March 1999 arXiv papers — page 5

E. E. Benevolenskaya, J. T. Hoeksema, A. G. Kosovichev, P. H. Scherrer

The 11-year cycle of solar activity follows Hale's law by reversing the magnetic polarity of leading and following sunspots in bipolar regions during the minima of activity. In the 1996-97 solar minimum, most solar activity emerged in narrow longitudinal zones - `active longitudes' but over a range in latitude. Investigating the distribution of solar

R. A. Remillard, J. E. McClintock, G. J. Sobczak, C. D. Bailyn

We have investigated the X-ray timing properties of XTE J1550-564 during 60 RXTE PCA observations made between 1998 September 18 and November 28. We detect quasi-periodic oscillations (QPOs) near 185 Hz during four time intervals. The QPO widths (FWHM) are near 50 Hz, and the rms amplitudes are about 1% of the mean flux at 2-30 keV. This is the third Galacti

Zoltan Haiman, Lloyd Knox

The bulk of the hydrogen in the universe transformed from neutral to ionized somewhere in the redshift interval 5 < z < 40, most likely due to ionizing photons produced by an early generation of stars or mini-quasars. The resulting free electrons, interacting with the CMB photons via Thomson scattering, are a mixed blessing, providing both a probe of the epo

Roger Bidaux, Nino Boccara

We study a family of correlated one-dimensional random walks with a finite memory range M.These walks are extensions of the Taylor&#39;s walk as investigated by Goldstein, which has a memory range equal to one. At each step, with a probability p, the random walker moves either to the right or to the left with equal probabilities, or with a probability q=1-p

Yi Li, Rick Riolo, Robert Savit

In this paper we study the minority game in the presence of evolution. In particular, we examine the behavior in games in which the dimension of the strategy space, m, is the same for all agents and fixed for all time. We find that for all values of m, not too large, evolution results in a substantial improvement in overall system performance. We also show t

H. Fujii, D. Kharzeev

We consider the scattering of two color dipoles (e.g., heavy quarkonium states) at low energy - a QCD analog of Van der Waals interaction. Even though the couplings of the dipoles to the gluon field can be described in perturbation theory, which leads to the potential proportional to (N_c^2-1)/R^{7}, at large distances R the interaction becomes totally non-p

Sergei V. Shabanov

By comparision with numerical results in the maximal Abelian projection of lattice Yang-Mills theory, it is argued that the nonperturbative dynamics of Yang Mills theory can be described by a set of fields that take their values in the coset space SU(2)/U(1). The Yang-Mills connection is parameterized in a special way to separate the dependence on the coset

Takeshi Chiba

Dynamical vacuum energy or quintessence, a slowly varying and spatially inhomogeneous component of the energy density with negative pressure, is currently consistent with the observational data. One potential difficulty with the idea of quintessence is that couplings to ordinary matter should be strongly suppressed so as not to lead to observable time variat

Eric G. Blackman, George B. Field

We consider the backreaction of the magnetic field on the magnetic dynamo coefficients and the role of boundary conditions in interpreting whether numerical evidence for suppression is dynamical. If a uniform field in a periodic box serves as the initial condition for modeling the backreaction on the turbulent EMF, then the magnitude of the turbulent EMF and

Eduard Masso, Ramon Toldra

We obtain the photon spectrum induced by a cosmic background of unstable neutrinos. We study the spectrum in a variety of cosmological scenarios and also we allow for the neutrinos having a momentum distribution (only a critical matter dominated universe and neutrinos at rest have been considered until now). Our results can be helpful when extracting bounds

H. A. Chamblin, H. S. Reall

Motivated by the ``universe as a brane&#39;&#39; idea, we investigate the motion of a $(D-2)$-brane (or domain wall) that couples to bulk matter. Usually one would expect the spacetime outside such a wall to be time dependent however we show that in certain cases it can be static, with consistency of the Israel equations yielding relationships between the bu

Nathan Seiberg, Edward Witten

We study the conformal field theory of the D1/D5 system compactified on X (X is T^4 or K3). It is described by a sigma model whose target space is the moduli space of instantons on X. For values of the parameters where the branes can separate, the spectrum of dimensions in the conformal field theory exhibits a continuum above a gap. This continuum leads to a

