December 1998 arXiv papers — page 15

Joseph Krasil'shchik, Michal Marvan

Using covering theory approach (zero-curvature representations with the gauge group SL2), we insert the spectral parameter into the Gauss-Mainardi-Codazzi equations in Tchebycheff and geodesic coordinates. For each choice, four integrable systems are obtained.

F. Simmel, R. H. Blick, J. P. Kotthaus, W. Wegscheider

We present measurements on the Kondo-effect in a small quantum dot connected strongly to one lead and weakly to the other. The conductance of the dot reveals an offset of the Kondo resonance at zero magnetic field. While the resonance persists in the negative bias regime, it is suppressed in the opposite direction. This demonstrates the pinning of the Kondo

Debashish Chowdhury, Ludger Santen, Andreas Schadschneider, Shishir Sinha

The spatio-temporal organizations of vehicular traffic in cellular-automata models with "slow-to-start" rules are qualitatively different from those in the Nagel-Schreckenberg (NaSch) model of highway traffic. Here we study the effects of such a slow-to-start rule, introduced by Benjamin, Johnson and Hui (BJH), on the the distributions of the distanc

EROS Collaboration

We present the analysis of the first two years of a search for microlensing of stars in the Small Magellanic Cloud with the EROS (Expérience de Recherche d'Objets Sombres) project. A single event is detected, already present in the first year analysis. This low event rate allows us to put new constraints on the fraction of the Galactic Halo mass due to c

P. Jönsson, T. Jonsson, J. L. García-Palacios, P. Svedlindh

The linear and cubic dynamic susceptibilities of solid dispersions of nano-sized maghemite particles have been measured for three samples with a volume concentration of magnetic particles ranging from 0.3 % to 17 %, in order to study the effect of dipole-dipole interactions. Significant differences between the dynamic response of the three samples are observ

Dipanjan Mitra, Sushan Konar, Dipankar Bhattacharya

The evolution of the multipolar structure of the magnetic field of isolated neutron stars is studied assuming the currents to be confined to the crust. We find that except for multipoles of very high order ($l\gsim 25$) the evolution is similar to that of a dipole. Therefore no significant evolution is expected in pulse shape of isolated radio pulsars due to

Kirill N. Alekseev, Jan Perina

We develop a method for the determination of thecdynamics of dissipative quantum systems in the limit of large number of quanta N, based on the 1/N-expansion of Heidmann et al. [ Opt. Commun. 54, 189 (1985) ] and the quantum-classical correspondence. Using this method, we find analytically the dynamics of nonclassical states generation in the higher-order an

Indrani Bose, Saurabh Gayen

A two chain ladder model is considered described by the strong coupling $t-t^\prime-J-J^\prime$ Hamiltonian. For the case of two holes moving in a background of antiferromagnetically interacting spins, exact, analytical results are derived for the ground state energy and low-lying excitation spectrum. The ground state is a bound state of two holes with total

M. Kashiwara, T. Tanisaki

In this paper we prove the Kazhdan-Lusztig type character formula for irreducible highest weight modules with positive rational highest weights over symmetrizable Kac-Moody Lie algebras.

Xin-Nian Wang

High-$p_T$ particle spectra in $p+p$ ($\bar p + p$), $p+A$ and $A+B$ collisions are calculated within a QCD parton model in which intrinsic transverse momentum, its broadening due to initial multiple parton scattering, and jet quenching due to parton energy loss inside a dense medium are included phenomenologically. The intrinsic $k_T$ and its broadening in

Jongbae Hong, Jeong-Young Ji, Heekyong Kim

The signal generated by a weak impulse propagates in an oscillatory way and dispersively in a gravitationally compacted granular chain. For the power-law type contact force, we show analytically that the type of dispersion follows power-laws in depth. The power-law for grain displacement signal is given by $h^{-1/4(1-1/p)}$ where $h$ and $p$ denote depth and

Tal Mor

Disentanglement is the process which transforms a state $ρ$ of two subsystems into an unentangled state, while not effecting the reduced density matrices of each of the two subsystems. Recently Terno showed that an arbitrary state cannot be disentangled into a tensor product of its reduced density matrices. In this letter we present various novel results reg

