September 1995 arXiv papers — page 2

Jan de Boer, Bas Peeters, Kostas Skenderis, Peter van Nieuwenhuizen

We construct the path integral for one-dimensional non-linear sigma models, starting from a given Hamiltonian operator and states in a Hilbert space. By explicit evaluation of the discretized propagators and vertices we find the correct Feynman rules which differ from those often assumed. These rules, which we previously derived in bosonic systems \cite{pape

Douglas Singleton

In Abelian theories of monopoles the magnetic charge is required to be enormous. Using the electric-magnetic duality of electromagnetism it is argued that the existence of such a large, non-perturbative magnetic coupling should lead to a phase transition where magnetic charge is permanently confined and the photon becomes massive. The apparent masslessness o

R. J. Cova

The scattering properties of the non-linear $O(3)$ model in (2+1)-D, modified by the addition of both a potential-like term and a Skyrme-like term, are considered. Most of the work is numerical. The skyrmion-scattering is found to be quasi-elastic, the skyrmions' energy density profiles remaining unscathed after collisions. In low-energy processes the sk

Bernd Kuckert

Recently Borchers has shown that in a theory of local observables, certain unitary and antiunitary operators, which are obtained from an elementary construction suggested by Bisognano and Wichmann, commute with the translation operators like Lorentz boosts and \pct-operators, respectively. We conclude from this that as soon as the operators considered implem

Shaisultanov R

Using the Schwinger-Keldysh (closed time path or CTP) and Feynman-Vernon influence functional formalisms we obtain a Langevin equation for the description of the charged particle creation in electric field and of backreaction of charged quantum fields and their fluctuations on time evolution of this electric field. We obtain an expression for the influence f

M. F. Mourad, R. Sasaki

In the context of integrable field theory with boundary, the integrable non-linear sigma models in two dimensions, for example, the $O(N)$, the principal chiral, the ${\rm CP}^{N-1}$ and the complex Grassmannian sigma models are discussed on a half plane. In contrast to the well known cases of sine-Gordon, non-linear Schrödinger and affine Toda field theorie

L. C. Kwek, C. H. Oh

We present a succinct way of obtaining all possible higher dimensional generalization of Quantum Yang-Baxter Equation (QYBE). Using the scheme, we could generate the two popular three-simplex equations, namely: Zamolodchikov's tetrahedron equation (ZTE) and Frenkel and Moore equation (FME).

S Chaturvedi

A general formula for the canonical partition function for a system obeying any statistics based on the permutation group is derived. The formula expresses the canonical partition function in terms of sums of Schur functions. The only hitherto known result due to Suranyi [ Phys. Rev. Lett. {\bf 65}, 2329 (1990)] for parasystems of order two is shown to arise

A. B. Arbuzov, E. A. Kuraev, N. P. Merenkov, L. Trentadue

Radiative corrections due to the production of virtual as well as real soft and hard pairs in small-angle Bhabha scattering are calculated analytically. Both the collinear and the semi-collinear kinematical regions of hard pair production are considered. The calculation, within the leading and next-to-leading logarithmic approximation, provides an accuracy o

Marcus Hutter

The proton form factors are reduced to vacuum correlators of 4 quark fields by assuming independent constituent quarks. The axial singlet quark and gluonic form factors are calculated in the instanton liquid model. A discussion of gauge(in)dependence is given.

Marcus Hutter

The QCD gauge field is modeled as an ensemble of statistically independent selfdual and antiselfdual regions. This model is motivated from instanton physics. The scale anomaly then allows to relate the topological susceptibility to the gluon condensate. With the help of Wittens formula for m_eta' and an estimate of the suppression of the gluon condensate

Frank Cuypers

We study slepton pair-production in polarized $γγ$ scattering. It turns out that the combined use of polarization and angular correlations greatly enhances the resolving power of this reaction.

