June 2002 arXiv papers — page 4

Mohsen Alishahiha, Masumeh Ghasemkhani

We study classical solutions describing rotating and boosted membranes on AdS_7 x S^4 background in M-theory. We find the dependence of the energy on the spin and R-charge of these solutions. In the flat space limit we get E ~ S^{2/3}, while for AdS at leading order E-S grows as S^{1/3}. The membranes on AdS_4 x S^7 background have briefly been studied as we

C. Ledoux, R. Srianand, P. Petitjean

We report the detection of H_2, CI, CI*, CI** and Cl I lines in a near Solar-metallicity ([Zn/H]=-0.13) damped Lyman-alpha (DLA) system at z_abs=1.962 observed on the line of sight to the quasar Q 0551-366. The iron-peak elements, X=Fe, Cr and Mn are depleted compared to zinc, [X/Zn] -0.8, probably because they are tied up onto dust grains. Among the three d

Angelo Bassi, GianCarlo Ghirardi

We exhibit a general procedure to purify any given ensemble by identifying an appropriate interaction between the physical system S of the ensemble and the reference system K. We show that the interaction can be chosen in such a way to lead to a spatial separation of the pair S-K. As a consequence, one can use it to prepare at a distance different equivalent

Riccardo D'Auria, Sergio Ferrara, Silvia Vaula'

We analyze the properties of a spontaneously broken D=4, N=4 supergravity without cosmological constant, obtained by gauging translational isometries of its classical scalar manifold. This theory offers a suitable low energy description of the super-Higgs phases of certain Type-IIB orientifold compactifications with 3-form fluxes turned on. We study its N=3,

C. Emary, R. F. Bishop

The two-photon Rabi Hamiltonian is a simple model describing the interaction of light with matter, with the interaction being mediated by the exchange of two photons. Although this model is exactly soluble in the rotating-wave approximation, we work with the full Hamiltonian, maintaining the non-integrability of the model. We demonstrate that, despite this n

Corneliu Sochichiu

We discuss the continuum limits of Berenstein-Maldacena-Nastase matrix model. They give rise to Poisson bracket gauge field theories on the ordinary two sphere or on a set of two spheres with a gauge groups U(n) depending on the degeneracy of the classical solution about which the model is considered. We show that these models fail to be equivalent among eac

Ferenc Iglói, Loïc Turban

We study first- and second-order phase transitions of ferromagnetic lattice models on scale-free networks, with a degree exponent $γ$. Using the example of the $q$-state Potts model we derive a general self-consistency relation within the frame of the Weiss molecular-field approximation, which presumably leads to exact critical singularities. Depending on th

Hwayong Noh, M. P. Lilly, D. C. Tsui, J. A. Simmons

The metallic conductivity of dilute two-dimensional holes in a GaAs HIGFET (Heterojunction Insulated-Gate Field-Effect Transistor) with extremely high mobility and large $r_{s}$ is found to have a linear dependence on temperature, consistent with the theory of interaction corrections in the ballistic regime. Phonon scattering contributions are negligible in

X. Vinas, P. Schuck, M. Farine, M. Centelles

Thomas-Fermi theory is developed to evaluate nuclear matrix elements averaged on the energy shell, on the basis of independent particle Hamiltonians. One- and two-body matrix elements are compared with the quantal results and it is demonstrated that the semiclassical matrix elements, as function of energy, well pass through the average of the scattered quant

Wenbing Hu, Daan Frenkel, Vincent B. F. Mathot

We report Monte Carlo simulations of the melting of a single-polymer crystallite. We find that, unlike most atomic and molecular crystals, such crystallites can be heated appreciably above their melting temperature before they transform to the disordered "coil" state. The surface of the superheated crystallite is found to be disordered. The thickness

Kevin Stokely, Ari Diacou, Scott V. Franklin

We investigate the two-dimensional packing of extremely prolate (aspect ratio $α=L/D>10$) granular materials, comparing experiments with Monte-Carlo simulations. The average packing fraction of particles with aspect ratio $α=12$ is $0.68\pm0.03$. We quantify the orientational correlation of particles and find a correlation length of two particle lengths. The

