November 1998 arXiv papers — page 2

Victor M. Burlakov

An impact of kink-type solitons on infrared lattice vibrations is studied for incommensurate Frenkel-Kontorova model. It is shown that the vibration of particles involved into the kink formation is very similar to that in a gap mode around the force constant defect. IR phonon mode intensity is found to possess a universal dependence on the system parameters

J M Pons, D C Salisbury, L C Shepley

We present a reduction procedure for gauge theories based on quotienting out the kernel of the presymplectic form in configuration-velocity space. Local expressions for a basis of this kernel are obtained using phase space procedures; the obstructions to the formulation of the dynamics in the reduced phase space are identified and circumvented. We show that

Marcel Griesemer, Christian Tix

For a pseudo-relativistic model of matter, based on the no-pair Hamiltonian, we prove that the inclusion of the interaction with the self-generated magnetic field leads to instability for all positive values of the fine structure constant. This is true no matter whether this interaction is accounted for by the Breit potential, by an external magnetic field w

Amol Dighe

Here we shall outline a few methods that use the flavor SU(3) symmetry in the decays of B mesons to determine the angles of the unitarity triangle and to identify the decay modes which would display a significant CP violation.

C. A. Boe, O. M. Ogreid, P. Osland, Jian-zu Zhang

We review the production of scalar Higgs-like particles in high-energy electron-electron collisions, via the fusion of electroweak gauge bosons. The emphasis is on how to distinguish a CP-even from a CP-odd Higgs particle. Among the more significant differences, we find that in the CP-odd case, the Higgs spectrum is much harder, and the dependence of the tot

Pascal Perret

A summary of the most recent and important measurements in b physics is presented. The production of beauty particles in Z decays, b quark couplings, lifetimes, B0-B0bar oscillations, semileptonic b decays and studies of the number of charm quarks produced in b decays are reviewed. Extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |V_{td}|, |

Robert Shrock, Shan-Ho Tsai

We present exact calculations of the zero-temperature partition function $Z(G,q,T=0)$ and ground-state degeneracy $W(\{G\},q)$ for the $q$-state Potts antiferromagnet on a number of families of graphs $G$ for which (generalizing $q$ from ${\mathbb Z}_+$ to ${\mathbb C}$) the boundary ${\cal B}$ of regions of analyticity of $W$ in the complex $q$ plane is non

Sergei I. Mukhin

A quantum interference mechanism of the stripe phase instability in quasi one-dimensional (1D) repulsive electron system is proposed. The leading spin-charge coupling term in Landau functional is derived microscopically. It is shown that away from half filling, periodic lattice potential causes cooperative condensation of the spin and charge superlattices, w

Nicolas Sourlas

I will show that there is a deep relation between error-correction codes and certain mathematical models of spin glasses. In particular minimum error probability decoding is equivalent to finding the ground state of the corresponding spin system. The most probable value of a symbol is related to the magnetization at a different temperature. Convolutional cod

Junfang Zhang, Ronald Blaak, Emmanuel Trizac, Jose A. Cuesta

We consider the effect of intermolecular interactions on the optimal size-distribution of $N$ hard spheres that occupy a fixed total volume. When we minimize the free-energy of this system, within the Percus-Yevick approximation, we find that no solution exists beyond a quite low threshold ($η\thickapprox 0.260$). Monte Carlo simulations reveal that beyond t

Sitabhra Sinha, Jayanta Basak

Neural network models comprising elements which have exclusively excitatory or inhibitory synapses are capable of a wide range of dynamic behavior, including chaos. In this paper, a simple excitatory-inhibitory neural pair, which forms the building block of larger networks, is subjected to external stimulation. The response shows transition between various t

Luca Amendola, Joshua A. Frieman, Ioav Waga

We consider the prospects for detecting weak gravitational lensing by underdensities (voids) in the large-scale matter distribution. We derive the basic expressions for magnification and distortion by spherical voids. Clustering of the background sources and cosmic variance are the main factors which limit in principle the detection of lensing by voids. We c

Brian D. Fields, John Ellis

Live $^{60}$Fe has recently been reported in a deep-ocean ferromanganese crust. Analysis of the isotopic ratios in the sample suggests that the measured $^{60}$Fe abundance exceeds the levels generated by terrestrial and cosmogenic sources, and it has been proposed that the excess of $^{60}$Fe is a signature of a supernova that exploded near the earth severa

