September 1996 arXiv papers — page 14

Carlos Simpson

The purpose of this article is to define the topological realization of a simplicial presheaf and to prove (under appropriate conditions) that it is homotopy-invariant under Illusie weak equivalence. In particular this applies to the site of schemes over $Spec (\cc)$ with the etale or Zariski topologies. As an application we show how to calculate the topolog

M. K. Liou, R. Timmermans, B. F. Gibson

A relativistic and manifestly gauge-invariant soft-photon amplitude, which is consistent with the soft-photon theorem and satisfies the Pauli Principle, is derived for the proton-proton bremsstrahlung process. This soft-photon amplitude is the first two-u-two-t special amplitude to satisfy all theoretical constraints. The conventional Low amplitude can be ob

F. Ghielmetti, G. Colò, E. Vigezzi, P. F. Bortignon

The quadrupole strength function of $^{28}O$ is calculated making use of the SIII interaction, within the framework of continuum-RPA and taking into account collisions among the nucleons (doorway coupling). The centroid of the giant resonance is predicted at $\approx 14$ MeV, that is much below the energy expected for both isoscalar and isovector quadrupole

S. Teis, W. Cassing, M. Effenberger, A. Hombach

We investigate the production of pions in heavy-ion collisions in the energy range of $1$ - $2$ GeV/A. The dynamics of the nucleus-nucleus collisions is described by a set of coupled transport equations of the Boltzmann-Uehling-Uhlenbeck type for baryons and mesons. Besides the $N(938)$ and the $Δ(1232)$ we also take into account nucleon resonances up to mas

S. Balaska, J. Maeder, W. Ruehl

We construct representations of the Heisenberg algebra by pushing the perturbation expansion to high orders. If the multiplication operators $B_{1,2}$ tend to differential operators of order $l_{2,1}$, respectively, the singularity is characterized by $(l _{1},l_{2})$. Let $l_{1} \geq l_{2}$. Then the two cases A : ``$l_{2}$ does not divide $l_{1}$''

A. V. Barabanschikov, S. F. Prokushkin, M. A. Vasiliev

We reformulate free equations of motion for massive spin 0 and spin 1/2 matter fields in 2+1 dimensional anti-de Sitter space in the form of some covariant constantness conditions. The infinite-dimensional representation of the anti-de Sitter algebra underlying this formulation is shown to admit a natural realization in terms of the algebra of deformed oscil

Stefano De Leo, Khaled Abdel-Khalek

In order to obtain a consistent formulation of octonionic quantum mechanics (OQM), we introduce left-right barred operators. Such operators enable us to find the translation rules between octonionic numbers and $8\times 8$ real matrices (a translation is also given for $4\times 4$ complex matrices). We develop an octonionic relativistic free wave equation, l

Stefano De Leo, Khaled Abdel-Khalek

The use of complex geometry allows us to obtain a consistent formulation of octonionic quantum mechanics (OQM). In our octonionic formulation we solve the hermiticity problem and define an appropriate momentum operator within OQM. The nonextendability of the completeness relation and the norm conservation is also discussed in details.

A. V. Razumov, M. V. Saveliev

On the base of Lie algebraic and differential geometry methods, a wide class of multidimensional nonlinear systems is obtained, and the integration scheme for such equations is proposed.

A. V. Razumov, V. I. Yasnov

The structure of the reduced phase space arising in the Hamiltonian reduction of the phase space corresponding to a free particle motion on the group ${\rm SL}(2, {\Bbb R})$ is investigated. The considered reduction is based on the constraints similar to those used in the Hamiltonian reduction of the Wess--Zumino--Novikov--Witten model to Toda systems. It is

Kazuo Fujikawa

The path integral for the hydrogen atom, for example, is formulated as a one-dimensional quantum gravity coupled to matter fields representing the electron coordinates. The (renormalized) cosmological constant, which corresponds to the energy eigenvalue, is thus quantized in this model. Possible implications of the quantized cosmological constant are briefly

M. Hotta, H. Inoue, I. Joichi, M. Tanaka

We shall discuss various kinds of geometric bremsstrahlung processes in the spatially flat Robertson-Walker universe. Despite that the temperature of the universe is much higher than particle masses and the Hubble parameter, the transition probability of these processes do not vanish. It is also pointed out that explicit forms of the probability possess a ne

