January 2002 arXiv papers — page 4

A. M. Martin, K. A. Benedict, F. W. Sheard, L. Eaves

In samples used to maintain the US resistance standard the breakdown of the dissipationless integer quantum Hall effect occurs as a series of dissipative voltage steps. A mechanism for this type of breakdown is proposed, based on the generation of magneto-excitons when the quantum Hall fluid flows past an ionised impurity above a critical velocity. The calcu

Chiaki Yamaguchi, Naoki Kawashima

We propose a method for Monte Carlo simulation of statistical physical models with discretized energy. The method is based on several ideas including the cluster algorithm, the multicanonical Monte Carlo method and its acceleration proposed recently by Wang and Landau. As in the multibondic ensemble method proposed by Janke and Kappler, the present algorithm

D. Wilczak, P. Zgliczynski

The restricted circular three-body problem is considered for the following parameter values $C=3.03$, $μ=0.0009537$ - the values for {\em Oterma} comet in the Sun-Jupiter system. We present a computer assisted proof of an existence of homo- and heteroclinic cycle between two Lyapunov orbits and an existence of symbolic dynamics on four symbols built on this

Somdatta Bhattacharya, Shibaji Roy

We consider a minimally coupled massless scalar propagating in the background of NS5-branes in the presence of a 2-form RR electric field. The supergravity solution also called the (NS5,D1) bound state in the appropriate decoupling limit is the holographic dual of Open D-string (OD1) theory. Using this information, we compute the two-point function of the op

B. V. Ivanov

It is shown that for realistic anisotropic star models the surface redshift can not exceed the values 3.842 or 5.211 when the tangential pressure satisfies the strong or the dominant energy condition respectively. Both values are higher than 2, the bound in the perfect fluid case.

F. Saulnier, E. Raphael, P. -G. de Gennes

Dewetting of ultra-thin polymer films near the glass transition exhibits unexpected front morphologies [G. Reiter, Phys. Rev. Lett., 87, 186101 (2001)]. We present here the first theoretical attempt to understand these features, focusing on the shear-thinning behaviour of these films. We analyse the profile of the dewetting film, and characterize the time ev

Evan Scannapieco, Andrea Ferrara, Piero Madau

Supernova-driven outflows from early galaxies may have had a large impact on the kinetic and chemical structure of the intergalactic medium (IGM). We use three-dimensional Monte Carlo cosmological realizations of a simple linear peaks model to track the time evolution of such metal-enriched outflows and their feedback on galaxy formation. We find that at mos

Palash B. Pal

We propose a fundamental relation for a classical ideal gas that is valid at all temperatures with remarkable accuracy. All thermodynamical properties of classical ideal gases can be deduced from this relation at arbitrary temperature.

M. Kormos, L. Palla

The semi-classical quantisation of the two lowest energy static solutions of boundary sine-Gordon model is considered. A relation between the Lagrangian and bootstrap parameters is established by comparing their quantum corrected energy difference and the exact one. This relation is also confirmed by studying the semi-classical limit of soliton reflections o

Pieter Kok, Kae Nemoto, William J. Munro

We investigate and define dark and semi-dark states for multiple qudit systems. For two-level systems, semi-dark and dark states are equivalent. We show that the semi-dark states are equivalent to the singlet states of the rotation group. They exist for many multiple qudit systems, whereas dark states are quite rare. We then show that when a dark state is co

J. Gemmer, G. Mahler

For a closed bi-partite quantum system partitioned into system proper and environment we interprete the microcanonical and the canonical condition as constraints for the interaction between those two subsystems. In both cases the possible pure-state trajectories are confined to certain regions in Hilbert space. We show that in a properly defined thermodynami

J. Gemmer, G. Mahler

Entanglement may be considered a resource for quantum-information processing, as the origin of robust and universal equilibrium behaviour, but also as a limit to the validity of an effective potential approach, in which the influence of certain interacting subsystems is treated as a potential. Here we show that a closed three particle (two protons, one elect

Thomas Jennewein, Gregor Weihs, Jian-Wei Pan, Anton Zeilinger

Quantum teleportation strikingly underlines the peculiar features of the quantum world. We present an experimental proof of its quantum nature, teleporting an entangled photon with such high quality that the nonlocal quantum correlations with its original partner photon are preserved. This procedure is also known as entanglement swapping. The nonlocality is

A. G. Chirkov, A. N. Ageev

A theoretical analysis of the excitation of an infinitely long solenoid by oscillating current has revealed the existence of specific potentials in the space outside the solenoid, which can affect electron diffraction in an experiment similar to the Aharonov-Bohm effect. Thus, these time-dependent potentials are physical fields possessing a number of specifi

Volodymyr Krasnoholovets

Based on the theory of submicroscopic quantum mechanics recently constructed by the author the mass of elementary spatial excitations called inertons, which accompany a moving particle, is estimated herein. These excitations are treated as carriers of both inertial and gravitational properties of the particle.

