December 1998 arXiv papers — page 8

Hsiao-Wen Chen, Alberto Fernandez-Soto, Kenneth M. Lanzetta, Sebastian M. Pascarelle

We present an electronic catalog of infrared and optical photometry and photometric redshifts of 323 galaxies in the Hubble Deep Field South NICMOS field at http://www.ess.sunysb.edu/astro/hdfs/home.html. The analysis is based on infrared images obtained with the Hubble Space Telescope using the Near Infrared Camera and Multi-Object Spectrograph and the Spac

Geza Gyuk, Chris Flynn, N. Wyn Evans

This paper reports the star count predictions of warped and flaring models of the outer Milky Way disk. These have been suggested as possible locations of the lenses responsible for the microlensing events towards the Large Magellanic Cloud (LMC). Three such models are investigated in detail and the theoretical predictions are confronted with {\it Hubble Spa

R. Vilela Mendes

Clustering and correlation effects are frequently observed in chaotic systems in situations where, because of the positivity of the Lyapunov exponents, no dimension reduction is to be expected. In this paper, using a globally coupled network of Bernoulli units, one finds a general mechanism by which strong correlations and slow structures are obtained at the

Johan Rathsman

A new model for hadronic string reinteractions based on a generalised area law is presented. The model describes both the hadronic final states in $e^+e^-$ annihilation and the diffractive structure function in deep inelastic scattering. The model also predicts a shift in the W-mass reconstructed from hadronic decays of W-pairs of the order 65 MeV.

J. S. Frasier, V. Celli, T. Blum

We present a theory of resonant processes in a frozen gas of atoms interacting via dipole-dipole potentials that vary as $r^{-3}$, where $r$ is the interatomic separation. We supply an exact result for a single atom in a given state interacting resonantly with a random gas of atoms in a different state. The time development of the transition process is calcu

T. Csorgo, B. Lorstad, J. Schmidt-Sorensen, A. Ster

We study the influence of a possible coherent component in the boson source on the two-, three- and $n$-particle correlation functions in a generalized core/halo type of boson-emitting source. In particular, a simple formula is presented for the strengh of the $n$-particle correlation functions for such systems. Graph rules are obtained to evaluate the corre

Ralph Blumenhagen, Lars Goerlich

We consider certain four dimensional supersymmetric and non-supersymmetric asymmetric orbifolds with vanishing cosmological constant up to two loops and gauge the world sheet parity transformation. This leads to new string vacua, in which Dp and D(p-4) branes or Dp and anti-D(p-4) are identified. Moreover, it is shown that different degrees of supersymmetry

Fabrizio Gabbiani

We perform a chiral one-loop calculation of the unitarity corrections to the processes K+ -> pi+ gamma l+l- up to O(E^6), taking into account pi+pi- intermediate states. Branching ratios and differential branching ratios are computed and presented to demonstrate the importance of the above corrections.

Sidney Coleman, Sheldon L. Glashow

We develop a perturbative framework with which to discuss departures from exact Lorentz invariance and explore their potentially observable ramifications. Tiny non-invariant terms introduced into the standard model Lagrangian are assumed to be renormalizable (dimension $\le 4$), invariant under $SU(3)\otimes SU(2)\otimes U(1)$ gauge transformations, and rota

Rosario Martin, Enric Verdaguer

Assuming that the mechanism proposed by Gell-Mann and Hartle works as a mechanism for decoherence and classicalization of the metric field, we formally derive the form of an effective theory for the gravitational field in a semiclassical regime. This effective theory takes the form of the usual semiclassical theory of gravity, based on the semiclassical Eins

Tad Hogg

The structure of satisfiability problems is used to improve search algorithms for quantum computers and reduce their required coherence times by using only a single coherent evaluation of problem properties. The structure of random k-SAT allows determining the asymptotic average behavior of these algorithms, showing they improve on quantum algorithms, such a

T. Montaruli, F. Ronga

We look for space-time correlations between 2233 gamma-bursts in the Batse Catalogs and 894 upward-going muons produced by neutrino interactions in the rock below or inside MACRO. Considering a search cone of 10 degrees around GRB directions and a time window of 200 s we find 0 events to be compared to 0.035 expected background events due to atmospheric neut

