November 1995 arXiv papers — page 7

R. D. Ball

We review the perturbative evolution of the polarized structure functions g_1 and their associated parton distribution functions, with particular emphasis on the anomalous coupling of the first moment of the polarized gluon distribution. We also describe the small x behaviour of polarized parton distributions, contrasting it with that of the unpolarized dist

A. H. Castro Neto, Daniel Hone

We study the properties of the striped phases that have been proposed for the doped cuprate planar quantum antiferromagnets. We invoke an effective, spatially anisotropic, non-linear sigma model in two space dimensions. Our theoretical predictions are in {\it quantitative} agreement with recent experiments. We focus on (i) the staggered magnetization at $T=0

Ashok Das, Chung Kao

A two Higgs doublet model with special Yukawa interactions for the top quark and a softly broken discrete symmetry in the Higgs potential is proposed. In this model, the top quark is much heavier than the other quarks and leptons because it couples to a Higgs doublet with a much larger vacuum expectation value. The electric dipole moment (EDM) of the electro

George Leibbrandt, Mark Staley

We apply the method of \underline{zeta} functions, together with the $n_μ^*$-prescription for the temporal gauge, to evaluate the thermodynamic pressure in QCD at finite temperature $T$. Working in the imaginary-time formalism and employing a special version of the unified-gauge prescription, we show that the pure-gauge contribution to the pressure at two lo

Carlo Lucheroni

A simple but accurate mesh current analysis is performed on a XY model and on a SIMF model to derive the equations for a Josephson junction array. The equations obtained here turn out to be different from other equations already existing in the literature. Moreover, it is shown that the two models come from an unique hidden structure

Halina Abramowicz

This is a short review of the properties of electron proton interactions characterized by the presence of large rapidity gaps (LRG) in the measured hadronic final state as obtained by the ZEUS Collaboration at the HERA Collider. In the deep inelastic neutral current $ep$ interactions, the factorization properties of the LRG events interpreted as due to the d

Jochen Mueller, Jochen Rau

We employ projection operator techniques in Hilbert space to derive a continuous sequence of effective Hamiltonians which describe the dynamics on successively larger length scales. We show for the case of ϕ^4 theory that the masses and couplings in these effective Hamiltonians vary in accordance with 1-loop renormalization group equations. This is evidence

Francois David

These lectures deal with: (1) a brief review of the theory of flexible random manifolds (with fixed intrinsic metric), connected to the physics of polymerized membranes, and of the effect of extrinsic curvature (crumpling transitions); (2) a discussion of the effect of self-avoidance and its renormalization group treatment in term of a non-local field theory

K. C. Chou, Y. L Wu

Fermion masses and mixing angles are studied in an SUSY $SO(10)\times Δ(48)\times U(1)$ model with small $\tanβ$. Thirteen parameters involving masses and mixing angles in the quark and charged lepton sector are successfully predicted by a single Yukawa coupling and three ratios of VEVs caused by necessary symmetry breaking. Ten relations among the low energ

S. A. Abel, W. N. Cottingham, I. B. Whittingham

We analyse the electric dipole moment of the neutron in the MSSM, induced by the renormalisation of the soft-susy breaking terms. We run the RGEs using two-loop expressions for gauge and Yukawa couplings and retaining family dependence. The $μ$ and $B$ parameters were determined by minimising the full one-loop Higgs potential, and we find that the neutron ED

Rafael Bautista, Sergio Torres

A precise determination of the primordial spectrum of matter density fluctuations at super-horizon scales is essential in understanding large scale structure in the universe. Attempts to constrain or obtain the primordial spectrum using data on cosmic microwave background (CMB) anisotropies has relied on statistical and correlation analyses that assume a pow

B. Pasquini, S. Boffi

Nuclear Compton scattering in the $Δ$-resonance region is reconsidered within the framework of the $Δ$-hole model. The different role of the resonant and non-resonant contributions to the transition amplitudes is discussed and their effect is investigated by comparing the results of calculation with recent data also taken with polarized photons.

