June 1998 arXiv papers — page 4

Peter Kostädt, Mario Liu

A system's invariance under Galilean transformation implies three locally conserved densities. Including them as variables, the thermodynamics is rendered explicitly frame independent, dissipative mass currents are shown to vanish, and spontaneously broken Galilean symmetry becomes a sensible concept in condensed systems.

Yimin Jiang, Mario Liu

A hydrodynamic-type, macroscopic theory was set up recently to simultaneously account for dissipation and dispersion of electromagnetic field, in nonstationary condensed systems of nonlinear constitutive relations~\cite{JL}. Since it was published in the letter format, some algebra and the more subtle reasonings had to be left out. Two of the missing parts a

Tetsufumi Tanamoto, Shinobu Fujita

The effect of resonant tunneling on magnetoresistance (MR) is studied theoretically in a double junction system. We have found that the ratio of the MR of the resonant peak current is reduced more than that of the single junction, whereas that of the valley current is enhanced depending on the change of the discrete energy-level under the change of magnetic

G. R. Facer, B. E. Kane, A. S. Dzurak, R. J. Heron

We report measurements of GaAs/AlGaAs undoped field-effect transistors in which two-dimensional electron gases (2DEGs) of exceptional quality and versatility are induced without modulation doping. Electron mobilities at T=4.2 K and density 3 E11 /cm^2 exceed 4 E6 cm^2/Vs. At lower temperatures, there is an unusually large drop in scattering, such that the mo

Thomas Schreiber

This paper reports on the application to field measurements of time series methods developed on the basis of the theory of deterministic chaos. The major difficulties are pointed out that arise when the data cannot be assumed to be purely deterministic and the potential that remains in this situation is discussed. For signals with weakly nonlinear structure,

Wen Xu, Li-Zhi Fang, Xiang-Ping Wu

We investigate the dependence of cluster abundance $n(>M,r_{cl})$, i.e., the number density of clusters with mass larger than $M$ within radius $r_{cl}$, on scale parameter $r_{cl}$. Using numerical simulations of clusters in the CDM cosmogonic theories, we notice that the abundance of rich clusters shows a simple scale invariance such that $n[>(r_{cl}/r_0)^

D. Mitsouras, R. Brandenberger, P. Hickson

The results of numerical simulations are presented which demonstrate that liquid mirror telescope galaxy redshift surveys such as the current UBC-NASA Multi-Narrowband Survey and the future LZT Survey have the potential of discriminating between the predictions of different theories of structure formation. Most of the currently studied theories of structure

T. Corbard, G. Berthomieu, J. Provost, L. Blanc-Féraud

Inversions of rotational splittings have shown that the surface layers and the so-called solar tachocline at the base of the convection zone are regions in which high radial gradients of the rotation rate occur. The usual regularization methods tend to smooth out every high gradients in the solution and may not be appropriate for the study of a zone like the

Marco Fatuzzo, Fulvio Melia

EGRET (20 MeV to 30 GeV) on board the Compton GRO has observed high-energy emission from about 40-50 Active Galactic Nuclei. Theoretical models of this emission based on the upscattering of thermal disk photons by cooling, relativistic electrons can successfully account for the EGRET observations, but they predict a considerably greater X-ray flux than that

Subrata Pal, Debades Bandyopadhyay, Somenath Chakrabarty

We investigate the influence of a strong interior magnetic field on the structure and composition of a protoneutron star allowing quark-hadron phase transition. In contrast to protoneutron stars with noninteracting quark phase, the stars with interacting quark phase have smaller maximum star masses than those of neutrino-free stars. The strong field makes th

Masafumi Noguchi

A new idea is proposed for the origin of bulges in spiral galaxies. Numerical simulations for the protogalactic collapse suggest strongly that galactic bulges have been assembled from massive clumps formed in the galactic disks in their early evolutionary phase. These clumps result from the gravitational instability of the gas-rich disks of young galaxies. T

R. Capuzzo-Dolcetta

This short report is concerned with the well known and not yet satisfactorily answered problem of the existence of two well distinct typical mass scales of primordial halo objects: solar size objects (halo field stars) and globular cluster size objects (10^5 solar masses and more). A likely possibility is that almost all the gaseous content of the halo fragm

