June 1996 arXiv papers — page 14

Anh Kiet Nguyen, A. Sudbo, R. E. Hetzel

We study the interplay between a novel vortex-loop unbinding in finite magnetic field at T=T_V and flux-line lattice (FLL) melting at T=T_M in type-II superconductors. The FLL melts due to nucleation of vortex loops parallel to c-axis, connected to flux lines. For moderate anisotropy, phase coherence along c-axis is lost at T_V > T_M due to an ab-plane vorte

Götz S. Uhrig, H. J. Schulz

Motivated by recent measurements on CuGeO$_3$ the spectrum of magnetic excitations of an antiferromagnetic $S=\frac{1}{2}$ chain with alternating coupling strength is investigated. Wave vector dependent magnons and a continuum with square root behavior at the band edges are found. The spectral density of the continua is calculated. Spin rotation symmetry fix

Andrew R. Golding

Two classes of methods have been shown to be useful for resolving lexical ambiguity. The first relies on the presence of particular words within some distance of the ambiguous target word; the second uses the pattern of words and part-of-speech tags around the target word. These methods have complementary coverage: the former captures the lexical ``atmospher

T. W. Hijmans, G. V. Shlyapnikov, A. L. Burin

We discuss the role of light absorption by pairs of atoms (radiative collisions) in the context of a model for an atom laser. The model is applied to the case of VSCPT cooling of metastable triplet helium. We show that, because of radiative collisions, for positive detuning of the driving light fields from an atomic resonance the operating conditions for the

Yu. Kagan, E. L. Surkov, G. V. Shlyapnikov

We discuss the dynamic properties of a trapped Bose-condensed gas under variations of the confining field and find analytical scaling solutions for the evolving coherent state (condensate). We further discuss the characteristic features and the depletion of this coherent state.

George M. Frichter, John P. Ralston, Douglas W. McKay

Interactions of ultrahigh energy neutrinos of cosmological origin in large volumes of radio-transparent South Polar ice can be detected via coherent Cherenkov emission from accompanying electromagnetic showers. A pilot experiment employing buried radio receivers has been successfully deployed at the South Pole and data are now being collected. The physics of

John P. Ralston, Douglas W. McKay, George M. Frichter

The ultra-high energy neutrino nucleon cross section grows at a surprising rate with energy due to QCD effects in the target. Recent electroproduction data allows an update of earlier predictions. We compare the results of our own calculations with those of other groups, and critically review the foundation and reliability of the calculations. The question o

Luc Simard, Christopher J. Pritchet

Low-mass starbursting galaxies have been proposed as the explanation of the excess of faint galaxies observed at intermediate redshifts. If this hypothesis is correct, then intermediate redshift galaxies should rotate more slowly than nearby galaxies with the same rest-frame luminosity. We present the results of a survey of the internal kinematics of interme

Jesus Pando, Li-Zhi Fang

Using a discrete wavelet based space-scale decomposition (SSD), the spectrum of the skewness and kurtosis is developed to describe the non-Gaussian signatures in cosmologically interesting samples. Because the basis of the discrete wavelet is compactly supported, the one-point distribution of the father function coefficients (FFCs) taken from one realization

Amy J. Mioduszewski, Philip A. Hughes, G. Comer Duncan

A series of simulated maps showing the appearance in total intensity of flows computed using a recently developed relativistic hydrodynamic code (Duncan \& Hughes 1994: ApJ, 436, L119) are presented. The radiation transfer calculations were performed by assuming the flow is permeated by a magnetic field and fast particle distribution in energy equipartition,

Andrew Gould, B. Scott Gaudi

We show that it is possible to image the structure of a distant quasar on scales of $\sim 1\,$AU by constructing a telescope which uses a nearby dwarf star as its ``primary lens'' together with a satellite-borne ``secondary''. The image produced by the primary is magnified by $\sim 10^5$ in one direction but is contracted by 0.5 in the other,

H. -W. Rix, P. Guhathakurta, M. Colless, K. Ing

We present measurements of the OII(3727) emission line width for a complete sample of 24 blue field galaxies (21.25<B<22, B-R<1.2) at <z>=0.25, obtained with the AUTOFIB fibre spectrograph on the Anglo-Australian Telescope. Most emission lines are spectrally resolved, yet all have dispersions sigma<100km/s. Five of the 24 sample members have OII doublet line

Peter Schenzel

There is a spectral sequence technique in order to estimate the local cohomology of a ring by the local cohomology of a certain form ring. As applications there are information on the descent of homological properties (Cohen-Macaulay, Buchsbaum etc.) from the form ring to the ring itself. In the case of Buchsbaum ring there is a discussion of the descent of