Jonathan L. Feng, Nir Polonsky, Scott Thomas

Supersymmetric models are typically taken to have $μ$ parameter and all soft supersymmetry breaking parameters at or near the weak scale. We point out that a small window of allowed values exists in which $μ$ and the electroweak gaugino masses are in the few GeV range. Such models naturally solve the supersymmetry $CP$ problem, can reduce the discrepancy in

Attila Csoto, Karlheinz Langanke

We study the parity-violating alpha+d decay of the lowest 0+ state of Li-6 in a microscopic three-cluster model. The initial bound and the final scattering states are described consistently within the same model. The parity-violating decay width is calculated in perturbation theory using the parity-nonconserving nucleon-nucleon interaction of Desplanques, Do

Saharon Shelah

We prove consistency of the following sentence: ``ZFC + every real function is continuous on a non-meagre set'', answering a question of Fremlin.

Albert Schwarz, Oleg Zaboronsky

We study conditions under which an odd symmetry of the integrand leads to localization of the corresponding integral over a (super)manifold. We also show that in many cases these conditions guarantee exactness of the stationary phase approximation of such integrals.

Alexander Astashkevich, Alexander Belopolsky

We consider the theory of bosonic closed strings on the flat background R(25,1). We show how the BRST complex can be extended to a complex where the string center of mass operator, x^mu_0, is well defined. We investigate the cohomology of the extended complex. We demonstrate that this cohomology has a number of interesting features. Unlike in the standard BR

Bryce DeWitt, Carmen Molina-Paris

A quantum effective action for gauge field theories is constructed that is gauge invariant and independent of the choice of gauge breaking terms and the ghost determinant.

I. Antoniadis, S. Ferrara, T. R. Taylor

We study quantum effects in five dimensions in heterotic superstring theory compactified on K_3 x S_1 and analyze the conjecture that its dual effective theory is eleven-dimensional supergravity compactified on a Calabi-Yau threefold. This theory is also equivalent to type II superstring theory compactified on the same Calabi-Yau manifold, in an appropriate

M. Fichtmueller, A. Lorek, J. Wess

A q-deformed two-dimensional phase space is studied as a model for a noncommutative phase space. A lattice structure arises that can be interpreted as a spontaneous breaking of a continuous symmetry. The eigenfunctions of a Hamiltonian that lives on such a lattice are derived as wavefunctions in ordinary $x$-space.

Itzhak Bars, Shimon Yankielowicz

We employ an algebraic approach for unifying perturbative and non-perturbative superstring states on an equal footing, in the form of U-duality multiplets, at all excited string levels. In compactified type-IIA supertring theory we present evidence that the multiplet is labelled by two spaces, ``index'' space and ``base'' space, on which U ac

Xiao-Ming Xu, D. Kharzeev, H. Satz, Xin-Nian Wang

Short-distance QCD is employed to calculate the $J/ψ$ survival probability in an equilibrating parton gas, whose evolution is governed by a set of master rate equations. Partons in the early stage of high-energy nuclear collisions may initially not be in equilibrium, but their average transverse momentum is sufficiently high to break up a $Q\bar{Q}$ bound st

M. Martinis, V. Mikuta-Martinis

We give reasons in support of the use of an effective intensity-dependent pion-nucleon coupling Hamiltonian for describing the properties of the pion multiplicity distribution and the corresponding factorial moments within the thermal-density matrix approach.We explain the appearance of the negative-binomial (NB) distribution for pions and the well-known emp

Juha T. Peltoniemi

The role of the sterile neutrinos to the r-process nucleosynthesis in supernova explosions is studied. Previously it has been argued that a large part of neutrino mixing can be excluded if the supernovae are the origin of the heavy elements. It is shown that a conversion to sterile neutrinos may evade those limits. The possibility that such conversions can e

M. A. Sanchis-Lozano

Several integrals involving powers and ordinary hypergeometric functions are rederived by means of a generalized hypergeometric function of two variables (Appell's function) recovering some well-known expressions as particular cases. Simple connections between dilogarithms and a kind of Appell's function are shown. A relationship is generalized to po

John Ellis, Klaus Geiger

The time-evolution of jets in hadronic e+e- events at LEP is investigated in both position- and momentum-space, with emphasis on effects due to color flow and particle correlations. We address dynamical aspects of the four simultanously-evolving, cross-talking parton cascades that appear in the reaction e+e- -> gamma/Z0 -> W+W- -> q1 q~2 q3 q~4, and compare

