July 1999 arXiv papers — page 19

Jens Hoppe, Vladimir Kazakov, Ivan K. Kostov

We study the quantum mechanical model obtained as a dimensional reduction of N=1 super Yang-Mills theory to a periodic light-cone "time". After mapping the theory to a cohomological field theory, the partition function (with periodic boundary conditions) regularized by a massive term appears to be equal to the partition function of the twisted matrix

Fuqiang Wang

We investigate the residual effect of lambda-proton strong interactions in pp correlations with one proton from lambda decays. It is found that the residual correlation is about 10% of the lambda-proton correlation strength, and has a broad distribution centered around q~40 MeV/c. The residual correlation cannot explain the observed structure on the tail of

Uwe Mueller, Gerhard Weigt

Gauged WZNW models are integrable conformal field theories. We integrate the classical \slu{} theory with periodic boundary conditions, which describes closed strings moving in a curved target-space geometry. We calculate its Poisson bracket structure by solving an initial state problem. The results differ from previous field-theoretic calculations due to ze

K. K. S. Wu, A. C. Fabian, P. E. J. Nulsen

The strong deviation in the properties of X-ray clusters from simple scaling laws highlights the importance of non-gravitational heating and cooling processes in the evolution of proto-cluster gas. We investigate this from two directions: by finding the amount of `excess energy' required in intra-cluster gas in order to reproduce the observed X-ray clust

Adam Doliwa, Paolo Maria Santini

We present a detailed study of the geometric and algebraic properties of the multidimensional quadrilateral lattice (a lattice whose elementary quadrilaterals are planar; the discrete analogue of a conjugate net) and of its basic reductions. To make this study, we introduce the notions of forward and backward data, which allow us to give a geometric meaning

M. Faber, A. N. Ivanov, N. I. Troitskaya, M. Zach

We discuss the derivation of the path integral representation over gauge degrees of freedom for Wilson loops in SU(N) gauge theory and 4-dimensional Euclidean space-time by using well-known properties of group characters. A discretized form of the path integral is naturally provided by the properties of group characters and does not need any artificial regul

Denis Dalidovich, Philip Phillips

We analyze here the fluctuation conductivity in the vicinity of the critical point in a 2D Josephson junction array shunted by an Ohmic resistor.We find that at the Gaussian level, the conductivity acquires a logarithmic dependence on $T/(T-T_c)$ when the dissipation is sufficiently small. In the renormalized classical regime, this logarithmic dependence giv

D. E. Feldman

The large distance behaviors of the random field and random anisotropy O(N) models are studied with the functional renormalization group in 4-εdimensions. The random anisotropy Heisenberg (N=3) model is found to have a phase with the infinite correlation radius at low temperatures and weak disorder. The correlation function of the magnetization obeys a power

S. Nagataki

We study the effects of jet-like explosion in SN 1987A. Calculations of the explosive nucleosynthesis and the matter mixing in a jet-like explosion are performed and their results are compared with the observations of SN 1987A. It is shown that the jet-like explosion model is favored because the radioactive nuclei 44Ti is produced in a sufficient amount to e

S. Nagataki, G. Watanabe

We present a new input parameter set of the Pagel model (Pagel & Tautvai$\rm \breve{s}$ien$\rm \dot{e}$ 1998) for the Large Magellanic Cloud (LMC) in order to reproduce the observations, including the star formation rate (SFR) history. It is concluded that the probability for (3-8)$M_{\odot}$ stars to explode as SNe Ia has to be quite high ($\sim 0.17$) in t

Sayandeb Basu, Somshubhro Bandyopadhyay, Guruprasad Kar, Dipankar Home

We argue that for a \emph{single particle} Bell's inequality is a consequence of noncontextuality and is \emph{incompatible} with statistical predictions of quantum mechanics. Thus noncontextual models can be empirically falsified, \emph{independent} of locality condition. For this an appropriate entanglement between \emph{disjoint} Hilbert spaces pertai

M. M. Sheikh-Jabbari, A. Shirzad

In this article we show that boundary conditions can be treated as Lagrangian and Hamiltonian constraints. Using the Dirac method, we find that boundary conditions are equivalent to an infinite chain of second class constraints which is a new feature in the context of constrained systems. Constructing the Dirac brackets and the reduced phase space structure

