November 1999 arXiv papers — page 13

Y. Kinar, E. Schreiber, J. Sonnenschein, N. Weiss

We discuss the impact of quadratic quantum fluctuations on the Wilson loop extracted from classical string theory. We show that a large class of models, which includes the near horizon limit of D_p branes with 16 supersymmetries, admits a Lüscher type correction to the classical potential. We confirm that the quantum determinant associated with a BPS configu

Marcelo Gleiser, Mark Trodden

We study weakly first order cosmological phase transitions in finite temperature field theories. Focusing on the standard electroweak theory and its minimal supersymmetric extension, we identify the regimes of Higgs masses for which the phase transition in these models proceeds by significant phase mixing and the coarsening of the subsequent domain network.

Santo Fortunato, Helmut Satz

The deconfinement transition in SU(2) gauge theory and the magnetization transition in the Ising model belong to the same universality class. The critical behaviour of the Ising model can be characterized either as spontaneous breaking of the Z_2 symmetry of spin states or as percolation of appropriately defined spin clusters. We show that deconfinement in S

T. L. Boyadjiev, M. D. Todorov, P. P. Fiziev, S. S. Yazadjiev

A model of static boson-fermion star with spherical symmetry based on the scalar-tensor theory of gravity with massive dilaton field is investigated numerically. Since the radius of star is \textit{a priori} an unknown quantity, the corresponding boundary value problem (BVP) is treated as a nonlinear spectral problem with a free internal boundary. The Contin

M. A. Kimber, A. D. Martin, M. G. Ryskin

We introduce a general expression which enables the parton distribution, unintegrated over the parton transverse momentum, to be obtained from the conventional parton densities. We use the formalism to study the effects of the transverse momentum q_t of the incoming partonic system on the calculation of the transverse momentum spectra of prompt photons produ

S. J. Papadakis, E. P. De Poortere, M. Shayegan, R. Winkler

Experiments on high-quality GaAs (311)A two-dimensional holes at low temperatures reveal a remarkable dependence of the magnetoresistance, measured with an in-plane magnetic field ($B$), on the direction of $B$ relative to both the crystal axes and the current direction. The magnetoresistance features, and in particular the value of $B$ above which the resis

G. L. Granato, L. Silva, P. Monaco, P. Panuzzo

Direct and indirect observational evidence leads to the conclusion that high redshift QSOs did shine in the core of early type proto-galaxies during their main episode of star formation. Exploting this fact, we derive the rate of formation of this kind of stellar systems at high redshift by using the QSO Luminosity Function. The elemental proportions in elli

G. Cvetic, Ji-Young Yu

In strong (quasi-)Abelian fields, even at the one-loop level of the coupling constant, quantum fluctuations of fermions induce an effective Lagrangian density whose imaginary (absorptive) part is purely nonperturbative and known to be responsible for the fermion-antifermion pair creation. On the other hand, the induced real (dispersive) part has perturbative

Joakim Bergli, Yuri Galperin

The acoustelectric current for composite fermions in a two-dimensional electron gas (2DEG) close to the half-filled Landau level is calculated in the random phase approximation. The Boltzmann equation is used to find the nonequilibrium distribution of composite fermions to second order in the acoustic field.It is shown that the oscillating Chern-Simons field

R. M. Crocker, F. Melia, R. R. Volkas

It has recently been demonstrated that the $γ$-ray emission spectrum of the EGRET-identified, central Galactic source 2EG J1746-2852 can be well fitted by positing that these photons are generated by the decay of $π^0$'s produced in p-p scattering at or near an energizing shock. Such scattering also produces charged pions which decay leptonically.The rat

Ashoke Sen

Using string field theory, we argue that the tachyon potential on a D-brane anti-D-brane system in type II string theory in arbitrary background has a universal form, independent of the boundary conformal field theory describing the brane. This implies that if at the minimum of the tachyon potential the total energy of the brane antibrane system vanishes in

Boris V. Fine

The long-time behavior of certain fast-decaying infinite temperature correlation functions on one-, two- and three-dimensional lattices of classical spins with various kinds of nearest-neighbor interactions is studied numerically, and evidence is presented that the functional form of this behavior is either simple exponential or exponential multiplied by cos

