June 1996 arXiv papers — page 4

R. Moessner, J. T. Chalker

We study a two-dimensional electron system in a magnetic field with a fermion hardcore interaction and without disorder. Projecting the Hamiltonian onto the n-th Landau level, we show that the Hartree-Fock theory is exact in the limit n \rightarrow \infty, for the high temperature, uniform density phase of an infinite system; for a finite-size system, it is

Ekkehard Lange

The anomalous properties of the Hall constant in the normal state of high-$T_c$ superconductors are investigated within the single-band Hubbard model. We argue that the Mori theory is the appropriate formalism to address the Hall constant, since it aims directly at resistivities rather than conductivities. More specifically, the frequency dependent Hall cons

Boris A Khoruzhenko

The density of complex eigenvalues of random asymmetric $N\times N$ matrices is found in the large-$N$ limit. The matrices are of the form $H_0+A$ where $A$ is a matrix of $N^2$ independent, identically distributed random variables with zero mean and variance $N^{-1}v^2$. The limiting density $ρ(z,z^*)$ is bounded. The area of the support of $ρ(z,z^*)$ canno

Alexei M. Khorunzhy, Boris A. Khoruzhenko, Leonid A. Pastur

We study the normalized trace $g_n(z)=n^{-1} \mbox{tr} \, (H-zI)^{-1}$ of the resolvent of $n\times n$ real symmetric matrices $H=\big[(1+δ_{jk})W_{jk}/\sqrt n\big]_{j,k=1}^n$ assuming that their entries are independent but not necessarily identically distributed random variables. We develop a rigorous method of asymptotic analysis of moments of $g_n(z)$ for

Yan V. Fyodorov, Boris A. Khoruzhenko, Hans-Juergen Sommers

We consider an ensemble of large non-Hermitian random matrices of the form $\hat{H}+i\hat{A}_s$, where $\hat{H}$ and $\hat{A}_s$ are Hermitian statistically independent random $N\times N$ matrices. We demonstrate the existence of a new nontrivial regime of weak non-Hermiticity characterized by the condition that the average of $N\mbox{Tr} \hat{A}_s^2$ is of

J. Loos, H. Fehske

Analyzing the motion of low--spin $(s=1/2)$ holes in a high--spin $(S=1)$ background, we derive a sort of generalized t--J Hamiltonian for the $\rm NiO_2$ planes of Sr--doped nickelates. In addition to the rather complex carrier--spin and spin--spin couplings we take into account the coupling of the doped holes to in--plane oxygen breathing modes by a Holste

C. Schindelin, U. Trapper, H. Fehske, H. B"uttner

We present a self-consistent theory of magnetic short-range order based on a spin-rotation-invariant slave-boson representation of the 2D t-J model. In the functional-integral scheme, at the nearest-neighbour pair-approximation level, the bosonized t-J Lagrangian is transformed to a classical Heisenberg model with an effective (doping-dependent) exchange int

M. Sigrist, A. Furusaki

Low-temperature thermodynamic properties of the spin-1/2 Heisenberg ladder system with non-magnetic impurities are discussed using an effective Hamiltonian for the impurity-induced spins in the background of a spin liquid with a gap. It is shown that the uniform susceptibility shows Curie-like behavior in high-, intermediate-, and low-temperature regimes, wi

U. Trapper, D. Ihle, H. Fehske

A theory of magnetic short--range order for high--$T_c$ cuprates is presented on the basis of the one--band $t$--$t^{\prime}$--Hubbard model combining the four--field slave--boson functional integral technique with the Bethe cluster method. The ground--state phase diagram evaluated self--consistently at the saddle--point and pair--approximation levels shows

U. Trapper, D. Ihle, H. Fehske

The uniform static spin susceptibility in the paraphase of the one-band Hubbard model is calculated within a theory of magnetic short--range order (SRO) which extends the four-field slave-boson functional-integral approach by the trans- formation to an effective Ising model and the self-consistent incorporation of SRO at the saddle point. This theory describ

F. Kun, H. J. Herrmann

We study the phenomena associated with the low-velocity impact of two solid discs of equal size using a cell model of brittle solids. The fragment ejection exhibits a jet-like structure the direction of which depends on the impact parameter. We obtain the velocity and the mass distribution of the debris. Varying the radius and the initial velocity of the col