Kazuyuki Fujii

The purpose of this paper is to introduce several basic theorems of coherent states and generalized coherent states based on Lie algebras su(2) and su(1,1), and to give some applications of them to quantum information theory for graduate students or non--experts who are interested in both Geometry and Quantum Information Theory. In the first half we make a g

G. H. Rawitscher, S. Y. Kang, I. Koltracht, E. Zerrad

In the Hartree-Fock approximation the Pauli exclusion principle leads to a Schroedinger Eq. of an integro-differential form. We describe a new spectral noniterative method (S-IEM), previously developed for solving the Lippman-Schwinger integral equation with local potentials, which has now been extended so as to include the exchange nonlocality. We apply it

O. -A. Al-Hujaj, P. Schmelcher

We investigate the helium atom embedded in a superstrong magnetic field gamma=100-10000 au. All effects due to the finite nuclear mass for vanishing pseudomomentum are taken into account. The influence and the magnitude of the different finite mass effects are analyzed and discussed. Within our full configuration interaction approach calculations are perform

N. Marwan, M. Thiel, N. R. Nowaczyk

The method of recurrence plots is extended to the cross recurrence plots (CRP), which among others enables the study of synchronization or time differences in two time series. This is emphasized in a distorted main diagonal in the cross recurrence plot, the line of synchronization (LOS). A non-parametrical fit of this LOS can be used to rescale the time axis

R. Bijker, A. Frank

The phenomenom of emerging regular spectral features from random interactions is addressed in the context of the vibron model. A mean-field analysis links different regions of the parameter space with definite geometric shapes. The results that are, to a large extent, obtained in closed analytic form, provide a clear and transparent interpretation of the hig

Ning Wang, Zhuxia Li, Xizhen Wu

An improved Quantum Molecular Dynamics model is proposed. By using this model, the properties of ground state of nuclei from $^{6}$Li to $^{208}$Pb can be described very well with one set of parameters. The fusion reactions for $^{40}$Ca+$^{90}$Zr, $^{40}$Ca+$^{96}$Zr and $^{48}$Ca+$^{90}$Zr at energy near barrier are studied by this model. The experimental

M. Gyulassy, P. Levai, I. Vitev

We apply the GLV Reaction Operator formalism to compute the effects of multiple elastic scatterings of jets propagating through dense matter. We derive the elastic Reaction Operator and demonstrate that the recursion relations have a closed form solution that reduces to the familiar Glauber form. We also investigate the accuracy of the Gaussian dipole approx

Krzysztof Marciniak, Maciej Blaszak

We perform variable separation in the quasi-potential systems of equations of the form $\ddot{q}=-A^{-1}\nabla k=-\tilde{A}^{-1}\nabla\tilde{k}${}, where $A$ and $\tilde{A}$ are Killing tensors, by embedding these systems into a bi-Hamiltonian chain and by calculating the corresponding Darboux-Nijenhuis coordinates on the symplectic leaves of one of the Hami

S. Meljanac, M. Milekovic, M. Stojic

We study permutation invariant oscillator algebras and their Fock space representations using three equivalent techniques, i.e. (i) a normally ordered expansion in creation and annihilation operators, (ii) the action of annihilation operators on monomial states in Fock space and (iii) Gram matrices of inner products in Fock space. We separately discuss permu

A. Dimca, A. Nemethi

We consider an arbitrary polynomial map $f:{\mathbb C}^{n+1}\to {\mathbb C} $ and we study the Alexander invariants of ${\mathbb C}^{n+1}\setminus X$ for any fiber $X$ of $f$. The article has two major messages. First, the most important qualitative properties of the Alexander modules are completely independent of the behaviour of $f$ at infinity, or about t

John Lott

In this paper, which is a sequel to math.DG/9902111, we analyze the limit of the p-form Laplacian under a collapse with bounded sectional curvature and bounded diameter to a singular limit space. As applications, we give results about upper and lower bounds on the j-th eigenvalue of the p-form Laplacian, in terms of sectional curvature and diameter.

