January 2000 arXiv papers — page 3

A. Effern, K. Lehnertz, T. Schreiber, T. Grunwald

We present a new wavelet based method for the denoising of {\it event related potentials} ERPs), employing techniques recently developed for the paradigm of deterministic chaotic systems. The denoising scheme has been constructed to be appropriate for short and transient time sequences using circular state space embedding. Its effectiveness was successfully

U. D. Jentschura, P. J. Mohr, G. Soff

We present a nonperturbative numerical evaluation of the one-photon electron self energy for hydrogenlike ions with low nuclear charge numbers Z=1 to 5. Our calculation for the 1S state has a numerical uncertainty of 0.8 Hz for hydrogen and 13 Hz for singly-ionized helium. Resummation and convergence acceleration techniques that reduce the computer time by a

D. Zschiesche, P. Papazoglou, S. Schramm, J. Schaffner-Bielich

A nonlinear chiral SU(3) approach including the spin 3/2 decuplet is developed to describe dense matter. The coupling constants of the baryon resonances to the scalar mesons are determined from the decuplet vacuum masses and SU(3) symmetry relations. Different methods of mass generation show significant differences in the properties of the spin-3/2 particles

A. V. Afanasjev, P. Ring, J. Konig

Cranked Relativistic Hartree-Bogoliubov theory without and with approximate particle number projection by means of the Lipkin-Nogami method is presented in detail as an extension of Relativistic Mean Field theory with pairing correlations to the rotating frame. Pairing correlations are taken into account by a finite range two-body force of Gogny type. The ap

Gabor Papp, Gergely Barnafoeldi, George Fai, Peter Levai

The intrinsic transverse momentum distribution of partons in the nucleon can be used to explain a large amount of high-$p_T$ hadron and photon production data in high-energy nucleon-nucleon collisions at energies $\sqrt{s} \approx 20$ to 1800 GeV. However, proton-nucleus experiments at energies $\approx 30$ GeV show an extra enhancement (Cronin effect) in th

Kestutis Staliunas

It is shown, that diffusion of saturated gain (e.g. diffusion of population inversion in lasers) causes, and/or enhances a modulational instability of generated light field. In case of a subcritical system (e.g. a laser with saturable absorber) the enhancement of the modulational instability stabilizes spatial solitons. These predictions are made for general

Apoloniusz Tyszka

Let a finite non-empty X is equipped with discrete topology. We prove that S \subseteq X^ωis of second category if and only if for each f:ω-> \bigcup_{n \in ω} X^n there exists a sequence {a_n}_{n \in ω} belonging to S such that for infinitely many i \in ωthe infinite sequence {a_{i+n}}_{n \in ω} extends the finite sequence f(i).

Gennady A. Noskov

For an arbitrary Euclidean building we define a certain combing, which satisfies the `fellow traveller property' and admits a recursive definition. Using this combing we prove that any group acting freely, cocompactly and by order preserving automorphisms on a Euclidean building of one of the types A_n,B_n,C_n admits a biautomatic structure.

Kazuo Habiro

We introduce the concept of `claspers,' which are surfaces in 3-manifolds with some additional structure on which surgery operations can be performed. Using claspers we define for each positive integer k an equivalence relation on links called `C_k-equivalence,' which is generated by surgery operations of a certain kind called `C_k-moves'. We pro

Randall Dougherty, Alexander S. Kechris

A Borel equivalence relation on a Polish space is said to be countable if all of its equivalence classes are countable. Standard examples of countable Borel equivalence relations (on the space of subsets of the integers) that occur in recursion theory are: recursive isomorphism, Turing equivalence, arithmetic equivalence, etc. There is a canonical hierarchy

Emil Cornea, Ralph Howard, Per-Gunnar Martinsson

A detailed study of solutions to the first order partial differential equation H(x,y,z_x,z_y)=0, with special emphasis on the eikonal equation z_x^2+z_y^2=h(x,y), is made near points where the equation becomes singular in the sense that dH=0, in which case the method of characteristics does not apply. The main results are that there is a strong lack of uniqu

Dmitry Jakobson, Igor Rivin

We define a number of natural (from geometric and combinatorial points of view) deformation spaces of valuations on finite graphs, and study functions over these deformation spaces. These functions include both direct metric invariants (girth, diameter), and spectral invariants (the determinant of the Laplace operator, or complexity; bottom non-zero eigenval

