September 1997 arXiv papers — page 11

Shigehiro Nagataki, Masa-aki Hashimoto, Katsuhiko Sato, Shoichi Yamada

Explosive nucleosynthesis under the axisymmetric explosion in Type II supernova has been performed by means of two dimensional hydrodynamical calculations. We have compared the results with the observations of SN 1987A. Our chief findings are as follows: (1) $^{44}Ti$ is synthesized so much as to explain the tail of the bolometric light curve of SN 1987A. We

V. Lakshmibai, Peter Magyar

A result of Zelevinsky states that an orbit closure in the space of representations of the equioriented quiver of type $A_h$ is in bijection with the opposite cell in a Schubert variety of a partial flag variety $SL(n)/Q$. We prove that Zelevinsky's bijection is a scheme-theoretic isomorphism, which shows that the universal degeneracy schemes of Fulton a

Changhyun Ahn, Kyungho Oh, Radu Tatar

We study M theory fivebranes to understand the moduli space of vacua of N=1 supersymmetric SO(N_c) gauge theory with N_f flavors in four dimensions. We discuss how the various branches of this theory arise in the string/M theory brane configurations and compare our results with the ones obtained earlier by Intriligator and Seiberg in the context of field the

Hsiu-Hau Lin

Single-wall carbon nanotubes with on-site interaction $U \ll t$ are studied by a controlled renormalization group method. When formulated as a system of $N_{f}$ flavors of interacting Dirac fermions, the effective model at generic filling resembles a set of quasi-1D Hubbard chains. For the undoped $(N_{y}, N_{y})$-armchair and the $(N_{x}, -N_{x})$-zigzag wi

Igor R. Klebanov, Leonard Susskind

In a recent paper it was shown that the properties of Schwarzschild black holes in 8 dimensions are correctly described up to factors of order unity by Matrix theory compactified on T^3. Here we consider compactifications on tori of general dimension d. Although in general little is known about the relevant d+1 dimensional theories on the dual tori, there ar

Paul J. Ellis, Hua-Bin Tang

We study pion--nucleon scattering with a chiral lagrangian of pions, nucleons, and $Δ$-isobars. The scattering amplitude is evaluated to one-loop $Q^3$ order, where $Q$ is a generic small momentum, using a new approach which is equivalent to heavy baryon chiral perturbation theory. We obtain a good fit to the experimental phase shifts for pion center-of-mass

Z. Maassarani, P. Mathieu

The natural su(N) generalization of the XX model is introduced and analyzed. It is defined in terms of the characterizing properties of the usual XX model: the existence of two infinite sequences of mutually commuting conservation laws and the existence of two infinite sequences of mastersymmetries. The integrability of these models, which cannot be obtained

R. Dijkgraaf, E. Verlinde, H. Verlinde

We review some recent developments in the study of M-theory compactifications via Matrix theory. In particular we highlight the appearance of IIA strings and their interactions, and explain the unifying role of the M-theory five-brane for describing the spectrum of the T^5 compactification and its duality symmetries. The 5+1-dimensional micro-string theory t

Stephen L. Adler, Achim Kempf

We study the leading corrections to the emergent canonical commutation relations arising in the statistical mechanics of matrix models, by deriving several related Ward identities, and give conditions for these corrections to be small. We show that emergent canonical commutators are possible only in matrix models in complex Hilbert space for which the number

R. Banerjee, C. Wotzasek

We develop a technique that solders the dual aspects of some symmetry following from the bosonisation of two distinct fermionic models, thereby leading to new results which cannot be otherwise obtained. Exploiting this technique, the two dimensional chiral determinants with opposite chirality are soldered to reproduce either the usual gauge invariant express

Johan Linde, Tommy Ohlsson, Hakan Snellman

The Coleman-Glashow sum-rule for magnetic moments is always fulfilled in the chiral quark model, independently of SU(3) symmetry breaking. This is due to the structure of the wave functions, coming from the non-relativistic quark model. Experimentally, the Coleman-Glashow sum-rule is violated by about ten standard deviations. To overcome this problem, two mo

T. Hambye, R. B. Mann, U. Sarkar

A breakdown of the Local Lorentz Invariance and hence the special theory of relativity in the Kaon system can, in principle, induce oscillations between the $K^0$ and $\bar{K}^0$ states. We construct a general formulation in which simultaneous pairwise diagonalization of mass, momentum and weak eigenstates is not assumed and the maximum attainable speeds of

P. Furlan, A. Ch. Ganchev, V. B. Petkova

We derive the fusion rules for a basic series of admissible representations of $\hat{sl}(3)$ at fractional level $3/p-3$. The formulae admit an interpretation in terms of the affine Weyl group introduced by Kac and Wakimoto. It replaces the ordinary affine Weyl group in the analogous formula for the fusion rules multiplicities of integrable representations.

