December 1996 arXiv papers — page 13

Ahmad Shariati

Using a simple ansatz for the solutions of the three dimensional generalization of the sine--Gordon and Toda model introduced by Konopelchenko and Rogers, a class of solutions is found by elementary methods. It is also shown that these equations are not evolution equations in the sense that solution to the initial value problem is not unique.

Kurt Haller

We derive an expression for the relation between two scattering transition amplitudes which reflect the same dynamics, but which differ in the description of their initial and final state vectors. In one version, the incident and scattered states are elements of a perturbative Fock space, and solve the eigenvalue problem for the `free' part of the Hamilt

Anjan Kundu

Various aspects of the theory of quantum integrable systems are reviewed. Basic ideas behind the construction of integrable ultralocal and nonultralocal quantum models are explored by exploiting the underlying algebraic structures related to the Yang-Baxter equations. Physical meaning of abstract mathematical notions like universal R-matrix, quantized algebr

Oleg Andreev

By generalizing a fermionic construction, a natural relation is found between SL(2) degenerate conformal field theories and some N=2 discrete superconformal series. These non-unitary models contain, as a subclass, N=2 minimal models. The construction permits one to investigate the properties of chiral operators in the N=2 models. A chiral ring reveals a clos

A. V. Belitsky, E. A. Kuraev

We construct the evolution equations for the twist-3 chiral-odd spin independent fracture functions in QCD. The Gribov-Lipatov reciprocity relation is fulfilled at the one-loop level for the quasi-partonic two-particle cut vertices only. It is found that the rang of the anomalous dimensions matrix is infinite for any given moment of the three-parton fracture

Markus Finkemeier, Johann Kühn, Erwin Mirkes

Predictions for decay rates and distributions for $τ$ decays into final states with kaons are discussed and compared with recent measurements. Special emphasis is put on new constraints for the vector current contribution in the $KKπ$ decay modes. For the $Kππ$ modes, disagreements with the experimental results can be traced back to the $K_1$ widths.

O. J. P. Eboli, M. C. Gonzalez-Garcia, J. K. Mizukoshi

We analyze the constraints on vector leptoquarks coming from radiative corrections to $Z$ physics. We perform a global fitting to the LEP data including the oblique and non-universal contributions of the most general effective Lagrangian for vector leptoquarks, which exhibits the $SU(2)_L \times U(1)_Y$ gauge invariance. We show that the $Z$ physics leads to

A. H. Mueller

Limits on the regions of $Q^2$ and x where the operator product expansion canbe safely used, at small values of x are given. For a fixed large $Q^2$ there is an $x_0(Q^2)$ such that for Bjorken x-values below $x_0$ the operator product expansion breaks down with significant nonperturbative corrections occurring in the leading twist coefficient and anomlous d

M. Stratmann, W. Vogelsang

We determine the two-loop 'time-like' Altarelli-Parisi splitting functions, appearing in the next-to-leading order Q^2-evolution equations for fragmentation functions, via analytic continuation of the corresponding 'space-like' splitting functions for the evolution of parton distributions. We do this for the case of unpolarized fragmentation

L. B. Okun

A brief review, from basic atomic constants to "Mendeleev Table" of leptons, quarks, fundamental bosons, and then to superunification of all forces and particles.

L. B. Okun

A few remarks concerning theoretical suggestions and experimental tests of CPT during 1980's - 1990's. Is it worth to search for the particle-antiparticle mass differences in sectors other than $K^0\bar{K}^0$?

A. A. Bel'kov, M. Dillig

In the framework of the path integral approach we develop the velocity component formalism for spin-1/2 and -3/2 baryons coupled with pseudoscalar mesons in the limit of heavy baryons. Starting from the most general chiral meson-baryon lagrangian including the invariance of spin-3/2 fields under point transformation we detail various problems in integrating

R. Foot, R. R. Volkas

The assumption of exact, unbroken parity symmetry leads directly to a simple predictive resolution of the atmospheric and solar neutrino puzzles. This is because the existence of this symmetry implies the existence of a set of mirror neutrinos which must mix maximally with the known neutrinos if neutrinos have mass. The maximal mixing of the electron neutrin