I. Ichinose, T. Matsui

Mechanism of the particle-flux separation in the Chern-Simons gauge theory coupled with nonrelativistic fermions is studied in a nonperturbative method. This problem is very important for the composite fermion approach to the fractional quantum Hall effect. We show that due to repulsive interactions between electrons the composite fermions are stable quasiex

Takamichi Terao, Tsuneyoshi Nakayama, Hideo Aoki

To probe the universality class of the quantum Hall system at the metal-insulator critical point, the multifractality of the wave function $ψ$ is studied for higher Landau levels, $N=1,2$, for various range $(σ)$ of random potential. We have found that, while the multifractal spectrum $f(α)$ (and consequently the fractal dimension) does vary with $N$, the pa

Sean P. Engelson, Ido Dagan

Corpus-based methods for natural language processing often use supervised training, requiring expensive manual annotation of training corpora. This paper investigates methods for reducing annotation cost by {\it sample selection}. In this approach, during training the learning program examines many unlabeled examples and selects for labeling (annotation) onl

Paul M. Harvey, Beverly J. Smith, James DiFrancesco, Cecilia Colome

We present results of observations at 47 and 95 microns from the Kuiper Airborne Observatory of several ``Vega-like'' stars. Spatial cuts and aperture photometry are presented for Beta Pictoris, Fomalhaut, and HD 135344, 139614, 142527, and 169142, four stars that had been suggested to possibly represent more distant examples of the Vega phenomenon b

Pierre Sikivie

It is argued that the spectrum of cold dark matter particles on Earth has peaks in velocity space associated with particles falling onto the Galaxy for the first time and with particles which have fallen in and out of the Galaxy only a small number of times in the past. Estimates are given for the sizes and velocity magnitudes of the first few peaks. The est

Andreas Schweitzer, Peter H. Hauschildt, France Allard, G. Basri

We use a preliminary version of our ``NextGen'' grid of cool star model atmospheres to compute synthetic line profiles which fit high resolution Keck spectra of the cool M~dwarf VB10 satisfactorily well. We show that the parameters derived from the Keck data are consistent with the parameters derived from lower resolution spectra with larger waveleng

G. Hasinger, B. Aschenbach, J. Trümper

X-ray observations of SN 1987A in the Magellanic Clouds have been performed throughout the ROSAT mission, using the PSPC and the HRI detectors. We present the X-ray light curve based on all observations in the years 1991-1995. For the first time a significant increase of the X-ray flux from SN 1987A can be seen, corresponding to X-ray luminosities (0.5-2 keV

Mordehai Milgrom

Eisenstein Loeb and Turner (ELT) have recently proposed a method for estimating the dynamical masses of large-scale filaments, whereby the filament is modeled by an axisymmetric, isothermal cylinder, for which ELT derive a global relation between the (constant) velocity dispersion and the total line density. We first show that the model assumptions of ELT ca

P. H. Chankowski, D. Choudhoury, S. Pokorski

We review briefly the indications for some relatively light superpartners based on the ~$R_b$ ~anomaly and discuss the dependence of the potential increase in $R_b$ on the assumption about ~$R-$parity (non)conservation. We point out that the exotic 4-jet events reported by ALEPH may constitute a signal for supersymmetry with such a light spectrum and with ex

Dror Bar-Natan

We present a ``reasonable'' statement about Lie algebras that is equivalent to the Four Color Theorem. The notions appearing in the statement also appear in the theory of finite-type invariants of knots (Vassiliev invariants) and 3-manifolds.

A. Leviatan

We discuss the notion of partial dynamical symmetry in relation to nuclear spectroscopy. Explicit forms of Hamiltonians with partial $SU(3)$ symmetry are presented in the framework of the interacting boson model of nuclei. An analysis of the resulting spectrum and electromagnetic transitions demonstrates the relevance of such partial symmetry to the spectros

J. Terasaki, H. Flocard, P. -H. Heenen, P. Bonche

We study the properties of the superdeformed (SD) bands of 195Pb and 193Hg by the cranked Hartree-Fock-Bogoliubov method. Our calculations reproduce the flat behavior of the dynamical moment of inertia of two of the SD bands of 195Pb measured recently. We discuss possible configuration assignments for the observed bands 3 and 4 of 195Pb. We also calculate th

Greg. W. Anderson, Andrei Linde, Antonio Riotto

Fluctuations of scalar fields produced at the stage of preheating after inflation are so large that they can break supersymmetry much stronger than inflation itself. These fluctuations may lead to symmetry restoration along flat directions of the effective potential even in the theories where the usual high temperature corrections are exponentially suppresse

V. K. Mitrjushkin

It is shown that the zero--momentum modes can strongly affect the values of the masses, for example the magnetic screening mass $m_m$, calculated from gauge--dependent correlators with zero momentum.

