November 1998 arXiv papers — page 16

S. K. Dutta, C. P. Vlahacos, D. E. Steinhauer, Ashfaq S. Thanawalla

By scanning a fine open-ended coaxial probe above an operating microwave device, we image local electric fields generated by the device at microwave frequencies. The probe is sensitive to the electric flux normal to the face of its center conductor, allowing different components of the field to be imaged by orienting the probe appropriately. Using a simple m

K. Moriarty, J. Machta, L. Y. Chayes

Simulations of the two-dimensional Ising and 3-state Potts models at their critical points are performed using the invaded cluster (IC) algorithm. It is argued that observables measured on a sub-lattice of size l should exhibit a crossover to Swendsen-Wang (SW) behavior for l sufficiently less than the lattice size L, and a scaling form is proposed to descri

M. Potthoff, W. Nolting

The correlation-driven transition from a paramagnetic metal to a paramagnetic Mott-Hubbard insulator is studied within the half-filled Hubbard model for a thin-film geometry. We consider simple-cubic films with different low-index surfaces and film thickness d ranging from d=1 (two-dimensional) up to d=8. Using the dynamical mean-field theory, the lattice (f

M. Potthoff, W. Nolting

Using the dynamical mean-field theory, we calculate the effective electron mass in the Hubbard model on a semi-infinite lattice. At the surface the effective mass is strongly enhanced. Near half-filling this gives rise to a correlation-driven one-electron surface mode.

M. Potthoff, W. Nolting

The correlation-driven metal-insulator (Mott) transition at a solid surface is studied within the Hubbard model for a semi-infinite lattice by means of the dynamical mean-field theory. The transition takes place at a unique critical strength of the interaction. Depending on the surface geometry, the interaction strength and the wave vector, we find one-elect

Alexander Altland, B D Simons

The long-range properties of the random flux model (lattice fermions hopping under the influence of maximally random link disorder) are shown to be described by a supersymmetric field theory of non-linear sigma model type, where the group GL(n|n) is the global invariant manifold. An extension to non-abelian generalizations of this model identifies connection

B. C. den Hertog, A. J. Berlinsky, C. Kallin

We derive the qualitative behavior of superconductor-antiferromagnet- superconductor (SAS) Josephson junctions described by Zhang's SO(5) theory. The main differences between these junctions and conventional SIS junctions arise from the non-sinusoidal current-phase relation derived by Demler et al. for thin SAS junctions. Using a simple approximation to

Vaclav Drchal, Josef Kudrnovsky, Patrick Bruno, Peter Dederichs

We study the combined effect of temperature and disorder in the spacer on the interlayer exchange coupling. The temperature dependence is treated on ab initio level. We employ the spin-polarized surface Green function technique within the tight-binding linear muffin-tin orbital method and the Lloyd formulation of the IEC. The integrals involving the Fermi-Di

Arkadi A. Odintsov, Hideo Yoshioka

Effective low-energy Hamiltonian of interacting electrons in conducting single-wall carbon nanotubes with arbitrary chirality is derived from the microscopic lattice model. The parameters of the Hamiltonian show very weak dependence on the chiral angle, which makes the low energy properties of conducting chiral nanotubes universal. The strongest Mott-like el

S. Caprara, M. Sulpizi, A. Bianconi, C. Di Castro

We study the single-particle spectral properties of a model for coexisting AFM and ICDW critical fluctuations coupled to electrons, which naturally arises in the context of the stripe-quantum-critical-point scenario for high-Tc superconducting materials. Within a perturbative approach, we show that the on-shell inverse scattering time deviates from the norma

D. A. W. Hutchinson

We present a self-consistent mean field model of the extraction of atoms from a Bose-Einstein condensate to form a CW atom laser. The model is based upon the Hartree-Fock Bogoliubov equations within the Popov approximation, modified by the inclusion of spatially dependent source and sink terms, which lead to current flow within the condensate. The effects of

V. A. Osipov, S. E. Krasavin

We show that the experimentally observed behavior of thermal conductivity of dielectric glasses over a wide temperature range can be explained by a combination of two scattering processes. The first one comes from the phonon scattering due to biaxial dipoles of wedge disclinations while the second one is the Rayleigh type scattering. The results obtained sup

