February 1999 arXiv papers — page 8

Dieter Breitschwerdt, Thomas Schmutzler

We present the first dynamically and thermally self-consistent calculations of fast adiabatically expanding gas flows from the Galactic disk into the halo. It is shown that in a hot plasma (T >= 10^6 K) with a high overpressure with respect to the ambient medium, the dynamical time scale is much shorter than the intrinsic time scales (e.g. for recombination,

J. H. Krolik

Qualitative arguments are presented to demonstrate that the energy density of magnetic fields in matter accreting onto a black hole inside the marginally stable orbit is automatically comparable to the rest-mass energy density of the accretion flow. Several consequences follow: magnetic effects must be dynamically significant, but cannot be so strong as to d

Steven Gratton, Neil Turok

We compute, from first principles, the quantum fluctuations about instanton saddle points of the Euclidean path integral for Einstein gravity coupled to a scalar field. The Euclidean two-point correlator is analytically continued into the Lorentzian region where it describes the quantum mechanical vacuum fluctuations in the state described by no boundary pro

V. Celebonovic

A simple method for determining the thermal component of the EOS of solids under high pressure is proposed.Application to the interior of the Earth gives results in agreement with recent geophysical data.

J. A. Stevens, W. K. Gear

Observations at millimetre wavelengths are presented for a representative sample of 22 X-ray-selected BL Lac objects (XBLs). This sample comprises 19 High-energy cutoff BL Lacs objects (HBLs), 1 Low-energy cutoff BL Lac object (LBL) and 2 `intermediate' sources. Data for LBLs, which are mostly radio selected BL Lac objects (RBLs) are taken from the liter

Valerio Faraoni, Edgard Gunzig

Late time mild inflation (LTMI) proposes to solve the age of the universe problem and the discrepancy between locally and globally measured values of the Hubble parameter. However, the mechanism proposed to achieve LTMI is found to be physically pathological by applying the theory of tails for the solutions of wave equations in curved spaces. Alternative mec

A. Kraus, A. Quirrenbach, A. P. Lobanov, T. P. Krichbaum

We present radio observations at three frequencies and contemporaneous optical monitoring of the peculiar BL Lac object AO 0235+164. During a three-week campaign with the VLA we observed intraday variability in this source and found a distinct peak which can be identified throughout the radio frequencies and tentatively connected to the R-band variations. Th

Igor V. Igumenshchev

Numerical, two-dimensional, time-dependent hydrodynamical models of geometrically thick accretion discs around black holes are presented. Accretion flows with non-effective radiation cooling (ADAFs) can be both convectively stable or unstable depending on the value of the viscosity parameter α. The high viscosity flows (α~1) are stable and have a strong equa

Hee-Won Lee, Myeong-Gu Park

In this paper, we argue that in the symbiotic star RR Tel the existence of an accretion disk around the hot companion is strongly implied by the characteristic features exhibited by the Raman-scattered O VI lines around 6830 Åand 7088 Å. High degrees of polarization and double-peaked profiles in the Raman-scattered lines and single-peak profiles for other em

R. Gilli, A. Comastri, G. Brunetti, G. Setti

The contribution of the iron emission line, commonly detected in the X-ray spectra of Seyfert (Sey) galaxies, to the cosmic X-ray background (XRB) spectrum is evaluated in the framework of the XRB synthesis models based on AGN unification schemes. To derive the mean line properties, we have carried out a search in the literature covering a sample of about 70

Simone Bianchi, Jonathan I. Davies, Paul B. Alton

We have derived the dust emissivity in the Far-Infrared (FIR) using data available in the literature. We use two wavelength dependences derived from spectra of Galactic FIR emission (Reach et al. 1995). A value for the emissivity, normalised to the extinction efficiency in the V band, has been retrieved from maps of Galactic FIR emission, dust temperature an

V. R. Chitnis, P. N. Bhat

Atmospheric Cherenkov technique is an established methodology to study TeV energy gamma rays. Here we carry out systematic monte carlo simulation studies of the timing information of Cherenkov photons. Extensive studies have already been carried out in this regard. Most of these are carried out at higher energies with the aim of studying the elemental compos

Inger Jorgensen

Mean ages and metal abundances are estimated for the stellar populations in a sample of 115 E and S0 galaxies in the central 64&#39;x70&#39; of the Coma cluster. The estimates are based on the line indices Mg2, <Fe> and Hbeta, and the mass-to-light ratios (M/L). Stellar population models from Vazdekis et al. were used to transform from the measured parameter