Ivan Horvath

The phase diagram of the Schwinger model on the lattice with Wilson fermions is investigated in the Hartree-Fock approximation. In case of single flavour (not directly amenable to simulations), the calculation indicates the existence of the parity violating phase at both weak and intermediate-to-strong couplings. Hartree-Fock vacuum sustains a nonzero electr

Jerome Martin

Cosmological perturbations on a manifold admitting signature change are studied. The background solution consists in a Friedmann-Lemaitre-Robertson- Walker (FLRW) Universe filled by a constant scalar field playing the role of a cosmological constant. It is shown that no regular solution exist satisfying the junction conditions at the surface of change. The c

Sean A. Hayward

For a contravariant 4-metric which changes signature from Lorentzian to Riemannian across a spatial hypersurface, the mixed Einstein tensor is manifestly non-singular. In Gaussian normal coordinates, the metric contains a step function and the Einstein tensor contains the Dirac delta function with support at the junction. The coefficient of the Dirac functio

A. M. S. Macedo

A Brownian motion model is proposed to study parametric correlations in the transmission eigenvalues of open ballistic cavities. We find interesting universal properties when the eigenvalues are rescaled at the hard edge of the spectrum. We derive a formula for the power spectrum of the fluctuations of transport observables as a response to an external adiab

R. J. Radtke, V. N. Kostur, K. Levin

Recent measurements of the London penetration depth tensor in the cuprates find a weak temperature dependence along the c-direction which is seemingly inconsistent with evidence for d-wave pairing deduced from in-plane measurements. We demonstrate in this paper that these disparate results are not in contradiction, but can be explained within a theory based

Rodney Price, S. Das Sarma

We present the results of a variational Monte Carlo calculation of the exchange-correlation energy for a spin-polarized two-dimensional electron gas in a perpendicular magnetic field. These energies are a necessary input to the recently developed current-density functional theory. Landau-level mixing is included in a variational manner, which gives the energ

S L A de Queiroz

Transfer-matrix methods on finite-width strips with free boundary conditions are applied to lattice site animals, which provide a model for randomly branched polymers in a good solvent. By assigning a distinct fugacity to sites along the strip edges, critical properties at the special (adsorption) and ordinary transitions are assessed. The crossover exponent

A. Paintner, F. Süss, U. Krey

By means of self-consistent semi-empirical LCAO calculations we study the itinerant magnetism of (Fe_{0.65}Ni_{0.35})_{1-y} Mn_y alloys for y between 0 and 0.22 at T=0 K, neglecting only the transverse spin components. We find that the magnetic behaviour is quite complicated on a local scale. In addition to ferromagnetic behaviour, also metastable spin-glass

S. Stringari

The temperature dependence of the moment of inertia of a dilute Bose gas confined in a harmonic trap is determined. Deviations from the rigid value, due to the occurrence of Bose-Einstein condensation, reveal the superfluid behaviour of the system. In the noninteracting gas these deviations become important at temperatures of the order of $T_c N^{-1/12}$. Th

Anne Bohle, Robert Hołyst, Thomas Vilgis

We apply density functional theory to study the influence of polydispersity on the stability of columnar, smectic and solid ordering in the solutions of rodlike macromolecules. For sufficiently large length polydispersity (standard deviation $σ>0.25$) a direct first-order nematic-columnar transition is found, while for smaller $σ$ there is a continuous nemat

S. Krompiewski, F. Süss, U. Krey

We perform first-principles calculations for the three multilayer systems (100)-Co_1/Cu_n, -NiCo_2Ni/Cu_n and -Co_4/Cu_n, and find from a comparison x of the results for system 2 and 3 that amplitude and phase of the exchange coupling are sensitive to the magnetic-slab/nonmagnetic-spacer interface. Moreover, we observe that for the system 1 and 2 the average

Md Maruf Hasan

Chinese text processing systems are using Double Byte Coding , while almost all existing Sanskrit Based Indian Languages have been using Single Byte coding for text processing. Through observation, Chinese Information Processing Technique has already achieved great technical development both in east and west. In contrast,Indian Languages are being processed

Niall D. Whelan

Diffraction, in the context of semiclassical mechanics, describes the manner in which quantum mechanics smooths over discontinuities in the classical mechanics. An important example is a billiard with sharp corners; its semiclassical quantisation requires the inclusion of diffractive periodic orbits in addition to classical periodic orbits. In this paper we

Chris L. Fryer, Willy Benz, Marc Herant

We present an extensive study of accretion onto neutron stars in which the velocity of the neutron star and structure of the surrounding medium is such that the Bondi-Hoyle accretion exceeds .001 Msun/y. For most cases, hypercritical accretion due to rapid neutrino cooling allows the neutron star to accrete above the Bondi-Hoyle rate as previously pointed ou