M. R. Ejtehadi, N. Hamedani, V. Shahrezaei

Geometrical properties of protein ground states are studied using an algebraic approach. It is shown that independent from inter-monomer interactions, the collection of ground state candidates for any folded protein is unexpectedly small: For the case of a two-parameter Hydrophobic-Polar lattice model for $L$-mers, the number of these candidates grows only a

N. Hamamoto, N. Onishi, G. F. Bertsch

We analyze the adiabatic magnetization of ferromagnetic clusters in an intermediate coupling regime, where the anisotropic potential is comparable to other energy scales. We find a non-monotonic behavior of the magnetic susceptibility as a function of coupling with a peak. Coriolis coupling effects are calculated for the first time; they reduce the susceptib

K. Shizuya

A numerical study is made of current distributions in finite-width Hall bars with disorder and some theoretical observations are verified. The equilibrium current and the Hall current are substantially different in distribution. It is observed that in the Hall-plateau regime the Hall current tends to concentrate near the sample edges while it diminishes on a

S. H. Tessmer, P. I. Glicofridis, R. C. Ashoori, L. S. Levitov

The unusual properties of two-dimensional electron systems that give rise to the quantum Hall effect have prompted the development of new microscopic models for electrical conduction. The bulk properties of the quantum Hall effect have also been studied experimentally using a variety of probes including transport, photoluminescence, magnetization, and capaci

Norman Margolus

A cellular automaton is a deterministic and exactly computable dynamical system which mimics certain fundamental aspects of physical dynamics such as spatial locality and finite entropy. CA systems can be constructed which have additional attributes that are basic to physics: systems which are exactly invertible at their finest scale, which obey exact conser

D. A. Wisniacki, E. Vergini

The quantum dynamics of a chaotic billiard with moving boundary is considered in this work. We found a shape parameter Hamiltonian expansion which enables us to obtain the spectrum of the deformed billiard for deformations so large as the characteristic wave length. Then, for a specified time dependent shape variation, the quantum dynamics of a particle insi

C. D. Fassnacht, R. D. Blandford, J. G. Cohen, K. Matthews

We have discovered a new gravitational lens in the Cosmic Lens All-Sky Survey (CLASS). B2045+265 is a four-image system with a maximum separation of 1.9 arcsec. A fifth radio component is detected, but its radio spectrum and its positional coincidence with infrared emission from the lensing galaxy strongly suggests that it is the radio core of the lensing ga

Brad K. Gibson, Bart P. Wakker

A highly colloquialized summary of the Stromlo Workshop on High-Velocity Clouds, held Aug 14-15, 1998, at Mount Stromlo Observatory. The proceedings will be edited by Brad Gibson and Mary Putman, and published as part of the ASP Conference Series.

A. Vankov

The suggested alternative cosmology is based on the idea of barion symmetric universe, in which our home universe is a representative of multitude of typical matter and antimatter universes. This alternative concept gives a physically reasonable explanation of all major problems of the Standard Cosmological Model. Classification Code MSC: Cosmology 524.8 Key

Arthur Kosowsky

Temperature and polarization power spectra of the cosmic microwave background can provide essentially incontrovertible evidence for coherent acoustic oscillations in the early universe. A simple model calculation demonstrates explicitly how polarization couples to velocities at the surface of last scatter and is nearly independent of gravitational or density

Rita M. Sambruna

Being dominated by non-thermal emission from aligned relativistic jets, blazars allow us to elucidate the physics of extragalactic jets, and, ultimately, how energy is extracted from the central black hole. Crucial information about jet structure is provided by the spectral energy distributions from radio to gamma-rays, their trends with luminosity, and corr

Bianca Garilli, Dario Maccagni, Stefano Andreon

We constructed the composite Luminosity Function (LF) of cluster galaxies in the g,r and i bands from the photometry of a mixed (Abell and X-ray selected) sample of the cores of 65 clusters, ranging in redshift from 0.05 to 0.25. The composite LF has been obtained from complete samples of ~2200 galaxies in the magnitude range -23<M<-17.5 (-18 in i). Cluster

Alexander Knebe

Numerical simulations of variants of the CDM~model with different cosmological parameters are used to compare statistical measures such as mass spectra, merger processes, and autocorrelation functions, for different models with relevant observations. The degree of virialisation of the halos is checked, and also which properties distinguish recent mergers. Me

