May 1999 arXiv papers — page 20

Philippe Brax, Jerome Martin

In the context of quintessence, the concept of tracking solutions allows to address the fine-tuning and coincidence problems. When the field is on tracks today, one has $Q\approx m_{\rm Pl}$ demonstrating that, generically, any realistic model of quintessence must be based on supergravity. We construct the most simple model for which the scalar potential is

Francisco J. Plaza Martín

This paper was withdrawn by the authors.

S. Pedersen, C. B. Sorensen, A. Kristensen, P. E. Lindelof

We have for the first time experimentally investigated the weak localisation magnetoresistance in a AlGaAs/GaAs p-type quantum well. The peculiarity of such systems is that spin-orbit interaction is strong. On the theoretical side it is not possible to treat the spin-orbit interaction as a perturbation. This is in contrast to all prior investigations of weak

A. I. Karanikas, C. N. Ktorides

The worldline casting of a gauge field system with spin-1/2 matter fields has provided a, particle-based, first quantization formalism in the framework of which the Bern-Kosower algorithms for efficient computations in QCD acquire a simple interpretation. This paper extends the scope of applicability of the worldline scheme so as to include open fermionic pa

Toru Tanimori, Yuji Nishi, Atsuhiko Ochi, Yasuro Nishi

The development of gaseous detectors has been exciting again since the appearance of a MicroStrip Gas Chamber(MSGC) in 1988, which is made using a micro-electronics technology. These days lots of variations of the advanced gaseous detectors are being intensively studied in the world. We have developed the two-dimensional MSGC having a 10 cm square detection

Frantisek Slanina

We analyze the theory of optimal investment in risky assets, developed recently by Marsili, Maslov and Zhang [Physica A 253 (1998) 403]. When the real data are used instead of abstract stochastic process, it appears that a non-trivial investment strategy is rarely possible. We show that non-zero transaction costs make the applicability of the method even mor

Mark D. Gould, Yao-Zhong Zhang

The minimal irreducible representations of $U_q[gl(m|n)]$, i.e. those irreducible representations that are also irreducible under $U_q[osp(m|n)]$ are investigated and shown to be affinizable to give irreducible representations of the twisted quantum affine superalgebra $U_q[gl(m|n)^{(2)}]$. The $U_q[osp(m|n)]$ invariant R-matrices corresponding to the tensor

B. G. Sidharth

Recently the anomalous behaviour of Fermions below the Fermi temperature was analysed in detail from different viewpoints. In the present communication we obtain a justification for this anomalous semionic behaviour and also obtain the Cooper pair type scenario of superconductivity from an alternative standpoint. Finally an earlier result in one dimension th

Burkhard D. Burow

During its execution, a task is independent of all other tasks. For an application which executes in terms of tasks, the application definition can be free of the details of the execution. Many projects have demonstrated that a task system (TS) can provide such an application with a parallel, distributed, heterogeneous, adaptive, dynamic, real-time, interact

Ranjan Mukhopadhyay, Anand Yethiraj, John Bechhoefer

We study theoretically the effect of an external field on the nematic-smectic-A (NA) transition close to the tricritical point, where fluctuation effects govern the qualitative behavior of the transition. An external field suppresses nematic director fluctuations, by making them massive. For a fluctuation-driven first-order transition, we show that an extern

R. Narayanan, Thomas Vojta, D. Belitz, T. R. Kirkpatrick

The effects of quenched disorder on the critical properties of itinerant quantum antiferromagnets and ferromagnets are considered. Particular attention is paid to locally ordered spatial regions that are formed in the presence of quenched disorder even when the bulk system is still in the paramagnetic phase. These rare regions or local moments are reflected

Andrey V. Novikov-Borodin

The quantum mechanics description of a physical object stretched in space and stable in time from the relativistic space-time properties point of view, introduced in special theory of relativity, is considered and analysed. The mathematical model of physical objects is proposed. This model gives a possibility to unite a description of corpuscular and wave pr

N. Gurappa, Prasanta K. Panigrahi, T. Soloman Raju

A procedure for constructing bound state potentials is given. We show that, under the natural conditions imposed on a radial eigenvalue problem, the only special cases of the general central potential, which are exactly solvable and have infinite number of energy eigenvalues, are the Coulomb and harmonic oscillator potentials.