L. -H. Reydellet, P. Roche, D. C. Glattli, B. Etienne

We show experimentally that even when no bias voltage is applied to a quantum conductor, the electronic quantum partition noise can be investigated using GHz radiofrequency irradiation of a reservoir. Using a Quantum Point Contact configuration as the ballistic conductor we are able to make an accurate determination of the partition noise Fano factor resulti

Wenbing Hu, Daan Frenkel, Vincent B. F. Mathot

We report Monte Carlo simulations of a lattice-polymer model that can account for both polymer crystallization and liquid-liquid demixing in solutions of semiflexible homopolymers. In our model, neighboring polymer segments can have isotropic interactions that affect demixing, and anisotropic interactions that are responsible for freezing. However, our simul

M. Carfora, C. Dappiaggi, A. Marzuoli

We show that the introduction of triangulations with variable connectivity and fluctuating egde-lengths (Random Regge Triangulations) allows for a relatively simple and direct analyisis of the modular properties of 2 dimensional simplicial quantum gravity. In particular, we discuss in detail an explicit bijection between the space of possible random Regge tr

P. Rosenbusch, V. Bretin, J. Dalibard

We study experimentally the line of a single quantized vortex in a rotating prolate Bose-Einstein condensate confined by a harmonic potential. In agreement with predictions, we find that the vortex line is in most cases curved at the ends. We monitor the vortex line leaving the condensate. Its length is measured as a function of time and temperature. For a l

Taichi Itoh, Sang-Jin Sin

After reviewing D-branes as conjugacy classes and various charge quantizations (modulo $k$) in WZW model, we develop the classification and systematic construction of all possible untwisted D-branes in Lie groups of A-D-E series. D-branes are classified according to their positions in the maximal torus. The moduli space of D-branes is naturally identified wi

N. E. J. Bjerrum-Bohr

We consider the leading post-Newtonian and quantum corrections to the non-relativistic scattering amplitude of charged scalars in the combined theory of general relativity and scalar QED. The combined theory is treated as an effective field theory. This allows for a consistent quantization of the gravitational field. The appropriate vertex rules are extracte

B. I. Lev, A. A. Semenov, C. V. Usenko, J. R. Klauder

We consider relativistic coherent states for a spin-0 charged particle that satisfy the next additional requirements: (i) the expected values of the standard coordinate and momentum operators are uniquely related to the real and imaginary parts of the coherent state parameter; (ii) these states contain only one charge component. Three cases are considered: f

Ph. Hagler, B. Pire, L. Szymanowski, O. V. Teryaev

The interference of Pomeron and Odderon amplitudes gives rise to a charge asymmetry in the diffractive electroproduction of a pi+pi- -pair. We calculate this charge asymmetry in perturbative QCD in the Born approximation and on the leading Q^2-level. The numerical evaluation shows a sizeable asymmetry in an experimentally accessible kinematical region. We fi

Y. Ono, M. Potthoff, R. Bulla

Mott metal-insulator transitions in an M-fold orbitally degenerate Hubbard model are studied by means of a generalization of the linearized dynamical mean-field theory. The method allows for an efficient and reliable determination of the critical interaction U_c for any integer filling n and different M at zero temperature. For half-filling a linear dependen

Haakon Dahle, Steen Hannestad, Jesper Sommer-Larsen

We measure the average gravitational shear profile of 6 massive clusters (M_vir ~ 10^15 M_sun) at z=0.3 out to a radius ~2h^-1 Mpc. The measurements are fitted to a generalized NFW-like halo model ρ(r) with an arbitrary r -> 0 slope α. The data are well fitted by such a model with a central cusp with α~ 0.9 - 1.6 (68% confidence interval). For the standard-N

S. Alisauskas

The corrected triple sum expression of Ališauskas (1987) for the recoupling (Racah) coefficients (6j-symbols) of the symmetric (most degenerate) representations of the orthogonal groups SO(n) (previously derived from the fourfold sum expression of Ališauskas also related to result of Hormeßand Junker 1999) is rearranged into three new different double sum ex

Takeshi Nihei, Leszek Roszkowski, Roberto Ruiz de Austri

Coannihilation processes provide an important additional mechanism for reducing the density of stable relics in the Universe. In the case of the stable lightest neutralino of the MSSM, and in particular the Constrained MSSM (CMSSM), the coannihilation with sleptons plays a major role in opening up otherwise cosmologically excluded ranges of supersymmetric pa

