March 1995 arXiv papers — page 10

Hinrich Schuetze

This paper presents an algorithm for tagging words whose part-of-speech properties are unknown. Unlike previous work, the algorithm categorizes word tokens in context instead of word types. The algorithm is evaluated on the Brown Corpus.

Mary Dalrymple, Stuart M. Shieber, Fernando C. N. Pereira

We present a new method for characterizing the interpretive possibilities generated by elliptical constructions in natural language. Unlike previous analyses, which postulate ambiguity of interpretation or derivation in the full clause source of the ellipsis, our analysis requires no such hidden ambiguity. Further, the analysis follows relatively directly fr

Joerg P. Rachen

We give an outline of possible extragalactic explanations of the highest energy cosmic ray events. We give a classification of the possible particles which could have caused the events and try to find suitable sources for each class. In contrast to some previous investigations of other authors, we find a possible candidate of a local FR-II radio galaxy close

Joachim Wambsganss, Tomislav Kundic

We present a quantitative analysis of the effect of microlensing caused by random motion of individual stars in the galaxy which is lensing a background quasar. We calculate a large number of magnification patterns for positions of the stars slightly offset from one frame to the next, and in this way obtain light curves for fixed quasar and galaxy positions,

D. W. Koerner, A. I. Sargent

We have detected circumstellar molecular gas around a small sample of T Tauri stars through aperture synthesis imaging of CO(2-1) emission at ~2-3'' resolution. RY Tauri, DL Tauri, DO Tauri, and AS 209 show resolved and elongated gaseous emission. For RY Tau, the deconvolved, half-maximum radius along the direction of elongation, PA~48deg, is 110 AU.

R. MacKenzie

In the abelian Higgs model, among other situations, it has recently been realized that the head-on scattering of $n$ solitons distributed symmetrically around the point of scattering is by an angle $π/n$, independant of various details of the scattering. In this note, it is first observed that this result is in fact not entirely surprising: the above is one

Peter A. Thompson, Mark O. Robbins, Gary S. Grest

Simulations of the structure and dynamics of fluid films confined to a thickness of a few molecular diameters are described. Confining walls introduce layering and in-plane order in the adjacent fluid. The latter is essential to transfer of shear stress. As the film thickness is decreased, by increasing pressure or decreasing the number of molecular layers,

H. Awata, Y. Matsuo, S. Odake, J. Shiraishi

Using the collective field method, we find a relation between the Jack symmetric polynomials, which describe the excited states of the Calogero-Sutherland model, and the singular vectors of the $W_N$ algebra. Based on this relation, we obtain their integral representations. We also give a direct algebraic method which leads to the same result, and integral r

J. R. Espinosa

An upper bound on the tree-level mass of the lightest Higgs boson of the Supersymmetric Singlet Majoron Model is obtained. Contrary to some recent claims, it is shown to be of the same form as the general mass bound previously calculated for supersymmetric models with an extended Higgs sector. Soft-breaking masses or exotic vacuum expectation values do not e

J. O. Madsen, E. Ragoucy

Recently, it has been shown how to perform the quantum hamiltonian reduction in the case of general $sl(2)$ embeddings into Lie (super)algebras, and in the case of general $osp(1|2)$ embeddings into Lie superalgebras. In another development it has been shown that when $H$ and $H'$ are both subalgebras of a Lie algebra $G$ with $H'\subset H$, then cla

K. J. Eskola

Initial conditions for quark-gluon plasma formation at $τ=0.1\fm$ are considered in lowest order perturbative QCD. Chemical composition, thermalization of the formed semihard quark-gluon system and especially implications of the new HERA parton distributions with the enhancement at small $x$ are studied. The plasma at $τ=0.1\fm$ is shown to be strongly gluon

Frank Cuypers

We describe a simple method to compute the Cramer-Rao limit of a high energy experiment, i.e., the smallest error with which a parameter can in principle be determined in a reaction. This precision remains a theoretical paradigm since it assumes perfect experimental conditions. Nevertheless, it is shown at hand of an example that for simple processes this as

N. I. Kochelev

It is shown that specific spin-flavour properties of the nonperturbative interaction between quarks induced by instantons allow us to explain the peculiarities of the OZI rule violation in $N \bar N$ annihilation. New experiments to test the instanton mechanism of the OZI rule violation are proposed.

