April 1994 arXiv papers — page 5

Dong Lai, Frederic A. Rasio, Stuart L. Shapiro

We develop a new formalism to study the dynamics of fluid polytropes in three dimensions. The stars are modeled as compressible ellipsoids and the hydrodynamic equations are reduced to a set of ordinary differential equations for the evolution of the principal axes and other global quantities. Both viscous dissipation and the gravitational radiation reaction

Mary M. Crone, August E. Evrard, Douglas O. Richstone

We use N-body simulations to study the shape of mean cluster density and velocity profiles formed via gravitational instability. The dependence of the final structure on both cosmology and initial density field is examined, using a grid of cosmologies and scale-free initial power spectra P\propto k^n. For each model, we stack clusters to define an average de

Sangeeta Malhotra

A population of molecular clouds with a significantly greater scale height than that of Giant Molecular Clouds has been identified by examining maps of the latitude distribution of the $^{12}CO(1-0)$ emission in the first quadrant of the Galaxy. These clouds are found by identifying emission more than 2.6 times the scale-height away from the galactic midplan

Sangeeta Malhotra

We examine the vertical structure and equilibrium of the molecular gas layer in the galactic disk, measuring its scale height and velocity dispersion as a function of Galactic radius by modeling the CO emission at the tangent points. The model takes into account emission from a large path length along the line of sight, corresponding to an interval \Delta R

Wesley N. Colley

We consider the feasibility of directly observing gravitational microlensing in extra-galactic sources, whose stars are not generally resolved. This precludes use of the simple optical depth to microlensing formulation, which is applicable only to resolved stars. We, instead, extend this method to consider observational constraints, such as seeing, sky backg

K. Z. Stanek, M. Mateo, A. Udalski, M. Szymanski

The color-magnitude diagrams of $\sim 5\times 10^5$ stars obtained for 13 fields towards the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump stars. We find that the distributions of the extinction-adjusted apparent magnitudes of the red clump stars in fields lying at $l=\pm5°$ in galactic longitude differ by $0.37\pm0

Yukari Ito

The purpose of this paper is to construct a crepant resolution of quotient singularities by trihedral groups ( finite subgroups of SL(3,C) of certain type ), and prove that each Euler number of the minimal model is equal to the number of conjugacy classes. Trihedral singularities are 3-dimensional version of D_n-singularities, and they are non-isolated and m

Zhenping Li

In this paper, we show that the low energy theorem (LET) of the threshold pion-photoproduction can be fully recovered in the quark model. An essential result of this investigation is that the quark-pion operators are obtained from the effective chiral Lagrangian, and the low energy theorem does not require the constraints on the internal structures of the nu

Chris Ford

Using the renormalisation group and a conjecture concerning the perturbation series for the effective potential, the leading logarithms in the effective potential are exactly summed for $O(N)$ scalar and Yukawa theories.

Yacov Kantor, Mehran Kardar

Polyampholytes (PAs) are polymers composed of (quenched) random sequences of positive and negatively charged monomeric groups. We show that the radius of gyration, $R_g$, of a PA strongly depends on its overall excess charge $Q$, and is very weakly influenced by other aspects of the sequence. For $Q<Q_c\approx q_0 \sqrt{N}$, where $N$ is the number of monome

E. Adi, S. Solomon

We describe a new geometrical solution to the Wheeler-DeWitt equation in two dimensional quantum gravity. The solution is the amplitude of a surface whose boundary consists of two tangent loops. We further discuss a new method for estimating singular geometries amplitudes, which uses explicit recursive counting of discrete surfaces.

Sen-Ben Liao, Chengqian Gong

Effective potential for scalar $λϕ^4$ theory is obtained using the exact renormalization group method which includes both the usual one-loop contribution as well as the dominant higher loop effects. Our numerical calculation indicates a breakdown of naive one-loop result for sufficiently large renormalized coupling constant.

