August 1998 arXiv papers — page 17

Shahverdiev E. M

Chaos synchronization in one of charge-carrier dynamical systems in photoconductors is studied within both the replica and nonreplica approaches.It has been shown that using the boundedness of the solutions of the dynamical systems, nonreplica approach to chaos synchronization and Routh-Hurwitz criteria, it is possible to make negative all the conditional Ly

Masatoshi Imada, Fakher F. Assaad, Hirokazu Tsunetsugu, Yukitoshi Motome

Quantum transitions between the Mott insulator and metals by controlling filling in two-dimensional square lattice are characterized by a large dynamical exponent $z=4$ where the origin of unusual metallic properties near the Mott insulator are ascribed to the proximity of the transition. The scaling near the transition indicates the formation of flat disper

A. Kristensen, H. Bruus, A. Forchel, J. B. Jensen

The 0.7 conductance anomaly in the quantized conductance of trench etched GaAs quantum point contacts is studied experimentally. The temperature dependence of the anomaly measured with vanishing source-drain bias reveals the same activated behavior as reported earlier for top-gated structures. Our main result is that the zero bias, high temperature 0.7 anoma

Julio Gonzalo, Felisa Verdejo, Irina Chugur, Juan Cigarran

The classical, vector space model for text retrieval is shown to give better results (up to 29% better in our experiments) if WordNet synsets are chosen as the indexing space, instead of word forms. This result is obtained for a manually disambiguated test collection (of queries and documents) derived from the Semcor semantic concordance. The sensitivity of

Scott M. Zoldi, Jun Liu, Kapil M. S. Bajaj, Henry S. Greenside

By analyzing large-aspect-ratio spiral-defect-chaos (SDC) convection images, we show that the Karhunen-Loève decomposition (KLD) scales extensively for subsystem-sizes larger than 4d (d is the fluid depth), which strongly suggests that SDC is extensively chaotic. From this extensive scaling, the intensive length ξ_KLD is computed and found to have a differen

Giovanni Gallavotti

A mechanism for the validity of a local version of the fluctuation theorem, uniform in the system size, is discussed for a reversible chain of weakly coupled Anosov systems.

Giovanni Gallavotti

Chaotic systems arise naturally in Statistical Mechanics and in Fluid Dynamics. A paradigm for their modelization are smooth hyperbolic systems. Are there consequences that can be drawn simply by assuming that a system is hyperbolic? here we present a few model independent general consequences which may have some relevance for the Physics of chaotic systems.

Y. Alhassid, Yan V. Fyodorov

We derive the statistical limit of the spectral autocorrelation function and of the survival probability for the indirect photodissociation of molecules in the regime of non-overlapping resonances. The results are derived in the framework of random matrix theory, and hold more generally for any chaotic quantum system that is weakly coupled to the continuum.

R. E. Rothschild, D. L. Band, P. R. Blanco, D. E. Gruber

The Rossi X-ray Timing Explorer made a short (10 ks) observation of the radio galaxy Centaurus A on 14 August 1996. Analysis of the combined 2.5-240 keV spectrum has revealed a heavily absorbed(NH=9.42+/-0.24 e22 cm-2) primary power law (index=1.86+/-0.015) and an iron line due to fluorescence of cold matter (EW=162+/-25 eV). Flux from either a jet, primary

Christopher J. Stockdale, W. Romanishin, John J. Cowan

Using ROSAT, we have made the first deep X-ray observations of NGC 7331, discovering a nuclear X-ray source coincident with the previously determined radio and optical nuclear centers. Positions, luminosities, and fluxes of X-ray sources in the field are compared to previously identified radio and optical sources. The nucleus of NGC 7331 has been analyzed to

Stephen Eales, Simon Lilly, Walter Gear, Loretta Dunne

We present the first results of a deep unbiased submillimetre survey carried out at 450 and 850 microns. We detected 12 sources at 850 microns, giving a surface density of sources with 850-micron flux densities > 2.8mJy of of 0.49+-0.16 per square arcmin. The sources constitute 20-30% of the background radiation at 850 microns and thus a significant fraction

