March 1998 arXiv papers — page 17

A. C. C. Coolen, D. Saad

We study the dynamics of supervised learning in layered neural networks, in the regime where the size $p$ of the training set is proportional to the number $N$ of inputs. Here the local fields are no longer described by Gaussian probability distributions. We show how dynamical replica theory can be used to predict the evolution of macroscopic observables, in

Wellington da Cruz

We obtain for an anyon gas in the high temperature limit a relation between the exclusion statistics parameter $g$ and the Hausdorff dimension $h$, given by $g=h(2-h)$. The anyonic excitations are classified into equivalence classes labeled by Hausdorff dimension, $h$, and in that limit, the parameter $g$ give us the second virial coefficient for any statist

Mordehai Milgrom

I investigate stable equilibria of bodies in potential fields satisfying a generalized Poisson equation: divergence[m(grad phi) grad phi]= source density. This describes diverse systems such as nonlinear dielectrics, certain flow problems, magnets, and superconductors in nonlinear magnetic media; equilibria of forced soap films; and equilibria in certain non

S. Gluzman, V. I. Yukalov

Two possible definitions of fixed points in the self-similar analysis of time series are considered. One definition is based on the minimal-difference condition and another, on a simple averaging. From studying stock market time series, one may conclude that these two definitions are practically equivalent. A forecast is made for the stock market indices for

Thomas Schreiber, Marcus Richter

We introduce a modified algorithm to perform nonlinear filtering of a time series by locally linear phase space projections. Unlike previous implementations, the algorithm can be used not only for a posteriori processing but includes the possibility to perform real time filtering in a data stream. The data base that represents the phase space structure gener

Michael Chertkov

Forced advection of passive scalar by a smooth $d$-dimensional incompressible velocity in the presence of a linear damping is studied. Acting separately advection and dumping do not lead to an essential intermittency of the steady scalar statistics, while being mixed together produce a very strong non-Gaussianity in the convective range: $q$-th (positive) mo

D. Marsden, R. E. Rothschild, C. Kouveliotou, S. Dieters

We discuss observations of the quiescent emission from the soft gamma repeater SGR 1806-20 by the Rossi X-ray Timing Explorer. We find that the 2-20 keV RXTE data is consistent with a constant spectral shape during both active bursting periods and periods of relative quiescence, and is best described by a nonthermal (power law) spectral shape. Using archival

G. Steigman

During its hot, dense, early evolution the Universe was a primordial nuclear reactor, synthesizing the light nuclides D, 3He, 4He and 7Li in the first thousand seconds. The presently observed abundances of these relic nuclides provide a unique window on the early Universe. The implications of current observations for cosmology (the universal density of nucle

S. Huettemeister, G. Dahmen, R. Mauersberger, C. Henkel

Multiline observations of C18O and SiO isotopomers toward 33 molecular peaks in the Galactic center region, taken at the SEST, JCMT and HHT telescopes, are presented. The C18O presumably traces the total H_2 column density, while the SiO traces gas affected by shocks and high temperature chemistry. The J =2-1 line of SiO is seen only in few regions of the Ga

M. R. Merrifield, K. Kuijken

We show that the kinematics of the shells seen around some elliptical galaxies provide a new, independent means for measuring the gravitational potentials of elliptical galaxies out to large radii. A numerical simulation of a set of shells formed in the merger between an elliptical and a smaller galaxy reveals that the shells have a characteristic observable

A. Yahil

Research in cosmology traditionally divided into two separate lines. On the one hand was the search for initial conditions: the cosmological parameters H, Omega, Omega_b, and Lambda, and the power spectrum P(k). On the other hand was the study of the formation and evolution of structures, from globular-cluster sized objects to large-scale structures. These l

I. M. George, T. J. Turner, R. F. Mushotzky, K. Nandra

We present the results from ASCA observations of NGC 3783 carried out during 1993 and 1996. Variability is observed both between the two epochs and within the individual observations, the latter due to a non-stationary process. We find the spectra at both epochs to contain features due to absorption by ionized material, predominantly due to Ovii and Oviii. W

Coryn A. L. Bailer-Jones, Mike Irwin, Ted von Hippel

We investigate the application of neural networks to the automation of MK spectral classification. The data set for this project consists of a set of over 5000 optical (3800-5200 AA) spectra obtained from objective prism plates from the Michigan Spectral Survey. These spectra, along with their two-dimensional MK classifications listed in the Michigan Henry D