E. E. Fenimore, R. W. Klebesadel, J. G. Laros

The March 5th, 1979 gamma-ray transient has long been thought to be fundamentally different from the classic gamma-ray bursts (GRBs). It had recurrences, pulsations, and a soft spectral component unlike classic GRBs. With the exception of the soft component reported from the Konus experiment, the unusual characteristics of March 5th were detectable main peak

Renu Malhotra

The Solar system beyond Neptune is believed to house a population of small primordial bodies left over from the planet formation process. The region up to heliocentric distance $\sim 50 AU$ (a.k.a. the Kuiper Belt) may be the source of the observed short period comets. In this region, the phase space structure near orbital resonances with Neptune is of speci

Ramesh Narayan, Insu Yi, Rohan Mahadevan

Viscous rotating accretion flows around black holes become advection-dominated when the accretion rate $\dot M$ is sufficiently low. Most of the accretion energy in such flows is stored within the gas and advected radially inward. The temperature is therefore very high, and much of the radiation comes out in hard X-rays and $γ$-rays. We have constructed an a

Insu Yi, Ramesh Narayan, Didier Barret, Jeffrey E. McClintock

When the mass accretion rate onto a black hole (BH) falls below a critical rate, ${\dot M}_{crit}\sim α^2 {\dot M}_{Edd}$, accretion can occur via a hot optically thin flow where most of the dissipated energy is advected inward. We present such an advection-dominated model for the soft X-ray transient (SXT) A0620-00. This source has a puzzlingly low X-ray lu

Rohan Mahadevan

Soft cyclo-synchrotron photons produced by thermal electrons moving in a magnetic field can be subsequently Comptonized to produce hard X-ray and $γ$-ray emission. An accurate determination of the amount of soft cyclo-synchrotron photons produced from such plasmas is clearly necessary. We present the complete solution to the cyclo-synchrotron problem. We cal

Joseph C. Shields, Robert C. Kennicutt

Dust and associated depletion of heavy elements from the gas phase can modify the thermal properties of HII regions from the dust-free case, with significant consequences for the emergent optical spectrum. We present the results of theoretical calculations illustrating the effects of grains on the spectra of giant, extragalactic HII regions, with emphasis on

Piero Madau, J. Michael Shull

The recent discovery by Cowie \etal and Tytler \etal of metals in the \Lya clouds shows that the intergalactic medium (IGM) at high redshift is contaminated by the products of stars, and suggests that ionizing photons from massive star formation may be a significant contributor to the UV background radiation at early epochs. We assess the validity of the ste

Demetrios N. Matsakis, Roger S. Foster

Terrestrial timescales show instabilities due to the physical limitations of the atomic clocks. Stricter environmental isolation and increased numbers of improved cesium clocks and cavity-tuned hydrogen masers have resulted in time scales more accurate by a factor of about five. The use of different clock ensembles results in measurable changes in some milli

Albion Lawrence, Emil Martinec

We attempt to understand the fate of spacelike gravitational singularities in string theory via the quantum stress tensor for string matter in a fixed background. We first approximate the singularity with a homogeneous anisotropic background and review the minisuperspace equations describing the evolution of the scale factors and the dilaton. We then review

John H. Schwarz

This talk is divided into two parts. The first part reviews some of the duality relationships between superstring theories. These relationships are interpreted as providing evidence for the existence of a unique underlying fundamental theory. The second part describes my recent work on the SL(2,Z) duality group of the type IIB superstring theory in ten dimen

Todd A. Brun, Ian C. Percival, Rüdiger Schack

Except for the universe, all quantum systems are open, and according to quantum state diffusion theory, many systems localize to wave packets in the neighborhood of phase space points. This is due to decoherence from the interaction with the environment, and makes the quasiclassical limit of such systems both more realistic and simpler in many respects than

Herbert Weigel

The description of baryons as soliton solutions of effective meson theories for three flavor (up, down, strange) degrees of freedom is reviewed and the phenomenological implications are illuminated. In the collective approach the soliton configuration is equipped with baryon quantum numbers by canonical quantization of the coordinates describing the flavor o

