January 1995 arXiv papers — page 9

Lev Mikheev

A general case of a spatially nonuniform planar layered Ising model, or an equivalent quantum Ising chain, is analysed with an exact functional real space renormalization group. Various surface, finite size, quasiperiodic and random layer (McCoy-Wu) universality classes are obtained and discussed within a single theoretical framework leading to new insights

A. G. Rojo, C. A. Balseiro

We address the question of whether an anisotropic gap $d_{x^2-y^2}$ symmetry is compatible with localized states in the normal phase. The issue is important in high $T_c$ superconductors where a superconductor to insulator transition is observed in the underdoped regime, together with a number of experiments that support $d$-wave pairing. We find a reentrant

T. Xiang, J. M. Wheatley

A numerical approach to disordered 2D superconductors described by BCS mean field theory is outlined. The energy gap and the superfluid density at zero temperature and the quasiparticle density of states are studied. The method involves approximate self-consistent solutions of the Bogolubov-de$\,$Gennes equations on finite square lattices. Where comparison i

S. Voropaev

"Free" ( non-scattered ) Schroedinger anyons are considered. It is shown that for this special type of contact interactions scattering does not arise. By formulating the problem for the two particles system with a finite region of interaction which is then allowed to go to zero, it is established that this type of the above interactions is analog of

Martin R. Zirnbauer

The conductance coefficients of disordered mesoscopic devices with $n$ probes are investigated within the noninteracting electron approximation at zero temperature. The probes are eliminated from the theoretical description at the expense of introducing nonlocal boundary conditions at the position of the contacts. Conductors with a large number of weak conta

H. Nakamura, N. Hatano, M. Takahashi

The finite-size scaling function of the magnetization of the ferromagnetic Heisenberg chain is argued to be universal with respect to the magnitude of the spin. The finite-size scaling function is given explicitly by an analytical calculation in the classical limit $S=\infty.$ The universality is checked for $S=1/2$ and $1$ by means of numerical calculations

A. Fujita, S. Hikami

We investigate a gauged matrix model in the large $N$ limit which is closely related to the superconductor fluctuation and the flux lattice melting in two dimensions. With the use of saddle point method the free energy is expanded up to eighth order for the coupling constant $g$. In the case that the coefficient of quadratic term of the Ginzburg-Landau matri

John N. Bahcall, Sofia Kirhakos, Donald P. Schneider

HST observations of eight intrinsically luminous quasars with redshifts between $0.16$ and~$0.29$ are presented. Seven companion galaxies brighter than $M_V = -16.5$ lie within a projected distance of 25 kpc of the quasars; three of the companions are located closer than $3''$ (6 kpc projected distance) from the quasars, well within the volume that w

Lars Hernquist, Steinn Sigurdsson, Greg L. Bryan

We describe a version of an algorithm for evolving self-gravitating collections of particles that should be nearly ideal for parallel architectures. Our method is derived from the ``self-consistent field'' (SCF) approach suggested previously by Clutton-Brock and others. Owing to the use of a global description of the gravitational field, the particle

Roy Maartens, George F. R. Ellis, William R. Stoeger

We consider directly the equations by which matter imposes anisotropies on freely propagating background radiation, leading to a new way of using anisotropy measurements to limit the deviations of the Universe from a Friedmann-Robertson-Walker (FRW) geometry. This approach is complementary to the usual Sachs-Wolfe approach: the limits obtained are not as det

DI NELLA Helene, PATUREL Georges, Observatoire de Lyon

The distribution of galaxies up to a distance of 200 Mpc (650 million light-years) is flat and shows a structure like a shell roughly centered on the Local Supercluster (Virgo cluster). This result clearly confirms the existence of the hypergalactic large scale structure noted in 1988. This is presently the largest structure ever seen.

Juhi-Lian Julian Ting

A simple one-dimensional semi-classical model with a Morse potential is used to investigate the possibility of two-color infrared multi-photon dissociation of vibrationally excited nitrogen oxide. The amplitude ratio effects and adiabatic effects are investigated. Some initial states are found to have thresholds smaller than expected from single-mode conside

Asher Peres

In the standard physical interpretation of quantum theory, prediction and retrodiction are not symmetric. The opposite assertion by some authors results from their use of non-standard interpretations of the theory.

