June 2001 arXiv papers — page 2

NOMAD Collaboration, P. Astier

Results from the nu_tau appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic tau decays, significantly improving the overall sensitivity of the experiment to oscillations. The "blind analysis" of all topologies yields no evidence for an oscillation signal. In the two-family oscill

Maia Kalmakhelidze, Nina Roinishvili, Manana Svanidze

Primary Cosmic Ray Chemical Composition is investigated in energy region close to 10**16 eV. Studies are based on comparisons of gamma-hadron families observed by Pamir and Pamir-Chacaltaya Collaboration, with families generated by means of quasi-scaling model MC0. It is shown, that all characteristics of observed families, including their intensity, are in

D. I. Jones, N. Andersson

In this paper we model the gravitational wave emission of a freely precessing neutron star. The aim is to estimate likely source strengths, as a guide for gravitational wave astronomers searching for such signals. We model the star as a partly elastic, partly fluid body with quadrupolar deformations of its moment of inertia tensor. The angular amplitude of t

D. Yu. Tsipenyuk, V. A. Andreev

In present work the generalization of Einstein's special theory of relativity on 5-dimentional space is considered, in which as fifth coordinates we consider the interval s of a particle. 5-dimentional vectors in this space are isotropic both for mass, and for massless of particles. In extended space, offered by the authors, there is a possibility in add

Henning Christiansen

Grammars written as Constraint Handling Rules (CHR) can be executed as efficient and robust bottom-up parsers that provide a straightforward, non-backtracking treatment of ambiguity. Abduction with integrity constraints as well as other dynamic hypothesis generation techniques fit naturally into such grammars and are exemplified for anaphora resolution, coor

Vasiliki Plerou, Parameswaran Gopikrishnan, Xavier Gabaix, H. Eugene Stanley

We address the question of how stock prices respond to changes in demand. We quantify the relations between price change $G$ over a time interval $Δt$ and two different measures of demand fluctuations: (a) $Φ$, defined as the difference between the number of buyer-initiated and seller-initiated trades, and (b) $Ω$, defined as the difference in number of shar

E. E. Vdovin, Yu. N. Khanin, A. V. Veretennikov, A. Levin

We use magnetotunnelling spectroscopy as a non-invasive probe to produce two-dimensional spatial images of the probability density of an electron confined in a self-assembled semiconductor quantum dot. The images reveal clearly the elliptical symmetry of the ground state and the characteristic lobes of the higher energy states.

Y. -D. Chuang, A. D. Gromko, D. S. Dessau, T. Kimura

We used high resolution angle-resolved photoemission spectroscopy to reveal the Fermi surface and key transport parameters of the metallic state of the layered Colossal Magnetoresistive (CMR) oxide La1.2Sr1.8Mn2O7. With these parameters the calculated in-plane conductivity is nearly one order of magnitude larger than the measured DC conductivity. This discre

T. Uezu

In a previous letter, we studied learning from stochastic examples by perceptrons with Ising weights in the framework of statistical mechanics. Under the one-step replica symmetry breaking ansatz, the behaviours of learning curves were classified according to some local property of the rules by which examples were drawn. Further, the conditions for the exist

Niels Boye Olsen, Tage Christensen, Jeppe C. Dyre

Based on the Tool-Narayanaswami formalism for structural relaxation we propose an experiment which independent of the relaxation time distribution determines the structural relaxation rate by subtracting relaxations following two different temperature jumps. In particular, the experiment makes it possible to evaluate the relaxation rate immediately following

B. Jackson, E. Zaremba

In this paper, we develop a numerical procedure for investigating the dynamics of trapped Bose gases based on the ZGN theory. The dynamical equations used consist of a generalized Gross-Pitaevskii equation for the condensate order parameter and a semiclassical kinetic equation for the thermal cloud. The former is solved using a fast Fourier transform split-o

Shu Chen, H. Buettner, J. Voit

We investigate an asymmetric zig-zag spin ladder with different exchange integrals on both legs using bosonization and renormalization group. When the leg exchange integrals and frustration both are sufficiently small, renormalization group analysis shows that the Heisenberg critical point flows to an intermediate-coupling fixed point with gapless excitation

Goran Johansson, Andreas Kack, Goran Wendin

We calculate the spectral density of voltage fluctuations in a Single Electron Transistor (SET), biased to operate in a transport mode where tunneling events are correlated due to Coulomb interaction. The whole spectrum from low frequency shot noise to quantum noise at frequencies comparable to the SET charging energy $(E_{C}/\hbar)$ is considered. We discus