Daniel Koranyi, Margaret J. Geller, Joseph J. Mohr, Gary Wegner

We have measured redshifts and Kron-Cousins R-band magnitudes for a sample of galaxies in the poor cluster AWM 7. We have measured redshifts for 172 galaxies; 106 of these are cluster members. We determine the luminosity function from a photometric survey of the central 1.2 h^{-1} x 1.2 h^{-1} Mpc. The LF has a bump at the bright end and a faint-end slope of

W. N. Brandt, Th. Boller

Recent X-ray observations have advanced the study of ultrasoft Narrow-Line Seyfert 1 galaxies and have revealed strikingly clear correlations between optical emission line properties and the shape of the X-ray continuum. In particular, the strength of the soft X-ray excess relative to the hard X-ray power law appears to be directly related to the `primary ei

Charles F. Gammie, Ramesh Narayan, Roger Blandford

We consider the implications of recent infrared and radio observations of the nucleus of NGC 4258. There is no direct evidence that the nucleus has been steadily accreting on the viscous timescale of the outer masing disk, which is >~ 10^9 \yr. Thus the mass accretion rate in the outer disk need not be the same as in the inner accretion flow where most of th

Chung-Pei Ma, Todd A. Small, Wallace L. W. Sargent

We present a summary report on a detailed study of the mass and dynamical state of the Corona Borealis supercluster using the largest redshift survey of this object to date. Extensive $N$-body experiments are performed on simulated superclusters in both critically-flat and low-density cosmological models to test the robustness and errors of the mass estimato

Neil J. Cornish, Jeffrey R. Weeks

Since the dawn of civilization, humanity has grappled with the big questions of existence and creation. Modern cosmology seeks to answer some of these questions using a combination of mathematics and measurement. The questions people hope to answer include ``how did the universe begin?''; ``how will the universe end?''; ``is space finite or i

V. Celebonovic

Continuing previous work and using a simple change of variables, an analytical equation of state for a degenerate non-relativistic Fermi gas in a magnetic field is proposed.

Draza Markovic, Frederick K. Lamb

It has recently been suggested that gravitomagnetic precession of the inner part of the accretion disk, possibly driven by radiation torques, may be responsible for some of the quasi-periodic X-ray brightness oscillations (QPOs) at 20 - 300 Hz, observed in some low-mass binary systems containing accreting neutron stars and black hole candidates. We have expl

Vijay Balasubramanian, Per Kraus, Albion Lawrence, Sandip Trivedi

We describe probes of anti-de Sitter spacetimes in terms of conformal field theories on the AdS boundary. Our basic tool is a formula that relates bulk and boundary states -- classical bulk field configurations are dual to expectation values of operators on the boundary. At the quantum level we relate the operator expansions of bulk and boundary fields. Usin

Gustavo Medina Tanco, Alan A. Watson

The interesting possibility of measuring the masses of high energy cosmic ray particles by observing pairs of extensive air showers arriving at the earth nearly simultaneously was proposed some years ago by Gerasimova and Zatsepin (1960). Such showers would be created by the nuclear fragments originating as a result of the photodisintegration of massive nucl

Vadim Bednyakov, Amand Faessler, Sergey Kovalenko

We consider the neutrino oscillations within the minimal supersymmetric standard model with R-parity violation. The Super-Kamiokande atmospheric neutrino data are used to set limits on the bilinear R-parity violating terms. These very stringent limits are out of reach of the other experiments at present and in the near future.

BS Acharya, JM Figueroa-O'Farrill, CM Hull, B Spence

For supergavrity solutions which are the product of an anti-de Sitter space with an Einstein space X, we study the relation between the amount of supersymmetry preserved and the geometry of X. Depending on the dimension and the amount of supersymmetry, the following geometries for X are possible, in addition to the maximally supersymmetric spherical geometry

P. Podles

A survey of results on quantum Poincare groups and quantum Minkowski spaces is presented.

