November 1998 arXiv papers — page 3

A. M. Martin, J. F. Annett

We develop a method to solve the Bogoliubov de Gennes equation for superconductors self-consistently, using the recursion method. The method allows the pairing interaction to be either local or non-local corresponding to $s$ and $d$--wave superconductivity, respectively. Using this method we examine the properties of various $S-I-N$ and $D-I-N$ interfaces. I

R. Mallik, E. V. Sampathkumaran, P. L. Paulose

The results of heat-capacity, magnetic susceptibility, electrical resistivity and magnetoresistance $(Δρ/ρ)$ measurements on the compounds Tb$_2$PdSi$_3$ and Dy$_2$PdSi$_3$, are reported. The results establish that these compounds undergo long-range magnetic ordering (presumably with a complex magnetic structure) below (Tc=) 23 and 8 K respectively. The $Δρ/

L. Turban

We study the influence of an aperiodic extended surface perturbation on the surface critical behaviour of the two-dimensional Ising model in the extreme anisotropic limit. The perturbation decays as a power of the distance from the free surface with an oscillating amplitude following some aperiodic sequence. The asymptotic density is 1/2 so that the mean amp

R. Hayn, H. Rosner, V. Yu. Yushankhai, S. Haffner

Band structure calculations have been used to identify the different bands contributing to the polarisation-dependent photoemission spectra of the undoped model cuprate Sr$_2$CuO$_2$Cl$_2$ at the high-symmetry points of the CuO$_2$ plane $Γ$, $(π/a,0)$ and $(π/a,π/a)$ and along the high-symmetry directions $Γ- (π/a,π/a)$ and $Γ- (π/a,0)$. Results from calcul

F. F. Assaad, M. Imada

The dispersion relation of a doped hole in the half-filled 2D Hubbard model is shown to follow a k^4 law around the (0,pi) and (pi,0) points in the Brillouin zone. Upon addition of pair-hopping processes this dispersion relation is unstable towards a k^2 law. The above follows from T=0 Quantum Monte calculations of the single particle spectral function A(k,

Raquel Dominguez-Cascante, David Jou

We analyze the relation between the nonequilibrium Lagrange multipliers used in information theory and those used in Liu's technique to exploit the entropy inequality. We observe that there is not a complete equivalence between Liu's technique and information theory.

R. Mallik, E. V. Sampathkumaran, M. Strecker, G. Wortmann

Results on electrical resistivity, magnetoresistance, magnetic Results on electrical resistivity, magnetoresistance, magnetic susceptibility, heat capacity and Gd Mossbauer measurements on a Gd-based intermetallic compound, Gd$_{2}$PdSi$_{3}$ are reported. A finding of interest is that the resistivity unexpectedly shows a well-defined minimum at about 45 K,

Giovannni Gallavotti, Guido Gentile, Vieri MAstropietro

Interacting systems consisting of two rotators and a pendulum are considered, in a case in which the uncoupled systems have three very different characteristic time scales. The abundance of unstable quasi periodic motions in phase space is studied via Lindstedt series. The result is a strong improvement, compared to our previous results, on the domain of val

Paul A. Miller, Sarben Sarkar

The von Neumann entropy production for a quantum mechanical kicked rotor coupled to a thermal environment is calculated. This rate of entropy increase is shown to be a good criterion to distinguish between quantum mechanical counterparts of chaotic and regular classical motion. We show that for high temperatures the entropy production rate increases linearly

F. Moisy, P. Tabeling, H. Willaime

The Kolmogorov equation with a forcing term is compared to experimental measurements, in low temperature helium gas, in a range of microscale Reynolds numbers $R_λ$ between 120 and 1200. We show that the relation is accurately verified by the experiment (i.e. within +/- 3 % relative error, over ranges of scales extending up to three decades). Two scales are

B. Jouault, M. Greiner, P. Lipa

One-point time-series measurements limit the observation of three-dimensional fully developed turbulence to one dimension. For one-dimensional models, like multiplicative branching processes, this implies that the energy flux from large to small scales is not conserved locally. This then renders the random weights used in the cascade curdling to be different

S. Trudolyubov, E. Churazov, M. Gilfanov

The results of X-ray observations of Galactic superluminal jet source GRS 1915+105 during its low luminosity state and state transitions in October, 1996 - April, 1997 with PCA and HEXTE instruments aboard Rossi X-ray Timing Explorer (RXTE) are reported. Except some peculiarities, the major spectral and temporal properties of the source during this period we

