barkallil, G. Barnich, C. Schomblond

The so-called covariant Poincare lemma on the induced cohomology of the spacetime exterior derivative in the cohomology of the gauge part of the BRST differential is extended to cover the case of arbitrary, non reductive Lie algebras. As a consequence, the general solution of the Wess-Zumino consistency condition with a non trivial descent can, for arbitrary

J. J. M. in 't Zand, J. M. Miller, T. Oosterbroek, A. N. Parmar

XTE J1908+094 is an X-ray transient that went into outburst in February 2002. After two months it reached a 2-250 keV peak flux of 1 to 2 X 10-8 erg/s/cm2. Circumstantial evidence points to an accreting galactic black hole as the origin of the the X-radiation: pulsations nor thermonuclear flashes were detected that would identify a neutron star and the spect

Roberto Casadio, Lorenzo Mazzacurati

We propose a method to extend into the bulk asymptotically flat static spherically symmetric brane-world metrics. We employ the multipole (1/r) expansion in order to allow exact integration of the relevant equations along the (fifth) extra coordinate and make contact with the parameterized post-Newtonian formalism. We apply our method to three families of so

R. Meinel

As a consequence of Birkhoff's theorem, the exterior gravitational field of a spherically symmetric star or black hole is always given by the Schwarzschild metric. In contrast, the exterior gravitational field of a rotating (axisymmetric) star differs, in general, from the Kerr metric, which describes a stationary, rotating black hole. In this paper, I d

Shesansu Sekhar Pal

We find nonsupersymmetric and supersymmetric solutions of D3 brane configuration in the background of pp wave obtained as a Penrose limit of $AdS_5\times S^5$.

Sarmistha Banik, Debades Bandyopadhyay

We investigate $K^-$ and $\bar K^0$ condensation in $β$-equilibrated hyperonic matter within a density dependent hadron field theoretical model. In this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by the exchange of mesons. Density dependent meson-baryon coupling constants are obtained from microscopic Dirac Brueckner calculations us

Eduard Masso

We employ an effective Lagrangian approach and use LEP data to place severe bounds on universality violations of the couplings of $ν_e$, $ν_μ$, and $ν_τ$ to the $Z$ boson. Our results justify the assumption of universality in these couplings that is usually made, as for example in the analysis of solar neutrinos detected at SNO.

Yu. A. Simonov

Field-correlator method is used to calculate nonperturbative dynamics of quarks in a baryon. General expression for the 3q Green's function is obtained using Fock-Feynman-Schwinger (world-line) path integral formalism, where all dynamics is contained in the 3q Wilson loop with spin-field insertions. Using lowest cumulant contribution for Wilson loop one

T. Sogo, H. Yabu

Spin asymmetry of the ground states is studied for the trapped spin-degenerate (two-component) gases of the fermionic atoms with the repulsive interaction between different components, and, for large particle number, the asymmetric (collective ferromagnetic) states are shown to be stable because it can be energetically favorable to increase the fermi energy

Tomohiro Matsuda

We present a new scenario for the baryon number violation that may take place in models with large extra dimensions. Our idea is interesting because leptogenesis with a low reheating temperature requires an alternative source of the B+L violation to convert the produced leptons into baryons. If one considers a model with an intermediate compactification radi

George Siopsis

We discuss the Penrose limit of pure AdS space, which is flat Minkowski space. Even though there is no holographic principle, we construct a ``holographic screen'' on which information on the corresponding CFT is encoded. The screen is obtained as a gauge-fixing condition upon restricting the Hilbert space to the states that are annihilated by the ge

Hiroyuki Fuji, Yutaka Ookouchi

We examine a large N duality via geometric transition for N=1 SO/Sp gauge theories with superpotential for adjoint chiral superfield. In this paper, we find that the large N gauge theories are exactly analyzed for the classical quartic superpotentials by the finite rank SO/Sp gauge theories. With this classical superpotentials, we evaluate the confining phas

