June 1997 arXiv papers — page 9

U. Guenther, A. Zhuk

Inhomogeneous multidimensional cosmological models with a higher dimensional space-time manifold are investigated under dimensional reduction. In the Einstein conformal frame, small excitations of the scale factors of the internal spaces near minima of an effective potential have a form of massive scalar fields in the external space-time. Parameters of model

John L. Friedman, Jorma Louko, Stephen N. Winters-Hilt

We perform a Hamiltonian reduction of spherically symmetric Einstein gravity with a thin dust shell of positive rest mass. Three spatial topologies are considered: Euclidean (R^3), Kruskal (S^2 x R), and the spatial topology of a diametrically identified Kruskal (RP^3 - {a point at infinity}). For the Kruskal and RP^3 topologies the reduced phase space is fo

Robert Joynt

The question of anomalous transport due to a band of impurity states in unconventional superconductors is discussed. In general, the bound state energies are not in midgap, even in the unitarity limit. This implies that, generically, the states associated with impurities are broad resonances, not true bound states. There is no impurity band in the usual sens

M. -Carmen Miguel, Mehran Kardar

Two-sided flux decoration experiments indicate that threading dislocation lines (TDLs), which cross the entire film, are sometimes trapped in metastable states. We calculate the elastic energy associated with the meanderings of a TDL. The TDL behaves as an anisotropic and dispersive string with thermal fluctuations largely along its Burger's vector. Thes

Y. Chen, M. Wu, L. M. Song

We investigate the number of gamma-ray bursts in two particular strips of the sky using the data in 3B catalog of Burst and Transient Source Experiment (BATSE). One stripe is related to the plane in which the intergalactic globular clusters (R>25kpc) and Galactic satellite galaxies (45kpc<R<280kpc) concentrate, the other is concerned to nearby galaxies (1Mpc

Vladimir R. Zoller

We report an evaluation of subleading eigenvalues and eigenfunctions of the BFKL equation in the color dipole representation with a running gauge coupling. We present an expansion of the small-$x$ proton structure function $F_{2p}(x,Q^2)$ in terms of the rightmost BFKL-singularities. The BFKL-Regge phenomenology of DIS structure functions is developed which

Hume A. Feldman, Richard Watkins

We propose a new strategy to probe the power spectrum on large scales using galaxy peculiar velocities. We explore the properties of surveys that cover only two small fields in opposing directions on the sky. Surveys of this type have several advantages over those that attempt to cover the entire sky; in particular, by concentrating galaxies in narrow cones

Jun Furukawa

With the help of M-theory configuration of N=1 supersymmetric QCD, we analyze the strong coupling moduli of N=1 theory and its relation with S-duality transformation in N=2 supersymmetric QCD. As a result we confirm that two type-IIA descriptions for N=1 supersymmetric QCD, one of them being strong coupling description and another being weak, correspond to a

R. Horvat

This comment is withdrawn

Eanna E. Flanagan

We analyze the coupling between the internal degrees of freedom of neutron stars in a close binary, and the stars&#39; orbital motion. Our analysis is based on the method of matched asymptotic expansions and is valid to all orders in the strength of internal gravity in each star, but is perturbative in the ``tidal expansion parameter&#39;&#39; (stellar radiu

Marc Henneaux, Bernard Knaepen

We give the complete list of all first-order consistent interaction vertices for a set of exterior form gauge fields of form degree >1, described in the free limit by the standard Maxwell-like action. A special attention is paid to the interactions that deform the gauge transformations. These are shown to be necessarily of the Noether form "conserved antisym

T. M. Rice, Stephan Haas, Manfred Sigrist, Fu-Chun Zhang

The three-leg ladder has one odd-parity and two even-parity channels. At low doping these behave quite differently. Numerical calculations for a t-J model show that the initial phase upon hole doping has two components - a conducting Luttinger liquid in the odd-parity channel, coexisting with an insulating (i.e. undoped) spin liquid phase in the even-parity

A. Lange, M. Schröter, M. A. Scherer, A. Engel

The temporal evolution of a water-sand interface driven by gravity is experimentally investigated. By means of a Fourier analysis of the evolving interface the growth rates are determined for the different modes appearing in the developing front. To model the observed behavior we apply the idea of the Rayleigh-Taylor instability for two stratified fluids. Ca