Michael Yu. Lashkevich

Using the vertex operator approach we show that fusion of the RSOS models can be considered as a kind of coset construction which is very similar to the coset construction of minimal models in conformal field theory. We reproduce the excitation spectrum and $S$-matrix of the fusion RSOS models in the regime III and show that their correlation functions and f

J. S. Bagla, T. Padmanabhan

We investigate the transfer of power between different scales and coupling of modes during non-linear evolution of gravitational clustering in an expanding universe. We start with a power spectrum of density fluctuations that is exponentially damped outside a narrow range of scales and use numerical simulations to study evolution of this power spectrum. Non-

D. I. Gurevich, P. N. Pyatov, P. A. Saponov

We discuss how properties of Hecke symmetry (i.e., Hecke type R-matrix) influence the algebraic structure of the corresponding Reflection Equation (RE) algebra. Analogues of the Newton relations and Cayley-Hamilton theorem for the matrix of generators of the RE algebra related to a finite rank even Hecke symmetry are derived.

K. Kimura, J. Shiraishi, J. Uchiyama

A level-one representation of the quantum affine superalgebra $\U_q(\hat{\frak{sl}}(M+1|N+1))$ and vertex operators associated with the fundamental representations are constructed in terms of free bosonic fields. Character formulas of level-one irreducible highest weight modules of $\U_q(\hat{\frak{sl}}(2|1))$ are conjectured.

N. Hambli

We consider an embedding of the extremal four-dimensional Reissner-Nordström black hole into type $IIB$ string theory. The equivalent type $IIB$ configuration, in the D-brane weak-coupling picture, is a bound state of D1- and D5-branes threaded by fundamental type $IIB$ strings. The bound state involves also a NSNS solitonic 5-brane, mimicking the role of th

Taichi Itoh, Yoonbai Kim, Masaki Sugiura, Koichi Yamawaki

Dynamical fermion mass generation is studied in the three-dimensional Thirring model reformulated as a gauge theory by introducing hidden local symmetry. The analysis by use of Schwinger-Dyson equation is shown to exhibit a critical behavior as the number $N$ of four-component fermions approaches $N_{\rm cr}=128/3π^{2}$.

M. Beneke

I briefly review the nonrelativistic QCD picture of quarkonium production and its confrontation with experiment in various production processes.

John D. Stack, Roy J. Wensley, Steven D. Neiman

We resolve a discrepancy between the SU(2) spacial string tension at finite temperature, and the value obtained by monopoles in the maximum Abelian gauge. Previous work had incorrectly omitted a term due to Dirac sheets. When this term is included, the monopole and full SU(2) determinations of the spacial string tension agree to within the statistical errors

Daniel A. Hamburger-Lidar

The diffraction spectrum of coherent waves scattered from fractal supports is calculated exactly. The fractals considered are of the class generated iteratively by successive dilations and translations, and include generalizations of the Cantor set and Sierpinski carpet as special cases. Also randomized versions of these fractals are treated. The general res

A. V. Andreev, B. D. Simons, O. Agam, B. L. Altshuler

We construct a field theory to describe energy averaged quantum statistical properties of systems which are chaotic in their classical limit. An expression for the generating function of general statistical correlators is presented in the form of a functional supermatrix nonlinear $σ$-model where the effective action involves the evolution operator of the cl

Jason Eisner

Under categorial grammars that have powerful rules like composition, a simple n-word sentence can have exponentially many parses. Generating all parses is inefficient and obscures whatever true semantic ambiguities are in the input. This paper addresses the problem for a fairly general form of Combinatory Categorial Grammar, by means of an efficient, correct

James R. Graham, Arjun Dey

Infrared surveys have discovered a significant population of bright (K<19) extremely red (R-K>6) objects. Little is known about the properties of these objects on account of their optical faintness (R>24). Here, we report deep infrared imaging and spectroscopy of one of the extremely red objects (EROs) discovered by Hu \& Ridgway (1994) in the field of the z

Billy D. Jones, Robert J. Perry, Stanislaw D. Glazek

We study the QED bound-state problem in a light-front hamiltonian approach. Starting with a bare cutoff QED Hamiltonian, $H_{_{B}}$, with matrix elements between free states of drastically different energies removed, we perform a similarity transformation that removes the matrix elements between free states with energy differences between the bare cutoff, $Λ