Boris V. Fine

The long-time behavior of the infinite temperature spin correlation functions describing the free induction decay in nuclear magnetic resonance and intermediate structure factors in inelastic neutron scattering is considered. These correlation functions are defined for one-, two- and three-dimensional infinite lattices of interacting spins both classical and

K. N. Borozdin, S. P. Trudolyubov

The X-ray nova GRS1739-278 flared up near the Galactic center in the spring of 1996. Here we report on the discovery of a ~5-Hz quasi-periodic oscillations (QPO) in RXTE/PCA observations of GRS1739-278. The QPO were only present when the source was in its very high state, and disappeared later, when it made a transition down into the high state. We present t

Edward Frenkel, Evgeny Mukhin

We study finite-dimensional representations of quantum affine algebras using q-characters. We prove the conjectures from math.QA/9810055 and derive some of their corollaries. In particular, we prove that the tensor product of fundamental representations is reducible if and only if at least one of the corresponding normalized R-matrices has a pole.

Jonathan L. Feng, Yosef Nir, Yael Shadmi

Neutrino masses and mixings have important implications for models of fermion masses, and, most directly, for the charged lepton sector. We consider supersymmetric Abelian flavor models, where neutrino mass parameters are related to those of charged leptons and sleptons. We show that processes such as τto μγ, μto eγand μ-e conversion provide interesting prob

Aristophanes Dimakis, Folkert Muller-Hoissen

We associate bicomplexes with the finite Toda lattice and with a finite Toda field theory in such a way that conserved currents and charges are obtained by a simple iterative construction.

M. N. Sergeenko

The exactness of the semiclassical method for three-dimensional problems in quantum mechanics is analyzed. The wave equation appropriate in the quasiclassical region is derived. It is shown that application of the standard leading-order WKB quantization condition to this equation reproduces exact energy eigenvalues for all solvable spherically symmetric pote

H. K. Cummins, J. A. Jones

We implement an ensemble quantum counting algorithm on three NMR spectrometers with 1H resonance frequencies of 500, 600 and 750 MHz. At higher frequencies, the results deviate markedly from naive theoretical predictions. These systematic errors can be attributed almost entirely to off-resonance effects, which can be substantially corrected for using fully-c

Z. Hradil, M. Dusek

Scheme for optimal spin state estimation is considered in analogy with phase detection in interferometry. Recently reported coherent measurements yielding the average fidelity (N+1)/(N+2) for N particle system corresponds to the standard limit of phase resolution 1/\sqrt{N}. It provides the bound for incoherent measurements when each particle is detected sep

H. K. Avetissian, A. G. Markossian, G. F. Mkrtchian

The relativistic theory of above-threshold ionization (ATI) of hydrogen-like atoms in ultrastrong radiation fields, taking into account the photoelectron induced rescattering in the continuum spectrum is developed. It is shown that the contribution of the latter in the multiphoton ionization probability even in the Born approximation by Coulomb field is of t

Marcin Michalski

This paper has been withdrawn by the author, due a crucial error in the main idea.

J. R. Mureika

At the recent 1999 World Athletics Championships in Sevilla, Spain, Canada's Bruny Surin matched Donovan Bailey's National and former World Record 100 m mark of 9.84 s. The unofficial times for each, as read from the photo-finish, were 9.833 s and 9.835 s respectively. Who, then, is the fastest Canadian of all time? A possible solution is offered, ac

O. El Akramine, A. Makhoute

We present a theoretical study of strong laser-atom interactions, when the laser field parameters are subjected to random processes. The atom is modelled by a two-level and three-level systems, while the statistical fluctuations of the laser field are described by a pre-Gaussian model.

O. El Akramine, A. Makhoute, M. Zitane, M. Tij

The nonlinear dynamics of dissipative quantum systems in incoherent laser fields is studied in the framework of master equation with random model describing the laser noise and Markovian approximation for dealing with the system-bath couplings.

O. El Akramine, A. Makhoute, D. Khalfl, A. Maquet

The influence of linearly and circularly polarized laser fields on the dynamics of fast electron-impact excitation in atomic helium is discussed. A detailed analysis is made in the excitation of 2^1S, 3^1S and 3^1D dressed states of helium target.