K. Magaard, T. Shaska, S. Shpectorov, H. Voelklein

Let G be a finite group, and $g \geq 2$. We study the locus of genus g curves that admit a G-action of given type, and inclusions between such loci. We use this to study the locus of genus g curves with prescribed automorphism group G. We completely classify these loci for g=3 (including equations for the corresponding curves), and for $g \leq 10$ we classif

Marek Czachor

A degree of violation of the Bell inequality depends on momenta of massive particles with respect to a laboratory if spin plays a role af a "yes--no" observable. For ultra-relativistic particles the standard Ekert test has to take into accont this velocity dependent suppression of the degree of violation of the inequality. Otherwise Alice and Bob may

Rachel Sibug-Aga, Brian B. Laird

Molecular dynamics simulations are performed to study the [100] and [111] orientations of the crystal-melt interface between an ordered two-component hard sphere with a NaCl structure and its coexisting binary hard-sphere fluid. The diameter ratio of the two types of hard spheres making up the mixture is taken to be 0.414. This work complements our earlier i

AAke Ingerman, Shirley Booth

Physicists and physics students have been studied with respect to the variation in ways they expound on their topic of research and a physics problem, respectively. A phenomenographic approach has been employed; six fourth-year physics students and ten teacher/researcher physicists at various stages of their careers have been interviewed. Four qualitatively

Prabasaj Paul, Francis C. Ndi

We present an algorithm for the maximization of photonic bandgaps in two-dimensional crystals. Once the translational symmetries of the underlying structure have been imposed, our algorithm finds a global maximal (and complete, if one exists) bandgap. Additionally, we prove two remarkable results related to maximal bandgaps: the so-called `maximum contrast&#

T. Belytschko, S. P. Xiao, R. Ruoff

The failure stresses and strains of nanotubes given by theoretical or numerical predictions are much higher than observed in experiments. We show that defects can explain part of this discrepancy: for an n-atom defect with 2<=n<=8, the range of failure stresses for a molecular mechanics calculation is found to be 36GPa to 64GPa. This compares quite well with

M. Koide, F. Koike, R. Wehlitz, M. -T. Huang

The photoion spectrum of atomic potassium was measured over the 3s -> np excitation region with the photoion time-of-flight method and monochromatized synchrotron radiation. An unusual spectrum with paired windows structure was found instead of a simple regular Rydberg series. Such subsidiary windows have not been observed in the 3s -> np resonances of Ar, w

Michel Bounias

Various Hamiltonian models have been derived for chemical structures belonging to living organisms while the Hamiltonian concept was not applied to life as a whole. However, Hamiltonian components were recently defined for living organisms on the condition to take in consideration their evolutionary implications (Bounias, 2001: CASYS&#39;0l). This paper iden

E. Garrido, D. V. Fedorov, A. S. Jensen

The 1$^-$ excitations of the three--body halo nucleus $^{11}$Li are investigated. We use adiabatic hyperspherical expansion and solve the Faddeev equations in coordinate space. The method of complex scaling is used to compute the resonance states. The Pauli forbidden states occupied by core neutrons are excluded by constructing corresponding complex scaled p

Ben-Hao Sa, Zhong-Qi Wang, Xu Cai, Dai-Mei Zhou

The $ϕ$ meson productions in $Au+Au$ and/or $Pb+Pb$ collisions at AGS, SPS, RHIC, and LHC energies have been studied systematically with a hadron and string cascade model LUCIAE. After considering the energy dependence of the model parameter $α$ in string fragmentation function and adjusting it to the experimental data of charged multiplicity to a certain ex

Takayuki Myo, Shigeyoshi Aoyama, Kiyoshi Kato, Kiyomi Ikeda

We discuss the binding mechanism of 11Li based on an extended three-body model of Li+n+n. In the model, we take into account the pairing correlation of p-shell neutrons in 9Li, in addition to that of valence neutrons outside the 9Li nucleus, and solve the coupled-channel two- and three-body problems of 10Li and 11Li, respectively. The results show that degre

Leo P. Kadanoff

Book Review for: &#34;A New Kind of Science&#34;, by Stephen Wolfram (Wolfram Media, Inc. Champaign IL 2002).