A. Y. Potekhin, G. Chabrier, D. G. Yakovlev

The relationships between the effective surface (T_e) and internal temperatures of neutron stars (NSs) with and without accreted envelopes are calculated for T_e > 5\times10^4 K using new data on the equation of state and opacities in the outer NS layers. We examine various models of accreted layers (H, He, C, O shells produced by nuclear transformations in

Marc-Thierry Jaekel, Serge Reynaud

The relativistic conception of space and time is challenged by the quantum nature of physical observables. It has been known for a long time that Poincaré symmetry of field theory can be extended to the larger conformal symmetry. We use these symmetries to define quantum observables associated with positions in space-time, in the spirit of Einstein theory of

Marc-Thierry Jaekel, Serge Reynaud

Quantum fields possess zero-point or vacuum fluctuations which induce mechanical effects, namely generalised Casimir forces, on any scatterer. Symmetries of vacuum therefore raise fundamental questions when confronted with the principle of relativity of motion in vacuum. The specific case of uniformly accelerated motion is particularly interesting, in connec

Luis Gonzalez-Mestres

We discuss the implications of a recently proposed pattern of Lorentz symmetry violation on very high-energy cross sections. As a consequence of the breaking of local Lorentz invariance by the introduction of a fundamental length, $a$ , the kinematics is modified and the properties of final states are fundamentally different in collider-like (two incoming pa

Wolfram Just, Frank Matth&#34;aus, Hans Rainer V&#34;olger, Christine Just

The well known concept, to reduce the spatio-temporal dynamics beyond instabilities of trivial states to amplitude modulated patterns, is reviewed from the point of view of a formal perturbation expansion for general dissipative partial differential equations. For codimension one instabilities closed analytical formulas for all coefficients of the resulting

L. L. Bonilla, C. J. Perez Vicente, R. Spigler

The mean field Kuramoto model describing the synchronization of a population of phase oscillators with a bimodal frequency distribution is analyzed (by the method of multiple scales) near regions in its phase diagram corresponding to synchronization to phases with a time periodic order parameter. The richest behavior is found near the tricritical point were

P. B. Gossiaux, R. Puri, Ch. Hartnack, J. Aichelin

We present the first microscopic calculation of the spectator fragmentation observed in heavy ion reactions at relativistic energies which reproduces the slope of the kinetic energy spectra of the fragments as well as their multiplicity, both measured by the ALADIN collaboration. In the past both have been explained in thermal models, however with vastly dif

B. R. Schlei

Predominantly preliminary single and double inclusive momentum spectra of 158 AGeV Pb+Pb collisions, recently measured by the NA44 and NA49 Collaborations, are reproduced using the relativistic hydrodynamical model HYLANDER-C. Two different equations of state, which both contain a phase transition to a quark-gluon plasma, can be used to reproduce the (prelim

Marek Gazdzicki

A systematic analysis of data on strangeness and pion production in nucleon-nucleon and central nucleus-nucleus collisions is presented. It is shown that at all collision energies the pion/baryon and strangeness/pion ratios indicate saturation with the size of the colliding nuclei. The energy dependence of the saturation level suggests that the transition to

V. D. Efros, W. Leidemann, G. Orlandini

A four-nucleon calculation of the total ^4He photodisintegration cross section is performed. The full final-state interaction is taken into account for the first time. This is achieved via the method of the Lorentz integral transform. Semi-realistic NN interactions are employed. Different from the known partial two-body ^4He(γ,n)^3He and ^4He(γ,p)^3H cross s

Pradip Roy, Jane Alam, Sourav Sarkar, Bikash Sinha

The relativistic Fokker Planck equation has been used to study the evolution of the quark distribution in the quark gluon phase expected to be formed in ultra-relativistic heavy ion collisions. The effect of thermal masses for quarks and gluons is incorporated to take account of the in-medium properties. We find that the kinetic equilibrium is achieved befor

J. Acacio de Barros, Ilya L. Shapiro

The second alternative conformal limit of the recently proposed general higher derivative dilaton quantum theory in curved spacetime is explored. In this version of the theory the dilaton is transformed, along with the metric, to provide the conformal invariance of the classical action. We find the corresponding quantum theory to be renormalizable at one loo

E. Rabinovici, A. N. Schellekens

We classify all untwisted (2,1) heterotic strings. The only solutions are the three already known cases, having massless spectra consisting either of 24 chiral fermions, or of 24 bosons, or of 8 scalars and 8 fermions of each chirality.

