May 1997 arXiv papers — page 7

N. García, F. Guinea

The electronic distribution in devices with sufficiently small diemnsions may not be in thermal equilibrium with their surroundings. Systems where the occupancies of electronic states are solely determined by tunneling processes are analyzed. It is shown that the effective temperature of the device may be higher, or lower, than that of its environment, depen

Albert Stebbins, Scott Dodelson

Techniques for computing the CMBR anisotropy from simulations of topological defects are discussed with an eye to getting as much information from a simulation as possible. Here we consider the practical details of which sums and multiplications to do and how many terms there are.

T. Storchi-Bergmann, M. Eracleous, M. T. Ruiz, M. Livio

We present new spectroscopic observations of the LINER (and now Seyfert 1) nucleus of NGC 1097, and discuss the evolution of its broad, double-peaked Balmer lines. When originally discovered in 1991, the red peak of the double-peaked H-alpha line was stronger than the blue, while by 1994 the H-alpha profile had become almost symmetric and the integrated line

Bruno Jungwiert, Francoise Combes, David J. Axon

We present a near-IR, mainly H band, photometry of 72 nearby disk galaxies. The main goal of the survey was to search for isophotal twist inside their nuclear regions. As the twist can be due in some cases to projection effects, rather than resulting from a dynamical phenomenon, we deproject - under the simplifying assumption of a 2D geometry - all galaxies

Andrew Gould, Solange V. Ramirez

We show that observations by Backer and collaborators over the past two decades constrain the time derivative of the proper motion of Sgr A* to be less than 0.14 mas yr^{-2}. Using this result and a preliminary measurement by Eckart and Genzel of sigma ~500 kms for the velocity dispersion of the star cluster within 0.2" of Sgr A*, we derive the following

Rosalba Perna, Abraham Loeb, Matthias Bartelmann

Gravitational lensing of an optical QSO by a spiral galaxy is often counteracted by dust obscuration, since the line-of-sight to the QSO passes close to the center of the galactic disk. The dust in the lens is likely to be correlated with neutral hydrogen, which in turn should leave a Lyman-alpha absorption signature on the QSO spectrum. We use the estimated

Patrick Guillemin, Jacqueline Bergeron

We present the results of a survey of galaxies selected by their gas cross-section which give rise to MgII absorption lines in the spectra of background quasars. The sample comprises 11 galaxies covering the redshift range 0.7 < z < 1.2, and is combined with a lower redshift sample of 15 MgII absorbing galaxies. The spectra range from present-day elliptical

Hans J. Haubold, Willem Wamsteker

In 1990 the United Nations in cooperation with the European Space Agency initiated the organization of a series of annual Workshops on Basic Space Science for the benefit of astronomers and space scientists in Asia and the Pacific, Latin America and the Caribbean, Africa, Western Asia, and Europe. This article summarizes accomplishments of these Workshops an

Sabino Matarrese, Silvia Mollerach

The cosmological stochastic gravitational-wave background produced by the mildly non-linear evolution of density fluctuations is analyzed, in the frame of an Einstein-de Sitter model, by means of a fully relativistic perturbation expansion up to second order. The form of these gravitational-instability-induced gravitational waves is gauge-dependent. In the s

S. Colafrancesco, P. Mazzotta, N. Vittorio

We discuss the evolution of the cluster temperature function (TF) in different scenarios for structure formation. We use the commonly adopted procedure of fitting the model parameters to the local TF data, finding the best fit values and, most of all, the associated statistical errors. These errors yield an uncertainty in the prediction of the TF evolution.

Anne M Green, Andrew R Liddle, Antonio Riotto

Moduli fields, a natural prediction of any supergravity and superstring-inspired supersymmetry theory, may lead to a prolonged period of matter domination in the early Universe. This can be observationally viable provided the moduli decay early enough to avoid harming nucleosynthesis. If primordial black holes form, they would be expected to do so before or

John L. Tonry, Barry E. Burke, Paul L. Schechter

We have designed and built a new type of CCD that we call an orthogonal transfer CCD (OTCCD), which permits parallel clocking horizontally as well as vertically. The device has been used successfully to remove image motion caused by atmospheric turbulence at rates up to 100 Hz, and promises to be a better, cheaper way to carry out image motion correction for

