May 1994 arXiv papers — page 2

Neil Cornish

The general equations describing hydrostatic equilibrium are developed for Non-singular Gravity. A new type of astrophysical structure, a Super Dense Object (SDO) or "Dark Star", is shown to exist beyond Neutron star field strengths. These structures are intrinsically stable against gravitational collapse and represent the non-singular alternative to

Jian Ma, C. Quitmann, R. J. Kelley, G. Margaritondo

We present the first detailed angle-resolved photoemission evidence that there are two types of carriers that contribute to the photoemission superconducting condensate in $Bi_{2}Sr_{2}Ca_{1}Cu_{2}O_{8+x}$. Our data indicate that both itinerant and somewhat localized normal state carriers can contribute to the formation of Cooper pairs.

Matthias Troyer, Hirokazu Tsunetsugu, Diethelm Wuertz

We have developed an improved version of the quantum transfer matrix algorithm. The extreme eigenvalues and eigenvectors of the transfer matrix are calculated by the recently developed look-ahead Lanczos algorithm for non-Hermitian matrices with higher efficiency and accuracy than by the power method. We have applied this method to the Heisenberg ladder. The

K. A. Muttalib

It has been argued that despite remarkable success, existing random matrix theories are not adequate to describe disordered conductors in the metallic regime, due to the presence of certain two-body interactions in the effective Hamiltonian for the eigenvalues, in addition to the standard logarithmic interaction that arises entirely from symmetry considerati

Dean Prichard, James Theiler

Extensions to various information theoretic quantities used for nonlinear time series analysis are discussed, as well as their relationship to the generalized correlation integral. It is shown that calculating redundancies from the correlation integral can be more accurate and more efficient than direct box counting methods. It is also demonstrated that many

Dean Prichard

The effect differencing has on the estimated correlation dimension of a nongaussian time series is discussed. Two different methods for generating surrogate data sets are compared. The results suggest that any filtering should be applied to both the raw and surrogate time series, otherwise spurious results can occur.

Michael Gasser

This paper describes a modular connectionist model of the acquisition of receptive inflectional morphology. The model takes inputs in the form of phones one at a time and outputs the associated roots and inflections. Simulations using artificial language stimuli demonstrate the capacity of the model to learn suffixation, prefixation, infixation, circumfixati

Iosif Lapidus, Luciano Nobili, Roberto Turolla

We present estimates for the accretion rates in 13 X--ray bursting sources which exhibit photospheric expansion, basing on theoretical models of stationary, radiatively driven winds from neutron stars. The relatively high values obtained, $\Mdot_{acc}\magcir 10^{-9} \MS$, are in accordance with theoretical limits for unstable helium burning, and, at the same

Luciano Nobili, Roberto Turolla, Iosif Lapidus

A model for stationary, radiatively driven winds from X--ray bursting neutron stars is presented. General relativistic hydrodynamical and radiative transfer equations are integrated from the neutron star surface outwards, taking into account for helium nuclear burning in the inner, dense, nearly hydrostatic shells. Radiative processes include both bremsstrah

Vittorio Castellani, Scilla Degl'innocenti, Gianni Fiorentini, Marcello Lissia

For standard neutrinos, recent solar neutrino results together with the assumption of a nuclearly powered Sun imply severe constraints on the individual components of the total neutrino flux: \Phi_{Be}<0.7*10^9cm^-2 s^-1, \Phi_{CNO}< 0.6*10^9 cm^-2 s^-1, and $64*10^9 cm^-2 s^-1< \Phi_{pp+pep} < 65*10^9 cm^-2 s^-1 (at 1 \sigma level). The bound on \Phi_{Be} i

Yong Baek Kim, Akira Furusaki, Xiao-Gang Wen, Patrick A. Lee

We study a model of fermions interacting with a gauge field and calculate gauge-invariant two-particle Green&#39;s functions or response functions. The leading singular contributions from the self-energy correction are found to be cancelled by those from the vertex correction for small $q$ and $Ω$. As a result, the remaining contributions are not singular en

Igor Yu. Sokolov

Energy production due to the Casimir effect is considered for the case of a superdense state of matter, which can appear in such cosmological objects as white dwarfs, neutron stars, quasars and so on. The energy output produced by the Casimir effect during the creation of a neutron star turns out to be sufficient to explain nova and supernova explosions. It

