December 1998 arXiv papers — page 16

E. Grün, S. B. Peschke, M. Stickel, T. Müller

Comet Hale-Bopp was observed five times with ISOPHOT, the photometer on board the Infrared Space Observatory (ISO). Each time broadband photometry was performed using 4 different detectors, 5 apertures and, 10 filters covering the range between 3.6 to 175 $μ$m. Calibration measurements using the internal Fine Calibration Source were done together with each i

Robin Ciardullo, George H. Jacoby

We analyze the dependence of circumstellar extinction on core mass for the brightest planetary nebulae (PNe) in the Magellanic Clouds and M31. We show that in all three galaxies, a statistically significant correlation exists between the two quantities, such that high core mass objects have greater extinction. We model this behavior, and show that the relati

Sydney A. Barnes, Sabatino Sofia, Charles F. Prosser, John R. Stauffer

We present the results of a monitoring campaign aimed at deriving rotation periods for a representative sample of stars in the young (30 Myr) open cluster IC 2602. Rotation periods were derived for 29 of 33 stars monitored. The periods derived range from 0.2d (one of the shortest known rotation periods of any single open cluster star) to about 10d (which is

C. C. Steidel, K. L. Adelberger, M. Dickinson, M. Giavalisco

We report on the status of large surveys of photometrically selected star forming galaxies at z~3 and z~4, with particular emphasis on both the advantages and the limitations of selecting objects using the ``Lyman break'' technique. Current results on the luminosity functions, luminosity densities, color distribution, star formation rates, clustering

George H. Jacoby, Robin Ciardullo

We derive abundances and central star parameters for 15 planetary nebulae (PNe) in M31: 12 in the bulge and 3 in a disk field 14 kpc from the nucleus. No single abundance value characterizes the bulge stars: although the median abundances of the sample are similar to those seen for PNe in the LMC, the distribution of abundances is several times broader, span

J. Maiz-Apellaniz, C. Munoz-Tunon, G. Tenorio-Tagle, J. M. Mas-Hesse

We present in this paper a detailed study of the kinematical properties of the ionized gas around the young massive star clusters in the nucleus of NGC 4214. The analysis is based on bidimensional spectroscopical data, allowing to derive the spatial variation of different properties (intensity, velocity and width / line splitting) of the emission lines Hαand

A. V. Kopylov

The algorithm is proposed which by combination of the files with the events from linac and with the final data events from the observation of solar neutrinos enables to check correctness of the data treatment used in SuperKamiokande experiment.

Juan Maldacena, Jeremy Michelson, Andrew Strominger

Low-energy, near-horizon scaling limits of black holes which lead to string theory on AdS_2 x S^2 are described. Unlike the higher-dimensional cases, in the simplest approach all finite-energy excitations of AdS_2 x S^2 are suppressed. Surviving zero-energy configurations are described. These can include tree-like structures in which the AdS_2 x S^2 throat b

M. Frank, V. I. Paulsen, T. R. Tiballi

We consider existence and uniqueness of symmetric approximation of frames by normalized tight frames and of symmetric orthogonalization of bases by orthonormal bases in Hilbert spaces H . More precisely, we determine whether a given frame or basis possesses a normalized tight frame or orthonormal basis that is quadratically closest to it, if there exists suc

M. Yu. Khlopov, A. S. Sakharov, D. D. Sokoloff

It is shown, that the energy density of coherent axion field oscillations in the cosmology of standard invisible axion should be distributed in the Universe in the form of archioles, being nonlinear inhomogeneous structure, reflecting the large scale distribution of Brownian structure of axion strings in the very early Universe. Spectrum of inhomogeneities,

Mustafa Korkmaz, Burak Ozbagci

There exists a (relatively minimal) genus g Lefschetz fibration with only one singular fiber over a closed (Riemann) surface of genus h iff g>2 and h>1. The singular fiber can be chosen to be reducible or irreducible. Other results are that every Dehn twist on a closed surface of genus at least three is a product of two commutators and no Dehn twist on any c

D. Belitz, T. R. Kirkpatrick

The physical consequences of the spin-triplet, even-parity pairing that has been predicted to exist in disordered two-dimensional electron systems are considered in detail. We show that the presence of an attractive interaction in the particle-particle spin-triplet channel leads to an instability of the normal metal that competes with the localizing effects

