arXiv papers from September 1996

Mihaela Manoliu

We apply the geometric quantization method with real polarizations to the quantization of a symplectic torus. By quantizing with half-densities we canonically associate to the symplectic torus a projective Hilbert space and prove that the projective factor is expressible in terms of the Maslov-Kashiwara index. As in the quantization of a linear symplectic sp

M. T. Grisaru, A. Santambrogio, D. Zanon

We consider $N=2$ supergravity coupled to $N=2$ Yang--Mills matter and discuss the nature of one--loop divergences. Using $N=1$ superfields and superspace methods, we describe the quantization of the system in the abelian case.

S. Vera, H. Waelbroeck

Although several synonymous codons can encode the same aminoacid, this symmetry is generally broken in natural genetic systems. In this article, we show that the symmetry breaking can result from selective pressures due to the violation of the synonym symmetry by mutation and recombination. We conjecture that this enhances the probability to produce mutants

H. Waelbroeck, F. Zertuche

We propose a theory of deterministic chaos for discrete systems, based on their representations in binary state spaces $ \Omega $, homeomorphic to the space of symbolic dynamics. This formalism is applied to neural networks and cellular automata; it is found that such systems cannot be viewed as chaotic when one uses the Hamming distance as the metric for th

S. Emery, M. Krüger, J. Rant, M. Schweda

The two--dimensional topological BF model is quantized in the axial gauge. We show that this theory is trivially ultraviolet finite and that the usual infrared problem of the propagator of the scalar field in two dimensions is replaced by an easily solvable long distances problem inherent to the axial gauge. It will also be shown that contrarily to the 3--di

Myeong-Gu Park

The probability distribution of lens image separations is calculated for the ``standard'' gravitational lensing statistics model in an arbitrary, flat Robertson-Walker universe, where lensing galaxies are singular isothermal spheres that follow the Schechter luminosity function. In a flat universe, the probability distribution is independent of the source di

John F. Donoghue, Eugene Golowich, Alexey A. Petrov

We provide a new estimate of the long-distance component to the radiative transition $B \to \rho \gamma$. Our mechanism involves the soft-scattering of on-shell hadronic products of nonleptonic $B$ decay, as in the chain $B \to \rho\rho \to \rho\gamma$. We employ a phenomenological fit to scattering data to estimate the effect. The specific intermediate stat

E. Poppitz, S. P. Trivedi

We show that supersymmetry breaking in a class of theories with SU(N) x SU(N-2) gauge symmetry can be studied in a calculable sigma model. We use the sigma model to show that the supersymmetry breaking vacuum in these theories leaves a large subgroup of flavor symmetries intact, and to calculate the masses of the low-lying states. By embedding the Standard M

Sheldon Katz, Albrecht Klemm, Cumrun Vafa

Using the recent advances in our understanding of non-perturbative aspects of type II strings we show how non-trivial exact results for $N=2$ quantum field theories can be reduced to T-dualities of string theory. This is done by constructing a local geometric realization of quantum field theories together with a local application of mirror symmetry. This con

Ralf Hempfling

In supersymmetric models without $R$-parity neutrinos naturally become massive and mix with each other. We explore the predictions of a very restricted model with only three free parameters and find that this model naturally yields masses and mixing angles compatible with experimental results from solar and atmospheric neutrino experiments. Furthermore, ther

J. E. Santos

In this paper we address the relationship between zero temperature Glauber dynamics and the diffusion-annihilation problem in the free fermion case. We show that the well-known duality transformation between the two problems can be formulated as a similarity transformation if one uses appropriate (toroidal) boundary conditions. This allow us to establish and

S. Gavin, R. Vogt

Measurements of $\psi$ and $\psi'$ production at the CERN SPS are compared to predictions based on a hadronic model of charmonium suppression. Detailed information is presented to facilitate comparison to other analyses. Sensitivity of these conclusions to the model parameters is discussed.

