August 1998 arXiv papers — page 4

N. Shibata, K. Ueda

Recent developments of the theoretical investigations on the one-dimensional Kondo lattice model by using the density matrix renormalization group (DMRG) method are discussed in this review. Short summaries are given for the zero-temperature DMRG, the finite-temperature DMRG, and also its application to dynamic quantities. Away from half-filling, the paramag

Jae-Kwon Kim

A comment on PRL vol. 80, 4697 (1998) by Roder, Adler and Janke. Minior correction included.

James Shaw

In this paper, we provide an account of how to generate sentences with coordination constructions from clause-sized semantic representations. An algorithm is developed to generate sentences with ellipsis, gapping, right-node-raising, and non-constituent coordination constructions. Various examples from linguistic literature will be used to demonstrate that t

J. S. Bloom, D. A. Frail, S. R. Kulkarni, S. G. Djorgovski

We report on the discovery of the radio, infrared and optical transient coincident with an X-ray transient proposed to be the afterglow of GRB 980703. At later times when the transient has faded below detection, we see an underlying galaxy with R=22.6; this galaxy is the brightest host galaxy (by nearly 2 magnitudes) of any cosmological GRB thus far. In keep

Thierry Foglizzo

The excitation mechanism of low degree acoustic modes is investigated through the analysis of the stochastic time variations of their energy. The correlation between the energies of two different modes is interpreted as the signature of the occurrence rate of their excitation source. The different correlations determined by Foglizzo et al. (1998) constrain t

Harry I. Teplitz, Jonathan P. Gardner, Eliot M. Malumuth, Sara R. Heap

We present high resolution NICMOS images of random fields obtained in parallel to other HST observations. We present galaxy number counts reaching H=24. The H-band galaxy counts show good agreement with the deepest I- and K-band counts obtained from ground-based data. We present the distribution of galaxies with morphological type to H<23. We find relatively

F. Nicastro, F. Fiore, G. C. Perola, M. Elvis

In this paper we explore collisional ionization and time-evolving photoionization in the, X-ray discovered, ionized absorbers in Seyfert galaxies. These absorbers show temporal changes inconsistent with simple equilibrium models. We develop a simple code to follow the temporal evolution of non-equilibrium photoionized gas. As a result several effects appear

L. van Zee, J. J. Salzer, M. P. Haynes, A. A. O&#39;Donoghue

We present the results of low dispersion optical spectroscopy of 186 H II regions spanning a range of radius in 13 spiral galaxies. Abundances for several elements (oxygen, nitrogen, neon, sulfur, and argon) were determined for 185 of the H II regions. As expected, low metallicities were found for the outlying H II regions of these spiral galaxies. Radial ab

Bhuvnesh Jain, Edmund Bertschinger

The power spectrum P(k)\propto k^n with n=-2 is close to the shape of the measured galaxy spectrum on small scales. Unfortunately this spectrum has proven rather difficult to simulate. Further, 2-dimensional simulations have suggested a breakdown of self-similar scaling for spectra with n<-1 due to divergent contributions from the coupling of long wave modes

K. Iwasawa

We present ASCA results on four prototype powerful far-infrared galaxies, Mrk231, Mrk273, Arp220 and NGC6240. The soft X-ray spectra show signatures of thermal emission with temperatures of (0.5-1) keV, which is probably produced in starbursts. Their soft X-ray (0.5-2 keV) luminosities range from 4x10^40 erg/s to 7x10^41 erg/s. The X-ray properties are exami

D. L. Clements, W. J. Saunders, R. G. McMahon

We present the latest results in our efforts to produce a complete, large sample of Ultraluminous Infrared Galaxies (ULIRGs, L60 > 10^11.4 Lsun for H0=100kms^-1 Mpc^-1, q0=0.5) for use in the study of these objects and their evolution. We have been using an optical/IR colour technique to select those objects most likely to be ULIRGs. 65 of the 198 candidate

F. P. Israel, R. P. J. Tilanus, F. Baas

Emission from the 492 GHz CI tranition was detected towards the dark cloud D478 in M31. Using existing 12CO and 13CO measurements, models for the gas properties of D478 are discussed. The observed CO and C line ratios can be explained by two-component models (dense cores and tenuous envelopes); single-density models appear less likely. The models indicate te