Stoil Donev, Maria Tashkova

This paper considers a generalization of the existing concept of parallel (with respect to a given connection) geometric objects and its possible usage as a suggesting rule in searching for adequate field equations in theoretical physics. The generalization tries to represent mathematically the two-sided nature of the physical objects, the {\it change} and t

Dave Witte, Robert J. Zimmer

Let G = SL(n,R) (or, more generally, let G be a connected, noncompact, simple Lie group). For any compact Lie group K, it is easy to find a compact manifold M, such that there is a volume-preserving, connection-preserving, ergodic action of G on some smooth, principal K-bundle P over M. Can M can be chosen independent of K? We show that if M = H/L is a homog

Christian Haase, Ilia Zharkov

We describe in purely combinatorial terms dual pairs of integral affine structures on spheres which come from the conjectural metric collapse of mirror families of Calabi-Yau toric hypersurfaces. The same structures arise on the base of a special Lagrangian torus fibration in the Strominger-Yau-Zaslow conjecture. We study the topological torus fibration in t

Markus Perling

We give a complete classification of equivariant vector bundles of rank two over smooth complete toric surfaces and construct moduli spaces of such bundles. This note is a direct continuation of an earlier note where we developed a general description of equivariant sheaves on toric varieties. Here we give a first application of that description.

S. Terzic

We obtain explicit formulas for the rational homotopy groups of generalised symmetric spaces, i.e., the homogeneous spaces for which the isotropy subgroup appears as the fixed point group of some finite order automorphism of the group. In particular, this gives explicit formulas for the rational homotopy groups of all classical compact symmetric spaces.

Steven Bradlow, Oscar Garcia-Prada, Vicente Muñoz, Peter Newstead

Let $C$ be a curve of genus $g\geq 2$. A coherent system on $C$ consists of a pair $(E,V)$ where $E$ is an algebraic vector bundle of rank $n$ and degree $d$ and $V$ is a subspace of dimension $k$ of sections of $E$. The stability of the coherent systems depend on a parameter $τ$. We study the variation of the moduli space of coherent systems when we move th

A. Chojnowska-Michalik, B. Goldys

We provide necessary and sufficient conditions for a Hilbert space-valued Ornstein-Uhlenbeck process to be reversible with respect to its invariant measure $μ$. For a reversible process the domain of its generator in $L^p(μ)$ is characterized in terms of appropriate Sobolev spaces thus extending the Meyer equivalence of norms to any symmetric Ornstein-Uhlenb

S. Ya. Jitomirskaya, I. V. Krasovsky

We study discrete Schroedinger operators $(H_{α,θ}ψ)(n)= ψ(n-1)+ψ(n+1)+f(αn+θ)ψ(n)$ on $l^2(Z)$, where $f(x)$ is a real analytic periodic function of period 1. We prove a general theorem relating the measure of the spectrum of $H_{α,θ}$ to the measures of the spectra of its canonical rational approximants under the condition that the Lyapunov exponents of $H

Yong-Geun Oh

In this paper we first apply the chain level Floer theory to the study of Hofer&#39;s geometry of Hamiltonian diffeomorphism group in the cases without quantum contribution: we prove that any quasi-autonomous Hamiltonian path on weakly exact symplectic manifolds or any autonomous Hamiltonian path on arbitrary symplectic manifolds is length minimizing in its

Steven Abel, Katherine Freese, Ian Kogan

We demonstrate an inflationary solution to the cosmological horizon problem during the Hagedorn regime in the early universe. Here the observable universe is confined to three spatial dimensions (a three-brane) embedded in higher dimensions. The only ingredients required are open strings on D-branes at temperatures close to the string scale. No potential is