Ewan D. Stewart

The positive potential energy required for inflation spontaneously breaks supersymmetry and in general gives any would-be inflaton an effective mass of order the inflationary Hubble parameter thus ruling it out as an inflaton. In this paper I give simple conditions on the superpotential that eliminate some potential sources for this mass, and derive a form f

Damiano Anselmi, Pietro Fre&#39;, Luciano Girardello, Paolo Soriani

We derive a model of constrained topological gravity, a theory recently introduced by us through the twist of N=2 Liouville theory, starting from the general BRST algebra and imposing the moduli space constraint as a gauge fixing. To do this, it is necessary to introduce a formalism that allows a careful treatment of the global and the local degrees of freed

Volodymyr Lyubashenko

A category N of labeled (oriented) trivalent graphs (nets) or ribbon graphs is extended by new generators called fusing, braiding, twist and switch with relations which can be called Moore--Seiberg relations. A functor to N is constructed from the category Surf of oriented surfaces with labeled boundary and their homeomorphisms. Given an (eventually non-semi

Volodymyr Lyubashenko

An example of a finite dimensional factorizable ribbon Hopf C-algebra is given by a quotient H=u_q(g) of the quantized universal enveloping algebra U_q(g) at a root of unity q of odd degree. The mapping class group M_{g,1} of a surface of genus g with one hole projectively acts by automorphisms in the H-module H^{*\otimes g}, if H^* is endowed with the coadj

Maximo Banados

We use the Regge-Teitelboim method to treat surface integrals in gauge theories to find global charges in Chern-Simons theory. We derive the affine and Virasoro generators as global charges associated with symmetries of the boundary. The role of boundary conditions is clarified. We prove that for diffeomorphisms that do not preserve the boundary there is a c

Kazuo Fujikawa

In the generalized Pauli-Villars regularization of chiral gauge theory proposed by Frolov and Slavnov , it is important to specify how to sum the contributions from an infinite number of regulator fields. It is shown that an explicit sum of contributions from an infinite number of fields in anomaly-free gauge theory essentially results in a specific choice o

Hang Bae Kim, Jihn E. Kim

Since it became evident that the CDM model for cosmic structure formation predicts smaller power on large scales than observed, many alternatives have been suggested. Among them, the existence of late decaying particle can cure it by delaying the beginning of the matter domination and increasing the horizon length at that time. We discuss the realization of

R. Marnelius, Sh. M. Shvartsman

Gauge invariant complex covariant actions for superparticles are derived from the field equations for the chiral superfields in a precise manner. The massive and massless cases in four dimensions are treated both free and in interaction with an external super Maxwell field. By means of a generalized BRST quantization these complex actions are related to real

Aric Hagberg, Ehud Meron

Two front instabilities in a reaction-diffusion system are shown to lead to the formation of complex patterns. The first is an instability to transverse modulations that drives the formation of labyrinthine patterns. The second is a Nonequilibrium Ising-Bloch (NIB) bifurcation that renders a stationary planar front unstable and gives rise to a pair of counte

Domenico Giulini

We consider SU(N) Yang-Mills theories in 2n+1 Euclidean dimensions coupled to an even flavour-number of Dirac fermions. After integrating out the fermions the wave functional for the effective Yang-Mills theory inherits a non-trivial U(1)-connection which is computed in the limit of infinite fermion mass (adiabatic connection). Its Chern-class turns out to b

D. Anselmi, P. Fre&#39;, L. Girardello, P. Soriani

In this talk we review some results concerning a mechanism for reducing the moduli space of a topological field theory to a proper submanifold of the ordinary moduli space. Such mechanism is explicitly realized in the example of constrained topological gravity, obtained by topologically twisting the N=2 Liouville theory.

P. Cea, L. Tedesco

We study a generalization of the Gaussian effective potential for self-interacting scalar fields in one and two spatial dimensions. We compute the two-loop corrections and discuss the renormalization of the generalized Gaussian effective potential.

P. E. Gibbs

Field Theory on Event Symmetric space-time is constructed using the gauge group of discrete open strings. Models with invariant actions can be viewed as natural extensions of Matrix Models. The objective is to find a fundamental non-perturbative pre-theory for superstrings.

