October 1996 arXiv papers — page 15

M. Caselle

In the last few years several new Random Matrix Models have been proposed and studied. They have found application in various different contexts, ranging from the physics of mesoscopic systems to the chiral transition in lattice gauge theory. These new ensembles can be classified in terms of the same Dynkin diagrams and root lattices which are used in the cl

Charles A. Nelson

Model independent tests for symmetry violations in tau decays are important for determining whether the tau lepton is elementary or, instead, macroscopic. Such tests are also significant steps towards resolving the outstanding "e - mu - tau" puzzle. This talk reviews such tests in the context of a general treatment of two-body tau decays which only a

Edwin Langmann, Jack Lidmar, Manfred Salmhofer, Mats Wallin

We study a lattice fermion model for superconductivity in the presence of an antiferromagnetic background, described as a fixed external staggered magnetic field. We discuss the possibility that our model provides an effective description of coexistence of antiferromagnetic correlations and superconductivity, and its possible application to high temperature

M. A. Clayton

It is shown via the principle of path independence that the (time gauge) constraint algebra derived in (Class. Quantum Grav. 5 (1988) pg. 1405) for vielbein General Relativity is a generic feature of any covariant theory formulated in a vielbein frame. In the process of doing so, the relationship between the coordinate and orthonormal frame algebera is made

Almut Beige, Gerhard C. Hegerfeldt, Dirk G. Sondermann

The so-called quantum Zeno effect is essentially a consequence of the projection postulate for ideal measurements. To test the effect Itano et al. have performed an experiment on an ensemble of atoms where rapidly repeated level measurements were realized by means of short laser pulses. Using dynamical considerations we give an explanation why the projection

Kazuyuki Fujii, Kunio Funahashi

We show that the WKB approximation gives the exact result in the trace formula of ``$CQ^N$'', which is the non-compact counterpart of $CP^N$, in terms of the ``multi-periodic'' coherent state. We revisit the symplectic 2-forms on $CP^N$ and $CQ^N$ and, especially, construct that on $CQ^N$ with the unitary form. We also revisit the exact calcu

Gerrit Burgers

It is noted that the results of recent experiments on the enhancement of turbulent kinetic energy (TKE) dissipation below surface waves can be stated as follows. TKE dissipation is enhanced by a factor $15 H_{ws}/z$ at depths $0.5 H_{ws} < z < 20 H_{ws}$ with respect to the wall-layer result $ε= u_{*w}^3/κz$, where $u_{*w}$ is the friction velocity in water

P. Amore, R. Cenni, T. W. Donnelly, A. Molinari

Two different methods for establishing a space-like Coulomb sum rule for the relativistic Fermi gas are compared. Both of them divide the charge response by a normalizing factor such that the reduced response thus obtained fulfills the sum rule at large momentum transfer. To determine the factor, in the first approach one exploits the scaling property of the

T. Kubo, H. Sakamoto, T. Kammuri, T. Kishimoto

The theory of self-consistent effective interactions in nuclei is extended for a system with a velocity dependent mean potential. By means of the field coupling method, we present a general prescription to derive effective interactions which are consistent with the mean potential. For a deformed system with the conventional pairing field, the velocity depend

L. Alvarez-Ruso, P. Fernandez de Cordoba, E. Oset

A semiphenomenological approach to the nucleon self-energy in nuclear matter at finite temperatures is followed. It combines elements of Thermo Field Dynamics for the treatment of finite temperature with a model for the self-energy, which evaluates the second order diagrams taking the needed dynamics of the NN interaction from experiment. The approach proved

Haskell P. Rosenthal

A basic sequence in a Banach space is called wide-$(s)$ if it is bounded and dominates the summing basis. (Wide-$(s)$ sequences were originally introduced by I.~Singer, who termed them $P^*$-sequences). These sequences and their quantified versions, termed $λ$-wide-$(s)$ sequences, are used to characterize various classes of operators between Banach spaces,

A. Aghamohammadi, M. Khorrami, A. Shariati

Using a contraction procedure, we obtain Toda theories and their structures, from affine Toda theories and their corresponding structures. By structures, we mean the equation of motion, the classical Lax pair, the boundary term for half line theories, and the quantum transfer matrix. The Lax pair and the transfer matrix so obtained, depend nontrivially on th