F. Naef, Xiaoqun Wang

Using the transfer-matrix DMRG method, we study the nuclear spin relaxation rate 1/T_1 in the two-leg s=1/2 ladder as function of the inter-chain (J_{\perp}) and intra-chain (J_{|}) couplings. In particular, we separate the q_y=0 and πcontributions and show that the later contribute significantly to the copper relaxation rate ^{63}(1/T_1) in the experimental

H. Yamamura, K. Miyagawa, T. Mart, C. Bennhold

Inclusive $K^+$ and exclusive $K^+Y$ photoproduction on the deuteron are investigated theoretically. Modern hyperon-nucleon forces and a recently updated kaon photoproduction operator for the $γ+N\to K^++Y$ process are used. Sizable effects of the hyperon-nucleon final state interaction are found near the $K^+ΛN$ and $K^+ΣN$ thresholds in the inclusive react

Koji Fukao, Yoshihisa Miyamoto

The glass transition temperature $T_{\rm g}$ and the temperature $T_α$ corresponding to the peak in the dielectric loss due to the $α$-process have been simultaneously determined as functions of film thickness d through dielectric measurements for polystyrene thin films supported on glass substrate. The dielectric loss peaks have also been investigated as fu

Paul H. Frampton

If the standard model is embedded in a conformal theory, what is the simplest possibility? We analyse all abelian orbifolds for discrete symmetry $Z_p$ with $p \leq 7$, and find that the simplest such theory is indeed $SU(3)^7$. Such a theory predicts the correct electroweak unification (sin$^2 \theta \simeq 0.231$). A color coupling $\alpha_C(M) \simeq 0.07

Yasushi Suto, Kazuhiro Yamamoto, Tetsu Kitayama, Y. P. Jing

We have developed a model to describe two-point correlation functions of clusters of galaxies in X-ray flux-limited surveys. Our model properly takes account of nonlinear gravitational evolution of mass fluctuations, redshift-space distortion due to linear peculiar velocity field and to finger-of-god, cluster abundance and bias evolution on the basis of the

J. Balog, L. Feher, L. Palla

The precise relationship between the arbitrary monodromy dependent 2-form appearing in the chiral WZNW symplectic form and the `exchange r-matrix' that governs the corresponding Poisson brackets is established. Generalizing earlier results related to diagonal monodromy, the exchange r-matrices are shown to satisfy a new dynamical generalization of the cl

H. Kleinert, B. Van den Bossche

We argue that the spontaneous breakdown of symmetry in the chirally symmetric Nambu--Jona-Lasinio model which was supposed to illustrate the origin of the low mass of pions in hadron physics does not occur due to strong fluctuations in the sigma - pi field space. Although quarks acquire a constituent mass, sigma and pi turn out to have equal heavy masses of

Dongsu Bak, Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh

We study quantum mechanically the self-similar black hole formation by collapsing scalar field and find the wave functions that give the correct semiclassical limit. In contrast to classical theory, the wave functions for the black hole formation even in the supercritical case have not only incoming flux but also outgoing flux. From this result we compute th

Dongsu Bak, Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh

We propose a method to recover the time variable and the classical evolution of the Universe from the minisuperspace wave function of the Wheeler-DeWitt equation. Defining a Hamilton-Jacobi characteristic function $W$ as the imaginary part of the $\ln Ψ$ we can recover the classical solution, and quantum corrections. The key idea is to let the energy of the

Adam Doliwa, Paolo Maria Santini

We review recent results on Integrable Discrete Geometry. It turns out that most of the known (continuous and/or discrete) integrable systems are particular symmetries of the quadrilateral lattice, a multidimensional lattice characterized by the planarity of its elementary quadrilaterals. Therefore the linear property of planarity seems to be a basic geometr

Adam Doliwa

Geometric interpretation of the Hirota equation is presented as equation describing the Laplace sequence of two-dimensional quadrilateral lattices. Different forms of the equation are given together with their geometric interpretation: (i) the discrete coupled Volterra system for the coefficients of the Laplace equation, (ii) the gauge invariant form of the

Dmitry E. Pelinovsky, Catherine Sulem

A new (scalar) spectral decomposition is found for the Dirac system in two dimensions associated to the focusing Davey--Stewartson II (DSII) equation. Discrete spectrum in the spectral problem corresponds to eigenvalues embedded into a two-dimensional essential spectrum. We show that these embedded eigenvalues are structurally unstable under small variations

