August 1995 arXiv papers — page 8

A. Chaiken, R. P. Michel, M. A. Wall

Ion-beam sputtering has been used to prepare Fe/Si multilayers on a variety of substrates and over a wide range of temperatures. Small-angle x-ray diffraction and transmission electron microscopy experiments show that the layers are heavily intermixed although a composition gradient is maintained. When the spacer layer is an amorphous iron silicide, the magn

Lambros Cranias, Harris Papageorgiou, Stelios Piperidis

This paper addresses an important problem in Example-Based Machine Translation (EBMT), namely how to measure similarity between a sentence fragment and a set of stored examples. A new method is proposed that measures similarity according to both surface structure and content. A second contribution is the use of clustering to make retrieval of the best matchi

Jane C. Charlton, Christopher W. Churchill, Suzanne M. Linder

Study of Lyman-alpha absorption lines in the spectra of double line of sight (DLOS) quasars holds the promise of diagnosing the nature of the structures that give rise to Lyman-alpha absorption. Based on simulations of DLOS with various separations through a single population of absorbers, four tests have been designed to diagnose absorber mass distributions

Eli Tziperman, Steve Zebiak, Mark Cane

The mechanisms of interaction between the seasonal cycle and ENSO are investigated using the Zebiak and Cane ENSO prediction model. The most dominant seasonal effect is found to be due to the wind divergence field, as determined by the seasonal motion of the ITCZ, through its effect on the atmospheric heating. The next order seasonal effects are due to the s

Torsten Asselmeyer, Werner Ebeling

Several standard processes for searching minima of potential functions, such as thermodynamical strategies (simulated annealing) and biologically motivated selfreproduction strategies, are reduced to Schrödinger problems. The properties of the landscape are encoded in the spectrum of the Hamiltonian. We investigate this relation between landscape and spectru

Torsten Asselmeyer, Werner Ebeling, Helge Rose

We investigate an simple evolutionary game of sequences and demonstrate on this example the structure of fitness landscapes in discrete problems. We show the smoothing action of the genotype-phenotype mapping which still makes it feasible for evolution to work. Further we propose the density of sequence states as a classifying measure of fitness landscapes.

Thomas Ivey, J. M. Landsberg

In this paper we study critial isometric and minimal isometric embeddings of classes of Riemannian metrics which we call {\it quasi-$k$-curved metrics}. Quasi-$k$-curved metrics generalize the metrics of space forms. We construct explicit examples and prove results about existence and rigidity.

Dileep P. Jatkar, Bas Peeters

We demonstrate that type II string theory compactified on a singular Calabi-Yau manifold is related to $c=1$ string theory compactified at the self-dual radius. We establish this result in two ways. First we show that complex structure deformations of the conifold correspond, on the mirror manifold, to the problem of maps from two dimensional surfaces to $S^

R. Moessner

We calculate the probability distribution of a single component of peculiar velocities due to cosmic strings, smoothed over regions with a radius of several $h^{-1}$ Mpc. The probability distribution is shown to be Gaussian to good accuracy, in agreement with the distribution of peculiar velocities deduced from the 1.9 Jy IRAS redshift survey. Using the norm

H. Lu, C. N. Pope, E. Sezgin, K. S. Stelle

The elementary and solitonic supersymmetric $p$-brane solutions to supergravity theories form families related by dimensional reduction, each headed by a maximal (`stainless') member that cannot be isotropically dimensionally oxidized into higher dimensions. We find several new families, headed by stainless solutions in various dimensions $D\le 9$. In so

A. V. Sidorov

On the basis of the target mass corrections to structure functions of deep-inelastic scattering of leptons, we evaluate effective nucleon mass that turns out to be twice $M_{nucl.}$ for deep-inelastic scattering on the nucleus target and equals $M_{nucl.}$ for the hydrogen target.

L. Moriconi

The effects of three-dimensional perturbations in two-dimensional turbulence are investigated, through a conformal field theory approach. We compute scaling exponents for the energy spectra of enstrophy and energy cascades, in a strong coupling limit, and compare them to the values found in recent experiments. The extension of unperturbed conformal turbulenc

N. D. Lambert

We discuss the quantization of the ADHM sigma model. We show that the only quantum contributions to the effective theory come from the chiral anomalies and compute the first and second order terms. Finally the limit of vanishing instanton size is discussed.

