October 1997 arXiv papers — page 4

Ya. M. Blanter, F. W. J. Hekking, M. Buttiker

We show that the interaction constant governing the long-range electron-electron interaction in a quantum wire coupled to two reservoirs and capacitively coupled to a gate can be determined by a low frequency measurement. We present a self-consistent, charge and current conserving theory of the full conductance matrix. The collective excitation spectrum cons

V. Lien Nguyen, Enrique Canessa

We propose a simulation model to study the properties of directed percolation in two-dimensional (2D) anisotropic random media. The degree of anisotropy in the model is given by the ratio $μ$ between the axes of a semi-ellipse enclosing the bonds that promote percolation in one direction. At percolation, this simple model shows that the average number of bon

Peter Freche, Martin Janssen, Rainer Merkt

We demonstrate that network models for wave mechanical systems with quenched disorder cover the physics of mesoscopic electrons. The models are constructed as a network of random scattering matrices connecting incoming to outgoing wave amplitudes. The corresponding wave dynamics is given by a discrete unitary time evolution operator. We report on three diffe

Daniel Errandonea, J. F. Sánchez-Royo, A. Segura, A. Chevy

The effect of pressure on acceptor levels and hole scattering mechanisms in p-GaSe is investigated through Hall effect and resistivity measurements under quasi-hydrostatic conditions up to 4 GPa. The pressure dependence of the hole concentration is interpreted through a carrier statistics equation with a single (nitrogen) or double (tin) acceptor whose ioniz

Arno Schindlmayr, R. W. Godby

We present a general procedure for obtaining progressively more accurate functional expressions for the electron self-energy by iterative solution of Hedin's coupled equations. The iterative process starting from Hartree theory, which gives rise to the GW approximation, is continued further, and an explicit formula for the vertex function from the second

M. V. Simkin

It is identified numerically that the resistivity of a fully-frustrated Josephson-junction array is due to motion of domain walls in vortex lattice rather than to motion of single vortices.

Yoshihiro Nishiyama

Ground state of the bond-random antiferromagnetic S=1 Heisenberg chain with the biquadratic interaction -β\sum_i(S_i S_i+1)^2 is investigated by means of the exact-diagonalization method and the finite-size-scaling analysis. It is shown that the Haldane phase β\sim0 persists against the randomness; namely, no randomness-driven phase transition is observed un

Myeong-Hwa Lee, Jeong-No Lee, Kwang-Sup Soh

We investigate the time series of the segments from a Korean traditional song ``Gwansanyungma'' and a western song ``La Mamma Morta'' using chaotic analysis techniques. It is found that the phase portrait in the reconstructed state space of the time series of the segment from the Korean traditional song has a more complex structure in compari

R. E. Rothschild, P. R. Blanco, D. E. Gruber, W. A. Heindl

The High Energy X-ray Timing Experiment (HEXTE) is one of three scientific instruments aboard the Rossi X-ray Timing Explorer (RXTE), which was launched on December 30, 1995. RXTE performs timing and spectral studies of bright x-ray sources to determine the physical parameters of these systems. The HEXTE consists of two independent clusters of detectors, eac

Richard Barvainis, Danielle Alloin, Stephane Guilloteau, Robert Antonucci

We have detected CO(3-2) line emission from the gravitationally lensed quasar MG 0414+0534 at redshift 2.64, using the IRAM Plateau de Bure Interferometer. The line is broad, with Delta v_FWHM = 580 km/s. The velocity-integrated CO flux is comparable to, but somewhat smaller than, that of IRAS F10214+4724 and the Cloverleaf quasar (H1413+117), both of which

A. J. Barth, L. C. Ho, A. V. Filippenko, W. L. W. Sargent

We have obtained Hubble Space Telescope WFPC2 2200 A and optical V-band images of 20 low-luminosity active galactic nuclei, most of which are spectroscopically classified as LINERs, in order to search for a possible photoionizing continuum. Six (30%) of the galaxies are detected in the UV. Two of the detected galaxies (NGC 3642 and NGC 4203) have compact, un

Christopher A. Metzler, August E. Evrard

We use gas dynamic simulations to explore the effects of galactic winds on galaxy clusters. Two ensembles of 18 realizations, spanning a decade in temperature, are evolved with and without winds in an underlying biased CDM cosmology. Galaxies are identified as peaks in the initial density field, and are assumed to lose half their initial mass over a Hubble t