Jon Links

A new construction is given for obtaining R-matrices which solve the McGuire-Yang-Baxter equation in such a way that the spectral parameters do not possess the difference property. A discussion of the derivation of the supersymmetric U model is given in this context such that applied chemical potential and magnetic field terms can be coupled arbitrarily. As

Somshubhro Bandyopadhyay, Dipankar Home

We compute the time evolving probability of a Gaussian wave packet to be reflected from a rectangular potential barrier which is perturbed by reducing its height. A time interval is found during which this probability of reflection is enhanced (superarrivals) compared to the unperturbed case. Such a time evolving reflection probability implies that the effec

G. M. Tino

Recent experimental tests of the symmetrization postulate of quantum mechanics are discussed. It is shown that in a strict sense these experiments cannot test the validity of the symmetrization postulate, but in most cases do test the spin-statistics connection. An experiment is proposed that would allow to search for possible violations of the symmetrizatio

T. C. Choy, Debra Ziegeler

Recent discussions by Mermin [1] and Stapp [2] in this journal on non-locality and counterfactuality are shown to contain linguistic problems that require verification. As such they can at most provide us with two subjective choices for the meaning of 'counterfactual statements' in quantum mechanics. We shall show that the word 'counterfactual&#3

J. Audretsch, Th. Konrad, M. Mensky

Continuous weak or fuzzy measurement of the Rabi oscillation of a two level atom subjected to a $π-$pulse of a resonant light field is simulated numerically. We thereby address the question whether it is possible to measure characteristic features of the motion of the state of a single quantum system in real time. We compare two schemes of continuous measure

Gao Shan

We deeply analyze the possibility to achieve quantum superluminal communication beyond the domain of special relativity and present quantum theory, and show that when using the conscious object as one part of the measuring device, quantum superluminal communication may be a natural thing.

Gao Shan

We show that the quantum superluminal communication based on the quantum nonlocal influence, if exists, will not result in the causal loop, this conclusion is essentially determined by the peculiarity of the quantum nonlocal influence itself, according to which there must exist a preferred Lorentz frame for consistently describing the quantum nonlocal proces

Fumiaki Morikoshi

Recently a new entanglemenet dilution scheme has been constructed by Lo and Popescu. This paper points out that this result has a deep implication that the entanglement measure for bipartite pure states is independent of the distance between entangled two systems.

Tom Ostoma, Mike Trushyk

A new paradigm for the unification of physics is described. It is called Cellular Automata (CA) theory, which is the most massively parallel computer model currently known to science. We maintain that at the tiniest distance and time scales the universe is completely deterministic, and utterly simple. Our universe is a Cellular Automaton consisting of a huge

J. T. Gleeson, N. Gheorghiu, E. Plaut

We develop a characterization method of electroconvection structures in a planar nematic liquid crystal layer by a study of the electric current transport. Because the applied potential difference has a sinusoidal time dependence, we define two electric Nusselt numbers corresponding to the in-phase and out-of-phase components of the current. These Nusselt nu

B. R. Schlei

In 1996, D.H. Rischke and M. Gyulassy proposed to use the time-delay signal in Bose-Einstein correlations (BEC) as a signature for the possible formation of a quark-gluon plasma (QGP) in relativistic heavy-ion collisions. In particular, they suggested to measure the ratio of the transversal interferometry radii, $R_{out}/R_{side}$, which can be obtained by f

Jorgen Randrup

In order to elucidate the enhancement of pion production that may occur during dynamical scenarios of interest in connection with disoriented chiral condensates, we study the evolution of boson modes whose frequencies have a given arbitrary time dependence. The quantum-field treatment yields expressions for the time dependence of observables that depend only

V. Abrosimov, A. Dellafiore, F. Matera

Two different solutions of the linearized Vlasov equation for finite systems, characterized by fixed and moving-surface boundary conditions, are discussed in a unified perspective. A condition determining the eigenfrequencies of collective nuclear oscillations, that can be obtained from the moving-surface solution, is studied for isoscalar vibrations of lowe

