December 1994 arXiv papers — page 10

Wolfhard Janke, Tilman Sauer

We report results of a Monte Carlo simulation of the $ϕ^4$ quantum chain. In order to enhance the efficiency of the simulation we combine multigrid simulation techniques with a refined discretization scheme. The resulting accuracy of our data allows for a significant test of an analytical approximation based on a variational ansatz. While the variational app

Mehran Kardar, Attilio L. Stella, Giovanni Sartoni, Bernard Derrida

We study the criticality of a Potts interface by introducing a {\it froth} model which, unlike its SOS Ising counterpart, incorporates bubbles of different phases. The interface is fractal at the phase transition of a pure system. However, a position space approximation suggests that the probability of loop formation vanishes marginally at a transition domin

L. A. Fernandez, E. Marinari, J. J. Ruiz-Lorenzo

We discuss the tempering Monte Carlo method, and its critical slowing down in the $3d$ Ising model. We show that at $T_c$ the tempering does not change the critical slowing down exponent $z$. We also discuss the exponential slowing down for the transition from the plus to the minus state in the cold phase, and we show that tempering reduces it to a power law

Giorgio Parisi

We will review some of the theoretical progresses that have been in the study of complex systems in physics and of their applications to biology.

Diptiman Sen, R. Chitra

We consider the large-$U$ limit of the one-band Hubbard model at half-filling on a non-bipartite two-dimensional lattice. An external magnetic field can induce a three-spin chiral interaction at order $1 / U^2 ~$. We discuss situations in which, at low temperatures, the chiral term may have a larger effect than the Pauli coupling of electron spins to a magne

Robin Collier

This paper presents an overview of current research concerning knowledge extraction from technical texts. In particular, the use of empirical techniques during the identification and generation of a semantic representation is considered. A key step is the discovery of useful n-grams and correlations between clusters of these n-grams.

P. Collet, J. Xin

We consider the initial value problem for the thermal-diffusive combustion systems of the form: $u_{1,t}= Delta_{x}u_1 - u_1 u_2^m$, $u_{2,t}= d Delta_{x} u_2 + u_1 u_2^m$, $x in R^{n}$, $n geq 1$, $m geq 1$, $d > 1$, with bounded uniformly continuous nonnegative initial data. For such initial data, solutions can be simple traveling fronts or complicated dom

D. R. Martin, R. C. Nichol, C. A. Collins, S. A. Lumsden

We present here the results of a statistical search for cluster alignments using the Edinburgh/Milano cluster redshift survey. This survey is a unique cluster database which has been objectively constructed to help minimise the systematic biases associated with previous optical cluster catalogues. We find some evidence for cluster alignments out to spatial s

M. Kachelriess, D. Berg, G. Wunner

The infrared behavior of QED changes drastically in the presence of a strong magnetic field: the electron self-energy and the vertex function are infrared {\em finite}, in contrast with field-free QED, while new infrared divergences appear that are absent in free space. One famous example of the latter is the infrared catastrophe of magnetic Compton scatteri

Penny D. Sackett, Richard W. Pogge

Knowledge of the shape of dark matter halos is critical to our understanding of galaxy formation, dynamics, and of the nature of dark matter itself. Polar ring galaxies (PRGs) --- early-type galaxies defined by their outer rings of gas, dust and stars on orbits nearly perpendicular to those of the central host --- provide a rare probe of the vertical-to-radi

Eduard Looijenga

To a closed connected oriented surface $S$ of genus $g$ and a nonempty finite subset $P$ of $S$ is associated a simplicial complex (the arc complex) that plays a basic r\^ ole in understanding the mapping class group of the pair $(S,P)$. It is known that this arc complex contains in a natural way the product of the Teichmüller space of $(S,P)$ with an open s

Alexander Khodjamirian, Reinhold Rückl

We discuss the calculation of the $B \rightarrow π$ and $D \rightarrow π$ form factors based on an expansion in terms of pion wave functions on the light-cone with increasing twist and QCD sum rule methods. The results are compared with predictions of conventional QCD sum rules and other approaches.

H. C. Rosu

A simple, general discussion of the problem of inertia is provided both in classical physics and in the quantum world. After briefly reviewing the classical principles of equivalence (weak (WEP), Einstein (EEP), strong (SEP)), I pass to a presentation of several equivalence statements in nonrelativistic quantum mechanics and for quantum field vacuum states.

