February 1995 arXiv papers — page 2

W. Koepf, L. Wilets

We employ a relativistic quark bag picture, the chromo-dielectric soliton model, to discuss the quarks' symmetry structure and momentum distribution in the $N$-$N$ system. Six-quark clusters are constructed in a constrained mean-field calculation. The corresponding Hamiltonian contains not only an effective interaction between the quarks and a scalar fie

Witold Skiba

We investigate decays of the scalar bound state present in the Abbott-Farhi model. We show that decays with photons in the final state may have large branching ratios. We also show that operators coupling the scalar particle to two photons or to a photon and a Z^0 are not seriously constrained by electroweak data, unlike other sectors of the Abbott-Farhi mod

Juan M. Maldacena, Andreas W. W. Ludwig

Several Quantum Impurity problems with four flavors of bulk fermions have zero temperature fixed points that show non fermi liquid behavior. They include the two channel Kondo effect, the two impurity Kondo model, and the fixed point occurring in the four flavor Callan-Rubakov effect. We provide a unified description which exploits the SO(8) symmetry of the

H. C. Spruit

This is an introduction to accretion disk theory, with emphasis on aspects relevant for X-ray Binaries and Cataclysmic Variables. The text corrects some mistakes in an earlier version, which appeared in 'Lives of Neutron Stars', A. Alpar, Ü. Kizilo\u glu and J. van Paradijs (eds.), Kluwer, Dordrecht (NATO ASI series, 1994).

Brian L. Kooiman, Jack O. Burns, Anatoly A. Klypin

This paper presents an angular correlation analysis of the Green Bank 4.85 GHz radio catalog (Gregory \& Condon 1991) of 54,579 sources (S \gsim 25 mJy). The Green Bank catalog is found to be complete to S $\geq$ 35 mJy over 20$^{\circ} \leq δ< 74^{\circ}$, 0$^h \leq α< 24^h$, and Galactic latitude $|b| \geq 10^{\circ}$. The 2-point angular correlation funct

Guinevere Kauffmann

The tightness of the observed colour-magnitude and Mg$_{2}$- velocity dispersion relations for elliptical galaxies has often been cited as an argument against a picture in which ellipticals form by the merging of spiral disks. A common view is that merging would mix together stars of disparate ages and produce a large scatter in these relations. Here I use s

G. A. Luppino, I. M. Gioia

During the course of a gravitational lensing survey of distant, X-ray selected, EMSS clusters of galaxies, we have studied 6 X-ray luminous (Lx > 5x10^44 h_{50}^{-2} erg s^{-1}) clusters at redshifts exceeding z=0.5. All of these clusters are apparently massive. In addition to their high X-ray luminosity, two of the clusters at z~0.6 exhibit gravitationally

Amnon Yekutieli

A Beilinson completion algebra (BCA) A is a complete semilocal algebra over a perfect field k, whose residue fields are high dimensional local fields. In addition A is a semi-topological algebra. The completion of the structure sheaf of an algebraic k-variety along a saturated chain of points is the prototypical example of a BCA. We single out two kinds of h

Bastiaan J. Braams, Charles F. F. Karney

The collision operator for a relativistic plasma is reformulated in terms of an expansion in spherical harmonics. In this formulation the collision operator is expressed in terms of five scalar potentials which are given by one-dimensional integrals over the distribution function. This formulation is used to calculate the electrical conductivity of a uniform

Vladimir V. Kisil

Usually the only difference between relativistic quantization and standard one is that the Lagrangian of the system under consideration should be Lorentz invariant. The standard approaches are logically incomplete and produce solutions with unpleasant properties: negative-energy, superluminal propagation etc. We propose a two-projections scheme of (special)

Lior Goldenberg, Lev Vaidman

All existing quantum cryptosystems use non-orthogonal states as the carriers of information. Non-orthogonal states cannot be cloned (duplicated) by an eavesdropper. In result, any eavesdropping attempt must introduce errors in the transmission, and therefore, can be detected by the legal users of the communication channel. Orthogonal states are not used in q

S. Kuyucak, S. C. Li

The 1/$N$ expansion solutions for the interacting boson model are extended to higher orders using computer algebra. The analytic results are compared with those obtained from an exact diagonalization of the Hamiltonian and are shown to be very accurate. The extended formulas for level energies and E2 transitions will be useful in the analysis of high-spin st