R. I. Davies, W. Hackenberg, T. Ott, A. Eckart

The sodium laser guide star adaptive optics system ALFA has been constructed at the Calar Alto 3.5-m telescope. Following the first detection of the laser beacon on the wavefront sensor in 1997 the system is now being optimized for best performance. In this contribution we discuss the current status of the launch beam and the planned improvements and upgrade

William G. Mathews, Fabrizio Brighenti

The variation of temperature and density in the hot, X-ray emitting gas around massive, group dominant elliptical galaxies can be understood as a combination of gas ejected from evolving galactic stars and gas that accumulates in the outer halo by secondary cosmic infall. Beginning with an overdensity perturbation in a simple flat cosmology, we can duplicate

J. Larwood

In this letter recent results on the nodal precession of accretion discs in close binaries are applied to the discs in some X-ray binary systems. The ratio between the tidally forced precession period and the binary orbital period is given, as well as the condition required for the rigid precession of gaseous Keplerian discs. Hence the minimum precessional p

Marek Cieplak, Malte Henkel, Jayanth R. Banavar

The dynamics of two 12-monomer heteropolymers on the square lattice is studied exactly within the master equation approach. The time evolution of the occupancy of the native state is determined. At low temperatures, the median folding time follows the Arrhenius law and is governed by the longest relaxation time. For good folders, significant kinetic traps ap

C. Adloff

Di-jet event rates have been measured for deep-inelastic scattering in the kinematic domain ~5 < Q^2 < ~100 GeV^2 and ~10^(-4) < x_Bj < ~10^(-2), and for jet transverse momenta squared p_t^2 > ~Q^2. The analysis is based on data collected with the H1 detector at HERA in 1994 corresponding to an integrated luminosity of about 2 pb^(-1). Jets are defined using

Fernando C. Lombardo, Mario Castagnino, Luca Bombelli

We analyse the relationship between classical chaos and particle creation in Robertson-Walker cosmological models with gravity coupled to a scalar field. Within our class of models chaos and particle production are seen to arise in the same cases. Particle production is viewed as the seed of decoherence, which both enables the quantum to classical transition

N. Dupuis, Victor M. Yakovenko

We study the collective modes in the magnetic-field-induced spin-density-wave (FISDW) phases experimentally observed in organic conductors of the Bechgaard salts family. In phases that exhibit a sign reversal of the quantum Hall effect (Ribault anomaly), the coexistence of two spin-density waves gives rise to additional collective modes besides the Goldstone

S. J. Pollock, Nimai C. Mukhopadhyay, M. Ramsey-Musolf, H. -W. Hammer

We consider prospects for studying the parity-violating electroweak excitation of the $Δ(1232) $ resonance with polarized electron scattering (see nucl-th/9801025). We discuss the experimental feasibility and theoretical interpretability of such a measurement as well as the prospective implications for hadron structure theory. We also analyze the extent to w

M. Maltoni, M. I. Vysotsky

It happens that $s^2$ and $\hat s^2$ are equal with 0.1% accuracy, though they are split by radiative corrections and a natural estimate for their difference is 1%. This degeneracy occurs only for $m_t$ value close to $170\GeV$, so no deep physical reason can be attributed to it. However, another puzzle of the Standard Model, the degeneracy of $s_\Eff^2$ and

M. Magliocchetti, S. J. Maddox, O. Lahav, J. V. Wall

We discuss how different theoretical predictions for the variance $σ^2$ of the distribution of radio sources can be matched to measurements from the FIRST survey at different flux limits. The predictions are given by the integration of models for the angular correlation function $w(θ)$ for three different functional forms of the redshift distribution $N(z)$,

G. P. Salam

The NLL corrections to the BFKL kernel are known to be very large, to the extent that even for small values of alpha_s, they lead to physical cross sections which are not positive definite. It is shown in the context of a toy model, that such pathological behaviour is an artifact of the truncation at NLL order, and is associated in particular with double tra

N. Eicker, U. Glässner, S. Güsken, H. Hoeber

We present the final analysis of the light and strange hadron spectra from a full QCD lattice simulation with two degenerate dynamical sea quark flavours at $β= 5.6$ on a $16^3 \times 32$ lattice. Four sets of sea quark masses corresponding to the range $.69 \leq m_π/m_ρ\leq .83$ are investigated. For reference we also ran a quenched simulation at $β_{\sf ef