V. Delgado

This paper compares the proposal made in previous papers for a quantum probability distribution of the time of arrival at a certain point with the corresponding proposal based on the probability current density. Quantitative differences between the two formulations are examined analytically and numerically with the aim of establishing conditions under which

Claus O. Wilke, Thomas Martinetz

An exact formula for the distribution of lifetimes in coherent-noise models and related models is derived. For certain stress distributions, this formula can be analytically evaluated and yields simple closed expressions. For those types of stress for which a closed expression is not available, a numerical evaluation can be done in a straightforward way. All

A. Barrau, L. Gallin-Martel, J. Pouxe, O. Rossetto

An analog integrated circuit has been designed, in a BiCMOS 0.8 micron technology, for the feasability study of the signal processing of the AMS RICH photomultiplier tubes. This low power, three channel gated integrator includes its own gate and no external analog delay is requiered. It processes PMT pulses over a dynamic range of more than 100. A logic outp

J. Murray, W. Bauer, K. Haglin

We confirm the importance of standard medium effects (hadronic rescattering) in heavy-ion collisions by using a pQCD-based model to investigate the dilepton spectra from Pb+Au collisions at 158 GeV/nucleon.

Berndt Müller

This paper discusses attempts to numerically compute the effects of hard thermal loops in non-abelian gauge theories at finite temperature by means of solutions of Heinz' transport equation for an ensemble of classical colored particles interacting with a real-time lattice gauge field. Results for the real-time response functions and the Chern-Simons num

Joachim Asch, Andreas Knauf

Although quantum tunneling between phase space tori occurs, it is suppressed in the semiclassical limit $\hbar\searrow 0$ for the Schrödinger equation of a particle in $\bR^d$ under the influence of a smooth periodic potential. In particular this implies that the distribution of quantum group velocities near energy $E$ converges to the distribution of the cl

Beata Randrianantoanina

We show that injective isometries in Orlicz space $L_M$ have to preserve disjointness, provided that Orlicz function $M$ satisfies $Δ_2$-condition, has a continuous second derivative $M''$, satisfies another ``smoothness type'' condition and either $\lim_{t\to0} M''(t) = \infty$ or $M''(0) = 0$ and $M''(t)>0$ for all $

John Etnyre, Robert Ghrist

We consider the problem of realizing tight contact structures on closed orientable three-manifolds. By applying the theorems of Hofer et al., one may deduce tightness from dynamical properties of (Reeb) flows transverse to the contact structure. We detail how two classical constructions, Dehn surgery and branched covering, may be performed on dynamically-con

A. V. Odesskii, B. L. Feigin

We quantize the coordinate ring of the moduli space of B-bundles on the elliptic curve. Here B is a Borel subgroup of some semisimple Lie group. We construct some representations of these algebras and study intertwining operators for these representations. We apply our constructions to produce some objects: the elliptic Belavin R-matrix, the quantization of

M. Rovinsky

Given a smooth projective variety $X$ over a field $k$ of characteristic zero, we consider the composition of the de Rham cohomology cycle class map over $k$ from the Chow group $CH^q(X\times_kK)$, where $K$ is the field of fractions of henselization $A^h$ of the local ring of a smooth closed point of a variety over the field $k$ with an appropriate projecti

Donald M. Davis

Bousfield recently gave a formula for the odd-primary v1-periodic homotopy groups of a finite H-space in terms of its K-theory and Adams operations. We apply Bousfield's theorem to give explicit determinations of the v1-periodic homotopy groups of (E8,5) and (E8,3), thus completing the determination of all odd-primary v1-periodic homotopy groups of compa

Christian Bohr

We prove necessary and sufficient conditions for a smooth surface in a 4-manifold X to be pseudoholomorphic with respect to some almost complex structure on X. This provides a systematic approach to the construction of pseudoholomorphic curves that do not minimize the genus in their homology class.

A. Bis, P. G. Walczak

We show that the entropy of a hyperbolic group acting on its ideal boundary is closely related to the exponential rate of its growth.

Christian Bohr

We consider partial liftings of maps at fibrations and compare the primary obstruction to extend the lifting with the obstruction to extend the lifting as a simple map into the total space. A relation between these two obstructions is proved for the case when the fiber is an Eilenberg-MacLane space. Furthermore it is shown that this result specialises to wel

Ilka Agricola, Bernd Ammann, Thomas Friedrich

We compare the eigenvalues of the Dirac and Laplace operator on a two-dimensional torus with respect to the trivial spin structure. In particular, we compute their variation up to order 4 upon deformation of the flat metric, study the corresponding Hamiltonian and discuss several families of examples.