Peter Ashwin, James Montaldi

We consider robust relative homoclinic trajectories (RHTs) for equivariant vector fields. We give some conditions on the group and representation that imply existence of equivariant vector fields with such trajectories. Using these result we show very simply that abelian groups cannot exhibit relative homoclinic trajectories. Examining a set of group theoret

Alex Clark, Robbert Fokkink

Solenoids are inverse limit spaces over regular covering maps of closed manifolds. M.C. McCord has shown that solenoids are topologically homogeneous and that they are principal bundles with a profinite structure group. We show that if a solenoid is bihomogeneous, then its structure group contains an open abelian subgroup. This leads to new examples of homog

Oliver Dorn

A two-step shape reconstruction method for diffuse optical tomography (DOT) is presented which uses adjoint fields and level sets. The propagation of near-infrared photons in tissue is modeled by the time-dependent linear transport equation, of which the absorption parameter has to be reconstructed from boundary measurements. In the shape reconstruction appr

Jobst Heitzig

Actual individual preferences are neither complete (=total) nor antisymmetric in general, so that at least every quasi-order must be an admissible input to a satisfactory choice rule. It is argued that the traditional notion of ``indifference'' in individual preferences is misleading and should be replaced by `equivalence' and `undecidedness'

Joerg Schuermann

We explain our notion of a Nash geometric category, which allows an easy comparison between the following different axiomatic notions of geometric categories: o-minimal structures on the real field, analytic geometric categories and X-sets (as defined by van den Dries, Miller and Shiota).

James Montaldi, Tadashi Tokieda

We prove that for every proper Hamiltonian action of a Lie group G in finite dimensions the momentum map is locally G-open relative to its image (i.e. images of G-invariant open sets are open). As an application we deduce that in a Hamiltonian system with continuous Hamiltonian symmetries, extremal relative equilibria persist for every perturbation of the va

O. I. Mokhov

We prove that a local Hamiltonian operator of hydrodynamic type K_1 is compatible with a nondegenerate local Hamiltonian operator of hydrodynamic type K_2 if and only if the operator K_1 is locally the Lie derivative of the operator K_2 along a vector field in the corresponding domain of local coordinates. This result gives a natural invariant definition of

O. I. Mokhov

The nonlinear equations describing all the nonsingular pencils of metrics of constant Riemannian curvature are derived and the integrability of these nonlinear equations by the method of inverse scattering problem is proved. It is proved that all the nonsingular pairs of compatible metrics of constant Riemannian curvature are described by special integrable

Klaus-Dieter Kirchberg

Using Weitzenböck techniques on any compact Riemannian spin manifold we derive a general inequality depending on a real parameter and joining the spectrum of the Dirac operator with terms depending on the Ricci tensor and its first covariant derivatives. The discussion of this inequality yields vanishing theorems for the kernel of the Dirac operator $D$ and

U. Bunke

Given a family of Dirac operators with vanishing spectral flow we construct a thin-invariant rank-one field theory in the sense of Turner and Willerton arXiv:math.AT/0201116. Our construction of the field theory generalizes the one of the index gerbe by Lott, arXiv:math.DG/0106177, and it also complements the relation between gerbes and thin-invariant rank-o

Yuri Bakhtin

A stochastic differential equation with infinite memory is considered. The drift coefficient of the equation is a nonlinear functional of the past history of the solution. Sufficient conditions for existence and uniqueness of stationary solution are given.

F. Cantrijn, B. Langerock

A generalised notion of connection on a fibre bundle E over a manifold M is presented. These connections are characterised by a smooth distribution on E which projects onto a (not necessarily integrable) distribution on M and which, in addition, is `parametrised' in some specific way by a vector bundle map from a prescribed vector bundle over M into TM.