H. Pedersen, A. O. Jaunsen, T. Grav, R. Ostensen

Optical Transients from gamma-ray burst sources, in addition to offering a distance determination, convey important information on the physics of the emission mechanism, and perhaps also about the underlying energy source. As the gamma-ray phenomenon is extremely diverse, with time scales spanning several orders of magnitude, some diversity in optical counte

M. R. S. Hawkins

This paper argues that there is a large population of dark galaxies which reveals its presence by the gravitational lensing of quasars, and outnumbers normal galaxies by around 3:1. There are 8 double quasars with a separation greater than 2 arcseconds which have been classified as probable or certain gravitational lenses. Lensing galaxies have only been fou

A. Comastri, C. Vignali, M. Cappi, G. Matt

We present results of the ASCA observation of the Seyfert 2 galaxy NGC 4507. The 0.5-10 keV spectrum is rather complex and consists of several components: (1) a hard X-ray power law heavily absorbed by a column density of about 3 10^23 cm^-2, (2) a narrow Fe Kalpha line at 6.4 keV, (3) soft continuum emission well above the extrapolation of the absorbed hard

Ralf S. Klessen, Andreas Burkert

Using smoothed particle hydrodynamics in combination with the special-purpose hardware device GRAPE, we follow the fragmentation process and dynamical evolution in the interior of molecular clouds until most of the gas is converted to form a cluster of protostellar cores. The properties of this protostellar cluster are compared to observational data from sta

M. Unavane, Gerard Gilmore, N. Epchtein, G. Simon

We present the analysis of three colour optical/near-infrared images, in IJK, taken for the DENIS project. The region considered covers 17.4 square deg and lies within |l|<5 deg, |b|<1.5 deg. The adopted methods for deriving photometry and astrometry in these crowded images, together with an analysis of the deficiencies nevertheless remaining, are presented.

M. Unavane, Gerard Gilmore

We present survey data in the narrow-band L filter (nbL), taken at UKIRT, for a total area of 277 square arcmin, roughly equally divided between four regions at zero Galactic latitude and longitudes +-4.3 deg and +-2.3 deg. The 80% completeness level for these observations is at roughly magnitude 11.0. This magnitude limit, owing to the low coefficient for i

Sofia Feltzing, Bengt Gustafsson

We have derived elemental abundances of O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni for 47 G and K dwarf, with [Me/H]>0.1 dex. The selection of stars was based on their kinematics as well as on their uvby-photometry. One sample of stars on rather eccentric orbits traces the chemical evolution interior to the solar orbit and another, on circular orbits, the

Paolo Molaro, Miriam Centurion, Giovanni Vladilo

We present high-resolution UES spectra of the quasar PHL 957 obtained for studying the foreground Damped Ly-alpha galaxy at z=2.309. Measurements of absorption lines lead to accurate abundance determinations of Fe, S and N which complement measurements of Zn, Cr and Ni already available for this system. We find [Fe/H]= -2.0 (+/-0.1), [S/H]= -1.54 (+/-0.06) a

Tomonori Totani

Star formation history in galaxies is strongly correlated to their present-day colors and the Hubble sequence can be considered as a sequence of different star formation history. Therefore we can model the cosmic star formation history based on the colors of local galaxies, and comparison to direct observations of luminosity density evolution at high redshif

I. Neill Reid, Palomar Observatory, Caltech

We have used main-sequence fitting to calibrate the distances to the globular clusters NGC 6397, M5, NGC 288, M71 and 47 Tucanae, matching the cluster photometry against data for subdwarfs with precise Hipparcos parallax measurements and accurate abundance determinations. Both the cluster and subdwarf abundance scales are tied to high-resolution spectroscopi

Daniel J. Eisenstein, Wayne Hu, Joseph Silk, Alex Szalay

We assess the possibility that baryonic acoustic oscillations in adiabatic models may explain the observations of excess power in large-scale structure on 100h^-1 Mpc scales. The observed location restricts models to two extreme areas of parameter space. In either case, the baryon fraction must be large (Omega_b/Omega_0 > 0.3) to yield significant features.