Marcos Marino, Gregory Moore, Grigor Peradze

A compact oriented 4-manifold is defined to be of ``superconformal simple type'' if certain polynomials in the basic classes (constructed using the Seiberg-Witten invariants) vanish identically. We show that all known 4-manifolds of $b_2^+>1$ are of superconformal simple type, and that the numerical invariants of 4-manifolds of superconformal simple

Dominique Manchon

Nous definissons le front d'onde d'un vecteur-distribution pour une representation unitaire d'un groupe de Lie reel $G$ a l'aide du calcul pseudo-differentiel mis au point dans un travail anterieur. Cette notion precise celle de front d'onde d'une representation introduite par R. Howe. En application nous donnons une condition suffisa

Yu. I. Manin

We calculate a generating series for the virtual Euler-Poincaré characteristics of the spaces of stable maps of genus zero to flag spaces using the summation over trees technique.

Robert L. Bryant, Eric R. Sharpe

It was recently pointed out by E. Witten that for a D-brane to consistently wrap a submanifold of some manifold, the normal bundle must admit a Spin^c structure. We examine this constraint in the case of type II string compactifications with vanishing cosmological constant, and argue that in all such cases, the normal bundle to a supersymmetric cycle is auto

Sergei V. Ketov

A relation between confinement and Maldacena conjecture is briefly discussed. The gauge symmetry enhancement for two coincident D-6-branes is analyzed from the viewpoint of the hypermultiplet low-energy effective action given by the N=2 supersymmetric non-linear sigma-model with the Eguchi-Hanson (ALE) target space.

H. W. Braden, A. Marshakov, A. Mironov, A. Morozov

The prepotential and spectral curve are described for a smooth interpolation between an enlarged N=4 SUSY and ordinary N=2 SUSY Yang-Mills theory in four dimensions, obtained by compactification from five dimensions with non-trivial (periodic and antiperiodic) boundary conditions. This system provides a new solution to the generalized WDVV equations. We show

A. Nersessian, E. Ramos

We consider the simplest geometrical particle model associated with light-like curves in (2+1)-dimensions. The action is proportional to the pseudo-arc length of the particle's path. We show that under quantization it yields the (2+1)-dimensional anyonic field equation supplemented with a Majorana-like relation on mass and spin, i.e., $mass \times spin =

J. Lukierski

We describe three ways of modifying the relativistic Heisenberg algebra - first one not linked with quantum symmetries, second and third related with the formalism of quantum groups. The third way is based on the identification of generalized deformed phase space with the semidirect product of two dual Hopf algebras describing quantum group of motions and th

J. C. Montero, C. A. de S. Pires, V. Pleitez

We show that the Higgs resonance can be amplified in a 3-3-1 model with a multi-Higgs "leptophilic" scalar sector. This would allow the observation of the Higgs particle in muon colliders even for Higgs masses considerably higher than the ones expected to be seen in the electroweak standard model framework.

Alan Chodos, Hisakazu Minakata, Fred Cooper

We study a 2-dimensional model of Fermi fields that is closely related to the Gross-Neveu model, and show that to leading order in 1/N a <psi-psi> condensate forms. This effect is independent of the chemical potential, a peculiarity that we expect to be specific to 2 dimensions. We also expect the condensate to be unstable against corrections at higher order

J. R. Forshaw, G. P. Salam, R. S. Thorne

This is a summary of the contributions on the next-to-leading order corrections to the BFKL equation which were presented to the `Small-x and Diffraction&#39; working group at the 1998 Durham Workshop on HERA Physics.

