July 1995 arXiv papers — page 6

P. S. Montague

Following on from recent work describing the representation content of a meromorphic bosonic conformal field theory in terms of a certain state inside the theory corresponding to a fixed state in the representation, and using work of Zhu on a correspondence between the representations of the conformal field theory and representations of a particular associat

H. Kleinert

Recently-developed variational perturbation expansions converge exponentially fast for positive coupling constants. They do not, however, possess the correct left-hand cut in the complex coupling constant plane, implying a wrong large-order behavior of their Taylor expansion coefficients. We correct this deficiency and present a method of resumming divergent

Chong-Sun Chu, Pei-Ming Ho, Bruno Zumino

In a recent paper the quantum 2-sphere $S^2_q$ was described as a quantum complex manifold. Here we consider several copies of $S^2_q$ and derive their braiding commutation relations. The braiding is extended to the differential and to the integral calculus on the spheres. A quantum analogue of the classical anharmonic ratio of four points on the sphere is g

A. A. Vladimirov

We report some observations concerning two well-known approaches to construction of quantum groups. Thus, starting from a bialgebra of inhomogeneous type and imposing quadratic, cubic or quartic commutation relations on a subset of its generators we come, in each case, to a q-deformed universal enveloping algebra of a certain simple Lie algebra. An interesti

A. Kazarnovski-Krol

We analyze the situation which is related to zonal spherical functions of type $A_n$ and obtain a generalization of Selberg integral.

Francisco Melo, Paul Umbanhowar, Harry L. Swinney

Experiments on vertically oscillated granular layers in an evacuated container reveal a sequence of well-defined pattern bifurcations as the container acceleration is increased. Period doublings of the layer center of mass motion and a parametric wave instability interact to produce hexagons and more complicated patterns composed of distinct spatial domains

S. V. Efremov, E. Ya. Paryev

The experimental data on the production of $K^-$-mesons in pp-collisions are analyzed and a method of the unified description of these data in a broad energy range for primary protons is proposed. The $K^-$-mesons production in pA-collisions is considered. The simple formulas for inclusive cross sections of the $K^-$ production in these collisions are given.

Jorge Piekarewicz

We examine the effect of isospin-violating meson-nucleon coupling constants on low-energy pion-nucleon scattering. We compute the couplings in the context of a nonrelativistic quark model. The difference between the up and down constituent masses induces a coupling of the neutral pion to the proton that is slightly larger than the corresponding one for the n

E. Vinteler

We propose a possible resolution for the problem of why the semicircular law is not observed, whilst the random matrix hypothesis describes well the fluctuation of energy spectra. We show in the random 2-matrix model that the interactions between the quantum subsystems alter the semicircular law of level density. We consider also other types of interactions

Edwin Langmann

I discuss examples where basic structures from Connes' noncommutative geometry naturally arise in quantum field theory. The discussion is based on recent work, partly collaboration with J. Mickelsson.

B Basu-Mallick, Anjan Kundu

An algebraic construction more general and intimately connected with that of Faddeev$^1$, along with its application for generating different classes of quantum integrable models are summarised to complement the recent results of ref. 1 ( L.D. Faddeev, {\it Int. J. Mod. Phys. } {\bf A10}, 1845 (1995) ).

F. M. C. Witte

In this paper the classical limit of relativistic transport theories for spin 1/2 fermions is examined through a comparison with the classical kinetic theory derived from N=1 supersymmetric classical mechanics. The conclusion is that in the classical limit spindensities, i.e. the axial-vector contribution to the relativistic Wigner-function, vanishes and dip

Xiangdong Ji

I discuss a scheme to match perturbative and non-perturbative physics with power accuracy in the heavy-quark effective theory. I elaborate on two important aspects of the scheme: 1) a multi-loop subtraction of soft contributions from the perturbation series in the pole mass, 2) a perturbative regularization of the linearly-divergent heavy-quark self-energy i

R. D. Ball, S. Forte

We discuss how momentum conservation is implemented in perturbative computations based on expansions of anomalous dimensions appropriate at small $x$. We show that for any given choice of $F_2$ coefficient functions there always exists a factorization scheme where the gluon is defined in such a way that momentum is conserved at next to leading order.