Seungjoon Hyun, Jae-Suk Park

We study the path integrals of the holomorphic Yang-Mills theory on compact Kähler surface with $b_2^+ = 1$. Based on the results, we examine the correlation functions of the topological Yang-Mills theory and the corresponding Donaldson invariants as well as their transition formulas.

Juergen Audretsch, Ulf Jasper, Vladimir D. Skarzhinsky

We consider the problem of self-adjoint extension of Hamilton operators for charged quantum particles in the pure Aharonov-Bohm potential (infinitely thin solenoid). We present a pragmatic approach to the problem based on the orthogonalization of the radial solutions for different quantum numbers. Then we discuss a model of a scalar particle with a magnetic

Kai Hencken, Dirk Trautmann, Gerhard Baur

Effective photon-photon luminosities are calculated for various realistic hadron collider scenarios. The main characteristics of photon-photon processes at relativistic heavy-ion colliders are established and compared to the corresponding photon-photon luminosities at electron-positron and future Photon Linear Colliders (PLC). Higher order corrections as wel

Anton Deitmar

We define geometric zeta functions for locally symmetric spaces as generalizations of the zeta functions of Ruelle and Selberg. As a special value at zero we obtain the Reidemeister torsion of the manifold. For hermitian spaces these zeta functions have as special value the quotient of the holomorphic torsion of Ray and Singer and the holomorphic $L^2$-torsi

Randall Dougherty

In this paper, we continue the study of a left-distributive algebra of elementary embeddings from the collection of sets of rank less than lambda to itself, as well as related finite left-distributive algebras (which can be defined without reference to large cardinals). In particular, we look at the critical points (least ordinals moved) of the elementary em

L. Accardi, I. Ya. Aref'eva, S. V. Kozyrev, I. V. Volovich

In recent works by Singer, Douglas and Gopakumar and Gross an application of results of Voiculescu from non-commutative probability theory to constructions of the master field for large $N$ matrix field theories have been suggested. In this note we consider interrelations between the master field and quantum groups. We define the master field algebra and obs

A. Pasquinucci, K. Roland

We propose a way of bosonizing free world-sheet fermions for $4$-dimensional heterotic string theory formulated in Minkowski space-time. We discuss the differences as compared to the standard bosonization performed in Euclidean space-time.

Serdar Nergiz, Cihan Saclioglu

We recast the quaternionic Gursey-Tze solution, which is a fourfold quasi-periodic self-dual Yang-Mills field with a unit instanton number per Euclidean spacetime cell, into an ordinary coordinate formulation. After performing the sum in the Euclidean time direction, we use an observation by Rossi which suggests the solution represents an arrangement with a

H. J. Boonstra, M. de Roo

We reduce the dual version of $D=10$, $N=1$ supergravity coupled to $n$ vector fields to four dimensions, and derive the $SL(2,R)\times O(6,6+n)$ transformations which leave the equations of motion invariant. For $n=0$ $SL(2,R)$ is also a symmetry of the action, but for $n>0$ only those $SL(2,R)$ transformations which act linearly on all fields leave the act

Zhan-Ning Hu, Bo-Yu Hou

We find that the Boltzmann weight of the three-dimensional Baxter-Bazhanov model is dependent on four spin variables which are the linear combinations of the spins on the corner sites of the cube and the Wu-Kadanoff duality between the cube and vertex type tetrahedron equations is obtained explicitly for the Baxter-Bazhanov model. Then a three-dimensional ve

M. Dine

Recent work has made clear that we have far more control over the dynamics of supersymmetric than non-supersymmetric theories. Here, I discuss some issues in dynamical supersymmetry breaking both in ordinary field theory and in string theory. In string theory, in particular, it is possible to show, in some circumstances, that stringy non-perturbative effects

Z. Bern, G. Chalmers, L. Dixon, D. C. Dunbar

We review techniques simplifying the analytic calculation of one-loop QCD amplitudes with many external legs, for use in next-to-leading-order corrections to multi-jet processes. Particularly useful are the constraints imposed by perturbative unitarity, collinear singularities and a supersymmetry-inspired organization of helicity amplitudes. Certain sequence

Patrick J. O'Donnell, Q. P. Xu, Humphrey K. K. Tung

We study the form factors of heavy--to--heavy and heavy--to--light weak decays using the light--front relativistic quark model. For the heavy--to--heavy $B \ra D^{(\ast)}$ semileptonic decays we calculate the corresponding Isgur--Wise function for the whole kinematic region. For the heavy--to--light $B\ra P$ and $B\ra V$ semileptonic decays we calculate the