A. Doff, F. Pisano

The uniqueness of the hypercharge assignments in the three fermion families leptoquark-bilepton $SU(3)_C \times SU(4)_L \times U(1)_N$ model is established. Although the gauge group contains an explicit U(1) factor, freedom from triangle anomalies combined with the requirement of nonvanishing charged fermion masses uniquely fix the electric charges of all fe

A. A. Machado, F. Pisano

Flavordynamics chiral models of leptoquark fermions and bilepton gauge bosons with masses up to about 1 TeV, although coincident at low energy with the standard model, address the question of fermion mass hyerarchy and explain the flavor question. The presence of charged right-handed weak currents coupled to bileptons, which we point out herein, is another r

C. H. Llewellyn Smith

The history and present status of several sum rules for deep-inelastic lepton scattering are reviewed, with particular attention to the discovery of scaling, partons, quarks and QCD. Two outstanding issues are then discussed in more detail: the singlet (Ellis-Jaffe) nucleon spin sum rule and the Drell-Hearn-Gerasimov-Iddings sum rule.

Pierre Fayet

We start with a brief presentation of the Standard Model and the weak neutral current, in view of a discussion of parity-violation in electron-hadron electroweak interactions. We then discuss some limitations of this model, motivating the consideration of larger frameworks such as grand-unification and supersymmetry. We also comment about the possible effect

Chris Quigg

I summarize and comment upon some highlights of HQ98, the Workshop on Heavy Quarks (strange, charm, and beauty) at Fixed Target.

B. Badełek, J. Kwieciński

Theoretical expectations concerning the low $x$ and low $Q^2$ behaviour of $g_1$ are summarized and compared with the recent SMC data.

Merab Gogberashvili

In the model where the Universe is considered as a thin shell expanding in 5-dimensional hyper-space there is a possibility to obtain one scale for particle theory corresponding to the 5-dimensional cosmological constant and Universe thickness.

R. Lietava

A simple geometrical model (often quoted in literature as the Glauber model) of heavy ion collisions is recapitulated. It is shown that the transverse energy distribution of heavy ion collisions follow the geometry of the collision. An extension of the model to include rapidity and transverse mass particle spectra is discussed.

V. E. Markushin

The role of two step mechanisms in the OZI rule violation in NNbar annihilation at low energies is reviewed. The full calculation of two-meson doorway mechanisms shows that the off-mass-shell contributions are important. Moreover, for the (phi pi0) and (phi rho) annihilation channels three-meson doorway contributions are non-negligible and improve agreement

I. Amirkhanov, I. Puzynin, A. Tarasov, O. Voskresenskaya

The Schrödinger equation discribing the local potential model of a strong $π^+π^-$-interaction was studied. The influence of the strong $π^+π^-$-interaction of the behaviour of pionium nS-state wave functions at small distances is studied both analytically (perturbatively) and numerically. It is shown that in the whole the accounting of strong interaction re

E. Zabrodin, L. Bravina, H. Stoecker, W. Greiner

The general formalism of homogeneous nucleation theory is applied to study the hadronization pattern of the ultra-relativistic quark-gluon plasma (QGP) undergoing a first order phase transition. A coalescence model is proposed to describe the evolution dynamics of hadronic clusters produced in the nucleation process. The size distribution of the nucleated cl

Liu Lianshou, Fu Jinghua, Wu Yuanfang

The information on dynamical fluctuations that can be extracted from the anomalous scaling observed recently in hadron-hadron collision experiments is discussed in some detail. A parameter ``effective fluctuation strength&#39;&#39; is proposed to estimate the strength of dynamical fluctuations. The method for extracting its value from the experimentally obse

Markus A. Luty, John Terning

Building on recent work by N. Arkani-Hamed and the present authors, we construct realistic models that break supersymmetry dynamically and give rise to composite quarks and leptons, all in a single strongly-coupled sector. The most important improvement compared to earlier models is that the second-generation composite states correspond to dimension-2 &#34;m

Andreas S. Kronfeld

In lattice QCD, obtaining properties of heavy-light mesons has been easier said than done. Focusing on the $B$ meson&#39;s decay constant, it is argued that towards the end of 1997 the last obstacles were removed, at least in the quenched approximation. These developments, which resulted from a fuller understanding and implementation of ideas in effective fi

S. Gardner

I present two disparate examples of isospin violation in hadronic B-decays. In the first, the presence of ρ^0-ωmixing in the decay B^\mp\toρ^\mpρ^0(ω)\toρ^\mpπ^+ π^- permits the extraction of sgn(\sin α), where αis the usual angle of the unitarity triangle, with minimal hadronic uncertainty. In the second, the presence of π^0-η,η&#39; mixing can obscure the