Renata Kallosh

We discuss some recent attempts to reconcile cosmology with supergravity and M/string theory. First of all, we point out that in extended supergravities the scalar masses are quantized in terms of the cosmological constant in de Sitter vacua: the eigenvalues of the Casimir operator 3 m^2/Λtake integer values. For the current value of the cosmological constan

L. Stodolsky

Under certain conditions the number of photons radiated classically by a charged particle following a prescribed trajectory can be finite. An interesting formula for this number is presented and discussed.

C. D. Fosco

We study the Euclidean effective action and the full fermion propagator for a Dirac field in the presence of a scalar field with a domain wall defect, in 2+1 dimensions. We include quantum effects due to both fermion and scalar field fluctuations, in a one-loop approximation. The results are interpreted in terms of the quantum stability of the zero mode solu

Paul K. Townsend

The origins of the 11-dimensional supermembrane are recalled, and a curious property is discussed: the field theory limit of a supermembrane in a hyper-Kähler background is a 3-dimensional sigma-model with N=4 supersymmetry, but the higher-order fermion interactions of the supermembrane generically break this to N=3.

D. Bazeia, W. Freire, L. Losano, R. F. Ribeiro

We deal with the presence of topological defects in models for two real scalar fields. We comment on defects hosting topological defects, and we search for explicit defect solutions using the trial orbit method. As we know, under certain circumstances the second order equations of motion can be solved by first order differential equations. In this case we sh

Kurt Langfeld, Laurent Moyaerts, Holger Gies

The quantum action generated by fermions which are minimally coupled to abelian vortex background fields is studied in D=2+1 and D=3+1 Euclidean dimensions. We present a detailed analysis of single- and binary-vortex configurations using the recently developed method of worldline numerics. The dependence of the fermion-induced quantum action on the fermion m

M. Caicedo, M Lledo, A. Restuccia, J. Stephany

The effective action for the Brink-Schwarz Superparticle is constructed in an infinite dimensional phase space using a gauge invariant formulation.

A. I. Shoshi, F. D. Steffen, H. J. Pirner

The impact parameter dependent gluon distribution of the proton xG(x,Q^2,b) is investigated in a loop-loop correlation model that respects the S-matrix unitarity condition in impact parameter space. We find low-x saturation of G(x,Q^2,b) as a manifestation of S-matrix unitarity. The integrated gluon distribution xG(x,Q^2) does not saturate because of the gro

Edmond L. Berger, Cheng-Wei Chiang, Jing Jiang, Tim M. P. Tait

The remarkable agreement of electroweak data with standard model (SM) predictions motivates the study of extensions of the SM in which the Higgs boson is light and couples in a standard way to the weak gauge bosons. Postulated new light particles should have small couplings to the gauge bosons. Within this context it is natural to assume that the branching f

Jean-Philippe Uzan

This article describes the various experimental bounds on the variation of the fundamental constants of nature. After a discussion on the role of fundamental constants, of their definition and link with metrology, the various constraints on the variation of the fine structure constant, the gravitational, weak and strong interactions couplings and the electro

D. S. Gorbunov

I describe supersymmetric extensions of the Standard Model with light sgoldstinos and discuss the explanation of Ultra High Energy Cosmic Rays above GZK cutoff in these models. Also I briefly discuss the possibility to solve other cosmological and astrophysical puzzles, such as gamma-ray bursts and dimming of high-redshift supernovae, within the models with

F. Bezrukov, D. Gorbunov

The transverse lepton polarization asymmetry in pi_e2gamma decay may probe T-violating interactions beyond the Standard Model. Dalitz plot distributions of the expected effects are presented and compared to the contribution from the Standard Model final state interactions. We give an example of a phenomenologically viable model, where a considerable contribu