S. V. Chekanov

The uncertainties due to limited knowledge of the multi-hadron final state on the measurements of the top mass at future linear colliders are discussed. The study is performed for E+E- -> tt-bar annihilation events at the centre-of-mass energy of 500 GeV using Monte Carlo models tuned to LEP experiments. The uncertainties are determined for the all hadronic

Hiroshi Kontani

On the basis of the linear response transport theory, the general expressions for the thermoelectric transport coefficients, such as thermoelectric power (S), Nernst coefficient (ν), and thermal conductivity (κ), are derived by using the Fermi liquid theory. The obtained expression is exact as for the most singular term in terms of 1/γ_k^* (γ_k^* being the q

S. M. Kuzenko, I. N. McArthur

The effective action in gauge theories is known to depend on a choice of gauge fixing conditions. This dependence is such that any change of gauge conditions is equivalent to a field redefinition in the effective action. In this sense, the quantum deformation of conformal symmetry in the N = 4 super Yang-Mills theory, which was computed in 't Hooft gauge

M. Kuroda, D. Schildknecht

We explore the consequences for diffractive production, gamma* p --> X p, in deep inelastic scattering at low values of x\sim Q^2/W^2 <<1 that follow from our recent representation of the total photoabsorption cross section, sigma_{gamma* p}, in the generalized vector dominance/ color dipole picture(GVD/CDP) that is based on the generic structure of the two-

S. Ishikawa

A modified version of the Faddeev three-body equation to accommodate the Coulomb interaction, which was used in the study of three-nucleon bound states, is applied to the proton-deuteron scattering problem at energies below the three-body breakup threshold. A formal derivation of the equation in a time-independent scattering theory is given. Numerical result

Stoyan Karabunarliev, Eric. R. Bittner

The recombination of electron-hole pairs injected in extended conjugated systems is modeled as a multi-pathway vibron-driven relaxation in monoexcited state-space. The computed triplet-to-singlet ratio of exciton formation times $r = τ_T/τ_S$ increases from 0.9 for a model dimer to 2.5 for a 32-unit chain, in excellent agreement with experiments. Therewith w

J. S. Alcaniz, Deepak Jain, Abha Dev

Inspired by recent developments in particle physics, the so-called brane world cosmology seems to provide an alternative explanation for the present dark energy problem. In this paper, we use the estimated age of high-$z$ objects to constrain the value of the cosmological parameters in some particular scenarios based on this large scale modification of gravi

Rosalba Perna, Davide Lazzati

We present a time-dependent photoionization code that combines self-consistently metal evolution and dust destruction under an intense X-ray UV radiation field. Firstly, we extend the mathematical formulation of the time-dependent evolution of dust grains under an intense radiation flux with the inclusion of the process of ion field emission (IFE). We determ

C. R. Hagen

In a recent work Brevik \emph{et al.} have offered formal proofs of two results which figure prominently in calculations of the Casimir pressure on a sphere. It is shown by means of simple counterexamples that each of those proofs is necessarily incorrect.

J. G. Muga, I. L. Egusquiza, J. A. Damborenea, F. Delgado

The time of passage of the transmitted wave packet in a tunneling collision of a quantum particle with a square potential barrier becomes independent of the barrier width in a range of barrier thickness. This is the Hartman effect, which has been frequently associated with ``superluminality&#39;&#39;. A fundamental limitation on the effect is set by non-rela

Detlev Mueller

The baroclinic instability problem is considered in the framework of Laplacian tidal theory. The Hilbert space of the quasigeostrophic vorticity budget is spanned by spheroidal functions. The fluid is linearly stable against quasigeostrophic disturbances. As the essential source of irregular ocean-atmosphere motions, baroclinic instability is ruled out by ti

P. González, B. Juliá-Díaz, A. Valcarce, F. Fernández

By means of a $NN \to NN^*(1440)$ transition potential derived in a parameter-free way from a quark model, we determined simultaneously the $πNN^*(1440)$ and $σNN^*(1440)$ coupling constants.

