February 1998 arXiv papers — page 10

A. D. Mirlin, P. Woelfle, Y. Levinson, O. Entin-Wohlman

We study the effect of a periodic density modulation on surface acoustic wave (SAW) propagation along a 2D electron gas near Landau level filling $ν=1/2$. Within the composite fermion theory, the problem is described in terms of fermions subject to a spatially modulated magnetic field and scattered by a random magnetic field. We find that a few percent modul

J. G. Russo

The construction of $SL(2,Z)$ invariant amplitudes that generalizethe Virasoro amplitude is investigated in detail. We describe a number of mathematical properties that characterize the simplest example, and present pieces of evidence that it represents the tree-level four-graviton scattering amplitude in membrane theory on ${\bf R}^9\times T^2$ in the limit

P. Fosalba, E. Gaztanaga

Cosmological Perturbation Theory (PT) is a useful tool to study the cumulants of the density and velocity fields in the large scale structure of the Universe. In Papers I & II of this series we saw that the Spherical Collapse (SC) model provides with the exact solution to PT at tree-level and gives a good approximation to the loop corrections (next to leadin

M. Billo', P. Di Vecchia, M. Frau, A. Lerda

Using the boundary state formalism, we perform a microscopic string analysis of the interaction between two D-branes and provide a local interpretation for the R-R force in the D0-D8 brane system. To do so, we construct BRST invariant vertex operators for the massless R-R states in the asymmetric picture that are proportional to potentials rather than field

Yvonne Choquet-Bruhat, James W. York,, Arlen Anderson

We review curvature-based hyperbolic forms of the evolution part of the Cauchy problem of General Relativity that we have obtained recently. We emphasize first order symmetrizable hyperbolic systems possessing only physical characteristics.

Tanmay Vachaspati

Current theories of particle physics lead to the unavoidable conclusion that there must have been several phase transitions in the early universe. Further, in the context of these theories, it is possible that cosmological phase transitions would have produced topological defects that may be roaming our heavens today. A finding of these fossils from the earl

M. H. van Kerkwijk, Deepto Chakrabarty, J. E. Pringle, R. A. M. J. Wijers

Enigmatic transitions between spin-up and spin-down have been observed in several X-ray pulsars accreting matter via an accretion disk. In these transitions, the torque changes sign but remains at nearly the same magnitude. It has been noted previously that alternating prograde and retrograde disk flows would explain many features of the torque reversals, al

S. L. Bridle, M. P. Hobson, A. N. Lasenby, Richard Saunders

The maximum-entropy method is applied to the problem of reconstructing the projected mass density of a galaxy cluster using its gravitational lensing effects on background galaxies. We demonstrate the method by reconstructing the mass distribution in a model cluster using simulated shear and magnification data to which Gaussian noise is added. The mass distr

I. F. Ginzburg, A. Schiller

If a heavy Dirac monopole exists, the light to light scattering below the monopole production threshold is enhanced due to the strong coupling of monopoles to photons. This effect could be observable in the collision of virtual photons at proton colliders. At the Tevatron it will be seen as pair production of photons with energies 200--400 GeV and roughly co

Takayuki Nakajima, Jun Nishimura

We study the two-dimensional Eguchi-Kawai model as a toy model of the IIB matrix model, which has been recently proposed as a nonperturbative definition of the type IIB superstring theory. While the planar limit of the model is known to reproduce the two-dimensional Yang-Mills theory, we find through Monte Carlo simulation that the model allows a different l

F. Courbin, C. Lidman, B. Frye, P. Magain

New high quality Keck and ESO images of PKS 1830-211 are presented. Applying a powerful new deconvolution algorithm to these optical and infrared data, both images of the flat spectrum core of the radio source have been identified. An extended source is also detected in the optical images, consistent with the expected location of the lensing galaxy. The sour

A. Deandrea, N. Di Bartolomeo, R. Gatto, G. Nardulli

We describe the effective heavy meson lagrangian for S- and P-wave heavy-light mesons in terms of a model based on meson-quark interactions, where mesonic transition amplitudes are represented by diagrams with heavy mesons attached to loops containing heavy and light constituent quarks. The model is relativistic and incorporates the heavy quark symmetries. T