Shoji Yamamoto, Takahiro Fukui

We study thermodynamic properties of the one-dimensional Heisenberg ferrimagnet with antiferromagnetically exchange-coupled two kinds of spins 1 and 1/2. The specific heat and the magnetic susceptibility are calculated employing a modified spin-wave theory as well as a quantum Monte Carlo method. The specific heat is in proportion to $T^{1/2}$ at low enough

Clovis Wotzasek

The soldering mechanism has been shown to represent the quantum interference effect between self and anti-self dual aspects of a given symmetry. This mechanism was used to show that the massive mode of the 2D Schwinger model results from the constructive interference between the right and the left massless modes of chiral Schwinger models. Similarly, the top

M. Napsuciale

Calculations for inclusive J/psi production in Upsilon decay through the color-octet mechanisms b\bar b[^3S_1, 1] -> c \bar c[^{2s+1}L_J, 8] + g are presented. It is shown that these O(alpha^5_sv^4_c) contributions compete with other color-octet mechanisms considered in the literature. A critical numerical analysis of the color-octet contributions to Upsilon

Eyal Maoz

The compelling dynamical evidence for massive dark objects in galactic nuclei does not uniquely imply massive black holes (BHs). To argue convincingly that these objects are BHs we must rule out alternatives to a BH, and the alternative to a point mass is a cluster of some sort of nonluminous objects, such as a cluster of brown dwarfs or stellar remnants. We

S. Gluzman, V. I. Yukalov

An approach is suggested for analyzing time series by means of resummation techniques of theoretical physics. A particular form of such an analysis, based on the algebraic self-similar renormalization, is developed and illustrated by several examples from the stock market time series.

K. Farakos, N. E. Mavromatos

A review is given of a relativistic non-Abelian gauge theory approach to the physics of spin-charge separation in doped quantum antiferromagnetic planar systems, proposed recently by the authors. Emphasis is put on the effects of constant external magnetic fields on excitations about the superconducting state in the model. The electrically-charged Dirac ferm

S. Carlip

The dominant topologies in the Euclidean path integral for quantum gravity differ sharply according on the sign of the cosmological constant. For $Λ>0$, saddle points can occur only for topologies with vanishing first Betti number and finite fundamental group. For $Λ<0$, on the other hand, the path integral is dominated by topologies with extremely complicat

L. Brücher, J. Franzkowski, D. Kreimer

The aim of XLOOPS is to calculate one-particle irreducible Feynman diagrams with one or two closed loops for arbitrary processes in the Standard model of particles and related theories. Up to now this aim is realized for all one-loop diagrams with at most three external lines and for two-loop diagrams with two external lines.

Jayme De Luca

We study the linear stability of a circular orbit in a two-electron atom, with the inclusion of retardation and self-interaction effects. We calculate all the eigenvalues of the linear stability of the circular orbit, expanded up to third order in (v/c). We discuss how the linear stability results can be used to construct a resonant normal form constant of m

E. Elizalde, Yu. I. Shil&#39;nov, V. V. Chitov

An investigation of the Nambu-Jona-Lasino model with external constant electric and weak gravitational fields is carried out in three- and four- dimensional spacetimes. The effective potential of the composite bifermionic fields is calculated keeping terms linear in the curvature, while the electric field effect is treated exactly by means of the proper- tim

Harold W. Fearing

For nearly fifty years theoretical and experimental efforts in nucleon-nucleon bremsstrahlung (NN$γ$) have been devoted to measuring off-shell amplitudes and distinguishing among various NN potentials on the basis of their off-shell behavior. New experiments are underway, designed specifically to attain kinematics further off shell than in the past, and thus

A. Leike

This lecture contains a pedagogical approach to the description of Z&#39; physics in the formalism of form factors. Usually, only electroweak corrections are described by form factors, which modify the Weinberg angle and the overall normalization. It is demonstrated how this formalism can be extended to include different Born contributions. In the second par

Krzysztof Gawedzki, Pascal Tran-Ngoc-Bich

We revisit the Hitchin integrable system whose phase space is the bundle cotangent to the moduli space $N$ of holomorphic $SL_2$-bundles over a smooth complex curve of genus two. $N$ may be identified with the 3-dimensional projective space of theta functions of the second order, We prove that the Hitchin system on $T^*N$ possesses a remarkable symmetry: it

Gregory Moore

This is a summary of a review talk at the Trieste conference on duality symmetries in string theory, April 1997. We review some work that has been done on the relation of BPS states, automorphic forms and the geometry of the quantum ground states of string compactifications with extended supersymmetry, emphasizing the (hypothetically) central role of BPS alg