F. Atrio Barandela, J. P. Muecket

The power spectrum of temperature anisotropies induced by hot intracluster gas on the cosmic background radiation is calculated. For low multipoles it remains constant while at multipoles above $l>2000$ it is exponentially damped. The shape of the radiation power spectrum is almost independent of the average intracluster gas density profile, gas evolution hi

Anna Wolter, Ginevra Trinchieri, Angela Iovino

We present the first X-ray detection of the Cartwheel&#39;s ring. The impact that created the characteristic optical structure is responsible also for an enhanced level of star formation to which we can ascribe the relatively high level of X-ray emission observed. Deeper images and spectroscopic information are needed to confirm or disprove the hypothesis th

Elena Pian, Giuseppe Malaguti, Laura Maraschi, Gabriele Ghisellini

Only ~10 blazars have been detected in soft gamma-rays by OSSE and the PDS, often in flaring state. We investigate the impact of the imaging and spectral capabilities of the IBIS instrument on board INTEGRAL on the study of blazars. The objectives are: 1) to remove ambiguities in the identification of some blazars as soft gamma-ray emitters; 2) to determine

M. Semel, A. Lopez Ariste

The radiative transfer equation (RTE) for polarized light accepts a convenient exponential solution when the absorption matrix commutes with its integral. We characterize some of the matrix depth variations which are compatible with the commutation condition. Eventually the vector solution may be diagonalized and one may obtain four independent scalar soluti

Tomasz Bulik

The process of photon splitting, becomes allowed in the presence of strong magnetic field. We calculate the influence of magnetized plasma on the photon splitting absorption coefficient. We calculate the refraction coefficients and polarization vectors with the inclusion of the vacuum terms at an arbitrary value of the magnetic field, and then find photon sp

Noam Soker

I propose a model for the formation of the two outer rings of SN 1987A. The main new ingredient is a short-lived, few times 10 years, intermediate wind, of velocity of about 100 km/s and total mass of about 10^{-3} Mo - few times 10^{-2} Mo\odot which is concentrated near the equatorial plane. This intermediate wind was formed during the few orbital periods

M. Ramella, G. Zamorani, E. Zucca, G. M. Stirpe

In this paper we identify objectively and analyze groups of galaxies in the recently completed ESP survey. We find 231 groups above the number overdensity threshold delta(rho)/rho=80 in the redshift range 5000<cz <60000 km/s. These groups contain 1250 members, 40.5% of the 3085 ESP galaxies within the same redshift range. The median velocity dispersion (corr

F. Fiore, P. Giommi, F. La Franca, G. Matt

We have surveyed about 50 deg-2 of sky in the largely unexplored 5-10 keV band using the BeppoSAX MECS instrument, finding 180 sources. After correction for the non uniform sky coverage we find about 18 sources deg-2 with F(5-10keV) >= 5E-14 cgs, and resolve 30-40 % of the hard 5-10 keV Cosmic X-ray Background (XRB). Optical identification of a first small s

Eric Gawiser, Andrew Jaffe, Joseph Silk

Applying basic physical principles to recent observational results, we derive upper and lower limits on microwave anisotropy from point sources over the range of frequencies 10-1000 GHz. We examine the level of noise in the observations as a possible indication of source confusion at subarcminute scales. We also derive an upper limit on microwave anisotropy

P. N. Best, H. J. A. R&#34;ottgering, M. S. Longair

The results of a deep spectroscopic campaign on powerful radio galaxies with redshifts z ~ 1, to investigate in detail their emission line gas properties, are presented. Both the 2-dimensional velocity structure of the [OII] 3727 emission line and the ionisation state of the gas are found to be strongly dependent upon the linear size (age) of the radio sourc

E. Lastennet, T. Lejeune, P. Westera, R. Buser

The comprehensive knowledge of fundamental parameters of single stars is the basis of the modelling of star clusters and galaxies. Most fundamental stellar parameters of the individual components in SB2 eclipsing binaries are known with very high accuracy. Unfortunately, while masses and radii are well determined, the temperatures strongly depend on photomet

P. N. Best, S. A. Eales, S. Rawlings, H. J. A. R&#34;ottgering

Deep radio observations at 5 and 8 GHz are presented of a complete sample of 11 radio galaxies with redshifts 0.85 < z < 1.5, selected from the 6C sample of Eales. The radio data, taken using the VLA in A, B and C array configurations, provide a best angular resolution of 0.25&#39;&#39; and reach an rms noise level of order 20 microJy. Radio core candidates

Alexander Kusenko, Gino Segre

Neutrino oscillations can explain the observed motion of pulsars. We show that two different models of neutrino emission from a cooling neutron star are in good quantitative agreement and predict the same order of magnitude for the pulsar kick velocity, consistent with the data.