John D. hobbs

Preliminary results from a Fermilab study of the sensitivity for higgs production at the Tevatron in run II and beyond are presented. The study extends existing results by systematically combining all decay channels, considering the production of higher mass higgs bosons and interpreting the results in the context of supersymmetric higgs production as well a

S. A. Voloshin, V. Koch, H. G. Ritter

We discuss an event-by-event fluctuation analysis of particle production in heavy ion collisions. We compare different approaches to the evaluation of the event-by-event dynamical fluctuations in quantities defined on groups of particles, such quantities as mean transverse momentum, transverse momentum spectra slope, strength of anisotropic flow, etc.. The d

F. Aharonian

During the several months of the outburst of Mkn 501 in 1997 the source has been monitored in TeV gamma-rays with the HEGRA stereoscopic system of imaging atmospheric Cherenkov telescopes. Quite remarkably it turned out that the shapes of the daily gamma-ray energy spectra remained essentially stable throughout the entire state of high activity despite drama

T. Brotz, M. Ortiz, A. Ritz

We study the modular transformation properties of Euclidean solutions of 3D gravity whose asymptotic geometry has the topology of a torus. These solutions represent saddle points of the grand canonical partition function with an important example being the BTZ black hole, and their properties under modular transformations are inherited from the boundary conf

L. Guzzo, H. Boehringer, P. Schuecker, C. A. Collins

We give a general description of the optical observing strategy of the ROSAT-ESO Flux-Limited X-ray (REFLEX) cluster survey. This presently includes 460 clusters of galaxies selected from the ROSAT All-Sky Survey in the Southern hemisphere, to a flux limit of 3 10^{-12} erg s^{-1} cm^{-2}. Redshifts are now measured for 95% of this sample. Work is in progres

D. Kutasov, N. Seiberg

We clarify a number of issues regarding the worldsheet and spacetime descriptions of string propagation on AdS_3. We construct the vertex operators of spacetime current algebra and spacetime (super) Virasoro generators in the full interacting SL(2) WZW theory and study their Ward identities. We also explain the relation between the analysis in this note and

S. Oda, T. Yukawa

We consider random superstrings of type IIB in $d$-dimensional space. The discretized action is constructed from the supersymetric matrix model, which has been proposed as a constructive definition of superstring theory. Our action is invariant under the local N=2 super transformations, and doesn&#39;t have any redundant fermionic degrees of freedom.

Shashikant R. Dugad, Francesco Vissani

We discuss a possible test of neutrino oscillation hypothesis by proposing the combined analysis of high energy atmospheric neutrino induced muon events that have been detected around horizontal direction in the Kolar Gold Field (KGF) underground site and below the horizontal direction by many large detectors such as Super-Kamiokande and MACRO. Up/down asymm

Hiroaki Onishi, Masamichi Nishino, Naoki Kawashima, Seiji Miyashita

A quantum Monte Carlo method combining update of the loop algorithm with the global flip of the world line is proposed as an efficient method to study the magnetization process in an external field, which has been difficult because of inefficiency of the update of the total magnetization. The method is demonstrated in the one dimensional antiferromagnetic He

Gautam Bhattacharyya, Amitava Datta

In the standard model, direct CP-violating asymmetries for $B^\pm \to π^\pm K$ are roughly 2% based on perturbative calculation. Rescattering effects might enhance it to at most (20-25)%. We show that lepton-number-violating couplings in supersymmetric models without R-parity are capable of inducing as large as 100% CP asymmetry in this channel. Such effects

Andreas Freund

In the following, we will present a generalization of the proof of factorization for electroproduction of vector mesons to the production of several mesons such as $π^+π^-$ and a proof of factorization for exclusive $γ^* γ$ production of several hadrons for example $p \bar p$ or $π^+π^-$ to all orders in perturbation theory up to power suppressed terms.

Andreas Freund

In this paper we will discuss algorithms for extracting skewed parton distributions from experiment as well as the relevant process and experimental observable suitable for the extraction procedure.