Oliver Johnson

Consider a sphere of radius root(n) in n dimensions, and consider X, a random variable uniformly distributed on its surface. Poincare's Observation states that for large n, the distribution of the first k coordinates of X is close in total variation distance to the standard normal N(0,I_k). In this paper, we consider a larger family of manifolds, and X t

Wolter Groenevelt

The tensor product of a positive and a negative discrete series representation of the quantum algebra U_q(su(1,1)) decomposes as a direct integral over the principal unitary series representations. Discrete terms can appear, and these terms are a finite number of discrete series representations, or one complementary series representation. From the interpreta

Olaf Mueller

Aim of this note is to gain cohomological information about the infinite-dimensional manifold $\rm{Emb}_0 (M,N)$ of asymptotically fixed embeddings of M into N from the topology of the target manifold N. This paper has been withdrawn by the author due a conceptual mistake.

Bhupinder Singh Anand

In this paper, we argue that formal systems of first order Arithmetic that admit Goedelian undecidable propositions validly are abnormally non-constructive. We argue that, in such systems, the strong representation of primitive recursive predicates admits abnormally non-constructive, Platonistic, elements into the formal system that are not reflected in the

Jihun Park

We study del Pezzo fibrations of degree 1 with terminal singularities. A connection between singularities on del Pezzo surfaces of degree 1 and Kodaira's classification of elliptic singular fibers will be studied in this paper. By this investigation we obtain several results on birational maps of del Pezzo fibrations of degree 1 with terminal singulariti

Jason Fulman

Using symmetric function theory, we study the cycle structure and increasing subsequence structure of permutations after various shuffling methods, emphasizing the role of Cauchy type identities and the Robinson-Schensted-Knuth correspondence. One consequence is a cycle index for riffle shuffles when one deals from the bottom of the deck; conclusions are dra

R. de Lima Rodrigues, W. Pires de Almeida, I. Fonseca Neto

We present a review work on Supersymmetric Classical Mechanics in the context of a Lagrangian formalism, with $N=1-$supersymmetry. We show that the N=1 supersymmetry does not allow the introduction of a potential energy term depending on a single commuting supercoordinate, $ϕ(t;Θ)$.

Ralf Lehnert

We investigate the compatibility of Lorentz-violating quantum field theories with the requirements of causality and stability. A general renormalizable model for free massive fermions indicates that these requirements are satisfied at low energies provided the couplings controlling the breaking are small. However, for high energies either microcausality or e

Raffaele Marotta

We study the N=2 super Yang Mills theory living in the world volume of a bound state made of fractional D3/D7 branes at the orbifold R^{1,5}*R^4/ Z_2, by using the probe technique. We also discuss the boundary action for the system.

Matthias Burkardt, Frieder Lenz, Michael Thies

Chiral condensates in the trivial light-cone vacuum emerge if defined as short-time limits of fermion propagators. In gauge theories, the necessary inclusion of a gauge string in combination with the characteristic light-cone infrared singularities contain the relevant non-perturbative ingredients responsible for formation of the condensate, as demonstrated

J. Lukierski

We describe generalized D=11 Poincaré and conformal supersymmetries. The corresponding generalization of twistor and supertwistor framework is outlined with $OSp(1|64)$ superspinors describing BPS preons. The $\frac{k}{32}$ BPS states as composed out of $n=32 - k$ preons are introduced, and basic ideas concerning BPS preon dynamics is presented. The lecture

I. Runkel, G. M. T. Watts

Two dimensional conformal field theories with central charge one are discussed. After a short review of theories based on one free boson, a different CFT is described, which is obtained as a limit of minimal models.

R. P. Malik

We sketch briefly the essentials of the quantum groups and their application to the dynamics of a q-deformed simple harmonic oscillator moving on a quantum line, defined in the q-deformed cotangent (momentum phase) space. In this endeavour, the quantum group $GL_{qp} (2)$- and the conventional rotational invariances are respected together. During the course

J. L. Hewett, F. J. Petriello, T. G. Rizzo

We examine the signatures for noncommutative QED at $e^+e^-$ colliders with center of mass energies in excess of 1 TeV such as CLIC. For integrated luminosities of 1 ab$^{-1}$ or more, sensitivities to the associated mass scales greater than $\sqrt s$ are possible.