David Langlois

The observed CMBR dipole is generally interpreted as the consequence of the peculiar motion of the Sun with respect to the reference frame of the CMBR. This article proposes an alternative interpretation in which the observed dipole is the result of isocurvature perturbations on scales larger than the present Hubble radius. These perturbations are produced i

F. Ramirez, E. Cota, S. E. Ulloa

We study the capacitance spectra of artificial molecules consisting of two and three coupled quantum dots from an extended Hubbard Hamiltonian model that takes into account quantum confinement, intra- and inter-dot Coulomb interaction and tunneling coupling between all single particle states in nearest neighbor dots. We find that, for weak coupling, the inte

D. Rainer, J. A. Sauls, D. Waxman

We investigate the spectrum of quasiparticle excitations in the core of isolated pancake vortices in clean layered superconductors. Analysis of the spectral current density shows that both the circular current around the vortex center as well as any transport current through the vortex core is carried by localized states bound to the core by Andreev scatteri

Lauri Karttunen

This paper introduces to the finite-state calculus a family of directed replace operators. In contrast to the simple replace expression, UPPER -> LOWER, defined in Karttunen (ACL-95), the new directed version, UPPER @-> LOWER, yields an unambiguous transducer if the lower language consists of a single string. It transduces the input string from left to right

T. Shahbaz, Janet H. Wood

We obtain the NaI 8183,8195 absorption line radial velocity curves for the polars ST LMi and MR Ser, from which we find the semi-amplitudes to be K_abs=329=+/-6 kms-1 and K_abs=289+/-9 kms-1 respectively. We find that for both systems the effects on the \NaI absorption lines due to X-rays heating the inner face of the secondary are negligible, and so the val

Hans-Peter Nilles, Michal Spalinski

The Narain lattice construction of string compactifications is generalized to include spontaneously broken supersymmetry. Consistency conditions from modular invariance and Lorentz symmetry are solved in full generality. This framework incorporates models where supersymmetry breaking is inversely proportional to the radii of compact dimensions. The enhanced

S. Kharchev, A. Mironov, A. Zhedanov

We demonstrate that the generalization of the relativistic Toda chain (RTC) is a special reduction of two-dimensional Toda Lattice hierarchy (2DTL). This reduction implies that the RTC is gauge equivalent to the discrete AKNS hierarchy and, which is the same, to the two-component Volterra hierarchy while its forced (semi-infinite) variant is described by the

F. Sammarruca, R. Machleidt

For relativistic three-body calculations, essentially two different approaches are in use: field theory and relativistic direct interactions. Results for relativistic corrections of the triton binding energy obtained from the two approaches differ even in their sign, which is rather puzzling. In this paper, we discuss the origin of such discrepancy. We show

Y. Abulafia, A. Shaulov, Y. Wolfus, R. Prozorov

Local magnetic relaxation measurements in YBa$_2$Cu$_3$O$_{7-x}$ crystals show evidence for plastic vortex-creep associated with the motion of dislocations in the vortex lattice. This creep mechanism governs the vortex dynamics in a wide range of temperatures and fields below the melting line and above the field corresponding to the peak in the ''fis

A. Vourdas, C. Brif, A. Mann

The inner-outer part factorisation of analytic representations in the unit disk is used for an effective characterisation of the number-phase statistical properties of a quantum harmonic oscillator. It is shown that the factorisation is intimately connected to the number-phase Weyl semigroup and its properties. In the Barut-Girardello analytic representation

D. V. Gal'tsov, S. A. Sharakin

We show that the Einstein-Maxwell-Dilaton-Axion system with multiple vector fields (bosonic sector of the D=4, N=4 supergravity) restricted to spacetimes possessing a non-null Killing vector field admits a concise representation in terms of the Ernst-type matrix valued potentials. A constructive derivation of the SWIP solutions is given and a colliding waves

