July 2001 arXiv papers — page 6

Serge Tabachnik, Scott Tremaine

We investigate the distribution of mass M and orbital period P of extra-solar planets, taking account of selection effects due to the limited velocity precision and duration of existing surveys. We fit the data on 63 planets to a power-law distribution of the form dn=CM^{-alpha}P^{-beta}(dM/M)(dP/P), and find alpha=0.12+-0.10, beta=-0.26+-0.06 for M<10M_J, w

G. Ramalho, A. Arriaga, M. T. Peña

We compare the scattering amplitude resulting from the several quasipotential equations for scalar particles. We consider the Blankenbecler-Sugar, Spectator, Thompson, Erkelenz-Holinde and Equal-Time equations, which were solved numerically without decomposition into partial waves. We analyze both negative-energy state components of the propagators and retar

Holger Gies, Christof Wetterich

A renormalization group flow equation with a scale-dependent transformation of field variables gives a unified description of fundamental and composite degrees of freedom. In the context of the effective average action, we study the renormalization flow of scalar bound states which are formed out of fundamental fermions. We use the gauged Nambu--Jona-Lasinio

Rafael A. Molina, Dietmar Weinmann, Rodolfo A. Jalabert

We study the linewidth of the surface plasmon resonance in the optical absorption spectrum of metallic nanoparticles, when the decay into electron-hole pairs is the dominant channel. Within a semiclassical approach, we find that the electron-hole density-density correlation oscillates as a function of the size of the particles, leading to oscillations of the

Philippe de Forcrand, Lorenz von Smekal

We use &#39;t Hooft loops of maximal size on finite lattices to calculate the free energy in the sectors of SU(2) Yang-Mills theory with fixed electric flux as a function of temperature and (spatial) volume. Our results provide evidence for the mass gap. The confinement of electric fluxes in the low temperature phase and their condensation in the high temper

Ewa L. Lokas

We present predictions for the line-of-sight velocity dispersion profiles of dwarf spheroidal galaxies and compare them to observations in the case of the Fornax dwarf. The predictions are made in the framework of standard dynamical theory of spherical systems with different velocity distributions. The stars are assumed to be distributed according to Sersic

M. Franz, O. Vafek

We formulate an effective low energy theory for the fermionic excitations in d-wave superconductors in the presence of periodic vortex lattices. These can be modeled by an effective free Dirac Hamiltonian with renormalized velocities and possibly a small mass term. In the presence of random nonmagnetic impurities this will result in universal (i.e. field and

Kaushik Bhattacharya, Avijit K. Ganguly, Sushan Konar

Neutrino-photon processes, forbidden in vacuum, can take place in presence of a thermal medium or an external electro-magnetic field, mediated by the corresponding charged leptons (real or virtual). The effect of a medium or an electromagnetic field is two-fold - to induce an effective $ν-γ$ vertex and to modify the dispersion relations of all the particles

Guilherme F. Marranghello, Cesar A. Z. Vasconcellos, Manfred Dillig

Thermodynamical properties of nuclear matter are studied in the framework of an effective many-body field theory at finite temperature, considering the Sommerfeld approximation. We perform the calculations by using the nonlinear Boguta and Bodmer model, extended by the inclusion of the fundamental baryon octet and leptonic degrees of freedom. Trapped neutrin

Erika Andersson, Tommaso Calarco, Ron Folman, Mauritz Andersson

We describe the fundamental features of an interferometer for guided matter waves based on Y-beam splitters and show that, in a quasi two-dimensional regime, such a device exhibits high contrast fringes even in a multi mode regime and fed from a thermal source.

U. Frisch, T. Matsumoto

It is shown phenomenologically that the fractional derivative $ξ=D^αu$ of order $α$ of a multifractal function has a power-law tail $\propto |ξ| ^{-p_\star}$ in its cumulative probability, for a suitable range of $α$&#39;s. The exponent is determined by the condition $ζ_{p_\star} = αp_\star$, where $ζ_p$ is the exponent of the structure function of order $p$

M. J. Davis, R. J. Ballagh, K. Burnett

We develop an approximate formalism suitable for performing simulations of the thermal dynamics of interacting Bose gases. The method is based on the observation that when the lowest energy modes of the Bose field operator are highly occupied, they may be treated classically to a good approximation. We derive a finite temperature Gross-Pitaevskii equation fo