G. F. Bertsch, P. F. Bortignon, K. Hagino

We apply the time-dependent variational principle, the nuclear field theory, and the boson expansion method to the Lipkin model to discuss anharmonicities of collective vibrational excitations. It is shown that all of these approaches lead to the same anharmonicity to leading order in the number of particles. Comparison with the exact solution of the Lipkin

Qaisar Shafi, Zurab Tavartkiladze

We try to gain an understanding of the recent Superkamiokande data on neutrino oscillations and several other important phenomenological issues within the framework of supersymmetric $SU(4)_c \times SU(2)_L \times SU(2)_R$ ($\equiv G_{422}$). By supplementing $G_{422}$ with a U(1)-${\cal R}$ symmetry, we can provide an explanation of the magnitude $M_G$ ($\s

D. Bazeia, H. Boschi-Filho, F. A. Brito

In this work we investigate the role of the symmetry of the Lagrangian on the existence of defects in systems of coupled scalar fields. We focus attention mainly on solutions where defects may nest defects. When space is non-compact we find topological BPS and non-BPS solutions that present internal structure. When space is compact the solutions are nontopol

Alfio Bonanno, Martin Reuter

The structure of the Cauchy Horizon singularity of a black hole formed in a generic collapse is studied by means of a renormalization group equation for quantum gravity. It is shown that during the early evolution of the Cauchy Horizon the increase of the mass function is damped when quantum fluctuations of the metric are taken into account.

Ville Uski, Bernhard Mehlig, Rudolf A. Roemer

We have calculated wave functions and matrix elements of the dipole operator in the two- and three-dimensional Anderson model of localization and have studied their statistical properties in the limit of weak disorder. In particular, we have considered two cases. First, we have studied the fluctuations as an external Aharonov-Bohm flux is varied. Second, we

R. P. Mignani, P. A. Caraveo, G. F. Bignami

We report on the optical observations of the gamma-ray pulsar PSR1706-44 performed with the Test Camera of the VLT-UT1 during the telescope Science Verification programme. With a limiting magnitude of V~ 27.5, these are the deepest optical observations ever performed for this pulsar, for which, however, no likely counterpart has been detected. The non-detect

J. A. Belinchon

In this paper we apply dimensional analysis (D.A.) to two cosmological models: Einstein-de Sitter and one Friedmann-Robertson-Walker (FRW) with radiation predominance. We believe that this method leads to the simplest form of solution the differential equations that arise in both models and would be useful as a base for the solution of more complex models. T

V. P. Gusynin, V. A. Miransky, I. A. Shovkovy

We describe a (first, to the best of our knowledge) essentially soluble example of dynamical symmetry breaking phenomenon in a 3+1 dimensional gauge theory without fundamental scalar fields: QED in a constant magnetic field.

Andrei A. Bytsenko, Luciano Vanzo, Sergio Zerbini

The one-loop quantum corrections to the free energy associated with scalar field in a higher dimensional static curved space-time is investigated making use of the conformal transformation method. For a space-time with bifurcate horizon, horizon divergences are accounted for choosing the Planck length as natural cutoff. The leading term in the high temperatu

K. G. Chetyrkin, Stephan Narison, V. I. Zakharov

We consider the assumption that a tachyonic gluon mass imitates short-distance nonperturbative physics of QCD. The phenomenological implications include modifications of the QCD sum rules for correlators of currents with various quantum numbers. The new 1/Q^2 terms allow to resolve in a natural way old puzzles in the pion and scalar-gluonium channels. They l

Max Karlovini, Kjell Rosquist

Cubic invariants for two-dimensional Hamiltonian systems are investigated using the Jacobi geometrization procedure. This approach allows for a unified treatment of invariants at both fixed and arbitrary energy. In the geometric picture the invariant generally corresponds to a third rank Killing tensor, whose existence at a fixed energy value forces the metr

Eanna E. Flanagan

A possible explanation is suggested for the controversial star-crushing effect seen in numerical simulations of inspiraling neutron star binaries by Wilson, Mathews and Marronetti (WMM). An apparently incorrect definition of momentum density in the momentum constraint equation used by WMM gives rise to a post-1-Newtonian error in the approximation scheme. We