Marek Nowakowski, Apostolos Pilaftsis

The minimal supersymmetric Standard Model with explicit R-parity nonconservation contains bilinear terms involving the left-handed lepton superfields and the Higgs chiral multiplet with hypercharge Y=+1, which cannot in general be rotated away in the presence of soft-supersymmetry- breaking interactions. These bilinear lepton-number-violating terms are found

Joe Sato

We examine a superpotential for an SO(10) GUT and show that if the parameters of the superpotential are in a certain region, the SO(10) GUT has an intermediate symmetry ${\rm SU(2)}_L \otimes {\rm SU(2)}_R \otimes {\rm SU(3)}_C \otimes {\rm U(1)}_{B-L}$ which breaks down to the group of the Standard Model at an intermediate scale $10^{10-12}$ GeV. In the mod

T. Christen, M. Buttiker

We present a current and charge conserving theory for the low frequency admittance of a two-dimensional electron gas connected to ideal metallic contacts and subject to a quantizing magnetic field. In the framework of the edge-channel picture, we calculate the admittance up to first order with respect to frequency. The transport coefficients in first order w

Jeffrey M. Rabin

The ``new fields" or ``superconformal functions" on $N=1$ super Riemann surfaces introduced recently by Rogers and Langer are shown to coincide with the Abelian differentials (plus constants), viewed as a subset of the functions on the associated $N=2$ super Riemann surface. We confirm that, as originally defined, they do not form a super vector spac

D. Rohrlich, S. Popescu

Quantum mechanics and relativistic causality together imply nonlocality: nonlocal correlations (that violate the CHSH inequality) and nonlocal equations of motion (the Aharonov-Bohm effect). Can we invert the logical order? We consider a conjecture that nonlocality and relativistic causality together imply quantum mechanics. We show that correlations preserv

M. Ardehali

We describe a cryptographic protocol in which Wheeler's delayed choice experiment is used to generate the key distribution. The protocol, which uses photons polarized only along one axis, is secure against general attacks.

C. Spieles, C. Greiner, H. Stoecker, J. P. Coffin

We calculate the evolution of quark-gluon-plasma droplets during the hadronization in a thermodynamical model. It is speculated that cooling as well as strangeness enrichment allow for the formation of strangelets even at very high initial entropy per baryon $S/A^{\rm init}\approx 500$ and low initial baryon numbers of $A_{\rm B}^{\rm init}\approx 30$. It is

Tomoyuki Maruyama

We simulate the fragmentation processes in the \alAu collisions at the bombarding energy 5 GeV/u using the simplified RQMD approach. The statistical decay calculation is connected to obtain the final state. >From the simulation we find that the residual nucleus created by this collision has a annular eclipse shape, and then expands more strongly to the trans

David Hoffman, Hermann Karcher

We survey what is known about minimal surfaces in $\bold R^3 $ that are complete, embedded, and have finite total curvature. The only classically known examples of such surfaces were the plane and the catenoid. The discovery by Costa, early in the last decade, of a new example that proved to be embedded sparked a great deal of research in this area. Many new

Amit Giveon, Martin Roček

By studying an effective action description of the coupling of charged gauge fields in N=2 SU(n) supersymmetric Yang-Mills theories, we can describe regions of moduli space where one or more of these fields becomes unphysical. We discuss subtleties in the structure of the moduli space for SU(3).

Frank Krahe

We study quantized Yang-Mills theory with massive vector fields in the framework of causal perturbation theory. The most general form of the interaction which is invariant under operator gauge transformations is pointed out. The generator of these transformations generally fails to be nilpotent. This defect, however, is easily cured by including scalar field

Douglas O. Carlson

We discuss the physics of single-top quark production and decay at hadron colliders, such as the Tevatron, the \tevstar~and the LHC. Our study includes how to measure the mass and the width of the top quark produced from a {\hbox{single-$t$}} or a single-$\bar t$ process. We also show how to probe new physics by studying the couplings of $t$-${b}$-$W$ and sh

