March 1996 arXiv papers — page 6

Arnd Brandenburg

Top quark pairs are produced with strongly correlated spins in the partonic reactions $q\bar{q}\to t\bar{t}$ and $gg\to t\bar{t}$. A complete description of these effects in terms of the spin density matrix of the $t\bar{t}$ system in leading order QCD is given. We further discuss the prospects to observe the spin-spin correlations at $p\bar{p}$ and $pp$ col

Jürgen G. Körner

I present a mini-review on the physics of heavy flavour baryons where I concentrate on the HQET description of their exclusive decay modes. In particular I discuss the structure of current-induced bottom baryon to charm baryon transitions, and the structure of pion and photon transitions between heavy charm or bottom baryons in the Heavy Quark Symmetry limit

W. Bernreuther, O. Nachtmann

We discuss some issues arising in the search for CP violation in the decays Z -> tau+ tau- and Z -> b \bar b X. The form-factor and the effective Lagrangian approach to parametrize CP-violating effects are compared. We emphasize the interest to study both real and imaginary parts of CP-violating form factors like the weak dipole moment form factor d_tau^Z(m^

Fu-Guang Cao, Tao Huang, Bo-Qiang Ma

We perform a perturbative QCD analysis of the quark transverse momentum effect on the pion-photon transition form factors $F_{πγ}$ and $F_{πγ^*}$ in the standard light-cone formalism, with two phenomenological models of wavefunction as the input of the non-perturbative aspect of the pion. We point out that the transverse momentum dependence in both the numer

E. W. N. Glover, A. D. Martin, R. G. Roberts, W. J. Stirling

The recent CDF single jet inclusive measurements at Fermilab are incorporated in a global next-to-leading order parton analysis of the available deep inelastic and related data. We find that it is impossible to achieve a simultaneous QCD description of both the CDF jet distribution for transverse energies $E_T > 200$~GeV and the deep inelastic structure func

A. Fujitsu, N. Tsuda, T. Yukawa

Two-dimensional random surfaces are studied numerically by the dynamical triangulation method. In order to generate various kinds of random surfaces, two higher derivative terms are added to the action. The phases of surfaces in the two-dimensional parameter space are classified into three states: flat, crumpled surface, and branched polymer. In addition, th

G. S. Bali, V. Bornyakov, M. Mueller Preussker, K. Schilling

We perform a study of the effects from maximal abelian gauge Gribov copies in the context of the dual superconductor scenario of confinement, on the basis of a novel approach for estimation of systematic uncertainties from incomplete gauge fixing. We present numerical results, in SU(2) lattice gauge theory, using the overrelaxed simulated annealing gauge fix

Ph. de Forcrand, A. Galli

We present an exact local bosonic algorithm for the simulation of dynamical fermions in lattice QCD. It is based on a non-hermitian polynomial approximation of the inverse of the quark matrix and a global Metropolis accept/reject correction of the systematic errors. We show that this algorithm is a real alternative to the Hybrid Monte Carlo algorithm.

Robert Graham, Robert Paternoga

A class of exact solutions of the Wheeler-DeWitt equation for diagonal Bianchi type IX cosmologies with cosmological constant is derived in the metric representation. This class consists of all the ``topological solutions'' which are associated with the Bianchi type IX reduction of the Chern-Simons functional in Ashtekar variables. The different solu

Henk van Elst, Claes Uggla

The equations of the 1+3 orthonormal frame approach are explicitly presented and discussed. Natural choices of local coordinates are mentioned. A dimensionless formulation is subsequently given. It is demonstrated how one can obtain a number of interesting problems by specializing the general equations. In particular, equation systems for ``silent''

S. Stringari

By taking the hydrodynamic limit we derive, at $T=0$, an explicit solution of the linearized time dependent Gross-Pitaevskii equation for the order parameter of a Bose gas confined in a harmonic trap and interacting with repulsive forces. The dispersion law $ω=ω_0(2n^2+2n\ell+3n+\ell)^{1/2}$ for the elementary excitations is obtained, to be compared with the

Raymond Fresard, Klaus Doll

We use the Kotliar-Ruckenstein slave boson technique to treat the strong correlation of the Hubbard model. In a first part we discuss the metal to insulator transition that is occurring on the honeycomb lattice at half filling. We find the critical value for the interaction strength to be U/t=3.1. Above it a gap opens in the spectrum which behaves like (U-U_