A. P. Polychronakos

Solitons in the continuum limit of the Calogero model are derived and shown to correspond to one-particle excitations. The statistical mechanics of exclusion statistics particles is then formulated in terms of a priori probabilities and a path integral is thereoff constructed. (Talk delivered at the Trieste April 1995 Conference on statistical mechanics and

S. E. Koonin

Quantum Monte Carlo methods find fruitful application in large shell model problems. These methods reduce the imaginary-time many-body evolution operator to a coherent superposition of one-body evolutions in a fluctuating one-body field; the resultant path integral is evaluated stochastically. After a brief review of the capabilities and general strategy of

Ahmed Hindawi, Burt A. Ovrut, Daniel Waldram

A discussion of an extended class of higher-derivative classical theories of gravity is presented. A procedure is given for exhibiting the new propagating degrees of freedom, at the full non-linear level, by transforming the higher-derivative action to a canonical second-order form. For general fourth-order theories, described by actions which are general fu

D. F. Wang

One dimensional chiral Hubbard model reduces to the Haldane-Shastry spin chain at half-filling with large but finite on-site energy $U$.In this talk, we show that the Gutzwiller-Jastrow wavefunctions are the eigen-states of the Hubbard model at $U=+\infty$ at less than half-filling. The full energy spectrum and an infinite set of mutually commuting constants

Chris Allton

Results from recent lattice calculations of the decay constants $f_B$ and $f_D$ are reviewed. A discussion of the methods currently used is presented, together with an outline of the various systematic effects involved.

A. Z. Akheyan, N. S. Ananikian

The spin-1 Ising model with bilinear and biquadratic exchange interactions and single-ion crystal field is solved on the Bethe lattice using exact recursion equations. The general procedure of critical properties investigation is discussed and full set of phase diagrams are constructed for both positive and negative biquadratic couplings. In latter case we o

R. F. Peletier, M. Balcells

Colours of spiral galaxies generally are affected by the underlying old stellar population, younger stars, and extinction by dust. Old and young populations generally can be disentangled using a combination of blue and near-infrared colours. Extinction effects are very hard to take into account, except for galaxies with special orientations. In this paper we

Shin-ichi Kojima, Norisuke Sakai, Tadakatsu Sakai

Vacuum energies are computed in light-cone field theories to obtain effective potentials which determine vacuum condensate. Quantization surfaces interpolating between the light-like surface and the usual spatial one are useful to define the vacuum energies unambiguously. The Gross-Neveu, SU(N) Thirring, and O(N) vector models are worked out in the large $N$

Louis Funar

The aim of this note is to derive some invariants at infinity for open 3-manifolds in the framework of Topological Quantum Field Theories. These invariants may be used to test if an open manifold is simply connected at infinity as we done for Whitehead's manifold in case of the $sl_{2}({\bf C})$-TQFT in level 4.

B. Dionne, M. Silber, A. C. Skeldon

We consider the symmetry-breaking steady state bifurcation of a spatially-uniform equilibrium solution of E(2)-equivariant PDEs. We restrict the space of solutions to those that are doubly-periodic with respect to a square or hexagonal lattice, and consider the bifurcation problem restricted to a finite-dimensional center manifold. For the square lattice we

A. Ferrari, J. Ranft, S. Roesler, P. R. Sala

Based on a Monte Carlo realization of the Dual Parton Model we study the production of target associated particles and of nuclear fragments in high energy hadron-nucleus interactions. A formation zone intranuclear cascade of low energy secondaries inside the target nucleus is discussed. We calculate excitation energies of residual nuclei left after the intra

Gottfried Curio

Computation of the holomorphic $F_1$-function describing one-loop gravitational couplings of vectormultiplets is shown to confirm string-string duality of the proposed dual pair consisting of the heterotic string on $K3\times T^2$ with gauge group $U(1)^4$ and the type IIA string on the Calabi-Yau $WP^4_{1,1,2,8,12}(24)$.

Eric Bergshoeff

We discuss the duality symmetries of Type II string effective actions in nine, ten and eleven dimensions. As a by-product we give a covariant action underlying the ten--dimensional Type IIB supergravity theory. We apply duality symmetries to construct dyonic Type II string solutions in six dimensions and their reformulation as solutions of the ten--dimension

Shinji Hamamoto

In order to construct a massive tensor theory with a smooth massless limit, we apply the Batalin-Fradkin algorithm to the ordinary massive tensor theory. By introducing an auxiliary vector field all second-class constraints are converted into first-class ones. We find a gauge-fixing condition which produces a massive tensor theory of desirable property.