Kashif Alvi

As a black hole in a binary spirals in gradually from large separation, energy and angular momentum flow not only to infinity but also into or out of the hole. In addition, the hole&#39;s horizon area increases slowly during this process. In this paper, the changes in the black hole&#39;s mass, spin, and horizon area during inspiral are calculated for a hole

M. Veselsky

A production mechanism of highly excited nuclei formed in violent collisions in the Fermi energy domain is investigated. The collision of two nuclei is decomposed into several stages which are treated separately. Simplified exciton concept is used for the description of pre-equilibrium emission. A modified spectator-participant scenario is used where motion

Yuri V. Kovchegov

We derive expressions for the gluon production cross sections in the single diffractive proton-nucleus scattering and DIS processes in a quasi-classical approximation. The resulting cross sections include the effects of all multiple rescatterings in the classical background field of the target proton or nucleus, which remains intact after the scattering. We

Ed Boyda, Hitoshi Murayama, Aaron Pierce

We offer a guide to dimensional reduction (DRED) in theories with anomaly mediated supersymmetry breaking. Evanescent operators proportional to epsilon arise in the bare Lagrangian when it is reduced from d=4 to d= (4-2 epsilon) dimensions. In the course of a detailed diagrammatic calculation, we show that inclusion of these operators is crucial. The evanesc

Matthias Fitzi, Nicolas Gisin, Ueli Maurer

We present a solution to an old and timely problem in distributed computing. Like Quantum Key Distribution (QKD), quantum channels make it possible to achieve taks classically impossible. However, unlike QKD, here the goal is not secrecy but agreement, and the adversary is not outside but inside the game, and the resources require qutrits.

J. Mompart, R. Corbalan, L. Roso

The possibility of coherent population trapping in two electron states with aligned spins (ortho-system) is evidenced. From the analysis of a three-level atomic system containing two electrons, and driven by the two laser fields needed for coherent population trapping, a conceptually new kind of two-electron dark state appears. The properties of this trappin

S. Tanzilli, H. de Riedmatten, W. Tittel, H. Zbinden

We report on energy-time and time-bin entangled photon-pair sources based on a periodically poled lithium niobate (PPLN) waveguide. Degenerate twin photons at 1314 nm wavelength are created by spontaneous parametric down-conversion and coupled into standard telecom fibers. Our PPLN waveguide features a very high conversion efficiency of about 10^(-6), roughl

David Horn, Assaf Gottlieb

We propose a novel clustering method that is based on physical intuition derived from quantum mechanics. Starting with given data points, we construct a scale-space probability function. Viewing the latter as the lowest eigenstate of a Schrodinger equation, we use simple analytic operations to derive a potential function whose minima determine cluster center

M. S. Hussein, M. P. Pato, J. C. Wells

It is shown how initial conditions can be appropriately defined for the integration of Lorentz-Dirac equations of motion. The integration is performed \QTR{it}{forward} in time. The theory is applied to the case of the motion of an electron in an intense laser pulse, relevant to nonlinear Compton scattering.

Rainer E. Zimmermann

Conceptual consequences of recent results in loop quantum gravity are collected and discussed here in view of their implications for a modern philosophy of science which is mainly understood as one that totalizes scientific insight so as to eventually achieve a consistent model of what may be called fundamental heuristics on an onto-epistemic background whic

H. Lenske, C. M. Keil, F. Hofmann

The structure of nuclei far off beta-stability is investigated by nuclear many-body theory. In-medium interactions for asymmetric nuclear matter are obtained by (Dirac-) Brueckner theory thus establishing the link of nuclear forces to free space interactions. HFB and RPA theory is used to describe ground and excited states of nuclei from light to heavy masse

N. Kaiser

We calculate in heavy baryon chiral perturbation theory the local NN-potentials generated by the two-pion exchange diagrams at two-loop order. We give explicit expressions for the mass-spectra (or imaginary parts) of the corresponding isoscalar and isovector central, spin-spin and tensor NN-amplitudes. We find from two-loop two-pion exchange a sizeable isosc

H. Babacan, T. Babacan, A. Gokalp, O. Yilmaz

We investigate the possibility that the process of $ρ^{0}$-meson photoproduction on proton, $γ+p\to p+ρ^{0}$, in the near threshold region $E_γ< 2$ GeV, can be considered in the framework of model with $π$-, $σ$- and N-exchanges. This suggestion is based on a study of the t-dependence of differential cross section, $dσ(γp \to p ρ^{0})/dt$, which has been mea