Naoum Karchev

The renormalization-group method is used to analyze the low-temperature behaviour of a two-dimentional, spin-$s$ quantum Heisenberg ferromagnet. A set of recursion equations is derived in an one-loop approximation. The low-temperature asymptotics of the correlation length and the uniform susceptibility are obtained. For small spins ($s= 1/2,1$) the results a

Elisabeth Breidt

The usefulness of a statistical approach suggested by Church et al. (1991) is evaluated for the extraction of verb-noun (V-N) collocations from German text corpora. Some problematic issues of that method arising from properties of the German language are discussed and various modifications of the method are considered that might improve extraction results fo

Geunbae Lee, Jong-Hyeok Lee

A new tightly coupled speech and natural language integration model is presented for a TDNN-based continuous possibly large vocabulary speech recognition system for Korean. Unlike popular n-best techniques developed for integrating mainly HMM-based speech recognition and natural language processing in a {\em word level}, which is obviously inadequate for mor

Guido Gentile

The volume contraction in dissipative reversible transitive Anosov flows obeys a large deviation rule (fluctuation theorem).

Paul J. Green

Quasar emission lines are sensitive to both the luminosity and shape of the quasars' high energy continuum - primarily in the soft X-ray and the (obscured) extreme ultraviolet. We initiate the first large-scale, multi-line investigation of correlations between the QSO soft X-ray continuum and UV line emission, using an IUE/Einstein sample. We characteriz

Christopher W. Mauche

Quasi-coherent oscillations have been detected in the extreme ultraviolet flux of the dwarf nova SS Cygni during observations with the Extreme Ultraviolet Explorer satellite of the rise and plateau phases of an anomalous outburst in 1993 August and a normal outburst in 1994 June/July. On both occasions, the oscillation turned on during the rise to outburst a

John Dubinski

We describe a new implementation of a parallel N-body tree code. The code is load-balanced using the method of orthogonal recursive bisection to subdivide the N-body system into independent rectangular volumes each of which is mapped to a processor on a parallel computer. On the Cray T3D, the load balance in the range of 70-90\% depending on the problem size

Gopal-Krishna, Vasant Kulkarni, Paul J. Wiita

A key argument in favor of orientation based unification schemes is the finding that among the most powerful 3CRR radio sources the (apparent) median linear size of quasars is smaller than that of radio galaxies, which supports the idea that quasars are a subset of radio galaxies, distinguished by being viewed at smaller angles to the line of sight. Recent m

Alice K. Harding, Matthew G. Baring

The spectra of soft gamma-ray repeaters (SGRs), with the exception of the March 5, 1979 main burst, are characterized by high-energy cutoffs around 30 keV and low-energy turnovers that are much steeper than a Wien spectrum. Baring (1995) found that the spectra of cascades due to photon splitting in a very strong, homogeneous magnetic field can soften spectra

P. Vauterin, H. Dejonghe

We present a method for solving the two-dimensional linearized collisionless Boltzmann equation using Fourier expansion along the orbits. It resembles very much solutions present in the literature, but it differs by the fact that everything is performed in coordinate space instead of using action-angle variables. We show that this approach, though less elega

A. C. Quillen, Solange V. Ramírez, Jay A. Frogel

We describe a technique that uses radial color gradients in disk galaxies to detect the presence of bulk non-circular motion or elliptical orbits. In a disk galaxy with both a radial color gradient and non-circular motion, isochromes or iso-color contours should follow the shape of closed stellar orbits, and the ellipticity of the isophotes should vary as a

M. Salaris, S. Degl'Innocenti, A. Weiss

The age of three of the oldest clusters -- M15, M68, M92 -- has been redetermined. We use the latest EOS and opacity data available for calculating both isochrones and zero age horizontal branches and employ the brightness difference between turn-off and horizontal branch to determine the cluster age. Our best ages for all three clusters are about 13 Gyr, an

K. M. Leighly, R. F. Mushotzky, T. Yaqoob, H. Kunieda

Analysis results from ASCA and ROSAT observations of the narrow-line Seyfert 1 galaxy Mrk 766 are reported. In the ASCA observation we observed rapid variability with a doubling time scale of 1000 seconds. A spectral variability event was observed in which the spectrum softened and hardened above and below ~1 keV, respectively, as the flux increased. The spe