J. M. P. Carmelo, N. M. R. Peres, D. K. Campbell

We use a complete pseudoparticle operator representation to study the explicit form of the finite-frequency conductivity for the Hubbard chain. Our study reveals that the spectral weight is mostly concentrated at the \omega =0 Drude peak (except at density n=1) and at an absorption starting just below twice the value of the chemical potential whose \omega-de

Richard J. Szabo, John F. Wheater

We study the large-N limit of a class of matrix models for dually weighted triangulated random surfaces using character expansion techniques. We show that for various choices of the weights of vertices of the dynamical triangulation the model can be solved by resumming the Itzykson-Di Francesco formula over congruence classes of Young tableau weights modulo

D. Montes, E. L. Martin, M. J. Fernandez-Figueroa, M. Cornide

In this work we present spectroscopic observations centered in the spectral lines most widely used as optical indicators of chromospheric activity (H{alpha}, H{beta}, Ca II H & K, and He I D{3}) in a sample of F, G, K and M chromospherically inactive stars. The spectra have been obtained with the aim of providing a library of high and mid-resolution spectra

Aaron J. Romanowsky, Christopher S. Kochanek

Quantitative dynamical models of galaxies require deprojecting the observed surface brightness to determine the luminosity density of the galaxy. Existing deprojection methods for axisymmetric galaxies assume that a unique deprojection exists for any given inclination, even though the projected density is known to be degenerate to the addition of "konus dens

J. Ellis. N. Mavromatos, D. Nanopoulos

We discuss the scattering of a light closed-string state off a $D$ brane, taking into account quantum recoil effects on the latter, which are described by a pair of logarithmic operators. The light-particle and $D$-brane subsystems may each be described by a world-sheet with an external source due to the interaction between them. This perturbs each subsystem

C. Herzog, M. Ol'Shanii

It is well known that at the thermodynamic limit there are no observable differences in the results obtained by grand canonical and canonical descriptions of a many-body system. In the present paper, we test the validity of this statement for finite systems using as an example an ensemble of bosons trapped in a 1D harmonic potential well. We have found an an

Stephen L. Adler, Jeeva Anandan

We develop the theory of the nonadiabatic geometric phase, in both the Abelian and non-Abelian cases, in quaternionic Hilbert space.

Marika Taylor-Robinson

The existence of instantonic decay modes would indicate a semi-classical instability of the vacua of ten and eleven dimensional supergravity theories. Decay modes whose spin structures are incompatible with those of supersymmetric vacua have previously been constructed, and we present generalisations including those involving non trivial dilaton and antisymm

Marc Kamionkowski

Several ideas for new physics beyond the standard model may provide particle candidates for the dark matter in the Galactic halo. The two leading candidates are an axion and a weakly-interacting massive particle (WIMP), such as the neutralino in supersymmetric extensions of the standard model. Several possibilities for detection of such particles are discuss

S. Das Gupta, J. Pan, M. B. Tsang

Determination of temperature from experimental data has become important in searches for critical phenomena in heavy ion collisions. Widely used methods are ratios of isotopes (which rely on chemical and thermal equilibrium), population ratios of excited states etc. Using the lattice gas model we propose a new observable: $n_{ch}/Z$ where $n_{ch}$ is the cha

S. W. Allen, A. C. Fabian, A. C. Edge, M. W. Bautz

We present the results from a detailed ASCA/ROSAT X-ray study of three distant, massive cooling flows; Zwicky 3146 (z=0.291), Abell 1835 (z=0.252) and E1455+223 (Zwicky 7160; z=0.258). Using multiphase models fitted to the ASCA spectra, we determine values for the temperature, metallicity, luminosity and cooling rates in the clusters. These results are combi

D. Boyanovsky, D. Cormier, H. J. de Vega, R. Holman

The nonlinear time evolution of the quantum fields is studied in the O(N) model for large N in a radiation dominated FRW universe, with a view towards the phenomenon of explosive particle production due to either spinodal instabilities or parametric amplification, i.e. preheating. Quantum backreaction effects due to the produced particles are included consis

A. Staszczak, Z. Lojewski, A. Baran, B. Nerlo-Pomorska

Spontaneous-fission half-lives of the heaviest even-even nuclei are evaluated and compared with their alpha-decay mode. Calculations of spontaneous-fission half-lives are performed in the dynamical way with potential energy obtained by the macroscopic-microscopic method and the inertia tensor obtained by the cranking approximation. The alpha-decay half-lives