B. L. Hu, Alpan Raval

Mesoscopic physics deals with three fundamental issues: quantum coherence, fluctuations and correlations. Here we analyze these issues for atom optics, using a simplified model of an assembly of atoms (or detectors, which are particles with some internal degree of freedom) moving in arbitrary trajectories in a quantum field. Employing the influence functiona

Pascal Salières, Anne L&#39;Huillier, Philippe Antoine, Maciej Lewenstein

We apply the theory of high-order harmonic generation by low-frequency laser fields in the strong field approximation to the study of the spatial and temporal coherence properties of the harmonics. We discuss the role of dynamically induced phases of the atomic polarization in determining the optimal phase matching conditions and angular distributions of har

Jeong-Young Ji, Kwang-Sup Soh, Rong-Gen Cai, Sang Pyo Kim

We consider classical and quantum electromagnetic fields in a three-dimensional (3D) cavity and in a waveguide with oscillating boundaries of the frequency $Ω$. The photons created by the parametric resonance are distributed in the wave number space around $Ω/2 $ along the axis of the oscillation. When classical waves propagate along the waveguide in the one

Murray Gerstenhaber, Anthony Giaquinto

Boundary solutions to the quantum Yang-Baxter (qYB) equation are defined to be those in the boundary of (but not in) the variety of solutions to the ``modified&#39;&#39; qYB equation, the latter being analogous to the modified classical Yang-Baxter (cYB) equation. We construct, for a large class of solutions $r$ to the modified cYB equation, explicit ``bound

Susumu Okubo

We will derive both quaternion and octonion algebras as the Clebsch-Gordan algebras based upon the su(2) Lie algebra by considering angular momentum spaces of spin one and three. If we consider both spin 1 and 1/2 states, then the same method will lead to the Lie-super algebra osp(1,2). Also, the quantum generalization of the method is discussed on the basis

James P. M. Flude

The purpose of this paper is to provide definitions for, and proofs of, the asymptotic formulae given by Edmonds, which relate the 3j and 6j symbols to rotation matrices.

Abhinav Gupta, T. Padmanabhan

We study the electromagnetic fields of an arbitrarily moving charged particle and the radiation reaction on the charged particle using a novel approach. We first show that the fields of an arbitrarily moving charged particle in an inertial frame can be related in a simple manner to the fields of a uniformly accelerated charged particle in its rest frame. Sin

C. D. Roberts, M. A. Ivanov, Yu. L. Kalinovsky, P. Maris

A heavy-quark limit of the Dyson-Schwinger equations is introduced and used in an exploratory study of leptonic and semileptonic decays of heavy mesons. The application of this framework to heavy-to-light semileptonic decays, which require a good knowledge of light-quark propagation characteristics and light-meson bound state amplitudes, is illustrated.

P. Maris, C. D. Roberts

The quark Dyson-Schwinger equation shows that there are distinct differences between light and heavy quarks. The dynamical mass function of the light quarks is characterised by a sharp increase below 1 GeV, whereas the mass function of the heavy quarks is approximately constant in this infrared region. As a consequence, the heavy-meson masses increase linear

G. Baur, S. Typel, H. H. Wolter

Introduction Theory of electromagnetic excitation and dissociation (Inelastic scattering at high energies: one-photon exchange, semiclassical approach and Glauber theory; Higher order electromagnetic effects, small xi-approximation) Discussion of experimental results for nuclear structure Coulomb dissociation as a tool to measure radiative capture processes

S. K. Samaddar, J. N. De, S. Shlomo

In a finite temperature Thomas-Fermi theory, we construct caloric curves for finite nuclei enclosed in a freeze-out volume few times the normal nuclear volume, with and without inclusion of flow. Without flow, the caloric curve indicates a smooth liquid-gas phase transition whereas with flow, the transition may be very sharp. We discuss these results in the

Ovidiu Costin, Rodica Daniela Costin

We show that there exists a rational change of coordinates of Painlevé&#39;s P1 equation $y&#39;&#39;=6y^2+x$ and of the elliptic equation $y&#39;&#39;=6y^2$ after which these two equations become analytically equivalent in a region in the complex phase space where $y$ and $y&#39;$ are unbounded. The region of equivalence comprises all singularities of solut