A. Yahil, K. M. Lanzetta, A. Fernandez-Soto

Several conclusions have been reached over the last few years concerning high-redshift galaxies: (1) The excess of faint blue galaxies is due to dwarf galaxies. (2) Star formation peaks at redshifts z ~1-2. (3) It appears to occur piecemeal in any given galaxy and there is no evidence for starbursting throughout a large ~10 kpc galaxy. (4) There is significa

H. C. Harris, C. C. Dahn, R. L. Walker, C. B. Luginbuhl

Preliminary trigonometric parallaxes and BVI photometry are presented for two dwarf carbon stars, LP765-18 (= LHS1075) and LP328-57 (= CLS96). The data are combined with the literature values for a third dwarf carbon star, G77-61 (= LHS1555). All three stars have very similar luminosities (9.6<M_V<10.0) and very similar broadband colors across the entire vis

A. J. Connolly, A. S. Szalay, R. J. Brunner

For faint photometric surveys our ability to quantify the clustering of galaxies has depended on interpreting the angular correlation function as a function of the limiting magnitude of the data. Due to the broad redshift distribution of galaxies at faint magnitude limits the correlation signal has been extremely difficult to detect and interpret. We introdu

Ravi K. Sheth

This paper presents a new derivation of the Generalized Poisson distribution. This distribution provides a good fit to the evolved, counts-in-cells distribution measured in numerical simulations of hierarchical clustering from Poisson initial conditions. This new derivation can be used to construct a useful analytic model of the evolution of clustering measu

S. Nishiura, Y. Taniguchi

We have derived the masses of central objects ($M_{BH}$) of nine type 2 Seyfert nuclei using the observational properties of the hidden broad H$β$ emission. We obtain the average dynamical mass, log$(M_{BH} / M_\odot) \simeq 8.00 \pm 0.51 - 0.475 log (τ_{es}/1)$ where $τ_{es}$ is the optical depth for electron scattering. If $τ_{es} \sim 1$, this average mas

J. Machalski, W. Godlowski

A preliminary 1.4 GHz RLF at redshift of about 0.14 is derived from the Las Campanas Redshift Survey (LCRS) and the NVSS radio data. No significant evolution has been found at this redshift in comparison to the &#39;local&#39; RLF.

Cheryl Frost, John Lattanzio, Peter Wood

We report on the discovery of a new kind of thermal pulse in intermediate mass AGB stars. Deep dredge-up during normal thermal pulses on the AGB leads to the formation of a long, unburnt tail to the helium profile. Eventually the tail ignites under partially degenerate conditions producing a strong shell flash with very deep subsequent dredge-up. The carbon

R. Scaramella, L. Guzzo, G. Zamorani, E. Zucca

The issue of the approximate isotropy and homogeneity of the observable universe is one of the major topics in modern Cosmology: the common use of the Friedmann-Robertson-Walker [FWR] metric relies on these assumptions. Therefore, results conflicting with the ``canonical&#39;&#39; picture would be of the utmost importance. In a number of recent papers it has

Salam Tawfiq, Patrick J. O&#39;Donnel, J. G. Koerner

Light-Front quark model spin wave functions are employed to calculate the three independent couplings g_{Σ_c Λ_c π}, f_{Λ_{c1} Σ_c π} and f_{Λ^{*}_{c1} Σ_c π} of S-wave to S-wave and P-wave to S-wave one-pion transitions. It is found that g_{Σ_c Λ_c π}=6.81 MeV^{-1}, f_{Λ_{c1} Σ_c π}=1.16 and f_{Λ^{*}_{c1} Σ_c π}=0.96 . 10^{-4} MeV^{-2}. We also predict deca

G. Altarelli, R. D. Ball, S. Forte, G. Ridolfi

We review the analysis of polarized structure function data using perturbative QCD at next-to-leading order. We use the most recent experimental data to obtain updated results for polarized parton distributions, first moments and the strong coupling. We also discuss several theoretical issues involved in this analysis and in the interpretation of its results

J. A. Oller, E. Oset, J. R. Pelaez

We develop a coupled channel unitary approach describing the behavior at higher energies of systems whose low-energy dynamics is given by effective O(p^2) and O(p^4) chiral Lagrangians. Our free parameters are those of the O(p^4) Lagrangian. When applied to the meson-meson interaction, it yields a remarkable agreement with data up to sqrt{s}=1.2 GeV, dynamic