P. I. Krastev, S. T. Petcov

We analyze the latest published solar neutrino data assuming an arbitrary neutrino oscillation/conversion mechanism suppresses the electron neutrino flux from the Sun independent of energy. For oscillations/transitions into active (sterile) neutrinos such mechanisms are ruled out at 99.96 (99.9997) % C.L. assuming the standard solar model by Bahcall and Pinn

P. Burrows, S. Dawson, L. Orr, W. H. Smith

Despite many experimental verifications of the correctness of our basic understanding of QCD, there remain numerous open questions in strong interaction physics and we focus on the role of future colliders in addressing these questions. We discuss possible advances in the measurement of $α_s$, in the study of parton distribution functions, and in the underst

The DZero Collaboration, S. Abachi

We have measured the $WWγ$ gauge boson coupling parameters using $p\bar{p}\to \ellνγ+X$ ($\ell=e,μ$) events at $\sqrt{s}=1.8$ TeV. The data, corresponding to an integrated luminosity of 89.1 pb^{-1}, were collected using the D0 detector at the Fermilab Tevatron Collider. The measured cross section times branching ratio for $p\bar{p} \to Wγ+X$ with $p_T^γ$ >

W. Kummer, H. Liebl, D. V. Vassilevich

Local path integral quantization of generic 2D dilaton gravity is considered. Locality means that we assume asymptotic fall off conditions for all fields. We demonstrate that in the absence of `matter' fields to all orders of perturbation theory and for all 2D dilaton theories the quantum effective action coincides with the classical one. This resolves t

I. M. Benn, Philip Charlton

We show how, for all dimensions and signatures, a symmetry operator for the massless Dirac equation can be constructed from a conformal Killing-Yano tensor of arbitrary degree.

S. Zakrzewski

SL(N,C) is the phase space of the Poisson SU(N). We calculate explicitly the symplectic structure of SL(N,C), define an analogue of the Hamiltonian of the free motion on SU(N) and solve the corresponding equations of motion. Velocity is related to the momentum by a non-linear Legendre transformation.

S. Zakrzewski

The general framework of Legendre transformation is extended to the case of symplectic groupoids, using an appropriate generalization of the notion of generating function (of a Lagrangian submanifold).

S. Zakrzewski

Poisson plane and sphere --- homogeneous spaces of Poisson groups E(2) and SU(2) (resp.) --- have phase spaces (corresponding symplectic groupoids), in which a free Hamiltonian is naturally defined. We solve the equations of motion and point out some unexpected features: free motion on the plane is bounded (periodic) and free trajectories on the sphere are a

S. Zakrzewski

The existence of the theory of `twisted cotangent bundles' (symplectic groupoids) allows to study classical mechanical systems which are generalized in the sense that their configurations form a Poisson manifold. It is natural to study from this point of view first such systems which arise in the context of some basic physical symmetry (space-time, rotat

F. Lesage, H. Saleur

We discuss in more details the theory of low energy excitations in quantum impurity problems with an external field at vanishing temperature, giving further support to results of the previous paper. We then extend these results to the next order at low frequency, obtaining in particular the exact expression, as a function of the bias, of the first two deriva

Michael R. Geller

I present a theory of electron dynamics in semiconductors with slowly varying composition. I show that the frequency-dependent conductivity, required for the description of transport and optical properties, can be obtained from a knowledge of the band structures and momentum matrix elements of homogeneous semiconductor alloys. New sum rules for the electroni

G. T. Barkema, M. E. J. Newman

We discuss the repton model of agarose gel electrophoresis of DNA. We review previous results, both analytic and numerical, as well as presenting a new numerical algorithm for the efficient simulation of the model, and suggesting a new approach to the model's analytic solution.