Ana Achucarro, Julian Borrill, Andrew R Liddle

We carry out three-dimensional numerical simulations to investigate the formation rate of semilocal strings. We find that the back-reaction of the gauge fields on the scalar field evolution is substantial, and leads to a significant formation rate in the parameter regime where the semilocal strings are classically stable. The formation rate can be as large a

J. X. Lu, Shibaji Roy

It is well-known that the low energy string theory admits a non-singular solitonic super five-brane solution which is the magnetic dual to the fundamental string solution. By using the symmetry of the type IIB string theory, we construct an SL(2, Z) multiplet of magnetically charged super five-branes starting from this solitonic solution. These solutions are

D. E. Reichart, R. C. Nichol, F. J. Castander, D. J. Burke

From the Press-Schechter mass function and the empirical X-ray cluster luminosity-temperature (L-T) relation, we construct an X-ray cluster luminosity function that can be applied to the growing number of high-redshift, X-ray cluster luminosity catalogs to constrain cosmological parameters. In this paper, we apply this luminosity function to the Einstein Med

E. Knill, R. Laflamme

In standard quantum computation, the initial state is pure and the answer is determined by making a measurement of some of the bits in the computational basis. What can be accomplished if the initial state is a highly mixed state and the answer is determined by measuring the expectation of $σ_z$ on the first bit with bounded sensitivity? This is the situatio

Tal Mor

The no-cloning principle tells us that non-orthogonal quantum states cannot be cloned, but it does not tell us that orthogonal states can always be cloned. We suggest a situation where the cloning transformations are restricted, leading to a novel type of no-cloning principle. In the case of a composite system made of two subsystems: if the subsystems are on

Lov K. Grover

This paper shows how a basic property of unitary transformations can be used for meaningful computations. This approach immediately leads to search-type applications, where it improves the number of steps by a square-root - a simple minded search that takes N steps, can be improved to O(sqrt(N)) steps. The quantum search algorithm is one of several immediate

Stefano Mancini, David Vitali, Paolo Tombesi

We propose a simple optomechanical model in which a mechanical oscillator quadrature could be "cooled" well below its equilibrium temperature by applying a suitable feedback to drive the orthogonal quadrature by means of the homodyne current of the radiation field used to probe its position.

David Vitali, Paolo Tombesi

Photons in cavities have been already used for the realization of simple quantum gates [Q.A. Turchette, Phys. Rev. Lett. 75,4710 (1995)]. We present a method for combatting decoherence in this case.

Antoine Suarez

A new possible version of multisimultaneous causality is proposed, and real experiments allowing us to decide between this view and quantum mechanical retrocausation are further discussed. The interest of testing quantum mechanics against as many nonlocal causal models as possible is stressed.

Frank Antonsen

We use the definition of a star (or Moyal or twisted) product to give a phasespace definition of the $ζ$-function. This allows us to derive new closed expressions for the coefficients of the heat kernel in an asymptotic expansion for operators of the form $αp^2+v(q)$. For the particular case of the harmonic oscillator we furthermore find a closed form for th

V. I. Man'ko, L. Rosa, P. Vitale

In the probability representation of quantum mechanics, quantum states are represented by a classical probability distribution, the marginal distribution function (MDF), whose time dependence is governed by a classical evolution equation. We find and explicitly solve, for a wide class of Hamiltonians, new equations for the Green's function of such an equ

K. Ikematsu, Y. Iwata, K. Kaimi, M. Kaneta

We describe a start-timing detector for the PHENIX experiment at the relativistic heavy-ion collider RHIC. The role of the detector is to detect a nuclear collision, provide precise time information with an accuracy of 50ps, and determine the collision point along the beam direction with a resolution of a few cm. Technical challenges are that the detector mu

Toshiaki Iitaka

A numerical method is developed for calculating the real time Green's functions of very large sparse Hamiltonian matrices, which exploits the numerical solution of the inhomogeneous time-dependent Schroedinger equation. The method has a clear-cut structure reflecting the most naive definition of the Green's functions, and is very suitable to parallel