Takashi Hara, Gordon Slade

For independent nearest-neighbour bond percolation on Z^d with d >> 6, we prove that the incipient infinite cluster&#39;s two-point function and three-point function converge to those of integrated super-Brownian excursion (ISE) in the scaling limit. The proof is based on an extension of the new expansion for percolation derived in a previous paper, and invo

C. A. Dominguez, K. Schilcher

The ALEPH data on the (non-strange) vector and axial-vector spectral functions, extracted from tau-lepton decays, is used in order to search for evidence for a dimension-two contribution, $C_{2 V,A}$, to the Operator Product Expansion (other than $d=2$ quark mass terms). This is done by means of a dimension-two Finite Energy Sum Rule, which relates QCD to th

B. E. Kane, N. S. McAlpine, A. S. Dzurak, R. G. Clark

We present a method for measuring single spins embedded in a solid by probing two electron systems with a single electron transistor (SET). Restrictions imposed by the Pauli Principle on allowed two electron states mean that the spin state of such systems has a profound impact on the orbital states (positions) of the electrons, a parameter which SET&#39;s ar

David H. Evans, Benjamin Grinstein, Detlef R. Nolte

It was recently pointed out that the decays B^+ --> D^{*+}_s gamma and B^+ --> D^{*+} gamma can be used for an extraction of |V_{ub}|. The theory of these decays is poorly understood. It was shown that in a world of almost degenerate b and c-quarks the decay would be computable. The severe difficulties that are encountered in the realistic calculation stem p

Brian S. Mason, Erik M. Leitch, Steven T. Myers, John K. Cartwright

We report 32 GHz absolute flux density measurements of the supernova remnant Cas A, with an accuracy of 2.5%. The measurements were made with the 1.5-meter telescope at the Owens Valley Radio Observatory. The antenna gain had been measured by NIST in May 1990 to be $0.505 \pm 0.007 \frac{\rm mK}{\rm Jy}$. Our observations of Cas A in May 1998 yield $S_{cas,1

Michael Dine

Recently, a number of authors have challenged the conventional assumption that the string scale, Planck mass, and unification scale are roughly comparable. It has been suggested that the string scale could be as low as a TeV. The greatest obstacle to developing a string phenomenology is our lack of understanding of the ground state. We explain why the dynami

Donald Marolf, Amanda W. Peet

The search for intersecting brane solutions in supergravity is a large and profitable industry. Recently, attention has focused on finding localized forms of known `delocalized&#39; solutions. However, in some cases, a localized version of the delocalized solution simply does not exist. Instead, localized separated branes necessarily delocalize as the separa

E. K. Sklyanin

This is the second part of the paper devoted to the general proof of canonicity of Baecklund transformation (BT) for a Hamiltonian integrable system governed by SL(2)-invariant r-matrix. Introducing an extended phase space from which the original one is obtained by imposing a 1st kind constraint, we are able to prove the canonicity of BT in a new way. The ne

E. K. Sklyanin

For the Hamiltonian integrable systems governed by SL(2)-invariant r-matrix (such as Heisenberg magnet, Toda lattice, nonlinear Schroedinger equation) a general procedure for constructing Baecklund transformation is proposed. The corresponding BT is shown to preserve the Poisson bracket. The proof is given by a direct calculation using the r-matrix expressio

H. M. Wiseman

The standard quantum limit to the linewidth of a laser for which the gain medium can be adiabatically eliminated is $\ell_{0}=κ/2\bar{n}$. Here $κ$ is the intensity damping rate and $\bar{n}$ the mean photon number. This contains equal contributions from the loss and gain processes, so that simple arguments which attribute the linewidth wholly to phase noise

K. Yabana, G. F. Bertsch

The time-dependent local density approximation is applied to the optical response of the silver clusters, Ag_2, Ag_3, Ag_8 and Ag_9^+. The calculation includes all the electrons beyond the closed-shell Ag^{+11} ionic core, thus including for the first time explicitly the filled d-shell in the response. The excitation energy of the strong surface plasmon near

Tom Ostoma, Mike Trushyk

ElectroMagnetic Quantum Gravity (EMQG) is applied to the problem of the Cosmological Constant. EMQG is a quantum gravity theory (ref. 1) in which the virtual particles of the quantum vacuum play a very important role in all gravitational interactions, and also in accelerated motion. According to EMQG theory (and quantum field theory in general), empty space

