July 2001 arXiv papers — page 4

C. Lacroix

These three metallic systems do not exhibit any magnetic ordering despite experiments show the existence of localized moments with large antiferromagnetic exchange: this is a consequence of the strong geometric frustration (Y(Sc)Mn_{2} and LiV_{2}O_{4} have the Pyrochlore structure, while beta-Mn has a more complicated frustrated structure). Another common f

Jean-Michel Courty, A. Heidmann, M. Pinard

Thermal noise of a mirror can be reduced by cold damping. The displacement is measured with a high-finesse cavity and controlled with the radiation pressure of a modulated light beam. We establish the general quantum limits of noise in cold damping mechanisms and we show that the optomechanical system allows to reach these limits. Displacement noise can be a

T. G. Wang, Y. J. Lu

Controversy regarding whether Narrow Line Seyfert 1 galaxies (NLS1s) follow the same black hole --- galactic bulge relation as normal galaxies has been raised by Mathur et al. (2001) and Ferrarese et al. (2001). In this paper, the correlation between the black hole mass and the velocity dispersion of the narrow line region, indicated by the [OIII] line width

John Schliemann, A. H. MacDonald

We investigate the stability of the collinear ferromagnetic state in kinetic exchange models for (III,Mn)V semiconductors with randomly distributed Mn ions >. Our results suggest that {\em noncollinear ferromagnetism} is commom to these semiconductor systems. The instability of the collinear state is due to long-ranged fluctuations invloving a large fraction

I. Pagonabarraga, E. Trizac, T. P. C. van Noije, M. H. Ernst

We present a molecular dynamics and kinetic theory study of granular material, modeled by inelastic hard disks, fluidized by a random driving force. The focus is on collisional averages and short distance correlations in the non-equilibrium steady state, in order to analyze in a quantitative manner the breakdown of molecular chaos, i.e. factorization of the

L. Cappiello, W. Mueck

We study the thermodynamic relations of conformal field theories (CFTs), which are holographically dual to anti-de Sitter-Schwarzschild bulk space-times. A Cardy-Verlinde formula is derived thermodynamically for CFTs living on S^n x R with S^n having an arbitrary radius. The Hawking-Page phase transition of the CFT is described using Landau's theory of p

UKQCD Collaboration, C. R. Allton, S. P. Booth, K. C. Bowler

We present results for the static inter-quark potential, lightest glueballs, light hadron spectrum and topological susceptibility using a non-perturbatively improved action on a $16^3\times 32$ lattice at a set of values of the bare gauge coupling and bare dynamical quark mass chosen to keep the lattice size fixed in physical units ($\sim 1.7$ fm). By compar

Bernd Kuckert

According to the Second Law of Thermodynamics, cycles applied to thermodynamic equilibrium states cannot perform work (passivity property of thermodyamic equilibrium states). In the presence of matter this can hold only in the rest frame of the matter, as moving matter drives, e.g., windmills and turbines. If, however, a homogeneous and stationary state has

E. Gaztanaga, P. Fosalba, R. A. C. Croft

We present new perturbation theory (PT) predictions in the Spherical Collapse (SC) model for the 2-point moments of the large-scale distribution of dark matter density in the universe. We assume that these fluctuations grow under gravity from small Gaussian initial conditions. These predictions are compared with numerical simulations and with previous PT res

E. L. Bratkovskaya, V. Yu. Grishina, L. A. Kondratyuk, M. Buescher

We investigate the cross section for the reaction $NN \to NNa_0$ near threshold and at medium energies. An effective Lagrangian approach with one-pion exchange is applied to analyze different contributions to the cross section for different isospin channels. The Reggeon exchange mechanism is also considered. The results are used to calculate the contribution

E. Papantonopoulos

Inflation is now a basic ingredient of the modern cosmology. After reviewing the basic characteristics of inflation, we briefly discuss inflation in string and brane theories, focusing on the problem of the exit from inflation in these theories. We present a model, based on type-0 string theory, in which our universe after the inflationary phase, passes smoo

Takehide Miyazaki, Hidefumi Hiura, Toshihiko Kanayama

On the basis of a topological discussion as well as an {\it ab initio} calculation, we show that it is possible to construct a fullerene-like Si cage by doping of a transition metal atom. The cage is a simple 3-polytope which maximizes the number of its inner diagonals close to the metal atom. Our topological argument also reveals how closely the structure o

Nouredine Zekri, Jean-Pierre Clerc

We study numerically statistical properties and dynamical disease propagation using a percolation model on a one dimensional small world network. The parameters chosen correspond to a realistic network of school age children. We found that percolation threshold decreases as a power law as the short cut fluctuations increase. We found also the number of infec