S. J. Brodsky, A. H. Hoang, J. H. Kuhn, T. Teubner

Predictions for the angular distribution of massive quarks and leptons are presented, including QCD and QED corrections. Recent results for the fermionic part of the two-loop corrections to the electromagnetic form factors are combined with the BLM scale fixing prescription. Two distinctly different scales arise as arguments of $α_s(μ^2)$ near threshold: the

H. M. Asatrian, A. N. Ioannisian

The neutrino mass problem in $SU(4) \times SU(2)_{L} \times SU(2)_{R}$ SUSY GUT obtained from the compactification of $E_{8} \times E_{8}$ heterotic string is analyzed. The estimated values of the neutrino masses and mixing angles can explain the experimental data on solar neutrino flux.

A. Ali, D. London

We review and update the constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in the standard model and estimate the resulting CP asymmetries in $B$ decays, taking into account recent experimental and theoretical developments. In performing our fits, we use inputs from the measurements of the following quantities: (i) $\abseps$, the CP-

Kevin Cahill

By placing fermions only on the even sites of a lattice, one may halve the momentum spectrum and construct a theory without doublers. The interaction is nonlocal. The fermion propagator is not a sparse matrix, but because the unwanted fermionic states are absent from the formalism, it is 256 times smaller than the usual propagator.

Stefan Sint, Rainer Sommer

Starting from the Schrödinger functional, we give a non-perturbative definition of the running coupling constant in QCD. The spatial boundary conditions for the quark fields are chosen such that the massless Dirac operator in the classical background field has a large smallest eigenvalue. At one-loop order of perturbation theory, we determine the matching co

A. S. Hassan, M. Imachi, N. Tsuzuki, H. Yoneyama

Character expansion developed in real space renormalization group (RSRG) approach is applied to U(1) lattice gauge theory with $þ$-term in 2 dimensions. Topological charge distribution $P(Q)$ is shown to be of Gaussian form at any $\b$(inverse coupling constant). The partition function $Z(þ)$ at large volume is shown to be given by the elliptic theta functio

Jonathan L. Rosner

A project to detect the radio-frequency pulse associated with extensive air showers of cosmic rays is described briefly. Prototype work is being performed at the CASA/MIA array in Utah, with the intention of designing equipment that can be used in conjunction with the Auger Giant Array proposal.

R. Balasubramanian, B. S. Sathyaprakash, S. V. Dhurandhar

In this paper we deal with the measurement of the parameters of the gravitational wave signal emitted by a coalescing binary signal. We present the results of Monte Carlo simulations carried out for the case of the initial LIGO, incorporating the first post-Newtonian corrections into the waveform. Using the parameters so determined, we estimate the direction

Mikhail V. Karasev

A membrane technique, in which the symplectic and Ricci forms are integrated over surfaces in a complexification of the phase space, as well a ``creation" connection with zero curvature over lagrangian submanifolds, is used to obtain a unified quantization including a noncommutative algebra of functions, its representations, the Dirac axioms, coherent in

Howard L. Richards, Scott W. Sides, Mark A. Novotny, Per Arne Rikvold

Recently experimental techniques, such as magnetic force microscopy (MFM), have enabled the magnetic state of individual sub-micron particles to be resolved. Motivated by these experimental developments, we use Monte Carlo simulations of two-dimensional kinetic Ising ferromagnets to study the magnetic relaxation in a negative applied field of a grain with an

Erik Sorensen, Ian Affleck

We make a precise scaling conjecture, based on renormalization group ideas, regarding the screening cloud around an impurity spin in the Kondo effect and test it numerically using the Density Matrix Renormalization Group method.

Takashi Tonegawa, Makoto Kaburagi

Low-lying excited states as well as the ground state of the spin-1 antiferromagnetic Heisenberg chain with a spin-1/2 impurity are studied by means of a method of numerical diagonalization. The isotropic nearest-neighbor exchange coupling plus the uniaxial single-ion-type anisotropy energy is assumed for the host-system Hamiltonian. The energy differences be

István Szapudi, Alexander S. Szalay

We investigate in detail the effects of sampling on our ability to accurately reconstruct the distribution of galaxies from galaxy surveys. We use a simple probability theory approach, Bayesian classifier theory and Bayesian transition probabilities. We find the best Bayesian estimator for the case of low sampling rates, and show that even in the optimal cas