I. M. Harrus, P. O. Slane

We present the analysis of archival data from the Advanced Satellite for Cosmology and Astrophysics} (ASCA) of the supernova remnant (SNR) G39.2-0.3. G39.2-0.3 has been sometimes characterized as a shell-like remnant in the literature but our high-energy imaging and spectral analysis show the unambiguous composite nature of the remnant. We find that part of

A. J. Castro-Tirado, M. R. Zapatero-Osorio, J. Gorosabel, J. Greiner

We imaged the X-ray error box of GRB 980703, beginning 22.5 hours after the gamma--ray event, in both the optical R and near-infrared H bands. A fading optical/IR object was detected within the X-ray error box, coincident with the variable radio source reported by Frail et al. (1998a), who also detected the optical transient independently of us. Further imag

Michael S. Turner

For the first time, we have a plausible, complete accounting of matter and energy in the Universe. Expressed a fraction of the critical density it goes like this: neutrinos, between 0.3% and 15%; stars, 0.5%; baryons (total), 5%; matter (total), 40%; smooth, dark energy, 60%; adding up to the critical density. This accounting is consistent with the inflation

I. A. G. Snellen, R. T. Schilizzi, G. K. Miley, M. N. Bremer

GPS sources are the objects of choice to study the initial evolution of extragalactic radio sources, since it is most likely that they are the young counterparts of large scale radio sources. Correlations found between their peak frequency, peak flux density and angular size provide strong evidence that synchrotron self absorption is the cause of the spectra

D. Montes, S. H. Saar, A. Collier Cameron, Y. C. Unruh

We present high resolution optical echelle spectra and IUE observations during a strong flare on 1993 December 22 in the very active, young, rapidly rotating, single K2 dwarf LQ Hya. The initial impulsive phase of the flare, which started sometime between 2:42 UT and 4:07 UT, was characterized by strong optical continuum enhancement and blue-shifted emission

Yong Baek Kim

We study the localization of fermions in an anisotropic random magnetic field in two dimensions. It is assumed that the randomness in a particular direction is stronger than those in the other directions. We consider a network model of zero field contours, where there are two types of randomness - the random tunneling matrix element at the saddle points and

S. Bellucci, E. Ivanov, S. Krivonos

We describe the spontaneous partial breaking of $N=1 D=10$ supersymmetry to $N=(1,0) d=6$ and its dimensionally-reduced versions in the framework of the nonlinear realizations method. The basic Goldstone superfield is $N=(1,0) d=6$ hypermultiplet superfield satisfying a nonlinear generalization of the standard hypermultiplet constraint. We interpret the gene

J. C. Ahn, K. S. Kwak, B. H. Park, H. Y. Kang

We report a quantum ring-like toroidal cavity naturally formed in a vertical-cavity-like active microdisk plane due to Rayleigh's band of whispering gallery modes. The $\sqrt{T}$-dependent redshift and a square-law property of microampere-range threshold currents down to 2 $μ$A are consistent with a photonic quantum wire view, due to whispering gallery m

Prakash Mathews, Sreerup Raychaudhuri, K. Sridhar

The prospect of large extra dimensions and an effective theory of gravity at around a TeV has interesting experimental consequences. In these models, the Kaluza-Klein modes interact with Standard Model particles and these interactions lead to testable predictions at present and planned colliders. We investigate the effect of virtual exchanges of the spin-2 K

K. Amemiya, H. Suganuma

We study effective mass generation of off-diagonal gluons and infrared abelian dominance in the maximally abelian (MA) gauge. Using the SU(2) lattice QCD, we investigate the propagator and the effective mass of the gluon field in the MA gauge with the U(1)$_3$ Landau gauge fixing. The Monte Carlo simulation is performed on the $12^3 \times 24$ lattice with $

Subhendu Rakshit, Gautam Bhattacharyya, Amitava Raychaudhuri

The nontrivial structure of the neutrino mass matrix, suggested by the recent Super-Kamiokande results and data from other neutrino experiments, can be reproduced in R-parity-violating supersymmetric theories. This requires sets of products of R-parity-violating trilinear couplings to take appropriately chosen values. It is shown that the existing constraint

M. Bisset, O. C. W. Kong, C. Macesanu, L. H. Orr

R-parity conservation is an {\it ad hoc} assumption in the most popular version of the supersymmetric standard model. Most studies of models which do allow for R-parity violation have been restricted to various limiting scenarios. The single-VEV parametrization used in this paper provides a workable framework to analyze phenomenology of the most general theo

Andris Ambainis

We show that, for almost all N-variable Boolean functions f, at least N/4-O(\sqrt{N} log N) queries are required to compute f in quantum black-box model with bounded error.