J. Bartels, C. Ewerz, H. Lotter, M. Wuesthoff

We report on investigations concerning the production of large transverse momentum jets in DIS diffractive dissociation. These processes constitute a new class of events that allow for a clean test of perturbative QCD and of the hard (perturbative) pomeron picture. The measurement of the corresponding cross sections might possibly serve to determine the gluo

Richard Hong Tuan

Recently, we proposed a new approach for calculating Feynman graphs amplitude using the Gaussian representation for propagators which was proven to be exact in the limit of graphs having an infinite number of loops. Regge behavior was also found in a completely new way and the leading Regge trajectory calculated. Here we present symmetry arguments justifying

Stefano Catani, Michael H. Seymour

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

Matteo Cacciari

The present status of our understanding of onium production is reviewed. Different models are described and comparisons of theoretical predictions with experimental data are given.

S. Moretti, R. Munoz-Tapia, K. Odagiri

We briefly report about a possible settlement of the still ongoing dispute concerning the existence of SUSY signals in 4jet events at LEP1. We base our arguments on a simple selection strategy exploiting secondary vertex tagging and kinematical constraints, which could allow one to access or exclude gluino events for a broad range of masses and lifetimes.

V. A. Petrov

We discuss effects of unitarity on the low-x behaviour of the structure functions of deeply inelastic scattering. Particular attention is paid to the distinction between Regge and Renormalization Group $J$-plane singularities and their relative weight in defining the low-x asymptotics.

M. Baker, J. S. Ball, N. Brambilla, A. Vairo

Recently an electric and magnetic field correlator appearing in the description of the heavy quarkonium system was evaluated on the lattice. Here, we give a nonperturbative analytical evaluation of this field correlator using a dual description of long distance Yang--Mills theory and using the stochastic vacuum model. The two predictions are both compatible

Andrea Galli, Philippe de Forcrand

We present an exact local bosonic algorithm for the simulation of dynamical fermions in lattice QCD. We show that this algorithm is a viable alternative to the Hybrid Monte Carlo algorithm.

J. Grandy, G. Kilcup

We use lattice topology as a laboratory to compare the Wilson action (WA) with the Symanzik-Weisz (SW) action constructed from a combination of (1x1) and (1x2) Wilson loops, and the estimate of the renormalization trajectory (RT) from a renormalization group transformation (RGT) which also includes higher representations of the (1x1) loop. Topological charge

Alberto Saa

A propagating torsion model is derived from the requirement of compatibility between minimal action principle and minimal coupling procedure in Riemann-Cartan spacetimes. In the proposed model, the trace of the torsion tensor is derived from a scalar potential that determines the volume element of the spacetime. The equations of the model are written down fo

Horacio M. Pastawski, Gonzalo Usaj, Patricia R. Levstein

It was predicted that local spin polarization in a ring of five dipolar coupled spins should present a particular fingerprint of quantum interferences reflecting both the discrete and finite nature of the system [Phys. Rev. Lett. 75 (1995) 4310]. We report its observation for the proton system of a (C$_5$H$_5$)$_2$Fe molecule using a rare $^{13}$C as {\it lo

A. P. C. Malbouisson, F. S. Nogueira, N. F. Svaiter

We consider a topologically massive Ginzburg-Landau model of superconductivity. In the context of a mean field calculation, we show that there is an increase in the critical temperature driven by the topological term. It is shown that this effect persists even if we take into account the critical fluctuations. The renormalization group analysis gives further

F. F. Assaad, M. Imada, D. J. Scalapino

We consider a Hubbard model on a square lattice with an additional interaction, $W$, which depends upon the square of a near-neighbor hopping. At half-filling and a constant value of the Hubbard repulsion, increasing the strength of the interaction $W$ drives the system from an antiferromagnetic Mott insulator to a $d_{x^2 -y^2}$ superconductor. This conclus

K. Huang

The Bose condensate in an external potential is treated in the Thomas-Fermi approximation.

