October 2000 arXiv papers — page 6

Luis Benet, Thomas Rupp, Hans A. Weidenmueller

Using a novel approach, we investigate the shape of the average spectrum and the spectral fluctuations of the $k$-body embedded unitary ensemble in the limit of large matrix dimension. We identify the transition point between semicircle and Gaussian shape. The transition also affects the spectral fluctuations which deviate from Wigner-Dyson form and become P

D. Taras-Semchuk, Alexander Altland

We discuss a number of basic physical mechanisms relevant to the formation of the proximity effect in superconductor/normal metal (SN) systems. Specifically, we review why the proximity effect sharply discriminates between systems with integrable and chaotic dynamics, respectively, and how this feature can be incorporated into theories of SN systems. Turning

B. E. Cox, J. R. Forshaw

We have modified the HERWIG event generator to incorporate diffractive interactions. All standard HERWIG hard subprocesses are available.

Jerome Levine

We consider a homological enlargement of the mapping class group, defined by homology cylinders over a closed oriented surface (up to homology cobordism). These are important model objects in the recent Goussarov-Habiro theory of finite-type invariants of 3-manifolds. We study the structure of this group from several directions: the relative weight filtratio

T. Boeker, R. P. van der Marel, L. Mazzuca, H. -W. Rix

We have obtained 1-2 A resolution optical Echellette spectra of the nuclear star cluster in the nearby starburst galaxy NGC 4449. The light is clearly dominated by a very young (6-10 Myr) population of stars. For our age dating, we have used recent population synthesis models to interpret the observed equivalent width of stellar absorption features such as t

I. Jack, D. R. T. Jones

We consider the renormalisation of the Fayet-Iliopoulos D-term in a softly-broken supersymmetric gauge theory with a non-simple gauge group containing an abelian factor, and present the associated beta-function through three loops. We also include in an appendix the result for several abelian factors. We specialise to the case of the minimal supersymmetric s

D. C. Cabra, A. Dobry, G. L. Rossini

We study the long wavelength limit of a spin 1/2 Heisenberg antiferromagnetic two-leg ladder, treating the interchain coupling in a non-perturbative way. We perform a mean field analysis and then include exactly the fluctuations. This allows for a discussion of the phase diagram of the system and provides an effective field theory for the low energy excitati

Ashoke Sen

We show that the world-volume theory on a D-p-brane at the tachyonic vacuum has solitonic string solutions whose dynamics is governed by the Nambu-Goto action of a string moving in (25+1) dimensional space-time. This provides strong evidence for the conjecture that at this vacuum the full (25+1) dimensional Poincare invariance is restored. We also use this r

Mauro Mobilia, Pierre-Antoine Bares

A class of two-species ({\it three-states}) bimolecular diffusion-limited models of classical particles with hard-core reacting and diffusing in a hypercubic lattice of arbitrary dimension is investigated. The manifolds on which the equations of motion of the correlation functions close, are determined explicitly. This property allows to solve for the densit

M. Yamagami, K. Matsuyanagi, M. Matsuo

By performing fully 3D symmetry-unrestricted Skyrme-Hartree-Fock-Bogoliubov calculations, we discuss shape coexistence and possibility of exotic deformations simultaneously breaking the reflection and axial symmetries in proton-rich N=Z nuclei: 64Ge, 68Se, 72Kr, 76Sr, 80Zr and 84Mo. Results of calculation indicate that the oblate ground state of 68Se is extr

James W. Colbert, John S. Mulchaey, Ann I. Zabludoff

In order to study early type galaxies in their simplest environments, we have constructed a well-defined sample of 30 isolated galaxies. The sample contains all RC3 early-type galaxies with no other cataloged galaxy with known redshift lying within a projected radius of 1 (h_100)^{-1} Mpc and =/- 1000 km/s (where we use the recessional velocities in the RC3)

Salman Habib, Kurt Jacobs, Hideo Mabuchi, Robert Ryne

Viewed as approximations to quantum mechanics, classical evolutions can violate the positive-semidefiniteness of the density matrix. The nature of this violation suggests a classification of dynamical systems based on classical-quantum correspondence; we show that this can be used to identify when environmental interaction (decoherence) will be unsuccessful