Tamanna Rumin, Noboru Takigawa

Relativistic mean field calculations suggest that the charge and matter deformations significantly differ in some of the unstable neutron and proton rich nuclei. We discuss the effects of the difference on the fusion reactions induced by them at energies near and below the Coulomb barrier by taking the $^{19,25,37}$Na + $^{208}$Pb reactions as examples. We a

M. Krbalek, P. Seba

We present a cellular automaton simulating the behavior of public bus transport in several Mexican cities. The headway statistics obtained from the model is compared to the measured time intervals between subsequent bus arrivals to a given bus stop and to a spacing distribution resulting from a random matrix theory.

M. Krbalek

We present an exact solution of headway distribution of the asymmetric simple exclusion model with open boundary conditions and compare it to the headway distributions of the highway traffic.

E. V. Doktorov

It is argued that the integrable modified nonlinear Schroedinger equation with the nonlinearity dispersion term is the true starting point to analytically describe subpicosecond pulse dynamics in monomode fibers. Contrary to the known assertions, solitons of this equation are free of self-steepining and the breather formation is possible.

Lev Kaplan

Recent images of electron flow through a two-dimensional electron gas (2DEG) device show branching behavior that is reproduced in numerical simulations of motion in a correlated random potential [cond-mat/0010348]. We show how such branching naturally arises from caustics in the classical flow and find a simple scaling behavior of the branching under variati

Nicolas Macris

We consider a non relativistic particle on the surface of a semi-infinite cylinder of circumference $L$ submitted to a perpendicular magnetic field of strength $B$ and to the potential of impurities of maximal amplitude $w$. This model is of importance in the context of the integer quantum Hall effect. In the regime of strong magnetic field or weak disorder

Robert S. Maier

A minor error in the necessary conditions for the algebraic form of the Lamé equation to have a finite projective monodromy group, and hence for it to have only algebraic solutions, is pointed out. [See F. Baldassarri, &#34;On algebraic solutions of Lamé&#39;s differential equation&#34;, J. Differential Equations 41 (1981), 44-58.] It is shown that if the gr

David J. Kaup

We provide a brief review of some of the major research results arising from the method of the Inverse Scattering Transform.

Yehuda Pinchover

In this paper we study the large time behavior of the (minimal) heat kernel $k_P^M(x,y,t)$ of a general time independent parabolic operator $L=u_t+P(x, \partial_x)$ which is defined on a noncompact manifold $M$. More precisely, we prove that $$\lim_{t\to\infty} e^{λ_0 t}k_P^{M}(x,y,t)$$ always exists. Here $λ_0$ is the generalized principal eigenvalue of the

Rosina Hing, Gloria Nunez, Diosdado Villegas

038<p type=&#34;texpara&#34; tag=&#34;Body Text&#34; >The identification theory and realization of the dynamic systems is a medullary aspect in the modern control theory that consists fundamentally in that, starting from the knowledge of the behavior entrance-exit, obtained experimentally in the case of the identification, or given previously in the case of

Yanguang Charles Li

The spectral theorem of the linear 2D Euler operator in Sobolev spaces is presented as a corollary of the spectral theorem in $\ell_2$ space in [Li,00]. Study on the (dashed) line model introduced in [Li,01] is continued. Specifically, invariant manifolds for the line model is established. The corresponding line model for 2D Navier-Stokes equation is also in

Emilio De Santis

We study the Swendsen-Wang dynamics for disordered non ferromagnetic Ising models on cubic subsets of the hypercubic lattice Z^d and we show that for all small values of the temperature parameter T the dynamics has a slow relaxation to equilibrium (it is torpid). Looking into this dynamics from the point of view of the Markov chains theory we can prove that

Mark Davidson, Gestur Olafsson, Genkai Zhang

Let $\mathcal{D}=G/K$ be a complex bounded symmetric domain of tube type in a complex Jordan algebra $V$ and let $\mathcal{D}_{\mathbb{R}}=H/L\subset \mathcal{D}$ be its real form in a formally real Euclidean Jordan algebra $J\subset V$. We consider representations of $H$ that are gotten by the generalized Segal-Bargmann transform from a unitary $G$-space of

Atsushi Kamita

We shall give a uniform expression and a uniform calculation for the b-functions of prehomogeneous vector spaces of commutative parabolic type, which were previously calculated by case-by-case analysis. Our method is a generalization of Kashiwara&#39;s approach using the universal Verma modules. We shall also give a new proof for the criterion of the irreduc