R. Hofmann, Amand Faessler, Th. Gutsche

Quantum Hadrodynamics in mean field approximation describes the effective nucleon-nucleus potential (about -50 MeV deep) as resulting from a strong repulsive vector (about 400 MeV) and a strong attractive scalar (about -450 MeV) contribution. This scalar-vector Lorentz structure implies a significant lowering of the threshold for $p\bar{p}$ photoproduction o

Rami Atar, Paul Dupuis

This paper considers a formulation of a differential game with constrained dynamics, where one player selects the dynamics and the other selects the applicable cost. When the game is considered on a finite time horizon, its value satisfies an HJB equation with oblique Neumann boundary conditions. The first main result is uniqueness for viscosity solutions to

Zuzana Masáková, Jiří Patera, Edita Pelantová

The relation of s-convexity and sets modeling physical quasicrystals is explained for quasicrystals related to quadratic unitary Pisot numbers. We show that 1-dimensional model sets may be characterized by s-convexity for finite set of parameters s. It is shown that the three Pisot numbers $\frac12(1+\sqrt5)$, $1+\sqrt2$, and $2+\sqrt3$ related to experiment

Spyridon Kamvissis

In this paper, we take the first step towards an extension of the nonlinear steepest descent method of Deift, Its and Zhou to the case of operator Riemann-Hilbert problems. In particular, we provide long range asymptotics for a Fredholm determinant arising in the computation of the probability of finding a string of n adjacent parallel spins up in the antife

Carol E. Fan

A version of a conjecture of McMullen is as follows: Given a hyperbolizable 3-manifold M with incompressible boundary, there exists a uniform constant K such that if N is a hyperbolic 3-manifold homeomorphic to the interior of M, then the injectivity radius based at points in the convex core of N is bounded above by K. This conjecture suggests that convex co

Francois Labourie

We describe the "hyperbolic" properties of a riemann surface lamination M canonically associated to every compact three manifolds of curvature less than 1. More precisely, if the geodesic flow is the phase space attached to an ordinary differential equation, our space M is the "phase space" attached to a certain elliptic equation, which geome

Dmitry Jakobson, Igor Rivin

In this paper we are concerned with various graph invariants (girth, diameter, expansion constants, eigenvalues of the Laplacian, tree number) and their analogs for weighted graphs -- weighing the graph changes a combinatorial problem to one in analysis. We study both weighted and unweighted graphs which are extremal for these invariants. In the unweighted c

Antoine Chambert-Loir

We extend to the case of semi-abelian varieties the statements of various variants of the conjecture alla Bogomolov about the non-density of small points of small height in abelian varieties. Inspired by recent work of Ullmo, Zhang and Bilu, we then prove these conjectures when the semi-abelian variety is almost split. The proof uses Arakelov geometry and eq

F. Bonechi, N. Ciccoli, R. Giachetti, E. Sorace

We study the coisotropic subgroup structure of standard SL_q(2,R) and the corresponding embeddable quantum homogeneous spaces. While the subgroups S^1 and R_+ survive undeformed in the quantization as coalgebras, we show that R is deformed to a family of quantum coisotropic subgroups whose coalgebra can not be extended to an Hopf algebra. We explicitly descr

David A. Lowe

Recently Bousso conjectured the entropy crossing a certain light-like hypersurface is bounded by the surface area. We point out a number of difficulties with this conjecture.

Ivan K. Kostov

In these notes we explain how the CFT description of random matrix models can be used to perform actual calculations. Our basic example is the hermitian matrix model, reformulated as a conformal invariant theory of free fermions. We give an explicit operator construction of the corresponding collective field theory in terms of a bosonic field on a hyperellip

M. Trunk

A reparametrization invariant model, introduced by Montesinos, Rovelli and Thiemann, possessing an SL(2,R) gauge symmetry is treated along the guidelines of an algebraic constraint quantization scheme that translates the vanishing of the constraints into representation conditions for the algebra of observables. The application of this algebraic scheme to the

Carlo Angelantonj

We review the construction of non-supersymmetric open string vacua in various dimensions. They can be obtained either projecting the (compactified) non-supersymmetric 0B theory, or applying the Scherk-Schwarz mechanism to open strings. Generically, these vacua generate a non-vanishing cosmological constant. However, one can construct particular kinds of Sche