Yu. Dabaghian

A cycle expansion technique for discrete sums of several PF operators, similar to the one used in standard classical dynamical zeta-function formalism is constructed. It is shown that the corresponding expansion coefficients show an interesting universal behavior, which illustrates the details of the interference between the particlar mappings entering the s

V. Veerakumar, M. Daniel

In this letter we describe a new and simple approach for modulating the electromagnetic wave propagating in a dielectric medium in the form of solitons by considering the torque developed between the induced dipoles in the medium and external field without taking into account the nonlinear Kerr effect. A reductive perturbation method deduces the Maxwell equa

V. Veerakumar, M. Daniel

We study the reversal of magnetization in an isotropic ferromagnetic film free from charges by exposing it to a circularly polarized electromagnetic (EM) field. The magnetization excitations obtained in the form of line and lump solitons of the completely integrable modified KP-II equation which is derived using a reductive perturbation method from the set o

Christian Wagner, Hanns Walter Mueller, Klaus Knorr

We present measurements on parametrically driven surface waves (Faraday waves) performed in the vicinity of a bi-critical point in parameter space, where modes with harmonic and subharmonic time dependence interact. The primary patterns are squares in the subharmonic and hexagons in the harmonic regime. If the primary instability is harmonic we observe a hys

H. R. Karadayi, M. Gungormez

For finite Lie algebras, it is shown that characters can be defined first for Weyl orbits and then for irreducible representations. For $A_N$ Lie algebras, weight multiplicities can then be calculated by only stating that characters are equivalent to Schur functions. This also means that to calculate characters there is no need to sum over Weyl groups. The c

Tom Leinster

Many people have proposed definitions of `weak n-category'. Ten of them are presented here. Each definition is given in two pages, with a further two pages on what happens when n = 0, 1, or 2. The definitions can be read independently. Chatty bibliography follows.

Albert Schwarz

Ordinary theta-functions can be considered as holomorphic sections of line bundles over tori. We show that one can define generalized theta-functions as holomorphic elements of projective modules over noncommutative tori (theta-vectors). The theory of these new objects is not only more general, but also much simpler than the theory of ordinary theta-function

Paolo Aluffi, Jean-Paul Brasselet

We show that the Chern-Schwartz-MacPherson class of a hypersurface X in a nonsingular variety M `interpolates&#39; between two other notions of characteristic classes for singular varieties, provided that the singular locus of X is smooth and that certain numerical invariants of X are constant along this locus. This allows us to define a lift of the Chern-Sc

Volker Betz

We prove existence of infinite volume Gibbs measures relative to Brownian motion. We require the pair potential W to fulfill a uniform integrability condition, but otherwise our restrictions on the potentials are relatively weak. In particular, our results are applicable to the massless Nelson model. We also prove an upper bound for path fluctuations under t

W. Bruns, J. Gubeladze

We investigate the minimal number of generators $μ$ and the depth of divisorial ideals over normal semigroup rings. Such ideals are defined by the inhomogeneous systems of linear inequalities associated with the support hyperplanes of the semigroup. The main result is that for every bound $C$ there exist, up to isomorphism, only finitely divisorial ideals $I

M. H. Dehghani, A. M. Ghezelbash, R. B. Mann

We show that the Abelian Higgs field equations in the background of the four dimensional AdS-Schwarzschild black hole have a vortex line solution. This solution, which has axial symmetry, is a generalization of the AdS spacetime Nielsen-Olesen string. By a numerical study of the field equations, we show that black hole could support the Abelian Higgs field a

Richard Corrado, Krzysztof Pilch, Nicholas P. Warner

We find M-theory solutions that are holographic duals of flows of the maximally supersymmetric N=8 scalar-fermion theory in (2+1) dimensions. In particular, we construct the M-theory solution dual to a flow in which a single chiral multiplet is given a mass, and the theory goes to a new infra-red fixed point. We also examine this new solution using M2-brane

Richard Wigmans

It is shown that high-energy features of the cosmic ray spectrum, in particular the kink around 4 PeV and the corresponding change in spectral index, may be explained from interactions between highly energetic cosmic protons and relic Big Bang antineutrinos, if the latter have a rest mass of about 0.4 eV/$c^2$. This explanation is supported by experimental d

