August 1998 arXiv papers — page 15

A. Sherman, M. Schreiber

We apply the modified spin-wave theory with the constraint of zero staggered magnetization to investigate normal-state spectral and magnetic properties of the 2D t-J model in the paramagnetic state. A set of self-energy equations for hole and magnon Green's functions is solved numerically in the self-consistent Born approximation. The constraint can be f

S. K. Nikogosyan, A. A. Sahakyan, H. N. Yeritsyan, V. A. Grigoryan

The influence of the bulk density of YBa2Cu3-xFexOy (0 < x < 0.01) ceramics on the intergranular superconducting (SC) properties was studied using the temperature dependence of AC magnetic susceptibility measurements. It was found that the simultaneous variation of the sample&#39;s density and the iron impurity concentration does not influence effectively th

I. Simonsen, A. A. Maradudin

Electromagnetic wave scattering from planar dielectric films deposited on one-dimensional, randomly rough, perfectly conducting substrates is studied by numerical simulations for both p- and s-polarization. The reduced Rayleigh equation, which is the integral equation satisfied by the scattering amplitude after eliminating the fields inside the film, is the

Jie Liu, Bambi Hu, Baowen Li

The geometric phases of the cyclic states of a generalized harmonic oscillator with nonadiabatic time-periodic parameters are discussed in the framework of squeezed state. A class of cyclic states are expressed as a superposition of an infinte number of squeezed states. Then, their geometric phases are obtained explicitly and found to be $-(n+1/2)$ times the

M. Matsuda, T. Yoshihama, K. Kakurai, G. Shirane

Neutron scattering experiments have been performed on Sr$_{14}$Cu$_{24}$O$_{41}$ which consists of both chains and ladders of copper ions. We observed that the magnetic excitations from the CuO$_2$ chain have two branches and that both branches are weakly dispersive along the $a$ and $c$ axes. The $ω$-$Q$ dispersion relation as well as the intensities can be

Matthias Steinmetz, Julio Navarro

We use high-resolution cosmological simulations that include the effects of gasdynamics and star formation to investigate the origin of the Tully-Fisher relation in the standard Cold Dark Matter cosmogony. Luminosities are computed for each model galaxy using their full star formation histories and the latest spectrophotometric models. We find that at z=0 th

Rosanne Di Stefano, Richard A. Scalzo

We propose and evaluate the feasibility of a new strategy to search for planets via microlensing. This new strategy is designed to detect planets in &#34;wide&#34; orbits, i.e., with orbital separation, $a$ greater than $\sim 1.5 R_E$. Planets in wide orbits may provide the dominant channel for the microlensing discovery of planets, particularly low-mass (e.

Bayram Tekin, Kamran Saririan, Yutaka Hosotani

We investigate the three dimensional Georgi-Glashow model with a Chern-Simons term. We find that there exist complex monopole solutions of finite action. They dominate the path integral and disorder the Higgs vacuum, but electric charges are not confined. Subtleties in the gauge fixing procedure in the path integral and issues related to Gribov copies are no

V. A. Kazakov, P. Zinn-Justin

Using recently developed methods of character expansions we solve exactly in the large N limit a new two-matrix model of hermitean matrices A and B with the action S={1\over 2}(\tr A^2+\tr B^2)-{α\over 4}(\tr A^4+\tr B^4) -{β\over 2} \tr(AB)^2. This model can be mapped onto a special case of the 8-vertex model on dynamical planar graphs. The solution is para

A. Z. Mekjian, B. R. Schlei, D. Strottman

Various models for pion multiplicity distributions produced in relativistic heavy ion collisions are discussed. The models include a relativistic hydrodynamic model, a thermodynamic description, an emitting source pion laser model, and a description which generates a negative binomial description. The approach developed can be used to discuss other cases whi

Christian Maulbetsch, Sergei V. Shabanov

We study the problem of the existence of a local quantum scalar field theory in a general affine metric space that in the semiclassical approximation would lead to the autoparallel motion of wave packets, thus providing a deviation of the spinless particle trajectory from the geodesics in the presence of torsion. The problem is shown to be equivalent to the

A. Strumia, N. Tetradis, C. Wetterich

We examine the region of validity of Langer&#39;s picture of homogeneous nucleation. Our approach is based on a coarse-grained free energy that incorporates the effect of fluctuations with momenta above a scale k. The nucleation rate I = A_k exp(-S_k) is exponentially suppressed by the action S_k of the saddle-point configuration that dominates tunnelling. T

