March 1995 arXiv papers — page 6

Timothy Banks, R. J. Dodd, D. J. Sullivan

Johnson {\it BV} CCD observations have been made of the young Large Magellanic Cloud cluster NGC~2214 and a nearby field using the Anglo-Australian Telescope. It has been suggested in the literature that this elliptical cluster is actually two clusters in the process of merging. No evidence is found from profile fitting or the colour--magnitude diagrams to s

Alex Kamenev, Yuval Gefen

A microscopic theory of zero wavelength (q=0) interaction in finite--size systems is proposed. Its exact solution interpolates between the Coulomb blockade and the perturbative Altshuler--Aronov theory, in the strong and weak interaction limits respectively. The tunneling density of states and the quasiparticle life--time are calculated. The physical nature

Hideki Takayasu, Y-h. Taguchi, Tomoo Katsuyama

We propose a simple stochastic model of cascading transport in wave number space to clarify the origin of intermittent behavior of fully-developed fluid turbulence. In spite of lack of nonlinearity and viscosity the model gives non-Gaussian fluctuations and multifractal scalings consistent with experimental data.

H. -J. He, Y. -P. Kuang, C. -P. Yuan

Based upon our recent study on the Lorentz non-invariance ambiguity in the longitudinal weak-boson scatterings and the precise conditions for the validity of the Equivalence Theorem (ET), we further examine the intrinsic connection between the longitudinal weak-boson scatterings and probing the electroweak symmetry breaking (EWSB) mechanism. We reveal the pr

C. Claude, J. Leon

By using the inverse spectral transform, the SRS equations are solved and the explicit output data is given for arbitrary laser pump and Stokes seed profiles injected on a vacuum of optical phonons. For long duration laser pulses, this solution is modified such as to take into account the damping rate of the optical phonon wave. This model is used to interpr

Q. P. Liu

A supersymmetric version is proposed for the well known Harry Dym system. A general class super Lax operator which leads to consistent equations is considered.

C. Quesne

Deformations of the Lie algebras so(4), so(3,1), and e(3) that leave their so(3) subalgebra undeformed and preserve their coset structure are considered. It is shown that such deformed algebras are associative for any choice of the deformation parameters. Their Casimir operators are obtained and some of their unitary irreducible representations are construct

Erik Verlinde

About twenty years ago Hawking made the remarkable suggestion that the black hole evaporation process will inevitably lead to a fundamental loss of quantum coherence. The mechanism by which the quantum radiation is emitted appears to be insensitive to the detailed history of the black hole, and thus it seems that most of the initial information is lost for a

Robert M. Konik, Andre LeClair

We examine the two-point correlation functions of the fields exp(i$αΦ$) in the sine-Gordon theory at all values of the coupling constant $\hatβ$. Using conformal perturbation theory, we write down explicit integral expressions for every order of the short distance expansion. Using a novel technique analagous to dimensional regularisation, we evaluate these i

N. G. Deshpande, Xiao-Gang He

Electroweak penguin operators become important when $m_t \approx 174$ GeV. We discuss their implications for measuring CP violating phases $α$, $β$ and $γ$.

Sandip Pakvasa

I discuss how a 1 KM3 neutrino detector can be used to study $ν_τ$ oscillations at PeV energies with neutrinos from AGN's and to study neutrinos from GRB's.

John D. Anderson, Eunice L. Lau, Timothy P. Krisher, Duane A. Dicus

We improve, using a larger set of observations including Voyager 2 Neptune flyby data, previous bounds on the amount of dark matter (DM) trapped in a spherically symmetric distribution about the sun. We bound DM by noting that such a distribution would increase the effective mass of the sun as seen by the outer planets and by finding the uncertainty in that

Zurab Berezhiani, Enrico Nardi

We study an extension of the supersymmetric standard model with four families and gauged horizontal symmetry $SU(4)_H$, in which R parity automatically follows as a consequence of gauge invariance and of the field content of the model. Beyond ensuring R parity conservation, the horizontal symmetry allows for the dynamical generation of a hierarchical pattern