C. L. Fryer, S. A. Colgate, P. A. Pinto

Neutron stars formed in Type II supernovae are likely to be initially obscured by late-time fallback. Although much of the late-time fallback is quickly accreted via neutrino cooling, some material remains on the neutron star, forming an atmosphere which slowly accretes through photon emission. In this paper, we derive structure equations of the fallback atm

J. G. Bartlett, A. Blanchard, D. Barbosa

The potential of the Sunyaev-Zel&#39;dovich (SZ) effect for cluster studies has long been appreciated, although not yet fully exploited. Recent technological advances and improvements in observing strategies have changed this, to the point where it is now possible to speak of this subject at a meeting devoted to {\em surveys} in Cosmology. We will discuss SZ

Osmi Vilhu, Jukka Nevalainen

The Galactic superluminal source GRS 1915+105 was found to experience a peculiar X-ray variability in a narrow count rate range of the PCA detector onboard RXTE. This can be seen as a ring-shaped pattern in the two-color diagram of count rates, where the hard hardness F(13-40keV)/F(2-13keV) is plotted against the soft hardness F(5-13keV)/F(2-5keV). The syste

M. E. Degaudenzi, C. M. Arizmendi

The most abundant biological particles in the atmosphere are pollen grains and spores. Self protection of pollen allergy is possible through the information of future pollen contents in the air. In spite of the importance of airborne pol len concentration forecasting, it has not been possible to predict the pollen concentrations with great accuracy, and abou

Roman Scoccimarro, H. M. P. Couchman, Joshua A. Frieman

The bispectrum provides a characteristic signature of gravitational instability that can be used to probe the Gaussianity of the initial conditions and the bias of the galaxy distribution. We study how this signature is affected by redshift distortions using perturbation theory and high-resolution numerical simulations. We obtain perturbative results for the

G. Korniss, B. Schmittmann, R. K. P. Zia

Biased diffusion of two species with conserved dynamics on a 2xL periodic lattice is studied via Monte Carlo simulations. In contrast to its simple one-dimensional version on a ring, this quasi one-dimensional model surprisingly exhibits phase separation in its steady state, which is characterized by one macroscopic particle cluster. We study the order param

R. Bundschuh, C. Cassanello, D. Serban, M. R. Zirnbauer

Starting from a random matrix model, we construct the low-energy effective field theory for the noninteracting gas of quasiparticles of a disordered superconductor in the mixed state. The theory is a nonlinear sigma model, with the order parameter field being a supermatrix whose form is determined solely on symmetry grounds. The weak localization correction

J. Park, A. M. Uranga

We construct the T duals of certain type IIA brane configurations with one compact dimension (elliptic models) which contain orientifold planes. These configurations realize four-dimensional $\NN=2$ finite field theories. For elliptic models with two negatively charged orientifold six-planes, the T duals are given by D3 branes at singularities in the presenc

Stefano Moretti, W. J. Stirling

Existence of discrepancies between experimental data and Monte Carlo predictions for angular distributions in four-jet production via $e^+e^-$ annihilation has been known for some time at LEP1. As such QCD processes constitute significant backgrounds to $e^+e^-\to W^+W^-\to 4$-jet production at LEP2, we consider the possibility that an erroneous modelling of

P. S. Howe, E. Sokatchev, P. C. West

Three-point functions of analytic (chiral primary) operators in N=4 Yang-Mills theory in four dimensions are calculated using the harmonic superspace formulation of this theory. In the case of the energy-momentum tensor multiplet anomaly considerations determine the coefficient. Analyticity in N=2 harmonic superspace is explicitly checked in a two-loop calcu

Tarek Gharib, Wolfgang Bauer, Scott Pratt

Multiplicity fluctuations of intermediate-mass fragments are studied with the percolation model. It is shown that super-Poissonian fluctuations occur near the percolation transition and that this behavior is associated with the fragmentative nature of the percolation model. The consequences of various choices in defining and binning fragments are also evalua

David Vitali, Paolo Tombesi

We show how it is possible to suppress decoherence using tailored external forcing acting as pulses. In the limit of infinitely frequent pulses decoherence and dissipation are completely frozen; however, a significant decoherence suppression is already obtained when the frequency of the pulses is of the order of the reservoir typical frequency scale. This me