Asantha R. Cooray

We calculate the expected number of strongly lensed radio sources in a sample of 6500 sources observed with the Very Large Array as part of the Cosmic Lens All Sky Survey (CLASS) during the first two sessions of its observations. A comparison between the predicted and the observed number of lensed radio sources allows a determination of the current value of

Michael S. Turner

For two decades the hot big-bang model as been referred to as the standard cosmology -- and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and point to a grander theory. The best candidate for that grander theory is inflation + cold dark matter; it can extend our

Tom Richtler, Jochen M. Braun

The Workshop 'The Magellanic Clouds and Other Dwarf Galaxies' was held at the Physikzentrum Bad Honnef in January 1998. The proceedings comprise 79 contributions. About 1/3 of the 352 pages contain the following Reviews: The Violent Interstellar Medium in Dwarf Galaxies: Atomic Gas (Elias Brinks and Fabian Walter), Hot Gas in the Large Magellanic Clo

S. Mereghetti

The AGILE $γ$-ray telescope (Tavani et al. 1998) will have a relatively uniform sensitivity over a very wide field of view. This allows to simultaneously monitor several AGN's and to react quickly with multiwavelength observations in the case of flaring activity. The large cumulative sky coverage will also lead to a significant increase in the number of

K. Hurley, T. Cline, E. Mazets, S. Barthelmy

Soft gamma repeaters are high-energy transient sources associated with neutron stars in young supernova remnants. They emit sporadic, short (~ 0.1 s) bursts with soft energy spectra during periods of intense activity. The event of March 5, 1979 was the most intense and the only clearly periodic one to date. Here we report on an even more intense burst on Aug

B. Fuchs, H. Jahreiss, R. Wielen

A sample of subdwarfs with accurate space velocities and standarized metallicities is presented. This was constructed by combining Hipparcos parallaxes ond proper motions with radial velocities and metallicities from Carney et al. (1994; CLLA). The accurate Hipparcos parallaxes lead to an - upward - correction factor of 11% of the photometric distance scale

Osmi Vilhu

Classical modelling suggests that, during the RXTE observations studied, GRS 1915+105 was near or above the critical accretion rate and the optically thick inner disk penetrated inside the advection-dominated flow. The system was very unstable leading to a rich pattern of variability, e.g. the Rings which might be characteristic to disk instabilities very cl

Paul P. van der Werf, D. L. Clements, P. A. Shaver, M. R. S. Hawkins

We have developed a method for selecting the most luminous galaxies detected by IRAS based on their extreme values of R, the ratio of 60 micron and B-band luminosity. These objects have optical counterparts that are close to or below the limits of Schmidt surveys. We have tested our method on a 1079 deg^2 region of sky, where we have selected a sample of IRA

P. M. W. Kalberla, J. Kerp

We investigated a hydrostatic equilibrium model of the Milky Way following Parker (1966), to constrain the large scale properties of the interstellar medium. In our approach we found an excellent agreement between our simple hydrostatic equilibrium model of the Milky Way and the recent all-sky survey data rangeing from the gamma-ray to the radio regime. On l

P. M. W. Kalberla, J. Kerp

In 1998 several papers claim the detection of an ubiquitous gaseous phase within the Galactic halo. Here we like to focus on the detections of X-ray emitting gas within the Galactic halo as well as the discovery of a pervasive neutral Galactic halo gas. We discuss critically the major differences between the recent publications as well as the limitations of

J. F. Olive, D. Barret, L. Boirin, J. E. Grindlay

The X-ray burster 1E1724-3045 located in the globular cluster Terzan 2 is known as one of the persistent (though variable) hard X-ray sources as shown by the SIGMA observations of the Galactic Center region. 1E1724-3045 was observed with the PCA and HEXTE experiments onboard the RXTE on November 1996 for about 100 ksec. The broad band spectral capability and

P. M. W. Kalberla, J. Kerp, U. Haud

We study the hypothesis that high-velocity clouds (HVCs) may originate from instabilities within the gaseous phase of the Galactic halo. According to the hydrostatic equilibrium model of Kalberla & Kerp (1998), we determine the probability distribution of occurrence of instabilities within the Galactic halo. Instabilities may produce condensations within the