Zurab Berezhiani

The supersymmetric $SU(6)$ model equipped by the flavour-blind discrete gauge symmetry $Z_3$ is considered. It provides simultaneous solution to the doublet-triplet splitting problem, $μ$-problem and leads to natural understanding of fermion flavour. The Higgs doublets arise as Goldstone modes of the spontaneously broken {\em accidental} global symmetry $SU(

Masato JIMBO, MINAMI-TATEYA collaboration

We introduce a new method to treat Majorana fermions on the GRACE system which has been developed for the automatic computation of the matrix elements for the processes of the standard model. In the GRACE system, we already have such particles as Dirac fermions, gauge bosons and scalar bosons within the standard model. On the other hand, in the SUSY models t

Masato JIMBO, Hidekazu TANAKA, Toshiaki KANEKO, Tadashi KON

We introduce a new method to treat Majorana fermions on the GRACE system which has been developed for the computation of the matrix elements for the processes of the standard model. In the standard model, we already have such particles as Dirac fermions, gauge bosons and scalar bosons in the system. On the other hand, in the SUSY models there are Majorana fe

S. Guesken

We present selected topics on heavy-light physics on the lattice in order to illustrate the current status of this field. In particular results concerning $f_B$, semileptonic decays, the decay $B \rightarrow K^*γ$ and heavy baryon masses are discussed. Special emphasis is paid to the question of systematic effects which stem from the lattice discretization o

David B. Kaplan

Baryogenesis during the electroweak phase transition is a plausible scenario for for the origin of matter in the Universe. Furthermore, it has the advantage over other scenarios in that one can imagine that much of the physics involved may be experimentally probed before long. In the past year a consensus has developed about major mechanisms involved. In thi

S. Abachi

The results of a search for $W$ boson pair production in $p\bar{p}$ collisions at $\sqrt{s}=1.8$ TeV with subsequent decay to dilepton ($eμ, ee $, and $μμ$) channels are presented. One event is observed with an expected background of $0.56\pm0.13$ events with an integrated luminosity of approximately 14 pb$^{-1}$. %$13.9\pm1.7$ pb$^{-1}$. Assuming equal stre

J. M. Butterworth

At HERA, the electron-proton collider at DESY, Hamburg, the large flux of almost on-shell photons accompanying the lepton beam is being used to shed new light on the structure of the photon. Recent results are reviewed and discussed, with emphasis on those aspects of the photon's nature which should be understandable using perturbative QCD.

Erick J. Weinberg

In these lectures the properties of magnetically charged black holes are described. In addition to the standard Reissner-Nördstrom solution, there are new types of static black holes that arise in theories containing electrically charged massive vector mesons. These latter solutions have nontrivial matter fields outside the horizon; i.e., they are black hole

S. SENGUPTA

The importance of general relativity to the induced electric field exterior to pulsars has been investigated by assuming aligned vacuum and non-vacuum magnetosphere models. For this purpose the stationary and axisymmetric vector potential in Schwarzschild geometry has been considered and the corresponding expressions for the induced electric field due to the

Stellan Ostlund, Stefan Rommer

The density matrix renormalization group (``DMRG'') discovered by White has shown to be a powerful method to understand the properties of many one dimensional quantum systems. In the case where renormalization eventually converges to a fixed point we show that quantum states in the thermodynamic limit with periodic boundary conditions can be simply r

Steven R. White

I introduce two continuous transformations between the $S=1$ Heisenberg chain and the antiferromagnetic $S=1/2$ Heisenberg ladder. Both transformations couple diagonally situated {\it next nearest neighbor} $S=1/2$'s to form each $S=1$. Using the density matrix renormalization group, I demonstrate that the two systems are in the same phase. Furthermore,

R. Heid

The thermodynamic stability of odd-frequency pairing states is investigated within an Eliashberg-type framework. We find the rigorous result that in the weak coupling limit a continuous transition from the normal state to a spatially homogeneous odd-in-$ω$ superconducting state is forbidden, irrespective of details of the pairing interaction and of the spin