Vipul Periwal, Oyvind Tafjord

The proposal of Dijkgraaf, Verlinde and Verlinde for the emergence of smooth strings from a supersymmetric U(N) Yang-Mills theory assumes that conjugacy classes in the symmetric group with a few long cycles dominate the dynamics about the infrared fixed point. It is shown that the average number of cycles in a conjugacy class of $S_{N}$ is bounded below by $

Wolfgang Lucha, Michael Moser

By imposing on the most general renormalizable quantum field theory the requirement of the absence of ultraviolet-divergent renormalizations of the physical parameters (masses and coupling constants) of the theory, finite quantum field theories in four space-time dimensions may be constructed. Famous prototypes of these form certain well-known classes of sup

Subir Ghosh

A new model for anyon is proposed, which exhibits the classical analogue of the quantum phenomenon - Zitterbewegung. The model is derived from existing spinning particle model and retains the essential features of anyon in the non-relativistic limit.

L. Alvero, J. C. Collins, M. Strikman, J. J. Whitmore

We present calculations of several pp scattering cross sections with potential applications at the LHC. Significantly large rates for momentum fraction, x, as low as 10^-7 are obtained, allowing for possible extraction of quark and gluon densities in the proton and nuclei down to these small x values provided a detector with good acceptance at maximal rapidi

Richard F. Lebed, Karl Schilcher

We use both old and new theoretical developments in QCD dispersion relation constraints on the scalar form factor in the decay K --> πl ν_l to obtain constraints on the strange quark mass. The perturbative QCD side of the calculation incorporates up to four-loop corrections, while the hadronic side uses a recently developed parameterization constructed expli

R. Akhoury, V. I. Zakharov

We discuss non perturbative corrections to the Coulomb-like potential of heavy quarks at short distances. We consider both the standard framework provided by infrared renormalons and the assumption that confinement does not allow weak fields to penetrate the vacuum. In the former case the leading correction at short distances turns out to be quadratic in r f

R. Peschanski

Using the dipole picture describing the $1/N_C$ limit of QCD at small $x$ and the conformal invariance properties of the BFKL kernel in transverse coordinate space, we show that the 1->p dipole densities can be expressed in terms of dual Shapiro-Virasoro amplitudes B_{2p+2} and their generalization including non-zero conformal spins. We discuss the possibili

M. Genovese, J. -M. Richard, B. Silvestre-Brac, K. Varga

We study electromagnetic mass splittings of charmed baryons. We point out discrepancies among theoretical predictions in non-relativistic potential models. None of them seems supported by experimental data. A new calculation is presented.

A. Niégawa

This is a comprehensive review on the perturbative hot QCD including the recent developments. The main body of the review is concentrated upon dealing with physical quantities like reaction rates. Contents: \S1. Introduction, \S2. Perturbative thermal field theory: Feynman rules, \S3. Reaction-rate formula, \S4. Hard-thermal-loop resummation scheme in hot QC

K. -I. Izawa

We consider an inflationary universe scenario with multiple stages of inflation. The primary inflation, which may start at the Planck epoch, is followed by secondary inflations, which include the cosmological inflation that causes the primordial density fluctuations of our universe. We point out that an initial condition for a secondary inflation is naturall

Kang Young Lee

We explore the nonuniversal interaction effects in terms of the precision variables epsilons with the recent LEP data reported by the Electroweak Working Group. The epsilon variables with the nonuniversal interactions are calculated and constrained by the experimental ellipses in the $ε_1$--$ε_b$, $ε_2$--$ε_b$, and $ε_3$--$ε_b$ planes. We find that the new d

Sunil Mukhi

At the present time, string theory (and its generalizations) remain relatively abstruse subjects to the particle phenomenologist and experimentalist. Yet, striking developments of the last two years offer hope that a fundamental non-perturbative formulation of this theory will be found, and that this formulation will permit us to make contact with supersymme

Herbert Neuberger

A truncation of the overlap (domain wall fermions) is studied and a criterion for reliability of the approximation is obtained by comparison to the exact overlap formula describing massless quarks. We also present a truncated version of regularized, pure gauge, supersymmetric models. The mechanism for generating almost masslessness is shown to be a generaliz

Hartmut Wittig

The lattice method for the calculation of weak decay amplitudes of heavy quark systems is introduced. Results for leptonic and semi-leptonic decays of heavy mesons and $B-\bar{B}$ mixing are reviewed.