J. Bernabéu, G. A. González-Sprinberg, J. Vidal

We show that coherent $η$ and $\etap$ photoproduction by means of the Primakoff Effect on the proton depends on the strange component of the neutral axial current coupling. We construct polarization asymmetries that are sensitive to this coupling through the $γ- Z$ interference. The $η^\prime$ is not a Goldstone boson of a spontaneously broken chiral symmetr

Phillip Helbig, Rainer Kayser

For known gravitational lens systems the redshift distribution of the lenses is compared with theoretical expectations for $10^{4}$~Friedmann-Lema\^ıtre~cosmological models, which more than cover the range of possible cases. The comparison is used for assigning a relative probability to each of the models. The entire procedure is repeated for different value

S. A. Bass, C. Hartnack, H. Stoecker, W. Greiner

Triple differential cross sections of pions in heavy ion collisions at 1 GeV/nucl. are studied with the IQMD model. After discussing general properties of $Δ$ resonance and pion production we focus on azimuthal correlations: At projectile- and target-rapidities we observe an anticorrelation in the in-plane transverse momentum between pions and protons. At c.

R. Jackiw

Conventional quantization of two-dimensional diffeomorphism and Weyl invariant theories sacrifices the latter symmetry to anomalies, while maintaining the former. When alternatively Weyl invariance is preserved by abandoning diffeomorphism invariance, we find that some invariance against coordinate redefinition remains: one can still perform at will transfor

E. Elizalde, S. D. Odintsov

Unlike Einstein gravity, dilaton-Maxwell gravity with matter is renormalizable in $2+ε$ dimensions and has a smooth $ε\to 0$ limit.By performing a renormalization- group study of this last theory we show that the gravitational coupling constant $G$ has a non-trivial,ultraviolet stable fixed point (asymptotic freedom) and that the dilatonic coupling functions

A. K. Kapoor, Pankaj Sharan

We briefly review a hamiltonian path integral formalism developed earlier by one of us. An important feature of this formalism is that the path integral quantization in arbitrary co-ordinates is set up making use of only classical hamiltonian without addition of adhoc $\hbar^2$ terms. In this paper we use this hamiltonian formalism and show how exact path in

J. Engel, P. I. Krastev, K. Lande

We study the potential benefits of an iodine-based solar-neutrino detector for testing hypotheses that involve neutrino oscillations. We argue that such a detector will have a good chance of distinguishing the two allowed regions of $Δm^2$ -- $\sin^22θ$ parameter space if neutrino conversion is occurring in the sun. It should also be able to detect seasonal

Lali Chatterjee, Cheuk-Yin Wong

We investigate $e^+ e^- \to t\bar t$ by taking into account wave function distortion effects in the near-threshold region and interpolating the correction factor to the high-energy perturbative QCD region. The strong color attraction between the color singlet $t$ and $\bar t$ enhances the cross section over the tree level results near threshold. The rise of

H. Kurki-Suonio, M. Laine

The classification of the hydrodynamical growth mechanisms for the spherical bubbles of the low-temperature phase in cosmological phase transitions is completed by showing that the bubbles can grow as supersonic deflagrations. Such deflagrations consist of a Jouguet deflagration, followed by a rarefaction wave. Depending on the amount of supercooling, the ma

Tord Riemann

At LEP~1, cross sections and cross section asymmetries may be analysed model independently. Cross sections depend on four, asymmetries on two free parameters. As an example, I discuss the model independent $Z$ boson mass determination from the $Z$ line shape and compare it to the Standard Model approach.

V. S. Fadin, V. A. Khoze, A. D. Martin, A. Chapovsky

We calculate the Coulomb effects on the cross section for e+ e- --> W+ W- taking into account the instability of the W bosons. We carefully explain the consequences of instability throughout the energy range which will be accessible at LEP2. We present a formula which allows these effects to be easily implemented.