Mark Shimozono, Mike Zabrocki

A family of vertex operators that generalizes those given by Jing for the Hall-Littlewood symmetric functions is presented. These operators produce symmetric functions related to the Poincare polynomials referred to as generalized Kostka polynomials in the same way that Jing's operator produces symmetric functions related to Kostka-Foulkes polynomials. T

Andreas Cap, Jan Slovak

Motivated by the rich geometry of conformal Riemannian manifolds and by the recent development of geometries modeled on homogeneous spaces $G/P$ with $G$ semisimple and $P$ parabolic, Weyl structures and preferred connections are introduced in this general framework. In particular, we extend the notions of scales, closed and exact Weyl connections, and Rho--

V. A. Buslov

By natural way the hierarchy structure is introduced on directed graphs with weighted adjacencies. Embedded system of algebras of subsets of the set of vertices of such digraph and it's consolidations, which vertices are the elementary sets of corresponding algebra, are constructed. Weights of arcs of consolidated graphs are determined.

Andreas Cap, Jan Slovak, Vladimir Soucek

This paper is devoted to the study of geometric structures modeled on homogeneous spaces G/P, where G is a real or complex semisimple Lie group and $P\subset G$ is a parabolic subgroup. We use methods from differential geometry and very elementary finite-dimensional representation theory to construct sequences of invariant differential operators for such geo

V. A. Buslov

Formulas for matrix determinants, algebraic adjunctions, characteristic polynomial coefficients, components of eigenvectors are obtained in the form of signless sums of matrix elements products taking by special graphs. Signless formulas are very important for singular and stochastic problems. They are also useful for spectral analysis of large very sparse m

Riccardo Benedetti, Carlo Petronio

We provide combinatorial realizations, according to the usual objects/moves scheme, of the following three topological categories: (1) pairs (M,v) where M is a 3-manifold (up to diffeomorphism) and v is a (non-singular vector) field, up to homotopy; here possibly the boundary of M is non-empty and v may be tangent to the boundary, but only in a concave fashi

Dmitri I. Panyushev

A well-known result of Kostant gives a description of the G-module structure for the exterior algebra of Lie algebra $\frak g$. We give a generalization of this result for the isotropy representations of symmetric spaces. If $\frak g={\frak g}_0+{\frak g_1}$ is a Z_2-grading of a simple Lie algebra, we explicitly describe a ${\frak g}_0$-module $Spin_0({\fra

R. Breslav, A. Stavrova, R. R. Zapatrin

Earlier an arbitrary poset $P$ was proved to be isomorphic to the collection of subsets of a space $M$ with two closures which are closed in the first closure and open in the other. As a space $M$ for this representation an algebraic dual space $P^*$ was used. Here we extend the theory of algabraic duality for posets generalizing the notion of an ideal. This

John Madore, Stefan Schraml, Peter Schupp, Julius Wess

We introduce a formulation of gauge theory on noncommutative spaces based on the concept of covariant coordinates. Some important examples are discussed in detail. A Seiberg-Witten map is established in all cases.

JM Figueroa-O'Farrill, S Stanciu

We analyse the possible D-brane configurations in an AdS_3xS^3xS^3xS^1 background with a NS-NS B field, by using the boundary state formalism. We study their geometry and we determine the fraction of spacetime supersymmetry preserved by these solutions.

A. N. Schellekens

Some applications of simple current techniques and fixed point resolution to theories of open strings are discussed. In addition to a brief review of work presented in two recent papers with L. Huiszoon and N. Sousa, some new results concerning uniqueness of crosscap coefficients are presented, as well as a strange sum rule for the modular matrix implied by

N. Mankoc Borstnik, H. B. Nielsen

Polynomials in Grassmann space can be used to describe all the internal degrees of freedom of spinors, scalars and vectors, that is their spins and charges. It was shown that Kähler spinors, which are polynomials of differential forms, can be generalized to describe not only spins of spinors but also spins of vectors as well as spins and charges of scalars,

C. Burdik, A. Pashnev, M. Tsulaia

The method of construction of auxiliary representations for a given Lie algebra is discussed in the framework of the BRST approach. The corresponding BRST charge turns out to be non -- hermitian. This problem is solved by the introduction of the additional kernel operator in the definition of the scalar product in the Fock space. The existence of the kernel

E. E. Donets, A. Pashnev, J. J. Rosales, M. Tsulaia

The multidimensional N=4 supersymmetric quantum mechanics (SUSY QM) is constructed and the various possibilities for partial supersymmetry breaking are discussed. It is shown that quantum mechanical models with one quarter, one half and three quarters of unbroken(broken) supersymmetries can exist in the framework of the multidimensional N=4 SUSY QM.