Andres Aguado, Francisco Lopez-Gejo, Jose M. Lopez

Ab initio perturbed ion plus polarization calculations are reported for doubly-charged nonstoichiometric (MgO)nMg2+ (n=1-29) cluster ions. We consider a large number of isomers with full relaxations of the geometries, and add the correlation correction to the Hartree-Fock energies for all cluster sizes. The polarization contribution is included at a semiempi

J. Schnack

The ongoing discussion whether thermodynamic properties can be extracted from a (possibly approximate) quantum mechanical time evolution using time averages is fed with an instructive example. It is shown for the harmonic oscillator how the Hilbert space or an appropriately defined phase space must be populated in terms of coherent states in order to obtain

Munshi Golam Mustafa, Abhijit Sen, Lina Paria

We show that requiring the quark partition function to be color singlet of SU(3) color gauge group leads to reordering the thermodynamic potential in terms of the colorless multi-quark modes ($q{\bar q}, qqq, {\bar q}{\bar q}{\bar q}, ...$) at any given temperature. In accord with the &#34;preconfinement&#34; property of QCD, under a suitable confining mecha

K. Yoshida, H. Toki

Spin longitudinal and transverse response function are studied by means of the relativistic many-body theory. The spin response functions in the relativistic theory are largely reduced from those in the non-relativistic theory. The local density approximation with the eikonal approximation is applied to the the nuclear absorption in the $(\vec{p},\vec{n})$ r

Avinash Khare, C. Quesne

We apply the exchange operator formalism in polar coordinates to a one-parameter family of three-body problems in one dimension and prove the integrability of the model both with and without the oscillator potential. We also present exact scattering solution of a new family of three-body problems in one dimension.

V. E. Adler

The main purpose of the paper is to demonstrate that condition of invariance with respect to the Legendre transformations allows effectively isolate the class of integrable difference equations on the triangular lattice, which can be considered as discrete analogues of relativistic Toda type lattices. Some of obtained equations are new, up to the author know

Mauro Fortunato, Gil Harel, G. Kurizki

With the help of some remarkable examples, it is shown that conditional measurements performed on two-level atoms just after they have interacted with a resonant cavity field mode are able to recover the coherence of number-state superpositions, which is lost due to dissipation.

J. A. Jones, M. Mosca

We demonstrate the implementation of a quantum algorithm for estimating the number of matching items in a search operation using a two qubit nuclear magnetic resonance (NMR) quantum computer.

B. G. Sidharth

Motivated by recent work on nano tubes indicating one dimensional quantum effects and studies of two dimensional electron gas, we consider a recent model of Fermions as Kerr-Newman type black holes with quantum mechanical effects. Such an anyonic fractionally charged quasi-electron picture is deduced and identified with quarks.

B. G. Sidharth

In the context of a recent description of Fermions as Kerr-Newman type black holes with Quantum Mechanical inputs, it is shown how the quark picture can be recovered. The advantage is that in the process we obtain a rationale for such features as the puzzling fractional charges of the quarks, their masses, confinement and handedness in a unified scheme.

Mauro Fortunato, Paolo Tombesi, Wolfgang P. Schleich

We present a new indirect method to measure the quantum state of a single mode of the electromagnetic field in a cavity. Our proposal combines the idea of (endoscopic) probing and that of tomography in the sense that the signal field is coupled via a quantum-non-demolition Hamiltonian to a meter field on which then quantum state tomography is performed using

Masanori Ohya

The study of mutual entropy (information) and capacity in classica l system was extensively done after Shannon by several authors like Kolmogor ov and Gelfand. In quantum systems, there have been several definitions of t he mutual entropy for classical input and quantum output. In 1983, the autho r defined the fully quantum mechanical mutual entropy by means

Wim van Dam

In this note we study the power of so called query-limited computers. We compare the strength of a classical computer that is allowed to ask two questions to an NP-oracle with the strength of a quantum computer that is allowed only one such query. It is shown that any decision problem that requires two parallel (non-adaptive) SAT-queries on a classical compu

R. A. Treumann

We extend the recently developed non-gaussian thermodynamic formalism \cite{tre98} of a (presumably strongly turbulent) non-Markovian medium to its most general form that allows for the formulation of a consistent thermodynamic theory. All thermodynamic functions, including the definition of the temperature, are shown to be meaningful. The thermodynamic pote