B. Ricci, V. Berezinsky, S. Degl&#39;Innocenti, W. A. Dziembowski

The central solar temperature T and its uncertainties are calculated in helioseismologically-constrained solar models. From the best fit to the convective radius, density at the convective radius and seismically determined helium abundance the central temperature is found to be T=1.58x10^7 K, in excellent agreement with Standard Solar Models. Conservatively,

Montserrat Teixidor-i-Bigas

Let C be an algebraic curve of genus g. Consider extensions E of a vector bundle F&#39;&#39; of rank n&#39;&#39; by a vector bundle F&#39; of rank n&#39;. The following statement was conjectured by Lange: If 0<n&#39;deg F&#39;&#39;-n&#39;&#39;degF&#39;\le n&#39;n&#39;&#39;(g-1), then there exist extensions like this with E stable. We prove this result for th

Ingo Gaida

N=2 supersymmetric quantum black holes in the heterotic S-T-U model are presented. In particular three classes of axion-free quantum black holes with half the N=2, D=4 supersymmetries unbroken are considered. First, these quantum black holes are investigated at generic points in moduli space. Then linearized non-abelian black holes are investigated represent

S. M. Barr, S. Raby

It is shown that the doublet-triplet splitting problem can be solved in SO(10) using the Dimopoulos-Wilczek mechanism with a very economical Higgs content and simple structure. Only one adjoint Higgs field is required, together with spinor and vector fields. The successful SUSY GUT prediction of gauge coupling unification is preserved. Higgsino-mediated prot

S. G. Naculich, H. J. Schnitzer

We construct a one-to-one map between the primary fields of the N=2 superconformal Kazama-Suzuki models G(m,n,k) and G(k,n,m) based on complex Grassmannian cosets, using level-rank duality of Wess-Zumino-Witten models. We then show that conformal weights, superconformal U(1) charges, modular transformation matrices, and fusion rules are preserved under this

Juergen Schaffner-Bielich, Carsten Greiner, Horst Stoecker, Axel Vischer

We examine the properties of both forms of strange matter, small lumps of strange quark matter (strangelets) and of strange hadronic matter (Metastable Exotic Multihypernuclear Objects: MEMOs) and their relevance for present and future heavy ion searches. The strong and weak decays are discussed separately to distinguish between long-lived and short-lived ca

Clifford V. Johnson

Dualities between certain supersymmetric gauge field theories in three and four dimensions have been studied in considerable detail recently, by realizing them as geometric manipulations of configurations of extended objects in type II string theory. These extended objects include `D-branes&#39; and `NS-(five)branes&#39;. In constructing the brane configurat

D. V. Ahluwalia

In this essay a generalized notion of flavor-oscillation clocks is introduced. The generalization contains the element that various superimposed mass eigenstates may have different relative orientation of the component of their spin with respect to the rotational axis of the the gravitational source. It is found that these quantum mechanical clocks do not al

Harry J. Lipkin, Patrick J. O&#39;Donnell

Hyperfine interactions in the light meson and baryon sectors are generalized to the charm and bottom systems. It is pointed out that an attempt to increase the value of the wave function at the origin to account for the unusual ratio of $Λ_{b}$ to the $B^0$ lifetimes could spoil the good agreement among the baryon and meson hyperfine mass-splitting. Includin

Matt Visser

Can we give the graviton a mass? Does it even make sense to speak of a massive graviton? In this essay I shall answer these questions in the affirmative. I shall outline an alternative to Einstein Gravity that satisfies the Equivalence Principle and automatically passes all classical weak-field tests (GM/r approx 10^{-6}). It also passes medium-field tests (

Sergei F. Shandarin, Capp Yess

We employ a percolation technique developed for pointwise distributions to analyze two-dimensional projections of the three northern and three southern slices in the Las Campanas Redshift Survey. One of the goals of this paper is to compare the visual impressions of the structure within distributions with objective statistical analysis. We track the growth o

V. F. Gantmakher, L. P. Kozeeva, A. N. Lavrov, D. A. Pushin

A scan of the superconductor -- nonsuperconductor transformation in single crystals YBa_2Cu_3O_{6+x} (x about 0.37) was done in two alternative ways, namely, by applying the magnetic field and by reducing the hole concentration through the oxygen rearrangement. The in-plane normal-state resistivity ρ_{ab} obtained in both cases was quite similar; its tempera