B. Huke, M. Lücke, P. Büchel, Ch. Jung

Rayleigh-Bénard convection in horizontal layers of binary fluid mixtures heated from below with realistic horizontal boundary conditions is studied theoretically using multi-mode Galerkin expansions. For positive separation ratios the main difference between the mixtures and pure fluids lies in the existence of stable three dimensional patterns near onset in

Anne Juel, John M. Burgess, W. D. McCormick, J. B. Swift

Two superposed liquid layers display a variety of convective phenomena that are inaccessible in the traditional system where the upper layer is a gas. We consider several pairs of immiscible liquids. Once the liquids have been selected, the applied temperature difference and the depths of the layers are the only independent control parameters. Using a perflu

R. Machleidt

For the past 40 years, Brueckner theory has proven to be a most powerful tool to investigate systematically models for nuclear matter. I will give an overview of the work done on nuclear matter theory, starting with the simplest model and proceeding step by step to more sophisticated models by extending the degrees of freedom and including relativity. The fi

J. C. Lemm, B. G. Giraud, A. Weiguny

The time independent mean field method (TIMF) for scattering defines biorthonormal sets of single-particle wave functions and corresponding creation and annihilation operators. 2p - 2h correlations can be introduced through a generalized random phase approximation; 1p - 1h contributions vanish (Brillouin theorem). While the general variational method for sca

R. Lednicky, V. Lyuboshitz, K. Mikhailov, Yu. Sinyukov

The influence of multiboson effects on pion multiplicities, single-pion spectra and two-pion correlation functions is discussed in terms of an analytically solvable model. The applicability of its basic factorization assumption is clarified. An approximate scaling of the basic observables with the phase space density is demonstrated in the low density (gas)

Stijn Janssen, Jan Ryckebusch, Wim Van Nespen, Dimitri Debruyne

The effect of central, tensor and spin-isospin nucleon-nucleon correlations upon semi-exclusive ^{16}O(e,e'p) reactions is studied for Q^2 and Bjorken x values in the range $0.2 \lesssim Q^2 \lesssim 1.1 (GeV/c)^2$ and 0.15 $\lesssim$ x $\lesssim$ 2. The fully unfactorized calculations are performed in a framework that accounts not only for the dynamical

Oe. Elgaroey, T. Engeland, M. Hjorth-Jensen, E. Osnes

Finite nuclei such as those found in the chain of even tin isotopes from ^{102}Sn to ^{130}Sn, exhibit a near constancy of the 2^+_1-0^+_1 excitation energy, a constancy which can be related to strong pairing correlations and the near degeneracy in energy of the relevant single particle orbits. Large shell-model calculations for these isotopes reveal that th

Tsunehiro Kobayashi

Equivalence in physics is discussed on the basis of experimental data accompanied by experimental errors. It is pointed out that the introduction of the equivalence being consistent with the mathematical definition is possible only in theories constructed on non-standard number spaces by taking the experimental errors as infinitesimal numbers. Following the

David M. J. Calderbank, Paul Tod

We obtain explicitly all solutions of the SU(infinity) Toda field equation with the property that the associated Einstein-Weyl space admits a 2-sphere of divergence-free shear-free geodesic congruences. The solutions depend on an arbitrary holomorphic function and give rise to new hyperKahler and selfdual Einstein metrics with one dimensional isometry group.

Jozef H. Przytycki

We show that for the Kauffman bracket skein module over the field of rational functions in variable A, the module of a connected sum of 3-manifolds is the tensor product of modules of the individual manifolds.

Stefan Schroeer

We characterize contractible curves on proper normal algebraic surfaces in terms of complementary Weil divisors. Using this we generalize the classical criteria of Castelnuovo and Artin. As application we derive a finiteness result on homogeneous spectra defined by Weil divisors on surfaces.

David M. J. Calderbank, H. Pedersen

We study the Jones and Tod correspondence between selfdual conformal 4-manifolds with a conformal vector field and abelian monopoles on Einstein-Weyl 3-manifolds, and prove that invariant complex structures correspond to shear-free geodesic congruences. Such congruences exist in abundance and so provide a tool for constructing interesting selfdual geometries

H. Gillet, C. Soulé

We develop a formalism of direct images for metrized vector bundles in the context of the non-archimedean Arakelov theory introduced in our previous joint work with S. Bloch, and we prove a Riemann-Roch-Grothendieck theorem for this direct image.