Domenico Giulini

It is well known that the dynamical mechanism of decoherence may cause apparent superselection rules, like that of molecular chirality. These `environment-induced' or `soft' superselection rules may be contrasted with `hard' superselection rules, like that of electric charge, whose existence is usually rigorously demonstrated by means of certain

N. Klipa, S. D. Bosanac

Dynamics of a particle is formulated from classical principles that are amended by the uncertainty principle. Two best known quantum effects: interference and tunneling are discussed from these principles. It is shown that identical to quantum results are obtained by solving only classical equations of motion. Within the context of interference Aharonov-Bohm

K. S. Mallesh, Swarnamala Sirsi, Mahmoud A. A. Sbaih, P. N. Deepak

The notion of spin squeezing has been discussed in this paper using the density matrix formalism. Extending the definition of squeezing for pure states given by Kitagawa and Ueda in an appropriate manner and employing the spherical tensor representation, we show that mixed spin states which are non-oriented and possess vector polarization indeed exhibit sque

D. M. Snyder

The personal spatial structure of an observer is introduced as a central element in the positioning of objects in space. The link between a reference frame used by an observer and his personal spatial structure is discussed. Research on inversion or reversal of incoming light in psychology indicates that the personal spatial structure of an individual, as we

V. A. Kuz'menko

Time invariance problem of a photon absorption process in atoms and molecules is discussed.

G. Roati, W. Jastrzebski, A. Simoni, G. Modugno

We report on trapping of fermionic 40K atoms in a red-detuned standing-wave optical trap, loaded from a magneto-optical trap. Typically, 10^6 atoms are loaded at a density of 10^12 cm^-3 and a temperature of 65 microK, and trapped for more than 1 s. The optical trap appears to be the proper environment for performing collisional measurements on the cold atom

G. D'Agostini

Criticisms of so called `subjective probability' come on the one hand from those who maintain that probability in physics has only a frequentistic interpretation, and, on the other, from those who tend to `objectivise' Bayesian theory, arguing, e.g., that subjective probabilities are indeed based `only on private introspection'. Some of the common misconcept

A. V. Titov, N. S. Mosyagin, A. B. Alekseyev, R. J. Buenker

The generalized relativistic effective core potential (GRECP) approach is employed in the framework of multireference single- and double-excitation configuration interaction (MRD-CI) method to calculate the spin-orbit (SO) splitting in the $^2P^o$ ground state of the Tl atom and spectroscopic constants for the $0^+$ ground state of TlH. The 21-electron GRECP

D. M. Snyder

Bennett et al.'s original article on quantum teleportation did not address explicitly synchronizing the orientation of the local spatial reference frames from and to which teleportaton occurs where the state teleported is spin 1/2 along the z axis. They wrote that only two bits of information need to be conveyed classically where the state to be teleport

S. J. Wallace

Recent progress is reviewed in four areas where new experimental data have been obtained: proton-proton bremsstrahlung, threshold pion production in proton-proton collisions, elastic electron-deuteron scattering and deuteron photodisintegration at several GeV photon energy. Relativistic effects are expected to be significant in these processes. High energy p

T. Duguet, P. Bonche, P. -H. Heenen, J. Meyer

The odd-even mass staggering (OES) of nuclei is analyzed in the context of self-consistent mean-field calculations. The procedure developed allows to understand the OES for spherical as well as for deformed nuclei. Comparison with results at the Hartree-Fock level shows the non-perturbative effect on this observable of the inclusion of pairing correlations.

L. V. Bravina, E. E. Zabrodin, M. Bleicher, S. A. Bass

The equilibration of hot and dense nuclear matter produced in the central region in central Au+Au collisions at $\sqrt{s}=200$ AGeV is studied within the microscopic transport model UrQMD. The pressure here becomes isotropic at $t \approx 5$ fm/c. Within the next 15 fm/c the expansion of the matter proceeds almost isentropically with the entropy per baryon r

S. Y. Panitkin

Source imaging analysis was performed on two-pion correlations in central Au + Au collisions at beam energies between 2 and 8$A$ GeV. We apply the imaging technique by Brown and Danielewicz, which allows a model-independent extraction of source functions with useful accuracy out to relative pion separations of about 20 fm. We found that extracted source func

S. Sultansoy

Construction of the TESLA linear electron-positron collider tangentially to the HERA proton ring will provide a number of new facilities for particle and nuclear physics research. In this paper main parameters and physics goals of eA, gamma-A and FEK gamma-A colliders, as well as fixed target experiments are discussed.