M. Kawasaki, T. Moroi, T. Yanagida

We study the Polonyi problem in the framework of no-scale type supergravity models. We show that the lightest superparticle (LSP) produced in the decay of the Polonyi field may contribute too much to the present density of the universe. By requiring that LSP should not overclose the universe, we obtain a stringent constraint on the reheating temperature afte

H. Zhang

We investigate more generally the possible unification Yang-Mills groups $G_{YM}$ and representations with CP as a gauge symmetry. Besides the possible Yang-Mills groups $E_8$, $E_7$, $SO(2n+1)$, $SO(4n)$, $SP(2n)$, $G_2$ or $F_4$ (or a product of them) which only allow self-contragredient representations, we present other unification groups $G_{YM}$ and rep

A. Abada, H. Weigel, H. Reinhardt

We study the radiative decays of $J^π=\frac{3}{2}^+$ baryons in the framework of the SU(3) collective approach to the Skyrme model. We present the predictions for the decay widths and the corresponding $E2/M1$ ratios. We find that all considered ratios are negative and of the order of a few percent only. We discuss the effects of flavor symmetry breaking and

M. Quirós

Depending on the Higgs-boson and top-quark masses, $M_H$ and $M_t$, the effective potential of the {\bf Standard Model} can develop a non-standard minimum for values of the field much larger than the weak scale. In those cases the standard minimum becomes metastable and the possibility of decay to the non-standard one arises. Comparison of the decay rate to

B. de Carlos, J. A. Casas

We evaluate the branching ratio BR($b\rightarrow s,γ$) in the minimal supersymmetric standard model (MSSM), determining the corresponding phenomenological restrictions on two attractive supergravity scenarios, namely minimal supergravity and a class of models with a natural solution to the $μ$ problem. We have included in the calculation some one--loop refin

H. -W. Hammer, Ulf-G. Meißner, D. Drechsel

We update Jaffe's estimate of the strange isoscalar radius and magnetic moment of the nucleon. We make use of a recent dispersion--theoretical fit to the nucleon electromagnetic form factors and an improved description of symmetry breaking in the vector nonet. We find $μ_s = -0.24 \pm 0.03$~n.m. and $r_s^2 = 0.21 \pm 0.03$~fm$^2$. The strange formfactor

E. H. Simmons, R. S. Chivukula, J. Terning

We review the connection between $m_t$ and the $Zb\bar b$ vertex in ETC models and demonstrate the power of the resulting experimental constraint on models with weak-singlet ETC bosons. Some efforts to bring ETC models into agreement with experimental data on the $Zb\bar b$ vertex are mentioned, and the most promising one (non-commuting ETC) is discussed in

Cheuk-Yin Wong

The observed features of $ψ'$ to $J/ψ$ suppression in $pA$ and nucleus-nucleus collisions can be explained in terms of a two-component absorption model. For the hard component of the absorption due to the interaction of the produced $c\bar c$ systems with baryons at high relative energies, the absorption cross sections are insensitive to the radii of the

Orlando Panella

We give a brief review of the existing bounds on effective couplings for excited states ($e^*, ν^*, u^*, d^* $) of the ordinary quarks and leptons arising from a composite model scenario. We then explore the phenomenological implications of the hypothesis that the excited neutrino $ν^*$ might be of Majorana type. Recent bounds on the half-life of the $ΔL =2

H. Fritzsch, Z. Z Xing

Starting from the symmetry of lepton flavor democracy, we propose and discuss a simple pattern for the mass generation and flavor mixing of the charged leptons and neutrinos. The three neutrino masses are nearly degenerate, and the flavor mixing angles can be calculated. The observed deficit of solar and atmospheric neutrinos can be interpreted as a conseque

S. F. Tuan

Here we discuss three separate topics in charmonium physics. (1) The Omicron \OMC as $1^{--}$ trigluonia, and the charmonium puzzle; the $η_c' (3600)$ search. (2) The decay $ψ(^1P_1) \to π^o + J/ψ$ and isospin violating charmonium decays. (3) How to search for $χ_c' = χ_c(2P)$ charmonium states.