Gia Dvali

We show that in generic supergravity theories the mass of the moduli during inflation is larger (or at least of the same order of magnitude) than the Hubble constant. This fact does not depends on the details of the inflation and on the value of the Hubble parameter during it. The reason is that inflationary universe is dominated by large F-term (or D-term)

V. Barger, M. S. Berger, K. Fujii, J. F. Gunion

This working group report focuses on the physics potential of $μ^+μ^-$ colliders beyond what can be accomplished at linear $e^+e^-$ colliders and the LHC. Particularly interesting possibilities include (i)~$s$-channel resonance production to discover and study heavy Higgs bosons with $ZZ$ and $WW$ couplings that are suppressed or absent at tree-level (such a

Mikhail Bilenky, Arcadi Santamaria

We discuss some applications of the effective quantum field theory to the description of the physics beyond the Standard Model. We consider two different examples. In the first one we derive, at the one-loop level, an effective lagrangian for an extension of the Standard Model with a charged scalar singlet by ``integrating out'' the heavy scalar. In

I. F. Ginzburg, K. Melnikov

It is shown that the methods which have been used up to now to determine the $W$ width from the $p\bar p$ data confirm the SM predictions for some combinations of various phenomenological parameters, however, they do not give an independent value for the $W$ width. Moreover, the accuracy that could be achieved in future experimental checks of SM predictions

Pyungwon Ko

$η\rightarrow π^{0} γγ$ and $\ggpipi$ are considered in $O(p^{6})$ chiral perturbation theory. In addition to the usual $ρ,ω$ contributions, there are two $O(p^{6})$ operators (${\cal L}_{6,m}$) arising from explicit chiral symmetry breaking. Since only one of the two operators contributes to $\etapigg$, the coefficient of this operator ($\equiv d_3$) can be

Sreerup Raychaudhuri, D. P. Roy

We explore the prospect of charged Higgs boson search in top quark decay at the Tevatron collider upgrade, taking advantage of the opposite states of $τ$ polarization resulting from the $H^\pm$ and $W^\pm$ decays. Methods of distinguishing the two contributions in the inclusive 1-prong hadronic decay channel of $τ$ are suggested. The resulting signature and

M. Vänttinen

We present a higher-twist production mechanism for $η_c$ and $χ_J$ charmonium at large momentum fraction $x_F$ in pion-nucleon collisions. The higher-twist contribution is essentially independent of $x_F$ and therefore becomes dominant at large $x_F$, where the leading-twist contribution falls off as $(1-x_F)^3$. We show that the higher-twist mechanism produ

G. Bhattacharya, Pat Kalyniak, I. Melo

Small neutrino masses can arise in some grand unified models or superstring theories. We consider a model with an enhanced fermion sector containing Dirac neutral heavy leptons. The dependence on the mass and mixing parameters of these new fermions is investigated for several measurable quantities. We study the flavor-conserving leptonic decays of the Z boso

J. L. Alonso, Ph. Boucaud, A. J. van der Sijs

We discuss the phase structure of chiral Yukawa models in the mean-field approximation. In particular, we examine under which conditions a ferrimagnetic phase appears, by calculating the slopes of possible second order phase transition lines near a critical point. Our results contrast with some statements which appeared in the literature recently.

Andrzej Królak, Kostas D. Kokkotas, Gerhard Schäfer

The effect of the recently obtained 2nd post-Newtonian corrections on the accuracy of estimation of parameters of the gravitational-wave signal from a coalescing binary is investigated. It is shown that addition of this correction degrades considerably the accuracy of determination of individual masses of the members of the binary. However the chirp mass and

Yasufumi Kojima, Nils Andersson, Kostas D. Kokkotas

Quasinormal modes of ultra compact stars with uniform energy density have been calculated. For less compact stars, there is only one very slowly damped polar mode (corresponding to the Kelvin f-mode) for each spherical harmonic index $l$. Further long-lived modes become possible for a sufficiently compact star (roughly when $M/R \ge 1/3$). We compare the cha

Pedro F. Gonzalez-Diaz

By allowing the lightcones to tip over according to the conservation laws of an one-kink in static, Schwarzschild metric, we show that there also exists an instanton which represents production of pairs of chargeless, nonrotating black holes with mass $M$, joined on an interior surface beyond the horizon ar $r=M$. Evaluation of the thermal properties of each