A. Stern

We write down a general geometric action principle for spinning strings in $d$-dimensional Minkowski space, which is formulated without the use of Grassmann coordinates. Instead, it is constructed in terms of the pull-back of a left invariant Maurer-Cartan form on the $d$-dimensional Poincaré group to the world sheet. The system contains some interesting spe

Tonatiuh Matos, Cesar Mora

We present two new classes of axisymmetric stationary solutions of the Einstein-Maxwell-Dilaton equations with coupling constant $α^2=3$. Both classes are written in terms of two harmonic maps $λ$ and $τ$. $λ$ determines the gravitational potential and $τ$ the electromagnetic one in such a form that we can have an arbitrary electromagnetic field. As examples

A. Niégawa

We determine self-consistently the hard-quark and hard-gluon modes in hot QCD. The damping-rate part in resummed hard-quark or hard-gluon propagators, rather than the thermal-mass part, plays the dominant role.

J. Feinberg, A. Zee

As has long been known, it is energetically favorable for massive fermions to deform the homogeneous vacuum around them, giving rise to extended bag-like objects. We study this phenomenon non-perturbatively in a model field theory, the $1+1$ dimensional Massive Gross-Neveu model, in the large $N$ limit. We prove that the bags in this model are necessarily ti

Youngjai Kiem, Dahl Park

We find an analog of the electric-magnetic duality, which is a $Z_2$ transformation between magnetic and electric sectors of the static and rotationally symmetric solutions in a class of (2+1)-dimensional Einstein-Maxwell-Dilaton gravity theories. The theories in our consideration include, in particular, one parameter class of theories continuously connectin

Peter Arnold, David Wright

Gauge theories broken by a single Higgs field are known to have first-order phase transitions in temperature if $\lambda/g^2 \ll 1$, where $g$ is the gauge coupling and $\lambda$ the Higgs self-coupling. If the theory is extended from one to $N$ Higgs doublets, with U($N$) flavor symmetry, the transition is known to be second order for $\lambda/g^2 \gtrsim 1

L. Rezzolla

One of the most interesting questions regarding a possible first order cosmological quark--hadron phase transition concerns the final fate of the baryon number contained within the disconnected quark regions at the end of the transition. We here present a detailed investigation of the hydrodynamical evolution of an evaporating quark drop, using a multi-compo

Brian J. Gough, George M. Hockney, Aida X. El-Khadra, Andreas S. Kronfeld

We investigate the masses of the light quarks with lattice QCD. We show that most of the large dependence on the lattice spacing, a, observed in previous determinations using Wilson fermions is removed with the use of an O(a) corrected action. In the quenched approximation, we obtain for the strange quark MS bar mass m_s(2 GeV) = 95 (16) MeV, and for the ave

Rathin Adhikari, Utpal Sarkar

We propose a simple scenario for baryogenesis in supersymmetric models where baryon number is broken alongwith R-parity. The lightest supersymmetric particle (neutralino) decays to three quarks and $CP-$ violation comes from interference of tree and one loop box diagrams. The bounds on the $R-$parity breaking couplings from the out-of-equilibrium condition a

M. V. Chizhov

It is shown that in the one-flavour NJL model the vector and axial-vector quasiparticles described by the antisymmetric tensor field are generated. These excitations have tensor interactions with quarks in contrast to usual vector ones. Phenomenological applications are discussed.

A. A. Gvozdev, N. V. Mikheev, L. A. Vassilevskaya

The radiative decay of the massive neutrino $ν_i \rightarrow ν_j γ$ is investigated in the framework of the Standard Model in external electromagnetic fields of various configurations: constant crossed field, constant uniform magnetic field, plane monochromatic wave&#39;s field. The effect of significant enhancement of the neutrino decay probability by the e

V. E. Lyubovitskij, A. G. Rusetsky

The expression for the $(π^+π^-)$ atom lifetime is derived within the Bethe-Salpeter approach. First-order perturbative corrections due to the contribution of strong interactions are taken into account. It is demonstrated that the atom lifetime can be expressed in terms of the solutions of the Coulombic problem (the wave function of the $1S$ state at the ori

Michael Rueter

The total energy and action, which is stored in the flux-tube between a static quark-antiquark pair, can be compared with the potential of the pair with the help of two low energy theorems. The flux-tube and the potential are calculated in the framework of the model of the stochastic vacuum. Using the low energy theorems we obtain consistency of the results

Giovanni Ridolfi

I review recent theoretical results on polarized deep inelastic lepton nucleon scattering. Some specific issues, like $Q^2$ evolution of structure functions, the small $x$ behaviour, and the determination of polarized parton densities, are discussed in some detail.

