February 1997 arXiv papers — page 9

M. M. Fogler, A. Yu. Dobin, V. I. Perel, B. I. Shklovskii

We study a two-dimensional motion of a charged particle in a weak random potential and a perpendicular magnetic field. The correlation length of the potential is assumed to be much larger than the de Broglie wavelength. Under such conditions, the motion on not too large length scales is described by classical equations of motion. We show that the phase-space

Patrick A. Lee, Xiao-Gang Wen

There is increasing experimental evidence that the superconducting energy gap $Δ_0$ in the underdoped cuprates is independent of doping concentration $x$ while the superfluid density is linear in $x$. We show that under these conditions, thermal excitation of the quasiparticles is very effective in destroying the superconducting state, so that $T_c$ is propo

J. M. Tranquada

Recent neutron diffraction studies have yielded evidence that, in a particular cuprate family, holes doped into the CuO(2) planes segregate into stripes that separate antiferromagnetic domains. Here it is shown that such a picture provides a quantitatively consistent interpretation of the spin fluctuations measured by neutron scattering in La(1.85)Sr(0.15)Cu

Reinhold Egger, Hermann Grabert, Ulrich Weiss

The destruction of quantum coherence by environmental influences is investigated taking the damped harmonic oscillator and the dissipative two-state system as prototypical examples. It is shown that the location of the coherent-incoherent transition depends to a large degree on the dynamical quantity under consideration.

B. A. Ivanov, A. K. Kolezhuk

In presence of a strong external magnetic field the dynamics of solitons in a one-dimensional easy-plane Heisenberg antiferromagnet exhibits a number of peculiarities. Dynamics of internal soliton degrees of freedom is essentially quantum, and they are strongly coupled to the "translational" mode of soliton movement. These peculiarities lead to consi

Thomas Guhr, Axel Mueller-Groeling

Motivated by questions of present interest in nuclear and condensed matter physics we consider the superposition of a diagonal matrix with independent random entries and a GUE. The relative strength of the two contributions is determined by a parameter $λ$ suitably defined on the unfolded scale. Using results for the spectral two-point correlator of this mod

C. Castellani, C. Di Castro, M. Grilli

A scenario is presented, in which the presence of a quantum critical point due to formation of incommensurate charge density waves accounts for the basic features of the high temperature superconducting cuprates, both in the normal and in the superconducting states. Specifically, the singular interaction arising close to this charge-driven quantum critical p

Gilles Poirot

We develop a polymer expansion with large/small field conditions for the mean resolvent of a weakly disordered system. Then we show that we can apply our result to a two-dimensional model, for energies outside the unperturbed spectrum or in the free spectrum provided the potential has an infra-red cut-off. This leads to an asymptotic expansion for the densit

N. Q. Balaban, U. Meirav, Hadas Shtrikman, V. Umansky

We report phase sensitive measurements of microwave propagation through a high mobility two dimensional electron gas subjected to a perpendicular magnetic field. Two types of configurations were used, one that allows all wave vectors q, and one that selects only specific q values. The spectrum of edge excitations was studied over a broad frequency span, whic

M. Markosova, M. H. Jensen, K. B. Lauritsen, K. Sneppen

We study transport properties in a slowly driven diffusive system where the transport is externally controlled by a parameter $p$. Three types of behavior are found: For $p<p&#39;$ the system is not conducting at all. For intermediate $p$ a finite fraction of the external excitations propagate through the system. Third, in the regime $p>p_c$ the system becom

Serge Galam, Alain Mauger

In a recent paper, we have reported a universal power law for both site and bond percolation thresholds for any lattice of cubic symmetry. Extension to anisotropic lattices is discussed.

Michal Rokni, Y. Levinson

A recipe for the generalization of the Boltzmann equation to a quantum kinetic equation is given for cases in which only level shift and broadening are considered, while coherence phenomena can be neglected. We also consider a specific problem: Hot luminescence from a quantum wire near the threshold for optical phonon emission. The problem is first discussed

A. E. Alahverdian, N. S. Ananikian, S. K. Dallakian

We investigate complex temperature singularities of the three-site interacting Ising model on the Husimi tree in the presentce of magnetic field. We show that at certain magnetic field these singularities lie at a dense set and as a consequence the phase transition condensation take place.