A. Marecki, H. Falcke, J. Niezgoda, S. T. Garrington

Observations with MERLIN at 408 MHz have been used to establish the low-frequency part of the spectra of more than a hundred compact radio sources taken from the part of the Jodrell Bank--VLA Astrometric Survey limited by 35 deg. < δ< 75 deg. These sources were selected from JVAS and other catalogues to have convex spectra between 1.4 and 8.4 GHz, characteri

Ben Moore, George Lake, Thomas Quinn, Joachim Stadel

We follow the evolution of disk galaxies within a cluster that forms hierarchically in a cold dark matter N-body simulation. At a redshift z=0.5 we select several dark matter halos that have quiet merger histories and are about to enter the newly forming cluster environment. The halos are replaced with equilibrium high resolution model spirals that are const

A. M. Khvedelidze, H. -P. Pavel, G. Röpke

The unconstrained classical system equivalent to spatially homogeneous SU(2) Yang-Mills theory with theta angle is obtained and canonically quantized. The Schrödinger eigenvalue problem is solved approximately for the low lying states using variational calculation. The properties of the groundstate are discussed, in particular its electric and magnetic prope

Bernard Deconinck

The KP equation has a large family of quasiperiodic multiphase solutions. These solutions can be expressed in terms of Riemann-theta functions. In this paper, a finite-dimensional canonical Hamiltonian system depending on a finite number of parameters is given for the description of each such solution. The Hamiltonian systems are completely integrable in the

Erika Andersson, Marcia T. Fontenelle, Stig Stenholm

This paper proposes groove-like potential structures for the observation of quantum information processing by trapped particles. As an illustration the effect of quantum statistics at a 50-50 beam splitter is investigated. For non-interacting particles we regain the results known from photon experiments, but we have found that particle interactions destroy t

J. Steinbach, J. Twamley

We examine the dynamics of a qubit stored in the motional degrees of freedom of an ultra-cold ion in an ion trap which is subject to the decoherence effects of a finite-temperature bath. We discover an encoding of the qubit, in two of the motional modes of the ion, which is stable against the occurrence of either none or one quantum jump. For the case of a z

A. V. Bogdanov, A. S. Gevorkyan

The problem of random motion of 1D quantum reactive harmonic oscillator (QRHO) is formulated in terms of a wave functional regarded as a complex probability process in an extended space. In the complex stochastic differential equation (SDE) for this process the variables are separated with the help of the Langevin-type model SDE introduced in the functional

M. Castans, J. A. Belinchon

In this paper, we want to make to see the convenience of the amplification of the Planck`s system of absolute units through the introduction of two new constant, the dynamical constant and the permitividad of the vacuum upon rejecting that the electron charge has mechanical dimensions and adopting it as Planck`s charge. We apply these results to clarify the

Martin J. Savage, Kevin A. Scaldeferri, Mark B. Wise

The radiative capture process n+p-> d+gamma provides clear evidence for meson exchange currents in nuclear physics. We compute this process at low energies using a recently developed power counting for the effective field theory that describes nucleon-nucleon interactions. The leading order contribution to this process comes from the photon coupling to the n

Aurel Bulgac, Siu A. Chin, Harald A. Forbert, Piotr Magierski

The positioning of one or more bubbles inside a many fermion or boson system, does not affect the volume, surface or curvature terms in the liquid drop expansion of the total energy. If Coulomb effects are irrelevant, the only contribution to the ground state energy of a system with one or more voids arises from quantum effects, which is similar to the Casim

J. E. Amaro, T. W. Donnelly

The cross section for coincidence, quasielastic proton knock-out by electrons from a polarized K39 nucleus is computed in DWIA using an optical potential in describing the wave function of the ejected nucleon. The dependence of the FSI on the initial polarization angles of the nucleus is analyzed and explained in a new, semi-classical picture of the reaction

Myung Ki Cheoun, K. S. Kim, B. S. Han, Il-Tong Cheon

The recent TRIUMF experiment for $μ^- p \to n ν_μ γ$ gave a surprising result that the induced pseudoscalar coupling constant $g_P$ was larger than the value obtained from $μ^- p \to n ν_μ$ experiment as much as 44 %. Reexamining contribution of the axial vector current in electromagnetic interaction, we found an additional term to the matrix element which w

