December 2003 arXiv papers — page 10

Tohru Eguchi, Hiroaki Kanno

We consider the geometric transition and compute the all-genus topological string amplitudes expressed in terms of Hopf link invariants and topological vertices of Chern-Simons gauge theory. We introduce an operator technique of 2-dimensional CFT which greatly simplifies the computations. We in particular show that in the case of local Calabi-Yau manifolds d

Maarten Boonekamp, Tibor Kucs

We extend the POMWIG Monte Carlo generator developed by B.Cox and J.Forshaw, to include new models of central production through inclusive and exclusive Double Pomeron Exchange in proton-proton collisions. Double photon Exchange processes are described as well, both in proton-proton and heavy-ion collisions. In all contexts, various models have been implemen

L. M. Castellanos, F. E. Lopez

A theoretical description in terms of the coherence propagation is given for self-focussing. The concept of coherence length is defined in terms of free, self-focussing propagation giving results in accordance with well known experimental criteria for the laser. Extension of the method is given for an Atom Laser showing good results in agreement with recents

E. Bagan, M. Baig, A. Monras, R. Munoz-Tapia

We analyse the reconstruction of an unknown pure qubit state. We derive the optimal guess that can be inferred from any set of measurements on N identical copies of the system with the fidelity as a figure of merit. We study in detail the estimation process with individual von Neumann measurements and demonstrate that they are very competitive as compared to

Markus Grassl, Thomas Beth, Martin Roetteler

We present families of quantum error-correcting codes which are optimal in the sense that the minimum distance is maximal. These maximum distance separable (MDS) codes are defined over q-dimensional quantum systems, where q is an arbitrary prime power. It is shown that codes with parameters [[n,n-2d+2,d]]_q exist for all 3 <= n <= q and 1 <= d <= n/2+1. We a

Jose M. Cervero, Alberto Rodriguez

A real band condition is shown to exist for one dimensional periodic complex non-hermitian potentials exhibiting PT-symmetry. We use an exactly solvable ultralocal periodic potential to obtain the band structure and discuss some spectral features of the model, specially those concerning the role of the imaginary parameters of the couplings. Analytical result

F. Schmidt-Kaler, H. Häffner, M. Riebe, G. P. T. Lancaster

We report the realization of an elementary quantum processor based on a linear crystal of trapped ions. Each ion serves as a quantum bit (qubit) to store the quantum information in long lived electronic states. We present the realization of single-qubit and of universal two-qubit logic gates. The qwo-qubit operation relies on the coupling of the ions through

Ricard V. Sole, Pau Fernandez

Background: Recent models of genome-proteome evolution have shown that some of the key traits displayed by the global structure of cellular networks might be a natural result of a duplication-diversification (DD) process. One of the consequences of such evolution is the emergence of a small world architecture together with a scale-free distribution of intera

Michael Small, Pengliang Shi, Chi Kong Tse

Using daily infection data for Hong Kong we explore the validity of a variety of models of disease propagation when applied to the SARS epidemic. Surrogate data methods show that simple random models are insufficient and that the standard epidemic susceptible-infected-removed model does not fully account for the underlying variability in the observed data. A

John D. Perreault, Alexander D. Cronin, T. A. Savas

In atom optics a material structure is commonly regarded as an amplitude mask for atom waves. However, atomic diffraction patterns formed using material gratings indicate that material structures also operate as phase masks. In this study a well collimated beam of sodium atoms is used to illuminate a silicon nitride grating with a period of 100 nm. During pa

J. M. Donoso, A. Fernandez-Ranada, J. L. Trueba

It has been long admitted that a consequence of the virial theorem is that there can be no equilibrium configurations of a system of charges in electromagnetic interaction in the absence of external forces. However, recent results have shown that the virial theorem can not preclude the existence of certain nontrivial equilibrium configurations. Although some

Christian C. Fleck, Roland R. Netz

We investigate numerically and on the scaling level the adsorption of a charged colloid on an oppositely charged flexible membrane. We show that the long ranged character of the electrostatic interaction leads to a wrapping reentrance of the complex as the salt concentration is varied. The membrane wrapping depends on the size of the colloid and on the salt