Charles W. Johnson, George Fai

We examine saturation properties of a quark-based picture of nuclear matter. Soliton matter consisting of nonlocal confining solitons is used to model nuclear matter. Each composite nucleon is described by a non-topological soliton as given by the Global Color Model. We apply techniques and concepts from the discription of crystal lattices. In particular, th

W. Poeschl

A finite element method using B-splines is presented and compared with a conventional finite element method of Lagrangian type. The efficiency of both methods has been investigated at the example of a coupled non-linear system of Dirac eigenvalue equations and inhomogeneous Klein-Gordon equations which describe a nuclear system in the framework of relativist

E. E. Kolomeitsev, D. N. Voskresensky

Production of negative strangeness in reactions of inelastic anti-neutrino scattering on a nucleus provides information on the modification of strange degrees of freedom in nuclear matter. We calculate cross-sections of the reaction channels $\barν_{e(μ)}\to e^+(μ^+) + K^{-}$ and $\barν_{e(μ)} + p \to \Lb + e^+(μ^+)$ and investigate their sensitivity to the

Attila Csoto, G. M. Hale

The d+N systems are studied in a three-body model, using phenomenological N-N interactions. The scattering matrices are calculated by using the Kohn-Hulthen variational method. Then, they are analytically continued to complex energies and their singularities are localized. We find a virtual state at E=-1.66 MeV in H-3 and a pair of states at E=(-0.42+-i0.52)

R. Ganz

Strangeness production in heavy-ion collisions, when compared to proton proton collisions, is potentially a sensitive probe for collective energy deposition and therefore for reaction mechanisms in general. It may therefore provide insight into possible QGP formation in dense nuclear matter. To establish an understanding of the observed yields, a systematic

R. Ganz

The large acceptance TPCs of the NA49 spectrometer allow for a systematic multidimensional study of two-particle correlations in different part of phase space. Results from Bertsch-Pratt and Yano-Koonin-Podgoretskii parametrizations are presented differentially in transverse pair momentum and pair rapidity. These studies give an insight into the dynamical sp

Alexander Krasulin

In this part of the series I discuss the five-vector generalizations of affine connection and gauge fields. I also give definition to the exterior derivative of nonscalar-valued five-vector forms and consider the five-vector analogs of the field strength tensor. In conclusion I discuss the nonspacetime analogs of five-vectors.

Robert I McLachlan

We consider the problem of constructing spatial finite difference approximations on a fixed, arbitrary grid, which have analogues of any number of integrals of the partial differential equation and of some of its symmetries. A basis for the space of of such difference operators is constructed; most cases of interest involve a single such basis element. (The

Rolf Kaellstroem

A Lie algebroid on a variety X/k is an extension α: g_X \to T_X of the tangent sheaf both as O_X-module and Lie algebra over the base field, with the obvious compatibilities; and given a Lie algebroid one has its associated ring of differential operators D(g_X). Letting g&#39;_X be some Lie sub-algebroid of g_X, a smooth coherent g_X-module M is one in which

Bernard de Wit, Bas Kleijn, Stefan Vandoren

We discuss superconformally invariant systems of hypermultiplets coupled to gauge fields associated with target-space isometries.

Bjorn Andreas

We review aspects of N=1 duality between the heterotic string and F-theory. After a description of string duality intended for the non-specialist the framework and the constraints for heterotic/F-theory compactifications are presented. The computations of the necessary Calabi-Yau manifold and vector bundle data, involving characteristic classes and bundle mo

D. Altschuler, P. Ruelle, E. Thiran

We examine general aspects of parity functions arising in rational conformal field theories, as a result of Galois theoretic properties of modular transformations. We focus more specifically on parity functions associated with affine Lie algebras, for which we give two efficient formulas. We investigate the consequences of these for the modular invariance pr

Stefano Moretti

We study electron-positron annihilations into six jets at the parton level in perturbative Quantum Chromo-Dynamics (QCD), via the elementary processes $e^+e^-\ar q\bar q gggg$, $e^+e^-\ar q\bar q q&#39;\bar q&#39; gg$ and $e^+e^-\ar q\bar q q&#39;\bar q&#39; q&#39;&#39;\bar q&#39;&#39;$, for massive quarks $q, q&#39;$ and $q&#39;&#39;$ and massless gluons $g