Carlos Castro

$p'$-brane solutions to rank $p+1$ composite antisymmetric tensor field theories of the kind developed by Guendelman, Nissimov and Pacheva are found when the dimensionality of spacetime is $D=(p+1)+(p'+1)$. These field theories posses an infinite dimensional group of global Noether symmetries, that of volume-preserving diffeomorphisms of the target s

Apostolos Pilaftsis

A mu+ mu- collider is an appealing machine to probe resonant CP-violating transitions of a CP-even Higgs particle into the Z boson or into another CP-odd Higgs scalar. These phenomena are studied within a manifestly gauge-invariant approach implemented by the pinch technique. The CP invariance of an extended Higgs sector motivated by supersymmetric E_6 model

Dmitri Diakonov

'Constituent quarks' means massive quarks, in contrast to the nearly massless u,d,s quarks of the QCD lagrangian. The dynamical or constituent masses appear owing to the spontaneous chiral symmetry breaking in QCD. A realistic mechanism of the chiral symmetry breaking is provided by instantons. Therefore, I review the present status of the QCD instan

David Kutasov, Emil Martinec, Martin O'Loughlin

String and membrane dynamics may be unified into a theory of 2+2 dimensional self-dual world-volumes living in a 10+2 dimensional target space. Some of the vacua of this M-theory are described by the N=(2,1) heterotic string, whose target space theory describes the world-volume dynamics of 2+2 dimensional `M-branes'. All classes of string and membrane th

Achim Kempf

We discuss a recent approach to quantum field theoretical path integration on noncommutative geometries which imply UV/IR regularising finite minimal uncertainties in positions and/or momenta. One class of such noncommutative geometries arise as `momentum spaces' over curved spaces, for which we can now give the full set of commutation relations in coord

Sergio Albeverio, Shao-Ming Fei

Poisson algebraic structures on current manifolds (of maps from a finite dimensional Riemannian manifold into a 2-dimensional manifold) are investigated in terms of symplectic geometry. It is shown that there is a one to one correspondence between such current manifolds and Poisson current algebras with three generators. A geometric meaning is given to q-def

Ashoke Sen

It is shown that many of the conjectured dualities involving orbifold compactification of M-theory follow from the known dualities involving M-theory and string theory in ten dimensions, and the ansatz that orbifolding procedure commutes with the duality transformation. This ansatz also leads to a new duality conjecture, namely that M-theory compactified on

B. J. Schroers

Gauged linear sigma models with C^m-valued scalar fields and gauge group U(1)^d, d \leq m, have soliton solutions of Bogomol'nyi type if a suitably chosen potential for the scalar fields is also included in the Lagrangian. Here such models are studied on (2+1)-dimensional Minkowski space. If the dynamics of the gauge fields is governed by a Maxwell term

W. Hollik

The predictions of the \sm and the minimal supersymmetric standard model (MSSM) for the electroweak precision parameters are discussed in the light of the recent precision data. The results from global fits yield lower $χ^2$ values in the MSSM than in the Standard model. The fits prefer regions in the MSSM parameter space with $M_2 \simeq |μ| $ and allow cha

A. M. Rudin, I. L. Aleiner, L. I. Glazman

For the first time, we study the tunneling density of states (DOS) of the interacting electron gas beyond the diffusive limit. A strong correction to the DOS persists even at electron energies exceeding the inverse transport relaxation time, which could not be expected from the well-known Altshuler-Aronov-Lee (AAL) theory. This correction originates from the

Gregory L. Eyink

We establish exact inequalities for the structure-function scaling exponents of a passively advected scalar in both the inertial-convective and viscous-convective ranges. These inequalities involve the scaling exponents of the velocity structure functions and, in a refined form, an intermittency exponent of the convective-range scalar flux. They are valid fo

Colin Norman, Avery Meiksin

Motivated by the observations of high Faraday rotation measures measured in cooling flow clusters we propose a model relevant to plasmas with comparable thermal and magnetic pressures. Magnetic field reconnection may play a major role in changing the topology of the magnetic field in the central cooling flow regions. The effect of the topology change is that

A. Burkert, P. Ruiz-Lapuente

Some dwarf spheroidal galaxies have experienced many Gyrs long periods without star formation. We show that Type Ia supernovae, formed from a first generation of stars, can delay a second epoch of star formation by several Gyrs, if the total gas mass in the dwarf spheroidals is smaller than $10^8 M_{\odot}$. The details depend on the assumed Type Ia supernov