M. R. Tarbutt, H. L. Bethlem, J. J. Hudson, V. L. Ryabov

Cold supersonic beams of molecules can be slowed down using a switched sequence of electrostatic field gradients. The energy to be removed is proportional to the mass of the molecules. Here we report deceleration of YbF, which is 7 times heavier than any molecule previously decelerated. We use an alternating gradient structure to decelerate and focus the mol

Z. Batiz, M. T. Pena, A. Stadler

We studied meson-meson interactions using the &#39;t Hooft model, which represents QCD in 1+1 dimensions and assumes a large number of colors ($N_c$). The dominant interactions in this large $N_c$ limit are generated by quark exchange. Our results show that QCD in 1+1 dimensions allows the realization of a constituent-type quark model for the mesons, and gen

Takashi Nakatsukasa, Kazuhiro Yabana

The time-dependent Hartree-Fock calculation with a full Skyrme energy functional has been carried out on the three-dimensional Cartesian lattice space to study E1 giant dipole resonances (GDR) in light nuclei. The outgoing boundary condition for the continuum states is treated by the absorbing complex potential. The calculation for GDR in O-16 suggests a sig

Takashi Nakatsukasa, Manabu Ueda, Kazuhiro Yabana

We study E1 resonances, breakup and fusion reactions for weakly bound Be nuclei. The absorbing-boundary condition (ABC) is used to describe both the outgoing and incoming boundary conditions. The neutron continuum plays important roles in response and reaction of neutron drip-line nuclei.

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

The Borromean nucleus $^{17}$Ne ($^{15}$O$ + p + p$) is investigated by using the hyperspheric adiabatic expansion for a a three-body system. The measured size of $^{15}$O and the low-lying resonances of $^{16}$F ($^{15}$O$ + p$) are first used as constraints to determine both central and spin-dependent two-body interactions. Then, the ground state structure

Darryl D. Holm, Jerrold E. Marsden

We study the dynamics of measure-valued solutions of what we call the EPDiff equations, standing for the {\it Euler-Poincaré equations associated with the diffeomorphism group (of $\mathbb{R}^n$ or an $n$-dimensional manifold $M$)}. Our main focus will be on the case of quadratic Lagrangians; that is, on geodesic motion on the diffeomorphism group with respe

Olivier Giraud, Andy Thain, John H. Hannay

The shrunk loop theorem presented here is an integral identity which facilitates the calculation of the relative probability (or probability amplitude) of any given topology that a free, closed Brownian or Feynman path of a given &#39;duration&#39; might have on the twice punctured plane (the plane with two marked points). The result is expressed as a scatte

Olivier Giraud

Isospectral domains are non-isometric regions of space for which the spectra of the Laplace-Beltrami operator coincide. In the two-dimensional Euclidean space, instances of such domains have been given. It has been proved for these examples that the length spectrum, that is the set of the lengths of all periodic trajectories, coincides as well. However there

Vasily E. Tarasov

In this paper fractional generalization of Liouville equation is considered. We derive fractional analog of normalization condition for distribution function. Fractional generalization of the Liouvile equation for dissipative and Hamiltonian systems was derived from the fractional normalization condition. This condition is considered considered as a normaliz

L. Martinez Alonso, A. B. Shabat

The diagonal hydrodynamic reductions of a hierarchy of integrable hydrodynamic chains are explicitly characterized. Their compatibility with previously introduced reductions of differential type is analyzed and their associated class of hodograph solutions is discussed.

Massimo Conti, Azi Lipshtat, Baruch Meerson

We analyze a recent experiment of Sharon \textit{et al.} (2003) on the coarsening, due to surface tension, of fractal viscous fingering patterns (FVFPs) grown in a radial Hele-Shaw cell. We argue that an unforced Hele-Shaw model, a natural model for that experiment, belongs to the same universality class as model B of phase ordering. Two series of numerical

Taisei Kaizoji

The aim of this paper is to propose a heterogeneous agent model of stock markets that develop complicated endogenous price fluctuations. We find occurrences of non-stationary chaos, or speculative bubble, are caused by the heterogeneity of traders&#39; strategies. Furthermore, we show that the distributions of returns generated from the heterogeneous agent m