Hugh Osborn

The implications of N=1 superconformal symmetry for four dimensional quantum field theories are studied. Superconformal covariant expressions for two and three point functions of quasi-primary superfields of arbitrary spin are found and connected with the operator product expansion. The general formulae are specialised to cases involving a scalar superfield

Juan I. Collar

The case for a stable population of solar-bound Earth-crossing Weakly Interacting Massive Particles (WIMPs) is reviewed. A practical general expression for their speed distribution in the laboratory frame is derived under basic assumptions. If such a population exists -even with a conservative phase-space density-, the next generation of large-mass, low-thre

E. Gotsman, E. Levin, U. Maor, E. Naftali

A systematic study of $\frac{\partial F_2(x,Q^2)}{\partial \ln Q^2}$ and $\frac{\partial \ln F_2(x,Q^2)}{\partial \ln (1/x)}$ is carried out in pQCD taking screening corrections into account. The result of calculations, which are different from the non screened DGLAP prediction, are compared and shown to agree with the available experimental data as well as

Prashanta Das, Pankaj Jain, Douglas W. McKay

We study the $p\bar p$ production and decay of exotic quarks that are predicted by the SU(3)$\times$U(1) extension of the Standard Model. We show that recent experimental searches for SUSY particles at the Tevatron limit the mass of these quarks to be above 250 GeV. Run II will extend the reach to 320 GeV. This is one example of SUSY search signatures that a

R. P. Malik

We discuss the Becchi-Rouet-Stora-Tyutin (BRST) cohomology and Hodge decomposition theorem for the two dimensional free U(1) gauge theory. In addition to the usual BRST charge, we derive a local, conserved and nilpotent co(dual)-BRST charge under which the gauge-fixing term remains invariant. We express the Hodge decomposition theorem in terms of these charg

Toru Goto, Takeshi Nihei

We reanalyze the proton decay in the minimal SU(5) SUGRA GUT model. Unlike previous analyses, we take into account a Higgsino dressing diagram of dimension 5 operator with right-handed matter fields ($RRRR$ operator). It is shown that this diagram gives a dominant contribution for $p\to K^+\barν_τ$ over that from $LLLL$ operator, and decay rate of this mode

Yuichi Chikira, Naoyuki Haba, Yukihiro Mimura

The singular seesaw mechanism can naturally explain the atmospheric neutrino deficit by the maximal oscillation between $ν_{μ_L}$ and $ν_{μ_R}$. This mechanism can also induce three different scales of neutrino mass squared differences, which can explain the neutrino deficits of three independent experiments (solar, atmospheric, and LSND) by neutrino oscilla

Vladimir A. Lefebvre, Yuri N. Efremov

The bizarre patterns of rapid flashes and bursts in the X-ray source MXB 1730-335 (Rapid Burster) have been puzzling researchers for two decades; especially intriguing are its peculiarities in the time-invariant decay profiles of many type II bursts of the Rapid Burster. We have discovered that they are similar to certain regularities found in cognitive psyc

R Delbourgo, Dongsheng Liu, M D Scadron

We demonstrate that a $u-d$ mass difference (which we estimate to be about 4 MeV) within quantum loops, can reproduce the effects of the Coleman-Glashow electromagnetic tadpole operator.

C A Jackson, J V Wall

We show that a dual-population unification scheme provides a successful paradigm with which to describe the evolution and beaming of all bright extragalactic radio sources. The paradigm consists of two intrinsic radio-source populations, based on the two distinct radio-galaxy morphologies of Fanaroff-Riley classes I and II. These represent the `unbeamed&#39;

Pawel Caban, Jakub Rembieliński

In this paper the relativistic quantum mechanics is considered in the framework of the nonstandard synchronization scheme for clocks. Such a synchronization preserves Poincar{é} covariance but (at least formally) distinguishes an inertial frame. This enables to avoid the problem of a noncausal transmision of information related to breaking of the Bell&#39;s

Sara Schneider, Daniel F. V. James, Gerard J. Milburn

We present a novel method of performing quantum logic gates in trapped ion quantum computers which does not require the ions to be cooled down to their vibrational center of mass (CM) mode ground state. Our scheme employs adiabatic passages and the conditional phase shift first investigated by D&#39;Helon and Milburn (C.~D&#39;Helon and G.J.~Milburn, Phys. R

David M. Schmidt

Recent approaches to the problem of inferring a continuous probability distribution from a finite set of data have used a scalar field theory for the form of the prior probability distribution. This letter presents a more general form for the prior distribution that has a geometrical interpretation which is useful for tailoring prior distributions to the nee