Bogdan G. Dimitrov

A cubic algebraic equation for the effective parametrizations of the standard gravitational Lagrangian has been obtained without applying any variational principle.It was suggested that such an equation may find application in gravity theory, brane, string and Rundall-Sundrum theories. The obtained algebraic equation was brought by means of a linear-fraction

Suhyoung Choi, William Goldman

We determine that the deformation space of convex real projective structures, that is, projectively flat torsion-free connections with the geodesic convexity property on a compact 2-orbifold of negative Euler characteristic is homeomorphic to a cell of certain dimension. The basic techniques are from Thurston's lecture notes on hyperbolic 2-orbifolds, an

D. L. Kaplan, S. R. Kulkarni, D. A. Frail, M. H. van Kerkwijk

We present HST/STIS, Keck J- and K_s-band, and VLA 332-MHz and 1400-MHz images of the region around the Soft Gamma-ray Repeater SGR 1900+14. No non-stellar sources were detected at the position of SGR 1900+14, giving 3-sigma limits of S_{332 MHz} < 6 mJy, S_{1.4 GHz} < 1.5 mJy, m_{50CCD} > 29.0 mag, J > 22.8 mag, K_s > 20.8 mag (point sources), and S_{332 MH

G. K. Brennen, I. H. Deutsch, C. J. Williams

We study the deterministic entanglement of a pair of neutral atoms trapped in an optical lattice by coupling to excited-state molecular hyperfine potentials. Information can be encoded in the ground-state hyperfine levels and processed by bringing atoms together pair-wise to perform quantum logical operations through induced electric dipole-dipole interactio

D. V. Shirkov

The paper is devoted to application of recently devised ghost-free Analytic Perturbation Theory (APT) for analysis of some QCD observables. We start with the discussion of the main problem of the perturbative QCD -- ghost singularities and with the resume of this trouble solution within the APT. By a few examples in the various energy and momentum transfer r

Stephen M. Barnett, David T. Pegg, John Jeffers, Ottavia Jedrkiewicz

We derive the master equation that governs the evolution of the measured state backwards in time in an open system. This allows us to determine probabilities for a given set of preparation events from the results of subsequent measurements, which has particular relevance to quantum communication.

Kh. M. Beshtoev

At electromagnetic interactions of particles there arises defect of masses, i.e. the energy is liberated since the particles of the different charges are attracted. It is shown that this change of the effective mass of a particle in the external electrical field (of a nucleus) results in displacement of atomic levels of electrons. The expressions describing

Vladimir A. Cherepenin, Victor V. Kulagin

The formation of relativistic electron mirror produced via ionization of thin solid target by ultraintense femtosecond laser pulse is considered with the help of computer simulations. It is shown that the reflection of weak counter-propagating wave from such a mirror can produce the coherent radiation in X-ray and gamma-ray bands. The spectrum of up-converse

F. Sattin

In this paper we study theoretically the process of electron capture between one-optical-electron atoms (e.g. hydrogenlike or alkali atoms) and ions at low-to-medium impact velocities ($v/v_e \approx 1$) working on a modification of an already developed classical In this work we present an improvement over the Over Barrier Model (OBM) described in a recent p

Daniel M. Zuckerman, Thomas B. Woolf

From a variety of long simulations of all-atom butane using both stochastic and fully-solved molecular dynamics, we have uncovered striking generic behavior which also occurs in one-dimensional systems. We find an apparently universal distribution of transition event durations, as well as a characteristic speed profile along the reaction coordinate. An appro

Daniel M. Zuckerman, Thomas B. Woolf

We perform an extrapolative analysis of &#34;fast-growth&#34; free-energy-difference (DF) estimates of a computer-modeled, fully-solvated ethane<->methanol transformation. The results suggest that extrapolation can greatly reduce the systematic error in DF estimated from a small number of very fast switches. Our extrapolation procedure uses block-averages of

Charles N. Baroud, Brendan B. Plapp, Zhen-Su She, Harry L. Swinney

Our velocity measurements on a quasi-two-dimensional turbulent flow in a rapidly rotating annulus yield an inverse cascade with E(k)~k^{-2} rather than the expected E(k)~k^{-5/3}. The probability distribution functions for longitudinal velocity differences, δ_v(r)=v(x+r)-v(x), are self-similar (scale independent) but strongly non-Gaussian, which suggests tha