A. J. Berlinsky, A. L. Fetter, M. Franz, C. Kallin

Ginzburg-Landau theory is used to study the properties of single vortices and of the Abrikosov vortex lattice in a $d_{x^2-y^2}$ superconductor. For a single vortex, the $s$-wave order parameter has the expected four-lobe structure in a ring around the core and falls off like $1/r^2$ at large distances. The topological structure of the $s$-wave order paramet

Jaichul Yi, Geoff S. Canright

It has recently been shown that one-dimensional Ising problems can have degenerate, disordered ground states (GSs) over a finite range of coupling onstants, ie, without `fine tuning'. The disorder is however of a special kind, consisting of arbitrary mixtures of a short-period structure and its symmetry-degenerate partner or partners. In this exploratory

D. N. Sheng, Z. Y. Weng

Delocalization problem for a two-dimensional non-interacting electron system is studied under a random magnetic field. With the presence of a random magnetic field, the Hall conductance carried by each eigenstate can become nonzero and quantized in units of $e^2/h$. Extended states are characterized by nonzero Hall conductance, and by studying finite-size sc

R. Holyst, P. Oswald

Dislocations in soft condensed matter systems such as lamellar systems of polymers, liquid crystals and ternary mixtures of oil, water and surfactant (amphiphilic systems) are described in the framework of continuum elastic theory. These systems are the subject of studies of physics, chemistry and biology. They also find applications in the industry. Here we

Malte Henkel, Gunter Schütz

Local scale invariance for lattice models is studied using new realizations of the Schrödinger algebra. The two-point function is calculated and it turns out that the result can be reproduced from exact two-point correlation functions evaluated in the stationary state of several simple stochastic models.

Yacov Kantor, Mehran Kardar

We perform an exact enumeration study of polymers formed from a (quenched) random sequence of charged monomers $\pm q_0$. Such polymers, known as polyampholytes, are compact when completely neutral and expanded when highly charged. Our exhaustive search included all spatial conformations and quenched sequences for up to 12--step (13--site) walks. We investig

P. de Sa, A. M. Tsvelik

We study the exact solution of the XXZ spin-1/2 Heisenberg chain with a boundary magnetic field in the region where the bulk excitations are gapless. It is shown that a bound state is created near the boundary with a total spin $S = 1/2(π/γ- 1)$ where $\cosγ$ is the anisotropy parameter. When $γ< π/2$ this spin remains underscreened giving rise to non-analyt

H. Kleinert

We survey the various uses of singular gauge fields which render an ideal description of ensembles of line- and surface-like excitations and explain phase transitions with the help of simple quadratic actions. Near a transition, the singular gauge fields can be transformed into ordinary complex fields called disorder fields which differ from Landau&#39;s ord

Xiaowen Shan, Gary Doolen

A previously proposed [X. Shan and H. Chen, Phys. Rev. E {\bf 47}, 1815, (1993)] lattice Boltzmann model for simulating fluids with multiple components and interparticle forces is described in detail. Macroscopic equations governing the motion of each component are derived by using Chapman-Enskog method. The mutual diffusivity in a binary mixture is calculat

Pierre Sablayrolles

In this paper we present a semantic study of motion complexes (ie. of a motion verb followed by a spatial preposition). We focus on the spatial and the temporal intrinsic semantic properties of the motion verbs, on the one hand, and of the spatial prepositions, on the other hand. Then, we address the problem of combining these basic semantics in order to for

G. Hinshaw, A. J. Banday, C. L. Bennett, K. M. Gorski

We compute the three-point temperature correlation function of the COBE Differential Microwave Radiometer (DMR) two-year sky maps to search for evidence of non-Gaussian temperature fluctuations. We detect three-point correlations in our sky with a substantially higher signal-to-noise ratio than from the first year data. However, the magnitude of the signal i

C. Moellenhoff, M. Matthias, O. E. Gerhard

Visual, NIR, and H_alpha surface photometry of the oval disk galaxy M94 (NGC 4736) was performed to study the distribution of mass in old stars and the distribution of the warm emission line gas. The radial profile of the inner stellar disk is steeper than exponential and displays twisted and deformed isophotes. Dust is not responsible for these deviations.