R. J. Rivers, F. C. Lombardo, F. D. Mazzitelli

Classical defects (monopoles, vortices, etc.) are a characteristic consequence of many phase transitions of quantum fields. We show a model in which the onset of classical probability distributions, for the long-wavelength modes at early times, allows the identification of line-zeroes of the field with vortex separation. We obtain a refined version of Kibble

John Ellis, D. V. Nanopoulos, J. Walker

Minimal supersymmetric SU(5) GUTs are being squeezed by the recent values of alpha_s, sin^2 theta_W, the lower limit on the lifetime for p to nubar K decay, and other experimental data. We show how the minimal flipped SU(5) GUT survives these perils, accommodating the experimental values of alpha_s and sin^2 theta_W and other constraints, while yielding a p

V. I. Yukalov, E. P. Yukalova

An overview is given of different approaches to describing the process of deconfinement in quantum chromodynamics. The analysis of the known approaches demonstrates that the detailed picture of how deconfinement really occurs has not yet been understood. Therefore, one has to be rather cautious when interpreting experimental signals as attributed to deconfin

M. Boonekamp, A. De Roeck, R. Peschanski, C. Royon

We study Higgs boson production via Double Pomeron Exchange allowing for the presence of Pomeron remnants. We estimate the number of events produced at the LHC collider, as a function of the Higgs boson mass and its decay channel. The model which successfully describes the high mass dijet spectrum observed at Tevatron (run I) is used to predict rates of even

R. Vogt

We describe updated calculations of $Q \bar Q$ production in $pp$ and $π^- p$ interactions. We compare these results to total cross section data and discuss how the baseline cross sections extrapolate to heavy ion collider energies. We touch upon the differences between leading and next-to-leading order heavy quark production. Finally, we discuss the implica

W. Buchmüller

Data on solar and atmospheric neutrinos provide evidence for neutrino masses and mixings. We review some basic neutrino properties, the status of neutrino oscillations and implications for grand unified theories, including leptogenesis.

Guy Wilkinson

Results on LEP 2 e+e-->ffbar and gamma gamma (gamma) production are presented. These are compared with Standard Model predictions, and then used to set limits on various New Physics models, including Low Scale Gravity. Finally the status of the LEP beam energy determination from radiative return events is summarised.

The BABAR Collaboration, B. Aubert

We report evidence for the $b\to u$ transition $B^0 \to D_s^{+}π^-$ and the results of a search for $B^0 \to D_s^{*+} π^-$ from a sample of $61.6\times 10^6$ $Y(4S)$ decays into $B$ meson pairs collected with the BaBar detector at the PEP II asymmetric $e^{+}e^{-}$ collider. The observed $B^0 \to D_s^{+} π^-$ yield has a probability of $4.4 \times 10^{-4}$ t

Davide Boscherini

Signals of physics beyond the Standard Model at HERA have been searched for by the H1 and ZEUS collaborations. Results are reported about searches of contact interaction effects, leptoquarks, R-parity violating squarks, excited fermions and single top production. The analyses used the data set collected during the HERA phase I, consisting in about 110 (15) p

Belle Collaboration, K. Abe

The production of the χ_{c2} charmonium state in two-photon collisions has been measured with the Belle detector at the KEKB e^+e^- collider. A clear signal for χ_{c2} --> γJ/ψ, J/ψ--> l^+l^- is observed in a 32.6fb^{-1} data sample accumulated at center-of-mass energies near 10.6GeV, and the product of its two-photon decay width and branching fraction is de

Fermilab E791 Collaboration

We report differential cross sections for the production of D*(2010) produced in 500 GeV/c pi^- nucleon interactions from experiment E791 at Fermilab, as functions of Feynman-x (x_F) and transverse momentum squared (p_T^2). We also report the D* +/- charge asymmetry and spin-density matrix elements as functions of these variables. Investigation of the spin-d