T. Antal, Z. Racz, L. Sasvari

We study the nonequilibrium steady states of an Ising chain in a transverse field, h, by investigating the effect of a field, lambda, which drives the current of energy. The zero-temperature, h-lambda phase diagram is determined exactly and it is found that the energy current appears continuously above a threshold, lambda > lambda_c(h). The long-range magnet

Qiming Li, Jun Zang, A. R. Bishop, C. M. Soukoulis

The metallic or insulating nature of the paramagnetic phase of the colossal-magnetoresistance manganites is investigated via a double exchange Hamiltonian with diagonal disorder. Mobility edge trajectory is determined with the transfer matrix method. Density of states calculations indicate that random hopping alone is not sufficient to induce Anderson locali

A. Damascelli, K. Schulte, D. van der Marel, A. A. Menovsky

From an investigation of the optical conductivity of FeSi single crystals using FTIR spectroscopy in the frequency range from 30 to 20000 wavenumbers we conclude that the transverse effective charge of the Fe and Si ions is approximately 4e. Of the five optical phonons which are allowed by symmetry we observe only four, three of which have a Fano line shape

Anthony P. Roberts

The intersection volume of two independent 2-level cut Gaussian random fields is proposed to model the open-cell microstructure of organic aerogels. The experimentally measured X-ray scattering intensity, surface area and solid thermal conductivity of both polymeric and colloidal organic aerogels can be accounted for by the model.

S. Komineas, N. Papanicolaou

The dynamics of vortices in a 2D Heisenberg antiferromagnet with an easy-plane anisotropy is studied numerically within the discrete spin model as well as analytically within a continuum approximation based on a suitable extension of the relativistic nonlinear sigma model. We find that two like vortices scatter at 90 degrees during a head-on collision, where

F. Dalfovo, M. Guilleumas, A. Lastri, L. Pitaevskii

We study the scattering of atoms, rotons and phonons at the free surface of $^4$He at normal incidence and calculate the evaporation, condensation and reflection probabilities. Assuming elastic one-to-one processes and using general properties of the scattering matrix, such as unitarity and time reversal, we argue that all nonzero probabilities can be writte

Taksu Cheon, T. Shigehara

The coherent tunneling phenomenon is investigated in rectangular billiards divided into two domains by a classically unclimbable potential barrier. We show that by placing a pointlike scatterer inside the billiard, we can control the occurrence and the rate of the resonance tunneling. The key role of the avoided crossing is stressed. Keywords: chaotic tunnel

P. Nugent, E. Baron, D. Branch, A. Fisher

We present detailed NLTE synthetic spectra of hydrodynamic SNe Ia models. We make no assumptions about the form of the spectrum at the inner boundary. We calculate both Chandrasekhar-mass deflagration models and sub-Chandrasekhar ``helium detonators.'' Gamma-ray deposition is handled in a simple, accurate manner. We have parameterized the storage of

D. Kunth, J. Lequeux, J. M. Mas-Hesse, E. Terlevich

HST spectroscopical observations of 8 HII galaxies are reported. Ly alpha emission was detected in 4 of them. We find that the velocity structure of the gas is the main determining factor for the escape of the Ly alpha photons, and not the abundance of dust. The rest of the sample shows broad damped Ly alpha absorption attributed to large HI column densities

Gabriele Ghisellini

Although the gamma-ray emission in blazars dominates the power output, there are crucial informations carried by the X-rays. Indeed, their paucity, together with the short variability timescales observed both at X and gamma-ray energies constrains the location, along the jet, of the active region responsible for most of the emission. Furthermore, the knowled

A. Comastri, G. Fossati, G. Ghisellini, S. Molendi

ROSAT observations of a large sample of bright gamma-ray (E > 100 MeV) blazars are presented. Results of a detailed spectral analysis in the soft $\sim$ 0.1-2.0 keV energy range are discussed in relation to the overall energy distribution with particular emphasis on the relation between X-ray and gamma-ray properties. A significant anti-correlation between X

A. B. Goldin, M. S. Kowitt, E. S. Cheng, D. A. Cottingham

Whole disk brightness ratios for Jupiter, Saturn, and Mars are reported at 5.7, 9.5, 16.4, and 22.5 cm$^{-1}$. Using models for the brightness temperature of Mars, the whole disk brightness temperatures for Jupiter and Saturn are also given for the four frequencies.