Th. Bornath, D. Kremp, M. Schlanges

The two-particle problem within a nonequilibrium many-particle system is investigated in the framework of real-time Green&#39;s functions. Starting from the dynamically screened ladder approximation of the nonequlibrium Bethe-Salpeter equation, a nonequilibrium Dyson equation is given for two-time two-particle Green&#39;s functions. Thereby the well-known Ka

Pavel S. Kamenov

In this paper it is shown that if one accept assumption of de Broglie that &#34;unitary wave-particle&#34; exists simultaneously and this coexistence is real, then one can find the mean life time of the hydrogen atom of Bohr (intensities). Something more, the acceptance of de Broglie&#39;s ideas show that a single excited hydrogen atom decays at exactly pred

Gerd van de Sand, Jan M Rost

The spectrum of higher harmonics in atoms calculated with a uniformized semiclassical propagator is presented and it is shown that higher harmonic generation is an interference phenomenon which can be described semiclassically. This can be concluded from the good agreement with the quantum spectrum. Moreover, the formation of a plateau in the spectrum is spe

Xiaochun Mei

The definition of nonequilibrium entropy is provided for the general nonequilibrium processes by connecting thermodynamics with statistical physics, and the principle of entropy increment in the nonequilibrium processes is also proved in the paper. The result shows that the definition of nonequilibrium entropy is not unique.

Sven Soff, Steffen A. Bass, Marcus Bleicher, Horst Stoecker

We compare microscopic transport model calculations to recent data on the directed and elliptic flow of various hadrons in 2 - 10 A GeV Au+Au and Pb (158 A GeV) Pb collisions. For the Au+Au excitation function a transition from the squeeze-out to an in-plane enhanced emission is consistently described with mean field potentials corresponding to one incompres

U. Heinz, U. A. Wiedemann

We report on work done in collaboration with Klaus Kinder-Geiger and John Ellis which aims at connecting the space-time structure of event generator simulations with observable output.

E. Epelbaum, Ulf-G. Meißner

I discuss isospin violation in an effective field theory appraoch of the nucleon-nucleon interaction. The observed leading order charge independence breaking is explained in terms of one-pion exchange together with a four-nucleon contact term. A general classification scheme of corrections to this leading order results is presented and an explanation is offe

Hanno Hammer

We examine consequences of non-trivial topology in background spacetimes and super-spacetimes: It is shown how the semi-invariance of a brane Lagrangian under supertranslations gives rise to topological extensions of the Noether charge algebra carried by D-branes. We investigate how isometry groups of lightlike compactified spacetimes admit an extension to a

Takashi Hara, Gordon Slade

This is the first of two papers on the critical behaviour of bond percolation models in high dimensions. In this paper, we obtain strong joint control of the critical exponents eta and delta, for the nearest-neighbour model in very high dimensions d>>6 and for sufficiently spread-out models in all dimensions d>6. The exponent eta describes the low frequency

Xianzhe Dai, Weiping Zhang

We present the details of our embedding proof of the Atiyah-Patodi-Singer index theorem for Dirac operators on manifolds with boundary.

C. Quesne

$GL_h(n) \times GL_{h&#39;}(m)$-covariant (hh&#39;)-bosonic (or (hh&#39;)-fermionic) algebras ${\cal A}_{hh&#39;\pm}(n,m)$ are built in terms of the corresponding R_h and $R_{h&#39;}$-matrices by contracting the $GL_q(n) \times GL_{q^{\pm1}}(m)$-covariant q-bosonic (or q-fermionic) algebras ${\cal A}^{(α)}_{q\pm}(n,m)$, $α= 1, 2$. When using a basis of ${\ca

E. V. Ferapontov

Some of the most important classes of surfaces in projective 3-space are reviewed: these are isothermally asymptotic surfaces, projectively applicable surfaces, surfaces of Jonas, projectively minimal surfaces, etc. It is demonstrated that the corresponding projective &#34;Gauss-Codazzi&#34; equations reduce to integrable systems which are quite familiar fro

Helmut Prodinger

For words of length $n$, generated by independent geometric random variables, we consider the mean and variance of the number of inversions and of a parameter of Knuth from permutation in situ. In this way, $q$--analogues for these parameters from the usual permutation model are obtained.