Adolfo E. Trumper

We study the phase diagram at T=0 of the antiferromagnetic Heisenberg model on the triangular lattice with spatially-anisotropic interactions. For values of the anisotropy very close to J_alpha/J_beta=0.50, conventional spin wave theory predicts that quantum fluctuations melt the classical structures, for S=1/2. For the regime J_beta<J_alpha, it is shown tha

L. Cappiello, A. Liccardo, R. Pettorino, F. Pezzella

We give, in the framework of the bosonic string theory, simple prescriptions for computing, at tree and one-loop levels, off-shell string amplitudes for open and closed string massless states. In particular we obtain a tree amplitude for three open strings that in the field theory limit coincides with the three-gluon vertex in the usual covariant gauge and t

E. Winstanley

We consider black holes in EYM theory with a negative cosmological constant. The solutions obtained are somewhat different from those for which the cosmological constant is either positive or zero. Firstly, regular black hole solutions exist for continuous intervals of the parameter space, rather than discrete points. Secondly, there are non-trivial solution

A. V. Leonidov, D. M. Ostrovsky

The azimuthal asymmetry of minijet system produced at the early stage of nucleon-nucleon and nuclear collisions in a central rapidity window is studied. We show that in pp collisions the minijet transverse energy production in a central rapidity window is essentially unbalanced in azimuth due to asymmetric contributions in which only one minijet hits the acc

Ben Craps, Frederik Roose

The direct string computation of anomalous D-brane and orientifold plane couplings is extended to include the curvature of the normal bundle. The normalization of these terms is fixed unambiguously. New, non-anomalous gravitational couplings are found.

Dean Lee

We derive the spherical field formalism for fermions. We find that the spherical field method is free from certain difficulties which complicate lattice calculations, such as fermion doubling, missing axial anomalies, and computational problems regarding internal fermion loops.

K. A. Muttalib, J. R. Klauder

The Dorokhov-Mello-Pereyra-Kumar (DMPK) equation, which describes the distribution of transmission eigenvalues of multichannel disordered conductors, has been enormously successful in describing a variety of detailed transport properties of mesoscopic wires. However, it is limited to the regime of quasi one dimension only. We derive a one parameter generaliz

Eric Laenen, Stephane Keller

We extend the phase space slicing method of Giele, Glover and Kosower for performing next-to-leading order jet cross section calculations in two important ways: we show how to include fragmentation functions and how to include massive particles. These extensions allow the application of this method to not just jet cross sections but also to cross sections in

Gert Aarts, Jan Smit

The 1+1 dimensional abelian Higgs model with fermions is a toy model for the theory of electroweak baryogenesis. We study the dynamics of the model with axially coupled fermions in real-time. The model is defined on a spacetime lattice to preserve gauge invariance and to obtain numerical stability in a simple way. We take into account the phenomenon of latti

R. Raimondi, P. Schwab

We review recent work on resonant Andreev tunneling through a strongly interacting quantum dot connected to a normal and to a superconducting lead. We derive a general expression for the current flowing in the structure and discuss the linear and non-linear transport in the nonperturbative regime. New effects associated to the Kondo resonance combined with t

E. Brocato, V. Castellani, G. Raimondo, M. Romaniello

This paper presents theoretical HST and broad band colours from population synthesis models based on an homogeneous set of stellar evolutionary tracks as computed under canonical (no overshooting) assumptions, covering the range of cluster ages from t=8 Myr to t=5 Gyr for three different metallicities (Z=0.02, 0.006, and 0.001). Statistical fluctuations in t

Rahul Basu, Sourendu Gupta

Double scaling may be observed in the Drell-Yan process at the Tevatron and in the ALICE detector at the Large Hadron Collider in a window of masses. In the double scaling limit of the cross section, the higher order QCD corrections are quite large, and are driven by the rise in gluon densities in the double scaling regime. The naive parton model cannot be v

D. Bellisai, F. Fucito, A. Tanzini, G. Travaglini

In this lecture we review some non-perturbative results obtained in globally supersymmetric theories and show how they can be obtained in the framework of topological theories.