Jon warren

The weak solution of Tanaka's SDE is not a function of the driving Brownian motion, and therefore it has no Wiener chaos expansion. However in some sense explained here it has a generalised chaos expansion involving infinite products of stochastic differentials accumulating at the minimum of the Brownian path. This is related to the existence of a non-cl

A. U. Klimyk

We describe properties of the nonstandard q-deformation $U'_q({\rm so}_n)$ of the universal enveloping algebra $U({\rm so}_n)$ of the Lie algebra ${\rm so}_n$ which does not coincide with the Drinfeld--Jimbo quantum algebra $U_q({\rm so}_n)$. Irreducible representations of this algebras for q a root of unity q^p=1 are given. These representations act on

Tatyana Foth

Automorphic forms on a bounded symmetric domain D=G/K can be viewed as holomorphic sections of $L^{\otimes k}$, where L is a quantizing line bundle on a compact quotient of D and k is a positive integer. Let $Γ$ be a cocompact discrete subgroup of SU(n,1) which acts freely on SU(n,1)/U(n). We suggest a construction of relative Poincaré series associated to l

Bernd Ammann

The Willmore conjecture states that any immersion F:T^2 -> R^n of a 2-torus into flat euclidean space satisfies $\int_{T^2} H^2\geq 2π^2$. We prove it under the condition that the L^p-norm of the Gaussian curvature is sufficiently small.

John M. Cornwall

It has been remarked in several previous works that the combination of center vortices and nexuses (a nexus is a monopole-like soliton whose world line mediates certain allowed changes of field strengths on vortex surfaces) carry topological charge quantized in units of 1/N for gauge group SU(N). These fractional charges arise from the interpretation of the

M. Leo, R. A. Leo, G. Soliani, P. Tempesta

An algebraic method is devised to look for non-local symmetries of the pseudopotential type of nonlinear field equations. The method is based on the use of an infinite-dimensional subalgebra of the prolongation algebra $L$ associated with the equations under consideration. Our approach, which is applied by way of example to the Dym and the Korteweg-de Vries

V. Dmitrasinovic

Starting from the Fierz transform of the two-flavour 't Hooft interaction (a four-fermion Lagrangian with antisymmetric Lorentz tensor interaction terms augmented by an NJL type Lorentz scalar inetraction responsible for dynamical symmetry breaking and quark mass generation), we show that: (1) antisymmetric tensor Nambu-Goldstone bosons appear provided t

H. R. Christiansen, N. Grandi, F. A. Schaposnik, G. Silva

Non-BPS dyon solutions to D3-brane actions are constructed when one or more scalar fields describing transverse fluctuations of the brane, are considered. The picture emerging from such non-BPS configurations is analysed, in particular the response of the D-brane-string system to small perturbations.

Chanyong Park, Sang-Jin Sin, Sunggeun Lee

We study the effect of the Dp-brane gas in string cosmology. When one kind of Dp-brane gas dominates, we find that the cosmology is equivalent to that of the Brans-Dicke theory with the perfect fluid type matter. We obtain $γ$, the equation of state parameter, in terms of p and the space-time dimension.

Yang-Hui He

D-brane probes, Hanany-Witten setups and geometrical engineering stand as a trichotomy of the currently fashionable techniques of constructing gauge theories from string theory. Meanwhile, asymptotic freedom, finitude and IR freedom pose as a trichotomy of the beta-function behaviour in quantum field theories. Parallel thereto is a trichotomy in set theory o

I. P. Ennes, S. G. Naculich, H. Rhedin, H. J. Schnitzer

Methods are reviewed for computing the instanton expansion of the prepotential for N=2 Seiberg-Witten (SW) theory with non-hyperelliptic curves. These results, if compared with the instanton expansion obtained from the microscopic Lagrangian, will provide detailed tests of M-theory. We observe group-theoretic regularities of the one-instanton prepotential wh

G. Scharf, M. Wellmann

In the framework of causal perturbation theory we analyze the gauge structure of a massless self-interacting quantum tensor field. We look at this theory from a pure field theoretical point of view without assuming any geometrical aspect from general relativity. To first order in the perturbation expansion of the $S$-matrix we derive necessary and sufficient

