September 1997 arXiv papers — page 4

G. Goldoni, F. Rossi, E. Molinari

We review the effects of Coulomb correlation on the linear and non-linear optical properties of semiconductor quantum wires, with emphasis on recent results for the bound excitonic states. Our theoretical approach is based on generalized semiconductor Bloch equations, and allows full three-dimensional multisubband description of electron-hole correlation for

H. W. J. Blöte, M. T. Batchelor, B. Nienhuis

We numerically investigate the influence of self-attraction on the critical behaviour of a polymer in two dimensions, by means of an analysis of finite-size results of transfer-matrix calculations. The transfer matrix is constructed on the basis of the O($n$) loop model in the limit $n \to 0$. It yields finite-size results for the magnetic correlation length

Shou-Cheng Zhang

In this talk I outline the general strategy behind the SO(5) theory of high $T_c$ superconductivity. Progress in the direction of exact SO(5) models, numerical exact diagonalization and possible experimental tests are reviewed. I also address the criticisms raised recently against the SO(5) theory and point out directions for future exploration.

Yaakov Yaari

We propose a method for segmentation of expository texts based on hierarchical agglomerative clustering. The method uses paragraphs as the basic segments for identifying hierarchical discourse structure in the text, applying lexical similarity between them as the proximity test. Linear segmentation can be induced from the identified structure through applica

M. de Sousa Vieira, A. J. Lichtenberg

We show that the separate properties of weak synchronization (WS) and strong synchronization (SS), reported recently by Pyragas [K. Pyragas, Phys. Rev. E, 54, R4508 (1996)], in unidirectionally coupled chaotic systems, are not generally distinct properties of such systems. In particular, we find analytically for the tent map and numerically for some paramete

S. D. Bloom, R. C. Hartman, H. Terasranta, M. Tornikoski

We have conducted a multiwavelength study of several radio sources within or near the error boxes of EGRET unidentified sources at mid to high Galactic latitude, under the hypothesis that the radio sources are blazars and are thus the best identification candidates for the EGRET objects. We show that one of these radio sources, PMN 0850-12, has a flux of 1.5

A. Burrows, M. Marley, W. B. Hubbard, D. Sudarsky

Since October of 1995, employing Doppler spectroscopy astronomers have discovered as many as 20 giant planets and brown dwarfs, including companions to $τ$ Boo, 51 Peg, $\upsilon$ And, 55 Cnc, $ρ$ CrB, 70 Vir, 16 Cyg B, and 47 UMa. These discoveries have excited the planetary science community, astronomers, and the public at large. Within hours of the announ

L. Pietronero, F. Sylos Labini, M. Montuori

We introduce the basic techniques used for the analysis of three dimensional and two dimensional galaxy samples. We report the correlation analysis of various redshift surveys which shows that the available data are consistent with each other and manifest fractal correlations (with dimension $D \simeq 2$) up to the present observational limits without any te

Suzanne M. Linder

While it is possible to explain Lyman alpha absorber counts at low redshift using gas which is associated with moderately extended galaxies (Linder 1997), absorbers are often observed to be associated with galaxies at larger impact parameters from quasar lines of sight than are expected from calculated galaxy absorption cross sections in such absorber-galaxy

Suzanne M. Linder

A scenario is explored in which Lyman alpha absorbers at low redshift arise from lines of sight through extended galaxy disks, including those of dwarf and low surface brightness galaxies. A population of galaxies is simulated based upon observed distributions of galaxy properties, and the gas disks are modeled using pressure and gravity confinement. Some pa

John P. Hughes

I re-examine mass estimates of the Coma cluster from pre-ASCA X-ray spectral observations. A large range of model dark matter distributions are examined, under the assumptions of hydrostatic equilibrium and spherical symmetry, to determine the widest possible allowed range on the total mass of the cluster. Within a radius of 1 Mpc, the total cluster mass is

Matias Zaldarriaga

We discuss the analysis of polarization experiments with particular emphasis on those that measure the Stokes parameters on a ring on the sky. We discuss the ability of these experiments to separate the $E$ and $B$ contributions to the polarization signal. The experiment being developed at Wisconsin university is studied in detail, it will be sensitive to bo

Pauline Barmby, John P. Huchra

The Hercules Supercluster consists of the Abell clusters 2147, 2151, and 2152. Previous studies of the kinematics have been confounded by the difficulty of correctly assigning galaxies to the individual clusters, which are not well-separated. Our study has a total of 468 available velocities for galaxies in the region, 175 of them new. 414 galaxies are in th