I. S. Aranson, L. S. Tsimring, V. M. Vinokur

The order parameter model based on parametric Ginzburg-Landau equation is used to describe high acceleration patterns in vibrated layer of granular material. At large amplitude of driving both hexagons and interfaces emerge. Transverse instability leading to formation of ``decorated'' interfaces and labyrinthine patterns, is found. Additional sub-har

D. Kharzeev

The strong "anomalous" J/Psi suppression observed recently by the NA50 Collaboration at CERN SPS has attracted considerable attention. Is it the first signature of a long-awaited quark-gluon plasma, or just a peculiar combination of "conventional" effects acting together to produce the puzzling pattern observed experimentally? This talk is an

A. Sibirtsev, W. Cassing

We analyse the $pp \to p ΛK$ cross section recently measured at COSY arguing that the enhancement of the production cross section at energies close to the reaction threshold should be due to the $Λp$ final state interaction. We find that the experimental $Λp$ elastic scattering data as well as the predictions from the Jülich-Bonn model are in reasonable agre

Jean-Yves Ollitrault

The various flow phenomena observed at energies between 50 AMeV and 160 AGeV are reviewed. I first define three types of flow: directed flow and elliptic flow, which are the two first Fourier components of the azimuthal distribution in non-central collisions; radial flow, which is deduced from an analysis of transverse momentum spectra in central collisions.

Mihail Frumosu, Steven Rosenberg

Mathai-Quillen forms are used to give an integral formula for the Lefschetz number of a smooth map of a closed manifold. Applied to the identity map, this formula reduces to the Chern-Gauss-Bonnet theorem. The formula is computed explicitly for constant curvature metrics. There is in fact a one-parameter family of integral expressions. As the parameter goes

Claude Cibils

We describe the structure of the Grothendieck ring of projective modules of basic Hopf algebras using a positive integer determined by the composition series of the principal indecomposable projective module.

Atsushi Takahashi

In this paper, we will describe the mathematical foundation of topological Landau-Ginzburg (LG) models coupled to gravity at genus 0 in terms of primitive forms. We also discuss the mirror symmetry for Calabi-Yau manifolds and CP^1 in our context. We will show that the mirror partner of CP^1 is the theory of primitive form associated to f=z+qz^{-1}.

Ron Y. Donagi

In this talk we discuss the description of the moduli space of principal G-bundles on an elliptic fibration X-->S in terms of cameral covers and their distinguished Prym varieties. We emphasize the close relationship between this problem and the integrability of Hitchin's system and its generalizations. The discussion roughly parallels that of [D2], but

Ron Y. Donagi

The heterotic string compactified on an (n-1)-dimensional elliptically fibered Calabi-Yau Z-->B is conjectured to be dual to F-theory compactified on an n-dimensional Calabi-Yau X-->B, fibered over the same base with elliptic K3 fibers. In particular, the moduli of the two theories should be isomorphic. The cases most relevant to the physics are n=2, 3, 4, i

John Brodie, Peter Cho, Kenneth Intriligator

We investigate the low energy dynamics of N=1 supersymmetric SO(N) gauge theories with a single symmetric tensor matter field. These theories exhibit non-trivial matching of global 't Hooft anomalies at the origin of moduli space. We argue that their quantum moduli spaces possess distinct Higgs and confining branches which touch at the origin in an inter

Vipul Periwal

Wilsonian effective actions are interpreted as free energies in ensembles with prescribed field expectation values and prescribed connected two-point functions. Since such free energies are directly obtained from two-particle-irreducible functionals, it follows that Wilsonian effective actions satisfy elementary perturbative consistency conditions, and non-p

Mark Wellmann

In this article we review the quantization of the Dirac-field on a curved spacetime. For that purpose we describe the construction of the local observable algebras in the algebraic approach to quantum field theory. Among the possible states we single out the so called Hadamard-states, which are the ones relevant for physics. Finally, as an example, we give a

G. Bandelloni, S. Lazzarini

In complete analogy with the Beltrami parametrization of complex structures on a (compact) Riemann surface, we use in this paper the Kodaira-Spencer deformation theory of complex structures on a (compact) complex manifold of higher dimension. According to the Newlander-Nirenberg theorem, a smooth change of local complex coordinates can be implemented with re

