February 1998 arXiv papers — page 2

V. I. Dokuchaev, Yu. N. Eroshenko, L. M. Ozernoy

A new cosmological scenario for the origin of gamma ray bursts (GRBs) is proposed. In our scenario, a highly evolved central core in the dense galactic nucleus is formed containing a subsystem of compact stellar remnants (CSRs), such as neutron stars and black holes. Those subsystems result from the dynamical evolution of dense central stellar clusters in th

Rex A. Saffer, Mario Livio, Lev R. Yungelson

We describe radial velocity observations of a large sample of apparently single white dwarfs (WDs), obtained in a long-term effort to discover close, double-degenerate (DD) pairs which might comprise viable Type Ia Supernova (SN Ia) progenitors. We augment the WD sample with a previously observed sample of apparently single subdwarf B (sdB) stars, which are

C. Adami, R. C. Nichol, A. Mazure, F. Durret

As a continuation of our study of the faint galaxy luminosity function in the Coma cluster of galaxies, we report here on the first spectroscopic observations of very faint galaxies (R $\le$ 21.5) in the direction of the core of this cluster. Out of these 34 galaxies, only one may have a redshift consistent with Coma, all others are background objects. The p

C. Adami, P. Amram, G. Comte

We show that a 2D projection is representative of its corresponding 3D distribution at a confidence level of 90 % if it follows a King profile and if we consider the whole spatial distribution. The level is significantly lower and not decisive in the vicinity of the 2D cluster center. On another hand, if we verify the reciprocal statement of the Mattig's

Carlos Allende Prieto, Basilio Ruiz Cobo, Ramon J. Garcia Lopez

An inversion technique has been developed to recover LTE one-dimensional model photospheres for late-type stars from very high resolution, high signal-to-noise stellar line profiles. It is successfully applied to the Sun by using a set of clean Ti I, Ca I, Cr I, and Fe I normalized line profiles with accurate transition probabilities and taking advantage of

L. A. Phillips, Edwin L. Turner

We analyze bright-end (K = 10 -17) galaxy counts from a number of near-infrared galaxy surveys. All studies available as of mid-1997, considered individually or collectively, show that the observed near-infrared galaxy number counts at low magnitudes are inconsistent with a simple no-evolution model. We examine evolutionary effects and a local underdensity m

A. W. Jones, S. Hancock, A. N. Lasenby, R. D. Davies

The complete set of data from the Tenerife 10 GHz (8 degree FWHM) twin-horn, drift scan experiment is described. These data are affected by both long-term atmospheric baseline drifts and short term noise. A new maximum entropy procedure, utilising the time invariance and spatial continuity of the astronomical signal, is used to achieve a clean separation of

V. R. Eke, S. Cole, C. S. Frenk, J. P. Henry

The evolution of the galaxy cluster abundance depends sensitively on the value of the cosmological density parameter, Omega_0. Recent ASCA data are used to quantify this evolution as measured by the X-ray temperature function. A chi^2 minimisation fit to the cumulative temperature function, as well as a maximum likelihood estimate (which requires additional

T. J. O'Brien, Judith G. Cohen

Recently, it has been claimed that the recurrent nova T Pyx exhibits oppositely directed jets of ejecta apparent in features seen in H alpha emission. Here we demonstrate that these features are in fact emission in the [N II] lines which lie either side of H alpha and arise from the expanding shell associated with this object rather than from collimated jets

F. K. Lamb, M. C. Miller, D. Psaltis

One of the most dramatic discoveries made so far with the Rossi X-Ray Timing Explorer is that many accreting neutron stars with weak magnetic fields generate strong, remarkably coherent, high-frequency X-ray brightness oscillations. The 325-1200 Hz quasi-periodic oscillations (QPOs) observed in the accretion-powered emission are almost certainly produced by

Micha Berkooz

We suggest a supergravity dual for the $(1,0)$ superconformal field theory in six dimensions which has $E_8$ global symmetry. Compared to the description of the (2,0) field theory, the 4-sphere is replaced by a 4-hemisphere, or by orbifolding the 4-sphere.