G. Berkolaiko, E. B. Bogomolny, J. P. Keating

We derive an exact expression for the two-point correlation function for quantum star graphs in the limit as the number of bonds tends to infinity. This turns out to be identical to the corresponding result for certain Seba billiards in the semiclassical limit. Reasons for this are discussed. The formula we derive is also shown to be equivalent to a series e

D. Levi, J. Negro, M. A. del Olmo

We show on the example of the discrete heat equation that for any given discrete derivative we can construct a nontrivial Leibniz rule suitable to find the symmetries of discrete equations. In this way we obtain a symmetry Lie algebra, defined in terms of shift operators, isomorphic to that of the continuous heat equation.

S. Besio, A. Mazzino, C. F. Ratto

Numerical studies performed with a primitive equation model on two-dimensional sinusoidal hills show that the local velocity profiles behave logarithmically to a very good approximation, from a distance from the surface of the order of the maximum hill height almost up to the top of the boundary layer. This behavior is well known for flows above homogeneous

Andrea Mazzino, Paolo Muratore-Ginanneschi

Exploiting a Lagrangian strategy we present a numerical study for both perturbative and nonperturbative regions of the Kraichnan advection model. The major result is the numerical assessment of the first-order $1/d$-expansion by M. Chertkov, G. Falkovich, I. Kolokolov and V. Lebedev ({\it Phys. Rev. E}, {\bf 52}, 4924 (1995)) for the fourth-order scalar stru

N. G. Marchuk

We suggest a tensor equation on Riemannian manifolds which can be considered as a generalization of the Dirac equation for the electron. The tetrad formalism is not used. Also we suggest a new form of the tensor Dirac equation with a Spin(1,3) gauge symmetry in Minkowski space.

Hongjun Gao, Jinqiao Duan

In this paper, the averaging principle for quasi-geostrophic motions with rapidly oscillating forcing is proved, both on finite but large time intervals and on the entire time axis. This includes comparison estimate, stability estimate, and convergence result between quasi-geostrophic motions and its averaged motions. Furthermore, the existence of almost per

Tevian Dray, Jason Janesky, Corinne A. Manogue

We discuss our preliminary attempts to extend previous work on 2x2 Hermitian octonionic matrices with non-real eigenvalues to the 3x3 case.

David Bessis, Francois Digne, Jean Michel

We state a conjecture about centralizers of certain roots of central elements in braid groups, and check it for Artin braid groups and some other cases. Our proof makes use of results by Birman-Ko-Lee; we give a new intrinsic account of these results.

F. Jouhet, J. Zeng

Some new identities for Schur functions are proved. In particular, we settle in the affirmative a recent conjecture of Ishikawa-Wakayama and solve a problem raised by Bressoud.

Jan Adriaenssens, Lieven Le Bruyn

In this paper we introduce and study the local quiver as a tool to investigate the etale local structure of moduli spaces of theta-stable representations of quivers. As an application we determine the dimension vectors associated to irreducible representations of torus knot groups.

I. Heckenberger, A. Schueler

We study the q-Clifford algebras Cl_q(N,c), called FRT-Clifford algebras, introduced by Faddeev, Reshetikhin and Takhtajan. It is shown that Cl_q(N,c) acts on the q-exterior algebra Λ(O_q^N). Moreover, explicit formulas for the embedding of U_q(so_N) into Cl_q(N,c) and its relation to the vector and spin representations of U_q(so_N) are given and proved. Key

U. Bruzzo, F. Pioli

By means of a Fourier-Mukai transform we embed moduli spaces of stable bundles on an algebraic curve C as isotropic subvarieties of moduli spaces of mu-stable bundles on the Jacobian variety J(C). When g(C)=2 this provides new examples of special Lagrangian submanifolds.