Jordi Atserias, Salvador Climent, Xavier Farreres, German Rigau

This paper explores the automatic construction of a multilingual Lexical Knowledge Base from preexisting lexical resources. First, a set of automatic and complementary techniques for linking Spanish words collected from monolingual and bilingual MRDs to English WordNet synsets are described. Second, we show how resulting data provided by each method is then

K. Fabricius, U. Löw

The dynamical structure factor of the frustrated spin 1/2 Heisenberg model for a series of frustration parameters at finite temperatures is presented. A sharp upper boundary of the spinon continuum is found. A simple method to extract the nearest neighbour coupling J from the spectral width is suggested. Signatures of frustration are discussed and a comparis

M. Meyer-Hermann, A. Schäfer

The chiral-odd distribution function $h_1$ is discussed in the framework of the renormalon approach. Using a bag-model calculation for $h_1$, we calculate its intrinsic uncertainty due to renormalon poles. The result is given as a function of Bjorken-$x$ as well as for the first moments separately. We also extract the perturbative corrections to the first mo

G. E. Volovik

Using the semiclassical approach to the energy levels of the fermions bound to the vortex core, we found the difference between the states in nonchiral and chiral superconductors, determined by the Berry phase. The bound states of fermions in the singly quantized vortex in the layered superconductor with the symmetry of superfluid 3He-A is E=n\omega_0 (as di

K. A. Oganessyan, H. R. Avakian, N. Bianchi, P. Di Nezza

We consider the azimuthal asymmetries in semi-inclusive deep inelastic leptoproduction arising due to both perturbative and nonperturbative effects at HERMES energies and show that the $k_T^2/Q^2$ order corrections to $< \cosϕ>$ and $< \cos2ϕ>$ are significant. We also reconsider the results of perturbative effects for $< \cosϕ>$ at large momentum transfers

A. Taruya, Y. Nambu

We investigate the cosmological perturbation of two-scalar field model during the reheating phase after inflation. Using the exact solution of the perturbation in long-wavelength limit, which is expressed in terms of the background quantities, we analyze the behavior of the metric perturbation. The oscillating inflaton field gives rise to the parametric reso

Max Tegmark

As cutting-edge experiments display ever more extreme forms of non-classical behavior, the prevailing view on the interpretation of quantum mechanics appears to be gradually changing. A (highly unscientific) poll taken at the 1997 UMBC quantum mechanics workshop gave the once all-dominant Copenhagen interpretation less than half of the votes. The Many Worlds

A. Kempf

We review known and we present new results on three types of short distance structures of observables which typically appear in studies of quantum group related algebras. In particular, one of the short distance structures is shown to suggest a new mechanism for the introduction of internal symmetries.

V. D. Gershun

The differential and variational calculus on the $SL_{q}(2,R)$ group is constructed. The spontaneous breaking symmetry in the WZNW model with $SL_{q}(2,R)$ quantum group symmetry and in the $σ$-models with ${SL_{q}(2,R)/U_{h}(1)}$ ,$C_{q}(2|0)$ quantum group symmetry is considered. The Lagrangian formalism over the quantum group manifolds is discussed. The c

G. Roepke, A. Wierling

A multiple-moment approach to the dielectric function of a dense non-ideal plasma is treated beyond RPA including collisions in Born approximation. The results are compared with the perturbation expansion of the Kubo formula. Sum rules as well as Ward identities are considered. The relations to optical properties as well as to the dc electrical conductivity

J. R. Mureika

In the wake of numerous injuries and Donovan Bailey&#39;s media-stamped &#34;sub-par&#34; 100m victory of 10.03s at the 1997 Canadian Track and Field Championships, a medal hope at the 1997 World Championships seems grim for the Olympic Champion and World Record holder. However, when one considers that the 10.03s was run into a hefty head-wind (-2.1 m/s), a