Dong Lai, Y. -Z. Qian

In proto-neutron stars with strong magnetic fields, the cross section for $ν_e$ ($\barν_e$) absorption on neutrons (protons) depends on the local magnetic field strength due to the quantization of energy levels for the $e^-$ ($e^+$) produced in the final state. If the neutron star possesses an asymmetric magnetic field topology in the sense that the magnitud

Paul Benioff

Quantum robots and their interactions with environments of quantum systems are described and their study justified. A quantum robot is a mobile quantum system that includes a quantum computer and needed ancillary systems on board. Quantum robots carry out tasks whose goals include specified changes in the state of the environment or carrying out measurements

Yu-Chung N. Cheng, Lawrence M. Krauss

We examine whether a cosmologically significant distribution of dark galaxy group or cluster-sized objects can have an optical depth for multiple imaging of distant background sources which is comparable to that from known galaxies while at the same time producing angular splittings of the same order of magnitude. Our purpose is to explore whether such objec

M. Athanas

We have observed the decay of the $B^-$ meson into $D^0 K^-$, using 3.3 million $B\bar B$ pairs collected with the CLEO II detector at the Cornell Electron Storage Ring. We find the branching fractions of this decay to be suppressed relative to the decay into $D^0 π^-$ by $0.055 \pm 0.014 \pm 0.005$.

J. A. de Azcarraga, J. C. Perez Bueno

The problem of gauging a closed form is considered. When the target manifold is a simple Lie group G, it is seen that there is no obstruction to the gauging of a subgroup H\subset G if we may construct from the form a cocycle for the relative Lie algebra cohomology (or for the equivariant cohomology), and an explicit general expression for these cocycles is

C. Ford, U. G. Mitreuter, J. Pawlowski, T. Tok

We consider pure Yang Mills theory on the four torus. A set of non-Abelian transition functions is presented which encompass all instanton sectors. It is argued that these transition functions are a convenient starting point for gauge fixing. In particular, we give an extended Abelian projection with respect to the Polyakov loop, where $A_0$ is independent o

G. Camici, M. Grazzini, L. Trentadue

By using Jet Calculus as a consistent framework to describe multiparton dynamics we explain the peculiar evolution equation of fracture functions by means of the recently introduced extended fracture functions.

S. B. Dubovichenko

Radiative capture processes in 4He12C channel of 16O nucleus are considered on the basis of potential two-cluster model with intercluster interactions which contain forbidden states and reproduce phase shifts of elastic scattering and some characteristics of bound states. Astrophysical S-factors are calculated at low energies. It was shown that the model use

S. B. Dubovichenko, A. V. Dzhazairov-Kakhramanov

Radiative capture in the 4He3H and 4He3He channels are considered for the 7Li and 7Be nuclei. The analysis is based on the corresponding two-cluster models. The potentials of cluster interaction include forbidden states and are made to be consistent with the phase shifts of elastic scattering at energies up to 20 MeV. Such an approach is shown to describe th

Troels Harmark

The theory of eleven dimensional supergravity on R^10 x S^1/Z_2 with super Yang-Mills theory on the boundaries is reconsidered. We analyse the general solution of the modified Bianchi identity for the four-form field strength using the equations of motion for the three-form and find that the four-form field strength has a unique value on the boundaries of R^

A. D. Mirlin, P. Woelfle

We calculate the magnetoresistivity of a two-dimensional electron gas in the presence of a periodic potential within classical transport theory, using realistic models of impurity scattering. The magnetooscillations induced by geometric resonance of the cyclotron orbits in the periodic grating, known as Weiss oscillations, are shown to be affected strongly b

R. Jimenez, A. Kashlinsky

Accurate synthetic models of stellar populations are constructed and used in evolutionary models of stellar populations in forming galaxies. Following their formation, the late type galaxies are assumed to follow the Schmidt law for star formation, while early type galaxies are normalized to the present-day fundamental plane relations assumed to mimic the me

Hajime Yoshino

The aging effects of a 'diffusing glass', a single elastic string diffusing in a two-dimensional disordered media assisted by thermal noise are studied by Monte Carlo (MC) simulations. We find for the first time convincing numerical evidence of non-trivial aging effects both in the linear response against transverse force and the associated correlati

Abhas Mitra

In a recent paper (Ushov, PRL, 80, 230, 1998), it has been claimed that the bare surface of a strange star can emit electron-positron pairs of luminosity \~10^{51} ergs/s for about 10s. If true, obviously, this mechanism may explain the origin of cosmic Gamma Ray Bursts. However, we point out that such a mechanism is does not work because (i) if pair product