Hideyuki Umeda, Ken&#39;ichi Nomoto, Hitoshi Yamaoka, Shinya Wanajo

Recent observations have revealed that Type Ia supernovae (SNe Ia) are not perfect standard candles but show some variations in their absolute magnitudes, light curve shapes, and spectra. The C/O ratio in the SNe Ia progenitors (C-O white dwarfs) may be related to this variation. In this work, we systematically investigate the effects of stellar mass (M) and

M. Bastero-Gil, S. F. King

We show that a particular class of effective low energy supergravity theories motivated by string theory can provide a promising framework for models of hybrid inflation in which the potential energy which drives inflation originates from the F-term of the effective supergravity theory. In the class of models considered the inflaton is protected from receivi

Takeshi Chiba, Naoshi Sugiyama, Takashi Nakamura

We study gravitational lensing statistics, matter power spectra and the angular power spectra of the cosmic microwave background (CMB) radiation in x-matter models. We adopt an equation-of-state of x-matter which can express a wide range of matter from the pressureless dust to the cosmological constant. A new ingredient in this model is the sound speed of th

G. F. Helminck, J. W. van de Leur

We shown that, if you have two planes in the Segal-Wilson Grassmannian that have an intersection of finite codimension, then the corresponding solutions of the KP hierarchy are linked by Bäcklund-Darboux transformations (BDT). The pseudodifferential operator that performs this transformation is shown to be built up in a geometric way from elementary BDT&#39;

L. V. Bogdanov, B. G. Konopelchenko

Integrable lattice equations arising in the context of singular manifold equations for scalar, multicomponent KP hierarchies and 2D Toda lattice hierarchy are considered. These equation generate the corresponding continuous hierarchy of singular manifold equations, its Bäcklund transformations and different forms of superposition principles. They possess rat

S. Lee, Julian J. -L. Ting, S. Kim

Linear theory for phonon scattering by discrete breathers in the discrete nonlinear Schroedinger equation using the transfer matrix approach is presented. Transmission and reflection coefficients are obtained as a function of the wave vector of the input phonon. The occurrence of a nonzero transmission, which in fact becomes perfect for a symmetric breather,

Giuseppe Castagnoli, Dalida Monti

We describe a plausible-speculative form of quantum computation which exploits particle (fermionic, bosonic) statistics, under a generalized, counterfactual interpretation thereof. In the idealized situation of an isolated system, it seems that this form of computation yields to NP-complete=P.

Arvind, N. Mukunda

The connection between quantum optical nonclassicality and the violation of Bell&#39;s inequalities is explored. Bell type inequalities for the electromagnetic field are formulated for general states(arbitrary number or photons, pure or mixed) of quantised radiation and their violation is connected to other nonclassical properties of the field. Classical sta

V. P. Drachev, S. V. Perminov

The new mechanism for obtaining a nonlinear phase shift has been proposed and the schemes are described for its implementation. As it is shown, the interference of two waves with intensity-dependent amplitude ratio coming from the second harmonic generation should produce the nonlinear phase shift. The sign and amount of nonlinear distortion of a beam wavefr

E. C. Aschenauer, J. Baehr, V. Gapienko, B. Hoffmann

A fiber detector concept has been realized allowing to registrate particles within less than 100 nsec with a space point precision of about 0.1 mm at low occupancy. Three full size prototypes have been build by different producers and tested at a 3 GeV electron beam at DESY. After 3 m of light guides 8-10 photoelectrons were registrated by multichannel photo

Su Houng Lee, Hungchong Kim

Using the QCD Operator Product Expansion, we derive the real part of the transverse and longitudinal vector vector correlation function with the $ρ,ω$ quantum numbers to leading order in density and in ${\bf q}^2$ at $-ω^2\to \infty $. To dimension 6, only twist-2 and 4 operators contribute. These OPE, through the energy dispersion relation, provide model in

P. Bozek, Y. B. He, J. Huefner

The stability of an expanding parton plasma is analyzed within quasi-particle models. The effective mass of the parton is calculated self-consistently from a gap equation which is either obtained from the Nambu Jona-Lasinio Lagrangian or from a fit to observables calculated on the lattice. The latter shows an effective confinement. At thermal equilibrium the

Tien-Cuong Dinh, Frederic Sarkis

We give a wedge removability theorem for metrically thin sets of two codimensional Hausdorff null measure. This removability theorem combined with the wedge removability theorem of Merker for closed subsets of two codimensional manifolds, gives a CR-meromorphic extension theorem in the greater codimensional case.