A. V. Kotikov

The paper presents the QCD description of the small $x$ behaviour of parton distribution functions in the leading twist of Wilson operator product expansion. The smooth transition between the cases of the soft and hard Pomerons is obtained. The results are in qualitative agreement with deep inelastic experimental data.

M. Knecht, B. Moussallam, J. Stern, N. H. Fuchs

The low-energy $ππ$ amplitude is computed explicitly to two-loop accuracy in the chiral expansion. It depends only on six independent (combinations of) low-energy constants which are not fixed by chiral symmetry. Four of these constants are determined {\it via} sum rules which are evaluated using $ππ$ scattering data at higher energies. Dependence of the low

M. Quiros

Depending on the Higgs-boson and top-quark masses, $M_H$ and $M_t$, the effective potential of the Standard Model can develop a non-standard minimum for values of the field much larger than the weak scale. In those cases the standard minimum becomes metastable and the possibility of decay to the non-standard one arises. Comparison of the decay rate to the no

A. A. Penin, A. A. Pivovarov

We study a new $K\rightarrowππ$ decay channel with gluons in intermediate state which is normally neglected within the factorization framework. Both short-distance and long-distance parts of the amplitude are calculated. The chiral Lagrangian approach is used for obtaining the long-distance contribution. The nonperturbative contribution gives an additional e

Hideo Kodama

This is the first of a series of papers in which a new formulation of quantum theory is developed for totally constrained systems, that is, canonical systems in which the hamiltonian is written as a linear combination of constraints $h_α$ with arbitrary coefficients. The main purpose of the present paper is to make clear that classical dynamics of a totally

Ernesto Medina, Mehran Kardar, Rafael Rangel

We investigate the magneto-conductance (MC) anisotropy in the variable range hopping regime, caused by quantum interference effects in three dimensions. When no spin-orbit scattering is included, there is an increase in the localization length (as in two dimensions), producing a large positive MC. By contrast, with spin-orbit scattering present, there is no

Marc Albrecht, Frederic Mila

We study the competition between magnetic order and valence bond order in a two dimensional (2D) frustrated Heisenberg model introduced some time ago by Shastry and Sutherland ({\sc B. Sriram Shastry} and {\sc Bill Sutherland}, {\em Physica} 108{\bf B},1069 (1981) ) for which a configuration of dimers is known to be the ground state in a certain range of par

M. Franco, L. Brey

We analyze the effect that the Coulomb interaction has on the edge excitations of an electron gas confined in a bar of thickness $W$, and in presence of a magnetic field corresponding to filling factor 1 Quantum Hall effect. We find that the long-range interaction between the edges leads the system to a ground state with a quasi-long range order, similar to

A Fledderjohann, M Karbach, K-H Mütter, P Wielath

We compute the energies and transition probabilities for low excitations in the one dimensional antiferromagnetic spin-1/2 Heisenberg model by means of the recursion method. We analyse finite size effects in the euclidian time ($τ$)-representation and compare the resulting estimate for the thermodynamical limit with two parametrizations for the dynamical str

N. A. Modine, Efthimios Kaxiras

We study the spin-$\frac{1}{2}$ Heisenberg antiferromagnet on a series of finite-size clusters with features inspired by the fullerenes. Frustration due to the presence of pentagonal rings makes such structures challenging in the context of quantum Monte-Carlo methods. We use an exact diagonalization approach combined with a truncation method in which only t

Karsten Flensberg, Ben Yu-Kuang Hu

We derive an expression for the drag rate (i.e., interlayer momentum transfer rate) for carriers in two coupled two-dimensional gases to lowest nonvanishing order in the screened interlayer electron--electron interaction, valid for {\sl arbitrary} intralayer scattering mechanisms, using the Boltzmann transport equation. We calculate the drag rate for experim

Jean M. Quashnock

I describe a new likelihood technique, based on counts-in-cells statistics, that I use to analyze repeating in the BATSE 1B and 2B catalogues. Using the 1B data, I find that repeating is preferred over non-repeating by 4.3:1 odds, with a well-defined peak at 5-6 repetitions per source. I find that the post-1B data are consistent with the repeating model infe