Matthias Heyssler, Vassilis C. Spanos

Our aim is to test a model recently presented, motivated by the reported $R_b$ and $R_c$ ``crisis", which contains extra vector fermions. We suggest an alternative indirect test of the possible existence of new heavy quark flavours at the LEP2 collider, which turns out to give the clearest signal. We calculate $q\bar{q}$ cross sections within this framework,

C. Chiappini, F. Matteucci, R. Gratton

In this paper we present a new chemical evolution model for the Galaxy which assumes two main infall episodes for the formation of halo-thick disk and thin disk, respectively. We do not try to take into account explicitly the evolution of the halo but we implicitly assume that the timescale for the formation of the halo was of the same order as the timescale

A. P. Szczepaniak, E. S. Swanson

A model which combines the perturbative behavior of QCD with low energy phenomenology in a unified framework is developed. This is achieved by applying a similarity transformation to the QCD Hamiltonian which removes interactions between the ultraviolet cutoff and an arbitrary lower scale. Iteration then yields a renormalization group improved effective Hami

Fernando C. Lombardo, Francisco D. Mazzitelli

The Einstein-Langevin equations take into account the backreaction of quantum matter fields on the background geometry. We present a derivation of these equations to lowest order in a covariant expansion in powers of the curvature. For massless fields, the equations are completely determined by the running coupling constants of the theory.

P. Bowcock

We find classical solutions to the simply-laced affine Toda equations which satisfy integrable boundary conditions using solitons which are analytically continued from imaginary coupling theories. Both static `vacuum' configurations and the time-dependent perturbations about them which correspond to classical vacua and particle scattering solutions respectiv

Thomas R. Powers, Raymond E. Goldstein

A new category of front propagation problems is proposed in which a spreading instability evolves through a singular configuration before saturating. We examine the nature of this front for the viscous Rayleigh instability of a column of one fluid immersed in another, using the marginal stability criterion to estimate the front velocity, front width, and the

Goetz S. Uhrig

The dynamic conductivity $\sigma(\omega)$ of strongly correlated electrons in a symmetry broken phase is investigated in the present work. The model considered consists of spinless fermions with repulsive interaction on a simple cubic lattice. The investigated symmetry broken phase is the charge density wave (CDW) with wave vector $Q=(\pi,\pi,\pi)^\dagger$ w

Jens Hoppe

For the simplest case of a supermembrane matrix model, various symmetry reductions are given, with the fermionic contribution(s) (to an effective Schr\"odinger equation) corresponding to an attractive $\delta$-function potential (towards zero-area configurations). The differential equations are real, and are shown not to admit square-integrable real solution

Rainer Verch

We derive for a pair of operators on a symplectic space which are adjoints of each other with respect to the symplectic form (that is, they are sympletically adjoint) that, if they are bounded for some scalar product on the symplectic space dominating the symplectic form, then they are bounded with respect to a one-parametric family of scalar products canoni

Ya. M. Blanter, A. D. Mirlin, B. A. Muzykantskii

We study influence of electron-electron interaction on statistics of Coulomb blockade peak spacings in disordered quantum dots. It is shown that the interaction combined with fluctuations of eigenfunctions of the Fermi sea, enhances the peak spacing fluctuations, in accordance with recent experiments. In addition, account of the spin degrees of freedom leads

J. Lopez, D. Nanopoulos, A. Zichichi

We explore and contrast the single-photon and diphoton signals expected at LEP 2, that arise from neutralino-gravitino (e^+ e^- -> chi + gravitino -> gamma + E_miss) and neutralino-neutralino (e^+ e^- -> chi + chi -> gamma + gamma + E_miss) production in supersymmetric models with a light gravitino. LEP 1 limits imply that one may observe either one, but not

Per Frojdh, Marcel den Nijs

Directed percolation is one of the generic universality classes for dynamic processes. We study the crossover from isotropic to directed percolation by representing the combined problem as a random cluster model, with a parameter $r$ controlling the spontaneous birth of new forest fires. We obtain the exact crossover exponent $y_{DP}=y_T-1$ at $r=1$ using Co