Brendan B. Plapp, David A. Egolf, Eberhard Bodenschatz, Werner Pesch

For Rayleigh-Benard convection of a fluid with Prandtl number σ\approx 1, we report experimental and theoretical results on a pattern selection mechanism for cell-filling, giant, rotating spirals. We show that the pattern selection in a certain limit can be explained quantitatively by a phase-diffusion mechanism. This mechanism for pattern selection is very

E. Hernandez, E. Oset

A new mechanism for the pp --> pp pi0 reaction close to threshold is suggested coming from the isoscalar excitation of the Roper and its decay into N(pi pi)S-wave, with one of the pi0 emitted and the other one reabsorbed on the second nucleon. The mechanism can lead to important interference with other mechanisms and, together with experiment, serves to excl

Leonid Frankfurt, Mikkel Johnson, Misak Sargsian, Mark Strikman

Properties of excited baryonic states are investigated in the context of electroproduction of baryon resonances off the deuteron. In particular, the hadronic radii and the compositeness of baryon resonances are studied for kinematic situations in which their hadronic reinteraction is the dominant contribution. Specifically, we study the reaction $d(e,e&#39;S

Hieu Nguyen

We prove that M. Kramer&#39;s classification of list of spherical pairs coincides with that for weakly symmetric spaces by examining the linear isotropy representation of the corresponding homogeneous space associated to each pair.

Schiffmann Olivier

In this short note, we show that the Ginzburg-Vasserot map between the quantum affine algebra of type A_(n-1) and the equivariant K-theory group of the Steinberg Variety (of n-step flags in C^d) restricts and remains surjective at the level of the integral forms. In particular, this shows that the parametrization of irreducible, finite-dimensional modules an

D. Shklyarov, S. Sinel&#39;shchikov, L. Vaksman

Our previous work (math.QA/9808015) introduces the basic notions and announces some results on function theory in the quantum disc. The present paper establishes a relationship between those results and the quantum groups theory.

Alain Connes, Dirk Kreimer

We explore the relation between the Hopf algebra associated to the renormalization of QFT and the Hopf algebra associated to the NCG computations of transverse index theory for foliations.

A. Jevicki, Y. Kazama, T. Yoneya

We show how the linear special conformal transformation in four-dimensional N=4 super Yang-Mills theory is metamorphosed into the nonlinear and field-dependent transformation for the collective coordinates of Dirichlet 3-branes, which agrees with the transformation law for the space-time coordinates in the anti-de Sitter (AdS) space-time. Our result provides

Yi-Bing Ding, Xue-Qian Li, Peng-Nian Shen

The wave function at the origin (WFO) is an important quantity in studying many physical problems concerning heavy quarkonia. However, when one used the variational method with fewer parameters, in general, the deviation of resultant WFO from the &#34;accurate&#34; solution was not well estimated. In this paper, we discuss this issue by employing several pot

D. de Florian, S. Frixione, A. Signer, W. Vogelsang

We present a next-to-leading order computation in QCD of one-jet and two-jet cross sections in polarized hadronic collisions. Our results are obtained in the framework of a general formalism that deals with soft and collinear singularities using the subtraction method. We construct a Monte Carlo program that generates events at the partonic level. We use thi

Anjan S. Joshipura

The current searches for neutrino oscillations seem to suggest an approximate $L_e-L_\m-L_τ$ flavor symmetry. This symmetry implies a pair of degenerate neutrinos with mass $m_0$ and large leptonic mixing. We explore the possibility that gravitational interactions break this global symmetry. The Planck scale suppressed breaking of the $L_e-L_\m-L_τ$ symmetry

R. Jeannerot

It is shown that thermal inflation arises naturally in rank greater than five unified theories when non-renormalisable terms are introduced. Thermal inflation is driven by two Higgs fields Φ_{B-L} and \barΦ_{B-L} which also break U(1)_{B-L} when acquiring vevs at the end of inflation. The inflationary period provides enough e-foldings to solve the monopole p

Uma Mahanta

If supersymmetry is spontaneously at a low energy scale then the resulting gravitino would be very light. The interaction strength of the longitudinal components of such a light gravitino to electron-selectron pair then becomes comparable to that of electroweak interactions. Such a light gravitino could modify the cross-section for $e^_L e^_R-->\tilde {e}_L\

Sinya Aoki, Roberto Frezzotti, Peter Weisz

The coefficient $c_{\rm sw}$ appearing in the Sheikholeslami-Wohlert improved action is computed to one loop perturbation theory for improved gluon actions including six-link loops. The O($a$) improvement coefficients for the dimension three isovector composite operators bilinear in the quark fields are also computed to one loop order of perturbation theory