M. Fontannaz, J. Ph. Guillet, G. Heinrich

We study the photoproduction of an isolated photon and a jet based on a code of partonic event generator type which includes the full set of next-to-leading order corrections. We compare our results to a recent ZEUS analysis in which an effective k_T of the incoming partons has been determined. We find that no additional intrinsic k_T is needed to describe t

E. A. Paschos, J. Y. Yu

We calculate neutrino induced cross-sections relevant for oscillation experiments, including the $τ$-lepton threshold for quasi-elastic, resonance and deep inelastic scattering. In addition to threshold effects, we include nuclear corrections for heavy targets which are moderate for quasi-elastic and large for single pion production. Nuclear effects for deep

Dariusz Prorok

A model for $J/Ψ$ suppression at a high energy heavy ion collision is presented. The main (and the only) reason for the suppression is $J/Ψ$ inelastic scattering within hadron matter. The hadron matter is in the form of a multi-component non-interacting gas. Also the evolution of the gas, both longitudinal and transverse, is taken into account. It is shown t

N. V. Mikheev, E. N. Narynskaya

Emission of a familon caused by the processes $e^- \to e^- + ϕ$, $ e^- \to μ^- + ϕ$ in dense magnetized plasma is investigated in the model in which a familon have both direct and no direct coupling to leptons via plasmon. The process probabilities and the integral familon action on plasma are calculated. It is shown that the $ P$ odd interference phenomenon

Neal Weiner

The logarithmic running of the gauge couplings alpha_1, alpha_2 and alpha_3, indicates that they may unify at some scale M_GUT ~ 10^16. This is often taken to imply that the standard model gauge group is embedded into some larger simple group in which quarks and leptons are placed in the same multiplet. These models have generic features, such as proton deca

F. Karsch, E. Laermann, Ch. Schmidt

We determine the second order endpoint of the line of first order phase transitions, which occur in the light quark mass regime of 3-flavour QCD at finite temperature, and analyze universal properties of this chiral critical point. A detailed analysis of Binder cumulants and the joint probability distributions of energy like and ordering-field like observabl

Martin Hasenbusch

We propose a modification of the Hybrid-Monte-Carlo algorithm that allows for a larger step-size of the integration scheme at constant acceptance rate. The key ingredient is that the pseudo-fermion action is split into two parts. We test our proposal at the example of the two-dimensional lattice Schwinger model with two degenerate flavours of Wilson-fermions

T. Affolder

We report the first observation of diffractive $J/ψ(\to μ^+μ^-)$ production in $\bar pp$ collisions at $\sqrt{s}$=1.8 TeV. Diffractive events are identified by their rapidity gap signature. In a sample of events with two muons of transverse momentum $p_T^μ>2$ GeV/$c$ within the pseudorapidity region $|η|<$1.0, the ratio of diffractive to total $J/ψ$ producti

T. Affolder

We present results from a measurement of double diffraction dissociation in $\bar pp$ collisions at the Fermilab Tevatron collider. The production cross section for events with a central pseudorapidity gap of width $Δη^0>3$ (overlapping $η=0$) is found to be $4.43\pm 0.02{(stat)}{\pm 1.18}{(syst) mb}$ [$3.42\pm 0.01{(stat)}{\pm 1.09}{(syst) mb}$] at $\sqrt{s

Jeremy D. Schnittman, Frederic A. Rasio

We investigate the orbits of compact binary systems during the final inspiral period before coalescence by integrating numerically the second-order post-Newtonian equations of motion. We include spin-orbit and spin-spin coupling terms, which, according to a recent study by Levin [J. Levin, Phys. Rev. Lett. 84, 3515 (2000)], may cause the orbits to become cha

Nicolas Arnaud, Matteo Barsuglia, Marie-Anne Bizouard, Philippe Canitrot

Detecting gravitational wave bursts (characterised by short durations and poorly modelled waveforms) requires to have coincidences between several interferometric detectors in order to reject non-stationary noise events. As the wave amplitude seen in a detector depends on its location with respect to the source direction and as the signal to noise ratio of t

Igor Rivin

We study the convergence speed of the batch learning algorithm, and compare its speed to that of the memoryless learning algorithm and of learning with memory (as analyzed in joint work with N. Komarova). We obtain precise results and show in particular that the batch learning algorithm is never worse than the memoryless learning algorithm (at least asymptot