Vladimir V. Kisil, Enrique Ramírez de Arellano

We present a Riesz-like hyperholomorphic functional calculus for a set of non-commuting operators based on the Clifford analysis. Applications to the quantum field theory are described. Keywords: Functional calculus, Weyl calculus, Riesz calculus, Clifford analysis, quantization, quantum field theory. AMSMSC Primary:47A60, Secondary: 81T10

Bernd Esser, Holger Schanz

The dynamical properties of exciton transfer coupled to polarization vibrations in a two site system are investigated in detail. A fixed point analysis of the full system of Bloch - oscillator equations representing the coupled excitonic - vibronic flow is performed. For overcritical polarization a bifurcation converting the stable bonding ground state to a

Ivan Barvik, Bernd Esser, Holger Schanz

We study the interplay between nonlinearity in exciton transport and trapping due to a sink site for the dimer and the trimer with chain configuration by a numerical integration of the discrete nonlinear Schroedinger equation. Our results for the dimer show, that the formation of a self trapped state due to the nonlinear coupling increases the life time of t

Holger Schanz, Uzy Smilansky

We obtained the spectrum of the Sinai billiard as the zeroes of a secular equation, which is based on the scattering matrix of a related scattering problem. We show that this quantization method provides an efficient numerical scheme, and its implementation for the present case gives a few thousands of levels without encountering any serious difficulty. We u

Yasuyuki Kachi

Let $g : X \to Y$ be the contraction of an extremal ray of a smooth projective 4-fold $X$ such that $\dim Y=3$. Then $g$ may have a finite number of 2-dimensional fibers. We shall classify those fibers. Especially we shall prove that any two points of such a fiber is joined by a chain of rational curves of length at most 2 with respect to $-K_X$, and that $|

Thomas Appelquist, Myckola Schwetz, Stephen B. Selipsky

We argue that a strongly first order electroweak phase transition is natural in the presence of strong symmetry-breaking interactions, such as technicolor. We demonstrate this using an effective linear scalar theory of the symmetry-breaking sector.

B. A. Faizullaev, M. M. Musakhanov, N. K. Pak

The problem of the higher-loop contributions to the axial anomaly is reexamined by a new method. We demonstrate that these contributions depend on the order of the calculations. If the divergence of the axial current by nonperturbative Fujikawa method is calculated first and then average it over the photon field in the presence of an external photon source,

C. Arvanitis, H. F. Jones, C. S. Parker

The convergence of the linear $δ$ expansion for the connected generating functional of the quantum anharmonic oscillator is proved. Using an order-dependent scaling for the variational parameter $λ$, we show that the expansion converges to the exact result with an error proportional to $\exp(-cN^{1/3})$.

Tamas Fulop

The $SL(2,\R)$ WZNW $\rightarrow$ Liouville reduction leads to a nontrivial phase space on the classical level both in $0+1$ and $1+1$ dimensions. To study the consequences in the quantum theory, the quantum mechanics of the $0+1$ dimensional, point particle version of the constrained WZNW model is investigated. The spectrum and the eigenfunctions of the obt

Ka Yi Ng

Given a positive integer $n$, we say that two knots are $V_n$-equivalent if they have the same Vassiliev invariants of order $\le n$. We showed that the $V_n$-equivalence classes of ribbon knots form a group, the operation being induced by the connected sums of knots. The group is free abelian and its rank is equal to the dimension of the space of primitive

Karl Glazebrook, J. A. Peacock, L. Miller, C. A. Collins

We present a redshift survey of 124 galaxies, from an imaging $K$-band survey complete to $K\simeq 17.3$. The optical-to-infrared colours are consistent with the range expected from synthetic galaxy spectra, although there are some cases of very red nuclei. Our data show no evidence for evolution of the $K$-band luminosity function at $z<0.5$, and the result

M. Cvetic, B. Ovrut, W. A. Sabra

By employing the symmetries of the underlying conformal field theory, the tree-level Kähler potentials for untwisted moduli of the heterotic string compactifications on orbifolds with continuous Wilson lines are derived. These symmetries act linearly on bosonic (toroidal and $E_8\times E_8$ gauge) string coordinates as well as on the untwisted (toroidal and