P. A. Movilla Fernández, O. Biebel, S. Bethke, the JADE Collaboration

e^+e^- annihilation data recorded by the JADE detector at PETRA were used to measure the C-parameter for the first time at sqrt{s}= 35 and 44 GeV. The distributions were compared to a resummed QCD calculation which recently became available for this observable. % In addition, we applied extended resummed calculations to the heavy and wide jet broadening vari

A. Yu. Neronov

We consider a quantum mechanical black hole model introduced in {\it Phys.Rev.}, {\bf D57}, 1118 (1998) that consists of the selfgravitating dust shell. The Schroedinger equation for this model is a finite difference equation with the shift of the argument along the imaginary axis. Solving this equation in quasiclassical limit in complex domain leads to quan

Rashmi Ray

The $ν= 1$ quantum Hall ground state in materials like GaAs is well known to be ferromagnetic in nature. The exchange part of the Coulomb interaction provides the necessary attractive force to align the electron spins spontaneously. The gapless Goldstone modes are the angular deviations of the magnetisation vector from its fixed ground state orientation. Fur

Rashmi Ray

The $ν=1$ quantum Hall ground state in samples like GaAs is well known to be ferromagnetic. The global SU(2) spin symmetry of the microscopic action is broken down to a U(1) symmetry by the ground state. The Goldstone bosons corresponding to this spontaneous breaking of symmetry are the ferromagnetic magnons which are neutral spin waves. In addition, there a

Mark A. Miller, Jonathan P. K. Doye, David J. Wales

We perform a comprehensive survey of the potential energy landscapes of 13-atom Morse clusters, and describe how they can be characterized and visualized. Our aim is to detail how the global features of the funnel-like surface change with the range of the potential, and to relate these changes to the dynamics of structural relaxation. We find that the landsc

Jian-Hui Dai, Yupeng Wang, U. Eckern

We study the boundary impurity-induced critical behavior in an integrable SU(2)-invariant model consisting of an open Heisenberg chain of arbitrary spin-$S$ (Takhatajian-Babujian model) interacting with an impurity of spin $\vec{S&#39;}$ located at one of the boundaries. For $S=1/2$ or $S&#39;=1/2$, the impurity interaction has a very simple form $J\vec{S}_1

I. L. Aleiner, B. L. Altshuler, M. E. Gershenson

In a recent paper, Phys. Rev. Lett. 81, 1074 (1998), Golubev and Zaikin (GZ) found that ``zero-point fluctuations of electrons&#39;&#39; contribute to the dephasing rate extracted from the magnetoresistance. As a result, the dephasing rate remains finite at zero temperature. GZ claimed that their results ``agree well with the experimental data&#39;&#39;. We

L. Frachebourg

An exact expression for the mass distribution $ρ(M,t)$ of the ballistic aggregation model in one dimension is derived in the long time regime. It is shown that it obeys scaling $ρ(M,t)=t^{-4/3}F(M/t^{2/3})$ with a scaling function $F(z)\sim z^{-1/2}$ for $z\ll 1$ and $F(z)\sim \exp(-z^3/12)$ for $z\gg 1$. Relevance of these results to Burgers turbulence is d

Nobuo Furukawa, Yutaka Moritomo, K. Hirota, Y. Endoh

Scaling relations in the charge and spin excitations of (La,Sr)MnO3 are studied from both theoretical and experimental points of view. In the ferromagnetic metal phase, we investigate optical conductivity and neutron inelastic scattering, and compare with a theoretical calculation based on the dynamical mean-field theory of the double-exchange hamiltonian. S

Helge Frauenkron, Maria Serena Causo, Peter Grassberger

We present simulations of self-avoiding random walks on 2-d lattices with the topology of an infinitely long cylinder, in the limit where the cylinder circumference L is much smaller than the Flory radius. We study in particular the L-dependence of the size h parallel to the cylinder axis, the connectivity constant mu, the variance of the winding number arou

Christoph Theis, Rolf Schilling

The intermediate scattering function S(q,t) for neutron scattering is expanded with respect to a complete set of correlation functions which describe the dynamical correlations in a molecular liquid. For the static ns-structure factor S(q) of a system of diatomic molecules the results of the expansion are compared with the exact results from a MD-imulation a