William S. Brower, Hans P. Paar

We introduce a new method for selecting exclusive semileptonic charmless B-decays in the presence of a large background. The method can be applied to charged and neutral B-mesons decaying into any exclusive neutral or charged hadronic final state. The method is designed for high luminosity $\eplemi$ colliders operating at the $Υ(4S)$. It employs an improved

Bruce Allen, Joseph D. Romano

We analyze the signal processing required for the optimal detection of a stochastic background of gravitational radiation using laser interferometric detectors. Starting with basic assumptions about the statistical properties of a stochastic gravity-wave background, we derive expressions for the optimal filter function and signal-to-noise ratio for the cross

H. C. Rosu

Following Grischuk and Sidorov [Phys. Rev. D 42 (1990) 3413] in putting the Bogolubov-Hawking coefficient of Schwarzschild black-holes in the squeezing perspective, we provide a short discussion of Schwarzschild black holes as radiometric standards

P. V. Moniz

In this report we advance the current repertoire of quantum cosmological models to incorporate inhomogenous field modes in a supersymmetric manner. In particular, we introduce perturbations about a supersymmetric FRW model. A quantum state of our model has properties typical of the no-boundary (Hartle--Hawking) proposal. This solution may then lead to a scal

Vicente Muñoz

We give a presentation for the Floer cohomology ring $HF^*(Σ\times S^1)$, where $Σ$ is a Riemann surface of genus bigger than one, which coincides with the conjectural presentation for the quantum cohomology ring of the moduli space of flat SO(3)-connections of odd degree over $Σ$. We study the spectrum of the action of the homology of $Σ$ on the Floer cohom

E. V. Ferapontov

We introduce two basic invariant forms which define generic surface in 3-space uniquely up to Lie sphere equivalence. Two particularly interesting classes of surfaces associated with these invariants are considered, namely, the Lie-minimal surfaces and the diagonally-cyclidic surfaces. For diagonally-cyclidic surfaces we derive the stationary modified Veselo

S. G. den Hartog, B. J. van Wees, Yu. V. Nazarov, T. M. Klapwijk

We have investigated the bias-voltage dependence of the phase-dependent differential resistance of a disordered T-shaped 2-dimensional electron gas coupled to two superconducting terminals. The resistance oscillations first increase upon lowering the energy. For bias voltages below the Thouless energy, the resistance oscillations are suppressed and disappear

Peter F. Arndt, Thomas Heinzel

We investigate time-dependent properties of a single particle model in which a random walker moves on a triangle and is subjected to non-local boundary conditions. This model exhibits spontaneous breaking of a Z_2 symmetry. The reduced size of the configuration space (compared to related many-particle models that also show spontaneous symmetry breaking) allo

Norbert Elstner, Rajiv. R. P. Singh

By combining conventional finite-temperature many-body perturbation theory with cluster expansions, we develop a systematic method to carry out high order arbitrary temperature perturbative calculations on the computer. The method is well suited to studying the thermodynamic properties of quantum disordered and quantum critical phases at finite temperatures.

S. G. den Hartog, B. J. van Wees

Recently, Hecker et al. [Phys. Rev. Lett. 79, 1547 (1997)] experimentally studied magnetoconductance fluctuations in a mesoscopic Au wire connected to a superconducting Nb contact. They claimed to have observed an enhancement of the rms magnitude of these conductance fluctuations in the superconducting state (rms(Gns)) relative to that in the normal state (r

H. Westfahl, A. O. Caldeira, D. Baeriswyl, E. Miranda

The absorption and emission spectra of transitions between a localized level and a two-dimensional electron gas, subjected to a weak magnetic field, are calculated analytically. Adopting the Landau level bosonization technique developed in previous papers, we find an exact expression for the relative intensities of spectral lines. Their envelope function, go

S. G. den Hartog, S. J. van der Molen, B. J. van Wees, T. M. Klapwijk

The Coulomb interaction contribution to the conductance is investigated in a phase-coherent disordered 2-dimensional electron gas, which resistance can be varied by an overall gate electrode. Its magnitude of dGeei=-0.3 e^2/h is obtained by applying a bias voltage to suppress the Coulomb anomaly. In contrast to theoretical predictions, dGeei is suppressed by

Alexander Kuzmany, Herbert Spohn

We consider the two-dimensional Lorentz gas with Poisson distributed hard disk scatterers and a constant magnetic field perpendicular to the plane of motion. The velocity autocorrelation is computed numerically over the full range of densities and magnetic fields with particular attention to the percolation threshold between hopping transport and pure edge c