V. Sunilkumar, B. A. Bambah, P. K. Panigrahi, V. Srinivasan

We provide a unified approach for finding the coherent states of various deformed algebras, including quadratic, Higgs and q-deformed algebras, which are relevant for many physical problems. For the non-compact cases, coherent states, which are the eigenstates of the respective annihilation operators, are constructed by finding the canonical conjugates of th

Lars Petter Endresen, Nils Skarland

In recent decades, several mathematical models describing the pacemaker activity of the rabbit sinoatrial node have been developed. We demonstrate that it is not possible to establish the existence, uniqueness, and stability of a limit cycle oscillation in those models. Instead we observe an infinite number of limit cycles. We then display numerical results

Charles A. Weatherford

In the present work, a new time-dependent exchange theory is presented wherein the symmetry constraints, on a multi-electron wavefunction, are properly accounted for. In so doing, the equations of motion, incorporating the required symmetry, are derived and a solution algorithm employing an implicit split-operator procedure is described. A technique (using a

V. B. Soubbotin, X. Vinas

The one-particle exchange in the double folded model is analyzed. To this aim the Extended Thomas-Fermi approach to the one-body density matrix is used. The nucleon- nucleon force with Yukawa, Gauss and Coulomb-type form factors are considered. The energy dependence of the exchange part of the double folded potential is investigated and a comparison of the p

A. M. Green, S. Wycech

The coupled pi+N, eta+N, gamma+N systems are described by a K-matrix method. The parameters in this model are adjusted to get an optimal fit to pi+N -> pi+N, pi+N -> eta+N, gamma+N -> pi+N and gamma+N -> eta+N data in an energy range of about 100 MeV each side of the eta-threshold. The coupling of photons to the N(1535) state is extracted and also an alterna

Volker E. Oberacker, A. Sait Umar

Our goal is to carry out high-precision nuclear structure calculations in connection with Radioactive Ion Beam Facilities. The main challenge for the theory of drip line nuclei is that the outermost nucleons are weakly bound (implying a large spatial distribution) and that these states are strongly coupled to the particle continuum. For these reasons, the tr

Daqing Wan

This expository paper is based on the author's series of lectures delivered at the January 1999 Mini-course in Number Theory, held at Sogang University (Seoul). The aim is to give an elementary and self-contained introduction to the theory of Newton polygons (namely, the $p$-adic Riemann hypothesis) for L-functions of exponential sums over a finite field

H. -O. Georgii, O. Häggström, C. Maes

This is a (long) survey about applications of percolation theory in equilibrium statistical mechanics. The chapters are as follows: 1. Introduction 2. Equilibrium phases 3. Some models 4. Coupling and stochastic domination 5. Percolation 6. Random-cluster representations 7. Uniqueness and exponential mixing from non-percolation 8. Phase transition and percol

Chiteng'a John Chikunji

In [1], finite associative rings wih identity and such that the set of all zero-divisors form and ideal M, called the Jacobson Radical, of cube zero and square non-zero, were constructed for all the characteristics. These rings are completely primary and we call them rings with property(T). In this paper, we associate with each ring with property(T) and char

Wladyslaw Marcinek

The concept of exchange braid statistics is generalized. The cross statistics is studied as a result of interaction. An algebraic model of a system of particles equipped with such statistics is described. The corresponding Fock space representation is also given.

A. Panov

We classify Manin triples of the type $(g(R),W,g(R)\oplus g(R))$ up to weak and gauge equivalence.

Gabriella Böhm

The theory of Doi-Hopf modules is generalized to Weak Hopf algebras.

Jan Dymara, Tadeusz Januszkiewicz

The group of simplicial automorphisms of a Tits-Kac-Moody ininite building of thickness q associated to a cocompact reflexion group with fundamental domain a simplex, is Kazhdan for q sufficiently large. Thus we obtain families of new Kazhdan groups: two in dimension 3 and one in dimension 4. The proof uses continuos cohomology, in particular a lemma of Bore

J. Merker

In this note, our purpose is to establish shortly the algebraicity of a holomorphic mapping between real algebraic CR manifolds under a double reflection condition which generalizes the classical single reflection. A complete study of various double reflection conditions is also provided.