A. A. Andrianov, V. A. Andrianov

We discuss the low energy effective action of QCD in the quark sector. When it is built at the CSB (chiral symmetry breaking) scale by means of perturbation theory it has the structure of a generalized Nambu-Jona-Lasinio (NJL) model with CSB due to attractive forces in the scalar channel. We show that if the lowest scalar meson state is sufficiently lighter

William J. Marciano

An overview of KAON 99 with commentary is presented. Emphasis is placed on the state of CKM mixing and CP violation. The Jarlskog invariant, J_{CP}, is shown to provide a useful quantitative comparison of K and B phenomenology. The potential of future rare and ``forbidden'' decay experiments to probe O(3000 TeV) ``New Physics'' is also descri

L. L. Frankfurt, M. V. Polyakov, M. Strikman, M. Vanderhaeghen

The cross sections and transverse spin asymmetries in the hard exclusive electroproduction of decuplet baryons are calculated in the large N_c limit and found to be comparable to that of octet baryons. Large N_c selection rules for the production amplitudes are derived, leading to new sensitive tests of the spin aspects of the QCD chiral dynamics both in the

Victor Novozhilov, Yuri Novozhilov

We present main points of some of Fock papers in Quantum Theory, which were not properly followed when published.

L. Micu

The space-like electromagnetic form factor is expressed in terms of the overlap integral of the initial and final meson wave functions written as Lorentz covariant distributions of internal momenta. The meson constituents are assumed to be valence quarks and an effective vacuum-like field. The momentum of the latter represents a relativistic generalization o

N. G. Stefanis

The modern formulation of exclusive reactions within Quantum Chromodynamics is reviewed, the emphasis being placed on the pivotal ideas and methods pertaining to perturbative and non-perturbative topics. Specific problems, related to scale locality, infrared safety, gluonic radiative corrections (Sudakov effects), and the role of hadronic size effects (intri

A. Jakovac

A general real-time formalism is developed to resum the self-energy operator of broken symmetry scalar field theories in form of self-consistent gap equations for the spectral function. The solution of the equations is approximated with finite lifetime quasi-particles. In the Landau damping rates viscosity terms, analogous to gauge theories, appear, what lea

J. Soffer

We review in this talk some aspects of the exciting field of hyperon polarization phenomena in high energy reactions, over the last twenty years or so. On the experimental side, a large amount of significant polarization data for hyperon and antihyperon inclusive production, has been accumulated in a rather broad energy range. Many theoretical attempts to ex

M. Beccaria, F. M. Renard, S. Spagnolo, C. Verzegnassi

We consider lepton-antilepton annihilation into a fermion-antifermion pair at variable c.m. energy. We propose for this process a simple parametrization of the virtual effects of the most general model of new physics of \underline{universal} type. This parametrization is based on a recent approach, that uses the experimental results of LEP1, SLC as theoretic

Raju Venugopalan

In hadrons and nuclei at very small x, parton distributions saturate at a scale Q_s(x). Since the occupation number is large, and $Q_s(x)>>Λ_{QCD}$, classical weak coupling methods may be used to study this novel regime of non-linear classical fields in QCD. In these lectures, we apply these methods to compute structure functions in deeply inelastic scatteri

S. J. Brodsky

Some of the most difficult theoretical challenges of QCD occur at the interface of the perturbative and nonperturbative regimes. Exclusive and semi-exclusive processes, the diffractive dissociation of hadrons into jets, and hard diffractive processes such as vector meson leptoproduction provide new testing grounds for QCD and essential information on the str

G. Burgio, R. De Pietri, H. A. Morales-Tecotl, L. F. Urrutia

We show that in the spin-network basis it is possible to compute the matrix elements of any given operator of the Hamiltonian formulation of Lattice Gauge Theory (LGT). We give the explicit calculation for the case of the plaquette operator.

P. N. Burrows

The unique SLD CCD vertex detector combined with the highly-polarised electron beam allow us to search for an anomalous chromomagnetic coupling of the b-quark, as well as P-odd, T_N-odd and CP-odd processes at the b bbar g vertex.