J. A. Vallejo

It is proved that given a divergence operator on the structural sheaf of graded commutative algebras of a supermanifold, it is possible to construct a generating operator for the Krashil&#39;shchik-Schouten bracket. This is a particular case of the construction of generating operators for a special class of bigraded Gerstenhaber algebras. Also, some comments

Mark Naber

The Riemann-Liouville formula for fractional derivatives and integrals (differintegration) is used to derive formulae for matrix order derivatives and integrals. That is, the parameter for integration and differentiation is allowed to assume matrix values. It is found that the computation of derivatives and integrals to matrix order is well defined for any s

Sergio Albeverio, Saidakhmat N. Lakaev, Zakhriddin I. Muminov

A system of three quantum particles on the three-dimensional lattice $\Z^3$ with arbitrary &#34;dispersion functions&#34; having non-compact support and interacting via short-range pair potentials is considered. The energy operators of the systems of the two-and three-particles on the lattice $\Z^3$ in the coordinate and momentum representations are describe

Eric Mourre

This article introduces a method, which starting from simple and quite general mathematical data, allows to construct linear algebras of operators which are, each of them, endowed with a bialgebra structure (coproduct and counity). Moreover under some explicit and natural conditions on theses mathematical data we obtain linear algebras of operators with the

S. Yu. Vernov

The generalized Henon-Heiles system has been considered. In two nonintegrable cases with the help of the Painleve test new special solutions have been found as Laurent series, depending on three parameters. The obtained series converge in some ring. One of parameters determines the singularity point location, other parameters determine coefficients of series

M. Bakonyi, T. Constantinescu

Motivated by the remarkable interplay between (chordal) graphs and matrix algebra, we associate to each graph a so-called completion number that might encode some aspects of that interplay. We show that this number is not trivial, and we ask for a graph theoretic characterization of those graphs with a given completion number.

T. Banks, T. Constantinescu, J. L. Johnson

This semi-expository paper surveys results concerning three classes of orthogonal polynomials: in one non-hermitian variable, in several isometric non-commuting variables, and in several hermitian non-commuting variables. The emphasis is on some dilation theoretic techniques that are also described in some details.

Peter Bubenik

Let $Y$ be the space obtained by attaching a finite-type wedge of cells to a simply-connected, finite-type CW-complex. We introduce the free and semi-inert conditions on the attaching map which broadly generalize the previously studied inert condition. Under these conditions we determine $H_*(ΩY;R)$ as an $R$-module and as an $R$-algebra respectively. Under

Howard Masur, Saul Schleimer

The authors prove that for a closed surface of genus at least 3, the graph of pants decompositions has only one end.

David Joyner, Amy Ksir

If G is a finite subgroup of the automorphism group of a projective curve X and D is a divisor on X stabilized by G, then under the assumption that D is nonspecial, we compute a simplified formula for the trace of the natural representation of G on Riemann-Roch space L(D).

Gunther Cornelissen, Thanases Pheidas, Karim Zahidi

We prove that Hilbert&#39;s Tenth Problem for a ring of integers in a number field K has a negative answer if K satisfies two arithmetical conditions (existence of a so-called division-ample set of integers and of an elliptic curve of rank one over K). We relate division-ample sets to arithmetic of abelian varieties.

Jean-Marc Bouclet

We define scattering phases associated to pairs of Laplacians on asymptotically hyperbolic manifolds, and prove some spectral asymptotics for them. These result are applications of Isozaki-Kitada&#39;s constructions which we adapt to this framework.

Alberto S. Cattaneo, Benoit Dherin, Giovanni Felder

The multiplicative structure of the trivial symplectic groupoid over $\mathbb R^d$ associated to the zero Poisson structure can be expressed in terms of a generating function. We address the problem of deforming such a generating function in the direction of a non-trivial Poisson structure so that the multiplication remains associative. We prove that such a

P P Martin

We show that a certain tensor space representation of the blob algebra (an affine Hecke algebra quotient) is faithful.