Andrew D. Kent, Ulrich Rüdiger, Jun Yu, Luc Thomas

We review our recent magnetotransport and micromagnetic studies of lithographically defined epitaxial thin film structures of bcc Fe and hcp Co with stripe domains. Micromagnetic structure and resistivity anisotropy are shown to be the predominant sources of low field magnetoresistance (MR) in these microstructures, with domain wall (DW) effects smaller but

Alexander S. Rozhavsky, Yurij V. Pershin, Igor A. Romanovsky

We derive equations for the collective CDW-current transverse conducting chains in a quasi-one-dimensional CDW-conductor. Generalized Frohlich relations between the transverse currents and phase gradients are due to the polarization corrections to the 1+1 chiral anomaly Lagrangean. The CDW Hall constant is calculated.

M. V. Medvedev, P. H. Diamond

The spatial structure, fluctuations as well as all state probabilities of self-organized (steady) states of cellular automata can be found (almost) exactly and {\em explicitly} from their Markovian dynamics. The method is shown on an example of a natural sand pile model with a gradient threshold.

Yuli Lyanda-Geller, Paul M. Goldbart

Mesoscopic phenomena - including population oscillations and persistent currents driven by quantal phases - are explored theoretically in the context of multiply-connected Bose-Einstein systems composed of trapped alkali-metal gas atoms. These atomic phenomena are bosonic analogues of electronic persistent currents in normal metals and Little-Parks oscillati

Marti Pi, Ricardo Mayol, Manuel Barranco

We have investigated how helium atoms are distributed within a mixed $^3$He$_{N_3}$-$^4$He$_{N_4}$ large drop with $N_3 \gg N_4$. For drops doped with a SF$_6$ molecule or a Xe atom, we have found that the number of $^3$He atoms within the volume containing the first two solvation shells increases when $N_4$ decreases in a way such that these dopants may be

Pramod Gupta, S. Teitel

We consider the effect of positional disorder on a Josephson junction array with an applied magnetic field of f=1/2 flux quantum per unit cell. This is equivalent to the problem of random Gaussian phase shifts in the fully frustrated 2D XY model. Using simple analytical arguments and numerical simulations, we present evidence that the ground state vortex lat

V. A. Skrebnev, R. N. Zaripov

An experimental study of the applicability of mechanics equations to describing the process of equilibrium establishing in an isolated spin system was performed. The time-reversion effects were used at the experiments. It was demonstrated, that the equations of mechanics do not describe the experimental results. The demonstration of the incomleteness of quan

V. Kagalovsky, B. Horovitz, Y. Avishai, J. T. Chalker

We study a delocalization transition for non-interacting quasiparticles moving in two dimensions, which belongs to a new symmetry class. This symmetry class can be realised in a dirty, gapless superconductor in which time reversal symmetry for orbital motion is broken, but spin rotation symmetry is intact. We find a direct transition between two insulating p

Bruce M. Boghosian

Tsallis has proposed a generalization of Boltzmann-Gibbs thermostatistics by introducing a family of generalized nonextensive entropy functionals with a single parameter $q$. These reduce to the extensive Boltzmann-Gibbs form for $q=1$, but a remarkable number of statistical and thermodynamic properties have been shown to be $q$-invariant -- that is, valid f

Christian Holm, Kurt Kremer

We present a short overview over recent MD simulations of systems of fully flexible polyelectrolyte chains with explicitly treated counter ions using the full Coulomb potential. The main emphasis is given on the conformational properties of the polymers, with a short discussion on counter ion condensation.

T. Herrmann, W. Nolting

The magnetic behavior of thin ferromagnetic itinerant-electron films is investigated within the strongly correlated single-band Hubbard model. For its approximate solution we apply a generalization of the modified alloy analogy (MAA) to deal with the modifications due to the reduced translational symmetry. The theory is based on exact results in the limit of

B. Irmer, F. Simmel, R. H. Blick, H. Lorenz

A new technique is presented which enables the fabrication of highly transparent Josephson junctions in combination with mesoscopic devices. We utilize a modified AFM tip to plough grooves into superconducting material, thus defining a weak link. This weak link is made within the superconducting split-gates, which are used to electrostatically form a convent