N. Rogado, M. A. Hayward, K. A. Regan, Yayu Wang

We report the fabrication of MgB2 with bulk superconducting properties by conventional solid state methods at temperatures as low as 550 C. Mg deficiencies of the type Mg1-xB2 were tested. Tc was found to decrease by about 1K at large x, though the amount of non-stoichiometry, if any, is likely to be very small. For specific processing conditions, indication

Gabor Zala, B. N. Narozhny, I. L. Aleiner

We investigate the effect of electron-electron interaction on the temperature dependence of the Hall coefficient of 2D electron gas at arbitrary relation between the temperature $T$ and the elastic mean-free time $τ$. At small temperature $Tτ\ll \hbar$ we reproduce the known relation between the logarithmic temperature dependences of the Hall coefficient and

A. A. Polyanskii, A. Gurevich, J. Jiang, D. C. Larbalestier

We present a detailed magneto-optical investigation of the magnetic flux penetration in polycrystalline MgB2 slabs made by direct reaction of B and Mg. Our results unambiguously indicate a uniform, Bean critical state magnetization behavior with almost no electromagnetic granularity. From the measured magnetic flux profiles we were able to extract the temper

J. C. Phillips, J. Jung, D. Shimada, N. Tsuda

We examine experiments on energy gaps in high temperature superconductors (HTSC) in terms of experimental probes that utilize momentum, position, or neither. Experiments on very high quality mechanical tunnel junctions show a sharp energy gap with a maximum anisotropy of ~ 10%, while ultrahigh precision ARPES experiments show 100% anisotropy (d-wave pairing)

V. M. Villalba, A. Rincon Maggiolo

In this paper we obtain exact solutions of a 2D relativistic Dirac oscillator in the presence of a constant magnetic field. We compute the energy spectrum and discuss its dependence on the spin and magnetic field strength.

Alberto Rosso, Werner Krauth

In this paper, we compute the roughness exponent zeta of a long-range elastic string, at the depinning threshold, in a random medium with high precision, using a numerical method which exploits the analytic structure of the problem (`no-passing&#39; theorem), but avoids direct simulation of the evolution equations. This roughness exponent has recently been s

Christian Knetter, Kai P. Schmidt, Götz S. Uhrig

The excitation spectrum of the 2-leg S=1/2 Heisenberg ladder is examined perturbatively. Using an optimally chosen continuous unitary transformation we expand the Hamiltonian and the Raman operator about the limit of isolated rungs leading to high order series expansions allowing to calculate spectral densities quantitatively. The 2-particle sector is examin

B. Velický, C. Caroli

We study the dependence on the external pressure $P$ of the velocities $v_{L,T}$ of long wavelength sound waves in a confined 2D h.c.p. lattice of 3D elastic frictional balls interacting via one-sided Hertz-Mindlin contact forces, whose diameters exhibit mild dispersion. The presence of an underlying long range order enables us to build an effective medium d

G. Kälbermann

The phenomenon of wavepacket diffraction in space and time is investigated numerically and analytically, for a one-dimensional array of equally spaced finite-depth wells. Theoretical predictions for the lattice at long times and at low scattering energies, coincide exactly with the results for a single well. At intermediate and short times compared to the cl

D. V. Regelman, U. Mizrahi, D. Gershoni, E. Ehrenfreund

We investigate the intensity correlation properties of single photons emitted from an optically excited single semiconductor quantum dot. The second order temporal coherence function of the photons emitted at various wavelengths is measured as a function of the excitation power. We show experimentally and theoretically, for the first time, that a quantum dot

B. Davoudi, M. P. Tosi

We evaluate the charge and longitudinal spin response functions of a two-dimensional electron gas with $e^2/r$ interactions in an arbitrary state of spin polarization, using a structurally self-consistent approach to treat exchange and correlations. From the results we assess the nature of the magnetic order in the electronic ground state in zero magnetic fi

V. I. Yukalov, E. P. Yukalova

The relation between the notion of crystalline symmetry and characteristic time intervals when this symmetry could be observed is analyzed. Several time scales are shown to exist for a system of interacting particles. It is only when the observation time is much larger than the mesoscopic fluctuation time, the notion of crystalline symmetry becomes physicall

Yusuke Kato, Nobuhiko Hayashi

The pair-potential and current density around a single vortex of the two-dimensional chiral p-wave superconductor with ${\mib d}={\mib z}(p_x \pm \iu p_y)$ are determined self-consistently within the quasiclassical theory of superconductivity. Shrinking of the vortex core at low temperatures are considered numerically and analytically. Temperature-dependence