V. A. Yurovsky, A. Ben-Reuven, P. S. Julienne, Y. B. Band

Two problems incorporating a set of horizontal linear potentials crossed by a sloped linear potential are analytically solved and compared with numerical results: (a) the case where boundary conditions are specified at the ends of a finite interval, and (b) the case where the sloped linear potential is replaced by a piecewise-linear sloped potential and the

A. Kempf

In Noncommutative Geometry, as in quantum theory, classically real variables are assumed to correspond to self-adjoint operators. We consider the relaxation of the requirement of self-adjointness to mere symmetry for operators $X_i$ which encode space-time information.

Shi-Hai Dong, Xi-Wen Hou, Zhong-Qi Ma

In terms of the irreducible bases of the group space of the octahedral double group {\bf O'}, an analytic formula is obtained to combine the spin states $|j,μ\rangle$ into the symmetrical adapted bases, belonging to a given row of a given irreducible representation of {\bf O'}. This method is effective for all double point groups. However, for the su

Shi-Hai Dong, Xi-Wen Hou, Zhong-Qi Ma

The irreducible bases in the icosahedral group space are calculated explicitly by reducing the regular representation. The symmetry adapted bases of the system with {\bf I} or {\bf I}$_{h}$ symmetry can be calculated easily and generally by applying those irreducible bases to wavefunctions of the system, if they are not vanishing. As examples, the submatrice

A. I. Davydychev, P. Osland, O. V. Tarasov

Recent results from the study of the two-loop three-gluon and ghost-gluon vertices are reviewed. The relevant Ward-Slavnov-Taylor (WST) identities and Renormalization Group (RG) quantities are discussed.

Yasuhiro Okada

Three topics on phenomenology in supersymmetric models are reviewed, namely, the Higgs sector in the supersymmetric model, B and K meson decay in the supergravity model and lepton flavor violation processes in supersymmetric grand unified theory.

Yongqiang Xue, Supriyo Datta, Seunghun Hong, R. Reifenberger

The conductance-voltage spectrum of molecular nanostructures measured by scanning tunneling spectroscopy (STS) is generally assumed to reflect the local density of states of the molecule. This excludes the possibility of observing negative differential resistance (NDR). We report here the observation of NDR in the scanning tunneling microscope (STM) current-

A. Lopatin, G. Kotliar

We investigate the influence of order parameter fluctuations on the transition between normal and mixed superconducting states at low temperatures. We show that in case of clean quasi-two-dimensional superconductors the transition can be described by the functional of the Ginzburg-Landau type. We consider the large-N generalization of this functional and usi

Krzysztof Gawedzki, Massimo Vergassola

The paper studies the behavior of the trajectories of fluid particles in a compressible generalization of the Kraichnan ensemble of turbulent velocities. We show that, depending on the degree of compressibility, the trajectories either explosively separate or implosively collapse. The two behaviors are shown to result in drastically different statistical pro

Arindam Ghosh, A. K. Raychaudhuri, R. Sreekala, M. Rajeswari

In this paper we report measurements of 1/f noise in a crystalline metallic oxide with perovskite structure down to 4.2K. The results show existence of localized excitations with average activation energy $\approx$ 70-80 meV which produce peak in the noise at T $\approx$ 35-40K. In addition, it shows clear evidence of tunnelling type two-level-systems (as in

V. N. Pyrkov, V. M. Burlakov

General molecular dynamic approach, making possible direct calculation of eigen values and eigen functions for a quantum-mechanical system of an arbitrary symmetry is proposed. The method is based on analogy between discrete representation of the Schrödinger equation and the system of Newton equations describing dynamics of specially constructed virtual latt

Takahiro Hatano

The problem of the diverging thermal conductivity in one-dimensional (1-D) lattices is considered. By numerical simulations, it is confirmed that the thermal conductivity of the diatomic Toda lattice diverges, which is opposite to what one has believed before. Also the diverging exponent is found to be almost the same as the FPU chain. It is reconfirmed that