A. Ringwald, F. Schrempp

We present a status report of our systematic theoretical and phenomenological study of QCD-instanton induced processes in deep-inelastic scattering. We show that this regime plays a distinguished role for studying manifestations of QCD-instantons, since the typical hard momentum scale $Q$ provides a dynamical infrared cutoff for the instanton size $ρ\lwig O(

V. M. Braun

I review the theoretical status of hadronization corrections to hadronic event observables and discuss their impact on the determination of $α_s$.

V. Barone, U. D&#39;Alesio, M. Genovese

We review the present theoretical knowledge of the charm--strange contribution to charged--current DIS structure functions. In particular, the uncertainties arising from the choice of the factorization scale, of the massive QCD scheme, and of the parton fit are discussed.

L. Del Debbio, M. Faber, J. Greensite, S. Olejnik

We find, in close analogy to abelian dominance in maximal abelian gauge, the phenomenon of center dominance in maximal center gauge for $SU(2)$ lattice gauge theory. Maximal center gauge is a gauge-fixing condition that preserves a residual $Z_2$ gauge symmetry; ``center projection&#39;&#39; is the projection of $SU(2)$ link variables onto $Z_2$ center eleme

Leonardo Rastelli, Paolo Rossi, Ettore Vicari

We construct sequences of ``field theoretical&#39;&#39; (analytical) lattice topological charge density operators which formally approach geometrical definitions in 2-d $CP^{N-1}$ models and 4-d $SU(N)$ Yang Mills theories. The analysis of these sequences of operators suggests a new way of looking at the geometrical method, showing that geometrical charges c

Masahiro Fukushima, Atsunori Tanaka, Shoich Sasaki, Hideo Suganuma

We study the relation between the instanton distribution and the monopole loop length in the SU(2) gauge theory with the abelian gauge fixing. We measure the monopole current from the multi-instanton ensemble on the $16^4$ lattice using the maximally abelian gauge. When the instanton density is dilute, there appear only small monopole loops. On the other han

Dario Alfe&#39;, Stefano Baroni

The structure of CO adsorbates on the Rh(110) surface is studied at full coverage using first-principles techniques. The relative energies of different adsorbate geometries are determined by means of accurate structure optimizations. In agreement with experiments, we find that a p2mg(2x1) 2CO structure is the most stable. The CO molecules sit on the short-br

Tai-Kai Ng

In this paper we study the effect of non-magnetic impurities in spin-Peierls system $CuGeO_3$ within the framework of non-linear sigma model plus topological term. We show that local moments are induced in both the $Zn$-doped and $Si$-doped $CuGeO_3$ compounds. Effective low energy theories for the impurity-induced local moments are derived in both cases whe

O. A. Starykh, R. R. P. Singh, A. W. Sandvik

Low temperature dynamics of the S=1/2 Heisenberg chain is studied via a simple ansatz generalizing the conformal mapping and analytic continuation procedures to correlation functions with multiplicative logarithmic factors. Closed form expressions for the dynamic susceptibility and the NMR relaxation rates 1/T_1 and 1/T_{2G} are obtained, and are argued to i

Giorgio Amati, Sauro Succi, Roberto Benzi

A coarse-grained version of the Lattice Boltzmann (LB) method is developed with the intent of enhancing its geometrical flexibility so as to be able to tackle a wider class of flows of engineering interest. To this purpose, the original uniform LB technique is combined with standard finite-volume techniques based upon a blend of piecewise constant and piecew

Mark Dras, Mike Johnson

Some verbs have a particular kind of binary ambiguity: they can carry their normal, full meaning, or they can be merely acting as a prop for the nominal object. It has been suggested that there is a detectable pattern in the relationship between a verb acting as a prop (a \term{support verb}) and the noun it supports. The task this paper undertakes is to dev