Shinsei Ryu, Yasuhiro Hatsugai

The Dirac fermion in the random chiral models is studied which includes the random gauge field model and the random hopping model. We focus on a connection between continuum and lattice models to give a clear perspective for the random chiral models. Two distinct structures of density of states (DoS) around zero energy, one is a power-law dependence on energ

J. J. Garcia-Ripoll, V. M. Perez-Garcia

We study in detail the counterintuitive result that in elongated rotating Bose--Einstein condensates the ground state is composed of one or more vortex lines which bend even in completely symmetric setups. This symmetry breaking allows the condensate to smoothly adapt to rotation and to produce tightly packed arrays of vortex lines.

Brian D. Fields, Frederic Daigne, Michel Casse, Elisabeth Vangioni-Flam

We investigate a possible nucleosynthetic signature of highly energetic explosions of C-O cores (&#34;hypernovae,&#34; HNe) which might be associated with gamma-ray bursts (GRBs). We note that the direct impact of C- and O-enriched hypernova ejecta on the ambient hydrogen and helium leads to spallation reactions which can produce large amounts of the light n

Wayne A. Barkhouse, Michael J. West, Gregory D. Bothun

We present the first measurement of the globular cluster populations of galaxies in Hickson compact groups, in order to investigate the effect of these high density environments on the formation and evolution of globular cluster systems. Based on V and R band images that we obtained of HCG 22a and HCG 90c with the ESO New Technology Telescope (NTT), we find

Stacy McGaugh

Stars have mass; halos lack cusps.

Yves Grosdidier, Anthony F. J. Moffat, Sébastien Blais-Ouellette, Gilles Joncas

With HST-WFPC2 we have obtained a deep, H-alpha image of the WR nebula M1-67. With the interferometer of the Universite Laval (Quebec, Canada), we have obtained complementary Fabry-Perot H-alpha data using CFHT MOS/SIS. On the deep H-alpha image we have performed continuous wavelet transforms to isolate stochastic structures of different characteristic size

Yukikatsu. Terada, M. Ishida, K. Makishima, T. Imanari

Extremely strong ionized Fe emission lines, with the equivalent width reaching about 4000 eV, were discovered with ASCA from a few Galactic compact objects, including AX J2315-0592, RX J1802.1+1804 and AX J1842.8-0423. These objects are thought to be binary systems containing magnetized white dwarfs (WDs). A possible interpretation of the strong Fe-K line is

Helen J. Fraser, Mark P. Collings, Martin R. S. McCoustra, David A. Williams

Water (H2O) ice is an important solid constituent of many astrophysical environments. To comprehend the role of such ices in the chemistry and evolution of dense molecular clouds and comets, it is necessary to understand the freeze-out, potential surface reactivity, and desorption mechanisms of such molecular systems. Consequently, there is a real need from

Enrico Costa, Paolo Soffitta, Ronaldo Bellazzini, Alessandro Brez

In astronomy there are basically four kinds of observations to extract the information carried by electromagnetic radiation: photometry, imaging, spectroscopy and polarimetry. By optimal exploitation of the first three techniques, X-ray astronomy has been able to unveil the violent world of compact high energy sources. Here we report on a new instrument that

Joanne C. Baker

Results are presented from a survey for CIV associated absorption in a complete low-frequency-selected sample of quasars. In agreement with previous work, associated absorbers are most common in steep-spectrum and lobe-dominated quasars, indicative of an anisotropic cloud distribution. Furthermore, we find the strongest CIV absorption occurs in sources of sm

G. Lyle Hoffman, E. E. Salpeter, Nathan J. Carle

Mapping of the HI disk of the isolated irregular galaxy DDO 154 with the C array of the Very Large Array and with the 3.2&#39; upgraded Arecibo beam is presented. Our results show a truncation (or temporary drop) of the HI disk at a column density around 10^19 atoms cm^-2, consistent with theoretical expectations for the truncation produced by the extragalac

S. Muehle, S. Huettemeister, U. Klein, E. M. Wilcots

A tremendous starburst, that ended about 4 million years ago, has had a very strong impact on the dwarf galaxy NGC 1569. Evidence for this event is still prominent in the different components of the galaxy: For example, photometric studies of the resolved stellar population close to the very luminous super-star clusters hint at past star formation rates of u