A. Yu. Smirnov

These are remarks (mainly on the solar neutrinos) written in anticipation of 1996 - the year which can be crucial for the neutrino physics. Recent results on solar neutrinos are discussed. The topics include: (solar) model independent approach to the solar neutrino problem, status of different solutions of the problem, standard and non-standard scenarios of

Boris Kayser

We discuss the testing of the Standard Model of CP violation, and the search for CP-violating effects from beyond the Standard Model, in $B$ decays. We then focus on the quantum mechanics of the experiments on CP violation to be performed at $B$ factories. These experiments will involve very pretty Einstein-Podolsky-Rosen correlations. We show that the physi

I. Fukui, N. Setoh

The Bethe-Salpeter amplitudes of the bound states formed by two scalar particles with unequal masses are analyzed in the massive scalar particle exchange ladder model. The norms of the amplitudes are calculated numerically, and it is confirmed that the norm vanishes for the bound state corresponding to the complex eigenvalue of the coupling constant. The beh

Steven Gottlieb, K. Rummukainen

Most hadronic particles are resonances: for example, the rho meson appears as a resonance in the elastic scattering of two pions. A method by Luescher enables one to measure the properties of the resonance particles from finite lattices. We present here a more general method which includes scattering processes where the total momentum of the particles is non

M. Alford, T. Klassen, P. Lepage

We investigate a new light fermion action (the ``D234'' action), which is accurate up to $Ø(a^3)$ and tadpole-improved $Ø(a α_s)$ errors. Using D234 with Symanzik- and tadpole-improved glue we find evidence that continuum results for the quenched hadron spectrum (pion, rho and nucleon) can be obtained on coarse lattices.

K. Farakos, K. Kajantie, M. Laine, K. Rummukainen

We study the phase transition in SU(2)-Higgs model on the lattice using the 3D dimensionally reduced formalism. The 3D formalism enables us to obtain highly accurate Monte Carlo results, which we extrapolate both to the infinite volume and to the continuum limit. Our formalism also provides for a well-determined and unique way to relate the results to the pe

C. T. Sachrajda

The calculation of higher twist (or dimension) corrections to physical quantities using operator product expansions is delicate. If dimensional regularization is used to regulate the ultra-violet divergences then there are ambiguities in the Wilson coefficient functions due to infra-red renormalon singularities. With a hard ultra violet cut-off, such as the

Valeri Marachevsky, Dmitri Vassilevich

We suggest a method of construction of general diffeomorphism invariant boundary conditions for metric fluctuations. The case of $d+1$ dimensional Euclidean disk is studied in detail. The eigenvalue problem for the Laplace operator on metric perturbations is reduced to that on $d$-dimensional vector, tensor and scalar fields. Explicit form of the eigenfuncti

G. 't Hooft

When it comes to performing thought experiments with black holes, Einstein-Bohr like discussions have to be re-opened. For instance one can ask what happens to the quantum state of a black hole when the wave function of a single ingoing particle is replaced by an other one that is orthogonal to the first, while keeping the total energy and momentum unaffecte

I. V. Krive, P. Sandström, R. I. Shekhter, M. Jonson

We show that in a ring-shaped Luttinger Liquid (LL) in contact with an electron reservoir --- the chemical potential in the ring being controlled by a gate voltage $V_g$ --- both the average ring charge and the persistent current in the ring are step-like functions of $V_g$ at low temperatures. The step positions are determined by the LL parameter $α=v_F/s$,

Stefano Zapperi, Kent Baekgaard Lauritsen, H. Eugene Stanley

We discuss mean-field theories for self-organized criticality and the connection with the general theory of branching processes. We point out that the nature of the self-organization is not addressed properly by the previously proposed mean-field theories. We introduce a new mean-field model that explicitly takes the boundary conditions into account; in this

R. J. Radtke, V. N. Kostur

Measurements of the $c$-axis penetration depth $λ_c$ in the cuprates reveal a low-temperature $T$ dependence which is inconsistent with simple models of coupling between the CuO$_2$ layers. In this paper, we examine whether a model based on {\it incoherent} hopping between the layers can account for this low-$T$ behavior. We compute $λ_c$ directly from linea