Thomas Vojta

We investigate the spreading of damage in Ising models with Kawasaki spin-exchange dynamics which conserves the magnetization. We first modify a recent master equation approach to account for dynamic rules involving more than a single site. We then derive an effective-field theory for damage spreading in Ising models with Kawasaki spin-exchange dynamics and

Joaquim Gomis, David Mateos, Joan Simón, Paul K. Townsend

We derive the dynamics of M-brane intersections from the worldvolume action of one brane in the background supergravity solution of another one. In this way we obtain an effective action for the self-dual string boundary of an M2-brane in an M5-brane, and show that the dynamics of the 3-brane intersection of two M5-branes is described by a Dirac-Born-Infeld

L. Castellani, A. Ceresole, R. D&#39;Auria, S. Ferrara

We prove the existence of a new class of BPS saturated M-branes. They are in one-to-one correspondence with the Freund--Rubin compactifications of M-theory on either (AdS_4) x (G/H) or (AdS_7) x (G/H), where G/H is the seven (or four) dimensional Einstein coset manifolds classified long ago in the context of Kaluza Klein supergravity. The G/H M-branes are so

Tobias Hurth, Kostas Skenderis

We present a general method for constructing consistent quantum field theories with global symmetries. We start from a free non-interacting quantum field theory with given global symmetries and we determine all consistent perturbative quantum deformations assuming the construction is not obstructed by anomalies. The method is established within the causal Bo

P. Moskal, J. T. Balewski, A. Budzanowski, H. Dombrowski

The $pp \to pp η^{\prime}$ (958) reaction has been measured at COSY using the internal beam and the COSY-11 facility. The total cross sections at the four different excess energies \mbox{$ Q = ~1.5 ~MeV, ~1.7 ~MeV, ~2.9 ~MeV,$ and $ ~4.1 MeV$} have been evaluated to be \mbox{$ σ= 2.5 \pm 0.5~nb$, $~~~ 2.9 \pm 1.1~nb$, $~~~ 12.7 \pm 3.2~nb$, ~ and $~~~ 25.2 \

D. J. BenDaniel

We look for a deep connection between mathematics and physics. Our approach is to propose a set theory T which leads to a concise mathematical description of physical fields and to a finite unit of action. The concept of &#34;definability&#34; of fields is then introduced. Definabilty of fields in T is necessary and sufficient for quantization and sufficient

Giampiero Esposito, Alexander Yu. Kamenshchik

Recent work in the literature has studied fourth-order elliptic operators on manifolds with boundary. This paper proves that, in the case of the squared Laplace operator, the boundary conditions which require that the eigenfunctions and their normal derivative should vanish at the boundary lead to self-adjointness of the boundary-value problem. On studying,

Osvaldo Chandia, Jorge Zanelli

The supersymmetric Lagrangian compatible with the presence of torsion in the background spacetime requires, in addition to the minimal coupling, an interaction between the spin and the torsion of the form ${1/2} N_{μνλρ}ψ^μψ^νψ^λψ^ρ$, where $N$ is the Nieh-Yan 4-form. This gives rise to a coupling between helicity ($h$) and the Nieh-Yan density of the form $

C. Chandre, H. R. Jauslin

We give a proof of the KAM theorem on the existence of invariant tori for weakly perturbed Hamiltonian systems, based on Thirring&#39;s approach for Hamiltonians that are quadratic in the action variables. The main point of this approach is that the iteration of canonical transformations on which the proof is based stays within the space of quadratic Hamilto

F. Benatti, M. Fannes

We use multi-time correlation functions of quantum systems to construct random variables with statistical properties that reflect the degree of complexity of the underlying quantum dynamics.

A. Hasegawa, Y. Iwasaki, K. Sakamoto, N. Noda

An enhancement of antiprotons produced in p+d reaction in comparison with ones in p+p elementary reaction is investigated. In the neighborhood of subthreshold energy the enhancement is caused by the difference of available energies for antiproton production. The cross section in p+d reaction, on the other hand, becomes just twice of the one in elementary p+p

Yeuk-Kwan E. Cheung, Morten Krogh

We study D0-branes in type IIA on $T^2$ with a background B-field turned on. We calculate explicitly how the background B-field modifies the D0-brane action. The effect of the B-field is to replace ordinary multiplication with a noncommutative product. This enables us to find the matrix model for M-theory on $T^2$ with a background 3-form potential along the

A. Accardi, A. Belli, M. Martellini, M. Zeni

Using the first order formalism (BFYM) of the Yang-Mills theory we show that it displays an embedded topological sector corresponding to the field content of the Topological Yang-Mills theory (TYM). This picture arises after a proper redefinition of the fields of BFYM and gives a clear representation of the non perturbative part of the theory in terms of the