B. Spence

We propose that the effective field theories of certain wrapped D-branes are given by topological actions based on Born-Infeld theory. In particular, we present a Born-Infeld version of the Abelian Donaldson-Witten theory. We then consider wrapping D3 branes on calibrated submanifolds and for the Calabi-Yau four-fold case, discuss how the resulting theory co

Marco Cavaglia, Vittorio de Alfaro

Two-dimensional matterless dilaton gravity is a topological theory and can be classically reduced to a (0+1)-dimensional theory with a finite number of degrees of freedom. If quantization is performed, a simple gauge invariant quantum mechanics is obtained. The properties of the gauge invariant operators and of the Hilbert space of physical states can be det

Kazuyuki Fujii, Tatsuo Suzuki

A universal disentangling formula (such as the Baker-Campbell-Hausdorff one) for coherent states of Perelomov's type ($ |z \ra = \exp (z\Adag -\bar{z}A) |0 \ra $) which are defined for generalized oscillator algebras is given.

Y. M. Cho, Haewon Lee, D. G. Pak

We derive a generalized Skyrme-Faddeev action as the effective action of QCD in the low energy limit. Our result demonstrates the existence of a mass gap in QCD which triggers the confinement of color.

S. K. Lamoreaux, R. Golub

A new limit for the neutron electric dipole moment has been recently reported. This new limit is obtained by combining the result from a previous experiment with the result from a more recent experiment that has much worse statistical accuracy. We show that the old result has a systematic error possibly four times greater than the new limit, and under the ci

M. Wobisch, T. Wengler

The size of non-perturbative corrections to high E_T jet production in deep-inelastic scattering is reviewed. Based on predictions from fragmentation models, hadronization corrections for different jet definitions are compared and the model dependence as well as the dependence on model parameters is investigated. To test whether these hadronization correctio

D. A. Demir

In the minimal supersymmetric standard model with explicit CP violation, associated production of the lightest Higgs boson with heavier ones is analyzed. Due to explicit CP violation, the Higgs bosons are no longer CP eigenstates so that both of the heavy Higgs bosons contribute to the process. While the radiative corrections in the Higgs sector turn out to

Benjamin Svetitsky

I review some of the history of the flux-tube model, concentrating on work done by the Los Alamos-Tel Aviv collaboration on particle creation and back-reaction in uniform fields and in the central rapidity region. I discuss the incorporation of more realistic geometry and structure of the flux tube via application of the dual superconductor model of confinem

A. Foland

I derive the expressions for the CP-violating asymmetry arising from interference between mixed and direct decays in the Upsilon(4S) system, for the case in which only one of the B decay times is observed, integrating over the decay time of the other B. I observe that neither the difference of the decay times Delta t, nor even their time-ordering, need be de

Nadia Fettes, Véronique Bernard, Ulf-G. Meißner

Single pion production off nucleons is studied in the framework of heavy baryon chiral perturbation theory to third order in the chiral expansion. Using total and some older differential cross section data to pin down the low-energy constants, most of the recent differential cross sections and angular correlation functions can be described as well as total c

Biswarup Mukhopadhyaya

Motivated by the recent SuperKamiokande results on atmospheric neutrinos, we incorporate massive neutrinos, with large angle oscillation between the second and third generations, in a theory with R-parity violating supersymmetry. The general features of such a theory are briefly reviewed. We emphasize its testability through the observation of comparable num

Hsiang-nan Li

We demonstrate that both the $k_T$ and threshold resummations can be performed in the Collins-Soper resummation formalism by evaluating soft gluon emissions with infrared cutoffs for the longitudinal and transverse loop momenta, respectively. The reason the $k_T$ resummation for a parton distribution function leads to suppression in the large $b$ region, $b$

D0 Collaboration

We present a measurement of the differential cross section as a function of transverse momentum of the Z boson in ppbar collisions at sqrt{s}=1.8 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider during 1994--1996. We find good agreement between our data and the NNLO resummation prediction and extract values of the non-perturbat

Yu. A. Baurov, Yu. G. Sobolev, V. F. Kushniruk, A. N. Kuznetzov

The experimental data on continuous investigation of changes in beta-decay count rate of Cs-137 and Co-60 from 9.12.98 till 30.04.99, are presented. The 27-day and 24-hour periods in these changes, inexplicable by traditional physics, have been found.