Krešimir Veselić

We present a new and simple bound for the exponential decay of second order systems using the spectral shift. This result is applied to finite matrices as well as to partial differential equations of Mathematical Physics. The type of the generated semigroup is shown to be bounded by the upper real part of the numerical range of the underlying quadratic opera

Evans M. Harrell

Commutator relations are used to investigate the spectra of Schrödinger Hamiltonians, $H = -Δ+ V({x}),$ acting on functions of a smooth, compact $d$-dimensional manifold $M$ immersed in $\bbr^ν, ν\geq d+1$. Here $Δ$ denotes the Laplace-Beltrami operator, and the real-valued potential--energy function $V(x)$ acts by multiplication. The manifold $M$ may be com

Wang Gong-bao, Ma Ji-pu

A complete characterization of near subnormality for bilateral weighted shifts is obtained. As an application of the main results, many new answers to the Hilbert space problem 160 are presented at the end of the paper.

Karin Baur, Jan Draisma

We try to write (generic) elements of classical simple Lie algebras as sums of as few elements of the orbit C of long root vectors as possible. If the Lie algebra in question is sl_n or sp_n, then C consists of all rank 1 matrices in the Lie algebra, and an element of rank k is the sum of k elements of C. If, on the other hand, the Lie algebra is o_n, then C

Sorin Popa, Roman Sasyk

We prove that if $G$ is a countable, discrete group having infinite, normal subgroups with the relative property (T), then the Bernoulli shift action of $G$ on ${\underset g \in G \to Π} (X_0, μ_0)_g$ for $(X_{0},μ_{0})$ an arbitrary probability space, has first cohomology group isomorphic to the character group of $G$.

Misja Nuyens

In this paper we study the maximum queue length $M$ (in terms of the number of customers present) in a busy cycle in the M/G/1 queue. Assume that the service times have a logconvex density. For such (heavy-tailed) service-time distributions the Foreground Background service discipline is optimal. This discipline gives service to the customer(s) that have rec

Sorin Popa

We prove that a type II$_1$ factor $M$ can have at most one Cartan subalgebra $A$ satisfying a combination of rigidity and compact approximation properties. We use this result to show that within the class $\Cal H \Cal T$ of factors $M$ having such Cartan subalgebras $A \subset M$, the Betti numbers of the standard equivalence relation associated with $A \su

John B. Etnyre, Lenhard L. Ng, Joshua M. Sabloff

We provide a translation between Chekanov&#39;s combinatorial theory for invariants of Legendrian knots in the standard contact R^3 and a relative version of Eliashberg and Hofer&#39;s Contact Homology. We use this translation to transport the idea of ``coherent orientations&#39;&#39; from the Contact Homology world to Chekanov&#39;s combinatorial setting. A

A. Kleinschmidt, P. West

We consider the decomposition of the adjoint and fundamental representations of very extended Kac-Moody algebras G+++ with respect to their regular A type subalgebra which, in the corresponding non-linear realisation, is associated with gravity. We find that for many very extended algebras almost all the A type representations that occur in the decomposition

Debashis Ghoshal, Dileep P. Jatkar, Maximilian Kreuzer

We argue that a semi-infinite D6-brane ending on an NS5-brane can be obtained from the condensation of the tachyon on the unstable D9-brane of type IIA theory. The construction uses a combination of the descriptions of these branes as solitons of the worldvolume theory of the D9-brane. The NS5-brane, in particular, involves a gauge bundle which is operator v

M. A. Vasiliev, V. N. Zaikin

Explicit form of two-point and three-point Sp(2M) invariant Green functions is found.

M. El Baz, A. El Hassouni, Y. Hassouni, E. H. Zakkari

We construct an associative differential algebra on a two-parameter quantum plane associated with a nilpotent endomorphism $d$ in the two cases $d^{2}=0$ and $d^3=0$ $(d^2\neq 0).$ The correspondent curvature is derived and the related non commutative gauge field theory is introduced.

Xi Yin

Instanton matrix models (IMM) for two dimensional string theories are obtained from the matrix quantum mechanics (MQM) of the T-dual theory. In this paper we study the connection between the IMM and MQM, which amounts to understand T-duality from the viewpoint of matrix models. We show that type 0A and type 0B matrix models perturbed by purely closed string

Takashi Tamaki, Sugumi Kanno, Jiro Soda

Non-uniform black strings in the two-brane system are investigated using the effective action approach. It is shown that the radion acts as a non-trivial hair of black strings. The stability of solutions is demonstrated using the catastrophe theory. The black strings are shown to be non-uniform.