I. P. Goulden, D. M. Jackson

An explicit expression is obtained for the generating series for the number of ramified coverings of the sphere by the double torus, with elementary branch points and prescribed ramification type over infinity. Thus we are able to prove a conjecture of Graber and Pandharipande, giving a linear recurrence equation for the number of these coverings with no ram

Walter Seaman

A new class of Higgs bundles is introduced in a natural setting. Existence and nonexistence results for Higgs-Hermitian-Yang-Mills metrics are proved.

Terry Fuller

Let M be a smooth 4-manifold which admits a relatively minimal hyperelliptic genus h Lefschetz fibration over the 2-sphere. If all of the vanishing cycles for this fibration are nonseparating curves, then we show that M is a 2-fold cover of a 2-sphere bundle over the 2-sphere, branched over an embedded surface. If the collection of vanishing cycles for this

Terry Fuller

This paper is withdrawn by the author. See math.GT/9811093 for replacement.

P. H. Frampton, C. Vafa

We propose the existence of a non-supersymmetric conformal field theory softly broken at the TeV scale as a new mechanism for solving the hierarchy problem. We find the imposition of conformal invariance to be very restrictive with many predictive consequences, including severe restrictions on the field content, the number of families as well as on the struc

R. L. Karp, F. Mansouri, J. S. Rno

We make use of product integrals to provide an unambiguous mathematical representation of Wilson line and Wilson loop operators. Then, drawing upon various properties of product integrals, we discuss such properties of these operators as approximating them with partial sums, their convergence, and their behavior under gauge transformations. We also obtain a

L. Mangiarotti, G. Sardanashvily

The polysymplectic phase space of covariant Hamiltonian field theory can be provided with the current algebra bracket.

Jean-Loup Gervais

In a recent paper (hep-th/9811108), Saveliev and the author showed that there exits an on-shell light cone gauge where the non-linear part of the field equations reduces to a (super) version of Yang&#39;s equations which may be solved by methods inspired by the ones previously developed for self-dual Yang-Mills equations in four dimensions. Here, the analogy

S. Iso, H. Kawai

We pursue the study of the type IIB matrix model as a constructive definition of superstring. In this paper, we justify the interpretation of space-time as distribution of eigenvalues of the matrices by showing that some low energy excitations indeed propagate in it. In particular, we show that if the distribution consists of small clusters of size $n$, low

Masayuki Noguchi, Seiji Terashima, Sung-Kil Yang

We study mass deformations of N=2 superconformal field theories with ADE global symmetries on a D3-brane. The N=2 Seiberg-Witten curves with ADE symmetries are determined by the Type IIB 7-brane backgrounds which are probed by a D3-brane. The Seiberg-Witten differentials $λ$ for these ADE theories are constructed. We show that the poles of $λ$ with residues

Andrei Afanasev, Carl E. Carlson, Christian Wahlquist

Hard, or high transverse momentum, pion photoproduction can be a tool for probing the parton structure of the beam and target. We estimate the soft contributions to this process, with an eye toward delineating the region where perturbatively calculable processes dominate. Our soft process estimate is based on vector meson dominance and data based parameteriz

J. A. Casas, G. B. Gelmini, A. Riotto

A supersymmetric inflationary stage dominated by an $F$-term has the problem that the flatness of the potential is spoiled by supergravity corrections, that is the slow-roll parameter $η$ gets contributions of order unity. We show that in $F$-term inflationary models based on strings there is natural way of obtaining small values of $η$. This happens in mode

F. Vannucci

The radiative decay of muon-neutrinos in matter with a scheme of mass-degenerate neutrinos could be the common origin of the appearance of anti-electron-neutrinos at LSND and the disappearance of muons-neutrinos at SuperKamiokande. With the decay probability fixed by the LSND signal, the deficit of atmospheric neutrinos can be satisfactorily reproduced.