Andrea Begliuomini, Luciano Bracci

We study the time required for a wave packet to tunnel beyond a square barrier, or to be reflected, by envisaging a physical clock which ticks only when the particle is within the barrier region. The clock consists in a magnetic moment initially aligned with the $x$ axis which in the barrier region precesses around a constant magnetic field aligned with the

Dilip Kumar Ghosh, Rohini M. Godbole, Sreerup Raychaudhuri

We investigate the possibility that the excess of four-jet events in $e^+e^-$ collisions at LEP-1.5 which has been reported by the ALEPH Collaboration could be due to the production of charginos or neutralinos, followed by their decay into quark jets through baryon number-violating ($λ^{\prime\prime}$) couplings. An estimate at the parton level shows, howeve

L. Clavelli, I. Terekhov

In the light gluino variant of the minimal supersymmetric model gluino pairs can be readily produced in collider experiments even if the squarks are arbitrarily heavy. This enhances the jet transverse energy distributions. In addition the slower running of the strong coupling constant in the presence of light gluinos leads to a further enhancement at higher

Jerzy Plebanski, Maciej Przanowski

The action for the su(N) SDYM equations is shown to give in the limit $N \to \infty$ the action for the six-dimensional version of the second heavenly equation. The symmetry reductions of this latter equation to the well known equations of self-dual gravity are given. The Moyal deformation of the heavenly equations are also considered.

R. I. Brafman, M. Tennenholtz

Motivated by the control theoretic distinction between controllable and uncontrollable events, we distinguish between two types of agents within a multi-agent system: controllable agents, which are directly controlled by the system&#39;s designer, and uncontrollable agents, which are not under the designer&#39;s direct control. We refer to such systems as pa

S. Bhansali, G. A. Kramer, T. J. Hoar

An important problem in geometric reasoning is to find the configuration of a collection of geometric bodies so as to satisfy a set of given constraints. Recently, it has been suggested that this problem can be solved efficiently by symbolically reasoning about geometry. This approach, called degrees of freedom analysis, employs a set of specialized routines

K. Ziegler

A two-dimensional array of quantum dots in a magnetic field is considered. The electrons in the quantum dots are described as unitary random matrix ensembles. The strength of the magnetic field is such that there is half a flux quantum per plaquette. This model exhibits the Integer Quantum Hall Effect. For $N$ electronic states per quantum dot the limit $N\t

F. V. Kusmartsev, M. Saarela

Thin $^4$He films adsorbed to weakly attractive substrates form nearly 2D layers. We describe the vortices in 2D superfluid $^4$He like quasiparticles. With the aid of a variational many-body calculation we estimate their inertial mass and describe their interactions with the $^4$He particles and other vortices. Third sound measurements revealed anomalous be

F. V. Kusmartsev

We describe a &#34;train&#34; effect which may exist in small metallic and semiconductor rings and might be associated with the long-standing problem of the persistent current enhancement. The current is associated with the cooperative motion of N electrons constituing the N-electron &#34;train&#34;. The train arises via an excitation or a backflow of spin w

F. V. Kusmartsev

We propose very general vortex nucleation mechanisms analogous to a hydrodynamic instability and calculate associated critical velocity in agreement with experiments. The creation of vortices via extrinsic mechanism is driven by a formation of the surface vorticity sheet created by the flow, which reaches a critical size. Such a sheet screens an attraction o

John H. Jefferson, Wolfgang Häusler

It is shown that at low densities, quantum dots with few electrons may be mapped onto effective charge-spin models for the low-energy eigenstates. This is justified by defining a lattice model based on a many-electron pocket-state basis in which electrons are localised near their classical ground-state positions. The equivalence to a single-band Hubbard mode

Alberto Suarez, Jean Pierre Boon, Patrick Grosfils

In systems removed from equilibrium, intrinsic microscopic fluctuations become correlated over distances comparable to the characteristic macroscopic length over which the external constraint is exerted. In order to investigate this phenomenon, we construct a microscopic model with simple stochastic dynamics using lattice gas automaton rules that satisfy loc

Alexander Gromov

The Cauchy problem in the LTB model is formulated. The rules of calculating three undetermined functions which defined a solution in the LTB model are presented. One example of exact nonhomogeneous model is studied. The limit transformation to the FRW model is shown.

Xiang-Ping Wu, Li-Zhi Fang, Zonghong Zhu, Bo Qin

The associations of the angular positions of background quasars with foreground galaxies, clusters of galaxies and quasars are often attributed to the statistical lensing by gravitational potentials of the matter along the lines of sight, although it has been known that none of the individual objects (galaxies, clusters or quasars) are able to fully explain