Irina Dymnikova

In the spherically symmetric case the requirements of regularity of density and pressures and finiteness of the ADM mass $m$, together with the weak energy condition, define the family of asymptotically flat globally regular solutions to the Einstein minimally coupled equations which includes the class of metrics asymptotically de Sitter as $r\to 0$. A sourc

Alexander A. Chernitskii

A general model of nonlinear electrodynamics with dyon singularities is considered. We consider the field configuration having two dyon singularities with identical electric and opposite magnetic charges and we name it bidyon. We investigate the sum of two dyon solutions as an initial approximation to the bidyon solution. We consider the case when the veloci

A. B. Balantekin, H. Yuksel

We discuss the physics potential of the solar neutrino experiments i) To explore the parameter space of neutrino mass and mixings; ii) To probe the physics of the Sun; iii) To explore nuclear physics of the neutrino-target interactions. Examples are given for these three classes.

L. B. Okun, M. V. Rotaev, M. G. Schepkin, I. S. Tsukerman

Manipulation with ill-defined notions creates an illusion of a simple derivation of the standard phase of neutrino oscillations in hep-ph/0311241 and hep-ph/0312180.

Otto Nachtmann

We review some theoretical ideas concerning diffractive processes. We discuss the Regge Ansatz for the pomeron and the two pomeron model. Then we present the results obtained from nonperturbative QCD for high energy scattering. There we can extract from elastic scattering data the parameters describing the QCD vacuum, in particular the string tension.

Marcus Bleicher, Horst Stöcker

Yields, rapidity and transverse momentum spectra of $Δ^{++}(1232)$, $Λ(1520)$, $Σ^\pm(1385)$ and the meson resonances $K^0(892)$, $Φ$, $ρ^0$ and $f_0(980)$ are predicted. Hadronic rescattering leads to a suppression of reconstructable resonances, especially at low $p_\perp$. A mass shift of the $ρ$ of 10 MeV is obtained from the microscopic simulation, due t

A. Gokalp, O. Yilmaz

We investigate the $a_0K^+K^-$-vertex in the framework of light cone QCD sum rules. We estimate the coupling constant g$_{a_0K^+K^-}$ which is an essential ingredient in the analysis of physical processes involving $a_0(980)$ meson. Our result is somewhat larger than the previous determinations of this coupling constant.

Stephen Mrenna, Peter Richardson

We report on our exploration of matching matrix element calculations with the parton-shower models contained in the event generators HERWIG and Pythia. We describe results for e+e- collisions and for the hadroproduction of W bosons and Drell--Yan pairs. We compare methods based on (1) a strict implementation of ideas proposed by Catani, et al., (2) a general

Marina Artuso

The Cabibbo-Kobayashi-Maskawa parameter $|V_{cb}|$ plays an important role among the experimental constraints of the Yukawa sector of the Standard Model. The present status of our knowledge will be summarized with particular emphasis to the interplay between theoretical and experimental advances needed to improve upon present uncertainties.

Joel Giedt

We study expectation values related to the dynamical lattice spacing that occurs in the recent supersymmetric 2d lattice Yang-Mills constructions of Cohen et al. [hep-lat/0307012]. For the purposes of this preliminary analysis, we restrict our attention to the bosonic part of that theory. That is, we compute observables in the fully quenched ensemble, equiva

Karl M. Ecklund

I report B physics results from the CLEO collaboration, highlighting measurements of the Cabibbo-Kobayashi-Maskawa matrix elements |Vcb| and |Vub|. I report a recent measurement of |Vub| through study of the q^2 dependence of B -> pi l nu and B -> rho l nu. I also describe new measurements of the inclusive semileptonic branching fraction BF(B -> X e nu) and

Karl M. Ecklund

I report results from the CLEO collaboration on semileptonic B decays, highlighting measurements of the Cabibbo-Kobayashi-Maskawa matrix elements Vcb and Vub. I describe the techniques used to obtain the recent improvements in precision for these measurements, including the use of the b -> s gamma photon spectrum to reduce hadronic uncertainties in semilepto

Cristian R. Ghezzi, Patricio S. Letelier

We present preliminar results and tests of a new general relativistic code to simulate the hydrodynamic collapse of a 21 solar masses star. We have assumed spherical symmetry and used the formalism of Misner and Sharp to construct a finite-difference scheme to solve the Einstein&#39;s equations, energy-momentum conservation equations and baryonic conservatio