J. Kerp, P. M. W. Kalberla, M. J. Freyberg, Dap Hartmann

The ROSAT mission gave us the unique possibility to study the galactic interstellar medium by ``shadowing'' observations on arcmin angular resolution level. The high sensitivity of the ROSAT PSPC in combination with the large field of view allows the detailed study of individual clouds, while the ROSAT all-sky survey is the main source for studies of

Jaan Einasto

Recent analysis of the distribution of clusters of galaxies is reviewed. Clusters of galaxies located in rich superclusters form a quasiregular lattice. The mean power spectrum of galaxies and clusters has been found, it has a peak at wavelength $λ_0=120$~\Mpc corresponding to the lattice step. The power spectrum of galaxies is reduced to that of matter. The

L. R. Abramo, R. P. Woodard

We consider quantum mechanical corrections to a homogeneous, isotropic and spatially flat geometry whose scale factor expands classically as a general power of the co-moving time. The effects of both gravitons and the scalar inflaton are computed at one loop using the manifestly causal formalism of Schwinger with the Feynman rules recently developed by Iliop

L. R. Abramo, R. P. Woodard

We extend, for the case of a general scalar potential, the inflaton-graviton Feynman rules recently developed by Iliopoulos {\it et al.} As an application we compute the leading term, for late co-moving times, of the one loop back reaction on the expansion rate for $V(ϕ) = \frac12 m^2 ϕ^2$. This is expressed as the logarithmic time derivative of the scale fa

J. Einasto

We calculate the mean power spectrum of galaxies using published power spectra of galaxies and clusters of galaxies. The mean power spectrum has a relatively sharp maximum on scale 120 Mpc (for Hubble constant h=1), followed by an almost exact power-law spectrum of index n = -1.9 toward smaller scales. The power spectrum found from APM 2-D galaxy distributio

R. Coker, F. Melia

It is thought that many characteristics of the gaseous features within the central parsec of our Galaxy, are associated with the accretion of ambient plasma by a central concentration of mass. Using a 3D hydrodynamical code, we have been simulating this process in order to realistically model the gaseous flows in the center of our Galaxy. In the most recent

Ana Heller, Elchanan Almoznino, Noah Brosch

We present H-alpha and red continuum observations for a sample of late-type low surface brightness (LSB) dwarf irregular galaxies(DIGs), consisting of all the m_B<17.2 ImIV and V galaxies in the Virgo cluster (VC), and compare them with a representative sample of VC high surface brightness (HSB) DIGs. Line fluxes and equivalent widths are listed for individu

D. L. Khokhlov

The model of the homogenous and isotropic universe is considered in which the coordinate system of reference is not defined by the matter but is a priori specified. The scale factor of the universe changes following the linear law. The scale of mass changes proportional to the scale factor. The temperature of the relativistic matter changes inversly proporti

H. M. Cataldo, M. A. Despósito, D. M. Jezek

We examine the transverse and longitudinal components of the drag force upon a straight vortex line due to the scattering of liquid $^4$He excitations. For this purpose, we consider a recently proposed Hamiltonian that describes the dissipative motion of a vortex, giving an explicit expression for the vortex-quasiparticle interaction. The involved dissipativ

H. M. Cataldo

The stability of a quasicrystalline structure, recently obtained in a molecular-dynamics simulation of rapid cooling of a binary melt, is analyzed for binary hard-sphere mixtures within a density-functional approach. It is found that this quasicrystal is metastable relative to crystalline and fluid phases for diameter ratios above 0.83. Such trend is partial

Michael Martin Nieto, D. Rodney Truax

Using the transformations from paper I, we show that the Schrödinger equations for: (1)systems described by quadratic Hamiltonians, (2) systems with time-varying mass, and (3) time-dependent oscillators, all have isomorphic Lie space-time symmetry algebras. The generators of the symmetry algebras are obtained explicitly for each case and sets of number-opera

Michael Martin Nieto, D. Rodney Truax

In this paper, we focus on a general class of Schrödinger equations that are time-dependent and quadratic in X and P. We transform Schrödinger equations in this class, via a class of time-dependent mass equations, to a class of solvable time-dependent oscillator equations. This transformation consists of a unitary transformation and a change in the ``time&#3

M. Fischer, S. Groote, J. G. Körner, M. C. Mauser

We consider the decay of a polarized top quark into a polarized W-boson plus a bottom quark, followed by the decay of the W-boson into a pair of leptons or quarks. The polar angle distribution of the top spin relative to the W-momentum and the polar angle distribution of the lepton (or quark) in the W-rest frame is governed by three polarized and three unpol