K. Murakami, Y. Hemmi, H. Kurashige, Y. Matono

We report on results of a search for the decay mode K_L -> pi^0 gamma e^+ e^- conducted by the E162 experiment at KEK. We observed no events and set a 90% confidence level upper limit of Br(K_L -> pi^0 gamma e^+ e^-)< 7.1x10^{-7} for its branching ratio. This is the first published experimental result on this decay mode.

William Krivan

Motivated by results of recent analytic studies, we present a numerical investigation of the late-time dynamics of scalar test fields on Kerr backgrounds. We pay particular attention to the issue of mixing of different multipoles and their fall-off behavior at late times. Confining ourselves to the special case of axisymmetric modes with equatorial symmetry,

Maja Buric, Voja Radovanovic

We calculate the quantum corrections of geometric and thermodynamic quantities for the Reisner-Nordstrom charged black hole, within the context of 2D spherically symmetric dilaton gravity model. Special attention is payed to the quantum corrections of the extreme Reisner-Nordstrom solution. We find a state of the extreme black hole with regular behaviour on

Ke-Jian Jin, Yuan-Zhong Zhang, Zong-Hong Zhu

We investigate a two-component model for gravitational lenses, i.e., the fermion-fermion star as a dark matter self-gravitating system made from two kinds of fermions with different masses. We calculate the deflection angles varying from arcseconds to even degrees. There is one Einstein ring. In particular, we find three radial critical curves for radial mag

J. -M. Gerard, S. Pireaux

The physical deflection angle of a light ray propagating in a space-time supplied with an asymptotically flat metric has to be expressed in terms of the impact parameter.

A. A. Logunov, M. A. Mestvirishvili

In this paper a solution for a static spherically symmetric body is thoroughly considered in the framework of the Relativistic Theory of Gravitation. By the comparison of this solution with the Schwarzschild solution in General Relativity their substantial difference is established in the region close to the Schwarzschild sphere. Just this difference exclude

Massimo Pauri, Michele Vallisneri

Although the Unruh and Hawking phenomena are commonly linked to field quantization in &#34;accelerated&#34; coordinates or in curved spacetimes, we argue that they are deeply rooted at the classical level. We maintain in particular that these effects should be best understood by considering how the special-relativistic notion of &#34;particle&#34; gets blurr

Anand Venkataraman, Ray Kemp

In this short article, we look at an old logical puzzle, its solution and proof and discuss some interesting aspects concerning its representation in a logic programming language like Prolog. We also discuss an intriguing information theoretic aspect of the puzzle.

John Carroll, Guido Minnen, Ted Briscoe

We describe a recently developed corpus annotation scheme for evaluating parsers that avoids shortcomings of current methods. The scheme encodes grammatical relations between heads and dependents, and has been used to mark up a new public-domain corpus of naturally occurring English text. We show how the corpus can be used to evaluate the accuracy of a robus

Guido Minnen

We propose a parser for constraint-logic grammars implementing HPSG that combines the advantages of dynamic bottom-up and advanced top-down control. The parser allows the user to apply magic compilation to specific constraints in a grammar which as a result can be processed dynamically in a bottom-up and goal-directed fashion. State of the art top-down proce

Daniel Loss, Guido Burkard, Eugene V. Sukhorukov

If the states of spins in solids can be created, manipulated, and measured at the single-quantum level, an entirely new form of information processing, quantum computing and quantum communication, will be possible. We review our proposed spin-quantum dot architecture for a quantum computer and review some recent results on a deterministic source of entanglem

Philip B. Allen, Joseph L. Feldman, Jaroslav Fabian, Frederick Wooten

Numerical studies of amorphous silicon show that the lowest 4% of vibrational modes are plane-wave like (&#34;propagons&#34;) and the highest 3% of modes are localized (&#34;locons&#34;). The rest are neither plane-wave like nor localized. We call them &#34;diffusons.&#34; Since diffusons are by far the most numerous, we try to characterize them by calculati

M. Pustilnik, Y. Avishai, K. Kikoin

We study an influence of a finite magnetic field on a small spin-degenerate quantum dot with even number of electrons, attached to metallic leads. It is shown that, under certain conditions, the low energy physics of the system can be described by the S=1/2 antiferromagnetic Kondo model.