William J. Bruno, Emanuel Knill, David J. Balding, D. C. Bruce

We describe efficient methods for screening clone libraries, based on pooling schemes which we call ``random $k$-sets designs''. In these designs, the pools in which any clone occurs are equally likely to be any possible selection of $k$ from the $v$ pools. The values of $k$ and $v$ can be chosen to optimize desirable properties. Random $k$-sets desi

J. Donin, S. Shnider

Let $G$ be a semisimple Lie group, ${\frak g}$ its Lie algebra. For any symmetric space $M$ over $G$ we construct a new (deformed) multiplication in the space $A$ of smooth functions on $M$. This multiplication is invariant under the action of the Drinfeld--Jimbo quantum group $U_h{\frak g}$ and is commutative with respect to an involutive operator $\tilde{S

M. Khorrami, A. Shariati, M. Abolhassani, A. Aghamohammadi

Contracting the $h$-deformation of $\SL(2,\Real)$, we construct a new deformation of two dimensional Poincaré algebra, the algebra of functions on its group and its differential structure. It is also shown that the Hopf algebra is triangular, and its universal R matrix is also constructed explicitly. Then, we find a deformation map for the universal envelopi

Timothy R. Klassen

By (a) using an expression for the LATTICE potential of QCD in terms of a CONTINUUM running coupling and (b) globally parameterizing this coupling to interpolate between 2- (or higher-) loop QCD in the UV and the flux tube prediction in the IR, we can perfectly fit lattice data for the potential down to ONE lattice spacing and at the same time extract the ru

Frank Gaitan

A microscopic analysis of the non-dissipative force F_nd acting on a line vortex in a type-II superconductor at T=0 is given. All work assumes a charged BCS superconductor. We first examine the Berry phase induced in the BCS ground state by movement of the vortex and show how this phase enters into the hydrodynamic action S_hyd of the condensate. Appropriate

A. Galperin, E. Sokatchev

We present the (0,4) superspace version of Witten's sigma model construction for ADHM instantons. We use the harmonic superspace formalism, which exploits the three complex structures common to both (0,4) supersymmetry and self-dual Yang-Mills theory. A novel feature of the superspace formulation is the manifest interplay between the ADHM construction an

I. G. Aznauryan

We show that in photoproduction experiments there are propitious conditions to study the exotic state $1^{-+}$ in the $πη$ and $πη'$ channels. We show that for unpolarized photon beam the contributions with natural and unnatural parity exchanges do not interfere with each other, the fact which gives additional arguments in the estimation of the correctne

S. P. de Alwis, N. Ohta

We show that the partition function for a scalar field in a static spacetime background can be expressed as a functional integral in the corresponding optical space, and point out that the difference between this and the functional integral in the original metric is a Liouville type action. A general formula for the free energy is derived in the high tempera

Thomas Jech, Saharon Shelah

There exists a family $\{B_α\}_{α<ω_1}$ of sets of countable ordinals such that o $\max B_α=α$, o if $α\in B_β$ then $B_α\subseteq B_β$, o if $λ\leq α$ and $λ$ is a limit ordinal then $B_α\capλ$ is not in the ideal generated by the $B_β$, $β<α$, and by the bounded subsets of $λ$, o there is a partition $\{A_n\}_{n=0}^{\infty}$ of $ω_1$ such that for every $α

S. V. Esaibegyan, S. N. Tamaryan

It is shown, that the correct account of quark interaction generated by instanton medium gives the possibility of description on the same ground of both pseudoscalar channel and low lying bound states in the vector channel. It must be noted, that all calculations are made in the approximation, taking into account only zero modes.