Zoltan Ligeti, Aneesh V. Manohar

In the large $N_c$ limit, the nonleptonic width of the B meson is determined by the lepton mass spectrum in semileptonic B decay and the hadron mass spectrum in $τ$ decay. This result can be compared with the nonleptonic width computed using the operator product expansion and local duality, to estimate the violation of local duality in B decay. In the absenc

Valery S. Dryuma

The law of transformation of affine connection for n-dimensional manifolds as the system of nonlinear equations on local coordinates of manifold is considered. The extension of the Darboux-Lame system of equations to the spaces of constant negative curvature is demonstrated. Geodesic deviation equation as well as the equations of geodesics are presented in t

Valery S. Dryuma, Makoto Matsumoto

A two dimensional Finsler space associated with the differential equation $y&#39;&#39;=Y_3 y&#39;^3+Y_2 y&#39;^2+Y_1 y&#39;+Y_0$ is characterized by a tensor equation and called the Douglas space. An application to the Lorenz nonlinear dynamical equation is discussed from the standpoint of Finsler geometry.

A. Widom, E. Sassaroli, Y. N. Srivastava, J. Swain

One loop field theory calculations of free energies quite often yield violations of the stability conditions associated with the thermodynamic second law. Perhaps the best known example involves the equation of state of black holes. Here, it is pointed out that the Casimir force between two parallel conducting plates also violates a thermodynamic stability c

Riccardo Giannitrapani

Recently it has been proposed, using the formalism of positive-operator-valued measures, a possible definition of quantum coordinates for events in the context of quantum mechanics. In this short note we analyze this definition from the point of view of local algebras in the framework of local quantum theories.

H. D. Doebner

Motivated by recent proposals (Bialynicki-Birula, Mycielski; Haag, Bannier; Weinberg; Doebner, Goldin) for nonlinear quantum mechanical evolution equations for pure states some principal difficulties in the framework of usual quantum theory, which is based on its inherent linear structure, are discussed. A generic construction of nonlinear evolution equation

S. M. Apenko

We study the critical behaviour near the threshold where a first bound state appears at some value of coupling constant in an attractive short-range potential in $2+ε$ dimensions. We obtain general expression for the binding energy near the threshold and also demonstrate that the critical region is correctly described by an effective separable potential. The

X. Z. Tang, A. H. Boozer

From a kinematical point of view, the geometrical information of hamiltonian chaos is given by the (un)stable directions, while the dynamical information is given by the Lyapunov exponents. The finite time Lyapunov exponents are of particular importance in physics. The spatial variations of the finite time Lyapunov exponent and its associated (un)stable dire

D. Flamm

This paper gives a short review of the history of statistical physics starting from D. Bernoulli&#39;s kinetic theory of gases in the 18th century until the recent new developments in nonequilibrium kinetic theory in the last decades of this century. The most important contributions of the great physicists Clausius, Maxwell and Boltzmann are sketched. It is

Zhenquan Li, A. J. Roberts

Models and simulations of the flow of thin films of fluids have many important applications in industrial and natural processes. We consider the motion of a thin layer of an incompressible, Newtonian fluid over an arbitrary solid, stationary curved substrate. Earlier work by Roy, et al has modeled slow fluid flows in which inertia is negligible. However, in

H. Herndl, R. Hofinger, H. Oberhummer

We discuss models to calculate one- and two-neutron capture reactions on light nuclei. These are applied to calculate the reaction rates of 15N(n,gamma)16N, 16N(n,gamma)17}N and 4He(2n,gamma)6He. The possible astrophysical importance is discussed.

P. Sarriguren, E. Moya de Guerra, A. Escuderos, A. C. Carrizo

We study the properties of $^{74}$Kr, and particularly the Gamow Teller strength distribution, using a deformed selfconsistent HF+RPA method with Skyrme type interactions. Results are presented for two density-dependent effective two-body interactions, including the dependence on deformation of the HF energy that exhibits two minima at close energies and dis

J. T. Balewski, A. Budzanowski, H. Dombrowski, W. Eyrich

The energy dependence of the total cross section for the pp \to pK^+Λreaction was measured in the threshold region covering the excess energy range up to 7MeV. Existing model calculations describe the slope of the measured cross sections well, but are too low by a factor of two to three in rate. The data were used for a precise determination of the beam mome