M. Mehrafarin

Regarding metric fluctuations as generating {\it roughness} on the fabric of the otherwise smooth vacuum, it is shown that in its simplest form, the effect can be described by the scalar $ϕ^4$ model. The model exhibits a second order phase transition between a smooth (low-temperature) phase and a rough (high-temperature) one, corroborating the absence of met

P. Salgado, M. Cataldo, S. del Campo

It is shown that the Stelle-West Grignani-Nardelli-formalism allows, both when odd dimensions and when even dimensions are considered, constructing actions for higher dimensional gravity invariant under local Lorentz rotations and under local Poincarè translations. It is also proved that such actions have the same coefficients as those obtained by Troncoso a

K. A. Bronnikov, S. Grinyok

Static, spherically symmetric, traversable wormhole solutions with electric or magnetic charges are shown to exist in general relativity in the presence of scalar fields nonminimally coupled to gravity. These wormholes, however, turn out to be unstable under spherically symmetric perturbations. The instability is related to blowing-up of the effective gravit

T. Prokopec, O. Tornkvist, R. P. Woodard

We compute the one loop vacuum polarization from massless, minimally coupled scalar QED in a locally de Sitter background. Gauge invariance is maintained through the use of dimensional regularization, whereas conformal invariance is explicitly broken by the scalar kinetic term as well as through the conformal anomaly. A fully renormalized result is obtained.

J. Makela, A. Peltola

We show, by using Regge calculus, that the entropy of any finite part of a Rindler horizon is, in the semi-classical limit, one quarter of the area of that part. We argue that this result implies that the entropy associated with any horizon of spacetime is, in semi-classical limit, one quarter of its area. As an example, we derive the Bekenstein-Hawking entr

Slava G. Turyshev, B-G Andersson

We have studied the science rationale, goals and requirements for a mission aimed at using the gravitational lensing from the Sun as a way of achieving high angular resolution and high signal amplification. We find that such a mission concept is plagued by several practical problems. Most severe are the effects due to the plasma in the solar atmosphere which

Larry Wos

The likelihood of an automated reasoning program being of substantial assistance for a wide spectrum of applications rests with the nature of the options and parameters it offers on which to base needed strategies and methodologies. This article focuses on such a spectrum, featuring W. McCune&#39;s program OTTER, discussing widely varied successes in answeri

Samir Khuller, Balaji Raghavachari, Neal E. Young

The traditional multi-commodity flow problem assumes a given flow network in which multiple commodities are to be maximally routed in response to given demands. This paper considers the multi-commodity flow network-design problem: given a set of multi-commodity flow demands, find a network subject to certain constraints such that the commodities can be maxim

K. M. Rabe

A first-principles method, based on density functional perturbation theory, is presented for computing the leading order tunability of high-dielectric-constant materials.

Coen de Graaf, Iberio de P. R. Moreira, Francesc Illas, Oscar Iglesias

The magnetic structure of the edge sharing cuprate compound Li2CuO2 has been investigated by means of ab initio electronic structure calculations. The first and second neighbor in-chain magnetic interactions are calculated to be -142 K and 22 K, respectively. The ratio between the two parameters is smaller than suggested previously in the literature. The int

Eduardo Fradkin, Vishnu Jejjala, Robert G. Leigh

The quantum Hall system is known to have two mutually dual Chern-Simons descriptions, one associated with the hydrodynamics of the electron fluid, and another associated with the statistics. Recently, Susskind has made the claim that the hydrodynamic Chern-Simons theory should be considered to have a non-commutative gauge symmetry. The statistical Chern-Simo

Oscar Iglesias, Amilcar Labarta

We study the effect of a magnetic field on the thermal relaxation of non-interacting small monodomain particle systems particles with a distribution of anisotropy constants and random easy-axes directions. Numerical calculations of the relaxation curves for different distribution widths, and under different magnetic fields $H$ and temperatures $T$, have been

L. Pal

By introducing the notions of living and dead nodes a new model of random tree evolution with continuous time parameter has been constructed. It is assumed that two random variables, the lifetime and the offspring number of living nodes control the evolution process. It has been shown that the generating function of the probability to find the evolving tree

Vito Latora, Massimo Marchiori

A short review of the recent results and models of complex networks.