M. S. Brotherton

Moderate-resolution spectra of the H$β$--[O III] $λ$5007 region have been obtained for 41 radio-loud quasars in order to investigate relationships among their broad- and narrow-line profiles, radio structures, and X-ray properties. Spectra from the literature have been included to form a data set of 60 radio-loud quasars. A variety of statistical analyses ha

M. G. Baring

The modelling of gamma-ray burst (GRB) spectra has considerable potential for increasing the understanding of these enigmatic sources. A diversity of ideas and analyses has been generated over the last two decades to explain line features and continuum shapes, encompassing both older galactic neutron star and ``new age'' cosmological source models. T

Riccardo Rattazzi

I consider the superfield derivation of the effective theory of softly broken supersymmetry below the GUT scale. I point out the role of supergauge invariance in determining the form of the result, which is rather restricted in interesting classes of models. As an example I discuss sfermion mass splittings for matter embedded in a single GUT multiplet. Inter

P. S. Montague

We consider representations of meromorphic bosonic chiral conformal field theories, and demonstrate that such a representation is completely specified by a state within the theory. The necessary and sufficient conditions upon this state are derived, and, because of their form, we show that we may extend the representation to a representation of a suitable la

A. V. Ilinskaia, K. N. Ilinski

The generalization of Agranovich-Toshich representation of paulion operators in terms of bosonic ones for the case of truncated oscillators of higher ranks is represented. We use this generalization to introduce a new constraint free bosonic description of truncated oscillator systems. The corresponding functional integral representations for thermodynamic q

I. A. Shovkovy, V. M. Turkowski

The effective dimensional reduction of fermion-antifermion pairing dinamics in Nambu-Jona-Lasinio model in external chromomagnetic field is considered. It is shown that such a field causes the reduction of the space dimension by one unit in contrast to an ordinary magnetic field which reduces it by two units. The enhancement of the dynamical chiral symmetry

Mark Dickinson

New ground-based and HST observations of distant clusters make it possible to trace the history of E/S0 galaxies to lookback times of ~10 $h_{50}^{-1}$ Gyr. The data strongly favor a scenario in which cluster ellipticals formed very early with a narrow spread in ages. By z = 1.2 there are changes in color and luminosity consistent with simple passive evoluti

Janusz Kaluzny, Wojciech Krzeminski, Beata Mazur

We report discovery of two contact binaries and two detached eclipsing binaries in the central part of NGC 2243.

Lennox L. Cowie, Antoinette Songaila

We report new upper limits on any possible long-term time variation of the ratio of the electron to proton masses, $(m_e/m_p)$, the fine-structure constant, ($α$), and the quantity $α^2 g_p(m_e/m_p)$, where $g_p$ is the proton gyromagnetic ratio. These limits are based on extremely high precision observations of H$_2$, Si$^{3+}$, C$^0$ and H$^0$ in high-reds

Otto C. W. Kong

We give a preliminary report of a new quark mass matrix model basing on a $SU(5)\otimes SU(5)\otimes Q_{12}$ symmetry embedding into a fully gauged $SU(5)\otimes SU(5)\otimes SU(2)$.~\cite{fk} The two $SU(5)$'s contain the standard SUSY $SU(5)$ as a diagonal subgroup, while the $Q_{12}$ or $SU(2)$ is horizontal. Starting by assuming a judiciously-chosen

Y. Alhassid, G. F. Bertsch, D. J. Dean, S. E. Koonin

We present Shell Model Monte Carlo calculations for nuclei within the full major shell 50-82 for both protons and neutrons. The interaction is determined solely by self-consistency and odd-even mass differences. The methods are illustrated for ${}^{124}$Sn, ${}^{128}$Te and ${}^{124}$Xe. We calculate shape distributions, moments of inertia and pairing correl

G. E. Brown, Mannque Rho

A unified treatment of normal nuclear matter described by Walecka's mean field theory and kaon condensed matter described by chiral perturbation theory is proposed in terms of mean fields of an effective chiral Lagrangian. The BR scaling is found to play a key role in making the link between the ground state properties of nuclear matter and the fluctuati

Saharon Shelah

Let us draw a graph R on {0,1,...,n-1} by having an edge {i,j} with probability p_(|i-j|), where sum_i p_i is finite and let M_n=(n,<,R). For a first order sentence psi let a^n_psi be the probability of ``M_n satisfies psi&#39;&#39;. We prove that the limit of a^n_psi-a^{n+1}_psi is 0, as n goes to infinity.