W. McRae, O. Sushkov

The one dimensional spin 1/2 Heisenberg antiferromagnet is considered using a simple quasiparticle picture - an interacting Fermi gas of kinks. Using this picture the low temperature heat capacity, and the magnetic susceptibility with logarithmic field and temperature corrections are derived. The results obtained are in agreement with previous computations a

T. K. Ng, C. M. Varma

The flux-line lattice in the compound $ErNi_2B_2C$, which has a tendency to ferromagnetic order in the a-b plane is studied with external magnetic field direction close to the c-axis. We show the existence of an instability where the direction of flux-lines spontaneously tilts away from that of the applied field near the onset of ferromagnetic order. The enh

Chengxiang Zhai

Information Retrieval (IR) is an important application area of Natural Language Processing (NLP) where one encounters the genuine challenge of processing large quantities of unrestricted natural language text. While much effort has been made to apply NLP techniques to IR, very few NLP techniques have been evaluated on a document collection larger than severa

Ted Pedersen, Rebecca Bruce, Janyce Wiebe

Statistical models of word-sense disambiguation are often based on a small number of contextual features or on a model that is assumed to characterize the interactions among a set of features. Model selection is presented as an alternative to these approaches, where a sequential search of possible models is conducted in order to find the model that best char

T. Dittrich, B. Mehlig, H. Schanz, U. Smilansky

We consider a quasi one-dimensional chain of N chaotic scattering elements with periodic boundary conditions. The classical dynamics of this system is dominated by diffusion. The quantum theory, on the other hand, depends crucially on whether the chain is disordered or invariant under lattice translations. In the disordered case, the spectrum is dominated by

R. P. van der Marel, P. T. de Zeeuw, H. W. Rix, G. D. Quinlan

Massive black holes are thought to reside at the centres of many galaxies, where they power quasars and active galactic nuclei. But most galaxies are quiescent, indicating that any central massive black hole present will be starved of fuel and therefore detectable only through its gravitational influence on the motions of the surrounding stars. M32 is a near

Sarbani Basu, W. J. Chaplin, J. Christensen-Dalsgaard, Y. Elsworth

Observations of the Sun with the LOWL instrument provide a homogeneous set of solar p-mode frequencies from low to intermediate degree which allows one to determine the structure of much of the solar interior avoiding systematic errors that are introduced when different data sets are combined, i.e., principally the effects of solar cycle changes on the frequ

J. D. Monnier, M. Bester, W. C. Danchi, M. A. Johnson

Measurements by the U.C. Berkeley Infrared Spatial Interferometer at 11.15 micron have yielded strong evidence for multiple dust shells and/or significant asymmetric dust emission around NML Cyg. New observations reported also include multiple 8-13 micron spectra taken from 1994-1995 and N band (10.2 micron) photometry from 1980-1992. These and past measurem

M. Brüggen, D. O. Gough

There has been some controversy over the expression for the so-called `interaction energy&#39; due to screening of charged particles in a plasma. Even in the relatively simple case of weak screening, first discussed in the context of astrophysical plasmas by Salpeter (1954), there is disagreement. In particular, Shaviv and Shaviv (1996) have claimed recently

N. Pirzkal, E. J. Spillar, H. M. Dyck

We present the result of IR observations in the K band of 39 bright AeBe stars in the northern hemisphere. Using the shift-and-add technique, we were able to detect nearby objects as close as 0.4&#39;&#39; from the primary star. We found 9 stars that have one or more companions. Adjusting for completeness, we compute that the AeBe star binary rate is 85%. Th

M. E. J. Newman

A number of authors have in recent years proposed that the processes of macroevolution may give rise to self-organized critical phenomena which could have a significant effect on the dynamics of ecosystems. In particular it has been suggested that mass extinction may arise through a purely biotic mechanism as the result of so-called coevolutionary avalanches

Uwe Müller, Gerhard Weigt

The gauged SL(2,R)/U(1) Wess-Zumino-Novikov-Witten (WZNW) model is classically an integrable conformal field theory. We have found a Lax pair representation for the non-linear equations of motion, and a B&#34;acklund transformation. A second-order differential equation of the Gelfand-Dikii type defines the Poisson bracket structure of the theory, and its fun

