July 2000 arXiv papers — page 6

Thomas Appelquist, Myck Schwetz

We decribe properties of 2+1-dimensional Nambu-Jona-Lasinio (NJL) models at finite-temperature, beginning with the model with a discrete chiral symmetry. We then consider the model with a continuous $U(1) \times U(1)$ chiral symmetry, describing the restoration of the symmetry at finite temperature. In each case, we compute the free energy and comment on a r

Michael W. Castelaz, Donald G. Luttermoser, Daniel B. Caton, Robert A. Piontek

Spectroscopic measurements of Mira variable stars, as a function of phase, probe the stellar atmospheres and underlying pulsation mechanisms. For example, measuring variations in TiO, VO, and ZrO with phase can be used to help determine whether these molecular species are produced in an extended region above the layers where Balmer line emission occurs or be

A. Cervera, A. Donini, M. B. Gavela, J. J. Gomez Cadenas

The precision and discovery potential of a neutrino factory based on muon storage rings is summarized. For three-family neutrino oscillations, we analyze how to measure or severely constraint the angle $θ_{13}$, CP violation, MSW effects and the sign of the atmospheric mass difference $Δm^2_{23}$. The appearance of ``wrong-sign muons'' at three refer

Michio Watanabe, Masashi Morishita, Youiti Ootuka

We have determined the magnetoresistance of RuO_2-based resistors (Scientific Instruments RO-600) between 0.05 K and 0.3 K in magnetic fields up to 8 T. The magnetoresistance is negative around 0.5 T and then becomes positive at larger fields. The magnitude of the negative magnetoresistance increases rapidly as the temperature is lowered, while that of the p

CLEO collaboration

We determine the CKM matrix element |Vcb| using a sample of 3.33 million BBbar events in the CLEO detector at CESR. We determine the yield of reconstructed B --> D*+ l nu decays as a function of w = v_B . v_D*, and from this we obtain the differential decay rate dΓ/dw. By extrapolating the differential decay rate to w=1, the kinematic point at which the D* i

M. Fukuma, T. Sakai

We consider possible ambiguities in the holographic Weyl anomaly that are caused by local terms in the flow equation. We point out that such ambiguities actually do not give physically meaningful contributions to the Weyl anomaly.

W. Rabaud, L. Saminadayar, D. Mailly, K. Hasselbach

We report measurements of the low temperature magnetic response of a line of 16 GaAs/GaAlAs \emph{connected} mesoscopic rings whose total length is much larger than $l_ϕ$. Using an on-chip micro-\textsc{squid} technology, we have measured a periodic response, with period $h/e$, corresponding to persistent currents in the rings of typical amplitude $0.40\pm 0

William H. Kinney, Alessandro Melchiorri, Antonio Riotto

The recent data from the Boomerang and MAXIMA-1 balloon flights have marked the beginning of the precision era of Cosmic Microwave Background anisotropy (CMB) measurements. We investigate the observational constraints from the current CMB anisotropy measurements on the simplest inflation models, characterized by a single scalar field $ϕ$, in the parameter sp

L. O'Raifeartaigh, V. V. Sreedhar

It has recently been found that supernova explosions can be simulated in the laboratory by implosions induced in a plasma by intense lasers. A theoretical explanation is that the inversion transformation, ($Σ: t \to -1/t,~ {\bf x}\to {\bf x}/t$), leaves the Euler equations of fluid dynamics, with standard polytropic exponent, invariant. This implies that the

M. Axenides, E. G. Floratos, L. Perivolaropoulos

Motivated by recent work we study rotating ellipsoidal membranes in the framework of the light-cone supermembrane theory. We investigate stability properties of these classical solutions which are important for the quantization of super membranes. We find the stability modes for all sectors of small multipole deformations. We exhibit an isomorphism of the li

G. Kang, Y. S. Myung

We investigate the zero mode dimensional reduction of the Kaluza-Klein unifications in the presence of a single brane in the infinite extra dimension. We treat the brane as fixed, not a dynamical object, and do not require the orbifold symmetry. It seems that, contrary to the standard Kaluza-Klein models, the 4D effective action is no longer invariant under

A. Leviatan

Partial dynamical symmetries (PDS) are shown to be relevant to the interpretation of the $K=0_2$ band and to the occurrence of F-spin multiplets of ground and scissors bands in deformed nuclei. Hamiltonians with bosonic and fermionic PDS are presented.