L. W. Bruch, F. Y. Hansen

The normal modes of a commensurate monolayer solid may be damped by mixing with elastic waves of the substrate. This was shown by B. Hall et al., Phys. Rev. B 32, 4932 (1985), for perpendicular adsorbate vibrations in the presence of an isotropic elastic medium. That work is generalized with an elastic continuum theory of the response of modes of either para

Pramod Gupta, S. Teitel

We use Monte Carlo simulations to map out the phase diagram of the two dimensional Coulomb gas on a square lattice, as a function of density and temperature. We find that the Kosterlitz-Thouless transition remains up to higher charge densities than has been suggested by recent theoretical estimates.

T. Senthil, Subir Sachdev

We show that many of the unusual properties of the one-dimensional random quantum Ising model are shared also by dilute quantum Ising systems in the vicinity of a certain quantum transition in {\em any} dimension $d > 1$. Thus, while these properties are not an artifact of $d=1$, they do require special circumstances in higher dimensions.

Chen Zeng, A. Alan Middleton, Y. Shapir

We apply optimization algorithms to the problem of finding ground states for crystalline surfaces and flux lines arrays in presence of disorder. The algorithms provide ground states in polynomial time, which provides for a more precise study of the interface widths than from Monte Carlo simulations at finite temperature. Using $d=2$ systems up to size $420^2

A. Lessard, T. H. Moos, W. Huebner

The magnetocrystalline anisotropy energy E(anis) of free-standing monolayers and thin films of Fe and Ni is determined using two different semi-empirical schemes. Within a tight-binding calculation for the 3d bands alone, we analyze in detail the relation between bandstructure and E(anis), treating spin-orbit coupling non-pertubatively. We find important con

Robert A. Smith, Vinay Ambegaokar

We examine the destruction of superconducting pairing in metallic grains as their size is decreased for both even and odd numbers of electrons. This occurs when the average level spacing d is of the same order as the BCS order parameter. The energy levels of these grains are randomly distributed according to random matrix theory, and we must work statistical

P. Claudin, J. -P. Bouchaud

We propose a simple model for arch formation in silos. We show that small pertubations (such as the thermal expansion of the beads) may lead to giant stress fluctuations on the bottom plate of the silo. The relative amplitude $Δ$ of these fluctuations are found to be power-law distributed, as $Δ^{-τ}$, $τ\simeq 1.0$. These fluctuations are related to large s

R. Sappey, E. Vincent, J. Hammann, F. Chaput

The magnetization relaxation rate of small gamma-Fe2O3 particles dispersed in a silica matrix has been measured from 60 mK to 5 K. It shows a minimum around 150 mK, that can be discussed in terms of either thermal or quantum relaxation regime.

Dmitri B. Chklovskii

A reproducible resonance structure in the conductance through an incompressible strip in the quantized Hall regime was recently reported by Zhitenev {\it et al}. Although the authors disfavored the explanation of the conductance resonances based on resonant tunneling (RT) through an impurity state, I believe that it should not be dismissed and can explain a

C. Megan Urry

Blazars are characterized by rapid variability at virtually all wavelengths from radio through TeV gamma-rays. The challenge since their discovery has been to understand the origin of their luminous, apparently nonthermal, nuclear emission. Considerable progress has been made in recent years thanks to a handful of multiwavelength monitoring campaigns with hi

P. Sikivie, I. I. Tkachev, Yun Wang

The spectrum of cold dark matter particles on Earth is expected to have peaks in velocity space associated with particles which are falling onto the Galaxy for the first time and with particles which have fallen in and out of the Galaxy only a small number of times in the past. We obtain estimates for the velocity magnitudes and the local densities of the pa

Matthias Steinmetz, Simon D. M. White

We show that discreteness effects related to classical two-body relaxation produce spurious heating of the gaseous component in numerical simulations of galaxy formation. A simple analytic model demonstrates that this artificial heating will dominate radiative cooling in any simulation where the mass of an individual dark matter particle exceeds a certain cr