M. W. Wu, H. Haug

We investigate the femtosecond kinetics of an optically excited 2D magneto-plasma at intermediate and high densities under a strong magnetic field perpendicular to the quantum well (QW). We assume an additional weak lateral confinement which lifts the degeneracy of the Landau levels partially. We calculate the femtosecond dephasing and relaxation kinetics of

Zhan-hai Dong, Shiping Feng

The spin liquid state of the antiferromagnetic Heisenberg model on a triangular lattice is studied within the self-consistent Green&#39;s function method. It is shown that the spin excitation spectra is gapless, and ground-state energy per site is $E_{g}/NJ=-0.966$, which is in very good agreement with the results obtained within the variational Monte Carlo

Yukito Iba

Variable selection for a multiple regression model (Noisy Linear Perceptron) is studied with a mean field approximation. In our Bayesian framework, variable selection is formulated as estimation of discrete parameters that indicate a subset of the explanatory variables. Then, a mean field approximation is introduced for the calculation of the posterior avera

V. Gurarie

We find an analog of Zamolodchikov&#39;s c-theorem for disordered two dimensional noninteracting systems in their supersymmetric representation. For this purpose we introduce a new parameter b which flows along the renormalization group trajectories much like the central charge for unitary two dimensional field theories. However, it is not known yet if this

Philip Resnik

Parallel corpora are a valuable resource for machine translation, but at present their availability and utility is limited by genre- and domain-specificity, licensing restrictions, and the basic difficulty of locating parallel texts in all but the most dominant of the world&#39;s languages. A parallel corpus resource not yet explored is the World Wide Web, w

A. Parravano, M. G. Cosenza

A procedure to predict the occurrence of periodic clusters in a system of globally coupled maps displaying a constant mean field is presented. The method employs the analogy between a system of globally coupled maps and a single map driven by a constant force. By obtaining the asymptotic orbits of the driven map, an associated coupling function can be constr

Antonio Bonelli, Stefano Ruffo

Successive pairs of pseudo-random numbers generated by standard linear congruential transformations display ordered patterns of parallel lines. We study the ``ordered&#39;&#39; and ``chaotic&#39;&#39; distribution of such pairs by solving the eigenvalue problem for two-dimensional modular transformations over integers. We conjecture that the optimal uniformi

Gustavo Medina Tanco

The possibility that the magnetic field is strongly correlated with the large-scale structure of the universe has been recently considered in the literature. In this scenario the intergalactic magnetic field has a strong ($μ$G) regular component spanning tens of Mpc but localized in sheets and filaments, while the vast voids in between are almost free of mag

S. R. Oliveira, O. D. Miranda, J. C. N. de Araujo, R. Opher

In this article we extend the study performed in our previous article on the collapse of primordial objects. We here analyze the behavior of the physical parameters for clouds ranging from $10^7M_\odot$ to $10^{15}M_\odot$. We studied the dynamical evolution of these clouds in two ways: purely baryonic clouds and clouds with non-baryonic dark matter included

E. V. Liverts

Nonlinear solutions for the large-scale flow of interstellar gas in the presence of a spiral gravitational field have received considerable attention because this model allows to explain a lot of observations for galaxy disks. However this investigations were forced to limit by numerable analysis of the problem because of its nonlinearity. In this paper we w

S. R. Oliveira, O. D. Miranda, J. C. N. de Araujo, R. Opher

We present here studies of collapse of purely baryonic Population III objects with masses ranging from $10M_\odot$ to $10^6M_\odot$. A spherical Lagrangian hydrodynamic code has been written to study the formation and evolution of the primordial clouds, from the beginning of the recombination era ($z_{rec} \sim 1500$) until the redshift when the collapse occ

H. Plana, Cl. Mendes de Oliveira, P. Amram, J. Boulesteix

We present kinematic observations of H$α$ emission for two early-type galaxies and one disk system, members of the Hickson compact group 90 (HCG 90) obtained with a scanning Fabry-Perot interferometer and samplings of 16 $km$ $s^{-1}$ and 1$\arcsec$. Mapping of the gas kinematics was possible to $\sim$ 2 r$_{eff}$ for the disk galaxy N7174 and to $\sim$ 1.3

R. Elson, N. Tanvir, G. Gilmore, R. A. Johnson

We present deep luminosity functions derived from HST STIS data for three rich LMC clusters (NGC 1805, NGC 1868, and NGC 2209), and for one Galactic globular cluster (NGC 6553). All of the LMC cluster luminosity functions are roughly consistent with a Salpeter IMF or with the solar neighbourhood IMF from Kroupa, Tout & Gilmore (1993). They continue to rise a