Robert Ghrist

Configuration spaces of distinct labeled points on the plane are of practical relevance in designing safe control schemes for Automated Guided Vehicles (robots) in industrial settings. In this announcement, we consider the problem of the construction and classification of configuration spaces for graphs. Topological data associated to these spaces (eg, dimen

Anton Bovier, Veronique Gayrard

We prove a large deviation principle on path space for a class of discrete time Markov processes whose state space is the intersection of a regular domain $Ł\subset \R^d$ with some lattice of spacing $\e$. Transitions from $x$ to $y$ are allowed if $\e^{-1}(x-y)\in \D$ for some fixed set of vectors $\D$. The transition probabilities $p_\e(t,x,y)$, which them

R. D. M. De Paola, R. B. Rodrigues, N. F. Svaiter

The zero-point energy of a massless fermion field in the interior of two parallel plates in a D-dimensional space-time at zero temperature is calculated. In order to regularize the model, a mix between dimensional and zeta-function regularization procedure is used and it is found that the regularized zero-point energy density is finite for any number of spac

L. Birke, J. Fuchs, C. Schweigert

Symmetry breaking boundary conditions for WZW theories are discussed. We derive explicit formulae for the reflection coefficients in the presence of boundary conditions that preserve only an orbifold subalgebra with respect to an involutive automorphism of the chiral algebra. The characters and modular transformations of the corresponding orbifold theories a

Paul S. Aspinwall, M. Ronen Plesser

We show that T-duality can be broken by nonperturbative effects in string coupling. The T-duality in question is that of the 2-torus when the heterotic string is compactified on K3 x T2. This case is compared carefully to a situation where T-duality appears to work. A holonomy argument is presented to show that T-dualities (and general U-dualities) should on

L. Accardi, I. Ya. Aref'eva, I. V. Volovich

Non-equilibrium quantum field theory studies time dependence of processes which are not available for the S-matrix description. One of the new methods of investigation in non-equilibrium quantum theory is the stochastic limit method. This method is an extension of the works by Bogoliubov, van Hove and Prigogine and it permits to study not only the system but

Ion V. Vancea

We study the relation between the D8-branes wrapped on an orientable compact manifold $W$ in a massive Type IIA supergravity background and the M9-branes wrapped on a compact manifold $Z$ in a massive d=11 supergravity background from the K-theoretic point of view. By speculating on the use of the dimensional reduction to relate the two theories in different

Jan de Boer, Samson L. Shatashvili

Various exact two-dimensional conformal field theories with AdS_{2d+1} target space are constructed. These models can be solved using bosonization techniques. Some examples are presented that can be used in building perturbative superstring theories with AdS backgrounds, including AdS_5.

Brandon Carter, Patrick Peter

The effect of fermionic string conductivity by purely right (or purely left) moving ``zero modes'' is shown to be governed by a simple Lagrangian characterising a certain ``chiral'' (null current carrying) string model whose dynamical equations of motion turn out to be explicitly integrable in a flat spacetime background.

Patrick B. Greene

Coherent oscillations of the inflaton field at the end of inflation can parametrically excite fermions in much the same way that bosons are created in preheating. Although Pauli-blocking prohibits the occupation number of created fermions from growing exponentially, fermion production occurs in a manner significantly different from the expectations of simple

W. M. Alberico, S. M. Bilenky

A review of the problem of neutrino mass, mixing and oscillations is given. Possible phenomenological schemes of neutrino mixing are discussed. The most important consequences of neutrino mixing--neutrino oscillations are considered in some details. The data of atmospheric, solar and LSND experiments are discussed. The results of phenomenological analyses of

D. Ebert, K. G. Klimenko, M. A. Vdovichenko, A. S. Vshivtsev

The phase structures of Nambu-Jona-Lasinio models with one or two flavours have been investigated at non-zero values of $μ$ and $H$, where $H$ is an external magnetic field and $μ$ is the chemical potential. In the phase portraits of both models there arise infinitely many massless chirally symmetric phases, as well as massive ones with spontaneously broken

Dubravko Klabucar, Dalibor Kekez

We review the pion-photon transition form factor calculated in the Schwinger-Dyson approach and an impulse approximation. We present results for it far above the scales presently accessible for measurement, up to 36 GeV^2, and demonstrate agreement with the analytically inferred asymptotic behavior, for which we also provide a new derivation. We discuss how