Yosuke Imamura

We analyze gauge symmetry enhancements $SO(16)\to E_8$ on eight D7-branes and $SO(14)\times U(1)\to E_8$ on seven D7-branes from open strings. String configurations which we present in this paper are closely related to the ones given by Gaberdiel and Zwiebach. Our construction is based on $SO(8)\times SO(8)$ decomposition and its relation to the D8-brane cas

V. P. Nair, S. Randjbar-Daemi

In this paper we consider brane solutions of the form $G/H$ in M(atrix) theory, showing the emergence of world volume coordinates for the cases where $G=SU(N)$. We examine a particular solution with a world volume geometry of the form ${\bf CP}^2 \times S^1$ in some detail and show how a smooth manifold structure emerges in the large $N$ limit. In this limit

Marcos Marino, Gregory Moore

We study correlation functions in topologically twisted $\mathcal{N}=2, d=4$ supersymmetric Yang-Mills theory for gauge groups of rank larger than one on compact four-manifolds $X$. We find that the topological invariance of the generator of correlation functions of BRST invariant observables is not spoiled by noncompactness of field space. We show how to ex

Yan Jie, Zhou Haijun, Ou-Yang Zhong-can

The instability and periodic deformation of bilayer membranes during freezing processes are studied as a function of the difference of the shape energy between the high and the low temperature membrane states. It is shown that there exists a threshold stability condition, bellow which a planar configuration will be deformed. Among the deformed shapes, the pe

E. Ivanov

We point out that the N=4 supersymmetric KdV hierarchy, when written through the prepotentials of the bosonic chiral and antichiral N=2 supercurrents, exhibits a freedom related to the possibility to choose different gauges for the prepotentials. In particular, this implies that the Lax operator for the N=4 SKdV system and the associated realization of N=4 s

R. Myrzakulov

The briefly review on the common spin description of the nonlinear evolution equations.

J. G. Muga, R. F. Snider

A one parameter solvable model for three bosons subject to delta function interactions in one-dimension with periodic boundary conditions is studied. The energy levels and wave functions are classified and given explicitly in terms of three momenta. In particular, eigenstates and eigenvalues are described as functions of the model parameter, c. Some of the s

C. Quesne, N. Vansteenkiste

$C_λ$-extended oscillator algebras are realized as generalized deformed oscillator algebras. For $λ= 3$, the spectrum of the corresponding bosonic oscillator Hamiltonian is shown to strongly depend on the algebra parameters. A connection with cyclic shape invariant potentials is noted. A bosonization of PSSQM of order two is obtained.

R. Mirman

Baryon and lepton numbers are conserved. Why? Baryon number must be because baryons are subject to strong interactions, leptons are not. Conservation of baryons leads to that of leptons. This raises further questions which are noted.

B. Pasquini, G. Salme`

Nucleon generalized polarizabilities are investigated within a relativistic framework, defining such quantities through a Lorentz covariant multipole expansion of the amplitude for virtual Compton scattering. The key physical ingredients in the calculation of the nucleon polarizabilities are the Lorentz invariant reduced matrix elements of the electromagneti

Paul S. Aspinwall

A type IIA string (or F-theory) compactified on a Calabi-Yau threefold is believed to be dual to a heterotic string on a K3 surface times a 2-torus (or on a K3 surface). We consider how the resulting moduli space of hypermultiplets is identified between these two pictures in the case of the E8xE8 heterotic string. As examples we discuss SU(2)-bundles and G2-

G. Curio, D. Lust

Making use of non-perturbative U-duality symmetries of type II strings we construct new `superstring' vacua in three dimensions with N=1 supersymmetry. This has an interpretation as compactifying formally from 13 dimensions (S-theory) on Calabi-Yau 5-folds possessing a $T^3 \x T^2$ fibration. We describe some part of the massless multiplets, given by the

T. Fujiwara, H. Igarashi, Y. Takimoto

Quantum $A_2$-Toda field theory in two dimensions is investigated based on the method of quantizing canonical free field. Toda exponential operators associated with the fundamental weights are constructed to the fourth order in the cosmological constant. This leads us to a conjecture for the exact operator solution.