Roy Maartens

Gravity waves in irrotational dust spacetimes are characterised by nonzero magnetic Weyl tensor $H_{ab}$. In the linearised theory, the divergence of $H_{ab}$ is set to zero. Recently Lesame et al. [Phys. Rev. D {\bf 53}, 738 (1996)] presented an argument to show that, in the exact nonlinear theory, $div H=0$ forces $H_{ab}=0$, thus implying a linearisation

Beverly K. Berger, David Garfinkle, Eugene Strasser

We present a new numerical algorithm for evolving the Mixmaster spacetimes. By using symplectic integration techniques to take advantage of the exact Taub solution for the scattering between asymptotic Kasner regimes, we evolve these spacetimes with higher accuracy using much larger time steps than previously possible. The longer Mixmaster evolution thus all

S. Dawson, X. -G. He, G. Valencia

We study the capability of a $2 TeV$ $p\overline{p}$ collider with an integrated luminosity of $10 fb^{-1}$ to study CP violation in the processes $p \bar{p} \ra W^\pm \gamma$ and $p \bar{p} \ra Z \gamma$. We assume the existence of new CP violating interactions beyond the standard model which we describe with an effective Lagrangian. We find that the study

Peter Prelovsek

The dynamical Hall response in a correlated electronic system is analysed within the linear response theory for tight binding models. At $T=0$ the d.c. Hall constant for a single quasiparticle is expressed explicitly via the charge stiffness, and a semiclassical result is recovered. As expected a hole-like response is found for the mobile hole introduced int

E. C. Marino

We consider the Maxwell-Higgs system in the broken phase, described in terms of a Kalb-Ramond field interacting with the electromagnetic field through a topological coupling. We then study the creation operators of states which respectively carry a point charge and a closed magnetic string in the electromagnetic language or a point topological charge and a c

E. J. Doedel, M. J. Friedman, B. I. Kunin

A successive continuation method for locating connecting orbits in parametrized systems of autonomous ODEs is considered. A local convergence analysis is presented and several illustrative numerical examples are given.

C. T. Sachrajda

The principal difficulty in deducing weak interaction properties from experimental measurements of $B$-decays lies in controlling the strong interaction effects. In this talk I review the status of theoretical calculations of the amplitudes for exclusive leptonic and semileptonic decays, in the latter case with special emphasis on the extraction of the $V_{c

U. Bunke, M. Olbrich

A Kleinian manifold Y is a quotient of a rank-one symmetric space of non-compact type by a convex-cocompact discrete group of isometries. We describe the spectral decomposition of the space of square integrable sections of locally homogeneous bundles on Y with respect to locally invariant differential operators. In the course of the proof we obtain meromorph

Stefano Catani, Michael H. Seymour

We briefly describe a new general algorithm for carrying out QCD calculations to next-to-leading order in perturbation theory. The algorithm can be used for computing arbitrary jet cross sections in arbitrary processes and can be straightforwardly implemented in general-purpose Monte Carlo programs. We show numerical results for the specific case of jet cros

F. M. Renard, C. Verzegnassi

The theoretical merits of longitudinal polarization asymmetries of electron-positron annihilation into two final fermions at future colliders are examined, using a recently proposed theoretical description. A number of interesting features, valid for searches of virtual effects of new physics, is underlined, that is reminiscent of analogous properties valid

Alfredo E. Dominguez, Carlos N. Kozameh, Malcolm Ludvigsen

Using the continuity of the scalar $\Psi_2$ (the mass aspect) at null infinity through $i_o$ we show that the space of radiative solutions of general relativity can be thought of a fibered space where the value of $\Psi_2$ at $i_o$ plays the role of the base space. We also show that the restriction of the available symplectic form to each ``fiber'' is degene

Nobuhito Maru, Shinsaku Kitakado

We point out that the similarities in N = 1 supersymmetric SO, SP gauge theories can be explained by using the trick of extrapolating the groups to the negative dimensions. One of the advantages of this trick is that anomaly matching is automatically satisfied.

A. H. MacDonald

In the strong magnetic field fractional quantum Hall regime, electrons in a two-dimensional electron system are confined to their lowest Landau level. Because of the macroscopic Landau level degeneracy nearly all physical properties at low energies and temperatures are then entirely determined by electron-electron interactions. The properties of these non-Fe

Analia N. Cillis, Diego D. Harari

We reconsider the effects of photon-graviton conversion in a primordial magnetic field upon the cosmic microwave background radiation. We argue that plasma effects make the photon-graviton conversion process negligible.