Y. Meurice, G. Ordaz, V. G. J. Rodgers

Using a renormalization group method, we calculate 800 high-temperature coefficients of the magnetic susceptibility of the hierarchical Ising model. The conventional quantities obtained from differences of ratios of coefficients show unexpected smooth oscillations with a period growing logarithmically and can be fitted assuming corrections to the scaling law

A. A. Grib, R. R. Zapatrin

The collection of all topologies on the set of three points is studied treating the topology as quantum-like observable. It turns out to be possible under the assumption of the asymmetry between the spaces of bra- and ket-vectors. The analogies between the introduced topologimeter and the Stern-Gerlach experiments are outlined.

L. S. Levitov, A. V. Shytov

We argue that the tunneling between two 2D electron gases in a weak magnetic field is of resonance character, and involves a long lifetime excitonic state of an electron and hole {\it uniformly spread} over cyclotron orbits. We find that the tunneling gap is linear in the field, in agreement with the experiment, and is anomalously sensitive to the electron d

Klaus Frahm, Axel Müller--Groeling

Using the supersymmetry method we analytically calculate the local density of states, the localiztion length, the generalized inverse participation ratios, and the distribution function of eigenvector components for the superposition of a random band matrix with a strongly fluctuating diagonal matrix. In this way we extend previously known results for ordina

F. Tzschichholz, A. Hansen, S. Roux

We study the roughness of randomly crumpled elastic sheets. Based on analytical and numerical calculations, we find that they are self affine with a roughness exponent equal to one. Such crumpling occurs {\it e.g.\/} when wet paper dries. We also discuss the case of correlated crumpling, which occurs in connection with flattening of randomly folded paper.

A. C. Fabian, K. Nandra, C. S. Reynolds, W. N. Brandt

The X-ray spectrum obtained by Tanaka et al from a long observation of the active galaxy MCG$-6-30-15$ shows a broad iron K$α$ line skewed to low energies. The simplest interpretation of the shape of the line is that it is due to doppler and gravitational redshifts from the inner parts of a disk about a massive black hole. Similarly broad lines are evident i

J. M. Prats, F. Lopez-Aguilar

We address the Kondo lattice with one conduction band by introducing a representation of the (s=1/2) local moments consisting in an s=1 triplet of spin fluctuations of a vacuum state. The excitation of these fluctuations by the electronic field results in the creation of new fermionic modes. It is shown that, in the one-electron case, the zero-temperature sp

Z. Z. Xing

By use of current experimental data, we carry out an isospin analysis of the weak decays $B\rightarrow Dπ, D^{*}π$ and $Dρ$. It is found that only in $B\rightarrow Dρ$ the strong phase shift of two different isospin amplitudes can be approximately neglected. We derive some useful relations between the $CP$-violating measurables and the weak and strong transi

L. K. Patel, N. Dadhich, A. Beesham

We attempt to solve the Einstein equations for string dust and null flowing radiation for the general axially symmetric metric, which we believe is being done for the first time. We obtain the string-dust and radiating generalizations of the Kerr and the NUT solutions. There also occurs an interesting case of radiating string-dust which arises from string-du

Pushpalatha C. Bhat

We report on the search for the top quark in proton-antiproton collisions at the Fermilab Tevatron in the di-lepton and lepton+jets channels using multivariate methods. An H-matrix analysis of the e-mu data corresponding to an integrated luminosity of about 13.5 pb-1 yields one event with a likelihood to be a top event (assuming top mass of 180 GeV/c**2) tha

Dorje Brody, Bernhard Meister

For a given ensemble of $N$ independent and identically prepared particles, we calculate the binary decision costs of different strategies for measurement of polarised spin 1/2 particles. The result proves that, for any given values of the prior probabilities and any number of constituent particles, the cost for a combined measurement is always less than or

Israel Gelfand, Vladimir Retakh

A version of the classical Vieta theorem for free noncommuting variables is given. It leads to a new start in a construction of noncommutative symmetric functions