J. Gutowski, G. Papadopoulos

We compute the moduli metrics of worldvolume 0-brane solitons of D-branes and the worldvolume self-dual string solitons of the M-5-brane and examine their geometry. We find that the moduli spaces of 0-brane solitons of D-4-branes and D-8-branes are hyper-Kähler manifolds with torsion and octonionic Kähler manifolds with torsion, respectively. The moduli spac

Carl M. Bender, Kimball A. Milton

Recently, it has been observed that a quantum field theory need not be Hermitian to have a real, positive spectrum. What seems to be required is symmetry under combined parity and time-reversal transformations. This idea is extended to massless electrodynamics, in which the photon couples to the axial-vector current with an imaginary coupling constant. The e

Christos Kokorelis

The perturbative prepotential and the Kähler metric of the vector multiplets of the N=2 effective low-energy heterotic strings is calculated directly in N=1 six-dimensional toroidal compactifications of the heterotic string vacua. This method provides the solution for the one loop correction to the N=2 vector multiplet prepotential for compactifications of t

P. K. Townsend

These lectures explore what can be learnt about M-theory from its superalgebra. The first three lectures introduce the 'basic' branes of M-theory, and type II superstring theories, and show how the duality relations between them are encoded in the respective spacetime superalgebras. The fourth lecture introduces brane intersections and explains how t

Howard Baer, Chih-hao Chen, Manuel Drees, Frank Paige

The Yukawa couplings of the tau lepton and the bottom quark become comparable to, or even exceed, electroweak gauge couplings for large values of the SUSY parameter $\tanβ$. As a result, the lightest tau slepton $\ttau_1$ and bottom squark $\tb_1$ can be significantly lighter than corresponding sleptons and squarks of the first two generations. Gluino, charg

Yuri V. Kovchegov, A. H. Mueller

We calculate gluon production in deep inelastic scattering of the current j= - (1/4) F_{μν}^a F_{μν}^a off a large nucleus and in nucleon-nucleus collisions. In a covariant gauge calculation the transverse momentum spectrum of the gluon is determined by the final state interactions of the gluon with the nucleons in the nucleus. In a light-cone gauge calculat

Stefano Catani

We discuss the structure of infrared singularities in on-shell QCD amplitudes at two-loop order. We present a general factorization formula that controls all the $\ep$-poles of the dimensionally regularized amplitudes. The dependence on the regularization scheme is considered and the coefficients of the $1/\ep^4, 1/\ep^3$ and $1/\ep^2$ poles are explicitly g

J Bordes, HM Chan, J. Pfaudler, ST Tsou

It is noted that the CKM matrix elements for both quarks and leptons as conceived in the Dualized Standard Model (DSM) can be interpreted as direction cosines obtained by moving the Darboux trihedron (a 3-frame) along a trajectory on a sphere traced out through changing energy scales by a 3-vector factorized from the mass matrix. From the `Darboux' analo

Mauro Anselmino

Spin observables may reveal much deeper properties of non perturbative hadronic physics than unpolarized quantities. We discuss the polarization of hadrons produced in $e^+e^-$ annihilation at LEP. We show how final state $q \bar q$ interactions may give origin to non zero values of the off-diagonal element $ρ^{\,}_{1,-1}$ of the helicity density matrix of v

A. V. Bannikov, G. A. Chelkov, Z. K. Silagadze

It is shown, using a track-level simulation, that the use of the $D_s^- \to K^{*0}K^-$ decay channel for $D_s^-$ reconstruction, in additioon with the previously studied $D_s^- \to ϕπ^-$ mode, enables two fold gain in the ATLAS $B_s^0$-mixing signal statistics through $B_s^0 \to D_s^-a_1$ $B_s^0$-decay channel. A new modification of the amplitude fit method

Robert Fleischer

A general parametrization of the $B^+\toπ^+ K^0$ and $B_d^0\toπ^- K^+$ decay amplitudes is presented. It relies only on the isospin symmetry of strong interactions and the phase structure of the Standard Model and involves no approximations. In particular, this parametrization takes into account both rescattering and electroweak penguin effects, which limit

D. de Florian, M. Stratmann, W. Vogelsang

We study the production of longitudinally polarized Lambda-baryons in single-spin pp collisions at RHIC and HERA-N as a means of determining the spin-dependent Lambda fragmentation functions. It is shown that a measurement of the rapidity distribution of the Lambda's would provide an excellent way of clearly discriminating between various recently sugges

Carlo Oleari

In this thesis we describe the calculation of the process e+ e- --> Z/gamma -> Q Qbar + X, where Q is a heavy quark, X is anything else at order alpha_s^2.