L. Chkhaidze, T. Djobava, L. Kharkhelauri

Azimuthal correlations between protons and between pions have been investigated in central CNe, MgMg, CCu and OPb collisions at energy of 3.7 GeV/nucleon. &#34;Back-to-back&#34; (negative) correlations have been observed for protons in CNe, CCu and for pi^{-}-mesons in CNe and MgMg collisions. For pi^{-}-mesons &#34;side-by-side&#34; (positive) azimuthal cor

S. Pakuliak, S. Sergeev

Matrix elements of quantum intertwiner as well as the modified Q-operator for the quantum relativistic Toda chain at root of unity are constructed explicitly. Modified Q-operators make isospectrality transformations of quantum transfer matrices so that the classical counterparts of Q-operators correspond to the Baecklund isospectrality transformations of the

R. Aldrovandi, A. L. Barbosa

A geometrization of the Yang-Mills field, by which an SU(2) gauge theory becomes equivalent to a 3-space geometry - or optical system - is examined. In a first step, ambient space remains Euclidean and current problems on flat space can be looked at from a new point of view. The Wu-Yang ambiguity, for example, appears related to the multiple possible torsion

Nils Berglund, Barbara Gentz

We investigate the properties of hysteresis cycles produced by a one-dimensional, periodically forced Langevin equation. We show that depending on amplitude and frequency of the forcing and on noise intensity, there are three qualitatively different types of hysteresis cycles. Below a critical noise intensity, the random area enclosed by hysteresis cycles is

Aaron Robertson

We give two lower bound formulas for multicolored Ramsey numbers. These formulas improve the bounds for several small multicolored Ramsey numbers.

Michael G. Eastwood, C. Robin Graham

This paper studies microlocal regularity properties of the distributions f on a strongly noncharacteristic submanifold E of a hypo-analytic manifold M that arise as the boundary values of solutions on wedges in M with edge E. The hypo-analytic wave-front set of f in the sense of Baouendi-Chang-Treves is constrained as a consequence of the fact that f extends

Dan Burghelea, Stefan Haller

For a closed symplectic manifold $(M,ω)$, a compatible almost complex structure $J$, a 1-periodic time dependent symplectic vector field $Z$ and a homotopy class of closed curves $γ$ we define a Floer complex based on 1-periodic trajectories of $Z$ in the homotopy class $γ$. We suppose that the closed 1-form $i_{Z_t}ω$ represents a cohomology class $β(Z):=β$

Yogish I. Holla, Nitin Nitsure

This paper begins with a description of cohomological invariants of non-degenerate quadric bundles, in terms of the cohomology rings of the classifying spaces of the general orthogonal groups. Following this, the Main Theorem of the paper determines the behavior of these invariants under the Gysin boundary map, when a quadric bundle degenerates over a diviso

Bin Wang, Elcio Abdalla, R. B. Mann

We consider the evolution of a scalar field coupled to curvature in topological black hole spacetimes. We solve numerically the scalar wave equation with different curvature-coupling constant $ξ$ and show that a rich spectrum of wave propagation is revealed when $ξ$ is introduced. Relations between quasinormal modes and the size of different topological blac

Kimball A. Milton

If quantum fields exist in extra compact dimensions, they will give rise to a quantum vacuum or Casimir energy. That vacuum energy will manifest itself as a cosmological constant. The fact that supernova and cosmic microwave background data indicate that the cosmological constant is of the same order as the critical mass density to close the universe supplie

Jacques Bros, Henri Epstein

A new presentation of the Borchers-Buchholz result of the Lorentz-invariance of the energy-momentum spectrum in theories with broken Lorentz symmetry is given in terms of properties of the Green&#39;s functions of microcausal Bose and Fermi-fields. Strong constraints based on complex geometry phenomenons are shown to result from the interplay of the basic pr

Elisabeth Kraus

We extend the gauge coupling of Super-Yang-Mills theories to an external superfield composed out of a chiral and an antichiral superfield and perform renormalization in the extended model. In one-loop order we find an anomalous breaking of supersymmetry which vanishes in the limit to constant coupling. The anomaly arises form non-local contributions and its

V. A. Karmanov, J. Carbonell, M. Mangin-Brinet

We show that in the system of two fermions interacting by scalar exchange, the solutions for J$^π$=$0^+$ bound states are stable without any cutoff regularization, for values of the coupling constant $α$ below a critical value $α_c$. This latter is calculated from an eigenvalue equation.