Denis V. Juriev

A geometric interpretation of approximate ($HS$-projective or $TC$-projective) representations of the Witt algebra $w^C$ by $q_R$-conformal symmetries in the Verma modules $V_h$ over the Lie algebra $sl(2,C)$ is established and some their characteristics are calculated. It is shown that the generators of representations coincide with the Nomizu operators of

Thomas Bauer

Consider a polarized abelian variety $(A,L)$ over the field of complex numbers. Following Demailly, one can associate to $(A,L)$ a real number $ε(A,L)$, its {\em Seshadri constant}, which in effect measures how much of the positivity of $L$ can be concentrated at any given point of $A$. There has been considerable recent interest in finding bounds on the Ses

Christoph Adam

The massive Schwinger model may be analysed by a perturbation expansion in the fermion mass. However, the results of this mass perturbation theory are sensible only for sufficiently small fermion mass. By performing a renormal-ordering, we arrive at a chiral perturbation expansion where the expansion parameter remains small even for large fermion mass. We us

Christoph Adam

Within mass perturbation theory, already the first order contribution to the chiral condensate of the massive Schwinger model is UV divergent. We discuss the problem of choosing a proper normalization and, by making use of some bosonization results, we are able to choose a normalization so that the resulting chiral condensate may be compared, e.g., with latt

Christoph Adam

In some recent papers it is claimed that the physical significance of the vacuum angle theta for QCD-like theories depends on the chosen gauge condition. We criticise the arguments that were given in support of this claim, and show by explicit construction for the case of QED$_2$ that and why they fail, confirming thereby the commonly accepted point of view.

V. V. Nesterenko, I. G. Pirozhenko

The effect of the Gaussian curvature in the rigid string action on the interquark potential is investigated. The linearized equations of motion and boundary conditions, following from the modified string action, are obtained. The equation, defining the eigenfrequency spectrum of the string oscillations is derived. On this basis, the interquark potential, gen

C. N. Leung

The effects of an external field on the dynamics of chiral symmetry breaking are studied using quenched, ladder QED as our model gauge field theory. It is found that a uniform external magnetic field enables the chiral symmetry to be spontaneously broken at weak gauge couplings, in contrast with the situation when no external field is present. The broken chi

I. A. Batalin, S. L. Lyakhovich, I. V. Tyutin

Existence theorem is proven for the generating equations of the split involution constraint algebra. The structure of the general solution is established, and the characteristic arbitrariness in generating functions is described.

H. A. Kastrup

Generalizing previous quantum gravity results for Schwarzschild black holes from 4 to D>4 spacetime dimensions yields an energy spectrum E_n = n^{1-1/(D-2)} sigma E_P, n=1,2,..., sigma = O(1). Assuming the degeneracies of these levels to be given by g^n, g>1, leads to a partition function which is the same as that of the primitive droplet nucleation model fo

A. Dobado, M. J. Herrero, S. Penaranda

We explore analytically how does the Standard Model emerge as the quantum low energy effective theory of the Minimal Supersymmetric Standard Model (MSSM) in the decoupling limit where the sparticles are much heavier than the electroweak scale. In this work we integrate the sfermions to one-loop and compute their contributions to the effective action for stan

Lay Nam Chang, Oleg Lebedev, John N. Ng

We estimate the most important corrections to the branching ratios for the invisible decays of quarkonium states, arising from possible extensions of the standard model. Among the possibilities considered are the presence of extra Z-bosons, minimal supersymmetric extensions of the standard model with R-parity violation, and decays into goldstinos. Prospects

T. Han, M. Hosch, K. Whisnant, Bing-Lin Young

We calculate single top-quark production at hadron colliders via the chromo-magnetic flavor-changing neutral current couplings $\bar tcg$ and $\bar tug$. We find that the strength for the anomalous $\bar tcg$ ($\bar tug$) coupling may be probed to $κ_c / Λ= 0.092 {TeV}^{-1}$ ($κ_u / Λ= 0.026 {TeV}^{-1}$) at the Tevatron with $2 {fb}^{-1}$ of data and $κ_c /