M. T. Lopez--Arias, V. R. Manfredi, L. Salasnich

An interesting aspect of nuclear dynamics is the co--existence, in atomic nuclei, of regular and chaotic states. In the first part of the present work, we review the state of the art of nuclear dynamics and use a schematic shell model to show how a very simple and schematic nucleon--nucleon interaction can produce an order$\to$chaos transition. The second pa

Manuel Gonzalez, Eero Saksman, H. Tylli

For each $S \in L(E)$ (with $E$ a Banach space) the operator $R(S) \in L(E^{**}/E)$ is defined by $R(S)(x^{**}+E) = S^{**}x^{**}+E$ \quad ($x^{**}\in E^{**}$). We study mapping properties of the correspondence $S\to R(S),$ which provides a representation $R$ of the weak Calkin algebra $L(E)/W(E)$ (here $W(E)$ denotes the weakly compact operators on $E$). Our

Marius Junge

As is well known absolute convergence and unconditional convergence for series are equivalent only in finite dimensional Banach spaces. Replacing the classical notion of absolutely summing operators by the notion of 1 summing operators \[ \summ_k || Tx_k || \leq c || \summ_k e_k \otimes x_k ||_{\ell_1\otimes_{min}E}\] in the category of operator spaces, it t

Alvaro Arias, Gelu Popescu

The framework of the paper is that of the full Fock space ${\Cal F}^2({\Cal H}_n)$ and the Banach algebra $F^\infty$ which can be viewed as non-commutative analogues of the Hardy spaces $H^2$ and $H^\infty$ respectively. An inner-outer factorization for any element in ${\Cal F}^2({\Cal H}_n)$ as well as characterization of invertible elements in $F^\infty$ a

L. C. de Albuquerque, C. Farina, Silvio J. Rabello, Arvind N. Vaidya

We show explicitly that Schwinger&#39;s formula for one-loop effective actions corresponds to the summation of energies associated with the zero-point oscillations of the fields. We begin with a formal proof, and after that we confirm it using a regularization prescription.

Emilio Elizalde, Klaus Kirsten, Sergei Odintsov

A derivation of the one-loop effective Lagrangian in the self-interacting $O(N)$ scalar theory, in slowly varying gravitational fields, is presented (using $ζ$-regularization and heat-kernel techniques). The result is given in terms of the expansion in powers of the curvature tensors (up to quadratic terms) and their derivatives, as well as in derivatives of

Silvio J. Rabello, Arvind N. Vaidya

Using the BFV approach we quantize a pseudoclassical model of the spin one half relativistic particle that contains a single bosonic constraint, contrary to the usual locally supersymmetric models that display first and second class constraints.

Lorenzo Belardinelli, Enrico Onofri

The renormalization group equation describing the evolution of the metric of the non linear sigma models poses some nice mathematical problems involving functional analysis, differential geometry and numerical analysis. We describe the techniques which allow a numerical study of the solutions in the case of a two-dimensional target space (deformation of the

Mikhail S. Plyushchay

The simplest $N=2$ supersymmetric quantum mechanical system is realized in terms of the bosonic creation and annihilation operators obeying either ordinary or deformed Heisenberg algebra involving Klein operator. The construction comprises both the exact and spontaneously broken supersymmetry cases with the scale of supersymmetry breaking being governed by t

J. Comellas, P. E. Haagensen, J. I. Latorre

Based only on simple principles of renormalization in coordinate space, we derive closed renormalized amplitudes and renormalization group constants at 1- and 2-loop orders for scalar field theories in general backgrounds. This is achieved through a generic renormalization procedure we develop exploiting the central idea behind differential renormalization,

J. Sirkka, I. Vilja

We study the vacuum stability of the singlet Majoron model using full renormalization group improved scalar potential and Monte Carlo techniques. We show that in the perturbative regime of the various free parameters, the vacuum stability requirement together with LEP limits is passed by 18% of the parameter space if the scale of new physics is 10 TeV and 6%

I. M. Anderson, C. G. Torre

A generalized symmetry of a system of differential equations is an infinitesimal transformation depending locally upon the fields and their derivatives which carries solutions to solutions. We classify all generalized symmetries of the vacuum Einstein equations in four spacetime dimensions. To begin, we analyze symmetries that can be built from the metric, c

C. G. Torre

We present 2 recent results on the problems of time and observables in canonical gravity. (1) We cannot use parametrized field theory to solve the problem of time because, strictly speaking, general relativity is not a parametrized field theory. (2) We show that there are essentially no local observables for vacuum spacetimes.