Y. K. Ng

The photometric estimate of the metallicity and the age of the Azzopardi et al. (1991, A&AS 88, 265) carbon stars (Ng 1997, A&A 328, 211) is revised to respectively Z~0.004 and ~0.1 Gyr. Under the hypothesis that the carbon stars are located at a distance related to the Sagittarius dwarf galaxy, the broad velocity dispersion of the stars can only be explaine

R A E Fosbury, J Vernet, M Villar-Martin, M H Cohen

Keck spectropolarimetry, giving spectral coverage from Ly-$α$ to beyond CIII], and HST imaging of a sample of powerful radio galaxies with $z\sim2.5$\ has been obtained. These data are giving us a clear picture of the nature of the `alignment effect&#39; and are revealing new correlations between polarization and emission line ratios which may be interpreted

J. Siebert, W. Brinkmann, M. J. Drinkwater, W. Yuan

We investigate the X-ray properties of the Parkes sample of flat-spectrum radio sources using data from the ROSAT All-Sky Survey and archival pointed PSPC observations. In total, 163 of the 323 sources are detected. For the remaining 160 sources 2 sigma upper limits to the X-ray flux are derived. We present power-law photon indices for 115 sources, which wer

V. Milosevic-Zdjelar, S. Samurovic, M. M. Cirkovic

In this paper we present the ionization in the center of the Galaxy. We use Taylor & Cordes (1993) and Lazio & Cordes (1998) models to obtain the overall contribution of the Galactic center (GC) component to the total electron density. We also discuss local contributions from the GC area that come from a complex set of sources. Finally, we discuss the nature

S. Samurovic, M. M. Cirkovic, V. Milosevic-Zdjelar, J. Petrovic

We study the ionizing sources in spiral galaxies and examine in more detail our Galaxy. Using Taylor & Cordes (1993) model we analyze the electron density in different parts of the Galaxy, and emphasize the still unsolved problems. Finally, we compare the intensities of H$α$ emission in disk and halo.

K. Golap, N. Udaya Shankar, S. Sachdev, R. Dodson

A new, meter-wave radio telescope has been built in the North-East of Mauritius, an island in the Indian ocean, at a latitude of -20.14 deg. The Mauritius Radio Telescope (MRT) is a Fourier Synthesis T-shaped array, consisting of a 2048 m long East-West arm and a 880 m long South arm. In the East-West arm 1024 fixed helices are arranged in 32 groups and in t

Taro Kotani, Tadayasu Dotani, Fumiaki Nagase, John G. Greenhill

The X-ray binary pulsar GX 1+4 was observed with Ginga every year from 1987 to 1991, and with ASCA in 1994. During the Ginga observations, GX 1+4 was in the steady spindown phase, while the X-ray flux was not steady. The X-ray luminosity decreased down to L = 2.7\times10^{36} erg s^{-1} in 1991, after the peak activity of L = 1.2\times10^{37} erg s^{-1} in 1

Natarajan Visvanathan, Beverley J. Wills, .

Polarization measurements are presented for 52 radio-loud QSOs and BL Lac objects. For 9 highly polarized (p >3%) AGN, these are the first published polarization measurements. Of these 9, 7 are highly-polarized QSOs (HPQs), one is a BL Lac object and another is a likely BL Lac object. Polarization variability is confirmed for some of these new and previously

Beverley J. Wills, M. S. Brotherton, A. Laor, D. Wills

A unique, essentially complete sample of 22 QSOs, with high quality soft X-ray spectra from ROSAT, as well as HST and optical spectrophotometry from below Ly-alpha to above H-alpha, is being used to investigate the relationships among the ionizing continuum and the optical and UV continuum, emission and absorption lines. Here we present a first analysis show

Jonathan H. Kawamura, Colin R. Masson

A direct measurement of the expansion of W 3(OH) is made by comparing Very Large Array images taken about 10 yr apart. The expansion is anisotropic with a typical speed of 3 to 5 km/s, indicating a dynamical age of only 2300 yr. These observations are inconsistent with either the freely expanding shell model or a simple bow shock model. The most favored mode

R. Kallosh, J. Rahmfeld

We present a simple form of the Type IIB string action on $AdS_5\times S^5$. The result is achieved by fixing $κ$-symmetry in the Killing spinor gauge defined by the projector of the Killing spinor of the D3 brane. We show explicitly that in this gauge the superspace is greatly simplified which is the crucial ingredient for the simple string action.