A. Goussiou, M. McDermott, N. N. Nikolaev, R. Roosen

Recent experimental and theoretical developments in the understanding of high energy diffraction, presented in the working group on diffraction at DIS98 in Brussels, are summarised. A template, giving the definition of the most commonly used kinematical variables in diffraction, which was provided in the working group sessions, is reproduced as a appendix. R

S. Catani, M. L. Mangano, P. Nason

We present the explicit expressions for the resummation of large-x Sudakov effects in the transverse-energy distribution of prompt-photons produced in hadronic collisions, to next-to-leading logarithmic (NLL) accuracy. Fragmentation processes do not contribute to the Sudakov resummation at NLL level. In Mellin space, the resummed radiative factor factorizes

M. Wobisch

Recent results on dijet production in deep-inelastic scattering from the H1 experiment at the ep-collider HERA are presented. Internal jet structure has been studied in terms of jet shapes and subjet multiplicities in the Breit frame. Both observables are seen to be well described by QCD models. We observe a broadening of the jets towards the proton directio

C. J. A. P. Martins, E. P. S. Shellard

We study chiral vorton production for Witten-type superconducting string models in the context of a recently developed analytic formalism. We delineate three distinct scenarios: First, a low energy regime (including the electroweak scale) where vortons can be a source of dark matter. Secondly, an intermediate energy regime where the vorton density is too hig

Romuald A. Janik, Maciej A. Nowak, Gabor Papp, Ismail Zahed

We investigate the effects of a finite chemical potential $μ$ in QCD viewed as a disordered medium. In the quenched approximation, $A_4=iμ$ induces a complex electric Aharonov-Bohm effect that causes the diagonal contribution to the quark return probability to vanish at $μ=m_π/2$ (half the pion mass). In two-color QCD, the weak-localization contribution to t

Ja. V. Burdanov, G. V. Efimov, S. N. Nedelko

The transition form factor, decay width and charge form factor of pion are calculated within the model of induced nonlocal quark currents based on the assumption that the nonperturbative QCD vacuum can be characterized by a homogeneous (anti-)self-dual gluon field. It is shown that the interaction of the quark spin with the vacuum gluon field, being responsi

Romuald A. Janik, Maciej A. Nowak, Gabor Papp, Ismail Zahed

The results of a number of constituent quark models in matter may be understood in the mean-field approximation by using a simple four-fermi model in 0+1 dimensions.

Wim Beenakker, Ansgar Denner

We give an overview of the problems and developments associated with the calculation of radiative corrections to off-shell gauge-boson pair production in e^+ e^- collisions.

E. Oset, J. A. Oller, J. R. Pelaez, A. Ramos

A qualitative account of the meson-meson and meson-baryon interactions using chiral Lagrangians and the inverse amplitude method in coupled channels is done. The method, imposing exact unitarity, proves to be very useful tool to extend the information contained in the chiral Lagrangians at energies beyond the realm of applicability of chiral perturbation the

M. Beneke

We review in brief the threshold expansion, a method to perform the expansion of Feynman integrals near the heavy quark-antiquark threshold, and its relation to the construction of two effective theories, non-relativistic QCD (NRQCD) and potential-NRQCD. We then summarize recent next-to-next-to-leading order results on the decay $J/Ψ\to l^+ l^-$, the bottom

T. G. Kovács, E. T. Tomboulis

We consider the Wilson loop expectation in SU(2) lattice gauge theory in the presence of constraints. The constraints eliminate from the functional measure gauge field configurations whose physical interpretation is that of thick center vortices linking with the loop. We give a simple proof that, for dimension $d \geq 3$, the so constrained Wilson loop follo

K. Farakos, N. E. Mavromatos, D. McNeill

We discuss a phase diagram for a relativistic SU(2) x U_{S}(1) lattice gauge theory, with emphasis on the formation of a parity-invariant chiral condensate, in the case when the $U_{S}(1)$ field is infinitely coupled, and the SU(2) field is moved away from infinite coupling by means of a strong-coupling expansion. We provide analytical arguments on the exist

Miklos-Adam Halasz

A simple non-Hermitean random matrix (RM) model is used to study the Glasgow method of finite-density lattice QCD. The zeros of the RM partition function are evaluated through an averaging procedure, involving the zeros of the RM &#39;propagator matrix&#39; in the complex chemical-potential plane. The nature of the uncertainty affecting the results is simila