M. R. Rahimi Tabar, S. Rouhani

When Alf`ven effect is peresent in magnetohydrodynamics one is naturally lead to consider conformal field theories, which have logarithmic terms in their correlation functions. We discuss the implications of such logarithmic terms and find a unique conformal field theory with centeral charge $c=-\frac{209}{7}$, within the border of the minimal series, which

Sergei V. Ketov

Taking the N=2 strings as the starting point, we discuss the equivalent self-dual field theories and analyse their symmetry structure in 2+2 dimensions. Restoring the full `Lorentz' invariance in the target space necessarily leads to an extension of the N=2 string theory to a theory of 2+2 dimensional supermembranes propagating in 2+10 dimensional target

Csaba Csaki

The structure of the MSSM is reviewed. We first motivate the particle content of the theory by examining the quantum numbers of the known standard model particles and by the requirement of anomaly cancellation. Once the particle content is fixed we can write down the most general renormalizable superpotential. However such a superpotential will contain terms

David H. Lyth, Ewan D. Stewart

It is pointed out that hybrid inflation can be implemented with the inflaton field rolling away from the origin instead of towards it. This `inverted&#39; hybrid inflation has a spectral index $ n < 1 $, in contrast with ordinary hybrid inflation which has $ n \gtrsim 1 $, so a measured value of $n$ substantially different from 1 would distinguish the two. O

Nobuchika Okada, Osamu Yasuda

We discuss a model in which three active and one sterile neutrino account for the solar, the atmospheric and the LSND neutrino anomalies. It is shown that if $N_ν<4$ then these and other experiments and big bang nucleosynthesis constrain all the mixing angles severely, and allow only the small-angle MSW solution. If these neutrinos are of Majorana type, then

Gerhard A. Schuler, Ramona Vogt

Quarkonium production in high-energy reactions is found to exhibit a behaviour more universal than that expected from velocity scaling. Total rates of quarkonia produced in hadronic interactions as well as Feynman-x and transverse momentum distributions can be described over the full range of accessible energies (15 < sqrt{s} < 1800 GeV) by two-stage process

Tsuneo Suzuki

Recent studies of confinement based on the idea of abelian monopole condensation are reviewed briefly. Emphasis is placed on the approach to get the effective monoole action using the blockspin transformation on the dual lattice. The trajectory obtained looks to be the renormalized one in $SU(2)$ QCD. A disorder parameter of confinement is constructed. Monop

J. Jersak, C. B. Lang, T. Neuhaus

We investigate the confinement-Coulomb phase transition in the four-dimensional (4D) pure compact U(1) gauge theory on spherical lattices. The action contains the Wilson coupling beta and the double charge coupling gamma. The lattice is obtained from the 4D surface of the 5D cubic lattice by its radial projection onto a 4D sphere, and made homogeneous by mea

The DZero Collaboration, S. Abachi

We present results from a search for anomalous WW and WZ production in ppbar collisions at sqrt(s) = 1.8 TeV. We used ppbar->evjjX events observed during the 1992-1993 run of the Fermilab Tevatron collider, corresponding to an integrated luminosity of 13.7 +- 0.7 pb^-1. A fit to the transverse momentum spectrum of the W boson yields direct limits on the CP-c

D. V. Khveshchenko

We compute the electron diffusion thermopower at compressible Quantum Hall states corresponding to even denominator fractions in the framework of the composite fermion approach. It is shown that the deviation from the linear low temperature behavior of the termopower is dominated by the logarithmic temperature corrections to the conductivity and not to the t

Sumio Ishihara, Masanori Yamanaka, Naoto Nagaosa

We study the effects of the degeneracy of the $e_g$ orbitals as well as the double exchange interaction with $t_{2g}$ spins in perovskite transition-metal oxides. In addition to the spin field ${\vec S}_i$, the isospin field ${\vec T}_i$ is introduced to describe the orbital degrees of freedom. The isospin is the quantum dynamical variable, and is represente

Jason Pinkney, Jon Holtzman, Chris Garasi, Alan M. Watson

We present WFPC2 images of the core of the cooling flow cD galaxy in Abell 1795. An irregular, asymmetric dust lane extends 7 \h75 kpc in projection to the north-northwest. The dust shares the morphology observed in the H$α$ and excess UV emission. We see both diffuse and knotty blue emission around the dust lane, especially at the ends. The dust and emissio