M. Castagnino, F. Lombardo

It is demonstrated that almost any S-matrix of quantum field theory in curved spaces posses an infinite set of complex poles (or branch cuts). These poles can be transformed into complex eigenvalues, the corresponding eigenvectors being Gamow vectors. All this formalism, which is heuristic in ordinary Hilbert space, becomes a rigorous one within the framewor

D. Boyanovsky, C. A. A. de Carvalho, E. S. Fraga

We present a study of the nucleation mechanism that allows the decay of the metastable phase (trans-cisoid) to the stable phase (cis-transoid) in quasi one-dimensional non-degenerate polymers within the continuum electron-phonon model. The electron-phonon configurations that lead to the decay, i.e. the critical droplets (or transition state), are identified

G. G. Batrouni, R. T. Scalettar, G. T. Zimanyi, A. P. Kampf

We use a combination of numeric and analytic techniques to determine the groun d state phase diagram of the Bose--Hubbard Hamiltonian with longer range repulsi ve interactions. At half filling one finds superfluidity and an insulating solid phase. Depending on the relative sizes of near--neighbor and next near--neighbor interactions, this solid either follow

M. J. M. de Jong, C. W. J. Beenakker

A review is given of the shot-noise properties of metallic, diffusive conductors. The shot noise is one third of the Poisson noise, due to the bimodal distribution of transmission eigenvalues. The same result can be obtained from a semiclassical calculation. Starting from Oseledec&#39;s theorem it is shown that the bimodal distribution is required by Ohm&#39

A. M. S. Macedo

We study the effects of an arbitrary external perturbation in the statistical properties of the S-matrix of quantum chaotic scattering systems in the limit of isolated resonances. We derive, using supersymmetry, an exact non-perturbative expression for the parameter dependent autocorrelator of two S-matrix elements. Universality is obtained by appropriate re

A. M. S. Macedo

We extend a recent theory of parametric correlations in the spectrum of random matrices to study the response to an external perturbation of eigenvalues near the soft edge of the support. We demonstrate by explicit non-perturbative calculation that the two-point function for level density fluctuations becomes, after appropriate rescaling, a universal express

J. M. Deutsch

A method is developed which speeds up averaging in quantum simulations where minus signs cause difficulties. A Langevin equation method in conjunction with a replication algorithm is used enabling one to average over a continuously varying complex number. Instead of ensemble averaging this number directly, the phase of the complex number is followed over tim

Simon Davis

The divergences that arise in the regularized partition function for closed bosonic string theory in flat space lead to three types of perturbation series expansions, distinguished by their genus dependence. This classification of infinities can be traced to geometrical characteristics of the string worldsheet. Some categories of divergences may be eliminate

F. Englert, S. Massar, R. Parentani

The emergence of Hawking radiation from vacuum fluctuations is analyzed in conventional field theories and their energy content is defined through the Aharonov weak value concept. These fluctuations travel in flat space-time and carry transplanckian energies sharply localized on cisplanckian distances. We argue that these features cannot accommodate gravitat

A. Culatti

It was recently shown that unbroken N=1 Susy relates, in a model independent way, the magnetic transitions between states of different spin within a given charged massive supermultiplet. We verify explicitly these sum rules for a vector multiplet in the case of massless and massive fermions. The purpose of this analysis is to provide the ground for the broke

P. H. Damgaard, M. Hasenbusch

Deconfinement and screening of higher-representation sources in finite-temperature $SU(2)$ lattice gauge theory is investigated by both analytical and numerical means. The effective Polyakov-line action at strong coupling is simulated by an efficient cluster-updating Monte Carlo algorithm for the case of $d\!=\!4$ dimensions. The results compare very favoura

A. Casher, F. Englert

The area entropy $A/4$ and the related Hawking temperature in the presence of event horizons are rederived, for de Sitter and black hole topologies, as a consequence of a tunneling of the wave functional associated to the classical coupled matter and gravitational fields. The extension of the wave functional outside the barrier provides a reservoir of quantu

G. Bimonte, F. Lizzi, G. Sparano

Using the tools of noncommutative geometry we calculate the distances between the points of a lattice on which the usual discretized Dirac operator has been defined. We find that these distances do not have the expected behaviour, revealing that from the metric point of view the lattice does not look at all as a set of points sitting on the continuum manifol

G. K. Leontaris, N. D. Tracas

In the context of the radiative electroweak symmetry breaking scenario, we investigate the implications of a heavy top quark mass, close to its infrared fixed point, on the low energy parameters of the minimal supersymmetric standard model. We use analytic expressions to calculate the Higgs masses as well as the supersymmetric masses of the third generation.