Amand Faessler, A. J. Buchmann, M. I. Krivoruchenko, B. V. Martemyanov

The possibility for occurrence of a Bose condensate of dibaryons in nuclear matter is investigated within the framework of the Walecka model in the mean-field approximation. Constraints for the omega - and sigma - meson coupling constants with dibaryons following from the requirement of stability of dibaryon matter against compression are derived and the eff

C. Bennhold, T. Mart, D. Kusno

The electroproduction of kaons on the nucleon is shown to be an ideal tool to extract electromagnetic form factors of strange mesons and hyperons. Longitudinal n(e,e&#39;K0)Lambda cross sections are found to be sensitive to the K0 form factor, while sensitivity to the Lambda magnetic form factor can be seen in recoil-beam double polarization observables. The

P. Crochet, F. Rami, R. Dona, the FOPI Collaboration

Azimuthal distributions of charged particles and intermediate mass fragments emitted in Au+Au collisions at 600AMeV have been measured using the FOPI facility at GSI-Darmstadt. Data show a strong increase of the in-plane azimuthal anisotropy ratio with the charge of the detected fragment. Intermediate mass fragments are found to exhibit a strong momentum-spa

Mariusz Rabus, Saharon Shelah

For every uncountable cardinal mu there is a ccc Boolean algebra whose topological density is mu .

Paul C. Eklof, Saharon Shelah

We answer a long-standing open question by proving in ordinary set theory, ZFC, that the Kaplansky test problems have negative answers for aleph_1-separable abelian groups of cardinality aleph_1. In fact, there is an aleph_1-separable abelian group M such that M is isomorphic to M oplus M oplus M but not to M oplus M .

Tapani Hyttinen, Saharon Shelah

In this paper we prove a strong nonstructure theorem for kappa (T)-saturated models of a stable theory T with dop.

Saharon Shelah, Lee Stanley

We present two different types of models where, for certain singular cardinals lambda of uncountable cofinality, lambda -> (lambda, omega+1)^2, although lambda is not a strong limit cardinal. We announce, here, and will present in a subsequent paper, that, for example, consistently, aleph_{omega_1} not-> (aleph_{omega_1}, omega+1)^2 and consistently, 2^{alep

John Hubbard, Peter Papadopol, Vladimir Veselov

In \cite {HO1}, it was shown that there is a topology on $\C^2\sqcup S^3$ homeomorphic to a 4-ball such that the Hénon mapping extends continuously. That paper used a delicate analysis of some asymptotic expansions, for instance, to understand the structure of forward images of lines near infinity. The computations were quite difficult, and it is not clear h

John W. Milnor

This is a preliminary investigation of the geometry and dynamics of rational maps with only two critical points. (originally titled ``On Bicritical Rational Maps&#39;&#39; in September 1997; revised and retitled April 1999)

Adam L. Epstein

Let ${\cal H}$ be a hyperbolic component of quadratic rational maps possessing two distinct attracting cycles. We show that ${\cal H}$ has compact closure in moduli space if and only if neither attractor is a fixed point.

Jan Felipe van Diejen, Luc Vinet

We quantize a compactified version of the trigonometric Ruijse\-naars-Schneider particle model with a phase space that is symplectomorphic to the complex projective space CP^N. The quantum Hamiltonian is realized as a discrete difference operator acting in a finite-dimensional Hilbert space of complex functions with support in a finite uniform lattice over a

Al Baernstein, Stephen J. Montgomery-Smith

We discuss some conjectural inequalities that are related to singular integrals, martingales, quasiconformal mappings, and the calculus of variations. Specifically, we present evidence for a conjecture of Iwaniec concerning the best constant for the Beurling-Ahlfors Operator.

S. James Gates,

Preliminary evidence is presented that a long overlooked and critical element in the fundamental definition of a general theory of integration over curved Wess-Zumino superspace lies with the imposition of ``the Ethereal Conjecture&#39;&#39; which states the necessity of the superspace to be topologically ``close&#39;&#39; to its purely bosonic sub-manifold.