Sangwook Park, John P. Finley, Steven L. Snowden, Thomas M. Dame

A mosaic of 7 ROSAT PSPC pointed observations in the direction of (l,b ~ 10,0 deg) reveals deep X-ray shadows in the 0.5-2.0 keV band cast by dense molecular gas. The comparison between the observed on-cloud and off-cloud X-ray fluxes indicates that ~43% of the diffuse X-ray background in this direction in both the 3/4 keV and 1.5 keV bands originates behind

Stefanie Komossa, Henner Fink

We present and analyze a pointed ROSAT PSPC observation of the Seyfert galaxy NGC 4051. The X-ray spectrum consists of a powerlaw modified by absorption edges and an additional soft excess during the high-state in source flux. Modeling the spectrum in terms of warm absorption yields a large column density of the ionized material of log N_w = 22.7 and an ioni

Marco Chiaberge, Gabriele Ghisellini

We calculate the time dependent electron distribution under the assumption of continuous injection of new relativistic particles, and assuming radiative cooling (by sinchrotron and inverse Compton) and particle escape. Resulting photon spectra are calculated taking into account the time delays introduced by the different light travel times across the source.

J. Greiner, K. Bickert, R. Luthardt, R. Viotti

We present the results of an extensive campaign of coordinated X-ray (ROSAT) and UV (IUE) observations of the symbiotic star AG Dra during a long period of quiescence (1990-1993) followed by two optical outbursts in 1994 and 1995. The hot component (i.e. X-ray emitting compact object) turns out to be very luminous during the quiescent phase: (9.5+/-1.5)*10^3

Jean-Luc Brylinski

We give a dual to the McKay correspondence, involving conjugacy classes of subgroups of SU(2). We prove a determinantal formula involving both correspondences. We pose some questions concerning a non-commutative Fourier transform.

Roland E. Allen

A new kind of fundamental superfield is proposed, with an Ising-like Euclidean action. Near the Planck energy it undergoes its first stage of symmetry-breaking, and the ordered phase is assumed to support specific kinds of topological defects. This picture leads to a low-energy Lagrangian which is similar to that of standard physics, but there are interestin

Vadim A. Brazhnikov

We study $su(2)_k$ WZW model perturbed by a multiplet of primary fields. The theory has a rich variety of particles. Presence of nontrivial decay processes is a peculiarity of the model. We prove integrability by explicit construction of quantum conserved currents. The scattering theory is briefly discussed.

A. N. Kuznetsov, F. V. Tkachov

The results of the mathematical theory of asymptotic operation developed in hep-th/9612037 are applied to problems of immediate physical interest. First, the problem of UV renormalizationis analyzed from the viewpoint of asymptotic behaviour of integrands in momentum representation. A new prescription for UV renormalization in momentum space representation i

Arjun Berera

In the standard picture, the inflationary universe is in a supercooled state which ends with a short time, large scale reheating period, after which the universe goes into a radiation dominated stage. An alternative is proposed here in which the radiation energy density smoothly decreases all during an inflation-like stage and with no discontinuity enters th

Nils A. Tornqvist

The mechanism where flavour symmetry is broken spontaneously is demonstated for a model involving nonets of pseudoscalar and vector mesons. Degenerate bare nonets of vector and pseudoscalar mesons coupling sufficiently strongly to each others lead to unstable self-consistency equations, such that the SU3$_f$ symmetric spectrum breaks down into a stable isosp

J. Papavassiliou, E. de Rafael, N. J. Watson

In quantum electrodynamics with fermions f = e,μ..., knowledge of the vacuum polarization spectral function determined from the tree level e^+e^- -> f^+f^- cross sections, together with a single low energy measurement of the fine structure constant α, enables the construction of the one-loop effective charge α_eff(q^2) for all q^2. It is shown how an identic

S. E. Parkhomenko

The supersymmetric generalization of Poisson-Lie T-duality in superconformal WZNW models is considered. It is shown that the classical N=2 superconformal WZNW models posses a natural Poisson-Lie symmetry which allows to construct dual $σ$- models.