H. Aoki, S. Iso, H. Kawai, Y. Kitazawa

We derive a long distance effective action for space-time coordinates from a IIB matrix model. It provides us an effective tool to study the structures of space-time. We prove the finiteness of the theory for finite $N$ to all orders of the perturbation theory. Space-time is shown to be inseparable and its dimensionality is dynamically determined. The IIB ma

E. T. Akhmedov, M. N. Chernodub, M. I. Polikarpov

We derive the string representation of the Abelian Higgs theory in which dyons are condensed. It occurs that in such representation the topological interaction exists in the expectation value of the Wilson loop. Due to this interaction the dynamics of the string spanned on the Wilson loop is non-trivial.

S. Lazzarini

Since the appearance of the paper by Bilal & al. in 1991, it has been widely assumed that W-algebras originating from the Hamiltonian reduction of an SL(n,C)-bundle over a Riemann surface give rise to a flat connection, in which the Beltrami differential may be identified. In this Letter, it is shown that the use of the Beltrami parametrisation of complex st

Kun Shen, Yu-Ping Kuang

We derive Ward-Takahashi identities including composite fields in Abelian gauge theories and the matching condition between the elementary field description and the composite field description. With these we develop an approach to dynamical symmetry breaking in Abelian gauge theories including the study of the dynamically generated masses of the gauge boson,

Bernard de Wit

We review recent developments in the theory of supermembranes and their relation to matrix models.

Micha Berkooz

We argue that by taking a limit of SYM on a non-commutative torus one can obtain a theory on non-compact space with a finite non-locality scale. We also suggest that one can also obtain a similar generalization of the (2,0) field theory in 5+1 dimensions, and that the DLCQ of this theory is known.

Jifeng Yang

This is a further explanation of a new and simple renormalization approach recently proposed by the author (hep-th/9708104, Ref. [1], that is somewhat sketchy) for any ordinary QFT (whether renormalizable or not) in any spacetime dimension. We discussed the physical motivations of the new approach and its efficiency when compared to the existent renormalizat

Jifeng Yang, Guang-jiong Ni

Through more detailed calculations on QED$_{1+1}$ and QED$_{3+1}$ emplying a new treatment of Feynman Amplitudes, we attribute the regularization independent and hence definite origin of chiral anomaly in perturbation theory to an unambiguous term which is a rational function in momentum space. Some relevant remarks are presented.

Michael Gronau

The ratios of partial rates for charged B decays to the recently observed $D^0 K$ mode and to the two $D_{CP}K$ final states (CP = $\pm$) are shown to constrain the weak phase $γ\equiv {\rm Arg} (V_{ub}^*)$. The smaller color-suppressed rate, providing further information about the phase, can be determined from these rates alone. Present estimates suggest th

Carl H. Albright, K. S. Babu, S. M. Barr

A structure is proposed for the mass matrices of the quarks and leptons that arises in a natural way from the assumption that the breaking of SO(10) gauge symmetry is achieved by the smallest possible set of vacuum expectation values. This structure explains well many features of the observed spectrum of quarks and leptons. It reproduces the Georgi-Jarlskog

J. C. Montero, V. Pleitez, M. C. Rodriguez

Several parity violating left-right asymmetries in Møller electron-electron and muon-muon scattering are considered in the context of the electroweak standard model at tree level in fixed target and collider experiences. We show that in colliders the asymmetry with only one of the beam polarized is large enough to compensate the smaller cross section at high

Carsten Greiner, Stefan Leupold

In this more pedagogical study we want to elucidate on stochastic aspects inherent to the (non-)equilibrium real time Green's function description (or `closed time path Green's function' -- CTPGF) of transport equations, the so called `Kadanoff-Baym equations'. As a toy model we couple a free scalar boson quantum field to an exemplaric heat b

A. Harindranath, Rajen Kundu

Investigations have revealed a very complex structure for the coefficient functions accompanying the divergences for individual time ($x^+$) ordered diagrams in light-front perturbation theory. No guidelines seem to be available to look for possible mistakes in the structure of these coefficient functions emerging at the end of a long and tedious calculation

J. M. Yang, A. Datta, M. Hosch, C. S. Li

This talk is a brief review of the recent studies on probing new physics through single top quark processes and probing exotic top quark decays at the upgraded Tevatron.