O. Le Fevre, J. M. Deltorn, D. Crampton, M. Dickinson

We report here the spectroscopic identification of galaxies in the neighborhood of the radio-galaxy MRC0316-257, at a redshift $z\sim3.14$. Candidate cluster galaxies were selected from deep V and I images combined with narrow band imaging at the wavelength of redshifted Ly$α$. Follow-up multi-slit spectroscopy has allowed confirmation of the redshift of the

M. J. Drinkwater, R. L. Webster, P. J. Francis, J. J. Condon

We present a new sample of Parkes half-Jansky flat-spectrum radio sources having made a particular effort to find any previously unidentified sources. The sample contains 323 sources selected according to a flux limit of 0.5 Jy at 2.7 GHz, a spectral index measured between 2.7 and 5.0 GHz of alpha > -0.5 (where S(v) is proportional to v to the power of alpha

A. J. Banday, K. M. Gorski

We investigate the effect of a putative X-ray emitting halo surrounding the Local Group of galaxies, and specifically the possible temperature anisotropies induced in the COBE-DMR four-year sky maps by an associated Sunyaev-Zel'dovich effect. By fitting the isothermal spherical halo model proposed by Suto et.al. (1996) to the coadded four-year COBE-DMR 5

Chris Flynn, Olof Morell

We have developed a photometric abundance indicator for G and K dwarfs, based on accurate, spectroscopically determined abundances for G and K dwarfs of Morell, Källander and Butcher (1992) and Morell (1994). Broadband Cousins R-I photometry is used to estimate effective temperature and the Geneva b_1 colour to estimate line blanketing in the blue and hence

Philippe Jetzer

The French collaboration EROS and the American-Australian collaboration MACHO have reported the observation of altogether $\sim$ 10 microlensing events by monitoring during several years the brightness of millions of stars in the Large Magellanic Cloud. In particular the MACHO team announced the discovery of 8 microlensing candidates by analysing their first

Yasushi Suto, Yi-Peng Jing

We discuss the effect of the finite size of galaxies on estimating small-scale relative pairwise peculiar velocity dispersions from the cosmic virial theorem (CVT). Specifically we evaluate the effect by incorporating the finite core radius $r_c$ in the two-point correlation function of mass, i.e. $ξ_ρ(r) \propto (r+r_c)^{-γ}$ and the effective gravitational

Yasushi Suto

I discuss two cosmological tests to determine the cosmological density parameter Ω_0 the cosmological constant λ_0, which make use of the anisotropy of the two-point correlation functions due to the peculiar velocity field and the cosmological redshift-space distortion.

Zurab Kakushadze, S. -H. Henry Tye

We present two 3-family SU(5) grand unified models in the heterotic string theory. One model has 3 chiral families and 9 pairs of $5+{\overline 5}$ Higgs fields, and an asymptotically-free SU(2) X SU(2) hidden sector, where the two SU(2)s have different matter contents. The other model has 6 left-handed and 3 right-handed 10s, 12 left-handed and 9 right-hand

Juan Maldacena, Andrew Strominger

Black holes do not Hawking radiate strictly blackbody radiation due to well-known frequency-dependent greybody factors. These factors arise from frequency-dependent potential barriers outside the horizon which filter the initially blackbody spectrum emanating from the horizon. D-brane bound states, in a thermally excited state corresponding to near-extremal

Bernd A. Berg

It is considered to re-formulate quantum theory as it appears: A theory of continuous and causal time evolution, interrupted by discontinuous and stochastic jumps. To develop the (missing) theory of jumps a heuristic-phenomenological approach is suggested. Relying on a global reduction process, a hypothesis is introduced postulating spontaneous collapse of s

Norbert Straumann

Invited talk at the PSI Summer School on Physics with Neutrinos, Zuoz, Switzerland, August 4-10, 1996.