B. Borasoy, Ulf-G. Meißner

We analyze the effective low--energy field theory of Goldstone bosons and baryons chirally coupled to massive spin--1 fields. We use the electromagnetic baryon form factors to demonstrate the formal equivalence between the vector and the tensor field formulation for the spin--1 fields. We also discuss the origin of the so--called Weinberg term in pion--nucle

J. Dai, J. F. Gunion, R. Vega

We demonstrate that detection of the heavier minimal supersymmetric model CP-even Higgs boson $H^0$ will be possible at the LHC via its $H^0\to h^0h^0\to 4b$ and/or $H^0\to A^0A^0\to 4b$ decay channels for significant portions of the $( m_{A^0},\tanβ)$ model parameter space. At low $ m_{A^0}$ ($\lsim 60\gev$), {\it both} the $H^0\to A^0A^0\to 4b$ and $H^0\to

R. Vega, J. Wudka

We present an alternative approach for calculating helicity amplitudes for processes involving both massless and massive fermions. With this method one can easily obtain covariant expressions for the helicity amplitudes. The final expressions involve only four vector products and are independent of the basis for gamma matrices or specific form of the spinors

Christof Gattringer

We analyze the Schwinger model on an infinite lattice using the continuum definition of the fermion determinant and a linear interpolation of the lattice gauge fields. The possible class of interpolations for the gauge fields, compatible with gauge invariance is discussed. The effective action for the lattice gauge field is computed for the Wilson formulatio

Livio Conti, Claudio Parrinello, Silvano Petrarca, Anastassios Vladikas

We investigate the viability of the quasi-temporal gauge on the lattice. This is a complete gauge fixing condition that can be implemented on the lattice at a very low computational cost. As a test case, using the Clover action, we have evaluated the (gauge invariant) renormalisation constant of the non-singlet axial current, using Ward identities extracted

Roy Maartens, Neil Humphreys, David Matravers, Bill Stoeger

Isotropic inhomogeneous dust universes are analysed via observational coordinates based on the past light cones of the observer's galactic worldline. The field equations are reduced to a single first--order {\sc ode} in observational variables on the past light cone, completing the observational integration scheme. This leads naturally to an explicit exa

Alexei V Nesteruk, Roy Maartens

We consider quantum effects of an electromagnetic field in a radiation-dominated almost FRW spacetime. The dominant non-local quantum correction to the photon distribution is a quadrupole moment, corresponding to an effective anisotropic pressure in the energy-momentum tensor.

David R Taylor, Roy Maartens

In the $R+αR^2$ gravity theory, we show that if freely propagating massless particles have an almost isotropic distribution, then the spacetime is almost Friedmann-Robertson-Walker (FRW). This extends the result proved recently in general relativity ($α=0$), which is applicable to the microwave background after photon decoupling. The higher-order result is i

G. Blumberg, P. Abbamonte, M. V. Klein, L. L. Miller

We present results of low-temperature two-magnon resonance Raman excitation profile measurements for single layer Sr_2CuO_2Cl_2 and bilayer YBa_2Cu_3O_{6 + δ} antiferromagnets over the excitation region from 1.65 to 3.05 eV. These data reveal composite structure of the two-magnon line shape and strong nonmonotic dependence of the scattering intensity on exci

Richard Berkovits, Yshai Avishai

An expression for the conductance of interacting electrons in the diffusive regime as a function of the ensemble averaged persistent current and the compressibility of the system is presented. This expression involves only ground-state properties of the system. The different dependencies of the conductance and persistent current on the electron-electron inte

B. Jancovici, G. Tellez

This paper compares two methods of statistical mechanics used to study a classical Coulomb system S near an ideal conductor C. The first method consists in neglecting the thermal fluctuations in the conductor C and constrains the electric potential to be constant on it. In the second method the conductor C is considered as a conducting Coulomb system the cha

G. Goldoni, F. M. Peeters

We investigate the stability, the dynamical properties and melting of a two-dimensional (2D) Wigner crystal (WC) of classical Coulombic particles in a bi-layer structure. Compared to the single-layer WC, this system shows a rich phase diagram. Five different crystalline phases are stable; the energetically favoured structure can be tuned by changing either t

Matthias Troyer, Hiroshi Kontani, Kazuo Ueda

We have numerically investigated the 1/5-depleted Heisenberg square lattice representing CaV4O9 using the Quantum Monte Carlo loop algorithm. We have determined the phase diagram of the model as a function of the ratio of the two different couplings: bonds within a plaquette and dimer bonds between plaquettes. By calculating both the spin gap and the stagger