P. M. C. de Oliveira, S. M. Moss de Oliveira, C. E. Cordeiro, D. Stauffer

The finite-size scaling algorithm based on bulk and surface renormalization of de Oliveira (1992) is tested on q-state Potts models in dimensions D = 2 and 3. Our Monte Carlo data clearly distinguish between first- and second-order phase transitions. Continuous-q analytic calculations performed for small lattices show a clear tendency of the magnetic exponen

C. G. Carvalhaes, A. T. Costa, T. J. P. Penna

Preprocessing the input patterns seems the simplest approach to invariant pattern recognition by neural networks. The Fourier transform has been proposed as an appropriate and elegant preprocessor. Nevertheless, we show in this work that the performance of this kind of preprocessor is strongly affected by the number of stored informations. This is because th

T. J. P. Penna, D. Stauffer

A bit-string model of biological life-histories is parallelized, with hundreds of millions of individuals. It gives the desired drastic decay of survival probabilities with increasing age for 32 age intervals.

Thadeu J. P. Penna

We present a simple model for biological aging. We studied it through computer simulations and we have found this model to reflect some features of real populations.

W. von der Linden, R. Preuss, W. Hanke

Bayesian statistics in the frame of the maximum entropy concept has widely been used for inferential problems, particularly, to infer dynamic properties of strongly correlated fermion systems from Quantum-Monte-Carlo (QMC) imaginary time data. In current applications, however, a consistent treatment of the error-covariance of the QMC data is missing. Here we

Vladimir I. Fal'ko, G. B. Lesovik

Quantum conductance of 3D ballistic wires with idealy flat boundaries obeys fluctuations with the properties quite distinguishable from those of universal conductance fluctuations: Both their amplitude and the sensitivity to the magnetic field flux $Φ=HS$ penetrated into the sample cross-sectional area $S$ are different and depend on details of the cross-sec

Vladimir I. Fal'ko, K. B. Efetov

The distribution function of local amplitudes of eigenstates of a two-dimensional disordered metal is calculated. Although the distribution of comparatively small amplitudes is governed by laws similar to those known from the random matrix theory, its decay at larger amplitudes is non-universal and much slower. This leads to the multifractal behavior of inve

Vladimir I. Fal'ko

We study the effect of a single bistable scatterer on conductance of mesoscopic conductors in the crossover regime from open to closed systems. After the resistance of the contact between the metallic grain and bulk electrode exceeds the resistance of a grain, the effect of a bistability is enhanced and takes the universal form. Its efficiency scales with th

Karen A. Hallberg

I extend the scope of the density matrix renormalization group technique developed by White to the calculation of dynamical correlation functions. As an application and performance evaluation I calculate the spin dynamics of the 1D Heisenberg chain.

Heiko Rieger

We reconsider the model of the randomly pinned planar flux array (or the two-dimensional XY-model with random fields and no vortices) in extensive Monte Carlo simulations. We show that contrary to what has been reported recently [Phys.\ Rev.\ Lett.\ {\bf 72}, 4133 (1994)] the disorder-averaged displacement correlation function is different from the pure case

Stefan Schwarzer

We describe a method to address efficiently problems of two-phase flow in the regime of low particle Reynolds number and negligible Brownian motion. One of the phases is an incompressible continuous fluid and the other a discrete particulate phase which we simulate by following the motion of single particles. Interactions between the phases are taken into ac

Peter Kopietz

We use a bosonization approach to calculate the single-particle Green&#39;s function $G ( {\bf{r}} , τ)$ of non-relativistic fermions coupled to transverse gauge-fields in arbitrary dimension $d$. We find that in $d>3$ transverse gauge-fields do not destroy the Fermi liquid, although for $d < 6$ the quasi-particle damping is anomalously large. For $d \righta

A. O. Caldeira, A. H. Castro Neto

Making use of a simple unitary transformation we change the hamiltonian of a particle coupled to an one dimensional gas of bosons or fermions to a new form from which the many body degrees of freedom can be easily traced out. The effective dynamics of the particle allows us to compute its damping constant in terms of the reflection coefficient of the interac

Thomas Schürmann, Ingo Hoffmann

In the present work we investigate a new type of billiards defined inside of $n$--simplex regions. We determine an invariant ergodic (SRB) measure of the dynamics for any dimension. In using symbolic dynamics, the (KS or metric) entropy is computed and we find that the system is chaotic for all cases $n>2$.