C. Anastasiou, E. W. N. Glover, M. E. Tejeda-Yeomans

We present the NNLO QCD virtual corrections for qurak-antiquark -> gluon photon, quark-antiquark -> photon photon and the NNLO QED virtual corrections for electron positron -> photon photon and all processes related by crossing symmetry. We perform an explicit evaluation of the two-loop diagrams in conventional dimensional regularisation, and our results are

E. E. Boos, A. V. Sherstnev

We investigate spin properties of single top quark production at hadron colliders. Based on an analogy with single top production and polarized top quark decay, we reproduce in a simple way the results by G.Mahlon and S.Parke on the existence of preferred axes for the decomposition of the top quark spin. For the W*- and W-g fusion production modes these axes

G R Filewood

In this paper the techniques of discretised QCD developed in physics/0109024 are are extended to a study of ground-state pseudo-scalar mesons involving higher generation quarks. The correspondence with empirical data is good with the exception of the charmed-bottom meson with the predicted value of 6.911GeV varying considerably from the empirical value of 6.

Zhi-qiang Shi

In order to include massive neutrino theoretically, a new concept of the weak charges of the particles, fundamental fermions, intermediate bosons and hadrons, is introduced. A new conservation law of the weak charge is first reported. According to the chirality of the weak charge the origin of parity nonconservation in the weak interactions is reasonably exp

Anupam Mazumdar, Rouzbeh Allahverdi, Kari Enqvist, Abdel Pérez-Lorenzana

We describe how difficult it is to realise baryogenesis in models where the fundamental scale in nature is as low as TeV. The problem becomes even more challenging if we assume that there are only {\it two} extra compact spatial dimensions, because thermal history of such a Universe is strongly constrained by various cosmological and astrophysical bounds whi

Johan Bijnens, Ulf-G. Meißner, Andreas Wirzba

These are the proceedings of the workshop on ``Effective Field Theories of QCD'' held at the Physikzentrum Bad Honnef of the Deutsche Physikalische Gesellschaft, Bad Honnef, Germany from November 26 to 30, 2001. The workshop concentrated on Chiral Perturbation Theory in its various settings, its relations with lattice QCD and dispersion theory and th

R. Rajkhowa, J. K. Sarma

We present comlete solutions of singlet and non-singlet Altarelli-Parisi (AP) evolution equations in leading order at low-x. We obtain t-evolutions of proton and neutron structure functions and x-evolutions of deuteron structure functions at low-x from AP evolution eqiations. The results of t-evolutions are compared with HERA low-x and low-Q^2 data and those

R. Sekhar Chivukula, Hong-Jian He

The low-energy properties of a compactified five-dimensional gauge theory can be reproduced in a four-dimensional theory with a replicated gauge group and an appropriate gauge symmetry breaking pattern. The lightest vector bosons in these "deconstructed" or "remodeled" theories have masses and couplings approximately equal to those of the Kal

Z. K. Silagadze

It is shown that Feynman's derivation of Maxwell equations admits a generalization to the case of extra spatial dimensions. The generalization is unique and is only possible in seven dimensional space.

G. Fleming, E. Kinney, S. Lammers, S. Magill

We have considered the physics opportunities of future lepton-hadron colliders and how these opportunities might be realized in a possible polarized eRHIC facility and an e-p collider as part of a staged or final version VLHC. We evaluated the physics priorities based on experience at HERA and, using simulated data for e-p collisions with sqrt(s) > 1 TeV, sh

A. K. Ciftci, E. Recepoglu, S. Sultansoy, O. Yavas

Parameters for linac-ring type e^{-}e^{+} colliders with sqrt(s)=1020 MeV (phi factory), 3770 MeV (charm factory) and 4.2 GeV (tau factory) are discussed. It is shown that luminosities of the order of 10^{34} cm^{-2}s^{-1} can be achieved.

Sergio Dain, Gabriel Nagy

We show that there exist asymptotically flat almost-smooth initial data for Einstein-perfect fluid's equation that represent an isolated liquid-type body. By liquid-type body we mean that the fluid energy density has compact support and takes a strictly positive constant value at its boundary. By almost-smooth we mean that all initial data fields are smo

Joseph L. McCauley, Gemunu H. Gunaratne

In a seminal paper in 1973, Black and Scholes argued how expected distributions of stock prices can be used to price options. Their model assumed a directed random motion for the returns and consequently a lognormal distribution of asset prices after a finite time. We point out two problems with their formulation. First, we show that the option valuation is

Carl Lagoze, William Arms, Stoney Gan, Diane Hillmann

We describe the core components of the architecture for the (NSDL) National Science, Mathematics, Engineering, and Technology Education Digital Library. Over time the NSDL will include heterogeneous users, content, and services. To accommodate this, a design for a technical and organization infrastructure has been formulated based on the notion of a spectrum