T. S. Evans

Thermal field theory is reviewed briefly. It is noted that, until recently, it was not known what type of real-time Green function is being calculated in the Euclidean approach. The formal answer to this question is then given and the unexpectedly complicated answer is discussed. The physical implications of the results are then considered. (Talk given at th

J. E. Rankin

This paper presents the detailed, standard treatment of a simple, gauge invariant action for Weyl and Weyl-like Cartan geometries outlined in a previous paper. In addition to the familiar scalar curvature squared and Maxwell terms, the action chosen contains the logarithmic derivative of the scalar curvature combined with the intrinsic four vector (Weyl vect

Tae-Sun Park, Ian S. Towner, Kuniharu Kubodera

We calculate shell-model matrix elements of the axial-charge exchange current operators that have been obtained up to the next-to-leading order from heavy-fermion chiral perturbation theory. It is found that loop corrections to the soft one-pion-exchange contribution are small (around 10 \%) and have no significant dependence on the nuclear mass number or on

Moustafa Awada, David Zoller

Ordinary QED formulated in the Feynman&#39;s space-time picture is equivalent to a one dimensional field theory. In the large N limit there is no phase transition in such a theory. In this letter, we show a phase transition does exist in a generalization of QED characterized by the addition of the curvature of the world line (rigidity) to the Feynman&#39;s s

Moustafa Awada, David Zoller

Polyakov has argued that the QCD string should have long range order. We show that a phase transition does exist in a generalization of string theory characterized by the addition of the curvature of the world sheet (rigidity) and the long range Kalb-Ramond interactions to the Nambu-Goto action. Although rigid strings coupled to long range interactions exhib

Jerome P. Gauntlett

This article is based on a talk given at the IInd International Colloquium on Modern Quantum Field Theory, Bombay 1994. The Ernst solution of dilaton gravity describes charged black holes undergoing uniform accleration in a background magnetic field. By analytically continuing the Ernst solution one obtains instantons that describe the pair production of bla

J. M. Gracia-Bondia

I render the substance of the discussions I had with Robert E. Marshak shortly before his death, wherein the kinship between the ``neutrino paradigm&#39;&#39; ---espoused by Marshak--- and the central notion of K-cycle in noncommutative geometry (NCG) was found. In that context, we give a brief account of the Connes--Lott reconstruction of the Standard Model

C. M. Hull, Z. Khatun

The string theory defined by gauging $\W_{\infty/2}$, the sub-algebra of $\W_{\infty}$ generated by the currents of even spin, is discussed. The critical value of the central charge is calculated using zeta-function techniques and shown to be $c=1$. A critical string theory is constructed by coupling a free boson to $\W_{\infty/2}$-gravity and the physical s

E. G. B. Hohler, K. Olaussen

We investigate the possible form of local translation invariant conservation laws associated with the relativistic field equations $\partial\bar\partialϕ_i=-v_i(\bphi)$ for a multicomponent field $\bphi$. Under the assumptions that (i)~the $v_i$&#39;s can be expressed as linear combinations of partial derivatives $\partial w_j/\partialϕ_k$ of a set of functi

Ruth Gregory, Raymond Laflamme

We investigate the evolution of small perturbations around charged black strings and branes which are solutions of low energy string theory. We give the details of the analysis for the uncharged case which was summarized in a previous paper. We extend the analysis to the small charge case and give also an analysis for the generic case, following the behavior

M. Eliashvili

It is shown, that a spectrum generating algebras and wave functions for the integral and fractional quantum Hall effect are related by the non-unitary similarity transformation. This transformation corresponds to the introduction of the complex Chern-Simons gauge fields, in terms of which the second quantized form of FQHE can be developed

E. G. B. Hohler, K. Olaussen

We have performed some explicit calculations of the conservation laws for classical (affine) Toda field theories, and some generalizations of these models. We show that there is a huge class of generalized models which have an infinite set of conservation laws, with their integrated charges being in involution. Amongst these models we find that only the $A_m

G. E. Arutyunov, P. B. Medvedev

The general expression for the bicovariant bracket for odd generators of the external algebra on a Poisson-Lie group is given. It is shown that the graded Poisson-Lie structures derived before for $GL(N)$ and $SL(N)$ are the special cases of this bracket. The formula is the universal one and can be applied to the case of any matrix Lie group.