Pablo Minces, Victor O. Rivelles

We consider the AdS/CFT correspondence for theories with a Chern-Simons term in three dimensions. We find the two-point functions of the boundary conformal field theories for the Proca-Chern-Simons theory and the Self-Dual model. We also discuss particular limits where we find the two-point function of the boundary conformal field theory for the Maxwell-Cher

C. Barbero, F. Krmpotić, A. Mariano, D. Tadić

The recently developed formalism for the evaluation of nuclear form factors in neutrinoless double beta decay is applied to $^{48}Ca$, $^{76}Ge$, $^{82}Se$, $^{100}Mo$, $^{128}Te$ and $^{130}Te$ nuclei. Explicit analytical expressions that follows from this theoretical development, in the single mode model for the decay of $^{48}Ca$, have been worked out. Th

Anupam Mazumdar

It has been proposed that, without invoking supersymmetry, it is possible to solve the hierarchy problem provided the fundamental scale in the higher dimensional theory is at a much lower scale than the Planck scale. In this paper we consider a toy model where we allow $4+d$ dimensions to evolve from a region determined by the new fundamental scale, which is

A. Masiero, D. Montanino, M. Peloso

The standard CDM model fails to describe the power spectrum of fluctuations since it gives too much power at small scales. Among other possible improvements, it has been suggested that an agreement with observations can be achieved with the addition of a late decaying particle, through the injection of non-thermal radiation and the consequent increase of the

A. Kehagias, K. Sfetsos

We construct an explicit solution of type-IIB supergravity describing the strong coupling regime of a non-supersymmetric gauge theory. The latter has a running coupling with an ultraviolet stable fixed point corresponding to the N=4 SU(N) super-Yang-Mills theory at large N. The running coupling has a power law behaviour, argued to be universal, that is consi

A. N. Mitra

Soft-QCD effects of quark-level form factors in $γγ$ decay of $B_s$-mesons via $D{\bar D}$ intermediate states, suggested by Ellis et al, are examined in the &#34;Salpeter&#34; model [reinterpreted in terms of the Markov-Yukawa Transversality Principle (MYTP)] when formulated on a covariant light front (null-plane). The gluonic kernel in the infrared regime

J. M. Landsberg, Laurent Manivel

We present a new proof of the classification of complex simple Lie algebras via the projective geometry of homogeneous varieties. Our proof proceeds by constructing homogeneous varieties using the ideals of the secant and tangential varieties of homogeneous varieties already constructed. Our algorithms make no reference to root systems. Our proofs use proper

M. K. Parida, B. Purkayastha

Including contributions of scale-dependent vacuum expectation values of Higgs scalars, we derive new one-loop formulas analytically for running quark-lepton masses at higher scales in MSSM. Apart from the gauge-coupling dependence being different from earlier formulas, the third-generation- Yukawa-coupling effects are absent in the masses of the first two ge

Robert B. Griffiths

The interpretations of a particular quantum gedanken experiment provided by Bohmian mechanics and consistent histories are shown to contradict each other, both in the absence and in the presence of a measuring device. The consistent history result seems closer to standard quantum mechanics, and shows no evidence of the mysterious nonlocal influences present

Massimo Blasone, Peter A. Henning, Giuseppe Vitiello

We show the presence of a topological (Berry) phase in the time evolution of a mixed state. For the case of mixed neutrinos, the Berry phase is a function of the mixing angle only.

Attilio Cucchieri

We evaluate numerically the three-momentum-space gluon propagator in the lattice Landau gauge, for three-dimensional pure-SU(2) lattice gauge theory with periodic boundary conditions. Simulations are done for nine different values of the coupling $β$, from $β= 0$ (strong coupling) to $β= 6.0$ (in the scaling region), and for lattice sizes up to $V = 64^3$. I

M. Takeda, N. Hayashida, K. Honda, N. Inoue

With the Akeno Giant Air Shower Array (AGASA), 581 cosmic rays above 10^19eV, 47 above 4 x 10^19eV, and 7 above 10^20eV are observed until August 1998. Arrival direction distribution of these extremely high energy cosmic rays has been studied. While no significant large-scale anisotropy is found on the celestial sphere, some interesting clusters of cosmic ra