Stefan Mashkevich

It is well known that charges coupled to a pure Chern-Simons gauge field in (2+1) dimensions undergo an effective change of statistics, i.e., become anyons. We will consider several generalizations thereof, arising when the gauge field is more general. The first one is ``multispecies anyons&#39;&#39;---charged particles of several species coupled to one, or

Matthias Staudacher, Werner Krauth

We find the exact non-perturbative expression for a simple Wilson loop of arbitrary shape for U(N) and SU(N) Euclidean or Minkowskian two-dimensional Yang-Mills theory regulated by the Wu-Mandelstam-Leibbrandt gauge prescription. The result differs from the standard pure exponential area-law of YM_2, but still exhibits confinement as well as invariance under

Tim R. Morris

Over the last several years, there has been a resurgence of interest in using non-perturbative approximation methods based on Wilson&#39;s continuous renormalization group. In this lecture, I review progress particularly in the past year, concentrating on theoretical issues in the structure of the exact renormalization group and its approximations.

Bhabani Prasad Mandal, Subir Mukhopadhyay

We calculate the potential between bound states of D-branes of different dimension in IIB matrix model upto one loop order and find nice agreement with the open string calculations in short and large distance limit. We also consider the scattering of bound states of D-branes, calculate the scattering phase shift and analyze the effective potential in differe

A. Armoni, Y. Frishman, J. Sonnenschein

We compute the string tension in massive $QCD_2$. It is shown that the string tension vanishes when the mass of the dynamical quark is zero, with no dependence on the representations of the dynamical or of the external charges. When a small mass ($m\ll e$) is added, a tension appears and we calculate its value as a function of the representations.

Dmitri Ivanov, Kirill Melnikov

Using impact-factor representation, we consider the lepton pair production by an incident high-energy photon in a strong electromagnetic field of a nucleus. By summing leading terms of perturbation series, we obtain a simple formula for the amplitude, valid to all orders in ${\cal O}(αZ)$ and arbitrary field of the nucleus. Using these results, we derive, in

E. Gabrielli, V. A. Ilyin, B. Mele

We show that the Higgs production in $eγ$ collisions, through the one-loop reaction $eγ\to eH$ at large transverse momentum, can provide a precise determination of the $ZγH$ vertex. We concentrate on the analysis of signal rates vs background looking for strategies to improve the ratio $S/B$. Possible bounds on anomalous contributions to the $ZγH$ vertex are

Marc Knecht, Res Urech

The low energy scattering of pions is investigated in the presence of electromagnetic interactions at leading order and at next-to-leading order for the amplitudes involving at most one pair of charged pions. The size of the electromagnetic corrections to the S-wave scattering lengths is found to be comparable to the size of the two loop strong interaction c

I. I. Levintov

In the model the entire high-energy part of the amplitude (Regge power dependence from the total energy) comes as consequence of Gribov&#39;s diffusion of the constituent quarks in the space of rapidities and impact parameters. Charge exchange of the quarks, which goes at small quark anti-quark invariant masses, is described by low-energy Nambu - Jona-Lasini

K. Suzuki

We study the structure of constituent quarks by dressing bare quarks with the Goldstone bosons and its implications for quark distribution functions of hadrons $f_1(x)$, $g_1(x)$ and $h_1(x)$. In particular we discuss effects of the dressing on the nucleon spin structure, and find that contributions to chiral-odd $h_1(x)$ is quite different from those to $g_

Andreas Vogt

The QCD treatment of the photon structure is recalled. Emphasis is given to the recently derived momentum sum rule, and to the proper choice of the factorization scheme and/or boundary conditions for the evolution equations beyond the leading order. Parametrizations of the photon&#39;s parton content are examined and compared. The small-x behaviour of the ph

Yu. A. Simonov

Numerous aspects and mechanisms of color confinement in QCD are surveyed. After a gauge-invariant definition of order parameters, the phenomenon is formulated in the language of field correlators, to select a particular correlator responsible for confinement. In terms of effective Lagrangians confinement is viewed upon as a dual Meissner effect and a quantit

A. V. Leonidov, P. V. Ruuskanen

Using a Hagedorn resonance gas picture and quark-hadron duality we estimate the dilepton emission rate in the vicinity of the QCD deconfinement phase transition. The result is then used to calculate a dilepton spectrum in ultrarelativistic heavy ion collisions. We show that multibody contributions taken into account in the Hagedorn resonance gas approach pro

M. Diehl

The distribution of a suitably defined azimuthal angle in diffractive deep inelastic scattering contains information on the polarisation of the exchanged photon. In particular it allows one to constrain the longitudinal diffractive structure function. We investigate the potential of such bounds in general and for particular diffractive final states.