G. Grignani, G. Semenoff, P. Sodano, O. Tirkkonen

We show that the problem of computing the vacuum expectation values of gauge invariant operators in the strong coupling limit of topologically massive gauge theory is equivalent to the problem of computing similar operators in the $G_k/G$ model where $k$ is the integer coefficient of the Chern-Simons term. The $G_k/G$ model is a topological field theory and

Jacek Gruszczak

Differential properties of Klein-Gordon and electromagnetic fields on the space-time of a straight cosmic string are studied with the help of methods of the differential space theory. It is shown that these fields are smooth in the interior of the cosmic string space-time and that they loose this property at the singular boundary except for the cosmic string

L. Frappat, A. Sciarrino, S. Sciuto, P. Sorba

We give a realization of the quantum affine Lie superalgebras U_q(A(M,N))^(1) in terms of anyons defined on a one or two-dimensional lattice, the deformation parameter q being related to the statistical parameter $\nu$ of the anyons by q = exp(i\pi\nu). The construction uses anyons contructed from usual fermionic oscillators and deformed bosonic oscillators.

Johannes Roth, Christopher L. Henley

A structure model of atoms of two sizes, interacting with Lennard-Jones potentials and simulated by molecular dynamics, was observed to freeze into a decagonal quasicrystal dominated by Frank-Kasper coordination shells and closely related to the Henley-Elser model for icosahedral quasicrystals. Idealized structure models can be described as decorations of tr

J. Garriga, A. Vilenkin

The tunneling approach to the wave function of the universe has been recently criticized by Bousso and Hawking who claim that it predicts a catastrophic instability of de Sitter space with respect to pair production of black holes. We show that this claim is unfounded. First, we argue that different horizon size regions in de Sitter space cannot be treated a

Hartmut Frommert, Holger Schoor, Heinz Dehnen

The scalar background field and its consequences are discussed for the Friedmann type cosmological solutions of the scalar-tensor theory of gravity with the Higgs field of the Standard Model as the scalar gravitational field.

Oleg von Styp Rekowski, Hartmut Frommert

Within the scalar-tensor theory of gravity with Higgs mechanism without Higgs particles, we prove that the excited Higgs potential (the scalar field) vanishs inside and outside of the stellar matter for static spherically symmetric configurations. The field equation for the metric (the tensorial gravitational field) turns out to be essentially the Einsteinia

Yuri B. Suris

A new Lax representation for the Bogoyavlensky lattice is found, its $r$--matrix interpretation is elaborated. The $r$--matrix structure turns out to be related to a highly nonlocal quadratic Poisson structure on a direct sum of associative algebras. The theory of such nonlocal structures is developed, the Poisson property of the monodromy map is worked out

A. Ali, H. Schroeder

We review some selected topics in the decays of heavy flavours, beauty and charm, which are of principal interest at HERA-B and HERA. The topics in $B$ physics include: an update on the quark mixing matrix and CP violating phases, issues bearing on an improved resolution on the CP-violating phase $\Delta (sin 2 \beta)$, prospects of measuring radiative and s

Benno Rumpf

Domain walls of a discrete model of an anisotropic ferromagnet are studied. They can be described by sequences of two reversible mappings. Competition between the length scale of spatial structures and the lattice constant leads to a rich diversity of domain wall solutions related in a bifurcation scenario.

Hartmut Frommert

It is investigated if massless particles can couple to scalar fields in a special relativistic theory with classical particles. The only possible obvious theory which is invariant under Lorentz transformations and reparametrization of the affine parameter leads to trivial trajectories (straight lines) for the massless case, and also the investigation of the

P. Q. Hung, G. Isidori

We analyze the implications of a Higgs discovery on possible ``new-physics'' scenarios, for $m_H$ up to $\sim 700$ GeV. For this purpose we critically review lower and upper limits on the Higgs mass in the SM and in the MSSM, respectively. Furthermore, we discuss the general features of possible ``heavy'' ($m_H \gsim 2 m_Z$) Higgs scenarios by means of a sim