S. Boffi, P. Demetriou, M. Radici, R. F. Wagenbrunn

The electromagnetic form factors of the nucleon have been calculated in a chiral constituent-quark model. The nucleon wave functions are obtained by solving a Schrödinger-type equation for a semi-relativistic Hamiltonian with an effective interaction derived from the exchange of mesons belonging to the pseudoscalar octet and singlet and a linear confinement

W. Lerche, S. Stieberger, N. P. Warner

We show how certain F^4 couplings in eight dimensions can be computed using the mirror map and K3 data. They perfectly match with the corresponding heterotic one-loop couplings, and therefore this amounts to a successful test of the conjectured duality between the heterotic string on T^2 and F-theory on K3. The underlying quantum geometry appears to be a 5-f

Itai Benjamini, Gil Kalai, Oded Schramm

It is shown that a large class of events in a product probability space are highly sensitive to noise, in the sense that with high probability, the configuration with an arbitrary small percent of random errors gives almost no prediction whether the event occurs. On the other hand, weighted majority functions are shown to be noise-stable. Several necessary a

Giorgio Parisi, Federico Ricci-Tersenghi, Juan J. Ruiz-Lorenzo

We show that the numerical method based on the off-equilibrium fluctuation-dissipation relation does work and is very useful and powerful in the study of disordered systems which show a very slow dynamics. We have verified that it gives the right information in the known cases (diluted ferromagnets and random field Ising model far from the critical point) an

J. A. Hertz, David Sherrington, Th. M. Nieuwenhuizen

A mean-field multi-spin interaction spin glass model is analyzed in the presence of a ferromagnetic coupling. The static and dynamical phase diagrams contain four phases (paramagnet, spin glass, ordinary ferromagnet and glassy ferromagnet) and exhibit reentrant behavior. The glassy ferromagnet phase has anomalous dynamical properties. The results are consist

John Schliemann, Franz G. Mertens

We use coherent states as a time-dependent variational ansatz for a semiclassical treatment of the dynamics of anharmonic quantum oscillators. In this approach the square variance of the Hamiltonian within coherent states is of particular interest. This quantity turns out to have natural interpretation with respect to time-dependent solutions of the semiclas

Tapas K. Das

We compute mass outflow rate $R_{\dot m}$ from relativistic matter accreting quasi-spherically onto Schwarzschild black holes. Taking the pair-plasma pressure mediated shock surface as the {\it effective} boundary layer (of the black hole) from where bulk of the outflow is assumed to be generated, computation of this rate is done using combinations of exact

K. K. Jeong, C. S. Kim

We estimate the heavy quark effective theory parameter λ_1 from inclusive semileptonic B-meson decay spectrum. By using recent CLEO double lepton tagging data of B -> X e nu, which shows the lepton momentum as low as 0.6 GeV, we extracted λ_1 \sim -0.58 GeV^2. We also derived \barΛ\sim 0.46 GeV and |V_{cb}| = 0.041 \pm 0.002.

R Delbourgo, Dongsheng Liu, M D Scadron

We prove that recent data demonstrates unequivocally that the scalar meson $f_0$(980) is mostly composed of $s\bar{s}$ quarks and that the coupling of $f_0$ to photons and mesons is in agreement with the linear sigma model.

Markus Simonius

The problem of measurement in quantum mechanics is reanalyzed within a general, strictly probabilistic framework (without reduction postulate). Based on a novel comprehensive definition of measurement the natural emergence of objective events is demonstrated and their formal representation within quantum mechanics is obtained. In order to be objective an eve

Lutz Polley

The Schroedinger equation with scalar and vector potentials is the continuum limit of any coherent hopping process (where position eigenstates superpose with neighbouring eigenstates after a time step) whose hopping amplitudes are homogeneous in quadratic order of the inverse lattice spacing, inhomogeneous in first order, and satisfying a summability conditi

Tilman Sauer

Hilbert&#39;s paper on ``The Foundations of Physics (First Communication),&#39;&#39; is now primarily known for its parallel publication of essentially the same gravitational field equations of general relativity which Einstein published in a note on ``The Field Equations of Gravitation,&#39;&#39; five days later, on November 25, 1915. An intense corresponde