M. Chaichian, R. Gonzalez Felipe, H. Perez Rojas

Some cosmological consequences of including the adequate conserved quantities in the density matrix of the electroweak theory are investigated. Several arguments against including the charges associated to the spontaneously broken symmetry are presented. Special attention is focused on the phenomenon of $W$-boson condensation and its interplay with the phase

M. Chaichian, J. F. Gomes, R. Gonzalez Felipe

The relation between the spin and the mass of an infinite number of particles in a $q$-deformed dual string theory is studied. For the deformation parameter $q$ a root of unity, in addition to the relation of such values of $q$ with the rational conformal field theory, the Fock space of each oscillator mode in the Fubini-Veneziano operator formulation become

Amitabha Chakrabarti

Representations of $SO(5)_{q}$ are constructed explicitly on the Chevalley basis for all $q$, generic and root of unity. Matrix elements of the generators are obtained for all representations depending on three variable indices, the maximal number being 4. A prescription for contraction is given such that a complete Hopf algebra is immediately obtained for t

N. Bralic, D. Cabra, F. A. Schaposnik

We study the thermodynamics of the relativistic Quantum Field Theory of massive fermions in three space-time dimensions coupled to an Abelian Maxwell-Chern-Simons gauge field. We evaluate the specific heat at finite temperature and density and find that the variation with the statistical angle is consistent with the non-relativistic ideas on generalized stat

R. Roncaglia, A. Dzierba, D. B. Lichtenberg, E. Predazzi

There are striking regularities in the masses and mass differences of known hadrons. Some of these regularities can be understood from known general properties of the interactions of quarks without a need to specify the explicit form of the Hamiltonian. The Feynman--Hellmann theorem is one of the tools providing this understanding. If the mass regularities a

Thomas G. Rizzo

The Next Linear Collider(NLC) will provide a excellent tool for probing the detailed nature of the top quark. By extending the recent analysis of Dokshitzer, Khoze and Sterling, we perform a preliminary examination of the influence of an anomalous chromomagnetic moment for the top, $κ$, on the spectrum of gluon radiation associated with $t\bar t$ production.

R. B. Nevzorov, A. V. Novikov, M. I. Vysotsky

To obtain the value of electromagnetic coupling constant at $q^2=m^2_Z$, $\barα$, which plays a key role in electroweak physics one has to integrate the cross-section of $e^+e^-$-annihilation into hadrons divided by $(s-m^2_Z)$ over $s$ from threshold to infinity. By combining, for each flavor channel, the contribution of lowest resonance with the perturbati

S. Catani, F. Hautmann

High-energy factorization in QCD is investigated beyond leading order and its relationship to the factorization theorem of mass singularities is established to any collinear accuracy. Flavour non-singlet observables are shown to be regular at small x order by order in perturbation theory. In the singlet sector, we derive the relevant master equations for the

Burkhard Kleihaus, Jutta Kunz

We construct multisphaleron solutions in the Weinberg-Salam theory. The multisphaleron solutions carry Chern-Simons charge $n/2$, where $n$ is an integer, counting the winding of the fields in the azimuthal angle. The well-known sphaleron has $n=1$. The multisphalerons possess axial symmetry and parity reflection symmetry. We vary the Higgs mass and the mixi

Zoltan Kunszt, Adrian Signer, Zoltan Trocsanyi

We present analytic results for the one-loop corrections of the helicity amplitudes of the QCD five-parton subprocesses involving four quarks and one gluon obtained with a standard Feynman diagram calculation using dimensional reduction.

Alessandro Ballestrero, Ezio Maina, Stefano Moretti

Heavy quark production in multijet events at $e^+e^-$ colliders is studied at tree level. Total production rates are given and compared with the corresponding results for massless quarks. A new method of computing helicity amplitudes is briefly sketched. Talk presented at the XXIXth Rencontres de Moriond, QCD and High Energy Hadronic Interactions, Meribel, F

Xin-Nian Wang

Medium effects which include color screening and Landau-Pomeranchuk-Migdal suppression of induced radiation are discussed in connection with the equilibration of dense partonic system in ultrarelativistic heavy ion collisions. Taking into account of these medium effects, the equilibration rate for a gluonic gas are derived and the consequences are discussed.