D. Bailin, G. V. Kraniotis, A. Love

The phenomenological implications of the eleven dimensional limit of $M$-theory (strongly coupled $E_8\times E_8$) are investigated. In particular we calculate the supersymmetric particle spectrum subject to constraints of correct electroweak symmetry breaking and the requirement that the lightest supersymmetric particle provides the dark matter of the unive

Barry F. Madore, Wendy L. Freedman, N. Silbermann, Paul Harding

Using the Hubble Space Telescope (HST) 37 long-period Cepheid variables have been discovered in the Fornax Cluster spiral galaxy NGC 1365. The resulting V and I period-luminosity relations yield a true distance modulus of 31.35 +/- 0.07 mag, which corresponds to a distance of 18.6 +/- 0.6 Mpc. This measurement provides several routes for estimating the Hubbl

C. Jarlskog, M. Matsuda, S. Skadhauge, M. Tanimoto

We investigate neutrino masses and mixings within the framework of the Zee mass matrix, with three lepton flavors. It is shown that the bi-maximal solution is the only possibility to reconcile atmospheric and solar neutrino data, within this ansatz. We obtain two almost degenerate neutrinos, which are mixtures of all three neutrino flavors, with heavy masses

J. H. P. Wu, P. P. Avelino, E. P. S. Shellard, B. Allen

We describe the detailed study and results of high-resolution numerical simulations of string-induced structure formation in open universes and those with a non-zero cosmological constant. The effect from small loops generated from the string network has also been investigated. We provide a semi-analytical model which can reproduce these simulation results.

Wan Chen, Neil Gehrels

We show that (1) the newly discovered supernova remnant (SNR), GRO J0852--4642/RX J0852.0--4622, was created by a core-collapse supernova of a massive star, and (2) the same supernova event which produced the $^{44}$Ti detected by COMPTEL from this source is probably also responsible for a large fraction of the observed $^{26}$Al emission in the Vela region

N. S. Dzhalilov, V. B. Semikoz

It is shown that in the presence of a background magnetic field within solar interior a cavity for low frequency MHD eigen modes (with periods 1-10 days) near equatorial plane can arise. The lower boundary of the cavity coincides with the centre of the Sun while the upper one corresponds to the Alfven resonant layer where high accumulation of wave energy tak

V. M. Burlakov, M. Goeppert, A. Jolk, A. Dinger

We report on the IR spectroscopic studies in both reflection (50-900 cm^{-1}) and transmission (900-3000 cm^{-1}) mode of the vibration spectrum of the cuprous oxide. A detailed analysis based on a comparison of the temperature dependences of the absorption band at 1125 cm^{-1} and of IR and Raman active fundamental vibrations results in assignment of the fo

Winder A. Moura-Melo, N. Panza, J. A. Helayel-Neto

An Abelian gauge model, with vector and 2-form potential fields linked by a topological mass term that mixes the two Abelian factors, is shown to exhibit Dirac-like magnetic monopoles in the presence of a matter background. In addition, considering a "non-minimal coupling" between the fermions and the tensor field, we obtain a generalised quantisatio

Sandip K. Chakrabarti

Twenty five years have passed by since models of accretions and jets have separately emerged. Today, it is understood that these two objects are related to each other in a fundamental way. In a binary system, matter from an accretion disk enters into a black hole. A part of it is bounced back because of the centrifugal barrier, radiation pressure or magnetoh

S. Flach, Y. Zolotaryuk, K. Kladko

We develop a general mapping from given kink or pulse shaped travelling-wave solutions including their velocity to the equations of motion on one-dimensional lattices which support these solutions. We apply this mapping - by definition an inverse method - to acoustic solitons in chains with nonlinear intersite interactions, to nonlinear Klein-Gordon chains,

F. Hoyle, C. M. Baugh, T. Shanks, A. Ratcliffe

We present the power spectrum analysis of clustering in the Durham/UKST Galaxy Redshift Survey, which covers 1450 square degrees and consists of 2501 galaxy redshifts sampled at a rate of 1 in 3 to b_J = 17. The fluctuations that we measure can be expressed as sigma_{8} = 1.01 +/- 0.17 . We find remarkably good agreement between the power spectrum measured f

Byung-Jay Kahng

In our earlier work, we constructed a specific non-compact quantum group whose quantum group structures have been constructed on a certain twisted group C*-algebra. In a sense, it may be considered as a ``quantum Heisenberg group C*-algebra''. In this paper, we will find, up to equivalence, all of its irreducible *-representations. We will point out