I. Bandos, A. Nurmagambetov, D. Sorokin, D. Volkov

We consider a formulation of N=1 D=3,4 and 6 superparticle mechanics, which is manifestly supersymmetric on the worldline and in the target superspace. For the construction of the action we use only geometrical objects that characterize the embedding of the worldline superspace into the target superspace, such as target superspace coordinates of the superpar

Hermann Riecke

The dynamics of solitons of the nonlinear Schrödinger equation under the influence of dissipative and dispersive perturbations is investigated. In particular a coupling to a long-wave mode is considered using extended Ginzburg-Landau equations. The study is motivated by the experimental observation of localized wave trains (`pulses&#39;) in binary-liquid con

C. Zhou, H. J. Schulz

We study the magnetic excitations in the spiral phase of the two--dimensional Hubbard model using a functional integral method. Spin waves are strongly renormalized and a line of near--zeros is observed in the spectrum around the spiral pitch $\pm{\bf Q}$. The possibility of disordered spiral states is examined by studying the one--loop corrections to the sp

Jordi París

The nonlocal regularization method, recently proposed in ref.\,\ct{emkw91,kw92,kw93}, is extended to general gauge theories by reformulating it along the ideas of the antibracket-antifield formalism. From the interplay of both frameworks a fully regularized version of the field-antifield (FA) formalism arises, being able to deal with higher order loop correc

J. Speth, V. R. Zoller

We apply the light-cone technique to electroproduction reaction $ep\to eπ^+n$ long considered as a means of measuring the electromagnetic form factor of the pion. We show that the interpretation of the long-standing puzzle of large transverse cross section ($σ_T$) in terms of the $γ^*ρ\to π$ transition on the $ρ$ mesons in the light-cone proton is possible,

Yi-Yen Wu

This paper is motivated by three issues associated with the supersymmetric extension of the standard model: the $\mu$ problem, the possibility of raising the upper bound on the lightest-Higgs mass, and the triviality problem associated with the Higgs sector. A new scheme based on the Higgs-Higgs condensation is proposed, and it is shown that these three issu

Yi-Yen Wu

We study the implications of the triviality problem for the Higgs masses and other relevant parameters in the Next to Minimal Supersymmetric Standard Model (NMSSM). By means of triviality, a new way to constrain parameters is proposed, and therefore we are able to derive triviality bounds on the heaviest-Higgs mass, the lightest-Higgs mass, the soft SUSY- br

Lev Tsimring, Herbert Levine, Igor Aranson, Eshel Ben-Jacob

We study the formation of spot patterns seen in a variety of bacterial species when the bacteria are subjected to oxidative stress due to hazardous byproducts of respiration. Our approach consists of coupling the cell density field to a chemoattractant concentration as well as to nutrient and waste fields. The latter serves as a triggering field for emission

Dean L. Welch

In a recent paper it was suggested that some multi-black hole solutions in five or more dimensions have horizons that are not smooth. These black hole configurations are solutions to $d$-dimensional Einstein gravity (with no dilaton) and are extremally charged with a magnetic type $(d-2)$-form. In this work these solutions will be investigated further. It wi

V. E. Rochev, P. A. Saponov

A new approximation scheme for non-perturbative calculations in a quantum field theory is proposed. The scheme is based on investigation of solutions of the Schwinger equation with its singular character taken into account. As a necessary supplementary boundary condition the Green functions&#39; connected structures correspondence principle is used. Besides

Igor Bandos, Dmitrij Sorokin, Dmitrij Volkov

We revise the twistor--like superfield approach to describing super--p--branes by use of the basic principles of the group--manifold approach \cite{rheo}. A super--p--brane action is constructed solely of geometrical objects as the integral over a (p+1)--surface. The Lagrangian is the external product of supervielbein differential forms in world supersurface

P. S. Montague

We investigate orbifold constructions of conformal field theories from lattices by no-fixed-point automorphisms (NFPA&#39;s) $Z_p$ for $p$ prime, $p>2$, concentrating on the case $p=3$. Explicit expressions are given for most of the relevant vertex operators, and we consider the locality relations necessary for these to define a consistent conformal field th

M. I. Caicedo, R. Gianvittorio, A. Restuccia, J. Stephany

The off-shell nilpotent BRST charge and the BRST invariant effective action for non-abelian BF topological theories over D-dimensional manifolds are explicitly constructed. These theories have the feature of being reducible with exactly D-3 stages of reducibility. The adequate extended phase space including the different levels of ghosts for ghosts is explic