C. Parrinello

We define and evaluate on the lattice the amputated 3-gluon vertex function in momentum space. We give numerical results for $16^3 \times 40$ and $24^3 \times 40$ quenched lattices at $β=6.0$. A good numerical signal is obtained, at the price of enforcing the gauge-fixing condition with high accuracy. By comparing results from two different lattice volumes,

Vladimir D. Ivashchuk, Vitaly N. Melnikov

The n-time generalization of the Tangherlini solution [1] is considered. The equations of geodesics for the metric are integrated. For $n = 2$ it is shown that the naked singularity is absent only for two sets of parameters, corresponding to the trivial extensions of the Tangherlini solution. The motion of a relativistic particle in the multitemporal backgro

J. Audretsch, U. Jasper, V. D. Skarzhinsky

In the framework of QED we investigate the bremsstrahlung process for an electron passing by a straight static cosmic string. This process is precluded in empty Minkowski space-time by energy and momentum conservation laws. It happens in the presence of the cosmic string as a consequence of the conical structure of space, in spite of the flatness of the metr

Susan M. Scott, Peter Szekeres

A new scheme is proposed for dealing with the problem of singularities in General Relativity. The proposal is, however, much more general than this. It can be used to deal with manifolds of any dimension which are endowed with nothing more than an affine connection, and requires a family \calc\ of curves satisfying a {\em bounded parameter property} to be sp

Hideyuki Tagoshi, Misao Sasaki

Based upon the formalism recently developed by one of us (MS), we analytically perform the post-Newtonian expansion of gravitational waves from a test particle in circular orbit of radius $r_0$ around a Schwarzschild black hole of mass $M$. We calculate gravitational wave forms and luminosity up to $v^8$ order beyond Newtonian, where $v=(M/r_0)^{1/2}$. In pa

Jewan Kim, C. J. Park, Yongsung Yoon

We have considered the quantum behavior of a conformally induced gravity in the minimal Riemann-Cartan space. The regularized one-loop effective potential considering the quantum fluctuations of the dilaton and the torsion fields in the Coleman-Weinberg sector gives a sensible phase transition for an inflationary phase in De Sitter space. For this effective

S. V. Kravchenko, G. V. Kravchenko, J. E. Furneaux, V. M. Pudalov

We have studied the zero magnetic field resistivity of unique high- mobility two-dimensional electron system in silicon. At very low electron density (but higher than some sample-dependent critical value, $n_{cr}\sim 10^{11}$ cm$^{-2}$), CONVENTIONAL WEAK LOCALIZATION IS OVERPOWERED BY A SHARP DROP OF RESISTIVITY BY AN ORDER OF MAGNITUDE with decreasing temp

D. G. Barci, L. Moriconi

We study the tunneling between two quantum Hall systems, along a quasi one-dimensional interface. A detailed analysis relates microscopic parameters, characterizing the potential barrier, with the effective field theory model for the tunneling. It is shown that the phenomenon of fermion number fractionalization is expected to occur, either localized in conve

Matthew B. Hastings, A. Douglas Stone, Harold U. Baranger

We define a current-conserving approximation for the local conductivity tensor of a disordered system which includes the effects of weak localization. Using this approximation we show that the weak localization effect in conductance is not obtained simply from the diagram corresponding to the coherent back-scattering peak observed in optical experiments. Oth

Joonhyun Yeo, Gene F. Mazenko

The element of metastability is incorporated in the fluctuating nonlinear hydrodynamic description of the mode coupling theory (MCT) of the liquid-glass transition. This is achieved through the introduction of the defect density variable $n$ into the set of slow variables with the mass density $ρ$ and the momentum density ${\bf g}$. As a first approximation,

Raimundo R dos Santos

We study the phase diagram for the attractive ({\it i.e.,} negative-$U$) Hubbard model on a simple cubic lattice, through Monte Carlo simulations. We obtain the critical temperature, $T_c$, for superconductivity from a finite-size scaling analysis of the data for the pairing correlations. For fixed on-site attraction, $U$, $T_c$ displays a maximum near the f