Oliver Baerwald, Reinhold W. Gebert, Hermann Nicolai

In a recent paper (hep-th/9703084) it was conjectured that the imaginary simple roots of the Borcherds algebra $g_{II_{9,1}}$ at level 1 are its only ones. We here propose an independent test of this conjecture, establishing its validity for all roots of norm $\geq -8$. However, the conjecture fails for roots of norm -10 and beyond, as we show by computing t

E. Caglioti, V. Loreto, H. J. Herrmann, M. Nicodemi

We propose a two-dimensional geometrical model, based on the concept of geometrical frustration, conceived for the study of compaction in granular media. The dynamics exhibits an interesting inverse logarithmic law that is well known from real experiments. Moreover we present a simple dynamical model of $N$ planes exchanging particles with excluded volume pr

Takehisa Fujita, Makoto Hiramoto

We present a counter example which shows the violation of the S-matrix factorization in the massive Thirring model. This is done by solving the PBC equations of the massive Thirring model exactly but numerically. The violation of the S-matrix factorization is related to the fact that the crossing symmetry and the factorization do not commute with each other.

M. Kawasaki, K. Kohri, Katsuhiko Sato

Comparing Big Bang Nucleosynthesis predictions with the light element abundances inferred from observational data, we can obtain the strong constraints on some neutrino properties, e.g. number of neutrino species, mass, lifetime. Recently the deuterium abundances were measured in high red-shift QSO absorption systems. It is expected that they are close to th

Eugene Demler, Shou-Cheng Zhang, Stefan Meixner, Werner Hanke

Greiter claimed erroneously that the pi-excitation of the Hubbard model has an energy of the order of U. This mistake originates from a inconsistent treatment of the two particle Hartree energy and the Hartee correction to the chemical potential. In any self-consistent calculations, these two contributions cancel exactly, as shown by Kohn, Luttinger and Ward

Yu Cao, Susan Terebey, Thomas A. Prince, Charles A. Beichman

An atlas of the Galactic plane (-4.7 deg < b < 4.7 deg) plus the molecular clouds in Orion, Rho Oph, and Taurus-Auriga has been produced at 60 and 100 micron from IRAS data. The Atlas consists of resolution-enhanced coadded images having 1 arcmin -- 2 arcmin resolution as well as coadded images at the native IRAS resolution. The IRAS Galaxy Atlas, together w

M. Markevitch, A. Vikhlinin

We combine ASCA and ROSAT X-ray data to constrain the radial dark matter distribution in the primary cluster of A2256, free from the isothermality assumption. Both instruments indicate that the temperature declines with radius. The region including the central galaxy has a multicomponent spectrum, which results in a wide range of allowed central temperatures

N. Kim, Soo-Jong Rey

We study M(atrix) theory description of M theory compactified on T5/Z2 orbifold. In the large volume limit we show that M theory dynamics is described by N=8 supersymmetric USp(2N) M(atrix) quantum mechanics. Via zero-brane parton scattering, we show that each orbifold fixed point carries anomalous G-flux $\oint [G/2 π]= - 1/2$. To cancel the anomalous G-flu

V. Levinski, I. Rapoport, J. Cohen

The stability of shear flows of electrically conducting fluids, with respect to finite amplitude three-dimensional localized disturbances is considered. The time evolution of the fluid impulse integral, characterizing such disturbances, for the case of low magnetic Reynolds number is obtained by integrating analytically the vorticity equation. Analysis of th

Claude A. Laberge, Sven Sandow

We investigate the dynamics of a nonequilibrium interface between coexisting phases in a system described by a Cahn-Hilliard equation with an additional driving term. By means of a matched asymptotic expansion we derive equations for the interface motion. A linear stability analysis of these equations results in a condition for the stability of a flat interf

S. W. Hawking, Simon F. Ross

In quantum gravity, fields may lose quantum coherence by scattering off vacuum fluctuations in which virtual black hole pairs appear and disappear. Although it is not possible to properly compute the scattering off such fluctuations, we argue that one can get useful qualitative results, which provide a guide to the possible effects of such scattering, by con

M. Bonini, M. Simionato

We discuss a resummed perturbation theory based on the Wilson renormalization group. In this formulation the Wilsonian flowing couplings, which generalize the running coupling, enter directly into the loop expansion. In the case of an asymptotically free theory the flowing coupling is well defined since the infrared Landau pole is absent. We show this proper

J. Cruz, J. Navarro-Salas

We show that a canonical tranformation converts, up to a boundary term, a generic 2d dilaton gravity model into a bosonic string theory with a Minkowskian target space.