D. Yvon, V. Sushkov, R. Bernard, J. L. Bret

We implemented a low noise current preamplifier for the readout of resistive bolometers. We tested the apparatus on thermometer resistances ranging from 10 Ohm to 500 Mohm. The use of current preamplifier overcomes constraints introduced by the readout time constant due to the thermometer resistance and the input capacitance. Using cold JFETs, this preamplif

R. N. Hansen, M. Christensen, A. L. Larsen

We examine the question of collapse of Turok&#39;s two-parameter family of cosmic strings. We first perform a classification of the strings according to the specific time(s) at which the minimal string size is reached during one period. We then obtain an exact analytical expression for the probability of collapse to black holes for the Turok strings. Our res

Kazuyuki Furuuchi, Nobuyoshi Ohta, Jian-Ge Zhou

The spacetime superalgebra via the supermembrane probe in the background of AdS_4 \times S^7 is discussed to the lowest order in the spinor coordinate $\t$. To obtain the correct spacetime superalgebras, all $\t^2$ order corrections for supervielbein and super 3-form gauge potential have to be included. The central extension of the superalgebra OSp(8|4) of t

Y. Kikukawa, T. Noguchi

We derive the effective action of the light fermion field of the domain-wall fermion, which is referred as $q(x)$ by Furman and Shamir. The inverse of the effective Dirac operator turns out to be identical to the inverse of the truncated overlap Dirac operator, except a local contact term which would give the chiral symmetry breaking in the Ginsparg-Wilson r

Jeongwon Ho, Won T. Kim, Young-Jai Park

We consider the duality of the quasilocal black hole thermodynamics, explicitly the quasilocal black hole thermodynamic first law, in BTZ black hole solution as a special one of the three-dimensional low energy effective string theory.

Andrew S. Fruchter, S. E. Thorsett, Mark R. Metzger, Kailash C. Sahu

We report on HST and Palomar optical images of the field of GRB 990123, obtained on 8 and 9 February 1999. We find that the optical transient (OT) associated with GRB 990123 is located on an irregular galaxy, with magnitude V=24.20 +/- 0.15. The strong metal absorption lines seen in the spectrum of the OT, along with the low probability of a chance superposi

Vijay Balasubramanian, Per Kraus

We propose a procedure for computing the boundary stress tensor associated with a gravitating system in asymptotically anti-de Sitter space. Our definition is free of ambiguities encountered by previous attempts, and correctly reproduces the masses and angular momenta of various spacetimes. Via the AdS/CFT correspondence, our classical result is interpretabl

J. Harnad, J. McKay

Generalized Halphen systems are solved in terms of functions that uniformize genus zero Riemann surfaces, with automorphism groups that are commensurable with the modular group. Rational maps relating these functions imply subgroup relations between their automorphism groups and symmetrization relations between the associated differential systems.

Chie Bing Wang

We consider the polynomials $ϕ_n(z)= κ_n (z^n+ b_{n-1} z^{n-1}+ >...)$ orthonormal with respect to the weight $\exp(\sqrtλ (z+ 1/z)) dz/2 πi z$ on the unit circle in the complex plane. The leading coefficient $κ_n$ is found to satisfy a difference-differential (spatially discrete) equation which is further proved to approach a third order differential equati

Mark S. Byrd

The adiabatic geometric phases for general three state systems are discussed. An explicit parameterization for space of states of these systems is given. The abelian and non-abelian connection one-forms or vector potentials that would appear in a three dimensional quantum system with adiabatic characteristics are given explicitly. This is done in terms of th

E. Scapparone

The features of the HEMAS code are presented. The results of the comparison between the Monte Carlo expectation and the experimental data are shown.

David K. Lubensky, David R. Nelson

Motivated by experiments in which a polynucleotide is driven through a proteinaceous pore by an electric field, we study the diffusive motion of a polymer threaded through a narrow channel with which it may have strong interactions. We show that there is a range of polymer lengths in which the system is approximately translationally invariant, and we develop

Christian Elphick, Aric Hagberg, Ehud Meron

Periodic forcing of an oscillatory system produces frequency locking bands within which the system frequency is rationally related to the forcing frequency. We study extended oscillatory systems that respond to uniform periodic forcing at one quarter of the forcing frequency (the 4:1 resonance). These systems possess four coexisting stable states, correspond