Dirk Helbing, Michael Schreckenberg

A model for 1D traffic flow is developed, which is discrete in space and time. Like the cellular automaton model by Nagel and Schreckenberg [J. Phys. I France 2, 2221 (1992)], it is simple, fast, and can describe stop-and-go traffic. Due to its relation to the optimal velocity model by Bando et al. [Phys. Rev. E 51, 1035 (1995)], its instability mechanism is

Wolfgang Belzig, Frank K. Wilhelm, Christoph Bruder, Gerd Schön

Recent experiments on mesoscopic normal-metal--superconductor heterostructures resolve properties on length scales and at low temperatures such that the temperature is below the Thouless energy $k_B T \le E_{Th}$. We describe the properties of these systems within the framework of quasiclassical many-body techniques. Diffusive and ballistic systems are cover

J. Caro, L. L. Salcedo

The dynamics of systems composed of a classical sector plus a quantum sector is studied. We show that, even in the simplest cases, (i) the existence of a consistent canonical description for such mixed systems is incompatible with very basic requirements related to the time evolution of the two sectors when they are decoupled. (ii) The classical sector canno

Pei-Ming Ho, Yong-Shi Wu

Generalizing previous results for orbifolds, in this paper we describe the compactification of Matrix model on an orientifold which is a quotient space as a Yang-Mills theory living on a quantum space. The information of the compactification is encoded in the action of the discrete symmetry group G on Euclidean space and a projective representation U of G. T

Hidetoshi Fukuyama

Various aspects of close and interesting relationship between antiferromagnetism and singlet ground states are introduced for which neutron scattering have been playing vital roles. The special emphasis is on the disorder-induced antiferromagnetism in spin-Peierls systems, which can be viewed as a nucleation process of classical magnetic order in the backgro

Shi-Lin Zhu

We first derive the mass sum rules for the heavy hybrid mesons to obtain the binding energy and decay constants in the leading order of HQET. The pionic couplings between the lightest $1^{-+}$ hybrid $(Q\bar q g)$ and the lowest three heavy meson doublets are calculated with the light cone QCD sum rules. With $SU_f (3)$ flavor symmetry we calculate the width

J. A. White, S. E. Koonin, D. J. Dean

We utilize the Shell Model Monte Carlo (SMMC) method to study the structure of rare earth nuclei. This work demonstrates the first systematic ``full oscillator shell plus intruder&#39;&#39; calculations in such heavy nuclei. Exact solutions of a pairing plus quadrupole hamiltonian are compared with mean field and SPA approximations in several Dysprosium isot

A. N. Mitra

The Markov-Yukawa Transversality Principle (MYTP) on a 2-body Bethe-Salpeter kernel is formulated on a covariant Null Plane (NP) to reconstruct the 4D BS wave function for 2 fermion quarks in terms of 3D entities that satisfy a 3D BSE. This result is the null-plane counterpart of a 3D-4D interconnection for the 2-body BS wave functions found earlier by impos

Yutaka Okamoto, Masaki Yasue

A mechanism of radiatively generating neutrino masses is implemented in an SU(2)_L x U(1)_Y x SU(2)&#39;_L x U(1)&#39;_Y model, where the first and second families respect SU(2)_L x U(1)_Y while SU(2)&#39;_L x U(1)&#39;_Y is specific for the third family. The fourth neutrino, nu_s, that has a U(1)_Y x U(1)&#39;_Y coupling joins in the model to induce neutrin

Abdel Pérez-Lorenzana, William A. Ponce

We present a grand unified model based on the supersymmetric $SU(3)_L\otimes SU(3)_{CL}\otimes SU(3)_{CR}\otimes SU(3)_R$ gauge group, which unifies in one single step the three gauge couplings of the standard model at an scale $M\sim 10^{18}$ GeV, and spontaneously breaks down to $SU(3)_c\otimes U(1)_{EM}$ using only fundamental representations of SU(3). In

Per Berglund, John Ellis, Alon E. Faraggi, D. V. Nanopoulos

We study the elliptic fibrations of some Calabi-Yau three-folds, including the $Z_2\times Z_2$ orbifold with $(h_{1,1},h_{2,1})=(27,3)$, which is equivalent to the common framework of realistic free-fermion models, as well as related orbifold models with $(h_{1,1},h_{2,1})=(51,3)$ and (31,7). However, two related puzzles arise when one considers the $(h_{1,1

Doug Bilodeau

To understand the foundations of quantum mechanics, we have to think carefully about how theoretical concepts are rooted in -- and limited by -- the nature of experience, as Bohr attempted to show. Geometrical pictures of physical phenomena are favored because of their clarity. Quantum phenomena, however, do not permit them. Instead, the historical and dynam