Erik Bedos, Gerard J. Murphy, Lars Tuset

We study the concept of co-amenability for a compact quantum group. Several conditions are derived that are shown to be equivalent to it. Some consequences of co-amenability that we obtain are faithfulness of the Haar integral and automatic norm-boundedness of positive linear functionals on the quantum group's Hopf *-algebra (neither of these properties

Toshihiko Masuda

We construct approximately inner actions of discrete amenable groups on strongly amenable subfactors of type II_1 with given invariants, and obtain classification results under some conditions. We also study the lifting of the relative χgroup.

Jin-Hong Kim

Let X be a smooth closed oriented non-spin 4-manifold with even intersection form kE_8\oplus nH. In this article we show that n\geq |k| on X. Thus we confirm the 10/8-conjecture affirmatively. As an application, we also give an estimate of intersection forms of spin coverings of non-spin 4-manifolds with even intersection forms.

Tevian Dray, Jason Janesky, Corinne A. Manogue

We extend previous work on the eigenvalue problem for Hermitian octonionic matrices by discussing the case where the eigenvalues are not real, giving a complete treatment of the 2x2 case, and summarizing some prelimenary results for the 3x3 case.

S. Nussinov

In this short note we show that (I) in a QCD-like theory with four (rather than two) degenerate flavors $ud u'd'$, the $ππ'$ scattering length is positive (attractive); and (II) in QCD with only two (u,d) degenerate flavors the I=2 (say, $π^+π^+$ hadronic) scattering length is, in the large $N_C$ limit, repulsive. $π(π')$ are the lowest physi

S. Nussinov

We prove that the Fourier transform of the exponential $e^{-\b V(R)}$ of the {\bf static} interquark potential in QCD is positive. It has been shown by Eliott Lieb some time ago that this property allows in the same limit of static spin independent potential proving certain mass relation between baryons with different quark flavors.

R. R. Metsaev

Manifestly supersymmetric formulation of eleven dimensional supergravity in the framework of light-cone approach is discussed.

C. P. Burgess, B. Dolan

We show how particle-vortex duality implies the existence of a large non-abelian discrete symmetry group which relates the electromagnetic response for dual two-dimensional systems in a magnetic field. For conductors with charge carriers satisfying Fermi statistics (or those related to fermions by the action of the group), the resulting group is known to imp

Andrei Litvintsev

We study the supersymmetric kink with higher derivative and momentum cut-off regularization schemes. We introduce the new momentum cut-off regularization scheme which we call ``generalized momentum cut-off''. A new, explicit computation for the central charge anomaly for this scheme is described in detail. The calculation of the first order mass corr

H. Arfaei, M. H. Yavartanoo

In the context of the noncommutative QED we consider few phenomena which reflect the noncommutativity. In all of them the new interactions in the Feynmann diagrams that are responsible for the deviation from the standard QED results. These deviations appear as the violations of Lorentz symmetry. We suggest experimental situations where these effects may be o

Joan Simon

The relation among spacetime supersymmetry algebras and superbrane actions is further explored. It is proved that $SL(2,\bR)$ belongs to the automorphism group of the ${\cal N}=2$ D=10 type IIB SuperPoincaré algebra. Its SO(2) subgroup is identified with a non-local SO(2) transformation found in hep-th/9806161. Performing T-duality, new non-local transformat

Y. Artstein, V. Kaplunovsky, J. Sonnenschein

We study BPS saturated domain walls in supersymmetric SU(N) Yang-Mills theories in the large N limit. We focus on the Seiberg-Witten regime of ${\cal N}=2$ theory perturbed by a small mass ($m<O(\Lambda/N^4)$) and determine the wall profile by numerically minimizing its energy density. Similar to the SU(2) wall studied in a previous work, the SU(N) wall has

W. Melnitchouk

Quark-hadron duality addresses some of the most fundamental issues in strong interaction physics, in particular the nature of the transition from the perturbative to non-perturbative regions of QCD. I summarize recent developments in quark-hadron duality in lepton-hadron scattering, and outline how duality can be studied at future high-luminosity facilities

Michael S. Chanowitz

In scalar field theories the Landau pole is an ultraviolet singularity in the running coupling constant that indicates a mass scale at which the theory breaks down and new physics must intervene. However, new physics at the pole will in general affect the running of the low energy coupling constant, which will in turn affect the location of the pole and the