Yong-Geun Oh

In this paper, we prove that the two well-known natural normalizations of Hamiltonian functions on the symplectic manifold $(M,ω)$ canonically relates the action spectra of different normalized Hamiltonians on {\it arbitrary} symplectic manifolds $(M,ω)$. The natural class of normalized Hamiltonians consists of those whose mean value is zero for the closed m

Jae Choon Cha

We introduce a new algebraic topological technique to detect non-fibred knots in the three sphere using the twisted Alexander invariants. As an application, we show that for any Seifert matrix of a knot with a nontrivial Alexander polynomial, there exist infinitely many non-fibered knots with the given Seifert matrix. We illustrate examples of knots that hav

Annalisa Calini, Joel Langer

Differential equations are derived for a continuous limit of iterated Schwarzian reflection of analytic curves, and solutions are interpreted as geodesics in an infinite-dimensional symmetric space geometry.

G. Savvidy

We suggest supersymmetric extension of conformally invariant string theory which is exclusively based on extrinsic curvature action. At the classical level this is a tension-less string theory. The absence of conformal anomaly in quantum theory requires that the space-time should be 6-dimensional.

Michael Eastwood

Using the AdS/CFT correspondence, we identify the symmetry algebra of the Laplacian on Euclidean space as an explicit quotient of the universal enveloping algebra of the Lie algebra of conformal motions. We construct analogues of these symmetries on a general conformal manifold.

Y. Takimoto, T. Fujiwara

Quantum $A_N$-Toda field theory in two dimensions is investigated based on the method of quantizing canonical free field. Toda exponential operator associated with the fundamental weight $λ^1$ is constructed.

J. -P. Blaizot, E. Iancu, H. Weigert

We explore and clarify the connections between two different forms of the renormalisation group equations describing the quantum evolution of hadronic structure functions at small $x$. This connection is established via a Langevin formulation and associated path integral solutions that highlight the statistical nature of the quantum evolution, pictured here

A. Bashir, A. Raya

We study the gauge covariance of the massive fermion propagator in three as well as four dimensional Quantum Electrodynamics (QED). Starting from its value at the lowest order in perturbation theory, we evaluate a non-perturbative expression for it by means of its Landau-Khalatnikov-Fradkin (LKF) transformation. We compare the perturbative expansion of our f

J. A. Casas, J. R. Espinosa, I. Navarro

Conventionally, neutrino masses in a supersymmetric theory arise from non-renormalizable lepton-number (L)-violating operators in the superpotential. The alternative possibility of having such operators in the Kahler potential as the dominant source of neutrino masses has very interesting implications and differences with respect to the standard scenario: fi

Helder Chavez, Luis Masperi

The scattering and capture of right-handed neutrinos by an Abelian cosmic string in the SO(10) grand unification model are considered. The scattering cross-section of neutrinos per unit length due to the interaction with the gauge and Higgs fields of the string is much larger in its scaling regime than in the friction one because of the larger infrared cutof

M. Fiolhais, P. Alberto, B. Golli, S. Sirca

The Roper state is described in the framework of the chiral chromodielectric model as a single quark excitation in self-consistent meson potentials. The interplay between quark and meson excitations is discussed and we emphasise the role of non-quark degrees of freedom in the electroproduction of nucleon excitations.

Kari Enqvist, Shinta Kasuya, Anupam Mazumdar

The inflaton condensate associated with a global symmetry can fragment into quasistable Q balls, provided the inflaton oscillations give rise to an effective equation of state with negative pressure. We study chaotic inflation with a running inflaton mass and show that, depending on the sign of the radiative mass correction, the process of fragmentation into

Rainer Jakob

I will give an overview on fragmentation functions with particular emphasis on spin-dependence. A straightforward classification scheme permits to label all independent fragmentation functions for a given physical situation in an unambiguous way. In the context of light-cone quantisation the leading twist fragmentation functions have an intuitive probabilist

Matthias Burkardt

For an unpolarized target, the generalized parton distribution $H_q(x,0,t)$ is related to the distribution of partons in impact parameter space. The transverse distortion of this distribution for a transversely polarized target is described by $E_q(x,0,t)$.