Esko Keski-Vakkuri

Recently, the AdS/CFT conjecture of Maldacena has been investigated in Lorentzian signature by Balasubramanian et. al. We extend this investigation to Lorentzian BTZ black hole spacetimes, and study the bulk and boundary behaviour of massive scalar fields both in the non-extremal and extremal case. Using the bulk-boundary correspondence, we also evaluate the

A. Furusaki

Results of large-scale numerical simulations are reported on the Anderson localization in a two-dimensional square lattice tight-binding model with random flux. Localization lengths, fluctuations of the conductance, and the density of states are computed for quasi-one-dimensional geometry. Numerical results indicate that the model exhibits the same critical

Steffen A. Bass, B. Mueller, W. Poeschl

We propose a novel formalism for simultaneously describing both, the hard and soft parton dynamics in ultrarelativistic collisions of nuclei. The emission of gluons from the initially coherent parton configurations of the colliding nuclei and low-$p_t$ color coherence effects are treated in the framework of a Yang-Mills transport equation on a coupled lattic

Simeon Warner, Simon Catterall, Ray Renken

We use Monte Carlo simulation to study the phase diagram of three-dimensional dynamical triangulations with a boundary. Three phases are indentified and characterized. One of these phases is a new, boundary dominated phase; a simple argument is presented to explain its existence. First-order transitions are shown to occur along the critical lines separating

Danny Birmingham

We consider a class of black hole solutions to Einstein&#39;s equations in d dimensions with a negative cosmological constant. These solutions have the property that the horizon is a (d-2)-dimensional Einstein manifold of positive, zero, or negative curvature. The mass, temperature, and entropy are calculated. Using the correspondence with conformal field th

Eugene Kogan, Mark Auslender, Moshe Kaveh

Localization and dephasing of conduction electrons in a low carrier density ferromagnet due to scattering on magnetic fluctuations is considered. We claim the existence of the &#34;mobility edge&#34;, which separates the states with fast diffusion and the states with slow diffusion; the latter is determined by the dephasing time. When the &#34;mobility edge&

Alessandro Torcini, Mickael Antoni

A system of N classical particles in a 2D periodic cell interacting via long-range attractive potential is studied. For low energy density $U$ a collapsed phase is identified, while in the high energy limit the particles are homogeneously distributed. A phase transition from the collapsed to the homogeneous state occurs at critical energy U_c. A theoretical

Masato Arai, Hideaki Hiro-Oka, Nobuchika Okada, Shin Sasaki

We propose a new scenario to produce the superheavy dark matter based on the inflationary universe. In our scenario, the inflaton couples to both a boson and a stable fermion. Although the fermion is produced by the inflaton decay after inflation, almost energy density of the inflaton is transmitted into the radiation by parametric resonance which causes the

Granddon D. Yen, Mark I. Gorenstein

The preliminary data on hadron multiplicities measured in central Pb+Pb collisions at 158A GeV/c are analyzed. The ideal hadron gas model fails to give a reasonable explanation to the Pb+Pb data sets. We study the possible effects of pion enhancement due to different hard-core repulsion for pions and other hadrons and strangeness suppression because of incom

I. V. Krasovsky

The Harper equation describes an electron on a 2D lattice in magnetic field and a particle on a 1D lattice in a periodic potential, in general, incommensurate with the lattice potential. We find the distribution of the roots of Bethe ansatz equations associated with the Harper equation in the limit as alpha=1/Q tends to 0, where alpha is the commensurability

T. Barreiro, B. de Carlos, J. A. Casas, J. M. Moreno

The interplay between gaugino condensation and an anomalous Fayet-Iliopoulos term in string theories is not trivial and has important consequences concerning the size and type of the soft SUSY breaking terms. In this paper we examine this issue, generalizing previous work to the supergravity context. This allows, in particular, to properly implement the canc

J. Fleischer, A. V. Kotikov, O. L. Veretin

For a large class of two-loop selfenergy- and vertex-type diagrams with only one non-zero mass ($M$) and the vertices also with only one non-zero external momentum squared ($q^2$) the first few expansion coefficients are calculated by the large mass expansion. This allows to `guess&#39; the general structure of these coefficients and to verify them in terms

P. I. Melnikov, B. A. Knyazev, J. B. Greenly

A novel scheme is presented for production of a thin ($<1$ mm) uniform vapor layer over a large surface area ($>100$ cm$^2$) by pulsed laser ablation of a solid surface. Instead of dispersing the laser energy uniformly over the surface, a modified Fabry-Perot interferometer is employed to concentrate the laser energy in very narrow closely-spaced concentric

C. Giunti

Inspired by the recent proposal by Feldman and Cousins of a ``unified approach to the classical statistical analysis of small signals&#39;&#39; based on a choice of ordering in Neyman&#39;s construction of classical confidence intervals, I propose a new ordering principle for the classical statistical analysis of Poisson processes with background which minim

B. Alles, G. Cella, M. Dilaver, Y. Gunduc

Using high statistic numerical results we investigate the properties of the O(3) non-linear 2D sigma-model. Our main concern is the detection of an hypothetical Kosterlitz-Thouless-like (KT) phase transition which would contradict the asymptotic freedom scenario. Our results do not support such a KT-like phase transition.