Krzysztof Gawedzki

This is an introductory course on the open problems in the theory of fully developed turbulence. It discusses: 1. hydrodynamical equations, 2. existence of solutions, 3. statistical description of turbulent flows, 4. Kolmogorov scaling theory, 5. functional approach to turbulence: similarities and differences with field theory, 6. breakdown of the Kolmogorov

L. Greggio

Using current models of spectrophotometric properties of single age, single metallicity stellar populations I have computed the Mg2, Hbeta, Fe52 and Fe53 line strengths for stellar populations with a metallicity spread. The comparison of these models with the nuclear indices of early type galaxies yield the following major conclusions. The metallicity distri

D. B. Fairlie, R. Zhdanov

Field equations with general covariance are interpreted as equations for a target space describing physical space time co-ordinates, in terms of an underlying base space with conformal invariance. These equations admit an infinite number of inequivalent Lagrangian descriptions. A model for reparametrisation invariant membranes is obtained by reversing the ro

Michael Frank

We show three Hahn-Banach type extension criteria for (sets of) bounded C*-linear maps of Hilbert C*-modules to the underlying C*-algebras of coefficients. One criterion establishes an alternative description of the property of (AW*-) C*-algebras to be monotone complete or additively complete.

D. Roth, P. Buechel, M. Luecke, H. W. Mueller

The problem of pattern selection in absolutely unstable open flow systems is investigated by considering the example of Rayleigh-B\'{e}nard convection. The spatiotemporal structure of convection rolls propagating downstream in an externally imposed flow is determined for six different inlet/outlet boundary conditions. Results are obtained by numerical simula

Ch. Jung, M. Luecke, P. Buechel

We investigate how a horizontal plane Poiseuille shear flow changes linear convection properties in binary fluid layers heated from below. The full linear field equations are solved with a shooting method for realistic top and bottom boundary conditions. Through-flow induced changes of the bifurcation thresholds (stability boundaries) for different types of

P. Buechel, M. Luecke

A unique pattern selection in the absolutely unstable regime of driven, nonlinear, open-flow systems is reviewed. It has recently been found in numerical simulations of propagating vortex structures occuring in Taylor-Couette and Rayleigh-Benard systems subject to an externally imposed through-flow. Unlike the stationary patterns in systems without through-f

Jan F. van Diejen

Two families (type $A$ and type $B$) of confluent hypergeometric polynomials in several variables are studied. We describe the orthogonality properties, differential equations, and Pieri type recurrence formulas for these families. In the one-variable case, the polynomials in question reduce to the Hermite polynomials (type $A$) and the Laguerre polynomials

Yu. R. Musin

Minimal N=1/2 supersymmetric extension of bosonic Polyakov's string is constructed. This model is natural generalization of Di Vecchia-Ravndal superparticle. The classical sector of the model is investigated, Noether currents and Virosoro supercondition are found. Minimal spinning string is more simple, than the standard N=1 spinning string of Neveu-Schwarz-

A. Gramada, M. E. Raikh

A double--layer system in a strong perpendicular magnetic field is considered. We assume a random potential in each layer to be smooth. We also assume that there is no correlation between random potentials in different layers. Under these conditions the equipotential lines from different layers, corresponding to the same energy, may cross each other. We show

Yu Zhang, Peter Anninos, Michael L. Norman, Avery Meiksin

We simulate the Lya forest in a standard CDM universe using a 2-level hierarchical grid code to evolve the dark and baryonic matter components self-consistently. We solve the time-dependent ionization equations for hydrogen and helium, adopting the Haardt & Madau (1996) estimate for the metagalactic UV radiation background. We compare our simulation results

M. S. Berger

We examine the utility of employing polarized lepton (electron and muon) beams to perform indirect searches for scalar leptoquarks. We find that polarization can extend the reach in excluding leptoquark masses for both $e^+e^-$ and $\mu^+\mu^-$ machines. Polarization can also provide a diagnostic tool for determining leptoquark couplings.

Keith A. Kearnes, Emil W. Kiss

We establish a direct correspondence between two congruence poroperties for finite algebras. The first property is that minimal sets of type i omit tails. The second property is that congruence lattices omit pentagons of type i.