Paola Giacconi, Fabio Maltoni, Roberto Soldati

It is shown that Bose-Einstein condensation occurs for an ideal gas in two spatial dimensions in the presence of one impurity which is described quantum mechanically in terms of a point-like vortex and a contact interaction. This model is exactly solvable and embodies as a special case the analogous problem in three spatial dimensions.

A. Sedrakian, I. Wasserman

The tensor-virial method is applied for a study of oscillation modes of uniformly rotating Bose-Einstein condensed gases, whose rigid body rotation is supported by an vortex array. The second order virial equations are derived in the hydrodynamic regime for an arbitrary external harmonic trapping potential assuming that the condensate is a superfluid at zero

Jonathan Rubin, Daniel D. Lee, H. Sompolinsky

A theory of temporally asymmetric Hebb (TAH) rules which depress or potentiate synapses depending upon whether the postsynaptic cell fires before or after the presynaptic one is presented. Using the Fokker-Planck formalism, we show that the equilibrium synaptic distribution induced by such rules is highly sensitive to the manner in which bounds on the allowe

Charis Anastopoulos, Ntina Savvidou

We elaborate on the distinction between geometric and dynamical phase in quantum theory and show that the former is intrinsically linked to the quantum mechanical probabilistic structure. In particular, we examine the appearance of the Berry phase in the consistent histories scheme and establish that it is the basic building block of the decoherence function

E. M. Drobyshevski

A month-long observation of two horizontal ZnS(Ag) scintillating screens, 1 m^2 in area and located one above the other a certain distance apart, revealed about 10 correlated signals, whose time shift corresponds to an average velocity of only ~10-15 km/s. We assign the origin of these signals to the negative daemons, i.e. electrically charged Planckian part

V. Braun, R. J. Fries, N. Mahnke, E. Stein

We present the first systematic study of higher-twist light-cone distribution amplitudes of the nucleon in QCD. We find that the valence three-quark state is described at small transverse separations by eight independent distribution amplitudes. One of them is leading twist-3, three distributions are twist-4 and twist-5, respectively, and one is twist-6. A c

S. E. Korshunov

A low frequency dynamic response of a vortex manifold in type-II superconductor can be associated with thermally activated tunneling of large portions of the manifold between pairs of metastable states (two-level systems). We suggest that statistical properties of these states can be verified by using the same approach for the analysis of thermal fluctuation

Carsten Vogt

We discuss the scale dependence of a skewed parton distribution of the pion obtained from a generalized light-cone wave function overlap formula. Using a simple ansatz for the transverse momentum dependence of the light-cone wave function and restricting ourselves to the case of a zero skewedness parameter, the skewed parton distribution can be expressed thr

Thomas Mohaupt

We review work done over the last years on the macroscopic and microscopic entropy of supersymmetric black holes in fourdimensional N=2 supergravity and in N=2 compactifications of string theory and M-theory. Particular emphasis is put on the crucial role of higher curvature terms and of modifications of the area law in obtaining agreement between the macros

Jeffrey Bub

Unconditionally secure two-party bit commitment based solely on the principles of quantum mechanics (without exploiting special relativistic signalling constraints, or principles of general relativity or thermodynamics) has been shown to be impossible, but the claim is repeatedly challenged. The quantum bit commitment theorem is reviewed here and the central

Aya Bamba, Katsuji Koyama, Hiroshi Tomida

We report the ASCA (Advanced Satellite for Cosmology and Astrophysics) results of RCW 86, a shell-like supernova remnant (SNR). The bright region in the X-ray band traces the radio clumpy shell, although details of the structure are different. The X-ray spectrum from each part of the shell can not be fitted to a thin thermal plasma model, but requires, at le

Satoshi Fujimoto

We investigate magnetic properties induced by a spinless impurity in strongly correlated electron systems, i.e. the Hubbard model in the spatial dimension $D=1,2,$ and 3. For the 1D system exploiting the Bethe ansatz exact solution we find that the spin susceptibility and the local density of states in the vicinity of a spinless impurity show divergent behav

Y. Kanazawa, Yuji Koike

We present an estimate of a chiral-odd contribution to the single transverse-spin asymmetry in the large-$p_T$ pion production in the nucleon-nucleon collision. In this contribution the transversity distribution and the chiral-odd spin-independent twist-3 distribution appear. Because of the smallness of the corresponding hard cross section, this term turned