Perez Moses, Ross H. McKenzie

The interlayer magnetoresistance of layered metals in a tilted magnetic field is calculated for two distinct models for the interlayer transport. The first model involves coherent interlayer transport and makes use of results of semi-classical or Bloch-Boltzmann transport theory. The second model involves weakly incoherent interlayer transport where the elec

Estelle L. Basor, Harold Widom

The purpose of this paper is to describe asymptotic formulas for determinants of certain operators that are analogues of Wiener-Hopf operators. The determinant formulas yield information about the distribution functions for certain random variables that arise in random matrix theory when one rescales at the edge of the spectrum.

K. Agashe, N. G. Deshpande

We suggest a new technique to determine the CKM phase $γ$ {\em without} neglecting the (soft) final state rescattering effects. We use (time integrated) $B$ meson decay rates to $π$'s and $K$'s. A set of 5 $ΔS = 0$ (or 1 $ΔS =0$ and 4 $ΔS= 1$) decay rates is used to compute the strong phases and magnitudes of the tree level and penguin contributions

G. J. Milburn, S. L. Braunstein

We show how the partial entanglement inherent in a two mode squeezed vacuum state admits two different teleportation protocols. These two protocols refer to the different kinds of joint measurements that may be made by the sender. One protocol is the recently implemented quadrature phase approach of Braunstein and Kimble[Phys. Rev. Lett.{\bf 80}, 869 (1998)]

Subhash Kak

The note presents a formula for the prediction of the rotation periods of the planets and asteroids. This formula, which is like the Titius-Bode law, gives a good agreement with the rotation periods of most planets, shows that Venus is retrograde, and that there must be five objects between Mars and Jupiter. This formula may be of some relevance in understan

Gerd van de Sand, Jan M. Rost

A unified semiclassical time propagator is used to calculate the semiclassical time-correlation function in three cartesian dimensions for a particle moving in an attractive Coulomb potential. It is demonstrated that under these conditions the singularity of the potential does not cause any difficulties and the Coulomb interaction can be treated as any other

M. C. M. Rentmeester, R. A. M. Klomp, J. J. de Swart

In this updated and expanded version of our delayed Comment we show that the np backward cross section, as presented by the Uppsala group, is seriously flawed (more than 25 sd.). The main reason is the incorrect normalization of the data. We show also that their extrapolation method, used to determine the charged piNN coupling constant, is a factor of about

V. E. Markushin

Recent theoretical and experimental studies of the exotic atoms with Z=1 are reviewed. An interplay between the atomic internal and external degrees of freedom is essential for a good description of the atomic cascade. The perspective of ab initio cascade calculations is outlined.

M. Baldo, U. Lombardo, E. Saperstein, M. Zverev

The $^1S_0$-pairing gap in semi-infinite nuclear matter is evaluated microscopically using the effective pairing interaction recently found explicitly in the coordinate representation starting from the separable form of the Paris NN-potential. Instead of direct iterative solution of the gap equation, a new method proposed by V.A.Khodel, V.V.Khodel and J.W.Cl

B. Krippa

The constraints imposed by chiral symmetry on hadron correlation functions in nuclear medium are discussed. It is shown that these constraints imply some structure of the in-medium hadron correlators, lead to the cancellation of the order $ρm_π$ term in the in-medium nucleon correlator and result in the effect of mixing of the chiral partners correlators, re

B. K. Nandi, G. C. Mishra, B. Mohanty, D. P. Mahapatra

Event shape analysis has been used to look for DCC signals in simulated ultra-relativistic heavy-ion collision data at SPS energy. A simple redistribution of particles, with two detectors to detect charged particles and photons, is seen to result in the same flow direction with the flow angle difference peaking at zero. However, events where the neutral pion

V. Avrigeanu, S. Sudár, Cs. M. Buczkó, J. Csikai

Excitation functions of the $^{58}$Ni$(n,p)^{58}$Co$^{m,g}$ reactions were measured in the energy range from 2 to 15 MeV. The energy dependence of the isomeric cross-section ratio R=sigma_m/(sigma_m+sigma_g) is deduced from the measured data. The shape and magnitude of the R(E_n) function are described by model calculations using a consistent parameter set.