J. Sonnenschein

Talk presented in the 97 Karpatcz winter school. We describe Sen&#39;s work on F theory on K3 and its reflection on the world-volume field theory on a D3-brane probe. Field theories on a multiple of probes are analyzed. We construct a 4d N=1 superconformal probe theory which is invariant under electric-magnetic duality via a compactification to six dimension

Mathias Pillin

It is shown that the problem of calculating form factors in ADE affine Toda field theories can be reduced to the nonperturbative recursive calculation of polynomials symmetric in each sort of variables. We determine these recursion equations explicitly for the ADE series and characterize the polynomial solutions by an interplay between the weight space of th

Ranjan K. Ghosh, Sumathi Rao

We construct a new class of quasi-exactly solvable many-body Hamiltonians in arbitrary dimensions, whose ground states can have any correlations we choose. Some of the known correlations in one dimension and some recent novel correlations in two and higher dimensions are reproduced as special cases. As specific interesting examples, we also write down some n

Jeremy S. Heyl, Lars Hernquist

We consider the field equations of a static magnetic field including one-loop QED corrections, and calculate the corrections to the field of a magnetic dipole. PACS: 12.20.Ds, 97.60.Jd, 97.60.Gb

Jeremy S. Heyl, Lars Hernquist

We use an analytic form for the Heisenberg-Euler Lagrangian to calculate the birefringent and dichroic properties of the vacuum for arbitrarily strong wrenchless fields. PACS : 12.20.Ds, 42.25.Lc 97.60.Jd, 98.70.Rz

Shaouly Bar-Shalom

Extension of the SM with one extra Higgs doublet may give rise to flavor-changing-scalar coupling of a neutral Higgs to a pair of top-charm quarks. This coupling gives rise to a large tree-level effective W^+W^-;ZZ - Higgs - t bar-c interaction. We find that the reactions e^+e^- --> t bar-c nu_e bar-nu_e, t bar-c e^+e^-, t bar-c Z and the two rare top decays

A. A. Andrianov, V. A. Andrianov

We compare two QCD-inspired quark models with four-fermion interaction, without and with the remnant coupling to low-energy gluons, in the regime of dynamical chiral symmetry breaking (DCSB). The first one, the Nambu-Jona-Lasinio (NJL) model ensures the factorization of scalar and pseudoscalar meson poles in correlators, the well-known Nambu relation between

Axel Hoefer

Cross sections involving massive Dirac or Majorana neutrinos usually differ only by terms which are suppressed by the smallness of the neutrino mass. The process $e^+e^-\toνν$, however, is an example in which the two differential cross sections are quite distinct even in the limit $m_ν\to 0$ as long as $m_ν\not=0$. I discuss the cause of this phenomenon and

Alexander Kusenko

Solitosynthesis of Q-balls in the false vacuum can result in a phase transition of a new kind. Formation and subsequent growth of Q-balls via the charge accretion proceeds until the solitons reach a critical charge, at which point it becomes energetically favorable for the Q-ball interior to expand filling space with the true vacuum phase. Solitosynthesis ca

Francois Gelis

The production rate of soft real photons or soft lepton pairs by a hot QCD plasma is dominated by strong collinear divergences. As a consequence, it appears that the effective theory based on the resummation of hard thermal loops fails to handle properly these light-cone sensitive processes since some formally higher order diagrams are in reality the dominan

J. Gluza, T. Wohrmann

The chargino pair production in $e^-e^-$ collisions with their subsequent decays are considered within SUSY models with R-parity violation and with lepton number non-conservation. The production process ($\sqrt{s}=1$ TeV) is predicted to be large in a wide range of both sneutrino and chargino masses. The influence of all virtual sneutrino states and their mi

Zhi-zhong Xing

In many extensions of the standard model, new physics is possible to contribute significantly to B^0_s-\bar{B}^0_s mixing. We show that the effect of new physics, both its phase information and its magnitude, can be isolated from measurements of CP asymmetries in the semileptonic B_s transitions and in some nonleptonic B_s decays into hadronic CP eigenstates

Yoshio Kikukawa

Dynamical nature of the gauge degree of freedom and its effect to fermion spectrum are studied at $β=\infty$ for two-dimensional nonabelian chiral gauge theory in the vacuum overlap formulation. It is argue that the disordered gauge degree of freedom does not necessarily cause the massless chiral state in the (waveguide) boundary correlation function. An asy