A. Parreño, C. Bennhold, A. Ramos

We present a nonrelativistic transition potential for the weak strangeness-changing reaction $ΛN \to NN$. The potential is based on a one meson exchange model (OME), where, in addition to the long-ranged pion, the exchange of the pseudoscalar $K, η$, as well as the vector $ρ, ω, K^*$ mesons is considered. Results obtained for different hypernuclear decay obs

V. B. Soubbotin, X. Vinas

The one-body density matrix is derived within the Extended Thomas-Fermi approximation. This has been done starting from the Wigner-Kirkwood distribution function for a non-local single-particle potential. The links between this new approach to the density matrix with former ones available in the literature are widely discussed. The semiclassical Hartree-Fock

A. Schnell, G. Roepke, P. Schuck

Low-density nuclear matter at finite temperature is considered representing the strong coupling situation of a highly correlated fermion system. One-particle se lf-energies and the density of states in the vicinity of the pairing transition point are presented. Within the Green function approach model calculations are p erformed using the thermodynamic $T$ m

Dirk Schlingemann

This paper is concerned with constructive and structural aspects of euclidean field theory. We present a C*-algebraic approach to lattice field theory. Concepts like block spin transformations, action, effective action, and continuum limits are generalized and reformulated within the C*-algebraic setup. Our approach allows to relate to each family of lattice

Felipe Leitner

We investigate the twistor space and the Grassmannian fibre bundle of a Lorentzian 4-space with natural almost optical structures and its induced CR-structures. The twistor spaces of the Lorentzian space forms $\R^4_1, \Di{S}^4_1$ and $\Di{H}^4_1$ are explicitly discussed. The given twistor construction is applied to surface theory in Lorentzian 4-spaces. Im

Laura Mersini

The field-theoretical description of quantum fluctuations on the background of a tunneling field $σ$ is revisited in the case of a functional Schrodinger approach. We apply this method in the case when quantum fluctuations are coupled to the $σ$ field through a mass-squared term, which is &#39;time-dependent&#39; since we include the dynamics of $σ$ . The re

G. Veneziano

I argue that, in the chaotic version of string cosmology proposed recently, classical and quantum effects generate, at the time of exit to radiation, the correct amount of entropy to saturate a Hubble (or holography) entropy bound (HEB) and to identify, within our own Universe, the arrow of time. Demanding that the HEB be fulfilled at all times forces a cruc

Sze-Shiang Feng, Bin Wang, Xin-He Meng

The boundary charges which constitute the Virasoro algebra in 2+1 dimensional anti-de Sitter gravity are derived by way of Noether theorem and diffeomorphic invariance. It shows that the boundary charges under discussion recently exhaust all the independent nontrivial charges available. Therefore, the state counting via the Virasoro algebra is complete.

Elena Gubankova

The method of flow equations is applied to QED on the light front. Requiring that the particle number conserving terms in the Hamiltonian are considered to be diagonal and the other terms off-diagonal an effective Hamiltonian is obtained which reduces the positronium problem to a two-particle problem, since the particle number violating contributions are eli

G. Veneziano

Classical and quantum gravitational instabilities, can, respectively, inflate and warm up a primordial Universe satisfying a superstring-motivated principle of &#34;Asymptotic Past Triviality&#34;. A physically viable big bang is thus generated without invoking either large fine-tunings or a long period of post-big bang inflation. Properties of the pre-bangi

George W. S. Hou

The best place to search for direct CP violation is the already observed charmless $b\to s$ modes. In SM with FSI, $a_{CP}$ in $Kπ$ modes could be as large as 20-30% but differ in sign between $K^-π^+/K^-π^0$ and $\bar K^0 π^-$. We illustrate possible New Physics effects that could lead to $a_{CP}$ of order 40-60% in $Kπ$ and $ϕK$ modes distinguishable from

V. Kuvshinov, R. Shulyakovsky

The instanton-induced multiple events in high energy collisions are considered in nonperturbative quantum chromodynamics. Here we obtained unusual behaviour of ratio of correlation moments Hq for such processes which can be used for experimental search of instantons.

Hai-Yang Cheng

A way of circumventing the gauge and infrared problems with effective Wilson coefficients is shown. Implications of experimentally measured charmless $B$ decays are discussed.