Jiri Chyla

Elements of the alternative approach to hard collisions of photons, proposed recently by the author, are reviewed, with particular attention to QCD analysis of $F^γ_2$. This approach is based on clear separation of genuine QCD effects from those of pure QED origin and does not rely on the assumption that parton distribution functions of the photon behave as

A. Bueno, M. Campanelli, M. Laveder, J. Rico

The accurate prediction of the neutrino beam produced in muon decays and the absence of opposite helicity contamination for a particular neutrino flavor make a future neutrino factory the ideal place to look for the lepton flavor violating (LFV) decays of the kind $\mu^+\ra e^+\nuebar\numu$ and lepton number violating (LNV) processes like $\mu^-\ra e^-\nue\n

D. Schildknecht

We summarize recent work on low-x deep inelastic scattering. The generalized vector dominance/color-dipole picture (GVD/CDP) implies a scaling behavior for $σ_{γ^* p} (W^2, Q^2)\cong σ_{γ^* p}(η)$, with $η= (Q^2 + m^2_0)/Λ^2 (W^2)$ and yields an excellent representation of the experimental results on $σ_{γ^* p}(η)$.

F. O. Durães, F. S. Navarra, M. Nielsen

The $NDΛ_c$ and $ND^*Λ_c$ form factors are evaluated in a full QCD sum rule calculation. We study the double Borel sum rule for the three point function of one meson one nucleon and one $Λ_c$ current up to order six in the operator product expansion. The double Borel transform is performed with respect to the nucleon and $Λ_c$ momenta, and the form factor is

J. Bartels, H. Jung, A. Kyrieleis

We calculate the cross section for q(\bar q)g-production in diffractive DIS with finite fermion masses and zero momentum transfer. The calculation is done in the leading log(1/x_p) approximation and is valid for the region of high diffractive masses (small beta). We apply our cross section formula to diffractive charm production at HERA: in a Monte-Carlo-Sim

G. Ramachandran, P. N. Deepak

We show that it is possible to empirically partition the differential cross section for pp->pp pi0 into initial singlet and triplet differential cross sections in a model independent way which can be implemented using the existing technological capabilities at the PINTEX facility to study the reaction employing polarized beam or polarized target or both simu

M. Göckeler, H. Hehl, P. E. L. Rakow, A. Schäfer

We investigate the eigenvalues and eigenvectors of the staggered Dirac operator in the vicinity of the chiral phase transition of quenched SU(3) lattice gauge theory. We consider both the global features of the spectrum and the local correlations. In the chirally symmetric phase, the local correlations in the bulk of the spectrum are still described by rando

Michael Creutz

I discuss some of the historical circumstances that drove us to use the lattice as a non-perturbative regulator. This approach has had immense success, convincingly demonstrating quark confinement and obtaining crucial properties of the strong interactions from first principles. I wrap up with some challenges for the future.

S. Digal, E. Laermann, H. Satz

We propose that in QCD with dynamical quarks, colour deconfinement occurs when an external field induced by the chiral condensate strongly aligns the Polyakov loop. This effect sets in at the chiral symmetry restoration temperature $T_χ$ and thus makes deconfinement and chiral symmetry restoration coincide. The predicted singular behavior of Polyakov loop su

S. Collins, C. T. H. Davies

We describe a non-perturbative determination of $c_A$ using correlators containing the axial-vector and pseudoscalar currents at zero and non-zero momentum. We apply the method of Bhattacharya et al to extract $c_A$ from the requirement that the ratio of appropriate correlators for the PCAC relation becomes independent of time in the excited state region. We

L Del Debbio, A Di Giacomo, B Lucini

We construct the creation operator of a vortex for SU(2) pure gauge theory using the methods developed for monopoles. We interpret its vacuum expectation value as a disorder parameter for the deconfinement phase transition and find that it behaves in the vacuum in a similar way to monopoles. Results are extrapolated to the thermodynamical limit using finite-

S. Capitani, M. Gockeler, R. Horsley, B. Klaus

We present calculations of matrix elements of 4-quark operators in the pion and in the nucleon extracted from quenched Monte Carlo simulations at beta = 6.0 using Wilson fermions. These operators are relevant for higher-twist effects. We are particularly careful to avoid mixing with lower-dimensional operators by choosing appropriate flavour structures.