Satoko Itaya, Tatsuya Uezu

We study a dynamical system model of an idiotypic immune network with a small number of degrees of freedom, mainly focusing on the effect of a threshold above which antibodies can recognise antibodies. The response of the system to invasions by antigens is investigated in the both models with and without the threshold and it turns out that the system changes

Eduardo C. Marino, Marcello B. Silva Neto

We propose a model for high-T$_{c}$ superconductors, valid for $0\leqδ\leqδ_{SC}$, that includes both the spin fluctuations of the Cu$^{++}$ magnetic ions and of the O$^{--}$ doped holes. Spin-charge separation is taken into account with the charge of the doped holes being associated to quantum skyrmion excitations (holons) of the Cu$^{++}$ spin background.

S. Dattagupta, A. M. Jayannavar, N. Kumar

The problem of diamagnetism, solved by Landau, continues to pose fascinating issues which have relevance even today. These issues relate to inherent quantum nature of the problem, the role of boundary and dissipation, the meaning of thermodynamic limits, and above all, the quantum-classical crossover occasioned by environment-induced decoherence. The Landau

R. Torre, A. Taschin, M. Sampoli

The dynamics of the fragile glass-forming o-ter-phenyl is investigated by time-resolved transient grating experiment with an heterodyne detection technique in a wide temperature range. We investigated the dynamics processes of this glass-former over more then 6 decades in time with an excellent signal/noise. Acoustic, structural and thermal relaxations have

Raul O. Vallejos, Caio H. Lewenkopf, Yuval Gefen

We study the orthogonality catastrophe due to a parametric change of the single-particle (mean field) Hamiltonian of an ergodic system. The Hamiltonian is modeled by a suitable random matrix ensemble. We show that the overlap between the original and the parametrically modified many-body ground states, $S$, taken as Slater determinants, decreases like $n^{-k

S. Schwieger, W. Nolting

We investigate the influence of s-d or p-d hybridization to d-band ferromagnetism to estimate the importance of hybridization for the magnetic properties of transition metals. To focus our attention to the interplay between hybridization and correlation we investigate a simple model system consisting of two non-degenerated hybridized bands, one strongly corr

Jonathan P. K. Doye, David J. Wales, Wolfgang Branz, Florent Calvo

We locate putative global minima for (C_60)_N clusters modelled by the potential of Pacheco and Prates-Ramalho up to N=105. These minima are based on icosahedral packing up to N=15, but above this size the lowest-energy structures are decahedral or close-packed. Although structures based on the 98-molecule Leary tetrahedron, which have been inferred from exp

Raphael Exartier, Leticia F. Cugliandolo

We study numerically the time evolution of the transport properties of layered superconductors after different preparations. We show that, in accordance with recent experiments in BSCCO performed in the second peak region of the phase diagram (Portier et al, 2001), the relaxation strongly depends on the initial conditions and is extremely slow. We investigat

Pierre Sens, Hervé Isambert

The influence of an electric field on a poorly conductive membrane such as a lipid bilayer is studied theoretically. The unbalanced electric stress created by an ionic current across a non-perfectly flat membrane gives rise to a destabilizing surface energy enhancing undulations. The deformation of a membrane attached to a frame and the subsequent force on t

D. J. Bicout, T. W. Burkhardt

The probability that a randomly accelerated particle in two dimensions has not yet left a simply connected domain ${\cal A}$ after a time $t$ decays as $e^{-E_0t}$ for long times. The same quantity $E_0$ also determines the confinement free energy per unit length $Δf=k_BT\thinspace E_0$ of a semiflexible polymer in a narrow cylindrical pore with cross sectio

L. Turban

The conformal mapping w=(L/2π)\ln z transforms the critical plane with a radial perturbation αρ^{-y} into a cylinder with width L and a constant deviation α(2π/L)^y from the bulk critical point when the decay exponent y is such that the perturbation is marginal. From the known behavior of the homogeneous off-critical system on the cylinder, one may deduce th

S. Cowell, H. Heiselberg, I. E. Mazets, J. Morales

We calculate the energy and condensate fraction for a dense system of bosons interacting through an attractive short range interaction with positive s-wave scattering length $a$. At high densities, $n>>a^{-3}$, the energy per particle, chemical potential, and square of the sound speed are independent of the scattering length and proportional to $n^{2/3}$, as