Brett Ellman, Louis Taillefer, Mario Poirier

We have measured the transverse ultrasonic attenuation, $α_{qε}$, in a well-characterized single crystal of $UPt_3$ for propagation direction, ${\bf q}$, in the basal plane and polarization, $ε$, in and out of the plane. Unlike previous measurements, the sample was of sufficient purity to exhibit three well-defined phases as a function of temperature and mag

Terence Hwa, Michael Lassig

The detection of similarities between long DNA and protein sequences is studied using concepts of statistical physics. It is shown that mutual similarities can be detected by sequence alignment methods only if their amount exceeds a threshold value. The onset of detection is a continuous phase transition which can be viewed as a localization-delocalization t

A. A. Maksimov, D. A. Pronin, S. V. Zaitsev, I. I. Tartakovskii

Kinetics of the optical and Raman response in YBa_2Cu_3O_{6.4} were studied during room temperature annealing following heat treatment. The superconducting T_c, dc resistivity, and low-energy optical conductivity recover slowly, implying a long relaxation time for the carrier density. Short relaxation times are observed for the B_{1g} Raman scattering -- mag

Marilyn A. Walker

This paper shows how agents' choice in communicative action can be designed to mitigate the effect of their resource limits in the context of particular features of a collaborative planning task. I first motivate a number of hypotheses about effective language behavior based on a statistical analysis of a corpus of natural collaborative planning dialogue

Sidney van den Bergh

Review paper presented at the meeting "Formation of the Galactic Halo: Inside and Out", Tucson, October 1995.

Thomas Crawford, Jon Marr, Bruce Partridge, Michael Strauss

We employed the Very Large Array (VLA) of the National Radio Astronomy Observatory in C configuration to map 39 ultraluminous IRAS galaxies at 6~cm and 20~cm, at resolutions of ~ 4" and 15", respectively, and 24 sources at 6~cm with in the A configuration with a resolution of ~0.5". Most of the sources have radio spectral indices indicative of sy

Ravi K. Sheth, U. C. Berkeley

The distribution of pairwise, relative peculiar velocities, $f(u;r)$, on small nonlinear scales, $r$, is derived from the Press--Schechter approach. This derivation assumes that Press--Schechter clumps are virialized and isothermal. The virialized assumption requires that the circular velocity, $V_c \propto M^{1/3}$, where $M$ denotes the mass of the clump.

L. B. van den Hoek, W. J. G. de Blok

We investigate the star formation history and chemical evolution of Low Surface Brightness (LSB) spiral galaxies by means of their observed spectro-photometric and chemical properties. We present preliminary results for Johnson-Cousins UBVRI magnitudes and stellar [O/H] abundance ratios using a galactic chemical evolution model incorporating a detailed metal

Lauro Moscardini, Enzo Branchini, Paolo Tini Brunozzi, Stefano Borgani

We study the large-scale velocity fields traced by galaxy clusters in numerical simulations of a box of side 960 $h^{-1}$ Mpc, and compare them with available data on real clusters. In order to test the reliability of the simulations, which are based on an optimized version of the Zel'dovich approximation, we compare their cluster velocities with those o

Paolo Padovani, Paolo Giommi

We present a catalogue of 233 BL Lacertae objects compiled through an extensive bibliographic search updated to mid-1995. A large fraction of the sources listed in the catalogue belongs to well-defined samples and can be used for statistical purposes. A smaller fraction consists of miscellaneous (but confirmed) BL Lacs and of objects classified as BL Lac can

Stefan Åminneborg, Lars Bergström

We discuss self-similar solutions to $O(4)$ textures in Minkowski space and in flat Friedmann-Robertson-Walker backgrounds. We show that in the Minkowski case there exist no solutions with winding number greater than unity. However, we find besides the known solution with unit winding number also previously unknown solutions corresponding to winding number l

C. Otani, T. Kii, C. S. Reynolds, A. C. Fabian

We present the results of a 4 day ASCA observation of the Seyfert galaxy MCG-6-30-15, focussing on the nature of the X-ray absorption by the warm absorber, characterizd by the K-edges of the intermediately ionized oxygen, OVII and OVIII. We confirm that the column density of OVIII changes on a timescale of $\sim 10^4$~s when the X-ray continuum flux decrease