Michael B. Mensky

Definition of a quantum corridor describing monitoring a quantum observable in the framework of the phenomenological restricted-path-integral (RPI) approach is generalized for the case of a finite resolution of time. The resulting evolution of the continuously measured system cannot be presented by a differential equation. Monitoring of the position of a qua

Michael B. Mensky

It has been recently proved that a quantum jump may be reversed by a unitary process provided the initial state is restricted by some conditions. The application of such processes for preventing decoherence, for example in quantum computers, was suggested. We shall show that in the situation when the quantum jump is reversible it supplies no information abou

H. Batelaan

The Kapitza - Dirac effect is the diffraction of a well - collimated particle beam by a standing wave of light. Why is this interesting? Comparing this situation to the introductory physics textbook example of diffraction of a laser beam by a grating, the particle beam plays the role of the incoming wave and the standing light wave the role of the material g

Horst von Borzeszkowski, Michael B. Mensky

The problem of the measurability of the electromagnetic field is investigated 1) in the framework of the abstract restricted-path-integral method, and 2) by explicitly accounting the action of the field onto the meter and its back reaction. The meaning of the previously obtained results as well as of the classical results of Bohr and Rosenfeld are made clear

Michael B. Mensky, Horst von Borzeszkowski

Measurements of the position of a relativistic particle is considered in the framework of the Restricted-Path-Integral (RPI) approach. The amplitude describing such a measurement is shown to be exponentially small outside the light cone of the space-time point corresponding to the measurement output, in a qualitative agreement with the Hellwig and Kraus'

Michael B. Mensky

A continuously measured quantum system may be described by restricted path integrals (RPI) or equivalently by non-Hermitian Hamiltonians. The measured system is then considered as an open system, the influence of the environment being taken into account by restricting the path integral or by inclusion of an imaginary part in the Hamiltonian. This way of desc

R. M. Godbole

The last Nobel Prize of the Millenium in Physics has been awarded jointly to Professor Gerardus 't Hooft of the University of Utrecht in Holland and his thesis advisor Professor Emeritus Martinus J.G. Veltman of Holland. According to the Academy's citation, the Nobel Prize has been awarded for 'elucidating the quantum structure of electroweak int

V. A. Kuz'menko

Infrared-infrared double resonance measurements of the $ν_3$ absorption band of $SF_6$ using a $CO_2$ TEA laser radiation have been carried out. The results obtained in the present and in some earlier works are discussed taking into account existence of a wide component of lines, nondegenerative four photon mixing (NFPM) and time invariance violation in the

E. Epelbaum, H. Kamada, A. Nogga, H. Witala

Recently developed chiral nucleon-nucleon (NN) forces at next-to-leading order (NLO) that describe NN phase shifts up to about 100 MeV fairly well have been applied to 3N and 4N systems. Faddeev-Yakubovsky equations have been solved rigorously. The chiral NLO forces depend on a momentum cut-off Λlying between 540-600 MeV/c. The resulting 3N and 4N binding en

Peter Braun-Munzinger

We discuss recent experimental results on hadron multiplicities in ultra-relativistic nuclear collisions. The data for central collisions are in quantitative agreement with predictions of a thermal model assuming full chemical equilibration. It is argued that this provides strong, albeit indirect, evidence for the formation of a partonic phase in the collisi

W. E. Bies, L. Kaplan, E. J. Heller

The connection between scarring and tunneling in chaotic double-well potentials is studied in detail through the distribution of level splittings. The mean level splitting is found to have oscillations as a function of energy, as expected if scarring plays a role in determining the size of the splittings, and the spacing between peaks is observed to be perio

Marius Grigorescu

The paper contains the derivation of a general set of recurrence formulas for the calculus of the SU(3) Clebsch-Gordan coefficients. The first six sections are introductory, presenting the notations and placing SU(3) in the framework of the general group theory. The following eight sections are devoted to the detailed treatment of the carrier spaces of the i

Stephen C. Anco, James Isenberg

Wave maps (i.e. nonlinear sigma models) with torsion are considered in 2+1 dimensions. Global existence of smooth solutions to the Cauchy problem is proven for certain reductions under a translation group action: invariant wave maps into general targets, and equivariant wave maps into Lie group targets. In the case of Lie group targets (i.e. chiral models),

A. Borowiec, W. Marcinek

The concept of a crossed tensor product of algebras is studied from a few points of views. Some related constructions are considered. Crossed enveloping algebras and their representations are discussed. Applications to the noncommutative geometry and particle systems with generalized statistics are indicated.