Penny D. Sackett

Microlensing is the most promising method to study the statistical frequency of extra-solar planets orbiting typical (random) stars in the Milky Way, even those several kiloparsecs from Earth. The lensing zone corresponds to orbital separations of a few times the Earth-Sun distance (AU) -- a good match to many planets in our own Solar System -- and the proba

C. Adami, A. Biviano, A. Mazure

We analyse a sample of about 2000 galaxies in 40 regular clusters, to look for evidence of segregation with respect to galaxy luminosities and morphological types. We find evidence of luminosity segregation for galaxies brighter than $M_R < -21.5$, i.e. typically the four brightest members of each cluster. We also find evidence of morphological segregation:

V. E. Zavlin, G. G. Pavlov, J. Truemper

We re-analyzed soft X-ray data collected with the ROSAT and ASCA observatories on a candidate neutron star (NS) near the center of the supernova remnant PKS 1209-52. We fitted the observed spectra with NS atmosphere models. The hydrogen atmosphere fits yield more realistic parameters of the NS and the intervening hydrogen column than the traditional blackbod

Rob Ivison, A. P. Harrison, I. M. Coulson

We describe a search for redshifted [C II] in a z=3.137 damped Ly-alpha absorption system that has a large neutral hydrogen column density and which was controversially reported to be a source of CO emission, indicative of rapid star-formation (Frayer, Brown & Vanden Bout 1994; Braine, Downes & Guilloteau 1996). There is no sign of [C II] emission in our spe

Xiaohui Fan, Neta A. Bahcall, Renyue Cen

We present a method for determining the rms mass fluctuations on 8 h^-1 Mpc scale, sigma8. The method utilizes the rate of evolution of the abundance of rich clusters of galaxies. Using the Press-Schechter approximation, we show that the cluster abundance evolution is a strong function of sigma8: d log n/dz ~ -1/sigma8^2; low sigma8 models evolve exponential

B. Brent Gordon

We review what is known about the Hodge conjecture for abelian varieties, with some emphasis on how Mumford-Tate groups have been applied to this problem.

Robert Friedman, John W. Morgan, Edward Witten

This paper gives various methods for constructing vector bundles over elliptic curves and more generally over families of elliptic curves. We construct universal families over generalized elliptic curves via spectral cover methods and also by extensions, and then give a relative version of the construction in families. We give various examples and make Chern

Billy D. Jones

This dissertation presents the first theoretical investigation of the Lamb shift in a light-front hamiltonian approach: the dominant part of the splitting between the 2S(1/2) and 2P(1/2) energy levels in hydrogen is calculated. Also presented for the first time is an analytic calculation in a light-front hamiltonian approach of the singlet-triplet spin split

Maximo Banados, Mauricio Contreras

The Hamiltonian form of the Hilbert action in the first order tetrad formalism is examined. We perform a non-linear field redefinition of the canonical variables isolating the part of the spin connection which is canonically conjugate to the tetrad. The geometrical meaning of the constraints written in these new variables is examined.

Renzo Collina, Paolo Tomassini

We apply the method of the Renormalization Group (GR), following the Polchinski point of view, to a model of well developed and isotropic fluid turbulence. The Galilei-invariance is preserved and a universal behavior, related to the change of the stochastic stirring force, is evident by the numerical results in the inertial region, where a scale-invariant be

Luis Alvarez-Gaume, Frederic Zamora

These lectures give an introduction to duality in Quantum Field Theory. We discuss the phases of gauge theories and the implications of the electric-magnetic duality transformation to describe the mechanism of confinement. We review the exact results of N=1 supersymmetric QCD and the Seiberg-Witten solution of N=2 super Yang-Mills. Some of its extensions to

I. A. Batalin, I. V. Tyutin

The general solution to the quantum master equation (and its $Sp(2)$ symmetric counterpart) is constructed explicitly in case of finite number of variables. It is shown that the finite-dimensional solution is physically trivial and thus can not be extended directly to cover the case of a local field theory. In this way we conclude that the locality condition

J. Edelmann, G. Piller, W. Weise

We investigate polarized deuteron structure functions at small values of the Bjorken variable, x < 0.1. In this region contributions from the coherent interaction of diffractively excited hadronic states with both nucleons become important. A proper treatment of this process requires an extension of the Glauber-Gribov multiple scattering theory to include sp