LIGO Scientific Collaboration, B. Abbott

We present the analysis of between 50 and 100 hrs of coincident interferometric strain data used to search for and establish an upper limit on a stochastic background of gravitational radiation. These data come from the first LIGO science run, during which all three LIGO interferometers were operated over a 2-week period spanning August and September of 2002

Ernest Teniente, Toni Urpi

We show that database schema validation and update processing problems such as view updating, materialized view maintenance, integrity constraint checking, integrity constraint maintenance or condition monitoring can be classified as problems of either abductive or deductive nature, according to the reasoning paradigm that inherently suites them. This is don

Paolo Ferraris, Vladimir Lifschitz

We compare two recent extensions of the answer set (stable model) semantics of logic programs. One of them, due to Lifschitz, Tang and Turner, allows the bodies and heads of rules to contain nested expressions. The other, due to Niemela and Simons, uses weight constraints. We show that there is a simple, modular translation from the language of weight constr

A. Guillaume, J. F. Schneiderman, P. Delsing, H. M. Bozler

We have fabricated a single Cooper-pair box (SCB) in close proximity to a single electron transistor (SET) operated in the radio-frequency mode (RF-SET) with an inductor and capacitor lithographed directly on chip. The RF-SET was used to measure the charge state of the SCB revealing a 2e periodic charge quantization. We performed spectroscopy measurements to

R. Wang, R. W. Mair, M. S. Rosen, D. G. Cory

We report simultaneous measurements of the permeability and effective porosity of oil-reservoir rock cores using one-dimensional NMR imaging of the penetrating flow of laser-polarized xenon gas. The permeability result agrees well with industry standard techniques, whereas effective porosity is not easily determined by other methods. This novel NMR technique

A. Hosseini, D. M. Broun, D. E. Sheehy, T. P. Davis

In the cuprate superconductor $YBa_2Cu_3O_{6+x}$, hole doping in the $CuO_2$ layers is controlled by both oxygen content and the degree of oxygen-ordering. At the composition $\rm YBa_2Cu_3O_{6.35}$, the ordering can occur at room temperature, thereby tuning the hole doping so that the superconducting critical temperature gradually rises from zero to 20 K. H

Peter Thalmeier, Gertrud Zwicknagl

In this review article we present a survey of unconventional superconductors and their coexistence behaviour with magnetism. We focus on Ce- and U-based heavy fermion superconductors, in addition we discuss the rare earth borocarbide and skutterudite superconductors. We show that heavy fermion behaviour in Ce- and U- compounds should be described differently

Ha Youn Lee, Mehdi Yahyanejad, Mehran Kardar

Neurons in the visual cortex respond best to rod-like stimuli of given orientation. While the preferred orientation varies continuously across most of the cortex, there are prominent pinwheel centers around which all orientations a re present. Oriented segments abound in natural images, and tend to be collinear}; neurons are also more likely to be connected

G. E. Astrakharchik, D. Blume, S. Giorgini, L. P. Pitaevskii

Quasi-one-dimensional (quasi-1d) two-component Fermi gases with effectively attractive and repulsive interactions are characterized for arbitrary interaction strength. The ground-state properties of the gas confined in highly elongated harmonic traps are determined within the local density approximation. For strong attractive effective interactions the exist

Ginestra Bianconi, Matteo Marsili

We propose a simple model that aims at describing, in a stylized manner, how local breakdowns due unbalances or congestion propagate in real dynamical networks. The model converges to a self-organized critical stationary state in which the network shapes itself as a consequence of avalanches of rewiring processes. Depending on the model&#39;s specification,

Denis Ledue, Pierre-Emmanuel Berche, Renaud Patte

We investigate the thermal activated magnetisation reversal in a single ferromagnetic nanoparticle with uniaxial anisotropy using Monte Carlo simulations. The aim of this work is to reproduce the reversal magnetisation by uniform rotation at very low temperature in the high energy barrier hypothesis, that is to realize the Néel-Brown model. For this purpose

Andrea Cavagna, Irene Giardina, Giorgio Parisi

We study numerically the structure of metastable states in the Sherrington-Kirkpatrick spin glass. We find that all non-paramagnetic stationary points of the free energy are organized into pairs, consisting in a minimum and a saddle of order one, which coalesce in the thermodynamic limit. Within the annealed approximation, the entropic contribution of these