Pran Nath, Jizhi Wu, Richard Arnowitt

It is shown that analyses at the electroweak scale can be significantly affected due to Landau pole effects in certain regions of the parameter space. This phenomenon arises due to a large magnification of errors of the input parameters $m_t$, $α_G$ which have currently a 10 percent uncertainty in their determination. The influence of the Landau pole on the

M. Hirsch, H. V. Klapdor-Kleingrothaus, S. G. Kovalenko

Neutrinoless double beta decay ($\znbb$) induced by superparticle exchange is investigated. Such a supersymmetric (SUSY) mechanism of $\znbb$ decay arises within SUSY theories with R-parity non-conservation (\rp). We consider the minimal supersymmetric standard model (MSSM) with explicit \rp terms in the superpotential (\rp MSSM). The decay rate for the SUSY

G. T. Gabadadze, A. L. Kataev

It has been shown that the one-loop behavior of the axial anomaly, occurring when the axial current is appropriately normalized, leads to the cancellation of the corrections of type $C_F^N{\bar α}_s^N,~~ (N\geq 1) $ in the Crewther relation for the coefficient functions of deep-inelastic and annihilation processes. The arguments in favour of the overall fact

Jiri Chyla, A. Kataev

We discuss uncertainties of QCD predictions for the hadronic width of the $Z^0$ boson. Emphasis is put on quantitative estimates, taking into account the current precision of experimental data.

T. Kurimoto

It is shown that the complex phase of $B^0$--$\bar {B^0}$ mixing matrix element is same as that of the standard model one up to the minor correction of the order of $(m_c/m_t)^2$ or less in the SUSY standard model. This conclusion is valid as far as the Yukawa coupling constants are perturbative and realistic, and can be available for other realistic models

A. Patrascioiu, E. Seiler

We explain why in our view an extrapolation from small lattices containing only perturbative information cannot be sufficient to determine nonperturbative qunatities and therefore cannot lead to a trustworthy determination of the correlation length.

Barry Haddow

Purely magnetic spacetimes, in which the Riemann tensor satisfies $R_{abcd}u^bu^d=0$ for some unit timelike vector $u^a$, are studied. The algebraic consequences for the Weyl and Ricci tensors are examined in detail and consideration given to the uniqueness of $u^a$. Some remarks concerning the nature of the congruence associated with $u^a$ are made.

Eric Poisson, Clifford M. Will

The parameters of inspiralling compact binaries can be estimated using matched filtering of gravitational-waveform templates against the output of laser-interferometric gravitational-wave detectors. Using a recently calculated formula, accurate to second post-Newtonian (2PN) order [order $(v/c)^4$, where $v$ is the orbital velocity], for the frequency sweep

Ryusuke Ikeda

A hydrodynamical description for vortex states in type II superconductors with no pinning is presented based on the time-dependent GL equation, and the nonlocal conductivities are examined in terms of Kubo formula. Typically, the nonlocal conductivities deviate from the usual vortex flow expressions as the nonlocality parallel to the field becomes weaker tha

S. Luebeck, K. D. Usadel, B. Tadic

We study numerically the spatial properties of relaxation clusters in a two dimensional sandpile automaton with dynamic rules depending stochastically on a parameter p, which models the effects of static friction. In the limiting cases p=1 and p=0 the model reduces to the critical height model and critical slope model, respectively. At p=p_c, a continuous ph

A. Jagannathan

We present a simple model for the observed temperature dependence of the thermal conductivity of AlPdMn (Chernikov et al, Phys.Rev.B vol.51, (1995),153). We account for the low temperature data, upto and including the plateau of the thermal conductivity, and discuss the similarities and the differences between the quasicrystal and amorphous solids.

E. Mueller-Hartmann

Thirty years ago the Hubbard model was introduced by Gutzwiller, Hubbard and Kanamori with the main purpose of mimicking the ferromagnetism of transition metals. Soon after, Nagaoka and Thouless pointed out a basic mechanism for ferromagnetism in strongly correlated electron systems by studying the motion of a single hole in a half--filled Hubbard model. Thi

Debnarayan Jana

We show that charged scalar fields are always diamagnetic, even in the presence of interactions and at finite temperatures. This generalises earlier work on the diamagnetism of charged spinless bosons to the case of infinite degrees of freedom.