Masayuki Tanimoto, Tatsuhiko Koike, Akio Hosoya

Hamiltonian structures for spatially compact locally homogeneous vacuum universes are investigated, provided that the set of dynamical variables contains the \Teich parameters, parameterizing the purely global geometry. One of the key ingredients of our arguments is a suitable mathematical expression for quotient manifolds, where the universal cover metric c

Vladimir Pestov

We construct a continuous scalar-valued 2-polynomial, $W$, on the separable Hilbert space $l_2$ and an unbounded set $R\subset l_2$ such that (i) $W$ is bounded on an $ε$-neighbourhood of $R$; (ii) $W$ is unbounded on ${1/2} R$; (iii) consequently, $W$ does not factor through any bounded 1-polynomial on $l_2$ sending $R$ to a bounded set. This answers in the

A. E. Feiguin, J. A. Riera, A. Dobry, H. A. Ceccatto

We analyze several properties of the lattice solitons in the incommensurate phase of spin-Peierls systems using exact diagonalization and quantum Monte Carlo. These systems are modelled by an antiferromagnetic Heisenberg chain with nearest and next-nearest neighbor interactions coupled to the lattice in the adiabatic approximation. Several relations among fe

S. Lubeck

We consider the non Abelian sandpile model introduced by Y.-C. Zhang on a two-dimensional square lattice. The static and dynamical properties of the model are investigated and compared to the Abelian sandpile model of Bak, Tang and Wiesenfeld. A detailed analysis which takes the finite size effects into account yields that the exponents of the avalanche prob

M. E. Zhitomirsky, M. B. Walker

We show that an induced $s$-wave harmonic in the superconducting gap of an orthorhombic $d_{x^2-y^2}$ superconductor strongly affects the excitation spectrum near a twinning plane. In particular, it yields bound states of zero energy with areal density proportional to the relative weight of the $s$-wave component. An unusual scattering process responsible fo

Martin P. Gelfand, Zheng Weihong, C. J. Hamer, J. Oitmaa

Spin-S bilayer Heisenberg models (nearest-neighbor square lattice antiferromagnets in each layer, with antiferromagnetic interlayer couplings) are treated using dimer mean-field theory for general S and high-order expansions about the dimer limit for S=1, 3/2,...,4. We suggest that the transition between the dimer phase at weak intraplane coupling and the Ne

D. Thirumalai, B. -Y. Ha

We describe a simple meanfield variational approach to study a number of properties of intrinsically stiff chains which are appropriate models for a large class of biopolymers. We present the calculation of the distribution of end-to-end distance and the elastic response of stiff chains under tension using this approach. In the former example we find that th

G. -M. Zhang, A. C. Hewson, R. Bulla

We show that a Majorana fermion description of the two channel Kondo model can emerge quite naturally as a representation of the algebra associated with the spin currents in the two channels. Using this representation we derive an exact equivalent Hamiltonian for the two channel model expressed entirely in terms of Majorana fermions. The part of the Hamilton

Kaoru Awaka, Hidetoshi Fukuyama

The effect of low energy excitation on the dynamics of Josephson phase in SNS junction is investigated. From the microscopic Hamiltonian, the effective action for the phase variable is derived. The retardation effects due to low energy excitation in normal(N) region are seen to play important roles in the dynamics of the phase. By the self consistent harmoni

Fabian H. L. Essler, Alexei M. Tsvelik, Gesulado Delfino

We study weakly coupled antiferromagnetic spin chains in their ordered phase by combinining an exact solution of the single-chain problem with an RPA analysis of the interchain interaction. A single chain is described by a quantum Sine-Gordon model and dynamical staggered susceptibilities are determined by employing the formfactor approach to quantum correla

S. G. Lachenmann, T. Doderer, R. P. Huebener, T. J. Hagenaars

We study the dynamics of current-biased Josephson-junction arrays with a magnetic penetration depth smaller than the lattice spacing. We compare the dynamics imaged by low-temperature scanning electron microscopy to the vortex dynamics obtained from model calculations based on the resistively-shunted junction model, in combination with Maxwell&#39;s equation

Wolfram Brenig

A study is presented of a two-dimensional frustrated and dimerized quantum spin-system which models the effect of inter-chain coupling in a spin-Peierls compound. Employing a bond-boson method to account for quantum disorder in the ground state the elementary excitations are evaluated in terms of gapful triplet modes. Results for the ground state energy and