Tereasa Brainerd, Roger Blandford, Ian Smail

We report a significant detection of weak, tangential distortion of the images of cosmologically distant, faint galaxies due to gravitational lensing by foreground galaxies. A mean image polarisation of $<p>=0.011\pm 0.006$ is measured for 3202 pairs of source galaxies with magnitudes $23< r \le 24$ and lens galaxies with magnitudes $20\le r\le 23$. The sign

Giuliano Giuricin, Fusun Limboz Tektunali, Pierluigi Monaco, Fabio Mardirossian

Relying on samples of disk galaxies for which a detailed photometric bulge/disk decomposition has been provided in the literature, we examine the dependence of the bulge-to-disk luminosity ratio (B/D) on the blue absolute luminosity and on the environmental density. In our statistical analysis of various B/D data sets we pay particular attention to disentang

Bo Ilic

Let $X^n \subset P^N$ be a nonsingular, nondegenerate projective variety of dimension $n$ and codimension $N-n \ge 2$. Let $|C_X|$ be the linear system determined by the double-point divisor obtained by generically projecting $X$ to a hypersurface in $P^{n+1}$. We classify those varieties for which $C_X$ is not ample, or equivalently, does not separate point

L. Roszkowski, M. Shifman

We argue that supersymmetric grand unification of gauge couplings is not incompatible with small $α_s$, even without large GUT-scale corrections, if one relaxes a usual universal gaugino mass assumption. A commonly assumed relation $M_2\simeq m_{\rm gluino}/3$ is in gross contradiction with $α_s\approx 0.11$. Instead, small $α_s$ favors $M_2\gg m_{\rm gluino

Eric G. Gimon, Joseph Polchinski

We study superstrings with orientifold projections and with generalized open string boundary conditions (D-branes). We find two types of consistency condition, one related to the algebra of Chan-Paton factors and the other to cancellation of divergences. One consequence is that the Dirichlet 5-branes of the Type I theory carry a symplectic gauge group, as re

M. G. -H. Mostafa, Cheuk-Yin Wong, Lali Chatterjee, Zhong-Qi Wang

We calculate the dilepton production rate from a thermalized quark-gluon plasma in heavy-ion collisions at RHIC energies. Higher-order QCD corrections are included by using an analytical correction factor $K^{(i)}$, which takes into account the $q\bar q$ initial-state interactions. We show that the analytic correction factor gives very good agreement with ex

Geert Jan van Oldenborgh

The properties of hard photon radiation in $W$ pair production at LEP 2 are studied, with emphasis on the energy loss relevant to the W mass measurement. We use a combination of the exact 1-photon matrix element and leading logarithmic structure functions. Defining unobservable, observable and initial state photons in the phase space, it is shown that neithe

Bernd A. Berg

The problem of calculating multicanonical parameters recursively is discussed. I describe in detail a computational implementation which has worked reasonably well in practice.

Lee Smolin

I review several different calculations, coming from string theory, nonperturbative quantum gravity and analyses of black holes that lead to predictions of phenomena that would uniquely be signatures of quantum gravitational effects. These include: 1) deviations from a thermal spectra for evaporating black holes, 2) upper limits on the entropy and energy con

T. Gehrmann, W. J. Stirling

We have substantially extended our analysis of the partonic content of the pomeron. Ambiguities in the normalization of the pomeron flux and the possiblity of a direct coupling of the pomeron to single quarks are discussed, yielding two equally possible scenarios for the parton distributions in the pomeron. We discuss various experimental tests of these scen

Ghadir Abu Leil, Stefano Moretti

The production of the \sm\ Higgs $ϕ$ with intermediate mass at the proposed CERN LEP$\otimes$LHC $ep$ collider in $γq(\bar q)\rightarrow W^\pmϕq&#39;(\bar q&#39;)$, $γq(\bar q)\rightarrow Z^0ϕq(\bar q)$ and $gγ\rightarrow q\bar qϕ$ events is studied. This is done for all possible (massive) flavours of the quarks $q(q&#39;)$ and using photons generated via Co

A. Yu. Alekseev, A. Recknagel

The structure of block-spin embeddings of the U(1) lattice current algebra is described. For an odd number of lattice sites, the inner realizations of the shift automorphism areclassified. We present a particular inner shift operator which admits a factorization involving quantum dilogarithms analogous to the results of Faddeev and Volkov.