E. T. Harlaftis, T. R. Marsh

We present observations of OY Car, obtained with the Anglo-Australian Telescope, during a normal outburst in August 1991. Two sinusoidal components are resolved in the H$β$ trailed spectra and we determine the location of the narrow component to be on the secondary star with a maximum contributed flux of ~2.5 per cent to the total flux. Imaging of the line d

John Hibbard, Chris Mihos

Motivated by recent neutral hydrogen observations with the VLA, we have undertaken an investigation into the interaction that produced the well known merger remnant NGC 7252. Through fully self-consistent N-body simulations, we are able to reproduce the kinematic character of the HI observations quite well, including the velocity reversals observed along eac

Daniel C. Cohen, Alexander I. Suciu

Let $G$ be a group which admits the structure of an iterated semidirect product of finitely generated free groups. We construct a finite, free resolution of the integers over the group ring of $G$. This resolution is used to define representations of groups which act compatibly on $G$, generalizing classical constructions of Magnus, Burau, and Gassner. Our c

H. F. Chau

We consider simple examples of self-organized critical systems on one-dimensional superlattices without local particle conservation laws. The set of all recurrence states are also found in these examples using a method similar to the burning algorithm.

H. F. Chau, F. Wilczek

The Fredkin three-bit gate is universal for computational logic, and is reversible. Classically, it is impossible to do universal computation using reversible two-bit gates only. Here we construct the Fredkin gate using a combination of six two-body reversible (quantum) operators.

F. Boudjema, N. Dombey

We discuss the form of the amplitude for gauge boson pair production at or near threshold.We show that in the case of W-pair production at LEP2 near threshold only one anomalous electromagnetic coupling can contribute. This anomalous coupling is CP violating and contributes to the electric dipole moment of the $W$. Since this coupling is likely to be small,

M. Chertkov, G. Falkovich, I. Kolokolov, V. Lebedev

For a delta-correlated velocity field, simultaneous correlation functions of a passive scalar satisfy closed equations. We analyze the equation for the four-point function. To describe a solution completely, one has to solve the matching problems at the scale of the source and at the diffusion scale. We solve both the matching problems and thus find the depe

H. Awata, Y. Matsuo, S. Odake, J. Shiraishi

We review some recent results on the Calogero-Sutherland model with emphasis upon its algebraic aspects. We give integral formulae for excited states (Jack polynomials) of this model and their relations with W_n singular vectors and generalized matrix models.

E. Winstanley, N. E. Mavromatos

The stability of a new class of hairy black hole solutions in the coupled system of Einstein-Yang-Mills-Higgs is examined, generalising a method suggested by Brodbeck and Straumann and collaborators, and Volkov and Gal&#39;tsov. The method maps the algebraic system of linearised radial perturbations of the various field modes around the black hole solution i

Miao Li

The Schwinger-Dyson equations of the Makeenko-Migdal type, when supplemented with some simple equations as consequence of supersymmetry, form a closed set of equations for Wilson loops and related quantities in the two dimensional super-gauge theory. We solve these equations. It appears that the planar Wilson loops are described by the Nambu string without f

C. R. Hagen

The perturbation theory expansion of the Aharonov-Bohm scattering amplitude has previously been studied in the context of quantum mechanics for spin zero and spin-1/2 particles as well in Galilean covariant field theory. This problem is reconsidered in the framework of the model in which the flux line is considered to have a finite radius which is shrunk to

I. Ya. Aref&#39;eva, P. B. Medvedev, A. P. Zubarev

Starting from string field theory for 2d gravity coupled to c=1 matter we analyze N-point off-shell tree amplitudes of discrete states. The amplitudes exhibit the pole structure and we use the oscillator representation to extract the residues. The residues are generated by a simple effective action. We show that the effective action can be directly deduced f

C. Bachas

I study the spontaneous breakdown of supersymmetry when higher-dimensional Yang-Mills or the type-I $SO(32)$ string theory are compactified on magnetized tori. Because of the universal gyromagnetic ratio $g=2$, the splittings of all multiplets are given by the product of charge times internal helicity operators. As a result such compactifications have two re

Renata Kallosh

We classify states saturating a double or a single supersymmetric positivity bound of a four-dimensional N=4 supersymmetry. The massive four-dimensional double-bound states (Bogomolny states) are shown to form a light-like representation of ten-dimensional supersymmetry. The single-bound states form a massive representation (centrino multiplet) of a four-dim

Kajia Yuan

The untwisted moduli in four-dimensional fermionic string models are identified by considering world-sheet Abelian Thirring interactions. The full Kahler potentials of untwisted sector fields are given for a restricted class of models.