Yoshifumi Morita, Yasuhiro Hatsugai

Random Dirac fermions in a two-dimensional space are studied numerically. We realize them on a square lattice using the $π$-flux model with random hopping. The system preserves two symmetries, the time-reversal symmetry and the symmetry denoted by ${{\cal H},γ}=0$ with a $4\times 4$ matrix $γ$ in an effective field theory. Although it belongs to the orthogon

Jerry R. Hobbs, Douglas Appelt, John Bear, David Israel

FASTUS is a system for extracting information from natural language text for entry into a database and for other applications. It works essentially as a cascaded, nondeterministic finite-state automaton. There are five stages in the operation of FASTUS. In Stage 1, names and other fixed form expressions are recognized. In Stage 2, basic noun groups, verb gro

P. W. Brouwer, K. M. Frahm, C. W. J. Beenakker

We calculate the probability distribution of the matrix Q = -i \hbar S^{-1} dS/dE for a chaotic system with scattering matrix S at energy E. The eigenvalues τ_j of Q are the so-called proper delay times, introduced by E. P. Wigner and F. T. Smith to describe the time-dependence of a scattering process. The distribution of the inverse delay times turns out to

Christopher W. Churchill

By charting the kinematic, chemical, and ionization conditions of galactic and intergalactic gas over the redshift range 0 - 4 with QSO absorption lines, the evolution of chemical abundances, the UV meta-galactic background, and the clustering dynamics of galactic gas can be studied. HIRES/Keck Mg II 2796 profiles arising in <z> = 1 galaxies are presented an

Brian Yanny, Buell T. Jannuzi, Chris Impey

Hubble Space Telescope WFPC-2 I-band (F814W) images of the BL Lacertae object OJ 287 and the surrounding field are presented. We find evidence of associated extended nebulosity near OJ 287, as well as a small nebulosity to the West, which may be spatially coincident with the position of previously observed radio emission. The brightness of a host galaxy is d

Lori Clampitt, David Burstein

Photoelectric spectrophotometry is presented for 237 stars in the Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC~4665, and M39 open clusters. 16 bandpasses were observed from 350 nm to 778 nm, with 3.2 to 6.4 nm bandwidth. Data are standardized to the Hayes-Latham system to mutual accuracy of 0.016 mag per passband. By comparison to SIMBAD-avai

Francesco R. Ferraro, Barbara Paltrinieri, Flavio Fusi Pecci, Carla Cacciari

We present preliminary results from HST/WFPC2 observations of the central regions of the of the Galactic globular clusters M13 and M3. The clusters are almost identical in most respects including chemical composition, but there are dramatic differences in both the horizontal branch (HB) and blue straggler (BSS) populations. The M13 HB has a long blue tail ex

P. M. Ogle

Spectropolarimetry of broad absorption line quasi-stellar objects with the W. M. Keck Telescope is used to put constraints on their nuclear structure. If the continuum polarization is due to electron (or dust) scattering, then the scattered and direct rays probe the nucleus along multiple lines of sight, which suffer differing amounts of absorption. Multiple

D. Gondek, P. Haensel, J. L. Zdunik

Radial pulsations of newborn neutron stars (protoneutron stars) are studied for a range of internal temperatures and entropies per baryon predicted by the existing numerical simulations. Protoneutron star models are constructed using a realistic equation of state of hot dense matter, and under various assumptions concerning stellar interior (large trapped le

V. Berezinsky, Lars Bergström, H. R. Rubinstein

The recent observations of 50 TeV gamma radiation by HEGRA have the potential of determining the extragalactic flux of infrared radiation. The fact that radiation is observed in the range between 30 and 100 TeV sets an upper limit on the infrared flux, while a cutoff at $E_γ \approx 50$ TeV fixes this flux with a good accuracy. If the intrinsic radiation is

Z. Ivezic, M. Groenewegen, A. Menshchikov, R. Szczerba

When verifying a sophisticated numerical code, it is a usual practice to compare the results with reliable solutions obtained by other means. This work provides such solutions for the wavelength dependent dust radiative transfer problem. We define a set of benchmark problems in spherical geometry and solve them by three radiative transfer codes which impleme

Paul Wiegert, Scott Tremaine

We study the evolution of long-period comets by numerical integration of their orbits, following comets from their origin in the Oort cloud until their final escape or destruction, in a model solar system consisting of the Sun, the four giant planets and the Galactic tide. We also examine the effects of non-gravitational forces and the gravitational forces f