Martin Siebel

The study of the differences of the fragmentation of quarks and gluons to jets of hadrons gives insight into the fundamental structure of QCD. Results from different approaches to properties of quarks and gluons are shown. The colour factor ratio $C_A/C_F$ is measured in agreement with the QCD prediction. Identified particles in quark and gluon jets are inve

Masaru Shibata, Koji Uryu

We have performed 3D numerical simulations for merger of equal mass binary neutron stars in full general relativity. We adopt a $Γ$-law equation of state in the form $P=(Γ-1)ρε$ where P, $ρ$, $\varep$ and $Γ$ are the pressure, rest mass density, specific internal energy, and the adiabatic constant with $Γ=2$. As initial conditions, we adopt models of corotat

Andris Ambainis, John Watrous

We introduce 2-way finite automata with quantum and classical states (2qcfa's). This is a variant on the 2-way quantum finite automata (2qfa) model which may be simpler to implement than unrestricted 2qfa's; the internal state of a 2qcfa may include a quantum part that may be in a (mixed) quantum state, but the tape head position is required to be cl

John Watrous

We define a class of stochastic processes based on evolutions and measurements of quantum systems, and consider the complexity of predicting their long-term behavior. It is shown that a very general class of decision problems regarding these stochastic processes can be efficiently solved classically in the space-bounded case. The following corollaries are im

Takashi Hotta, Yasutami Takada, Hiroyasu Koizumi, Elbio Dagotto

The spin-charge-orbital complex structures of manganites are studied using topological concepts. The key quantity is the "winding number" w associated with the Berry-phase connection of an e_g electron parallel-transported through Jahn-Teller centers, along zigzag one-dimensional paths in an antiferromagnetic environment of t_{2g} spins. From these c

Chi-Yong Lin, M. S. Hussein, A. F. R. de Toledo Piza, E. Timmermans

The collective excitation of hybrid atomic-molecular condensate are studied using variational method. The dipole response of the system is studied in detail. We found that the out-of-phase dipole oscillation frequency increasing slowly with the detuning parameter and is only few times large than the trap frequency making the experimental observation of this

S. M. Nakhmanson, D. A. Drabold

Using empirical potential molecular dynamics we compute dynamical matrix eigenvalues and eigenvectors for a 4096 atom model of amorphous silicon and a set of models with voids of different size based on it. This information is then employed to study the localization properties of the low-energy vibrational states, calculate the specific heat C(T) and examine

D. P. DiVincenzo, G. Burkard, D. Loss, E. V. Sukhorukov

In this chapter we explore the connection between mesoscopic physics and quantum computing. After giving a bibliography providing a general introduction to the subject of quantum information processing, we review the various approaches that are being considered for the experimental implementation of quantum computing and quantum communication in atomic physi

L. Chekhov

The scattering process on multiloop infinite p+1-valent graphs (generalized trees) is studied. These graphs are discrete spaces being quotients of the uniform tree over free acting discrete subgroups of the projective group $PGL(2, {\bf Q}_p)$. As the homogeneous spaces, they are, in fact, identical to p-adic multiloop surfaces. The Ihara-Selberg L-function

A. Kaminski, L. I. Glazman

We show that randomness of the electron wave functions in a quantum dot contributes to the fluctuations of the positions of the conductance peaks. This contribution grows with the conductance of the junctions connecting the dot to the leads. It becomes comparable with the fluctuations coming from the randomness of the single particle spectrum in the dot whil

L. Spinu, H. Srikanth, E. E. Carpenter, C. J. O'Connor

A novel resonant method based on a tunnel-diode oscillator (TDO) is used to study the dynamic transverse susceptibility in a Fe nanoparticle system. The magnetic system consists of an aggregate of nanometer-size core (Au)-shell (Fe) structure, synthesized by reverse micelle methods. Static and dynamic magnetization measurements carried out in order to charac

J. Wiggins, H. Srikanth, K. -Y. Wang, L. Spinu

The magneto-impedance (MI) of glass-coated Fe-Ni-Cu microwires was investigated for longitudinal radio-frequency (RF) currents up to a frequency of 200 MHz using an RF lock-in amplifier method. The MI, defined as DZ/Z = [Z(H)-Z(H=0.3T)]/Z(H=0.3T), displays a peak structure (negative MI) at zero field for RF currents with frequencies less than 20MHz and this

A. Fontana, R. Dell'Anna, M. Montagna, F. Rossi

New Raman and incoherent neutron scattering data at various temperatures and molecular dynamic simulations in amorphous silica, are compared to obtain the Raman coupling coefficient $C(ω)$ and, in particular, its low frequency limit. This study indicates that in the $ω\to 0$ limit $C(ω)$ extrapolates to a non vanishing value, giving important indications on