A. A. Bytsenko, F. L. Williams

The global additive and multiplicative properties of Laplace type operators acting on irreducible rank 1 symmetric spaces are considered. The explicit form of the zeta function on product spaces and of the multiplicative anomaly is derived.

Atsushi Matsuo, Kiyokazu Nagatomo

The identities satisfied by two-dimensional chiral quantum fields are studied from the point of view of vertex algebras. The Cauchy-Jacobi identity (or the Borcherds identity) for three mutually local fields is proved and consequently a direct proof of Li&#39;s theorem on a local system of vertex operators is provided. Several characterizations of vertex alg

Jamal Jalilian - Marian, Alex Kovner, Andrei Leonidov, Heribert Weigert

We continue the study of the effective action for low $x$ physics based on a Wilson renormalization group approach. We express the full nonlinear renormalization group equation in terms of the average value and the average fluctuation of extra color charge density generated by integrating out gluons with intermediate values of $x$. This form clearly exhibits

Mikkel B. Johnson, Leonard S. Kisslinger

We develop a three-point formalism to treat vacuum susceptibilities used for the coupling of currents to hadrons within the method of QCD Sum Rules. By introducing nonlocal condensates, with the space-time structure taken from fits to experimental parton distrbutions, we show that one can treat hadronic coupling at zero or low momentum transfer as well as me

Yu. L. Dokshitzer

Recent developments in the QCD understanding of DIS are reviewed, as well as theoretical attempts to accommodate the HERA anomalous e+ p events.

Matteo Cacciari

The phenomenology of heavy quarkonia production in fixed target experiments and at the Tevatron and HERA colliders is reviewed. The latest theoretical results are presented and compared with data, with emphasis on the predictions of the factorization approach by Bodwin, Braaten and Lepage.

M. Braun

The amplitude for 4 interacting reggeized gluons is studied in the high-colour limit. The leading order amplitude is explicitly shown to reduce to a pair of reggeons, i.e to a single BFKL pomeron. The next-to-leading order diffractive amplitude is found to split into a double pomeron exchange and triple pomeron contribution. The obtained three-pomeron vertex

S. V. Faleev

The problem of reduction of the wave packet of a relativistic charged particle by emission of a photon is studied with help of the path integral approach. A general expression for arbitrary order correlation function of the electromagnetic field is obtained. As a specific example an ultrarelativistic electron circulating in a storage ring is considered. It i

J. Blümlein, A. Vogt

The numerical effects of the known all-order leading and next-to-leading logarithmic small-$x$ contributions to the anomalous dimensions and coefficient functions of the unpolarized singlet evolution are discussed for the structure functions $F_2^{ ep}(x,Q^2)$, $F_L^{ ep}(x,Q^2)$, and $F_2^{ eγ}(x,Q^2)$.

Bernd A. Kniehl, Gustav Kramer

The cross section for the photoproduction of large-p_T J/psi mesons at HERA is calculated at next-to-leading order, adopting a perturbative approach to describe the fragmentation of charm quarks and gluons into J/psi mesons. We treat the charm quark according to the massless factorization scheme, where it is assumed to be one of the active flavours inside th

J. M. LoSecco

Bounds are derived on the cross section, flux and energy density of new particles that may be responsible for the atmospheric neutrino anomaly. $4.6 \times 10^{-45} cm^2 < σ<2.4 \times 10^{-34} cm^2$ Decay of primordial homogeneous dark matter can be excluded.

Ulf-G. Meißner

I discuss recent progress made in calculating electromagnetic corrections in the framework of the effective field theory of QCD. In the case of elastic pion-pion scattering, strong interaction predictions have been worked out to two loop accuracy. I present first results for the electromagnetic corrections in the case of neutral pions. Here, the only sizeabl

C. J. Maxwell

We propose a generalization of Grunberg&#39;s method of effective charges in which, starting with the effective charge for some dimensionless QCD observable dependent on the single energy scale $Q, R(Q)$, we introduce an infinite set of auxiliary effective charges, each one describing the sub-asymptotic Q-evolution of the immediately preceding effective char

K. Zuber

The present status of neutrino oscillation searches with reactors and accelerators is reviewed. An outlook, especially on future long baseline neutrino oscillation projects, is given.