Richard L. Hall, Nasser Saad, Attila B. von Keviczky

Closed-form expressions for the singular-potential integrals <m| x^-alpha |n> are obtained with respect to the Gol&#39;dman and Krivchenkov eigenfunctions for the singular potential V(x) = B x^2 + A/x^2, B > 0, A >= 0. These formulas are generalizations of those found earlier by use of the odd solutions of the Schroedinger equation with the harmonic oscillat

H. Moya-Cessa, A. Vidiella-Barranco, J. A. Roversi, Dagoberto S. Freitas

In this contribution we investigate the interaction of a single ion in a trap with laser beams. Our approach, based on unitary transformating the Hamiltonian, allows its exact diagonalization without performing the Lamb-Dicke approximation. We obtain a transformed Jaynes-Cummings type Hamiltonian, and we demonstrate the existence of super-revivals in that sy

Martti Havukainen, Stig Stenholm

An oscillator with stochastic frequency is discussed as a model for evaluating the quantum coherence properties of a physical system. It is found that the choice of jump statistics has to be considered with care if unphysical consequences are to be avoided. We investigate one such model, evaluate the damping it causes, the decoherence rate and the correlatio

S. Schneider, G. J. Milburn

We consider two different kinds of fluctuations in an ion trap potential: external fluctuating electrical fields, which cause statistical movement (``wobbling&#39;&#39;) of the ion relative to the center of the trap, and fluctuations of the spring constant, which are due to fluctuations of the ac-component of the potential applied in the Paul trap for ions.

Mauro Fortunato, Paolo Tombesi, Wolfgang P. Schleich

We propose to measure the quantum state of a single mode of the radiation field in a cavity---the signal field---by coupling it via a quantum-non-demolition Hamiltonian to a meter field in a highly squeezed state. We show that quantum state tomography on the meter field using balanced homodyne detection provides full information about the signal state. We di

M. D. Betterton, Michael P. Brenner

This paper considers the effect of electrostatics on the stability of a charged membrane. We show that at low ionic strength and high surface charge density, repulsion between charges on the membrane renders it unstable to the formation of holes. A free straight edge is unstable to modulations with wavelength longer than the Debye screening length. Hence at

Le Anh Thu, Le Van Hoang, L I Komarov, T S Romanova

Using the operator representation of the Dirac Coulomb Green function the analytical method in perturbation theory is employed in obtaining solutions of the Dirac equation for a hydrogen-like atom in a time-dependent electric field. The relativistic dynamical polarizability of hydrogen-like atoms is calculated and analysed.

Ali Krikeb, Andre Martin, Jean-Marc Richard, Tai T. Wu

We present results on the stability of quantum systems consisting of a negative charge $-q_1$ with mass $m_{1}$ and two positive charges $q_2$ and $q_3$, with masses $m_{2}$ and $m_{3}$, respectively. We show that, for given masses $m_{i}$, each instability domain is convex in the plane of the variables $(q_{1}/q_{2}, q_{1}/q_{3})$. A new proof is given of t

S. Jin, P. McNamara

A new method of background subtraction is presented which uses the concept of a signal estimator to construct a confidence level which is always conservative and which is never better than e^-s. The new method yields stronger exclusions than the Bayesian method with a flat prior distribution.

T. Mizutani

The purpose of the present discussion is to supplement the talk, by B.~Saghai at this workshop, on the study of the electromagnetic production of strangeness on the nucleon based upon effective Lagrangian methods. Here we focus on the proper treatment of the spin 3/2 resonances and their associated effects due to the spin 1/2 component of the corresponding f

D. Knödler, H. Müther

The contributions of short-range nucleon-nucleon correlations, meson exchange current (MEC) corrections and the influence of Delta isobar excitations (isobaric currents, IC) on photon induced two-nucleon knockout reactions are investigated. The nuclear structure functions are evaluated for the system of infinite nuclear matter. This allows a systematic inves

L. Coraggio, A. Covello, A. Gargano

We have performed a shell-model study of the two nuclei 210Po and 206Hg, having and lacking two protons with respect to doubly magic 208Pb. In our calculations we have employed realistic effective interactions derived from the Bonn A nucleon-nucleon potential. The calculated results are compared with the available experimental data are, however, very scanty