R. Aloisio, V. Azcoiti, G. Di Carlo, A. Galante

We present the first results of an exact simulation of full QCD at finite density in the chiral limit. We have used a MFA (Microcanonical Fermionic Average) inspired approach for the reconstruction of the Grand Canonical Partition Function of the theory; using the fugacity expansion of the fermionic determinant we are able to move continuously in the ($β-μ$)

D. W. Sciama

Various recent observational developments are here used to make a more critical analysis of the parameter space of the decaying neutrino theory for the ionisation of the interstellar medium. These developments involve phenomena inside our Galaxy, outside the Galaxy but at essentially zero red shift, and at large red shifts. This new analysis leads to a viabl

Arnaud Buhot, Mirta B. Gordon

We determine the optimal performance of learning the orientation of the symmetry axis of a set of P = alpha N points that are uniformly distributed in all the directions but one on the N-dimensional sphere. The components along the symmetry breaking direction, of unitary vector B, are sampled from a mixture of two gaussians of variable separation and width.

W. Bietenholz

We construct an optimally local perfect lattice action for free scalars of arbitrary mass, and truncate its couplings to a unit hypercube. Spectral and thermodynamic properties of this ``hypercube scalar&#39;&#39; are drastically improved compared to the standard action. We also discuss new variants of perfect actions, using anisotropic or triangular lattice

Michio Jimbo, Jun&#39;ichi Shiraishi

An analog of the minimal unitary series representations for the deformed Virasoro algebra is constructed using vertex operators of the quantum affine algebra $U_q(\hat{sl}_2)$. A similar construction is proposed for the elliptic algebra $A_{q,p}(\hat{sl}_2)$.

Vadim Ponomarenko, Naoto Nagaosa

One-dimensional interacting electrons in a quantum wire connected to reservoirs are studied theoretically. The difference in the Tomonaga-Luttinger interaction constants between the wire (g) and reservoirs $(g_{\infty})$ produces the cross-correlation between the right- and left-going chiral components of the charge density wave field. The low energy asympto

Hiroshi Ito, M. J. Ramsey-Musolf

The form factor $g_{ρπ}^{(S)}(Q^{2})$ of the strange vector current transition matrix element $<ρ| \bar{s}γ_\mus|π>$ is calculated within the chiral quark model. A strange vector current of the constituent $U$- and D-quarks is induced by kaon radiative corrections and this mechanism yields the nonvanishing values of $g_{ρπ}^{(S)}(0)$. The numerical result at

Jin-fang Cai, Shi-kun Wang, Ke Wu, Chi Xiong

Based on Drinfeld realization of super Yangian Double DY(gl(1|1)), its pairing relations and universal R-matrix are given. By taking evaluation representation of universal R-matrix, another realization $L^{\pm}(u)$ of DY(gl(1|1)) is obtained. These two realizations of DY(gl(1|1)) are related by the supersymmetric extension of Ding-Frenkel map.

Arno Schindlmayr

We present a simple analytic scheme for calculating the binding energy of excitons in semiconductors that takes full account of the existing anisotropy in the effective mass, as a complement to the qualitative treatment in most textbooks. Results obtained for excitons in gallium nitride form the basis for a discussion of the accuracy of this approach.

Igor Aranson, Hugues Chate, Lei Han Tang

The response of spiral waves to external perturbations in a stable regime of the two-dimensional complex Ginzburg-Landau equation (CGLE) is investigated. It is shown that the spiral core has a finite mobility and performs Brownian motion when driven by white noise. Combined with simulation results, this suggests that defect-free and quasi-frozen states in th

D. Blaschke, Yu. L. Kalinovsky, S. Schmidt, H. -J. Schulze

We investigate possible consequences of resonant scalar interactions for dilepton production from a quark plasma at the chiral phase transition. It is found that this production mechanism is strongly suppressed compared to the Born process and has no significance for present experiments.