A. M. Chang, H. U. Baranger, L. N. Pfeiffer, K. W. West

We report experimental evidence that chaotic and non-chaotic scattering through ballistic cavities display distinct signatures in quantum transport. In the case of non-chaotic cavities, we observe a linear decrease in the average resistance with magnetic field which contrasts markedly with a Lorentzian behavior for a chaotic cavity. This difference in line-s

M. Kasner, W. Apel

The problem of interacting electrons moving under the influence of a strong magnetic field in two dimensions on a finite disk is reconsidered. First, the results of exact diagonalizations for up to $N=9$ electrons for Coulomb as well as for a short--range interaction are used in the search for a peculiar ground state corresponding to filling factor $1/3$. No

J. P. Bouchaud, M. Mezard

We consider a simple spin system without disorder which exhibits a glassy regime. We show that this model can be well approximated by a system with quenched disorder which is studied with the standard methods developped in spin glasses. We propose that the glass transition is a point where quenched disorder is self induced, a scenario for which the `cavity&#

H. Kato, D. Yoshioka

Effects of Coulomb interaction on persistent currents in disordered one-dimensional rings are numerically investigated. First of all effectiveness of the Hartree-Fock approximation is established on small systems. Then the calculations are done for systems with 40 electrons in 100 sites. It is found that the amplitude of the average persistent current in the

Mark-Jan Nederhof, Giorgio Satta

We show that more head-driven parsing algorithms can be formulated than those occurring in the existing literature. These algorithms are inspired by a family of left-to-right parsing algorithms from a recent publication. We further introduce a more advanced notion of ``head-driven parsing&#39;&#39; which allows more detailed specification of the processing o

Mark-Jan Nederhof

In this paper we relate a number of parsing algorithms which have been developed in very different areas of parsing theory, and which include deterministic algorithms, tabular algorithms, and a parallel algorithm. We show that these algorithms are based on the same underlying ideas. By relating existing ideas, we hope to provide an opportunity to improve som

Manny Rayner

The thesis describes a logical formalization of natural-language database interfacing. We assume the existence of a ``natural language engine&#39;&#39; capable of mediating between surface linguistic string and their representations as ``literal&#39;&#39; logical forms: the focus of interest will be the question of relating ``literal&#39;&#39; logical forms

Alon Lavie

GLR* is a recently developed robust version of the Generalized LR Parser, that can parse almost ANY input sentence by ignoring unrecognizable parts of the sentence. On a given input sentence, the parser returns a collection of parses that correspond to maximal, or close to maximal, parsable subsets of the original input. This paper describes recent work on d

J. D. Doll, D. L. Freeman

In the present paper we examine the effects of noise on Monte Carlo algorithms, a problem raised previously by Kennedy and Kuti (Phys. Rev. Lett. {\bf 54}, 2473 (1985)). We show that the effects of introducing unbiased noise into the acceptance/rejection phase of the conventional Metropolis approach are surprisingly modest, and, to a significant degree, larg

Jordi Miralda-Escude, Arif Babul

Long arcs in clusters of galaxies, produced by gravitational lensing, can be used to estimate the mass interior to the arcs and therefore, constrain the cluster mass distribution. The radial density distribution of the intracluster gas (ICM) can be extracted from the X-ray surface brightness observations. If the gas temperature is also known, it is then poss

Philippe Fischer, J. Anthony Tyson, Gary M. Bernstein, Puragra Guhathakurta

Luminous objects associated with the 7.06\arcsec\ separation double quasar Q2345+007 have, until now, escaped detection. In this letter we present the results of the deepest known imaging of the region surrounding the quasar. The total exposure times were 47600 seconds in B$_j$ (101 frames) and 32160 seconds in R (82 frames). The frames came from CFHT, CTIO,

Choi, Evans, Jaffe, Walker

Molecular outflows associated with GL 2591 and W28 A2 were observed in the 492 GHz [CI] line. Upper limits are set on the [CI] emission in the extremely high velocity line wings. These limits are discussed in terms of wind-driven and jet-driven models of molecular outflows.