Toru Goto, Yasuhiro Okada

We study the constraint on the mass of the charged Higgs boson in the minimal supergravity model based on the recent measurement of the inclusive $b\rightarrow sγ$ decay. It is shown that the lower bound for the charged Higgs mass crucially depends on the sign of the higgsino mass parameter ($μ$). For $μ<0$, the bound exceeds 400 GeV when the ratio of two Hi

Zhijian Tao

We propose a theory to describe fermion mixing. The theory respects the maximal abelian family symmetries which are spontaneously broken down at a large scale. We find that quark mixing can be well described in this theory. Some concrete models are constructed. The crucial point for model building is to introduce some new particles which are SU(2) gauge sing

Hiroshi Shiba

The structure of the flux tube is studied in $SU(2)$ QCD from the standpoint of the abelian projection theory. It is shown that the flux distributions of the orthogonal electric field and the magnetic field are produced by the effect that the abelian monopoles in the maximally abelian (MA) gauge are expelled from the string region.

Kazuhiro Yamamoto, Takahiro Tanaka, Misao Sasaki

Using the multi-dimensional wave function formalism, we investigate the quantum state of a scalar field inside a true vacuum bubble nucleated through false vacuum decay in flat spacetime. We developed a formalism which allows us a mode-by-mode analysis. To demonstrate its advantage, we describe in detail the evolution of the quantum state during the tunnelin

Biman B. Nath

The cocoons surrounding powerful radio sources can be extensive if the jet that feeds the cocoon is light and supersonic. They have been shown to remain overpressured with respect to the ambient medium for most of the life time of the sources. The observed lobes of the radio sources form parts of these extensive cocoons. We show that observations of the lobe

N. Deshpande, Xiao-Gang He, Josip Trampetic

We consider the long distance contributions to inclusive penguin processes through processes like $b\rightarrow s V$ and $b\rightarrow d V$ where $V$ are $^3S_1(c\bar c)$ states $\psi_i$ in the former case and include $\rho$, $\omega$ for the latter case. We carefully examine vector dominance for $\bar c c$ states, and conclude that there is a large suppress

A. J. Niemi, K. Palo

We construct a two dimensional nonlinear $σ$-model that describes the Hamiltonian flow in the loop space of a classical dynamical system. This model is obtained by equivariantizing the standard N=1 supersymmetric nonlinear $σ$-model by the Hamiltonian flow. We use localization methods to evaluate the corresponding partition function for a general class of in

Xavier A. Siemens, T. W. B. Kibble

A general formulation for describing odd-harmonic cosmic strings is developed and used to determine the self-intersection properties of high-harmonic loops. This is important because loop formation mechanisms produce high-harmonic components (kinks) which can only be eliminated very slowly by gravitational radiation, damping by the dense surrounding plasma i

J. Legare, J. W. Moffat

The field equations in the nonsymmetric gravitational theory are derived from a Lagrangian density using a first-order formalism. Using the general covariance of the Lagrangian density, conservation laws and tensor identities are derived. Among these are the generalized Bianchi identities and the law of energy-momentum conservation. The Lagrangian density is

Dmitri V. Fursaev, Sergey N. Solodukhin

One-loop divergences appearing in the entropy of a quantum black hole are proven to be completely eliminated by the standard renormalization of both the gravitational constant and other coefficients by the $R^2$-terms in the effective gravitational action. The essential point of the proof is that due to the higher order curvature terms the entropy differs fr

A. Wipf, S. Duerr

We investigate multi-flavour gauge theories confined in $d\es 2n$-dimensional Euclidean bags. The boundary conditions for the &#39;quarks&#39; break the axial flavour symmetry and depend on a parameter $θ$. We determine the $θ$-dependence of the fermionic correlators and determinants and find that a $CP$-breaking $θ$-term is generated dynamically. As an appl

Y. Kurihara, D. Perret-Gallix, Y. Shimizu

The complete tree level cross section for the process $e^+e^- \to e^- \barν_e u \bar{d}$ is computed using the GRACE system, a program package for automatic amplitude calculation. Special attention is brought to the gauge violation problem induced by the finite width of the $W$-boson. The {\it preserved gauge scheme} is introduced and an event generator whic

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis, D. Lenis

The symmetry algebra of the two-dimensional anisotropic quantum harmonic oscillator with rational ratio of frequencies, which is characterizing ``pancake&#39;&#39; nuclei, is identified as a non-linear extension of the u(2) algebra. The finite dimensional representation modules of this algebra are studied and the energy eigenvalues are determined using algeb

N. D. Whelan

Spectrum generating algebras are used in various fields of physics as models to determine quantum structure, including energy levels and transition strengths. The advantage of such models is that their group structure allows an extensive understanding of the system being studied. In addition they possess a simple classical limit, at least for bosonic systems