G. Martinez-Pinedo, K. Langanke, D. J. Dean

We calculate supernova electron capture and beta decay rates for various pf-shell nuclei using large-scale shell model techniques. We show that the centroid of the Gamow-Teller strength distribution has been systematically misplaced in previous rate estimates. Our total electron capture rates are significantly smaller than currently adopted in core collapse

A. I. Titov, B. Kämpfer, V. V. Shklyar

The sensitivity of polarization observables in the reaction $NN \to NN ϕ$ slightly above the threshold is studied with respect to the details of the one-boson exchange model and a possible admixture of hidden strangeness in the nucleon. It is shown that the finite-energy predictions differ strongly from the threshold predictions. A measurement of the beam -

M. Sugita, K. Uchiyama, K. Furuno

The B(E2:0_1^+ -> 2_1^+) values of the Ba isotopes (Z=56) exhibit a sharp increase in deformation as the neutron numbers approach the mid-shell value of N=66. This behavior is anomalous because the 2_1^+ level energies are very similar to those of the neighboring isotopes. By means of the axially-symmetric deformed Woods-Saxon (WS) hamiltonian plus the BCS m

F. Bentosela, P. Exner, V. A. Zagrebnov

We consider an electron with an anomalous magnetic moment, g>2, confined to a plane and interacting with a nonhomogeneous magnetic field B, and investigate the corresponding Pauli Hamiltonian. We prove a lower bound on the number of bound states for the case when B is of a compact support and the related flux is $N+ε, ε\in(0,1]$. In particular, there are at

Omar Foda, Trevor A. Welsh

We further develop the finite length path generating transforms introduced previously, and use them to obtain constant sign polynomial expressions that reduce, in the limit of infinite path lengths, to parafermion and ABF Virasoro characters. This provides us, in the ABF case, with combinatorial proofs of Melzer&#39;s boson-fermion polynomial identities.

A. A. Deriglazov, D. M. Gitman

We consider a possibility to describe spin one-half and higher spins of massive relativistic particles by means of commuting spinors. We present two classical gauge models with the variables $x^μ,ξ_α,χ_α$, where $ξ,χ$ are commuting Majorana spinors. In course of quantization both models reproduce Dirac equation. We analyze the possibility to introduce an int

Prem P. Srivastava

The bosonized Chiral Schwinger model (CSM) is quantized on the light-front (LF). The physical Hilbert space of CSM is obtained directly once the constraints on the LF phase space are eliminated. The discussion of the degenerate vacua and the absence in the CSM of the $θ$-vacua, as found in the Schwinger model (SM), becomes straightforward. The differences in

Toshihico Arimitsu

Quantum field theory is constructed upon the assumption of stabilities of the vacuum and of the one-particle state. For finite temperature, the one-particle state becomes unstable because of thermal fluctuations, whereas the thermal vacuum is still stable. In non-equilibrium situation, both the vacuum and the one-particle state lose their stability. Proposed

Vladimir Lugovoi

The qualitative results for string rotation in the frame of Relativistic Flux Tube Model and the quantitative and qualitative results for decay of massive open string states of string theory are used as the basic principles in the Monte Carlo implementation for decay of massive open string. The presented model can be used as an ingredient into any Monte Carl

Yukinori Nagatani

We propose a new scenario of the electroweak baryogenesis based on the properties of electroweak domain walls surrounding black holes in the Higgs phase vacuum of the extended Standard Model with 2-Higgs doublets. It is shown that there exists the electroweak domain walls and the symmetric regions surrounding black holes and that the Hawking radiation of the

A. V. Belitsky, D. Muller, A. Schafer

We prove a set of identities for the anomalous dimensions of the quark and gluon conformal operators in the flavour singlet channel in QCD. These relations arise from the graded commutator algebra of the N=1 superconformal group. We evaluate the rotation matrices for the quantities under study from the conventional dimensional regularization to the supersymm

W. Beenakker, F. A. Berends, A. P. Chapovsky

Radiative corrections to processes that involve the production and subsequent decay of unstable particles are complex due to various theoretical and practical problems. The so-called double-pole approximation offers a way out of these problems. This method is applied to the reaction $e^{+}e^{-} \to W^{+}W^{-} \to 4 $fermions, which allows us to address all t