Miao Li

We clarify the relation between the recently formulated holographic renormalization group equation and Polchinski's exact renormalization group equation.

Andre Wehner, James T. Wheeler

We extend 2n-dim biconformal gauge theory by including Lorentz-scalar matter fields of arbitrary conformal weight. For a massless scalar field of conformal weight zero in a torsion-free biconformal geometry, the solution is determined by the Einstein equation on an n-dim submanifold, with the stress-energy tensor of the scalar field as source. The matter fie

Yu. A. Simonov

Nonperturbative QCD approach is systematically derived starting from the QCD Lagrangian. Treating spin effects as a perturbation, one obtains the universal effective Hamiltonian describing mesons, hybrids and glueballs. Constituent mass of quark and gluon is calculated via string tension. The resulting spectrum of mesons, hybrids and glueballs obtained is in

Giovanni Amelino-Camelia, Franco Buccella

In recent work on experimental tests of quantum-gravity-motivated phenomenological models, a significant role has been played by the so-called ``$κ$'' deformations of Poincaré symmetries. Sensitivity to values of the relevant deformation length $λ$ as small as $5 \cdot 10^{-33}m$ has been achieved in recent analyses comparing the structure of $κ$-Poi

S. M. Lietti, Hitoshi Murayama

The effect of new operators that give rise to CP-violating couplings of the type $Z t \bar{t}$ and $γt \bar{t}$ are examined at future electron positron Linear Colliders (FLC). The impact of these CP-violating interactions over Standard Model predictions was studied for the process e+ e^- -> t anti-t with the subsequent decays t -> b l+ nu_l and anti-t -> an

D. S. Gorbunov

We consider feasibility of electroweak baryogenesis in gauge mediated supersymmetry breaking models with messenger-matter mixing. We present a class of models where electroweak baryogenesis produces sufficient amount of baryon asymmetry. The main features of these models are ({\it i}) large mixing between messengers and right stop and ({\it ii}) fairly narro

V. I. Shevchenko, Yu. A. Simonov

Recent accurate measurements of static potentials between sources in various representations of the gauge group SU(3) performed by G.Bali provide a crucial test of the QCD vacuum models and different approaches to confinement. The Casimir scaling of the potential observed for all measured distances implies strong suppression of higher cumulant contributions.

A. Masiero, O. Vives

In this talk, we address the possibility of finding supersymmetry through indirect searches in the K and B systems. We prove that, in the absence of the Cabibbo-Kobayashi-Maskawa phase, a general Minimal Supersymmetric Standard Model with all possible phases in the soft-breaking terms, but no new flavor structure beyond the usual Yukawa matrices, can never g

A. Rajantie

The real-time dynamics of finite-temperature gauge theories can be approximated, to leading-order accuracy in the coupling constants, by a classical field theory with the hard thermal loop Lagrangian. I show how this approach can be used in numerical lattice simulations to study dynamics of the Abelian Higgs model in or slightly out of equilibrium.

M. Laine

Placing a high-Tc superconductor in an increasing external magnetic field, the flux first penetrates the sample through an Abrikosov vortex lattice, and then a first order transition is observed by which the system goes to the normal phase. We discuss the cosmological motivation for considering the electroweak phase transition in the presence of an external

Ralf Rapp

The significance of thermal dilepton radiation at intermediate invariant masses (1GeV<M<3GeV) in ultrarelativistic heavy-ion collisions is investigated. At CERN-SpS energies, a consistent explanation of the excess observed by NA50 can be given. At RHIC energies the thermal signal is dominated by early emission indicative for QGP formation. Chemical under-sat

Helen R. Quinn, Joao P. Silva

This paper reviews the Dalitz plot analysis for the decays $B^0(\bar B^0) \to ρπ\to π^+ π^- π^0$. We discuss what can be learned about the ten parameters in this analysis from untagged and from tagged time-integrated data. We find that, with the important exception of the interesting CP violating quantity $α$, the parameters can be determined from this data