Scott M. Zoldi, Henry S. Greenside

We show that the number of KLD (Karhunen-Lo`eve decomposition) modes D_KLD(f) needed to capture a fraction f of the total variance of an extensively chaotic state scales extensively with subsystem volume V. This allows a correlation length xi_KLD(f) to be defined that is easily calculated from spatially localized data. We show that xi_KLD(f) has a parametric

Martin Sieber, Nicolas Pavloff, Charles Schmit

We derive contributions to the trace formula for the spectral density accounting for the role of diffractive orbits in two-dimensional billiard systems with corners. This is achieved by using the exact Sommerfeld solution for the Green function of a wedge. We obtain a uniformly valid formula which interpolates between formerly separate approaches (the geomet

A. Refregier, D. J. Helfand, R. G. McMahon

Recent ROSAT surveys suggest that galaxies constitute the new class of X-ray sources required to explain the full phenomenology of the cosmic X-Ray Background (XRB). To test this hypothesis, we compute the two-point cross-correlation function Wxg(theta) between 62 Einstein-IPC fields (.81-3.5 keV) and the APM Northern galaxy catalog (13.5<E<19.0). At zero-la

Fabio La Franca, Stefano Cristiani

An ESO Key programme dedicated to an Homogeneous Bright QSO Survey (HBQS) has been completed. 327 QSOs (Mb<-23, 0.3<z<2.2) have been selected over 555 deg^2 with 15<B<18.75. For B<16.4 the QSO surface density turns out to be a factor 2.2 higher than what measured by the PG survey, corresponding to a surface density of 0.013+/-.006 deg^{-2}. If the Edinburgh

V. M. Lipunov, K. A. Postnov, M. E. Prokhorov

Based on evolutionary scenarios for binary stellar evolution we study the merging rates of relativistic binary stars (NS+NS, NS+BH, BH+BH) under different assumptions of BH formation. We find the BH+BH merging rate in the range one per 200,000 -- 500,000 year in a Milky-Way type galaxy, while the NS+NS merging rate $R_{ns}$ is approximately 10 times as high,

Matthew G. Baring, Keith Ogilvie, Donald Ellison, Robert Forsyth

The most stringent test of theoretical models of the first-order Fermi mechanism at collisionless astrophysical shocks is a comparison of the theoretical predictions with observational data on particle populations. Such comparisons have yielded good agreement between observations at the quasi-parallel portion of the Earth&#39;s bow shock and three theoretica

K. Dimopoulos, A. C. Davis

A new mechanism for the evolution of primordial magnetic fields is described and analysed. The field evolution is followed from the time of its creation until the epoch of structure and galaxy formation. The mechanism takes into account the turbulent behaviour of the early universe plasma, whose properties determine strongly the evolution of the field config

S. Ettori, L. Guzzo, M. Tarenghi

We analyse a set of new pencil-beam galaxy redshift data in three small regions around the South Galactic Pole (SGP) area. We investigate whether we can find any evidence of the quasi-periodic peaks discovered by Broadhurst et al. (1990) in the distribution of galaxies along the NGP-SGP directions. We use both a power spectrum analysis and a cross-correlatio

J. -M. Hameury, H. Ritter

We give a simple, but accurate method that can be used to account for illumination in compact binary systems which have a low-mass companion, even if spherically symmetric illumination of the secondary star (not necessarily on the main sequence) is not assumed. This is done by introducing a multiplicative factor Phi in the Stefan-Boltzmann surface boundary c

J. R. Mattox, S. J. Wagner, M. Malkan, T. A. McGlynn

We report the observation by the Compton Gamma Ray Observatory of a spectacular flare of radio source PKS 1622-297. A peak flux of 17E-6 cm^-2 s^-1 (E > 100 MeV) was observed. The corresponding isotropic luminosity is 2.9E49 erg/s. We find that PKS 1622-297 exhibits gamma-ray intra-day variability. A flux increase by a factor of at least 3.6 was observed to

Daniela Pfannkuche, Allan H. MacDonald

We consider the influence of an external periodic potential on the fractional quantum Hall effect of two-dimensional interacting electron systems. For many electrons on a torus, we find that the splitting of incompressible ground state degeneracies by a weak external potential diminishes as $\exp ( - L/ ξ)$ at large system size $L$. We present numerical resu

F. Colaiori, A. Flammini, A. Maritan, J. R. Banavar

We analyze the Optimal Channel Network model for river networks using both analytical and numerical approaches. This is a lattice model in which a functional describing the dissipated energy is introduced and minimized in order to find the optimal configurations. The fractal character of river networks is reflected in the power law behaviour of various quant

Dimitra Karabali, V. P. Nair

In terms of a gauge-invariant matrix parametrization of the fields, we give an analysis of how the mass gap could arise in non-Abelian gauge theories in two spatial dimensions.