F. Abe

The lifetime of the Bs0 meson is measured using the semileptonic decay Bs0 --> Ds- l+ nu X. The data sample consists of about 110 pb^-1 of pp= collisions at sqrt{s} = 1.8 TeV collected by the CDF detector at Fermilab. Four different Ds- decay modes are reconstructed resulting in approximately 600 Ds-l+ signal events. The Bs0 meson lifetime is determined to b

K. Shiokawa, B. L. Hu

Bose-Einstein condensation of a relativistic ideal Bose gas in a rectangular cavity is studied. Finite size corrections to the critical temperature are obtained by the heat kernel method. Using zeta-function regularization of one-loop effective potential, lower dimensional critical temperatures are calculated. In the presence of strong anisotropy, the conden

A. Dellafiore, F. Matera, F. A. Brieva

A microscopic theory of linear response based on the Vlasov equation is extended to systems having spheroidal equilibrium shape. The solution of the linearized Vlasov equation, which gives a semiclassical version of the random phase approximation, is studied for electrons moving in a deformed equilibrium mean field. The deformed field has been approximated b

P. Herrera-Siklódy

The heavy singlet field is integrated out from the U_L(3) x U_R(3) Chiral Perturbation Theory and it is shown how its effects on the low-energy dynamics are reduced to effective vertices for the light mesons. The results are matched against the standard SU_L(3) x SU_R(3) Chiral Perturbation Theory in order to establish the relations between the coupling cons

D. A. Garanin, E. M. Chudnovsky

The quantum-classical transition of the escape rate of the spin model \cal H= -DS_z^2 - H_zS_z + B S_x^2 is investigated by a perturbative approach with respect to B [D. A. Garanin, J. Phys A {\bf 24}, L61 (1991)]. The transition is first order for B<B_c(H_z), the boundary line going to zero as B_c/D ~ 1 - H_z/(2SD) in the strongly biased limit. The range of

Ivan Horvath

It is shown that it is impossible to construct a free theory of fermions on infinite hypercubic Euclidean lattice in four dimensions that is: (a) ultralocal, (b) respects symmetries of hypercubic lattice, (c) corresponding kernel satisfies D gamma5 + gamma5 D = D gamma5 D (Ginsparg-Wilson relation), (d) describes single species of massless Dirac fermions in

Barbara Niethammer, Robert L. Pego

The classical Lifshitz-Slyozov-Wagner theory of domain coarsening predicts asymptotically self-similar behavior for the size distribution of a dilute system of particles that evolve by diffusional mass transfer with a common mean field. Here we consider the long-time behavior of measure-valued solutions for systems in which particle size is uniformly bounded

William E. Brown, Juan P. Garrahan, Ian I. Kogan, Alex Kovner

We analyze the instanton transitions in the framework of the gauge invariant variational calculation in the pure Yang-Mills theory. Instantons are identified with the saddle points in the integration over the gauge group which projects the Gaussian wave functional onto the gauge invariant physical Hilbert space. We show that the dynamical mass present in the

M. P. Blencowe, A. Y. Shik

We describe theoretically the acoustoconductance (AC) of quantum contacts. One characteristic of a contact which distinguishes it from a long, uniform wire is a strong, energy-dependent transmission probability. This has several consequences for AC. Electrons which are forward scattered by phonons can contribute to AC and, furthermore, AC can have positive s

N. V. Shevchenko, S. A. Rakityansky, S. A. Sofianos, V. B. Belyaev

The scattering length for the eta-meson collision with deuteron is calculated on the basis of rigorous few-body equations (AGS) for various eta-N input. The results obtained strongly support the existence of a resonance or quasi-bound state close to the eta-d threshold.

Dror Bar-Natan, Stavros Garoufalidis, Lev Rozansky, Dylan P. Thurston

Continuing the work started in Part I and II of this series (see q-alg/9706004 and math.QA/9801049), we prove the relationship between the Aarhus integral and the invariant $Ω$ (henceforth called LMO) defined by T.Q.T. Le, J. Murakami and T. Ohtsuki in q-alg/9512002. The basic reason for the relationship is that both constructions afford an interpretation as

Takeshi Chiba, Takashi Nakamura

The second derivative of the luminosity distance with respect to the redshift is written in terms of the deceleration parameter $q_0$. We point out that the third derivative contains the information regarding the sound speed of cosmic matter as well as the curvature of the universe. We restrict physically possible parameter ranges of the coefficients. It is

S. Carlip, R. Scranton

In a recent article in {\em Modern Physics Letters} {\bf A}, Gentry proposed a new static cosmological model that seeks to explain the Hubble relation as a combination of gravitational and Doppler red shifts. We show that Gentry&#39;s model, although supposedly based on general relativity, is inconsistent with the Einstein field equations; that it requires d

A. Lima-Santos

Via explicit diagonalization of the chiral $SU(N)_{2}$ fusion matrices, we discuss the possibility of representing the fusion ring of the chiral SU(N) models, at level K=2, by a polynomial ring in a single variable when $N$ is odd and by a polynomial ring in two variables when $N$ is even.