B. Zheng, M. Schulz, S. Trimper

Based on the short-time dynamic scaling form, a novel dynamic approach is proposed to tackle numerically the Kosterlitz-Thouless phase transition. Taking the two-dimensional XY model as an example, the exponential divergence of the spatial correlation length, the transition temperature $T_{KT}$ and all critical exponents are computed. Compared with Monte Car

H. J. Luo, B. Zheng

Dynamic relaxation of the XY model and fully frustrated XY model quenched from an initial ordered state to the critical temperature or below is investigated with Monte Carlo methods. Universal power law scaling behaviour is observed. The dynamic critical exponent $z$ and the static exponent $η$ are extracted from the time-dependent Binder cumulant and magnet

B. Zheng, M. Schulz, S. Trimper

A kinetic Ising model is analyzed where spin variables correspond to lattice cells with mobile or immobile particles. Introducing additional restrictions for the flip processes according to the n-spin facilitated kinetic Ising model and using Monte Carlo methods we study the freezing process under the influence of an additional nearest-neighbor interaction.

O. Mauritz, G. Goldoni, F. Rossi, E. Molinari

A theoretical description of local absorption is proposed in order to investigate spectral variations on a length scale comparable with the extension of the relevant quantum states. A general formulation is derived within the density-matrix formalism including Coulomb correlation, and applied to the prototypical case of coupled quantum wires. The results sho

Beat Ammon, Matthias Troyer, T. M. Rice, N. Shibata

Accurate numerical simulations of a doped t-J model on a two-leg ladder are presented for the particle number, chemical potential, magnetic susceptibility and entropy in the limit of large exchange coupling on the rung using a finite temperature density matrix renormalization group (TDMRG) method. This required an improved algorithm to achieve numerical stab

K. Haule, J. Bonca

Our objective is to study resonant tunneling of an electron in the presence of inelastic scattering by optical phonons. Using a recently developed technique, based on exact mapping of a many-body problem onto a one-body problem, we compute transmission through a single site at finite temperatures. We also compute current through a single site at finite tempe

Yoshiyuki Kurokawa, Shintaro Nomura, Tadashi Takemori, Yoshinobu Aoyagi

We report a numerical calculation of the two-photon absorption coefficient of electrons in a binding potential using the real-time real-space higher-order difference method. By introducing random vector averaging for the intermediate state, the task of evaluating the two-dimensional time integral is reduced to calculating two one-dimensional integrals. This

W. -J. Zhu, C. L. Henley

From relaxation simulations of decoration-based quasicrystal structure models using microscopically based interatomic pair potentials, we have calculated the (usually neglected) phonon-phason coupling constant. Its sign is opposite for the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its magnitude relative to the phonon and phason e

Bing-Hong Wang, Y. R. Kwong, P. M. Hui, Bambi Hu

Three cellular automaton (CA) models of increasing complexity are introduced to model driven diffusive systems related to the generalized Frenkel-Kontorova (FK) models recently proposed by Braun [Phys.Rev.E58, 1311 (1998)]. The models are defined in terms of parallel updating rules. Simulation results are presented for these models. The features are qualitat

A. Vaknin, A. Frydman, Z. Ovadyahu

The current-voltage characteristics of Au/InOx/Pb tunnel junctions exhibit peculiar zero-bias anomalies. At low temperature the zero-bias resistance attains values that are smaller than the normal state resistance by a factor that often esceeds 2. The width of this anomaly increases with the thickness of the InOx layer. The possibility that these features ar

A. Stern, B. I. Halperin, F. von Oppen, S. H. Simon

In this paper we study the relation between the conventional Fermion-Chern-Simons (FCS) theory of the half-filled Landau level (nu=1/2), and alternate descriptions that are based on the notion of neutral quasi-particles that carry electric dipole moments. We have previously argued that these two approaches are equivalent, and that e.g., the finite compressib

T. Startseva, T. Timusk, A. V. Puchkov, D. N. Basov

The ab-plane optical spectra of two single crystals of underdoped La_(2-x)Sr_xCuO_4 were investigated. The reflectivity of La_(1.87)Sr_(0.13)CuO_4 has been measured in the frequency range 30- 9,000 cm-1 (0.004 -- 1 eV) both parallel and perpendicular to the CuO_2 planes, whereas La_(1.86)Sr_(0.14)CuO_4 was studied only in the ab-plane. The extended Drude mod