M. Bertolini, A. Ceresole, R. D&#39;Auria, S. Ferrara

We give a coordinate-free description of real manifolds occurring in certain four dimensional supergravity theories with antisymmetric tensor fields. The relevance of the linear multiplets in the compactification of string and five-brane theories is also discussed.

C. S. Lam

The success of the spinor helicity technique for tree processes is reviewed. To apply it to multiloop diagrams one is naturally led to the Schwinger proper-time representation, whose properties are discussed. This representation also serves as a useful link between field theories and string theories.

J. Schechter

After a brief discussion of how chiral dynamics has evolved from the ``universal V-A theory of weak interactions&#39;&#39;, we present some evidence that symmetry breaking for the vector meson multiplet is not simpler than but rather analogous to that for the pseudoscalar multiplet. This provides a motivation for speculating on how to extend in a systematic

N. Di Bartolomeo, R. Gatto

The problem of electroweak symmetry breaking is reviewed with discussion of future relevant experimentation at LHC and $e^+e^-$ linear colliders. The possibility of strong electroweak symmetry breaking is examined in more detail, using the BESS (Breaking Electroweak Symmetry Strongly) model as a basis for the discussion. The formal constructions are briefly

Edi Halyo

We investigate a scenario in which the CKM matrix arises from leptoquark--down quark mixing in a particular standard--like superstring model. We find that for some choices of F and D flat directions realistic quark mixing can be obtained without any phenomenological problems. This scenario predicts a symmetric (in absolute value) CKM matrix.

A. Ya. Parkhomenko, A. D. Smirnov

The decay of heavy orthoquarkonium into quark-antiquark pair and two gluons is considered. The differential probability of the decay in the tree approximation is calculated and the probability distributions of quarks and gluons are obtained. The collinear enhancement of the bottomonium decay is shown to take place at the uū--, dd and ss-- pair production and

Koichi HAYASHI, Toshiharu SAMURA

The metrics of gravitational shock waves for a Schwarzschild black hole in ordinary coordinates and for a Kerr black hole in Boyer-Lindquist coordinates are derived. The Kerr metric is discussed for two cases: the case of a Kerr black hole moving parallel to the rotational axis, and moving perpendicular to the rotational axis. Then, two properties from the d

G. Sardanashvily

In view of the well-known correspondence between gravitational fields and space-time distributions on a world manifold X, the criterion of gravitation singularities as singularities of these distributions is suggested. In the germ terms, singularities of a (3+1) distribution look locally like singularities of a foliation whose leaves are level surfaces of a

Peter Neu, Roland Speicher

Starting from the deformed commutation relations \ba a_q(t) \,a_q^†(s) \ - \ q\,a_q^†(s)\,a_q(t) \ = \ \Gam(t-s) {\bf 1} , \quad -1\ \le \ q\ \le\ 1\nn \ea with a covariance $\Gam(t-s)$ and a parameter $q$ varying between $-1$ and $1$, a stochastic process is constructed which continuously deforms the classical Gaussian and classical compound Poisson process

H. Steffan, R. Kühn

The phenomenon of replica symmetry breaking is investigated for the retrieval phases of Hopfield-type network models. The basic calculation is done for the generalized version of the standard model introduced by Horner [1] and by Perez-Vicente and Amit [2] which can exhibit low mean levels of neural activity. For a mean activity $\bar a =1/2$ the Hopfield mo

Nigel B. Wilding, Marcus Mueller

We present a new Monte-Carlo method for estimating the chemical potential of model polymer systems. The method is based upon the gradual insertion of a penetrable `ghost&#39; polymer into the system and is effective for large chain lengths and at high densities. Insertion of the ghost chain is facilitated by use of an expanded ensemble in which weighted tran