H. Haberzettl, C. Bennhold, T. Mart, T. Feuster

The general gauge-invariant photoproduction formalism given by Haberzettl is applied to kaon photoproduction off the nucleon at the tree level, with form factors describing composite nucleons. Numerical results show that this gauge-invariance procedure, when compared to Ohta&#39;s, leads to a much improved description of experimental data. Predictions for th

Il-Tong Cheon, Myung Ki Cheoun

The recent TRIUMF experiment for $μ^- p \to n ν_μ γ$ gave a surprising result that the induced pseudoscalar coupling constant $g_P$ was larger than the value obtained from $μ^- p \to n ν_μ$ experiment as much as 44 %. Reexamining contribution of the axial vector current, we found an additional term to the matrix element of Beder and Fearing which was used to

C. A. Gagliardi, R. E. Tribble, A. Azhari, H. L. Clark

The ${}^{16}O ({}^{3}He,d) {}^{17}F$ reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ${}^{17}F$. The coefficients provide the normalization for the tails of the overlap functions for ${}^{17}F \to{}^{16}O + p$ and allow us to calculate the S-factors for ${}^{16}O (p,γ){}^{17}

C. Alexa

The Lie symmetry group for 1+1 dimensional relativistic heat-conducting fluid is calculated for two different theories, Eckart and Israel-Stewart and a comparison between the group-invariant solutions has been made. Both fluids were founded to be physical acceptable in the sense that during the evolution of the fluid there are three velocity solutions that a

David Griffiths

In recently published work Maskit constructs a fundamental domain D_g for the Teichmueller modular group of a closed surface S of genus g>1. Maskit&#39;s technique is to demand that a certain set of 2g non-dividing geodesics C_{2g} on S satisfies certain shortness criteria. This gives an a priori infinite set of length inequalities that the geodesics in C_{2

Dan Abramovich, Angelo Vistoli

This note is but a research announcement, summarizing and explaining results proven and detailed in forthcoming papers. When one studies families of objects over curves, and the objects are parametrized by a Deligne-Mumford stack M, then the families are equivalent to morphisms of curves into M. In order to have complete moduli for such families, one needs t

Paul J. Sanders

For a prime p and natural number n with p greater than or equal to n, we establish the existence of a non-functorial one-to-one correspondence between isomorphism classes of groups of order p^n whose derived subgroup has exponent dividing p, and isomorphism classes of nilpotent p^n-element Lie algebras L over the truncated polynomial ring F_p[T]/(T^n) in whi

Shahn Majid, Robert Oeckl

We show that the crossed modules and bicovariant different calculi on two Hopf algebras related by a cocycle twist are in 1-1 correspondence. In particular, for quantum groups which are cocycle deformation-quantisations of classical groups the calculi are obtained as deformation-quantisation of the classical ones. As an application, we classify all bicovaria

Nicolas Ressayre

Let $X$ be a projective variety with an action of a reductive group $G$. Each ample $G$-line bundle $L$ on $X$ defines an open subset $X^{\rm ss}(L)$ of semi-stable points. Following Dolgachev and Hu, define a GIT-class as the set of algebraic equivalence classes of $L&#39;$s with fixed $X^{\rm ss}(L)$. We show that the GIT-classes are the relative interiors

Mark. D. Gould, Yao-Zhong Zhang, Phillip S. Isaac

We show how to construct, starting from a quasi-Hopf (super)algebra, central elements or Casimir invariants. We show that these central elements are invariant under quasi-Hopf twistings. As a consequence, the elliptic quantum (super)groups, which arise from twisting the normal quantum (super)groups, have the same Casimir invariants as the corresponding quant

Charles Rezk

We show that homotopy pullbacks of sheaves of simplicial sets over a Grothendieck topology distribute over homotopy colimits; this generalizes a result of Puppe about topological spaces. In addition, we show that inverse image functors between categories of simplicial sheaves preserve homotopy pullback squares. The method we use introduces the notion of a sh

Richard P. Stanley

Kontsevich conjectured that the number f(G,q) of zeros over the finite field with q elements of a certain polynomial connected with the spanning trees of a graph G is polynomial function of q. We have been unable to settle Kontsevich&#39;s conjecture. However, we can evaluate f(G,q) explicitly for certain graphs G, such as the complete graph. We also point o