E. J. Mele, G. V. Krishna, S. C. Erwin

Competing magnetically ordered structures in polymerized orthorhombic A1C60 are studied. A mean-field theory for the equilibrium phases is developed using an Ising model and a classical Heisenberg model to describe the competition between inter- and intra-chain magnetic order in the solid. In the Ising model, the limiting commensurate one-dimensional and thr

Ph. Ghosez, X. Gonze, Ph. Lambin, J. -P. Michenaud

The Born effective charge tensors of Barium Titanate have been calculated for each of its 4 phases. Large effective charges of Ti and O, also predicted by shell model calculations and made plausible by a simplified model, reflect the partial covalent character of the chemical bond. A band by band decomposition confirms that orbital hybridization is not restr

Supriya Kar, Jnanadeva Maharana

We present a systematic study of high energy scattering of non-abelian gauge particles in (3+1) dimensional Einstein gravity using semi-classical techniques of Verlinde and Verlinde. It is shown that the BRST gauge invariance of the Yang-Mills action in presence of quantum gravity at Planckian energy regime is maintained and the vertex operator is invariant

L. Crane, D. Yetter

We show that reasonably well behaved 3d and 4D TQFts must contain certain algebraic structures. In 4D, we find both Hopf categories and trialgebras.

A. Mukherjee

We discuss the properties of the large phase space of the genus-0 topological minimal $A_{k + 1}$ model coupled to 2d topological gravity. The minimal action is perturbed by adding all possible gravitational descendants with non-trivial couplings which form the infinite-dimensional large phase space. Some general identities (valid on the large phase space) a

N. Banerjee, Subir Ghosh

We propose a new model for interacting (electrically charged) anyons, where the 2+1-dimensional Darwin term is responsible for interactions. The Hamiltonian is comparable with the one used previously (in the RPA calculation).

J. Boguszynski, H. D. Dahmen, R. Kretschmer, L. Lukaszuk

The dynamics of massive particles in the collinear high momentum regime is investigated. Methods hitherto exploiting large time asymptotic Hamiltonians in the Dirac picture for the treatment of infrared divergences are adapted to the collinear asymptotic dynamics. The essential role of time ordering of the dressing operators is brought out.

Sumio Ishikawa, Yasuhiro Iwama, Tadashi Miyazaki, Motowo Yamanobe

The Kalb-Ramond action, derived for interacting strings through an action-at-a-distance force, is generalized to the case of interacting p-dimensional objects (p-branes) in D-dimensional space-time. The open p-brane version of the theory is especially taken up. On account of the existence of their boundary surface, the fields mediating interactions between o

N. Aizawa, S. Sachse, H-T. Sato

We discuss quantum algebraic structures of the systems of electrons or quasiparticles on a sphere of which center a magnetic monople is located on. We verify that the deformation parameter is related to the filling ratio of the particles in each case.

N. Itzhaki

We discuss a Gedanken experiment in which we construct a physical coordinate system which covers the universe. Using general properties of quantum gravity we find that the minimum uncertainty of the coordinate system is $\sqrt[5]{R}$ where $R$ is the radius of the universe

N. Itzhaki

We give an indication that gravity coupled to an infinite number of fields might be a renormalizable theory. A toy model with an infinite number of interacting fermions in four-dimentional space-time is analyzed. The model is finite at any order in perturbation theory. However, perturbation theory is valid only for external momenta smaller than $λ^{-\frac{1}

Alok Kumar, Koushik Ray

Entropy for two dimensional extremal black holes is computed explicitly in a finite-space formulation of the black hole thermodynamics and is shown to be zero {\it locally}. Our results are in conformity with the recent one by Hawking et al in four dimensions.

Zhan-Ning Hu, Bo-Yu Hou

{}From the cyclic quantum dilogarithm the shift operator is constructed with $q$ is a root of unit and the representation is given for the current algebra introduced by Faddeev $et ~al$. It is shown that the theta-function is factorizable also in this case by using the star-square equation of the Baxter-Bazhanov model.