David Eisenbud, Barry Mazur

Given a reduced local algebra $T$ over a suitable ring or field $k$ we study the question of whether there are nontrivial algebra surjections $R\to T$ which induce isomorphisms $Ω_{R/k}\otimes T \to Ω_{T/k}$. Such maps, called evolutions, arise naturally in the study of Hecke algebras, as they implicitly do in the recent work of Wiles, Taylor-Wiles, and Flac

D. J. Gross, I. R. Klebanov, A. V. Matytsin, A. V. Smilga

We show that, in 1+1 dimensional gauge theories, a heavy probe charge is screened by dynamical massless fermions both in the case when the source and the dynamical fermions belong to the same representation of the gauge group and, unexpectedly, in the case when the representation of the probe charge is smaller than the representation of the massless fermions

Peter Cho, Adam K. Leibovich

We calculate the lowest order hadronic cross sections for producing colored heavy quark-antiquark pairs in $L=S=0$ and $L=S=1$ configurations. Such $Q\Qbar[{}^1S_0^{(8)}]$ and $Q\Qbar[{}^3P_J^{(8)}]$ states hadronize into $ψ_\Q$ quarkonia at the same order in the NRQCD velocity expansion as previously considered $Q\Qbar[{}^3S_1^{(8)}]$ pairs. Their contribut

B. Z. Kopeliovich, J. Nemchik

Study of color transparency (CT) effects at moderate energies is more problematic than is usually supposed. Onset of CT can be imitated by other mechanisms, which contain no explicit QCD dynamics. In the case of the $(e,e'p)$ reaction the standard inelastic shadowing well known in the pre-QCD era, causes a substantial growth of nuclear transparency with $Q^2

C. Arvanitis, F. Geniet, M. Iacomi, J. -L. Kneur

We show how to perform systematically improvable variational calculations in the $O(2N)$ Gross-Neveu model for generic $N$, in such a way that all infinities usually plaguing such calculations are accounted for in a way compatible with the perturbative renormalization group . The final point is a general framework for the calculation of non-perturbative quan

Wen-Xiu Ma, Benno Fuchssteiner

Some explicit traveling wave solutions to a Kolmogorov-Petrovskii-Piskunov equation are presented through two ans\"atze. By a Cole-Hopf transformation, this Kolmogorov-Petrovskii-Piskunov equation is also written as a bilinear equation and further two solutions to describe nonlinear interaction of traveling waves are generated. B\"acklund transformations of

K. J. Barnes, J. M. Generowicz, P. J. Grimshare

The two dimensional surface of a sphere can be parametrized by coordinates representing two charged pions acting as Goldstone bosons of a broken $SU_2$ symmetry. We construct in full concrete detail, and in a general class of coordinate systems, all the relevant structure forming a framework for this low energy effective theory.

Belal E. Baaquie

A lagrangian for gauge fields coupled to fermions with the Kac-Moody group as its gauge group yields, for the pure fermions sector, an ideal gas of Kac-Moody fermions. The canonical partition function for the $\hat U(1)$ case is shown to have a maximum temperature $kT_{M} = |λ| /π$, where $λ$ is the coupling of the super charge operator $G_0 $ to the fermion

C. Bizdadea, S. O. Saliu

In this paper we show how the BRST quantization can be applied to systems possessing only second-class constraints through their conversion to some first-class ones starting with our method exposed in [Nucl.Phys. B456 (1995)473]. Thus, it is proved that i) for a certain class of second-class systems there exists a standard coupling between the variables of t

A. Kazarnovski-Krol

Integral of a certain multivalued form over cycle $\pmbΔ$ provides zonal spherical function of type $A_n$. This paper is devoted to quantum group analysis and verification of monodromy properties of the distinguished cycle $\pmbΔ$. Zonal spherical function is a particular conformal block of $WA_n$-algebra.