K. Hurley, D. H. Hartmann, C. Kouveliotou, R. M. Kippen

We examine the recent claims that cosmic gamma-ray bursts are associated with either radio-quiet quasars or Abell clusters. These associations were based on positional coincidences between cataloged quasars or Abell clusters, and selected events from the BATSE 3B catalog of gamma-ray bursts. We use a larger sample of gamma-ray bursts with more accurate posit

Tobias Hurth, Kostas Skenderis

We review our recent work, hep-th/9803030, on the constraints imposed by global or local symmetries on perturbative quantum field theories. The analysis is performed in the Bogoliubov-Shirkov-Epstein-Glaser formulation of perturbative quantum field theory. In this formalism the S-matrix is constructed directly in the asymptotic Fock space with only input cau

S. Gubser, N. Nekrasov, S. L. Shatashvili

This paper lays groundwork for the detailed study of the non-trivial renormalization group flow connecting supersymmetric fixed points in four dimensions using string theory on AdS spaces. Specifically, we consider D3-branes placed at singularities of Calabi-Yau threefolds which generalize the conifold singularity and have an ADE classification. The $\mathca

M. Kawasaki, K. Kohri, Naoshi Sugiyama

We investigate cosmological effects concerning the late-time entropy production due to the decay of non-relativistic massive particles. The thermalization process of neutrinos after the entropy production is properly solved by using the Boltzmann equation. If a large entropy production takes place at late time t$\simeq$ 1 sec, it is found that a large fracti

R. Dawid

Holography suggests a considerable reduction of degrees of freedom in theories with gravity. However it seems to be difficult to understand how holography could be realized in a closed re--contracting universe. In this letter we claim that a scenario which achieves that goal will eliminate all spatial degrees of freedom. This would require a different concep

Mike Bisset, Otto C. W. Kong, Cosmin Macesanu, Lynne H. Orr

R-parity stands as an ad hoc assumption in the most popular version of the supersymmetric standard model. More than fifteen years' studies of R-parity violations have been restricted to various limiting scenarios. We illustrate how the single-VEV parametrization provides a workable framework to analyze the phenomenology of the complete theory of supersym

Govindan Rajesh

We study, as hypersurfaces in toric varieties, elliptic Calabi-Yau fourfolds for F-theory compactifications dual to E8xE8 heterotic strings compactified to four dimensions on elliptic Calabi-Yau threefolds with some choice of vector bundle. We describe how to read off the vector bundle data for the heterotic compactification from the toric data of the fourfo

P. Raychaudhuri, A. K. Nigam, R. Pinto, Sujeet Chaudhary

We study the spin polarised tunnelling mechanism through magnetisation and magnetoresistance in the granular polycrystalline colossal magnetoresistive manganite, La0.55Ho0.15Sr0.3MnO3. This system has a ferromagnetic transition temperature (Tc) of 255 K associated with a metal-insulator transition around the same temperature. We have investigated dependence

Andrea Gamba, Marco Grilli, Claudio Castellani

We investigate the behavior of the zero-temperature quantum non-linear sigma model in d dimensions in the presence of a damping term of the form f(w)~ |w|^alpha, with 1 \le alpha <2. We find two fixed points: a spin-wave fixed point FP1 showing a dynamic scaling exponent z=1 and a dissipative fixed point FP2 with z>1. In the framework of the \epsilon-expansi

G. L. Kotkin, E. A. Kuraev, A. Schiller, V. G. Serbo

We consider the ortho-- and parapositronium production in the process $AA \to AA+$ Ps where A is a nucleus with the charge number Z. The inclusive cross section and the energy distribution of the relativistic Ps are calculated which are of primary interest from the experimental point of view. The accuracy of the corresponding cross sections is given by omitt

D. Dicus, T. Stelzer, Z. Sullivan, S. Willenbrock

We argue that the leading-order subprocess for Higgs-boson production in association with bottom quarks is (b\bar{b} -> H). This process is an important source of Higgs bosons with enhanced Yukawa coupling to bottom quarks. We calculate the corrections to this cross section at next-to-leading-order in 1/ln(m_H/m_b) and alpha_s and at next-to-next-to-leading

Kurt Broderix, Henning Loewe, Peter Mueller, Annette Zippelius

We investigate the static shear viscosity on the sol side of the vulcanization transition within a minimal mesoscopic model for the Rouse-dynamics of a randomly crosslinked melt of phantom polymers. We derive an exact relation between the viscosity and the resistances measured in a corresponding random resistor network. This enables us to calculate the visco