Peter Minkowski, Wolfgang Ochs

The evidence for the low mass J^{PC}=0^{++} states is reconsidered. We suggest classifying the isoscalars f_0(980) and f_0(1500) as members of the 0^{++} nonet, with a mixing rather similar to that of the pseudoscalars η' and η. The broad state called f_0(400-1200) or `sigma'' and the state f_0(1370) are considered as different signals from a sin

L. A. Anchordoqui, M. T. Dova, S. J. Sciutto

An analysis of the differences introduced by the hadronic interaction event generators during the development of the showers is presented. We have generated proton and nuclei induced air showers with energies up to $10^{20.5}$ eV, ``herded up'' by the code aires + sibyll/ qgsjet. The most relevant observables are taken into account for the comparison

Reinhard Stock

Hadronic yields and yield ratios observed in Pb+Pb collisions at the SPS energy of 158 GeV per nucleon are known to resemble a thermal equilibrium population at T=180 +/- 10 MeV, also observed in elementary e+ + e- to hadron data at LEP. We argue that this is the universal consequence of the QCD parton to hadron phase transition populating the maximum entrop

S. M. Bilenky, C. Giunti

The notion of sterile neutrinos is discussed. The schemes of mixing of four massive neutrinos, which imply the existence of sterile neutrinos, are briefly considered. Several model independent methods that allow to reveal possible transitions of solar neutrinos into sterile states are presented.

D. Dutta, K. Kumar, A. K. Mohanty, R. K. Choudhury

The chemical equilibration of a highly unsaturated quark-gluon plasma has been studied at finite baryon density. It is found that in the presence of small amount of baryon density, the chemical equilibration for gluon becomes slower and the temperature decreases less steeply as compared to the baryon free plasma. As a result, the space time integrated yield

CPLEAR Collaboration, M. P. Locher, V. E. Markushin

We apply a forward dispersion relation to the regeneration amplitude for kaon scattering on 12C using all available data. The CPLEAR data at low energies allow the determination of the net contribution from the subthreshold region which turns out to be much smaller than earlier evaluations, solving a long standing puzzle.

Jemal Guven, Niall O' Murchadha

We examine the solution of the constraints in spherically symmetric general relativity when spacetime has a flat spatial hypersurface. We demonstrate explicitly that given one flat slice, a foliation by flat slices can be consistently evolved. We show that when the sources are finite these slices do not admit singularities and we provide an explicit bound on

Tonatiuh Matos, Guillermo Arreaga, Gabriela Piccinelli

Beginning from an effective theory in eight dimensions, Macias, Camacho and Matos proposed an effective model for the electroweak part of the Standard Model of particles in curved spacetime. Using this model, we investigate the cosmological consequences of the electroweak interaction in the early universe. We use the approximation that, near the Planck epoch

Damian H. Zanette

It is shown that Tsallis' generalized statistics provides a natural frame for the statistical-thermodynamical description of anomalous diffusion. Within this generalized theory, a maximum-entropy formalism makes it possible to derive a mathematical formulation for the mechanisms that underly Levy-like superdiffusion, and for solving the nonlinear Fokker-

T. Dasgupta, Durga P. Choudhury, S. Sridhar

The nonlinear surface impedance of a thin superconducting strip carrying a microwave current has been calculated numerically from first principles based upon flux penetration due to a current-induced critical state. The calculations approach analytic results in the appropriate limit. The technique is useful for design of passive superconducting microwave cir

Y. Alhassid

We derive closed expressions for the universal weak localization peak of the average conductance peak heights in Coulomb blockade quantum dots in the crossover from orthogonal to unitary symmetry. The scale for the crossover is independent of the number of channels in each lead, in contrast with the case of open dots. The functional form of the weak localiza

David McNamara, A. Alan Middleton, Chen Zeng

We have performed numerical simulation of a 3-dimensional elastic medium, with scalar displacements, subject to quenched disorder. We applied an efficient combinatorial optimization algorithm to generate exact ground states for an interface representation. Our results indicate that this Bragg glass is characterized by power law divergences in the structure f

L. Frachebourg, Ph. A. Martin

The one dimensional Burgers equation in the inviscid limit with white noise initial condition is revisited. The one- and two-point distributions of the Burgers field as well as the related distributions of shocks are obtained in closed analytical forms. In particular, the large distance behavior of spatial correlations of the field is determined. Since highe