Francesco Haardt, Laura Maraschi, Gabriele Ghisellini

We propose that the X--ray emission from radio quiet AGN and galactic black holes is due to Comptonization of soft thermal photons emitted by the underlying accretion disk in localized structures (blobs). The power per unit area produced by the blobs, impinging on the disk, can easily dominate the radiation internally produced by the disk. In this case the e

Toshiyuki Fukushige, Douglas C. Heggie

This paper is concerned with collisionless aspects of the early evolution of model star clusters. The effects of mass loss through stellar evolution and of a steady tidal field are modelled using $N$-body simulations. Our results (which depend on the assumed initial structure and the mass spectrum) agree qualitatively with those of Chernoff \& Weinberg (1990

Hajime Susa, Misao Sasaki, Takahiro Tanaka

We consider the joint probability distribution function for the mass contrast and angular momentum of over-density regions on the proto- galactic scale and investigate the formation of massive black holes at redshift $z\gsim10$. We estimate the growth rate of the angular momentum by the linear perturbation theory and the decay rate by the Compton drag and ap

Gary A. Mamon

The DENIS 2 micron survey is described. It&#39;s ability to probe galaxies at very low galactic latitudes is computed using simulated images. This analysis indicates that DENIS will be able to separate galaxies from stars, right through the Galactic Plane, for galactic longitudes $45^\circ \leq \ell \leq 315^\circ$, with a maximum loss in the magnitude limit

Robert C. Myers

Black hole entropy is studied for an exactly solvable model of two-dimensional gravity\cite{rst1}, using recently developed Noether charge techniques\cite{wald1}. This latter approach is extended to accomodate the non-local form of the semiclassical effective action. In the two-dimensional model, the final black hole entropy can be expressed as a local quant

Janna Levin

It is shown here that a dynamical Planck mass can drive the scale factor of the universe to accelerate. The negative pressure which drives the cosmic acceleration is identified with the unusual kinetic energy density of the Planck field. No potential nor cosmological constant is required. This suggests a purely gravity driven, kinetic inflation. Although the

Vladimir Hinich, Vadim Schechtman

A description of a ring of functions on the base of a universal formal deformation for several moduli problems is given. The answer is given in terms of a homology group of a certain dg Lie algebra canonically (up to an essentially unique quasi-isomorphism) associated with a problem.

J. A. de Azcárraga, P. P. Kulish, F. Rodenas

The structure and properties of possible $q$-Minkowski spaces is discussed, and the corresponding non-commutative differential calculi are developed in detail and compared with already existing proposals. This is done by stressing its covariance properties as described by appropriate reflection equations. Some isomorphisms among the space-time and derivative

F. de Campos, J. W. F. Valle, A. Lopez-Fernandez, J. C. Romão

Talk presented at the XXIX Rencontres de Moriond, Electroweak Interactions and Unified Theories, March 12-19, 1994, Meribel

Arlen Anderson

A proposal is made for a mathematically unambiguous treatment of evolution in the presence of closed timelike curves. In constrast to other proposals for handling the naively nonunitary evolution that is often present in such situations, this proposal is causal, linear in the initial density matrix and preserves probability. It provides a physically reasonab

A. P. Ramirez, P. Chandra, P. Coleman, Z. Fisk

We present the nonlinear susceptibility as a direct test of the quadrupolar Kondo scenario for heavy fermion behavior, and apply it to the case of cubic crystal-field symmetry. Within a single-ion model we compute the nonlinear susceptibility resulting from low-lying Γ_3 (5f^2 and Kramers (5f^3) doublets. We find that nonlinear susceptibility measurements on

D. Braak, F. Sievers, K. Ziegler

We consider a system of spin-dependent fermions on a one-dimensional lattice which is coupled to phonons. The phonons create either a Peierls instability by breaking the translational invariance or create long range correlations. On the other hand, there is a spin-dependent Hubbard-like interaction which competes with the effective fermion-fermion interactio

Jochem Fleischer, Fred Jegerlehner, Karol Kolodziej, Geert Jan van Oldenborgh

We describe a generator for the process $e^+e^- \to W^+W^-$ including all one-loop and leading log photonic two-loop contributions. It includes polarization of the beam and $W$ bosons, and the possibility to study the effect of anomalous couplings.