N. N. Achasov, V. V. Gubin

We describe the interference between amplitudes $e^ + e^-\toρ\toγπ^+π^-$ and $e^ + e^-\toϕ\toγ(f_0 + σ) \toγπ^ + π^-$, with regard to the phase of the elastic $ππ$ scattering background and mixing of the $f_0$ and $σ$ mesons. It is shown that the Fermi-Watson theorem for the final state interaction in the reaction $e^ + e^-\toρ\toγπ^ + π^-$ is not valid in t

J. Blümlein

We investigate to which extent an interpretation of the recently observed excess of events in the high $Q^2$ range at HERA in terms of single leptoquark production is compatible with bounds from other experiments.

Tsvi Piran

The concepts of negative gravitational mass and gravitational repulsion are alien to general relativity. Still, we show here that small negative fluctuations - small dimples in the primordial density field - that act as if they have an effective negative gravitational mass, play a dominant role in shaping our Universe. These initially tiny perturbations repe

Eue Jin Jeong

The dynamic shift of the center of mass for a rotating hemisphere prompts us the question of what might be its physical consequences. Despite the fact that accelerating object is known to create gravitational field, there is no known external dynamic gravitational force from a rotating sphere where the individual mass components are in constant acceleration.

J. Madore

A fuzzy version of the ordinary round 2-sphere has been constructed with an invariant curvature. We here consider linear connections on arbitrary fuzzy surfaces of genus zero. We shall find as before that they are more or less rigidly dependent on the differential calculus used but that a large number of the latter can be constructed which are not covariant

R. Beig, N. Ó Murchadha

A time-symmetric Cauchy slice of the extended Schwarzschild spacetime can be evolved into a foliation of the $r>3m/2$-region of the spacetime by maximal surfaces with the requirement that time runs equally fast at both spatial ends of the manifold. This paper studies the behaviour of these slices in the limit as proper time-at-infinity becomes arbitrarily la

Radu P. Mondescu, M. Muthukumar

We consider the dynamics of freely translating and rotating diblock (A-B), Gaussian copolymers, in dilute solutions. Using the multiple scattering technique, we have computed the diffusion and the friction coefficients D_AB and Zeta_AB, and the change Eta_AB in the viscosity of the solution as functions of x = N_A/N and t = l_B/l_A, where N_A, N are the numb

Robert Shrock, Shan-Ho Tsai

We report several results concerning $W(Λ,q)=\exp(S_0/k_B)$, the exponent of the ground state entropy of the Potts antiferromagnet on a lattice $Λ$. First, we improve our previous rigorous lower bound on $W(hc,q)$ for the honeycomb (hc) lattice and find that it is extremely accurate; it agrees to the first eleven terms with the large-$q$ series for $W(hc,q)$

J. V. Andersen, L. J. Lewis

We introduce a model where an isotropic, dynamically-imposed stress induces fracture in a thin film. Using molecular dynamics simulations, we study how the integrated fragment distribution function depends on the rate of change and magnitude of the imposed stress, as well as on temperature. A mean-field argument shows that the system becomes unstable for a c

D. M. Danchev, J. G. Brankov, M. E. Amin

A modified three-dimensional mean spherical model with a L-layer film geometry under Neumann-Neumann boundary conditions is considered. Two spherical fields are present in the model: a surface one fixes the mean square value of the spins at the boundaries at some $ρ> 0$, and a bulk one imposes the standard spherical constraint (the mean square value of the s

M. Fabrizio, R. Mélin

We present a numerical study of single chain models of doped spin 1 compounds. We use low energy effective one-dimensional models for both the cases of paramagnetic and spin-1/2 doping. In the case of paramagnetic doping, the effective model is equivalent to the bond disordered spin-1/2 chain model recently analyzed by means of real space renormalization gro

D. R. Leadley, R. J. Nicholas, D. K. Maude, A. N. Utjuzh

Fractional quantum Hall effect energy gaps have been measured in GaAs/GaAlAs heterojunctions as a function of Zeeman energy, which is varied by applying hydrostatic pressure up to 20 kbar. The gap at v=1/3 decreases with pressure until the g-factor changes sign when it again increases. The behavior is similar to that seen at v=1 and shows that excitations fr