A. D. Kennedy, Brian Pendleton

We study analytically the computational cost of the Generalised Hybrid Monte Carlo (GHMC) algorithm for free field theory. We calculate the autocorrelation functions of operators quadratic in the fields, and optimise the GHMC momentum mixing angle, the trajectory length, and the integration stepsize. We show that long trajectories are optimal for GHMC, and t

Levan Babukhadia

We have made a precise measurement of the inclusive jet cross section at $\sqrt{s}$=1800 GeV. The result is based on an integrated luminosity of 92 pb^{-1} collected at the Fermilab Tevatron $\bar{p}p$ Collider with the DØdetector. The measurement is reported as a function of jet transverse energy (60 GeV <= E_{T} < 550 GeV), and in the pseudorapidity interv

R. Godang, CLEO Collaboration

We report on a search for D0-D0B mixing made by studying the `wrong-sign&#39; process D0->K^+pi^-. The data come from an integrated luminosity of 9.0 1/fb of e^+e^- collisions at s^(1/2) of approximately 10 GeV recorded with the CLEO II.V detector. We measure the time integrated rate of the `wrong-sign&#39; process D0->K^+pi^- relative to that of the Cabibbo

Matt Visser, Carlos Barcelo

The energy conditions of general relativity permit one to deduce very powerful and general theorems about the behaviour of strong gravitational fields and cosmological geometries. However, the energy conditions these theorems are based on are beginning to look a lot less secure than they once seemed: (1) there are subtle quantum effects that violate all of t

Rosario Martin, Enric Verdaguer

The semiclassical Einstein-Langevin equations which describe the dynamics of stochastic perturbations of the metric induced by quantum stress-energy fluctuations of matter fields in a given state are considered on the background of the ground state of semiclassical gravity, namely, Minkowski spacetime and a scalar field in its vacuum state. The relevant equa

O. Bertolami

We show that estimates of the Lorentz symmetry violation extracted from ultra-high energy cosmic rays beyond the GZK cut-off set bounds on the parameters of a Lorentz-violating extension of the Standard Model. Moreover, we argue that correlated measurements of the difference in the arrival time of gamma-ray photons and neutrinos emitted from Active Galactic

I. Schmelzer

We present a metric theory of gravity with Lagrangian L = (8πG)^{-1}(Ξg^{ii} - Υg^{00})\sqrt{-g} + L_{GR} + L_{matter} motivated by classical equations \partial_t ρ+ \partial_i (ρv^i) = 0 \partial_t (ρv^j) + \partial_i (ρv^i v^j + p^{ij}) = 0 for a medium in Newtonian space-time. We obtain stable ``frozen stars&#39;&#39; instead of black holes and a ``big bo

M. Gasperini

We estimate the signal-to-noise ratio for two gravitational detectors interacting with a stochastic background of massive scalar waves. We find that the present experimental level of sensitivity could be already enough to detect a signal from a light but non-relativistic component of dark matter, even if the coupling is weak enough to exclude observable devi

L. C. Garcia de Andrade

Variation of the 4-D string cosmology action with dynamical torsion and massless dilatons lead to an expression of torsion in terms of massless dilatons in the case of de Sitter inflation.The solution is approximated according to the COBE data.

Fredrik Andersson

We perform a complete rho-integration of the GHP equations for all spacetimes that admit a geodesic shear-free expanding null congruence, whose Ricci spinor is aligned to the congruence and whose Ricci scalar is constant. We also deduce the system of GHP equations after the integration is completed, and discuss a few applications.

Joseph Y. Halpern, Ron van der Meyden

Abadi has introduced a logic to explicate the meaning of local names in SDSI, the Simple Distributed Security Infrastructure proposed by Rivest and Lampson. Abadi&#39;s logic does not correspond precisely to SDSI, however; it draws conclusions about local names that do not follow from SDSI&#39;s name resolution algorithm. Moreover, its semantics is somewhat

Joseph O&#39;Rourke

Recent results on curve reconstruction are described.

John J. Quinn, Arkadiusz Wojs

The composite Fermion (CF) picture offers a simple intuitive way of understanding many of the surprising properties of a strongly interacting two-dimensional electron fluid in a large magnetic field. The simple way in which the mean field CF picture describes the low lying bands of angular momentum multiplets for any value of the applied magnetic field is il

G. Ouillon, D. Sornette

We report new tests of the critical earthquake concepts performed on rockbursts in deep South African mines. We extend the concept of an optimal time and space correlation region and test it on the eight main shocks of our catalog provided by ISSI. In a first test, we use the simplest signature of criticality in terms of a power law time-to-failure formula.