Jorge Alfaro, Ricardo Medina, Luis F. Urrutia

We compute the Itzykson-Zuber (IZ) integral for the superunitary group U(m|n). As a consequence, we are able to find the non-zero correlations of superunitary matrices

Stanley J. Brodsky, Felix Schlumpf

We discuss a number of novel applications of Quantum Chromodynamics to nuclear structure and dynamics, such as the reduced amplitude formalism for exclusive nuclear amplitudes. We particularly emphasize the importance of light-cone Hamiltonian and Fock State methods as a tool for describing the wavefunctions of composite relativistic many-body systems and th

L. Kisslinger, Zhenping Li

The isospin mass splittings of the pseudoscalar and vector D and B light-heavy quark system have been calculated using the method of QCD sum rules. Nonperturbative QCD effects are shown to be very small, so that mass splittings arise almost completely from current quark mass splitting and electromagnetic effects, for which a new gauge invariant QED treatment

M. R. Frank, K. L. Mitchell, C. D. Roberts, P. C. Tandy

The $γ^* π^0 \rightarrow γ$ form factor, including the extension off the pion mass-shell, is obtained from a generalized impulse approximation within a QCD-based model field theory known to provide an excellent description of the pion charge form factor. This approach implements dressing of the vertex functions and propagators consistent with dynamical chira

K. Huitu, J. Maalampi, M. Raidal

We review here our study of a supersymmetric left-right model (SLRM). In the model the $R$-parity is spontaneously broken. Phenomenologically novel feature of the model is the occurrance of the doubly charged particles in the Higgs sector, which are possibly light enough to be seen in the next linear collider. Detection of the doubly charged higgsinos in the

T. S. Evans, A. C. Pearson

We argue that the asymptotic condition should not be applied in the derivation of the real time formalism of thermal field theory. It is shown that, contrary to popular belief, the generating functional of time ordered Green functions does not factorise. When no asymptotic condition is applied to the real time formalism, we find that the normal two component

C. -P. Yuan

I discuss strategies for probing CP properties in the top quark system at $e^-e^+$ and hadron Colliders. The magnitudes of CP violation effects predicted by various models are reviewed. I also discuss the potential of various current and future colliders in measuring the CP asymmetry associated with the productions and/or decays of the top quarks.

Marc Kamionkowski, Kim Griest, Gerard Jungman, Bernard Sadoulet

We compare the rate for elastic scattering of neutralinos from various nuclei with the flux of upward muons induced by energetic neutrinos from neutralino annihilation in the Sun and Earth. We consider both scalar and axial-vector interactions of neutralinos with nuclei. We find that the event rate in a kg of germanium is roughly equivalent to that in a $10^

Steven Gottlieb

We extend previous work on finite-size effects with dynamical staggered quarks to the quenched approximation. We again emphasize the large volume limit that is of interest for spectrum calculations which may hope to approach the experimental values. Relying on new calculations at $6/g^2=5.7$ and recent work with weaker couplings, we extrapolate to the contin

H. B. Thacker

The generalization of Lorentz invariance to solvable two-dimensional lattice fermion models has been formulated in terms of Baxter&#39;s corner transfer matrix. In these models, the lattice Hamiltonian and boost operator are given by fermionized nearest-neighbor Heisenberg spin chain operators. The transformation properties of the local lattice fermion opera

Ch. Schlichter, G. S. Bali, K. Schilling

Results of a high statistics study of chromo field distributions around static sources in pure SU(2) gauge theory on lattices of volumes $16^4$, $32^4$, and $48^3\times 64$ at $β=2.5$, $2.635$, and $2.74$ are presented. We establish string formation up to physical distances as large as 2 fm.

G. ~Cella, V. K. ~Mitrjushkin, A. ~Viceré

We study the dependence on $T$ of the static potential $V(T;{\vec R})$ defined from Wilson loops and from Polyakov loop correlators on a finite lattice. For this study we employ a simple model with confinement, and compare with MC results.

Jan Smit, Wai Hung Tang

New results for the rate are presented using the canonical ensemble in the classical approximation on a spatial lattice. We find that the rate at high temperatures is proportional to $T^2$, and strongly dependent on the lattice spacing $a$. We conclude that a better effective action is needed for the classical approximation.