R. Skibiński, J . Golak, H. Witała, W. Glöckle

The mu-capture process on 3He leading to a neutron, a deuteron and a mu-neutrino in the final state is studied. Three-nucleon Faddeev wave functions for the initial 3He bound and the final neutron-deuteron scattering states are calculated using the BonnB and Paris nucleon-nucleon potentials. The nuclear weak current operator is restricted to impulse approxim

Mannque Rho

How chiral symmetry -- which is a basic ingredient of quantum chromodynamics (QCD) for light-quark hadrons -- enters and plays an eminent role in nuclear physics is discussed. This is done in two steps. In the first step, I introduce the notion of the Cheshire Cat Principle which describes how a strong-interaction phenomenon can be described in various diffe

Hasan R. Karadayi, Meltem Gungormez

It is known that summations over Weyl groups of Lie algebras is a problem which enters in many areas of physics as well as in mathematics. For this, a method which we would like to call {\bf permutation weights} has been previously proposed for pairs $(G_N, A_{N-1})$ of Lie algebras. It is now extended for $(E_7, A_7)$ and also $(E_8, A_8)$. It is clear that

Bernadette Perrin-Riou

Let V be a crystalline p-adic representation of the absolute Galois group G_K of an finite unramified extension K of Q_p and T a lattice of V stable by G_K. We prove the following result: Let Fil^1 V be the maximal sub-representation of V with Hodge-Tate weights strictly positive and Fil^1 T=T \cap Fil^1 V. Then, the projective limit of the H^1_g(K(μ_{p^n}),

Ravi Vakil

We derive a closed-form expression for all genus 1 Hurwitz numbers, and give a simple new graph-theoretic interpretation of Hurwitz numbers in genus 0 and 1. (Hurwitz numbers essentially count irreducible genus g covers of the sphere, with arbitrary specified branching over one point, simple branching over other specified points, and no other branching. The

Mikhail Grinberg, David Kazhdan

Let X be a complex algebraic variety, and L(X) be the scheme of formal arcs in X. Let f be an arc whose image is not contained in the singularities of X. We show that the formal neighborhood of f in L(X) admits a decomposition into a product of an infinite-dimensional smooth piece, and a piece isomorphic to the formal neighborhood of a closed point of a sche

Octavian Cornea

The ambient framed bordism class of the connecting manifold of two consecutive critical points of a Morse-Smale function is estimated by means of a certain Hopf invariant. Applications include new examples of non-smoothable Poincare duality spaces as well as an extension of the Morse complex.

Chunsheng Ban, Lee J. McEwan

We describe the embedded resolution of a quasi-ordinary surface singularity (V,p) which results from applying the canonical resolution of Bierstone-Milman to (V,p). We show that this process depends solely on the characteristic pairs of (V,p), as predicted by Lipman. We describe the process explicitly enough that a resolution graph for (V,p) could in princip

A. Balan

We obtain an explicit formula for the symplectic form over the double quotient with help of the Green function of a Riemann surface.

Vadim V. Varlamov

Representations of Dirac-Hestenes and Dirac spinor fields via coordinates of surfaces conformally immersed into 4-dimensional complex space are proposed. A relation between time evolution of spinor fields and integrable deformations of surfaces is discussed.

Paolo Aluffi

We introduce a class extending the notion of Chern-Mather class to possibly nonreduced schemes, and use it to express the difference between Schwartz-MacPherson&#39;s Chern class and the class of the virtual tangent bundle of a singular hypersurface of a nonsingular variety. Applications include constraints on the possible singularities of a hypersurface and

Ivan K. Babenko, Iskander A. Taimanov

For any $N \geq 5$ nonformal simply connected symplectic manifolds of dimension $2N$ are constructed. This disproves the formality conjecture for simply connected symplectic manifolds which was introduced by Lupton and Oprea.