A. B. Dzyubenko, A. Yu. Sivachenko, H. A. Nickel, T. M. Yeo

Internal spin-singlet and spin-triplet transitions of charged excitons X- in magnetic fields in quantum wells have been studied experimentally and theoretically. The allowed X- transitions are photoionizing and exhibit a characteristic double-peak structure, which reflects the rich structure of the magnetoexciton continua in higher Landau levels (LL&#39;s).

Woonki Chung, J. K. Freericks

The exact solution of the spin-1/2 Falicov-Kimball model on an infinite-coordination Bethe lattice is analyzed in the regime of ``classical&#39;&#39; intermediate valence. We find (i) either phase separation or a direct metal-insulator transition preclude intermediate valence over a large portion of the phase diagram and (ii) within the intermediate valence

Benito Groh, Bela Mulder

The freezing transition of hard spheres has been well described by various versions of density-functional theory (DFT). These theories should possess the close-packed crystal as a special limit, which represents an extreme testing ground for the quality of such liquid-state based theories. We therefore study the predictions of DFT for the structure and therm

A. M. S. Macedo

We present an exact solution of a supersymmetric nonlinear sigma model describing the crossover between a quantum dot and a disordered quantum wire with unitary symmetry. The system is coupled ideally to two electron reservoirs via perfectly conducting leads sustaining an arbitrary number of propagating channels. We obtain closed expressions for the first th

Peter Olsson, Petter Holme

The three dimensional uniformly frustrated XY model is used as a model of a high temperature superconductor in an applied magnetic field parallel to the CuO-planes. Through Monte Carlo simulations with anisotropy $η^2 = 10$ on large lattices we find evidence for a first order transition. Earlier simulations and theoretical treatments are discussed and the ex

Kazuo Hida

The low energy behavior of the $S=1/2$ antiferromagnetic Heisenberg chains with precious mean quasiperiodic exchange modulation is studied by the density matrix renormalization group method. Based on the scaling behavior of the energy gap distribution, it is found that the ground state of this model belongs to the universality class different from that of th

B. I. Belevtsev, V. B. Krasovitsky, D. G. Naugle, K. D. D. Rathnayaka

A sharp distinction between magnetoresistance (MR) behavior for the magnetic fields applied perpendicular (H_{perp}) and parallel (H_{par}) to the film plane is found in colossal-magnetoresistance film La_{1-x}Ca_{x}MnO_{3} (x \approx 3). At increasing of H_{perp} the MR is first negative (at H_{perp} < 4 kOe), then positive (4 kOe < H_{perp} < 12 kOe), and

John Cardy, Peter Suranyi

We investigate a lattice scalar field theory in the presence of a bias favouring the establishment of an energy current, as a model for stationary nonequilibrium processes at low temperature in a non-integrable system. There is a transition at a finite value of the bias to a gapless modulated phase which carries a classical current; however, unlike in simila

S. S. Banerjee et al

The magnetic field dependence of the critical current is studied in single crystal samples of the weak pinning type-II superconductor 2H-NbSe$_2$ in the high temperature and the low field region of the (H,T) phase space, in the vicinity of the reentrant peak effect. The experimental results demonstrate various pinning regimes : a collective pinned quasi-orde

Evgenii E. Narimanov, Gregor Hackenbroich, Philippe Jacquod, A. Douglas Stone

We develop a perturbation theory for the lifetime and emission intensity for isolated resonances in asymmetric resonant cavities. The inverse lifetime $Γ$ and the emission intensity $I(θ)$ in the open system are expressed in terms of matrix elements of operators evaluated with eigenmodes of the closed resonator. These matrix elements are calculated in a semi

V. Martisovits, G. Zaránd, D. L. Cox

We construct a two component Ginzburg-Landau theory with coherent pair motion and incoherent quasiparticles for the phase diagram of $U_{1-x}Th_xBe_{13}$. The two staggered superconducting states live at the Brillouin zone center and the zone boundary, and coexist for temperatures $T\le T_{c2}$ at concentrations $x_{c1}\approx 0.02\le x \le x_{c2}\approx 0.0