E. Eisenstein, I. Kanter, D. A. Kessler, W. Kinzel

Generation and prediction of time series is analyzed for the case of a Bit-Generator: a perceptron where in each time step the input units are shifted one bit to the right with the state of the leftmost input unit set equal to the output unit in the previous time step. The long-time dynamical behavior of the Bit-Generator consists of cycles whose typical per

Italo Marino

We study two-dimensional frustrated Josephson arrays driven by a combined DC plus AC current. We propose {\it ansatz} solutions that are a generalization of the solutions obtained in the DC case by Marino and Halsey (PRB {\bf 50}, 6289 (1994)). Using these solutions we derive expressions for the Shapiro step widths for $f=1/2$ and $f=1/3$ for the first few w

Patrick Sturt

This paper describes an implementation based on a recent model in the psycholinguistic literature. We define a parsing operation which allows the reanalysis of dependencies within an incremental and monotonic processing architecture, and discuss search strategies for its application in a head-initial language (English) and a head-final language (Japanese).

Christopher C. Huckle

This paper (cmp-lg/yymmnnn) has been accepted for publication in the student session of EACL-95. It outlines ongoing work using statistical and unsupervised neural network methods for clustering words in untagged corpora. Such approaches are of interest when attempting to understand the development of human intuitive categorization of language as well as for

Saliha Azzam

This paper concerns both anaphora resolution and prepositional phrase (PP) attachment that are the most frequent ambiguities in natural language processing. Several methods have been proposed to deal with each phenomenon separately, however none of proposed systems has considered the way of dealing both phenomena. We tackle this issue, proposing an algorithm

David K. Campbell, Roza Galeeva, Charles Tresser, David J. Uherka

We formulate and study analytically and computationally two families of piecewise linear degree one circle maps. These families offer the rare advantage of being non-trivial but essentially solvable models for the phenomenon of mode-locking and the quasi-periodic transition to chaos. For instance, for these families, we obtain complete solutions to several q

J. Gonzalez, F. Guinea, M. A. H. Vozmediano

A model of interacting two dimensional electrons near a Van Hove singularity is studied, using renormalization group techniques. In hole doped systems, the chemical potential is found to be pinned near the singularity, when the electron-electron interactions are repulsive. The RG treatment of the leading divergences appearing in perturbation theory give rise

Berthold Stech

Assuming simple properties of the spectator particle in weak decays the form factors of hadronic current matrix elements are shown to be related to a single universal function. The Isgur-Wise result for heavy-to-heavy transitions follows as well as similar relations for heavy-to-light decay processes. The approximation should hold for total energies of the f

D. L. Wiltshire

The properties of static spherically symmetric black holes, which carry electric and magnetic charges, and which are coupled to the dilaton in the presence of a cosmological term (Liouville-type potential, or cosmological constant) are reviewed.

D. R. Phillips, I. R. Afnan

We derive a set of coupled four-dimensional integral equations for the $NN-πNN$ system using our modified version of the Taylor method of classification-of-diagrams. These equations are covariant, obey two and three-body unitarity and contain subtraction terms which eliminate the double-counting present in some previous four-dimensional $NN-πNN$ equations. T

Murray Gerstenhaber, Mary E. Schaps

To each partition $\frak p$ of $n$ we associate in a canonical way a simple $S_n$ module with an orthogonal basis indexed by Young diagrams in a way which carries over immediately to the quantized case. With this we show that the Hecke algebra of $S_n$ is a global solution to the Donald--Flanigan problem for $S_n.$ The procedure gives ``canonical&#39;&#39; p

M. S. Fayache, S. Shelly Sharma, L. Zamick

Shell model calculations are performed for magnetic dipole excitations in $^8{Be}$ and $^{10}{Be}$ in which all valence configurations plus $2\hbarω$ excitations are allowed (large space). We study both the orbital and spin excitations. The results are compared with the `valence space only&#39; calculations (small space). The cumulative energy weighted sums

Hungchong Kim, J. Piekarewicz, C. J. Horowitz

We compute the cross section for the charged-current reaction ${}^{12}{\rm C}(ν_μ,μ^{-})$ near threshold using a relativistic mean-field formalism. A reduced value of the nucleon mass in the medium --- coupled to the finite muon mass --- leads to a 30\% reduction in the cross section relative to a free Fermi-gas estimate. Isovector RPA correlations, which ar