F. Csikor, Z. Fodor, J. Hein, K. Jansen

Numerical simulations are performed to study the finite temperature phase transition in the SU(2) Higgs model on the lattice. The strength of the first order phase transition is investigated by determining the latent heat and the interface tension on $L_t=2$ lattices. The values of the Higgs boson mass presently chosen are below 50 GeV. Our results are in qu

Itzhak Bars, Jürgen Schulze

We find all the classical solutions (minimal surfaces) of open or closed strings in {\it any} two dimensional curved spacetime. As examples we consider the SL(2,R)/R two dimensional black hole, and any 4D black hole in the Schwarzschild family, provided the motion is restricted to the time-radial components. The solutions, which describe longitudinaly oscill

Heinz Konig

I present the results of the QCD corrections to the H+ --> t anti-b decay within the minimal supersymmetric standard model, if gluinos and scalar quarks are taken within the relevant loop diagram. I include the mixing of the scalar partners of the left- and right-handed top quark, which is proportional to the top quark mass. The standard corrections via gluo

M. Dine, Y. Shirman

In supersymmetric theories, one can obtain striking results and insights by exploiting the fact that the superpotential and the gauge coupling function are holomorphic functions of the model parameters. The precise meaning of this holomorphy is subtle, and has been explained most clearly by Shifman and Vainshtein, who have stressed the role of the Wilsonian

Martin Kummer

We study in which way Kolmogorov complexity and instance complexity affect properties of r.e. sets. We show that the well-known 2log n upper bound on the Kolmogorov complexity of initial segments of r.e.\ sets is optimal and characterize the T-degrees of r.e. sets which attain this bound. The main part of the paper is concerned with instance complexity of r.

R. Ferraro, M. Henneaux, M. Puchin

It is shown that the BRST path integral for reducible gauge theories, with appropriate boundary conditions on the ghosts, is a solution of the constraint equations. This is done by relating the BRST path integral to the kernel of the evolution operator projected on the physical subspace.

Niclas Engberg, Bengt E. W. Nilsson, Anders Westerberg

Recently an algorithm was found by means of which one can calculate terms at arbitrary oscillator level in the four-Ramond vertex obtained by sewing. Here we show that this algorithm is applicable also to the case of ${\bf Z}_2$-twisted scalars and derive the full propagator for scalars on the Riemann sphere with two branch cuts. The relation to similar resu

Sigurd Schelstraete, Henri Verschelde

Using a simple identity between various partial derivatives of the energy of the vector model in 0+0 dimensions, we derive explicit results for the coefficients of the large N expansion of the model. These coefficients are functions in a variable $ρ^2$, which is the expectation value of the two point function in the limit $N=\infty$. These functions are anal

Jin-Ho Cho, Jae-Kwan Kim

The `classical&#39; model for a massive spinning particle, which was recently proposed, is derived from the isotropic rotator model. Through this derivation, we note that the spin can be understood as the relativistic extension of the isotropic rotator. Furthermore, the variables $t_\m$ corresponding to the $\p^*$ of the `pseudo-classical&#39; model, are nec

S. P. Misra

We relate here the vacuum structure of chiral symmetry breaking to a wide class of low energy hadronic properties to examine consistency with experimental results. Phase transition of chiral symmetry breaking is described through explicit vacuum realignment. We find that for the present ansatz, vacuum structure of the light quark sector can be determined fro

Roger Decker, Markus Finkemeier

In a previous paper we have calculated the decay $τ\toπν_τγ$. We used a given relative sign between the internal bremsstrahlung and the structure dependent radiation, which has been used by several other authors before. However, we believe that there are good arguments why the opposite sign is the physical one. We briefly discuss these arguments and then inv

Andrei Leonidov

The propagation of massive coloured particles in stochastic background chromoelectric field is studied using the semiclassical equations of motion. Depending on the nature of the stochastic background we obtain the formulae for the energy losses of heavy coloured projectile in nonperturbative hadronic medium and for the energy gains in the stochastic field p

J. Maalampi, J. Sirkka, I. Vilja

We consider the baryon number generation by charge transport mechanism in the electroweak phase transition taking properly into account thermal fluxes through the wall separating true and false vacuum in the spatial space. We show that the diffusion from the true vacuum to the false one has a large diminishing effect on the baryon number unless the wall velo

Howard E. Haber

An introduction to spin techniques in particle physics is given. Among the topics covered are: helicity formalism and its applications to the decay and scattering of spin-1/2 and spin-1 particles, techniques for evaluating helicity amplitudes (including projection operator methods and the spinor helicity method), and density matrix techniques. The utility of