S. Zvyagin, A. Angerhofer, K. V. Kamenev, L. -C. Brunel

Transmittance of the colossal magnetoresistive compound Nd_0.5Sr_0.5MnO_3 showing metal-insulator phase transition has been studied by means of the submm- and mm-wavelength band spectroscopy. An unusually high transparency of the material provided direct evidence for the significant suppression of the coherent Drude weight in the ferromagnetic metallic state

Sergio O. Valenzuela, Boris Maiorov, Eduardo Osquiguil, Victoria Bekeris

We report on transport and ac susceptibility studies below the peak effect in twinned YBa2Cu3O7 single crystals. We find that disorder generated at the peak effect can be partially inhibited by forcing vortices to move with an ac driving current. The vortex system can be additionally ordered below a well-defined temperature where elastic interactions between

S. Biermann, A. Georges, T. Giamarchi, A. Lichtenstein

We review some properties of quasi-one-dimensional organic conductors, such as the Bechgaard salts, with an emphasis on aspects related to the crossovers between a Mott insulating state to a metallic state, and crossovers between different metallic behaviors. We discuss why a theoretical description of these issues is a particularly challenging problem, and

J. R. Bezerra, R. Silva, J. A. S. Lima

We discuss the basic transport phenomena in gases and plasmas obeying the $q$-nonextensive velocity distribution (power-law). Analytical expressions for the thermal conductivity ($K_q$) and viscosity ($η_q$) are derived by solving the Boltzmann equation in the relaxation-time approximation. The available experimental results to the ratio {$K_q$}/$η_q$ constr

Richard M. Neumann

Using the criterion that the mechanical unzipping transition in a bound homopolymer is triggered when the average force exerted by the single unbound strands on the first base pair in the bound section exceeds the force binding the pair together, the temperature dependence of the critical unzipping force is obtained. In the resulting phase diagram, the criti

G. Blumberg, A. Koitzsch, A. Gozar, B. S. Dennis

Low energy polarized electronic Raman scattering of the electron doped superconductor Nd_1.85Ce_0.15CuO_4 (T_c=22 K) has revealed a nonmonotonic d_{x^2-y^2} superconducting order parameter. It has a maximum gap of 4.4 k_BT_c at Fermi surface intersections with antiferromagnetic Brillouin zone (the ``hot spots'') and a smaller gap of 3.3 k_BT_c at fer

A. A. Ovchinnikov, M. Ya. Ovchinnikova

The mean field study of bands and the Fermi surfaces (FS's) are carried out for 3-band model of ruthenate. In particular, the lowest spiral state with incommensurate vector Q=2π(1/3,1/3) corresponding to nesting of bands display a set of FS's around electro pockets and shadow sheets along $Γ-M$ lines. The latter may provide a new interpretation of th

A. Rodriguez, M. A. Martin-Delgado, J. Rodriguez-Laguna, G. Sierra

The standard one-parameter scaling theory predicts that all eigenstates in two-dimensional random lattices are weakly localized. We show that this claim fails in two-dimensional dipolar Frenkel exciton systems. The linear energy dispersion at the top of the exciton band, originating from the long-range inter-site coupling of dipolar nature, yields the same s

R. Combescot, X. Leyronas

We consider the hydrodynamic modes for dense trapped ultracold gases, where the interparticle distance is comparable to the scattering length. We show that the experimental determination of the hydrodynamic mode frequencies allows to obtain quite directly the equation of state of a dense gas. As an example we investigate the case of two equal fermionic popul

Shigeru Tsukamoto, Kikuji Hirose

We present first-principles calculations on electron transport through Na nanowires at finite bias voltages. The nanowire exhibits a nonlinear current-voltage characteristic and negative differential conductance. The latter is explained by the drastic suppression of the transmission peaks which is attributed to the electron transportability of the negatively

Robert Urbanczik

The article is a lightly edited version of my habilitation thesis at the University Wuerzburg. My aim is to give a self contained, if concise, introduction to the formal methods used when off-line learning in feedforward networks is analyzed by statistical physics. However, due to its origin, the article is not a comprehensive review of the field but is high