Pedro Freitas

We consider the problem of minimizing the eigenvalues of the Schrödinger operator $H=-Δ+αF(\ka)$ ($α>0$) on a compact $n-$manifold subject to the restriction that $\ka$ has a given fixed average $\ka_{0}$. In the one-dimensional case our results imply in particular that for $F(\ka)=\ka^{2}$ the constant potential fails to minimize the principal eigenvalue fo

Alexander Barvinok

We introduce a new notion of the determinant, called symmetrized determinant, for a square matrix with the entries in an associative algebra $Å$. The monomial expansion of the symmetrized determinant is obtained from the standard expansion of the commutative determinant by averaging the products of entries of the matrix in all possible orders. We show that f

E. Artal Bartolo, J. Carmona Ruber, J. I. Cogolludo, Hiro-o Tokunaga

In this paper we show a Zariski pair of sextics which is not a degeneration of the original example given by Zariski. This is the first example of this kind known. The two curves of the pair have a trivial Alexander polynomial. The difference in the topology of their complements can only be detected via finer invariants or techniques. In our case the generic

A. Borowiec, G. A. Vazquez Coutino

Free Hopf modules and bimodules over a bialgebra are studied with some details. In particular, we investigate a duality in the category of bimodules in this context. This gives the correspondence between Woronowicz's quantum Lie algebra and algebraic vector fields.

Tim Hoffmann

Bäcklund transformations for smooth and ``space discrete'' Hashimoto surfaces are discussed and a geometric interpretation is given. It is shown that the complex curvature of a discrete space curve evolves with the discrete nonlinear Schrödinger equation (NLSE) of Ablowitz and Ladik, when the curve evolves with the Hashimoto or smoke ring flow. A dou

Oleg Pikhurko

We present bijections enumerating (k,m)-trees, k-gon trees, edge labelled (2,1)-trees, and other tree-like structures. Our constructions are based on Foata's (1971) bijection for cycle-free functions, which is simplified here.

Lin WENG

In this paper, we introduce and study two new types of non-abelian zeta functions for curves over finite fields, which are defined by using (moduli spaces of) semi-stable vector bundles and non-stable bundles. A Riemann-Weil type hypothesis is formulated for zeta functions associated to semi-stable bundles, which we think is more canonical than the other one

Lothar Goettsche

We determine the class of the Hilbert scheme of points on a surface in the Grothendieck group of varieties. As a corollary we obtain its class in the Grothendieck group of motives. We give some applications to moduli spaces of sheaves on surfaces. The paper is related to math/0005249 of de Cataldo and Migliorini.

Joel Merker

Corollary: Two germs of minimal real analytic CR-generic manifolds are formally equivalent if and only if they are biholomorphic.

Cynthia L. Curtis

We provide related Dehn surgery descriptions for rational homology spheres and a class of their regular finite cyclic covering spaces. As an application, we use the surgery descriptions to relate the Casson invariants of the covering spaces to that of the base space. Finally, we show that this places restrictions on the number of finite and cyclic Dehn filli

J. F. Vazquez-Poritz

We calculate the absorption probabilities for a class of massless fields whose linear perturbations leave the near-extremal D3-brane background metric unperturbed. It has previously been found that, for extremal D3-branes, these fields share the same absorption probability as that of the dilaton-axion. We find that these absorption probabilities diverge from

Arjan Keurentjes

In this thesis we discuss recent new insights in the structure of the moduli space of flat connections of Yang-Mills theory on a 3-torus. Chapter 2 discusses the computation of Witten's index for 4-dimensional gauge theories, and the paradox that arises in comparing various computations. This was resolved by the discovery that for orthogonal and exceptio

Tohru Eguchi, Ezra Getzler, Chuan-Sheng Xiong

We calculate the genus 2 correlation functions of two-dimensional topological gravity, in a background with two primary fields, using the genus 2 topological recursion relations.