P. Petitjean, E. Pecontal, D. Valls-Gabaud, S. Charlot

There is a growing consensus that the emergence of quasars at high redshifts is related to the onset of galaxy formation, suggesting that the detection of concentrations of gas accompanying such quasars should provide clues about the early history of galaxies. Quasar companions have been recently identified at redshifts up to $z \approx 3$. Here we report ob

N. Hata, G. Steigman, S. Bludman, P. Langacker

Constraints on big bang nucleosynthesis (BBN) and on cosmological parameters from conflicting deuterium observations in different high red-shift QSO systems are discussed. The high deuterium observations by Carswell et al., Songaila et al., and Rugers & Hogan is consistent with 4He and 7Li observations and Standard BBN (N_nu =3) and allows N_nu \leq 3.6 at 9

I. L. Aleiner, A. I. Larkin

We study the weak localization correction (WLC) to transport coefficients of a system of electrons in a static long-range potential (e.g. an antidot array or ballistic cavity). We found that the weak localization correction to the current response is delayed by the large time $t_E = λ^{-1} |\ln \hbar|$, where $λ$ is the Lyapunov exponent. In the semiclassica

Edmond L. Berger, Harry Contopanagos

Our calculation of the total cross section for inclusive production of $t\bar{t}$ pairs in hadron collisions is presented. The principal ingredient of the calculation is resummation of the universal leading-logarithm effects of gluon radiation to all orders in the quantum chromodynamics coupling strength, restricted to the region of phase space that is demon

Victor Buchstaber, Victor Enolskii, Dmitri Leykin

We develop the theory of hyperelliptic Kleinian functions. As applications we consider construction of the explicit matrix realization of the hyperelliptic Kummer varieties, differential operators to have the hyperelliptic curve as spectral variety, solution of the KdV equations by Kleinian functions.

L. P. Kaptari, A. Yu. Umnikov, S. G. Bondarenko, K. Yu. Kazakov

Extended calculations of the deuteron's static properties, based on the numerical solution of the Bethe-Salpeter equation, are presented. A formalism is developed, which provides a comparative analysis of the covariant amplitudes in various representations and nonrelativistic wave functions. The magnetic and quadrupole moments of the deuteron are calcula

W. Melnitchouk, A. W. Thomas

The spin-averaged structure function of the neutron, F_2^n, is extracted from recent deuteron data, taking into account the small but significant corrections due to nuclear effects in the deuteron. At small x, the F_2D/F_2p ratio measured by the New Muon and Fermilab E665 Collaborations is interpreted to suggest a small amount of shadowing in deuterium, whic

J. Noguchi, T. Ochiai

This is a list of corrections for the book: J. Noguchi and T. Ochiai, Geometric Function Theory in Several Complex Variables, xi + 282 pp., Math.\ Monographs Vol.\ {\bf 80}, Amer.\ Math.\ Soc., Providence, 1990. The authors hope that this distribution will be helpful for readers to avoid unnecessary confusions.

Marialuisa Frau, Alberto Lerda, Stefano Sciuto, Guillermo R. Zemba

We propose an approach to treat (1+1)--dimensional fermionic systems based on the idea of algebraic bosonization. This amounts to decompose the elementary low-lying excitations around the Fermi surface in terms of basic building blocks which carry a representation of the W_{1+\infty} \times {\overline W_{1+\infty}} algebra, which is the dynamical symmetry of

J. D. Kim, Y. Yoon

The principle of boundary bootstrap plays a significant role in the algebraic study of the purely elastic boundary reflection matrix $K_a(θ)$ for integrable quantum field theory defined on a space-time with a boundary. However, general structure of that principle in the form as was originally introduced by Fring and Köberle has remained unclear. In terms of

Gary Horowitz, Juan Maldacena, Andrew Strominger

A six-parameter family of five-dimensional black hole solutions is constructed which are labeled by their mass, two asymptotic scalar fields and three charges. It is shown that the Bekenstein-Hawking entropy is exactly matched, arbitrarily far from extremality, by a simple but mysterious duality-invariant extension of previously derived formulae for the numb

H. Asatrian, A. Ioannissian

The direct CP-violation in the left-right symmetric $SU(2) \times SU(2) \times U(1)$ model is investigated for the decay $b \rightarrow sγ$. The calculated CP-asymmetry for the wide range of parameters can be larger than in standard model and can have an opposite sign.