M. Letz, A. Latz

An important aspect of molecular fluids is the relation between orientation and translation parts of the two-particle correlations. Especially the detailed knowledge of the influence of orientation correlations is needed to explain and calculate in detail the occurrence of a nematic phase. The simplest model system which shows both orientation and translatio

H. Kino, H. Kontani

We study the electronic states of quasi-one-dimensional organic conductors using the single band Hubbard model at half-filling. We treat the effects of the on-site Coulomb interaction by the fluctuation-exchange (FLEX) method, and calculate the phase diagram and physical properties. The calculated pressure dependence of the Neel temperature coincides well wi

B. Mottelson

The low energy quantal spectrum is considered as a function of the total angular momentum for a system of weakly interacting bosonic atoms held together by an external isotropic harmonic potential. It is found that besides the usual condensation into the lowest state of the oscillator, the system exhibits two additional kinds of condensate and associated the

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

We obtain an analytical solution of a one-dimensional sandpile problem in a thick flow regime, when it can be formulated in terms of linear equations. It is shown that a space periodicity takes place during the sandpile evolution even for a sandpile of only one type of particles. Similar periodicity was observed previo usly for many component sandpiles. Spac

A. A. Kordyuk, V. V. Nemoshkalenko, A. I. Plyushchay, R. V. Viznichenko

We have developed a set of experimental techniques with levitation to investigate the macroscopic magnetic properties of bulk HTS: (i) resonance oscillation technique; (ii) high speed magnetic rotor technique; (iii) the method of viscous motion of a permanent magnet through a HTS aperture under a steady force. Early, we used these techniques to investigate t

Sumathi Rao

We give a brief introduction to Luttinger liquids and to the phenomena of electronic transport or conductance in quantum wires. We explain why the subject of transport in Luttinger liquids is relevant and fascinating and review some important results on tunneling through barriers in a one-dimensional quantum wire and the phenomena of persistent currents in m

Yuri S. Kivshar, Tristram J. Alexander

We analyse systematically, from the viewpoint of the nonlinear physics of solitary waves, the effect of the spatial dimension (D = 1,2,3) on the structure and stability of the Bose-Einstein condensates (BECs) trapped in an external anisotropic parabolic potential. While for the positive scattering length the stationary ground-state solutions of the Gross-Pit

Jacek Dziarmaga

Time-dependent Ginzburg-Landau model with noise for neutral s-wave superconductor is derived from real-time finite-temperature quantum field theory by integrating over fermions in the density matrix propagator. Quantum decoherence due to environment of pair breaking fluctuations is identified. Dynamics is described by Langevin equation in the near critical r

Bruce M. Boghosian

We review the class of cellular automata known as lattice gases, and their applications to problems in physics and materials science. The presentation is self-contained, and assumes very little prior knowledge of the subject. Hydrodynamic lattice gases are emphasized, and non-lattice-gas cellular automata -- even those with physical applications -- are not t

Mark Nelkin, Shiyi Chen

The mean square particle acceleration in high Reynolds number turbulence is dominated by the mean square pressure gradient. Recent experiments by Voth et al [Phys. Fluids {\bf 10}, 2268 (1998)] indicate that this quantity, when normalized by the 1941 Kolmogorov value, $ε^{3/2}ν^{-1/2}$, is independent of Reynolds number at high Reynolds number. This is to be

B. Eckhardt, U. Dörr, U. Kuhl, H. -J. Stöckmann

We consider the fluctuations of electromagnetic fields in chaotic microwave cavities. We calculate the transversal and longitudinal correlation function based on a random wave assumption and compare the predictions with measurements on two- and three-dimensional microwave cavities.

C. Gallart, D. Martinez-Delgado, A. Aparicio, W. L. Freedman

We present observations of the new Local Group galaxy candidates Cassiopeia dSph, Pegasus dSph=AndVI and Camelopardalis A. Our deep color-magnitude diagrams show that the first two galaxies are certainly Local group members, and likely dSph galaxies at a distance similar to that of the Andromeda galaxy. Cam A seems to be a star forming galaxy considerably fu

Neal J. Evans

The physical conditions in molecular clouds control the nature and rate of star formation, with consequences for planet formation and galaxy evolution. The focus of this review is on the conditions that characterize regions of star formation in our Galaxy. A review of the tools and tracers for probing physical conditions includes summaries of generally appli