Mina Yoon, M. Y. Choi, Beom Jun Kim

The lattice effects on the current-voltage characteristics of two-dimensional arrays of resistively shunted Josephson junctions are investigated. The lattice potential energies due to the discrete lattice structure are calculated for several geometries and directions of current injection. We compare the energy barrier for vortex-pair unbinding with the latti

Roberto Franzosi, Marco Pettini, Lionel Spinelli

We report upon the numerical computation of the Euler characteristic χ(a topologic invariant) of the equipotential hypersurfaces Σ_v of the configuration space of the two-dimensional lattice $ϕ^4$ model. The pattern χ(Σ_v) vs. v (potential energy) reveals that a major topology change in the family {Σ_v}_{v\in R} is at the origin of the phase transition in th

Daniel Boese, Markus Lischka, L. E. Reichl

We study the conductance properties of a straight two-dimensional electron waveguide with an s-like scatterer modeled by a single delta-function potential with a finite number of modes. Even such a simple system exhibits interesting resonance phenomena. These resonances are explained in terms of quasi-bound states both by using a direct solution of the Schro

T. Borzsonyi, A. Buka, A. P. Krekhov, O. A. Scaldin

Elliptic shear applied to a homeotropically oriented nematic above the electric bend Freedericks transition (FT) generates slow precession of the director. The character of the accompanying nonlinear waves changes from diffusive phase waves to dispersive ones exhibiting spirals and spatio-temporal chaos as the FT is approached from above. An exact solution o

Nobuki Maeda

Using a mean field theory on the von Neumann lattice, we study compressible anisotropic states around $ν=l+1/2$ in the quantum Hall system. The Hartree-Fock energy of the UCDW are calculated self-consistently. In these states the unidirectional charge density wave (UCDW) seems to be the most plausible state. We show that the UCDW is regarded as a collection

Salman Habib, Grant Lythe

We investigate the nucleation, annihilation, and dynamics of kinks in a classical (1+1)-dimensional Phi^4 field theory at finite temperature. From large scale Langevin simulations, we establish that the nucleation rate is proportional to the square of the equilibrium density of kinks. We identify two annihilation time scales: one due to kink-antikink pair re

R. Gatt

The paper compares the K-dependence of the superconducting gap in different doping ranges. The fine behavior of the leading edge gap indicates that the pairing susceptibility is peaked at special regions on the Fermi surface. These hot regions are found to be centered away from nominal "hot spots". This behavior is attributed to a feedback effect on

Jinqiao Duan, Hongjun Gao, Xinchu Fu

The authors investigate the impact of external sources on the pattern formation of concentration profiles of passive tracers in a two-dimensional shear flow. By using the pullback attractor technique for the associated nonautonomous dynamical system, it is shown that a unique time-almost periodic concentration profile exists for time-almost periodic external

A. Yu. Shahverdian

The paper establishes the property of splittability of billiard boundary sequences in n dimensional cube into subsequences of fractional parts. This reveals a new property of integrable and weak perturbated Hamilton systems: under a simple assumption, the boundary motion of elliptic orbits on stable KAM tori, if considering in cartesian coordinates, can be s

Roberto Soria, Kinwah Wu, Richard Hunstead

We have obtained optical spectra of the soft X-ray transient GRO J1655-40 during different X-ray spectral states (quiescence, high-soft and hard outburst) between 1994 Aug and 1997 Jun. Characteristic features observed during the 1996-97 high-soft state were: a) broad absorption lines at Halpha and Hbeta, probably formed in the inner disk; b) double-peaked H

Ivan Hubeny, Eric Agol, Omer Blaes, Julian Krolik

We have constructed a grid of non-LTE disk models for a wide range of black hole mass and mass accretion rate, for several values of viscosity parameter alpha, and for two extreme values of the black hole spin: the maximum-rotation Kerr black hole, and the Schwarzschild (non-rotating) black hole. Our procedure calculates self-consistently the vertical struct