Fabrice Thalmann, Chandan Dasgupta, Denis Feinberg

We consider the phase diagram of a classical fluid in the presence of a random pinning potential of arbitrary strength. Introducing replicas for averaging over the quenched disorder, we use the hypernetted chain approximation to calculate the correlations in the replicated liquid. The freezing transition of the liquid into a nearly crystalline state is studi

Yuriy Makhlin, Gerd Schoen, Alexander Shnirman

The quantum measurement process by a single-electron transistor or a quantum point contact coupled to a quantum bit is studied. We find a unified description of the statistics of the monitored quantity, the current, in the regime of strong measurement and expect this description to apply for a wide class of quantum measurements. We derive the probability dis

Martin Wilkens, Fabrizio Illuminati, Meret Kraemer

We compute the critical temperature T_c of a weakly interacting uniform Bose gas in the canonical ensemble, extending the criterion of condensation provided by the counting statistics for the uniform ideal gas. Using ordinary perturbation theory, we find in first order $(T_c-T_c^0)/T_c^0 = -0.93 aρ^{1/3}$, where T_c^0 is the transition temperature of the cor

D. F. Agterberg, R. Heeb, P. G. Kealey, T. M. Riseman

Recent experimental results indicate that superconductivity in Sr2RuO4 is described by the p-wave E_u representation of the D_{4h} point group. Results on the vortex lattice structures for this representation are presented. The theoretical results are compared with experiment.

Dirk Helbing, Bernardo A. Huberman, Sebastian M. Maurer

We show how optimization methods from economics known as portfolio strategies can be used for minimizing download times in the Internet and travel times in freeway traffic. While for Internet traffic, there is an optimal restart frequency for requesting data, freeway traffic can be optimized by a small percentage of vehicles coming from on-ramps. Interesting

S. N. Dorogovtsev, J. F. F. Mendes

We study the growth of a reference network with aging of sites defined in the following way. Each new site of the network is connected to some old site with probability proportional (i) to the connectivity of the old site as in the Barabási-Albert&#39;s model and (ii) to $τ^{-α}$, where $τ$ is the age of the old site. We consider $α$ of any sign although rea

Francis J. Alexander, Bruce M. Boghosian, Richard C. Brower, S. Roy Kimura

Fourier acceleration has been successfully applied to the simulation of lattice field theories for more than a decade. In this paper, we extend the method to the dynamics of discrete particles moving in continuum. Although our method is based on a mapping of the particles&#39; dynamics to a regular grid so that discrete Fourier transforms may be taken, it sh

S. Sengupta, P. Nielaba, K. Binder

Elastic moduli and dislocation core energy of the triangular solid of hard disks of diameter $σ$ are obtained in the limit of vanishing dislocation- antidislocation pair density, from Monte Carlo simulations which incorporates a constraint, namely that all moves altering the local connectivity away from that of the ideal triangular lattice are rejected. In t

Elisa Ercolessi, Giuseppe Morandi, Pierbiagio Pieri, Marco Roncaglia

We present here a nonlinear sigma-model (NL$σ$M) study of a spin-1 antiferromagnetic Heisenberg chain in an external commensurate staggered magnetic field. We find, already at the mean-field level, excellent agreement with recent and very accurate Density Matrix Renormalization Group (DMRG) studies, and that up to the highest values of the field for which a

Guang-Ming Zhang, Lu Yu

Majorana fermion representations of the algebra associated with spin, charge, and flavor currents have been used to transform the two-channel Kondo Hamiltonian. Using a path integral formulation, we derive a reduced effective action with long-range impurity spin-spin interactions at different imaginary times. In the semiclassical limit, it is equivalent to a

J. Kaupuzs

The Ginzburg-Landau phase transition model is considered in d=4-epsilon dimensions within the renormalization group (RG) approach. The problem of existence of the non-Gaussian fixed point is discussed. An equation is derived from the first principles of the RG theory (under the assumption that the fixed point exists) for calculation of the correction-to-scal

Avinash Singh

A new decoupling scheme is developed for the Hubbard model which provides a unified description of the spin-symmetric (paramagnetic metallic and insulating) phases as well as the broken-symmetry AFI phase. Independent of magnetic ordering, the scheme yields, in the lowest order, the correct strong-coupling bandwidth of order J (for the NN hopping model) and