A. P. Fairall, P. A. Woudt, R. C. Kraan-Korteweg

In our systematic optical galaxy search behind the southern Milky Way, 3760 (mostly unknown) galaxies with diameters D > 0.2 arcminutes were identified in the Crux region (287 < l < 318 degrees, |b| < 10 degrees, Woudt & Kraan-Korteweg 1997). Prior to this investigation, only 65 of these galaxies had known redshifts. In order to map the galaxy distribution i

Shunsuke Hozumi

A particle method for reproducing the phase space of collisionless stellar systems is described. The key idea originates in Liouville&#39;s theorem which states that the distribution function (DF) at time t can be derived from tracing necessary orbits back to t=0. To make this procedure feasible, a self-consistent field (SCF) method for solving Poisson&#39;s

Bono Giuseppe, Marconi Marcella

We present nonlinear theoretical results concerning the predicted pulsation behaviour of stellar models suitable for the sample of Cepheids belonging to the Large Magellanic Cloud (LMC) star cluster NGC 1866. The blue and red edges of the instability strip, transformed into the observative plane (V, B-V) by adopting current values for the distance modulus (D

Rebecca A. W. Elson, Gerard F. Gilmore, Basilio X. Santiago

We present $V$ and $I$ photometry, obtained with the Hubble Space Telescope, for $\sim 15,800$ stars in a field in the inner disk of the Large Magellanic Cloud. We confirm previous results indicating that an intense star formation event, probably corresponding to the formation of the LMC disk, occurred a few times $10^9$ years ago. We find a small but real d

S. E. Woosley, A. Heger, T. A. Weaver, N. Langer

Ten years later, astronomers are still puzzled by the stellar evolution that produced SN 1987A --- a blue supergiant. In single star models, the new OPAL opacities make blue solutions more difficult to achieve, though still possible for certain choices of convection physics. We also consider rotation, which has the desirable effect of producing large surface

Zoltan Haiman, Abraham Loeb

We calculate the observable signatures of the first generation of stars at high redshift (5<z<100). To determine the cosmic star-formation history, we use an extension of the Press-Schechter formalism for Cold Dark Matter (CDM) cosmologies that incorporates gas pressure. We calibrate the fraction of gas converted into stars to be 6% so as to reproduce the 1%

Jun-ichi Inoue, Hidetoshi Nishimori, Yoshiyuki Kabashima

We investigate the generalization ability of a perceptron with non-monotonic transfer function of a reversed-wedge type in on-line mode. This network is identical to a parity machine, a multilayer network. We consider several learning algorithms. By the perceptron algorithm the generalization error is shown to decrease by the $α^{-1/3}$-law similarly to the

S. P. de Alwis

We discuss issues involving p(D)- brane charge quantization and the normalization of effective actions, in string/M-theory. We also construct the action of (the bosonic sector of) eleven dimensional supergravity in the presence of two- and five- branes and discuss (perturbative) anomaly cancellation.

J. F. C. Wardle, R. A. Perley, M. H. Cohen

We show that recent radio and optical observations of polarized radiation from well-resolved high redshift quasars and radio galaxies rule out the cosmological rotation of the plane of polarization claimed recently by Nodland and Ralston. A least squares fit to the radio data has a slope only 2% of their claimed effect.

O. G. Balev, P. Vasilopoulos

A treatment of edge magnetoplasmons (EMP), based on a microscopic evaluation of the local contributions to the current density, is presented. It is valid in the quantum Hall regime for filling factor ν=1 or 2 and low temperatures when the dissipation is localized near the edge. The confining potential, flat in the interior of the channel, is assumed smooth o

B. S. Acharya, M. O'Loughlin, B. Spence

We present a Donaldson-Witten type field theory in eight dimensions on manifolds with $Spin(7)$ holonomy. We prove that the stress tensor is BRST exact for metric variations preserving the holonomy and we give the invariants for this class of variations. In six and seven dimensions we propose similar theories on Calabi-Yau threefolds and manifolds of $G_2$ h

L. Bonora, C. S. Chu

It has been proposed recently that, in the framework of M(atrix) theory, N=8 supersymmetric U(N) Yang-Mills theory in 1+1 dimensions gives rise to type IIA long string configurations. We point out that the quantum moduli space of $SYM_{1+1}$ gives rise to two quantum numbers, which fit very well into the M(atrix) theory. The two quantum numbers become famili