A. Cruz, D. Iniguez, A. Tarancon, L. A. Fernandez

We find a first order Coulomb--Higgs phase transition at moderately large values of the coupling $λ$, and no evidence for a change of order at any finite value of it.

Jon Ivar Skullerud

We report on the status of a study of the quark propagator and quark-gluon vertex in momentum space. Quark propagators have been generated at beta=6.0 using the O(a)-improved Sheikholeslami-Wohlert action and fixed to the Landau gauge. The first results for the quark pole mass and field renormalisation constant are reported, and plans for future work are pre

Juan M. Nieves

We present results of a lattice computation of the matrix elements of the vector and axial-vector currents which are relevant for the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$. The computations are performed in the quenched approximation to lattice QCD on a $24^3 \times 48$ lattice at $β=6.2$ using an $O(a)$-improved fermionic action.

Y. Iwasaki, K. Kanaya, S. Kaya, S. Sakai

The finite temperature transition in QCD is studied using Wilson quarks for the cases of $N_F=2$, 3 and 2+1. For $N_F=2$ the transition is smooth in the chiral limit on both $\nt=4$ and 6 lattices. For $N_F=3$, clear two state signals are observed for $β\leq4.7$ on $8^2\times10 \times4$ and $12^3\times4$ lattices, which implies the transition is first order

R. Enomoto

The differential cross section of $dσ(e^+e^-\to e^+e^-D^{*\pm}X)/dP_T$ was measured using a soft-pion analysis of $D^{*\pm}\to π_s^\pm D^0(\bar{D^0})$ at TRISTAN. The average $\sqrt{s}$ was 58.1 GeV and the integrated luminosity used in this analysis was 198 pb$^{-1}$, respectively.

J. W. Moffat

A dynamical model of the decaying vacuum energy is presented, which is based on Jordan-Brans-Dicke theory with a scalar field $ϕ$. The solution of an evolutionary differential equation for the scalar field $ϕ$ drives the vacuum energy towards a cosmological constant at the present epoch that can give for the age of the universe, $t_0\sim 13.5$ Gyr for $Ω_0=1

David Garfinkle

A numerical simulation is performed of the gravitational collapse of a spherically symmetric scalar field. The algorithm uses the null initial value formulation of the Einstein-scalar equations, but does {\it not} use adaptive mesh refinement. A study is made of the critical phenomena found by Choptuik in this system. In particular it is verified that the cr

Tao Chen, S. Teitel

We carry out simulations of a lattice London superconductor in a magnetic field B, with a finite magnetic penetration length λ. We find that superconducting coherence parallel to B persists into the vortex line liquid. We argue that the length scale relevant to this effect is Λ=ϕ_0^2/8πT_m.

Diptiman Sen

We conjecture that a two-dimensional anyon system reduces, when confined to a narrow channel, to a one-dimensional bose gas with a repulsive two-body $δ$-function interaction. We verify this conjecture in first-order perturbation theory near bosons. If the channel width is reduced to zero, the one-dimensional system is fermionic for all anyons other than bos

Michel Ramin, Bertrand Reulet, Helene Bouchiat

We have computed persistent currents in a disordered mesoscopic ring in the presence of small electron-electron interactions, treated in first order perturbation theory. We have investigated both a contact (Hubbard) and a nearest neighbour interaction in 1D and 3D. Our results show that a repulsive Hubbard interaction produces a paramagnetic contribution to

P. -A. Bares

We propose a simple idea to construct 1D integrable models with impurities. We illustrate the strategy for a supersymmetric $t-J$ Hamiltonian in considerable detail. The impurity comprises the local deformation of the hopping and exchange integrals as well as a three-body charge-current interactions on neighboring sites. We explore the thermodynamic properti

Hans-Benjamin Braun

The magnetization reversal rate via thermal creation of soliton pairs in quasi-1D ferromagnetic systems is calculated. Such a model describes e.g. the time dependent coercivity of elongated particles as used in magnetic recording media. The energy barrier that has to be overcome by thermal fluctuations corresponds to a soliton-antisoliton pair whose size dep

Hans-Benjamin Braun

Soliton excitations and their stability in anisotropic quasi-1D ferromagnets are analyzed analytically. In the presence of an external magnetic field, the lowest lying topological excitations are shown to be either soliton-soliton or soliton-antisoliton pairs. In ferromagnetic samples of macro- or mesoscopic size, these configurations correspond to twisted o