V. A. Kuzmin, I. I. Tkachev

The highest energy cosmic rays, above the Greisen-Zatsepin-Kuzmin cut-off of cosmic ray spectrum, may be produced in decays of superheavy long-living X-particles. We conjecture that these particles may be produced naturally in the early Universe from vacuum fluctuations during inflation and may constitute a considerable fraction of Cold Dark Matter. We predi

Philippe de Forcrand, Margarita Garcia Perez, James E. Hetrick, Ion-Olimpiu Stamatescu

We study on the lattice the topology of SU(2) and SU(3) Yang-Mills theories at zero temperature and of QCD at temperatures around the phase transition. To smooth out dislocations and the UV noise we cool the configurations with an action which has scale invariant instanton solutions for instanton size above about 2.3 lattice spacings. The corresponding "

The OPAL Collaboration, K. Ackerstaff et al

Inclusive production of the f_0(980), f_2(1270) and ϕ(1020) resonances has been studied in a sample of 4.3 million hadronic Z^0 decays from the OPAL experiment at LEP. A coupled channel analysis has been used for the f_0 in simultaneous fits to the resonances in inclusive π+π- and K+K- mass spectra. Fragmentation functions are reported for the three states.

ZEUS Collaboration

Inclusive jet differential cross sections for the reaction e+ p --> e+ + jet + X with quasi-real photons have been measured with the ZEUS detector at HERA. These cross sections are given for the photon-proton centre-of-mass energy interval 134 < W < 277 GeV and jet pseudorapidity in the range -1 < eta(jet) < 2 in the laboratory frame. The results are present

Sergei A. Klioner, Michael Soffel

Rotational motion of extended celestial bodies is discussed in the framework of the Parametrized Post-Newtonian (PPN) formalism with the two parameters $γ$ and $β$. A local PPN reference system of a massive extended body being a member of a system of N massive extended bodies is constructed. In the local PPN reference system the external gravitational field

D. S. Salopek

A Green&#39;s function method is developed for solving strongly-coupled gravity and matter in the semiclassical limit. In the strong-coupling limit, one assumes that Newton&#39;s constant approaches infinity. As a result, one may neglect second order spatial gradients, and each spatial point evolves like an homogeneous universe. After constructing the Green&

Igor F. Herbut

I argue that the system of interacting bosons at zero temperature and in random external potential possesses a simple critical point which describes the proliferation of disorder-induced topological defects in the superfluid ground state, and which is located at weak disorder close to and above one dimension. This makes it possible to address the critical be

C. P. Vlahacos, D. E. Steinhauer, S. K. Dutta, B. J. Feenstra

We describe a technique for extracting topographic information using a scanning near-field microwave microscope. By monitoring the shift of the system&#39;s resonant frequency, we obtain quantitative topographic images of uniformly conducting metal surfaces. At a frequency of 9.572 GHz, our technique allows for a height discrimination of about 55 nm at a sep

M. N. Tamashiro, Yan Levin, Marcia C. Barbosa

We formulate an extension of the Debye-Hueckel-Bjerrum theory [M. E. Fisher and Y. Levin, Phys. Rev. Lett. 71, 3826 (1993)] to the fluid state of a highly asymmetric charged colloid. Allowing for the formation of clusters consisting of one polyion and n condensed counterions, the total Helmholtz free energy of the colloidal suspension is constructed. The the

M. N. Tamashiro, Yan Levin, Marcia C. Barbosa

We consider a system composed of a monodisperse charge-stabilized colloidal suspension in the presence of monovalent salt, separated from the pure electrolyte by a semipermeable membrane, which allows the crossing of solvent, counterions, and salt particles, but prevents the passage of polyions. The colloidal suspension, that is in a crystalline phase, is co

D. Sornette

We propose a formulation of the term structure of interest rates in which the forward curve is seen as the deformation of a string. We derive the general condition that the partial differential equations governing the motion of such string must obey in order to account for the condition of absence of arbitrage opportunities. This condition takes a form simil