R. Alkofer, H. Reinhardt, H. Weigel

The description of baryons as chiral solitons of the Nambu--Jona--Lasinio (NJL) model is reviewed. A motivation for the soliton description of baryons is provided from large $N_C$ QCD. Rigorous results on the spontaneous breaking of chiral symmetry in QCD are discussed. It is then argued that the NJL model provides a fair description of low--energy hadron ph

A. Billoire

I review some numerical ways to determine the parameters of systems close to a first order phase transition point: energy and specific heat of the coexisting phases and interface tension. Numerical examples are given for the 2-d $q$ states Potts model.

R. Enomoto

We have carried out inclusive measurements of $Λ(\barΛ)$ production in two-photon processes at TRISTAN. The mean $\sqrt{s}$ was 58 GeV and the integrated luminosity was 265 pb$^{-1}$. Inclusive $Λ(\barΛ)$ samples were obtained under such conditions as no-electron, anti-electron, and remnant-jet tags. The data were compared with theoretical calculations. The

Xuejun Zhu, P. B. Littlewood, M. S. Hybertsen, T. M. Rice

We propose that the exciton condensate may form in a well-controlled way in appropriately arranged semiconductor quantum well structures. The mean-field theory of Keldysh and Kopaev, exact in both the high density and the low density limits, is solved numerically to illustrate our proposal. The electron-hole pairing gap and the excitation spectrum of the exc

N. Read

The charged excitations in the system of the title are vortex-antivortex pairs in the spin-texture described in the theory by Yang et al which, in the commensurate phase, are bound together by a ``string''. It is shown that their excitation energy drops as the string lengthens as the parallel magnetic field approaches the critical value, then goes up

R. Eder, Y. Ohta, S. Maekawa

We present an exact diagonalization study of the dynamical spin and density correlation function of the 2D t-J model for hole doping < 25%. Both correlation functions show a remarkably regular, but completely different scaling behaviour with both hole concentration and parameter values: the density correlation function is consistent with that of bosons corre

E. Bashkin, N. Pavloff, J. Treiner

3He atoms dissolved in superfluid 4He may form dimers (3He)2 in two-dimensional geometries. We study dimer formation in films of dilute 3He-4He mixture. After designing a schematic 3He-3He interaction potential we calculate the dimer binding energy for various substrates. It is shown that 3He impurity states localized near the substrate give rise to the larg

F. D. M. Haldane

A criterion is given for topological stability of Abelian quantum Hall states, and of Luttinger liquids at the boundaries between such states; this suggests a selection rule on states in the quantum Hall hierarchy theory. The linear response of Luttinger liquids to electromagnetic fields is described: the Hall conductance is quantized, irrespective of whethe

Paola Andreani, Fabienne Casoli, Maryvonne Gerin

Using IRAM 30m, SEST 15m, and Nancay radiotelescopes, we have gathered the 1mm continuum emission, spectra of the J=1--0 CO line and of the HI line at 21cm for two samples of IRAS galaxies. Using these data, we have estimated the HI masses, the H$_2$ masses and the dust masses. We find that for far-infrared selected galaxies: (1) the median value of M$_{H2}$

V. Faraoni, F. I. Cooperstock, J. M. Overduin

A class of Kaluza-Klein cosmologies recently proposed is compared with observations of the cosmic microwave background. Some models are ruled out, while others turn out to be viable, with the number of extra dimensions being constrained by the COBE and Tenerife experiments.

Patrick Gilmer

Let $(V,Z)$ be a Topological Quantum Field Theory over a field $f$ defined on a cobordism category whose morphisms are oriented $n+1$-manifolds perhaps with extra structure. Let $(M,χ)$ be a closed oriented $n+1$-manifold $M$ with this extra structure together with $χ\in H^1(M).$ Let $M_{\infty}$ denote the infinite cyclic cover of $M$ given by $χ.$ Consider

Y. Aharonov, L. Vaidman

It is shown that the ``retrodiction paradox&#39;&#39; recently introduced by Peres arises not because of the fallacy of the time-symmetric approach as he claimed, but due to an inappropriate usage of retrodiction.

Lajos Diosi, B. Lukacs

Based on a relation between inertial time intervals and the Riemannian curvature, we show that space--time uncertainty derived by Ng and van Dam implies absurd uncertainties of the Riemannian curvature.