S. Scarpetta, A. de Candia, A. Coniglio

The dynamical properties of the site frustrated percolation model are investigated and compared with those of glass forming liquids. When the density of the particles on the lattice becomes high enough, the dynamics of the model becomes very slow, due to geometrical constraints, and rearrangement on large scales is needed to allow relaxation. The autocorrela

S. A. van Langen, P. G. Silvestrov, C. W. J. Beenakker

We show (analytically and by numerical simulation) that the zero-temperature limit of the distribution of the thermopower S of a one-dimensional disordered wire in the localized regime is a Lorentzian, with a disorder-independent width of 4 pi^3 k_B^2 T/3eΔ(where T is the temperature and Δthe mean level spacing). Upon raising the temperature the distribution

A. Fierro, A. de Candia, A. Coniglio

We study the dynamical properties of the fully frustrated Ising model. Due to the absence of disorder the model, contrary to spin glass, does not exhibit any Griffiths phase, which has been associated to non-exponential relaxation dynamics. Nevertheless we find numerically that the model exhibits a stretched exponential behavior below a temperature T_p corre

R. van Zon, H. van Beijeren, Ch. Dellago

The largest Lyapunov exponent $λ^+$ for a dilute gas with short range interactions in equilibrium is studied by a mapping to a clock model, in which every particle carries a watch, with a discrete time that is advanced at collisions. This model has a propagating front solution with a speed that determines $λ^+$, for which we find a density dependence as pred

P. Rosati, R. Della Ceca, C. Norman, R. Giacconi

We present the X-ray Luminosity Function (XLF) of the ROSAT Deep Cluster Survey (RDCS) sample over the redshift range 0.05-0.8. Our results are derived from a complete flux-limited subsample of 70 galaxy clusters, representing the brightest half of the total sample, which have been spectroscopically identified down to the flux limit of 4*10^{-14} erg/cm^2/s

M. Ester Giannuzzo, Marco Mignoli, Giovanna M. Stirpe, Andrea Comastri

We present part of the results from a spectroscopic monitoring programme on a sample of AGNs, relative to Narrow Line Seyfert 1 Galaxies: following the idea that Balmer-line variability can help discriminate among the possible models for these objects, and on the basis of a first monitoring project with long time-scales, we now add to the previous database n

Hanadi M. AbdelSalam, Prasenjit Saha, Liliya L. R. Williams

We propose a new technique to reconstruct non-parametrically the projected mass distribution of galaxy clusters from their gravitational lens effect on background galaxies. The beauty of our technique, is that it combines information from multiple imaging (strong lensing) and shear (weak lensing) as linear constraints on the projected mass distribution. More

Daniel Proga, James M. Stone, Janet E. Drew

We study the 2-D, time-dependent hydrodynamics of radiation-driven winds from accretion disks in which the radiation force is mediated by spectral lines. If the dominant contribution to the total radiation field comes from the disk, then we find the outflow is intrinsically unsteady and characterised by large amplitude velocity and density changes. Both infa

J. Christopher Clemens, I. Neill Reid, John E. Gizis, M. Sean O&#39;Brien

The color-magnitude diagram of the lower main sequence, as measured from a volume-limited sample of nearby stars, shows an abrupt downward jump between Mv = 12 and 13. This jump indicates that the observed mass-radius relationship steepens between 0.3 and 0.2 solar masses, but theoretical models show no such effect. It is difficult to isolate the source of t

Jens Schmalzing

Minkowski functionals have recently been introduced into cosmology as novel tools for studying the large-scale distribution of matter in the Universe. We present a brief overview of the method, including its mathematical foundations as well as some completed and upcoming applications.