H. Weigel, L. Gamberg, H. Reinhardt

We study polarized-spin structure functions of the nucleon within the bosonized Nambu-Jona-Lasinio model where the nucleon emerges as a chiral soliton. We present the electromagnetic polarized structure functions, $g_{1}(x)$ and $g_{2}(x)$ for $ep$ scattering and discuss various sum rules in the valence quark approximation. This approximation is justified be

J. Aichelin

To know the space time evolution of a heavy ion reaction is of great interest, especially in cases where the measured spectra do not allow to ascertain the underlying reaction mechanism. In recent times it became popular to believe that the comparison of Hanbury-Brown Twiss correlation functions obtained from classical or semiclassical transport theories, li

Andrei N. Leznov, Emil A. Yuzbashyan

We construct hierarchies of integrable systems invariant under the two-dimensional Darboux-Toda mapping for noncommuting objects, thus generalizing to the noncommutative case the integrable mapping approach to nonlinear dynamical systems. Besides the usual setup with one time and two space dimensions, we consider the case when the unknown functions also depe

Priyamvada Natarajan, Jean-Paul Kneib

Weak shear maps of the outer regions of clusters have been successfully used to map the distribution of mass at large radii from the cluster center. The typical smoothing lengths employed thus far preclude the systematic study of the effects of galactic-scale substructure on the measured weak lensing signal. In this paper, we present two methods to infer the

Hyun-Chul Kim, Maxim V. Polyakov, Klaus Goeke

The induced pseudotensor constant (weak electricity) of the nucleon is calculated in the framework of the chiral quark soliton model. This quantity originates from the G-parity violation and hence is proportional to $m_u-m_d$. We obtain for $m_u-m_d=-5 MeV$ a value of $g_T/g_A =-0.0038$.

Avinash Khare, Koushik Ray

We obtain the exact ground state for the Calogero-Sutherland problem in arbitrary dimensions. In the special case of two dimensions, we show that the problem is connected to the random matrix problem for complex matrices, provided the strength of the inverse-square interaction $g = 2$. In the thermodynamic limit, we obtain the ground state energy and the pai

Bogdan A. Dobrescu

We discuss conditions that should be satisfied by axion models for solving the strong CP problem. It has been observed that Planck scale effects may render the axion models ineffective if there are gauge invariant operators of dimension less than 10 which break explicitly the Peccei-Quinn (PQ) symmetry. We argue that only those operators formed of fields whi

Satoshi Fujimoto, Norio Kawakami

The competition between the Mott transition and the Anderson localization in one dimensional electron systems is studied based upon the bosonization and the renormalization group method. The beta function is calculated up to the second order in the strength of diagonal disorder by using a replica trick. It is found that the sufficiently strong forward scatte

M. Göckeler, R. Horsley, H. Perlt, P. Rakow

We compute the light hadron mass spectrum in quenched lattice QCD at $β= 6.0$ using the Sheikholeslami-Wohlert fermionic action. The calculation is done for several choices of the coefficient $c_{SW}$, including $c_{SW} = 0$ and the recently proposed optimal value $c_{SW} = 1.769$. We find that the individual masses change by up to 30\% under $O(a)$ improvem

Ken-ichi Ishikawa, Tomohiro Inagaki, Kenji Fukazawa, Kezuhiro Yamamoto

We consider a four-fermion theory as a simple model of dynamical symmetry breaking in flat space with non-trivial topology, motivated from recent studies in similar considerations in curved space. The phase structure is investigated, by developing a useful formalism to evaluate the effective potential in arbitrary compactified flat space in 3- and 4-dimensio

Helen Au-Yang, Jacques H. H. Perk

In this talk, we give a brief overview of several aspects of the theory of the chiral Potts model, including higher-genus solutions of the star-triangle and tetrahedron equations, cyclic representations of affine quantum groups, basic hypergeometric functions at root of unity, and possible applications.

C. M. Ko, G. Q. Li, G. E. Brown, H. Sorge

Dilepton production in proton- and nucleus-induced reactions at SPS energies is studied in the relativistic transport model using initial conditions determined by the string dynamics from RQMD. It is found that both the CERES and HELIOS-3 data for dilepton spectra in proton-nucleus reactions can be well described by the conventional mechanism of Dalitz decay

T. Rauscher, K. -L. Kratz, H. Oberhummer, J. Dobaczewski

The prediction of cross sections for nuclei far off stability is crucial in the field of nuclear astrophysics. For spherical nuclei close to the dripline the statistical model (Hauser-Feshbach) approach is not applicable and direct contributions may dominate the cross sections. For neutron-rich, even-even Sn targets, we compare the resulting neutron capture