I. M. DREMIN

QCD equations for generating functionals are solved at coinciding momenta of particles. As a result, the relations for $q$-particle correlation functions at equal momenta are obtained. They are directly connected to previously derived results about the factorial and cumulant moments of multiplicity distributions. It is predicted that the correlations at coin

F. Abe

We have used 19 pb**-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to dijets. We exclude at 95% confidence level models containing the following new particles: axigluons with mass between 200 and 870 GeV, excited quarks with mass between 80 and 570 GeV, and color octet technirhos with mass between 320 and 480

Claus Kiefer

It is shown how the programme of decoherence can be applied in the context of quantum field theory. To illustrate the role of gauge invariance, we first discuss the charge superselection rule in quantum electrodynamics in some detail. We then present an example where macroscopic electromagnetic fields are ``measured&#34; through interaction with charges and

L. Vaidman

Comment on L. Hardy, Phys. Rev. Lett. {\bf 73}, 2279 (1994). It is argued that the experiment proposed by Hardy should not be considered as a single photon experiment.

Jesus Bastero, J. Bernues, A. Pena

The classical Brunn-Minkowski inequality states that for $A_1,A_2\subset\R^n$ compact, $$ |A_1+A_2|^{1/n}\ge |A_1|^{1/n}+|A_2|^{1/n}\eqno(1) $$ where $|\cdot|$ denotes the Lebesgue measure on $\R^n$. In 1986 V. Milman {\bf [Mil 1]} discovered that if $B_1$ and $B_2$ are balls there is always a relative position of $B_1$ and $B_2$ for which a perturbed invers

A. K. Kapoor, Pankaj Sharan

Inspired by the usefulness of local scaling of time in the path integral formalism, we introduce a new kind of hamiltonian path integral in this paper. A special case of this new type of path integral has been earlier found useful in formulating a scheme of hamiltonian path integral quantization in arbitrary coordinates. This scheme has the unique feature th

S. Randjbar-Daemi, J. Strathdee

In this letter we show that the overlap formulation of chiral gauge theories correctly reproduces the gravitational Lorentz anomaly in 2-dimensions. This formulation has been recently suggested as a solution to the fermion doubling problem on the lattice. The well known response to general coordinate transformations of the effective action of Weyl fermions c

S. Naftulin

We discuss the structure of one-loop counterterms for the two-dimensional theory of gravitation in the covariant scheme and study the effect of quantum reparametrizations. Some of them are shown to be equivalent to the introduction of $2+ε$-dimensional terms into the initially 2-dimensional theory. We also argue that the $β$-function for the Einstein constan

J. Karkowski, Z. Swierczynski, P. Wegrzyn

We examine the relativistic Nambu-Goto model with Gauss-Bonnet boundary term added to the action integral. The system is analysed using an invariant representation of dynamical string degrees of freedom by complex Liouville fields. The solutions of classical equations of motion for open strings are described.

Pawel Wegrzyn

At the classical level we study open bosonic strings. A generic description of string self-interactions localized at string ends is given. Self-interactions are characterized by two dimensionless coupling constants. The model is rewritten using complex Liouville fields. Using these Lorentz and reparametrization invariant variables, equations of motion get gr

X. Zhang, B. -L. Young

A non-universal interaction associated with top quark induces flavor changing neutral currents (FCNC) among light fermions. The size of the FCNC effect depends crucially on the dynamics of the fermion mass generation. In this paper, we study the effect of a non-universal interaction on $Z b b$, $Z b s$ {\it etc}, by using an effective lagrangian technique an

Sunil V. Somalwar

Recent and upcoming Fermilab experiments to probe the origin of CP violation and to search for CPT violation are reviewed for an audience of theoretical particle physics graduate students.

M. Martinis, V. Mikuta-Martinis, A. Švarc, J. Črnugelj

We study the posibility of large isospin fluctuations in high-energy heavy-ion collisions by assuming that pions are produced semiclassically both directly and in pairs through the isovector channel. The leading-particle effect and the factorization property of the scattering amplitude in the impact parameter space are used to define the classical pion field

Probir Roy

Preliminary remarks, theoretical scenarios, cosmological constraints, couplings of very heavy neutrinos, production mechanisms and detection, summary.