Augusto Sagnotti

The perturbative analysis of models of open and closed superstrings presents a number of surprises. For instance, variable numbers of antisymmetric tensors ensure their consistency via generalized Green-Schwarz cancellations and a novel type of singularity occurs in their moduli spaces. All these features are related, in one way or another, to the presence o

David Heyrovsky, Abraham Loeb

We present an efficient method for computing lightcurves of an elliptical source which is microlensed by a point mass. The amplification of an extended source involves a two-dimensional integral over its surface brightness distribution. We show that for a general surface brightness profile with an elliptical symmetry, this integral can be reduced to one dime

R. Shankar, Ganpathy Murthy

We present a Chern-Simons theory of the fractional quantum Hall effect in which flux attachment is followed by a transformation that effectively attaches the correlation holes. We extract the correlated wavefunctions, compute the drift and cyclotron currents (due to inhomogeneous density), exhibit the Read operator, and operators that create quasi-particles

P. M. Ferreira, I. Jack, D. R. T. Jones

We present calculations of the leading and O(1/N) terms in a large-N expansion of the β-functions for various supersymmetric theories: a Wess-Zumino model, supersymmetric QED and a non-abelian supersymmetric gauge theory. In all cases N is the number of a class of the chiral superfields in the theory.

M. A. Semenov-Tian-Shansky, A. V. Sevostyanov

The paper is the sequel to q-alg/9704011. We extend the Drinfeld-Sokolov reduction procedure to q-difference operators associated with arbitrary semisimple Lie algebras. This leads to a new elliptic deformation of the Lie bialgebra structure on the associated loop algebra. The related classical r-matrix is explicitly described in terms of the Coxeter transfo

G. E. Volovik

In the d-wave superconductors the electronic entropy associated with an isolated vortex diverges logarithmically with the size of the system even at low temperatures. In the vortex array the entropy per vortex per layer, $S_V$, is much larger than $k_B$ and depends on the distribution of the velocity field $v_s$ around the vortex. If there is a first order t

Yu Shi

Spontaneous symmetry breaking originats in quantum mechanical measurement of the relevant observable defining the physical situation, order parameter is the average of this observable. A modification is made on the random-phase postulate validating the ensemble description. Off-diagonal long-range order, macroscopic wavefunction and interference effects in m

D. A. Rasheed

The Zeroth and First Laws of Black Hole Mechanics are derived in the context of non-linear electrodynamics coupled to gravity. The Zeroth Law is shown to hold quite generally even if the Dominant Energy Condition is violated. The derivation of the First Law is discussed in detail for general matter fields coupled to gravity. The general mass variation formul

V. Vedral, M. B. Plenio, M. A. Rippin, P. L. Knight

We present conditions every measure of entanglement has to satisfy and construct a whole class of &#39;good&#39; entanglement measures. The generalization of our class of entanglement measures to more than two particles is straightforward. We present a measure which has a statistical operational basis that might enable experimental determination of the quant

Vladimir Hinich

We define closed model category structures on different categories connected to the world of operad algebras over the category C(k) of (unbounded) complexes of k-modules: on the category of operads, on the category of algebras over a fixed operad, on the category of modules over a fixed operad algebra. In Sections 2 - 6 we define the necessary structures and

Peilong Chen, Jorge Vinals

We present a systematic nonlinear theory of pattern selection for parametric surface waves (Faraday waves), not restricted to fluids of low viscosity. A standing wave amplitude equation is derived from the Navier-Stokes equations that is of gradient form. The associated Lyapunov function is calculated for different regular patterns to determine the selected

Thomas D. Cohen, Wojciech Broniowski

Infinite sets of sum rules involving the excitations of infinite nuclear matter are derived using only completeness, the current algebra implicit in QCD, and relativistic covariance. The sum rules can be used for isospin-asymmetric nuclear matter, including neutron matter. They relate the chiral condensate and the isospin density to weighted sums over states

R. Cenni, F. Conte, P. Saracco

The splitting between the charge-longitudinal and spin-transverse responses is explained in a model whose inputs are the effective interactions in the particle-hole channels in the frame of the first order boson loop expansion. It is shown that the interplay between $ω$-meson exchange and box diagrams (two-meson exchange with simultaneous excitation of one o