Edmond Iancu

I discuss some non-perturbative aspects of hot gauge theories as related to the unscreened static magnetic interactions. I first review some of the infrared divergences which cause the breakdown of the perturbation theory. Then I show that kinetic theory, as derived from quantum field theory, is a powerful tool to construct effective theories for the soft mo

Mei Huang, Pengfei Zhuang, Weiqin Chao

Within the general framework of SU(2) Nambu-Jona-Lasinio model beyond mean-field approximation, the S-wave $π- π$ scattering lengths $a_0^0$ and $a_0^2$ are calculated. The numerical results are in agreement with that analyzed from recent experiment $πN \to ππN$ data by using Chew-Low-Goebel technique, and the corresponding chiral condensate $<{\bar q}q>$ is

M. Fukugita, M. Tanimoto, T. Yanagida

We explore the phenomenological quark-lepton mass matrices, which are devised following the S$_3$ flavour symmetry principle, yet fully consistent with SU(5) gauge models with the Higgs particles of {\bf 5}, {\bf 45} and their conjugates. The model contains 10 free parameters altogether. When 6 parameters are fixed by charge 2/3 quark and charged lepton mass

Jisuke Kubo

Applications of the principle of reduction of couplings to the standard model and supersymmetric grand unified theories are reviewed. Phenomenological applications of renormalization group invariant sum rules for soft supersymmetry-breaking parameters are also reviewed.

Paolo Lipari

The neutrinos of long baseline beams travel inside the Earth&#39;s crust where the density is approximately rho = 2.8 g cm^-3. If electron neutrinos participate in the oscillations, matter effects will modify the oscillation probabilities with respect to the vacuum case. Depending on the sign of Delta m^2 an MSW resonance will exist for neutrinos or anti-neu

J. van Leusen, L. M. Sehgal

Paper has been withdrawn by the authors.

János Balog, Max Niedermaier, Ferenc Niedermayer, Adrian Patrascioiu

The renormalized coupling $\gr$ defined through the connected 4-point function at zero external momentum in the non-linear O(3) sigma-model in two dimensions, is computed in the continuum form factor bootstrap approach with estimated error $\sim 0.3%$. New high precision data are presented for $\gr$ in the lattice regularized theory with standard action for

Mark R. Convery, Representing the SLD Collaboration

We present three preliminary results from SLD on B decays: an inclusive search for the process b-> s gluon, a measurement of the branching ratio for the process B -> D D-bar X, and measurements of the charged and neutral B lifetimes. All three measurements make use of the excellent vertexing efficiency and resolution of the CCD Vertex Detector and the first

Christopher Holck, representing the CDF Collaboration

We report results of three searches for scalar top quark. Two of the searches look for direct production of scalar top quark followed by the decay of the scalar quark to charm quark and neutralino or bottom and chargino. The third search looks for top quark decaying to scalar top and neutralino followed by the decay of scalar top to bottom quark and neutrali

J. A. Valiente-Kroon

Asymptotically flat spacetimes with one Killing vector field are considered. The Killing equations are solved asymptotically using polyhomogeneous expansions (i.e. series in powers of 1/r an ln r), and solved order by order. The solution to the leading terms of these expansions yield the asymptotic form of the Killing vector field. The possible classes of Ki

Diego A. R. Dalvit, Francisco D. Mazzitelli

In this talk we will argue that, when gravitons are taken into account, the solution to the semiclassical Einstein equations (SEE) is not physical. The reason is simple: any classical device used to measure the spacetime geometry will also feel the graviton fluctuations. As the coupling between the classical device and the metric is non linear, the device wi

E. S. Rodrigues, E. V. Anda, P. Orellana

We study non-linear phenomena in quantum dots. Non linearities are reflected in the I-V characteristic curve as bistabilities, instabilities and time dependent oscillations of the currents. The nature of the non-linear behavior depends upon the parameters that define the system.

Richard T Giles, Feodor V Kusmartsev

We have determined the ground state for both a ladder array of Josephson junctions and a ladder of thin superconducting wires. We find that the repulsive interaction between vortices falls off exponentially with separation. The fact that the interaction is short-range leads to novel phenomena. The ground state vortex density exhibits a complete devil&#39;s s

Eshel Ben-Jacob, Inon Cohen, Ido Golding, Yonathan Kozlovsky

In nature, microorganisms must often cope with hostile environmental conditions. To do so they have developed sophisticated cooperative behavior and intricate communication capabilities, such as: direct cell-cell physical interactions via extra-membrane polymers, collective production of extracellular &#34;wetting&#34; fluid for movement on hard surfaces, lo