Marco Falcioni, Mark Bowick, Emmanuel Guitter, Gudmar Thorleifsson

A remarkable theoretical prediction for a crystalline (polymerized) surface is that its Poisson ratio (σ) is negative. Using a large scale Monte Carlo simulation of a simple model of such surfaces we show that this is indeed true. The precise numerical value we find is (σ\simeq -0.32) on a (128^2) lattice at bending rigidity (kappa = 1.1). This is in excelle

M. Asorey, J. L. López, I. L. Shapiro

We analyze the perturbative implications of the most general high derivative approach to quantum gravity based on a diffeomorphism invariant local action. In particular, we consider the super-renormalizable case with a large number of metric derivatives in the action. The structure of ultraviolet divergences is analyzed in some detail. We show that they are

Neda Sadooghi, Heinz J. Rothe

A lattice action for QED is considered, where the derivatives in the Dirac operator are replaced by one-sided lattice differences. A systematic expansion in the lattice spacing of the one-loop contribution to the fermion self energy, vacuum polarization tensor and vertex function is carried out for an arbitrary choice of one-sided lattice differences. It is

Toshiyuki Fukushige, Junichiro Makino

Observed cusps with density profiles $ρ\propto r^{-1}$ or shallower, in the central regions of galaxies, cannot be reproduced in the standard Cold Dark Matter (CDM) picture of hierarchical clustering. Previous claims to the contrary were based on simulations with relatively few particles, and substantial softening. We present simulations with particle number

Daniel Dominguez, Niels Gronbech-Jensen, A. R. Bishop

We study the melting of a moving vortex lattice through numerical simulations with the current driven 3D XY model with disorder. We find that there is a first-order phase transition even for large disorder when the corresponding equilibrium transition is continuous. The low temperature phase is an anisotropic moving glass.

Markus Peter

The static potential between an infinitely heavy quark and antiquark is derived in the framework of perturbative QCD to three loops by performing a full calculation of the two-loop diagrams and using the renormalization group. The contribution of massless fermions is included.

E. Kolbe, S. Krewald, H. Weigel

The electroweak form factors of the nucleon as obtained within a three flavor pseudoscalar vector meson soliton model are employed to predict the ratio of the proton and neutron yields from $^{12}C$, which are induced by quasi-elastic neutrino reactions. These predictions are found to vary only moderately in the parameter space allowed by the model. The anti

B. Czerny, H. J. Lehto

The analysis of eight EXOSAT X-ray lightcurves of six active galactic nuclei by nonlinear prediction methods indicates that the observed short time-scale variability is truly stochastic and is not caused by deterministic chaos. This result favors X-ray emission models with mutliple centers of production of hot, possibly relativistic electrons.

Jeongwon Ho, Yongduk Kim, Young-Jai Park

We investigate whether the gravitational thermodynamic properties of the scalar-tensor theory of gravity are affected by the conformal transformation or not. As an explicit example, we consider an electrically charged static spherical black hole in the 4-dimensional low energy effective theory of bosonic string.