J. A. Templon, B. A. Raue, L. C. Bland, K. Murphy

The inclusive 12C(p,p&#39;) and exclusive 12C(p,p&#39;X) reactions have been studied with a beam energy of 156 MeV and for X = p and alpha. The study focuses on the (p,p&#39;X) reaction mechanism and on the structure of 12C just above the particle-emission threshold, 14 < E_x < 28 MeV. Cross sections were simultaneously measured for all three reactions. The

Miklós Bóna

Solving the first nonmonotonic, longer-than-three instance of a classic enumeration problem, we obtain the generating function $H(x)$ of all 1342-avoiding permutations of length $n$ as well as an {\em exact} formula for their number $S_n(1342)$. While achieving this, we bijectively prove that the number of indecomposable 1342-avoiding permutations of length

Michael E. Peskin

These lectures provide an introduction to the behavior of strongly-coupled supersymmetric gauge theories. After a discussion of the effective Lagrangian in nonsupersymmetric and supersymmetric field theories, I analyze the qualitative behavior of the simplest illustrative models. These include supersymmetric QCD for $N_f < N_c$, in which the superpotential i

D. Fliegner, P. Haberl, M. G. Schmidt, C. Schubert

Higher order coefficients of the inverse mass expansion of one-loop effective actions are obtained from a one-dimensional path integral representation. For the case of a massive scalar loop in the background of both a scalar potential and a (non Abelian) gauge field explicit results to $O(T^5)$ in the proper time parameter are presented.

Stephen Pinsky

QCD without matter and quantized on a light-cone spatial cylinder is considered. For the gauge group SU(N) the theory has N-1 quantum mechanical degrees of freedom, which describe the color fux that circulates around the the spatial cylinder. In 1+1 dimensions this problem can be solved analytically. I use the solution for SU(2) to compute the Wilson loop ph

Z. Popowicz

We describe how it is possible to introduce the interaction between superconformal fields of the same conformal dimensions. In the classical case such construction can be used to the construction of the Hirota - Satsuma equation. We construct supersymmetric Poisson tensor for such fields, which generates a new class of Hamiltonin systems. We found Lax repres

Richard Battye, Paul Sutcliffe

We present candidates for the global minimum energy solitons of charge one to nine in the Skyrme model, generated using sophisticated numerical algorithms. Assuming the Skyrme model accurately represents the low energy limit of QCD, these configurations correspond to the classical nuclear ground states of the light elements. The solitons found are particular

Leith Cooper, Ian I. Kogan, Richard J. Szabo

We show how the spectral flow between the Neveu-Schwarz and Ramond sectors of N=2 superconformal field theories can be described in three dimensions in terms of the propagation of charged particles coupled to a a Chern-Simons gauge theory. Quantum mechanical mixing between the degenerate Chern-Simons vacua interpolates between the different boundary conditio

Francesca M. Borzumati

We study the Minimal Messenger Model, a minimal version of Gauge Mediated Supersymmetry Breaking models. Boundary conditions equal to zero for trilinear and bilinear soft parameters at the messenger scale make this model free from the supersymmetric CP problem and extremely predictive. These boundary conditions and the vicinity of the messenger scale to the

Raman Sundrum

The existence of hadronic string is derived as a consequence of confinement in QCD. A state of ``stretched glue&#39;&#39;, created by a Polyakov loop operator, is shown to have translational zero-modes which are stringy degrees of freedom. These modes are described by an effective string theory, valid for world- sheets which are locally flat on length scales

K. Whisnant, Jin Min Yang, Bing-Lin Young, X. Zhang

We list all possible dimension-six CP-conserving $SU_c(3)\times SU_L(2) \times U_Y(1)$ invariant operators involving the third-family quarks which could be generated by new physics at a higher scale. Expressions for these operators after electroweak gauge symmetry breaking and the induced effective couplings $Wt\bar b$, $Xb\bar b$ and $Xt\bar t$ $( X=Z,γ,g,H

Francisco Guerrero, Joaquim Prades

We study the kaon polarizabilities in the framework of Chiral Perturbation Theory to order $p^4$. For the neutral kaon we find that them vanish and they have the first non-zero contribution to order $p^6$. We also emphasize the theoretical potential of an eventual measuremnet of the kaon polarizabilities, in particular of the neutral kaon ones.