Chan Hong-Mo, J. Faridani, Tsou Sheung Tsun

The classic question of a nonabelian Yang-Mills analogue to electromagnetic duality is here examined in a minimalist fashion at the strictly 4-dimensional, classical field and point charge level. A generalisation of the abelian Hodge star duality is found which, though not yet known to give dual symmetry, reproduces analogues to many dual properties of the a

C. Michael, P. S. Spencer

We present results of an investigation into the nature of instantons in 4-dimensional pure gauge lattice $SU(2)$\ obtained from configurations which have been cooled using an under-relaxed cooling algorithm. We discuss ways of calibrating the cooling and the effects of different degrees of cooling, and compare our data for the shapes, sizes and locations of

Shuxue Ding, Yasushige Maeda, Masaru Siino

We investigate topology changing processes in the WKB approximation of four dimensional quantum cosmology with a negative cosmological constant. As Riemannian manifolds which describe quantum tunnelings of spacetime we consider constant negative curvature solutions of the Einstein equation i.e. hyperbolic geometries. Using four dimensional polytopes, we can

J. M. F. Labastida, M. Mariño

We present a topological quantum field theory which corresponds to the moduli problem associated to Witten&#39;s monopole equations for four-manifolds. The construction of the theory is carried out in purely geometrical terms using the Mathai-Quillen formalism, and the corresponding observables are described. These provide a rich set of new topological quant

J. P. Ma

The functions of the gluon fragmentation into $^3P_J$ quarkonium are calculated to order $α_s^2$. With the recent progress in analysing quarkonium systems in QCD we show explicitly how the socalled divergence in the limit of the zero-binding energy, which is related to $P$-wave quarkonia, is treated correctly in the case of fragmentation functions. The obtai

Robert J. Finkelstein

We describe a q-deformation of the Lorentz group in terms of a q-deformation of the van der Waerden spinor algebra.

Andrzej Sitarz

We build the $q=-1$ defomation of plane on a product of two copies of algebras of functions on the plane. This algebra constains a subalgebra of functions on the plane. We present general scheme (which could be used as well to construct quaternion from pairs of complex numbers) and we use it to derive differential structures, metric and discuss sample field

Naoya Hata, Wick Haxton

We argue that, prior to the recent GALLEX $^{51}$Cr source experiment, the excited state contributions to the $^{71}$Ga capture cross section for $^{51}$Cr and $^7$Be neutrinos were poorly constrained, despite forward-angle (p,n) measurements. We describe the origin of the uncertainties and estimate their extent. We explore the implications of the source exp

E. O. Alt, A. S. Kadyrov, A. M. Mukhamedzhanov, M. Rauh

The driving terms in three-body theories of elastic and inelastic scattering of a charged particle off a bound state of two other charged particles contain the fully off-shell two-body Coulomb T-matrix describing the intermediate-state Coulomb scattering of the projectile with each of the charged target particles. Up to now the latter is usually replaced by

Donald E. Knuth

A combinatorial construction proves an identity for the product of the Pfaffian of a skew-symmetric matrix by the Pfaffian of one of its submatrices. Several applications of this identity are followed by a brief history of Pfaffians.

Michael J. Dinneen

We show that an important problem ($k$-ICG) in computational biology is equivalent to a colored version of a well-known graph layout problem ($k$-CVS).

N. Asmar, Stephen J. Montgomery-Smith

We extend ideas of Garling to consider the so called Hardy martingales in a more general setting of H^p theory of compact abelian groups with ordered dual. As a consequence, we obtain a new proof of a result of Helson and Lowdenslager which generalizes Jensen&#39;s Inequality for H^1 functions.