J. A. S. Lima, M. Trodden

We consider a nonsingular deflationary cosmological model with decaying vacuum energy density in universes of arbitrary spatial curvature. Irrespective of the value of $k$, the models are characterized by an arbitrary time scale $H_I^{-1}$ which determines the initial temperature of the universe and the largest value of the vacuum energy density, the slow de

Curtis S. Gehman, Fred C. Adams, Marco Fatuzzo, Richard Watkins

We study the linear evolution of small perturbations in self-gravitating fluid systems in two spatial dimensions; we consider both cylindrical and cartesian (i.e., slab) geometries. The treatment is general, but the application is to molecular clouds. We consider a class of equations of state which heuristically take into account the presence of turbulence;

Charles D. Dermer, Thomas J. Weiler

We review models of cosmological gamma-ray bursts (GRBs). The statistical and $γ$-ray transparency issues are summarized. Neutron-star and black-hole merger scenarios are described and estimates of merger rates are summarized. We review the simple fireball models for GRBs and the recent work on non-simple fireballs. Alternative cosmological models, including

Guenter Sigl

Extrapolation of perturbative nucleon spin fluctuation rates seems to suggest a strong suppression of weak interactions in supernova cores. We derive a new sum rule for the dynamical spin-density structure function which relates the spin fluctuation rate to the average nuclear interaction energy. For a bremsstrahlung like structure function profile we show t

Philip D. Mannheim

We make a first application of the linear gravitational potentials of the conformal gravity theory to the distance scale associated with clusters of galaxies, with the theory being found to give a reasonable value for the mean velocity of the virialized core of the typical Coma cluster, with no need to invoke the existence of dark matter.

R. S. Ellis

I review the general progress made in the study of galaxy evolution concentrating on the impact of systematic ground-based spectroscopic surveys of faint galaxies and high resolution imaging with Hubble Space Telescope. The picture emerging is one where massive regular galaxies have changed little since redshift $z\simeq$1, whereas there has been a marked de

Slavek M. Rucinski

The orbital period is a measure of the size of a contact binary star, and can be combined with color to predict its luminosity to a fraction of stellar magnitude. This novel application of contact binary systems currently has limitations that we describe in the text but is potentially capable of providing a reasonable means of estimating distances to stellar

F. J. Castander, R. G. Bower, R. S. Ellis, A. Aragon-Salamanca

Clusters of galaxies are the largest gravitationally bound systems and therefore provide an important way of studying the formation and evolution of the large scale structure of the Universe. Cluster evolution can be inferred from observations of the X-ray emission of the gas in distant clusters, but interpreting these data is not straightforward. In a simpl

Anders Wallander, Albert Zijlstra

Remote observing can be broadly defined as those observations where the astronomer is not physically present at the telescope. Different implementations presently in use include robotic telescopes, service observing with or without eavesdropping and active remote observing. We briefly describe the terminology, the pros and cons, the observing modes, and thei

Jean Audouze, Joseph Silk

We argue that extreme metal-poor stars show a high dispersion in metallicity, because their abundances are the outcome of very few supernova events. Abundance anomalies should appear because of the discrete range of progenitor masses. There is a natural metallicity threshold of $Z/Z_\odot\sim 10^{-4}$ below which one would expect to find very few, if any, ha

M. R. Pratt, C. Alcock, R. A. Allsman, D. Alves

Real-time detection of microlensing has moved from proof of concept in 1994 to a steady stream of events this year. Global dissemination of these events by the MACHO and OGLE collaborations has made possible intensive photometric and spectroscopic followup from widely dispersed sites confirming the microlensing hypothesis. Improved photometry and increased t

Jon Pumplin

Two possible ways to improve the mass resolution for observing hadronic top quark decay $t \to bW \to 3 jets$ are studied: (1) using fixed cones in the rest frames of the $t$ and $W$ to define the decay jets, instead of the traditional cones in the rest frame of the detector; and (2) using the jet angles in the top rest frame to measure $m_t/m_W$. By Monte C