Lutz Wisotzki

We have analysed the optical luminosity-redshift distribution properties of bright QSOs, using a new large sample from the Hamburg/ESO survey. The sample provides insight into the hitherto poorly sampled bright tail of the luminosity function, allowing to monitor its evolution with redshift up to $z\approx 3$. The slope increases significantly towards higher

A. G. Lyne, F. Camilo, R. N. Manchester, J. F. Bell

We are undertaking a high-frequency survey of the Galactic plane for radio pulsars, using the 13-element multibeam receiver on the 64-m Parkes radio telescope. We describe briefly the survey system and some of the initial results. PSR J1811-1736, one of the first pulsars discovered with this system, has a rotation period of 104 ms. Subsequent timing observat

Chris L. Fryer, Vassiliki Kalogera

We derive the theoretical distribution function of black hole masses by studying the formation processes of black holes. We use the results of recent 2D simulations of core-collapse to obtain the relation between remnant and progenitor masses and fold it with an initial mass function for the progenitors. We examine how the calculated black-hole mass distribu

J. Fischer, M. L. Luhman, S. Satyapal, M. A. Greenhouse

Based on far-infrared spectroscopy of a small sample of nearby infrared-bright and ultraluminous infrared galaxies (ULIRGs) with the ISO Long Wavelength Spectrometer, we find a dramatic progression in ionic/atomic fine-structure emission line and molecular/atomic absorption line characteristics in these galaxies extending from strong [O III]52,88 and [N III]

Joseph Kapusta

About eight minutes before a black hole expires it has a decreasing mass of 10^{10} g, an increasing temperature of 1 TeV, and an increasing luminosity of 7x10^{27} erg/s. I show that such a black hole is surrounded by a quasi-stationary shell of matter undergoing radial hydrodynamic expansion. The inner radius of this shell is bounded by ten times the Schwa

Masaru Shibata, Thomas W. Baumgarte, Stuart L. Shapiro

We perform 3D numerical simulations in full general relativity to study the stability of rapidly rotating, supramassive neutron stars at the mass-shedding limit to dynamical collapse. We adopt an adiabatic equation of state with $Γ= 2$ and focus on uniformly rotating stars. We find that the onset of dynamical instability along mass-shedding sequences nearly

B. H. Hong, G. J. Qiao, B. Zhang, J. L. Han

We propose that the violent breakdown of the Ruderman-Sutherland type vacuum gap above the pulsar polar cap region may produce copious primary particles and make the charge density above the gap in excess of the Goldreich-Julian density. Such an excess residue of charge density may arise some re-acceleration regions above the gap due to the space-charge-limi

G. J. Qiao, J. F. Liu, Y. Wang, X. J. Wu

We carried out the Gaussian fitting to the profile of PSR B1237+25 and found that six components rather than five are necessary to make a good fit. In the central part, we found that the core emission is not filled pencil beam but is a small hollow cone. This implies that the impact angle could be $β<0.5^\circ$. The ``hollow core&#39;&#39; is in agreement wi

J. L. Han, R. N. Manchester, G. J. Qiao

Polarization profiles of several hundred pulsars have been published recently (eg. Gould & Lyne 1998, GL98; Weisberg et al. 1999). In this report, we summarize the characteristics of circular and high linear polarizations of pulsar profiles, based on all previously published data.

P. Rodriguez-Gil, J. Casares, V. S. Dhillon, I. G. Martinez-Pais

We present R-band photometry of the SW Sex-type cataclysmic variable WX Arietis made in October 1995 and August 1998-February 1999. Contrary to previous results, we find that WX Ari is an eclipsing system with an orbital inclination of ~72 deg. The R-band light curves display highly variable, shallow eclipses ~0.15-mag deep and ~40 min long. The observed ecl

A. B. Peck, G. B. Taylor

Recent VLBI observations have identified several compact radio sources which have symmetric structures on parsec scales, and exhibit HI absorption which appears to be associated with the active nucleus. These sources are uniquely well suited to investigations into the physics of the central engines, in particular to studies of the kinematics of the gas withi

A. B. Peck, G. B. Taylor

The class of radio sources known as Compact Symmetric Objects (CSOs) is of particular interest in the study of the evolution of radio galaxies. CSOs are thought to be young (probably ~10^4 years), and a very high fraction of them exhibit HI absorption toward the central parsecs. The HI, which is thought to be part of a circumnuclear torus of accreting gas, c