Sung-Sik Lee, Sung-Ho Suck Salk

In order to obtain a reasonable phase diagram involving hole-pair condensation for hole-doped cuprate systems, we propose a modified t-J Hamiltonian in which a Coulomb repulsion term between nearest neighbor holes is considered. We show from the investigation of free energy that holon pair condensation can occur as a result of symmetry breaking. In addition,

P. Dahlqvist

We estimate the error in the semiclassical trace formula for the Sinai billiard under the assumption that the largest source of error is due to Penumbra diffraction, that is diffraction effects for trajectories passing within a distance R O((kR)^(-2/3) to the disk and trajectories being scattered in very forward directions. Here k is the momentum and R the r

Cristopher Moore, Porus Lakdawala

We examine the one-humped map at the period-doubling transition to chaos, and ask whether its long-term memory is stack-like (last-in, first-out) or queue-like (first-in, first-out). We show that it can be recognized by a real-time automaton with one queue, or two stacks, and give several new grammatical characterizations of it. We argue that its memory has

Toshio Tsuchiya, Naoteru Gouda

The relation between relaxation, the time scale of Lyapunov instabilities, and the Kolmogorov-Sinai time in a one-dimensional gravitating sheet system is studied. Both the maximum Lyapunov exponent and the Kolmogorov-Sinai entropy decrease as proportional to $N^{-1/5}$. The time scales determined by these quantities evidently differ from any type of relaxati

Yoshihiro Hirata, Tetsuro Konishi

We analytically compute asymptotic expansions of a 1-dimensional sub-manifold of stable and unstable manifolds in a 4-dimensional symplectic mapping by using the method called asymptotic expansions beyond all orders. This method enables us to capture exponentially small splitting of separatrices and also to obtain explicit functional approximations of the su

W. B. Hubbard, T. Guillot, M. S. Marley, A. Burrows

We present evolutionary sequences for Jupiter and Saturn, based on new nongray model atmospheres, which take into account the evolution of the solar luminosity and partitioning of dense components to deeper layers. The results are used to set limits on the extent to which possible interior phase separation of hydrogen and helium may have progressed in the tw

R. Rengelink, M. Nonino, L. da Costa, S. Zaggia

This paper presents ground-based data obtained from deep optical and infrared observations carried out at the ESO 3.5 New Technology Telescope (NTT) of a field selected for its low HI content for deep observations with AXAF. These data were taken as part of the ESO Imaging Survey (EIS) program, a public survey conducted in preparation for the first year of o

R. A. Webb, B. Zuckerman, I. Platais, J. Patience

We report the discovery of five T Tauri star systems, two of which are resolved binaries, in the vicinity of the nearest known region of recent star formation, the TW Hydrae Association. The newly discovered systems display the same signatures of youth (namely high X-ray flux, large Li abundance and strong chromospheric activity) and the same proper motion a

William H. Waller, Christine Winslow, Michael Fanelli, Theodore B. Stecher

Imaging in the restframe ultraviolet has proven to be an effective and vital means of tracing dynamical patterns of star formation in galaxies out to high redshifts. Using images from the Ultraviolet Imaging Telescope (UIT), Hubble Space Telescope (HST) and complementary groundbased telescopes, we have investigated the starburst activity and associated dynam

P. J. Lowrance, C. McCarthy, E. E. Becklin, B. Zuckerman

We present the discovery of a candidate substellar object in a survey of young stars in the solar vicinity using the sensitivity and spatial resolution afforded by the NICMOS coronagraph on the Hubble Space Telescope. The H=12.1 mag object was discovered approximately 2 arcsec from the TW Hydrae Association member CoD -33 7795 (TWA 5), and the photometry imp

M. Revnivtsev, M. Gilfanov, E. Churazov, R. Sunyaev

Using ASCA observations of several X-ray bursters in the low spectral state Lx~1-5x10^{36} erg/s) restrictions on the parameters of the accretion disk and the boundary layer were obtained. The low state spectra of X-ray bursters observed with ASCA often can be well described by a power law with photon index of 1.7--2.2 and are not consistent with significant

In-Saeng Suh, G. J. Mathews

We explore constraints on the strength of the primordial magnetic field based upon the weak reaction freeze-out in the early universe. We find that limits on the strength of the magnetic field found in other works are recovered simply by examining the temperature at which the rate of weak reactions drops below the rate of universal expansion ($\Gamma_{w} \le