E. Elizalde, S. D. Odintsov

The Higgs-Yukawa model in curved spacetime (renormalizable in the usual sense) is considered near the critical point, employing the $1/N$--expansion and renormalization group techniques. By making use of the equivalence of this model with the standard NJL model, the effective potential in the linear curvature approach is calculated and the dynamically genera

D. C. Cabra, K. D. Rothe

We obtain a fermionic coset realization of the primaries of minimal unitary models and show how their four-point functions may be calculated by the use of a reduction formula. We illustrate the construction for the Ising model, where we obtain an explicit realization of the energy operator, Onsager fermions, as well as of the order and disorder operators rea

G. Grignani, G. Semenoff, P. Sodano

We discuss SU(N) gluo-dynamics at finite temperature and on a spatial circle. We show that the effective action for the Polyakov Loop operator is a one dimensional gauged SU(N) principle chiral model with variables in the loop space and loop algebra of the gauge group. We find that the quantum states can be characterized by a discrete $θ$-angle which appears

J. Ambjorn, J. Jurkiewicz, Y. Watabiki

We show how it is possible to formulate Euclidean two-dimensional quantum gravity as the scaling limit of an ordinary statistical system by means of dynamical triangulations, which can be viewed as a discretization in the space of equivalence classes of metrics. Scaling relations exist and the critical exponents have simple geometric interpretations. Hartle-

Andreas Honecker

First, an algebraic criterion for integrability is discussed -the so-called `superintegrability&#39;- and some results on the classification of superintegrable quantum spin Hamiltonians based on sl(2) are obtained. Next, the massive phases of the Z_n-chiral Potts quantum spin chain (a model that violates parity) are studied in detail. It is shown that the ex

Andrzej Sitarz

We discuss two concepts of metric and linear connections in noncommutative geometry, applying them to the case of the product of continuous and discrete (two-point) geometry.

Estia J. Eichten, Chris Quigg

We tabulate values of the radial Schrödinger wave function or its first nonvanishing derivative at zero quark-antiquark separation, for $c\bar{c}$, $c\bar{b}$, and $b\bar{b}$ levels that lie below, or just above, flavor threshold. These quantities are essential inputs for evaluating production cross sections for quarkonium states.

Thomas W. Kephart, Tanmay Vachaspati

We propose a criterion to classify hybrid defects occurring in field theoretic models such as the standard electroweak model. This criterion leads us to consider the minimal extension of the electroweak model in which electroweak magnetic monopoles and $Z$-strings are topological. We briefly discuss the cosmology of such defects.

S. Moretti, J. B. Tausk

We analyze the impact of using $b$-tagged samples in studying non-Abelian effects due to QCD in $e^+e^-\ar 4$jet events at $\sqrt s=M_{Z^0}$, using angular variable analyses and comparisons with $e^+e^-\ar 3 \mbox{jet}γ$ events. We find that QCD effects are largely enhanced in $b$-quark samples with respect to `unflavoured&#39; ones, where energy-ordering is

V. I. Matveev, S. G. Tolmanov

The energy losses at collisions of heavy multiply charged ions with light atoms and polarization losses at moving through the matter have been considered under circumstances the ion charge Z>>1 and the relative colliding velocity v>>1, so that Z~v=<c, where c - the light velocity (atomic units are used). In this region of parameters the Born approximation ar

J. Baacke

The fluctuation determinant which determines the preexponential factor of the transition rate for minimal bubbles is computed for the electroweak theory with $\sin Θ_W = 0$. As the basic action we use the three-dimensional high-temperature action including, besides temperature dependent masses, the $T Φ^3$ one-loop contribution which makes the phase transiti

John Ellis, Klaus Geiger

We propose a new and universal approach to the hadronization problem that incorporates both partonic and hadronic degrees of freedom in their respective domains of relevance, and that describes the conversion between them within a kinetic field theory formulation in real time and full 7-dimensional phase space. We construct a scale-dependent effective theory

A. Dumitru, U. Katscher, J. A. Maruhn, H. Stöcker

The rapidity distribution of thermal photons produced in Pb+Pb collisions at CERN-SPS energies is calculated within scaling and three-fluid hydrodynamics. It is shown that these scenarios lead to very different rapidity spectra. A measurement of the rapidity dependence of photon radiation can give cleaner insight into the reaction dynamics than pion spectra,

Ann E. Nelson

Relatively simple models can be constructed in which supersymmetry is dynamically broken at energies of $10^5-10^7$ GeV. Models of this kind do not suffer from the naturalness and cosmological difficulties of conventional supergravity models, and make definite predictions for the spectrum of supersymmetric particle masses. Thus ``Renormalizable Visible Secto

Mirta Iriondo, Edward Malec, Niall Ó Murchadha

We investigate the formation of trapped surfaces in asymptotically flat spherical spacetimes, using constant mean curvature slicing.