Igor A. Shovkovy

The catalysis of chiral symmetry breaking in the massless weakly coupled QED in a magnetic field is studied. It is shown that the effect is due to the dimensional reduction $D\to D-2$ in the dynamics of fermion pairing in a magnetic field. The dynamical mass of fermions (energy gap in the fermion spectrum) is determined. The temperature of the symmetry resto

L. Conti

We present a high statistics study of the D- and B-meson decay constants. The results were obtained by using the Clover and Wilson lattice actions at $β=6.0$ and 6.2.

Tamas G. Kovacs, E. T. Tomboulis

We exhibit the appropriate variables allowing the plus-minus (Z(2)) `reduction&#39; of the Wilson loop operator which provides a direct measure of the thin, thick and `mixed&#39; Z(2) topological, gauge-invariant vortices in SU(2) LGT. Simulations with the Wilson action, as well as a perfect action smoothing procedure, show the string tension to be reproduce

Simon Hands

Results are presented from a Monte Carlo simulation of the Nambu -- Jona-Lasinio model with SU(2)xSU(2) chiral symmetry and N_f=2 flavors of fermion. We show that fits to the equation of state are sensitive to the shape and extent of the assumed scaling region; the best fits favour a triviality scenario predicted by the large-N_f approximation, in which the

F. Farchioni, V. Laliena

We compute the fixed point action of a properly defined renormalization group transformation for the Schwinger model through an expansion in the gauge field. It is local, with couplings exponentially suppressed with the distance. We check its perfection by computing the 1-loop mass gap at finite spatial volume, finding only exponentially vanishing cut off ef

M. N. Chernodub, F. V. Gubarev, M. I. Polikarpov

The correlations of the topological charge (Q), the electric (Je) and the magnetic (Jm) currents in the SU(2) lattice gauge theory in the Maximal Abelian projection are investigated. A nonzero value of the correlator <Q Je Jm> is obtained for a wide range of values of the bare charge, as well as under the cooling.

B. L. G. Bakker, M. N. Chernodub, M. I. Polikarpov

By numerical calculations we show that the abelian monopole currents are locally correlated with the density of SU(2) lattice action. This fact is established for the maximal abelian projection. Thus, in the maximal abelian projection the monopoles are physical objects, they carry SU(2) action. Calculations on the asymmetric lattice show that the correlation

V. Bornyakov, G. Schierholz, A. Thimm

We pursue further an approach to lattice chiral fermions in which the fermions are treated in the continuum. To render the effective action gauge invariant, counterterms have to be introduced. We determine the counterterms for smooth gauge fields, both analytically and numerically. The final result is that the imaginary part of the effective action can be co

R. B. Mann

I describe the general mathematical construction and physical picture of topological black holes, which are black holes whose event horizons are surfaces of non-trivial topology. The construction is carried out in an arbitrary number of dimensions, and includes all known special cases which have appeared before in the literature. I describe the basic feature

Douglas N. Arnold, Arup Mukherjee, Luc Pouly

According to the theory of general relativity, the relative acceleration of masses generates gravitational radiation. Although gravitational radiation has not yet been detected, it is believed that extremely violent cosmic events, such as the collision of black holes, should generate gravity waves of sufficient amplitude to detect on earth. The massive Laser

Neil J. Cornish, Janna J. Levin

The Mixmaster or Bianchi IX cosmological model has become one of the archetypal settings for studying gravitational dynamics. The past decade has seen a vigourous debate about whether or not the Mixmaster&#39;s dynamics is chaotic. In this talk we review our recent work in uncovering a chaotic invariant set of orbits in the Mixmaster phase space, and how we

Neil J. Cornish

The study of dynamics in general relativity has been hampered by a lack of coordinate independent measures of chaos. Here I review a variety of invariant measures for quantifying chaotic dynamics in relativity that exploit the coordinate independence of fractal dimensions and symbolic entropies.