S. A. Smolyansky, A. V. Prozorkevich, S. Schmidt, D. Blaschke

We present an approach to derive a relativistic kinetic equation of the Vlasov type. Our approach is especially reliable for the description of quantum field systems with many internal degrees of freedom. The method is based on the Heisenberg picture and leads to a kinetic equation which fulfills the conservation laws. We apply the approach to the standard W

Yu. E. Titarenko, O. V. Shvedov, M. M. Igumnov, R. Michel

The results of experimental and computer simulation studies of the yields of residual product nuclei in Bi-209 thin targets irradiated by 130 MeV and 1.5 GeV protons are presented. The yields were measured by direct high-precision gamma-spectrometry. The gamma-spectrometer resolution was 1.8 keV in the 1332 keV line. The gamma-spectra were processed by the A

H. W. L. Naus

Starting from relativistic quantum field theories, describing interacting nucleons and pions coupled to the dynamical electromagnetic field, the pion degrees of freedom are eliminated by means of functional integration. Apart from taking into account some operators perturbatively in $e$, e.g. the vacuum polarization, this procedure is exact, giving effective

T. Sakai, J. Mori, A. J. Buchmann, K. Shimizu

We investigate the interaction between H-dibaryons employing a quark cluster model with a one-gluon-exchange potential and an effective meson exchange potential (EMEP). A deeply-bound state of two H-dibaryons due to the medium range attraction of the EMEP is obtained. The bound H--H system has a size of about 0.8 $\sim$ 0.9 fm because of the short-range repu

A. W. Schreiber, C. Alexandrou, R. Rosenfelder

There has been growing interest in studying the behaviour of QED in its strong coupling limit. The reason for this is not only that it serves as a simple prototype gauge theory for testing nonperturbative calculational techniques which one then goes on to apply to QCD, but also because the theory exhibits interesting behaviour in its own right. In particular

J. Gegenberg, G. Kunstatter

In the talk, the relationship between black holes in Jackiw-Teitelboim(JT) dilaton gravity and solitons in sine-Gordon field theory is described. The well-known connection between solutions of the sine-Gordon equation and constant curvature metrics is reviewed and expanded. In particular, it is shown that solutions to the dilaton field equations for a given

D. V. Vassilevich

We formulate criteria of applicability of the Faddeev-Popov trick to gauge theories on manifolds with boundaries. With the example of Euclidean Maxwell theory we demonstrate that the path integral is indeed gauge independent when these criteria are satisfied, and depends on a gauge choice whenever these criteria are violated. In the latter case gauge depende

D. V. Gal&#39;tsov, E. E. Donets, M. Yu. Zotov

Recent results concerning the internal structure of static spherically-symmetric non-Abelian black holes in the Einstein-Yang-Mills (EYM) theory and its generalizations including scalar fields are reviewed and discussed with an emphasis on the problem of a generic singularity in black holes. It is argued that in the theories admitting a violation of the naiv

Hisakazu Minakata, Alan Chodos

The Gross-Neveu model with chemical potential is investigated as a low-energy effective theory of polyacetylene. In particular, we focus on the abrupt change in the features of electric conductivity such as sharp rise in the Pauli paramagnetism at dopant concentration of about 6%. We will try to explain it by the finite density phase transition in the Gross-

J. M. Figueroa-O&#39;Farrill, A. Imaanpur, J. McCarthy

We consider the dimensional reduction of supersymmetric Yang-Mills on a Calabi-Yau 3-fold. We show by construction how the resulting cohomological theory is related to the balanced field theory of the Kaehler Yang-Mills equations introduced by Donaldson and Uhlenbeck-Yau.

Harald W. Griesshammer

Magnetically charged Abelian defects are shown to arise on most compact base manifolds and in most Abelian projection gauges. They obey the Dirac quantisation condition and give rise to homogeneous magnetic background fields. The reasons for their occurrence are global failures of the procedure with which gauge covariant operators are diagonalised or their e

L. Burakovsky, T. Goldman

We prove the validity of Schwinger&#39;s quartic nonet mass formula for a general nonet structure with the isoscalar singlet mass being shifted from its ``ideal&#39;&#39; value. We apply this formula to the problem of the correct q\bar{q} assignment for the scalar meson nonet. The results favor scalar isoscalar singlet and isoscalar octet masses in the vicin

C. Bernard

Lattice attempts to compute the leptonic decay constants of heavy-light pseudoscalar mesons are described. I give a short historical overview of such attempts and then discuss some current calculations. I focus on three of the most important sources of systematic error: the extrapolation to the continuum, the chiral extrapolation in light quark mass, and the