B. M. Gaensler, B. W. Stappers, T. J. Getts

We report on the detection of radio emission from the accretion-powered X-ray millisecond pulsar SAX J1808.4-3658, using the Australia Telescope Compact Array. We detected a ~0.8 mJy source at the position of SAX J1808.4-3658 on 1998 April 27, approximately one day after the onset of a rapid decline in the X-ray flux; no such source was seen on the previous

Eric Woods, Abraham Loeb

We investigate the hydrodynamic evolution of Gamma--Ray Burst (GRB) remnants at late times (>> 1 year), by extending the standard fireball model into the nonrelativistic Sedov--Taylor regime. We calculate the associated synchrotron luminosity as a function of remnant age. The radio luminosity of old remnants depends strongly on the power-law index p= (dlogN/

Hugo van Woerden, Ulrich J. Schwarz, Reynier F. Peletier, Bart P. Wakker

The high-velocity clouds of atomic hydrogen, discovered about 35 years ago, have velocities inconsistent with simple Galactic rotation models that generally fit the stars and gas in the Milky Way disk. Their origins and role in Galactic evolution remain poorly understood, largely for lack of information on their distances. The high-velocity clouds might resu

V. Hill, L. Pasquini

We present the analysis of FEROS commissioning spectra of 3 giants in the metal poor cluster Be 21. One of the giants has an exceptionally high Li content, comparable to the original Li in the solar system. These objects are very rare (only a handful are known), and this is the first Super Lithium Rich giant (SLIR) discovered in an open cluster. The reasons

Patrick Cote, J. B. Oke, Judith G. Cohen

We have obtained spectra for 50 candidate red giants in Andromeda II (a dwarf spheroidal companion of M31) using LRIS on the Keck II telescope. After eliminating background galaxies and Galactic foreground stars, we are left with a sample of 42 red giants for which membership in Andromeda II can be established unambiguously from radial velocities. Line indic

Andrew J. S. Hamilton, Robert A. Fesen

Ultraviolet imaging of the remnant of Supernova 1885 in M31 with the Hubble Space Telescope using the F255W filter on the WFPC2 reveals a dark spot of Fe II absorption at the remnant&#39;s known position in the bulge of M31. The diameter of the absorbing spot is 0&#34;55 +- 0&#34;15, slightly smaller than, but consistent with, the 0&#34;70 +- 0&#34;05 diamet

Ashok Das, Otto C. W. Kong

In the framework of a Kaluza-Klein type theory with the Standard Model fields localized on a 4-dimensional section while gravity propagates in a full $4+δ$-dimensional space-time, we examine a mechanism of naturally small neutrino mass generation through couplings of Standard Model singlet fermion(s) living also in the full space-time. A numerical studies is

S. G. Lemay, R. E. Thorne, Y. Li, J. D. Brock

We have observed an unusual form of creep at low temperatures in the charge-density-wave (CDW) conductor NbSe$_3$. This creep develops when CDW motion becomes limited by thermally-activated phase advance past individual impurities, demonstrating the importance of local pinning and related short-length-scale dynamics. Unlike in vortex lattices, elastic collec

G. F. Lewis, A. Babul, N. Katz, T. Quinn

We present the analysis of a suite of simulations of a Virgo mass galaxy cluster. Undertaken within the framework of standard cold dark matter cosmology, these simulations were performed at differing resolutions and with increasingly complex physical processes, with the goal of identifying the effects of each on the evolution of the cluster. We focus on the

Pawan Kumar

We estimate the fraction of the total energy in a Gamma-Ray Burst (GRB) that is radiated in photons during the main burst. Random internal collisions among different shells limit the efficiency for converting bulk kinetic energy to photons. About 1% of the energy of explosion is converted to radiation, in 10-1000 kev energy band in the observer frame, for lo

Pierluigi Monaco, Paolo Salucci, Luigi Danese

Older and more recent pieces of observational evidence suggest a strong connection between QSOs and galaxies; in particular, the recently discovered correlation between black hole and galactic bulge masses suggests that QSO activity is directly connected to the formation of galactic bulges. The cosmological problem of QSO formation is analyzed in the framewo

R. B. Barreiro

We review the current status of the cosmic microwave background (CMB) radiation, including a brief discussion of some basic theoretical aspects as well as a summary of anisotropy detections and CMB experiments. We focus on the description of some relevant characteristics of the microwave foregrounds, on the discussion of the different estimators proposed in