N. G. Kelkar, E. Oset, P. Fernandez de Cordoba

We calculate cross sections for coherent pion production in nuclei induced by neutrinos and antineutrinos of the electron and muon type. The analogies and differences between this process and the related ones of coherent pion production induced by photons, or the (p,n) and $(^3 He, t)$ reactions are discussed. The process is one of the several ones occurring

Klaus Doll, Michael Dolg, Hermann Stoll

A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using ab-initio quantum chemical methods for evaluating individual increments, we obtain 80% of the difference between the experimental and Hartree-Fock cohesive energies. Lattice const

Georg Junker

In this talk we briefly review the concept of supersymmetric quantum mechanics using a model introduced by Witten. A quasi-classical path-integral evaluation for this model is performed, leading to a so-called supersymmetric quasi-classical quantization condition. Properties of this quantization condition are compared with those derived from the standard WKB

R. Dijkgraaf

We study general perturbations of two-dimensional conformal field theories by holomorphic fields. It is shown that the genus one partition function is controlled by a contact term (pre-Lie) algebra given in terms of the operator product expansion. These models have applications to vertex operator algebras, two-dimensional QCD, topological strings, holomorphi

K. Konishi

By using the standard perturbation theory we study the mass as well as $θ$ parameter dependence of the Seiberg-Witten theory with $SU(2)$ gauge group, supplemented with a $N=1$ supersymmetric as well as a smaller nonsupersymmetric (e.g.) gaugino mass. Confinement persists at all values of the bare vacuum parameter $θ_{ph}$; as it is varied there is however a

Martin Joerss

Starting from a conformal Haag-Kastler net in 1+1 dimensions, Wightman functions are constructed.

J. Berges, C. Wetterich

We investigate phase transitions in three dimensional scalar matrix models, with special emphasis on complex $2 \times 2$ matrices. The universal equation of state for weak first order phase transitions is computed. We also study the coarse grained free energy. Its dependence on the coarse graining scale gives a quantitative criterion for the validity of the

Erwin Mirkes, Dieter Zeppenfeld

The production of forward jets of transverse momentum $p_T(j)\approx Q$ and large momentum fraction $x_{jet}\gg x$ probes the onset of BFKL dynamics at HERA. A full ${\cal O}(α_s^2)$ calculation of the inclusive forward jet cross section is presented and compared to the expected BFKL cross section. The kinematical region populated by these events and the sca

V. L. Eletsky, B. L. Ioffe

Mass shifts $Δm$ of particles in nuclear matter relative to their vacuum values are considered. A general formula relating $Δm(E)$ ($E$ is the particle energy) to the real part of the forward particle-nucleon scattering amplitude ${\rm Re} f(E)$ is presented and its applicability domain is formulated. The $ρ$-meson mass shift in nuclear matter is calculated

G. Wilk, Z. Wlodarczyk

The requirements for observing Centauro-like phenomena and their role as possible probes of deeply penetrating component in Cosmic Rays are discussed.

J. M. Butterworth, M. E. Hayes, M. H. Seymour, L. E. Sinclair

An excess of events with a rapidity gap between jets, over what would be expected from non-diffractive processes, has been observed at HERA. A process based on a perturbative QCD calculation of colour singlet exchange has been added to HERWIG. With this addition, HERWIG is able to describe the number of events with a gap between jets over the number without

Edmond Iancu, Service de Physique Theorique, Saclay, France

The study of the ultrarelativistic plasmas in perturbation theory is plagued with infrared divergences which are not eliminated by the screening corrections. They affect, in particular, the computation of the lifetime of the elementary excitations, thus casting doubt on the validity of the quasiparticle picture. We show that, for Abelian plasmas at least, th

Edmond Iancu, Service de Physique Theorique, Saclay, France

The perturbative calculation of the lifetime of charged excitations in ultrarelativistic plasmas is plagued with infrared divergences which are not eliminated by the screening corrections. The physical processes responsible for these divergences are the collisions involving the exchange of longwavelength, quasistatic, magnetic gluons (or photons), which are