Tom Weidig

We study the structure of minimal-energy solutions of the baby Skyrme models for any topological charge n; the baby multi-skyrmions. Unlike in the (3+1)D nuclear Skyrme model, a potential term must be present in the (2+1)D Skyrme model to ensure stability. The form of this potential term has a crucial effect on the existence and structure of baby multi-skyrm

A. Recknagel, V. Schomerus

Boundary conformal field theory is the suitable framework for a microscopic treatment of D-branes in arbitrary CFT backgrounds. In this work, we develop boundary deformation theory in order to study the changes of boundary conditions generated by marginal boundary fields. The deformation parameters may be regarded as continuous moduli of D-branes. We identif

P. Jizba, E. S. Tututi

We calculate the off-equilibrium hydrostatic pressure for the O(N) Phi^{4} theory to the leading order in 1/N. The present paper, the first of a series, concentrates on the calculation of pressure in the non-equilibrium but translationally invariant medium. The Jaynes-Gibbs principle of maximal entropy is used to introduce the relevant density matrix which i

L. Baudis, J. Hellmig, G. Heusser, H. V. Klapdor--Kleingrothaus

New results after 0.69 kg yr of measurement with an enriched 76Ge detector of the Heidelberg--Moscow experiment with an active mass of 2.758 kg are presented. An energy threshold of 9 keV and a background level of 0.042 counts/(kg d keV) in the energy region between 15 keV and 40 keV was reached.The derived limits on the WIMP--nucleon cross section are the m

Kazuo Fujikawa

We study the implications of the index theorem and chiral Jacobian in lattice gauge theory, which have been formulated by Hasenfratz, Laliena and Niedermayer and by Lüscher, on the continuum formulation of the chiral Jacobian and anomaly. We take a continuum limit of the lattice Jacobian factor without referring to perturbative expansion and recover the resu

Detlev Buchholz

In this article a non--technical survey is given of the present status of Axiomatic Quantum Field Theory and interesting future directions of this approach are outlined. The topics covered are the universal structure of the local algebras of observables, their relation to the underlying fields and the significance of their relative positions. Moreover, the p

M. Rocek, A. A. Tseytlin

We show that the connection between partial breaking of supersymmetry and nonlinear actions is not accidental and has to do with constraints that lead directly to nonlinear actions of the Born-Infeld type. We develop a constrained superfield approach that gives a universal way of deriving and using these actions. In particular, we find the manifestly supersy

V. Barger, Chung Kao

The prospects for detecting trilepton events ($\ell = e$ or $μ$) from chargino-neutralino ($χ^\pm_1 χ^0_2$) associated production are investigated for the upgraded Fermilab Tevatron Collider in the context of the minimal supergravity model (mSUGRA). In some regions of parameter space, $χ^\pm_1$ and $χ^0_2$ decay dominantly into final states with $τ$ leptons

I. I. Bigi, A. I. Sanda

Several experiments are about to measure the CP asymmetry for $B \to ψK_S$ and other decays. The standard model together with the Kobayashi-Maskawa ansatz for CP violation predicts the sign as well as the magnitude for this asymmetry. In this note we elucidate the physics and conventions which lead to the prediction for the sign of the asymmetry.

Hungchong Kim, Su Houng Lee, Makoto Oka

Within the framework of the conventional QCD sum rules, we study the pion two-point correlation function, $i\int d^4x e^{iq\cdot x} < 0| T J_N(x) {\bar J}_N(0)|π(p)>$, beyond the soft-pion limit. We construct sum rules from the three distinct Dirac structures, $i γ_5 \notp, i γ_5, γ_5 σ_{μν} {q^μp^ν}$ and study the reliability of each sum rule. The sum rule

Andrey Tsiganov

For the Stackel family of the integrable systems a non-canonical transformation of the time variable is considered. This transformation may be associated to the ambiguity of the Abel map on the corresponding hyperelliptic curve. For some Stackel&#39;s systems with two degrees of freedom the 2x2 Lax representations and the dynamical r-matrix algebras are cons

N. V. Vitanov, K. -A. Suominen, B. W. Shore

We discuss a simple scheme for preparing atoms and molecules in an arbitrary preselected coherent superposition of quantum states. The technique, which we call fractional stimulated Raman adiabatic passage ({\it f-STIRAP}), is based upon (incomplete) adiabatic population transfer between an initial state $ψ_1$ and state $ψ_3$ through an intermediate state $ψ