T. W. B. Kibble, Alexander Vilenkin

We discuss the problem of estimating the characteristic length scale $ξ_{\rm s}$, and hence the initial density, of a system of cosmic strings formed at a continuous, second-order phase transition in the early universe. In particular, we examine the roles of the correlation length (or string width) $ξ_{\rm c}$ and the Ginzburg length $ξ_{\rm G}$ which define

Y. Xian

Some rigorous results are presented for a first-order quantum phase transition between the dimerized state and Haldane-type state (i.e., a state similar to the ground state of the one-dimensional spin-1 Heisenberg chain) in the spin-1/2 coupled chains with nearest-neighbour and next-nearest-neighbour Heisenberg interactions. Also presented are the exact exci

Emilio N. M. Cirillo, Giuseppe Gonnella

We study the phase diagram of statistical systems of closed and open interfaces built on a cubic lattice. Interacting closed interfaces can be written as Ising models, while open surfaces as Z(2) gauge systems. When the open surfaces reduce to closed interfaces with few defects, also the gauge model can be written as an Ising spin model. We apply the lower b

M. J. M. de Jong, C. W. J. Beenakker

The Boltzmann-Langevin equation is used to relate the shot-noise power of a mesoscopic conductor to classical transmission probabilities at the Fermi level. This semiclassical theory is applied to tunneling through n barriers in series. For n -> infinity the shot noise approaches one third of the Poisson noise, independent of the transparency of the barriers

M. H. Ernst, H. J. Bussemaker

Non-Gibbsian stationary states occur in dissipative non-equilibrium systems. They are closely connected with the lack of detailed balance and the absence of a fluctuation-dissipation theorem. These states exhibit spatial correlations that are long ranged under generic conditions, even in systems with short range interactions, provided the system has slow mod

M. R. Haggerty

The efficacy and accuracy of Bogomolny&#39;s method of the quantum surface of section is evaluated by applying it to the quantization of the motion of a particle in a smooth 2-D potential. This method defines a transfer operator T in terms of classical trajectories of one Poincaré crossing; knowledge of T provides information about the eigenstates of the qua

Roberto Markarian, Sylvie Oliffson Kamphorst, Sonia Pinto de Carvalho

The elliptical stadium is a curve constructed by joining two half-ellipses, with half axes a>1 and b=1, by two straight segments of equal length 2h. In this work we find bounds on h, for a close to 1, to assure the positiveness of a Lyapunov exponent. We conclude that, for these values of a and h, the elliptical stadium billiard mapping is ergodic and has th

J. J. Mohr, A. E. Evrard, D. G. Fabricant, M. J. Geller

We use a representative sample of 65 galaxy clusters observed with the Einstein IPC to constrain the range of cluster X-ray morphologies. We develop and apply quantitative and reproducible measures to constrain the intrinsic distributions of emission weighted centroid variation, axial ratio, orientation, and the radial fall--off. We then use the range of clu

J. J. Brainerd, C. A. Meegan, Michael S. Briggs, G. N. Pendleton

A time dependent two-point correlation-function analysis of the BATSE 2B catalog finds no evidence of burst repetition. As part of this analysis, we discuss the effects of sky exposure on the observability of burst repetition and present the equation describing the signature of burst repetition in the data. For a model of all burst repetition from a source o

Abraham Loeb

Quasars are the earliest objects known to exist. We examine their origin in the context of popular models for structure formation in the universe. We show that seeds for quasar black holes could have originated from the initial cosmological collapse of overdense regions with unusually small rotation. Most of these seeds have a mass of order 10^6 solar masses

Carlo Angelantonj, Luca Amendola, Marco Litterio, Franco Occhionero

Following a suggestion by Gasperini and Veneziano, that String Cosmology can be reconciled with Inflation and, hence, with the Standard Big Bang, we display an analytical solution which possesses four interesting properties: (1) it is non-singular; (2) it distinguishes the dynamics of the external scale factor, $a(t)$, from that of the internal one, $b(t)$;

W. Becker, K. T. S. Barzier, J. Truemper

We report on the detection of PSR 1706-44 in two ROSAT-PSPC observations. The recorded source counts are unpulsed with a $2σ$ pulsed fraction upper limit of 18%. Spectral analysis did not distinguish between black-body and power law models; however, we argue that the lack of pulsations and the similarity in the pulsar&#39;s spin parameters to those of the Ve