A. Belyaev, E. Boos L. Dudko, A. Pukhov

Results of calculation of all subprocesses in proton-antiproton collisions which contribute to the W+2jets final state are presented at Tevatron energy. The calculation has been carried out by means of the CompHEP software package. A detail comparison with VECBOS generator results for cross sections and various distributions shows an agreement at the level o

Matteo G. A. Paris

The determination of the quantum properties of a single mode radiation field by heterodyne or double homodyne detection is studied. The realistic case of not fully efficient photodetectors is considered. It is shown that a large amount of quite {\em precise} information is avalaible whereas the completeness of such information is also discussed. Some example

D. Dürr, S. Goldstein, N. Zanghi

In order to arrive at Bohmian mechanics from standard nonrelativistic quantum mechanics one need do almost nothing! One need only complete the usual quantum description in what is really the most obvious way: by simply including the positions of the particles of a quantum system as part of the state description of that system, allowing these positions to evo

Masahiro Morikawa

We derive dissipative effective Hamiltonian for the unstable Lee model without any ad hoc coarse graining procedure. Generalized radiative corrections, utilizing the in-in formalism of quantum field theory, automatically yield irreversibility as well as the decay of quantum coherence. Especially we do not need to extend the ordinary Hilbert space for describ

S. Simula

Inclusive $A(e,e')X$ and semi-inclusive $A(e,e'N)X$ deep inelastic electron scattering processes off few-nucleon systems are investigated at $x > 1$, showing some of the relevant features of the cross section which are sensitive to the effects arising from nucleon-nucleon correlations and possible exotic multiquark cluster configurations at short int

Sayan Kar

Schild's null (tensionless) strings are discussed in certain flat and curved backgrounds. We find closed, stationary, null strings as natural configurations existing on the horizons of spacetimes which possess such null hypersurfaces. Examples of these are obtained in Schwarzschild and Rindler spacetimes. A dynamic null string is also identified in Rindl

P. A. Marchetti

We show that abelian bosonization of 1+1 dimensional fermion systems can be interpreted as duality transformation and, as a conseguence, it can be generalized to arbitrary dimensions in terms of gauge forms of rank $d-1$, where $d$ is the dimension of the space. This permit to treat condensed matter systems in $d>1$ as gauge theories. Furthermore we show tha

Alexander Moroz

The spectral properties of the Dirac Hamiltonian in the the Aharonov-Bohm potential are discussed. By using the Krein-Friedel formula, the density of states (DOS) for different self-adjoint extensions is calculated. As in the nonrelativistic case, whenever a bound state is present in the spectrum it is always accompanied by a (anti)resonance at the energy. T

Anisur Rahaman

A new generalization of the vector Schwinger model is considered where gauge symmetry is broken at the quantum mechanical level. By proper extension of the phase space this broken symmetry has been restored. Also an equivalent first class theory is reformulated in the actual phase space using Mitra and Rajaraman's prescription \cite{mr1,mr2}. A BRST inva

S. Ansoldi, A. Aurilia, E. Spallucci

We study a functional field theory of membranes coupled to a rank--three tensor gauge potential. We show that gauge field radiative corrections lead to membrane condensation which turns the gauge field into a {\it massive spin--0 field}. This is the Coleman--Weinberg mechanism for {\it membranes}. An analogy is also drawn with a type--II superconductor. The

Alon E. Faraggi

The three generation superstring models in the free fermionic models have had remarkable success in describing the real--world. The most explored models use the NAHE set to obtain three generations and to separate the hidden and observable sectors. It is of course well known that the full NAHE set is not required in order to construct three generation free f

J. Antonio Garcia, J. David Vergara, Luis F. Urrutia

We introduce an operator version of the BRST-BFV effective action for arbitrary systems with first-class constraints. Using the Schwinger action principle we calculate the propagators corresponding to: (i) the parametrized non-relativistic free particle, (ii) the relativistic free particle and (iii) the spining relativistic free particle. Our calculation cor

Tony Gherghetta, Gerard Jungman, Erich Poppitz

In models with low-energy supersymmetry breaking, an anomalous Abelian horizontal gauge symmetry can simultaneously explain the fermion mass hierarchy and the values of the $μ$ and $B$ terms. We construct an explicit model where the anomaly is cancelled by the Green-Schwarz mechanism at the string scale. We show that with our charge assignments, the breaking

Alec J. Schramm, Daniel H. Reeves

We estimate the impact parameter dependence of the production cross section for $η_c$ and $η_b$ mesons in peripheral heavy-ion collisions collisions. Total and elastic $γγ$ cross sections are calculated in an equivalent photon approximation.