S. Sanvito, C. J. Lambert, J. H. Jefferson

We analyze the interplay between disorder and band structure in current perpendicular to the planes (CPP) giant magnetoresistance (GMR). We consider finite magnetic multilayers attached to pure crystalline leads, described by a tight-binding simple cubic two-band model (s-d). Several models of disorder are considered, including random on-site potentials, lat

J. -Ch. Anglès d&#39;Auriac

The vicinity of the critical point of the three-state Potts model on a Kagomé lattice is studied by mean of Random Matrix Theory. Strong evidence that the critical point is integrable is given.

S. Azakov, M. Dilaver, A. M. Oztas

Thermal properties of the ordered phase of the spin 1/2 isotropic Heisenberg Antiferromagnet on a d-dimensional hypercubical lattice are studied within the fermionic representation when the constraint of single occupancy condition is taken into account by the method suggested by Popov and Fedotov. Using saddle point approximation in path integral approach we

Alain Verberkmoes, Bernard Nienhuis

Using Monte Carlo simulation, Van Duijneveldt and Lekkerkerker [Phys. Rev. Lett. 71, 4264 (1993)] found gas-liquid-solid behaviour in a simple two-dimensional lattice model with two types of hard particles. The same model is studied here by means of numerical transfer matrix calculations, focusing on the finite size scaling of the gaps between the largest fe

Kinneret Keren, Ady Stern, Uri Sivan

The electron-electron scattering rate of single particle excitations in atoms is estimated and compared with the corresponding rate in quantum dots. It is found that in alkali atoms single particle excitations do not acquire a width due to electron-electron interaction, while in complex atoms they may. This width is typically smaller than the single particle

Steffen Trimper, Simone Artz

Starting from a master equation in a quantum Hamilton form we study analytically a nonequilibrium system which is coupled locally to two heat bathes at different temperatures. Based on a lattice gas description an evolution equation for the averaged density in the presence of a temperature gradient is derived. Firstly, the case is analysed where a particle i

Hisashi Kondo, Tôru Moriya

Spin fluctuation-induced superconductivity in quasi-two dimensional organic compounds, κ-BEDT-TTF salts, is investigated within a fluctuation exchange (FLEX) approximation using a half-filled Hubbard model with a right-angled isosceles triangular lattice (transfer matrices -τ, -τ^\prime), extending a previous work above T_c. An energy gap of A_2 or (x^2-y^2)

Karyn Le Hur

Using a precise coset Ising-Bose representation, we show how backscattering of electrons off a magnetic impurity destabilizes the two-channel Kondo fixed point and drives the system to a new fixed point, in agreement with previous results. In addition, we verify the scaling proposed by Furusaki and Nagaosa and prove that the other possible critical fixed poi

V. I. Anisimov, M. A. Korotin, M. Zolfl, T. Pruschke

The electronic structure of the first reported heavy fermion compound without f-electrons LiV_2O_4 was studied by an ab-initio calculation method. In the result of the trigonal splitting and d-d Coulomb interaction one electron of the $d^{1.5}$ configuration of V ion is localized and the rest partially fills a relatively broad conduction band. The effective

S. Franz, M. Mezard, G. Parisi, L. Peliti

We discuss the response of aging systems with short-range interactions to a class of random perturbations. Although these systems are out of equilibrium, the limit value of the free energy at long times is equal to the equilibrium free energy. By exploiting this fact, we define a new order parameter function, and we relate it to the ratio between response an

Darryl D. Holm, Shinar Kouranbaeva, Jerrold E. Marsden, Tudor Ratiu

This paper develops the geometry and analysis of the averaged Euler equations for ideal incompressible flow in domains in Euclidean space and on Riemannian manifolds, possibly with boundary. The averaged Euler equations involve a parameter $α$; one interpretation is that they are obtained by ensemble averaging the Euler equations in Lagrangian representation

Darryl D. Holm, Jerrold E. Marsden, Tudor S. Ratiu

Recent theoretical work has developed the Hamilton&#39;s-principle analog of Lie-Poisson Hamiltonian systems defined on semidirect products. The main theoretical results are twofold: (1) Euler-Poincaré equations (the Lagrangian analog of Lie-Poisson Hamiltonian equations) are derived for a parameter dependent Lagrangian from a general variational principle o