O. Philipsen

The static sectors of the electroweak Standard Model and QCD at finite temperatures are described by 3d SU(N) Higgs models with scalars in the fundamental and adjoint representation, respectively. I summarize the non-perturbative physics of these theories like mass spectrum, string tension, screening of the static potential and non-perturbative corrections t

V. M. Braun, S. E. Derkachov, G. P. Korchemsky, A. N. Manashov

We develop a new theoretical framework for the description of leading twist light-cone baryon distribution amplitudes which is based on integrability of the helicity $λ=3/2$ evolution equation to leading logarithmic accuracy. A physical interpretation is that one can identify a new `hidden&#39; quantum number which distinguishes components in the $λ=3/2$ dis

F. Karsch, M. Oevers, P. Petreczky

We study the Landau gauge propagators of the lattice SU(2) 3d adjoint Higgs model, considered as an effective theory of high temperature 4d SU(2) gauge theory. From the long distance behaviour of the propagators we extract the screening masses. It is shown that the pole masses extracted from the propagators agree well with the screening masses obtained recen

C. Boros, A. W. Thomas

We calculate the parton distributions for both polarized and unpolarized octet and decuplet baryons, using the MIT bag, dressed by mesons. We show that the hyperfine interaction responsible for the $\Delta - N$ and $\Sigma^0 - \Lambda$ splittings leads to large deviations from SU(3) and SU(6) predictions. For the $\Lambda$ we find significant polarized, non-

Andreas Freund, Vadim Guzey

In this paper, we discuss the algorithms used in the LO evolution program for nondiagonal parton distributions in the DGLAP region and discuss the stability of the code. Furthermore, we demonstrate that we can reproduce the case of the LO diagonal evolution within 0.5% of the original code as developed by the CTEQ-collaboration.

Attilio Cucchieri, Tereza Mendes

We discuss critical slowing-down of several gauge-fixing algorithms for the so-called lambda-gauges in the SU(2) case at zero temperature. For these gauges we also evaluate the gluon propagator using different definitions of the lattice gluon field, corresponding to discretization errors of different orders.

L. C. Garcia de Andrade

The gravitational weak field of a global monopole in the Einstein-Cartan theory of gravity is investigated.To obtain this solution we assume that Cartan torsion takes the form of the Newtonian gravitational potential.From the geodesics it is possible to show that the torsionic monopole produces a repulsive gravitational force.

Amir H. Abbassi

According to Birkhoff&#39;s theorem the only spherically symmetric solution of the vacuum Einstein field equations is the Schwarzschild solution. Inspite of imposing asymptotically flatness and staticness as initial conditions we obtain that these equations have general solutions with the Schwarzschild metric as merely a special and simplest form of them. It

Y. J. Kim, R. J. Birgeneau, M. A. Kastner, Y. S. Lee

We report a quantum Monte Carlo study of the thermodynamic properties of arrays of spin ladders with various widths ($n$), coupled via a weak inter-ladder exchange coupling $αJ$, where $J$ is the intra-ladder coupling both along and between the chains. This coupled ladder system serves as a simplified model for the magnetism of presumed ordered spin and char

Anders Johansen, Didier Sornette, Adam Espe Hansen

We present experimental evidence and theoretical arguments showing that the time-evolution of freely decaying 2-d turbulence is governed by a {\it discrete} time scale invariance rather than a continuous time scale invariance. Physically, this reflects that the time-evolution of the merging of vortices is not smooth but punctuated, leading to a prefered scal

D. L. Shepelyansky

It is shown that the Coulomb interaction can lead to delocalization of two electron states in two-dimensional (2D) disordered potential in a way similar to the Anderson transition in three dimensions (3D). At fixed disorder strength the localized phase corresponds to low electron density and large value of parameter r_s.

M. Damnjanovic, I. Milosevic, T. Vukovic, R. Sredanovic

The full symmetry groups for all single- and multi-wall carbon nanotubes are found. As for the single-wall tubes, the symmetries form nonabelian nonsymorphic line groups, enlarging the groups reported in literature. In the multi-wall case, any type of the line and the axial point groups can be obtained, depending on single-wall constituents and their relativ

Matthew J. W. Dodgson, Vadim B. Geshkenbein, Gianni Blatter

We establish a new interstitial-vacancy unbinding transition of the Berezinskii-Kosterlitz-Thouless type, transforming the three dimensional pancake vortex lattice of a decoupled layered superconductor into a defected solid. This transition is the natural finite-field extension of the vortex-anti-vortex unbinding transition establishing the zero-field superf