Matteo G. A. Paris

We study the entanglement between the two beams exiting a Mach-Zehnder interferometer fed by a couple of squeezed-coherent states with arbitrary squeezing parameter. The quantum correlations at the output are function of the internal phase-shift of the interferometer, with the output state ranging from a totally disentangled state to a state whose degree of

B. G. Sidharth

Motivated by the latest direct detection of time assymetry in Kaon decay at CERN and Fermilab, we suggest a theoretical rationale for this puzzle, in terms of quantized time.

J. Finkelstein

A definition is proposed to give precise meaning to the counterfactual statements that often appear in discussions of the implications of quantum mechanics. Of particular interest are counterfactual statements which involve events occurring at space-like separated points, which do not have an absolute time ordering. Some consequences of this definition are d

D. A. Baiko, A. D. Kaminker, A. Y. Potekhin, D. G. Yakovlev

The dynamical structure factor of a Coulomb crystal of ions is calculated at arbitrary temperature below the melting point taking into account multi-phonon processes in the harmonic approximation. In a strongly coupled Coulomb ion liquid, the static structure factor is split into two parts, a Bragg-diffraction-like one, describing incipient long-range order

A. Y. Potekhin, G. Chabrier, Yu. A. Shibanov, J. Ventura

We study hydrogen plasmas at magnetic fields B ~ 10^{12}-10^{13} Gauss, densities ~ 10^{-3}-10^3 g/cc and temperatures T ~ 10^{5.5}-10^{6.5} K, typical of photospheres of middle-aged cooling neutron stars. We construct an analytical free energy model of the partially ionized plasma, including into consideration the decentred atomic states, which arise due to

Takeshi Iizuka, Yuri Kivshar

We demonstrate an important role of the process of optical rectification in the theory of nonlinear wave propagation in quadratically nonlinear [or $χ^{(2)}$ ] periodic optical media. We derive a novel physical model for gap solitons in $χ^{(2)}$ nonlinear Bragg gratings.

Jörn Knoll, GSI, Darmstadt

The propagation of short life time particles with consequently broad mass width are discussed in the context of transport descriptions. In the first part some known properties of finite life time particles such as resonances are reviewed and discussed at the example of the $ρ$-meson. Grave deficiencies in some of the transport treatment of broad resonances a

B. K. Agrawal, S. K. Samaddar, Tapas Sil, J. N. De

A systematic study of the effect of fragment$-$fragment interaction, quantum statistics, $γ$-feeding and collective flow is made in the extraction of the nuclear temperature from the double ratio of the isotopic yields in the statistical model of one-step (Prompt) multifragmentation. Temperature is also extracted from the isotope yield ratios generated in th

J. N. De, B. K. Agrawal, S. K. Samaddar

We construct the equation of state (EOS) of finite nuclei including surface and Coulomb effects in a Thomas-Fermi framework using a finite range, momentum and density dependent two-body interaction. We identify critical temperatures for nuclei below which the EOS so constructed shows clear signals for liquid-gas phase transition in these finite systems. Comp

U. Mosel

In this talk I first discuss predictions based on QCD sum rules and on hadronic models for the properties of vector mesons in the nuclear medium. I then describe possible experimental signatures and show detailed predictions for dilepton invariant mass spectra with a special emphasis on nuclear reactions involving elementary incoming beams and nuclear target

W. Skulski, J. Toke, W. U. Schroeder

It is found that the total IMF-transverse-energy (E_t) spectra in multi-IMF events are well represented by synthetic spectra obtained by folding of the single-IMF spectrum. Using the experimental IMF multiplicity distribution, the observed trends in the IMF multiplicity distribution for fixed values of E_t are reproduced. The synthetic distributions show bin

Paul E. Ehrlich, Miguel Sanchez

Lorentzian versions of classical Riemannian volume comparison theorems by Gunther, Bishop and Bishop-Gromov, are stated for suitable natural subsets of general semi-Riemannian manifolds. The problem is more subtle in the Bishop-Gromov case, which is extensively discussed. For the general semi-Riemannian case, a local version of the Gunther and Bishop theorem

Ferruccio Orecchia

In this paper we extend the properties of ordinary points of curves [10] to ordinary closed points of one-dimensional affine reduced schemes and then to ordinary subvarieties of codimension one.