Marc Chemtob, Grégory Moreau

We examine the effect of the R parity odd renormalizable interactions on flavor non-diagonal rates and CP violation asymmetries in the production of slepton pairs at $e^- - e^+$ leptonic colliders, for center of mass energies spanning the interval from the Z-boson pole up to 1000 GeV. The lepton number violating interactions, associated with the lepton numbe

Sacha Davidson

This is a review of the cosmological bounds on $B-L$ violating interactions, and the loopholes in the argument that gives these constraints. If one assumes that the baryon asymmetry we observe today was present above the electroweak phase transition in equilibrium with the non-perturbative $B+L$ violating processes, then interactions that violate all three o

Mauro Anselmino, Francesco Murgia

We consider several single spin asymmetries in inclusive, transversely polarized proton(antiproton) - proton processes as higher twist QCD contributions, taking into account spin and intrinsic transverse momentum effects in the quark distribution functions. This approach has been previously applied to the description of the single spin asymmetries observed i

Sacha Davidson

The magnitude of R-parity violating coupling constants depends on which direction in the space of weak doublets with hypercharge = -2 corresponds to the Higgs. To address this ``basis dependence&#39;&#39;, one can construct combinations of coupling constants that are invariant under these basis transformations, and which parametrise how much R parity violati

Amitava Datta, Shyamapada Maity

It is shown that if the charginos decay into very soft leptons or hadrons + $\not{E}$ due to degeneracy/ near- degeneracy with the LSP or the sneutrino, the observability of the recently proposed signal via the single photon (+ soft particles) + $\not{E}$ channel crucially depends on the magnitude of the $\SNU$ mass due to destructive interferences in the ma

A. Ringwald, F. Schrempp

We review the present status of our ongoing systematic study of the discovery potential of QCD-instanton induced events in deep-inelastic scattering at HERA.

J. Bijnens, G. Colangelo, G. Ecker

We determine the full structure of the leading (double-pole) divergences of O(p^6) in the meson sector of chiral perturbation theory. The field theoretic basis for this calculation is described. We then use an extension of this result to determine the p^6 contributions containing double chiral logarithms (L^2), single logarithms times p^4 constants (L x L_i^

Z. Papp

The treatment of confining interactions in non-relativistic three-quark systems is revised. Usually in the Faddeev equations the Faddeev components are coupled by the total potential. In the new treatment the Faddeev components are coupled only by the non-confining short-range part of the potential, allowing thus its channel-by-channel investigation. The con

Kyungsik Kang, Sin Kyu Kang, C. S. Kim, Sun Myoung Kim

In view of the recent announcement on non-zero neutrino mass from Super-Kamiokande experiment, it would be very timely to investigate all the possible scenarios on masses and mixings of light neutrinos. Recently suggested mass matrix texture for the quark CKM mixing, which can be originated from the family permutation symmetry and its suitable breakings, is

G. Damm, W. Kerler

In 4D compact U(1) lattice gauge theory with a monopole term added to the Wilson action we first reveal some properties of a third phase region at negative $β$. Then at some larger values of the monopole coupling $λ$ by a finite-size analysis we find values of the critical exponent $ν$ close to, however, different from the Gaussian value.

Alan C. Irving, UKQCD Collaboration

We argue that lattice simulations of full QCD with varying quark mass are best conducted at fixed lattice spacing rather than at fixed $β$. We present techniques which enable this to be carried out effectively, namely the tuning in bare parameter space and efficient stochastic estimation of the fermion determinant. Results and tests of the method are present

R. Frezzotti, K. Jansen

We compare the performance of the PHMC algorithm with the one of the HMC algorithm in practical simulations of lattice QCD. We show that the PHMC algorithm can lead to an acceleration of numerical simulations. It is demonstrated that the PHMC algorithm generates configurations carrying small isolated eigenvalues of the lattice Dirac operator and hence leads

D. B. Leinweber, J. I. Skullerud, A. G. Williams

The gluon propagator in Landau gauge is calculated in quenched QCD on a large (32^3X64) lattice at beta=6.0. In order to assess finite volume and finite lattice spacing artefacts, we also calculate the propagator on a smaller volume for two different values of the lattice spacing. New structure seen in the infrared region survives conservative cuts to the la