Paolo Casati, Gregorio Falqui, Franco Magri, Marco Pedroni

We use the method of Darboux coverings to discuss the invariant submanifolds of the KP equations, presented as conservation laws in the space of monic Laurent series in the spectral parameter (the space of the Hamiltonian densities). We identify a special class of these submanifolds with the rational invariant submanifolds entering matrix models of $2D$--gra

Isaac L. Chuang, M. A. Nielsen

We give an explicit prescription for experimentally determining the evolution operators which completely describe the dynamics of a quantum mechanical black box -- an arbitrary open quantum system. We show necessary and sufficient conditions for this to be possible, and illustrate the general theory by considering specifically one and two quantum bit systems

E. V. Damaskinsky, P. P. Kulish

Different generators of a deformed oscillator algebra give rise to one-parameter families of $q$-exponential functions and $q$-Hermite polynomials related by generating functions. Connections of the Stieltjes and Hamburger classical moment problems with the corresponding resolution of unity for the $q$-coherent states and with &#39;coordinate&#39; operators

W-S. Chung

In this paper some realization of $gl_q(n)$-covariant oscillators is obtained when $q$ is a root of unity. And the $gl_q(n)$-covariant q-Virasoro algebra is presented by using the $gl_q(n)$-covariant oscillators.

Robert Karrlein, Hermann Grabert

Using the exact path integral solution for the damped harmonic oscillator it is shown that in general there does not exist an exact dissipative Liouville operator describing the dynamics of the oscillator for arbitrary initial bath preparations. Exact non-stationary Liouville operators can be found only for particular preparations. Three physically meaningfu

G. G. Adamian, R. V. Jolos, A. K. Nasirov, A. I. Muminov

Based on the microscopic model, the friction coefficient for the relative motion of nuclei in deep-inelastic heavy-ion collisions is calculated. The radial dependence of the friction coefficient is studied and the results are compared with those found by other methods. Based on this result, it was demonstrated that the kinetic energy dissipation in deep-inel

Alexander Kiselev

We show that for integral operators of general form the norm bounds in Lorentz spaces imply certain norm bounds for the maximal function. As a consequence, the a.e. convergence for the integral operators on the Lorentz spaces follows from the appropriate norm estimates.

Alexander Kiselev

We prove new criteria of stability of the absolutely continuous spectrum of one-dimensional Schrödinger operators under slowly decaying perturbations. As applications, we show that the absolutely continuous spectrum of the free and periodic Schrödinger operators is preserved under perturbations by all potentials $V(x)$ satisfying $|V(x)| \leq C(1+x)^{-\frac{

Alexander Koldobsky

We define embedding of an $n$-dimensional normed space into $L_{-p},\ 0<p<n$ by extending analytically with respect to $p$ the corresponding property of the classical $L_p$-spaces. The well-known connection between embeddings into $L_p$ and positive definite functions is extended to the case of negative $p$ by showing that a normed space embeds in $L_{-p}$ i

Pascal J. Thomas

We propose two possible definitions for the notion of a sampling sequence (or set) for Hardy spaces of the disk. The first one is inspired by recent work of Bruna, Nicolau, and Øyma about interpolating sequences in the same spaces, and it yields sampling sets which do not depend on the value of $p$ and correspond to the result proved for bounded functions ($

Stephen S. Pinsky, Richard Mohr

We consider SU(2) Yang-Mills theory in 1+1 dimensions coupled to massless adjoint fermions. With all fields in the adjoint representation the gauge group is actually SU(2)/Z_2, which possesses nontrivial topology. In particular, there are two distinct topological sectors and the physical vacuum state has a structure analogous to a θvacuum. We show how this f

Kwan-Leung Chan

A class of four-dimensional static supersymmetric black hole solutions of effective supergravity Lagrangian of IIA superstring compactified on $T^6$ is constructed by explicitly solving Killing spinor equations (KSEs). These solutions are dyonic black holes parametrized by four charges, with dilaton and diagonal internal metric components as the only non-zer

Norma Mankoc Borstnik

In space of d ordinary and d Grassmann coordinates, with d \ge 15, the charges unify with the spin: the Lorentz group SO(1, d-1) in Grassmann space manifests under certain conditions as SO(1,3) (in d=4 subspace) times SO(10) \supset SU(3) \times SU(2) \times U(1) (in the rest of the space), accordingly the symmetry group of the S- matrix, which is approximat

Uwe Grimm, Bernard Nienhuis

The dilute A_3 model is a solvable IRF (interaction round a face) model with three local states and adjacency conditions encoded by the Dynkin diagram of the Lie algebra A_3. It can be regarded as a solvable version of an Ising model at the critical temperature in a magnetic field. One therefore expects the scaling limit to be governed by Zamolodchikov&#39;s

Jordi Comellas

The development of the Exact Renormalization Group for fermionic theories is presented, together with its application to the chiral Gross-Neveu model. We focus on the reliability of various approximations, specifically the derivative expansion and further truncations in the number of fields. The main differences with bosonic theories are discussed.