D. G. C. McKeon

Vortex solutions to the classical field equations in a massive, renormalizable U(1) gauge model are considered in (2+1) dimensions. A vector field whose kinetic term consists of a Chern-Simons term plus a Stuekelberg mass term is coupled to a scalar field. If the classical scalar field is set equal to zero, then there are classical configurations of the vect

Francesco Antonuccio, Oleg Lunin, Stephen Pinsky

We consider three dimensional SU(N) N=1 super-Yang-Mills compactified on the space-time R X S^1 X S^1. In particular, we compactify the light-cone coordinate x^- on a light-like circle via DLCQ, and wrap the remaining transverse coordinate on a spatial circle. By retaining only the first few excited modes in the transverse direction, we are able to solve for

K. Z. Win

A general condition for the existence of fermion zero modes is derived for the M-5-brane, the M-2-brane and the D=4, N=2 Majumdar-Papapetrou 0-brane. The fermion zero modes of these p-branes do not exist if the supersymmetry spinor generator goes to a constant at the horizon and they exist only if it vanishes there. In particular it is shown that the fermion

Adam D. Helfer

I review some recent results showing that the physics of negative energy densities, as predicted by relativistic quantum field theories, is more complicated than has generally been appreciated. On the one hand, in external potentials where there is a time--dependence, however slight, the Hamiltonians are unbounded below. On the other, there are limitations o

Morten Krogh

We consider the 5-brane placed at one end of the world in the Heterotic $E_8 \times E_8$ theory. The low energy theory is a 6 dimensional $(1,0)$ superconformal theory with $E_8$ as a global symmetry. We calculate the two-point correlator of the $E_8$ current in 6 dimensions and in 4 dimensions after compactification on $\MT{2}$. This correlator is derived i

Richard Battye, Paul Sutcliffe

Using numerical simulations of the full nonlinear equations of motion we investigate topological solitons of a modified O(3) sigma model in three space dimensions, in which the solitons are stabilized by the Hopf charge. We find that for solitons up to charge five the solutions have the structure of closed strings, which become increasingly twisted as the ch

H. Arodź

Improved expansion in width is applied to a curved domain wall in nonrelativistic dissipative $λ(Φ^2 - v^2)^2 $ model with real scalar order parameter $Φ$. Approximate analytic description of such a domain wall to second order in the width is presented.

R. A. Battye, B. Carter

We extend a recent analysis of gravitational perturbations on Dirac-Nambu-Goto strings, membranes and higher dimensional branes. In an arbitrary gauge, it is shown that the relevant first order equations governing the displacement vector of the worldsheet and metric perturbation are obtainable from a variational principle whose Lagrangian is constructed as a

Aleksandar Bogojevic, Olivera Miskovic

We investigate the connection between Abelian bosonization in the Minkowski and Euclidean formalisms. The relation is best seen in the complex time formalism of S. A. Fulling and S. N. M. Ruijsenaars \cite{fulling}.

E. Ruiz Arriola, L. L. Salcedo

The chiral and scale anomalies of a very general class of non local Dirac operators are computed using the $ζ$-function definition of the fermionic determinant. For the axial anomaly all new terms introduced by the non locality are shown to be removable by counterterms and such counterterms are also explicitly computed. It is verified that the non local Dira

Ilya L. Shapiro

We discuss the theoretical basis for the search of the possible experimental manifestations of the torsion field at low energies. First, the quantum field theory in an external gravitational field with torsion is reviewed. The renormalizability requires the nonminimal interaction of torsion with spinor and scalar (Higgs) fields. The Pauli-like equation conta

T. Ioannidou, B. Piette, W. J. Zakrzewski

We show that any solution of the SU(2) Skyrme model can be used to give a topologically trivial solution of the SU(4) one. In addition, we extend the method introduced by Houghton et al. and use harmonic maps from S2 to CP(N-1) to construct low energy configurations of the SU(N) Skyrme models. We show that one of such maps gives an exact, topologically trivi

D. G. Barci, L. E. Oxman, S. P. Sorella

General results on the structure of the bosonization of fermionic systems in $(2+1)$d are obtained. In particular, the universal character of the bosonized topological current is established and applied to generic fermionic current interactions. The final form of the bosonized action is shown to be given by the sum of two terms. The first one corresponds to