Edmond Iancu

I discuss finite-temperature gauge theories as a framework to describe the quark-gluon plasma in the regime of high temperature where the gauge coupling is small, $g << 1$. I review recent progress in the understanding of the long-range physics, with emphasis on the collective phenomena and their consequences for the screening of the gauge interactions. I co

T. Huang, W. Lu, Z. J. Tao

We systematically investigate the possibility of finding CP/T violation in the $τ$ sector at Tau-Charm Factory. CP/T violation may occur at $τ$ pair production process, expressed as electric dipole moment, and at $tau$ decay processes. By assuming that electric dipole moment as large as $10^{-19}$e-cm and CP/T violation effect orignating from $τ$ decay as la

M. B. Voloshin

It is shown that contrary to a recent claim in the literature, the domain walls made of scalar field are diamagnetic due to presence of massless fermionic modes on the wall. The diamagnetism vanishes at high temperature. Thus the domain walls could produce no effect on a primordial magnetic field in the early universe.

Jisuke Kubo, Myriam Mondragon, George Zoupanos

Perturbative unification of soft supersymmetry--breaking (SSB) parameters is proposed in Gauge-Yukawa unified models. The method, which can be applied in any finite order in perturbation theory, consists in searching for renormalization group invariant relations among the SSB parameters, which are consistent with perturbative renormalizability. For the minim

Stefano Capitani, Giancarlo Rossi

In this talk I present the complete 1-loop perturbative computation of the renormalization constants and mixing coefficients of quark and gluon lattice operators of rank two and three whose hadronic elements enter in the determination of the first and second moment of Deep Inelastic Scattering Structure Functions, making use of the nearest-neighbor improved

Emanuele Panizzi

APEmille is a SIMD parallel processor under development at the Italian National Institute for Nuclear Physics (INFN). APEmille is very well suited for Lattice QCD applications, both for its hardware characteristics and for its software and language features. APEmille is an array of custom arithmetic processors arranged on a tridimensional torus. The replicat

S. Aoki, K. Nagai

We carry out a numerical simulation of a domain-wall model in (4+1) dimensions, in the presence of a quenched U(1) dynamical gauge field only in an extra dimension, corresponding to the weak coupling limit of a (4-dimensional) physical gauge coupling. Our numerical data suggest that the zero mode seems absent in the symmetric phase, so that it is difficult t

Sang Pyo Kim

We elaborate the recently introduced asymptotically exact semiclassical quantum gravity derived from the Wheeler-DeWitt equation by finding a particular coherent state representation of a quantum scalar field in which the back-reaction of the scalar field Hamiltonian exactly gives rise to the classical one. In this coherent state representation classical spa

Bhargavi Srinivasan, S. Ramasesha, H. R. Krishnamurthy

We present in detail the recently developed multi-configurational symmetrized projector quantum Monte Carlo (MSPQMC) method for excited states of the Hubbard model. We describe the implementation of the Monte Carlo method for a multi-configurational trial wavefunction. We give a detailed discussion of issues related to the symmetry of the projection procedur

J. V. Andersen, D. Sornette, K. -T. Leung

We discover a qualitatively new behavior for systems where the load transfer has limiting stress amplification as in real fiber composites. We find that the disorder is a relevant field leading to tri--criticality, separating a first-order regime where rupture occurs without significant precursors from a second-order regime where the macroscopic elastic coef

Ping Ao

We present a semiclassical study of a transport process, the tunneling, in the presence of a magnetic field and a dissipative environment. We have found that the problem can be mapped onto an effective one-dimensional one, and the tunneling rate is strongly affected by the magnetic field, such as a complete suppression by a large parallel magnetic field, an

Raquel Dominguez-Cascante, Jordi Faraudo

The physical interpretation of the nonequilibrium corrections in the pressure tensor for radiation submitted to an energy flux obtained in some previous works is revisited. Such pressure tensor is shown to describe a moving equilibrium system but not a real nonequilibrium situation.