N. B. Kopnin, G. E. Volovik, Ü. Parts

Nondissipative force acting on a vortex in Fermi superfluids and superconductors is calculated from the spectral flow of fermion zero modes in the vortex core. The spectral flow effect casts a new light on the problem of mutual friction in superfluids. We demonstrate that, for vortices in an isotropic system, the reactive mutual friction parameter D'(T)

E. Bogomolny, F. Leyvraz, C. Schmit

The two-point correlation function of energy levels for free motion on the modular domain, both with periodic and Dirichlet boundary conditions, are explicitly computed using a generalization of the Hardy-Littlewood method. It is shown that ion the limit of small separations they show an uncorrelated behaviour and agree with the Poisson distribution but they

D. A. Frail, N. E. Kassim, T. J. Cornwell, W. M. Goss

We present deep images of a region around the Crab nebula made with the VLA, utilizing new imaging and deconvolution algorithms in a search for a faint radio shell. The existence of a high-velocity, hydrogen-rich envelope has been predicted to account for the low total mass and kinetic energy of the observed nebula. No radio emission was detected from an ext

Richard E. Leonard, Robert J. Scherrer

A decaying particle that dominates the energy density of the universe and then decays with a lifetime $\sim 10^{-1}$ sec into electromagnetically-interacting particles can heat the background electron neutrinos more than the $μ$ and $τ$ neutrinos, resulting in a decrease in the primordial $^4$He abundance. Previous calculations of this effect assumed sudden

Tomonori Totani, Katsuhiko Sato, Yuzuru Yoshii

The spectrum of the supernova relic neutrino background (SRN) from collapse-driven supernovae ever occurred in the universe is calculated by using a realistic, time-dependent supernova rate derived from a standard model of galaxy evolution based on the population synthesis method. The SRN spectrum we show here is the most realistic at present, because the la

Takahiko Matsubara, Yasushi Suto

The genus statistics is studied using large $N$-body simulations for several cosmological models. We consider the effects of nonlinear gravitational evolution, smoothing the particle data in fully nonlinear regime, and the redshift-space distortion on the genus curve. Detailed comparison between the theoretical prediction in weakly nonlinear theory and the a

D. Gieseker

The Toda hierarchy of size $N$ is well known to be analogous to the KdV hierarchy at $N$ goes to infinity. This paper shows that given $f$ a periodic function, there is a canonical way of defining the initial data for the Toda lattice equations so that the evolution of this data under the Toda lattice hierarchy looks asymptotically like the evolution of $f$

Ahmed Hindawi, Burt A. Ovrut, Daniel Waldram

A discussion of the field content of quadratic higher-derivative gravitation is presented, together with a new example of a massless spin-two field consistently coupled to gravity. The full quadratic gravity theory is shown to be equivalent to a canonical second-order theory of a massive scalar field, a massive spin-two symmetric tensor field and gravity. Th

Alexander Nazarenko, Adriana Moreo, Jose Riera, Elbio Dagotto

Motivated by the phenomenology of the high-Tc cuprates, a two dimensional fermionic model with attractive interactions is here discussed. The exact solution to the two particle problem leads to a bound state in the $d_{x^2 - y^2}$ subspace. Numerical techniques suggest that the model has $d_{x^2 - y^2}$ superconductivity (SC) in the ground state at low fermi

Andrew Chamblin

We investigate the causal structure of spacetimes $(M, g)$ for which the metric $g$ is singular on a set of points.

Paul Howe, P. West

The multiplets that occur in four dimensional rigidly supersymmetric theories can be described either by chiral superfields in Minkowski superspace or analytic superfields in harmonic superspace. The superconformal Ward identities for Green's functions of gauge invariant operators of these types are derived. It is shown that there are no chiral superconf

Abir Bandyopadhyay, Jagdish Rai

We propose a simple experimental procedure to produce squeezing and other non-classical properties like photon antibunching of radiation, and amplification without population inversion. The method also decreases the uncertainties of the angular-momentum quadratures representing the two-level atomic system in the interaction of the two-level atoms with quanti