L. Turban

The critical behaviour of directed self-avoiding walks is studied on parabolic-like systems with a free boundary at x=\pm Ct^α. Using a scaling argument, 1/C is shown to be a marginal variable when α=ν_\perp/ν_\parallel=1/2, i.e., on a parabola. As a consequence the directed walk may display varying local exponents. Such a behaviour is indeed observed for re

F. Igloi, L. Turban, B. Berche

We consider m two-dimensional semi-infinite planes of Ising spins joined together through surface spins and study the critical behaviour near to the junction. The m=0 limit of the model - according to the replica trick - corresponds to the semi-infinite Ising model in the presence of a random surface field (RSFI). Using conformal mapping, second-order pertur

L Turban, J-M Debierre

Using the numerical results of the finite-size scaling study of the q-state Potts model by Bloete and Nightingale, we obtain conjectured expressions for the universal amplitude of the free energy density.

S. N. Burmistrov, T. Satoh

We study the oscillation spectrum and acoustic properties of a liquid drop in the phase-separated fluid when the interfacial dynamics of phase conversion can be described in terms of the kinetic growth coefficient. For a readily mobile interface, i.e., as the growth coefficient becomes comparable with a reciprocal of the acoustic impedance, anomalous behavio

Tsunehiko Araki, Makoto Tsubota, Sergey K. Nemirovskii

The energy spectrum of superfluid turbulence in the absence of the normal fluid is studied numerically. In order to discuss the statistical properties, we calculated the energy spectra of the 3D velocity field induced by dilute and dense vortex tangles respectively, whose dynamics is calculated by the Biot-Savart law. In the case of a dense tangle, the slope

Yueh-Nan Chen, Der-San Chuu, T. Brandes, B. Kramer

The superradiant decay rate and frequency shift of a Wannier exciton in a one-dimensional quantum wire are studied. It is shown that the dark mode exciton can be examined experimentally when the quantum wire is embedded in a planar microcavity. It is also found that the decay rate is greatly enhanced as the cavity length $L_{c}$ is equal to the multiple wave

Swapan K. Pati, S. Ramasesha, Diptiman Sen

Quantum magnetism in low dimensions has been one of the central areas of theoretical research for many decades now. One of the key reasons for the long standing interest in this field has been the existence of simplified models, which serve as paradigms for understanding the role of strong interactions in many-electron systems. Although simple, these models

Izumi Hase, Kunihiko Yamaji

First principle FLAPW band calculations of the new superconductor MgB2 were performed and the polarization function P12(Q) between the two p-bands mainly formed of boron pz-orbital was calculated. We found that P12(Q) is substantially enhanced around Q=(0,0,p/c), which supports the two-band mechanism of superconductivity for MgB2. P12(Q) peaks at Qz ~ 0.3(2p

J. R. Anglin

A combination of analytical and numerical approaches obtains the complete dispersion curve for surface excitations in a condensate held in a plane linear potential. This improvement on previous approximate results yields an accurate formula for the local Landau critical velocity for vortex nucleation at the surface of a sufficiently large condensate, which a

Daijiro Yoshioka

Effect of periodic potential on the stripe phase realized in the higher Landau levels is investigated by the Hartree-Fock approximation. The period of the potential is chosen to be two to six times of the fundamental period of the stripe phase. It is found that the stripe aligns perpendicularly to the external potential in contrast to a naive expectation and

H. K. Lee, R. H. Swendsen

In recent years, a second fluid-fluid phase transition has been reported in several materials at pressures far above the usual liquid-gas phase transition. In this paper, we introduce a new model of this behavior based on the Lennard-Jones interaction with a modification to mimic the different kinds of short-range orientational order in complex materials. We

J. B. Hutchings, G. A. Kriss, R. F. Green, M. Brotherton

Spectroscopic data in wavelengths 900--3000A have been obtained in a low flux state of the nucleus of the Seyfert 1 galaxy NGC 3516. The line profiles show P Cygni characteristics, particularly in O VI 1032A, and are compared with data from an earlier higher state. The profiles are suggestive of, and consistent with, an accelerating wind driven by a disk con

Rosanne Di Stefano, L. H. Ford, Hongwei Yu, D. J. Fixsen

The problem of formulating a fully consistent quantum gravity theory (QGT) has not yet been solved. Even before we are able to work out the details of a complete theory, however, we do know some important qualitative features to be expected in any quantum theory. Fluctuations of the metric, for example, are expected and are associated with fluctuations of th