Rosario N. Mantegna, H. Eugene Stanley

Analogies between the price dynamics in the foreign exchange market and 3-dimensional fully developed turbulence were recently presented in Nature vol. 381, 767-769 (1996). Independently, we have carried out a study comparing the parallel of the dynamical properties of the S&P 500 index and of the time evolution of a 3-dimensional fully turbulent fluid, but

G. Fano, F. Ortolani, L. Ziosi

Numerical results are presented for a generalized resonance valence bond state which includes both ionic and covalent contributions in each bond ; non nearest-neighbor bonds are also considered. Variational calculations have been performed and the space group symmetry has been taken into account. The results for the Hubbard Hamiltonian are compared with the

Johannes Roth, Franz Gaehler

We present a molecular dynamics study on atomic self-diffusion in Frank-Kasper type dodecagonal quasicrystals. It is found that the quasicrystal-specific flip mechanism for atomic diffusion as predicted by Kalugin and Katz, indeed occurs in this system. However, in order to be effective, this mechanism needs to be catalyzed by other defects such as half-vaca

Y. Mellier, L. van Waerbeke, F. Bernardeau, B. Fort

The gravitational lensing effect is one of the most promising tools for cosmology. Indeed it probes directly the total mass distribution in large-scale structures and can as well provide valuable informations on the values of the density parameter Omega and the cosmological constant lambda. In this review we summarize the most spectacular observational and t

Noah Brosch

I present an up-to-date description of the TAUVEX UV imager, constructed to operate on the Spectrum X-Gamma international space observatory. The projected performance and the expected scientific yield of TAUVEX are described.

Robert Garisto, James D. Wells

By using relations derived from renormalization group equations (RGEs), we find that strong indirect constraints can be placed on the top squark mixing phase in At from the electric dipole moment of the neutron (dn). Since mtop is large, any GUT-scale phase in At feeds into other weak scale phases through RGEs, which in turn contribute to dn. Thus CP-violati

S. L. Sondhi, S. M. Girvin, J. P. Carini, D. Shahar

A quantum system can undergo a continuous phase transition at the absolute zero of temperature as some parameter entering its Hamiltonian is varied. These transitions are particularly interesting for, in contrast to their classical finite temperature counterparts, their dynamic and static critical behaviors are intimately intertwined. We show that considerab

Arshad Momen

We discuss BF theories defined on manifolds with spatial boundaries. Variational arguments show that one needs to augment the usual action with a boundary term for specific types of boundary conditions. We also show how to use this procedure to find the boundary actions for theories of gravity with first order formulations. Possible connection with the membr

Raj Gandhi, Chris Quigg, M. H. Reno, Ina Sarcevic

We evaluate neutrino-nucleon cross section for energies up to $10^{21} eV$ in light of new information on the small-$x$ behavior of parton distributions. We give predictions for large underground neutrino telescope event rates for ultrahigh-energy neutrinos from Active Galactic Nuclei and from the decay of topological defects formed in the early Universe.

Richard D. Ball, Abhay Deshpande, Stefano Forte, Vernon W. Hughes

We present estimates of possible data on spin-dependent asymmetries in inclusive scattering of high energy polarized electrons by high energy polarized protons at HERA, including statistical errors, and discuss systematic uncertainties. We show that these data would shed light on the small x behaviour of the polarized structure function g_1, and would reduce

Lusheng Chen, Mario Belloni, Kurt Haller

In this work, we prove a previously published conjecture that a prescription we gave for constructing states that implement Gauss's law for `pure glue' QCD is correct. We also construct a unitary transformation that extends this prescription so that it produces additional states that implement Gauss's law for QCD with quarks as well as gluons. Furthermore, w

Chi-Keung Chow

Within the context of flux tube models, heavy quark fragmentation takes place through the breaking of flux tubes with the production of a (di)quark-anti(di)quark pair. It is found that the (di)quark produced are more likely to be found in an $L_z=0$ state. This naturally leads to an supression of the polarization distribution parameters $w_{3/2}$ and $\tilde