M. C. J. M. Vissenberg, M. J. M. de Jong

The dynamics of excitons in disordered molecular solids is studied theoretically, taking into account migration between different sites, recombination, and dissociation into free charge carriers in the presence of an electric field. The theory is applied to interpret the results of electric field-induced photoluminescence (PL) quenching experiments on molecu

M. C. J. M. Vissenberg, M. Matters

The field-effect mobility in an organic thin-film transistor is studied theoretically. From a percolation model of hopping between localized states and a transistor model an analytic expression for the field-effect mobility is obtained. The theory is applied to describe the experiments by Brown et al. [Synth. Met. 88, 37 (1997)] on solution-processed amorpho

J. van den Brink, G. A. Sawatzky

We study the screening of the Coulomb interaction in non polar systems by polarizable atoms. We show that in low dimensions and small finite size systems this screening deviates strongly from that conventionally assumed. In fact in one dimension the short range interaction is strongly screened and the long range interaction is anti-screened thereby strongly

Hisao Hayakawa, Ken Nakanishi

We review the current understanding on universal behaviors in granular flows through a vertical pipe and traffic flows. We carry out weakly nonlinear analysis of a model for traffic flows based on the technique of soliton perturbations, and determine the selected propagating velocity, the amplitude, the width of interfaces connecting between jam phase and no

M. Stapper, T. A. Vilgis

We present a field-theoretic renormalization group analysis of a polymer chain immersed in a binary good solvent close to its critical demixing point. We first show that this problem can be mapped on a bicritical field theory, i.e. a $(Φ^{2})^{2}$-model with a mass anisotropy. This implies that the end-to-end distance of the polymer is now controlled by a ne

T. Fukui, N. Kawakami

We investigate the spectral flow of the integrable non-hermitian Heisenberg spin chain under boundary conditions with complex twist angle. It is shown that the period of the spectral flow is $4π$ up to a certain critical imaginary twist, beyond which the period jumps successively to higher values. We argue that this phenomenon caused by non-hermitian propert

Simon C. Benjamin, Neil F. Johnson

We present a novel scheme for data processing which is well-suited for implementation at the nanometer scale. The logic circuits comprise two-state cellular units which are driven by externally applied updates, in contrast to earlier proposals which relied on ground-state relaxation. The present structures can simultaneously process many inputs and are suita

A. J. Bracken, X. -Y. Ge, Y. -Z. Zhang, H. -Q. Zhou

The recently introduced two-parameter eight-state $U_q[gl(3|1)]$ supersymmetric fermion model is extended to include boundary terms. Nine classes of boundary conditions are constructed, all of which are shown to be integrable via the graded boundary quantum inverse scattering method. The boundary systems are solved by using the coordinate Bethe ansatz and th

Alexander Shnirman, Gerd Schoen

Low-capacitance Josephson junction systems as well as coupled quantum dots, in a parameter range where single charges can be controlled, provide physical realizations of quantum bits, discussed in connection with quantum computing. The necessary manipulation of the quantum states can be controlled by applied gate voltages. In addition, the state of the syste

Terence Hwa, Michael Lassig

The statistical properties of local alignment algorithms with gaps are analyzed theoretically for uncorrelated and correlated DNA sequences. In the vicinity of the log-linear phase transition, the statistics of alignment with gaps is shown to be characteristically different from that of gapless alignment. The optimal scores obtained for uncorrelated sequence

Peter Ashwin, Eurico Covas, Reza Tavakol

We consider the behaviour of attractors near invariant subspaces on varying a parameter that does not preserve the dynamics in the invariant subspace but is otherwise generic, in a smooth dynamical system. We refer to such a parameter as ``non-normal&#39;&#39;. If there is chaos in the invariant subspace that is not structurally stable, this has the effect o

G. Gallavotti

On place quelques applications récentes de la théorie du Chaos en perspective avec la théorie classique de Boltzmann.