H. Neuberger

During the last several years a non-perturbative formulation of exact chiral symmetry on the lattice has been developed. I shall outline the main ideas of these developments and discuss prospects for the future. The focus will be on the basic concepts enciphered in a new jargon consisting of terms like ``infinite number of fermions&#39;&#39;, ``domain wall f

E143 collaboration

Measurements were made at SLAC of the cross section for scattering 29 GeV electrons from carbon at a laboratory angle of 4.5 degrees, corresponding to 0.03<x<0.1 and 1.3<Q^2<2.7 GeV^2. Values of R=sigma_L/sigma_T were extracted in this kinematic range by comparing these data to cross sections measured at a higher beam energy by the NMC collaboration. The res

OPAL Collaboration, G. Abbiendi et al

Di-jet production is studied in collisions of quasi-real photons radiated by the LEP beams at e+e- centre-of-mass energies 161 and 172 GeV. The jets are reconstructed using a cone jet finding algorithm. The angular distributions of direct and double-resolved processes are measured and compared to the predictions of leading order and next-to-leading order per

M. Rainer, A. Zhuk

Inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold M= M_0 x M_1 ...x M_n are investigated under dimensional reduction to a D_0-dimensional effective non-minimally coupled sigma-model which generalizes the familiar Brans-Dicke model. It is argued that the Einstein frame should be considered as the physical one. Th

J. Frauendiener

We discuss the issue of radiation extraction in asymptotically flat space-times within the framework of conformal methods for numerical relativity. Our aim is to show that there exists a well defined and accurate extraction procedure which mimics the physical measurement process. It operates entirely intrisically within $\scri^+$ so that there is no further

J. J. Halliwell

We address the issue of coupling variables which are essentially classical to variables that are quantum. Two approaches are discussed. In the first (based on collaborative work with L.Diósi), continuous quantum measurement theory is used to construct a phenomenological description of the interaction of a quasiclassical variable $X$ with a quantum variable $

James B. Hartle

Usually quantum theory is formulated in terms of the evolution of states through spacelike surfaces. However, a generalization of this formulation is needed for field theory in spacetimes not foliable by spacelike surfaces, or in quantum gravity where geometry is not definite but a quantum variable. In particular, a generalization of usual quantum theory is

G. Preosti, Y. M. Vilk, M. R. Norman

We study the pairing pseudogap in the spectral function as a function of interplane coupling. The analytical expressions for the self-energy in the critical regime are obtained for any degree of anisotropy. The frequency dependence of the self-energy is found to be qualitatively different in two and three dimensions, and the crossover from two to three dimen

Sergei Maslov, Yi-Cheng Zhang

We study the risk criterion for investments based on the drawdown from the maximal value of the capital in the past. Depending on investor&#39;s risk attitude, thus his risk exposure, we find that the distribution of these drawdowns follows a general power law. In particular, if the risk exposure is Kelly-optimal, the exponent of this power law has the borde

Victor M. Villalba, Ramiro Pino

We compute the energy levels of a 2D Hydrogen atom when a constant magnetic field is applied. With the help of a mixed-basis variational method, we calculate the energy eigenvalues of the 1S, 2P- and 3D- levels. We compare the computed energy spectra with those obtained via a generalization of the mesh point technique as well as the shifted 1/N method. We sh

Hans Nielsen

For a two dimensional electron system in a strong perpendicular magnetic field B, there are extended states at each Landau level. We show that if the inverse compressibility is negative, then the extended states float downward in energy when B decreases. We set up a condition for the case where all extended states are below the fermi energy in the low B limi

Javier Rodriguez-Laguna

A numerical real-space version of the Inverse Renormalization Group proposed by Gawedzky et al is developed. It has been tested to obtain the scaling behaviour of the random-forced heat equation in the short scales limit. Prospectives are described, and the most important target for the procedure is fully developed turbulence.