Haye Hinrichsen

With appropriate boundary conditions the anisotropic $XY$ chain in a magnetic field is known to be invariant under quantum group transformations. We generalize this model defining a class of integrable chains with several fermionic degrees of freedom per site. In order to maintain the quantum group symmetry a general condition on the parameters of these syst

F. Perez-Rodriguez, Wei Wang, E. Canessa

A macroscopic characterization of fractals showing up a structural transition from dense to multibranched growth is made using optical diffraction theory. Such fractals are generated via the numerical solution of the 2D Poisson and Biharmonic equations and are compared to more &#39;regular&#39;irreversible clusters such as diffusion limited and Laplacian agg

Minoru Takahashi

The dynamical structure factor $S(Q,ω)$ of the $S=1$ antiferromagnetic Heisenberg chain with length 20 at zero temperature is calculated. The lowest energy states have the delta-function peak at the region $π\ge \vert Q\vert >0.3π$. At $\vert Q\vert<0.3π$ the lowest energy states are the lower-edge of the continuum of the scattering state, the strength of wh

Andrew Ulmer

Interactions of grazing incidence, ultra high energy cosmic rays with the earth&#39;s atmosphere may provide a new method of studying energetic cosmic rays with gamma-ray satellites. It is found that these cosmic ray interactions may produce gamma-rays on millisecond time scales which may be detectable by satellites. An extremely low gamma-ray background for

K. Hulek, J. Spandaw

In this paper the authors consider a certain toroidal compactification of the moduli space of degenerations of (1,p)-polarized abelian surfaces with (canonical) level structure. Using Hodge theory we give a proof that a degenerate abelian surface associated to a corank 1 boundary point is (almost) completely determined by the boundary point. The crucial ingr

Todd A. Brun

In choosing a family of histories for a system, it is often convenient to choose a succession of locations in phase space, rather than configuration space, for comparison to classical histories. Although there are no good projections onto phase space, several approximate projections have been used in the past; three of these are examined in this paper. Expre

Denis Bernard, Yong-Shi Wu

We show that the thermodynamic Bethe ansatz equations for one-dimensional integrable many-body systems can be reinterpreted in such a way that they only code the statistical interactions, in the sense of Haldane, between particles of identical or different momenta. Thus, the thermodynamic properties of these systems can be characterized by the generalized id

T. Alm, G. Roepke, M. Schmidt

The in-medium nucleon-nucleon cross section is calculated starting from the thermodynamic T-matrix at finite temperatures. The corresponding Bethe-Salpeter-equation is solved using a separable representation of the Paris nucleon-nucleon-potential. The energy-dependent in-medium N-N cross section at a given density shows a strong temperature dependence. Espec

L. Tiator, C. Bennhold, S. S. Kamalov

Low-energy eta photoproduction on the nucleon is studied in an effective Lagrangian approach that contains Born terms, vector meson and nucleon resonance contributions. The resonance sector includes the $S_{11}(1535)$, $P_{11}(1440)$ and $D_{13}(1520)$ states whose couplings are fixed by independent electromagnetic and hadronic data. The available $(γ,η)$ da

P. Navratil, H. B. Geyer, J. Dobes, J. Dobaczewski

It is shown how the boson mapping formalism may be applied as a useful many-body tool to solve a fermion problem. This is done in the context of generalized Ginocchio models for which we introduce S-, D-, and G-pairs of fermions and subsequently construct the sdg-boson realizations of the generalized Dyson type. The constructed SO(12) and Sp(10) fermion mode

Joerg Wenzel

In this article, we characterize the $UMD$--property of a Banach space $X$ by ideal norms associated with trigonometric orthonormal systems. The asymptotic behavior of that numerical parameters can be used to decide whether or not $X$ is a $UMD$--space. Moreover, in the negative case, we obtain a measure that shows how far $X$ is from being a $UMD$--space. T

Joerg Wenzel

The powerful concept of an operator ideal on the class of all Banach spaces makes sense in the real and in the complex case. In both settings we may, for example, consider compact, nuclear, or $2$--summing operators, where the definitions are adapted to each other in a natural way. This paper deals with the question whether or not that fact is based on a gen