Sergei A. Shlapakov, Megumi Saigo, Anatoly A. Kilbas

The paper is devoted to study the inversion of the integral transform $$(\mbox{\boldmath$H$}f)(x)=\int^\infty_0H^{m,n}_{\thinspace p,q} \left[xt\left|\begin{array}{c}(a_i,α_i)_{1,p}\\[1mm](b_j,β_j)_{1,q} \end{array}\right.\right]f(t)dt$$ involving the $H$-function as the kernel in the space $\euf114_{ν,r}$ of functions $f$ such that $$\int^\infty_0\left|t^νf

Megumi Saigo, Rajendra K. Saxena

In this article three expansion formulas for a generalized hypergeometric function $_4F_3$ are derived, when its upper parameters differ by integers. Though the results are special cases of a general continuation formula for $_pF_q$, they are sufficiently general and unify a number of known results.

Arak Mathai Mathai

Input-output, growth-decay, production-consumption type situations abound in many practical problems. When the input and output variables are independently gamma distributed, various aspects of the residual effect are already tackled by the author. Matrix-variate analogues, their connections to quadratic and bilinear forms, matrix-variate Whittaker functions

Anatoly A. Kilbas, Megumi Saigo

The paper is devoted to study the $H$-function defined by the Mellin-Barnes integral $$H^{m,n}_{\thinspace p,q}(z)={\frac1{2πi}}\int_{\Lss} \HHs^{m,n}_{\thinspace p,q}(s)z^{-s}ds,$$ where the function $\HH^{m,n}_{\thinspace p,q}(s)$ is a certain ratio of products of Gamma functions with the argument $s$ and the contour $\LL$ is specially chosen. The conditio

Naihuan Jing

We introduce an affinization of the quantum Kac-Moody algebra associated to a symmetric generalized Cartan matrix. Based on the affinization, we construct a representation of the quantum Kac-Moody algebra by vertex operators from bosonic fields. We also obtain a combinatorial indentity about Hall-Littlewood polynomials.

Mark Hovey, Brooke Shipley, Jeff Smith

The long hunt for a symmetric monoidal category of spectra finally ended in success with the simultaneous discovery of the third author&#39;s discovery of symmetric spectra and the Elmendorf-Kriz-Mandell-May category of S-modules. In this paper we define and study the model category of symmetric spectra, based on simplicial sets and topological spaces. We pr

C. S. Chu, P. S. Howe, E. Sezgin, P. C. West

Open branes ending on other branes, which may be referred to as the host branes, are studied in the superembedding formalism. The open brane, host brane and the target space in which they are both embedded are all taken to be supermanifolds. It is shown that the superspace constraints satisfied by the open brane are sufficient to determine the corresponding

H. J. de Vega, A. L. Larsen, N. Sánchez

We consider classical and quantum strings in the conformally invariant background corresponding to the SL(2,R) WZWN model. This background is locally anti-de Sitter spacetime with non-vanishing torsion. Conformal invariance is expressed as the torsion being parallelized. The precise effect of the conformal invariance on the dynamics of both circular and gene

Jordi París, Jaume Roca

We make a first step to extend to the supersymmetric arena the effective action method, which is used to covariantly deduce the low energy dynamics of topological defects directly from their parent field theory. By focussing on two-dimensional supersymmetric theories we are able to derive the appropriate change of variables that singles out the low energy de

V. A. Franke, S. A. Paston, E. V. Prokhvatilov

A lattice gauge theory with an action polynomial in independent field variables is considered. The link variables are described by unconstrained complex matrices instead of unitary ones. A mechanism which permits to switch off in the continuous limit the arising extra fields is discussed. The Euclidean version of the theory with an 4-dimensional lattice is d

Eric G. Gimon, Martin Gremm

We consider N=1 supersymmetric SU(N_c) gauge theories, using the type IIB brane construction recently proposed by Hanany and Zaffaroni. At non-zero string coupling, we find that the bending of branes imposes consistency conditions that allow only non-anomalous gauge theories with stable vacua, i.e., N_f >= N_c, to be constructed. We find qualitative differen

L. Hadasz, M. Sadzikowski, P. Wegrzyn

We consider mirrors of the spherical shape, that can expand or contract. Due to the excitation of the vacuum around, some spherical waves radiated from vibrating mirrors are encountered. Using experience from well-known literature on studies of two-dimensional conformal models, we adopt a similar framework to investigate such quantum phenomena in four dimens

Hyun Seok Yang, Inbo Kim, Bum-Hoon Lee

We construct a locally supersymmetric worldsheet formulation of a non-Abelian Ramond-Neveu-Schwarz (NARNS) string theory where the string coordinates are noncommuting matrices in a group U(N). This is described by the two dimensional supergravity coupled to supersymmetric Yang-Mills fields and adjoint matters in the gauge group U(N). We show that our NARNS s

Robert Carroll

We organize and review some material from various sources about prepotentials, Riemann surfaces and kernels, WDVV, and the renormalization group, provide some further connections and information, and indicate some directions and problems.