Harold W. Fearing, Randy Lewis, Nader Mobed, Stefan Scherer

We have evaluated the amplitude for muon capture by a proton, mu + p --> n + nu, to O(p^3) within the context of heavy baryon chiral perturbation theory (HBChPT) using the new O(p^3) Lagrangian of Ecker and Mojzis (E&M). We obtain expressions for the standard muon capture form factors and determine three of the coefficients of the E&M Lagrangian, namely, b_7

S. Moretti, K. Odagiri

We study charged Higgs boson production at future electron-proton colliders in the framework of the Minimal Supersymmetric Standard Model. We focus our attention to the case of single-top production and decay through the channel $t\to bH^\pm$ and of vector-scalar fusion via $W^{\pm*} Φ^*\to H^\pm$ (where $Φ=H,h$ and $A$). We consider the signature $H^\pm\to

Changhao Jin

We extend the approach based on the light-cone expansion and the heavy quark effective theory to the inclusive semileptonic decay of an unpolarized $b$-flavored hadron. It is applied to calculate the semileptonic decay width of the $Λ_b$ baryon and its ratio to that of the B meson. We obtain $Γ_{SL}(Λ_b)= 51\pm 9 |V_{cb}|^2{ps}^{-1}$ and $Γ_{SL}(Λ_b)/Γ_{SL}(

T. R. Hemmert, B. R. Holstein, G. Knoechlein, S. Scherer

We discuss the virtual Compton scattering reaction $e^-p\to e^-pγ$ at low energies. We present results for the generalized polarizabilities of the nucleon obtained in heavy baryon chiral perturbation theory at $O(p^3)$.

E. Maina, R. Pittau, M. Pizzio

One-loop QCD corrections to the full gauge invariant set of electroweak diagrams describing the charged current processes $e^+ e^- \to u \bar d μ\barν_μ$ (CC10), $e^+ e^- \to u \bar d e^- \barν_e$ (CC20) and $e^+ e^- \to u \bar d s \bar c$ (CC11) are computed. We compare the exact calculation with a ``naive&#39;&#39;approach to strong radiative corrections w

Ulf-G. Meißner, S. Steininger

We construct the complete effective chiral pion-nucleon Lagrangian in the presence of virtual photons to one loop. As an application, we consider strong and electromagnetic isospin violation for scattering of neutral pions off nucleons. We show that for the scattering lengths these isospin violating terms are of the same size as the purely hadronic ones. We

M. Grazzini, L. Trentadue, G. Veneziano

Using a generalized cut vertex expansion we introduce the concept of an extended fracture function for the description of semi-inclusive deep inelastic processes in the target fragmentation region. Extended fracture functions are shown to obey a standard homogeneous DGLAP-type equation which, upon integration over t, becomes the usual inhomogeneous evolution

Ken Kiers, Nathan Weiss

Motivated by the effect of matter on neutrino oscillations (the MSW effect) we have studied the propagation of neutrinos in a dense medium. The dispersion relation for massive neutrinos in a medium is known to have a minimum at nonzero momentum $p\sim G_Fρ/\sqrt{2}$. We have studied in detail the origin and consequences of this dispersion relation for both D

Howard E. Haber

The minimal supersymmetric extension of the Standard Model (MSSM) is reviewed. In the most general framework with minimal field content and R-parity conservation, the MSSM is a 124-parameter model (henceforth called MSSM-124). An acceptable phenomenology occurs only at exceptional points (and small perturbations around these points) of MSSM-124 parameter spa

Yubing Luo

We have studied $O(a^2)$ improved lattice QCD with the staggered fermion by using Symanzik&#39;s program. We find that there are 5 dimension-6 fermion bilinears and gauge operators. In addition, there are 10 four-fermion operators which are absent at the tree-level and tadpole-improved tree-level.

Stephan Elser, Burkhard Bunk

We compare the CPU cost of HMC to various implementations of the Hermitean variant of Lüscher&#39;s local bosonic algorithm (LBA) for 2D massive QED with two flavours of Wilson fermions. We carefully scan a 3-dimensional parameter subspace and find flat behaviour around the optimum. The gain factor of the LBA, as compared to HMC, is slightly smaller for the

B. B. Beard, R. C. Brower, S. Chandrasekharan, D. Chen

A new non-perturbative approach to quantum field theory --- D-theory --- is proposed, in which continuous classical fields are replaced by discrete quantized variables which undergo dimensional reduction. The 2-d classical O(3) model emerges from the (2+1)-d quantum Heisenberg model formulated in terms of quantum spins. Dimensional reduction is demonstrated