Ll. Ametller, J. Bijnens, A. Bramon, P. Talavera

The process eta -> pi0 pi0 gamma gamma is discussed in Chiral Perturbation Theory (ChPT) extending two recent analyses. Special attention is devoted to one-loop corrections, eta-eta&#39; mixing effects and vector-meson dominance of ChPT counter-terms. The less interesting eta -> pi^+ pi^- gamma gamma transition is briefly discussed too.

Igor V. Terekhov

We consider the effects of a light gluino on the dijet angular distributions in p - pbar collisions at sqrt(s)=1800 GeV. We show that the slower running of alpha_s and the production q qbar, g g -> Gino Gino do not significantly alter the expected angular distributions. On the other hand, single U, D squark production q g -> Q Gino with subsequent Q -> q g r

C. Glenn Boyd, Martin J. Savage

We give a pedagogical discussion of the physics underlying dispersion relation-derived parameterizations of form factors describing B -> pi l nu and B -> D l nu. Moments of the dispersion relations are shown to provide substantially tighter constraints on the f_+ (t) form factor describing B -> pi l nu than the unweighted dispersion relation alone. Heavy qua

G. Damm, W. Kerler

We investigate SU(2) lattice gauge theory in four dimensions in the maximally abelian projection. Studying the effects on different lattice sizes we show that the deconfinement transition of the fields and the percolation transition of the monopole currents in the three space dimensions are precisely related. To arrive properly at this result the uses of a m

Robert M. Wald

We review the remarkable relationship between the laws of black hole mechanics and the ordinary laws of thermodynamics. It is emphasized that - in analogy with the laws of thermodynamics - the validity the laws of black hole mechanics does not appear to depend upon the details of the underlying dynamical theory (i.e., upon the particular field equations of g

Domenico Giulini

Within the Hamiltonian formulation of diffeomorphism invariant theories we address the problem of how to determine and how to reduce diffeomorphisms outside the identity component.

Pietro Menotti, Pier Paolo Peirano

A summary is given of recent exact results concerning the functional integration measure in Regge gravity.

Chi-Keung Ng

In this paper, we will give a natural definition for morphisms between multiplicative unitaries. We will then discuss some equivalences of this definition and some interesting properties of them. Moreover, we will define normal sub-multiplicative unitaries for multiplicative unitaries of discrete type and prove an imprimitivity type theorem for discrete mult

A. V. Gorbunov, G. F. Us

We study an infinite dimensional analysis with respect to the measure on Schwartz space of tempered distributions, corresponding to the distributional derivative of gamma process. Laguerre polynomials being orthogonal with respect to gamma noise measure turn out to be generalized Appell ones. This fact enables to generalize the white noise functional approac

Victor Nistor, Alan Weinstein, Ping Xu

We construct an algebra of pseudodifferential operators on each groupoid in a class that generalizes differentiable groupoids to allow manifolds with corners. We show that this construction encompasses many examples. The subalgebra of regularizing operators is identified with the smooth algebra of the groupoid, in the sense of non-commutative geometry. Symbo

Stefan Ivanov, Irina Petrova

It is proved that every locally conformal flat Riemannian manifold all of whose Jacobi operators have constant eigenvalues along every geodesic is with constant principal Ricci curvatures. A local classification (up to an isometry) of locally conformal flat Riemannian manifold with constant Ricci eigenvalues is given in dimensions 4,5,6,7 and 8. It is shown

G. Ayton, M. J. P. Gingras, G. N. Patey

In a recent letter [Phys. Rev. Lett. {\bf 75}, 2360 (1996)] we briefly discussed the existence and nature of ferroelectric order in positionally disordered dipolar materials. Here we report further results and give a complete description of our work. Simulations of randomly frozen and dynamically disordered dipolar soft spheres are used to study ferroelectri

D. S. Golubev, Jürgen König, Herbert Schoeller, Gerd Schön

We describe electron transport through small metallic grains with Coulomb blockade effects beyond the perturbative regime. For this purpose we study the real-time evolution of the reduced density matrix of the system. In the first part of the paper we present a diagrammatic expansion for not too high junction conductance, $h/4π^2e^2 R_t \lesssim 1$, in a bas