Jochen Schwiening, representing the BABAR-DIRC Collaboration

The DIRC, a novel type of Cherenkov ring imaging device, is the primary hadronic particle identification system for the BABAR detector at the asymmetric B-factory, PEP-II at SLAC. BABAR began taking data with colliding beams mode in late spring 1999. This paper describes the performance of the DIRC during the first 16 months of operation.

G. Raven

Using 8.5M B-anti-B events recorded by the BABAR detector the yield of inclusive J/psi, the branching ratios of psi(2S) and chi_C1 are presented. Combining the charmonium state with either a K+,KS, K*+ or K*0 exclusive B decays are reconstructed and their branching ratios determined. Using the fully reconstructed decays, both the B0 and B+ masses and their d

A. K. Ciftci, S. Sultansoy, O. Yavas, M. Yilmaz

Main parameters of linac-ring type $phi$ factory and 1-5 GeV energy proton synchrotron proposed in the framework of the Turkic Accelerator Complex (TAC) Project are discussed

M. I. Wanas

Absolute parallelism (AP) geometry is frequently used for physical applications. Although it is wider than Riemannian geometry, it has two main defects. The first is that its path equation does not represent physical trajectories of any test particle. The second is the identical vanishing of its curvature tensor. The present work shows that parameterizing th

Richard Kerner, Jerome Martin, Salvatore Mignemi, Jan-Willem van Holten

We study in detail the equations of the geodesic deviation in multidimensional theories of Kaluza-Klein type. We show that their 4-dimensional space-time projections are identical with the equations obtained by direct variation of the usual geodesic equation in the presence of the Lorentz force, provided that the fifth component of the deviation vector satis

Jerzy Matyjasek

The approximate renormalized stress-energy tensor of the quantized massive conformally coupled scalar field in the spacetime of electrically charged nonlinear black hole is constructed. It is achieved by functional differentiation of the lowest order of the DeWitt-Schwinger effective action involving coincidence limit of the Hadamard-Minakshisundaram-DeWitt-

Alexander I. Nesterov

We obtain the integral formulae for computing the tetrads and metric components in Riemann normal coordinates and Fermi coordinate system of an observer in arbitrary motion. Our approach admits essential enlarging the range of validity of these coordinates. The results obtained are applied to the geodesic deviation in the field of a weak plane gravitational

Steven Bird, Mark Liberman

`Linguistic annotation&#39; covers any descriptive or analytic notations applied to raw language data. The basic data may be in the form of time functions - audio, video and/or physiological recordings - or it may be textual. The added notations may include transcriptions of all sorts (from phonetic features to discourse structures), part-of-speech and sense

F. M. Ramos, C. Rodrigues Neto, R. R. Rosa

We describe a simple and accurate framework for modeling the statistical behavior of both fully developed turbulence and short-term dynamics of financial markets based on the formalism of Tsallis&#39; generalized non-extensive thermostatistics. Within this framework, we show that intermittency and non-extensivity are naturally linked by the entropic paramete

Michael N. Leuenberger, Daniel Loss

Quantum computing and quantum communication are remarkable examples of new information processing technologies that arise from the coherent manipulation of spins in nanostructures. We review our theoretical proposal for using electron spins in quantum-confined nanostructures as qubits. We present single- and two-qubit gate mechanisms in laterally as well as

Anders W. Sandvik

In Phys. Rev. Lett. 84, 4204 (2000) (cond-mat/9905379), Kato et al. presented quantum Monte Carlo results indicating that the critical concentration of random non-magnetic sites in the two-dimensional antiferromagnetic Heisenberg model equals the classical percolation density; pc=0.407254. The data also suggested a surprising dependence of the critical expon

Neepa T. Maitra, Kieron Burke

Time-dependent density functionals in principle depend on the initial state of the system, but this is ignored in functional approximations presently in use. For one electron it is shown there is no initial-state dependence: for any density, only one initial state produces a well-behaved potential. For two non-interacting electrons with the same spin in one-