R. Baier, M. Dirks, K. Redlich

A systematic study of low mass dilepton production from $π-ρ$ interactions in a hot medium is presented. Applying finite temperature perturbation theory the dilepton rate, respectively the virtual photon rate, is computed up to order $g_ρ^2$. For dilepton masses below the $ρ$ the two-body reactions $ππ\to ργ^*$, $πρ\to πγ^*$, and the decay process $ρ\to ππγ^

Joao P. Silva, L. Wolfenstein

The standard CKM model can be tested and New Physics detected using only CP-violating phase measurements in B decays. This requires the measurement of a phase factor which is small in the Standard Model, in addition to the usual large phases $β$ and $γ$. We also point out that identifying violations of the unitarity of the CKM matrix is rather difficult, and

G. P. Korchemsky

We study the power corrections to the cross-section of Drell-Yan production within the Wilson line approach and apply the methods of QCD asymptotic dynamics to identify the leading renormalon contribution.

V. Barone, M. Genovese

Nuclear shadowing arises from multiple scattering of the hadronic fluctuations of the virtual photon in a nucleus. We predict different longitudinal and transverse shadowing and an A-dependence of R which can be up to a 50% effect. The possibility of detecting nuclear effects on R at HERA is discussed.

L. Mankiewicz, T. Weigl

The most striking feature of quark distribution functions transformed to the longitudinal distance representation is the recognizable separation of small and large longitudinal distances. While the former are responsible for the average properties of parton distributions, the latter can be shown to determine specifically their small-$x$ behavior. In this pap

V. A. Khoze, S. Lupia, W. Ochs

The analytical perturbative approach, if taken to the limit of its applicability, allows one to predict an energy independent limit for the one-particle invariant density in QCD jets E dn/d^3p at very small momenta p. This is a direct consequence of the colour coherence in soft gluon branching. The existing data on the charged and identified particle inclusi

J. Blümlein, A. Vogt

The impact of the resummation of leading small-$x$ terms in the anomalous dimensions is briefly summarized for the evolution of non--singlet and singlet polarized structure functions.

G. Amelino-Camelia, J. D. Bjorken, S. E. Larsson

We review recent progress in the description and understanding of disoriented chiral condensates. Certain important unsolved issues are underlined, and the preliminary results of our program of investigation of these issues in the framework of the classical linear sigma model are reported. We also briefly review a formalism which could be useful at the full

Indranil Dasgupta, Ryan Rohm

In this paper we investigate the dynamical properties of binary cosmic strings. We find extrinsic curvature dependence of the string action and show that kinks on binary strings are eroded while cusps can play a major role in their evolution.

L. A. Averchenkova, K. V. Petrov, V. K. Petrov, G. M. Zinovjev

The role of lattice asymmetry parameter in description of the SU(2) gluodynamics phase structure at finite temperature is studied analytically. The fact that renormalization group relations which permit to remove the lattice asymmetry parameter from the thermodynamical quantities in the &#34;naive&#34; limit don&#39;t do the same in the approximation SU(N) =

Eric Torrence, The SLD Collaboration

We present an improved measurement of the left-right cross section asymmetry Alr for Z boson production by e+e- collisions. The measurement was performed at a center-of-mass energy of 91.28 GeV with the SLD detector at the SLAC Linear Collider (SLC) during the 1994-95 running period. The luminosity-weighted average polarization of the SLC electron beam durin

Pedro F. Gonzalez-Diaz

By allowing the light cones to tip over on hypersurfaces according to the conservation laws of an one-kink in static, Schwarzschild black hole metric, we show that in the quantum regime there also exist instantons whose finite imaginary action gives the probability of occurrence of the kink metric corresponding to single chargeless, nonrotating black hole ta

V. P. Ladygin, N. B. Ladygina

The model independent analysis of the $dp$ elastic scattering in the collinear geometry has been performed. It is shown that the measurements of 10 polarization observables of the first and second order realize the complete experimental program on the determination of the amplitudes of the $dp$ backward elastic scattering reaction.