Frank E. Close, Harry J. Lipkin

The mass difference of $c$ and $u$ quarks is similar to the energy needed to excite gluonic degrees of freedom in strong QCD. This underpins the degeneracy of $D$ and a recently observed candidate hybrid excitation of the $π$ at$\sim 1.8$GeV and may generate a strong analogue of Penguin mixing together with a measurable CP-violation in $D$ and $D_s$ decays.

Hans Peter Nilles

We discuss the possible applications supersymmetric theories might find in the field of elementary particle physics. The supersymmetric generalization of the $SU(3)\times SU(2)\times U(1)$ standard model is discussed in detail. Special attention has been devoted to the question of gauge coupling constant unification in the framework of supersymmetric grand u

Naoyuki Haba, Chuichiro Hattori, Masahisa Matsuda, Takeo Matsuoka

In the context of the Calabi-Yau string model we discuss the origin of characteristic pattern of quark-lepton masses and the CKM matrix. The discrete $R$-symmetry $Z_{2k+1} \times Z_2$ is introduced and the $Z_2$ is assigned to the $R$-parity. The gauge symmetry at the string scale is broken into the standard model gauge group at an intermediate energy scale

Ruibin Meng, Fredrick I. Olness, Davison E. Soper

Measurement of the distribution of hadronic energy in the final state in deeply inelastic electron scattering at HERA can provide a good test of our understanding of perturbative QCD. For this purpose, we consider the energy distribution function, which can be computed without needing final state parton fragmentation functions. We compute this distribution f

Rodolfo Gambini, Jorge Pullin

We show that the second coefficient of the Conway knot polynomial is annihilated by the Hamiltonian constraint of canonically quantized general relativity in the loop representation. The calculations are carried out in a fully regularized lattice framework. Crucial to the calculation is the explicit form of the skein relations of the second coefficient, whic

Luciane R. de Freitas, M. Novello

We present a new field theory of gravity. It incorporates a great part of General Relativity (GR) and can be interpreted in the standard geometrical way like GR as far as the interaction of matter to gravity is concerned. However, it differs from GR when treating gravity to gravity interaction. The most crucial distinction concerns the velocity of propagatio

G. Giachetta, G. Sardanashvily

Our investigation of differential conservation laws in Lagrangian field theory is based on the first variational formula which provides the canonical decomposition of the Lie derivative of a Lagrangian density by a projectable vector field on a bundle (Part 1: gr-qc/9510061). If a Lagrangian density is invariant under a certain class of bundle isomorphisms,

Kwai-Kong Ng, Fu Chun Zhang, Michael Ma

We study the ground state and the phase transitions of the bilayered spin-$S$ antiferromagnetic Heisenberg model using the Schwinger boson mean field theory. The interplane coupling initially stabilizes but eventually destroys the long-range antiferromagnetic order. The transition to the disordered state is continuous for small $S$, and first order for large

Samuel Moukouri, Liang Chen, Laurent G. Caron

A 1D model hamiltonian that is motivated by the recent discovery of the heavy-fermion behavior in the cuprates of the $Nd_2CuO_4$ type is studied. It consists of $t-J$ interacting conduction electrons coupled to a lattice of localized spins through a Kondo exchange term $J_K$. Exact diagonalization and density matrix renormalization group methods are used. T

B. Garni, Jian Ma, N. Perkins, Jutong Liu

We report scanning tunneling microscopy (STM) images of surfaces of GaN films and the observation of luminescence from those films induced by highly spatially localized injection of electrons or holes using STM. This combination of scanning tunneling luminescence (STL) with STM for GaN surfaces and the ability to observe both morphology and luminescence in G

M. A. Continentino, G. M. Japiassu, A. Troper

Although predicted theoretically excitonic phase transitions have never been observed. Recently it has been claimed that they can occur in some strongly correlated materials. We study the possibility of an excitonic transition in a two-band model and show that a true phase transition never occurs in the presence of hybridization. We suggest an alternative in

J. Bonet Avalos, I. Pagonabarraga

In this paper we address the problem of consistently construct Langevin equations to describe fluctuations in non-linear systems. Detailed balance severely restricts the choice of the random force, but we prove that this property together with the macroscopic knowledge of the system is not enough to determine all the properties of the random force. If the ca