C. A. Bertulani, L. F. Canto, M. S. Hussein, A. F. R. de Toledo Piza

We study the effects of channel coupling in the excitation dynamics of giant resonances in relativistic heavy ions collisions. For this purpose, we use a semiclassical approximation to the Coupled-Channels problem and separate the Coulomb and the nuclear parts of the coupling into their main multipole components. In order to assess the importance of multi-st

Derek F. Holt

This note contains a report of a proof by computer that the Fibonacci group F(2,9) is automatic. The automatic structure can be used to solve the word problem in the group. Furthermore, it can be seen directly from the word-acceptor that the group generators have infinite order, which of course implies that the group itself is infinite.

Alexey Myasnikov, Vladimir Remeslennikov

For a CSA group $G$ and a wide class of abelian groups $A$ we give an explicit construction for the tensor $A$-completion of $G$ using free products with amalgamations. We apply the obtained results to the study of basic properties of $A$-free groups. In particular, canonical and reduced forms of elements in $A$-free groups are introduced, and then commuting

Ryan Rohm, Indranil Dasgupta

The properties of cosmic strings have been investigated in detail for their implications in early-universe cosmology. Although many variations of the basic structure have been discovered, with implications for both the microscopic and macroscopic properties of cosmic strings, the cylindrical symmetry of the short-distance structure of the string is generally

A. K Kapoor, Pankaj Sharan

A method for deriving the Schrodinger equation for Lagrangian path integral with scaling of local time is given.

K. H. Kim, Dae-Yup Song

We study the nonlinear $O(N)$ sigma model on $S^2$ with the gravitational coupling term, by evaluating the effective potential in the large-$N$ limit. It is shown that there is a critical curvature $R_c$ of $S^2$ for any positive gravitational coupling constant $ξ$, and the dynamical mass generation takes place only when $R<R_c$. The critical curvature is an

G. Bimonte, G. Lozano

We study the effect of next-to-leading order contributions on the phenomenon of symmetry non-restoration at high temperature in an $O(N_1)\times O(N_2)$ model.

Marcelo Gleiser

The dynamics of phase transitions plays a crucial rôle in the so-called interface between high energy particle physics and cosmology. Many of the interesting results generated during the last fifteen years or so rely on simplified assumptions concerning the complex mechanisms typical of nonequilibrium field theories. In particular, whenever first order phase

Adam F. Falk, Thomas Mehen

We examine the decays of excited heavy mesons, including the leading power corrections to the heavy quark limit. We find a new and natural explanation for the large deviation of the width of the $D_1(2420)$ from the heavy quark symmetry prediction. Our formalism leads to detailed predictions for the properties of the excited bottom mesons, some of which rece

S. Baumgärtner, H. J. Pirner, K. Königsmann, B. Povh

We calculate the differential cross section for semi-inclusive pion production in electron proton reactions using a model where the physical quark fluctuates with some probability to quark plus pion. The kinematic regions for a determination of this `pion cloud&#39; are evaluated.

D. M. Jensen, J. Madsen

Strangelets with non-zero entropy are studied within the MIT bag model. Explicit account is taken of the constraints that strangelets must be color neutral and have a fixed total momentum. In general, masses increase with increasing entropy per baryon, and the constraints work so as to increase masses further. This has an important destabilizing effect on st

D. V. Semikoz, I. I. Tkachev

We study the kinetic regime of the Bose-condensation of scalar particles with weak $λϕ^4$ self-interaction. The Boltzmann equation is solved numerically. We consider two kinetic stages. At the first stage the condensate is still absent but there is a nonzero inflow of particles towards ${\bf p} = {\bf 0}$ and the distribution function at ${\bf p} ={\bf 0}$ g

Aik Hui Chan, Zhi-zhong Xing

In the context of the standard electroweak model, we emphasize that $B_d\rightarrow D^0_{CP}K_S$ ($D^0_{CP}$ denotes a $CP$ eigenstate of $D^0$ or $\bar{D}^0$) can compete with $B_d\rightarrow π^+π^-$ in studying $CP$ violation and probing the Cabibbo-Kobayashi-Maskawa unitarity triangle. We discuss the measurables of direct and indirect $CP$ asymmetries in