Christof Gattringer

We discuss a new approach for putting gauge theories on the lattice. The gauge fields are defined on the lattice only, but are interpolated to the interior of the lattice cells, where they couple to continuum fermions. The purpose of this approach is to avoid doublers and keep the chiral symmetry of the action intact. In two dimensional models (Schwinger mod

Maya Paczuski, Stefan Boettcher

Recent numerical results for a model describing dispersive transport in rice piles are explained by mapping the model to the depinning transition of an interface that is dragged at one end through a random medium. The average velocity of transport vanishes with system size $L$ as $<v> \sim L^{2-D}\sim L^{-0.23}$, and the avalanche size distribution exponent

M. Drinkwater, F. Combes, T. Wiklind

We describe a search for molecular absorption at millimetre wavelengths associated with dusty molecular tori in active galactic nuclei (AGN). The sample observed consists of 11 flat-spectrum radio sources known to have red optical to infra-red colours plus two steep-spectrum narrow-line radio galaxies. Spectra of the sources were obtained in the 3-, 2- and 1

B. S. Sathyaprakash, V. Sahni, S. F. Shandarin

The morphological nature of structures that form under gravitational instability has been of central interest to cosmology for over two decades. A remarkable feature of large scale structures in the Universe is that they occupy a relatively small fraction of the volume and yet show coherence on scales comparable to the survey size. With the aid of a useful s

Martin Rugers, Craig J. Hogan

We present a new analysis of an absorption system in the spectrum of Q0014+813, with particular attention to a single cold cloud at redshift $z=2.797957$. Features are identified at this redshift corresponding to SiIII, SiIV, CIV, DI, and HI, all consistent with purely thermal broadening at $T\approx 19,000$K. The deuterium identification is confirmed by its

Kirill V. Krasnov

We adopt the point of view that (Riemannian) classical and (loop-based) quantum descriptions of geometry are macro- and micro-descriptions in the usual statistical mechanical sense. This gives rise to the notion of geometrical entropy, which is defined as the logarithm of the number of different quantum states which correspond to one and the same classical g

Gabriel Lopes Cardoso, Gottfried Curio, Dieter Lüst, Thomas Mohaupt

In this note, we comment on Calabi-Yau spaces with Hodge numbers $h_{1,1}=3$ and $h_{2,1}=243$. We focus on the Calabi-Yau space $WP_{1,1,2,8,12}(24)$ and show how some of its instanton numbers are related to coefficients of certain modular forms. We also comment on the relation of four dimensional exchange symmetries in certain $N=2$ dual models to six dime

Sergio Zerbini, Guido Cognola, Luciano Vanzo

The off-shell entropy for a massless scalar field in a D-dimensional Rindler-like space-time is investigated within the conical Euclidean approach in the manifold $C_\be\times\M^N$, $C_\be$ being the 2-dimensional cone, making use of the zeta-function regularisation. Due to the presence of conical singularities, it is shown that the relation between the zeta

Gianfranco Pradisi

We review the basic principles of the construction of open and unoriented superstring models and analyze some representative examples.

Anirban Kundu, Probir Roy

A reexamination is made of one-loop oblique electroweak corrections. General definitions are given of the oblique parameters without reference to any $q^2$-expansion scheme. The old oblique parameters S,T and U are defined as differences of gauge boson vacuum polarization $Π$-functions and suffice to describe certain observable ratios on the Z-peak and the $

J. Maharana, H. Singh

The symmetries of the tree level string effective action are discussed. An appropriate effective action is constructed starting from the manifestly SL(2,R) invarint form of string effective action introduced by Schwarz and Sen. The conserved charges are derived and generators of infinitesimal transformations are obtained in the Hamiltonian formalism. Some in

Alexander Antonov, Boris Feigin

In this paper we propose algebraic universal procedure for deriving &#34;fusion rules&#34; and Baxter equation for any integrable model with $U_q(\widehat{sl}_2)$ symmetry of Quantum Inverse Scattering Method. Universal Baxter Q- operator is got from the certain infinite dimensional representation called q-oscillator one of the Universal R- matrix for $U_q(\

M. Aizenman, G. M. Graf

Mathematical analysis of the Anderson localization has been facilitated by the use of suitable fractional moments of the Green function. Related methods permit now a readily accessible derivation of a number of physical manifestations of localization, in regimes of strong disorder, extreme energies, or weak disorder away from the unperturbed spectrum. The pr