K. H. Andersen, M. Abel, J. Krug, C. Ellegaard

Vortex ripples in sand are studied experimentally in a one-dimensional setup with periodic boundary conditions. The nonlinear evolution, far from the onset of instability, is analyzed in the framework of a simple model developed for homogeneous patterns. The interaction function describing the mass transport between neighboring ripples is extracted from expe

A. Sherman, M. Schreiber

Using the description in terms of the Hubbard operators hole and spin Green's functions of the two-dimensional t-J model are calculated in an approximation which retains the rotation symmetry of the spin susceptibility in the paramagnetic state and has no predefined magnetic ordering. In this approximation, Green's functions are represented by contin

H. Kitano, R. Matsuo, K. Miwa, A. Maeda

Microwave study using cavity perturbation technique revealed that the conductivity of antiferromagnet (NH$_3$)K$_{3-x}$Rb$_x$C$_{60}$ at 200K is already 3-4 orders of magnitude smaller than those of superconductors, K$_3$C$_{60}$ and (NH$_3$)$_x$NaRb$_2$C$_{60}$, and that the antiferromagnetic compounds are {\it insulators} below 250K without metal-insulator

D. F. Schroeter, S. Doniach

We propose that the pseudogap state observed in the transition metal oxides can be explained by a three-dimensional flux state, which exhibits spontaneously generated currents in its ground state due to electron-electron correlations. We compare the energy of the flux state to other classes of mean field states, and find that it is stabilized over a wide ran

Wei Bao, G. Aeppli, A. D. Christianson, Z. Fisk

Some recent neutron scattering works on CeRhIn5 and Ce2RhIn8, together with related resistivity and specific heat measurements, are summarized. In spite of its layered crystal structure, CeRhIn5 is shown to be 3-dimensional both magnetically and in transport. We also find that the Fisher-Langer behavior is closely followed in CeRhIn5. This may circumvent the

Carsten Raas, Ute Löw, Götz S. Uhrig, Rainer W. Kühne

We investigate the antiadiabatic limit of an antiferromagnetic S=1/2 Heisenberg chain coupled to Einstein phonons via a bond coupling. The flow equation method is used to decouple the spin and the phonon part of the Hamiltonian. In the effective spin model longer range spin-spin interactions are generated. The effective spin chain is frustrated. The resultin

Sylvain Veilleux

The recent results from a deep Fabry-Perot survey of nearby active and star-forming galaxies are presented. Line-emitting material is detected over two orders of magnitude in galactocentric radius, from the 100-pc scale of the active or starbursting nucleus out to several 10s of kpc, sometimes well beyond the optical confines of the host galaxies. The excita

Nathan Smith, Robert D. Gehrz, Phillip M. Hinz, William F. Hoffmann

We present thermal infrared images of the bipolar nebula surrounding eta Carinae at six wavelengths from 4.8 to 24.5 microns. These were obtained with the MIRAC3 camera system at the Magellan Observatory. Our images reveal new intricate structure in the bright core of the nebula, allowing us to re-evaluate interpretations of morphology seen in images with lo

Peter Klinko, Bruce N. Miller

The role of thermodynamics in the evolution of systems evolving under purely gravitational forces is not completely established. Both the infinite range and singularity in the Newtonian force law preclude the use of standard techniques. However, astronomical observations of globular clusters suggests that they may exist in distinct thermodynamic phases. Here

S. Silich, G. Tenorio-Tagle, C. Munoz-Tunon, L. M. Cairos

The recent history of star formation in the BCD galaxy VII Zw403, is analysed with accounts for the dynamics of the remnant generated either by an instantaneous burst or by a continuous star formation event. We have re-observed VII Zw403 with a better sensitivity corresponding to the threshold H$_α$ flux $8.15 \times 10^{-17}$ erg cm$^{-2}$ s$^{-1}$. The tot

I. Trujillo, A. Asensio Ramos, J. A. Rubino-Martin, Alister W. Graham

We have investigated the structural and dynamical properties of triaxial stellar systems whose surface brightness profiles follow the r^{1/n} luminosity law - extending the analysis of Ciotti (1991) who explored the properties of spherical r^{1/n} systems. A new `analytical' expression that accurately reproduces the spatial (i.e. deprojected) luminosity