Robert Garisto, Lucien Hardy

We define a new measurement of entanglement, the entanglement of projection, and find that it is natural to write the entanglements of formation and assistance in terms of it. Our measure allows us to describe a new class of quantum erasers which restore entanglement rather than just interference. Such erasers can be implemented with simple quantum computer

Milos V. Lokajicek

The question has been solved whether Bell&#39;s inequalities cover all possible kinds of hidden-variable theories. It has been shown that the given nequalities can be hardly derived when the changing space position of photon-pair source together with the microscopic space structure of measuring devices are taken into account; and when corresponding impact pa

Ananda Dasgupta

Using the underlying su(2) algebra of the Jaynes-Cummings Model (JCM), we construct a time dependent interaction term that allows analytical solution for even off-resonance conditions. Exact solutions for the time evolution of any state has been found. The effect of detuning on the Rabi oscillations and the collapse and revival of inversion is indicated. It

Jeong-Young Ji, Jongbae Hong

For $N$-coupled generalized time-dependent oscillators, primary invariants and a generalized invariant are found in terms of classical solutions. Exact quantum motions satisfying the Heisenberg equation of motion are also found. For number states and coherent states of the generalized invariant, the uncertainties in positions and momenta are obtained.

S. Antoci, L. Mihich

Abraham&#39;s force seems to have been observed in very low frequency experiments, but the existence of an Abraham&#39;s force exerted by light is still to be proved. Twenty years ago Brevik proposed an experiment for checking what forces light exert in the interior of a transparent medium. It is argued that his proposal is feasible today with a detection me

Kenneth Dalton

We obtain Hamilton equations for the gravitational field and demonstrate the conservation of total energy. We derive the Poisson bracket equation for a general dynamical variable.

A. W. Thomas, S. V. Wright

We present an elementary introduction to some of the quark models used to understand the properties of light mesons and baryons. These lectures are intended for both theoretical and experimental graduate students beginning their study of the strong interaction.

F. M. Forger, R. S. Sachse

It has been proposed that the degeneracy of the genetic code,i.e., the phenomenon that different codons (base triplets) of DNA are transcribed into the same amino acid, may be interpreted as the result of a symmetry breaking process. In the initial work of Hornos & Hornos this picture was developed in the framework of simple Lie algebras. Here, we explore th

Mihai Ciucu

We prove that the number of cyclically symmetric, self-complementary plane partitions contained in a cube of side $2n$ equals the square of the number of totally symmetric, self-complementary plane partitions contained in the same cube, without explicitly evaluating either of these numbers. This appears to be the first direct proof of this fact. The problem

Mihai Ciucu, Christian Krattenthaler

We present new, simple proofs for the enumeration of five of the ten symmetry classes of plane partitions contained in a given box. Four of them are derived from a simple determinant evaluation, using combinatorial arguments. The previous proofs of these four cases were quite complicated. For one more symmetry class we give an elementary proof in the case wh

Joel David Hamkins

The automorphism tower of a group is obtained by computing its automorphism group, the automorphism group of THAT group, and so on, iterating transfinitely. Each group maps canonically into the next using inner automorphisms, and so at limit stages one can take a direct limit and continue the iteration. The tower is said to terminate if a fixed point is reac

Joel David Hamkins

The lottery preparation, a new general kind of Laver preparation, works uniformly with supercompact cardinals, strongly compact cardinals, strong cardinals, measurable cardinals, or what have you. And like the Laver preparation, the lottery preparation makes these cardinals indestructible by various kinds of further forcing. A supercompact cardinal kappa, fo

Tom Banks, Michael R. Douglas, Gary T. Horowitz, Emil Martinec

We explore the extent to which a local string theory dynamics in anti-de Sitter space can be determined from its proposed Conformal Field Theory (CFT) description. Free fields in the bulk are constructed from the CFT operators, but difficulties are encountered when one attempts to incorporate interactions. We also discuss general features of black hole dynam

Anastasia Doikou, Rafael I. Nepomechie

We formulate the notion of parity for the periodic XXZ spin chain within the Quantum Inverse Scattering Method. We also propose an expression for the eigenvalues of the charge conjugation operator. We use these discrete symmetries to help classify low-lying S^z=0 states in the critical regime, and we give a direct computation of the S matrix.