Valeri A. Gritsenko, Viacheslav V. Nikulin

We extend our variant of mirror symmetry for K3 surfaces \cite{GN3} and clarify its relation with mirror symmetry for Calabi-Yau manifolds. We introduce two classes (for the models A and B) of Calabi-Yau manifolds fibrated by K3 surfaces with some special Picard lattices. These two classes are related with automorphic forms on IV type domains which we studie

Marc Achhammer, Ulrich Heinz, Stefan Leupold, Urs Achim Wiedemann

We pick up a method originally developed by Cheng and Tsai for vacuum perturbation theory which allows to test the consistency of different sets of Feynman rules on a purely diagrammatic level, making explicit loop calculations superfluous. We generalize it to perturbative calculations in thermal field theory and we show that it can be adapted to check the g

Kiyoshi Ezawa, Atushi Ishikawa

We demonstrate the close relationship between Chern-Simons gauge theory with gauge group Osp(1|2) and N=1 induced supergravity in two dimensions. More precisely, the inner product of the physical states in the former yields the partition function of the latter evaluated in the Wess-Zumino supergauge. It is also shown that the moduli space of flat Osp(1|2) co

H. Belich, R. Paunov

We present an elementary derivation of the soliton-like solutions in the $A_n^{(1)}$ Toda models which is alternative to the previously used Hirota method. The solutions of the underlying linear problem corresponding to the N-solitons are calculated. This enables us to obtain explicit expression for the element which by dressing group action, produces a gene

C. R. Gattringer, L. D. Paniak, G. W. Semenoff

We examine the statistical mechanics of a 1-dimensional gas of both adjoint and fundamental representation quarks which interact with each other through 1+1-dimensional U(N) gauge fields. Using large-N expansion we show that, when the density of fundamental quarks is small, there is a first order phase transition at a critical temperature and adjoint quark d

Phillial Oh, Chaiho Rim

We obtain a self-dual formulation of the conventional nonlinear Schrödinger equation (NLSE) in the 1+1 dimension by studying the dimensional reduction of the self-dual Chern-Simons nonlinear Schrödinger model (NLSM) in the 2+1 dimension. It is found that this self-dual formulation allows us to find not only the well-known soliton solutions from the Bogomol&#

Uwe Grimm

Many of the known solutions of the Yang-Baxter equation, which are related to solvable lattice models of vertex- and IRF-type, yield representations of the Birman-Wenzl-Murakami algebra. From these, representations of a two-colour generalization of the Birman-Wenzl-Murakami algebra can be constructed, which in turn are used to derive trigonometric solutions

Gilles Brassard, Peter Hoyer

We investigate the power of quantum computers when they are required to return an answer that is guaranteed correct after a time that is upper-bounded by a polynomial in the worst case. In an oracle setting, it is shown that such machines can solve problems that would take exponential time on any classical bounded-error probabilistic computer.

D. Koks, A. Matacz, B. L. Hu

We define the entropy S and uncertainty function of a squeezed system interacting with a thermal bath, and study how they change in time by following the evolution of the reduced density matrix in the influence functional formalism. As examples, we calculate the entropy of two exactly solvable squeezed systems: an inverted harmonic oscillator and a scalar fi

A. Ludu, R. A. Ionescu, W. Greiner

We generalize the non-linear one-dimensional equation of a fluid layer for any depth and length as an infinite order differential equation for the steady waves. This equation can be written as a q-differential one, with its general solution written as a power series expansion with coefficients satisfying a nonlinear recurrence relation. In the limit of long

Zhenping Li

The meson photoproductions off nucleons in the chiral quark model are described. The role of the S-wave resonances in the second resonance region is discussed, and it is particularly important for the Kaon, $η$ and $η'$ photoproductions.

H. Nakada, T. Otsuka

We present a new method by which wavefunctions with simple structure are renormalized so as to contain more complicated structure. This method, called $H^n$-cooling method, is applied to the study of the quadrupole collective motion of $^{56}$Fe, $^{54}$Cr, $^{58}$Fe and $^{56}$Cr. The shell-model wavefunctions of lowest-lying states of these nuclei are well

Rita Gitik

We prove several generalisations of the ping-pong lemma for negatively curved groups.