Peter L. Biermann

The search for the origin of cosmic rays is a quest of almost a hundred years. A recent theoretical proposal gives quantitative predictions, which can be tested with data. Specifically, it has been suggested, that all cosmic rays can be attributed to just three source sites: i) supernova explosions into the interstellar medium, ii) supernova explosions into

Douglas A. Swartz, Peter G. Sutherland, Robert P. Harkness

Solutions to the energy-independent (gray) radiative transfer equations are compared to results of Monte Carlo simulations of the \Ni and \Co radioactive decay \GR energy deposition in supernovae. The comparison shows that an effective, purely absorptive, gray opacity, \KG $\sim (0.06 \pm 0.01)Y_e$ cm$^2$ g$^{-1}$, where $Y_e$ is the total number of electron

Mark D. Smucker, E. Ann Stanley, Dan Ashlock

The Iterated Prisoner&#39;s Dilemma with Choice and Refusal (IPD/CR) is an extension of the Iterated Prisoner&#39;s Dilemma with evolution that allows players to choose and to refuse their game partners. From individual behaviors, behavioral population structures emerge. In this report, we examine one particular IPD/CR environment and document the social net

J M Aguirregabiria, A Chamorro, K S Virbhadra

We show that the pseudotensors of Einstein, Tolman, Landau and Lifshitz, Papapetrou, and Weinberg (ETLLPW) give the same distributions of energy, linear momentum and angular momentum, for any Kerr-Schild metric. This result generalizes a previous work by G\"urses and G\"ursey that dealt only with the pseudotensors of Einstein and Landau and Lifshitz. We comp

M. Rösgen, R. Varnhagen

An explicit construction is presented for the action of the su(1,1) subalgebra of the Virasoro algebra on path spaces for the c(2,q) minimal models. In the case of the Lee-Yang edge singularity, we show how this action already fixes the central charge of the full Virasoro algebra. For this case, we additionally construct a representation in terms of generato

Misha Verbitsky

Let M be a compact simply connected hyperkähler (or holomorphically symplectic) manifold, \dim H^2(M)=n. Assume that M is not a product of hyperkaehler manifolds. We prove that the Lie algebra so(n-3,3) acts by automorphisms on the cohomology ring H^*(M). Under this action, the space H^2(M) is isomorphic to the fundamental representation of so(n-3,3). Let A^

M. A. de Andrade, O. M. Del Cima

In this work the supersymmetric gauge invariant action for the massive Abelian $N$$=$$1$ super-{\QED} in the Atiyah-Ward space-time ({\DDdd}) is formulated. The questions concerning the scheme of the gauge invariance in {\DDdd} by means of gauging the massive $N$$=$$1$ super-{\QED} are investigated. We study how to ensure the gauge invariance at the expenses

Vyjayanthi Chari, Andrew Pressley

We describe a connection between finite--dimensional representations of quantum affine algebras and affine Hecke algebras.

Lev S. Tsimring

Structure and dynamics of penta-hepta defects in hexagonal patterns is studied in the framework of coupled amplitude equations for underlying plane waves. Analytical solution for phase field of moving PHD is found in the far field, which generalizes the static solution due to Pismen and Nepomnyashchy (1993). The mobility tensor of PHD is calculated using com

Ramesh Abhiraman, Charles M. Sommerfield

One of the methods used to extend two-dimensional bosonization to four space-time dimensions involves a transformation to new spatial variables so that only one of them appears kinematically. The problem is then reduced to an Abelian version of two-dimensional bosonization with extra ``internal&#39;&#39; coordinates. On a formal level, putting these internal

Geoffrey Dixon

I present here another example of a lattice fibration, a discrete version of the highest dimensional Hopf fibration: $S^{7}\longrightarrow S^{15} \longrightarrow S^{8}$.