E. S. C. Ching, P. T. Leung, W. M. Suen, K. Young

It is well-known that the dominant late time behavior of waves propagating on a Schwarzschild spacetime is a power-law tail; tails for other spacetimes have also been studied. This paper presents a systematic treatment of the tail phenomenon for a broad class of models via a Green&#39;s function formalism and establishes the following. (i) The tail is govern

E. S. C. Ching, P. T. Leung, W. M. Suen, K. Young

The dynamics of relativistic stars and black holes are often studied in terms of the quasinormal modes (QNM&#39;s) of the Klein-Gordon (KG) equation with different effective potentials $V(x)$. In this paper we present a systematic study of the relation between the structure of the QNM&#39;s of the KG equation and the form of $V(x)$. In particular, we determi

A. Ghosh, P. Mitra

The temperature of an extremal Reissner - Nordstrom black hole is not restricted by the requirement of absence of a conical singularity. It is demonstrated how Kruskal-like coordinates may be constructed corresponding to any temperature whatsoever. A recently discovered stringy extremal black hole which apparently has an infinite temperature is also shown to

L. K. Patel, Naresh Dadhich

We obtain a one parameter class of stationary rotating string cosmological models of which the well-known G$\ddot o $del Universe is a particular case. By suitably choosing the free parameter function, it is always possible to satisfy the energy conditions. The rotation of the model hinges on the cosmological constant which turns out to be negative.

Kiyoshi Shiraishi

We study the interaction of maximally-charged dilatonic black holes at low velocity. We compute the metric on moduli space for three extreme black holes under a simple constraint. The Hamiltonian of the multi-black hole system of $O(v^2)$ is also calculated for the $a=1$ and $a=1/\sqrt{3}$ cases, where $a$ is the dilaton coupling constant. The behavior of th

Don N. Page

Quantum cosmology is the quantum theory of the entire universe. Although strange at first sight, it is appropriate because (1) our world appears to be fundamentally quantum, (2) the classical description of gravity breaks down at singularities it would give at the beginning of the universe, and (3) our universe has many properties that cannot be explained by

E. Westerberg, A. Furusaki, M. Sigrist, P. A. Lee

Quantum Heisenberg spin chains with random couplings and spin sizes are studied using a real-space renormalization group technique. These systems belong to a new universality class of disordered quantum spin systems realized in {\it e.g.} ${\rm Sr}_3{\rm CuPt}_{1-x}{\rm Ir}_x {\rm O}_6$. The low-energy fixed point is characterized by the formation of weakly

X. C. Xie, Song He

Using finite size calculations on the surface of a sphere we study the topological (skyrmion) excitation in quantum Hall system with spin degree of freedom at filling factors around $ν=1$. In the absence of Zeeman energy, we find, in systems with one quasi-particle or one quasi-hole, the lowest energy band consists of states with $L=S$, where $L$ and $S$ are

G. Varelogiannis, A. Perali, E. Cappelluti, L. Pietronero

Momentum decoupling arises when small momentum transfer processes dominate the electron-phonon scattering and implies that anisotropies in superconductivity are driven by the anisotropies of the density of states. Considering an isotropic s-wave interaction in the momentum decoupling regime we give a natural simultaneous explanation to various aspects of ARP

Yanmin Li

The effect of conduction electron interactions for an Anderson impurity is investigated in one dimension using a scaling approach. The flow diagrams are obtained by solving the renormalization group equations numerically. It is found that the Anderson impurity case is different from its counterpart -- the Kondo impurity case even in the local moment region.