J. Yu

We discuss prospects of deep inelastic scattering physics capabilities at the future muon collider facility. In addition to mu^+ mu^- collider itself, the facility provides other possibilities. Among the possibilities, we present muon-proton collider and neutrino fixed target programs at the muon collider facility. This mu-p collider program extends kinemati

The NuTeV, D0, CDF collaborations, J. Yu et. al

We present the preliminary result of sin^2theta_W from nu-N deep inelastic scattering experiment, NuTeV, at Fermilab. This measurement of sin^2theta_W comes from measuring the Paschos-Wolfenstein parameter R-=sigma_NC^nu-sigma_NC^nubar/(sigma_CC^{nu}-sigma_CC^nubar), using separate beams of nu and nubar, utilizing the SSQT. The resulting value of sin^2θ_W^(o

NuTeV Collaboration, J. Yu et. al

We present recent QCD results in nu-N scattering at the Fermilab CCFR/NuTeV experiments. We present the latest Next-to-Next-Leading order strong coupling constant, alpha-s, extracted from Gross-Llewellyn-Smith sum rule. The value of alpha-s from this measurement, at the mass of Z boson, is alpha-s^{NNLO}(M_Z**2)=0.114^{+0.009}_{-0.012}. We also present a pre

NuTeV Collaboration, J. Yu et. al

We present the latest Next-to-Next-Leading order strong coupling constant, alpha-s, extracted from Gross-Llewellyn-Smith sum rule. The value of alpha-s from this measurement, at the mass of Z boson, is alpha-s^{NNLO}(M_Z**2)=0.114^{+0.009}_{-0.012}. We discuss the previous strange sea quark measurement from the CCFR experiment and the prospects for improveme

C. Adloff

Events with a (2+1) jet topology in deep-inelastic scattering at HERA are studied in the kinematic range 200 < Q^2< 10,000 GeV^2. The rate of (2+1) jet events has been determined with the modified JADE jet algorithm as a function of the jet resolution parameter and is compared with the predictions of Monte Carlo models. In addition, the event rate is correct

Dimitri Bourilkov

A review of the measurements of hadron, flavour-tagged and lepton-pair production cross-sections and lepton-pair forward-backward asymmetries performed by the four LEP experiments ALEPH, DELPHI, L3 and OPAL at energies between 130 and 183 GeV is given. All 183 GeV results are preliminary. The searches by the four collaborations for new physics phenomena like

F. Abe

$B^0_d$-$\bar{B}{}^0_d$ oscillations are observed in ``self-tagged&#39;&#39; samples of partially reconstructed $B$ mesons decaying into a lepton and a charmed meson collected in $p\bar p$ collisions at $\sqrt{s} = 1.8$ TeV. A flavor tagging technique is employed which relies upon the correlation between the flavor of $B$ mesons and the charge of nearby part

Luis A. Anchordoqui

A two-way traversable wormhole solution in Brans-Dicke theory with torsion is obtained using the method of massive thin shells. The solution goes over general relativity for an infinite large value of the coupling parameter, however, the Brans-Dicke scalar could never be the ``carrier&#39;&#39; of exoticity that threads the wormhole throat.

Ll. Bel, A. Molina

We consider, in the framework of General Relativity, the linear approximation of the gravitational field of the Earth taking into account its mass, its quadrupole moment, its shape and its diurnal rotation. We conclude that in the frame of reference co-moving with the Earth the local anisotropy of the space is of the order of $10^{-12}-10^{-13}$ and could be

S. Foster

The singularity structure of cosmological models whose matter content consists of a scalar field with arbitrary non-negative potential is discussed. The special case of spatially flat FRW space-time is analysed in detail using a dynamical systems approach which may readily be generalised to more complicated space-times. It is shown that for a very large and

L. Chayes, J. Machta, O. Redner

A graphical representation based on duplication is developed that is suitable for the study of Ising systems in external fields. Two independent replicas of the Ising system in the same field are treated as a single four-state (Ashkin-Teller) model. Bonds in the graphical representation connect the Ashkin-Teller spins. For ferromagnetic systems it is proved

Rick Tully, George Reiter

We show that in a broad class of directed abelian sandpile models that had been expected to have the same exponents as the Dhar-Ramaswamy model, the avalanche exponent depends upon the details of the interaction, calling into question the general existence of universality classes in self organized critical models.