Darryl D. Holm

We formulate equations for the slow time dynamics of fluid motion that self consistently account for the effects of the variability upon the mean. The time-average effects of the fluctuations introduce nonlinear dispersion that acts to spatially smooth the transport velocity of the mean flow relative to its circulation or momentum velocity, by the inversion

S. Chen, C. Foias, D. D. Holm, E. Olson

In this paper we discuss recent progress in using the Camassa-Holm equations to model turbulent flows. The Camassa-Holm equations, given their special geometric and physical properties, appear particularly well suited for studying turbulent flows. We identify the steady solution of the Camassa-Holm equation with the mean flow of the Reynolds equation and com

Joseph Silk

Have we converged on the definitive model of cosmology? I present a critical assessment of the current paradigms for the evolution of large-scale structure.

Gregory A. Shields

Astronomers knew early in the twentieth century that some galaxies have emission-line nuclei. However, even the systematic study by Seyfert (1943) was not enough to launch active galactic nuclei (AGN) as a major topic of astronomy. The advances in radio astronomy in the 1950s revealed a new universe of energetic phenomena, and inevitably led to the discovery

James E. Rhoads

The beaming angle (zeta) is the main uncertainty in gamma ray burst energy requirements today. We summarize predictions for the light curves of beamed bursts, and model the R band light curve of GRB 970508 to derive zeta > 30 degrees. This yields an irreducible minimum energy requirement of 3.4 times 10^{49} ergs to power the afterglow alone.

James E. Rhoads

The energy requirements of gamma ray bursts have in past been poorly constrained because of three major uncertainties: The distances to bursts, the degree of burst beaming, and the efficiency of gamma ray production. The first of these has been resolved, with both indirect evidence (the distribution of bursts in flux and position) and direct evidence (redshi

R. K. Jain, C. D. Bailyn, J. A. Orosz, R. A. Remillard

We report the identification of the optical counterpart of the X-ray transient XTE J1550-564 described in two companion papers by Sobczak et al (1999) and Remillard et al (1999). We find that the optical source brightened by approximately 4 magnitudes over the quiescent counterpart seen at B~22 on a SERC survey plate, and then decayed by approximately 1.5 ma

G. J. Sobczak, J. E. McClintock, R. A. Remillard, A. M. Levine

Excellent coverage of the 1998 outburst of the X-ray Nova XTE J1550-564 was provided by the Rossi X-ray Timing Explorer. XTE J1550-564 exhibited an intense (6.8 Crab) flare on 1998 September 19 (UT), making it the brightest new X-ray source observed with RXTE. We present a spectral analysis utilizing 60 Proportional Counter Array spectra from 2.5-20 keV span

C. Marinoni, P. Monaco, G. Giuricin, B. Costantini

In this paper we derive the galaxy luminosity function from the Nearby Optical Galaxy (NOG) sample, which is a nearly complete, magnitude-limited (B<14 mag), all-sky sample of nearby optical galaxies (~6400 galaxies with cz<5500 km/s). For this local sample, we use galaxy distance estimates based on different peculiar velocity models. Therefore, the derivati

J. Dyks, B. Rudak, T. Bulik

We calculate gamma-ray spectra of pulsars for a set of electron acceleration models within the polar-cap scenario. We discuss our results in the light of the recent analysis (Kanbach 1999) of temporal properties of the Vela pulsar in the EGRET energy range.

F. Mantovani, W. Junor, C. Valerio, I. McHardy

The results of VLBI observations of the quasar 3C273, obtained during a multi-frequency campaign in late 1992 in the radio, millimeter and X-ray bands are presented and discussed. The VLBI observations were made at 22 GHz with a Global Array and at 43 GHz with the Very Long Baseline Array. Hybrid maps and modelfits were made in order to look for any short ti

N. Wex

The discovery of frame-dragging effects in binary pulsar timing experiments requires a compact companion with sufficiently large spin. A pulsar orbiting a fast rotating black hole could provide an appropriate test system. In this paper we address questions concerning the identification of a black hole companion in such a system, the measurability of the fram