S. G. Djorgovski, D. A. Frail, S. R. Kulkarni, R. Sari

Cosmic gamma-ray bursts are one of the great frontiers of astrophysics today. They are a playground of relativists and observers alike. They may teach us about the death of stars and the birth of black holes, the physics in extreme conditions, and help us probe star formation in the distant and obscured universe. In this review we summarise some of the remar

James Muzerolle, Lynne Hillenbrand, Nuria Calvet, Lee Hartmann

We present an analysis of the accretion properties of the members of the TW Hydrae association. The Halpha emission line profile provides explicit evidence of an active accretion flow in 3 out of 23 observed members of the association; we use radiative transfer models to derive approximate accretion rates for these 3 objects. The resulting accretion rates fo

Philip Kaaret

Six x-ray point sources, with luminosities of $4 \times 10^{38} - 2 \times 10^{39} \rm ergs s^{-1}$ in the 0.4--7 keV band, were detected in Chandra observations of the spiral galaxy M100. One source is identified with supernova SN 1979C and appears to have roughly constant x-ray flux for the period 16--20 years after the outburst. The x-ray spectrum is soft

Lori M. Lubin, Allan Sandage

We review a sample of the early literature in which the reality of the expansion is discussed, explain Hubble's reticence to accept the expansion as real, and contrast the Tolman surface brightness test with three other modern tests. We search for the Tolman surface brightness depression with redshift using the Hubble Space Telescope (HST) data from Pape

G. T. Birk, A. R. Crusius--Waetzel, H. Lesch

Extremely flat and inverted radio spectra as observed in galactic nuclei and BL Lac sources are still a challenge for fast particle acceleration models. Continuous acceleration by electric fields in reconnection regions can result in almost constant particle distributions and thereby in inverted synchrotron spectra independent from the details of the injecte

Richard de Grijs

The last tidal encounter between M82 and M81, some 500 Myr ago, had a major impact on what was probably an otherwise normal, quiescent disc galaxy. It caused a concentrated burst of star formation in the form of massive star clusters, which decreased rapidly, within a few 100 Myr. The current starburst in the centre of the galaxy is likely either due to larg

Lori M. Lubin, Allan Sandage

Photometric data for 34 early-type galaxies in the three high-redshift clusters Cl 1324+3011 (z = 0.76), Cl 1604+4304 (z = 0.90), and Cl 1604+4321 (z = 0.92), observed with the Hubble Space Telescope (HST) and with the Keck 10-meter telescopes by Oke, Postman & Lubin, are analyzed to obtain the photometric parameters of mean surface brightness, magnitudes fo

Rudiger Schopper, Guido T. Birk, Harald Lesch

Magnetic Reconnection is an efficient and fast acceleration mechanism by means of direct electric field acceleration parallel to the magnetic field. Thus, acceleration of particles in reconnection regions is a very important topic in plasma astrophysics. This paper shows that the conventional analytical models and numerical test particle investigations can b

S. Jordan, P. Schmelcher, W. Becken

In only three of the 61 known magnetic white dwarfs helium has been identified unambiguously while about 20% of all non-magnetic stars of this class are known to contain HeI or HeII. Until recently, data for HeI data were available only for magnetic fields below 20MG. This changed with the publication of extensive data by the group in Heidelberg. The corresp

N. A. Arkhipova, T. Kahniashvili, V. N. Lukash

The time evolution of galaxy cluster abundance is used to constrain cosmological parameters in dark matter models containing a fraction of hot particles (massive neutrino). We test the modified MDM models with cosmic gravitational waves which are in agreement with observational data at $z=0$, and show that they do not pass the cluster evolution test and ther

R. H. Sanders

Milgrom has proposed that the appearance of discrepancies between the Newtonian dynamical mass and the directly observable mass in astronomical systems could be due to a breakdown of Newtonian dynamics in the limit of low accelerations rather than the presence of unseen matter. Milgrom's hypothesis, modified Newtonian dynamics or MOND, has been remarkabl

R. Arlt, A. Brandenburg

The possibility of non-helical large scale dynamo action is investigated using three-dimensional simulations of global accretion discs as well as idealized local simulations without rotation and only shear. Particular emphasis is placed on a certain correlation between vorticity and azimuthal velocity gradient which has been predicted to drive large scale dy

N. Lehner, A. W. Fullerton, K. R. Sembach, D. L. Massa

A primary goal of the FUSE mission is to understand the origin of the O VI ion in the interstellar medium of the Galaxy and the Magellanic Clouds. Along sightlines to OB-type stars, these interstellar components are usually blended with O VI stellar wind profiles, which frequently vary in shape. In order to assess the effects of this time-dependent blending