Christine Altseimer

This paper gives a characterisation of the group G_2(K) over an algebraically closed field K of characteristic not 2 inside the class of simple K*-groups of finite Morley rank not interpreting a bad field using the structure of centralizers of involutions. This implies a general characterisation of tame K*-groups od odd type whose centralizers have a certain

Christine Altseimer

In this paper we prove that any strongly embedded subgroup of a K*-group G of finite Morley rank and odd type that does not interpret any bad field is solvable if its Pruefer 2-rank is at least 2. If the normal 2-rank of G is at least 3 this has two important consequences: If G contains a non-solvable centraliser of an involution, then G does not contain any

Sylvain Gervais

We give a finite presentation of the mapping class group of an oriented (possibly bounded) surface of genus greater or equal than 1, considering Dehn twists on a very simple set of curves.

Mark Andrea A. de Cataldo, Luca Migliorini

We prove that a standard realization of the direct image complex via the so-called Douady-Barlet morphism associated with a smooth complex analytic surface admits a natural decomposition in the form of an injective quasi-isomorphism of complexes. This is a more precise form of a special case of the decomposition theorems of Beilinson-Bernstein-Deligne-Gabber

Sultan Catto, Jonathan Huntley, Jay Jorgenson, David Tepper

Let H be the homogeneous space associated to the group PGL_3(R). Let X=Γ/H where Γ=SL_3(Z) and consider the first non-trivial eigenvalue λ_1 of the Laplacian on L^2(X). Using geometric considerations, we prove the inequality λ_1<pi^2/10. Since the continuous spectrum is represented by the band [1,\infty), our bound on λ_1 can be viewed as an analogue of Selb

Manabu Yamaguchi

Let A_k denote the twisted group algebra of the symmetric group S_k, whose representations correspond to the nonlinear projective representations of S_k. We establish a duality relation between A_k and a Lie superalgebra q(n), sometimes called the ``queer&#39;&#39; Lie superalgebra. This duality clarifies Schur&#39;s formula, in the sense that the Schur-Weyl

C. G. Beneventano, M. De Francia, E. M. Santangelo

We study the problem of a Dirac field in the background of an Aharonov-Bohm flux string. We exclude the origin by imposing spectral boundary conditions at a finite radius then shrinked to zero. Thus, we obtain a behaviour of the eigenfunctions which is compatible with the self-adjointness of the radial Hamiltonian and the invariance under integer translation

S. Gogilidze, N. Ilieva, V. N. Pervushin

The finite-volume QED$_{1+1}$ is formulated in terms of Dirac variables by an explicit solution of the Gauss constraint with possible nontrivial boundary conditions taken into account. The intrinsic nontrivial topology of the gauge group is thus revealed together with its zero-mode residual dynamics. Topologically nontrivial gauge transformations generate co

David Brungs, Werner Nahm

Modulo the ideal generated by the derivative fields, the normal ordered product of holomorphic fields in two-dimensional conformal field theory yields a commutative and associative algebra. The zero mode algebra can be regarded as a deformation of the latter. Alternatively, it can be described as an associative quotient of the algebra given by a modified nor

F. Aldabe, A. L. Larsen

A two dimensional anomaly cancellation argument is used to construct the SO(32) heterotic and type IIB membranes. By imposing different boundary conditions at the two boundaries of a membrane, we shift all of the two dimensional anomaly to one of the boundaries. The topology of these membranes is that of a 2-dimensional cone propagating in the 11-dimensional

Massimo Bianchi, Stefano Kovacs

We report on the computation of the one-instanton contribution to the 16-point Green function of fermionic composite operators in N=4 Super YM theory. The remarkable agreement, initially found in the case of an SU(2) gauge group, with the one D-instanton contribution to the corresponding type IIB superstring amplitude on $AdS_5\times S^5$ is reviewed here. T

Flavio Pereira, Erasmo Ferreira

The eikonal profile function $J(b)$ obtained from the Model of the Stochastic Vacuum is parametrized in a form suitable for comparison with experiment. The amplitude and the extended profile function (including imaginary and real parts) are determined directly from the complete pp and $\bar{\rm p}$p elastic scattering data at high energies. Full and accurate