Zala&#39;n Horva&#39;th, Ga&#39;bor Taka&#39;cs

The possibility of the application of the free field representation developed by Lukyanov for massive integrable models is investigated in the context of the O(3) sigma model. We use the bootstrap fusion procedure to construct a free field representation for the O(3) Zamolodchikov- Faddeev algebra and to write down a representation for the solutions of the f

Igor Batalin, Robert Marnelius

By means of a generalized quartet mechanism we show in a model independent way that a BRST quantization on an inner product space leads to physical states of the form |ph>=e^{[Q, ψ]} |ph>_0 where Q is the nilpotent BRST operator, ψa hermitian fermionic gauge fixing operator, and |ph>_0 BRST invariant states determined by a hermitian set of BRST doublets in i

Robert Marnelius, Ulrich Quaade

Some general formulas are derived for the solutions of a BRST quantization on inner product spaces of finite dimensional bosonic gauge theories invariant under arbitrary Lie groups. A detailed analysis is then performed of SL(2,R) invariant models and some possible geometries of the Lagrange multipliers are derived together with explicit results for a class

N. Brambilla, G. M. Prosperi

We give a nonperturbative derivation of the Bethe--Salpeter equation based on the Feynman--Schwinger path integral representation of the one--particle propagator in an external field. We apply the method to the quark--antiquark system in scalar QCD and obtain a confining BS equation assuming the Wilson area law in the straight line approximation. The result

N. V. Krasnikov

The status of coupling constant unification in standard supersymmetric SU(5) model and its extensions is discussed. Taking into account uncertainties related with the initial coupling constants and threshold corrections at low and high scales we find that in supersymmetric SU(5) model the scale of supersymmetry breaking could be up to $10^8$ Gev. In the exte

J. Bartels, J. R. Forshaw, H. Lotter. L. N. Lipatov, M. G. Ryskin

We investigate the coupling of the BFKL-Pomeron to quarks and to colorless states. Special emphasis is given to the effective quark-quark scattering amplitude of Mueller and Tang.

P. A. Henning, R. Sollacher

We consider the partition functions of QCD and QED at high temperature assuming small coupling constants, and present arguments in favor of an improved perturbative expansion in terms of unstable excitations. Our effective propagators are derived from spectral functions with a constant width. These spectral functions describe screening and damping of gluons

Andreas S. Kronfeld, Fermilab

We discuss lattice artifacts for matrix elements of hadrons containing one or more heavy quark. In particular, we analyze interrelations between lattice artifacts and the $1/m_Q$ expansion. The implications for calculations of heavy-light decay constants and of semi-leptonic form factors are discussed.

Vladimir V. Kisil

We describe an explicit connection between solutions to equations $Df=0$ (the Generalized Cauchy-Riemann equation) and $(D+M)f=0$, where operators $D$ and $M$ commute. The described connection allows to construct a ``function theory&#39;&#39; (the Cauchy theorem, the Cauchy integral, the Taylor and Laurent series etc.) for solutions of the second equation fr

C. W. J. Beenakker, J. A. Melsen, P. W. Brouwer

It is shown analytically and by numerical simulation that the angular distribution of Andreev reflection by a disordered normal-metal -- superconductor junction has a narrow peak at the angle of incidence. The peak is higher than the well-known coherent backscattering peak in the normal state, by a large factor G/G_0 (where G is the conductance of the juncti

Steffen D. ~Frischat, Reimer Kühn

We investigate families of generalized mean--field theories that can be formulated using the Peierls--Bogoliubov inequality. For test--Hamiltonians describing mutually non--interacting subsystems of increasing size, the thermodynamics of these mean--field type systems approaches that of the infinite, fully interacting system except in the immediate vicinity

Leo Radzihovsky

I study the normal-to-superconducting (NS) transition within the Ginzburg-Landau (GL) model, taking into account the fluctuations in the $m$-component complex order parameter $ψ\a$ and the vector potential $\vec A$ in the arbitrary dimension $d$, for any $m$. I find that the transition is of second-order and that the previous conclusion of the fluctuation-dr

Rachel A. Pildis, Joel N. Bregman, August E. Evrard

We have systematically analyzed a sample of 13 new and archival ROSAT PSPC observations of compact groups of galaxies: 12 Hickson Compact Groups plus the NCG 2300 group. We find that approximately two-thirds of the groups have extended X-ray emission and, in four of these, the emission is resolved into diffuse emission from gas at a temperature of $k$T $\sim