Robert V. Harlander

The virtual corrections to the production cross section of a Standard Model Higgs boson are computed up to order α_s^4. Using an effective Lagrangian for the limit M_t -> \infty, we evaluate the relevant massless two-loop vertex diagrams by mapping them onto three-loop two-point functions, following a method recently introduced by Baikov and Smirnov. As a re

F. Deliot, G. Moreau, C. Royon

We study the single productions of supersymmetric particles at Tevatron Run II which occur in the $2 \to 2-body$ processes involving R-parity violating couplings of type $ł'_{ijk} L_i Q_j D_k^c$. We focus on the single gaugino productions which receive contributions from the resonant slepton productions. We first calculate the amplitudes of the single ga

U. Baur

We discuss the O(alpha) electroweak radiative corrections to W and Z boson production and their impact on the measurement of the W mass at hadron colliders. The results of recent improved calculations are presented. We also briefly discuss the O(alpha) corrections to Drell-Yan production in the high invariant mass region.

K. J. Abraham, K. Whisnant, Jin Min Yang, Bing-Lin Young

We examine the possibility of observing exotic top quark decays via R-violating SUSY interactions at the Fermilab Tevatron and CERN LHC. We present cross-sections for $t\bar t$ production followed by the subsequent decay of either $t$ or $\bar t$ via the R-violating interaction while the other undergoes the SM decay. With suitable kinematic cuts, we find tha

Savely G. Karshenboim

We give a review of experimental and theoretical results on the precision study of hydrogen-like atoms with low value of the nuclear charge Z.

S. Y. Choi, M. Guchait, H. S. Song, W. Y. Song

We provide a detailed analysis of the supersymmetric tri-lepton signals for sparticle searches at the Tevatron in the minimal supersymmetric standard model with general CP-violating phases but without flavor mixing among sfermions of different generation. The stringent experimental constraints on the CP-violating phases from the electron and neutron electric

S. N. Cherry, M. R. Pennington

I present the results of a recent calculation to determine the number of strange scalar resonances below 1.8 GeV based on the analytic properties of the experimental pi K scattering amplitude. Only one resonance was found in the data, and this is readily identifiable as the K_0^*(1430). We found no evidence to support the kappa(900).

E. Gotsman, E. Ferreira, E. Levin, U. Maor

In this investigation we present a detailed study of $\partial F_2/\partial \ln Q^2$ which is supported by a coupled analysis of $J/Ψ$ photo and DIS production. Both channels are directly proportional to $xG(x,Q^2)$, and as such serve as excellent discriminators between different approaches and models. We then show that taking GRV98NLO as input and correctin

A. Caldwell, S. Paganis, F. Sciulli

The HERA luminosity upgrade is expected to provide statistically significant measurements of the proton structure functions at 0.5<x<0.7 and very high Q2 (Q2>>M_{Z}^2). The behaviour of the parton densities (PDFs) in this high x, Q2 regime is predicted from DGLAP evolution of PDF parametrizations from lower Q2 fits of the data. Uncertainties in the PDFs at h

D. V. Shirkov

We establish direct connection between ghost-free formulations of RG-invariant perturbation theory in the both Euclidean and Minkowskian regions. By combining the trick of resummation of the $π^2$-terms for the invariant QCD coupling and observables in the time-like region with fresh results on the &#34;analyticized&#34; coupling $α_{\rm an}(Q^2)$ and observ

T. Blum, P. Chen, N. Christ, C. Cristian

Quenched QCD simulations on three volumes, $8^3 \times$, $12^3 \times$ and $16^3 \times 32$ and three couplings, $β=5.7$, 5.85 and 6.0 using domain wall fermions provide a consistent picture of quenched QCD. We demonstrate that the small induced effects of chiral symmetry breaking inherent in this formulation can be described by a residual mass ($\mres$) who

Y. Meurice, S. Niermann

We construct series expansions for the scaling variables (which transform multiplicatively under a renormalization group (RG) transformation) in examples where the RG flows, going from an unstable (Wilson&#39;s) fixed point to a stable (high-temperature) fixed point, can be calculated numerically. The examples are Dyson&#39;s hierarchical model and a simplif

T. Suzuki

A block-spin transformation on the dual lattice leads us to an almost perfect lattice action for monopoles and strings in QCD. The perfect operator for a static quark potential is fixed when we compare the above action with the perfect action obtained analytically after infinite-step block-spin transformations in a simple case. The continuum rotational invar