James B. Hartle

Usual quantum mechanics requires a fixed, background, spacetime geometry and its associated causal structure. A generalization of the usual theory may therefore be needed at the Planck scale for quantum theories of gravity in which spacetime geometry is a quantum variable. The elements of generalized quantum theory are briefly reviewed and illustrated by gen

C. C. Homes, T. Timusk, D. A. Bonn, R. Liang

The c-axis polarized phonon spectra of single crystals of YBCO_{6+x} have been measured for the doping range x=0.5 -> 0.95, between 10 K and 300 K. The low background electronic conductivity, determined by Kramers-Kronig analysis of the reflectance, leads to a rich phonon structure. With decreased doping the five normally-active B_{1u} modes broaden and the

Harry G. Blundell, Stephen Godfrey

We calculated the decay widths of the $1^3F_2$ and $1^3F_4$ $s\bar{s}$ mesons and compared them to the measured properties of the $\xi(2220)$ (now known as the $f_4(2220)$). Including previously neglected decay modes we found that the width of the $^3F_2$ state $s\bar{s}$ meson is much larger than previously believed making this explanation unlikely. On the

Daniel Armand-Ugon, Rodolfo Gambini, Octavio Obregon, Jorge Pullin

We study several aspects of the canonical quantization of supergravity in terms of the Asthekar variables. We cast the theory in terms of a $GSU(2)$ connection and we introduce a loop representation. The solution space is similar to the loop representation of ordinary gravity, the main difference being the form of the Mandelstam identities. Physical states a

H. M. Asatrian, G. K. Yeghiyan

The Higgs boson mass problem is considered in the next to minimal supersymmetric standard model. The Higgs potential and the renormalization group equations for the gauge, Yukawa and scalar coupling constants are analyzed. The restrictions for the Higgs boson masses are found for the cases of presence and absence of spontaneous CP- violation.

T. Kloesch, T. Strobl

We provide a concise approach to generalized dilaton theories with and without torsion and coupling to Yang-Mills fields. Transformations on the space of fields are used to trivialize the field equations locally. In this way their solution becomes accessible within a few lines of calculation only. In this first of a series of papers we set the stage for a th

Alexander Altland, Martin R. Zirnbauer

A new universality class distinct from the standard Wigner-Dyson ones is identified. This class is realized by putting a metallic quantum dot in contact with a superconductor, while applying a magnetic field so as to make the pairing field effectively vanish on average. A random-matrix description of the spectral and transport properties of such a quantum do

A. Brignole, L. E. Ibanez, C. Munoz, C. Scheich

We study the structure of the soft SUSY-breaking terms obtained from some classes of 4-D strings under the assumption of dilaton/moduli dominance in the process of SUSY-breaking. We generalize previous analysis in several ways and in particular consider the new features appearing when several moduli fields contribute to SUSY breaking (instead of an overall m

Ewa L. Lokas, Roman Juszkiewicz, Francois R. Bouchet, Eric Hivon

We present a series of N-body experiments which confirm the reality of the previrialization effect. We also use weakly nonlinear perturbative approach to study the phenomenon. These two approaches agree when the rms density contrast, $σ$, is small; more surprisingly, they remain in agreement when $σ\approx 1$. When the slope of the initial power spectrum is

E. Knill

It was recently shown that for reasonable notions of approximation of states and functions by quantum circuits, almost all states and functions are exponentially hard to approximate [Knill 1995]. The bounds obtained are asymptotically tight except for the one based on total variation distance (TVD). TVD is the most relevant metric for the performance of a qu

E. Knill

In a recent preprint by Deutsch et al. [1995] the authors suggest the possibility of polynomial approximability of arbitrary unitary operations on $n$ qubits by 2-qubit unitary operations. We address that comment by proving strong lower bounds on the approximation capabilities of g-qubit unitary operations for fixed g. We consider approximation of unitary op

H. -W. Hammer, D. Drechsel

Parity violating (PV) contributions due to interference between $γ$ and $Z^0$ exchange are calculated for pion electroproduction off the nucleon. A phenomenological model with effective Lagrangians is used to determine the resulting asymmetry for the energy region between threshold and $Δ(1232)$ resonance. The $Δ$ resonance is treated as a Rarita-Schwinger f