M. S. Ferreira, J. d'Albuquerque e Castro, D. M. Edwards, J. Mathon

It is shown how the exchange coupling between two ferromagnetic planes embedded in an infinite non-magnetic metal, regarded as a function of the distance between the planes, may contain important components which oscillate with periods not predicted by RKKY theory. The interesting case of a FCC(110) structure with a Cu-like Fermi surface is discussed in deta

Thomas Obermeier, Thomas Pruschke, Joachim Keller

We study the one-particle properties of the t-J model within the framework of Vollhardt's dynamical mean field theory. By introducing an AB - sublattice structure we explicitely allow for a broken symmetry for the spin degrees of freedom and are thus able to calculate the one-particle spectral function in the antiferromagnetic phase. We observe surprisin

Fabio Bagarello

We discuss in many details two quantum mechanical models of planar electrons which are very much related to the Fractional Quantum Hall Effect. In particular, we discuss the localization properties of the trial ground states of the models starting from considerations on the numerical results on the energy. We conclude that wavelet theory can be conveniently

A. Kadigrobov, R. Shekhter, M. Jonson

In relatively pure normal samples contacting a superconductor we consider the excess resistance effect (that is a decrease of the total electrical resistance of the sample after transition of the superconducting part into the normal state) and determine conditions under which the effect arises.

I. A. McDonald, F. D. M. Haldane

The double layer $ν=2/3$ fractional quantum Hall system is studied using the edge state formalism and finite-size diagonalization subject to periodic boundary conditions. Transitions between three different ground states are observed as the separation as well as the tunneling between the two layers is varied. Experimental consequences are discussed.

Carlo Graziani, Donald Q. Lamb

We develop a likelihood methodology which can be used to search for evidence of burst repetition in the BATSE catalog, and to study the properties of the repetition signal. We use a simplified model of burst repetition in which a number $N_{\rm r}$ of sources which repeat a fixed number of times $N_{\rm rep}$ are superposed upon a number $N_{\rm nr}$ of non-

M. A. Pahre, S. G. Djorgovski, R. R. de Carvalho

We use the intercept of the elliptical galaxy radius--surface brightness (SB) relation at a fixed metric radius as the standard condition for the Tolman SB test of the universal expansion. We use surface photometry in the optical and near-IR of elliptical galaxies in Abell~2390 ($z=0.23$) and Abell~851 ($z=0.41$), and compare them to the Coma cluster at $z\a

A. C. Fabian, R. Terlevich

We report the detection of SN1988Z in X-rays with the ROSAT High Resolution Imager. The inferred X-ray luminosity of about $10^{41}\ergps$ can be well explained by assuming that the supernova occurred in a dense circumstellar medium, consistent with optical observations. SN1988Z is the most distant supernova yet detected in X-rays.

R. R. Ross, A. C. Fabian

We present self-consistent models for the radiative transfer in Shakura-Sunyaev accretion discs in bright low-mass X-ray binaries (LMXB). Our calculations include the full effects of incoherent Compton scattering and the vertical temperature structure within the disc, as well as the effects of Doppler blurring and gravitational redshift. We find that the obs

Richard G Bower

These notes collect together current work on the effect of the environment on galaxy formation and evolution. They are broken into four distinct parts. The first deals with the observational debate surrounding the question of whether galaxies are initially created the same and have only recently been modified by their environment, or whether galaxy formation

David E. Brahm, James Walden

We investigate the relations that must hold among baryonic Isgur-Wise functions $η_i$ in the large-N_c limit from unitarity constraints, and compare to those found by Chow using the Skyrme model [or SU(4)]. Given the exponential dropoff of the $η_i$ away from threshold, unitarity requires only that the usual normalization conditions hold at w=1, and that $η=

Victor Ginzburg

An intrinsic construction of the tensor category of finite dimensional representations of the Langlands dual group of G in terms of a tensor category of perverse sheaves on the loop group, LG, is given. The construction is applied to the study of the topology of the affine Grassmannian of G and to establishing a Langlands type correspondence for "automor

Jose Gaite, Denjoe O'Connor

We consider entropy and relative entropy in Field theory and establish relevant monotonicity properties with respect to the couplings. The relative entropy in a field theory with a hierarchy of renormalization group fixed points ranks the fixed points, the lowest relative entropy being assigned to the highest multicritical point. We argue that as a consequen