Edward Malec, Niall Ó Murchadha

We investigate the formation of trapped surfaces in cosmological spacetimes, using constant mean curvature slicing. Quantitative criteria for the formation of trapped surfaces demonstrate that cosmological regions enclosed by trapped surfaces may have matter density exceeding significantly the background matter density of the flat and homogeneous cosmologica

E. R. Bezerra de Mello, V. B. Bezerra, C. Furtado, F. Moraes

In this paper we calculate the magnetic and electric self-forces, induced by the conical structure of a cosmic string space-time, on a long straight wire which presents either a constant current or a linear charge density. We also show how these self-forces are related by a Lorentz tranformation and, in this way, explain what two different inertial observers

Alexander G. Reznikov

From the cohomological point of view the symplectomorphism group $Sympl (M)$ of a symplectic manifold is `` tamer&#39;&#39; than the diffeomorphism group. The existence of invariant polynomials in the Lie algebra $\frak {sympl }(M)$, the symplectic Chern-Weil theory, and the existence of Chern-Simons-type secondary classes are first manifestations of this pr

A. H. Castro Neto, D. K. Campbell, Philip Phillips

We report a class of {\it integrable} one-dimensional interacting electronic sy$ with {\it off-diagonal disorder}. For these systems, the disorder can be ``gauged away,&#39;&#39;and the spectrum can be mapped completely onto the spectrum of the ordered problem, which can be solved by Bethe ansatz or by bosonization. We study the magnetic properties of the pe

R. A. Roemer, H. -P. Eckle, B. Sutherland

We report on the closing of gaps in the ground state of the critical Heisenberg-Ising chain at momentum $π$. For half-filling, the gap closes at special values of the anisotropy $Δ= \cos(π/Q)$, $Q$ integer. We explain this behavior with the help of the Bethe Ansatz and show that the gap scales as a power of the system size with variable exponent depending on

Gunter M. Schütz

We study the effect of an external driving force on a simple stochastic reaction-diffusion system in one dimension. In our model each lattice site may be occupied by at most one particle. These particles hop with rates $(1\pmη)/2$ to the right and left nearest neighbouring site resp. if this site is vacant and annihilate with rate 1 if it is occupied. We sho

Marilyn A. Walker

A discourse strategy is a strategy for communicating with another agent. Designing effective dialogue systems requires designing agents that can choose among discourse strategies. We claim that the design of effective strategies must take cognitive factors into account, propose a new method for testing the hypothesized factors, and present experimental resul

Marilyn A. Walker

In dialogues in which both agents are autonomous, each agent deliberates whether to accept or reject the contributions of the current speaker. A speaker cannot simply assume that a proposal or an assertion will be accepted. However, an examination of a corpus of naturally-occurring problem-solving dialogues shows that agents often do not explicitly indicate

Eric Woods, Abraham Loeb

We discuss several constraints on the properties of gamma-ray bursts (GRB) at cosmological distances. First we use the requirement that burst sources must be optically thin to pair production by photon-photon collisions in order to produce the observed nonthermal spectra. We derive probability distributions for the minimum Lorentz expansion factor, the radia

Elisabete M. de Gouveia Dal Pino

Highly collimated supersonic jets are observed to emerge from a wide variety of astrophysical objects, ranging from Active Nuclei of Galaxies (AGN&#39;s) to Young Stellar Objects (YSOs) within our own Galaxy. Despite their different physical scales (in size, velocity, and amount of energy transported), they have strong morphological similarities. Thanks to t