P. Eden, G. Gustafson

While the hard phase of the strong interaction is well described by perturbative QCD, the soft hadronization phase is less understood. Benefiting from the high statistics from e+e- experiments at the Z0 resonance, it is possible to impose strong two-jet cuts on the data without loosing the statistical significance. In these events perturbative activity is su

David Delepine, Utpal Sarkar

In the supersymmetric extensions of the standard model, neutrino masses and leptogenesis requires existence of new particles. We point out that if these particles with lepton number violating interactions have standard model gauge interactions, then they may not be created after reheating because of the gravitino problem. This will rule out all existing mode

Mark Smith

At LEP II it is hoped to measure the W mass to an accuracy of around 40 MeV. This will require direct reconstruction of the mass of the W from its decay products in both the semi-leptonic and hadronic decay channels. Final state perturbative reconnection effects in hadronic decays are considered and their effect on 6-jet distributions and the reconstructed m

M. Czakon, J. Gluza, M. Zralek

Transition magnetic moments of Majorana neutrinos are discussed in the frame of the most natural version of the LR model (with left- and right-handed triplets and a bidoublet in the Higgs sector). We show that their largest values could be at most $6\cdot 10^{-13} μ_B$ from diagrams with $W_L$ in the loop. This could happen for specific models where (i) neut

D. Blaschke, Yu. L. Kalinovsky, P. C. Tandy

A simple confining separable interaction Ansatz for the rainbow-ladder truncated QCD Dyson-Schwinger equations is used to study quark deconfinement and meson states at finite temperature. The model is fixed at T=0 to implement quark confinement while preserving the Goldstone mechanism for the $π$. Within the Matsubara formalism, a very slow temperature depen

Herbert Nachbagauer

We propose a new approximation-technique to deal with the exact macroscopic integro-differential evolution equations of statistical systems which self-consistently accounts for dissipative effects. Concentrating on one and two point equal-time correlators, we develop the self-consistent method and apply it to a scalar field theory with quartic self-interacti

R. Aloisio, V. Azcoiti, G. Di Carlo, A. Galante

QCD at finite chemical potential is analytically investigated in the region of large bare fermion masses. We show that, contrary to the general wisdom, the phase of the fermion determinant is irrelevant at zero temperature. However if the system is put at finite temperature, the contribution of the phase is finite. We also discuss on the quenched approximati

A. Buonanno, T. Damour

We map the general relativistic two-body problem onto that of a test particle moving in an effective external metric. This effective-one-body approach defines, in a non-perturbative manner, the late dynamical evolution of a coalescing binary system of compact objects. The transition from the adiabatic inspiral, driven by gravitational radiation damping, to a

C. Bracco, P. Teyssandier

We study the scintillation produced by time-varying gravitational fields within scalar-tensor theories of gravity. The problem is treated in the geometrical optics approximation for a very distant light source emitting quasi plane monochromatic electromagnetic waves. We obtain a general formula giving the time dependence of the photon flux received by a free

S. Bonazzola, E. Gourgoulhon, J. -A. Marck

We present spectral methods developed in our group to solve three-dimensional partial differential equations. The emphasis is put on equations arising from astrophysical problems in the framework of general relativity.

A. Criscuolo, H. Waelbroeck

We construct a quantum measure on the power set of non-cyclic oriented graphs of N points, drawing inspiration from 1-dimensional directed percolation. Quantum interference patterns lead to properties which do not appear to have any analogue in classical percolation. Most notably, instead of the single phase transition of classical percolation, the quantum m

C. Pepin, M. Lavagna

We present a new supersymmetric approach to the Kondo lattice model in order to describe simultaneously the quasiparticle excitations and the low-energy magnetic fluctuations in heavy-Fermion systems. This approach mixes the fermionic and the bosonic representation of the spin following the standard rules of superalgebra. Our results show the formation of a

C. Pepin, M. Lavagna

The dynamical spin susceptibility is studied in the magnetically-disordered phase of heavy-Fermion systems near the antiferromagnetic quantum phase transition. In the framework of the $S=1/2$ Kondo lattice model, we introduce a perturbative expansion treating the spin and Kondo-like degrees of freedom on an equal footing. The general expression of the dynami

Arindam Ghosh, A. K. Raychaudhuri, R. Sreekala, M. Rajeswari

In this paper we report the observation of curent induced change of resistance of thin metallic oxide films. The resistance changes at a very low current (current density $J \geq 10^{3}$ A/cm$^{2}$). We find that the time dependence associated with the processes (increase of resistance) show a streched exponential type dependence at lower temperature, which