E. Bender, K. W. Schmid, Amand Faessler

A systematic numerical investigation of a recently developed nuclear structure approach is presented which diagonalizes the Hamiltonian in the space of the symmetry-projected Hartree-Fock-Bogoliubov (HFB) vacuum and symmetry-projected quasiparticle excitations with respect to it. The underlying HFB transformation, which is assumed to be time-reversal and axi

P. Halse, P. Van Isacker, B. R. Barrett

Sum rules for $B(M1,0^+_1\rightarrow1^+_i)$ strength are derived for even-even nuclei in the isospin-invariant forms of the IBM, IBM-3 and IBM-4, in the cases where the respective natural internal symmetries, isospin $U$(3) and $U(6)\supset SU$(4), are conserved. Subsequently, the total strength is resolved into its component partial sums to the allowed isos

M. A. Fradkin

Elastic matrix distortion around a growing inclusion of a new phase is analyzed and the associated contribution to the Gibbs free energy is considered. The constant-composition transformation from the parent to product phase is considered within the frame of Landau theory of phase transitions. The volume misfit between the inclusion and matrix is assumed to

Emanuel Knill

Bennett's pebble game was introduced to obtain better time/space tradeoffs in the simulation of standard Turing machines by reversible ones. So far only upper bounds for the tradeoff based on the pebble game have been published. Here we give a recursion for the time optimal solution of the pebble game given a space bound. We analyze the recursion to obta

A. Dimakis, C. Tzanakis

The basic mathematical assumptions for autonomous linear kinetic equations for a classical system are formulated, leading to the conclusion that if they are differential equations on its phase space $M$, they are at most of the 2nd order. For open systems interacting with a bath at canonical equilibrium they have a particular form of an equation of a general

P. H. Damgaard, F. De Jonghe, K. Bering

One Lagrangian BRST quantization principle is that of imposing correct Schwinger-Dyson equations through the BRST Ward identities. In this paper we show how to derive the analogous $Sp(2)$-symmetric quantization condition in flat coordinates from an underlying $Sp(2)$-symmetric Schwinger-Dyson BRST symmetry. We also show under what conditions this can be rec

Martin J. Savage

The masses of the charmed baryons in the ${\bf 6}$ representation of $SU(3)$ obey an equal spacing rule at lowest order in $SU(3)$ breaking, ${\cal O}(m_s)$. We compute the corrections to this relation at order ${\cal O}(m_s^{3/2})$ arising from meson loops using chiral perturbation theory combined with heavy quark symmetry and find them to be small. We also

Aida X. El-Khadra

Quarkonia -- mesons made of a heavy quark and anti-quark -- have been extensively studied experimentally. Theoretical calculations of quarkonia based on lattice QCD are possible with control over the systematic errors. The comparison with experimental measurements of the quarkonia spectra leads to determinations of Standard Model parameters: the strong coupl

G. L. Kane, Graham D. Kribs, Stephen P. Martin, James D. Wells

We discuss the production and two-photon decay of the lightest Higgs boson (h) of the minimal supersymmetric standard model at the CERN Large Hadron Collider. Since the observability of the signal is quite model dependent, we conduct a thorough scan of the parameter space of minimal supersymmetry, including experimental and theoretical constraints. If kinema

R. N. Faustov, V. O. Galkin, A. Yu. Mishurov

The method of calculating electroweak decay matrix elements between heavy-heavy and heavy-light meson states is developed in the framework of relativistic quark model based on the quasipotential approach in quantum field theory. This method is applied for the study of exclusive semileptonic $B\toπ(ρ)$ decays. It is shown that the large value of the final $π(

Leif Lonnblad

The jet structure in events with Drell-Yan-produced W bosons is discussed, and a new model for describing such event is presented. The model is shown to explain recent measurements of the W-jet rapidity correlation and predicts a transverse energy flow at high W rapidities (corresponding to probing small-x partons in one of the incoming protons) higher than

Michelangelo L. Mangano

We review the physics of heavy quark and quarkonium production in high energy hadronic collisions. We discuss the status of the theoretical calculations and compare the current results with the most recent measurements from the Tevatron collider experiments.