Pavlos M. Vranas

Domain Wall Fermions utilize an extra space time dimension to provide a method for restoring the regularization induced chiral symmetry breaking in lattice vector gauge theories even at finite lattice spacing. The breaking is restored at an exponential rate as the size of the extra dimension increases. As a precursor to lattice QCD studies the dependence of

O. Borisenko, M. Faber, G. Zinovjev

The phase structure of hot gauge theories with dynamical matter fields is reexamined in the canonical ensemble with respect to triality. We discuss properties of chromoelectric and chromomagnetic sectors of the theory and show whereas electric charges carrying a unit of Z(N) charge are screened at high temperatures via dynamical matter loops, this is not the

W. Bock, M. Golterman, Y. Shamir

In this more technical part we give additional details on the gauge-fixing approach presented in hep-lat/9709113. We also explain how the gauge-fixing approach evades the Nielsen-Ninomiya no-go theorem.

Ch. Schlichter, G. S. Bali, K. Schilling

Various field strength correlators are investigated in the maximal abelian projection of pure SU(2) lattice gauge theory. High precision measurements of the colour fields, monopole currents, their curl and divergence allow for detailed checks of the dual superconductor scenario. A further decomposition of abelian observables into monopole and photon parts re

W. Bock, M. Golterman, Y. Shamir

We report on recent progress with the definition of lattice chiral gauge theories, using a lattice action that includes a discretized Lorentz gauge-fixing term. This gauge-fixing term has a unique global minimum, and allows us to use perturbation theory in order to study the influence of the gauge degrees of freedom on the fermions. For the abelian case, we

Jun Nishimura

We show that the idea to use the overlap formalism to formulate 4D N=1 super Yang-Mills theory on the lattice without fine-tuning can be applied to 3D N=1 case as well. Another application we propose is a regularization of the IIB matrix model, which is large N reduced model of 10D N=1 super Yang-Mills theory.

J. Adams

We searched for the appearance of pi+pi- pairs with invariant mass greater than 648 MeV in a neutral beam. Such an observation could signify the decay of a long-lived light neutral particle. We find no evidence for this decay. Our null result severely constrains the existence of an R0 hadron, which is the lightest bound state of a gluon and a light gluino, a

H. Kleinert, S. V. Shabanov

As a contribution to the ongoing discussion of trajectories of spinless particles in spaces with torsion we show that the geometry of such spaces can be induced by embedding their curves in a euclidean space without torsion. Technically speaking, we define the tangent (velocity) space of the embedded space imposing non-holonomic constraints upon the tangent

Pavel Exner, Simeon Vugalter

We consider the discrete spectrum of the Dirichlet Laplacian on a manifold consisting of two adjacent parallel strips or planar layers coupled by a finite number N of windows in the common boundary. If the windows are small enough, there is just one isolated eigenvalue. We find upper and lower asymptotic bounds on the gap between the eigenvalue and the essen

Rugang Ye

In this paper, the existence and uniqueness of foliations by constant mean curvature spheres on asymptotically flat manifolds of nonzero ADM mass in all dimensions were established. (A similar result in the case of positive mass was obtained independently by G. Huisken and S. T. Yau, see the introduction of this paper and their paper in Inv. Math.)

H. C. Manoharan, Y. W. Suen, T. S. Lay, M. B. Santos

Experiments reveal that a confined electron system with two equally-populated layers at zero magnetic field can spontaneously break this symmetry through an interlayer charge transfer near the magnetic quantum limit. New fractional quantum Hall states at unusual total filling factors such as ν= 11/15 (= 1/3 + 2/5) stabilize as signatures that the system defo

A. V. Balatsky

It is argued that the $d_{x^2-y^2}$ superconductor exhibits the transition into $d_{x^2-y^2} + id_{xy}$ state in the presence of magnetic impurities in certain conditions. Linear coupling between impurity magnetization and the $d_{xy}$ component drives this transition. Violation of time-reversal symmetry and parity occurs spontaneously via the second order t

Pramod Gupta, S. Teitel, Michel J. P. Gingras

We carry out extensive Monte Carlo simulations on the Coulomb gas dual to the uniformly frustrated two dimensional XY model, for a sequence of frustrations f converging to the irraltional (3-sqrt 5)/2. We find in these systems a sharp first order equilibrium phase transition to an ordered vortex structure at a T_c which varies only slightly with f. This orde