Bohuslav Balcar, Wieslaw Glowczynski, Thomas Jech

We investigate the sequential topology $τ_s$ on a complete Boolean algebra $B$ determined by algebraically convergent sequences in $B$. We show the role of weak distributivity of $B$ in separation axioms for the sequential topology. The main result is that a necessary and sufficient condition for $B$ to carry a strictly positive Maharam submeasure is that $B

J. Balog, M. Niedermaier

The off-shell dynamics of the O(3) nonlinear sigma-model is probed in terms of spectral densities and two-point functions by means of the form factor approach. The exact form factors of the Spin field, Noether-current, EM-tensor and the topological charge density are computed up to 6-particles. The corresponding $n\leq 6$ particle spectral densities are used

A. N. Kuznetsov, F. V. Tkachov, V. V. Vlasov

We present a systematic description of the mathematical techniques for studying multiloop Feynman diagrams which constitutes a full-fledged and inherently more powerful alternative to the BPHZ theory. The new techniques emerged as a formalization of the reasoning behind a recent series of record multiloop calculations in perturbative quantum field theory. It

Jens Hoppe, Tudor Ratiu

For a variety of diffeomorphism-invariant field theories describing hypersurface motions (such as relativistic M-branes in space-time dimension M+2) we perform a Hamiltonian reduction ``at level 0'', showing that a simple algebraic function of the normal velocity is canonically conjugate to the shape Σof the hypersurface. The Hamiltonian dependence o

L. Galli, I. Scimemi

We study the properties of ultraviolet renormalons in the vectorial $(\vecϕ^{2})^{2}$ model. This is achieved by studying the effective potential of the theory at next to leading order of the $1/N$ expansion, the appearence ofthe renormalons in the perturbative series and their relation to the imaginary part of the potential. We also consider the mechanism o

Masahiko Miyamoto

We study a vertex operator algebra containing a tensor product of Ising models. It is a direct sum of code vertex operator algebra and its irreducible modules. Therefore, we classify all irreducible modules of code vertex operator algebras and show a new construction of vertex operator algebras.

B. Holdom, Qing Wang

By introducing auxiliary fields, which by their quantum numbers vanish in perturbation theory, we relate the dynamical perturbation theory of Pagels and Stokar and a successful gauged nonlocal constituent quark model to $U(N)$ gauge theory and to QCD. This sheds light on the duality between quark models and resonance models. We then derive the effective acti

Michael S. Chanowitz

Sigma models are exhibited which have tree amplitudes for Goldstone boson scattering that satisfy elastic unitarity exactly. The models have imaginary coupling constants and the scalar propagators have poles on the imaginary axis in the complex p^2 plane. They are equivalent to K-matrix models, which are ad hoc unitarizations of low energy theorems for Golds

Stefano Catani, Michael H. Seymour

We briefly summarize theoretical methods for carrying out QCD calculations to next-to-leading order in perturbation theory. In particular, we describe a new general algorithm that can be used for computing arbitrary jet cross sections in arbitrary processes and can be straightforwardly implemented in general-purpose Monte Carlo programs.

G. Camici, M. Ciafaloni

We discuss the small-x behaviour of the next-to-leading BFKL equation, depending on various smoothing out procedures of the running coupling constant at low momenta. While scaling violations (with resummed and calculable anomalous dimensions) turn out to be always consistent with the renormalization group, we argue that the nature and the location of the so-

T. Hirano, S. Muroya, M. Namiki

We compare the numerical results of thermal photon distribution from the hot QCD matter produced by high energy nuclear collisions, based on hydrodynamical model, with the recent experimental data obtained by CERN WA80. Through the asymptotic value of the slope parameter of the transverse momentum distribution, we discuss the characteristic temperature of th

Fu-Guang Cao, Tao Huang

By reanalysing transverse momentum dependence in the perturbative calculation of pion form factor an improved expression of pion form factor which takes into account the transverse momentum dependenc in hard scattering amplitude and intrinsic transverse momentum dependence associated with pion wave functions is given to leading order, which is available for

Simonetta Frittelli, Carlos N. Kozameh, Ezra T. Newman, Carlo Rovelli

We define and discuss various quantum operators that describe the geometry of spacetime in quantum general relativity. These are obtained by combining the Null-Surface Formulation of general relativity, recently developed, with asymptotic quantization. One of the operators defined describes a ``fuzzy'' quantum light cone structure. Others, denoted ``

B. S. Sathyaprakash

In this lecture we describe the data analysis problem for insparlling binaries. We discuss the detection statistic, how to make realiable estimation and how to compute bias in the estimation of parameters. A combination of geometrical ideas and numerical methods are employed to estimate computational costs involved in searching for post-Newtonian wave forms.