F. Pisano, S. Shelly Sharma

Fundamental mechanisms for Majoron emitting neutrinoless double beta decay in SU(3)_C x G_W x U(1) models, for electroweak flavor chiral extensions, G_W = SU(3)_L and SU(4)_L are pointed out. Both kinds of known Majoron emitting processes, charged Majoron emitting where the massless Nambu-Goldstone boson itself carries lepton charge, $L=-2$, and the ordinary

M. Maris, S. T. Petcov

Using the results of a high precision calculation of the solar neutrino survival probability for Earth crossing neutrinos in the case of MSW $ν_e --> ν_s$ transition solution of the solar neutrino problem, we derive predictions for the one-year averaged day-night (D-N) asymmetries in the deformed recoil-$e^-$ spectrum and in the energy-integrated event rate

M. B. Voloshin

It is shown that the kinematical difference in the decays B^- -> D^0 \ell \tilde νand B^0 -> D^+ \ell \tilde νdue to the isotopic mass splittings of the B and D mesons is compensated in the total decay rate by an appropriate difference in the lepton spectra. Thus there is no effect on the total decay rates in the linear order in the isotopic mass splittings,

Nikolaos Kidonakis, Gianluca Oderda, George Sterman

In QCD hard scattering cross sections, the color content of the underlying hard scattering evolves with a factorization scale. This evolution is controlled by an anomalous dimension matrix, specific to each hard-scattering reaction. Anomalous dimensions are determined from the renormalization of products of ordered exponentials of the gauge field, which desc

L. K. Gelovani, G. L. Gogiberidze, E. K. G. Sarkisyan

Multifractality of charged particle pseudorapidity distributions is analyzed in central collisions of carbon and copper nuclei at 4.5 GeV/c per nucleon. Within the method of normalized factorial moments, modified to remove the bias of infinite statistics in the normalization, intermittency-like behavior (scaling) is observed up to eight-particle fluctuations

P. Rehberg

Using a Lagrangian which contains quarks as elementary degrees of freedom and mesons as bound states, a transport formalism is developed, which allows for a dynamical transition from a quark plasma to a state, where quarks are bound into hadrons. Simultaneous transport equations for both particle species are derived in a systematic and consistent fashion. Fo

C. Bourrely, E. Leader, O. V. Teryaev

We discuss the positivity of the hadron density matrix in QCD. This basic property is shown to be preserved by QCD evolution, provided the relation $|ΔP_{ij}(z)| \leq P_{ij}$ is valid for all kernels for $z < 1$, and the usual &#34;+&#34; prescription is used. We comment on the positivity restrictions for the choice of the NLO factorization scheme for the ev

Jian Zuo Yuan-Xing Gui

This paper discusses the analytic continuation in the thermal field theory by using the theory of $η-ξ$ spacetime. Taking a simple model as example, the $2\times 2$ matrix real-time propagator is solved from the equation obtained through continuation of the equation for the imaginary-time propagator. The geometry of the $η-ξ$ spacetime plays important role i

Joakim Hallin, David Persson

We consider thermal QCD in the large N_C limit, mainly in 1+1 dimensions. The gauge coupling is only taken into account to minimal order, by projection onto colour singlets. An expression for the free energy, exact as N_C goes to infinity, is then obtained. A third order phase transition will occur. The critical temperature depends on the ratio N_C/L, where

Xiangdong Ji, Wei Lu

Motivated by the need to understand hadron masses, we reexamine an old problem in QED - the composition of the electron mass - in a modern perspective. We find that in the unrenormalized QED, the vacuum subtraction plays an important role in understanding various sources of the electron mass. The same issue is also discussed in the modified minimal subtracti

J. Podolsky, K. Vesely

We present a coordinate system for a general impulsive gravitational pp - wave in vacuum in which the metric is explicitly continuous, synchronous and &#34;transverse&#34;. Also, it is more appropriate for investigation of particle motions.