Martin Bordemann, Nikolai Neumaier, Markus J. Pflaum, Stefan Waldmann

For every formal power series $B=B_0 + λB_1 + O(λ^2)$ of closed two-forms on a manifold $Q$ and every value of an ordering parameter $κ\in [0,1]$ we construct a concrete star product $\star^B_κ$ on the cotangent bundle $π: T^*Q\to Q$. The star product $\star^B_κ$ is associated to the formal symplectic form on $T^*Q$ given by the sum of the canonical symplect

Viacheslav V. Nikulin

We denote by FPMC the class of all non-singular projective algebraic surfaces X over C with a finite polyhedral Mori cone NE(X)\subset NS(X)\otimes R. If rho(X)=rk NS(X)\ge 3, then the set Exc(X) of all exceptional curves on X\in FPMC is finite and generates NE(X). Let δ_E(X) be the maximum of (-E^2) and p_E(X) the maximum of p_a(E) respectively for E\in Exc

Akikazu Hashimoto

We construct an explicit supergravity solution for a configuration of localized D4-brane ending on a D6-brane, restricted to the near horizon region of the latter. We generate this solution by dimensionally reducing the supergravity solution for a flat M5-brane in $R^{1,7} \times C^2/Z_N$ with the M5-brane partially embedded in $C^2/Z_N$. We describe the gen

Xinrui Hou, M. Shifman

Starting from a one-particle quasi-exactly solvable system, which is characterized by an intrinsic sl(2) algebraic structure and the energy-reflection symmetry, we construct a daughter N-body Hamiltonian presenting a deformation of the Calogero model. The features of this Hamiltonian are (i) it reduces to a quadratic combination of the generators of sl(N+1);

O. Obregón, J. J. Rosales, J. Socorro, V. I. Tkach

In this work we define a scalar product ``weighted&#39;&#39; with the scalar factor $R$ and show how to find a normalized wave function for the supersymmetric quantum FRW cosmological model using the idea of supersymmetry breaking selection rules under local n=2 conformal supersymmetry. We also calculate the expectation value of the scalar factor R in this m

Matthias Klein

We expand on an idea of Seiberg that an N=1 supersymmetric gauge theory shows confinement without breaking of chiral symmetry when the gauge symmetry of its magnetic dual is completely broken by the Higgs effect. This has recently been applied to some models involving tensor fields and an appropriate tree-level superpotential. We show how the confining spect

K. Foerger

We discuss heterotic corrections to quartic internal U(1) gauge couplings and check duality by calculating one-loop open string diagrams and identifying the D-instanton sum in the dual type I picture. We also compute SO(8)^4 threshold corrections and finally R^2 corrections in type I theory.

N. Berkovits, M. M. Leite

Using the manifestly spacetime-supersymmetric version of open superstring field theory, we construct the free action for the first massive states of the open superstring compactified to four dimensions. This action is in N=1 D=4 superspace and describes a massive spin-2 multiplet coupled to two massive scalar multiplets.

Stephane Gourmelen

We study the superconformally covariant pseudodifferential symbols defined on N=2 super Riemann surfaces. This allows us to construct a primary basis for N=2 super W_KP^(n)-algebras and, by reduction, for N=2 super W_n-algebras.

J. Bros, G. A. Viano

It is proven that for each given two-field channel - called the ``t-channel&#39;&#39;- with (off-shell) ``scattering angle&#39;&#39; $Θ_t$, the four-point Green&#39;s function of any scalar Quantum Fields satisfying the basic principles of locality, spectral condition together with temperateness admits a Laplace-type transform in the corresponding complex an

T. Gisiger, M. B. Paranjape

In this review we present a pedagogical introduction to recent, more mathematical developments in the Skyrme model. Our aim is to render these advances accessible to mainstream nuclear and particle physicists. We start with the static sector and elaborate on geometrical aspects of the definition of the model. Then we review the instanton method which yields

Jacques Bros, Daniel Iagolnitzer

Universal low-energy behaviour ${2 m c}\over{\ln |s-4m^2|}$ of the scattering function of particles of positive mass m near the threshold $s=4m^2$, and ${\pi} \over {\ln |s-4m^2|}$ for the corresponding S-wave phase-shift, is established for weakly coupled field theory models with a positive mass m in space-time dimension 3; c is a numerical constant indepen

Martin Cederwall, Ulf Gran, Magnus Holm, Bengt E. W. Nilsson

We consider brane solutions where the tensor degrees of freedom are excited. Explicit solutions to the full non-linear supergravity equations of motion are given for the M5 and D3 branes, corresponding to finite selfdual tensor or Born-Infeld field strengths. The solutions are BPS-saturated and half-supersymmetric. The resulting metric space-times are analys