Mihnea Popa

We present a new class of examples of base points for the generalized theta divisor on the moduli space of semistable vector bundles of trivial determinant on a compact Riemann surface and we prove that for sufficiently large rank the base locus is positive dimensional.

Charles Frohman, Razvan Gelca, Walter Lofaro

We develop an invariant of knots that depends on a complex parameter t, describing a left ideal in the noncommutative torus. When the parameter is set equal to -1 we recover the A-polynomial of the knot. We relate the invariant to the colored Jones polynomials of the knot.

P. Kurlberg

We study the distribution of spacings between squares modulo q as the number of prime divisors of q tends to infinity. In an earlier paper Kurlberg and Rudnick proved that the spacing distribution for square free q is Poissonian, this paper extends the result to arbitrary q.

Andreas Karch

I review certain aspects of Hanany-Witten setups and other approaches used to embed (and solve) gauge theories in string theory. Applications covered include dualities in 4 and 3 dimensions, fixed points in 6 dimensions, phase transitions between different geometric backgrounds and dualities between branes and geometry.

Jose F. Morales, Claudio A. Scrucca, Marco Serone

We study anomalous Wess-Zumino couplings of D-branes and O-planes in a general background and derive them from a direct string computation by factorizing in the RR channel various one-loop amplitudes. In particular, we find that Op-planes present gravitational anomalous couplings involving the Hirzebruch polynomial L, similarly to the roof genus A encoding D

V. Tretyak

Relativistic effects in the thermodynamical properties of interacting particle systems are investigated within the framework of the relativistic direct interaction theory in various forms of dynamics. In the front form of relativistic dynamics an exactly solvable model of a one-dimensional hard spheres gas is formulated and an equation of state and thermodyn

Christos kokorelis

The perturbative prepotential and the Kähler metric of the vector multiplets of the N=2 effective low-energy heterotic strings is calculated directly in N=1 six-dimensional toroidal compactifications of the heterotic string vacua. This method provides the solution for the one loop correction to the N=2 vector multiplet prepotential for compactifications of t

L. Andrianopoli, S. Ferrara

We analyze short and long multiplets which appear in the OPE expansion of ``chiral'' primary operators in N=4 Super Yang--Mills theory. Among them, higher spin long and new short multiplets appear, having the interpretation, in the AdS/CFT correspondence, of string states and supergravity multiparticle states respectively. We also analyze the decompo

G. Konisi, T. Saito, Z. Maki, M. Nakahara

The left-right symmetric model (LRSM) with gauge group $SU(2)_{L} \times SU(2)_{R} \times U(1)_{B-L}$ is reconstructed from the geometric formulation of gauge theory in $M_4 \times Z_2 \times Z_2$ where $M_4$ is the four-dimensional Minkowski space and $Z_2 \times Z_2$ the discrete space with four points. The geometrical structure of this model becomes clear

J. M. Speight

A spatially discrete version of the general kink-bearing nonlinear Klein-Gordon model in (1+1) dimensions is constructed which preserves the topological lower bound on kink energy. It is proved that, provided the lattice spacing h is sufficiently small, there exist static kink solutions attaining this lower bound centred anywhere relative to the spatial latt

Jaemo Park, Soo-Jong Rey

Green-Schwarz action of Type IIB string on $AdS_3 \times S^3$ is constructed via coset superspace approach. The construction relies exclusively on symplectically Majorana-Weyl spinor formalism, thus permitting it easier to prove $\kappa$-symmetry for on-shell Type IIB supergravity backgrounds.

D. T. Son

We argue that in quark matter at high densities, the color magnetic field remains unscreened and leads to the phenomenon of color superconductivity. Using the renormalization group near the Fermi surface, we find that the long-range nature of the magnetic interaction changes the asymptotic behavior of the gap $Δ$ at large chemical potential $μ$ qualitatively

Mary K. Gaillard, Paul D. Grannis, Frank J. Sciulli

Particle physics has evolved a coherent model that characterizes forces and particles at the most elementary level. This Standard Model, built from many theoretical and experimental studies, is in excellent accord with almost all current data. However, there are many hints that it is but an approximation to a yet more fundamental theory. We trace the develop

A. Widom, E. Sassaroli, Y. N. Srivastava

The physical interpretation of extensive measurements of electron neutrinos (in laboratories located on or somewhat below the Earth's surface) often require geophysical notions concerning the possible neutrino sources. Here, we discuss the notion that the Earth's core is a substantial source of low energy electron neutrinos.