M. Mangin-Brinet, J. Carbonell, V. A. Karmanov

The bound state solutions of two fermions interacting by a scalar exchange are obtained in the framework of the explicitly covariant light-front dynamics. The stability with respect to cutoff of the J$^π$=$0^+$ and J$^π$=$1^+$ states is studied. The solutions for J$^π$=$0^+$ are found to be stable for coupling constants $α={g^2\over4π}$ below the critical va

Mariano Cadoni, Paolo Carta

We investigate two-dimensional dilaton gravity models with a power-law dilaton potential, whose black hole solutions contain, among others, the dimensional reduction of the Schwarzschild black hole, the Anti-de Sitter black hole and Rindler spacetime. We show that the ground state of these models satisfies simple transformation laws under the SL(2,R) conform

Massimo Giovannini

Thick branes obtained from a bulk action containing Gauss-Bonnet self-interactions are analyzed in light of the localization properties of the various modes of the geometry. The entangled system describing the localization of the tensor, vector and scalar fluctuation is decoupled in terms of variables invariant for infinitesimal coordinate transformations. T

Brook Williams

The motion of a test Dq-brane in a Dp-brane background is studied. The induced metric on the test brane is then interpreted as the cosmology of the test brane universe. One is then able to resolve the resulting cosmological singularities. In particular, for a D3-brane in a D5-brane background, one finds a 3+1 dimensional FRW universe with equation of state $

T. S. Kosmas, Sergey Kovalenko, Ivan Schmidt

We found that in supersymmetric models with R-parity non-conservation the b-quarks may appreciably contribute to exotic neutrinoless muon-electron conversion in nuclei via the triangle diagram with two external gluons. This allowed us to extract previously overlooked constraints on the third generation trilinear R-parity violating parameters significantly mo

Peter Filip, Evgeni E. Kolomeitsev

Production of $ϕ$ mesons is considered in the course of heavy-ion collisions at SPS energies. We investigate the possible difference in momentum distributions of $ϕ$ mesons measured via their leptonic ($μ^+μ^-$) and hadronic ($K^+K^-$) decays. Rescattering of secondary kaons in the dense hadron gas together with the influence of in-medium kaon potential can

G. Moreau, M. Chemtob

Based on the R-parity violation option of the minimal supersymmetric Standard Model, we examine the scenario where the massive gravitino, relic from the hot big-bang, is the lightest supersymmetric particle and can decay through one or several of the trilinear R-parity violating interactions. We calculate the rates of the gravitino decay via the various thre

Aldo Deandrea

I consider a model based on a quark--meson interaction Lagrangian. The transition amplitudes are evaluated by computing diagrams in which heavy and light mesons are attached to quark loops. The light chiral symmetry relations and the heavy quark spin-flavour symmetry dictated by the heavy quark effective theory are implemented. The model allows to compute th

Vladimir G. Baryshevsky, Olga M. Lugovskaya

The spectral-angular and angular distributions of parametric X-radiation for case of backward diffraction (particular case of Bragg geometry scheme) is discussed. It is shown that in case of Bragg geometry it is necessary to use dynamical approach for PXR consideration. The comparison of the theory and experiment is carried out.

A. E. Kaloshin, A. E. Radzhabov

We study the effect of unitary mixing of scalar and vector fields in general $ξ$ gauge. This effect takes place for non-conserved vector currents and $ξ$ gauge generates some additional problems with unphysical scalar field. We obtained solutions of Dyson-Schwinger equations and perfomed the renormalization of full propagators. The key feature of renormaliza

Houri Ziaeepour

We obtain a class of solutions for the AdS$_5$ two-brane models by imposing the observed value of cosmological constant and Newton coupling constant on the visible brane. When all terms up to the first order of matter density are included, the cosmological evolution on the observable brane depends on the equation of state of the matter and consequently when

Lawrence K Gibbons

The proposed experimental program (CLEO-c) for a charm factory based on a modification of the Cornell Electron Storage Ring is summarized. The prospects for R measurements over the range 3 GeV to 7 GeV are examined in detail. Adapted from &#34;CLEO-c and CESR-c: A New Frontier of Weak and Strong Interactions&#34;, the CLEO-c project description, by the CLEO

The DELPHI Collaboration, P. Abreu

Lifetime and oscillations of B0s mesons have been studied in events with a large transverse momentum lepton and a Ds of opposite electric charge in the same hemisphere, selected from about 3.6 million hadronic Z0 decays accumulated by DELPHI between 1992 and 1995. The B0s lifetime and the fractional width difference between the two physical B0s states have b

The DELPHI Collaboration, P. Abreu

This paper describes a measurement of the Michel parameters, η, ρ, ξ, ξδ, and the average ν_τ helicity, h_{ν_τ}, in tau lepton decays together with the first measurement of the tensor coupling in the weak charged current. The tau+tau- pairs were produced at the LEP e+e- collider at CERN from 1992 through 1995 in the DELPHI detector. Assuming lepton universal