Miki Wadati, Hideaki Ujino

Integrability, algebraic structures and orthogonal basis of the Calogero model are studied by the quantum Lax and Dunkl operator formulations. The commutator algebra among operators including conserved operators and creation-annihilation operators has the structure of the W-algebra. Through an algebraic construction of the simultaneous eigenfunctions of all

A. Damascelli, K. Schulte, D. van der Marel, M. Fath

We measured the reflectivity of a single crystal of FeSi from the far-infrared to the visible region (50-20000 wavenumber), varying the temperature between 4 and 300 K. The optical conductivity function was obtained via Kramers-Kronig analysis. We observed a dirty metal-like behavior at room temperature and the opening of a gap of 70 meV at low temperature.

A. D. Bruce, N. B. Wilding, G. J. Ackland

We present a method for the direct evaluation of the difference between the free energies of two crystalline structures, of different symmetry. The method rests on a Monte Carlo procedure which allows one to sample along a path, through atomic-displacement-space, leading from one structure to the other by way of an intervening transformation that switches on

Janyce Wiebe, Tom O&#39;Hara, Kenneth McKeever, Thorsten Oehrstroem-Sandgren

This paper presents the results of an empirical investigation of temporal reference resolution in scheduling dialogs. The algorithm adopted is primarily a linear-recency based approach that does not include a model of global focus. A fully automatic system has been developed and evaluated on unseen test data with good results. This paper presents the results

Andrew C. Layden, Ata Sarajedini

We present a deep color-magnitude diagram in the VI passbands of the globular cluster M54, a member of the Sagittarius dwarf galaxy. The data extend below the cluster&#39;s main sequence turn-off, allowing us to estimate the cluster&#39;s age. We find that M54 is 0.5--1.5 gigayears older than the Galactic globulars M68 and M5. In absolute terms, the age is c

N. N. Gor&#39;kavyi, L. M. Ozernoy, J. C. Mather, T. Taidakova

The effect of solar or stellar radiation on dust particles&#39; trajectories (the Poynting-Robertson drag) has been studied by a number of authors and applied to interplanetary dust dynamics in numerical computations. Meanwhile some important features of dust flows can be studied analytically by implementing our novel hydrodynamical approach to use the conti

Boudewijn F. Roukema, Alastair C. Edge

The topology of the observable Universe is not yet known. The most significant observational sign of a non-trivial topology would be multiple images (``ghosts&#39;&#39;) of a single object at (in general) different sky positions and redshifts. It is pointed out that the previous search by Gott (1980) for ghost images of the Coma cluster can be extended by us

Tereasa G. Brainerd, David M. Goldberg, Jens Verner Villumsen

The formation history of rich clusters is investigated using a hybrid N-body simulation in which high spatial and mass resolution can be achieved self-consistently within a small region of a very large volume. The evolution of three massive clusters is studied via mass accretion, spherically-averaged density profiles, three-dimensional and projected shapes,

Robert Simcoe, K. K. McLeod, Jonathan Schachter, Martin Elvis

We define a new sample of 96 low-redshift (z<0.1), soft X-ray selected Seyferts from the catalog of the Einstein Slew Survey (Elvis etal. 1992, Plummer et al. 1994). We probe the geometry and column depth of obscuring material in the host-galaxy disks using galaxian axial ratios determined mainly from the Digitized Sky Survey. The distribution of host-galaxy

A. Lazarian, Alyssa A. Goodman, Philip C. Myers

A quantitative analysis of grain alignment in the filamentary dark cloud L1755 in Ophiuchus is presented. We show, that the observed decrease of the polarization to extinction ratio for the inner parts of this quiescent dark cloud can be explained as a result of the decrease of the efficiency of grain alignment.We make quantitative estimates of grain alignme

J. M. Cordes, David F. Chernoff

We study the field millisecond pulsar (MSP) population to infer its intrinsic distribution in spin period and luminosity and to determine its spatial distribution within the Galaxy. Our likelihood analysis on data from extant surveys (22 pulsars with periods <20 ms) accounts for important selection effects. We infer a minimum period cutoff P(min) > 0.65 ms (