K. S. Babu, B. Dutta, R. N. Mohapatra

In a large class of supersymmetric SO(10) and left-right models, requiring that the effective theory below the scale of $SU(2)_R$ breaking be the MSSM implies partial Yukawa unification with $Y_u=Y_d$ and $Y_e=Y_{ν^D}$. The same result also emerges in models with a horizontal $SU(3)_H$ symmetry. As a result, at the tree level, these models lead to vanishing

Michel C. Vetterli

This paper gives a pedagogical introduction to our knowledge of the spin structure of the nucleon. In particular, polarised deep inelastic lepton scattering is presented as a tool to study how the nucleon&#39;s constituents combine to generate its spin. The importance of semi-inclusive measurements is discussed and a window on future experiments in the field

H. G. Dosch, M. Eidemueller, M. Jamin

The gauge invariant two-point correlator for the gluon field strength tensor is analysed by means of the QCD sum rule method. To this end, we make use of a relation of this correlator to a two-point function for a quark-gluon hybrid in the limit of the quark mass going to infinity. From the sum rules a relation between the gluon correlation length and the gl

Y. A. Simonov

Dynamics of confinement, chiral symmetry breaking and thermal phase transition is considered at large $N_c$. It is argued that these phenomena are quantitatively well described within the Gaussian stochastic model of the QCD vacuum. Selfconsistent equations are written for the field correlators of the model, yielding important connection between gluonic corr

P. Ch. Christova, M. Jack, S. Riemann, T. Riemann

The status of predictions for fermion-pair production at LEP is summarized with emphasis on LEP2 energies and on the physics interest there. Some numerical comparisons with other programs are performed. We also present first results of a semi-analytical recalculation of photonic corrections with acollinearity cut in the ZFITTER approach.

A. Denner, S. Dittmaier

The $O(α)$ corrections to $γγ--> f \bar f$ in the Standard Model are calculated for arbitrary, light fermions $f$. The relevant analytical results are listed in a form that is appropriate for practical applications, and numerical results for integrated cross sections are discussed. The corresponding QED corrections are generally of the order of some per mill

Andreas Schaefer, Markus H. Thoma

A calculation of the thermal quark propagator is presented taking the gluon condensate above the critical temperature into account. The quark dispersion relation following from this propagator is derived.

N. V. Mikheev, A. Ya. Parkhomenko, L. A. Vassilevskaya

The axion decay $a \to e^+ e^-$ via a plasmon is investigated in an external magnetic field. The results we have obtained demonstrate a strong catalyzing influence of the field as the axion lifetime in the magnetic field of order $10^{15}$ G and at temperature of order 10 MeV is reduced to $10^4$ sec.

Michael Spira

The determination of the full SUSY QCD corrections to the production of squarks, gluinos and gauginos at hadron colliders is reviewed. The NLO corrections stabilize the theoretical predictions of the various production cross sections significantly and lead to sizeable enhancements of the most relevant cross sections. We discuss the phenomenological consequen

U. A. Yajnik, Hatem Widyan, Shobhit Mahajan, Amitabha Mukherjee

It is shown that the minimal left-right symmetric model admits cosmic string and domain wall solutions. The cosmic strings arise when the SU(2)_R is broken and can either be destabilized at the electroweak scale or remain stable through the subsequent breakdown to U(1)_{EM}. The strings carry zero modes of the neutrino fields. Two distinct domain wall config

Abdel Pérez--Lorenzana, William A. Ponce, Arnulfo Zepeda

We explore in a model independent way the possibility of achieving the non supersymmetric gauge coupling unification within left-right symmetric models, with the minimal particle content at the left-right mass scale which could be as low as 1 TeV in a variety of models, and with a unification scale M in the range $10^5$ GeV $< M< 10^{17.7}$ GeV.

Yu. A. Kubyshin, P. G. Tinyakov

The cross section of the multiparticle scattering processes in the non-perturbative sector of the scalar -lambda * phi^4 model is studied within the semiclassical approximation. For this purpose the exact formula for the residue of the propagator in the instanton background is derived. The exponent of the cross section is calculated at small energies both an

John Ellis, Dmitri Kharzeev

We propose a possible explanation of the kinematical dependence of the central production of the scalar glueball candidate observed recently by the WA91 and WA102 Collaborations, and discussed by Close and Kirk, in the context of the broken scale invariance of QCD. The dependences of glueball production on the transverse momenta and azimuthal angles of the f

Viktor Hund, Hartmut Pilkuhn

For the S-states of positronium and muonium, the terms of an expansion of energy levels in powers of the fine structure constant $α$ are also members of a &#34;recoil series&#34;. The first two terms of that series are calculated to all orders in $α$.