Takashi HAMAZAKI, Taichiro KUGO

Usual treatment of the Nambu--Jona-Lasinio (NJL) model using loop momentum cutoff suffers from ambiguities in choosing the loop momenta to be cut off and violation of (external) gauge invariance. We define the NJL model from the starting Lagrangian level by using a higher derivative fermion kinetic term with a cutoff parameter $Λ$. This definition is free fr

M. Baig, R. Villanova

We present the results of a finite-size analysis of the four dimensional abelian surface gauge model. This model is defined assigning abelian variables to the plaquettes of an hypercubical lattice, and is dual to the four dimensional Ising model. This last model is known to present a second order phase transition with mean field critical exponents. We have p

J. Ambjorn, G. Thorleifsson

A modified Wilson action which suppresses plaquettes which take negative values is used to study the scaling behavior of the string tension. The use of the $\b_E$ scheme gives good agreement with asymptotic two loop results.

Andrew M. Abrahams, Stuart L. Shapiro, Saul A. Teukolsky

The radial collapse of a homogeneous disk of collisionless particles can be solved analytically in Newtonian gravitation. To solve the problem in general relativity, however, requires the full machinery of numerical relativity. The collapse of a disk is the simplest problem that exhibits the two most significant and challenging features of strong-field gravi

L. P. Grishchuk

If the large-angular-scale anisotropy in the cosmic microwave background radiation is caused by the long-wavelength cosmological perturbations of quantum mechanical origin, they are, most likely, gravitational waves, rather than density perturbations or rotational perturbations.

John F. Donoghue

I describe the treatment of gravity as a quantum effective field theory. This allows a natural separation of the (known) low energy quantum effects from the (unknown) high energy contributions. Within this framework, gravity is a well behaved quantum field theory at ordinary energies. In studying the class of quantum corrections at low energy, the dominant e

Sean A. Hayward

The question of whether an observer can escape from a black hole is addressed, using a recent general definition of a black hole in the form of a future outer trapping horizon. An observer on a future outer trapping horizon must enter the neighbouring trapped region. It is possible for the observer to subsequently escape from the trapped region. However, if

Sven Sandow

Exclusive diffusion on a one-dimensional lattice is studied. In the model particles hop stochastically into both directions with different rates. At the ends of the lattice particles are injected and removed. The exact stationary probability measure is represented in form of a matrix product as a generalization of the solution given by Derrida et al \cite{de

J. J. Rodríguez-Núñez, S. Schafroth, R. Micnas, T. Schneider

We explore the effect of fluctuations for $T \geq T_c$ in the 2-D negative Hubbard model within the framework of the selfconsistent T-matrix formalism, which goes beyond the BCS approximation and includes pair fluctuations. We enter the regime where correlations are important, namely, $U/t = -4.0$, where $t$ denotes the hopping matrix element between nearest

Christer Samuelsson

Explanation-based generalization is used to extract a specialized grammar from the original one using a training corpus of parse trees. This allows very much faster parsing and gives a lower error rate, at the price of a small loss in coverage. Previously, it has been necessary to specify the tree-cutting criteria (or operationality criteria) manually; here

Gabriele Ghisellini, Francesco Haardt

We study $e^{\pm}$ pair plasmas in pair equilibrium, which emit high energy radiation by thermal Comptonization of soft photons. We find that the maximum luminosity to size ratio of the source (i.e. the compactness) depends not only on the hot plasma temperature, but also on the spectral index of the resulting Comptonized spectrum. In the observationally int

F. Vagnetti, R. Spera

We present a study of the distribution of quasars and radio galaxies in the plane (viewing angle - redshift) in the framework of the evolutionary unified scheme (Vagnetti et al. 1991). Results are presented for some illustrative cases, including a distribution of the Lorentz factors, and appropriate luminosity functions for quasars and their host galaxies. A

Shyamoli Chaudhuri, Stephen-wei Chung, Joseph D. Lykken

We explore the possibility of embedding supersymmetric GUT texture ideas into superstring models. We discuss the construction of GUT models using free fermionic strings. We find SO(10) models with adjoint scalars, three generations of chiral fermions, and a fundamental Higgs with a Yukawa coupling to only the third generation.