Luis Lafuente, Jose A. Cuesta

We present the extension of Rosenfeld&#39;s fundamental measure theory to lattice models by constructing a density functional for d-dimensional mixtures of parallel hard hypercubes on a simple hypercubic lattice. The one-dimensional case is exactly solvable and two cases must be distinguished: all the species with the same lebgth parity (additive mixture), a

Pierpaolo Bruscolini, Alessandro Pelizzola

A transfer-matrix formalism is introduced to evaluate exactly the partition function of the Munoz-Eaton model, relating the folding kinetics of proteins of known structure to their thermodynamics and topology. This technique can be used for a generic protein, for any choice of the energy and entropy parameters, and in principle allows the model to be used as

Yuriy A. Romanov, Julia Yu. Romanova, Lev G. Mourokh, Norman J. M. Horing

The phenomenon of transparency in two-dimensional and three-dimensional superlattices is analyzed on the basis of the Boltzmann equation with a collision term encompassing three distinct scattering mechanisms (elastic, inelastic and electron-electron) in terms of three corresponding distinct relaxation times. On this basis, we show that electron heating in t

Tiziano Zito, Christian Seidel

Monte Carlo simulations are used to study the non-uniform equilibrium charge distribution along a single annealed polyelectrolyte chain under theta-solvent conditions and with added salt. Within a range of the order of the Debye length charge accumulates at chain ends while a slight charge depletion appears in the central part of the chain. The simulation re

Ondrej Sipr

Interpretation of x-ray absorption near-edge structure (XANES) experiments is often done via analyzing the role of particular atoms in the formation of specific peaks in the calculated spectrum. Typically, this is achieved by calculating the spectrum for a series of trial structures where various atoms are moved and/or removed. A more quantitative approach i

Shobhana Narasimhan, Raghani Pushpa

We have studied the reconstruction of Pt(111) theoretically using a two-dimensional Frenkel-Kontorova model for which all parameters have been obtained from ab initio calculations. We find that the unreconstructed surface lies right at the stability boundary, and thus it is relatively easy to induce the surface to reconstruct into a pattern of FCC and HCP do

Sauro Succi, Iliya V. Karlin, Hudong Chen

In the last decade, minimal kinetic models, and primarily the Lattice Boltmann equation, have met with significant success in the simulation of complex hydrodynamic phenomena, ranging from slow flows in grossly irregular geometries to fully developed turbulence, to flows with dynamic phase transitions. Besides their practical value as efficient computational

Y. Malevergne, D. Sornette

Based on a recent theorem due to the authors, it is shown how the extreme tail dependence between an asset and a factor or index or between two assets can be easily calibrated. Portfolios constructed with stocks with minimal tail dependence with the market exhibit a remarkable degree of decorrelation with the market at no cost in terms of performance measure

Karen M. Leighly, Andrzej A. Zdziarski, Toshihiro Kawaguchi, Chiho Matsumoto

We present preliminary results from a long Chandra HETG observation of the luminous Narrow-line Seyfert 1 galaxy 1H 0707-495. We find a complex X-ray spectrum comprised of a two-component continuum with superimposed emission and absorption lines. The short time scale X-ray variability is different than observed in other AGN: the soft X-rays vary markedly les

B. Goldman, C. Afonso, Ch. Alard, J. -N. Albert

We are conducting a 377-square-degree proper motion survey in the ~V and I bands in order to determine the cool white dwarf contribution to the Galactic dark matter. Using the 250 square degrees for which we possess three epochs, and applying selection criteria designed to isolate halo-type objects, we find no candidates in a 5500 pc^3 effective volume for o

N. Bissantz, A. Munk

A common problem in physics is to fit regression data by a parametric class of functions, and to decide whether a certain functional form allows for a good fit of the data. Common goodness of fit methods are based on the calculation of the distribution of certain statistical quantities under the assumption that the model under consideration {\it holds true}.