David Chappell, John Scalo

It is often assumed that galaxies cannot generate large-scale coherent star- forming activity without some organizing agent, such as spiral density waves, bars, large-scale instabilities, or external perturbations due to encounters with other galaxies. We present simulations of a simple model of star formation in which local spatial couplings lead to large-s

J. Kuraszkiewicz, Z. Loska, B. Czerny

We study the extensively monitored Seyfert galaxy NGC 5548 and compare its nuclear emission with models of accretion disk with accreting corona. To obtain the intrinsic nuclear spectra from the observed spectra we had to estimate and subtract the contribution from circumnuclear components such as stars, the Balmer continuum and blended FeII lines, and the FC

B. Glenn Piner, Kerry A. Kingham

As part of an ongoing effort to observe high energy gamma-ray blazars with VLBI, we have produced 8 and 2 GHz VLBI images, at ten epochs spanning the years 1988 to 1996, of the quasar 1156+295. The VLBI data have been taken from the Washington VLBI correlator&#39;s geodetic database. We have detected detected four components and have measured their apparent

Remi A. Cabanac

We present preliminary results of observations made, during the spring of 1996, with the 3-m liquid mirror telescope of the NASA Orbital Debris Observatory. A 20-arcmin-wide strip of sky was observed at latitude of 32deg56 N using 10 narrow-band filters. Although the detector and the optical corrector were not optimized for astronomical observations, valuabl

S. De Grandi, S. Molendi, H. Böhringer, G. Chincarini

In this first paper of a series we develop a new technique to analyze clusters of galaxies observed during the ROSAT All-Sky Survey (RASS). We call this method the Steepness Ratio Technique (SRT). The SRT uses the convolution between the real RASS point-spread function and the cluster emission profile assumed to be a beta-model with the beta parameter fixed

N. Renaud, G. Henri

We present numerical simulation of bulk Lorentz factor of relativistic electron positron jet driven by Compton rocket effect from accretion disk radiation. The plasma is assumed to have a power-law energy distribution and is continuously reheated to compensate for radiation losses. We include Klein-Nishina (hereafter KN) corrections, and study the role of en

Chiara Brocca, Daniela Bettoni, Giuseppe Galletta

A statistical study of the environment around Polar Ring Galaxies is presented. Two kinds of search are performed: 1) a study of the concentration and diameters of all the objects surrounding the Polar Rings, within a search field 5 times the ring diameter. New magnitudes for polar ring galaxies are presented. 2) a search, in a wider field, for galaxies of s

Martin Pohl

EGRET data are usually analysed on the basis of the Maximum-Likelihood method \cite{ma96} in a search for point sources in excess to a model for the background radiation (e.g. \cite{hu97}). This method depends strongly on the quality of the background model, and thus may have high systematic uncertainties in region of strong and uncertain background like the

Martin Pohl

Here we investigate to what extent unresolved \gr pulsars contribute to the galactic diffuse emission, and further whether unresolved \gr pulsars can be made responsible for the excess of diffuse galactic emission above 1 GeV which has been observed by EGRET. Our analysis is based only on the properties of the six pulsars which have been identified in the EG

Luigi Guzzo, Michael A. Strauss, Karl B. Fisher, Riccardo Giovanelli

We study the distortions induced by peculiar velocities on the redshift-space correlation function of galaxies of different morphological types in the Pisces-Perseus redshift survey. Redshift-space distortions affect early- and late-type galaxies in different ways. In particular, at small separations, the dominant effect comes from virialized cluster cores,

Achim Weiss, Helmut Schlattl

We address the question how accurately stellar ages can be determined by stellar evolution theory. We select the star with the best observational material available - our Sun. We determine the solar age by fitting solar evolution models to a number of observational quantities including several obtained from helioseismology, such as photospheric helium abunda

Wayne Hu, Martin White

We present a pedagogical and phenomenological introduction to the study of cosmic microwave background (CMB) polarization to build intuition about the prospects and challenges facing its detection. Thomson scattering of temperature anisotropies on the last scattering surface generates a linear polarization pattern on the sky that can be simply read off from

Robert Milson

The present article discusses the connection between exactly-solvable Schrodinger equations and the Liouville transformation. This transformation yields a large class of exactly-solvable potentials, including the exactly-solvable potentials introduced by Natanzon. As well, this class is shown to contain two new families of exactly solvable potentials.