Richard Nisius, Michael H. Seymour

In deep inelastic electron-photon scattering in leading order QED, egamma->egamma*gamma->effbar, there are four non-zero structure functions. We calculate them for real photons retaining the full dependence on the fermion mass, and show numerical results of its effect.

N. G. Stefanis, W. Schroers, H. -Ch. Kim

We develop and discuss an infrared-finite factorization and optimized renormalization scheme for calculating exclusive processes which enables the inclusion of transverse degrees of freedom without entailing suppression of calculated observables, like form factors. This is achieved by employing an analytic, i.e., infrared stable, effective coupling $α_{s}(Q^

Hitoshi Yamamoto

We review recent results on hadronic B meson decays including rare as well as non-suppressed decays. The main emphasis is on those channels relevant to measurement of CP violation in the coming B factories. After briefly describing flavor-tagged charm counting, we cover B -> DK(*), B -> charmless 2-body decays, inclusive eta' production, and final-state-

S. J. Brodsky, M. Diehl, P. Hoyer, S. Peigne

We define and study hard ``semi-exclusive'' processes of the form $A+B \to C + Y$ which are characterized by a large momentum transfer between the particles $A$ and $C$ and a large rapidity gap between the final state particle $C$ and the inclusive system $Y$. Such reactions are in effect generalizations of deep inelastic lepton scattering, providing

M. W. Krasny

The H1 collaboration has recently reported the observation of events with an isolated high energy lepton and missing transverse momentum. All analysed Standard Model processes were found to fail in explaining the origin of muon events leaving a statistical fluctuation as the only explanation of their appearance. In this paper I discuss mechanisms by which St

B. D. Jones, R. M. Woloshyn

Lattice NRQCD with leading finite lattice spacing errors removed is used to calculate decay constants of mesons made up of heavy quarks. Quenched simulations are done with a tadpole improved gauge action containing plaquette and six-link rectangular terms. The tadpole factor is estimated using the Landau link. For each of the three values of the coupling con

R. Kenna, C. Pinto, J. C. Sexton

The weak coupling expansion is applied to the single flavour Schwinger model with Wilson fermions on a symmetric toroidal lattice of finite extent. We develop a new analytic method which permits the expression of the partition function as a product of pure gauge expectation values whose zeroes are the Lee-Yang zeroes of the model. Application of standard fin

Kamiokande collaboration

A measurement of the energy spectrum of recoil electrons from solar neutrino scattering in the Super--Kamiokande detector is presented. The results shown here are obtained from 504 days of data taken between the 31st of May, 1996 and the 25th of March, 1998. The shape of the measured spectrum is compared with the expectation for solar B8 neutrinos. The compa

John H. Schwarz

In this talk I will survey some of the basic facts about superstring theories in 10 dimensions and the dualities that relate them to M theory in 11 dimensions. Then I will mention some important unresolved issues.

K. Srinivasan, T. Padmanabhan

This paper discusses particle production in Schwarzchild-like spacetimes and in an uniform electric field. Both problems are approached using the method of complex path analysis. Particle production in Schwarzchild-like spacetimes with a horizon is obtained here by a new and simple semi-classical method based on the method of complex paths. Hawking radiation

David Karger, Rajeev Motwani, Madhu Sudan

We consider the problem of coloring k-colorable graphs with the fewest possible colors. We present a randomized polynomial time algorithm that colors a 3-colorable graph on $n$ vertices with min O(Delta^{1/3} log^{1/2} Delta log n), O(n^{1/4} log^{1/2} n) colors where Delta is the maximum degree of any vertex. Besides giving the best known approximation rati

David R. Karger

We significantly improve known time bounds for solving the minimum cut problem on undirected graphs. We use a ``semi-duality'' between minimum cuts and maximum spanning tree packings combined with our previously developed random sampling techniques. We give a randomized algorithm that finds a minimum cut in an m-edge, n-vertex graph with high probabi

F. M. Grosche, P. Agarwal, S. R. Julian, N. J. Wilson

Ambient pressure studies on high purity single crystals of the stoichiometric 4f-electron metal CeNi2Ge2 reveal anomalous low temperature forms of the resistivity which challenge our understanding of the metallic state. Comparisons are made with the isostructural and isoelectronic compound CePd2Si2 near the border of magnetism at high pressure, and possible