Koya Abe

We have made the first direct symmetry tests in the decays of polarized Z0 bosons into fully-identified b bbar g states, collected in the SLD experiment at SLAC. We searched for evidence of parity violation at the b bbar g vertex by studying the asymmetries in the b-quark polar- and azimuthal-angle distributions, and for evidence of T-odd, CP-even or odd, fi

Fran De Aquino

Gravity is related to gravitational mass of the bodies. According to the weak form of Einstein&#39;s General Relativity equivalence principle, the gravitational and inertial masses are equivalent. However recent calculations (gr-qc/9910036) have revealed that they are correlated by an adimensional factor, which depends on the incident radiation upon the part

Metin Gurses, Atalay Karasu

We study an even dimensional manifold with a pseudo-Riemannian metric with arbitrary signature and arbitrary dimensions. We consider the Ricci flat equations and present a procedure to construct solutions to some higher (even) dimensional Ricci flat field equations from the four diemnsional Ricci flat metrics. When the four dimensional Ricci flat geometry co

Vitaly N. Melnikov

Gravitation as a fundamental interaction that governs all phenomena at large and very small scales, but still not well understood at a quantum level, is a missing cardinal link to unification of all physical interactions. Problems of the absolute G measurements and its possible time and range variations are reflections of the unification problem. Integrable

J. F. Martins, J. A. Dente, A. J. Pires, R. Vilela Mendes

Formal language techniques have been used in the past to study autonomous dynamical systems. However, for controlled systems, new features are needed to distinguish between information generated by the system and input control. We show how the modelling framework for controlled dynamical systems leads naturally to a formulation in terms of context-dependent

J. Daude, L. Padro, G. Rigau

We present a robust approach for linking already existing lexical/semantic hierarchies. We used a constraint satisfaction algorithm (relaxation labeling) to select --among a set of candidates-- the node in a target taxonomy that bests matches each node in a source taxonomy. In particular, we use it to map the nominal part of WordNet 1.5 onto WordNet 1.6, wit

Ivan Png

Previous research has directly studied whether on-line retailing is more competitive than conventional retail markets. The evidence from books and music CDs is mixed. Here, I use an indirect approach to compare the competitiveness of on-line with conventional markets. Focusing on the retail market for books, I identify a peculiarity in the pricing of bestsel

F. T. Vasko, O. G. Balev, Nelson Studart

The lineshape of the tunneling conductance in double quantum wells with a large-scale roughness of heterointerfaces is investigated. Large-scale variations of coupled energy levels and scattering due to the short-range potential are taken into account. The interplay between the inhomogeneous broadening, induced by the non-screened part of large-scale potenti

Francisco Alonso-Sanchez, David Hochberg

Scaling concepts and renormalization group (RG) methods are applied to a simple linear model of human posture control consisting of a trembling or quivering string subject to damping and restoring forces. The string is driven by uncorrelated white Gaussian noise intended to model the corrections of the physiological control system. We find that adding a weak

J. C. Angles d&#39;Auriac, R. Melin, P. Chandra, B. Doucot

We study short-range ferromagnetic models residing on planar manifolds with global negative curvature. We show that the local metric properties of the embedding surface induce droplet formation from the boundary, resulting in the stability of a Griffiths phase at a temperature lower than that of the bulk transition. We propose that this behavior is independe

Dirk K. Morr

Recent experimental and theoretical studies have established that the spin-lattice relaxation rate, $1/T_1$, measured in nuclear magnetic resonance (NMR) experiments is a site-sensitive probe for the electronic spectrum in the mixed state of the high-$T_c$ cuprates. While some groups suggested that $1/T_1$ is solely determined by spin-flip scattering of BCS-

Canio Noce, Mario Cuoco

By means of the Boltzmann equation, we have calculated some magnetotransport quantities for the layered multi-orbital compound Sr$_2$RuO$_4$. The Hall coefficient, the magnetoresistance and the in-plane resistivity have been determined taking into account the Fermi surface curvature and different time collisions for the electrons in the $t_{2g}$ bands. A con

F. C. alcaraz, R. Z. Bariev

The exact solution of the asymmetric exclusion problem with particles of first and second class is presented. In this model the particles (size 1) of both classes are attached on lattice points and diffuse with equal asymmetric rates, but particles in the first class do not distinguish those in the second class from the holes (empty sites). We generalize and