A. V. Filippenko, A. G. Riess

We review the use of Type Ia supernovae for cosmological distance determinations. Low-redshift SNe Ia (z < 0.1) demonstrate that (a) the Hubble expansion is linear, (b) H_0 = 65 +/- 2 (statistical) km/s/Mpc, (c) the bulk motion of the Local Group is consistent with the COBE result, and (d) the properties of dust in other galaxies are similar to those of dust

Gastao B. Lima Neto, Daniel Gerbal, Isabel Marquez

Dynamical systems in equilibrium have a stationary entropy; we suggest that elliptical galaxies, as stellar systems in a stage of quasi-equilibrium, may have a unique specific entropy. This uniqueness, a priori unknown, should be reflected in correlations between the parameters describing the mass (light) distribution in galaxies. Following recent photometri

Inma Dominguez, Peter Hoeflich, Oscar Straniero, Craig Wheeler

Due to their high luminosity at maximum and degree of homogeneity, Type Ia supernovae have been extensively used for cosmological purpouses, in particular to estimate extragalactic distances and the Hubble constant. Recently the number of Type Ia supernovae detected at high redshift has increased, opening the possibility of determining the mass density param

C. Marinoni, G. Giuricin, B. Costantini, P. Monaco

In order to map the galaxy density field on small scales in the local universe, we use the Nearby Optical Galaxy (NOG) sample, which is currently one of the largest, nearly complete, magnitude-limited ($B\leq$ 14 mag), all-sky sample of nearby optical galaxies ($\sim$ 6400 galaxies with cz< 5500 km/s). We have corrected the redshift-dependent distances of th

Vladimir V. Vassiliev

VERITAS is a new major ground-based gamma-ray observatory with an array of seven 10 m optical reflectors to be built at the Whipple Observatory in southern Arizona, USA. It will consist of an array of imaging Cherenkov telescopes designed to conduct critical measurements of AGNs and SNRs in the energy range of 50 GeV - 50 TeV. The design of the array has bee

S. T. Myers, D. Rusin, C. D. Fassnacht, R. D. Blandford

The third phase of the Cosmic Lens All-Sky Survey (CLASS) has recently been completed, bringing the total number of sources imaged to over 15000 in the CLASS and JVAS combined survey. In the VLA observations carried out in March and April of 1998, two new candidate lensed systems were discovered: CLASS B1152+199 and B1359+154. B1152+199 is a 1.6 arcsecond do

A. B. Kaye, G. Handler, K. Krisciunas, E. Poretti

In this paper we describe a new class of pulsating stars, the prototype of which is the bright, early, F-type dwarf, Gamma Doradus. These stars typically have between 1 and 5 periods ranging from 0.4 to 3 days with photometric amplitudes up to 0.1 in Johnson V. The mechanism for these observed variations is high-order, low-degree, non-radial, gravity-mode pu

A. J. Turnbull, T. J. Bridges, D. Carter

We present photometric observations of two shell galaxies, NGC 474 and NGC 7600. We examine the photometric colours and surface brightnesses of the shells and their host galaxies, and the isophotal parameters of each galaxy. In the case of NGC 474, we find that the shell formation is consistent with a merger origin although it is possible that the close comp

I. G. Mitrofanov, D. S. Anfimov, M. L. Litvak, M. S. Briggs

Average cosmological invariant parameters (ACIPs) are calculated for six groups of BATSE cosmic gamma-ray bursts selected by their peak fluxes on the 1.024 s time scale. The ACIPs represent the average temporal and spectral properties of these events equally in the observer frame of reference and in the co-moving frames of outbursting emitters. The parameter

D. C. Ellison, J. P. Meyer

Assuming that refractory elements in cosmic rays originate in dust grains, we examine the viability of cosmic ray origin models wherein the bulk of present day cosmic rays are accelerated out of fresh supernova ejecta material before it mixes with the average interstellar medium (ISM). We conclude that the fresh ejecta scenarios that have been proposed thus

J. P. Meyer, D. C. Ellison

The composition of present day cosmic rays (CRs) is inconsistent with a significant acceleration of SN ejecta material (even with a preferential acceleration of ejecta grain material). Current CRs must result mainly from the acceleration of ISM (&#34;solar mix&#34;) and circumstellar (22Ne- and 12C-rich WR wind) gas and grain material. The CR source composit