P. Monthoux

We present a non-perturbative approach to the problem of quasiparticles coupled to spin-fluctuations. If the fully dressed spin-fluctuation propagator is used in the Feynman graph expansion of the single-particle Green&#39;s function, the problem of summing all spin-fluctuation exchange graphs (i.e without virtual fermion loops) can be cast as a functional i

Erik Koch, Olle Gunnarsson, Richard M. Martin

We study the static screening in a Hubbard-like model using quantum Monte Carlo. We find that the random phase approximation is surprisingly accurate almost up to the Mott transition. We argue that in alkali-doped Fullerenes the Coulomb pseudopotential $μ^\ast$ is not very much reduced by retardation effects. Therefore efficient screening is important in red

G. Bianconi, M. A. Munoz, A. Gabrielli, L. Pietronero

A recently introduced real space renormalization group technique, developed for the analysis of processes in the Kardar-Parisi-Zhang universality class, is generalized and tested by applying it to a different family of surface growth processes. In particular, we consider a growth model exhibiting a rich phenomenology even in one dimension. It has four differ

Kazuhito Itoh

We present exact ground states in spin models with orbital generacy in one and higher dimensions. A method to obtain the exact ground states of the models when the Hamiltonians are composed of the products of two commutable operators is proposed. For the case of the spin-1/2 model with two-fold degeneracy some exact ground states are given, such as the Valen

M. Pleimling

The properties of S = 1 anisotropic Heisenberg models with nondiagonal exchange between axial and planar spin components are investigated using Monte Carlo techniques. The quantum nature is taken into account in a semi-classical approximation. The ordering of the spins when applying an external field with axial and planar components is discussed. It is argue

A. Lucian, R. Hilfer

We discuss the problem of trapping and mobilization of nonwetting fluids during immiscible two phase displacement processes in porous media. Capillary desaturation curves give residual saturations as a function of capillary number. Interpreting capillary numbers as the ratio of viscous to capillary forces the breakpoint in experimental curves contradicts the

Hiroki Nakano, Masatoshi Imada

Charge dynamics of the two-dimensional Hubbard model is investigated. Lancz$\ddot{\rm o}$s-diagonalization results for the optical conductivity and the Drude weight of this model are presented. Near the Mott transition, large incoherence below the upper-Hubbard band is obtained together with a remarkably suppressed Drude weight in two dimensions while the cl

J. M. G. Vilar

In a recent paper, Diaz-Guilera et al. [Phys. Rev. E 57, 3820 (1998)] analyze the mechanisms of synchronization and pattern formation in a lattice of pulse-coupled oscillators. In essence, their analysis consists in the study of the stability of the fixed points of several linear return maps which are obtained from the original system by means of matrix mani

Shunya Ishioka, Nobuko Fuchikami

Landauer discussed the minimum energy necessary for computation and stated that erasure of information is accompanied by heat generation to the amount of kT ln2/bit. Modifying the above statement, we claim that erasure of information is accompanied by entropy generation k ln2/bit. Some new concepts will be introduced in the field of thermodynamics that are i

H. Lin, H. K. C. Yee, R. G. Carlberg, S. L. Morris

We examine the evolution of the galaxy luminosity function (LF) using a sample of over 2000 galaxies, with 0.12 < z < 0.55 and 17.0 < Rc < 21.5, drawn from the Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2), at present the largest such sample at intermediate redshifts. We use UBVRcIc photometry to classify our galaxies into

P. R. McCullough, J. E. Gaustad, W. Rosing, D. Van Buren

We summarize the relationship between the free-free emission foreground and Galactic H-alpha emission. H-alpha observations covering nearly the entire celestial sphere are described. These data provide a template to isolate and/or remove the effect of Galactic free-free emission from observations of the cosmic microwave background. Spectroscopy and imaging p

Ortwin E. Gerhard

Our Galaxy is a barred spiral. Recent work based on the COBE NIR data implies a small bulge-bar and a disk with a short scale-length. The corotation radius of the bar is in the range 3-4.5 kpc. The stellar density distribution beyond the end of the bar appears to be perturbed strongly by the Galaxy&#39;s spiral arms. Gas flow calculations in corresponding po