K. Hagiwara, N. Okamura

We explain the imbalance of the flavor mixing angles between the quark and the lepton sectors in the context of the SU(5) GUT with the see-saw mechanism. The quark masses and the CKM matrix elements are obtained by using, respectively, the Fritzsch and Branco - Silva-Marcos form for the up- and down-quark Yukawa matrices (y^u and y^d) at the GUT scale. The c

Peter Lichard

The widely accepted assumption that the decay of a resonance proceeds independently of its production, quantitatively expressed as a factorizing formula for the differential cross section in the invariant mass of unpolarized resonance debris, is put under scrutiny. It is shown that the factorization is always valid for scalar and pseudoscalar resonances, alt

Eduardo de Rafael

I report on recent work done in collaboration with M. Knecht on patterns of spontaneous chiral symmetry breaking in the large-Nc limit of QCD-like theories, and with S. Peris and M. Perrottet concerning the question of matching long and short distances in large-Nc QCD.

K. Yamamoto, S. Matsuki

Quantum analysis is made on the dynamical system consisting of the cosmic axions, photons and Rydberg atoms which are interacting in the resonant cavity. The atomic motion in a continuous incident beam is taken into account properly in order to make a precise estimate of the efficiency of the Rydberg atom cavity detector for dark matter axion search.

J. M. LoSecco

A lower bound on $Δm^{2}$ for atmospheric neutrino oscillations can be obtained from the global value of $R$ at a given energy. This bound may be more reliable than one based on the observed isotropy. Some global values of $R$ imply an anisotropy in the neutrino flux that may, or may not be manifest in the observed neutrino interactions. A limit of $Δm^{2}>0

Jun-Qin Jiang, Xiang-Qian Luo, Zhong-Hao Mei, Hamza Jirari

QCD in two dimensions is investigated using the improved fermionic lattice Hamiltonian proposed by Luo, Chen, Xu, and Jiang. We show that the improved theory leads to a significant reduction of the finite lattice spacing errors. The quark condensate and the mass of lightest quark and anti-quark bound state in the strong coupling phase (different from t&#39;H

T. DeGrand, C. DeTar, R. Sugar, D. Toussaint

We give here a compilation of papers presented at Lattice 98 (XVI Intl. Symposium on Lattice Field Theory, Boulder, Colorado, USA, 13-18 July 1998). The contents are in html form with clickable links to the papers that exist on the hep-lat archives. We hope that this will make it easier to access the presentations at the conference. Comments on, and correcti

Gerardo Ganis

Searches for supersymmetry at LEP allowing for R-parity violation are reviewed. The results are compared with the R-parity conserving scenarios.

Peter Dunsby, Bruce Bassett, George Ellis

The propagation of gravitational waves or tensor perturbations in a perturbed Friedmann-Robertson-Walker universe filled with a perfect fluid is re-examined. It is shown that while the shear and magnetic part of the Weyl tensor satisfy linear, homogeneous {\it second order} wave equations, for perfect fluids with a $γ$\hs law equation of state satisfying $\c

Bikash Chandra Gupta

Discrete nonlinear Schröginger equation (DNLS) of the form, $i \frac{dC_n} {dt}$ = $C_{n+1}$ + $C_{n-1}$ - $ χ_n [|C_{n+1}|^2 + |C_{n-1}|^2 - 2 |C_n|^2] C_n$ is used to study the formation of stationary localized states in one dimensional system due to a single as well as a dimeric nonlinear impurity. The fully nonlinear chain is also considered. The stabili

Adriaan M. J. Schakel

These lectures provide a pedagogical introduction to the theory of continuous quantum phase transitions. Various two-dimensional condensed matter systems, such as a superconducting film, a quantum Hall liquid, and an array of Josephson junctions, undergo such a phase transition at the absolute zero of temperature. The universality classes defined by repulsiv

Serguei B. Isakov, Thierry Martin, Stéphane Ouvry

The first quantized Landauer approach to conductance and noise is generalized to particles obeying exclusion statistics. We derive an explicit formula for the crossover between the shot and thermal noise limits and argue that such a crossover can be used to determine experimentally whether charge carriers in FQHE devices obey exclusion statistics.

Th. M. Nieuwenhuizen

A picture for thermodynamics of the glassy state is introduced. It assumes that one extra parameter, the effective temperature, is needed to describe the glassy state. This explains the classical paradoxes concerning the Ehrenfest relations and the Prigogine-Defay ratio. As a second part, the approach connects the response of macroscopic observables to a fie