P. A. Baikov, M. Steinhauser

The implementation of an algorithm for three-loop massive vacuum integrals, based on the explicit solution of the recurrence relations, in REDUCE and FORM is described.

M. W. Beinker, B. Kaempfer, G. Soff

We estimate the production rates of supersymmetric particles in central heavy-ion collisions at LHC. The parton cascade model is used to seek for possible collective phenomena which enlarge the production probability of very heavy particles. Even if there is some indication of such cooperative effects, higher energy and higher luminosity of proton beams at L

O. K. Kalashnikov

Photon and electron spectra in hot and dense QED are found in the high temperature limit for all $|\q|$ using the Feynman gauge and the one-loop self-energy. All spectra are split by the medium and their branches develop the gap (the dynamical mass) at zero momentum. The photon spectrum has two branches (longitudinal and transverse) with the common mass; but

V. V. Anisovich, D. V. Bugg, A. V. Sarantsev

We discuss a mechanism by which a set of $q\bar q$-states mixes with an exotic one, so that the exotic state accumulates the widths of the overlapping $\bar qq$ resonances. The broad state created this way acts as a 'locking' state for the others. Using results of a previous analysis of the $(IJ^{PC}=00^{++})$-wave, we estimate the mean radius square

Di Qing, Xiang-Song Chen, Fan Wang

A qualitative QCD analysis and a quantitative model calculation are given to show that the constituent quark model remains a good approximation even with the nucleon spin structure revealed in polarized deep inelastic scattering taking into account.

Sinya Aoki, Kei-ichi Nagai, Yusuke Taniguchi, Akira Ukawa

We calculate one-loop renormalization factors of bilinear quark operators for gluon action including six-link loops and $O(a)$-improved quark action in the limit of massless quark. We find that finite parts of one-loop coefficients of renormalization factors diminish monotonically as either of the coefficients $c_1$ or $c_2+c_3$ of the six-link terms are dec

G. Brandenburg

A measurement of the spin alignment of charged D^* mesons produced in continuum e^+ e^- \to c \bar{c} events at \sqrt{s}=10.5 GeV is presented. This study using 4.72 fb^{-1} of CLEO II data shows that there is little evidence of any D^* spin alignment.

Neil J. Cornish, Neil G. Turok

We present a method for finding the eigenmodes of the Laplace operator acting on any compact manifold. The procedure can be used to simulate cosmic microwave background fluctuations in multi-connected cosmological models. Other applications include studies of chaotic mixing and quantum chaos.

Eric W. Hirschmann, Anzhong Wang

We consider a general non-linear sigma model coupled to Einstein gravity and show that in spherical symmetry and for a simple realization of self-similarity, the spacetime can be completely determined. We also examine some more specific matter models and discuss their relation to critical collapse.

S. Antoci

Through a constructive method it is shown that the claim advanced in recent times about a clash that should occur between the Freud and the Bianchi identities in Einstein's general theory of relativity is based on a faulty argument.

Reinaldo Gleiser, Oscar Nicasio, Richard Price, Jorge Pullin

We study the head-on collision of black holes starting from unsymmetrized, Brill--Lindquist type data for black holes with non-vanishing initial linear momentum. Evolution of the initial data is carried out with the ``close limit approximation,'' in which small initial separation and momentum are assumed, and second-order perturbation theory is used.

N. V. Brilliantov, D. V. Kuznetsov, R. Klein

A new quantitative theory for polyelectrolytes in salt free dilute solutions is developed. Depending on the electrostatic interaction strength, polyelectrolytes in solutions can undergo strong stretching (with polyelectrolyte dimension R_g\sim l_B^{1/3}N, where l_B is the Bjerrum length and N is the number of the chain segments) or strong compression (with R

Andrey V. Chubukov, Oleg A. Starykh

We present an analytical result for the ratio of the physical correlation length in a 2D Heisenberg antiferromagnet on a square lattice, and the one which is actually computed in numerical simulations. This last correlation length is deduced from the second moment of the structure factor at the antiferromagnetic momentum Q. We show that the ratio is very clo