Michael Hutchings, Yi-Jen Lee

Let X be a compact oriented Riemannian manifold and let $ϕ:X\to S^1$ be a circle-valued Morse function. Under some mild assumptions on $ϕ$, we prove a formula relating: (a) the number of closed orbits of the gradient flow of $ϕ$ of any given degree; (b) the torsion of a ``Morse complex'', which counts gradient flow lines between critical points of $ϕ

Indrani Bose

We describe some antiferromagnetic systems which exhibit spin gaps. We also discuss the effect of doping one such system, namely, the spin-ladders, with holes. Some model antiferromagnetic systems with spin gap are reviewed for which exact results are available. Exact results for a doped spin-ladder model are also mentioned.

Z. Y. Weng, D. N. Sheng, Y. -C. Chen, C. S. Ting

We reexamine the problem of a hole moving in an antiferromagnetic spin background and find that the injected hole will always pick up a sequence of nontrivial phases from the spin degrees of freedom. Previously unnoticed, such a string-like phase originates from the hidden Marshall signs which are scrambled by the hopping of the hole. We can rigorously show

K. Gloos, F. B. Anders, B. Buschinger, C. Geibel

Mechanical-controllable break junctions of the heavy-fermion superconductors can show Josephson-like superconducting anomalies. But a systematic study on the contact size demonstrates that these anomalies are mainly due to Maxwell's resistance being suppressed in the superconducting heavy-fermion phase. Up to day, we could not find any superconducting fe

Ilya A. Gruzberg, N. Read, Subir Sachdev

We consider the directed network (DN) of edge states on the surface of a cylinder of length L and circumference C. By mapping it to a ferromagnetic superspin chain, and using a scaling analysis, we show its equivalence to a one-dimensional supersymmetric nonlinear sigma model in the scaling limit, for any value of the ratio L/C, except for short systems wher

P. L. Krapivsky, S. Redner

The dynamics of a point charged particle which is driven by a uniform external electric field and moves in a medium of elastic scatterers is investigated. Using rudimentary approaches, we reproduce, in one dimension, the known results that the typical speed grows with time as t^{1/3} and that the leading behavior of the velocity distribution is exp(-|v|^3/t)

V. E. Kravtsov, I. V. Yurkevich

It is shown that the quasi-localized states in weakly disordered systems can lead to the non-analytical distribution of level curvatures. In 2D systems the distribution function P(K) has a branching point at K=0. In quasi-1D systems the non-analyticity at K=0 is very weak, and in 3D metals it is absent at all. Such a behavior confirms the conjecture that the

Andreas Wacker, Antti-Pekka Jauho, Stefan Zeuner, S. James Allen

A theoretical and experimental study of transport in a low doped multiple quantum well structure shows that impurity bands are essential in understanding the electronic transport both with and without terahertz irradiation. A full self-contained model, which involves only the nominal parameters of the sample, agrees quantitatively with a wide range of experi

Rudolf A. R"omer, Michael Schreiber

We study two interacting particles in a random potential chain by means of the transfer matrix method. The dependence of the two-particle localization length $λ_2$ on disorder and interaction strength is investigated. Our results demonstrate that the recently proposed enhancement of $λ_2$ as compared to the results for single particles is entirely due to the

V. M. Zharkov

New functional representation for the strongly interacting systems is proposed which contains a new type of the quantum coherent state. As a result the new algebraic structure- so called "tower of algebras" appears which gives the tower (or hierarchy) of models. Generalization of Gutzwiller approximation in theory of metal-insulator phase transition

Massimiliano Capezzali, Hans Beck, Subodh R. Shenoy

Low -frequency dynamic impedance ($σ^{-1}(ω,T)\equiv(σ_{1}+iσ_{2})^{-1}$) measurements on Josephson junction arrays with finite vortex screening length $ξ$, found that $σ_{1}\sim |\logω|$, $σ_{2}\sim$ constant. This implies anomalously sluggish vortex mobilities $μ_{V}(ω)\simσ_{1}^{-1}$, and is in conflict with general dynamical scaling expressions that yiel

Grzegorz Haran, A. D. S. Nagi

The effect of weak anisotropic (momentum-dependent) impurity scattering in unconventional superconductors has been investigated. It is shown that the anisotropic scattering can lead either to a small reduction or a small enhancement of the isotropic pair-breaking effect. The influence of the anisotropy of the scattering potential becomes significant for the

G. Haran, J. Taylor, A. D. S. Nagi

The effect of a homogeneous magnetic field and nonmagnetic impurities on the critical temperature of an anisotropic superconductor has been investigated. The role of these pair-breakers in relation to the anisotropy of the order parameter is clarified.