F. Lema, A. A. Aligia

Using the self-consistent Born approximation, and the corresponding wave function of the magnetic polaron, we calculate the quasiparticle weight corresponding to destruction of a real electron (in contrast to creation of a spinless holon), as a funtion of wave vector for one hole in a generalized $t-J$ model and the strong coupling limit of a generalized Hub

E. M. Conwell, M. W. Wu

The variation of current I with voltage V for poly(phenylene vinylene) and other polymer light-emitting diodes has been attributed to carriers tunneling into broad conduction and valence bands. In actuality the electrons and holes tunnel into polaron levels and transport is by hopping among these levels. We show that for small injection the I-V characteristi

Klaus Frahm, Axel Mueller-Groeling, Jean-Louis Pichard

We consider two models for a pair of interacting particles in a random potential: (i) two particles with a Hubbard interaction in arbitrary dimensions and (ii) a strongly bound pair in one dimension. Establishing suitable correpondences we demonstrate that both cases can be described in terms familiar from theories of noninteracting particles. In particular,

Sutapa Mukherji

We study the growth of a crystal in presence of a correlated disorder on the substrate. Using functional renormalization group, we show, for a long range disorder correlation, an initial decay of the KPZ type nonlinearity, though over a large length scale the behavior can be governed by the nonlinearity.

Klaus Frahm, Axel Mueller-Groeling

Employing techniques recently developed in the context of the Fokker--Planck approach to electron transport in disordered systems we calculate the conductance length correlation function $< δg(L) δg(L+ΔL) >$ for quasi 1d wires. Our result is valid for arbitrary lengths L and $ΔL$. In the metallic limit the correlation function is given by a squared Lorentzia

P. Ruggerone, C. Ratsch, M. Scheffler

This chapter starts with a summary of the atomistic processes that occur during epitaxy. We then introduce density functional theory (DFT) and describe its implementation into state-of-the-art computations of complex processes in condensed matter physics and materials science. In particular we discuss how DFT can be used to calculate parameters of microscopi

C. Dalitz, E. H. de Groot

An explicit solution of the stationary one dimensional half-space boundary value problem for the linear Boltzmann equation is presented in the presence of an arbitrarily high constant external field. The collision kernel is assumed to be separable, which is also known as &#34;relaxation time approximation&#34;; the relaxation time may depend on the electron

K. B. Efetov

Quantum disordered problems with a direction (imaginary vector-potential) are discussed and mapped onto a supermatrix sigma-model. It is argued that the $0D$ version of the sigma-model may describe a broad class of phenomena that can be called directed quantum chaos. It is demonstrated by explicit calculations that these problems are equivalent to problems o

Axel Gross, Matthias Scheffler

According to the Heisenberg uncertainty principle of quantum mechanics, particles which are localized in space by a bounding potential must have a finite distribution of momenta. This leads, even in the lowest-possible energy state, to vibrations, and thus, to the so-called zero-point energy. For chemically bound hydrogen the zero-point energy can be quite s

H. Suderow, J. P. Brison, A. Huxley, J. Flouquet

We present new measurements of the thermal conductivity of UPt3 down to very low temperatures (16mK) and under magnetic fields (up to 4 T) which cover all the superconducting phases of UPt3. The measurements in zero field are compared with recent theoretical predictions for the thermal conductivity, which is dominated by impurity states at the lowest tempera

H. B. Chan, P. I. Glicofridis, R. C. Ashoori, M. L. Melloch

A new technique permits high fidelity measurement of the tunneling density of states (TDOS) of the two-dimensional electron gas. The obtained TDOS contains no distortions arising from low 2D in-plane conductivity and includes the contribution from localized tunneling sites. In a perpendicular magnetic field, a pseudogap develops in the TDOS at the Fermi leve

Stephan Busemann, Thierry Declerck, Abdel Kader Diagne, Luca Dini

Appointment scheduling is a problem faced daily by many individuals and organizations. Cooperating agent systems have been developed to partially automate this task. In order to extend the circle of participants as far as possible we advocate the use of natural language transmitted by e-mail. We describe COSMA, a fully implemented German language server for

H. Alt, H. -D. Graef, R. Hofferbert, H. Rehfeld

The spectral fluctuation properties of various two- and three-dimensional superconducting billiard systems are investigated by employing the correlation-hole method. It rests on the sensitivity of the spectral Fourier transform to long range correlations and is thus an alternative technique to study chaotic dynamics. First, we apply the method to the eigenfr