Anastasios C. Petkou, Nicholas D. Vlachos

We study the operator product expansion (OPE) of the auxiliary scalar field λ(x) with itself, in the conformally invariant O(N) Vector Model for 2<d<4, to leading order in 1/N in a strip-like geometry with one finite dimension of length L. We show that consistency of the finite-geometry OPE with bulk OPE calculations requires the physical conditions of, eith

Piotr H. Chankowski, John Ellis, Keith A. Olive, Stefan Pokorski

We study the extent to which the cosmological fine-tuning problem - why the relic density of neutralino cold dark matter particles $χ$ is similar to that of baryons - is related to the fine-tuning aspect of the gauge hierarchy problem - how one arranges that M_W << M_P without unnatural choices of MSSM parameters. Working in the minimal supergravity framewor

T. Csorgo, J. Zimanyi

A recently obtained exact analytic solution to the wave-packet version of the pion-laser model is presented. In the rare gas limit, a thermal behaviour is found while the dense gas limiting case corresponds to Bose-Einstein condensation of wave-packets to the wave-packet mode with the smallest possible energy.

Gregory Mahlon

We describe the off-diagonal spin basis for observing angular correlations in top quark pair production events at the Fermilab Tevatron. For events initiated by quark-antiquark annihilation, the top and antitop quark spins are 100% correlated in this basis: a spin-up top quark is always accompanied by a spin-down antitop quark and vice versa. Inclusion of th

J. C. Montero, V. Pleitez, O. Ravinez

We show that it is possible to implement soft superweak CP violation in the context of a 331 model with only three triplets. All CP violation effects come from the exchange of singly and doubly charged scalars. We consider the implication of this mechanism in the quark and lepton sectors. In particular it is shown that in this model, as in most of those whic

T. P. Cheng, Ling-Fong Li

A whole class of non-perturbative QCD studies, e.g. the instanton models, chiral quark models, etc. indicates that the effective degrees of freedom for the physics in the low Q^(2) < 1 GeV^(2) region could be the constituent quarks (CQs) and internal Goldstone bosons (IGBs). This leads to a nucleon structure with the spin being carried by three constituent q

M. Zielinski

We report on recent work concerning the phenomenology of initial-state parton-kt effects in direct-photon production and related processes in hadron collisions. After a brief summary of a kt-smearing model, we present a study of recent results on fixed-target and collider direct-photon production, using complementary data on diphoton and pion production that

Thomas R. Hemmert, Ulf-G. Meissner, Sven Steininger

We present an analytic and parameter-free expression for the momentum dependence of the strange magnetic form factor of the nucleon and its corresponding radius which has been derived in Heavy Baryon Chiral Perturbation Theory. We also discuss a model-independent relation between the isoscalar magnetic and the strange magnetic form factors of the nucleon bas

M. R. Pennington

The current status of the accepted glueball candidates is reviewed. The difference between bare and dressed hadrons is emphasised. What two photon processes, both production and decay, have taught us about these is discussed.

Kwei-Chou Yang

We review the B meson lifetime problems and nonspectator effects. The predictions of B meson lifetime ratios depend on four unknown hadronic parameters $B_1$, $B_2$, $ε_1$ and $ε_2$, where $B_1$ and $B_2$ parametrize the matrix elements of color singlet-singlet four-quark operators and $ε_1$ and $ε_2$ the matrix elements of color octet-octet operators. To un

A. N. Ivanov

The partial width of the decay D^*+_s -> D^+_s pi^0 going through the violation of isotopical symmetry is computed with respect to the partial width of the radiative decay D^*+_s -> D^+_s gamma in the effective quark model with chiral U(3)xU(3) symmetry incorporating Heavy quark effective theory (HQET) and Chiral perturbation theory at the quark level (CHPT)

Chris Stewart, Roman Koniuk

We present results on a new operator for the investigation of string-breaking effects in quenched SU(2)-colour QCD. The ground state of a spatially-separated static-light meson-antimeson pair is a combination of a state with two distinct mesons, expected to dominate for large separations, and a state where the light quarks have annihilated, which contributes

Chengzhong Sui

We present the results from full QCD simulations with four flavors of light stag gered dynamical quarks on {\it {\it QCDSP}} supercomputer. Previous results are reproduced and the simulation reported here yields new results consistent with o ur previous runs. The hadron spectrum obtained with Wilson valence fermions reported here will allow us to determine i