Michael Dine, Yosef Nir, Yael Shadmi

We study grand unified theories based on an SU(5)xSU(5) gauge group in which the GUT scale, M_{GUT}, is the VEV of an exact or approximate modulus, and in which fast proton decay is avoided through a combination of a large triplet mass and small triplet couplings. These features are achieved by discrete symmetries. In many of our models, M_{GUT} is generated

A. V. Efremov, K. Goeke, P. Schweitzer

Spin azimuthal asymmetries in pion electro-production in deep inelastic scattering off longitudinally polarized protons, measured by HERMES, are well reproduced theoretically with no adjustable parameters. Predictions for azimuthal asymmetries for a longitudinally polarized deuteron target are given. The z-dependence of the Collins fragmentation function is

J. W. van Holten

The dynamics of cosmic scalar fields with flat potential is studied. Their contribution to the expansion rate of the universe is analyzed, and their behaviour in a simple model of phase transitions is discussed.

J. Vijande, F. Fernandez, A. Valcarce, B. Silvestre-Brac

In this work we study tetraquark bound states in the framework of the constituent quark model of Ref. [2], which has been used for the description of non-strange two- and three-baryon systems and later on applied to the hadron spectra.

I. I. Bigi

The last three years have seen a phase transition in our knowledge about CP violation: (i) Direct CP violation has been established in $K_L \to ππ$. (ii) The first CP violation outside $K_L$ decays has been observed in $B_d \to ψK_S$: $<{\rm sin}2ϕ_1 > = 0.78 \pm 0.08$ in amazing agreement with the prediction from the CKM description. The latter is thus seen

John Yelton

A review of the experimental results on charmed baryons, with an accent on those reported most recently. Talk given at FPCP conference, U. Penn, May 2002.

Edward H. Thorndike

An informal review is given of the status and direction of experiments on radiative B decays -- b -> s gamma and b -> d gamma. Branching fractions for exclusive and inclusive b -> s gamma decays, CP asymmetry limits, the photon energy spectrum, and limits on the b -> d gamma exclusive branching fractions are covered, and implications of the measurements disc

Eunil Won

We present a measurement of CP-violating asymmetries in B0 -> pi+pi- decays based on 41.8 fb-1 data sample collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we obtain the CP-violating asymmetry parameters S_pi

Shane L. Larson, Ronald W. Hellings, William A. Hiscock

Unlike ground-based interferometric gravitational wave detectors, large space-based systems will not be rigid structures. When the end-stations of the laser interferometer are freely flying spacecraft, the armlengths will change due to variations in the spacecraft positions along their orbital trajectories, so the precise equality of the arms that is require

Yuri N. Obukhov, Thoralf Chrobok, Mike Scherfner

We demonstrate the existence of shear-free cosmological models with rotation and expansion which support the inflationary scenarios. The corresponding metrics belong to the family of spatially homogeneous models with the geometry of the closed universe (Bianchi type IX). We show that the global vorticity does not prevent the inflation and even can accelerate

P. Astone, D. Babusci, M. Bassan, P. Bonifazi

The interaction between cosmic rays and the gravitational wave bar detector NAUTILUS is experimentally studied with the aluminum bar at temperature of T=1.5 K. The results are compared with those obtained in the previous runs when the bar was at T=0.14 K. The results of the run at T = 1.5 K are in agreement with the thermo-acoustic model; no large signals at

Francesc Fayos, Jose M. M. Senovilla, Ramon Torres

We study the matching of a general spherically symmetric spacetime with a Vaidya-Reissner-Nordstrom solution. To that end, we study the properties of spherically symmetric electromagnetic fields and develop the proper gravitational and electromagnetic junction conditions. We prove that generic spacetimes can be matched to a Vaidya-Reissner-Nordstrom solution

Paulo F. Bedaque, Gautam Rupak

We study dilute gases with short range interactions and large two-body scattering lengths. At temperatures between the condensation temperature and the scale set by therange of the potential there is a high degree of universality. The first two terms in the expansion of thermodynamic functions in powers of the fugacity $z$, which measures the diluteness of t