Holger Frahm, Sergey I. Matveenko

Calogero-Sutherland models of type $BC_N$ are known to be relevant to the physics of one-dimensional quantum impurity effects. Here we represent certain correlation functions of these models in terms of generalized hypergeometric functions. Their asymptotic behaviour supports the predictions of (boundary) conformal field theory for the orthogonality catastro

Gregory M. Braverman, Sergey A. Gredeskul, Yshai Avishai

Equilibrium vortex configuration in conventional type II superconductors containing columnar defects is theoretically investigated. Near the upper critical field a single defect causes a strong local deformation of the vortex lattice. This deformation has $C_3$ or $C_6$ point symmetry, whose character strongly depends on the vortex-defect interaction. If the

E. V. Bezuglyi, A. L. Gaiduk, V. D. Fil, W. L. Johnson

The crossing of temperature dependences of the sound velocity in normal and superconducting state of metallic glasses points out unambiguously the renormalization of the intensity of sound interaction with two-level systems (TLS), caused by their coupling with electrons. We propose a simple scenario which allows us to describe qualitatively the influence of

J. P. Dekker, A. Lodder, J. van Ek

The impurity resistivity, also known as the residual resistivity, is calculated ab initio using multiple-scattering theory. The mean-free path is calculated by solving the Boltzmann equation iteratively. The resistivity due to low-symmetrical defects, such as an impurity-vacancy pair, is calculated for the FCC host metals Al and Ag and the BCC transition met

C. Castellano, M. Marsili, L. Pietronero

We introduce a non-perturbative renormalization approach which identifies stable fixed points in any dimension for the Kardar-Parisi-Zhang dynamics of rough surfaces. The usual limitations of real space methods to deal with anisotropic (self-affine) scaling are overcome with an indirect functional renormalization. The roughness exponent $α$ is computed for d

J. Dietel, Th. Koschny, W. Apel, W. Weller

We reconsider the theory of the half-filled lowest Landau level using the Chern-Simons formulation and study the grand-canonical potential in the random-phase approximation (RPA). Calculating the unperturbed response functions for current- and charge-density exactly, without any expansion with respect to frequency or wave vector, we find that the integral fo

V. V. Moshchalkov

The enigmatic scaling behaviour of the normal state properties of the high Tc cuprates has been explained by assuming that a crossover from the two- dimensional Heisenberg (2D-H) to the one-dimensional spin ladder (1D-SL) regime takes place at temperature T=T*. For T<T* stripe formation results in the quantum 1D transport with the characteristic inelastic le

Kazushige Machida, Tetsuo Ohmi

A NMR experiment recently done by Tou et al. on a heavy Fermion superconductor UPt$_3$ is interpreted in terms of a non-unitary spin-triplet pairing state which we have been advocating. The proposed state successfully explains various aspects of the seemingly complicated Knight shift behaviors probed for major orientations, including a remarkable d-vector ro

A. P. Potylitsin

Based on kinematic model of parametric X-ray Radiation (PXR), an approach for calculation of PXR characteristics (spectrum, intensity, polarization and yield) has been developed. The approach allows to take into account the beam divergence, mosaicity, aperture sizes, influence of $K$-edge, etc. using a uniform technique.

Leonid P. Pryadko, Steven Kivelson, Daniel W. Hone

We analyze the induced interactions between localized holes in weakly-doped Heisenberg antiferromagnets due to the modification of the quantum zero point spin wave energy; i.e. the analogue of the Casimir effect. We show that this interaction is uniformly attractive and falls off as r^{-2 d+1} in d dimensions. For ``stripes&#39;&#39;, i.e parallel (d-1)-dime

Per Dahlqvist

We apply periodic orbit theory to a quantum billiard on a torus with a variable number N of small circular scatterers distributed randomly. Provided these scatterers are much smaller than the wave length they may be regarded as sources of diffraction. The relevant part of the spectral determinant is due to diffractive periodic orbits only. We formulate this

B. L. Frye, F. Courbin, T. Broadhurst, W. J. W. Welch

We discuss BIMA (Berkeley Illinois Maryland Association) data and present new high quality optical and near-IR Keck images of the bright radio ring PKS 1830-211. Applying a powerful new deconvolution algorithm we have been able to identify both images of the radio source. In addition we recover an extended source in the optical, consistent with the expected