A. I. Sokolov, E. V. Orlov, V. A. Ul&#39;kov, S. S. Kashtanov

The RG expansions for renormalized coupling constants g_6 and g_8 of the 3D n-vector model are calculated in the 4-loop and 3-loop approximations respectively. Resummation of the RG series for g_6 by the Pade-Borel-Leroy technique results in the estimates for its universal critical values g_6^*(n) which are argued to deviate from the exact numbers by less th

Michael Klasen

We calculate three jet cross sections in photoproduction using exact matrix elements for the direct and resolved contributions. Numerical distributions are presented in a generic, irreducible set of variables that allows to disentangle the dynamics of partonic QCD subprocesses from each other and from pure phase space distributions. The results are compared

L. Burakovsky, T. Goldman

We study the origins of the inaccuracies of Schwinger&#39;s nonet mass, and the Sakurai mass-mixing angle, formulae for the pseudoscalar meson nonet, and suggest new versions of them, modified by the inclusion of the pseudoscalar decay constants. We use these new formulae to determine the pseudoscalar decay constants and mixing angle. The results obtained, $

L. Burakovsky, T. Goldman

We show that Regge trajectories for all flavors suggested recently by Filipponi et al. cannot combine both meson spectroscopy and additivity of intercepts. Other defects of these trajectories are also discussed.

Alexander Studenikin

A review of the theoretical and experimental values for the charged lepton (electron and muon) anomalous magnetic moment $a_l= (g_l-2)/2$ is presented. Employing the most accurate value for the fine structure constant $α^{-1}= 137.03599993(52) (0.0038 ppm)$ obtained \cite {Kin196} from the electron $(g-2)$ we find the new complete standard model prediction f

Mayumi Aoki, Noriyuki Oshimo

We discuss a decay rate asymmetry of the top squark, which is induced by a new source of CP violation intrinsic in the supersymmetric standard model. Although new sources of CP violation in this model are severely constrained from the electric dipole moment of the neutron, an unsuppressed CP-violating phase can still coexist with a top squark whose mass is a

Ian Balitsky

I demonstrate that the amplitude of the high-energy scattering can be factorized in a convolution of the contributions due to fast and slow fields. The fast and slow fields interact by means of Wilson-line operators -- infinite gauge factors ordered along the straight line. The resulting factorization formula gives a starting point for a new approach to the

Alexander Donnachie, Philip R. Page

We investigate theoretical interpretations of the 1.4 GeV J^PC exotic resonance reported by the E852 collaboration. A K-matrix analysis shows that the 1.4 GeV enhancement in the E852 eta pi data can be understood as an interference of a non-resonant Deck-type background and a resonance at 1.6 GeV.

Mark Strovink

I discuss new experimental results reported at this conference that bear directly on three previously reported anomalies: the excess of high Q^2 events at HERA; the excess of W + 1 jet events, relative to W&#39;s without jets, in D0 data; and the excess of high E_T inclusive jets observed by CDF. The new results all point in the direction of reducing the exp

P. Bialas, Z. Burda, D. Johnston

We discuss the phase diagram of the balls in boxes model, with a varying number of boxes. The model can be regarded as a mean-field model of simplicial gravity. We analyse in detail the case of weights of the form $p(q) = q^{-β}$, which correspond to the measure term introduced in the simplicial quantum gravity simulations. The system has two phases~: {\em e

S. Capozziello, A. Feoli, G. Lambiase

We propose a cosmological model which could explain, in a very natural way, the apparently periodic structures of the universe, as revealed in a series of recent observations. Our point of view is to reduce the cosmological Friedman--Einstein dynamical system to a sort of Schrödinger equation whose bound eigensolutions are oscillating functions. Taking into