Sandip K. Chakrabarti

We provide the complete set of global solutions of viscous transonic flows (VTFs) around black holes and neutron stars. These solutions describe the optically thick and optically thin flows from the horizon of the black hole or from the neutron star surface to the location where the flow joins with a Keplerian disk. We study the nature of the multiple sonic

Graciela Gelmini

Talks given at the V Taller de Particulas y Campos (V-TPyC) and V Taller Latinoam. de Fenomenologia de las Interac. Fundam. (V-TLFIF), Puebla, Mexico, 10/30 - 11/3 1995. These lectures are devoted to elementary particle physicists and assume the reader has very little or no knowledge of cosmology and astrophysics. After a brief historical introduction to the

M. A. Ivanov, T. Mizutani, Yu. M. Valit

We calculate the heavy-to-light form factors in the relativistic quark model with heavy infrapropagators. Their q^2-dependence in the physical region is defined by two parameters: the &#34;infrared&#34; parameter νcharacterizing the infrared behavior of the heavy quark and the mass difference of the heavy meson and heavy quark E=m_H-M_Q. It is found that the

Edward R. Goetze, Ralf J. Spatzier

Let G be a connected semisimple Lie group without compact factors whose real rank is at least 2, and let Γ\subset G be an irreducible lattice. We provide a C^\infty classification for volume-preserving Cartan actions of Γand G. Also, if G has real rank at least 3, we provide a C^\infty classification for volume-preserving, multiplicity free, trellised, Anoso

J. Ambjorn, K. N. Anagnostopoulos, U. Magnea, G. Thorleifsson

We provide evidence that the KPZ exponents in two-dimensional quantum gravity can be interpreted as scaling exponents of correlation functions which are functions of the invariant geodesic distance between the fields.

Jerrold Franklin

The new designation of heavy baryons proposed by Falk (hep-ph/9603389) is shown to violate minimal symmetry sum rules.

Bing An Li

A theory of tau mesonic decays is proposed. The general formula of the axial-vector currents of mesons is presented. The meson vertices are obtained from an effective chiral theory of mesons. The vertices depend on momentum. Many decay modes are studied. Theoretical results agree reasonably well with the data. There are predictions.

G. Wilk, Z. Wlodarczyk

We propose model of propagation of lumps of Strange Quark Matter (strangelets) through the atmosphere, which accounts for their apparent strong penetrability and normal nuclear-type sizes at the same time. The mass spectrum of strangelets reaching the Earth predicted by this model agrees very well with the existing data on the abundance of different elemets

H. L. Lai, J. Huston, S. Kuhlmann, F. Olness

The impact of recent precision measurements of DIS structure functions and inclusive jet production at the Tevatron on the global QCD analysis of parton distribution functions is studied in detail. Particular emphasis is placed on exploring the range of variation of the gluon distribution $G(x,Q)$ allowed by these new data. The strong coupling of $G(x,Q)$ wi

Ines Quandt

For a given base scheme, a correspondence is established between a class of sheaves on curves over this base scheme and certain points of infinite Grassmannians. This equivalence extends to a characterization of commutative algebras of ordinary differential operators with coefficients in the ring of formal power series over a given $k$-algebra. Our construct

Amihay Hanany, Igor R. Klebanov

We argue for the existence of phase transitions in $3+1$ dimensions associated with the appearance of tensionless strings. The massless spectrum of this theory does not contain a graviton: it consists of one $N=2$ vector multiplet and one linear multiplet, in agreement with the light-cone analysis of the Green-Schwarz string in $3+1$ dimensions. In M-theory

Richard B. Melrose, Victor Nistor

The Hochschild and cyclic homology groups are computed for the algebra of `cusp&#39; pseudodifferential operators on any compact manifold with boundary. The index functional for this algebra is interpreted as a Hochschild 1-cocycle and evaluated in terms of extensions of the trace functionals on the two natural ideals, corresponding to the two filtrations by

N. Hayashi, M. Ichioka, K. Machida

The electronic structure of vortices in a type II superconductor is analyzed within the quasi-classical Eilenberger framework. The possible origin of a sixfold ``star&#39;&#39; shape of the local density of states, observed by scanning tunneling microscope experiments on NbSe$_2$, is examined in the light of the three effects; the anisotropic pairing, the vo

M. S. Fayache, Y. Y. Sharon, L. Zamick

The effect of the ``$B$&#39;&#39; term in the interaction $-χQ\cdot Q(1+B\vecτ(1)\cdot \vecτ(2))$, which was previously considered in the $0p$ shell, is now studied in a larger space which includes $ΔN=2$ excitations. We still get a collapse of low-lying states below the conventional $J=0^+$ ground state when $B$ is made sufficiently negative.