B. G. Dimitrov

The purpose of this paper is to propose the implementation of some methods from algebraic geometry in the theory of gravitation, and more especially in the variational formalism. It has been assumed that the metric tensor depends on two vector fields, defined on a manifold, and also that the gravitational Lagrangian depends on the metric tensor and its first

Erik D. Demaine, Martin L. Demaine, David Eppstein

We show that, in John Conway&#39;s board game Phutball (or Philosopher&#39;s Football), it is NP-complete to determine whether the current player has a move that immediately wins the game. In contrast, the similar problems of determining whether there is an immediately winning move in checkers, or a move that kings a man, are both solvable in polynomial time

Nguyen Hoang Phuong, Guido Germano, Friederike Schmid

Density functional theories such as the Poniewierski-Stecki theory relate the elastic properties of nematic liquid crystals with their local liquid structure, i.e., with the direct correlation function (DCF) of the particles. We propose a way to determine the DCF in the nematic state from simulations without any approximations, taking into account the depend

Min Ouyang, Jin-Lin Huang, Charles M. Lieber

We characterized the energy band dispersion near the Fermi level in single-walled carbon nanotubes using low-temperature scanning tunneling microscopy. Analysis of energy dependent standing wave oscillations, which result from quantum interference of electrons resonantly scattered by defects, yield a linear energy dispersion near EF, and indicate the importa

You-Quan Li, Shi-Jian Gu, Zu-Jian Ying, Ulrich Eckern

Motivated by the experiment of two-component Bose-Einstein condensates produced in magnetically trapped $^{87}Rb$, we study one dimensional Boson systems with repulsive $δ$-function interaction in the presence of SU(2) intrinsic degree of freedom by means of coordinate Bethe ansatz. The ground state and low-lying excitations are solved by both numerical and

Elena Bascones, Francisco Guinea

We analyze the influence of the structure within a SNS junction on the multiple Andreev resonances in the subgap I-V characteristics. Coherent interference processes and incoherent propagation in the normal region are considered. The detailed geometry of the normal region where the voltage drops in superconducting contacts can lead to observable effects in t

Riccardo A. G. Cinelli, Vittorio Pellegrini, Aldo Ferrari, Paolo Faraci

A single-biomolecule optical toggle-switch is demonstrated based on a mutated green fluorescent protein (GFP). We have exploited molecular biology techniques to tailor GFP molecular structure and photophysical properties and give it optically-controlled bistability between two distinct states. We present optical control of the fluorescence dynamics with two

C. Bernhard, T. Holden, J. Humlíček, D. Munzar

The in-plane dielectric response of detwinned YBa$_{2}$Cu$_{3}$O$_{6.95}$ has been studied by far-infared ellipsometry. A surprisingly lare number of in-plane polarized modes are observed. Some of them correspond to pure phonon modes. Others posses a large electronic contribution which strongly increases in the superconducting state. The free carrier respons

Jeroen van den Brink

We study the recently observed orbital excitations, orbitons, and treat electron-electron correlations and lattice dynamics on equal footing. It is shown that the orbiton energy and dispersion are determined by both correlations and lattice-vibrations. The electron-phonon coupling causes satellite structures in the orbiton spectral function and the elementar

P. LeClair, J. K. Ha, H. J. M. Swagten, C. H. van de Vin

A magnetic &#34;spin filter&#34; tunnel barrier, sandwiched between a non-magnetic metal and a magnetic metal, is used to create a new magnetoresistive tunnel device, somewhat analogous to an optical polarizer-analyzer configuration. The resistance of these trilayer structures depends on the relative magnetization orientation of the spin filter and the ferro

P. LeClair, J. T. Kohlhepp, C. H. van de Vin, H. Wieldraaijer

Utilizing Co/Al$_2$O$_3$/Co magnetic tunnel junctions (MTJs) with Co electrodes of different crystalline phases, a clear relationship between electrode structure and junction transport properties is presented. For junctions with one fcc(111) textured and one polycrystalline (poly-phase and poly-directional) Co electrode, a strong asymmetry is observed in the

Sigmund Kohler, Fernando Sols

We study the decay of a two-component Bose-Einstein condensate with negative effective interaction energy. With a decreasing atom number due to losses, the atom-atom interaction becomes less important and the system undergoes a transition from a bistable Josephson regime to the monostable Rabi regime, displaying oscillations in phase and number. We study the