J. G. Oliveira, J. F. F. Mendes, G. Tripathy

We study the surface roughness of prototype models displaying self-organized criticality (SOC) and their noncritical variants in one dimension. For SOC systems, we find that two seemingly equivalent definitions of surface roughness yields different asymptotic scaling exponents. Using approximate analytical arguments and extensive numerical studies we conclud

Sergio A. Cannas, Daniel A. Stariolo, Francisco A. Tamarit

We analyze the nature of the phase transition from a smectic stripe phase to a tetragonal phase predicted in analytic studies by Abanov et al. (Phys. Rev. B 51, 1023 (1995)) and observed in experiments on ultra-thin magnetic films by Vaterlaus et al.(Phys. Rev. Lett. 84, 2247 (2000)). At variance with existent numerical evidence, for the first time we show r

Peter E. Krouskop, Julian Talbot

We examine the energy distribution in a three-dimensional model granular system contained in an open cylinder under the influence of gravity. Energy is supplied to the system by a vibrating base. We introduce spatially resolved, partial particle-particle ``dissipations&#39;&#39; for directions parallel and perpendicular to the energy input, respectively. Ene

Daniel E. Sheehy, T. P. Davis, M. Franz

We formulate a model describing the doping ($x$) and temperature ($T$) dependence of the $ab$-plane and c-axis penetration depth of a cuprate superconductor. The model incorporates the suppression of the superfluid density with underdoping as the system approaches the Mott-Hubbard insulating state by augmenting a d-wave BCS model with a phenomenological char

A Vindigni, N Regnault, Th Jolicoeur

We perform a theoretical study of a non-collinear Ising ferrimagnetic spin chain inspired by the compound Co(hfac)2NITPhOMe. The basic building block of its structure contains one Cobalt ion and one organic radical each with a spin 1/2. The exchange interaction is strongly anisotropic and the corresponding axes of anisotropy have a period three helical struc

H. P. Buchler, G. Blatter

We study the linear response and the dynamic structure factor of weakly interacting Bose gases at low temperatures. Going beyond lowest order in the weak coupling expansion allows us to determine the contribution of the thermal and quantum depletion of the condensate to the dynamic structure factor. We find that the quantum depletion produces a pronounced pe

Bertrand Lods, Giuseppe Toscani

We prove the existence and uniqueness of an equilibrium state with unit mass to the dissipative linear Boltzmann equation with hard--spheres collision kernel describing inelastic interactions of a gas particles with a fixed background. The equilibrium state is a universal Maxwellian distribution function with the same velocity as field particles and with a n

P. Delaney, J. C. Greer

Theoretical and experimental values to date for the resistances of single molecules commonly disagree by orders of magnitude. By reformulating the transport problem using boundary conditions suitable for correlated many-electron systems, we approach electron transport across molecules from a new standpoint. Application of our correlated formalism to benzene-

B. von Haeften, G. Izús, S. Mangioni, A. D. Sánchez

We study an extended system that without noise shows a monostable dynamics, but when submitted to an adequate multiplicative noise, an effective bistable dynamics arise. The stochastic resonance between the attractors of the \textit{noise-sustained dynamics} is investigated theoretically in terms of a two-state approximation. The knowledge of the exact noneq

N. G. Parker, N. P. Proukakis, C. F. Barenghi, C. S. Adams

The low temperature dynamics of a vortex in a trapped quasi-two-dimensional Bose-Einstein condensate are studied quantitatively. Precession of an off-centred vortex in a dimple trap, embedded in a weaker harmonic trap, leads to the emission of sound in a dipolar radiation pattern. Sound emission and reabsorption can be controlled by varying the depth of the

P. Ziesche, F. Tasnadi

The spin-polarized homogeneous electron gas with densities $ρ_\uparrow$ and $ρ_\downarrow$ for electrons with spin `up&#39; ($\uparrow$) and spin `down&#39; ($\downarrow$), respectively, is systematically analyzed with respect to its lowest-order reduced densities and density matrices and their mutual relations. The three 2-body reduced density matrices $γ_{