K. Ø. Rasmussen, T. Lookman, A. Saxena, A. R. Bishop

We show how the St.Venant compatibility relations for strain in three dimensions lead to twinning for the cubic to tetragonal transition in martensitic materials within a Ginzburg-Landau model in terms of the six components of the symmetric strain tensor. The compatibility constraints generate an anisotropic long-range interaction in the order parameter (dev

Toshiya Ueta, Margaret Meixner, Matthew Bobrowsky

We summarize results of our {\it HST} imaging survey of proto-planetary nebula (PPN) candidates, in which we discovered two types of axisymmetric reflection nebulosities. The Star-Obvious Low-level-Elongated (SOLE) nebulae show a bright central star embedded in a smooth, faint extended nebulosity, whereas the DUst-Prominent Longitudinally-EXtended (DUPLEX) n

A. Cha, M. Sahu, H. W. Moos, A. Blaauw

The first study of the local interstellar medium (LISM) toward Puppis-Vela (l = 245\degr to 275\degr, b = -15\degr to +5\degr, d < 200 pc) is presented in this paper. A study of the locations, sizes, and physical characteristics of local interstellar gas, i.e. ``astronephography,&#39;&#39; is included, and relies upon the improved distance measurements provi

A. S. Brun, J. P. Zahn

Recently helioseismic observations have revealed the presence of a shear layer at the base of the convective zone related to the transition from differential rotation in the convection zone to almost uniform rotation in the radiative interior, the tachocline. At present, this layer extends only over a few percent of the solar radius and no definitive explana

Yves A. Gallant, Abraham Achterberg, John G. Kirk, Axel W. Guthmann

We examine Fermi-type acceleration at relativistic shocks, and distinguish between the initial boost of the first shock crossing cycle, where the energy gain per particle can be very large, and the Fermi process proper with repeated shock crossings, in which the typical energy gain is of order unity. We calculate by means of numerical simulations the spectru

Carlos Allende Prieto, David L. Lambert

Analyses of the near-ultraviolet continuum of late-type stars have led to controversial results regarding the performance of state-of-the-art model atmospheres. The release of the homogeneous IUE final archive and the availability of the high-accuracy Hipparcos parallaxes provide an opportunity to revisit this issue, as accurate stellar distances make it pos

E. Bertone, G. Tagliaferri, G. Ghisellini, A. Treves

The BL Lacertae object PKS 2155-304 was observed by the Infrared Space Observatory in May and June 1996, during a multiwavelength campaign. These are the first observations in the mid- and far-infrared bands since IRAS. In the observing period, the source showed no detectable time variability at 4.0, 14.3, 60 and 90 micron. The spectrum from 2.8 to 100 micro

Nicolas Cretton, Hans-Walter Rix, Tim de Zeeuw

We present direct observational constraints on the orbital distribution of the stars in the giant elliptical NGC 2320. Long-slit spectra along multiple position angles are used to derive the stellar line-of-sight velocity distribution within one effective radius. In addition, the rotation curve and dispersion profile of an ionized gas disk are measured from

F. Tesch, F. J. Carrera, D. Engels, J. Hu

We present the first ROSAC results of an AGN clustering analysis. This study comprises a sample of 200 AGNs, 75% of which being at low redshifts z<0.5, in the Ursa Major constellation. The spatial 2-point-correlation function (SCF) as well as the minimal spanning tree (MST) technique were applied. Some evidence for clustering is found in the SCF, although wi

F. Tesch, D. Engels

We have examined the spatial distribution of 856 AGN detected by the ROSAT All-Sky Survey (RASS) using a direct search for structures with the minimal spanning tree. The AGNs were compiled from an area of 7000 deg^2, in which optical identifications of RASS sources were made with the help of the digitized objective prism plates of the Hamburg Quasar Survey (

E. Ros, J. M. Marcaide, J. C. Guirado, E. Sardon

Global Positioning System (GPS) satellites broadcast at frequencies of 1,575.42 MHz (L1) and of 1,227.60 MHz (L2). The dispersive property of the ionosphere can be used to combine independent measurements at the two frequencies to estimate the total electron content (TEC) between a GPS receiver site and a broadcasting satellite. Such measurements, made at si

R. P. Fender, M. A. Hendry

We summarise all the reported detections of, and upper limits to, the radio emission from persistent (i.e. non-transient) X-ray binaries. A striking result is a common mean observed radio luminosity from the black hole candidates (BHCs) in the Low/Hard X-ray state and the neutron-star Z sources on the horizontal X-ray branch. This implies a common mean intri