Bambi Hu, Baowen Li, Jie Liu, Ji-Lin Zhou

We have studied the effects of quantum fluctuations on dynamical behavior by using squeezed state approach. Our numerical results of the kicked harmonic oscillator demonstrate qualitatively and quantitatively that quantum fluctuations can not only enhance chaos but also suppress classical diffusion. In addition, the squeezed state approach also gives a simpl

Alexander Fillipov, Bambi Hu, Baowen Li, Alexander Zeltser

We study numerically time evolution of a system which consists of two attractors connected by Fermi-Pasta-Ulam (FPU) chain. It is found that after sufficiently long time there exits self-consistent large scale structure in the system. The wavelet transform is used to separate the modes in different scales. We found that the nonlinear long wavelength mode pro

E. Churazov, M. Gilfanov, W. Forman, C. Jones

We present a two dimensional map of the gas temperature distribution in the Centaurus cluster, based on ASCA observations derived using a novel approach to account for the energy dependent point spread function. Along with a cool region, centered on NGC4696, asymmetric temperature variations of moderate amplitude are detected. The hottest region roughly coin

Ari Laor

Observational evidence suggest that shocks may affect the spatial and velocity distributions of gas in the NLR/ENLR of some active galaxies. It thus seemed plausible that shocks may also energize the NLR. The observed emission line ratios strongly favor photoionization as the heating source, but it is not clear whether the ionizing radiation is generated in

Arjun Dey

I briefly review the current status of observations of AGN-powered UV/optical light, starlight, dust and outflow phenomena in high-redshift powerful radio galaxies. The existing data are consistent with the hypothesis that powerful radio galaxies undergo a major episode of star formation at high redshift z>4 during which they form most of their stars, and su

Olivia Puyoo, Lotfi Ben Jaffel

We propose a new method to constrain the actual state of the interstellar cloud that surrounds the solar system. Using Voyager UVS Lyman-alpha sky maps and the powerful principle of invariance, we derive the H distribution all along the spacecraft path. Provided current models of the heliopause interface between the solar and the interstellar winds, we extra

T. J. Galama, P. J. Groot, J. van Paradijs, C. Kouveliotou

We report on the results of optical follow-up observations of the counterpart of GRB 970508, starting 7 hours after the event. Multi-color U, B, V, R$_{c}$ and I$_{c}$ band observations were obtained during the first three consecutive nights. The counterpart was monitored regularly in R$_{c}$ until $\sim$ 4 months after the burst. The light curve after the m

R. P. Mignani, P. A. Caraveo, G. F. Bignami

New optical and near-UV HST observations of Geminga are presented. When compared with previous ground-based and HST imaging, the data confirm and better define the presence of an emission feature centered at 6,000 Angstrom and superimposed on the thermal continuum best fitting the extreme-UV/soft X-ray data. This feature may be interpreted in terms of cyclot

Filippo Frontera

Recent results on Gamma-Ray Bursts obtained with the X-ray Astronomy satellite BeppoSAX are reviewed. Main emphasis is given to the GRBs simultaneously detected with the Gamma-Ray Burst Monitor (40-700 keV) and the Wide Field Cameras (1.5-26 keV). These bursts were rapidly localized with high precision, which permitted a prompt pointing of their error boxes

A. Treves, M. Colpi, R. Turolla, S. Zane

Old neutron stars (ONSs) which have radiated away their internal and rotational energy may still shine if accreting the interstellar medium. Rather stringent limits from the analysis of ROSAT surveys indicate that most optimistic predictions on ONSs observability are in excess of a factor as large as $\sim 100$. Here we explore two possible evolutionary scen

E. E. Fenimore

The Gamma-Ray burst detector on Ginga consisted of a proportional counter to observe the x-rays and a scintillation counter to observe the gamma-rays. It was ideally suited to study the x-rays associated with gamma-ray bursts (GRBs). Ginga detected 120 GRBs and 22 of them had sufficient statistics to determine spectra from 2 to 400 keV. Although the Ginga an

Sidney van den Bergh

Nine presently known &#34;young&#34; Galactic globular clusters, which have ages / 3 Gyr smaller than the oldest clusters of similar metallicity, all have RGC > 15 kpc. Furthermore these young globulars are found to have below-average luminosities. These results suggest that (1) globular cluster formation extended over a considerable period of time in the ou

James Hormuzdiar, Stephen D. H. Hsu

We describe some detailed numerical simulations of Disoriented Chiral Condensates (DCCs), using the chiral lagrangian as a controlled long-wavelength description. We focus on the possibility of multiple, independently coherent domains, and investigate the degree to which the DCC signal is attenuated. As an intermediate step in our analysis we compute the exp

A. Giveon, D. Kutasov

We review some aspects of the interplay between the dynamics of branes in string theory and the classical and quantum physics of gauge theories with different numbers of supersymmetries in various dimensions.