D. M. Smith, R. P. Lin, J. McTiernan, A. S. Slassi-Sennou

In the summer of the year 2000, a NASA Small Explorer satellite, the High Energy Solar Spectroscopic Imager (HESSI), will be launched. It will consist of nine large, coaxial germanium detectors viewing the Sun through a set of Rotation Modulation Collimators and will accomplish high-resolution imaging and spectroscopy of solar flares in the x-ray and gamma-r

C. G. Mundell, A. Pedlar, D. L. Shone, A. Robinson

We present sensitive, high angular resolution (6&#34; x 5&#34;) 21-cm observations of the neutral hydrogen in the nearby barred Seyfert galaxy, NGC4151. These HI observations, obtained using the VLA in B-configuration, are the highest resolution to date of this galaxy, and reveal hitherto unprecedented detail in the distribution and kinematics of the HI on s

Alberto D. Bolatto, James M. Jackson, James G. Ingalls

We present a simple, semianalytical approach to compute the line emission of C+, C and CO in Photodissociation Regions of varying metallicity that depends on very few parameters and naturally incorporates the clumpiness of the interstellar medium into the calculations. We use it to study the dependence of the I_[C II]/I_CO and I_[C I]/I_CO line ratios on the

Michael A. Nowak, Joern Wilms, James B. Dove

Here we present timing analysis of a set of eight Rossi X-ray Timing Explorer (RXTE) observations of the black hole candidate GX 339-4 that were taken during its hard/low state. On long time scales, the RXTE All Sky Monitor data reveal evidence of a 240 day periodicity, comparable to timescales expected from warped, precessing accretion disks. On short times

C. L. Carilli, Karl M. Menten, C. P. Moore

We have searched for redshifted absorption in the 21 cm line of neutral hydrogen toward `red quasars&#39;, which are extragalactic radio sources with a steep spectral drop between optical and infrared wavelengths. The success rate for detecting HI 21cm absorption toward a representative sample of such sources is 80%. This compares to the much lower success r

Karl M. Menten, Christopher L. Carilli, Mark J. Reid

We have made radio- and millimeter-wavelength interferometric observations of a variety of molecular absorption lines toward the gravitational lens systems B0218+357 and PKS1830-211. The absorption occurs in the lensing galaxies at redshifts of 0.685 and 0.89, respectively. The high spatial resolution of our VLA and VLBA observations allows imaging of the ba

C. G. Mundell, D. L. Shone

We present sensitive, high resolution observations of neutral hydrogen (HI) in the unusually gas-rich, oval distortion of the Seyfert galaxy NGC4151. The gas dynamics of the oval are found to be consistent with those of a kinematically weak bar, fully confirming previous suggestions for the presence of a fat bar, and, for the first time, individual gaseous f

C. Vignali, A. Comastri, M. Cappi, G. G. C. Palumbo

This paper reports the X-ray spectral analysis of 5 high-redshift (z \ge 2) radio-quiet quasars observed by ASCA. A simple power law continuum plus cold Galactic absorption model well fits all the spectra (tipically between $\sim$ 2-30 keV in the sources frame). Neither the X-ray spectral hardening, attributed to a reflection component and observed in Seyfer

M. Boettcher, C. D. Dermer

In the cosmological blast-wave model for gamma ray bursts (GRBs), high energy (> 10 GeV) gamma-rays are produced either through Compton scattering of soft photons by ultrarelativistic electrons, or as a consequence of the acceleration of protons to ultrahigh energies. We describe the spectral and temporal characteristics of high energy gamma-rays produced by

John S. Gallagher, III, Linda J. Smith

We present high signal-to-noise optical spectra of two luminous super star clusters in the starburst galaxy M82. The data for cluster F and the nearby, highly reddened cluster L were obtained with the William Herschel Telescope (WHT) at a resolution of 1.6A. The blue spectrum (3250-5540A) of cluster F shows features typical of mid-B stars. The red spectra (5

Y. Mellier

Gravitational lenses can provide crucial information on the geometry of the Universe, on the cosmological scenario of formation of its structures as well as on the history of its components with look-back time. In this review, I focus on the most recent results obtained during the last five years from the analysis of the weak lensing regime. The interest of