Mihaela Manoliu

We give a construction of the abelian Chern-Simons gauge theory from the point of view of a 2+1 dimensional topological quantum field theory. The definition of the quantum theory relies on geometric quantization ideas which have been previously explored in connection to the nonabelian Chern-Simons theory [JW,ADW]. We formulate the topological quantum field t

J. R. Quinlan

First-order learning involves finding a clause-form definition of a relation from examples of the relation and relevant background information. In this paper, a particular first-order learning system is modified to customize it for finding definitions of functional relations. This restriction leads to faster learning times and, in some cases, to definitions

G. Zlotkin, J. S. Rosenschein

This paper lays part of the groundwork for a domain theory of negotiation, that is, a way of classifying interactions so that it is clear, given a domain, which negotiation mechanisms and strategies are appropriate. We define State Oriented Domains, a general category of interaction. Necessary and sufficient conditions for cooperation are outlined. We use th

Barbara Drossel, Mehran Kardar

We study analytically and numerically the winding of directed polymers of length $t$ around each other or around a rod. Unconfined polymers in pure media have exponentially decaying winding angle distributions, the decay constant depending on whether the interaction is repulsive or neutral, but not on microscopic details. In the presence of a chiral asymmetr

Barbara Drossel, Mehran Kardar

We study a simple growth model for (d+1)-dimensional films of binary alloys in which atoms are allowed to interact and equilibrate at the surface, but are frozen in the bulk. The resulting crystal is highly anisotropic: Correlations perpendicular to the growth direction are identical to a d-dimensional two-layer system in equilibrium, while parallel correlat

Barbara Drossel

Using stability arguments, this Brief Report suggests that a term that enhances the surface tension in the presence of large height fluctuations should be included in the Kardar-Parisi-Zhang equation. A one-loop renormalization group analysis then shows for interface dimensions larger than $\simeq 3.3$ an unstable strong-coupling fixed point that enters the

Luis A. Nunes Amaral, Kent B. Lauritsen

We investigate a one-dimensional rice-pile model. We show that the distribution of dissipated potential energy decays as a power law with an exponent $α=1.53$. The system thus provides a one-dimensional example of self-organized criticality. Different driving conditions are examined in order to allow for comparison with experiments.

Luis A. Nunes Amaral, Kent B. Lauritsen

We present a new model for relaxations in piles of granular material. The relaxations are determined by a stochastic rule which models the effect of friction between the grains. We find power-law distributions for avalanche sizes and lifetimes characterized by the exponents $τ= 1.53 \pm 0.05$ and $y = 1.84 \pm 0.05$, respectively. For the discharge events, w

T. E. Mason, C. P. Adams, S. A. M. Mentink, E. Fawcett

FeGe_2, and lightly doped compounds based on it, have a Fermi surface driven instability which drive them into an incommensurate spin density wave state. Studies of the temperature and magnetic field dependence of the resistivity have been used to determine the magnetic phase diagram of the pure material which displays an incommensurate phase at high tempera

Alex Buchel, James P. Sethna

We study a class of models for brittle fracture: elastic theory models which allow for cracks but not for plastic flow. We show that these models exhibit, at all finite temperatures, a transition to fracture under applied load similar to that at a first order liquid-gas transition. We study this transition at low temperature for small tension. We discuss the

Ian Affleck, Marcel Franz, M. H. Sharifzadeh Amin

We generalize the London free energy to include four-fold anisotropies which could arise from d-wave pairing or other sources in a tetragonal material. We use this simple model to study vortex lattice structure and discuss neutron scattering, STM, Bitter decoration and $μ$SR experiments.

W. J. Mullin

We examine several features of Bose-Einstein condensation (BEC) in an external harmonic potential well. In the thermodynamic limit, there is a phase transition to a spatial Bose-Einstein condensed state for dimension D greater than or equal to 2. The thermodynamic limit requires maintaining constant average density by weakening the potential while increasing

J. Kasparian, B. Krämer, J. P. Dewitz, S. Vajda

We present experimental and theoretical results for the angular dependence of third harmonic generation (THG) of water droplets in the micrometer range (size parameter $62<ka<248$). The THG signal in $p$- and $s$-polarization obtained with ultrashort laser pulses is compared with a recently developed nonlinear extension of classical Mie theory including mult