D. F. Agterberg

I investigate the vortex lattice structure of the Ginzburg Landau free energy for a two component order parameter in the weak-coupling clean-limit when the field is along the high symmetry axis in a tetragonal crystal. It is shown that the vortex lattice phase diagram as a function of the Ginzburg Landau free energy parameters includes phases with a hexagona

O. Bohigas, P. Leboeuf, M. J. Sanchez

We consider a single particle spectrum as given by the eigenvalues of the Wigner-Dyson ensembles of random matrices, and fill consecutive single particle levels with n fermions. Assuming that the fermions are non-interacting, we show that the distribution of the total energy is Gaussian and its variance grows as n^2 log n in the large-n limit. Next to leadin

F. F. Assaad

Auxiliary field quantum Monte Carlo methods for Hubbard models are generally based on a Hubbard-Stratonovitch transformation where the field couples to the z-component of the spin. This transformation breaks SU(2) spin invariance. The symmetry is restored only after summation over the auxiliary fields. Here, we analyze an alternative decomposition, which con

F. F. Assaad

We consider the repulsive Hubbard model on a square lattice with an additional term, W, which depends upon the square of a single-particle nearest-neighbor hopping. At half-band filling, constant W, we show that enhancing U/t drives the system from a d-wave superconductor to an antiferromagnetic Mott insulator. At zero temperature in the superconducting phas

Klaus Hecker, Helmut Hegger, Alexander Altland, Klaus Fiegle

In their comment cond-mat/9710285 [Phys. Rev. Lett. 80, 5024 (1998)] den Hartog and van Wees (HW) raise objections against our analysis of the experimental data presented in cond-mat/9708162 [Phys. Rev. Lett. 79, 1547 (1997)]. According to HW, we did not account for the quantum phase incoherence introduced by the Niobium compounds of the investigated Nb/Au h

Joachim Jacobsen, B. H. Cooper, James P. Sethna

We present a new method for simulating crystal growth by energetic beam deposition. The method combines a Kinetic Monte-Carlo simulation for the thermal surface diffusion with a small scale molecular dynamics simulation of every single deposition event. We have implemented the method using the effective medium theory as a model potential for the atomic inter

Pil Hun Song, Felix von Oppen

The propagation of an interacting particle pair in a disordered chain is characterized by a set of localization lengths which we define. The localization lengths are computed by a new decimation algorithm and provide a more comprehensive picture of the two-particle propagation. We find that the interaction delocalizes predominantly the center-of-mass motion

Marc Barthelemy, Henri Orland

In this article, we propose a new method to compute the effective properties of non-linear disordered media. We use the fact that the effective constants can be defined through the minimum of an energy functional. We express this minimum in terms of a path integral allowing us to use many-body techniques. We obtain the perturbation expansion of the effective

A. Sedrakyan

The model of lattice fermions in 2+1 dimensional space is formulated, the critical states of which are lying in the basis of such physical problems, as 3D Ising Model(3DIM) and the edge excitations in the Hall effect. The action for this exitations coincides with the action of so called sign-factor model in 3DIM at one values of its parameters, and represent

Mario Liu

A frame-independent, thermodynamically exact London equation is presented, which is especially valid for rotating superconductors. A direct result is the unexpectedly high accuracy ($\sim10^{-10}$) for the usual expression of the London moment.

Pierre-Antoine Rey, John Cardy

The reversible reactions A+A<=>C and A+B<=>C are investigated. From the exact Langevin equations describing our model, we set up a systematic approximation scheme to compute the approach of the density of C particles to its equilibrium value. We show that for sufficiently long time t, this approach takes the form of a power law At^(-d/2), for any dimension d

Andreas Volmer, Moshe Schwartz

In pure anisotropic or layered superconductors thermal fluctuations induce a van der Waals attraction between flux lines. This attraction together with the entropic repulsion has interesting consequences for the low field phase diagram; in particular, a first order transition from the Meissner phase to the mixed state is induced. We introduce a new variation

Mitake Miyazaki, Keita Kishigi, Yasumasa Hasegawa

The upper critical field $H_{c2}(T)$ of the tight-binding electrons in the three-dimensional lattice is investigated. The electrons make Cooper pairs between the eigenstates with the same energy in the strong magnetic field. The transition lines in the quasi-one dimensional case are shown to deviate from the previously obtained results where the hopping matr