R. Benzi, M. V. Struglia, R. Tripiccione

Using a code based on the Lattice Boltzmann Equation, we have performed numerical simulations of a turbulent shear flow. We investigate the scaling behaviour of the structure functions in presence of anisotropic homogeneous turbulence, and we show that although Extended Self Similarity does not hold when strong shear effects are present, a more generalized s

R. A. Kraenkel, M. A. Manna, J. C. Montero, J. G. Pereira

We apply a multiple-time version of the reductive perturbation method to study long waves as governed by the shallow water wave model equation. As a consequence of the requirement of a secularity-free perturbation theory, we show that the well known N-soliton dynamics of the shallow water wave equation, in the particular case of $α=2 β$, can be reduced to th

R. F. Peletier, M. Balcells

For a sample of bright nearby early-type galaxies we have obtained surface photometry in bands ranging from U to K. Since the galaxies have inclinations larger than 50 deg. it is easy to separate bulges and disks. By measuring the colours in special regions, we minimize the effects of extinction, and by looking at B-K colour gradients we can show that for th

HongSheng Zhao

I present a general family of dynamical models with simple analytical potential-density pairs suited to model galactic bulges and nuclei with double power-law radial density profiles and an optional central black hole. Analytical expressions for the potential and velocity dispersion of these models are given in the spherical case. Many previously known analy

Jose V. Romero, Jose M. Ibanez, Jose M. Marti, Juan A. Miralles

In this paper we present a full general relativistic one-dimensional hydro-code which incorporates a modern high-resolution shock-capturing algorithm, with an approximate Riemann solver, for the correct modelling of formation and propagation of strong shocks. The efficiency of this code in treating strong shocks is demonstrated by some numerical experiments.

Subir Sachdev

We consider finite temperature properties of the Ising chain in a transverse field in the vicinity of its zero temperature, second order quantum phase transition. New universal crossover functions for static and dynamic correlators of the ``spin'' operator are obtained. The static results follow from an early lattice computation of McCoy, and a metho

A. Tartaglia

It has been shown that the extension of the elasticity theory in more than three dimensions allows a description of space-time as a properly stressed medium, even recovering the Minkowski metric in the case of uniaxial stress. The fundamental equation for the metric in the theory is shown to be the equilibrium equation for the medium. Examples of spherical a

Phillial Oh

We investigate the classical and quantum properties of a system of $SU(N)$ non-Abelian Chern-Simons (NACS) particles. After a brief introduction to the subject of NACS particles, we first discuss about the symplectic structure of various $SU(N)$ coadjoint orbits which are the reduced phase space of $SU(N)$ internal degrees of freedom or isospins. A complete

P. G. Grinevich

We study the direct spectral transform for the heat equation, associated with the KP-2 equation. We show, that for real nonsingular exponentially decaying at infinity potentials the direct problem is nonsingular for arbitrary large potentials. Earlier this statement was proved only for potentials, satisfying the ``small norm'' assumption.

Yunbo Zeng

We show here the separability of Hamilton-Jacobi equation for a hierarchy of integrable Hamiltonian systems obtained from the constrained flows of the Jaulent-Miodek hierarchy. The classical Poisson structure for these Hamiltonian systems is constructed. The associated $r$-matrices depend not only on the spectral parameters, but also on the dynamical variabl

Chongying Dong, Haisheng Li, Geoffrey Mason

The admissible modules for $\hat{sl}_2$ are studied from the point of view of vertex operator algebra. If $l$ is rational such that $l+2={p\over q}$ for some coprime positive integers $p\ge 2$ and $q$, Kac and Wakimoto found finitely many distinguished irreducible representations for $\hat{sl}_2$, called admissible representations. In this paper we prove tha

R. A. Kraenkel, M. A. Manna, J. C. Montero, J. G. Pereira

We apply a multiple-time version of the reductive perturbation method to study long waves as governed by the Boussinesq model equation. By requiring the absence of secular producing terms in each order of the perturbative scheme, we show that the solitary-wave of the Boussinesq equation can be written as a solitary-wave satisfying simultaneously all equation

Sergej Flach

We study tangent bifurcation of band edge plane waves in nonlinear Hamiltonian lattices. The lattice is translationally invariant. We argue for the breaking of permutational symmetry by the new bifurcated periodic orbits. The case of two coupled oscillators is considered as an example for the perturbation analysis, where the symmetry breaking can be traced u