E. Marinari

I discuss results from numerical simulations of finite dimensional spin glass models, and show that they show all signatures of a mean field like behavior, basically coinciding with the one of the Parisi solution. I discuss the Binder cumulant, the probability distribution of the order parameter, the non self-averaging behavior. The determination of correlat

T. Senthil

We consider the effect of a random longitudinal field on the Ising model in a transverse magnetic field. For spatial dimension $d > 2$, there is at low strength of randomness and transverse field, a phase with true long range order which is destroyed at higher values of the randomness or transverse field. The properties of the quantum phase transition at zer

A. W. McConnell, T. Timusk, A. Dabkowski, H. A. Dabkowska

The reflectance of single crystal LaSrGaO4 has been measured from approx 50 to 40000 cm^-1 along the &#34;a&#34; and &#34;c&#34; axis. The optical properties have been calculated from a Kramers-Kronig analysis of the reflectance for both polarizations. The reflectance curves have been fit using a product of Lorentzian oscillators.

Raffaella Burioni, Davide Cassi

A good generalization of the Euclidean dimension to disordered systems and non crystalline structures is commonly required to be related to large scale geometry and it is expected to be independent of local geometrical modifications. The spectral dimension, defined according to the low frequency density of vibrational states, appears to be the best candidate

R. Pastor-Satorras, J. M. Rubi

We have studied the properties of clusters of colloidal magnetic particles generated from a 2D aggregation model with dipolar interparticle interactions. Particles diffuse off-lattice, experiencing dipolar interactions with the already attached particles until either they stick to the cluster or wander far away and are removed. Our results are interpreted in

Stefano Lepri, Roberto Livi, Antonio Politi

The problem of stationary heat transport in the Fermi-Pasta-Ulam chain is numerically studied showing that the conductivity diverges in the thermodynamic limit. Simulations were performed with time-reversible thermostats, both for small and large temperature gradients. In the latter case, fluctuations of the heat current are shown to be in agreement with the

A. Z. Akheyan, N. S. Ananikian, S. K. Dallakian

The antiferromagnetic Ising model in a magnetic field is considered on the Husimi tree. Using iteration technique we draw the plots of magnetization versus external field for different temperatures and construct the resulting phase diagram. We show that frustration effects essentially change the critical properties. The model exhibits three distinct critical

Jose Maria Gomez Hidalgo, Manuel de Buenaga Rodriguez

Automatic text categorization is a complex and useful task for many natural language processing applications. Recent approaches to text categorization focus more on algorithms than on resources involved in this operation. In contrast to this trend, we present an approach based on the integration of widely available resources as lexical databases and training

C. O. Escobar, R. A. Vázquez

We argue that magnetic monopoles can not be associated to the highest energy cosmic rays as recently suggested. Both the observed spectrum and the arrival direction disagree with observation.

Piero Madau

I review a technique for interpreting faint galaxy data which traces the evolution with cosmic time of the galaxy luminosity density, as determined from several deep spectroscopic samples and the HDF. The method relies on the rest frame UV and near-IR continua of galaxies as indicators, for a given IMF and dust content, of their instantaneous SFR and total s

C. J. Clarke, A. L. Kinney, J. E. Pringle

We present a new method for the statistical investigation into the distributions of the angle beta between the radio axis and the normal to the galactic disk for a sample of Seyfert galaxies. We discuss how further observations of the sample galaxies can strengthen the conclusions. Our data are consistent with the hypothesis that AGN jets are oriented random

Lynn D. Matthews, John S. Gallagher

We present B and V CCD aperture photometry for a morphologically-selected sample of forty-nine southern, extreme late-type spiral galaxies. All objects are moderate-to-low surface brightness Local Supercluster field galaxies that were detected previously in HI surveys. Our sample features objects that have optical luminosities, optical sizes, and HI masses w

Maarten Schmidt, Guenther Hasinger, James Gunn, Don Schneider

The ROSAT Deep Survey includes a complete sample of 50 X-ray sources with fluxes in the $0.5 - 2$ keV band larger than 5.5 $10^{-15}$ erg cm$^{-2}$ s$^{-1}$ in the Lockman field (Hasinger et al., Paper I). We have obtained deep broad-band CCD images of the field and spectra of many optical objects near the positions of the X-ray sources. We define systematic

Amri Wandel

We derive a theoretical relation between $R_{BLR}$, the size of the broad-emission-line region of active galactic nuclei, and the observed soft X-ray luminosity and spectrum. We show that in addition to the well known $R_{BLR}\sim L^{1/2}$ scaling, $R_{BLR}$ should depend also on the soft X-ray spectral slope and derive the expected relation between $R_{BLR}