Qimiao Si

We study both the spin and electrical conductivities in models of relevance to the high $T_c$ cuprates. These models describe metallic states with or without spin-charge separation. We demonstrate that, given a linear in temperature dependence of the electrical resistivity, the spin resistivity should also be linear in temperature in the absence of spin-char

Alain F. Veilleux, Anne-Marie Daré, Liang Chen, Y. M. Vilk

A combination of analytical approaches and quantum Monte Carlo simulations is used to study both magnetic and pairing correlations for a version of the Hubbard model that includes second-neighbor hopping $t^{\prime }=-0.35t$ as a model for high-temperature superconductors. Magnetic properties are analyzed using the Two-Particle Self-Consistent approach. The

Wayne Hu, Martin White

We present a new, more powerful and accurate, analytic treatment of cosmic microwave background (CMB) anisotropies in the weakly coupled regime. Three applications are presented: gravitational redshifts in a time dependent potential, the Doppler effect in reionized scenarios, and the Vishniac effect. The Vishniac effect can dominate primary anisotropies at s

M. G. Baring, A. K. Harding

The exotic quantum process of photon splitting has great potential to explain the softness of emission in soft gamma repeaters (SGRs) if they originate in neutron stars with surface fields above the quantum critical field $B_{\rm cr}=4.413\times 10^{13}$Gauss. Splitting becomes prolific at such field strengths: its principal effect is to degrade photon energ

Stacy S. McGaugh

I review the evolutionary status of the field populations of starbursting dwarf galaxies and low surface brightness spirals. Particular attention is paid to the long standing problem of the progenitors for star burst galaxies, which may be related to a population of small, low surface brightness dwarfs. Larger low surface brightness spirals are known to evol

A. P. Martin, A. C. Davis

Primordial magnetic fields seem to be a generic relic of phase transitions in the early universe. We consider a primordial electromagnetic field formed as a result of a second-order phase transition, and show that it is stable to thermal fluctuations in the period immediately following. We also show how such a field arises in first order phase transitions. I

G. Clementini, E. Carretta, R. Gratton, R. Merighi

We used moderately high-resolution, high S/N spectra to study the chemical composition of 10 field ab-type RR Lyrae stars. A new temperature scale was determined from literature Infrared Flux Method measures of subdwarfs and the Kurucz (1992) model atmospheres, and used to calibrate colors for both dwarfs and RR Lyraes. The applicability of Kurucz (1992) mod

Lennox L. Cowie, Esther M. Hu, Antoinette Songaila

We present very deep $HST$ WFPC2 images in the F814W filter of two Hawaii Survey fields, SSA13 and SSA22. Using these data with previous ground-based imaging and spectroscopy, we compare the colors, star-forming properties and morphologies of the faintest galaxies with a reference sample of bright nearby galaxies and analyze the changes in field galaxy morph

M. J. Iqbal, Xuemin Jin, Derek B. Leinweber

Based on the analysis of both Borel and Finite-Energy QCD sum rules, the inclusion of finite mesonic widths leads to a dramatic effect on the predictions for the momentum dependence of the rho-omega mixing matrix element. It is shown that the rho-omega mixing matrix element traditionally discussed in the literature, has the same sign and similar magnitude in

Kevin Krisciunas, Richard A. Crowe, Kenneth D. Luedeke, Mavourneen Roberts

$γ$ Doradus stars are photometrically variable early F-type stars on or just above the main sequence in the Hertzsprung-Russell Diagram. They vary by as much as 0.1 mag on time scales an order of magnitude slower than the fundamental radial pulsation period. These brightness variations are presumably due to non-radial gravity-mode pulsations. We obtained hig

Wolfgang Menzel

Previous approaches to robustness in natural language processing usually treat deviant input by relaxing grammatical constraints whenever a successful analysis cannot be provided by ``normal&#39;&#39; means. This schema implies, that error detection always comes prior to error handling, a behaviour which hardly can compete with its human model, where many er

Jacques Soffer

We summarize some theoretical issues, which have been considered of special importance in the discussions of the above working group session.

B. Abdesselam, J. Beckers, A. Chakrabarti, N. Debergh

We propose a new structure ${\cal U}^{r}_{\displaystyle{q}}(sl(2)) $. This is realized by multiplying $δ$ ($q=e^δ$, $δ\in \CC$) by $θ$, where $θ$ is a real nilpotent -paragrassmannian- variable of order $r$ ($θ^{r+1}=0$) that we call the order of deformation, the limit $r\rightarrow \infty$ giving back the standard ${\cal U}_{\displaystyle {q}}(sl(2))$. In p

Junichiro Kishine

The dynamical spin fluctuations in a two-dimensional square lattice in its paramagnetic phase are examined within the framework of Random Phase Approximation(RPA). Itinerant carriers with spin interact with each other via an antiferromagnetic Heisenberg interaction. Then there appear three fundamental scattering processes;a) scattering between parallel spins