Nikita Nekrasov

We propose a non-perturbative solution of N=2 supersymmetric gauge theory in five dimensions compactified on circle of a radius $R$. We consider the cases of the pure gauge theory as well as the theories with matter in the fundamental and in the adjoint representations. The pure theory as well as the one with adjoint hypermultiplet give rise to the known rel

I. Ya. Aref'eva, K. S. Viswanathan, I. V. Volovich

A generic Lagrangian, in arbitrary spacetime dimension, describing the interaction of a graviton, a dilaton and two antisymmetric tensors is considered. An isotropic p-brane solution consisting of three blocks and depending on four parameters in the Lagrangian and two arbitrary harmonic functions is obtained. For specific values of parameters in the Lagrangi

Richard E. Borcherds

We construct some families of automorphic forms on Grassmannians which have singularities along smaller sub Grassmannians, using Harvey and Moore's extension of the Howe (or theta) correspondence to modular forms with poles at cusps. Some of the applications are as follows. We construct families of holomorphic automorphic forms which can be written as infini

SLD Collaboration, K. Abe, K. Abe, I. Abt

We present the first measurement of the left-right charge asymmetry A_Q^{obs} in hadronic Z boson decays. This was performed at E_cm = 91.27 GeV with the SLD at the SLAC Linear Collider with a polarized electron beam. Using 89838 events, we obtain A_Q^{obs}=0.225+-0.056+-0.019 which leads to a measurement of the electron left-right asymmetry parameter, A_e=0

Noah Brosch

I review the development of UV and EUV astronomy, covering the spectral range from 5 to 300 nm, with emphasis on sky surveys for discrete sources. I discuss studies which resulted in lists of sources observed by imaging. The missions are compared in terms of their "survey power", a variable which combines sky coverage and survey depth. I describe UV missions

P. N. Burrows, T. Abraha, M. Samuel, E. Steinfelds

We have applied Pade approximants to perturbative QCD calculations of event shape observables in e+e- --> hadrons. We used the exact O(alpha_s^2) prediction and the [0/1] Pade approximant to estimate the O(alpha_s^3) term for 15 observables, and in each case determined alpha_s(M_Z^2) from comparison with hadronic Z^0 decay data from the SLD experiment. We fo

Wolfhard Janke, Tilman Sauer

We report recent progress in computer simulations of quantum systems described in the path-integral formulation. For the example of the $ϕ^4$ quantum chain we show that the accuracy of the simulation may greatly be enhanced by a combination of multigrid update techniques with a refined discretization scheme. This allows us to assess the accuracy of a variati

Wolfhard Janke, Hagen Kleinert

Variational weak-coupling perturbation theory yields converging approximations, uniformly in the coupling strength. This allows us to calculate directly the coefficients of `strong-coupling' expansions. For the anharmonic oscillator we explain the physical origin of the empirically observed convergence behavior which is exponentially fast with superimposed o

A. Ali Khan, T. Bhattacharya

We present preliminary results from our study of the heavy-light spectrum and decay constants. For the heavy quark, we use NRQCD at various masses around and above the $b$ quark mass. For the first time, the heavy quark action and the heavy-light current consistently include corrections at second order in the non-relativistic expansion, as well as the leadin

Wolfhard Janke, Stefan Kappler

We report numerical simulations of two-dimensional $q$-state Potts models with emphasis on a new quantity for the computation of spatial correlation lengths. This quantity is the cluster-diameter distribution function $G_{diam}(x)$, which measures the distribution of the diameter of stochastically defined cluster. Theoretically it is predicted to fall off ex

R. Gupta, T. Bhattacharya

We present estimates of light quarks masses using lattice data. Our main results are based on a global analysis of all the published data for Wilson and Staggered fermions, both in the quenched approximation and with $n_f=2$ dynamical flavors. The Wilson and Staggered results agree after extrapolation to the continuum limit for both the $n_f=0,2$ theories. O

Wolfhard Janke

Using two sets of high-precision Monte Carlo data for the two-dimensional XY model in the Villain formulation on square $L \times L$ lattices, the scaling behavior of the susceptibility $\chi$ and correlation length $\xi$ at the Kosterlitz-Thouless phase transition is analyzed with emphasis on multiplicative logarithmic corrections $(ln L)^{-2r}$ in the fini