M. Catelan, F. R. Ferraro, R. T. Rood

We present a detailed analysis of the "second-parameter pair" of globular clusters M3 (NGC 5272) and Palomar 3. Our main results can be summarized as follows: i) The horizontal-branch (HB) morphology of M3 is significantly bluer in its inner regions (observed with the Hubble Space Telescope) than in the cluster outskirts (observed from the ground), i

Silvano Molendi, Fabio Gastaldello

We revisit the XMM-Newton observation of M87 to make a new and more detailed measurement of the metal abundance profile. After having verified that spectral fits with single temperature models show a dramatic abundance drop within 1 arcmin of the cluster core, we show that more appropriate models, which include a multi-temperature component to account for th

Silvano Molendi, Fabio Pizzolato

Employing XMM-Newton EPIC data we perform a detailed comparison between different spectral models to test whether the gas in cooling-flows is multi-phase or not. Our findings all point in the same direction, namely that gas in cooling-flows does not show the wide distribution of temperatures expected from standard multi-phase models. This result has profound

A. Maccio`, A. Gardini, S. Ghigna, S. A. Bonometto

We examine how the statistics of the quadrupoles of (projected) cluster masses can discriminate between flat cold dark matter (CDM) universes with or without a cosmological constant term. Even in the era of high precision cosmology that cosmic microwave background experiments should open soon, it is important to devise self consistency tests of cosmogonic th

Takeshi Chiba

Various astronomical observations point towards the evidence for dark energy. One of the most mysterious problem is the coincidence problem: why dark energy becomes dominant only recently. We present a scenario based on extended quintessence models to explain the late-time domination of dark energy without severe fine-tuning of initial conditions and model p

Silviu Podariu, Bharat Ratra

We study constraints that anticipated DEEP survey galaxy counts versus redshift data will place on cosmological model parameters in models with and without a constant or time-variable cosmological constant $Λ$. This data will result in fairly tight constraints on these parameters. For example, if all other parameters of a spatially-flat model with a constant

Samvel Ter-Antonyan, Peter Biermann

High statistical accuracy of experiments KASCADE and ANI allowed to obtain approximations of primary energy spectra and elemental composition in the "knee" region. Obtained results point out to the correctness of QGSJET interaction model and 2-component model of primary cosmic ray origin up to 100 PeV energies.

Tom Banks, Michael Dine

The apparent observation of dark energy poses problems for string theory. In de Sitter space, or in quintessence models, one cannot define a gauge-invariant S-matrix. We argue that eternal quintessence does not arise in weakly coupled string theory, but point out that it is difficult to define an $S$-matrix even in the presence of perturbative potentials for

Z. Chacko, Patrick J. Fox, Ann E. Nelson, Neal Weiner

Models with extra dimensions have changed our understanding of the hierarchy problem. In general, these models explain the weakness of gravity by diluting gravity in a large bulk volume, or by localizing the graviton away from the standard model. In this paper, we show that the warped geometries necessary for the latter scenario can naturally induce the larg

Branislav K. Nikolic, J. K. Freericks, P. Miller

We study the energy and spatial dependence of the local density of states in a superconductor--correlated-metal--superconductor Josephson junction, where the correlated metal is a non-Fermi liquid (described by the Falicov-Kimball model). Many-body correlations are treated with dynamical mean-field theory, extended to inhomogeneous systems. While quasiclassi

K. A. Bugaev, M. Gazdzicki, M. I. Gorenstein

Recent results on transverse mass spectra of $J/ψ$ and $ψ^{\prime}$ mesons in central Pb+Pb collisions at 158 A$\cdot$GeV are considered. It is shown that those results support a hypothesis of statistical production of charmonia at hadronization and suggest the early thermal freeze--out of $J/ψ$ and $ψ^{\prime}$ mesons. Based on this approach the collective

Gary Shiu, S. -H. Henry Tye

The inflaton potential in four-dimensional theory is rather arbitrary, and fine-tuning is required generically. By contrast, inflation in the brane world scenario has the interesting feature that the inflaton potential is motivated from higher dimensional gravity, or more generally, from bulk modes or string theory. We emphasize this feature with examples. W

A. J. Baltz

If 7Be solar neutrinos can be observed in real time experiments, then an extended region of Delta m^2 can be probed by a proper analysis of the rapidly changing phase of vacuum oscillations due to the eccentricity of the earth's orbit about the sun. For the case of maximal vacuum mixing, a kind of Fourier analysis of expected data for one year's time