Jonathan P. Williams, Leo Blitz, Christopher F. McKee

We review the progress that has been made in observing and analyzing molecular cloud structure in recent years. Structures are self-similar over a wide range of scales with similar power law indices independent of the star forming nature of a cloud. Comparison of structures at parsec-scale resolution in a star forming and non-star forming cloud show that the

Pedro T. P. Viana, Andrew R. Liddle

We use the observed evolution of the galaxy cluster X-ray integral temperature distribution function between z=0.05 and z=0.32 in an attempt to constrain the value of the density parameter, Omega_0, for both open and spatially-flat universes. We conclude that when all the most important sources of possible error, both in the observational data and in the the

T. P. Downes, T. P. Ray

While it is generally thought that molecular outflows from young stellar objects (YSOs) are accelerated by underlying stellar winds or highly collimated jets, the actual mechanism of acceleration remains uncertain. The most favoured model, at least for low and intermediate mass stars, is that the molecules are accelerated at jet-driven bow shocks. Here we in

Igor V. Igumenshchev, Andrei F. Illarionov, Marek A. Abramowicz

Observed spectra of Active Galactic Nuclei (AGN) and luminous X-ray binaries in our Galaxy suggest that both hot (~10^9 K) and cold (~10^6 K) plasma components exist close to the central accreting black hole. Hard X-ray component of the spectra is usually explained by Compton upscattering of optical/UV photons from optically thick cold plasma by hot electron

John Ellis

The Cosmic Microwave Background (CMB) provides a precious window on fundamental physics at very high energy scales, possibly including quantum gravity, GUTs and supersymmetry. The CMB has already enabled defect-based rivals to inflation to be discarded, and will be able to falsify many inflationary models. In combination with other cosmological observations,

Steven V. W. Beckwith, Thomas Henning, Yoshitsugu Nakagawa

Recent research on the buildup of rocks from small dust grains has reaffirmed that grain growth in protoplanetary disks should occur quickly. Calculation of growth rates have been made for a variety of growth processes and generally predict high probabilities of sticking in low-velocity collisions that may be brought about in a number of ways in protoplaneta

Roelof Bottema

Presented are spectroscopic emission and absorption line observations along the major axis of the Sb galaxy NGC 7331. The kinematics of the ionized gas and the stars appears to be regular, but contrary to what one might expect, the emission line gas rotates slower than the stars in the inner regions. This may be caused by an inner inclined and warped gas lay

M. J. Page, F. J. Carrera, J. P. D. Mittaz, K. O. Mason

The X-ray variability of the narrow line Seyfert 1 galaxy Markarian 766 is studied using 9 ROSAT PSPC datasets. The spectrum is well described by a power law combined with a blackbody (kT~ 70 eV) soft excess. Examination of flux ratio changes and variability amplitude in 3 X-ray bands, shows that the power law component varies continuously on time-scales of

L. Boirin, D. Barret, J. F. Olive, J. E. Grindlay

The burster and dipper Low Mass X-ray Binary (LMXB) 4U1915-05 (also known as XB1916-053) was observed by the Rossi X-ray Timing Explorer (RXTE) 19 times for a total exposure of 140 ks between 1996 February and October. Here we report on the discovery of Low Frequency (10-40 Hz) Quasi-Periodic Oscillations (LFQPOs) from 4U1915-05. The properties of the LFQPOs

M. V. Medvedev

Thermodynamic and spectral properties of a photon gas in $e^+e^-γ$ plasmas are studied. The effect of a finite effective mass of a photon, associated with the plasma frequency cutoff, is self-consistently included. In the ultra-relativistic plasma, the photon spectrum turns out to be universal with the temperature normalized plasma frequency cutoff being a f

Anthony G. A. Brown, A. Blaauw, R. Hoogerwerf, J. H. J. de Bruijne

Since the previous (1990) edition of this meeting enormous progress in the field of OB associations has been made. Data from X-ray satellites have greatly advanced the study of the low-mass stellar content of associations, while astrometric data from the Hipparcos satellite allow for a characterization of the higher-mass content of associations with unpreced

R. Sagar, A. K. Pandey, V. Mohan, R. K. S. Yadav

The CCD magnitudes in Johnson $BV$ and Cousins $R$ photometric passbands are determined for the optical transient of GRB 990123. These observations have been taken approximately 12 hours after trigger of the gamma-ray burst. BVR photometric light curves are obtained by combining the published data with the present measurements. They indicate that the flux de