Nikolaos A. Batakis

A classification of all possible spatially homogeneous 4D string backgrounds (HSBs) has been obtained by appropriate ramification of the existing nine Bianchi types of homogeneous 3D spaces. A total of $24^2=576$ HSBs which have been classified as distinct contains a subclass of 192 which includes all possible FRW models as well as those in which SO(3) isotr

J. G. Körner, K. Melnikov, O. Yakovlev

We consider the small velocity sum rules for heavy flavour semileptonic transitions that are used to estimate the zero recoil values of semileptonic heavy flavour form factors. We analyze the complete O($α_S$) radiative correction to these sum rules. The corrections are universal and influence all &#34;model-independent&#34; bounds previously derived for sem

G. J. Gounaris, F. M. Renard, G. Tsirigoti

Taking into account the constraints from LEP1 and lower energy experiments, we identify the seven $SU(2)\times U(1)$ gauge invariant purely bosonic $dim=6$ operators which provide a quite general description of how New Physics could reflect in the bosonic world, if it happens that all new degrees of freedom are too heavy to be directly produced in the future

J. H. Kühn, M. Peter

QCD corrections to all the allowed decays of superheavy groundstate quarkonia into electroweak gauge and Higgs bosons are presented. For quick estimates, approximations that reproduce the exact results within less than at worst two percent are also given.

P. Colangelo, C. A. Dominguez, N. Paver

We propose a number of tests of factorization for the color-suppressed nonleptonic decay channels: $B \to K^{(*)} \; η_c$ and $B \to K^{(*)} \; η^\prime_c$. The relevant leptonic constants and form factors are calculated within the QCD sum rules approach.

Julius Kuti

It is shown that the infinite dimensional critical surface of general euclidean lattice actions in a generic four-dimensional scalar field theory with $Φ^4$ interactions has a domain of special multicritical points where higher dimensional operators play a special role. Renormalized trajectories of higher derivative continuum field theories with nontrivial i

F. Englert

In conventional field theories, the emission of Hawking radiation in the background of a collapsing star requires transplanckian energy fluctuations. These fluctuations are encoded in the weak values of the energy-momentum operator constructed from matrix elements between both -in and -out states. It is argued that taming of these weak values by back-reactio

Roh Suan Tung, Ted Jacobson

General relativity is derived from an action which is quadratic in the covariant derivative of certain spinor one-form gravitational potentials. Either a pair of 2-component spinor one-forms or a single Dirac spinor one-form can be employed. The metric is a quadratic function of these spinor one-forms. In the 2-component spinor formulation the action differs

Mark J. Gotay, Hendrik Grundling, C. A. Hurst

We prove that there does not exist a nontrivial quantization of the Poisson algebra of the symplectic manifold S^2 which is irreducible on the subalgebra generated by the components {S_1,S_2,S_3} of the spin vector. We also show that there does not exist such a quantization of the Poisson subalgebra P consisting of polynomials in {S_1,S_2,S_3}. Furthermore,

S. Moss de Oliveira, P. M. C. de Oliveira, F. C. Sa Barreto

Using the Finite Size Scaling Renormalisation Group we obtain the two-dimensional flow diagram of the Blume-Capel model, for S = 1 and S = 3/2. In the first case our results are similar to those of Mean Field Theory, which predicts the existence of first and second order transitions whith a tricritical point. In the second case, however, our results are diff

G. A. Georgakis, Qian Niu

A T-shaped field-effect transistor, made out of a pair of two-dimensional electron gases, is modeled and studied. A simple numerical model is developed to study the electron distribution vs. applied gate voltage for different gate lengths. The model is then improved to account for depletion and the width of the two-dimensional electron gases. The results are

J. K. Freericks, Mark Jarrell

The Holstein-Hubbard model is examined in the limit of infinite dimensions. Conventional folklore states that charge-density-wave (CDW) order is more strongly affected by Coulomb repulsion than superconducting order because of the pseudopotential effect. We find that both incommensurate CDW and superconducting phases are stabilized by the Coulomb repulsion,

Mohamed Azzouz, Thierry Dombre

The motion of holes on the triangular lattice is studied using the t-J model. Within the Born self-consistent approximation and the exact Lanczos diagonalization, the single hole physics is first analyzed. Then the spiral theory of Shraiman and Siggia is used to investigate the case of a finite density of holes.