Peter L. Biermann

We propose that cosmic rays originate mainly in three sites, a) normal supernova explosions into the interstellar medium, b) supernova explosions into stellar winds, and c) hot spots of powerful radio galaxies. The proposal depends on an assumption about the scaling of the turbulent diffusive transport in cosmic ray mediated shock regions; the proposal also

Itzhak Goldman, Amri Wandel

A self-consistent solution for a thin accretion disk with turbulent convection is presented. The disk viscosity and the convective flux are derived from a physical model for turbulence, and expressed in terms of the local physical conditions of the disk which, in turn, are controlled by the former two. In the gas pressure region, two distinct solutions are o

John David Crawford

The onset of collective behavior in a population of globally coupled oscillators with randomly distributed frequencies is studied for phase dynamical models with arbitrary coupling. The population is described by a Fokker-Planck equation for the distribution of phases which includes the diffusive effect of noise in the oscillator frequencies. The bifurcation

Yuri Smirnov, Alexander Turbiner

A certain representation for the Heisenberg algebra in finite-difference operators is established. The Lie-algebraic procedure of discretization of differential equations with isospectral property is proposed. Using $sl_2$-algebra based approach, (quasi)-exactly-solvable finite-difference equations are described. It is shown that the operators having the Hah

G. Boffi, M. Varagnolo

Let R be a commutative ring, q a unit of R and P a multiplicatively antisymmetric matrix with coefficients which are integers powers of q. Denote by SE(q,P) the multiparameter quantum matrix bialgebra associated to q and P.Slightly generalizing [Hashimoto-Hayashi,Tohoku Math.Tohoku Math.J. 44(1992)],we define a multiparameter deformation $L_{ł/μ}V_P$ of the

F. A. Smirnov

We consider the deformation of abelian integrals which arose from the study of SG form factors. Besides the known properties they are shown to satisfy Riemann bilinear identity. The deformation of intersection number of cycles on hyperelliptic curve is introduced.

Bao-An Li

It is shown that the large $π^{-}/π^{+}$ ratio at low pion energies recently observed in the reaction of Au+Au at $E_{beam}/A=1.0$ GeV at SIS/GSI is due to the strong Coulomb field of the reaction system.

Boban Velickovic, W. Hugh Woodin

The usual definition of the set of constructible reals is $Σ^1_2$. This set can have a simpler definition if, for example, it is countable or if every real is constructible. H. Friedman asked if the set of constructible reals can be analytic or even Borel in a nontrivial way. A related problem was posed by K. Prikry: can there exist a nonconstructible perfec

Fuad Saradzhev

We study the influence of the anomaly on the physical quantum picture of the chiral Schwinger model (CSM) defined on $S^1$. We show that such phenomena as the total screening of charges and the dynamical mass generation characteristic for the standard Schwinger model do not take place here. Instead of them, the anomaly results in the background linearly risi

R. D. Tangerman, P. J. Mulders

The azimuthal dependence of hadrons produced in lepton scattering off a polarized hadron probes the quark transverse-spin distributions. In the calculation of the asymmetries, transverse momenta of quarks in the distribution and fragmentation functions must be incorporated. In addition to the $\sin (ϕ+ ϕ_S)$ asymmetry for transversely polarized hadrons, know

S. Bauberger, M. Boehm

The scalar two-loop self-energy master diagram is studied in the case of arbitrary masses. Analytical results in terms of Lauricella- and Appell-functions are presented for the imaginary part. By using the dispersion relation a one-dimensional integral representation is derived. This representation uses only elementary functions and is thus well suited for a

H. R. Rubinstein, S. Solomon, T. Wittlich

We study the variation of the hadron masses in the presence of external magnetic fields of strength of the order of the masses themselves. We identify the main factors affecting the lattice simulation results: - the boundary discontinuities for $eB << 2π/ L^2 a^2$. - the SU(6) choice of the hadron wave-function. We confirm qualitatively the earlier theoretic

Claus Kiefer

We calculate the first quantum gravitational correction term to the trace anomaly in De Sitter space from the Wheeler-DeWitt equation. This is obtained through an expansion of the full wave functional for gravity and a conformally coupled scalar field in powers of the Planck mass. We also discuss a quantum gravity induced violation of unitarity and comment o