Marc Ruhlander, C. M. Soukoulis

Several phenomena related to the critical behaviour of non-interacting electrons in a disordered 2d tight-binding system with a magnetic field are studied. Localization lengths, critical exponents and density of states are computed using transfer matrix techniques. Scaling functions of isotropic systems are recovered once the dimension of the system in each

C. Stephen Hellberg

A theoretical model for the reentrant charge-order transition in the manganites is examined. This transition is studied with a purely electronic model for the Mn electrons: the extended Hubbard model. The electron-phonon coupling results in a large nearest-neighbor repulsion between electrons. Using a finite-temperature Lanczos technique, the model is diagon

C. Godreche, J. M. Luck

We present a systematic study of the statistics of the occupation time and related random variables for stochastic processes with independent intervals of time. According to the nature of the distribution of time intervals, the probability density functions of these random variables have very different scalings in time. We analyze successively the cases wher

M. Hervieu, R. Mahendiran, A. Maignan, C. Martin

We show that nanostructure and resistivity of Pr0.5Ca0.5Mn0.98Cr0.02O3 are sensitive to whether the sample is zero-field-cooled (ZFC) of field-cooled (FC) either in the &#39;self magnetic field (H = 2 T)&#39; of the electron microscope or under the external magnetic field of 2 T. FC resistivity at H = 2 T is lower than ZFC values below 140 K. The average val

M. Terraneo, I. Guarneri

We numerically analyze the distribution of scattering resonance widths in one- and quasi-one dimensional tight binding models, in the localized regime. We detect and discuss an algebraic decay of the distribution, similar, though not identical, to recent theoretical predictions.

Sebastian Risau-Gusman, Mirta B. Gordon

We study the typical properties of polynomial Support Vector Machines within a Statistical Mechanics approach that allows us to analyze the effect of different normalizations of the features. If the normalization is adecuately chosen, there is a hierarchical learning of features of increasing order as a function of the training set size.

C. Morais Smith, N. Hasselmann, A. H. Castro Neto

We investigate the stripe pinning produced by Nd and Zn co-dopants in cuprates via a renormalization group approach. The two dopants play fundamentally different roles in the pinning process. While Nd induces a correlated pinning potential that traps the stripes in a flat phase and suppresses fluctuations, Zn pins the stripes in a disordered manner and promo

Edward McCann, Vladimir I. Fal&#39;ko

We study subgap transport in a ferromagnet-superconductor junction at low temperature due to Andreev reflection. The mismatch of spin polarized current in the ferromagnet and spinless current in the superconductor results in an additional contact resistance which can be reduced by magnon emission in the ferromagnet. Using the s-f model and focusing on half-m

P. J. Jensen

The current efforts to fabricate non-volatile magnetic recording media with a high areal density is deteriorated by the increasing temporal instability of the stored information. If the stored energy per magnetic particle competes with the thermal energy, spontaneous magnetic reversal processes may occur. Deposition of the magnetic particles on top of an ant

C. Rascon, A. O. Parry

Experimental methods allow the shape and chemical composition of solid surfaces to be controlled at a mesoscopic level. Exposing such structured substrates to a gas close to coexistence with its liquid can produce quite distinct adsorption characteristics compared to that occuring for planar systems, which may well play an important role in developing techno

F. Hohls, U. Zeitler, R. J. Haug, K. Pierz

We present high frequency measurements of the diagonal conductivity sigma_xx of a two dimensional electron system in the integer quantum Hall regime. The width of the sigma_xx peaks between QHE minima is analyzed within the framework of scaling theory using both temperature T=100-700 mK and frequency f <= 6 GHz in a two parameter scaling ansatz. For the plat

A. Hasmy, E. Medina, P. A. Serena

Title: From favorable atomic configurations to supershell structures: a new interpretation of conductance histograms Authors: A. Hasmy (IVIC), E. Medina (IVIC), P.A. Serena (CSIC,IVIC) Comments: 7 pages, 3 figures, cond-mat.anwar.10825 Subj-class: Soft Condensed Matter

J. C. de Lima, V. H. F. dos Santos, T. A. Grandi, R. S. de Biasi

The hcp-fcc transformation induced in cobalt powder by ball milling at room temperature was studied using the excess Gibbs free energy for the metals, in nanometric form, to calculate the activation energy that the atoms need for the phase transformation to occur. The crystalline component of the nanocrystalline cobalt produced in our laboratory, via ball mi

Stefan Odenbach, Mario Liu

Direct and unambiguous experimental evidence for the magnetic force density being of the form $M\nabla B$ in a certain geometry - rather than being the Kelvin force $M\nabla H$ - is provided for the first time. (M is the magnetization, H the field, and B the flux density.)