D. Mitchell, D. Kusnezov

Universality of correlation functions obtained in parametric random matrix theory is explored in a multi-parameter formalism, through the introduction of a diffusion matrix $D_{ij}(R)$, and compared to results from a multi-parameter chaotic model. We show that certain universal correlation functions in 1-d are no longer well defined by the metric distance be

Tomaz Prosen

Local parametric statistics of zeros of Husimi representations of quantum eigenstates are introduced. It is conjectured that for a classically fully chaotic systems one should use the model of parametric statistics of complex roots of Gaussian random polynomials which is exactly solvable as demonstrated below. For example, the velocities (derivatives of zero

Tomaz Prosen

k-point correlations of complex zeros for Gaussian ensembles of Random Polynomials of order N with Real Coefficients (GRPRC) are calculated exactly, following an approach of Hannay for the case of Gaussian Random Polynomials with Complex Coefficients (GRPCC). It is shown that in the thermodynamic limit $N \to \infty$ of Gaussian random holomorphic functions

Henry S. Greenside

The dynamics of a nonequilibrium system can become complex because the system has many components (e.g., a human brain), because the system is strongly driven from equilibrium (e.g., large Reynolds-number flows), or because the system becomes large compared to certain intrinsic length scales. Recent experimental and theoretical work is reviewed that addresse

H. Liang, M. Pierre, A. Unewisse, R. W. Hunstead

We present an X-ray, radio and optical study of the cluster A2717. The central D galaxy is associated with a Wide-Angled-Tailed (WAT) radio source. A Rosat PSPC observation of the cluster shows that the cluster has a well constrained temperature of 2x10^7 K. The pressure of the intracluster medium was found to be comparable to the mininum pressure of the rad

Lee Smolin

A model of a galactic disk is presented which extends the homogeneous one zone models by incorporating propagation of material and energy in the disk. For reasonable values of the parameters the homogeneous steady state is unstable to the development of inhomogeneities, leading to the development of spatial and temporal structure. At the linearized level a p

S. W. Allen, A. C. Fabian

We present the results from a study of the spatial distributions of cooling gas and intrinsic X-ray absorbing material in a sample of nearby, X-ray bright cooling flow clusters observed with the Position Sensitive Proportional Counter (PSPC) on ROSAT. Our method of analysis employs X-ray colour profiles, formed from ratios of the surface brightness profiles

J. W. Fried

Very deep imaging data of three optically luminous radio-loud quasars with redshifts between z=0.9 and z=1.36 are presented. The data are complete for galaxies down to R=26. There is no evidence for excess numbers of galaxies around the quasars; foreground galaxy clusters are excluded by the data as well as clusters with richness classes greater than 1 assoc

C. Alcock et al

We consider simultaneous optical data obtained during the recent X-ray turn-off of CAL83. Combining the optical behaviour with the observed X-ray decay time, we show that a model of cessation of steady nuclear burning is viable if the white dwarf is massive. Our model provides a natural explanation for the subsequent return of the supersoft X-ray emission.

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

We study topological properties of large scale structure in a set of scale free N-body simulations using the genus and percolation curves as topological characteristics. Our results show that as gravitational clustering advances, the density field shows an increasingly pronounced departure from Gaussianity reflected in the changing shape of the percolation c

Pavel Kroupa

The Milky Way is surrounded by nine or more dwarf-spheroidal (dSph) satellite galaxies that appear to consist primarily of dark matter. Here I summarise research that shows that initially spherical bound low-mass satellites without dark matter, that are on orbits within a massive Galactic dark corona, can evolve into remnants that are non-spherical, have a n