H. Navelet, R. Peschanski, Ch. Royon

Using the colour dipole approach of the QCD perturbative (BFKL) Pomeron exchange in onium-onium scattering, we compute the cross section for small but hierarchically different onium sizes. A specific term dependent on the size-ratio is generated. In deep inelastic onium scattering it appears as a scaling violation contribution to the quark structure function

Luis P. Chimento, Alejandro S. Jakubi

We investigate cosmological models with a free scalar field and a viscous fluid. We find exact solutions for a linear and nonlinear viscosity pressure. Both yield singular and bouncing solutions. In the first regime, a de Sitter stage is asymptotically stable, while in the second case we find power-law evolutions for vanishing cosmological constant.

Donald E. Neville

The metric for gravitational plane waves has very high symmetry (two spacelike commuting Killing vectors). For this high symmetry, a simple renormalization of the lapse function is found which allows the constraint algebra for canonical quantum gravity to close; also, the vector constraint has the correct form to generate spatial diffeomorphisms. A measure i

Jacek Gruszczak

A physical interpretation of axioms of the differential structure of space-time is presented. Consequences of such interpretation for cosmic string's space-time with a scalar field are studied. It is shown that the assumption of smoothness of the scalar field leads either to modification of cosmic string's space-time global properties or to quantizat

Andrei Linde

In this review I consider several different issues related to inflation. I will begin with the wave function of the Universe. This issue is pretty old, but recently there were some new insights based on the theory of the self-reproducing inflationary universe. Then we will discuss stationarity of inflationary universe and the possibility to make predictions

J. Merikoski, T. Ala-Nissila

We study the dynamics of adatoms in a model of vicinal (11m) fcc metal surfaces. We examine the role of different diffusion mechanisms and their implications to surface growth. In particular, we study the effect of steps and kinks on adatom dynamics. We show that the existence of kinks is crucially important for adatom motion along and across steps. Our resu

Qisu Zou, Xiaoyi He

Pressure (density) and velocity boundary conditions inside a flow domain are studied for 2-D and 3-D lattice Boltzmann BGK models (LBGK) and new method to specify these conditions are proposed. These conditions are consistent with the boundary condition we proposed in a previous paper using an idea of bounce-back of non-equilibrium distribution. These condit

Ethan T. Vishniac, Changsong Zhang

Accretion disks in close binary systems are subject to a tidally driven parametric instability which leads to the growth of internal waves near the outer edges of such disks (Goodman 1993). These waves are important in understanding the torque exerted on a disk by tidal forces and may play a role in the structure of the disk at small radii. Here we calculate

Eli Waxman

The cosmic ray spectrum at $10^{19}{\rm eV}-10^{20}{\rm eV}$, reported by the Fly's Eye and the AGASA experiments, is shown to be consistent with a cosmological distribution of sources of protons, with a power law generation spectrum ${\rm d}\ln N/{\rm d}\ln E=-2.3\pm0.5$ and energy production rate of $4.5\pm1.5\times10^{44}{\rm erg}\ {\rm Mpc}^{-3}\ {\r

Mark J. Neeser, Stephen A. Eales, J. Duncan Law-Green, Patrick Leahy

Recent investigations of how the median size of extragalactic radio sources change with redshift have produced inconsistent results. Eales compared the radio and optical properties of a bright 3C and faint 6C sample and concluded that $D\propto(1+z)^{-1.1\pm0.5}$ ($Ω_0 = 0$), with $D$ being the median size of the radio sources at a given epoch and z the reds

A. Lecavelier des Etangs, A. Vidal-Madjar, R. Ferlet

We have evaluated the spatial distribution of dust in disks supplied by colliding or evaporating bodies spread in a small belt. The gradient of the distribution of dust expelled by radiation pressure is generally steeper than the one observed around \bp. It follows that, to generate the \bp\ disk distribution in such a way, one should extract relatively more

Vanda Silveira, Claudio M. G. de Sousa

Using the Newtonian approximation, we study rotating compact bosonic objects. The equations which describe stationary states with non-zero angular momentum are constructed and some numerical results are presented as examples. Limits on the applicability of the Newtonian approximation are discussed.