N. Macris, C. -A. Piguet

We give a criterion for the simultaneous existence or non existence of two long-range orders for two observables, at finite temperatures, for quantum lattice many body systems. Our analysis extends previous results of G.-S. Tian limited to the ground state of similar models. The proof involves an inequality of Dyson-Lieb-Simon which connects the Duhamel two-

P. Farkasovsky

The extrapolation of small-cluster exact-diagonalization calculations is used to examine the possibility of electronic ferroelectricity in the one dimensional spinless and spin-one-half Falicov-Kimball model (FKM). It is found that neither spinless nor spin-one-half version of the FKM does not allow for a ferroelectric ground state with a spontaneous polariz

Antonio Turiel, Angela del Pozo

It has been recently proven that natural images exhibit scaling properties analogue to those of turbulent flows. These properties allow regarding each image as a multifractal object, for which its most singular manifold conveys the most of the non-redundant structure. In the present work, we go further in this analysis, proposing a simple propagator that rec

Kheya Sengupta, V. A. Raghunathan, John Katsaras

We present electron density maps of the ripple phase of chiral and racemic dimyristoylphosphatidylcholine. The structures of the two systems are found to be identical within experimental errors, thus unambiguously showing that the chirality of the lipid molecules does not influence the structure of this phase.

F. Igloi, R. Juhasz, H. Rieger

We consider the paramagnetic phase of the random transverse-field Ising spin chain and study the dynamical properties by numerical methods and scaling considerations. We extend our previous work [Phys. Rev. B 57, 11404 (1998)] to new quantities, such as the non-linear susceptibility, higher excitations and the energy-density autocorrelation function. We show

T. P. Pareek, A. M. Jayannavar, N. Kumar

In recent years the notion of intrinsic decoherence and dephasing of a particle interacting with its environment is being investigated intensively. This has an important bearing on a plausible causal connection between incoherent c-axis resistivity and high-temperature superconductivity. In our work we study the tunnel supression and incoherent motion of a p

Tomoya Isoshima, Kazushige Machida

The stability of a quantized vortex state in Bose-Einstein condensation is examined within Bogoliubov theory for alkali atom gases confined in a harmonic potential under forced rotation. By solving the non-linear Bogoliubov equations coupled with the Gross-Pitavskii equation, the elementary excitations and the total energy of the systems are calculated as a

Alexander L. Fetter

This set of four lectures reviews various aspects of the theory of a dilute low-temperature trapped Bose gas, starting with (I) a review of the Bogoliubov description of the elementary excitations in a uniform system. The treatment is then generalized (II) to include the new physical effects of a confining harmonic trap potential on the condensate and its no

D. R. Bowler, M. J. Gillan

We analyze the problem of determining the electronic ground state within O(N) schemes, focusing on methods in which the total energy is minimized with respect to the density matrix. We note that in such methods a crucially important constraint is that the density matrix must be idempotent (i.e. its eigenvalues must all be zero or unity). Working within ortho

D. U. Matrasulov

Stochastic ionization of highly excited relativistic hydrogenlike atom in the monochromatic field is investigated. A theoretical analisis of chaotic dynamics of the relativistic electron based on Chirikov criterion is given for the cases of one- and three-dimensional atoms. Critical value of the external field is evaluated analitically. The diffusion coeffic

P. Teerikorpi, T. Ekholm, M. O. Hanski, G. Theureau

We study the influence of the assumption behind the use of the inverse Tully-Fisher relation: that there should be no observational cutoffs in the TF parameter log(V_M). It is noted how lower and upper cutoffs would be seen in a log(H_0) vs. ``normalized distance&#39;&#39; diagram. Analytical expressions, under the simplifying assumption of a normal distribu

L. V. E. Koopmans, A. G. de Bruyn, D. R. Marlow, N. Jackson

We present the discovery of a new gravitational lens system with two compact radio images separated by 0.701+-0.001 arcsec. The lens system was discovered in the Cosmic Lens All Sky Survey (CLASS) as a flat spectrum radio source. Both radio components show structure in a VLBA 8.4 GHz radio image. No further extended structure is seen in either the VLA, MERLI