U. Al Khawaja, H. T. C. Stoof

We explore the nonlinear coupling of the three scissors modes of an anisotropic Bose-Einstein condensate. We show that only when the frequency of one of the scissors modes is twice the frequency of another scissors mode, these two modes can be resonantly coupled and a down conversion can occur. We perform the calculation variationally using a gaussian trial

Kurt Broderix, Henning Löwe, Peter Müller, Annette Zippelius

Within the framework of a simple Rouse-type model we present exact analytical results for dynamical critical behaviour on the sol side of the gelation transition. The stress-relaxation function is shown to exhibit a stretched-exponential long-time decay. The divergence of the static shear viscosity is governed by the critical exponent $k=ϕ-β$, where $ϕ$ is t

Mendeli H. Vainstein, Jeferson J. Arenzon

The Prisoner&#39;s dilemma is the main game theoretical framework in which the onset and maintainance of cooperation in biological populations is studied. In the spatial version of the model, we study the robustness of cooperation in heterogeneous ecosystems in spatial evolutionary games by considering site diluted lattices. The main result is that due to di

L. S. Mohan, K. Kesava Rao, Prabhu R. Nott

A rigid-plastic Cosserat model for slow frictional flow of granular materials, proposed by us in an earlier paper, has been used to analyze plane and cylindrical Couette flow. In this model, the hydrodynamic fields of a classical continuum are supplemented by the couple stress and the intrinsic angular velocity fields. The balance of angular momentum, which

N. Shibata, K. Ueda

Thermodynamic properties of the S=1/2 Heisenberg chain in transverse staggered magnetic field H^y_s and uniform magnetic field H^x perpendicular to the staggered field is studied by the finite-temperature density-matrix renormalization-group method. The uniform and staggered magnetization and specific heat are calculated from zero temperature to high tempera

R. Mahendiran, C. Martin, A. Maignan, M. Hervieu

We investigated magnetic, magnetotransport and magnetostriction properties of the A-type antiferromagnet Pr$_{0.46}$Sr$_{0.54}$MnO$_3$ which undergoes a first order paramagnetic-antiferromagnetic transition below T$_N$ = 210 K while cooling and T$_N$ = 215 K while warming. The zero field ($μ_0$H = 0 T) resistivity shows a sudden jump at T$_N$ and a small bum

Prabal K. Maiti, Yves Lansac, Matthew A. Glaser, Noel A. Clark

We have developed a class of idealized models of chromonic molecules which are miscible in water, but which can form aggregates which in turn organize into lyotropic liquid crystal (LC) phases. By carrying out Monte Carlo simulation in a binary mixture of model chromonic and water molecules, we have studied the effect of concentration and molecular shape on

Prabal K. Maiti, Yves Lansac, Matthew A. Glaser, Noel A. Clark

Recent experiments indicate that doping low concentrations of bent-core molecules into calamitic smectic solvents can induce anticlinic and biaxial smectic phases. We have carried out Monte Carlo (MC) simulations of mixtures of rodlike molecules (hard spherocylinders with length/breadth ratio $L_{\rm rod}/D = 5$) and bow- or banana-shaped molecules (hard sph

Dennis Zaritsky, Anthony H. Gonzalez, Amy E. Nelson, Julianne J. Dalcanton

We present the Las Campanas Distant Cluster Survey, which has produced over a thousand galaxy cluster candidates at 0.35 < z < 1.1 (see Gonzalez et al. 2001 for the full catalog). We discuss the technique that enabled us to use short (~ 3 min) exposures and a small (1m) telescope to efficiently survey ~ 130 sq. deg. of sky. Follow-up imaging and spectroscopy

Alison L. Coil, Marc Davis, Istvan Szapudi

The DEEP2 project will obtain redshifts for ~60,000 galaxies between z~0.7-1.5 in a comoving volume of 7 10^6 Mpc/h^3 for an LCDM universe. The survey will map four separate 2 by 0.5 degree strips of the sky. To study the expected clustering, we have constructed mock galaxy catalogs from the GIF Virgo Consortium simulations. We present two- and three-point c

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

GRB 970828 was the first well-localized gamma-ray burst (GRB) X-ray afterglow for which no optical afterglow was found despite a prompt, deep search down to R_lim ~ 24.5 mag. We report the discovery of a short-lived radio flare within the X-ray localization error circle of this burst. Such radio flares are seen in about 25% of GRB afterglows and their origin

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

Observations of GRB host galaxies and their environments in general can provide valuable clues about the nature of progenitors. Bursts are associated with faint, <R> ~ 25 mag, galaxies at cosmological redshifts, <z> ~ 1. The host galaxies span a range of luminosities and morphologies, and appear to be broadly typical for the normal, evolving, actively star-f