Jian-Xin Zhu, A. V. Balatsky

The Josephson current in the presence of a precessing spin between various types of superconductors is studied. It is shown that the Josephson current flowing between two spin-singlet pairing superconductors is not modulated by the precession of the spin. When both superconductors have equal-spin-triplet pairing state, the flowing Josephson current is modula

Ronald Dickman, Ronaldo Vidigal

We introduce an operator description for a stochastic sandpile model with a conserved particle density, and develop a path-integral representation for its evolution. The resulting (exact) expression for the effective action highlights certain interesting features of the model, for example, that it is nominally massless, and that the dynamics is via cooperati

Carles Navau, Alvaro Sanchez

Stiffness and hysteretic energy losses are calculated for a magnetically levitating system composed of a type-II superconductor and a permanent magnet when a small vibration is produced in the system. We consider a cylindrically symmetric configuration with only vertical movements and calculate the current profiles under the assumption of the critical state

Jean-Christophe Baret, Damien Vandembroucq, Stephane Roux

An extremal model for the plasticity of amorphous materials is studied in a simple two-dimensional anti-plane geometry. The steady-state is analyzed through numerical simulations. Long-range spatial and temporal correlations in local slip events are shown to develop, leading to non-trivial and highly anisotropic scaling laws. In particular, the plastic strai

Jean Richert, Hans A. Weidenmuller

We study the transport properties of two electrons in a quasi one-dimensional disordered wire. The electrons are subject to both, a disorder potential and a short range two-body interaction. Using the approach developed by Iida et al. [ Ann. Phys. (N.Y.) 200 (1990) 219 ], the supersymmetry technique, and a suitable truncation of Hilbert space, we work out th

C. U. Jung, Heon-Jung Kim, Min-Seok Park, Mun-Seog Kim

We synthesized polycrystalline MgB2 from a stoichiometric mixture of Mg and the 11 B isotope under different conditions. All the samples showed bulk superconductivity with Tc = 38~39 K. The samples containing the least amount of unreacted Mg showed the highest Tc and the sharpest transition width (Delta_Tc). A residual resistivity ratio (RRR) of ~ 5.8, and a

Ines Caridi, Horacio Ceva

We calculate the standard deviation of (N1-N0), the difference of the number of agents choosing between the two alternatives of the minority game. Our approach is based on two approximations: we use the whole set of possible strategies, rather than only those distributed between the agents involved in a game; moreover, we assume that a period-two dynamics di

V. N. Narozhnyi, G. Fuchs, A. Handstein, A. Gümbel

We report on the results of a comparative investigation of highly dense bulk MgB$_2$ samples prepared by three methods: (i) hot deformation; (ii) high pressure sintering; and (iii) mechanical alloying of Mg and B powders with subsequent hot compaction. All types of samples were studied by ac-susceptibility, dc-magnetization and resistivity measurements in ma

Arno Schindlmayr

The good performance of the GW approximation for band-structure calculations in solids was long taken as a sign that the sum of self-energy diagrams is converged and that all omitted terms are small. However, with modern computational resources it has now become possible to evaluate self-consistency and vertex corrections explicitly, and the numerical result

D. V. Pakhnin, A. I. Sokolov, B. N. Shalaev

For the three-dimensional random Ising model, the effective sextic coupling constant v_6 and the nonlinear susceptibilities of the fourth (chi_4) and sixth (chi_6) orders are calculated at criticality. These quantities are shown to differ markedly from their counterparts for pure uniaxial magnets. In particular, the ratio v_6/v_{4}^2 entering the equation of

D. T. Adroja, P. C. Riedi, J. G. M. Armitage, D. Fort

We have investigated a single crystal of CeAgSb2 using low field ac-susceptibility, thermal expansion and magnetostriction measurements in the temperature range 1.5K to 90K. The ac-susceptibility exhibits a sharp peak at 9.7K for both B//c and B perp c due to the magnetic ordering of the Ce moment. The thermal expansion coefficient alpha, exhibits highly ani

G. Bilalbegovic

In the process of molecular dynamics simulation studies of gold nanowires an interesting structure is discovered. This is a finite double-wall nanowire with a large empty core similar to single-wall and double-wall carbon nanotubes. The structure of the 16-10 gold nanotube is studied at the room temperature. An investigation of the high-temperature stability