C. Vermeulen, W. Barford

We present a variational estimate for the binding energy of a Frenkel exciton in the insulating cuprate superconductors. Starting from the three band Hubbard model we perform a canonical transformation to O($t^2$), where $t$ is the bare nearest neighbour copper-oxygen hopping integral. An effective Hamiltonian is then derived to describe the hopping of the e

Peter Kopietz, Volker Meden, Kurt Schoenhammer

We use a bosonization approach to show that the three dimensional Coulomb interaction in coupled metallic chains leads to a Luttinger liquid for vanishing inter-chain hopping $t_{\bot}$, and to a Fermi liquid for any finite $t_{\bot}$. However, for small $t_{\bot} \neq 0$ the Greens-function satisfies a homogeneity relation with a non-trivial exponent $γ_{cb

Han-Yong Choi, E. J. Mele

We study the effects of non-magnetic impurity vertex correction on nuclear spin-lattice relaxation rate $1/{T_1} $ of conventional s-wave superconductors within the Eliashberg formalism. We obtain, with a self-consistent $t-$matrix treatment of impurity scatterings, the expressions for impurity vertex function and nuclear spin-lattice relaxation rate. The $1

Dominique Estival, Francoise Gayral

The work reported here is the result of a study done within a larger project on the ``Semantics of Natural Languages&#39;&#39; viewed from the field of Artificial Intelligence and Computational Linguistics. In this project, we have chosen a corpus of insurance claim reports. These texts deal with a relatively circumscribed domain, that of road traffic, there

Tanya Bowden

This paper is concerned with the detection and correction of sub-sentential English text errors. Previous spelling programs, unless restricted to a very small set of words, have operated as post-processors. And to date, grammar checkers and other programs which deal with ill-formed input usually step directly from spelling considerations to a full-scale pars

Geunbae Lee, Hanmin Jung, Jong-Hyeok Lee

A bi-directional Korean/English dialog translation system is designed and implemented using the memory-based translation technique. The system KEMDT (Korean/English Memory-based Dialog Translation system) can perform Korean to English, and English to Korean translation using unified memory network and extended marker passing algorithm. We resolve the word or

Kuang-hua Chen

This paper proposes a corpus-based language model for topic identification. We analyze the association of noun-noun and noun-verb pairs in LOB Corpus. The word association norms are based on three factors: 1) word importance, 2) pair co-occurrence, and 3) distance. They are trained on the paragraph and sentence levels for noun-noun and noun-verb pairs, respe

P. Vauterin, H. Dejonghe

We construct analytical phase-space solutions for perturbations of flat disks by performing a power series expansion for the radius and the velocity coordinates. We show that this approach translates into an elegant mathematical formulation which is easy to use for a wide variety of distribution functions, for as far as resonances do not play a role, such as

M. Kolesik, M. Suzuki

The antiferromagnetic three-state Potts model on the simple-cubic lattice is studied using the coherent-anomaly method (CAM). The CAM analysis provides the estimates for the critical exponents which indicate the XY universality class, namely $α=-0.011 $, $β= 0.351 $, $γ= 1.309 $ and $δ= 4.73 $. This observation corroborates the results of the recent Monte Ca

M. J. Martins

We have solved exactly the $Osp(1|2)$ spin chain by the Bethe ansatz approach. Our solution is based on an equivalence between the $Osp(1|2)$ chain and certain special limit of the Izergin-Korepin vertex model. The completeness of the Bethe ansatz equations is discussed for a system with four sites and it is noted the appearance of special string structures.