Eric Bergshoeff, Bert Janssen, Tomas Ortin

We propose an effective action for the eleven-dimensional (bosonic) Kaluza-Klein monopole solution. The construction of the action requires that the background fields admit an Abelian isometry group. The corresponding sigma-model is gauged with respect to this isometry. The gauged sigma-model is the source for the monopole solution. A direct (double) dimensi

J. I. Katz an d Tsvi Piran

The recent discovery of persistent GRB counterparts at lower frequencies permits several important conclusions to be drawn. The spectrum of GRB970508 is not consistent with an external shock origin for both the prompt GRB and the persistent emission, suggesting that at least the prompt radiation is produced by internal shocks. Comparisons among three GRB wit

J. P. B. C de Melo, T. Frederico

The rho-meson eletromagnetic form factors are calculated, both in covariant and light-front framework with constituintes quarks. The effect of the breakdown rotational symmetry for the one-body current operador in the null-plane is investigate by comparing calculations within ligth-front and covariant approaches.

M. F. Collins, O. A. Petrenko

In this article we review the effects of magnetic frustation in the stacked triangular lattice. Frustration increases the degeneracy of the ground state, giving rise to different physics. In particular it leads to unique phase diagrams with multicritical points and novel critical phenomena. We describe the confrontation of theory and experiment for a number

N. Shibata

The density matrix renormalization group (DMRG) method is applied to the anisotropic Heisenberg chain at finite temperatures. The free energy of the system is obtained using the quantum transfer matrix which is iteratively enlarged in the imaginary time direction. The magnetic susceptibility and the specific heat are calculated down to T=0.01J and compared w

S. A. Apikyan, C. J. Efthimiou

The Liouville field theory on Z_N-Riemann surfaces is studied and it is shown that it decomposes into a Liouville field theory on the sphere and N-1 free boson theories. Also, the partition function of the Liouville field theory on the Z_N-Riemann surfaces is expressed as a product of the correlation function for the Liouville vertex operators on the sphere

Cesar Bautista

A proof of Poincaré-Birkhoff-Witt theorem is given for a class of generalized Lie algebras closely related to the Gurevich S-Lie algebras. As concrete examples, we construct the positive (negative) parts of the quantized universal enveloping algebras of type A_n and M_{p,q,e}(n,K), which is a non-standard quantum deformation of GL(n). In particular, we get,

Pol Bernard Gossiaux, Joerg Aichelin

Using quantum molecular dynamics simulations, we investigate the formation of fragments in symmetric reactions between beam energies of E=30AMeV and 600AMeV. After a comparison with existing data we investigate some observables relevant to tackle equilibration: dsigma/dErat, the double differential cross section dsigma/pt.dpz.dpt,... Apart maybe from very en

Saharon Shelah, Jouko Väänänen

Let K^0_lambda be the class of structures < lambda,<,A>, where A subseteq lambda is disjoint from a club, and let K^1_lambda be the class of structures < lambda,<,A>, where A subseteq lambda contains a club. We prove that if lambda = lambda^{< kappa} is regular, then no sentence of L_{lambda^+ kappa} separates K^0_lambda and K^1_lambda. On the other hand, we

Saharon Shelah

The main result is that for lambda strong limit singular failing the continuum hypothesis (i.e. 2^lambda > lambda^+), a polarized partition theorem holds.

Mariusz Rabus, Saharon Shelah

It is consistent that for every function f:R x R-> R there is an uncountable set A subseteq R and two continuous functions f_0,f_1:D(A)-> R such that f(alpha, beta) in {f_0(alpha, beta),f_1(alpha, beta)} for every (alpha, beta) in A^2, alpha not = beta .