S. D. Watt, A. J. Roberts

Taylor&#39;s model of dispersion simply describes the long-term spread of material along a pipe, channel or river. However, often we need multi-mode models to resolve finer details in space and time. Here we construct zonal models of dispersion via the new principle of matching their long-term evolution with that of the original problem. Using centre manifol

N. D. Whelan

We study the scattering resonances between two confocal hyperbolae and show that the spectrum is dominated by the effect of a single periodic orbit. There are two distinct cases depending on whether the orbit is geometric or diffractive. A generalization of periodic orbit theory allows us to incorporate the second possibility. In both cases we also perform a

E. J. Kerins, B. J. Carr

If compact baryonic objects contribute significantly to the dark matter in our Galaxy, their mass function will present vital clues for galaxy formation theories and star formation processes in the early Universe. Here we discuss what one might expect to learn about the mass function of Galactic dark matter from microlensing and from direct searches in the i

K. Z. Stanek, G. R. Knapp, K. Young, T. G. Phillips

We present maps at $20&#39;&#39;$ resolution of the molecular emission around 18 evolved stars (14~asymptotic giant branch stars, one supergiant, two proto-planetary nebulae and one planetary nebula), mostly in the $^{12}$CO(3-2) line. Almost all molecular envelopes appear to be at least marginally resolved at this resolution. A substantial fraction of the m

Philip D. Mannheim

We discuss some implications of the current round of galactic dark matter searches for galactic rotation curve systematics and dynamics, and show that these new data do not invalidate the conformal gravity program of Mannheim and Kazanas which has been advanced as a candidate alternative to both the standard second order Newton-Einstein theory and the need f

S. R. Kulkarni, K. Matthews, G. Neugebauer, I. N. Reid

The soft gamma-ray repeater (SGR) 1806$-$20 is associated with the center-brightened non-thermal nebula G~10.0$-$0.3, thought to be a plerion. As in other plerions, a steady \Xray\ source, AX~1805.7$-$2025, has been detected coincident with the peak of the nebular radio emission. Vasisht et al.\ have shown that the radio peak has a core-jet appearance, and a

Wayne M. Raskind

We define a filtration on the Chow groups of a smooth projective variety X over a field k by using the cycle map into continuous l-adic etale cohomology. The main theorem says that if k is a function field in one variable over a finite field, this filtration for zero cycles is of length at most one modulo the kernel of the cycle map.

Max Tegmark, Emory Bunn

More than a dozen papers analyzing the COBE data have now appeared. We review the different techniques and compare them to a ``brute force&#34; likelihood analysis where we invert the full 4038 x 4038 Galaxy-cut pixel covariance matrix. This method is optimal in the sense of producing minimal error bars, and is a useful reference point for comparing other an

S. R. Corley, O. W. Greenberg

We consider the nonrelativistic quantum mechanics of a model of two spinless fermions interacting via a two-body potential. We introduce quantum fields associated with the two particles as well as the expansion of these fields in asymptotic ``in&#39;&#39; and ``out&#39;&#39; fields, including such fields for bound states, in principle. We limit our explicit

Angelica de Oliveira-Costa, George F. Smoot

The cosmic microwave background (CMB) is a unique probe of cosmological parameters and conditions. There is a connection between anisotropy in the CMB and the topology of the Universe. Adopting a universe with the topology of a 3-Torus, or a universe where only harmonics of the fundamental mode are allowed, and using 2-years of COBE/DMR data, we obtain const

G. W. Gibbons, Alan R. Steif

Solutions to the Yang-Mills field equations which describe exploding or imploding shells of gauge field and which may serve as approximations to the exploding sphaleron are discussed. The solutions are conformally related to $SO(2)\times SO(4)$ invariant Yang-Mills solutions. The behavior of fermions in the gauge field background and higher gauge groups are

Laszlo E. Szabo

Two problems will be considered: the question of hidden parameters and the problem of Kolmogorovity of quantum probabilities. Both of them will be analyzed from the point of view of two distinct understandings of quantum mechanical probabilities. Our analysis will be focused, as a particular example, on the Aspect-type EPR experiment. It will be shown that t