G. Khaliullin, P. Horsch

The density response function $N(q,ω)$ of the two-dimensional $t-J$ model is studied starting from a mixed gauge formulation of the slave boson approach. Our results for $N(q, ω)$ are in remarkable agreement with exact diagonalization studies, and provide a natural explanation of the anomalous features in the density response in terms of the spin polaron nat

F. van Wijland, S. Caser, H. J. Hilhorst

We study the support (i.e. the set of visited sites) of a t step random walk on a two-dimensional square lattice in the large t limit. A broad class of global properties M(t) of the support is considered, including, e.g., the number S(t) of its sites; the length of its boundary; the number of islands of unvisited sites that it encloses; the number of such is

D. Vollhardt

Attention is drawn to the observation that in many correlated systems (e.g. 3He, heavy fermion systems and Hubbard models) the specific heat curves, when plotted for different values of some thermodynamic variable (e.g. pressure, magnetic field, interaction), cross almost precisely at one or two characteristic temperatures. A quantitative explanation of this

N. Nagaosa, A. Furusaki, M. Sigrist, H. Fukuyama

The effect of non-magnetic impurities is discussed for both the two-leg Heisenberg ladder system and other spin liquids with excitation gap. It is shown that the random depletion of spins introduces a random Berry phase term to the non-linear sigma model. The classical nature of the antiferromagnetic correlation is enhanced by the topological decoherence, an

M. Stopa

We employ density functional theory to calculate the self consistent electronic structure, free energy and linear source-drain conductance of a lateral semiconductor quantum dot patterned via surface gates on the 2DEG formed at the interface of a $GaAs-AlGaAs$ heterostructure. The Schrödinger equation is reduced from 3D to multi-component 2D and solved via a

U. Trapper, D. Ihle, H. Fehske

On the basis of the one--band t-t&#39;-Hubbard model a self-consistent renormalization theory of magnetic short--range order (SRO) in the paramagnetic phase is presented combining the four-field slave-boson functional-integral scheme with the cluster variational method. Contrary to previous SRO approaches the SRO is incorporated at the saddle-point and pair-

Carlo F. Barenghi

We consider the vortex state solution for a rotating cloud of trapped, Bose Einstein - condensed alkali atoms and study finite temperature effects. We find that thermally excited vortex waves can distort the vortex state significantly, even at the very low temperatures relevant to the experiments.

R. K. Bhaduri, Avinash Khare, J. Law, M. V. N. Murthy

We discuss a many-body Hamiltonian with two- and three-body interactions in two dimensions introduced recently by Murthy, Bhaduri and Sen. Apart from an analysis of some exact solutions in the many-body system, we analyze in detail the two-body problem which is completely solvable. We show that the solution of the two-body problem reduces to solving a known

H. D. Drew, P. Coleman

We consider the optical Hall conductivity of a general electronic medium and prove that the optical Hall angle obeys a new sum rule. This sum rule governs the response of an electronic fluid to a Lorentz electric field and can thought of as the transverse counterpart to the f-sum rule in optical conductivity. The physical meaning of this sum rule is discusse

P. Coleman, A. J. Schofield, A. M. Tsvelik

We observe that the appearance of two transport relaxation times in the various transport coefficients of cuprate metals may be understood in terms of scattering processes that discriminate between currents that are even, or odd under the charge conjugation operator. We develop a transport equation that illustrates these ideas and discuss its experimental an

Claire Gardent, Michael Kohlhase, Noor van Neusen

We propose an analysis of corrections which models some of the requirements corrections place on context. We then show that this analysis naturally extends to the interaction of corrections with pronominal anaphora on the one hand, and (in)definiteness on the other. The analysis builds on previous unification--based approaches to NL semantics and relies on H

Darren J Wilkinson

In recent years there has been interest in the theory of local computation over probabilistic Bayesian graphical models. In this paper, local computation over Bayes linear belief networks is shown to be amenable to a similar approach. However, the linear structure offers many simplifications and advantages relative to more complex models, and these are exami

Jean M. Quashnock, Daniel E. Vanden Berk, Donald G. York

We have analyzed the clustering of C IV absorption line systems in an extensive new catalog of heavy element QSO absorbers. The catalog permits exploration of clustering over a large range in both scale (from about 1 to over 300 Mpc) and redshift (z from 1.2 to 4.5). We find significant evidence (5.0 sigma) that C IV absorbers are clustered on comoving scale