R. J. Weymann, S. N. Vogel, S. Veilleux, H. W. Epps

We report a new Fabry-Perot search for Halpha emission from the intergalactic cloud HI 1225+01 in an attempt to measure the low redshift ionizing background radiation. We set a new 2 sigma upper limit on Halpha emission of 8 mR (5 x 10^{-20} ergs cm^{-2} s^{-1} arcsec^{-2}). Conversion of this limit to limits on the strength of the ionizing background requir

Paul Goudfrooij, M. Victoria Alonso, Claudia Maraston, Dante Minniti

The giant merger remnant galaxy NGC 1316 (Fornax A) is an ideal probe for studying the long-term effects of a past major merger on star cluster systems, given its spectroscopically derived merger age of ~3 Gyr which we reported in a recent paper. Here we present new ground-based, large-area optical and near-IR imaging of star clusters in NGC 1316, complement

Matthew L. Lister

We discuss the impact of special relativistic effects on the observed light curves and variability duty cycles of AGNs. We model the properties of AGN light curves at radio wavelengths using a simulated shot noise process in which the occurrence of major flaring events in a relativistic jet is governed by Poisson statistics. We show that flaring sources whos

Mauro Orlandini, Daniele Dal Fiume

We review the physical processes occurring in the magnetosphere of accreting X-ray pulsars, with emphasis on those processes that give rise to observable effects in their high (E>10 keV) energy spectra. In the second part we compare the empirical spectral laws used to fit the observed spectra with theoretical models, at the light of the BeppoSAX results on t

Abraham Achterberg, Yves A. Gallant, John G. Kirk, Axel W. Guthmann

We consider the acceleration of charged particles near ultra-relativistic shocks, with Lorentz factor Gamma_s >> 1. We present simulations of the acceleration process and compare these with results from semi-analytical calculations. We show that the spectrum that results from acceleration near ultra-relativistic shocks is a power law, N(E) \propto E^{-s}, wi

M. A. Barstow, J. B. Holberg, I. Hubeny, S. A. Good

We present measurements of the effective temperatures and surface gravities for a sample of hot DA white dwarfs, using the Lyman line data available from the HUT, ORFEUS and FUSE far-UV space missions. Comparing the results with those from the standard Balmer line technique, we find that there is a general good overall agreement between the two methods. Howe

Luca Amendola

The estimation of cosmological parameters from cosmic microwave experiments has almost always been performed assuming gaussian data. In this paper the sensitivity of the parameter estimation to different assumptions on the probability distribution of the fluctuations is tested. Specifically, adopting the Edgeworth expansion, I show how the cosmological param

H. J. McCracken, O. Le Fevre, M. Brodwin, S. Foucaud

(abridged) Using the UH8K mosaic camera, we have measured the angular correlation function ω(θ) for 100,000 galaxies over four widely separated fields totalling ~1°^2 and reaching IAB~25.5. With this sample we investigate the dependence of ω(θ) at 1&#39;, A_ω(1&#39;), on sample median IAB magnitude in the range 19.5<I(AB-med)<24. Our results show that A_ω(1&

Michael Doran, Jan-Markus Schwindt, Christof Wetterich

We discuss the influence of dark energy on structure formation, especially the effects on σ_8. Our interest is particularly focused on quintessence models with time-dependent equation of state and non-negligible quintessence component in the early universe. We obtain an analytic expression for σ_8 valid for a large class of dark energy models. We conclude th

I. Ferreras, J. Silk

We present a simple phenomenological model of star formation in galaxies that describes the process with a set of a few parameters. The star formation efficiency and the fraction of gas and metals ejected in outflows are assumed to be the main drivers of star formation. The Tully-Fisher and the Faber-Jackson relations in different passbands are used as const

Emma Ryan-Weber, Rachel Webster, Lister Staveley-Smith

The cross-section of sky occupied by a particular neutral hydrogen column density provides insight into the nature of Lyman-alpha absorption systems. We have measured this column density distribution at z=0 using 21-cm HI emission from a blind survey. A subsample of HI Parkes All Sky Survey (HIPASS) galaxies have been imaged with the Australia Telescope Comp

J. M. Bai, Myung Gyoon Lee

In this paper, analytical arguments are presented that there exists a synchrotron X-ray jet on large scales in most radio-loud AGNs, based on the knowledge of the nature and physics of blazars. In blue blazars and blue-blazar-like radio galaxies, the large scale X-ray jet may get faint along the jet, while in most red blazars and red-blazar-like radio galaxi