Craig B. Markwardt, Hakki B. Ogelman

ROSAT observations of the Vela pulsar and its surroundings revealed a collimated X-ray feature almost 45&#39; in length (Markwardt & Ogelman 1995), interpreted as the signature ``cocoon&#39;&#39; of a one-sided jet from the Vela pulsar. We report on a new ASCA observation of the Vela pulsar jet at its head, the point where the jet is believed to interact wit

C. von Montigny

We present the results of the multi-wavelength campaigns on 3C 273 in 1993-1995. During the observations in late 1993 this quasar showed an increase of its flux for energies greater equal 100 MeV from about 2.1 x 10^-7 photons/cm^2/s to approximately 5.6 x 10^-7 photons/cm^2/s during a radio outburst at 14.5, 22 and 37 GHz. However, no one-to-one correlation

J. Christensen-Dalsgaard

The richness and very high accuracy of the observed frequencies of solar oscillations provide tight constraints on the structure of the solar interior and hence on the assumptions underlying the calculation of solar models. This permits the use of the Sun as a laboratory for investigating the physics of stellar interiors. Important examples are the study of

J. Christensen-Dalsgaard

Helioseismology has provided very precise information about the solar internal sound speed and density throughout most of the solar interior. The results are generally quite close to the properties of standard solar models. Since the solar oscillation frequencies do not provide direct information about temperature and composition, the helioseismic results to

Tsvi Piran, Re&#39;em Sari

The highly variable temporal structure observed in most GRBs provides us with unexpected clues. We show that variable GRBs cannot be produced by external shocks models and consequently cannot be produced by an ``explosive&#39;&#39; inner engine. The observed temporal structure must reflect the activity of the inner engine that must be producing unsteady and

L. Titarchuk, A. Mastichiadis, N. D. Kylafis

We study Compton upscattering of low-frequency photons in a converging flow of thermal plasma. The photons escape diffusively and electron scattering is the dominant source of opacity. We solve numerically and approximately analytically the equation of radiative transfer in the case of spherical, steady state accretion into black holes. Unlike previous work

Paul Martini, K. Sellgren, Joseph L. Hora

We present near-infrared spectroscopy of fluorescent molecular hydrogen (H_2) emission from molecular filaments in the reflection nebula NGC 7023. We derive the relative column densities of H_2 rotational-vibrational states from the measured line emission and compare these results with several model photodissociation regions covering a range of densities, in

M. Coleman Miller, Frederick K. Lamb, Dimitrios Psaltis

Quasi-periodic brightness oscillations (QPOs) with frequencies in the range 300-1200 Hz have been detected from at least nine neutron star low-mass X-ray binaries. Here we summarize the sonic-point model for these brightness oscillations, which we present in detail elsewhere. If the sonic-point interpretation of kilohertz QPOs is confirmed, measurements of k

Rosanne Di Stefano, Rosalba Perna

The microlensing monitoring programs have studied large numbers of standard light curves which seem to be due to lensing by a dark point mass. Theory predicts that many microlensing events should display significant deviations from the standard form. Lens binarity in particular is expected to be common. So far, however, only a handful of light curves exhibit

Igor Aranson, Lev Tsimring, Valerii Vinokur

Population dynamics on a rugged landscape is studied analytically and numerically within a simple discrete model for evolution of N individuals in one-dimensional fitness space. We reduce the set of master equations to a single Fokker-Plank equation which allows us to describe the dynamics of the population in terms of thermo-activated Langevin diffusion of

Hamish Cunningham

This technical memo describes Information Extraction from the point-of-view of a potential user of the technology. No knowledge of language processing is assumed. Information Extraction is a process which takes unseen texts as input and produces fixed-format, unambiguous data as output. This data may be used directly for display to users, or may be stored in

Javier P. Muniain, Jose Wudka

Anomalous contributions to the Jacobi identity of chromo-electric fields and non-Abelian vector currents are calculated using a non-perturbative approach that combines operator product expansion and a generalization of Bjorken-Johnson-Low limit. The failure of the Jacobi identity and the associated 3-cocycles are discussed.