H. Rieger, F. Igloi

We study the first passage time properties of an integrated Brownian curve both in homogeneous and disordered environments. In a disordered medium we relate the scaling properties of this center of mass persistence of a random walker to the average persistence, the latter being the probability P_pr(t) that the expectation value <x(t)> of the walker&#39;s pos

V. F. Elesin, L. A. Openov

Formation of clusters of interlayer interstitial carbon atoms in graphite is studied by means of molecular dynamics simulation. It is shown that the deformation potential is attractive for interstitials located in one interlayer region and repulsive for interstitials located in different interlayer regions. As a result, relatively small interstitial clusters

Niurka R. Quintero, Angel Sanchez

The ac driven sine-Gordon equation is studied analytically and numerically, with the aim of providing a full description of how soliton solutions behave. To date, there is much controversy about when ac driven dc motion is possible. Our work shows that kink solitons exhibit dc or oscillatory motion depending on the relation between their initial velocity and

H. Kawano, R. Kajimoto, H. Yoshizawa, Y. Tomioka

We report inelastic neutron scattering results on the spin dynamics in the 50 % hole-doped manganites, Pr{1/2}Sr{1/2}MnO3 and Nd{1/2}Sr{1/2}MnO3. In the paramagnetic phase, these systems exhibit a ridge-type diffuse scattering, indicating a two-dimensional ferromagnetic (FM) correlation. With decreasing temperature, the systems enter the FM state, but simult

Michele Cini, Gianluca Stefanucci, Adalberto Balzarotti

By a canonical transformation of the three-band Hubbard model, we introduce an effective Hamiltonian for the propagation of two holes doped into the ground state of the Cu-O plane. When the pair belongs to the $^{1}B_{2}$ or $% ^{1}A_{2}$ Irreducible Representations of the C$_{4v}$ Group, the bare holes do not interact by the on-site repulsion; the effective

Claire Cardie, David Pierce

Finding simple, non-recursive, base noun phrases is an important subtask for many natural language processing applications. While previous empirical methods for base NP identification have been rather complex, this paper instead proposes a very simple algorithm that is tailored to the relative simplicity of the task. In particular, we present a corpus-based

V. Pagel, N. Carbonell, Y. Laprie, J. Vaissiere

A radio speech corpus of 9mn has been prosodically marked by a phonetician expert, and non expert listeners. this corpus is large enough to train and test an automatic boundary spotting system, namely a time delay neural network fed with F0 values, vowels and pseudo-syllable durations. Results validate both prosodic marking and automatic spotting of prosodic

Cheongho Han, Kyongae Chang

In this paper, we investigate the applicability of the astrometric method to the determination of the lens parameters for gravitational microlensing events toward both the LMC and the Galactic bulge. For this analysis, we investigate the dependency of the astrometrically determined angular Einstein ring radius, $Δ(θ_{\rm E}/θ_{\rm E,0})$, on the lens paramet

E. J. Ostrander, R. C. Nichol, K. U. Ratnatunga, R. E. Griffiths

We present a new, objectively selected, sample of galaxy overdensities detected in the Hubble Space Telescope Medium Deep Survey. These clusters/groups were found using an automated procedure which involved searching for statistically significant galaxy overdensities. The contrast of the clusters against the field galaxy population is increased when morpholo

Rudy Wijnands, Michiel van der Klis

We analyzed the rapid aperiodic X-ray variability of the recently discovered millisecond X-ray pulsar SAX J1808.4-3658. The power density spectrum is dominated by a strong band-limited noise component, which follows a power-law with index 1.0-1.3 at high frequencies with a break that varies between 0.25 and 1.6 Hz, below which the spectrum is relatively flat

S. Terebey, D. Van Buren, D. L. Padgett, T. Hancock

HST/NICMOS images of the class I protostar TMR-1 (IRAS04361+2547) reveal a faint companion with 10.0&#34; = 1400 AU projected separation. The central protostar is itself resolved as a close binary with 0.31&#34; = 42 AU separation, surrounded by circumstellar reflection nebulosity. A long narrow filament seems to connect the protobinary to the faint companio

Colleen A. Wilson, Mark H. Finger, D. Matthew Scott

We report on X-ray observations of the 66 s period transient X-ray pulsar Cep X-4 (GS 2138+56) with the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory (CGRO) and with the Rossi X-ray Timing Explorer (RXTE). Two outbursts from Cep X-4 were observed with BATSE in 1993 June-July and 1997 July. Pulse frequencies of 15.0941 +/-