P. Haensel, J. P. Lasota, J. L. Zdunik

The lower bound on the period of uniform rotation of neutron stars (NS) with causal equation of state (EOS), P_ min, is shown to be determined, with a high precision, by the upper bound on the surface redshift of static neutron star models, z_ max. We obtain z_max=0.851, which turns out to be about 5% lower than upper bound obtained by Lindblom (1984). Using

Floris F. S. van der Tak, Ewine F. van Dishoeck, Neal J. Evans, Eric J. Bakker

The temperature, density and kinematics of the gas and dust surrounding the luminous young stellar object GL~2591 are investigated on scales as small as 100 AU, probed by 4.7 micron absorption spectroscopy, to over 60,000 AU, probed by single-dish submillimeter spectroscopy. These two scales are connected by interferometric 86-226 GHz images of size 60,000 A

Stefanie Komossa, Hans Boehringer

The NGC 383 group is a rich group of galaxies that harbours the central radio source 3C 31 = NGC 383. After presenting results from the X-ray analysis of the extended intra-group medium and the central radio galaxy, we discuss the spatial morphology of X-ray emitting gas as compared to the radio plasma and perform a comparison of the pressures of both compon

Inma Dominguez, Oscar Straniero, Jordi Isern

We show that the inclusion of axion emission during stellar evolution introduces important changes into the evolutionary behaviour of AGB stars. The mass of the resulting C/O white dwarf is much lower than the equivalent obtained from standard evolution. This implies a deficit in luminous AGB stars and in massive WDs. Moreover the total mass processed in the

F. A. Aharonian

Since its commissioning in fall 1996, the stereoscopic system of Imaging Atmospheric Cherenkov Telescope (IACTs) of HEGRA with an energy threshold of 500 GeV, an angular resolution of 0.1 degree and an energy resolution of 20% per individual photon, and an energy flux sensitivity nu F_nu at 1 TeV of 1E-11erg/cm**2 s (S/N = 5 sigma) for one hour of observatio

L. J. Tacconi, R. Genzel, M. Tecza, J. F. Gallimore

We report 0.5&#34;x0.9&#34; resolution, interferometric observations of the 1.3 mm CO J=2-1 line in the infrared luminous galactic merger NGC 6240. About half of the CO flux is concentrated in a rotating but highly turbulent, thick disk structure centered between the two radio and near-infrared nuclei. A number of gas features connect this ~500 pc diameter c

Stefan C. Keller

We present broad-band infrared photometry for 52 late-type supergiants in the young Magellanic Clouds clusters NGC 330, NGC 1818, NGC 2004 and NGC 2100. Standard models are seen to differ in the temperature they predict for the red supergiant population on the order of 300K. It appears that these differences most probably due to the calibration of the mixing

Paul Martini, K. Sellgren, D. L. DePoy

We present near-infrared spectroscopy of fluorescent molecular hydrogen (H_2) emission from NGC 1333, NGC 2023, NGC 2068, and NGC 7023 and derive the physical properties of the molecular material in these reflection nebulae. Our observations of NGC 2023 and NGC 7023 and the physical parameters we derive for these nebulae are in good agreement with previous s

M. Revnivtsev, A. Emelyanov, K. Borozdin

We present the results of observations of XTE J0421+560 X-ray transient with Rossi X-ray Timing Explorer in the beginning of April 1998. Lightcurve, obtained by ASM all-sky monitor, shows unusually fast decrease in the object&#39;s luminosity. Spectra from series of observations by PCA and HEXTE experiments were studied in detail. Two emission line regions w

Ilka Brunner, Arvind Rajaraman, Moshe Rozali

We construct D-brane states on an asymmetric orbifold of type IIA on a four-torus, which is modded out by T-duality. We find explicit boundary states charged under the twisted sector gauge fields. Unlike other cases, the boundary states involve an explicit dependence on the twist fields. The D-brane spectrum is consistent with the model being equivalent to t

Persis S. Drell, Thomas J. Loredo, Ira Wasserman

We explore the possible role of evolution in the analysis of data on SNe Ia at cosmological distances. First, using a variety of simple sleuthing techniques, we find evidence that the properties of the high and low redshift SNe Ia observed so far differ from one another. Next, we examine the effects of including simple phenomenological models for evolution i