C. R. Keeton, E. E. Falco, C. D. Impey, C. S. Kochanek

Infrared images of the Q 0957+561 gravitational lens obtained with the Hubble Space Telescope show two large (\sim 5 arcsec) lensed images of the z_s=1.41 quasar host galaxy. Parts of the host galaxy are doubly-imaged like the quasar, while other parts are quadruply-imaged. The distortions of the host galaxy offer the best probe yet of the global structure o

R. D. Blandford

Observations of jets from quasars and other types of accreting black hole are briefly summarized. The importance of beaming and $γ$-ray observations for understanding the origin of these jets is emphasised. It is argued that both the power source and the collimation are likely to be magnetic in origin, although the details remain controversial. Ultrarelativi

R. D. Blandford

Cosmic explosions are observed in many astrophysical environments. They range in scale from hydromagnetic instabilities in the terrestrial magnetotail and solar ``nanoflares&#39;&#39; to cosmological gamma ray bursts, supernovae and the protracted intervals of nuclear activity that produce the giant quasars and radio galaxies. There are many parallels in the

R. A. Stathakis, B. J. Boyle, D. H. Jones, M. S. Bessell

SN 1998bw holds the record for the most energetic Type Ic explosion, one of the brightest radio supenovae and probably the first supernova associated with a gamma-ray burst. In this paper we present spectral observations of SN 1998bw observed in a cooperative monitoring campaign using the AAT, UKST and the SSO 2.3-m telescope. We investigate the evolution of

Ann I. Zabludoff, John S. Mulchaey

We obtain R-band photometry for galaxies in six nearby poor groups for which we have spectroscopic data, including 328 new galaxy velocities. For the five groups with luminous X-ray halos, the composite group galaxy luminosity function (GLF) is fit adequately by a Schechter function with Mstar = -21.6 +/- 0.4 + 5log h and alpha = -1.3 +/- 0.1. We also find t

Li-Xin Li

With the Komar mass formula we calculate the electromagnetic energy for a charged Kerr black hole in a uniform magnetic field. We find that the total electromagnetic energy takes the minimum when the Kerr black hole possesses a non-zero net charge $Q = 2ξB_0 J_H$ where $B_0$ is the strength of the magnetic field, $J_H$ is the angular momentum of the black ho

Uros Seljak

We investigate an analytic model to compute nonlinear power spectrum of dark matter, galaxies and their cross-correlation. The model is based on Press-Schechter halos, which cluster and have realistic dark matter profiles. The total power spectrum is a sum of two contributions, one from correlations betwen the halos and one from correlations within the same

Cheongho Han, Seong-Hong Park

Detecting colour changes of a gravitational microlensing event induced by the limb-darkened extended source effect is important to obtain useful information both about the lens and source star. However, precise measurements of the colour changes are hampered by blending, which also causes colour changes of the event. In this paper, we show that although the

Gordon Chalmers

S and U-duality dictate that graviton scattering amplitudes in IIB superstring theory be automorphic functions on the appropriate fundamental domain which describe the inequivalent vacua of (compactified) theories. A constrained functional form of graviton scattering is proposed using Eisenstein series and their generalizations compatible with: a) two-loop s

Savdeep Sethi, Mark Stern

We consider quantum mechanical Yang-Mills theories with eight supercharges and a $Spin(5) \times SU(2)_R$ flavor symmetry. We show that all normalizable ground states in these gauge theories are invariant under this flavor symmetry. This includes, as a special case, all bound states of D0-branes and D4-branes. As a consequence, all bound states of D0-branes

G. Akemann, E. Kanzieper

We show that integrable structure of chiral random matrix models incorporating global symmetries of QCD Dirac operators (labeled by the Dyson index beta=1,2, and 4) leads to emergence of a connection relation between the spectral statistics of massive and massless Dirac operators. This novel link established for beta-fold degenerate massive fermions is used

Christian Schubert

The string-inspired technique is used for the calculation of vacuum polarisation tensors in constant electromagnetic fields. In the first part of this series, we give a detailed exposition of the method for the case of the QED one-loop N-photon amplitude in a general constant electromagnetic background field. The two-point cases are calculated explicitly, le