Guenther Hasinger, Richard Burg, Riccardo Giacconi, Maarten Schmidt

The ROSAT Deep Survey in the Lockman Hole is the most sensitive X-ray survey performed to date, encompassing an exposure time of 207 ksec with the PSPC and a total of 1.32 Msec with the HRI aboard ROSAT. Here we present the complete catalogue of 50 X-ray sources with PSPC fluxes (0.5--2 keV) above $ 5.5 \times 10^{-15} erg cm^{-2} s^{-1}$. The optical identi

Tommy Wiklind, Francoise Combes

New millimeter wave observations of the molecular absorption line system in the gravitational lens to PKS1830-211 at z=0.88582 is presented. Self-calibrated interferometer data shows unequivocally that the previously detected absorption component is associated with the gravitationally lensed south-west image of the background source. A second absorption line

P. Garnavich, A. Noriega-Crespo, A. Raga, K. H. Bohm

We present new narrow-band near-infrared images together with K band spectra of highly collimated bipolar jets close to the IRAS 05487+0255 source. The jets are located at 50&#34; West of the Herbig-Haro 110 outflow. The jets are not visible at optical wavelengths, and therefore, do not fall into the `standard&#39; Herbig-Haro object classification scheme. N

Valentina D&#39;Odorico

We report the detection of a significant clustering signal on scales $Δv < 300$ km/s, for a sample of 71 C IV absorbers. This result confirms previous findings and, together with data at lower column density, it points to a trend of decreasing clustering amplitude with decreasing column density, analogous to that observed for Lyman alpha lines.

Wolfgang Brandner, You-Hua Chu, Frank Eisenhauer, Eva K. Grebel

We have performed a detailed study of the morphology and kinematics of the hourglass-shaped nebula around the blue supergiant Sher 25 in the galactic giant HII region NGC 3603. Near-infrared high resolution adaptive optics images in the Br gamma line and HST/NICMOS images in the HeI 1.08mu line were compared with iso-velocity maps in the H alpha and [NII] li

Adam Dobrzycki, Jill Bechtold

We present the analysis of a sample of the Ly-$α$ forest spectra of 152 quasars taken with the HST FOS. The Ly-$α$ lines show little evolution at $0<z<1.7$. We see a difference between the evolution indices for weak and strong lines.

A. Ortiz-Gil, K. M. Lanzetta, J. K. Webb, X. Barcons

We present here new GHRS observations of Lyman-alpha absorption lines associated with groups or clusters toward the QSOs 1545+2101 and 0850+4400. In the first case we have identified at least eight distinct Lyman-alpha absorption features, with a mean redshift of <z> = 0.2648 \pm 0.0002 and a velocity dispersion of 163 \pm 57 km/s. We have also identified a

A. Fernandez-Soto, K. M. Lanzetta, A. Yahil, H. -W. Chen

We use our catalog of photometric redshifts in the Hubble Deep Field (HDF) to estimate the Luminosity Function (LF) of galaxies up to z=2. Using the obtained LF and a relationship between luminosity and halo size, we calculate the expected density of galactic halo crossings for any arbitrary line of sight. This density is then compared with the known one of

Y. Markov, V. Tarasov, A. Varchenko

We consider a function $U=e^{-f_0}\prod_j^N f_j^{α_j}$ on a real affine space, here $f_0,..,f_N$ are linear functions, $α_1, ...,α_N$ complex numbers. The zeros of the functions $f_1, ..., f_N$ form an arrangement of hyperplanes in the affine space. We study the period matrix of the hypergeometric integrals associated with the arrangement and the function $U

Y. Aharonov, J. Oppenheim, S. Popescu, B. Reznik

It is argued that the time-of-arrival cannot be precisely defined and measured in quantum mechanics. By constructing explicit toy models of a measurement, we show that for a free particle it cannot be measured more accurately then $Δt_A \sim 1/E_k$, where $E_k$ is the initial kinetic energy of the particle. With a better accuracy, particles reflect off the m

Geza Odor, Nora Menyhard

The damage spreading (DS) transitions of two one-dimensional stochastic cellular automata suggested by Grassberger (A and B) and the kinetic Ising model of Menyhárd (NEKIM) have been investigated on the level of kinks and spins. On the level of spins the parity conservation is not satisfied and therefore studying these models provides a convenient tool to un