D. W. Fox, D. L. Kaplan, S. R. Kulkarni, D. A. Frail

We present the results of Chandra, RXTE, and VLA observations of SGR 1900+14 in the immediate aftermath of its 2001 April 18 giant flare event. In the X-ray band we find the source in a pulsating and bursting state, with time-averaged 2--10 keV flux initially elevated by 20% above the source&#39;s previous quiescent periods. In the radio we establish upper l

Cheongho Han

An extra-solar planet can be detected by microlensing because the planet can perturb the smooth lensing light curve created by the primary lens. However, it was shown by Gaudi that a subset of binary-source events can produce light curves that closely resemble those produced by a significant fraction of planet/star lens systems, causing serious contamination

Cheongho Han, Heon-Young Chang, Jin H. An, Kyongae Chang

In this paper, we show that the pattern of microlensing light curve anomalies induced by multiple planets are well described by the superposition of those of the single-planet systems where the individual planet-primary binary pairs act as independent lens systems. Since the outer deviation regions around the planetary caustics of the individual planets occu

Michael Rauch, Wallace L. W. Sargent, Thomas A. Barlow, Robert F. Carswell

Spectra from the Keck HIRES instrument of the Lyman alpha forests in the lines of sight to the A and C components of the gravitationally lensed QSO Q1422+231 were used to investigate the structure of the intergalactic medium at mean redshift z = 3.3 on sub-kpc scales. We measured the cross-correlation amplitude between the two Lyman alpha forests for a mean

Neven Bilic, Robert J. Lindebaum, Gary B. Tupper, Raoul D. Viollier

Through reformulating the cold, self-gravitating fermion gas as a Bose condensate by identifying their mutual Thomas-Fermi limits, the dissipationless formation of a heavy neutrino star in gravitational collapse is numerically demonstrated. Such stars offer an alternative to supermassive black holes for the compact dark objects at the centers of galaxies.

Luis Bento, Zurab Berezhiani

We propose a lepto-baryogenesis mechanism in which the non-zero B-L of the universe is produced in out-of-equilibrium, lepton number and CP violating scattering processes that convert ordinary particles into particles of some hidden sector. In particular, we consider the processes $l ϕ> l&#39; ϕ&#39;, \bar l&#39; \bar phi&#39;$ mediated by the heavy Majorana

Hsin-Chia Cheng, Konstantin T. Matchev, Jing Wang

We construct a supersymmetric grand unified model in the framework of a latticized extra dimension. The SU(5) symmetries on the lattice are broken by the vacuum expectation values of the link fields connecting adjacent SU(5) sites, leaving just the MSSM at low energies. Below the SU(5) breaking scale, the theory gives rise to a similar spectrum as in orbifol

Colin Borys, Scott Chapman, Mark Halpern, Douglas Scott

Using the 850 micron SCUBA camera on the JCMT and a scanning technique different from other sub-mm surveys, we have obtained a 125 square arcminute map centered on the Hubble Deep Field. The one-sigma sensitivity to point sources is roughly 3 mJy and thus our map probes the brighter end of the sub-mm source counts. We find 6 sources with a flux greater than

J. M. Miller, R. Wijnands, P. M. Rodriguez-Pascual, P. Ferrando

We report on an XMM-Newton Reflection Grating Spectrometer observation of the black hole candidate and Galactic microquasar GRS 1758-258. The source entered a peculiar &#34;off/soft&#34; state in late February, 2001, in which the spectrum softened while the X-ray flux -- and the inferred mass accretion rate -- steadily decreased. We find no clear evidence fo

L. Da Rold, C. D. Fosco, A. P. C. Malbouisson

We consider a Dirac field in 2+1 Euclidean dimensions, in the presence of a linear domain wall defect in its mass, and a constant electromagnetic field. We evaluate the exact fermionic determinant for the situation where the defect is assumed to be rectilinear, static, and the gauge field is minimally coupled to the fermions. We discuss the dependence of the

Pontus Svenson, Des Johnston

We study damage-spreading in the ferromagnetic Ising model on small world networks using Monte Carlo simulation with Glauber dynamics. The damage spreading temperature $T_d$ is determined as a function of rewiring probability $p$ for small world networks obtained by rewiring the 2D square and 3D cubic lattices. We find that the damage for different values of

H. B. Sandvik, J. D. Barrow, J. Magueijo

We investigate the cosmological consequences of a simple theory in which the electric charge $e$ is allowed to vary. The theory is locally gauge and Lorentz invariant, and satisfies general covariance. We find that in this theory the fine structure &#39;constant&#39;, $α$, remains almost constant in the radiation era, undergoes small increase in the matter e