M. Gyulassy, D. H. Rischke, B. Zhang

Mini-jet production in ultra-relativistic nuclear collisions leads to initial conditions characterized by large fluctuations of the local energy density (hot spots) and of the collective flow field (turbulence). Assuming that local equilibrium is reached on a small time scale, $\sim 0.5$ fm/c, the transverse evolution of those initial conditions is computed

Thomas D. Cohen

Regularization and renormalization is discussed in the context of low-energy effective field theory treatments of two or more heavy particles (such as nucleons). It is desirable to regulate the contact interactions from the outset by treating them as having a finite range. The low energy physical observables should be insensitive to this range provided that

E. L. Briggs, D. J. Sullivan, J. Bernholc

We describe a set of techniques for performing large scale ab initio calculations using multigrid accelerations and a real-space grid as a basis. The multigrid methods provide effective convergence acceleration and preconditioning on all length scales, thereby permitting efficient calculations for ill-conditioned systems with long length scales or high energ

A. V. Isaev, S. G. Krantz

We give a complete description of bounded Reinhardt domains of finite boundary smoothness that have non-compact automorphism group. As part of this program, we show that the classification of domains with non-compact automorphism group and having only finite boundary smoothness is considerably more complicated than the classification of such domains that hav

U. Aglietti, L. Griguolo, R. Jackiw, S. -Y. Pi

We show that excitations in a recently proposed gauge theory for anyons on a line in fact do not obey anomalous statistics. On the other hand, the theory supports novel chiral solitons. Also we construct a field-theoretic description of lineal anyons, but gauge fields play no role.

J. Ambjorn, G. K. Savvidy, K. G. Savvidy

Using the Steiner-Weyl expansion formula for parallel manifolds and the so called gonihedric principle we find a large class of discrete integral invariants which are defined on simplicial manifolds of various dimensions. These integral invariants include the discrete version of the Hilbert-Einstein action found by Regge and alternative actions which are lin

J. -S. Caux, I. Kogan, A. Lewis, A. M. Tsvelik

We study the operator product expansion in the bosonic $SU(2)_0$ and SUSY $SU(2)_2$ WZNW models. We find that these OPEs contain both logarithmic operators and new conserved currents, leading to an extension of the symmetry group.

Charles Nash, Denjoe O&#39; Connor

We give a lattice theory treatment of certain one and two dimensional quantum field theories. In one dimension we construct a combinatorial version of a non-trivial field theory on the circle which is of some independent interest in itself while in two dimensions we consider a field theory on a toroidal triangular lattice. We take a continuous spin Gaussian

Tadeusz Wibig

A procedure is proposed to extract experimental information about the primary cosmic Ray composition from the data taken with the KASCADE setup.

Gautam Bhattacharyya, Rabindra N. Mohapatra

The $\eegg$ event reported recently by the CDF Collaboration has been interpreted as a signal of supersymmetry in several recent papers. In this article, we report on an alternative non-supersymmetric interpretation of the event using an extension of the standard model which contains new physics at the electroweak scale that does not effect the existing prec

K. J. Eskola, A. V. Leonidov, P. V. Ruuskanen

Minijet production in hadronic and nuclear collisions through a BFKL pomeron ladder is studied for the energies of the future LHC heavy-ion collisions. We use unintegrated gluon densities compatible with the small-$x$ increase of parton distributions observed at HERA. We show that at LHC energies the BFKL minijet and transverse energy production is at most o

I. I. Bigi

The heavy quark expansion implemented through an operator product expansion provides us with a treatment of inclusive decays of beauty and charm hadrons that is genuinely derived from QCD,though it requires one additional assumption, namely that of &#39;local&#39; quark-hadron duality. Subtleties in the application of factorization to hadronic expectation va

Taco Nieuwenhuis, J. A. Tjon

The Feynman-Schwinger representation is used to construct scalar-scalar bound states for the set of all ladder and crossed-ladder graphs in a ϕ^2χtheory in (3+1) dimensions. The results are compared to those of the usual Bethe-Salpeter equation in the ladder approximation and of several quasi-potential equations. Particularly for large couplings, the ladder