Robert G. Edwards, Urs M. Heller, Rajamani Narayanan

We study the spectral flow of the Wilson-Dirac operator H(m) with and without an additional Sheikholeslami-Wohlert (SW) term on a variety of SU(3) lattice gauge field ensembles in the range $0\le m \le 2$. We have used ensembles generated from the Wilson gauge action, an improved gauge action, and several two-flavor dynamical quark ensembles. Two regions in

Akakii Melikidze

In this paper we predict many interesting new properties of vortices in highly anisotropic density wave systems subject to strong transverse electric fields. We mainly concentrate on ground state properties. Besides electric field-induced vortices we consider also thermally activated vortices. A new type of temperature-driven transition between two different

Max Tegmark, Angelica de Oliveira-Costa

For high-precision cosmic microwave background (CMB) experiments, contamination from extragalactic point sources is a major concern. It is therefore useful to be able to detect and discard point source contaminated pixels using the map itself. We show that the sensitivity with which this can be done can often be greatly improved (by factors between 2.5 and 1

M. Banados, T. Brotz, M. Ortiz

We calculate the density of states of the 2+1 dimensional BTZ black hole in the micro- and grand-canonical ensembles. Our starting point is the relation between 2+1 dimensional quantum gravity and quantised Chern-Simons theory. In the micro-canonical ensemble, we find the Bekenstein--Hawking entropy by relating a Kac-Moody algebra of global gauge charges to

M. F. M. Lutz

We consider $K^-$ nucleon elastic and inelastic scattering in isospin symmetric nuclear matter. It is found that the proper description of the $Λ(1405)$ resonance structure in nuclear matter requires a self-consistent approach. Then the $Λ(1405) $ resonance mass remains basically unchanged, however, the resonance acquires an increased decay width as nuclear

E787 Collaboration, S. Adler, M. S. Atiya, I-H. Chiang

An upper limit on the branching ratio for the decay K+ --> e+ nu mu+ mu- is set at 5.0 x 10^{-7} at 90% confidence level, consistent with predictions from chiral perturbation theory.

T. Hambye, G. O. Koehler, E. A. Paschos, P. H. Soldan

We calculate long-distance contributions to the amplitudes A(K^0 --> pi pi, I) induced by the gluon and the electroweak penguin operators Q_6 and Q_8, respectively. We use the 1/N_c expansion within the effective chiral lagrangian for pseudoscalar mesons. In addition, we adopt a modified prescription for the identification of meson momenta in the chiral loop

L. Weissman, C. Broude, G. Goldring, R. Hadar

A novel scheme for measuring the cross section of the 7Be(p,gamma)8B reaction, the major source of high energy neutrinos from t he sun, is presented. The scheme involves a strictly uniform particle beam and overcomes some of the recognized experimental uncertainties of previous measurements. A new measurement of sigma[7Li(d,p)8Li] has been carried out using

Patricia Ball, V. M. Braun, Y. Koike, K. Tanaka

We present a systematic study of twist three light-cone distribution amplitudes of vector mesons in QCD, which is based on conformal expansion and takes into account meson and quark mass corrections. A complete set of distribution amplitudes is constructed for rho, omega, K* and phi mesons, which satisfies all (exact) equations of motion and constraints from

L. L. Salcedo

An expansion in the number of spatial covariant derivatives is carried out to compute the $ζ$-function regularized effective action of 2+1-dimensional fermions at finite temperature in an arbitrary non-Abelian background. The real and imaginary parts of the Euclidean effective action are computed up to terms which are ultraviolet finite. The expansion used p

Andreas Albrecht

Recent research has severely constrained the standard ``defect&#39;&#39; models of cosmic structure formation. Here I discuss the nature of the problems with defect models, and place this discussion in the context of the big picture of cosmic structure formation. In particular, I classify models of cosmic structure formation as either ``causal&#39;&#39; or `