Brian M. Andersen, Per Hedegard

We discuss recent elastic neutron scattering and scanning tunneling experiments on high-T_c cuprates exposed to an applied magnetic field. In particular we show that a physical picture consisting of antiferromagnetic vortex cores operating as pinning centers for surrounding stripes is qualitatively consistent with the neutron data provided the stripes have t

Ramin Golestanian, Armand Ajdari

The conventional assumption that the self-diffusion coefficient of a small tracer can be obtained by a local and instantaneous application of Einstein&#39;s relation in a temperature field with spatial and temporal heterogeneity is revisited. It is shown that hydrodynamic fluctuations contribute to the self-diffusion tensor in a universal way, i.e. independe

S. V. Kozyrev

p-Adic and noncommutative analysis are applied to describe phase transitions in disordered systems. In the noncommutative replica approach we replicate the disorder instead of the system degrees of freedom. The noncommutatibe replica symmetry breaking is formulated using the language of noncommutative analysis. This allows to derive the ultrametric space of

A. Doressoundiram, N. Peixinho, C. de Bergh, S. Fornasier

We have started since 1997 the Meudon Multicolor Survey of Outer Solar System Objects with the aim of collecting a large and homogeneous set of color data for Trans-Neptunian and Centaurs objects [...] We have a combined sample of 52 B-R color measurements for 8 Centaurs, 22 Classicals, 13 Plutinos, 8 Scattered objects and 1 object with unidentified dynamica

D. E. Harris, H. Krawczynski, G. B. Taylor

During the course of an investigation on the interaction of the radio galaxy 3C129 and its ambient cluster gas, we found excess X-ray emission aligned with the northern radio jet. The emission extends from the weak X-ray core of the host galaxy approximately 2.5&#34; to the first resolved radio knot. On a smaller scale, we have also detected a weak radio ext

D. Bersier, B. McLeod, P. M. Garnavich, M. J. Holman

We report polarization measurements and photometry for the optical afterglow of the gamma-ray burst GRB 020405. We measured a highly significant 9.9% polarization (in V band) 1.3 days after the burst and argue that it is intrinsic to the GRB. The light curve decay is well fitted by a $t^{-1.72}$ power-law; we do not see any evidence for a break between 1.24

Fabrizio Brighenti, William G. Mathews

The density irregularities and holes visible in many Chandra X-ray images of cluster and galactic cooling flows can be produced by symmetrically heated gas near the central galactic black hole. As the heated gas rises away from the galactic center, a relatively small number of large plumes and bubbles are formed in qualitative agreement with the observed fea

Jesper Sommer-Larsen, Martin Gotz, Laura Portinari

We have performed TreeSPH simulations of galaxy formation in a standard LCDM cosmology, including effects of star formation, energetic stellar feedback processes and a meta-galactic UV field, and obtain a mix of disk, lenticular and elliptical galaxies. The disk galaxies are deficient in angular momentum by only about a factor of two compared to observed dis

Alexander D. Dolgov, Dario Grasso, Alberto Nicolis

Turbulence may have been produced in the early universe during several kind of non-equilibrium processes. Periods of cosmic turbulence may have left a detectable relic in the form of stochastic backgrounds of gravitational waves. In this paper we derive general expressions for the power spectrum of the expected signal. Extending previous works on the subject

C. Brocksopp, R. P. Fender, G. G. Pooley

We present model lightcurves which have been created in order to explain the orbital modulation observed in the radio emission of Cyg X-1. We invoke variable absorption by the stellar wind as the black hole jet orbits around the OB companion star and find that a very simple model is able to reproduce the amplitudes and frequency dependence of the observed li

M. Reinecke, W. Hillebrandt, J. C. Niemeyer

We present the results of three-dimensional hydrodynamical simulations of the subsonic thermonuclear burning phase in type Ia supernovae. The burning front model contains no adjustable parameters so that variations of the explosion outcome can be linked directly to changes in the initial conditions. In particular, we investigate the influence of the initial

E. Meinkoehn, S. Richling

A finite element method for solving the resonance line transfer problem in moving media is presented. The algorithm works in three spatial dimensions on unstructured grids which are adaptively refined by means of an a posteriori error indicator. Frequency discretization is implemented via a first-order Euler scheme. We discuss the resulting matrix structure