Andreas Albrecht

When discussing the black hole information problem the term ``information flow&#39;&#39; is frequently used in a rather loose fashion. In this article I attempt to make this notion more concrete. I consider a Hilbert space which is constructed as a tensor product of two subspaces (representing for example inside and outside the black hole). I discuss how the

E. Elizalde, S. D. Odintsov, I. L. Shapiro

We consider a multiplicatively renormalizable higher-derivative scalar theory which is used as an effective theory for quantum gravity at large distances (infrared phase of quantum gravity). The asymptotic regimes (in particular, the asymptotically free infrared regime) for the coupling constants ---specifically the Newtonian and the cosmological constant---

K. Sfetsos, A. A. Tseytlin

We present a number of D=4 bosonic and heterotic string solutions with a covariantly constant null Killing vector which, like the solution of Nappi and Witten (NW), correspond to (gauged) WZW models and thus have a direct conformal field theory interpretation. A class of exact plane wave solutions (which includes the NW solution) is constructed by `boosting&

Nikolaos Kalogeropoulos

We present an analysis of the cocycle appearing in the vertex operator representation of simply-laced, affine, Kac-Moody algebras. We prove that it can be described in the context of $R$-commutative geometry, where $R$ is a Yang-Baxter operator, as a strong $R$-commutative algebra. We comment on the Hochschild, cyclic and dihedral homology theories that appe

A. A. Andrianov, F. Cannata, J. -P-Dedonder, M. V. Ioffe

Extensions of standard one-dimensional supersymmetric quantum mechanics are discussed. Supercharges involving higher order derivatives are introduced leading to an algebra which incorporates a higher order polynomial in the Hamiltonian. We study scattering amplitudes for that problem. We also study the role of a dilatation of the spatial coordinate leading t

T. Arens, L. M. Sehgal

We re-examine the question of a possible difference in the partial decay widths of $t$ and $\overline t$, induced by an intermediate scalar boson $H^+$ with $CP$-violating couplings. The interference of $W^+$ and $H^+$ exchanges is analysed by constructing the $2\times 2$ propagator matrix of the $W^+-H^+$ system, and determining its absorptive part in terms

Ma Wen-Gan, Sun La-Zhen, Liu Yao-Yang, Jiang Yi

Having taken the QED radiative correction and one-loop weak corrections into account, we have computed the unpolarized forward-backward asymmetry in the process $e^+e^- -> μ^+μ^-$ at a very reasonable accuracy. Special attention to the effects around the LEP 200 energy, induced by the possible $Z&#39;$ boson of the left-right symmetric model $SU(2)_{L} \time

Ralf Hempfling

It is generally assumed that the dynamical generation of the Higgs mass parameter of the superpotential, $μ$, implies the existence of a light singlet at or below the supersymmetry breaking scale, $\msusy$. We present a counter-example in which the singlet field can receive an arbitrarily heavy mass (\eg, of the order of the Planck scale, $M_{\rm P}\approx 1

R. D. Peccei

A summary of the contributions to this topical conference is presented. The topics discussed ranged from detailing what we know about CP violation, to what we hope to learn in the future, to still unsolved mysteries in the subject.

Tom Blum, Thomas A. DeGrand, Carleton DeTar, Steven Gottlieb

We have extended our study of the high temperature transition with two flavors of Wilson quarks on 12^3 x 6 lattices to kappa=0.19. We have also performed spectrum calculations on 12^3 x 24 lattices at kappa=0.19 to find the physical lattice spacing and quark mass. At this value of kappa the transition is remarkable in that the plaquette and psi-bar-psi show

Paul Sommers

Interpretation problems are eliminated from quantum theory by picturing a quantum history as having been sampled from a probability distribution over the set of histories which are permitted by all relevant boundary conditions. In laboratory physics, the final measurement plays a crucial role in defining the set of allowed histories by constraining the final

Terence Hwa, Thomas Nattermann

The competition in the pinning of a directed polymer by a columnar pin and a background of random point impurities is investigated systematically using the renormalization group method. With the aid of the mapping to the noisy-Burgers&#39; equation and the use of the mode-coupling method, the directed polymer is shown to be marginally localized to an arbitra