The WA102 Collaboration, D. Barberis et al

A study of the centrally produced ppbar, ppbarpi, ppbarpipi and lambda lambda channels has been performed in pp collisions using an incident beam momentum of 450 GeV/c. No significant new structures are observed in the mass spectra, however, important new information on the production dynamics is obtained. A systematic study of the production properties of t

DELPHI Collaboration

Measurements of α_s from event shapes in e^{+} e^{-} annihilation are discussed including recent determinations using experimentally optimized scales, studies of theoretically motivated scale setting prescriptions, and recently observed problems with predictions in Next to Leading Logarithmic Approximation. Other recent precision measurements of α_s are brie

Ll. Bel

We define a Frame of reference as a two ingredients concept: A meta-rigid motion, which is a generalization of a Born motion, and a chorodesic synchronization, which is an adapted foliation. At the end of the line we uncover a low-level 3-dimensional geometry with constant curvature and a corresponding coordinated proper-time scale. We discuss all these aspe

Gerhard Rein, Alan D. Rendall

Equilibrium states in galactic dynamics can be described as stationary solutions of the Vlasov-Poisson system, which is the non-relativistic case, or of the Vlasov-Einstein system, which is the relativistic case. To obtain spherically symmetric stationary solutions the distribution function of the particles (stars) on phase space is taken to be a function of

I. B. Khriplovich

The probability of a charged particle production by the electric field of a charged black hole depends essentially on the particle energy. This probability is found in the nonrelativistic and ultrarelativistic limits. The range of values for the mass and charge of a black hole is indicated where the discussed mechanism of radiation is dominating over the Haw

Arne L. Larsen, Argyris Nicolaidis

The phenomenon of string spreading on the black hole horizon, as originally discussed by Susskind, is considered in the {\it exact} curved Schwarzschild background. We consider an oscillating string encircling the black hole and contracting towards the horizon. We then compute the angular and radial spreading of the string, as seen by a static observer at sp

Wu Zhong Chao

The seeds for quantum creations of universes are constrained gravitational instantons. For all compact constrained instantons with U(1) isometry, the period $β$ of the group parameter $τ$ is identified as the reciprocal of the temperature. If $β$ remains a free parameter under the constraints, then the Euclidean action becomes the negative of the &#34;entrop

O. G. Balev, P. Vasilopoulos, Nelson Studart

A quasi-microscopic treatment of edge magnetoplasmons (EMP) is presented for very low temperatures and confining potentials smooth on the scale of the magnetic length $\ell_{0}$ but sufficiently steep at the edges such that Landau level (LL) flattening can be discarded. The profile of the unperturbed electron density is sharp and the dissipation taken into a

G. Salis, P. Wirth, T. Heinzel, T. Ihn

The Drude scattering times of electrons in two subbands of a parabolic quantum well have been studied at constant electron sheet density and different positions of the electron distribution along the growth direction. The scattering times obtained by magnetotransport measurements decrease as the electrons are displaced towards the well edges, although the lo

E. A. Livesay, R. N. West, S. B. Dugdale, G. Santi

Materials that exhibit colossal magnetoresistance (CMR) are currently the focus of an intense research effort, driven by the technological applications that their sensitivity lends them to. Using the angular correlation of photons from electron-positron annihilation, we present a first glimpse of the Fermi surface of a material that exhibits CMR, supported b

M. Paraskevopoulos, J. Hemberger, A. Loidl, A. A. Mukhin

We report on detailed transprort measurements of single crystalline La(1-x)Sr(x)MnO(3) (x<=0.2). We have found a giantpositive magnetoresistance in the compositions range between 0.1<=x<=0.125 and give an explaination in terms of orbital ordering due to the interplay between superexchange interactions and Jahn-Teller distortions.

J. J. Hogan-O&#39;Neill, A. M. Martin, James F. Annett

We calculate the s- and d-wave superconductor order parameter in the vicinity of a tilt grain boundary. We do this self-consistently within the Bogoliubov de Gennes equations, using a realistic microscopic model of the grain boundary. We present the first self-consistent calculations of supercurrent flows in such boundaries, obtaining the current-phase chara