A. B. Kukushkin, V. A. Rantsev-Kartinov

The presence of skeletal structures of the same distinctive topology (cartwheels, tubules, etc.), in the range 10^{-5} - 10^23 cm, and a trend toward self-similarity of these structures are found. These evidences come from the electron micrography of dust deposits in tokamak (10^{-6} - 10^{-3}cm), the images of plasma taken in laboratory electric discharges

G. Handler, E. Romero-Colmenero, M. H. Montgomery

We present the analysis of one week of single-site high-speed CCD photometric observations of the cool ZZ Ceti star HS 0507+0434B. Ten independent frequencies are detected in the star&#39;s light variations: one singlet and three nearly-equally spaced triplets. We argue that these triplets are due to rotationally split modes of spherical degree l=1. This is

Feng Yuan, Sera Markoff, Heino Falcke, Peter L. Biermann

Low-luminosity AGNs (LLAGNs) are a very important class of sources since they occupy a significant fraction of local galaxies. Their spectra differ significantly from the canonical luminous AGNs, most notably by the absence of the ``big blue bump&#39;&#39;. In the present paper, taking a typical LLAGN--NGC4258--as an example, we investigate the origin of the

Annette Ferguson, Mike Irwin, Rodrigo Ibata, Geraint Lewis

We report the discovery of significant stellar substructure in the halo and outer disk of our nearest large galactic neighbour, M31. Our deep panoramic survey with the Isaac Newton Telescope Wide Field Camera currently maps out an area of ~25 square degrees around M31, extending along the semi-major axis to 55 kpc, and is the first to allow an uninterrupted

A. Franceschini, V. Braito, D. Fadda

We critically review the basic assumptions of the standard model for the synthesis of the XRB in the light of new data from ultradeep surveys by Chandra and XMM, resolving major parts of it. Important constraints come in particular from the observed z-distributions of faint hard X-ray sources -- showing large excesses at redshifts (z~0.8) much lower than exp

Yakiv V. Pavlenko, T. R. Geballe

Theoretical spectral energy distributions computed for a grid of hydrogen-deficient and carbon-rich model atmospheres have been compared with the observed infrared (1--2.5 $μ$m) spectra of V4334 Sgr (Sakurai&#39;s Object) on 1997 April 21 and July 13. The comparison yields an effective temperature of \Tef = 5500 $\pm$ 200 K for the April date and \Tef = 5250

Marek Sikora, Michal Blazejowski, Rafal Moderski, Greg Madejski

Broad-band spectra of the FSRQ (flat-spectrum-radio quasars) detected in the high energy gamma-ray band imply that there may be two types of such objects: those with steep gamma-ray spectra, hereafter called MeV-blazars, and those with flat gamma-ray spectra, GeV-blazars. We demonstrate that this difference can be explained in the context of the ERC (externa

Takashi Nakamura

If there exists the quark star of maximum mass $\sim 0.7\sol$ as suggested by recent Chandra observations, we show that the general relativistic collapse of a neutron star of mass greater than the maximum mass of the neutron star with angular momentum parameter $q\equiv cJ/GM^2 > 1$ may lead to such a strange star. Here $J$ and $M$ are the angular momentum a

T. Kato, K. Haseda, H. Yamaoka, K. Takamizawa

We discovered that the Wolf-Rayet (WR)+OB star binary, WR 104, renowned for its associated &#34;dusty pinwheel nebula&#34; recently spatially resolved with infrared interferometry, exhibits strong quasi-periodic optical variations with a full amplitude of 2.7 mag. Such a large-amplitude, continuous variation has been unprecedented in a WR star. The optical q