Irena Knezevic, Zoran Radovic

The quasiparticle energy spectrum of an isolated vortex in a clean layered d-wave superconductor is calculated. The Bogoliubov--de Gennes equations are solved perturbatively, within the model of step-variation of the gap function, adjusting the Caroli, de Gennes and Matricon approach for low-lying excitations in cuprates. A large peak in the density of state

Irena Knezevic, Zoran Radovic

The quasiparticle excitation spectrum of isolated vortices in clean layered d-wave superconductors is calculated. A large peak in the density of states in the "pancake" vortex core is found, in an agreement with the recent experimental data for high-temperature superconductors.

Irena Knezevic, Zoran Radovic

The quasiparticle excitation spectrum of an isolated vortex in a clean layered d-wave superconductor is calculated, using both the Bogoliubov--de Gennes and the quasiclassical Eilenberger equations. Analytical solutions are obtained within the model of step-variation of the gap function, adjusting the Caroli, de Gennes and Matricon approach for low-lying exc

Randall D. Kamien

In the hexagonal columnar phase of chiral polymers a bias towards cholesteric twist competes with braiding along an average direction. When the chirality is strong, topological defects proliferate, leading to either a tilt grain boundary phase or a new ``moire state'' with twisted bond order. This moire phase can melt leading to a new phase: the chir

J. M. Carlson, John Doyle

We introduce highly optimized tolerance (HOT), a mechanism that connects evolving structure and power laws in interconnected systems. HOT systems arise, e.g., in biology and engineering, where design and evolution create complex systems sharing common features, including (1) high efficiency, performance, and robustness to designed-for uncertainties, (2) hype

M. Franz, Z. Tesanovic

We discuss the evolution of the local quasiparticle spectral density and the related tunneling conductance measurable by the scanning tunneling microscope, as a function of distance r and angle θfrom the vortex core in a d_{x^2-y^2} superconductor. We consider the effects of electronic disorder and of a strongly anisotropic tunneling matrix element, and show

Anatoli S. Polkovnikov, Georgy G. Zegrya

The principal mechanisms of Auger recombination of nonequilibrium carriers in semiconductor heterostructures with quantum wells are investigated. It is shown for the first time that there exist three fundamentally different Auger recombination mechanisms of (i) thresholdless, (ii) quasi-threshold, and (iii) threshold types. The rate of the thresholdless Auge

H. J. Luo, M. Schulz, L. Schuelke, S. Trimper

Using Monte Carlo methods, the short-time dynamic scaling behaviour of two-dimensional critical XY systems is investigated. Our results for the XY model show that there exists universal scaling behaviour already in the short-time regime, but the values of the dynamic exponent $z$ differ for different initial conditions. For the fully frustrated XY model, pow

Jeroen van den Brink, Peter Horsch, Frank Mack, Andrzej M. Oles

We consider a model of strongly correlated $e_g$ electrons interacting by superexchange orbital interactions in the ferromagnetic phase of LaMnO$_3$. It is found that the classical orbital order with alternating occupied $e_g$ orbitals has a full rotational symmetry at orbital degeneracy, and the excitation spectrum derived using the linear spin-wave theory

Thomas Gramespacher, Markus Buttiker

We use the scattering matrix approach to derive generalized Bardeen-like formulae for the conductances between the contacts of a phase-coherent multiprobe conductor and a tunneling tip which probes its surface. These conductances are proportional to local partial densities of states, called injectivities and emissivities. The current and the current fluctuat

D. H. E. Gross

Microcanonical statistics can be well applied to non-extensive systems like nuclei, atomic clusters and systems at phase transitions of first order with inhomogeneous configurations like phase separation. No thermodynamic limit has to be invoked. It allows to determine the transition temperature, latent heat and surface entropy. In the present paper this is

Christian von Ferber, Yurij Holovatch

We characterize the multifractal behavior of Brownian motion in the vicinity of an absorbing star polymer. We map the problem to an O(M)-symmetric phi^4-field theory relating higher moments of the Laplacian field of Brownian motion to corresponding composite operators. The resulting spectra of scaling dimensions of these operators display the convexity prope

L. Cannavacciuolo, A. de Candia, A. Coniglio

We investigate the crossover properties of the frustrated percolation model on a two-dimensional square lattice, with asymmetric distribution of ferromagnetic and antiferromagnetic interactions. We determine the critical exponents nu, gamma and beta of the percolation transition of the model, for various values of the density of antiferromagnetic interaction