S. F. Beaulieu, R. Elson, G. Gilmore, R. A. Johnson

We present details of the database from a large Cycle 7 HST project to study the formation and evolution of rich star clusters in the Large Magellanic Cloud (see Elson et al., this volume). Our data set, which includes NICMOS, WFPC2 and STIS images of the cores and outer regions of 8 clusters, will enable us to derive deep luminosity functions for the cluste

G. G. Raffelt

Recent observations of TeV gamma rays from distant sources provide new limits on the cosmic infrared background and thus on radiative decays of background neutrinos. I translate these limits into bounds on transition dipole moments and compare them with limits from the energy-loss of globular-cluster stars. The latter are more restrictive for neutrino masses

G. Clementini, R. G. Gratton, E. Carretta, C. Sneden

Homogeneous photometric data (Johnson V, B-V, V-K, Cousins V-I and Stromgren b-y), radial velocities, and abundances of Fe, O, Mg, Si, Ca, Ti, Cr and Ni are presented for 99 stars with high precision parallaxes measured by the Hipparcos satellite. These data have been previously used to assist the derivation of accurate distances and ages of galactic globula

J. Bednarz

The first-order cosmic ray acceleration at ultrarelativistic shocks is investigated using the Monte Carlo method. We apply a method of discrete particle momentum scattering as a model of particle pitch angle diffusion to reproduce highly anisotropic conditions at the shock wave. Shocks with Lorentz factors $γ$ up to 320 and varying magnetic field inclination

F. Aharonian

During 1997, the BL Lac Object Mkn 501 was the brightest known object in the TeV gamma-ray sky. The emission was characterized by dramatic variations in intensity with a mean flux exceeding by a factor of three the steady gamma-ray flux of the Crab Nebula. The stereoscopic HEGRA system of 4 Imaging Atmospheric Cherenkov Telescopes, with an energy threshold o

C. G. Tinney, X. Delfosse, T. Forveille, F. Allard

We present optical (6500-9200A) spectroscopy of eight cool dwarfs detected in a 231 square degree ``Mini-survey&#39;&#39; of the Deep NEar Infrared Survey (DENIS) data. We are able to confirm that the spectral types derived from the Mini-survey infrared spectroscopy are meaningful. We provide a spectral sequence which extends beyond the M-dwarf range and int

N. Dorey, V. V. Khoze, M. P. Mattis, S. Vandoren

We examine a certain 16-fermion correlator in {\cal N}=4 supersymmetric SU(N) gauge theory in 4 dimensions. Generalizing recent SU(2) results of Bianchi, Green, Kovacs and Rossi, we calculate the exact N-dependence of the effective 16-fermion vertex at the 1-instanton level, and find precise agreement in the large-N limit with the prediction of the type IIB

Igor Zutic, Oriol T. Valls

We study tunneling in ferromagnet/unconventional superconductor (F/S) junctions. We include the effects of spin polarization, interfacial resistance, and Fermi wavevector mismatch (FWM) between the F and S regions. Andreev reflection (AR) at the F/S interface, governing tunneling at low bias voltage, is strongly modified by these parameters. The conductance

W. Hollik, J. I. Illana, S. Rigolin, C. Schappacher

The one-loop Minimal Supersymmetric Standard Model (MSSM) contributions to the weak and electromagnetic dipole form factors of heavy fermions are reviewed. For the $Z$ boson on shell, the weak-magnetic and weak-electric dipole moments of the $τ$ lepton and the $b$ quark can be defined and directly connected to observables. But far from the $Z$ peak, the weak

Arvind Borde, Mark Trodden, Tanmay Vachaspati

Under certain circumstances, the collision of magnetic monopoles, topologically locked-in regions of false vacuum, leads to topological inflation and the creation of baby universes. The future evolution of initial data represented by the two incoming monopoles may contain a timelike singularity but this need not be the case. We discuss the global structure o

Vijay K. Narayanan, Andrew Gould

We propose and apply a test that can detect any systematic errors in the Hipparcos parallaxes towards the Hyades cluster at the level of 0.3 mas. We show that the statistical parallax method subsumes the classical moving cluster methods and provides more accurate and robust estimates of the distance and the first two moments of the velocity distribution of t

G. &#39;t Hooft

We glance back at the short period of the great discoveries between 1970 and 1974 that led to the restablishment of Quantum Field Theory and the discovery of the Standard Model of Elementary Particles, in particular Quantum Chromodynamics, and ask ourselves where we stand now.