Tadeusz Wibig

The problem of the estimation of distribution parameters in the case of experimentally limited information is discussed. As an example the determination of the total number of muons in Extensive Air Showers registered in the KASCADE experiment is studied in details. Some methods based on other than standard maximum-likelihood approach are examined. The advan

S. Thurner, M. Feurstein, H. Markum

We analyze the interplay of topological objects in four dimensional QCD. The distributions of color magnetic monopoles obtained in the maximum abelian gauge are computed around instantons in both pure and full QCD. We find an enhanced probability of encountering monopoles inside the core of an instanton on gauge field average. For specific gauge field config

J. Jersak, C. B. Lang, T. Neuhaus

The line of phase transitions, separating the confinement and the Coulomb phases in the four-dimensional pure compact U(1) gauge theory with extended Wilson action, is reconsidered. We present new numerical evidence that a part of this line, including the original Wilson action, is of second order. By means of a high precision simulation on homogeneous latti

Jonathan Gratus, Robin W Tucker

The causality structure of two-dimensional manifolds with degenerate metrics is analysed in terms of global solutions of the massless wave equation. Certain novel features emerge. Despite the absence of a traditional Lorentzian Cauchy surface on manifolds with a Euclidean domain it is possible to uniquely determine a global solution (if it exists), satisfyin

L. R. W. Abramo, J. A. S. Lima

The flat inflationary dust universe with matter creation proposed by Prigogine and coworkers is generalized and its dynamical properties are reexamined. It is shown that the starting point of these models depends critically on a dimensionless parameter $Σ$, closely related to the matter creation rate $ψ$. For $Σ$ bigger or smaller than unity flat universes c

Edward R. Goetze, Ralf J. Spatzier

We prove a generalization of Livsic&#39;s Theorem on the vanishing of the cohomology of certain types of dynamical systems. As a consequence, we strengthen a result due to Zimmer concerning algebraic hulls of Anosov actions of semisimple Lie groups. Combining this with Topological Superrigidity, we find a Holder geometric structure for multiplicity free Anos

Steven S. Plotkin, Jin Wang, Peter G. Wolynes

Energetic correlations due to polymeric constraints and the locality of interactions, in conjunction with the apriori specification of the existence of a particularly low energy state, provides a method of introducing the aspect of minimal frustration to the energy landscapes of random heteropolymers. The resulting funnelled landscape exhibits both a phase t

J. I. Katz

The tensile strength of fused silica fibers is believed to approach its intrinsic value at low temperature, and modern experiments indicate very small, perhaps unmeasured, intrinsic dispersion in this strength. I consider the application of classical ``weakest link&#39;&#39; models to this problem in an attempt to determine the number and therefore the natur

C. Zhou, D. M. Newns, J. A. Misewich, P. C. Pattnaik

Here we propose and analyze the behavior of a FET--like switching device, the Mott transition field effect transistor, operating on a novel principle, the Mott metal--insulator transition. The device has FET-like characteristics with a low ``ON&#39;&#39; impedance and high ``OFF&#39;&#39; impedance. Function of the device is feasible down to nanoscale dimens

J. E. Moore, F. D. M. Haldane

The spectrum of edge excitations is derived for the spin-unpolarized $ν= 2$ and $ν= 2/3$ FQHE. Numerical diagonalization of a system of six electrons on a disc confirms that the edge $ν= 2/3$ spin-singlet FQHE state consists of oppositely directed spin and charge branches on the same physical edge. The highly correlated $ν= 2/3$ singlet edge is shown to have

F. D. M. Haldane, Kun Yang

We study the effects of mixing of different Landau levels on the energies of one-body states, in the presence of a strong uniform magnetic field and a random potential in two dimensions. We use a perturbative approach and develop a systematic expansion in both the strength and smoothness of the random potential. We find the energies of the extended states sh

J. P. Rodriguez

The equivalence between the Lawrence-Doniach model for films of extreme type-II layered superconductors and a generalization of the back-scattering model for spin-1/2 electrons in one dimension is demonstrated. This fermion analogy is then exploited to obtain an anomalous $H_{\parallel}^{-1}$ tail for the parallel equilibrium magnetization of the minimal dou