Vladimir A. Kazakov, Matthias Staudacher, Thomas Wynter

We consider generalized one-matrix models in which external fields allow control over the coordination numbers on both the original and dual lattices. We rederive in a simple fashion a character expansion formula for these models originally due to Itzykson and Di Francesco, and then demonstrate how to take the large N limit of this expansion. The relationshi

Martin Luescher, Peter Weisz

We describe an efficient position space technique to calculate lattice Feynman integrals in infinite volume. The method applies to diagrams with massless propagators. For illustration a set of two-loop integrals is worked out explicitly. An important ingredient is an observation of Vohwinkel that the free lattice propagator can be evaluated recursively and i

G. I. Smirnov

It is suggested to determine the $A$ dependence of distortions of the nucleon structure function $F_2(x)$ by summing the distortions over an interval ($x_1, x_2$). It was found from the analysis of data on deep--inelastic scattering of muons and electrons from nuclei that the $A$ dependence of distortion magnitudes obtained in each of three regions under stu

J-L. Ballot, M. R. Robilotta, C. A. da Rocha

We show that chiral symmetry is responsible for large cancellations in the two-pion exchange nucleon-nucleon interaction, which are similar to those occuring in free pion-nucleon scattering.

Peter Kopietz, Joachim Hermisson, Kurt Schoenhammer

We use our recently developed functional bosonization approach to bosonize interacting fermions in arbitrary dimension $d$ beyond the Gaussian approximation. Even in $d=1$ the finite curvature of the energy dispersion at the Fermi surface gives rise to interactions between the bosons. In higher dimensions scattering processes describing momentum transfer bet

C. A. da Rocha, M. R. Robilotta

We argue that the minimal chiral background for the two-pion exchange nucleon-nucleon interaction has nowadays a rather firm conceptual basis, which entitles it to become a standard ingredient of any modern potential. In order to facilitate applications, we present a parametrized version of a configuration space potential derived previously. We then use it t

E. Elizalde S. D. Odintsov, A. Romeo

We investigate the phase structure and the infrared properties of higher-derivative quantum gravity (QG) with matter, in $4-\varepsilon$ dimensions. The renormalization group (RG) equations in $4-\varepsilon$ dimensions are analysed for the following types of matter: the $fφ^4$-theory, the $O(N) φ^4$-theory, scalar electrodynamics, and the $SU(2)$ model with

Malte Henkel, A. Brooks Harris, Marek Cieplak

We discuss several problems concerning domain walls in the spin $S$ Ising model at zero temperature in a magnetic field, $H/(2S)$, applied in the $x$ direction. Some results are also given for the planar ($y$-$z$) model in a transverse field. We treat the quantum problem in one dimension by perturbation theory at small $H$ and numerically over a large range

Stefan Berceanu

The intimate relationship between coherent states and geodesics is pointed out. For homogenous manifolds on which the exponential from the Lie algebra to the Lie group equals the geodesic exponential, and in particular for symmetric spaces, it is proved that the cut locus of the point $0$ is equal to the set of coherent vectors orthogonal to $\vert 0>$. A si

I. N. Kondrashuk

Exact mathematical solution of the minimization conditions of scalar the Higgs potential of the Finite Supersymmetric Grand Unification Theory is proposed and extremal field configurations are found. Types of extrema are investigated and masses of the new Higgs particles arisen after electroweak symmetry breaking are derived analytically. The conditions for

J. Abad, M. Rios

The reflection equations in a $su(3)$ spin chain with open boundary conditions are analyzed. We find non diagonal solutions to the boundary matrices. The corresponding hamiltonian is given. The solutions are generalized to $su(n)$.

Drazen Adamovic

Let $L((n-\tfrac 3 2)Λ_0)$, $n \in \Bbb N$, be a vertex operator algebra associated to the irreducible highest weight module $L((n-\tfrac 3 2)Λ_0)$ for a symplectic affine Lie algebra. We find a complete set of irreducible modules for $L((n-\tfrac 3 2)Λ_0)$ and show that every module for $L((n-\tfrac 3 2)Λ_0)$ from the category $\Cal O$ is completely reducib

Karlo Penc, Hiroyuki Shiba

Inspired by the recent experiments on Y$_{2-x}$Ca$_x$BaNiO$_5$, (J. F. DiTusa {\it et al.}, Phys. Rev. Lett. 73, 1857 (1994)), we discuss the dispersion relation of the $s$=1/2 particles in the $s$=1 Heisenberg and VBS model in the limit of small hopping amplitudes. The effective $s$=1/2 edge spins mix with the spin of the impurity resulting in one four--fol

M. Caselle

We show that, within the framework of suitably chosen approximate effective actions it is possible to evaluate analytically the string tension, the spacelike string tension and the deconfinement temperature of (2+1) dimensional lattice gauge theories. In the case of SU(2) gauge theory our results agree with those obtained through Montecarlo simulations.