Edi Halyo

We show that D--term inflation at the TeV scale is possible in the presence of large internal dimensions. This requires very small couplings and masses which arise from the large size of the compact dimensions. We show that acceptable number of e-folds, magnitude and spectrum of density perturbations $δρ/ρ$ and $η$ can be obtained in this scenario at the pri

C. Wexler, Alan T. Dorsey

We present a theoretical study of the excitations on the edge of a two-dimensional electron system in a perpendicular magnetic field in terms of a contour dynamics formalism. In particular, we focus on edge excitations in the quantum Hall effect. Beyond the usual linear approximation, a non-linear analysis of the shape deformations of an incompressible dropl

G. Bonini, S. Habib, E. Mottola, C. Rebbi

The properties of periodic instanton solutions of the classical SU(2) gauge theory with a Higgs doublet field are described analytically at low energies, and found numerically for all energies up to and beyond the sphaleron energy. Interesting new classes of bifurcating complex periodic instanton solutions to the Yang-Mills-Higgs equations are described.

N. F. Johnson, D. J. T. Leonard, P. M. Hui, T. S. Lo

We show that evolution in a population of adaptive agents, repeatedly competing for a limited resource, can come to an abrupt halt. This transition from evolutionary to non-evolutionary behavior arises as the global resource level is changed, and is reminiscent of a phase transition to a frozen state. Its origin lies in the inductive decision-making of the a

Daniel Dominguez, Cristina Wiecko, Jorge V. Jose

We study the effects of an electric-field in the transport properties of bulk granular superconductors with different kinds of disorder. We find that for a d-wave granular superconductor with random $π$-junctions the critical current always increases after applying a strong electric field, regardless of the polarity of the field. This result plus a change in

Daniel H. Linares, Ezequiel V. Albano, Roberto A. Monetti

Hot monomers are particles having a transient mobility (a ballistic flight) prior to being definitely absorbed on a surface. After arriving at a surface, the excess energy coming from the kinetic energy in the gas phase is dissipated through degrees of freedom parallel to the surface plane. In this paper we study the hot monomer-monomer adsorption-reaction p

Dietrich Bodeker

In hot non-Abelian gauge theories, processes characterized by the momentum scale $g^2 T$ (such as electroweak baryon number violation in the very early universe) are non-perturbative. An effective theory for the soft ($|\vec{p}|\sim g^2 T$) field modes is obtained by integrating out momenta larger than $g^2 T$. Starting from the hard thermal loop effective t

P. F. Henning, C. C. Homes, S. Maslov, G. L. Carr

In this paper we report the first experimental measurement of the infrared conductivity of ultra-thin quenched-condensed Pb films. For dc sheet resistances such that $\omega \tau \ll 1$ the ac conductance increases with frequency but is in disagreement with the predictions of weak localization. We attribute this behavior to the effects of an inhomogeneous gr

Erasmo Ferreira, Uri Maor

We investigate the possibility that the process of phi photoproduction may have a significant hard perturbative QCD component. This suggestion is based on a study of the energy dependence of the forward phi photoproduction cross section followed by a calculation where we show that a coherent sum of the pQCD and conventional soft Pomeron contributions provide

Alfredo T. Suzuki, Alexandre G. M. Schmidt

Perturbative quantum gauge field theory seen within the perspective of physical gauge choices such as the light-cone entails the emergence of troublesome poles of the type $(k\cdot n)^{-α}$ in the Feynman integrals, and these come from the boson field propagator, where $α= 1,2,...$ and $n^μ$ is the external arbitrary four-vector that defines the gauge proper

S. Pedersen, A. E. Hansen, A. Kristensen, C. B. Soerensen

We have investigated the Aharonov-Bohm effect in a one-dimensional GaAs/GaAlAs ring at low magnetic fields. The oscillatory magnetoconductance of these systems are for the first time systematically studied as a function of density. We observe phase-shifts of $π$ in the magnetoconductance oscillations, and halving of the fundamental $h/e$ period, as the densi

Kang Young Lee, H. S. Song, JeongHyeon Song, Chaehyun Yu

Large extra dimension effects on the spin configuration of the top quark pair at the $e^+ e^-\to t\bar{t}$ process are studied. It is shown that the TeV scale quantum gravity effects cause significant deviations from the Standard Model predictions for the spin configuration in the off-diagonal basis: they lead to substantial cross sections of the like-spin s