F. Naef X. Wang, X. Zotos, W. von der Linden

Extending the transfer matrix DMRG algorithm, we are able to calculate imaginary time spin autocorrelations with high accuracy (absolute error $<10^{-6}$) over a wide temperature range ($0<βJ<20$). After analytic continuation using the rules of probability theory along with the entropic prior (MaxEnt), we obtain real frequency spectra for the XY model, the i

Weixue Li, Tzuchiang Wang

On the basis of the pseudopotential plane-wave(PP-PW) method and the local-density-functional theory(LDFT), this paper studies energetics, stress-strain relation, stability and ideal strength of $β$-SiC under various loading modes, where uniform uniaxial extension and tension, biaxial proportional extension are considered along directions [001] and [111]. Th

K. Rejmer, S. Dietrich, M. Napiorkowski

We study the formation and the shape of a liquid meniscus in a wedge with opening angle $2ϕ$ which is exposed to a vapor phase. By applying a suitable effective interface model, at liquid-vapor coexistence and at a temperature $T_ϕ$ we find a filling transition at which the height of the meniscus becomes macroscopically large while the planar walls of the we

E Schloesser, D Saad, M Biehl

Different techniques, used to optimise on-line principal component analysis, are investigated by methods of statistical mechanics. These include local and global optimisation of node-dependent learning-rates which are shown to be very efficient in speeding up the learning process. They are investigated further for gaining insight into the learning rates&#39;

A. M. Selvam, D. Sen, S. M. S. Mody

The circadian rhythm in the occurrence of acute myocardial infarction (AMI) was assessed in three hundred and twenty three patients admitted with AMI during the two-year period June 1992 to May 1994. The influence of the following meteorological, solar-geophysical and cosmic parameters in the causation of an infarct was also considered : (1) surface pressure

Peter Englmaier, Ortwin E. Gerhard

We report simulations of the gas flow in the gravitational potential of the COBE NIR bulge and disk. These models lead to four--armed spiral structure between corotation of the bar and the Sun, in agreement with the observed spiral arm tangents. The 3-kpc-arm is identified with one of the arms emanating from the ends of the bar.

A. D. Gray, T. L. Landecker, P. E. Dewdney, A. R. Taylor

We have used polarimetric imaging to study the magneto-ionic medium of the Galaxy, obtaining 1420 MHz images with an angular resolution of 1&#39; over more than 40 square-degrees of sky around the W3/W4/W5/HB3 HII region/SNR complex in the Perseus Arm. Features detected in polarization angle are imposed on the linearly polarized Galactic synchrotron backgrou

I. A. Smith, E. P. Liang, D. Lin, M. Bottcher

GX 339-4 is an unusual black hole candidate in that it is a persistent source, being detected by X-ray telescopes most of the time, but it also has nova-like flaring states. In 1996 we performed radio, optical, X-ray, and gamma-ray observations of GX 339-4 when it was in a hard state (= soft X-ray low state). Here we present a brief summary of some of the re

I. A. Smith, A. V. Filippenko, D. C. Leonard

As part of our multiwavelength campaign of observations of GX 339-4 in 1996 we present our Keck spectroscopy performed on May 12 UT. At this time, neither the ASM on the RXTE nor BATSE on the CGRO detected the source. The optical emission was still dominated by the accretion disk with V approximately 17 mag. The dominant emission line is H alpha, and for the

I. A. Smith, E. P. Liang

As part of our multiwavelength campaign of GX 339-4 observations in 1996 we present the rapid X-ray variability observed July 26 using the RXTE when the source was in a hard state (= soft X-ray low state). We found that the source was extremely variable, with many bright flares. The flares have relatively symmetric time profiles. There are a few time interva

I. A. Smith, E. P. Liang, D. Lin, M. Moss

As part of our multiwavelength campaign of GX 339-4 observations in 1996 we present our radio, X-ray, and gamma-ray observations made in July, when the source was in a hard state (= soft X-ray low state). The radio observations were made at the time when there was a possible radio jet. We show that the radio spectrum was flat and significantly variable, and

J. B. Hutchings, D. Crampton, S. L. Morris, D. Durand

We have observed nine QSOs with redshifts 0.85 to 4.16 at near-IR wavelengths with the adaptive optics bonnette of the Canada-France-Hawaii telescope. Exposure times ranged from 1500 to 24000s (mostly near 7000s) in J, H, or K bands, with pixels 0.035 arcsec on the sky. The FWHM of the co-added images at the location of the quasars are typically 0.16 arcsec.