Dilip Kumar Ghosh, Sourendu Gupta, D. Indumathi

We present the results of a QCD fit to global data on deep-inelastic polarised lepton-hadron scattering. We find that it is possible to fit the data with strongly broken SU(2) flavour for the polarised sea densities. This can easily be tested in $W$ production at polarised RHIC. The data fails to pin down polarised singlet sea quark and gluon densities. We e

S. L. Dubovsky

Supersymmetric orbifold projection of N=1 SQCD with relatively small number of flavors (not larger than the number of colors) is considered. The purpose is to check whether orbifolding commutes with the infrared limit. On the one hand, one considers the orbifold projection of SQCD and obtains the low-energy description of the resulting theory. On the other h

Michael T. Anderson

It is proved that the only geodesically complete stationary vacuum solution of the Einstein equations is the empty Minkowski space, or a quotient of it by a discrete group of isometries, generalizing a classical result of Lichnerowicz. In addition, we obtain an apriori bound on the curvature of stationary vacuum solutions away from the boundary or horizon.

M. L. McConnell, J. M. Ryan, W. Collmar, V. Schoenfelder

The Compton Gamma-Ray Observatory (CGRO) has observed the Cygnus region on several occasions since its launch in 1991. The data collected by the COMPTEL experiment on CGRO represent the most sensitive observations to date of Cygnus X-1 in the 0.75-30 MeV range. A spectrum accumulated by COMPTEL over 10 weeks of observation time shows significant evidence for

Jose D. Edelstein, Wifredo Garcia Fuertes, Javier Mas, Juan Mateos Guilarte

We study the electric flux tubes that undertake color confinement in N=2 supersymmetric Yang-Mills theories softly broken down to N=1 by perturbing with the first two Casimir operators. The relevant Abelian Higgs model is not the standard one due to the presence of an off-diagonal coupling among different magnetic U(1) factors. We perform a preliminary study

J. M. Cline

The cosmology of a brane-universe embedded in a higher dimensional bulk spacetime presents some peculiarities not seen in ordinary (3+1) dimensional gravity. I summarize the current understanding, with emphasis on the suggestion by Randall and Sundrum that the bulk is 5-D anti-deSitter space, leading to a solution of the weak scale hierarchy problem.

Denis Perrot

We consider a smooth groupoid of the form Σ\rtimesΓwhere Σis a Riemann surface and Γa discrete pseudogroup acting on Σby local conformal diffeomorphisms. After defining a K-cycle on the crossed product C_0(Σ)\rtimesΓgeneralising the classical Dolbeault complex, we compute its Chern character in cyclic cohomology, using the index theorem of Connes and Moscovi

Patrick Dorey, Clare Dunning, Roberto Tateo

We present evidence for the existence of infinitely-many new families of renormalisation group flows between the nonunitary minimal models of conformal field theory. These are associated with perturbations by the $ϕ_{21}$ and $ϕ_{15}$ operators, and generalise a family of flows discovered by Martins. In all of the new flows, the finite-volume effective centr

B. Guberina, B. Melic, H. Stefancic

Large preasymptotic effects in beauty decays have been found using heavy-quark and SU(3) symmetry, as well as experimental data on charmed hyperons. Contrary to rather uniform beauty-meson lifetimes, a much larger spread of beauty-baryon lifetimes is predicted. However, it is highly unlikely that, theoretically, the $ τ(Λ_b)/τ(B_d^0) $ ratio, which at presen

Alan Dow, Klaas Pieter Hart

Steprans provided a characterization of betaN\N in the aleph_2-Cohen model that is much in the spirit of Parovicenko&#39;s characterization of this space under CH. A variety of the topological results established in the Cohen model can be deduced directly from the properties of betaN\N or P(N)/fin that feature in Steprans&#39; result.

M. Caselle, M. Hasenbusch, P. Provero, K. Zarembo

We discuss the spectrum of the three dimensional phi^4 theory in the broken symmetry phase. In this phase the effective potential between the elementary quanta of the model is attractive and bound states of two or more of them may exist. We give theoretical and numerical evidence for the existence of these bound states. Looking in particular at the Ising mod

A. L. Larsen, N. Sánchez

In this paper we make the connection between semi-classical string quantization and exact conformal field theory quantization of strings in 2+1 Anti de Sitter spacetime. More precisely, considering the WZWN model corresponding to SL(2,R) and its covering group, we construct quantum {\it coherent} string states, which generalize the ordinary coherent states o