Martin Harwit, David A. Neufeld, Gary J. Melnick, Michael J. Kaufman

Using the Long Wavelength Spectrometer (LWS) onboard the Infrared Space Observatory (ISO), we have observed thermal water vapor emission from a roughly circular field of view approximately 75 arc seconds in diameter centered on the Orion BN-KL region. The Fabry-Perot line strengths, line widths, and spectral line shifts observed in eight transitions between

John P. Hughes, Ichizo Hayashi, Katsuji Koyama

We present the results of X-ray spectroscopy of a flux-limited sample of seven middle-aged supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) (N23, N49, N63A, DEM71, N132D, 0453-68.5, and N49B), using nonequilibrium ionization Sedov-phase SNR models. All the remnants were well described by the model, allowing us to derive accurate values for their

V. V. Sokolov, A. I. Kopylov, S. V. Zharikov, M. Feroci

We present the results of photometric observations of the variable optical source associated to the remnant of the gamma-ray burst GRB970508 performed at SAO RAS (Russia) from May to August 1997. The observations were carried out with the standard (Johnson-Kron-Cousins) photometric BVRcIc system using the 1-meter and 6-meter telescopes. The brightness of the

E. Giallongo, S. D&#39;Odorico, A. Fontana, S. Cristiani

We present a deep BVrIK multicolor catalog of galaxies in the field of the high redshift (z=4.7) quasar BR 1202-0725. Reliable colors have been measured for galaxies selected down to R=25. The choice of the optical filters has been optimized to define a robust multicolor selection of galaxies at 3.8<z< 4.5. Within this interval the surface density of galaxy

K. Pottschmidt, M. Koenig, J. Wilms, R. Staubert

Cyg X-1 exhibits irregular X-ray variability on all measured timescales. The usually applied shot noise models describe the typical short-term behavior of this source by superposition of randomly occuring shots with a distribution of shot durations. We have reanalyzed EXOSAT ME observations of Cyg X-1 using the more general Linear State Space Models (LSSMs).

P. M. Chadwick, M. R. Dickinson, N. A. Dipper, T. R. Kendall

Centaurus X-3 is a well-studied high-mass accreting X-ray binary and a variable source of high energy gamma rays with energies from 100 MeV to 1 TeV. Previous results have suggested that the origin of the gamma rays is not the immediate vicinity of the neutron star but is sited in the accretion disc, perhaps in an accretion wake. The Durham Mark 6 gamma ray

K. Iwasawa, A. Comastri

We present an X-ray spectral study of the prototype far-infrared galaxy NGC6240 from ASCA. The soft X-ray spectrum (below 2 keV) shows clear signatures of thermal emission well described with a multi-temperature optically-thin plasma, which probably originates in a powerful starburst. Strong hard X-ray emission is also detected with ASCA and its spectrum abo

Michael L. Norman, Greg L. Bryan

We report on results of recent, high resolution hydrodynamic simulations of the formation and evolution of X-ray clusters of galaxies carried out within a cosmological framework. We employ the highly accurate piecewise parabolic method (PPM) on fixed and adaptive meshes which allow us to resolve the flow field in the intracluster gas. The excellent shock cap

I J Coleman, N Gray, J F L Simmons

We describe a method for determining the limb polarization and limb darkening of stars in eclipsing binary systems, by inverting photometric and polarimetric light curves. Because of the ill-conditioning of the problem, we use the Backus-Gilbert method to control the resolution and stability of the recovered solution, and to make quantitative estimates of th

J. A. Pons, J. A. Miralles, J. M. Ibanez

We calculate the Legendre expansion of the rate of the process $ν+ \barν \leftrightarrow e^+ + e^-$ up to 3rd order extending previous results of other authors which only consider the 0th and 1st order terms. Using different closure relations for the moment equations of the radiative transfer equation we discuss the physical implications of taking into accou

Ian A. Bonnell, Matthew R. Bate, Hans Zinnecker

We present a model for the formation of massive ($M > 10 M_\odot$) stars through accretion-induced collisions in the cores of embedded dense stellar clusters. This model circumvents the problem of accreting onto a star whose luminosity is sufficient to reverse the infall of gas. Instead, the central core of the cluster accretes from the surrounding gas, ther

G. Pojmanski

Results of the first two month of observations using the All Sky Automated Survey prototype camera are presented. More than 45 000 stars in 24 Selected Fields covering 140 sq. degrees were monitored a few times a night resulting in the I-band catalog containing 10^7 individual measurements. Period search revealed 126 periodic variables brighter than 13 mag.