JOANNIS PAPAVASSILIOU, KOSTAS PHILIPPIDES

Using the S--matrix pinch technique we obtain to one loop order, gauge independent $γW^-W^+$ and $Z W^-W^+$ vertices in the context of the standard model, with all incoming momenta off--shell. We show that the vertices so constructed satisfy simple QED--like Ward identities. These gauge invariant vertices give rise to expressions for the magnetic dipole and

Jonathan Bagger

In rigid supersymmetry, generic models of dynamical supersymmetry breaking contain a light Goldstone boson, called the R axion. We show that supergravity effects explicitly break the R symmetry and give mass to the R axion. For visible and renormalizable hidden sector models, the massive R axion is free from astrophysical and cosmological problems. For nonre

Herbert Nachbagauer

We establish a new framework of finite temperature field theory for Yang-Mills theories in the physical phase space eliminating all unphysical degrees of freedoms. Relating our method to the imaginary time formalism of James and Landshoff in temporal axial gauge, we calculate the two-loop pressure and provide a systematic and unique method to construct the a

Apostolos Pilaftsis

We examine the potential of constraining possible nondecoupling effects of heavy neutrinos and Higgs bosons at LEP and SLC that may show up in the nonoblique part of the $Zl_il_j$ couplings. We analyze this type of new-physics interactions within the context of low-energy scenarios motivated by unified theories, such as the Standard Model (SM) with neutral i

H. Weigel, A. Abada, R. Alkofer, H. Reinhardt

Within the Nambu--Jona--Lasinio model strange degrees of freedom are incorporated into the soliton picture using the collective approach of Yabu and Ando. The form factors of the nucleon associated with the nonet vector current are extracted. The numerical results provide limits for the strange magnetic moment: $-0.05\leμ_s\le0.25$. For the strange magnetic

Igor Halperin

We study a quantum analogue of the iterative perturbation theory by Kolmogorov used in the proof of the Kolmogorov-Arnold-Moser (KAM) theorem. The method is based on sequent canonical transformations with a &#34;running&#34; coupling constant $ \lm,\lm^{2},\lm^{4} $ etc. The proposed scheme, as its classical predecessor, is &#34;superconvergent&#34; in the s

A. D. Smirnov

A minimal extension of the Standard Model containing the four-color quark-lepton symmetry is proposed and discussed. The existence of a rather light extra $Z&#39;$-boson originated from the four-color quark-lepton symmetry is shown to be compatible with the current electroweak data. The cross sections $σ(e^+ e^- \rightarrow γ, Z, Z&#39; \rightarrow \bar f f)

A. Kizilersu, M. Reenders, M. R. Pennington

The one loop vertex in QED is calculated in arbitrary covariant gauges as an analytic function of its momenta. The vertex is decomposed into a longitudinal part, that is fully responsible for ensuring the Ward and Ward-Takahashi identities are satisfied, and a transverse part. The transverse part is decomposed into 8 independent components each being separat

M. G. Olsson, Ulf-G. Meißner, N. Kaiser, V. Bernard

Near threshold pion production experiments have been recently carried out and used to extract S--wave $ππ$ scattering lengths. We emphasize here that at present these processes are related only at the tree level (and its first correction) in chiral perturbation theory. Higher order corrections (including loops) must be evaluated before rigorous claims concer

Victor Matveev, Robert Shrock

Using exact results, we determine the complex-temperature phase diagrams of the 2D Ising model on three regular heteropolygonal lattices, $(3 \cdot 6 \cdot 3 \cdot 6)$ (kagomé), $(3 \cdot 12^2)$, and $(4 \cdot 8^2)$ (bathroom tile), where the notation denotes the regular $n$-sided polygons adjacent to each vertex. We also work out the exact complex-temperatu

H1-Collaboration

A measurement is presented, using data taken with the H1 detector at HERA, of the contribution of diffractive interactions to deep-inelastic electron-proton scattering. The diffractive contribution to the proton structure function is evaluated as a function of the appropriate deep-inelastic scattering variables using a class of deep-inelastic ep scattering e

ANDRZEJ KRÓLAK, KOSTAS D. KOKKOTAS, GERHARD SCHÄFER

The effect of the recently obtained 2nd post-Newtonian corrections on the accuracy of estimation of parameters of the gravitational-wave signal from a coalescing binary is investigated. It is shown that addition of this correction degrades considerably the accuracy of determination of individual masses of the members of the binary. However the chirp mass and

A. D. Y. Cheng, P. D. D&#39;Eath, P. R. L. V. Moniz

The theory of N = 1 supergravity with gauged supermatter is studied in the context of a k = + 1 Friedmann minisuperspace model. It is found by imposing the Lorentz and supersymmetry constraints that there are {\seveni no} physical states in the particular SU(2) model studied.