E. D. Stewart, M. Kawasaki, T. Yanagida

We argue that an extension of the Minimal Supersymmetric Standard Model that gives rise to viable thermal inflation, and so does not suffer from a Polonyi/moduli problem, should contain right-handed neutrinos which acquire their masses due to the vacuum expectation value of the flaton that drives thermal inflation. This strongly disfavours SO(10) Grand Unifi

Michele Fabrizio

We study the phase diagram of a one-dimensional Hubbard model where, in addition to the standard nearest neighbor hopping $t$, we also include a next-to-nearest neighbor hopping $t&#39;$. For strong enough on-site repulsion, this model has a transition at half filling from a magnetic insulator with gapless spin excitations at small $t&#39;/t$ to a dimerized

Jiri Horejsi

A pedagogical introduction to the equivalence theorem for longitudinal vector bosons in electroweak theories is presented and the problem of high-energy behaviour of scattering amplitudes in the Standard Model is briefly reviewed. To make the treatment self-contained, the basics of the Standard Model are summarized in an appendix.

Shinta Kasuya, Masahiro Kawasaki

We study parametric resonant decay of inflaton field with emphasis on its physical meaning. We show that the parametric resonance is indeed an induced process, which means that the more numbers of produced particles, the more inflaton field decays. We also consider the dissipative effects of produced particles and find that the dissipation reduces the resona

Mirjam Cvetic, Donam Youm

We present the most general rotating black hole solution of five-dimensional N=4 superstring vacua that conforms to the ``no hair theorem&#39;&#39;. It is chosen to be parameterized in terms of massless fields of the toroidally compactified heterotic string. The solutions are obtained by performing a subset of O(8,24) transformations, i.e., symmetry transfor

Paul J. Steinhardt

A proposed strategy for determining the deceleration parameter entails measuring the deviation from a linear (Hubble) distance-red shift relation. However, even at moderate red shifts, z > 0.2, the deviation does not depend on q_0 alone, but also on the equation-of-state of the universe.

Scott Burles, David Tytler

Standard big bang nucleosynthesis (BBNS) promises accurate predictions of the primordial abundances of deuterium, helium-3, helium-4 and lithium-7 as a function of a single parameter. Previous measurements have nearly always been interpreted as confirmation of the model (Copi, Schramm & Turner 1995). Here we present a measurement of the deuterium to hydrogen

Hiroyuki Yamane

In this paper, we give defining relations of the affine Lie superalgebras an and defining relations of a super-version of the Drinfeld[D]-Jimbo[J] affine quantized universal enveloping algebras. As a result, we can exactly define the affine quantized universal enveloping superalgebras with generators and relations. Moreover we give a Drinfeld&#39;s realizati

M. Noumi, M. S. Dijkhuizen, T. Sugitani

We present a one-parameter family of constant solutions of the reflection equation and define a family of quantum complex Grassmannians endowed with a transitive action of the quantum unitary group. By computing the radial part of a suitable Casimir operator, we identify the zonal spherical functions (i.e. infinitesimally bi-invariant matrix coefficients of

Martin Gilchrist, Saharon Shelah

An omega-coloring is a pair <f,B> where f:[B]^{2} ---> omega. The set B is the field of f and denoted Fld(f). Let f,g be omega-colorings. We say that f realizes the coloring g if there is a one-one function k:Fld(g) ---> Fld(f) such that for all {x,y}, {u,v} in dom(g) we have f({k(x),k(y)}) not= f({k(u),k(v)}) => g({x,y}) not= g({u,v}). We write f~g if f rea

V. D. Ivashchuk, V. N. Melnikov

A string-like model with the &#34;cosmological constant&#34; $Λ$ is considered. The Maki-Shiraishi multi-black-hole solution \cite{MS1} is generalized to space-times with a Ricci-flat internal space. For $Λ= 0$ the obtained solution in the one-black-hole case is shown to coincide with the extreme limit of the charged dilatonic black hole solution \cite{BI,BM

Federico Finkel, Artemio Gonzalez-Lopez, Miguel A. Rodriguez

In this paper we show that a quasi-exactly solvable (normalizable or periodic) one-dimensional Hamiltonian satisfying very mild conditions defines a family of weakly orthogonal polynomials which obey a three-term recursion relation. In particular, we prove that (normalizable) exactly-solvable one-dimensional systems are characterized by the fact that their a

J. C. Le Guillou, F. A. Schaposnik

We calculate the electric charge at finite temperature $T$ for non-Abelian monopoles in spontaneously broken gauge theories with a CP violating $θ$-term. A careful treatment of dyon&#39;s gauge degrees of freedom shows that Witten formula for the dyon charge at $T=0$, $ Q = e(n - θ/2π) $, remains valid at $T \ne 0$.