Hiroaki Nakamura, Kazuaki Ikeda, Satarou Yamaguchi

Generation of electric power by the Nernst effect is a new application of a semiconductor. A key point of this proposal is to find materials with a high thermomagnetic figure-of-merit, which are called Nernst elements. In order to find candidates of the Nernst element, a physical model to describe its transport phenomena is needed. As the first model, we beg

K. Ladavac, M. J. Konstantinovic, A. Belic, Z. V. Popovic

We present low temperature Raman spectra of $NaV_2O_5$ single crystal. The assignation of the observed modes is done on the basis of Monte Carlo calculation of excited states of Heisenberg dimerized Hamiltonian, without frustration. We found a good agreement between measured and calculated magnetic excitations for $δ=0.048$ and $J=452 K$. The singlet-triplet

Barbara Di Eugenio, Pamela W. Jordan, Johanna D. Moore, Richmond H. Thomason

We describe a corpus-based investigation of proposals in dialogue. First, we describe our DRI compliant coding scheme and report our inter-coder reliability results. Next, we test several hypotheses about what constitutes a well-formed proposal.

Michael Strube

I propose a model for determining the hearer&#39;s attentional state which depends solely on a list of salient discourse entities (S-list). The ordering among the elements of the S-list covers also the function of the backward-looking center in the centering model. The ranking criteria for the S-list are based on the distinction between hearer-old and hearer

A. M. Selvam, Suvarna Fadnavis, S. U. Athale

The variability of temporal (or spatial) fluctuations of any variable is represented in conventional statistical theory by the relative dispersion equal to the standard deviation divided by the mean . The Relative Dispersion decreases with increase in time(or space) resolution and for uncorrelated fluctuations dealt with in traditional statistics, is given a

Suvarna Fadnavis, A. M. Selvam

Atmospheric flows exhibit fluctuations of all scales (space -time) ranging from turbulence (millimeters-seconds) to climate (thousands of kilometers-years). The apparently random fluctuations however exhibit long-range spatio-temporal correlations manifested as the selfsimilar fractal geometry to the global cloud cover pattern concomitant with inverse power

Marc Kamionkowski

This is a short article on inflation, the geometry of the Universe, and the cosmic microwave background that appeared as a Perspective in Science magazine.

Robert E. Shirey

I have carried out a project to study the eccentric neutron-star binary Circinus X-1 through an extensive series of observational studies with the Rossi X-ray Timing Explorer satellite and through theoretical computer models I developed to explore mass transfer and evolution in an eccentric binary. I modeled the evolution of the energy spectrum during intens

Richard I. Davies, Hajime Sugai, Martin J. Ward

We present near-infrared emission line images of the circumnuclear ring in NGC1068. We have measured the Br_gamma fluxes in a number of star forming complexes and derived extinctions for each of these by comparison with H_alpha. We investigate the star forming histories of these regions and find that a short burst of star formation occured co-evally througho

Brett Gladman, JJ Kavelaars, Philip D. Nicholson, Thomas J. Loredo

We have conducted pencil-beam searches for outer solar system objects to a limiting magnitude of R ~ 26. Five new trans-neptunian objects were detected in these searches. Our combined data set provides an estimate of ~90 trans-neptunian objects per square degree brighter than ~ 25.9. This estimate is a factor of 3 above the expected number of objects based o

J. Kaluzny, A. Wysocka, K. Z. Stanek, W. Krzeminski

We present $BVI$ photometry for about 16000 stars from a 220 arcmin$^{2}$ field centered 8 arcmin east of the center of 47 Tuc. We have identified eight likely blue stragglers located in the outer parts of the cluster. Four of these objects are easy targets for spectroscopic studies with ground-based telescopes. Six candidates for blue horizontal branch star

R. Capuzzo-Dolcetta, A. Tesseri

The radial distribution of globular clusters in galaxies is always less peaked to the centre than the halo stars&#39;. Extending previous work to a sample of HST globular cluster systems in ellipticals, we evaluate the number of clusters lost to the galactic centre as the integrals of the difference between the observed globular cluster system distribution a

M. A. Malkov

A simplified model of particle transport at a quasiparallel one-dimensional collisionless shock is suggested. In this model the MHD-turbulence behind the shock is dominated by a circularly polarized, large amplitude Alfvén wave originated upstream from the turbulence excited by particles leaking from the downstream medium. It is argued that such a wave havin