Andrea Pelissetto, Paolo Rossi, Ettore Vicari

We study the critical behavior of frustrated spin models with noncollinear order, including stacked triangular antiferromagnets and helimagnets. For this purpose we compute the field-theoretic expansions at fixed dimension to six loops and determine their large-order behavior. For the physically relevant cases of two and three components, we show the existen

Zheng Weihong, J. Oitmaa, C. J. Hamer, R. J. Bursill

The Hubbard model on a two-leg ladder structure has been studied by a combination of series expansions at T=0 and the density-matrix renormalization group. We report results for the ground state energy $E_0$ and spin-gap $Δ_s$ at half-filling, as well as dispersion curves for one and two-hole excitations. For small $U$ both $E_0$ and $Δ_s$ show a dramatic dr

S. N. Dorogovtsev, J. F. F. Mendes

The avalanche mixing of granular solids in a slowly rotated 2D upright drum is studied. We demonstrate that the account of the difference $δ$ between the angle of marginal stability and the angle of repose of the granular material leads to a restricted value of the mixing time $τ$ for a half filled drum. The process of mixing is described by a linear discret

Giulia Iori

This paper reviews some of the phenomenological models which have been introduced to incorporate the scaling properties of financial data. It also illustrates a microscopic model, based on heterogeneous interacting agents, which provides a possible explanation for the complex dynamics of markets&#39; returns. Scaling and multi-scaling analysis performed on t

Subhradip Ghosh, Chhanda Basu Chaudhuri, Biplab Sanyal, Abhijit Mookerjee

We here study electronic structure and magnetic properties of bcc Co$_{x}$Fe$_{1-x}$, Cr$_{x}$Fe$_{1-x}$ and Mn$_{x}$Fe$_{1-x}$ in their ferromagnetic phases using Augmented Space Recursion technique coupled with tight-binding linearized muffin tin orbital (TB-LMTO) method. We make a systematic study of magnetic properties like magnetic moment and Curie temp

M. Kataoka, C. J. B. Ford, G. Faini, D. Mailly

We consider single-electron tunnelling through antidot states using a Coulomb-blockade model, and give an explanation for h/2e Aharonov-Bohm oscillations, which are observed experimentally when the two spins of the lowest Landau level form bound states. We show that the edge channels may contain compressible regions, and using simple electrostatics, that the

R. Metzler, W. Kinzel, I. Kanter

We introduce a deterministic, time-reversible version of the Ehrenfest urn model. The distribution of first-passage times from equilibrium to non-equilibrium states and vice versa is calculated. We find that average times for transition to non-equilibrium always scale exponentially with the system size, whereas the time scale for relaxation to equilibrium de

K. Bongs, S. Burger, S. Dettmer, D. Hellweg

We report on the creation of Bose-Einstein condensates of $^{87}$Rb in a specially designed hybrid, dipole and magnetic trap. This trap naturally allows the coherent transfer of matter waves into a pure dipole potential waveguide based on a doughnut beam. Specifically, we present studies of the coherence of the ensemble in the hybrid trap and during the evol

Ivan Saika-Voivod, Francesco Sciortino, Peter H. Poole

We conduct extensive molecular dynamics computer simulations of two models for liquid silica [the model of Woodcock, Angell and Cheeseman, J. Phys. Chem. 65, 1565 (1976); and that of van Beest, Kramer and van Santen, Phys. Rev. Lett. 64, 1955, (1990)] to determine their thermodynamic properties at low temperature T across a wide density range. We find for bo

S. C. Gallagher, W. N. Brandt, A. Laor, M. Elvis

Recent ROSAT studies have identified a significant population of Active Galactic Nuclei (AGN) that are notably faint in soft X-rays relative to their optical fluxes. Are these AGN intrinsically X-ray weak or are they just highly absorbed? Brandt, Laor & Wills have systematically examined the optical and UV spectral properties of a well-defined sample of thes

Christopher D. Matzner, Christopher F. McKee

Using a quantitative model for bipolar outflows driven by hydromagnetic protostellar winds, we calculate the efficiency of star formation assuming that available gas is either converted into stars or ejected in outflows. We estimate the efficiency of a single star formation event in a protostellar core, finding 25%-70% for cores with various possible degrees