Takeshi Chiba, Kei-ichi Maeda, Ken-ichi Nakao, Taro Tsukamoto

We study the apparent horizon for two boosted black holes in the asymptotically de Sitter space-time by solving the initial data on a space with punctures. We show that the apparent horizon enclosing both black holes is not formed if the conserved mass of the system (Abbott-Deser mass) is larger than a critical mass. The black hole with too large AD mass the

Philip Gibbs

A model of the universe as a very large white hole provides a useful alternative inhomogeneous theory to pit against the homogeneous standard FLRW big bang models. The white hole would have to be sufficiently large that we can fit comfortably inside the event horizon at the present time, so that the inhomogeneities of space-time are not in contradiction with

Karin Dahmen, Deniz Ertas, Yehuda Ben-Zion

The statistics of earthquakes in a heterogeneous fault zone is studied analytically and numerically in the mean field version of a model for a segmented fault system in a three-dimensional elastic solid. The studies focus on the interplay between the roles of disorder, dynamical effects, and driving mechanisms. A two-parameter phase diagram is found, spanned

R. S. Decca, H. D. Drew, B. Maiorov, J. Guimpel

We report the fabrication of high Tc superconducting wires by photodoping a GdBa2Cu3O{6.5} thin film. An optical near-field probe was used to locally excite carriers in the system at room temperature. Trapping of the photogenerated electrons define a confining potential for the conducting holes in the CuO planes. Spatially resolved reflectance measurements s

L. L. Bonilla, C. Perez-Vicente, F. Ritort, J. Soler

Populations of phase oscillators interacting globally through a general coupling function $f(x)$ have been considered. In the absence of precessing frequencies and for odd-coupling functions there exists a Lyapunov functional and the probability density evolves toward stable stationary states described by an equilibrium measure. We have then proposed a famil

T. M. Hong

We argue that the interface coupling, responsible for the positive exchange bias (HE) observed in ferromagnetic/compensated antiferromagnetic (FM/AF) bilayers, favors an antiferromagnetic alignment. At low cooling field this coupling polarizes the AF spins close to the interface, which spin configuration persists after the sample is cooled below the Neel tem

Igor Tsatskis

Local, or short-range, order in disordered alloys is an important and exciting phenomenon which is quantified in electron, X-ray and neutron scattering experiments. It is discussed in many excellent reviews and books, as well as in the multitude of original research papers. This relatively short review of the subject does not attempt to discuss all aspects o

P. Di Francesco

We study the problem of &#34;phantom&#34; folding of the two-dimensional square lattice, in which the edges and diagonals of each face can be folded. The non-vanishing thermodynamic folding entropy per face $s \simeq .2299(1)$ is estimated both analytically and numerically, by successively mapping the model onto a dense loop model, a spin model and a new 28

Min-Chul Cha, H. A. Fertig

We demonstrate for the first time an observation of the peak effect in simulations of magnetic vortices in a superconductor. The shear modulus $c_{66}$ of the vortex lattice is tuned by adding a fictitious {attractive} short range potential to the usual long-range repulsion between vortices. The peak effect is found to be most pronounced in low densities of

Y. Shimizu, O. Sakai, S. Suzuki

We investigate the non-Fermi-liquid (NFL) behavior of the impurity Anderson model (IAM) with non-Kramers doublet ground state of the f$^2$ configuration under the tetragonal crystalline electric field (CEF). The low energy spectrum is explained by a combination of the NFL and the local-Fermi-liquid parts which are independent with each other. The NFL part of

W. Apel, H. -U. Everts, U. Koerner

A coherent state representation for the electrons of ordered antiferromagnets is used to derive effective Hamiltonians for the dynamics of holes in such systems. By an appropriate choice of these states, the constraint of forbidden double occupancy can be implemented rigorously. Using these coherent states, one arrives at a path integral representation of th

I. L. Drichko, A. M. D&#39;yakonov, V. D. Kagan, A. M. Kreshchuk

The heating of a two-dimensional electron gas by an rf electric field generated by a surface acoustic wave, which can be described by an electron temperature $T_e$, has been investigated. It is shown that the energy balance of the electron gas is determined by electron scattering by the piezoelectric potential of the acoustic phonons with $T_e$ determined fr

M. Ipsen, F. Hynne, P. G. Soerensen

We present a systematic approach to deriving normal forms and related amplitude equations for flows and discrete dynamics on the center manifold of a dynamical system at local bifurcations and unfoldings of these. We derive a general, explicit recurrence relation that completely determines the amplitude equation and the associated transformation from amplitu