S. R. Vatsya

The action principle is frequently used to derive the classical equations of motion. The action may also be used to associate group elements with curves in the space-time manifold, similar to the gauge transformations. The action principle is shown here to be an equivalence relation between the infinitesimal elements so defined for a collection of closed cur

J. M. Figueroa-O&#39;Farrill

Let G be a finite-dimensional Lie algebra (not necessarily semisimple). It is known that if G is self-dual (that is, if it possesses an invariant metric) then there is a canonical N=1 superconformal algebra associated to its N=1 affinization---that is, it admits an N=1 (affine) Sugawara construction. Under certain additional hypotheses, this N=1 structure ad

O. M. Del Cima, F. A. B. Rabelo de Carvalho

Complex vector fields with Maxwell, Chern-Simons and Proca terms are minimally coupled to an Abelian gauge field. The consistency of the spectrum is analysed and 1-loop quantum corrections to the self-energy are explicitly computed and discussed. The incorporation of 2-loop contributions and the behaviour of tree-level scattering amplitudes in the limit of h

L. K. Wickham, J. P. Sethna

We study electromigration in a driven diffusive lattice gas (DDLG) whose continuous Monte Carlo dynamics generate higher particle mobility in areas with lower particle density. At low vacancy concentrations and low temperatures, vacancy domains tend to be faceted: the external driving force causes large domains to move much more quickly than small ones, prod

Jan Ambjorn

Some of the recent developments in the theory of random surfaces and simplicial quantum gravity is reviewed. For 2d quantum gravity this includes the failure of Regge calculus, our improved understanding of the $c>1$ regime, some surprises for q-state Potts models with $q > 4$, attempts to use renormalization group techniques, new critical behavior of random

Guo-Hong Wu

In extended technicolor (ETC) theories, while the sideways ETC boson exchange decreases the width $Γ_b \equiv Γ(Z\rightarrow b \bar{b})$, the flavor-diagonal ETC boson exchange tends to increase it, and the ETC-corrected $R_b \equiv Γ_b / Γ_{\mbox{\footnotesize had}}$ value could agree with recent measurements. The $τ$ asymmetry parameter may also increase i

Ubaldo Tambini, Roberto Onofrio, Carlo Presilla

The influence of continuous measurements of energy with a finite accuracy is studied in various quantum systems through a restriction of the Feynman path-integrals around the measurement result. The method, which is equivalent to consider an effective Schrödinger equation with a non-Hermitian Hamiltonian, allows one to study the dynamics of the wavefunction

Gustav W. Delius, Mark D. Gould, Jon R. Links, Yao-Zhong Zhang

The type-I quantum superalgebras are known to admit non-trivial one-parameter families of inequivalent finite dimensional irreps, even for generic $q$. We apply the recently developed technique to construct new solutions to the quantum Yang-Baxter equation associated with the one-parameter family of irreps of $U_q(gl(m|n))$, thus obtaining R-matrices which d

L. Bonora, C. P. Constantinidis, C. S. Xiong

We compute exact solutions of two--matrix models, i.e. detailed genus by genus expressions for the correlation functions of these theories, calculated without any approximation. We distinguish between two types of models, the unconstrained and the constrained ones. Unconstrained two--matrix models represent perturbations of $c=1$ string theory, while the con

F. J. Carrera, X. Barcons, J. A. Butcher, A. C. Fabian

We present here the results of cross-correlating the X-ray background measured by Ginga in the 2-10 keV band with several catalogues of extragalactic objects. Positive signals with an amplitude of a few per cent have been found for some catalogues implying that some fraction of the X-ray background is produced either by the class of catalogued sources or by

C. Bruder, A. van Otterlo, G. T. Zimanyi

The phenomenology of Josephson tunnel junctions between unconventional superconductors is developed further. In contrast to s-wave superconductors, for d-wave superconductors the direction dependence of the tunnel matrix elements that describe the barrier is relevant. We find the full I-V characteristics and comment on the thermodynamical properties of these

N. D. Lambert

In this paper we construct topological sigma models which include a potential and are related to twisted massive supersymmetric sigma models. Contrary to a previous construction these models have no central charge and do not require the manifold to admit a Killing vector. We use the topological massive sigma model constructed here to simplify the calculation