A. A. Tseytlin

We consider an extension of a special class of conformal sigma models (`chiral null models&#39;) which describe extreme supersymmetric string solutions. The new models contain both `left&#39; and `right&#39; vector couplings and should correspond to non-BPS backgrounds. In particular, we discuss a conformal six-dimensional model which is a combination of fun

P. F. Bedaque, A. Das, S. Naik

We discuss the cutting rules in the real time approach to finite temperature field theory and show the existence of cancellations among classes of cut graphs which allows a physical interpretation of the imaginary part of the relevant amplitude in terms of underlying microscopic processes. Furthermore, with these cancellations, any calculation of the imagina

T. Munehisa, J. Fujimoto, Y. Kurihara, Y. Shimizu

The generator QEDPS, a parton shower model in QED, developed by the present authors has been improved. By a careful study on the shower algorithm it was found that some finite contributions have been missed in the original version. They are small, but cannot be neglected when the contribution of the soft photons is dominant. A method is presented to correct

Jiri Horejsi, Miroslav Stohr

We examine the contribution of W boson loops to the amplitude of the process H --> γγwithin the dispersion relation approach, taking up an issue raised in this context recently. We show that the non-vanishing limit of the relevant formfactor for mW --> 0 is due to a finite subtraction induced by the value of the corresponding trace anomaly. The argument can

M. Dubinin, Y. Kurihara, Y. Shimizu

We calculate the cross section of Higgs boson production in the reaction e+e- -> neutrino anti-neutrino b b-bar for the case of left and right longitudinally polarized electron beam. Complete set of signal and irreducible background diagrams is considered. We propose a new critical test to identify the Higgs boson provided by the ratio of cross sections with

Peter Skala, Manfried Faber, Martin Zach

We propose a method for the determination of magnetic monopole currents in non-Abelian gauge theories which does not need a projection to Abelian degrees of freedom. With this definition we are able to determine the distribution of magnetic currents and electric fields for the gluonic flux tube between a pair of static charges. Further we check the validity

Kostas D. Kokkotas

In this paper we review the recent developments in the relativistic theory of stellar pulsations with special emphasis on the spacetime or w-modes. We discuss also the excitation of these modes and the information about the neutron star that we will be able to mine from their detection. The paper will appear in the Proceedings of the Les Houches School on As

A. López--Pinto, A. Tiemblo, R. Tresguerres

We develop a Hamiltonian formalism suitable to be applied to gauge theories in the presence of Gravitation, and to Gravity itself when considered as a gauge theory. It is based on a nonlinear realization of the Poincaré group, taken as the local spacetime group of the gravitational gauge theory, with $SO(3)$ as the classification subgroup. The Wigner--like r

P. Sitko, S. N. Yi, K. S. Yi, J. J. Quinn

Numerical results for the energy spectra of $N$ electrons on a spherical surface are used as input data to determine the quasiparticle energies and the pairwise ``Fermi liquid&#39;&#39; interactions of composite Fermion (CF) excitations in fractional quantum Hall systems. The quasiparticle energies and their interactions are then used to determine the energy

C. L. Kane, Matthew P. A. Fisher

We analyze thermal transport in the fractional quantum Hall effect (FQHE), employing a Luttinger liquid model of edge states. Impurity mediated inter-channel scattering events are incorporated in a hydrodynamic description of heat and charge transport. The thermal Hall conductance, $K_H$, is shown to provide a new and universal characterization of the FQHE s

Roland Fehrenbacher

An analysis of angle-resolved photoemission (ARPES) experiments in the superconducting state of the high \tc copper-oxides is presented. It is based on a phenomenological weak-coupling BCS model which incorporates the experimental normal state dispersion extracted from ARPES, and non-magnetic impurity scattering in the presence of a $d_{x^2-y^2}$ order param

V. B. Cherepanov, I. V. Kolokolov, E. V. Podivilov

The problem of the Kosterlitz-Thouless (KT) transition in the highly frustrated XY Kagomé antiferromagnet is solved. The problem is mapped onto that of the KT transition in the XY ferromagnet on the hexagonal lattice. The transition temperature is found. It is shown that the spin correlation function exponentially decays with distance even in the low-tempera