Benne W. Holwerda, Ronald J. Allen, Pieter C. van der Kruit

We have automated the ``Synthetic Field Method'' developed by Gonzalez et al.(1998) and used it to measure the opacity of the ISM in the Local Group dwarf galaxy Sextans A by using the changes in counts of background galaxies seen through the foreground system. The Sextans A results are consistent with the observational relation found by Cuillandre e

A. Pastorello, M. Turatto, S. Benetti, E. Cappellaro

We present the photometric and spectroscopic evolution of the type IIn SN 1995G in NGC 1643, on the basis of 4 years of optical and infrared observations. This supernova shows very flat optical light curves similar to SN 1988Z, with a slow decline rate at all times. The spectra are characterized by strong Balmer lines with multiple components in emission and

P. Boumis, F. Mavromatakis, E. V. Paleologou

Deep optical CCD images of the supernova remnant G 17.4-2.3 were obtained and faint emission has been discovered. The images, taken in the emission lines of Halpha+[N II], [S II] and [O III], reveal filamentary structures in the east, south-east area, while diffuse emission in the south and central regions of the remnant is also present. The radio emission i

Adriane Steinacker, John C. B. Papaloizou

We present global 3D MHD simulations of geometrically thin but unstratified accretion disks in which a near Keplerian disk rotates between two bounding regions with initial rotation profiles that are stable to the MRI. The inner region models the boundary layer between the disk and an assumed more slowly rotating central, non magnetic star. We investigate th

Patrick Petitjean, R. Srianand, Cédric Ledoux

We study the dust depletion pattern in eight well separated components of the z=1.973, logN(HI)=20.83, damped Lyman-alpha system toward Q0013-004, four of which have detectable H2 absorption. The apparent correlation between the abundance ratios [Fe/S] and [Si/S] in the components indicates that the abundance pattern is indeed due to dust-depletion. In parti

I. Felix Mirabel

Ultraluminous galaxies in the local universe (z$\leq$0.2) emit the bulk of their energy in the mid and far-infrared. The multiwavelength approach to these objects has shown that they are advanced mergers of gas-rich spiral galaxies. Galaxy-galaxy collisions took place on all cosmological time-scales, and nearby mergers serve as local analogs to gain insight

Coel Hellier

I review the observational evidence for stream-fed accretion in intermediate polars. Recent work on the discless system V2400 Oph confirms the pole-flipping model of stream-fed accretion, but this applies only to a minority of the flow. The bulk of the flow is in the form of blobs circling the white dwarf, a state which might have been a precursor to disc fo

Coel Hellier, Graham Wynn, David Buckley

The long white-dwarf spin periods in the magnetic cataclysmic variables EX Hya and V1025 Cen imply that if the systems possess accretion discs then they cannot be in equilibrium. It has been suggested that instead they are discless accretors in which the spin-up torques resulting from accretion are balanced by the ejection of part of the accretion flow back

Coel Hellier, A. P. Beardmore

RXTE observations confirm that the X-ray lightcurve of V2400 Oph is pulsed at the beat cycle, as expected in a discless intermediate polar. There are no X-ray modulations at the orbital or spin cycles, but optical line profiles vary with all three cycles. We construct a model for line-profile variations in a discless accretor, based on the idea that the accr

Luciana Pompeia, Beatriz Barbuy, Michel Grenon, Bruno Castilho

Li abundances are derived for a sample of bulgelike stars with isochronal ages of 10-11 Gyr. These stars have orbits with pericentric distances, Rp, as small as 2-3 kpc and Zmax < 1 kpc. The sample comprises G and K dwarf stars in the metallicity range -0.80<[Fe/H]< +0.40. Few data of Li abundances in old turn-off stars (> 4.5 Gyr) within the present metalli

A. Boselli, G. Gavazzi, J. Lequeux, D. Pierini

We present a calibration of the massive star formation rate vs. [CII] luminosity relation based on a sample of nearby, late-type galaxies observed with ISO-LWS and imaged in the Halpha+[NII] line. The relation holds for far-IR luminosities 10^8 < L_{FIR} < 10^{10.5} L (solar units). The derived star formation rates have an uncertainty of about a factor of 10

Daniel Huber, Daniel Pfenniger

Observed self-gravitating systems reveal often fragmented non-equilibrium structures that feature characteristic long-range correlations. However, models accounting for non-linear structure growth are not always consistent with observations and a better understanding of self-gravitating $N$-body systems appears necessary. Because unstable gravitating systems