R. A. Swaters, R. H. M. Schoenmakers, R. Sancisi, T. S. van Albada

Asymmetries in the distribution of light and neutral hydrogen are often observed in spiral galaxies. Here, attention is drawn to the presence of large-scale asymmetries in their kinematics. Two examples of kinematically lopsided galaxies are presented and discussed. The shape of the rotation curve --rising more steeply on one side of the galaxy than on the o

J. Einasto, P. Tenjes

We use detailed modeling of stellar populations of nearby galaxies to calculate population parameters. Our sample of galaxies includes most galaxies of the Local Group and several more distant giant galaxies. Available data are sufficient to decompose galaxies into the nucleus, the metal rich core, the bulge, the halo, the young and old disks, and the dark h

A. Del Popolo, M. Gambera

In this paper we show how non-radial motions, originating from the tidal interaction of the irregular mass distribution within and around protoclusters, can solve some of the problems of the CDM model. Firstly the discrepancy between the CDM predicted two-points correlation function of clusters and the observed one. We compare the two-points correlation func

P. T. Zycki, C. Done, D. A. Smith

We have analyzed archival Ginga data of a number of Soft X-ray Transient sources and modelled them in an attempt to constrain the geometry and physical properties of accretion. Our models include a self-consistent description of X-ray reprocessing, linking the properties of the reflected continuum and those of the iron fluorescence Kαline, and allowing for r

Toshiyuki Fukushige, Piet Hut, Jun Makino

The next decade will be an exciting time for computational physicists. After 50 years of being forced to use standardized commercial equipment, it will finally become relatively straightforward to adapt one&#39;s computing tools to one&#39;s own needs. The breakthrough that opens this new era is the now wide-spread availability of programmable chips that all

Piet Hut, Jun Makino

The GRAPE-4, the world&#39;s fastest computer in 1995-1997, has produced some major scientific results, through a wide diversity of large-scale simulations in astrophysics. Applications have ranged from planetary formation, through the evolution of star clusters and galactic nuclei, to the formation of galaxies and clusters of galaxies.

A. Retter, T. Naylor, E. M. Leibowitz

A method, based on the disc instability model, for testing the thermal stability of Cataclysmic Variables (CVs), is presented. It is shown that the border line between thermal stability and instability is crossed during some nova outbursts and decays, however it is not clear whether this is the general behaviour. We suggest two new evolutionary scenarios for

Ralf Bender, Roberto P. Saglia

The last decade of research on elliptical galaxies has produced a wealth of new information concerning both their detailed structure and their global scaling relations. We review the old and new results about isophote shapes and subcomponents (Sect. 1), scaling relations of global parameters and redshift evolution (Sect. 2), and the ages, metallicities (Sect

Radu Manuca, Yi Li, Rick Riolo, Robert Savit

In this paper we present results and analyses of a class of games in which heterogeneous agents are rewarded for being in a minority group. Each agent possesses a number of fixed strategies each of which are predictors of the next minority group. The strategies use a set of aggregate, publicly available information (reflecting the agents&#39; collective prev

Andrey L. Pankratov

This paper presents description of time evolution of averages of Markov process in wide range of noise intensity. Exact expression of time scale of average evolution has been obtained. It has been demonstrated numerically that for purely noise-induced transitions (transitions over potential barriers) the time evolution of mean coordinate is a simple exponent

O. G. Benvenuto, L. G. Althaus

We present detailed evolutionary calculations for carbon - oxygen - and helium - core white dwarf (WD) models with masses ranging from M= 0.1 to M= 1.2 solar masses and for metallicities Z= 0.001 and Z= 0. The sequences cover a wide range of hydrogen envelopes as well. We employed a detailed WD evolutionary code. In particular, the energy transport by convec

P. Berglund, P. Mayr

We use local mirror symmetry in type IIA string compactifications on Calabi-Yau n+1 folds $X_{n+1}$ to construct vector bundles on (possibly singular) elliptically fibered Calabi-Yau n-folds Z_n. The interpretation of these data as valid classical solutions of the heterotic string compactified on Z_n proves F-theory/heterotic duality at the classical level.

Roman Bezrukavnikov, Alexander Polishchuk

This paper is devoted to the study of the gluing construction for perverse sheaves on $G/U$ introduced by Kazhdan and Laumon ($G$ is a semisimple gourp, $U$ is the unipotent radical of a Borel subgroup in $G$). Kazhdan and Laumon conjectured that all Ext-groups in the glued category are finite-dimensional and that global cohomological dimension is finite. We