William T. Reach, Francois Boulanger, Alessandra Contursi, James Lequeux

The mid-infrared (5-16 micron) spectral energy distribution for an individual quiescent molecular cloud in the Small Magellanic Cloud (SMC) was observed using ISOCAM. The spectrum is dominated by broad emission bands at 6.2, 7.7, and 11.3 microns, with weaker bands at 8.6 and 12.7 microns. As these are the same bands, with similar shape and relative strength

J. D. Monnier, W. Fitelson, W. C. Danchi, C. H. Townes

The U. C. Berkeley Infrared Spatial Interferometer has been outfitted with a filterbank system to allow interferometric observations of mid-infrared spectral lines with very high spectral resolution (R ~ 10^5). This paper describes the design, implementation, and performance of the matched 32-channel filterbank modules, and new spectral line observations of

Yuichi Terashima, Luis C. Ho, Andrew F. Ptak

We report X-ray fluxes in the 2--10 keV band from LINERs (low-ionization nuclear emission-line regions) and low-luminosity Seyfert galaxies obtained with the ASCA satellite. Observed X-ray luminosities are in the range between 4e39 and 5e41 ergs/s, which are significantly smaller than that of the ``classical&#39;&#39; low-luminosity Seyfert 1 galaxy NGC 4051

Marco Chiaberge, Annalisa Celotti, Alessandro Capetti, Gabriele Ghisellini

We explore the viability of the unification of BL Lacs and FR I radio galaxies by comparing the core emission of radio galaxies with those of BL Lacs, taking advantage of the newly measured optical nuclear luminosity of FR I sources. The spectral properties of complete samples are studied in the radio-optical luminosity plane: we calculate the predicted lumi

L. Sidoli

The Galactic Center Region has been surveyed in 1997-1998 with the Narrow Field Instruments on-board the BeppoSAX satellite (2-10keV energy range). The X-ray emission from SgrA*, the putative supermassive black hole at the center of our Galaxy, has been measured and its spectrum studied, together with the X-ray emission from several bright X-ray sources, LMX

L. Sidoli, S. Mereghetti, G. L. Israel, F. Bocchino

We report the results of a BeppoSAX observation of the composite supernova remnant G0.9+0.1, located in the Galactic Center region. This new observation, in which the core of G0.9+0.1 is observed on-axis, confirms our previous results obtained from a pointing in which the supernova remnant was serendipitously observed at a large off-axis angle. The better qu

Maxim Lyutikov

Diffractive and refractive magnetospheric scintillations may allow a direct testing of the plasma inside the light cylinder. Unusual electrodynamics of the strongly magnetized electron-positron plasma allow separation of the magnetospheric and interstellar scattering. The most distinctive feature of the magnetospheric scintillations is their independence on

S. Safi-Harb, R. Petre, K. A. Arnaud, J. W. Keohane

We present an X-ray study of the radio bright supernova remnant (SNR) 3C 397 with ROSAT, ASCA, and RXTE. A central X-ray spot seen with the ROSAT High-Resolution Imager hints at the presence of a pulsar-powered component, and gives this SNR a composite X-ray morphology. Combined ROSAT and ASCA imaging show that the remnant is highly asymmetric, with its hard

Marco Fatuzzo, Fulvio Melia, Johann Rafelski

Maps of the Galactic electron-positron annihilation radiation show evidence for three distinct and significant features: (1) a central bulge source, (2) emission in the Galactic plane, and (3) an enhancement of emission at positive latitudes above the Galactic Center. In this paper, we explore the possibility that Sgr A East, a very prominent radio structure

Martin G. Haehnelt, Guinevere Kauffmann

Recent work has demonstrated that there is a tight correlation between the mass of a black hole and the velocity dispersion of the bulge of its host galaxy. We show that the model of Kauffmann & Haehnelt, in which bulges and supermassive black holes both form during major mergers, produces a correlation between M_bh and sigma with slope and scatter comparabl

K. Kuijken

Now that weak lensing signals on the order of a percent are actively being searched for (cosmic shear, galaxy-galaxy lensing, large radii in clusters...) it is important to investigate how accurately weak shears can be determined. Many systematic effects are present, and need to be understood. I show that the Kaiser et al. technique can leave residual system