Taku Seki, Yoshio Kuramoto, Tomotoshi Nishino

This paper investigates origin of the extra stability associated with particular values (magic numbers) of the total angular momentum of electrons in a quantum dot under strong magnetic field. The ground-state energy, distribution functions of density and angular momentum, and pair correlation function are calculated in the strong field limit by numerical di

Carl de Marcken

This paper discusses the problem of learning language from unprocessed text and speech signals, concentrating on the problem of learning a lexicon. In particular, it argues for a representation of language in which linguistic parameters like words are built by perturbing a composition of existing parameters. The power of this representation is demonstrated b

M. Yamada, K. Ohkitani

We study the scaling behavior of the Lyapunov spectra of a chaotic shell model for 3D turbulence. First, we quantify localization of the Lyapunov vectors in the wavenumber space by using the numerical results. Using dimensional arguments of Kolmogorov-type, we then deduce explicitly the asymptotic scaling behavior of the Lyapunov spectra. This in turn is con

Luiz N. da Costa, Wolfram Freudling, Gary Wegner, Riccardo Giovanelli

We present a new reconstruction of the mass density and the peculiar velocity fields in the nearby universe using recent measurements of Tully-Fisher distances for a sample of late spirals. We find significant differences between our reconstructed fields and those obtained in earlier work: overdensities tend to be more compact while underdense regions, consi

R. T. Boreiko, A. L. Betz

We have observed the 158 micron 2P3/2-2P1/2 fine-structure line of 12C II simultaneously with the F=2-1 and F=1-0 hyperfine components of this transition in 13C II in the Orion photodissociation region near theta1C . The line profiles were fully resolved using a heterodyne spectrometer with 0.5 km/s resolution. The relative intensities of these lines give a

Adam Frank, Garrelt Mellema

We explore the physics of time-dependent hydrodynamic collimation of jets from Young Stellar Objects (YSOs). Using parameters appropriate to YSOs we have carried out high resolution hydrodynamic simulations modeling the interaction of a central wind with an environment characterized by a moderate opening angle toroidal density distribution. The results show

Eric V. Linder

Cosmological inhomogeneities gravitationally deflect radiation propagating from distant sources, transforming the spatial and angular correlation functions of intrinsic source properties. For a gaussian distribution of deflections (e.g. from a primordial gaussian density perturbation spectrum or from the central limit theorem) we calculate the probability di

Wayne Hu, Martin White

We discuss how the curvature of the universe can be robustly measured employing only the gross features of the CMB anisotropy spectrum. Though the position of the first peak is not robust, uncertainties in the model for structure formation can be removed by using the spacing of the acoustic peaks and the location of the damping tail. Combined these provide i

J. B. Jones, S. P. Driver, S. Phillipps, J. I. Davies

At B magnitudes >~ 24 there is a well-known excess of galaxies (compared to standard models) which is probably due to an (evolving) population of sub-L* galaxies at moderate redshifts (<~ 0.4). One particular hypothesis which is hard to test directly via number counts or even redshift surveys is the possibility that the faint blue galaxies are in fact sub-ga

Martin White, Wayne Hu

We discuss ability of the harmonic pattern of peaks in the CMB angular power spectrum to test inflation. By studying robust features of alternate models, which must all be isocurvature in nature, we reveal signatures unique to inflation. Inflation thus could be validated by the next generation of experiments.

Graham R. Vincent, Mark Hindmarsh, Mairi Sakellariadou

We investigate scaling and correlations of the energy and momentum in an evolving network of cosmic strings in Minkowski space. These quantities are of great interest, as they must be understood before accurate predictions for the power spectra of the perturbations in the matter and radiation in the early Universe can be made. We argue that Minkowski space p

Alfred Gautschy

To improve the understanding of the pulsational instabilities of some of the PG1159-type pre-white dwarfs we performed detailed stability analyses on helium star evolutionary models. With the canonical chemical compositions, pulsational instabilities were encountered for all stellar masses considered (0.57, 0.63, 0.7 M_sol). The blue boundary agrees satisfac

Esther M. Hu, Richard G. McMahon

Studies of the formation and early history of galaxies have been hampered by the difficulties inherent in detecting faint galaxy populations at high redshift. As a consequence, observations at the highest redshifts (3.5 < z < 5) have been restricted to objects that are intrinsically bright. These include quasars, radio galaxies, and some Ly alpha-emitting ob