Denis Puy, Patrick Peter

The role played by a primordial magnetic field during the pre-recombination epoch is analysed through the cyclotron radiation (due to the free electrons) it might produce in the primordial plasma. We discuss the constraint implied by the measurement or lack thereof COBE on this primordial field.

Mariano Moles, Isabel Marquez, Jack W. Sulentic

We present new photometric and spectroscopic data for the galaxies in the compact group known as Stephan&#39;s Quintet. We find the strongest evidence for dynamical perturbation in the spiral component NGC7319. Most of the damage was apparently caused by nearby NGC 7320C which passed through the group a few times 10(^8) years ago. NGC7318B is a spiral galaxy

S. P. Driver

The longstanding faint blue galaxy problem is gradually subsiding as a result of technological advancement, most notably from high-resolution Hubble Space Telescope imaging. In particular two categorical facts have recently been established, these are: 1) The excess faint blue galaxies are of irregular morphologies, and, 2) the majority of these irregulars o

A. Cavaliere, V. Vittorini

The coherent rise and fall of the quasar population is discussed in terms of gas accretion onto massive black holes, governed by the hierarchically growing environment. The rise is related to plentiful accretion during the assemblage of the host galaxies; the fall to intermittent accretion when these interact with companions in a group. The LFs are computed

S. Kachru, E. Silverstein

We propose correspondences between 4d quantum field theories with N=2,1,0 (super)conformal invariance and Type IIB string theory on various orbifolds. We argue using the spacetime string theory, and check using the beta functions (exactly for N=2,1 and so far at 1-loop for the gauge couplings in the N=0 case), that these theories have conformal fixed lines.

J. F. Beacom, P. Vogel

The $ν_μ$ and $ν_τ$ neutrinos (and their antiparticles) from a Galactic core-collapse supernova can be observed in a water-Čerenkov detector by the neutral-current excitation of $^{16}$O. The number of events expected is several times greater than from neutral-current scattering on electrons. The observation of this signal would be a strong test that these n

Andrew de Laix, Tanmay Vachaspati

We study random bubble lattices which can be produced by processes such as first order phase transitions, and derive characteristics that are important for understanding the percolation of distinct varieties of bubbles. The results are relevant to the formation of topological defects as they show that infinite domain walls and strings will be produced during

Catherine Pépin, Patrick A. Lee

We solve the problem of $N$ non magnetic impurities in the staggered flux phase of the Heisenberg model which we assume to be a good mean-field approximation for the spin-gap phase of the cuprates. The density of states is evaluated exactly in the unitary limit and is porportional to $1/\left (ω\ln^2(|ω|/D))$, in analogy with the 1D case of doped spin-Peierl

Tao Han, Ren-Jie Zhang

We categorize general messenger and matter interactions in gauge-mediated SUSY breaking models by an R-parity for the messengers and study their phenomenological consequences. The new interactions may induce baryon- and lepton-number violating processes as well as flavor-changing neutral currents. Bounds on the couplings from low-energy data are generally we

I. V. Krasovsky

A second-order differential (q-difference) eigenvalue equation is constructed whose solutions are generating functions of the dual (q-)Hahn polynomials. The fact is noticed that these generating functions are reduced to the (little q-)Jacobi polynomials, and implications of this for quasi-exactly solvable problems are studied. A connection with the Azbel-Hof

H. Neuberger

The set of one dimensional lowest energy eigenspaces used to construct the overlap induces a two form on gauge orbit space which is the locally exact curl of Berry&#39;s connection. If anomalies do not cancel, examples of two dimensional closed sub-manifolds of orbit space are produced over which the integral of the above two form does not vanish. Based on t

M. Abou Zeid, C. M. Hull

New forms of Born-Infeld, D-brane and M theory five-brane actions are found which are quadratic in the abelian field strength. The gauge fields couple both to a background or induced metric and a new auxiliary metric, whose elimination reproduces the non-polynomial Born-Infeld action. This is similar to the introduction of an auxiliary metric to simplify the