Bambi Hu, Baowen Li, Wei-Min Zhang

The squeezed state is used to study the one-dimensional quantum mechanical Frenkel Kontorova model. A set of coupled equations for the particle&#39;s expectation value and the fluctuations for the ground state are derived. It is shown that quantum fluctuations renormalize the standard map to an effective sawtooth map. The mechanism underling provides an alte

Judith G. Cohen, John P. Blakeslee

We present spectroscopy of two clusters in the dwarf irregular galaxy NGC 6822. From these we deduce an age for Cluster VII of 11 Gyr and [Fe/H] = -1.95 +/- 0.15 dex. Cluster VII appears to be an analog of the metal-poor galactic globular clusters. Cluster VI is found to be much younger and more metal rich, with an age of approximately 2 Gyr. Its derived met

N. Aghanim, S. Prunet, 0. Forni, F. R. Bouchet

With the new generation of instruments for Cosmic Microwave Background (CMB) observations aiming at an accuracy level of a few percent in the measurement of the angular power spectrum of the anisotropies, the study of the contributions due to secondary effects has gained impetus. Furthermore, a reinvestigation of the main secondary effects is crucial in orde

J. R. Herrnstein

Multi-epoch VLBA observations of the maser in NGC 4258 have yielded a 4% geometrical distance to the galaxy. The potential scientific payoffs of finding similar objects at large distances, in the Hubble flow, are considerable. In this contribution, I discuss the plausibility of detecting high-redshift water masers, and describe a search strategy that we have

Stella Seitz, Peter Schneider, Matthias Bartelmann

We present a new method for reconstructing two-dimensional mass maps of galaxy clusters from the image distortion of background galaxies. In contrast to most previous approaches, which directly convert locally averaged image ellipticities to mass maps (direct methods), our entropy-regularized maximum-likelihood method is an inverse approach. Albeit somewhat

R. Capuzzo-Dolcetta, P. Miocchi

We have preliminary results on the parallelization of a Tree-Code for evaluating gravitational forces in N-body astrophysical systems. For our Cray T3D/CRAFT implementation, we have obtained an encouraging speed-up behavior, which reaches a value of 37 with 64 processor elements (PEs). According to the Amdahl&#39;law, this means that about 99% of the code is

Attila Grandpierre

Some possible ways of the energy production with fusion reactions in the Sun was explored theoretically in the first half of this century. Nowadays it is a standard view that the Sun produces its energy on a uniform level. I point out, that in the stellar and solar energy production a dynamic energy source is necessarily present behind the uniform one, and g

J. Machalski, M. Jamrozy

It is shown that the new observed redshift distributions of various flux-limited samples of radio sources in general are consistent with the predictions of two basic evolutionary models published by Condon (1984) and Dunlop and Peacock (1990), i.e. none of them can be rejected at the confidence level of about 95 per cent. However, the models allowing a free-

A. Cappi, L. N. da Costa, C. Benoist, S. Maurogordato

Recent analysis of the SSRS2 data based on cell-counts and two-point correlation function has shown that very luminous galaxies are much more strongly clustered than fainter galaxies. In fact, the amplitude of the correlation function of very luminous galaxies ($L > L^*$) asymptotically approaches that of $R \ge 0$ clusters. In this paper we investigate the

F. Herpin, A. Baudry, J. Alcolea, J. Cernicharo

We have undertaken toward 30 Mira or semi-regular variables and one OH/IR object highly sensitive observations of the v=1, J=2-1 and 3-2 transitions of SiO simultaneously with observations of the J=1-0 transition of CO during three observing sessions in the period 1995 to 1996. As in our previous observations of 1994, we observe that for several stars the Si

Eon-Chang Sung, Cheongho Han, Barbara, S. Ryden

In this paper, we measure the ellipticities of 30 LSB dI galaxies and compare the ellipticity distribution with that of 80 dEs (Ryden & Terndrup 1994; Ryden et al. 1998) and 62 BCDs (Sung et al. 1998). We find that the ellipticity distribution of LSB dIs is very similar to that of BCDs, and marginally different from that of dEs. We then determine the distrib

F. Governato, C. M. Baugh, C. S. Frenk, S. Cole

The discovery of a population of young galaxies at an epoch when the universe was about one tenth of its current age has shed new light on the question of when and how galaxies formed. Within the context of popular models this is the population of primeval galaxies that built themselves up to the size of present--day galaxies through the process of repeated