O. Bertolami, P. V. Moniz

Retrieval of classical behaviour in quantum cosmology is usually discussed in the framework of minisuperspace models in the presence of scalar fields together with the inhomogeneous modes of gravitational or scalar fields. In this work we propose alternatively a model where the scalar field is replaced by a massive vector field with global U(1) or SO(3) inte

Tatsuhiko Koike, Takashi Hara, Satoshi Adachi

A scenario is presented, based on renormalization group (linear perturbation) ideas, which can explain the self-similarity and scaling observed in a numerical study of gravitational collapse of radiation fluid. In particular, it is shown that the critical exponent $β$ and the largest Lyapunov exponent ${\rm Re\, } κ$ of the perturbation is related by $β= ({\

Madhavan Varadarajan

We consider 1 spacelike Killing vector field reductions of 4-d vacuum general relativity. We restrict attention to cases in which the manifold of orbits of the Killing field is $R^{3}$. The reduced Einstein equations are equivalent to those for Lorentzian 3-d gravity coupled to an SO(2,1) nonlinear sigma model on this manifold. We examine the theory in terms

Andrey V. Chubukov, Dirk K. Morr

We consider a two-layer Heisenberg antiferromagnet which can be either in the Néel-ordered or in the disordered phase at $T=0$, depending on the ratio of the intra- and interlayer exchange constants. We reduce the problem to an interacting Bose-gas and study the sublattice magnetization and the transverse susceptibility in the ordered phase, and the spectrum

Hans C. Fogedby, Anders B. Eriksson, Lev V. Mikheev

A continuum limit of the non-Hermitian spin-1/2 chain, conjectured recently to belong to the universality class of the noisy Burgers or, equivalently, Kardar-Parisi-Zhang equation, is obtained and analyzed. The Galilean invariance of the Burgers equation is explicitly realized in the operator algebra. In the quasi-classical limit we find nonlinear soliton ex

G. Forgacs, K. Ziegler

Polymer chains with hard-core interaction on a two-dimensional lattice are modeled by directed random walks. Two models, one with intersecting walks (IW) and another with non-intersecting walks (NIW) are presented, solved and compared. The exact solution of the two models, based on a representation using Grassmann variables, leads, surprisingly, to the same

Alain DASNIÈRES de VEIGY, Stéphane OUVRY, Division de Physique Théorique, IPN

In a recent letter -Phys. Rev. Lett. 73, 3331 (1995)-, the conclusion was reached that, in the one-dimensional Calogero model, only the second virial coefficient is affected by the statistical parameter $α$, where $α$ is related to the coupling constant $κ/ x_{ij}^2$ of the Calogero interaction by $κ=α(α+1)$. We argue that it is not so, i.e. all virial coeff

Enzo Granato

A model of a ladder of Josephson junctions in a magnetic field is considered. The topological features of the zero-temperature phase diagram, as a function of charging energy and small deviations from commensurability of the vortex lattice, are strongly dependent on the field. In addition to superconductor-insulator transitions, commensurate-incommensurate t

X. Barcons, A. Franceschini, G. De Zotti, L. Danese

We analyze the $2-10$~keV X-ray emission of complete samples of AGN and galaxies selected at 12$μ$m and recently compiled by Rush, Malkan \& Spinoglio (1993). As a necessary complement we also study the IR emissivity of the largest sample of hard X--ray selected AGN (Grossan 1992). Our purposes are to probe the unified scheme of active nuclei and to evaluate

S. Covino, S. Galletti, L. E. Pasinetti

Spectrophotometric indices for $18$ Galactic globular clusters, obtained from CCD observations and careful reductions, were used to determine reliable calibrations on metallicity $[Fe/H]$. The indices were measured in the bandpasses adopted by Burnstein et al. (\cite{BFGK84}). Adding other observations of Burnstein et al. (\cite{BFGK84}) we obtained our resu