Michael R. Merrifield

It has been suggested that the peanut-shaped bulges seen in some edge-on disk galaxies are produced when bars in these galaxies buckle. This paper reviews the modelling which seeks to show how bars buckle, and I present a very simple new model which captures the essential physics of this process. I then discuss the problems in establishing observationally th

Dennis Gaitsgory

This paper is a continuation of ``Operads, Grothendieck topologies and deformation theory'' (alg-geom/9502010). We show how to develop a cohomology theory that would control deformations of a sheaf of associative algebras over a scheme by means of introducing an appropriate site and considering sheaves on it.

Bruce W. Roberts, M. E. J. Newman

We present a model for evolution and extinction in large ecosystems. The model incorporates the effects of interactions between species and the influences of abiotic environmental factors. We study the properties of the model by approximate analytic solution and also by numerical simulation, and use it to make predictions about the distribution of extinction

R. D. Sorkin, E. Woolgar

We recast the tools of ``global causal analysis'' in accord with an approach to the subject animated by two distinctive features: a thoroughgoing reliance on order-theoretic concepts, and a utilization of the Vietoris topology for the space of closed subsets of a compact set. We are led to work with a new causal relation which we call $K^+$, and in t

J. - G. Demers

As it is well known, the Minkowski vacuum appears thermally populated to a quantum mechanical detector on a uniformly accelerating course. We investigate how this thermal radiation may contribute to the classical nature of the detector's trajectory through the criteria of decoherence. An uncertainty-type relation is obtained for the detector involving th

Donald Marolf

This paper explores in some detail a recent proposal (the Rieffel induction/refined algebraic quantization scheme) for the quantization of constrained gauge systems. Below, the focus is on systems with a single constraint and, in this context, on the uniqueness of the construction. While in general the results depend heavily on the choices made for certain a

G. Hermann, C. Köhler, T. Kutter, W. Hofmann

Imaging air Cherenkov telescopes are usually triggered on a coincidence of two or sometimes more pixels, with discriminator thresholds in excess of 20 photoelectrons applied for each pixel. These thresholds required to suppress night-sky background are significantly higher than expected on the basis of a Poisson distribution in the number of night-sky photoe

S. Chakrabarty, P. K. Sahu

We study the effect of a magnetic field on the strage quark matter and apply to strange star. We found that the strange star becomes more compact in presence of strong magnetic field.

Jonathan Thornburg

This paper presents a detailed discussion of the ``Newton's method'' algorithm for finding apparent horizons in 3+1 numerical relativity. We describe a method for computing the Jacobian matrix of the finite differenced $H(h)$ function by symbolically differentiating the finite difference equations, giving the Jacobian elements directly in terms of the finite

Peter Kopietz

We calculate the single-particle Green's function of electrons that are coupled to acoustic phonons by means of higher dimensional bosonization. This non-perturbative method is {\it{not}} based on the assumption that the electronic system is a Fermi liquid. For isotropic three-dimensional phonons we find that the long-range part of the Coulomb interactio

S. Aoki, A. Ukawa, T. Umemura

The long-standing issue of the nature of the critical line of lattice QCD with the Wilson quark action at finite-temperatures, defined to be the line of vanishing pion screening mass, and its relation to the line of finite-temperature chiral tansition is examined. Analytical and numerical evidence are presented that the critical line forms a cusp at a finite

Andrea Dal Corso, Francesco Mauri, Angel Rubio

We present a general scheme for the computation of the time dependent (TD) quadratic susceptibility ($χ^{(2)}$) of an extended insulator obtained by applying the `$2n+1$' theorem to the action functional as defined in TD density functional theory. The resulting expression for $χ^{(2)}$ includes self-consistent local-field effects, and is a simple functio

G. Aldazabal, A. Font, L. E. Ibanez, A. M. Uranga

We study in detail the structure of Grand Unified Theories derived as the low-energy limit of orbifold four-dimensional strings. To this aim, new techniques for building level-two symmetric orbifold theories are presented. New classes of GUTs in the context of symmetric orbifolds are then constructed. The method of permutation modding is further explored and

Nguyen Ai Viet, Kameshwar C. Wali

We consider an internal space of two discrete points in the fifth dimension of the Kaluza-Klein theory by using the formalism of noncommutative geometry developed in a previous paper \cite{VIWA} of a spacetime supplemented by two discrete points. With the nonvanishing internal torsion 2-form there are no constraints implied on the vielbeins. The theory conta