H. -Thomas Janka

Muon and tau neutrinos ($ν_x$) interact with protoneutron star matter only via neutral currents and exchange energy with the stellar gas predominantly by neutrino-electron scattering and neutrino-pair processes. In contrast, electron neutrinos and antineutrinos ($ν_e$ and $\barν_e$) are frequently absorbed and produced in charged-current mediated reactions w

A. C. Quillen, Jay. A. Frogel, L. E. Kuchinski, D. M. Terndrup

We present $B,V,R,J,H,K$ broad--band images of the barred galaxy NGC 1097. The optical and infrared colors maps trace the location of the major dust features. The dust lanes are relatively free of star formation and have low opacity. The depth of the dust lanes decreases as a function of wavelength so that they are deepest at $B$ and shallower at $H$ and $K$

A. C. Quillen, Solange V. Ramírez, Jay A. Frogel

We present visible and near-infrared images of the amorphous dwarf galaxy NGC 1705 in the $B$, $V$, $R$, $J$, $H$, and $K$ bands. Optical and near infrared colors in the galaxy are consistent with a composite population with colors similar to those of the bluest Sc nuclei. The contribution of young stars to the disk population of the galaxy decreases outward

Janusz Kaluzny, Slavek Rucinski

Three new photometric CCD-based datasets are presented for NGC~6791. They consist of deep UBV photometry (to $V_{lim} =24$, $B_{lim}=24$, $U_{lim} = 23$) of the central parts of the cluster and of selected fields around it, and of relatively shallower UBVI photometry for the whole cluster ($23&#39; \times 23&#39;$). The data have been used to discuss the red

P. Rosati, R. Della Ceca, R. Burg, C. Norman

We present the first results of a serendipitous search for clusters of galaxies in deep ROSAT-PSPC pointed observations at high galactic latitude. The survey is being carried out using a Wavelet based Detection Algorithm which is not biased against extended, low surface brightness sources. A new flux--diameter limited sample of 10 cluster candidates has been

L. Barbieri-Viale, V. Srinivas

Let $X$ be a non-singular projective complex surface. We can show that Bloch&#39;s conjecture (i.e., that if $p_g=0$ then the Albanese kernel vanishes) is equivalent to the following statement: If $p_g(X)=0$ then for any given Zariski open $U\subset X$ and $ω\in H^2(U,{\bf C})$ there is a smaller Zariski open $V\subset U$ such that $$ω\mid_V =ω&#39;+ζ$$ wher

János Kollár

The paper proves that if a reductive group scheme acts properly on a scheme then the geometric quotient exists as an algebraic space. As a consequence we obtain the existence of the moduli spcace of canonically polarized varieties over Spec Z.

Andreas Blumhofer, Richard Dawid, Manfred Lindner

Predictions for the ratio $M_W/m_t$ arise in top condensation models from different methods. One type of prediction stems from Pagels--Stokar relations based on the use of Ward Identities in the calculation of the \GB decay constants and expresses $M_W$ in terms of integrals containing the dynamically generated mass function $Σ_t(p^2)$. Another type of predi

B. Bergerhoff, F. Freire, D. Litim, S. Lola

The universal behaviour of superconductors near the phase transition is described by the three-dimensional field theory of scalar quantum electrodynamics. We approximately solve the model with the help of non-perturbative flow equations. A first- or second-order phase transition is found depending on the relative strength of the scalar versus the gauge coupl

David O&#39;Brien, Paul A. Pearce

The conformal spectra of the critical dilute A-D-E lattice models are studied numerically. The results strongly indicate that, in branches 1 and 2, these models provide realizations of the complete A-D-E classification of unitary minimal modular invariant partition functions given by Cappelli, Itzykson and Zuber. In branches 3 and 4 the results indicate that

Andrei Linde

We propose a simple version of chaotic inflation scenario which leads to a division of the universe into infinitely many open universes with all possible values of $Ω$ from 1 to 0.

H. B. O&#39;Connell, B. C. Pearce, A. W. Thomas, A. G. Williams

The suggestion of momentum dependence in the amplitude for rho-omega mixing has generated concern over related implications for vector meson dominance and the photon-rho coupling. We discuss two established representations of vector meson dominance and show that one of these is completely consistent with such a coupling. We then apply it to a calculation of