G. Fossati

We propose a new physical model for the unification of all Blazars. The blazar phenomenology can be accounted for by a sequence in the source power and intensity of the diffuse radiation field surrounding the relativistic jet. This regulates the equilibrium electron distribution and hence the shape of the spectral energy distribution (SED), and in turn the c

C. Terquem, J. Eisloffel, J. Papaloizou, R. Nelson

We consider several protostellar systems where either a precessing jet or at least two misaligned jets have been observed. We assume that the precession of jets is caused by tidal interactions in noncoplanar binary systems. For Cep E, V1331 Cyg and RNO 15-FIR the inferred orbital separations and disk radii are in the range 4-160 AU and 1-80 AU, respectively,

R. S. Miller, S. Westerhoff

The next generation all-sky monitor operating at TeV (0.1 - 30 TeV) energies should be capable of performing a continuous high sensitivity sky survey, and detecting transient sources, such as AGN flares, with high statistical significance on timescales of hours to days. We describe an instrument concept for a large area, wide aperture, TeV ground-based Gamma

Derck Massa, Edward L. Fitzpatrick

While the low dispersion IUE NEWSIPS data products represent a significant improvement over original IUE SIPS data, they still contain serious systematic effects which compromise their utility for certain applications. We show that NEWSIPS low resolution data are internally consistent to only 10-15% at best, with the majority of the problem due to time depen

Tom Abel, Michael L. Norman, Piero Madau

Many questions in physical cosmology regarding the thermal and ionization history of the intergalactic medium are now successfully studied with the help of cosmological hydrodynamical simulations. Here we present a numerical method that solves the radiative transfer around point sources within a three dimensional cartesian grid. The method is energy conservi

R. P. Fender, S. T. Garrington, D. J. McKay, T. W. B. Muxlow

We present high resolution MERLIN radio images of multiple relativistic ejections from GRS 1915+105 in 1997 October / November. The observations were made at a time of complex radio behaviour, corresponding to multiple optically-thin outbursts and several days of rapid radio flux oscillations. The radio imaging resolved four major ejection events from the sy

M. J. Hardcastle, D. M. Worrall, M. Birkinshaw

Models that seek to unify BL Lacs and low-power radio galaxies predict that the two types of object should show similar isotropically emitted X-ray emission. Testing this is usually limited by difficulties in separating strong X-ray emission from a BL Lac nucleus and surrounding low-surface brightness emission. In this paper we report ROSAT HRI observations

S. Moehler

Blue horizontal branch and UV bright stars in several globular clusters are analysed spectroscopically and the results are compared with predictions of stellar evolutionary theory. We find that the distribution of temperatures and surface gravities of the blue HB stars may be explained by the effects of deep mixing. The masses derived for these stars are too

S. Tremaine

Partially phase-mixed structures in galaxies occupy a complex surface of dimension D in six-dimensional phase space. The appearance of such structures to observers is determined by their projection into a subspace whose dimensionality K is determined by the number of observables (e.g. sky position, distance, radial velocity, etc.). We discuss the expected di

S. Tremaine, J. P. Ostriker

Why do galactic bars rotate with high pattern speeds, when dynamical friction should rapidly couple the bar to the massive, slowly rotating dark halo? This longstanding paradox may be resolved by considering the dynamical interactions between the galactic disk and structures in the dark halo. Dynamical friction between small-scale halo structure and the disk

Halton Arp

Observations increasingly demonstrate the spatial association of high redshift objects with larger, low redshift galaxies. These companion objects show a continuous range of physical properties - from very compact, high redshift quasars, through smaller active galaxies and finally to only slightly smaller companion galaxies of slightly higher redshift. The s

P. Kahabka, W. Pietsch, M. D. Filipovic, F. Haberl

We present the results of a systematic search for point-like and moderately extended soft (0.1-2.4 keV) X-ray sources in a raster of nine pointings covering a field of 8.95 deg^2 and performed with the ROSAT PSPC between October 1991 and October 1993 in the direction of the Small Magellanic Cloud. We detect 248 objects which we include in the first version o