C. R. Benn, M. Vigotti, R. Carballo, J. I. Gonzalez-Serrano

Webster et al (1995) claimed that up to 80% of QSOs may be obscured by dust. They inferred the presence of this dust from the remarkably broad range of B-K optical-infrared colours of a sample of flat-spectrum PKS radio QSOs. If such dust is typical of QSOs, it will have rendered invisible most of those which would otherwise been have detected by optical sur

M. R. Zapatero Osorio, R. Rebolo, E. L. Martin, G. Basri

We present intermediate and low resolution optical spectroscopy (650-915 nm) of seven faint, very red objects (20 > I >= 17.8, I-Z >= 0.5) discovered in a CCD-based IZ survey covering an area of 1 sq. deg in the central region of the Pleiades open cluster. The observed spectra show that these objects are very cool dwarfs, having spectral types in the range M

Edward M. Sion, F. H. Cheng, Paula Szkody, Warren Sparks

We obtained Hubble GHRS medium resolution (G160M grating) phase-resolved spectroscopic observations of the prototype dwarf nova U Geminorum during dwarf nova quiescence, 13 days and 61 days following the end of a narrow outburst. The spectral wavelength ranges were centered upon three different line regions: N V (1238Å, 1242Å), Si III (1300Å) and He II (1640

D. Grupe, K. Beuermann, H. -C. Thomas, K. Mannheim

We present results of an infrared-to-X-ray study of 76 bright soft X-ray selected Seyfert galaxies discovered in the ROSAT All-Sky Survey. These objects are characterized by steep X-ray spectra in the 0.2-2.0 keV bandpass with power law energy spectral indices in the range of 1.3 to 8 and a lack of internal absorption by neutral hydrogen. Our sample selectio

W. Hofmann

The stereoscopic reconstruction of air showers viewed by multiple imaging atmospheric Cherenkov telescopes (IACTs) allows a more precise reconstruction of shower energies and hence an improved determination of energy spectra. Reconstruction techniques and in particular new systematic checks are discussed on the basis of the large sample of gamma-rays from Mk

Bodo L. Ziegler, Ralf Bender

New observations of galaxies in the direction of the Leo group, which were classified as being candidates for M32-like dwarf galaxies by Ferguson & Sandage (1990), show that these galaxies are normal elliptical galaxies at redshifts between z=0.02 and z=0.06. This result adds further evidence that the faint end of the luminosity function of elliptical galaxi

Arlin Crotts

We present results from Keck HIRES, KPNO 4m/RC Spec and HST FOS spectra of a low-redshift, close QSO pair and a close, higher-redshift QSO triplet in order to explore the size evolution, shape and clustering of Ly alpha absorbers. The results we highlight here indicate that there is no strong evidence for evolution of Ly $α$ cloud size with redshift, that st

Arlin Crotts

The volume around the SN 1987A contains a variety of structures, including but certainly not limited to the three-ring nebula glowing in recombination lines. Many of these structures are revealed by light echoes, hence have been mapped in three dimensions by our optical imaging monitoring of the field around the SN. The three rings are part of a bipolar nebu

Enrique Arrondo

We classify those smooth (n-1)-folds in G(1,n) for which the restriction of the rank-(n-1) universal bundle has more than n+1 independent sections. As an aplication, we classify also those (n-1)-folds for which that bundle splits.

Rychard J. Bouwens, Tom Broadhurst, Joseph Silk

We present a model-independent method of quantifying galaxy evolution in high- resolution images, which we apply to the Hubble Deep Field (HDF). Our procedure is to k-correct the pixels belonging to the images of a complete set of bright galaxies and then to replicate each galaxy image to higher redshift by the product of its space density, 1/V_{max}, and th

C. Ahn, C. K. You

In this paper we compute the most general nondiagonal reflection matrices of the RSOS/SOS models and hard hexagon model using the boundary Yang-Baxter equations. We find new one-parameter family of reflection matrices for the RSOS model in addition to the previous result without any parameter. We also find three classes of reflection matrices for the SOS mod

Aephraim M. Steinberg

It is a commonplace to claim that quantum mechanics supports the old idea that a tree falling in a forest makes no sound unless there is a listener present. In fact, this conclusion is far from obvious. Furthermore, if a tunnelling particle is observed in the barrier region, it collapses to a state in which it is no longer tunnelling. Does this imply that wh

O. Elgaroy, M. Hjorth-Jensen

We discuss various properties of singlet S pairing in neutron and nuclear matter in terms of the bare nuclon-nucleon interaction. Relations to the NN phase shifts are discussed, as well as various properties of the BCS wave function and the coherence length for fermion superfluids in infinite matter.

K. Selivanov

An explicit self-dual classical solution of the type of perturbiner in Yang-Mills theory interacting with gravity is obtained. This allows one to describe the tree self-dual gluonic form-factors including any number of positive-helicity gravitons in addition to the positive helicity gluons.