P. Ziesche, F. Tasnadi

Recently, it has been shown, that the pair density of the homogeneous electron gas can be parametrized in terms of 2-body wave functions (geminals), which are scattering solutions of an effective 2-body Schrödinger equation. For the corresponding scattering phase shifts, new sum rules are reported in this paper. These sum rules describe not only the normaliz

P. Ziesche, F. Tasnadi

The methods of quantum chemistry and solid state theory to solve the many-body problem are reviewed. We start with the definitions of reduced density matrices, their properties (contraction sum rules, spectral resolutions, cumulant expansion, $N$-representability), and their determining equations (contracted Schrödinger equations) and we summarize recent ext

A. Kabakcioglu, A. L. Stella

After a discussion of the definition and number of pseudoknots, we reconsider the self-attracting homopolymer paying particular attention to the scaling of the number of pseudoknots at different temperature regimes in two and three dimensions. Although the total number of pseudoknots is extensive at all temperatures, we find that the number of pseudoknots fo

C. A. Marianetti, G. Kotliar, G. Ceder

Density functional theory (DFT) within the local density approximation (LDA) is used to understand the electronic properties of Na1/3CoO2 and Na1/3CoO2(H2O)4/3, which was recently found to be superconducting1. Comparing the LDA charge density of CoO2 and the Na doped phases indicates that doping does not simply add electrons to the t2g states. In fact, the e

Paolo Cazzato, Stefano Paolini, Saverio Moroni, Stefano Baroni

The rotational dynamics of CO single molecules solvated in small He clusters (CO@He_N) has been studied using Reptation Quantum Monte Carlo for cluster sizes up to N=30. Our results are in good agreement with the roto-vibrational features of the infrared spectrum recently determined for this system, and provide a deep insight into the relation between the st

S. Lupi, M. Ortolani, P. Calvani

The optical conductivity of single crystals of Na_xCoO_2 for $x$ = 0.57 is first reported between 295 and 30 K. In the far infrared, an &#34;anomalous Drude&#34; analysis leads to a carrier effective mass of 5 electron masses. That this high value is due to strong electron-phonon coupling is suggested by the Fano distortion of a phonon at 570 cm^-1. A peak a

Martin Hohnisch, Sabine Pittnauer, Sorin Solomon, Dietrich Stauffer

We propose a stochastic model of interactive formation of individual expectations regarding the business climate in an industry. Our model is motivated by a business climate survey cond ucted since 1960 in Germany by the Ifo-institute (www.ifo.de). In accordance with the data structure of this survey, in our model there is asso ciated to each economic agent

E. A. Muljarov, R. Zimmermann

A microscopic theory of optical transitions in quantum dots with carrier-phonon interaction is developed. Virtual transitions into higher confined states with acoustic phonon assistance add a quadratic phonon coupling to the standard linear one, thus extending the independent Boson model. Summing infinitely many diagrams in the cumulant, a numerically exact

E. Ben-Naim, P. L. Krapivsky

Fluctuations may govern the fate of an interacting particle system even on the mean-field level. This is demonstrated via a three species cyclic trapping reaction with a large, yet finite number of particles, where the final number of particles N_f scales logarithmically with the system size N, N_f ~ ln N. Statistical fluctuations, that become significant as

Z. Jiang, D. A. Dikin, V. V. Metlushko, V. V. Moshchalkov

We study the transport properties of a superconducting Nb film with a square lattice of artificial pinning centers (APCs) as a function of dc current, at a temperature close to the superconducting transition temperature of the film. We find that, at low dc currents, the differential resistance of the film shows the standard matching field anomaly, that is, t

Petter Minnhagen, Beom Jun Kim, A. Gronlund

It is shown from computer simulations that the current-voltage ($I$-$V$) characteristics for the two-dimensional XY model with resistively-shunted Josephson junction dynamics and Monte Carlo dynamics obeys a finite-size scaling form from which the nonlinear $I$-$V$ exponent $a$ can be determined to good precision. This determination supports the conclusion $

Tsutomu Momoi, Toshiya Hikihara

Using gauge transformations on electron bond operators, we derive exact duality relations between various order parameters for correlated electron systems. Applying these transformations, we find two duality relations in the generalized two-leg Hubbard ladder at arbitrary filling. The relations show that unconventional density-wave orders such as staggered f