F. Semadeni, A. Amato, B. Roessli, P. Böni

The temperature-concentration phase diagram of the Si-doped spin-Peierls compound CuGeO$_{3}$ is investigated by means of neutron scattering and muon spin rotation spectroscopy in order to determine the microscopic distribution of the magnetic and lattice dimerised regions as a function of doping. The analysis of the zero-field muon spectra has confirmed the

Francesca Colaiori, M. A. Moore

We study the mode-coupling approximation for the KPZ equation in the strong coupling regime. By constructing an ansatz consistent with the asymptotic forms of the correlation and response functions we determine the upper critical dimension d_c=4, and the expansion z=2-(d-4)/4+O((4-d)^2) around d_c. We find the exact z=3/2 value in d=1, and estimate the value

U. Michelucci, A. P. Kampf, A. Pimenov

The low temperature behaviour of the in-plane and c-axis conductivity of electron-doped cuprates like NCCO is examined; it is shown to be consistent with an isotropic quasiparticle scattering rate and an anisotropic interlayer hopping parameter which is non-zero for planar momenta along the direction of the d$_{x^2-y^2}$ order parameter nodes. Based on these

Kristen A. Fichthorn, Matthias Scheffler

When two or more atoms bind to a solid surface, the substrate can mediate an interaction between them. In this paper, we use density-functional theory to quantify the substrate-mediated pair interaction between two adatoms on a compressively strained Ag(111) surface and on unstrained Ag(111). On the strained surface, the elastic interaction is significant ov

Aleksey D. Drozdov, Al Dorfmann

Constitutive equations are derived for the viscoelastic response of rubbery polymers at finite strains. A polymer is thought of as a network of long chains connected to temporary junctions. At a random time, a chain detaches from a junction, which is treated at transition from its active state to the dangling state. A dangling chain randomly captures a new j

V. Lisy, B. Brutovsky

Beginning from the first neutron spin-echo study of the shape fluctuations of microemulsion droplets [J.S. Huang, S.T. Milner, B. Farago, and D. Richter, Phys. Rev. Lett. 59, 2600 (1987)] these experiments are incorrectly interpreted in the literature. This is due to an inappropriate account for the fluctuations and the erroneous application of the original

Takahiro Hatano, Shin-ichi Sasa

We study Langevin dynamics describing nonequilibirum steady states. Employing the phenomenological framework of steady state thermodynamics constructed by Oono and Paniconi [Prog. Theor. Phys. Suppl. {\bf130}, 29 (1998)], we find that the extended form of the second law which they proposed holds for transitions between steady states and that the Shannon entr

B. Roessli, U. Staub, A. Amato, D. Herlach

We report high-resolution x-ray diffraction, muon-spin-rotation spectroscopic and specific heat measurements in the double spin-chains compound $\rm LiCu_2O_2$. The x-ray diffraction results show that the crystal structure of $\rm LiCu_2O_2$ ~is orthorhombic down to T=10K. Anisotropic line-broadening of the diffraction peaks is observed, indicating disorder

Ar. Abanov, Andrey V. Chubukov, Jörg Schmalian

We demonstrate that the feedback effect from bosonic excitations on fermions, which in the past allowed one to verify the phononic mechanism of a conventional, $s-$wave superconductivity, may also allow one to experimentally detect the ``fingerprints&#39;&#39; of the pairing mechanism in cuprates. We argue that for spin-mediated $d-$wave superconductivity, t

F. Bertoldi, K. M. Menten, E. Kreysa, C. L. Carilli

We discuss results from sensitive, wide-field imaging of the millimeter extragalactic background using the Max-Planck Millimeter Bolometer array (MAMBO) at the IRAM 30m telescope.