G. Benfatto, E. Marinari, E. Olivieri

We study the block spin transformation for the 2D Ising model at the critical temperature $T_c$. We consider the model with the constraint that the total spin in each block is zero. An old argument by Cassandro and Gallavotti allows to show that the Gibbs potential for the transformed measure is well defined, provided that such model has a critical temperatu

Simon Robinson

We study the 4-probe bend conductance $G_{14,32}$ of a mesoscopic crossed wire structure in the ballistic regime in the absence of a magnetic field, which for normal devices is usually negative. We predict that for sufficiently large devices and for small applied voltages $G_{14,32}$ becomes positive in the presence of Andreev scattering, but at large voltag

Peter B. Thomas, M. K. Hari Menon, Deepak Dhar

We study the model of deposition-evaporation of trimers on a line recently introduced by Barma, Grynberg and Stinchcombe. The stochastic matrix of the model can be written in the form of the Hamiltonian of a quantum spin-1/2 chain with three-spin couplings given by $ H= \sum\displaylimits_i [(1 - σ_i^-σ_{i+1}^-σ_{i+2}^-) σ_i^+σ_{i+1}^+σ_{i+2}^+ + h.c]$. We s

Antti-Pekka Jauho, Ned S. Wingreen, Yigal Meir

We consider a mesoscopic region coupled to two leads under the influence of external time-dependent voltages. The time dependence is coupled to source and drain contacts, the gates controlling the tunnel- barrier heights, or to the gates which define the mesoscopic region. We derive, with the Keldysh nonequilibrium Green function technique, a formal expressi

N. Taniguchi, A. Hashimoto, B. D. Simons, B. L. Altshuler

Parametric correlations of energy spectra of quantum chaotic systems are presented in the orthogonal-unitary and symplectic-unitary crossover region. The spectra are allowed to disperse as a function of two external perturbations: one of which preserves time-reversal symmetry, while the other violates it. Exact analytical expressions for the parametric two-p

Marc Herant, Willy Benz, W. Raphael Hix, Chris F. Fryer

Condensed Abstract: We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 Msun and 25 Msun) in two dimensions. Our calculations begin at the onset of core collapse and stop several 100 ms after the bounce, at which time successful explosions of the appropriate magnitude have be

Toshinari Hirai, Kei-ichi Maeda

Using the covariant approach and conformal transformations, we present a gauge-invariant formalism for cosmological perturbations in generalized Einstein theories (GETs), including the Brans-Dicke theory, theories with a non-minimally coupled scalar field and certain curvature-squared theories. We find an enhancement in the growth rate of density perturbatio

Fabien Malbet, Michael Shao, Jeffrey Yu

In the field of planet and proto-planetary disk detection, achieving high angular resolution and high dynamic range is a necessity. Coronography coupled with adaptive optics on Hubble Space Telescope is a way to get both good spatial resolution and high dynamic range. However, because of the residual figure errors on the primary and on the secondary, HST has

Gerard van der Geer, Marcel van der Vlugt

We give a method to construct explicitly a supersingular curve of given genus g in characteristic 2.

S. L&#39;vovsky

In this paper we describe projective curves and surfaces such that almost all their hyperplane sections are projectively equivalent. Our description is complete for curves and close to being complete for smooth surfaces. In the appendix we make some remarks on connections between the mentioned property of a projective variety and its adjunction properties.

LADS collaboration, T. Alteholz, D. Androic, G. Backenstoss

Measurements have been made of pi+ absorption on He3 at T_pi+ = 118, 162, and 239 MeV using the Large Acceptance Detector System (LADS). The nearly 4pi solid angle coverage of this detector minimizes uncertainties associated with extrapolations over unmeasured regions of phase space. The total absorption cross section is reported. In addition, the total cros

G. M. T. Watts

We calculate the quantum mass corrections to the solitons in the C_2^(1) Affine Toda field theory. We find that the ratio of the masses of the two solitons is not constant.

James B. Hartle

In this universe, governed fundamentally by quantum mechanical laws, characterized by indeterminism and distributed probabilities, classical deterministic laws are applicable over a wide range of time, place, and scale. We review the origin of these laws in the context of the quantum mechanics of closed systems, most generally, the universe as a whole. There