A. C. Quillen, A. Alonso-Herrero, M. J. Rieke, C. McDonald

We construct near-infrared to visible broad band NICMOS/WFPC color maps for 4 early-type Seyfert galaxies with S-shaped or one-sided ionization cones. We find that dust lanes are near or connected to many of the features seen in the [OIII] and H$α$+[NII] line emission maps. This suggests that much of the structure of line emission in these ionization cones i

Michael Gutperle, Yuji Satoh

In this paper D-brane boundary states constructed in Gepner models are used to analyze some aspects of the dynamics of D0-branes in Calabi-Yau compactifications of type II theories to four dimensions. It is shown that the boundary states correspond to BPS objects carrying dyonic charges. By analyzing the couplings to closed string fields a correspondence bet

Graciela Gelmini, Alexander Kusenko

Relic neutrinos with mass 0.07 (+0.02/-0.04) eV, in the range consistent with Super-Kamiokande data, can explain the cosmic rays with energies in excess of the Greisen-Zatsepin-Kuzmin cutoff. The spectrum of ultra-high energy cosmic rays produced in this fashion has some distinctive features that may help identify their origin. Our mechanism does not require

Joshua Erlich, Amihay Hanany, Asad Naqvi

We study brane configurations for four dimensional N=1 supersymmetric gauge theories with quartic superpotentials which flow in the infrared to manifolds of interacting superconformal fixed points. We enumerate finite N=2 theories, from which a large class of marginal N=1 theories descend. We give the brane descriptions of these theories in Type IIA and Type

Robert G. Edwards, Urs M. Heller, Joe Kiskis, Rajamani Narayanan

Quark spectra in QCD are linked to fundamental properties of the theory including the identification of pions as the Goldstone bosons of spontaneously broken chiral symmetry. The lattice Overlap-Dirac operator provides a nonperturbative, ultraviolet-regularized description of quarks with the correct chiral symmetry. Properties of the spectrum of this operato

Werner Krauth, Matthias Staudacher

We investigate one-matrix correlation functions for finite SU(N) Yang-Mills integrals with and without supersymmetry. We propose novel convergence conditions for these correlators which we determine from the one-loop perturbative effective action. These conditions are found to agree with non-perturbative Monte Carlo calculations for various gauge groups and

E. Scapparone

The project of a large underground experiment (NOE) devoted to long baseline neutrino oscillation measurement is presented

D. N. Sheng, Z. Y. Weng

We demonstrate a universal scaling form of longitudinal resistance in the quantum critical region of metal-insulator transitions, based on numerical results of three-dimensional Anderson transitions (with and without magnetic field), two-dimensional quantum Hall plateau to insulator transition, as well as experimental data of the recently discovered two-dime

Apostolos Pilaftsis, Carlos E. M. Wagner

We study the Higgs-boson mass spectrum of the minimal supersymmetric standard model, in which the tree-level CP invariance of the Higgs potential is broken explicitly by loop effects of soft-CP-violating Yukawa interactions related to scalar quarks of the third generation. The analysis is performed by considering the CP-non-invariant renormalization-group im

Thomas Mehen, Iain W. Stewart, Mark B. Wise

We note that in the limit where the NN 1S0 and 3S1 scattering lengths, a^(1S0) and a^(3S1), go to infinity, the leading terms in the effective field theory for strong NN interactions are invariant under Wigner&#39;s SU(4) spin-isospin symmetry. This explains why the leading effects of radiation pions on the S-wave NN scattering amplitudes vanish as a^(1S0) a

Benjamin Grinstein, Richard F. Lebed

The decays B^+ --> D^{*+}_s gamma and B^+ --> D^{*+} gamma can be used for an extraction of |V_{ub}|. When the b and c quarks are nearly degenerate the rate for these modes can be determined in terms of other observed rates, namely B\bar{B} mixing and D^* --> D gamma decay. To this end we introduce a novel application of heavy quark and flavor symmetries. Al

Alexandra N. Cha, Kenneth R. Sembach, Anthony C. Danks

We have obtained high resolution Ca II and Na I absorption line spectra toward 68 OB stars in the direction of the Vela Supernova Remnant. The stars lie at distances of 190 -- 2800 pc as determined by Hipparcos and spectroscopic parallax estimations. The presence of high velocity absorption attributable to the remnant along some of the sight lines constrains