Heiko Leschhorn, Thomas Nattermann, Semjon Stepanow, Lei-Han Tang

The dynamics of a driven interface in a medium with random pinning forces is analyzed. The interface undergoes a depinning transition where the order parameter is the interface velocity $v$, which increases as $v \sim (F-F_c)^θ$ for driving forces $F$ close to its threshold value $F_c$. We consider a Langevin-type equation which is expected to be valid close

J. Gonzalez, F. Guinea, M. A. H. Vozmediano

The influence of electron-electron scattering on quasiparticle lifetimes in graphite is calculated. In the limit when the Fermi surface is reduced to isolated points in the Brillouin Zone, the suppression of screening leads to non Fermi liquid behavior. The inverse lifetime increases linearly with energy, in agreement with recent experiments. Similar feature

A. S. Alexandrov

A model of hybridized bosons and fermions is studied beyond the mean field approximation. The divergent boson self-energy at zero temperature makes the Cooper pairing of fermions impossible.The frequency and momentum dependence of the self- energy and the condensation temperature $T_{c}$ of initially localized bosons are calculated analytically. The value of

M. C. Bonsager, K. Flensberg, B. Y. -K. Hu, A. -P. Jauho

We use the Kubo formalism to calculate the transresistivity $ρ_{21}$ for carriers in coupled quantum wells in a large perpendicular magnetic field $B$. We find that $ρ_{21}$ is enhanced by approximately 50--100 times over that of the B=0 case in the interplateau regions of the integer quantum Hall effect. The presence of both electron--electron interactions

R. Aguado, J. Inarrea, G. Platero

We have analyzed the tunneling transmission probability and electronic current density through resonant heterostructures in the presence of an external electromagnetic field. In this work, we compare two different models for a double barrier : In the first case the effect of the external field is taken into account by spatially dependent AC voltages and in t

M. Apostol

It is shown that the one- and two-dimensional solids may exist and melt

Swapan Pati, R. Chitra, Diptiman Sen, S. Ramasesha

We use the density matrix renormalization group method to study the ground state `phase&#39; diagram and some low-energy properties of isotropic antiferromagnetic spin-$1 \over 2$ and spin-$1$ chains with a next-nearest neighbor exchange $J_2 ~$ and an alternation $δ$ of the nearest neighbor exchanges. In the spin-$1 \over 2$ chain, the system is gapless for

Dmitrii L. Maslov, Michael Stone

These are the lecture notes to be published in the Proceedings of XXXI Rencontres de Moriond conference ``Correlated Fermions and Transport in Mesoscopic Systems&#39;&#39;, (20-27 January 1996, Les Arcs, France). The notes are based on two recent papers [D L. Maslov and M. Stone, Phys. Rev. B 52, R5539 (1995), and D. L. Maslov, ibid., R14368 (1995)].

Hidetoshi Nishimori, Yoshihiko Nonomura

We develop the statistical mechanics of the Hopfield model in a transverse field to investigate how quantum fluctuations affect the macroscopic behavior of neural networks. When the number of embedded patterns is finite, the Trotter decomposition reduces the problem to that of a random Ising model. It turns out that the effects of quantum fluctuations on mac

Andrew N. Emerton, Peter V. Coveney, Bruce M. Boghosian

We investigate the dynamical behavior of both binary fluid and ternary microemulsion systems in two dimensions using a recently introduced hydrodynamic lattice-gas model of microemulsions. We find that the presence of amphiphile in our simulations reduces the usual oil-water interfacial tension in accord with experiment and consequently affects the non-equil

J. F. Poyatos, J. I. Cirac, P. Zoller

We show how to design different couplings between a single ion trapped in a harmonic potential and an environment. This will provide the basis for the experimental study of the process of decoherence in a quantum system. The coupling is due to the absorption of a laser photon and subsequent spontaneous emission. The variation of the laser frequencies and int

Robert Popham

We propose that FU Orionis outbursts may play an important role in maintaining the slow rotation of classical disk-accreting T Tauri stars. Current estimates for the frequency and duration of FU Orionis outbursts and the mass accretion rates of T Tauri and FU Orionis stars suggest that more mass may be accreted during the outbursts than during the T Tauri ph