P. Kleban, R. M. Ziff

We derive exact expressions for the excess number of clusters b and the excess cumulants b_n of a related quantity at the 2-D percolation point. High-accuracy computer simulations are in accord with our predictions. b is a finite-size correction to the Temperley-Lieb or Baxter-Temperley-Ashley formula for the number of clusters per site n_c in the infinite s

N. A. Rubin, A. J. Dahm

A recent experimental Physical Review Letter which claims to prove the existence of the single-electron ripplonic polaron associated with electrons on a helium film is examined. A correct evaluation of the holding field and a restriction of the polaron radius to the Wigner-Seitz radius lead to a gross discrepancy between experiment and theory. The polaron is

A. M. Sengupta, P. P. Mitra

The Singular Value Decomposition is a matrix decomposition technique widely used in the analysis of multivariate data, such as complex space-time images obtained in both physical and biological systems. In this paper, we examine the distribution of Singular Values of low rank matrices corrupted by additive noise. Past studies have been limited to uniform unc

M. E. Zhitomirsky, M. B. Walker

We consider excitation spectrum near a twin boundary in an orthorhombic $d+s$ superconductor. The low-energy spectrum is highly sensitive to the presence of the small amount of s-wave component. Robustness of the bound states at the Fermi level with respect to impurities and an extra boundary potential is investigated. The role of Andreev transmission proces

F. Bentosela, P. Exner, V. A. Zagrebnov

We discuss the discrete spectrum induced by bulges on threadlike mesoscopic objects, using two models, a continuous hard-wall waveguide and a discrete tight-binding model with two sorts of atomic orbitals. We show that elongated bulges induce numerous quasibound states. In the discrete model we also evaluate the probability of transition between the localize

P. Exner, P. Seba, A. F. Sadreev, P. Streda

We consider resonant vortices around nodal points of the wavefunction in electron transport through a mesoscopic device. With a suitable choice of the device geometry, the dominating role is played by single vortices of a preferred orientation. To characterize strength of the resulting magnetic moment we have introduced a magnetance, the quantity defined in

Matteo Campellone, Giorgio Parisi, Paola Ranieri

In this work we calculate the dynamical fluctuations at O(1/N) in the low temperature phase of the $p=2$ spherical spin glass model. We study the large-times asymptotic regimes and we find, in a short time-differences regime, a fluctuation dissipation relation for the four-point correlation functions. This relation can be extended to the out of equilibrium r

C. Castellani, C. Di Castro, M. Grilli

We underline and comment some features of the data obtained in the beautiful experiment by G. S. Boebinger, Y. Ando, A. Passner, T. Kimura, M. Okuya, J. Shimoyama, K. Kishio, K. Tamasaku, N. Ichikawa, and S. Uchida, Phys. Rev. Lett. 77, 5417 (1996). While in our general interpretation we agree with the authors that ``It is possible that charge ordering could

G. Iannaccone, G. Lombardi, M. Macucci, B. Pellegrini

We show that shot noise in a resonant tunneling diode biased in the negative differential resistance regions of the I-V characteristic is enhanced with respect to ``full&#39;&#39; shot noise. We provide experimental results showing a Fano factor up to 6.6, and show that it is a dramatic effect caused by electron-electron interaction through Coulomb force, en

P. Singha Deo, B. C. Gupta, A. M. Jayannavar, F. M. Peeters

It is known that the conductance of a quantum point contact is quantized in units of $2e^2/h$ and this quantization is destroyed by a non-adiabatic scatterer in the point contact, due to backscattering. Recently, it was shown [Phys. Rev. Lett. 71, 137 (1993)] that taking many non-adiabatic scatterers periodically in a quantum channel, the quantization can be

Arno Schindlmayr

We present a nontrivial model system of interacting electrons that can be solved analytically in the GW approximation. We obtain the particle number from the GW Green&#39;s function strictly analytically, and prove that there is a genuine violation of particle number conservation if the self-energy is calculated non-self-consistently from a zeroth order Gree

Ruihong Yue, Tetsuo Deguchi

The magnetic susceptibility and the low-temperature specific heat of the 1-dimensional Hubbard model under the integrable open-boundary conditions are discussed through the Bethe ansatz with the string hypothesis. The contributions of the boundary fields to both the susceptibility and the specific heat are obtained, and their exact expressions are analytical