S. Capozziello, R. de Ritis, A. A. Marino

For a general class of scalar--tensor gravity theories, we discuss how to recover asymptotic freedom regimes when cosmic time $t\to\pm\infty$. Such a feature means that the effective gravitational coupling $G_{eff}\to 0$, while cosmological solutions can asymptotically assume de Sitter or power--law behaviours. In our opinion, through this mechanism, it is p

Luis P. Chimento, Pablo Labraga

The solutions to the Einstein-Klein-Gordon equations without a cosmological constant are investigated for an exponential potential in a Bianchi VI_0 metric. There exists a two-parameter family of solutions which have a power-law inflationary behaviour when the exponent of the potential, k, satisfies k^2<2. In addition, there exists a two-parameter family of

Robert T Jantzen, Donato Bini, Paolo Carini

The somewhat fragmented body of current literature analyzing the properties of test particle motion in static and stationary spacetimes and in general spacetimes is pulled together and clarified using the framework of gravitoelectromagnetism.

R. Vilela Mendes

A survey is made of several aspects of the dynamics of networks, with special emphasis on unsupervised learning processes, non-Gaussian data analysis and pattern recognition in networks with complex nodes.

M. Henny, S. Oberholzer, C. Strunk, C. Schönenberger

We report low-temperature shot noise measurements of short diffusive Au wires attached to electron reservoirs of varying sizes. The measured noise suppression factor compared to the classical noise value $2e\left| I\right| $ strongly depends on the electric heat conductance of the reservoirs. For small reservoirs injection of hot electrons increases the meas

Joao Martins, R. Vilela Mendes

A correspondence is established between the elements of logic reasoning systems (knowledge bases, rules, inference and queries) and the hardware and dynamical operations of neural networks. The correspondence is framed as a general translation dictionary which, hopefully, will allow to go back and forth between symbolic and network formulations, a desirable

A. Manolescu, S. D. M. Zwerschke, M. Nita, U. J. Gossmann

We calculate the quantum states corresponding to the drifting and channeled classical orbits in a two-dimensional electron gas (2DEG) with strong magnetic and electric modulations along one spatial direction, $x$. The channeled states carry high, concentrated currents along the $y$ axis, and are confined in an effective potential well. The quantum and the cl

Samuel De Toro Arias, Christian Vanneste

The construction of discrete scalar wave propagation equations in arbitrary inhomogeneous media was recently achieved by using elementary dynamical processes realizing a discrete counterpart of the Huygens principle. In this paper, we generalize this approach to spinor wave propagation. Although the construction can be formulated on a discrete lattice of any

J. Tworzydlo, C. N. A. van Duin, J. Zaanen

It has been argued that the spin-dynamics in cuprate superconductors is governed by the proximity to a zero-temperature critical point. This critical point would be related to a transition from the superconducting phase to an ordered stripe state. Using a coupled spin-ladder model, we investigate to what extent the strong quantum spin-fluctuations in the ord

M. P. Blencowe

We first present a summary of recent results concerning the phononic energy transport properties of mesoscopic, suspended dielectric wires. We then discuss some related open problems concerning the fundamental lower limits on the vibrational damping rates of submicron-sized cantilever structures and also the possibility to create and detect quantum superposi

K. Pinn

I study the recurrence D(n)= D(D(n-1))+D(n-1-D(n-2)), D(1)=D(2)=1. Its definition has some similarity to that of Conway&#39;s sequence defined through a(n)= a(a(n-1))+a(n-a(n-1)), a(1)=a(2)=1. However, in contradistinction to the completely regular and predictable behaviour of a(n), the D-numbers exhibit chaotic patterns. In its statistical properties, the D

S. S. Manna, D. V. Khakhar

Avalanches of grain displacements can be generated by creating local voids within the interior of a granular material at rest in a bin. Modeling such a two-dimensional granular system by a collection of mono-disperse discs, the system on repeated perturbations, shows all signatures of Self-Organized Criticality. During the propagation of avalanches the compe

H. J. Schulz, G. Cuniberti, P. Pieri

In these lecture notes, the basic physics of Fermi liquids and Luttinger liquids is presented. Fermi liquids are discussed both from a phenomenological viewpoint, in relation to microscopic approaches, and as renormalization group fixed points. Luttinger liquids are introduced using the bosonization formalism, and their essential differences with Fermi liqui