Leszek Roszkowski, Roberto Ruiz de Austri, Takeshi Nihei

We analyze the implications of several recent cosmological and experimental measurements for the mass spectra of the Constrained MSSM (CMSSM). We compute the relic abundance of the neutralino and compare the new cosmologically expected and excluded mass ranges with those ruled out by the final LEP bounds on the lightest chargino and Higgs masses, with those

A. B. Kuklov, N. Chensincki, Joseph L. Birman

Implications of the internal symmetries on the dynamics of the trapped two-component atomic vapors are discussed. In the cases of $^{87}$Rb (bosons) as well as of $^{40}$K (fermions) trapped in the two hyperfine states, the intrinsic $su(2)$ symmetry can be realized with a very good precision. Such a symmetry protects the global operators, which are the gene

Matthew W. Craig, Marc Davis

The inability of standard non-interacting cold dark matter (CDM) to account for the small scale structure of individual galaxies has led to the suggestion that the dark matter may undergo elastic and/or inelastic scattering. We simulate the evolution of an isolated dark matter halo which undergoes both scattering and annihilation. Annihilations produce a cor

Antony Lewis, Anthony Challinor, Neil Turok

The full sky cosmic microwave background polarization field can be decomposed into 'electric' and 'magnetic' components. Working in harmonic space we construct window functions that allow clean separation of the electric and magnetic modes from observations over only a portion of the sky. Our construction is exact for azimuthally symmetric pa

Matthias Liebendoerfer, Stephan Rosswog, Friedrich-Karl Thielemann

We describe an implicit general relativistic hydrodynamics code. The evolution equations are formulated in comoving coordinates. A conservative finite differencing of the Einstein equations is outlined, and artificial viscosity and numerical diffusion are discussed. The time integration is performed with AGILE, an implicit solver for stiff algebrodifferentia

Claudio Coriano', Alon E. Faraggi

The supersymmetric evolution of the fragmentation functions (or timelike evolution) within N=1 $QCD$ is discussed and predictions for the fragmentation functions of the theory (into final protons) are given. We use a backward running of the supersymmetric DGLAP equations, using a method developed in previous works. We start from the usual QCD parameterizatio

Andrei A. Galiautdinov, David R. Finkelstein

The Dirac equation is not semisimple. We therefore regard it as a contraction of a simpler decontracted theory. The decontracted theory is necessarily purely algebraic and non-local. In one simple model the algebra is a Clifford algebra with 6N generators. The quantum imaginary $\hbar i$ is the contraction of a dynamical variable whose back-reaction provides

Shu-Chiuan Chang, Robert Shrock

We consider the $q$-state Potts model on families of self-dual strip graphs $G_D$ of the square lattice of width $L_y$ and arbitrarily great length $L_x$, with periodic longitudinal boundary conditions. The general partition function $Z$ and the T=0 antiferromagnetic special case $P$ (chromatic polynomial) have the respective forms $\sum_{j=1}^{N_{F,L_y,λ}}

Arjan Keurentjes

The discrete tensorial charges carried by orientifold planes define n-gerbes in space-time. The simplest way to ensure a consistent string compactification is to require these gerbes to be flat. This results in expressions for the local gerbe-holonomies around each orientifold plane, describing its charges. Inverting the procedure and considering all flat ge

R. Ruffini, C. L. Bianco, P. Chardonnet, F. Fraschetti

Given the very accurate data from the BATSE experiment and RXTE and Chandra satellites, we use the GRB 991216 as a prototypical case to test the EMBH theory linking the origin of the energy of GRBs to the electromagnetic energy of black holes. The fit of the afterglow fixes the only two free parameters of the model and leads to a new paradigm for the interpr

R. Mathieu, P. Nordblad, A. R. Raju, C. N. R. Rao

The low temperature phase of single crystals of Nd$_{0.5}$Ca$_{0.5}$MnO$_3$ and Gd$_{0.5}$Ca$_{0.5}$MnO$_3$ manganites is investigated by squid magnetometry. Nd$_{0.5}$Ca$_{0.5}$MnO$_3$ undergoes a charge-ordering transition at $T_{CO}$=245K, and a long range CE-type antiferromagnetic state is established at $T_N$=145K. The dc-magnetization shows a cooling r

Kaoru Hagiwara, Yosuke Uehara

We propose a new mechanism for explaining the very long lifetime of superheavy dark matter X, which is proposed as a source of the ultra high-energy cosmic rays above the GZK cutoff (5 \times 10^{19} eV). The singlet X particle couples to the MSSM particles only through a bulk singlet field which develops the v.e.v. in the ``hidden'' brane. The dista