Kenro Kawano, Minoru Takahashi

The antiferromagnetic Heisenberg spin systems on the three-leg ladder are investigated. Periodic boundary condition is imposed in the rung direction. The system has an excitation gap for all antiferromagnetic inter-chain coupling ($J_{\perp}>0$). The estimated gap for the strong coupling limit ($J_{\perp}/J_1 \to \infty$) is 0.28$J_1$. Although the interacti

L. B. Ioffe, D. Sherrington

We discuss a general formalism that allows study of transitions over barriers in spin glasses with long-range interactions that contain large but finite number, $N$, of spins. We apply this formalism to the Sherrington-Kirkpatrick model with finite $N$ and derive equations for the dynamical order parameters which allow &#39;&#39;instanton&#39;&#39; solutions

M. Chertkov, V. Yakhot

The dynamics of a thin Huygens front propagating through turbulent medium is considered. A rigorous asymptotic expression for the effective velocity $v_{F}$ proportional to the front area is derived. The small-scale fluctuations of the front position are shown to be strongly intermittent. This intermittency plays a crucial role in establishing a steady state

S. D. Bloom

The latest observations of BL Lacertae with the EGRET instrument on CGRO show that the gamma-ray flux was four times higher than the previous detection. Within the 1997 July 15-22 observation there was a dramatic factor of 2.5 increase in the gamma-ray flux, with a sharp peak of about 8 hours, and apparently preceding a brief optical flare by several hours.

Andrew Gould

Zhao has proposed that the microlensing events observed toward the Large Magellanic Cloud (LMC) could be due to faint stars in a dwarf galaxy or tidal debris lying along the line of sight to the LMC. Zaritsky & Lin claim to have detected such a structure which, they believe, could account for most of the observed microlensing optical depth. Here I show that

P. Lira, Nicholas B. Suntzeff, M. M. Phillips, Mario Hamuy

We present UBVRI light curves for the bright Type Ia supernovae SN 1990N in NGC 4639 and SN 1991T in NGC 4527 based on photometry gathered in the course of the Calan/Tololo supernova program. Both objects have well-sampled light curves starting several days before maximum light and spanning well through the exponential tail. These data supercede the prelimin

Ue-Li Pen

We present a generic algorithm for generating Gaussian random initial conditions for cosmological simulations on periodic rectangular lattices. We show that imposing periodic boundary conditions on the real-space correlator and choosing initial conditions by convolving a white noise random field results in a significantly smaller error than the traditional p

Matthias Steinmetz

The relation between high redshift galaxies and QSO absorption systems is discussed in the context of hierarchical galaxy formation. It is demonstrated that imprints of the reionization history of the universe are detectable in the $b$-parameter distribution of the \Lya forest at redshifts two to four, favoring models in which hydrogen and helium are reioniz

Carl. J. Grillmair, Jeremy R. Mould, Jon A. Holtzman, Guy Worthey

We present an F606W-F814W color-magnitude diagram for the Draco dwarf spheroidal galaxy based on Hubble Space Telescope WFPC2 images. The luminosity function is well-sampled to 3 magnitudes below the turn-off. We see no evidence for multiple turnoffs and conclude that, at least over the field of the view of the WFPC2, star formation was primarily single-epoc

P. Sreekumar, F. W. Stecker, S. C. Kappadath

The all-sky surveys in gamma-rays by the imaging Compton telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory for the first time allows detailed studies of the extragalactic diffuse emission at gamma-ray energies greater 1 MeV. A preliminary analysis of COMPTEL data indicates a significant de

P. Sreekumar

The all-sky survey in high-energy gamma rays (E$>$30 MeV) carried out by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions with the local int

C. Adami, A. Mazure, A. Biviano, P. Katgert

We have used the ESO Nearby Abell Cluster Survey (ENACS) in combination with the Cosmos Galaxy Catalogue, to investigate the existence of a Fundamental Plane (FP) for rich clusters of galaxies. The 20 clusters with the most regular projected galaxy distributions appear to define a quite narrow FP, which is similar to the FP found by Schaeffer et al., who use

G. G. Pavlov, V. E. Zavlin

Properties of X-ray radiation emitted from the polar caps of a radio pulsar depend not only on the cap temperature, size, and position, but also on the surface chemical composition, magnetic field, and neutron star&#39;s mass and radius. Fitting the spectra and the light curves with neutron star atmosphere models enables one to infer these parameters. As an