B. Abbott

The D0 collaboration has performed a measurement of the top quark mass based on six candidate events for the process t tbar -> b W+ bbar W-, where the W bosons decay to e nu or mu nu. This sample was collected during an exposure of the D0 detector to an integrated luminosity of 125 pb^-1 of sqrt(s)=1.8 TeV p-pbar collisions. We obtain mt = 168.4 +- 12.3 (sta

T. R. Bedding, D. Minniti, F. Courbin, B. Sams

We describe a first attempt to apply adaptive optics to the study of resolved stellar populations in galaxies. Advantages over traditional approaches are (i) improved spatial resolution and point-source sensitivity through adaptive optics, and (ii) use of the near-infrared region, where the peak of the spectral energy distribution for old populations is foun

D. A. Carter-Lewis, S. Biller, P. J. Boyle, J. H. Buckley

The Crab Nebula has become established as the standard candle for TeV gamma-ray astronomy using the atmospheric Cherenkov technique. No evidence for variability has been seen. The spectrum of gamma rays from the Crab Nebula has been measured in the energy range 500 GeV to 8 TeV at the Whipple Observatory by the atmospheric Cherenkov imaging technique. Two me

R. Srinivasan, P. J. Boyle, J. H. Buckley, A. M. Burdett

PSR B1951+32 is a gamma-ray pulsar detected by the Energetic Gamma Ray Experiment Telescope (EGRET) and identified with the 39.5 ms radio pulsar in the supernova remnant CTB 80. The EGRET data shows no evidence for a spectral turnover. Here we report on the first observations of PSR B1951+32 beyond 30 GeV. The observations were carried out with the 10m gamma

T. C. Weekes, C. Akerlof, S. Biller, A. C. Breslin

A next generation atmospheric Cherenkov observatory is described based on the Whipple Observatory $γ$-ray telescope. A total of nine such imaging telescopes will be deployed in an array that will permit the maximum versatility and give high sensitivity in the 50 GeV - 50 TeV band (with maximum sensitivity from 100 GeV to 10 TeV).

J. Quinn, I. H. Bond, P. J. Boyle, J. H. Buckley

Markarian 501 is only the second extragalactic source to be detected with high statistical certainty at TeV energies; it is similar in many ways to Markarian 421. The Whipple Observatory gamma-ray telescope has been used to observe the AGN Markarian 501 in 1996 and 1997, the years subsequent to its initial detection. The apparent variability on the one-day t

Hagai Netzer

Recent ultraviolet and X-ray observations suggest that the Fe/O ratio in the NLR gas in NGC 1068 is abnormally high. The X-ray analysis, which is presented elsewhere, suggests a large Fe/H and the data shown and discussed here, in particular the extremely weak Oiii] 1664 line, argue for small O/N and O/C. Models to support this claim are shown and discussed.

N. Brosch

I examine possible futures for UV astronomy, in view of the past history and collected knowledge of the UV sky through various missions since the early days of Space Astronomy. The last all-sky survey has been by TD-1 in the early 1970s, resulting in reasonable mapping of discrete sources brighter than ~9th mag (monochromatic, UV). Since TD-1, few advances w

Brad K. Gibson, Mike Loewenstein, Richard F. Mushotzky

We re-examine the respective roles played by supernovae (SNe) Types Ia and II in enriching the intracluster medium (ICM) of galaxy clusters, in light of the recent downward shift of the ASCA abundance ratios of alpha-elements to iron favoured by Ishimaru & Arimoto (1997, PASJ, 49, 1). Because of this shift, Ishimaru & Arimoto conclude that >50% of the ICM ir

V. V. Tugai, A. A. Zheltukhin

A possibility of an extension of the minimality principle for electromagnetic interactions of charged and neutral particles having spin 1/2 is investigated.

G. E. Volovik

The origin of the excess of matter over antimatter in our Universe remains one of the fundamental problems. The dynamical baryogenesis in the process of the broken symmetry electroweak transition in the expanding Universe is the widely discussed model where the baryonic asymmetry is induced by the quantum chiral anomaly. We discuss the modelling of this phen

Kun Yang, S. L. Sondhi

We study the response of a two dimensional $d_{x^2-y^2}$ superconductor to a magnetic field that couples only to the spins of the electrons. In contrast to the s-wave case, the $d_{x^2-y^2}$ state is modified even at small magnetic fields, with the gap nodes widening into normal, spin polarized, pockets. We discuss the promising prospects for observing this

Dennis Silverman, Herng Yao

After we have limited elements of the right-handed CKM matrix to satisfy the bounds for CP violation epsilon_K in K meson systems, the right-handed charged current gauge boson W_R is shown to substantially affect CP asymmetries in B systems. A joint chi-squared analysis is applied to B-Bbar mixing to constrain the right-handed CKM matrix elements. In (sin(2a