Rogerio Rosenfeld, Jonathan L. Rosner

The consequences of adding random perturbations (anarchy) to a baseline hierarchical model of quark masses and mixings are explored. Even small perturbations of the order of 5% of the smallest non-zero element can already give deviations significantly affecting parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, so any process generating the anarchy sh

E. Cuevas, M. Ortuno, V. Gasparian, A. Perez-Garrido

We investigate numerically the inverse participation ratio, $P_2$, of the 3D Anderson model and of the power-law random banded matrix (PRBM) model at criticality. We found that the variance of $\ln P_2$ scales with system size $L$ as $σ^2(L)=σ^2(\infty)-A L^{-D_2/2d}$, being $D_2$ the correlation dimension and $d$ the system dimension. Therefore the concept

Daniele Oriti

This is an introduction to spin foam models for non-perturbative quantum gravity, an approach that lies at the point of convergence of many different research areas, including loop quantum gravity, topological quantum field theories, path integral quantum gravity, lattice field theory, matrix models, category theory, statistical mechanics. We describe the ge

Stephen C. Davis

Cosmological brane world solutions are found for five-dimensional bulk spacetimes with a scalar field. A supergravity inspired method for obtaining static solutions is combined with a method for finding brane cosmologies with constant bulk energies. This provides a way to generate full (bulk and brane) cosmological solutions to brane worlds with bulk scalar

A. I. Bugrij, O. Lisovyy

Form factor representation of the correlation function of the 2D Ising model on a cylinder is generalized to the case of arbitrary disposition of correlating spins. The magnetic susceptibility on a lattice, one of whose dimensions ($N$) is finite, is calculated in both para- and ferromagnetic regions of parameters of the model. The singularity structure of t

J. Casares, G. Dubus, T. Shahbaz, C. Zurita

We present VLT low resolution spectroscopy of the neutron star X-ray transient XTE J2123-058 during its quiescent state. Our data reveal the presence of a K7V companion which contributes 77 % to the total flux at 6300 A and orbits the neutron star at K_2 = 287 +/- 12 km/s. Contrary to other soft X-ray transients (SXTs), the Halpha emission is almost exactly

A. Isacsson, L. Y. Gorelik, R. I. Shekhter, Y. M. Galperin

Transportation of Cooper-pairs by a movable single Cooper-pair-box placed between two remote superconductors is shown to establish coherent coupling between them. This coupling is due to entanglement of the movable box with the leads and is manifested in the supression of quantum fluctuations of the relative phase of the order parameters of the leads. It can

N. Kivel, L. Mankiewicz

We computed twist-4 part of the photon spin-flip amplitude in deeply virtual Compton scattering on a nucleon in the Wandzura-Wilczek approximation. We found a factorizable contribution, which arises from photon scattering on quarks with non-zero angular momentum along the collision axis. As the genuine twist-2 amplitude arises at the NLO, for moderate virtua

Chuan-Tsung Chan, Chiang-Mei Chen, Hyun Seok Yang

We study the topological properties of fuzzy sphere. We show that the topological charge is only defined modulo N+1, that is finite integer quotient Z_{N+1}, where N is a cut-off spin of fuzzy sphere. This periodic structure on topological charges is shown based on the boson realizations of SU(2) algebra, Schwinger vs. Holstein-Primakoff. We argue that this

D. Salgado, J. L. Sanchez-Gomez

Three basic postulates for Quantum Theory are proposed, namely the Probability, Maximum-Speed and Hilbert-Space postulates. Subsequently we show how these postulates give rise to well-known and widely used quantum results, as the probability rule and the linearity of quantum evolution. A discussion of the postulates in the light of Bell's theorem is incl

Ruben Minasian, Dimitrios Tsimpis

We use a series of reductions, T-dualities and liftings to construct connections between fractional brane solutions in IIA, IIB and M-theory. We find a number of phantom branes that are not supported by the geometry, however materialize upon untwisting and/or Hopf-reduction.

Edward Anderson, James E. Lidsey

A scheme is discussed for embedding n-dimensional, Riemannian manifolds in an (n+1)-dimensional Einstein space. Criteria for embedding a given manifold in a spacetime that represents a solution to Einstein's equations sourced by a massless scalar field are also discussed. The embedding procedures are illustrated with a number of examples.