S. Nishimoto, Y. Ohta

Optical conductivity of the trellis lattice t-J model at quarter filling is calculated by an exact-diagonalization technique on small clusters, whereby the valence state of V ions of NaV_2O_5 is considered. We show that the experimental features at \sim 1 eV, including peak positions, presence of shoulders, and anisotropic spectral weight, can be reproduced

M. Araki, Y. Tanii

Duality symmetries are discussed for non-linear gauge theories of (n-1)-th rank antisymmetric tensor fields in general even dimensions d=2n. When there are M field strengths and no scalar fields, the duality symmetry groups should be compact. We find conditions on the Lagrangian required by compact duality symmetries and show an example of duality invariant

R. Shrock, S. -H. Tsai

We study the ground state degeneracy per site (exponent of the ground state entropy) $W(Λ,(L_x=\infty) \times L_y,q)$ for the $q$-state Potts antiferromagnet on infinitely long strips with width $L_y$ of 2D lattices $Λ$ with free and periodic boundary conditions in the $y$ direction, denoted FBC$_y$ and PBC$_y$. We show that the approach of $W$ to its 2D the

H. Pierre Noyes, Tom Etter

We shall argue in this paper that a central piece of modern physics does not really belong to physics at all but to elementary probability theory. Given a joint probability distribution J on a set of random variables containing x and y, define a link between x and y to be the condition x=y on J. Define the {\it state} D of a link x=y as the joint probability

Kirill N. Alekseev

The squeezing in a nonlinear system with chaotic dynamics is considered. The model describing interaction of collection of two-level atoms with a single-mode of self-consistent field and an external field is analyzed. It is shown that in the semiclassical limit, in contrast to the regular behaviour, the chaotic dynamics result in: (i) an increase in squeezin

Wolfram Just, Frank Matthäus, Herwig Sauermann

We consider instabilities of a single mode with finite wavenumber in inversion symmetric spatially one dimensional systems, where the character of the bifurcation changes from sub- to supercritical behaviour. Starting from a general equation of motion the full amplitude equation is derived systematically and formulas for the dependence of the coefficients on

M. Bawin, S. A. Coon

We demonstrate in a solvable model the connection between the intrinsic electric polarizability $\barα$ and the value $α_{Sch}$ obtained from neutron-atom scattering.

S. A. Coon, M. D. Scadron

The scale of a phenomenologically successful charge-symmetry-violating nucleon-nucleon interaction, that attributed to meson exchange with a $ΔI =1$ rho-omega transition, is set by the Coleman-Glashow SU(2) breaking tadpole mechanism. A single tadpole scale has been obtained from symmetry arguments, electromagnetic meson and baryon measured mass splittings,

P. Danielewicz, P. -B. Gossiaux, R. A. Lacey

We specify a tractable transport model with thermodynamic properties close to those expected for the strongly interacting matter. In particular, at high temperatures, the matter undergoes a phase transition, such as to the quark-gluon plasma, with a drop in masses of elementary excitations and a rapid increase in the number of degrees of freedom. We show tha

R. Schiavilla, V. G. J. Stoks, W. Gloeckle, H. Kamada

The cross section for the proton weak capture reaction $^1H(p,e^+ν_e)^2H$ is calculated with wave functions obtained from a number of modern, realistic high-precision interactions. To minimize the uncertainty in the axial two-body current operator, its matrix element has been adjusted to reproduce the measured Gamow-Teller matrix element of tritium $β$ decay

Volker Enss

As a prototype of an evolution equation we consider the Schrödinger equation i (d/dt) Ψ(t) = H Ψ(t), H = H_0 + V(x) for the Hilbert space valued function Ψ(.) which describes the state of the system at time t in space dimension at least 2. The kinetic energy operator H_0 may be propotional to the Laplacian (nonrelativistic quantum mechanics), H_0 = \sqrt{-Δ+