March 1999 arXiv papers — page 13

J. Jewell, C. R. Lawrence, S. Levin

Our ability to extract the maximal amount of information from future observations at gigahertz frequencies depends on our ability to separate the underlying cosmic microwave background (CMB) from galactic and extragalactic foregrounds. We review the separation problem and its formulation within Bayesian inference, give examples of specific solutions with par

C. S. Rosenthal, J. Christensen-Dalsgaard, A. Nordlund, R. F. Stein

Differences between observed and theoretical eigenfrequencies of the Sun have characteristics which identify them as arising predominantly from properties of the oscillations in the vicinity of the solar surface: in the super-adiabatic, convective boundary layer and above. These frequency differences may therefore provide useful information about the structu

Marcus B. Pinto, Rudnei O. Ramos

The optimized linear $δ$-expansion is applied to the $λϕ^4$ theory at high temperature. Using the imaginary time formalism the thermal mass is evaluated perturbatively up to order $δ^2$. A variational procedure associated with the method generates nonperturbative results which are used to obtain the critical temperature for the phase transition. Our results

M. B. Halpern, C. Schwartz

We find an infinite dimensional free algebra which lives at large N in any SU(N)-invariant action or Hamiltonian theory of bosonic matrices. The natural basis of this algebra is a free-algebraic generalization of Chebyshev polynomials and the dual basis is closely related to the planar connected parts. This leads to a number of free-algebraic forms of the ma

Mikhail Plyushchay

The existence of intimate relation between generalized statistics and supersymmetry is established by observation of hidden supersymmetric structure in pure parabosonic systems. This structure is characterized generally by a nonlinear superalgebra. The nonlinear supersymmetry of parabosonic systems may be realized, in turn, by modifying appropriately the usu

Nakwoo Kim, Soo-Jong Rey, Jung-Tay Yee

Examples of stable, non-BPS M-theory membrane configuration are constructed via M(atrix) theory. The stable membranes are localized on O4 or O8 orientifolds, which projects Chan-Paton gauge bundle of M(atrix) zero-brane partons to USp-type. The examples are shown to be consistent with prediction based on K-theory analysis.

J. P. Norris, G. F. Marani, J. T. Bonnell

We suggest a connection between the pulse paradigm at gamma-ray energies and the recently demonstrated luminosity distribution in gamma-ray bursts: the spectral evolution timescale of pulse structures is anticorrelated with peak luminosity, and with quantities which might be expected to reflect the bulk relativistic Lorentz factor, such as spectral hardness

Daniel Jonathan, Martin B. Plenio

We find a minimal set of necessary and sufficient conditions for the existence of a local procedure that converts a finite pure state into one of a set of possible final states. This result provides a powerful method for obtaining optimal local entanglement manipulation protocols for pure initial states. As an example, we determine analytically the optimal d

Miguel S. Costa

We study intersecting D-branes in type 0 string theories and show that the D$p_{\pm}$-brane bound states obey similar intersecting rules as the D$p$-branes of the type II theories. The D$5_{\pm}$-D$1_{\pm}$ brane system is studied in detail. We show that the corresponding near-horizon geometry is the $AdS_3\times S^3\times T^4$ space and that there is no tac

Pavlos Vranas

Results from numerical simulations of full, two flavor QCD thermodynamics at N_t=4 with domain wall fermions are presented. For the first time a numerical simulation of the full QCD phase transition displays a low temperature phase with spontaneous chiral symmetry breaking but intact flavor symmetry and a high temperature phase with the full $SU(2) \times SU

J. L. Boldo, L. M. de Moraes, J. A. Helayel-Neto

We study and discuss some of the consequences of the inclusion of torsion in 3D Einstein-Chern-Simons gravity. Torsion may trigger the excitation of non-physical modes in the spectrum. Higher-derivative terms are then added up and tree-level unitarity is contemplated.