R. Enberg, L. Motyka, G. Ingelman

We study rapidity gaps between jets in ppbar collisions at the Tevatron by a novel solution of the nonforward BFKL equation including nonleading effects through the consistency constraint and running coupling. Results differ from earlier calculations based on the asymptotic Mueller-Tang formula, but agree with D0 data when including full event simulation usi

J. A. R. Cembranos, A. Dobado, A. L. Maroto

In the context of a brane world and including an induced curvature term in the brane action, we obtain the effective lagrangian for the Goldstone bosons (branons) associated with the spontaneous breaking of the translational invariance in the bulk. In addition to the branons, this effective action has Skyrmion-like solitonic states which can be understood as

T. Nord, L. Y. Gorelik, R. I. Shekhter, M. Jonson

We investigate the current-voltage (IV) characteristics of a model single-electron transistor where mechanical motion, subject to strong dissipation, of a small metallic grain is possible. The system is studied both by using Monte Carlo simulations and by using an analytical approach. We show that electromechanical coupling results in a highly nonlinear IV-c

N. N. Achasov, V. V. Gubin

We study the decay $ϕ\toγK^+K^-$ taking into account the scalar mesons production $ϕ\toγ(f_0+a_0) \toγK^+K^-$ and the final state radiation. We note that the relative sign between the final state radiation amplitude and the scalar meson production amplitude is fixed in the $K^+K^-$ loop model which describes data on the $ϕ\to γf_0\toγππ$ and $ϕ\toγa_0\toγπη$

JLQCD collaboration, S. Aoki, M. Fukugita, S. Hashimoto

We present a lattice QCD calculation of $B\to πl ν$ semileptonic decay form factors in the small pion recoil momentum region. The calculation is performed on a quenched $16^3 \times 48$ lattice at $β=5.9$ with the NRQCD action including the full 1/M terms. The form factors $f_1(v\cdot k_π)$ and $f_2(v\cdot k_π)$ defined in the heavy quark effective theory fo

Satish D. Joglekar

We consider the use of interpolating gauges (with a gauge function (F[A;alpha ]) in gauge theories to connect the results in a set of different gauges in the path-integral formulation. We point out that the results for physical observables are very sensitive to the epsilon term that we have to add to deal with singularities and thus cannot be left out of a d

A. Freund, M. F. McDermott

We present a next-to-leading order (NLO) QCD analysis of unpolarized and polarized deeply virtual Compton scattering (DVCS) amplitudes, for two different input scenarios, in the $\bar{MS}$ scheme. We illustrate and discuss the size of the NLO effects and the behavior of the amplitudes in skewedness, $\zeta$, and photon virtuality, $Q^2$. In the unpolarized c

K. Takahashi, T. Sensui, Y. Funato, J. Makino

We investigated the dynamical evolution of clusters of galaxies in virial equilibrium using Fokker-Planck models and self-consistent N-body models. In particular, we focused on the growth of a common halo, which is a cluster-wide halo formed by matter stripped from galaxies, and the development of a central density cusp. The Fokker-Planck models include the

C. R. Morton, A. C. Berriman, R. D. Butt, M. Dasgupta

The shape of the measured barrier distribution for the ^{34}S + ^{168}Er reaction is analysed using the coupled-channels description. The ^{168}Er nucleus is a good candidate to test current fusion models description of deformation since it has a large quadrupole deformation with an insignificant hexadecapole deformation. Coupling to weaker channels, the 2^+

Frederic D. R. Bonnet, Derek B. Leinweber, Anthony G. Williams, James M. Zanotti

The relative smoothing rates of various gauge field smoothing algorithms are investigated on ${\cal O}(a^2)$-improved $\suthree$ Yang--Mills gauge field configurations. In particular, an ${\cal O}(a^2)$-improved version of APE smearing is motivated by considerations of smeared link projection and cooling. The extent to which the established benefits of impro

N. Debergh, Fl. Stancu

We present the many-particle Hamiltonian model of Lipkin, Meshkov and Glick in the context of deformed polynomial algebras and show that its exact solutions can be easily and naturally obtained within this formalism. The Hamiltonian matrix of each $j$ multiplet can be split into two submatrices associated to two distinct irreps of the deformed algebra. Their

W. Hänsel, J. Reichel, P. Hommelhoff, T. W. Hänsch

We propose a configuration of a magnetic microtrap which can be used as an interferometer for three-dimensionally trapped atoms. The interferometer is realized via a dynamic splitting potential that transforms from a single well into two separate wells and back. The ports of the interferometer are neighboring vibrational states in the single well potential.