Gerald H. Ristow

The dynamics and the transition to the centrifugal regime are studied analytically and numerically for particles in rotating drum. The importance of the particle-wall friction coefficient is demonstrated by studying first the motion of one non-rotating particle where three different regimes are found in the transition to the centrifugal motion. When a few ro

Rebecca Hwa

We present an empirical study of the applicability of Probabilistic Lexicalized Tree Insertion Grammars (PLTIG), a lexicalized counterpart to Probabilistic Context-Free Grammars (PCFG), to problems in stochastic natural-language processing. Comparing the performance of PLTIGs with non-hierarchical N-gram models and PCFGs, we show that PLTIG combines the best

Renyue Cen

The COBE microwave background temperature fluctuations and the abundance of local rich clusters of galaxies provide the two most powerful constraints on cosmological models. When all variants of the standard cold dark matter (CDM) model are subject to the combined constraint, the power spectrum of any model is fixed to $\sim 10%$ accuracy in both the shape a

Colin Borys, Scott C. Chapman, Douglas Scott

The SCUBA instrument on the James Clerk Maxwell Telescope has already had an impact on cosmology by detecting relatively large numbers of dusty galaxies at high redshift. Apart from identifying well-detected sources, such data can also be mined for information about fainter sources and their correlations, as revealed through low level fluctuations in SCUBA m

F. Douchin, P. Haensel

We address the question concerning the maximum density, at which nuclei (and more generally -- nuclear structures) can exist in neutron star interiors. An absolute upper bound to such a density is obtained using the bulk approximation, in which surface and Coulomb effects are neglected. A very good approximation to the limiting density is given by the thresh

Marie E. Machacek, Greg L. Bryan, Peter Anninos, Avery Meiksin

In this paper we review the importance of the Lyman alpha forest as a probe of structure formation in the universe. We first discuss the statistics used to describe the Lyman alpha forest and the numerical techniques used to produce simulated spectra of the forest from a given cosmological model. We then discuss the physical picture of the absorbing structur

Paul Martini, Patrick S. Osmer

We present a study of M dwarfs discovered in a large area, multicolor survey. We employ a combination of morphological and color criteria to select M dwarfs to a limiting magnitude in V of 22, the deepest such ground-based survey for M dwarfs to date. We solve for the vertical disk stellar density law and use the resulting parameters to derive the M dwarf lu

D. M. Worrall, M. Birkinshaw, R. A. Remillard, A. Prestwich

We present new X-ray, radio, and optical data for the unusual galaxy/cluster system J2310-437. Our results confirm the presence of an active nucleus, and suggest an interpretation as an anomalous BL Lac object of bulk relativistic Doppler factor < 2, with an optically deficient radio-to-X-ray spectrum. The radio, optical, and soft X-ray flux densities could

Richard S Ellis

NGST offers unprecedented opportunities for charting the `dark ages&#39; beyond the limits of the deep optical surveys conducted with HST. An equally important motivation, however, is a detailed physical understanding of the later stages of cosmic history including the period 2<z<5 when most galaxies are thought to assemble and undergo dramatic changes in th

M. E. Putman, B. K. Gibson, L. Staveley-Smith, G. Banks

Interactions between galaxies are common and are an important factor in determining their physical properties such as position along the Hubble sequence and star-formation rate. There are many possible galaxy interaction mechanisms, including merging, ram-pressure stripping, gas compression, gravitational interaction and cluster tides. The relative importanc

D. Elbaz, H. Aussel, C. J. Cesarsky, F. X. Desert

Before having exhausted the helium in its tank on April 8, 1998, the Infrared Space Observatory had time to perform several complementary surveys at various depths and areas within selected regions of the sky. We present the results of some of the surveys done with the mid-infrared camera, ISOCAM, on-board ISO, and more specifically those surveys which were

Dmitri Novikov, Adrian Melott, Brian Wilhite, Michael Kaufman

Within Abell galaxy clusters containing wide-angle tailed radio sources, there is evidence of a ``prevailing wind&#39;&#39; which directs the WAT jets. We study the alignment of WAT jets and nearby clusters to test the idea that this wind may be a fossil of drainage along large-scale supercluster axes. We also test this idea with a study of the alignment of