Christopher S. Reynolds, Mitchell C. Begelman

The fluorescent iron Ka line is a powerful observational probe of the inner regions of black holes accretion disks. Previous studies have assumed that only material outside the radius of marginal stability can contribute to the observed line emission. Here, we show that fluorescence by material inside the radius of marginal stability, which is in the process

William E. Brown, Ian I. Kogan

The beta-function is calculated for an SU(N) Yang-Mills theory from an ansatz for the vacuum wavefunctional. Direct comparison is made with the results of calculations of the beta-function of QCD. In both cases the theories are asymptotically free. The only difference being in the numerical coefficient of the beta-function, which is found to be -4 from the a

Albrecht Klemm

An introduction to Seiberg-Witten theory and its relation to theories which include gravity.

G. Tiana, R. A. Broglia, H. E. Roman, E. Vigezzi

We study the impact of mutations (changes in amino acid sequence) on the thermodynamics of simple protein-like heteropolymers consisting of N monomers, representing the amino acid sequence. The sequence is designed to fold into its native conformation on a cubic lattice. It is found that quite a large fraction, between one half and one third of the substitut

Guy B. Standen, David J. Toms

We study the charged non-relativistic Bose gas interacting with a constant magnetic field but which is otherwise free. The notion of Bose-Einstein condensation for the three dimensional case is clarified, and we show that although there is no condensation in the sense of a phase transition, there is still a maximum in the specific heat which can be used to d

Nobuo Furukawa

Double-exchange system is investigated by the dynamical mean-field theory. We show that the chemical potential shifts as a function of temperature and magnetization, which is anomalously large. We also discuss the influences of dynamic Jahn-Teller effect to the shift of the chemical potential. Measurement of the shift of the chemical potential casts a constr

Tomohiro Inagaki, Kenzo Ogure, Joe Sato

We construct a non-perturbative method to investigate the phase structure of the scalar theory at finite temperature. The derivative of the effective potential with respect to the mass square is expressed in terms of the full propagator. Under a certain approximation this expression reduces to the partial differential equation for the effective potential. We

Maki Suginohara, Tatsushi Suginohara, David N. Spergel

Density inhomogeneities along the line-of-sight distort fluctuations in the cosmic microwave background. Usually, this effect is thought of as a small second-order effect that mildly alters the statistics of the microwave background fluctuations. We show that there is a first-order effect that is potentially observable if we combine microwave background maps

Masanao Ozawa

To find the Hermitian phase operatorof a single-mode electromagnetic field in quantum mechanics, the Schroedinger representation is extended to a larger Hilbert space augmented by states with infinite excitation by nonstandard analysis. The Hermitian phase operator is shown to exist on the extended Hilbert space. This operator is naturally considered as the

I. E. Lagaris, A. Likas, D. I. Fotiadis

We present a method to solve initial and boundary value problems using artificial neural networks. A trial solution of the differential equation is written as a sum of two parts. The first part satisfies the boundary (or initial) conditions and contains no adjustable parameters. The second part is constructed so as not to affect the boundary conditions. This

Igor Aranson, Alan Bishop

The dynamics of curved vortex filaments is studied analytically and numerically in the framework of a three-dimensional complex Ginzburg-Landau equation (CGLE). It is proved that a straight vortex line is unstable with respect to spontaneous stretching and bending in a certain range of parameters of the CGLE, resulting in formation of persistent entangled vo

F. Vendrell

An imploding shell of radiation is shown to create a 2-D black hole within the framework of the ``R=T&#39;&#39; theory. The radius of the horizon is given by 1/(2M), where M is the mass of the black hole. The topology of the central singularity is that of a corner. The radiation emitted very far from the black hole is thermal with temperature M/(2π). The bac

E. Alfinito, R. Manka, G. Vitiello

We discuss the canonical quantization of non-unitary time evolution in inflating Universe. We consider gravitational wave modes in the FRW metrics in a de Sitter phase and show that the vacuum is a two-mode SU(1,1) squeezed state of thermo field dynamics, thus exhibiting the link between inflationary evolution and thermal properties. In particular we discuss

Brian R. Greene, Tomislav Prokopec, Thomas G. Roos

We study the decay of the inflaton in a renormalizable two scalar theory. Since the dynamics of the system is dominated by states with large occupation numbers which admit a semiclassical description, the decay can be studied by solving the classical equations of motion on the lattice. Of particular interest is the case when the cross-coupling between the in