M. Ruffert, H. -Th. Janka, W. Keil, G. Schaefer

We investigate the dynamics and evolution of coalescing neutron stars. The three-dimensional Newtonian equations of hydrodynamics are integrated by the `Piecewise Parabolic Method&#39; However, we do include the effects of the emission of gravitational waves on the hydrodynamics. The properties of neutron star matter are described by the equation of state of

M. Ruffert

We investigate the hydrodynamics of three-dimensional classical Bondi-Hoyle accretion. A totally absorbing sphere of different sizes (1, 0.1 and 0.02 accretion radii) exerts gravity on and moves at different Mach numbers (0.6, 1.4, 3.0 and 10) relative to a homogeneous and slightly perturbed medium, which is taken to be an ideal gas ($γ=4/3$). We examine the

Bhuvnesh Jain, Edmund Bertschinger

The gravitational evolution of scale free initial spectra $P(k)\propto k^n$ in an Einstein-de Sitter universe is widely believed to be self-similar for $-3<n<4$. However, for $-3<n<-1$ the existence of self-similar scaling has not been adequately demonstrated. Here we investigate the possible breaking of self-similar scaling due to the nonlinear contribution

M. Santos-Lleo, J. Clavel, P. Barr, I. S. Glass

We discuss the results of a campaign to monitor spectral variations in the low-luminosity Seyfert~1 galaxy NGC~4593, at X-rays, ultraviolet, optical and near IR frequencies. The observations and data analysis have been described in a companion paper (Santos-Lleó et al. 1994; Paper~1). The active nucleus in this galaxy is strongly and rapidly variable in all

John C. Baez, James Dolan

The study of topological quantum field theories increasingly relies upon concepts from higher-dimensional algebra such as n-categories and n-vector spaces. We review progress towards a definition of n-category suited for this purpose, and outline a program in which n-dimensional TQFTs are to be described as n-category representations. First we describe a &#3

Z. Bern, G. Chalmers

Factorization properties of one-loop gauge theory amplitudes have been used as checks on explicitly computed amplitudes and in the construction of ansatze for higher-point ones. In massless theories, such as QCD at high energies, infrared divergences complicate factorization. Here we prove that factorization in such theories is described by a set of universa

Clifford V. Johnson, Robert C. Myers

A conformal field theory representing a four-dimensional classical solution of heterotic string theory is presented. The low-energy limit of this solution has U(1) electric and magnetic charges, and also nontrivial axion and dilaton fields. The low-energy metric contains mass, NUT and rotation parameters. We demonstrate that this solution corresponds to part

J. T. Londergan, G. T. Garvey, G. Q. Liu, E. N. Rodionov

We extend earlier investigations of charge symmetry violation in the valence quark distributions of the nucleon, and make similar estimates for the pion. The sensitivity of pion-induced Drell-Yan measurements to such effects is then examined. It is shown that combinations of $π^+$ and $π^-$ data on deuterium and hydrogen are sensitive to these violations, an

M. A. Fradkin

Thermoelastic phenomena associated with orientational phase transition in solid C60 are considered. Coupling of the order parameter with elastic strain is analyzed in the Landau theory of phase transitions. Wide range of possible coexistence of the FCC phase with SC one in C60 has been found from 260 K down to critical temperature 160 K of the instability of

H. Velazquez, S. D. M. White

We use numerical simulations to test the feasibility of the suggestion by Ibata et al. (1994) that the excess population of stars which they discovered in the Sagittarius region may be the disrupted remains of a dwarf spheroidal galaxy. We find that a Fornax-like model for the pre-disruption system can indeed reproduce the data. However, the galaxy must be o

EROS collaboration, E. Aubourg, P. Bareyre, S. Brehin

We present results from a search for gravitational microlensing of stars in the Large Magellanic Cloud by low mass objects in the Galactic Halo. The search uses the CCD light curves of about 82,000 stars with up to 46 measurements per night over a period of 10 months. No light curve exhibits a form that is consistent with a microlensing event of maximum ampl

Dung-Hai Lee, Ziqiang Wang

We show that the plateau transitions in the quantum Hall effect is the same as the dimerization transition of a half-filled, one dimensional, $U(2n)$ Hubbard model at $n=0$. We address the properties of the latter by a combination of perturbative renormalization group and Monte Carlo simulations. Results on both critical and off-critical properties are prese