J. Van der Jeugt, R. Jagannathan

For the quantum group $GL_{p,q}(2)$ and the corresponding quantum algebra $U_{p,q}(gl(2))$ Fronsdal and Galindo explicitly constructed the so-called universal $T$-matrix. In a previous paper we showed how this universal $T$-matrix can be used to exponentiate representations from the quantum algebra to get representations (left comodules) for the quantum grou

Yang Lu, R. D. Amado

We study two pion correlations from Skyrmion and antiSkyrmion collision, using the product ansatz and an approximate random grooming method for nucleon projection. The spatial-isospin coupling inherent in the Skyrme model, along with empirical averages, leads to correlations not only among pions of like charges but also among unlike charge types.

C. Ciofi degli Atti, S. Simula

By analysing the high momentum features of the nucleon momentum distribution in light and complex nuclei, it is argued that the basic two-nucleon configurations generating the structure of the nucleon Spectral Function at high values of the nucleon momentum and removal energy, can be properly described by a factorised ansatz for the nuclear wave function, wh

V. R. Pandharipande, C. J. Pethick, V. Thorsson

We discuss the role of kaon-nucleon and nucleon-nucleon correlations in kaon condensation in dense matter. Correlations raise the threshold density for kaon condensation, possibly to densities higher than those encountered in stable neutron stars.

Kazuharu Koide, Hiroaki Kouno, Akira Hasegawa, Masahiro Nakano

A method of cut-off regularization is proposed to evaluate vacuum corrections in nuclear matter in the framework of the Hartree approximation. Bulk properties of nuclear matter calculated by this method are a good agreement with results analyzed by empirical values. The vacuum effect is quantitatively evaluated through a cut-off parameter and its role for sa

Derek F. Holt

This paper provides a description of the algorithms employed by the Warwick AUTOMATA package for calculating the finite state automata associated with a short-lex automatic group. The aim is to provide an overview of the whole process, rather than concentrating on technical details, which have been already been published elsewhere. A number of related progra

Walter Neumann, Lawrence Reeves

Thurston has claimed (unpublished) that central extensions of word hyperbolic groups by finitely generated abelian groups are automatic. We show that they are in fact biautomatic. Further, we show that every 2-dimensional cohomology class on a word hyperbolic group can be represented by a bounded 2-cocycle. This lends weight to the claim of Gromov that for a

C. Quesne

A few years ago, Matsuo and Cherednik proved that from some solutions of the Knizhnik-Zamolodchikov (KZ) equations, which first appeared in conformal field theory, one can obtain wave functions for the Calogero integrable system. In the present communication, it is shown that from some solutions of generalized KZ equations, one can construct wave functions,

A. Bellini, M. Ciafaloni, P. Valtancoli

By defining a regular gauge which is conformal-like and provides instantaneous field propagation, we investigate classical solutions of (2+1)-Gravity coupled to arbitrarily moving point-like particles. We show how to separate field equations from self-consistent motion and we provide a solution for the metric and the motion in the two-body case with arbitrar

A. Bellini, M. Ciafaloni, P. Valtancoli

We construct a non-perturbative, single-valued solution for the metric and the motion of two interacting particles in ($2+1$)-Gravity, by using a Coulomb gauge of conformal type. The method provides the mapping from multivalued ( minkowskian ) coordinates to single-valued ones, which solves the non-abelian monodromies due to particles&#39;s momenta and can b

Hitoshi Sato

New geometrical features of the Landau-Ginzburg orbifolds are presented, for models with a typical type of superpotential. We show the one-to-one correspondence between some of the $(a,c)$ states with $U(1)$ charges $(-1,1)$ and the integral points on the dual polyhedra, which are useful tools for the construction of mirror manifolds. Relying on toric geomet

H. Grosse, C. Klimcik, P. Presnajder

A lattice-type regularization of the supersymmetric field theories on a supersphere is constructed by approximating the ring of scalar superfields by an integer-valued sequence of finite dimensional rings of supermatrices and by using the differencial calculus of non-commutative geometry. The regulated theory involves only finite number of degrees of freedom