John T. Stocke

We describe recent discoveries of low column density [N(HI) < 10^14.5 cm^-2] H I Ly-alpha absorbers made with the Hubble Space Telescope (HST), which have allowed us a first look at gas in local intergalactic space between us and the &#34;Great Wall&#34;. Despite the mere 2.4m aperture of HST, these new observations allow us to detect absorbers with column d

D. de Martino, G. Matt, K. Mukai, T. Belloni

We present RXTE and BeppoSAX observations of the Intermediate Polar V709 Cas acquired in 1997 and 1998 respectively. The X-ray emission from 0.1 to 30keV is dominated by the strong pulsation at the rotational period of the white dwarf (312.8s) with no sign of orbital or sideband periodicity, thus confirming previous ROSAT results. However, we detect changes

T. Lebzelter, K. H. Hinkle, B. Aringer

We present times series of high resolution spectra of AGB variables at 4mu. Line profiles from the major contributors to the spectra of oxygen rich stars at 4mu, OH, H$_2$O, HCl and SiO, are examined. The velocity as well as shape variations of these profiles with time are discussed. The line profiles investigated frequently have emission and multiple absorp

T. D. Thoroughgood, V. S. Dhillon, S. P. Littlefair, T. R. Marsh

We present spectroscopy of the eclipsing recurrent nova U Sco. The radial velocity semi-amplitude of the primary star was found to be K_W = 93 \pm 10 kms^{-1} from the motion of the wings of the HeII\lambda4686Åemission line. By detecting weak absorption features from the secondary star, we find its radial velocity semi-amplitude to be K_R = 170 \pm 10 kms^{

C. Brocksopp, P. J. Groot, J. Wilms

We have studied the long term variability of LMC X-3 in optical lightcurves spanning six years, in order to search for optical signatures which could confirm/refute the suggestion that the `modulation&#39; is the result of accretion rate variability rather than accretion disc precession. We find that there is no stable period in the optical lightcurves, that

D. G. Barnes, W. J. G. de Blok

As part of a continuing survey of nearby galaxies, we have mapped the neutral gas content of the low surface brightness, Magellanic-type galaxy NGC 3109 --- and its environment, including the Antlia dwarf galaxy --- at unprecedented velocity resolution and brightness sensitivity. The HI mass of NGC 3109 is measured to be (3.8 +/- 0.5) x 10^8 Msun. A substant

J. Michael Shull

Ultraviolet spectrographs aboard the Hubble Space Telescope (HST) and the Far Ultraviolet Spectroscopic Explorer (FUSE) have proved their value as sensitive probes of the low-density intergalactic medium (IGM) at low redshifts (z < 0.1). Recent observations in Ly-alpha, Ly-beta, and occasional higher Lyman lines show that warm photoionized gas in the low-z I

Misha Verbitsky

Let $M$ be a hyperkaehler manifold, and $F$ a torsion-free and reflexive coherent sheaf on $M$. Assume that $F$ (outside of its singularities) admits a connection with a curvature which is invariant under the standard SU(2)-action on 2-forms. If the curvature is square-integrable, then $F$ is stable and its singularities are hyperkaehler subvarieties in $M$.

Tomomi Muto, Taro Tani

We study phase structure of the moduli space of a D0-brane on the orbifold C^3/Z_2 \times Z_2 based on stability of quiver representations. It is known from an analysis using toric geometry that this model has multiple phases connected by flop transitions. By comparing the results of the two methods, we obtain a correspondence between quiver representations

Alexander Kusenko, Marieke Postma

We show that neutrinos can be produced through standard electroweak interactions in matter with time-dependent density.

Hitoshi Nishino, Subhash Rajpoot

We present the locally supersymmetric formulation of unimodular gravity theory in D (1\le D \le 11) dimensions, namely supergravity theory with the metric tensor whose determinant is constrained to be unity. In such a formulation, the usual fine-tuning of cosmological constant is no longer needed, but its value is understood as an initial condition. Moreover

Hitoshi Nishino, Subhash Rajpoot

We present a teleparallel complex gravity as the foundation for the formulation of noncommutative gravity theory. The negative energy ghosts in the conventional formulation with U(1,3) local Lorentz connection no longer exists, since the local Lorentz invariance is broken down to U(1,3) global Lorentz symmetry. As desired, our teleparallel complex gravity th

Chang S. Chan, Akikazu Hashimoto, Herman Verlinde

We investigate the complete phase diagram of the decoupled world-sheet theory of (P,Q) strings. These theories include 1+1 dimensional super Yang-Mills theory and non-commutative open string theory. We find that the system exhibits a rich fractal phase structure, including a cascade of alternating supergravity, gauge theory, and matrix string theory phases.