Yu. Kubyshin

The Polchinski version of the exact renormalization group equation is discussed and its applications in scalar and fermionic theories are reviewed. Relation between this approach and the standard renormalization group is studied, in particular the relation between the derivative expansion and the perturbation theory expansion is worked out in some detail.

I. Ya. Aref&#39;eva, M. G. Ivanov, O. A. Rytchkov

General properties of intersecting extremal p-brane solutions of gravity coupled with dilatons and several different d-form fields in arbitrary space-time dimensions are considered. It is show that heuristically expected properties of the intersecting p-branes follow from the explicit formulae for solutions. In particular, harmonic superposition and S-dualit

Julie D. Blum

We present a relatively simple argument showing that the H-dyon states required by S-duality of the heterotic string on $T^6$ are present provided that the BPS dyons required by S-duality of N=4 supersymmetric Yang-Mills theory are present. We also conjecture and provide evidence that H-dyons at singularities where the nonperturbative gauge symmetry is compl

K. Hagino, N. Takigawa, M. Dasgupta, D. J. Hinde

High precision measurements of the fusion excitation functions for the reactions ^{40}Ca + ^{194}Pt, ^{192}Os clearly demonstrate that projectile excitation significantly modifies the potential barrier distribution. In sharp contrast, fusion of ^{16}O + ^{144}Sm appears to show no influence of the projectile excitation on the shape of the barrier distributio

A. Marshakov

The properties of the N=2 SUSY gauge theories underlying the Seiberg-Witten hypothesis are discussed. The main ingredients of the formulation of the finite-gap solutions to integrable equations in terms of complex curves and generating 1-differential are presented, the invariant sense of these definitions is illustrated. Recently found exact nonperturbative

L. P. Grishchuk, Jérôme Martin

It is likely that the observed distribution of the microwave background temperature over the sky is only one realization of the underlying random process associated with cosmological perturbations of quantum-mechanical origin. If so, one needs to derive the parameters of the random process, as accurately as possible, from the data of a single map. These para

Kenji Harada, Naoki Kawashima

The helicity modulus of the S=1/2 XY model is precisely estimated through a world line quantum Monte Carlo method enhanced by a cluster update algorithm. The obtained estimates for various system sizes and temperatures are well fitted by a scaling form with L replaced by \log(L/L_0), which is inferred from the solution of the Kosterlitz renormalization group

S. Kretzer, I. Schienbein

We present formulae for the momentum (z) distributions of D-mesons produced in neutrino deep-inelastic scattering off strange partons. The expressions are derived within the variable flavor scheme of Aivazis et al. (ACOT-scheme), which is extended from its fully inclusive formulation to one-hadron inclusive leptoproduction. The dependence of the results on t

A. I. Sanda, Zhi-zhong Xing

We present an isospin analysis of the decay modes B\to D\bar{D}, D^*\bar{D}, D\bar{D}^* and D^*\bar{D}^*, which allows determination of the final-state interaction phases. As these transitions have branching ratios of the order 10^{-4} or larger, they could be useful in detecting the CP- violating phase ϕ_1 \equiv \arg (-V^*_{cb} V_{cd} V_{tb} V^*_{td} ) in

J. Rizos, K. Tamvakis

We construct and analyze an $SU(6)\times SU(2)$ GUT. The model is k=1 string embedable in the sense that we employ only chiral representations allowed at the k=1 level of the associated Kač-Moody Algebra. Both cases $SU(6)\times SU(2)_{L}$ and $SU(6)\times SU(2)_{R}$ are realized. The model is characterized by the $SU(6)\times SU(2) \to SU(4)\times SU(2)\tim

Matthias Troyer, Masatoshi Imada, Kazuo Ueda

We have performed a large scale quantum Monte Carlo study of the quantum phase transition in a planar spin-1/2 Heisenberg antiferromagnet with CaV4O9 structure. We obtain a dynamical exponent z=1.018+/-0.02. The critical exponents beta, nu and eta agree within our errors with the classical 3D O(3) exponents, expected from a mapping to the nonlinear sigma mod

Hideki Madokoro, Masayuki Matsuzaki

We formulate a general relativistic mean field theory for rotating nuclei starting from the special relativistic $\sigma - \omega$ model Lagrangian. The tetrad formalism is adopted to generalize the model to the accelerated frame.