J. Audretsch, V. D. Skarzhinsky

We consider QED - processes in the presence of an infinitely thin and infinitely long straight string with a magnetic flux inside it. The bremsstrahlung from an electron passing by the magnetic string and the electron-positron pair production by a single photon are reviewed. Based on the exact electron and positron solutions of the Dirac equation in the exte

Gia Dvali, Zurab Kakushadze

Dilaton stabilization may occur in a theory based on a single asymptotically free gauge group with matter due to an interplay between quantum modification of the moduli space and tree-level superpotential. We present a toy model where such a mechanism is realized. Dilaton stabilization in this mechanism tends to occur at strong coupling values unless some un

Valery P. Gusynin

The catalysis of chiral symmetry breaking by a magnetic field in the massless weak-coupling phase of QED is studied. The dynamical mass of a fermion (energy gap in the fermion spectrum) is shown to depend essentially nonanalytically on the renormalized coupling constant $α$ in a strong magnetic field. The temperature of the symmetry restoration is calculated

E791 Collaboration, E. M. Aitala et al

We report results of the first search for the pentaquark P_{{c bar}s} which is predicted to be a doublet of states: P^0_{{c bar}s}=({c bar} s u u d) and P^-_{{c bar}s}=({c bar} s d d u). A search was made for the decay P^0_{{c bar}s} --> phi,pi,p in data from Fermilab experiment E791, in which 500 GeV/c pi^- beam interacted with nuclear targets. We present u

James L. Anderson

The Thompson cross section for scattering of electromagnetic waves by a free electron in an expanding universe is derived here. The equations of motion of the electron are obtained using the Einstein-Infeld-Hoffmann (EIH) surface integral method. These integrals are evaluated approximately by perturbing off an Einstein-deSitter cosmological field. It is foun

Kazuaki Ikeda, Hiroaki Nakamura, Satarou Yamaguchi

On the measurement of thermoelectric power and Nernst coefficient, we used two kinds of shapes for a sample. One is &#34;Bridge shape&#34; and the other is, we call,&#34;Fat-Bridge shape&#34;. The latter has 5 times wider main body than the former. We used pure n-InSb in this experiment, whose carrier condensation measured at 77K was $6.6 \times 10^{-14} cm^

J. L. Higdon, R. J. Rand, S. D. Lord

We have imaged the kpc scale distribution of 12CO(J=1-0) emission in the ring galaxy Arp 143 (NGC 2444/5) using the OVRO millimeter array. We find two giant molecular complexes in the ring component (NGC 2445) and a bright central source. The ring complexes comprise 20-60% of the detected H_2 mass, depending on the relative I(CO)-N(H_2) for the ring & nucleu

Amri Wandel

In the common model supernova shock-acceleration of cosmic rays there are two open questions: 1. where does the high energy cosmic rays below the knee (10$^4-10^6$ Gev) come from, and 2. are cosmic ray accelerated only at their origin or contineuosly during their residence in the Galaxy. We show that $10^15$ eV light nuclei are probably accelerted by associa

A. G. Cohen, A. De Rujula

We ask whether the universe can be a patchwork consisting of distinct regions of matter and antimatter. In previous work we demonstrated that post-recombination matter-antimatter contact near regional boundaries leads to an observable (but unobserved) gamma-ray flux for domain sizes of less than a few thousand Mpc, thereby excluding such domains. In this pap

R. Riediger, P. Petitjean, J. P. Muecket

We study the evolution with redshift, from z=5 to z=0, of the Lyman-alpha forest in a CDM model using numerical simulations including collisionless particles only. The baryonic component is assumed to follow the dark matter distribution. We distinguish between two populations of particles: Population P{s} traces the filamentary structures of the dark matter,

Chigurupati Murali, Scott Tremaine

We determine the response of a self-similar isothermal stellar system to small adiabatic gravitational perturbations. For odd spherical harmonics, the response is identical to the response of the analogous isothermal fluid system. For even spherical harmonics, the response can be regarded as an infinite series of wavetrains in $\log r$, implying alternating

Michael Rauch

We briefly discuss the relevance of Lyman alpha forest observations for measuring cosmological parameters, comparing the properties of high z QSO spectra with those of artifical spectra from hydrodynamic simulations, based on hierarchical cosmologies. In particular, we describe a measurement of the baryon content of the universe obtained by matching the aver