Jacco Vink, J. Martin Laming, Jelle Kaastra, Johan Bleeker

We report the detection of the Sc-44 nuclear decay lines at 67.9 keV and 78.4 keV associated with the nuclear decay of Ti-44 in Cassiopeia A. The line emission was observed by the PDS instrument on board BeppoSAX, which recently observed the supernova remnant for over 500 ks. The detection of the line emission with a flux of (2.1 +/-0.7) 10^{-5} ph/cm^2/s in

the BABAR Collaboration, B. Aubert

We present a limit on the branching fraction for the decay $B^0 \to γγ$ using data collected at the $Υ(4S)$ resonance with the BABAR detector at the PEP-II asymmetric--energy $e^+e^-$ collider. Based on the observation of one event in the signal region, out of a sample of $21.3 \times 10^6$ $e^+e^- \to Υ(4S) \to B\bar B$ decays, we establish an upper limit o

J. Collins

In this talk, I reviewed the role of factorization in diffraction hard scattering.

M. Banados

We study linearized perturbations of eleven-dimensional $OSp(32|1)$ Chern-Simons supergravity. The action contains a term that changes the value of the cosmological constant, as considered by Horava. It is shown that the spectrum contains a 3-form and a 6-form whose field strengths are dual to each other, thus providing a link with the eleven-dimensional sup

D. Gomez Dumm, N. N. Scoccola

Chiral quark models with non-local covariant separable interactions at finite temperature and chemical potential are investigated. We develop a formalism in which the different quark properties are evaluated taking into account the analytic structure of the quark propagator. In this framework we study the chiral restoration phase transition for several defin

Ellen G. Zweibel

The interstellar magnetic field strength and gas density are observed to be correlated, but there is a large dispersion in this relation. In particular, the magnetic field is often observed to be weaker than expected. It is usually assumed that the field is frozen into the gas, except at very low ionization fraction, in which case ion-neutral drift, or ambip

E. M. C. Abreu, D. Dalmazi, E. A. Silva

For redundant second-class constraints the Dirac brackets cannot be defined and new brackets must be introduced. We prove here that the Jacobi identity for the new brackets must hold on the surface of the second-class constraints. In order to illustrate our proof we work out explicitly the cases of a fractional spin particle in 2+1 dimensions and the origina

N. D. Lambert, P. C. West

We discuss the dimensional reduction of various effective actions, particularly that of the closed Bosonic string and pure gravity, to two and three dimensions. The result for the closed Bosonic string leads to coset symmetries which are in agreement with those recently predicted and argued to be present in a new unreduced formulation of this theory. We also

G. J. Gounaris, C. Le Mouël, P. I. Porfyriadis

Applying Jarlskog&#39;s treatment of the CKM matrix, to the neutralino mass matrix in MSSM for real soft gaugino SUSY breaking and $μ$-parameters, we construct explicit analytical expressions for the four projectors which acting on any neutralino state project out the mass eigenstates. Analytical expressions for the neutralino mass eigenvalues in terms of th

V. B. Braginsky, S. E. Strigin, S. P. Vyatchanin

We present an approximate analysis of a nonlinear effect of parametric oscillatory instability in FP interferometer. The basis for this effect is the excitation of the additional (Stokes) optical mode and of the mirror&#39;s elastic mode when the optical energy stored in the FP resonator main mode exceeds the certain threshold. This effect is undesirable in

A. G. Grozin

Three-loop propagator diagrams in HQET can be reduced, using integration by parts, to 8 basis integrals: 5 trivial ones, two expressible via 3F2, and one only known up to ε^0. Calculation of the heavy-quark propagator in HQET is considerably simplified by the non-abelian exponentiation theorem.

M. B. Davies, A. R. King, H. Ritter

We investigate whether the recently-observed population of high-velocity white dwarfs can be derived from a population of binaries residing initially within the thin disk of the Galaxy. In particular we consider binaries where the primary is sufficiently massive to explode as a type II supernova. A large fraction of such binaries are broken up when the prima