Alberto Conti, Julia D. Kennefick, Paul Martini, Patrick S. Osmer

We focus on the search for unresolved faint quasars and AGN in the crude combine images using a multicolor imaging analysis that has proven very successful in recent years. Quasar selection was carried out both in multicolor space and in &#34;profile space,&#34; defined as the multi-parameter space formed by the radial profiles of the objects in the differen

D. A. Ivanov, M. V. Feigel&#39;man

In a superconducting quantum point contact, dynamics of the superconducting phase is coupled to the transitions between the subgap states. We compute this coupling and derive the two-level Hamiltonian of the contact.

Guido Burkard, Daniel Loss, David P. DiVincenzo

We consider a new quantum gate mechanism based on electron spins in coupled semiconductor quantum dots. Such gates provide a general source of spin entanglement and can be used for quantum computers. We determine the exchange coupling J in the effective Heisenberg model as a function of magnetic (B) and electric fields, and of the inter-dot distance (a) with

R. Rajesh, Deepak Dhar

We solve exactly a special case of the anisotropic directed bond percolation problem in three dimensions, in which the occupation probability is 1 along two spatial directions, by mapping it to a five-vertex model. We determine the asymptotic shape of the ininite cluster and hence the direction dependent critical probability. The exponents characterising the

Thomas D. Cohen, James M. Hansen

An analytic expression for the ${}^1S_0$ phase shifts in nucleon-nucleon scattering is derived in the context of the Schrödinger equation in configuration space with a short distance cutoff and with a consistent power counting scheme including pionic effects. The scheme treats the pion mass and the inverse scattering length over the intrinsic short distance

Peter Forgacs, Jozsef Gyurusi

Static, spherically symmetric monopole solutions of a spontaneously broken SU(2) gauge theory coupled to a massive dilaton field are studied in detail in function of the dilaton coupling strength and of the dilaton mass.

Lothar Goettsche

Let (S,H) be a rational algebraic surface with an ample divisor. We compute generating functions for the Hodge numbers of the moduli spaces of H-stable rank 2 sheaves on S in terms of certain theta functions for indefinite lattices that were introduced in the paper alg-geom/9612020 written jointly with Don Zagier. If H lies in the closure of the ample cone a

Dirk Lehmann

In an effective theory containing only quark degrees of freedom, such as the extended Nambu-Jona-Lasinio model, the influence of the axial anomaly can be incorporated by a self-interaction of the &#39;t Hooft determinant type. I will show that despite the theshold problem related to the eta-prime meson this leads to a significant suppression of the eta-prime

John A. Vaccaro

A mean-density description of spatially-inhomogeneous Bose-condensed gases based on Bogoliubov&#39;s method is introduced. The description assumes only a large mean atomic density and so remains valid when the mean field collapses due to phase diffusion. A spread in the number of particles in the condensate is shown to lead to an anomalous coupling between t

Angelo Tartaglia

The paper treats the issue of the length of a rotating circumference as seen from on board the moving disk and from an inertial reference frame. It is shown that, properly defining a measuring process, the result is in both cases 2piR thus dissolving the Ehrenfest paradox. The same holds good when considering that, for the rotating observer, the perceived ra

Yoshiaki Sofue

High-resolution nuclear-to-outer rotation curves for Sb, SBb, Sc, and SBc galaxies show generally a steep nuclear rise and flat rotation from the disk to halo. The high-velocity central rotation indicates massive core within bulges. Since this characteristics is common to most galaxies, the high-velocity central rotation cannot be due to a particular orienta

G. Modanese

We propose a method for the approximate computation of the Green function of a scalar massless field Phi subjected to potential barriers of given size and shape in spacetime. This technique is applied to the case of a 3D gaussian ellipsoid-like barrier, placed on the axis between two pointlike sources of the field. Instead of the Green function we compute it

T. P. Singh

We give a characterization of the central shell-focusing curvature singularity that can form in the spherical gravitational collapse of a bounded matter distribution obeying the dominant energy condition. This characterization is based on the limiting behaviour of the mass function in the neighbourhood of the singularity. Depending on the rate of growth of t