X. G. Feng, Dragana Popovic, S. Washburn, V. Dobrosavljevic

Experiments on a sufficiently disordered two-dimensional (2D) electron system in silicon reveal a new and unexpected kind of metallic behavior, where the conductivity decreases as σ(n_s,T)=σ(n_s,T=0)+A(n_s)T^2 (n_s-carrier density) to a non-zero value as temperature T->0. In 2D, the existence of a metal with dσ/dT>0 is very surprising. In addition, a novel t

M. S. Goes-Negrao, M. R. Negrao, A. B. Penna-Firme

Considering a class of (2,0)-super-Yang-Mills multiplets that accommodate a pair of independent gauge potentials in connection with a single symmetry group, we present here their coupling to ordinary matter and to non-linear $σ$-models in (2,0)-superspace. The dynamics and the couplings of the gauge potentials are discussed and the interesting feature that c

K. Golec-Biernat, M. Wusthoff

We successfully describe the HERA-data on diffractive deep inelastic scattering using a saturation model which has been applied in our earlier analysis of the inclusive $ep$-scattering data. No further parameters are needed. Saturation already turned out to be essential in describing the transition from large to small values of $Q^2$ in inclusive scattering.

M. Frau, L. Gallot, A. Lerda, P. Strigazzi

We use the boundary state formalism to study, from the closed string point of view, superpositions of branes and anti-branes which are relevant in some non-perturbative string dualities. Treating the tachyon instability of these systems as proposed by A. Sen, we show how to incorporate the effects of the tachyon condensation directly in the boundary state. I

Keshav Dasgupta, Jaemo Park

We present the evidence that $(-1)^{F_L}$ is a nonperturbative symmetry of Type II string theory. We argue that $(-1)^{F_L}$ is a symmetry of string theory as much as the $SL(2, Z)$ of the Type II string is and how the branes are mapped under the $(-1)^{F_L}$ modding. NS branes are mapped into the NS branes with the same world volume dimensions but with the

S. E. Thorsett, Z. Arzoumanian, F. Camilo, A. G. Lyne

The millisecond pulsar PSR B1620-26, in the globular cluster M4, has a white dwarf companion in a half-year orbit. Anomalously large variations in the pulsar's apparent spin-down rate have suggested the presence of a second companion in a much wider orbit. Using timing observations made on more than seven hundred days spanning eleven years, we confirm th

G. Mao, H. Stöcker, W. Greiner

We develop a relativistic model to describe the bound states of positive energy and negative energy in finite nuclei at the same time. Instead of searching for the negative-energy solution of the nucleon's Dirac equation, we solve the Dirac equations for the nucleon and the anti-nucleon simultaneously. The single-particle energies of negative-energy nucl

A. Yu. Segal, A. G. Sibiryakov

We develop two N=2 superfield formulations of free equations of motion for the joint model of all D=4 massless higher-superspin fields in generating form. The explicit Osp(2|4) supersymmetry is achieved without exploiting the harmonic superspace, and with adding no auxiliary component fields to those of N=1 superfields. The formulations are developed in two

Anton Alekseev, Eckhard Meinrenken, Chris Woodward

We introduce equivariant Liouville forms and Duistermaat-Heckman distributions for Hamiltonian group actions with group valued moment maps. The theory is illustrated by applications to moduli spaces of flat connections on 2-manifolds.

R. Rosenfelder

The contribution of virtual excitations to the energy levels of electronic and muonic hydrogen is investigated combining a model-independent approach for the main part with quark model predictions for the remaining corrections. Precise values for the polarization shifts are obtained in the long-wavelength dipole approximation by numerically integrating over

L. L. Salcedo

It is argued that the ambiguity introduced by the renormalization in the effective action of a four-dimensional renormalizable quantum field theory is at most a local polynomial action of canonical dimension four. The allowed ambiguity in the expected stress-energy tensor of a massive scalar field is severely restricted by this fact.

T K Rai Dastidar

The existence of a non-thermodynamic arrow of time was demonstrated in a recent paper (Mod.Phys.Lett. A13, 1265 (1998)), in which a model of non-local Quantum Electrodynamics was formulated through the principle of gauge invariance. In this paper we show that the Cosmic Microwave Background Radiation is capable of making every particle of the universe (excep

Alexander Moroz

The width $\triangle_L$ of the first Bragg's scattering peak in the (111) direction of a face-centered-cubic lattice of air spheres can be well approximated by a simple formula which only involves the volume averaged $ε$ and $ε^2$ over the lattice unit cell, $ε$ being the (position dependent) dielectric constant of the medium, and the effective dielectri

K. Colanero, M. -C. Chu

We study a Schrodinger particle in an infinite spherical well with an oscillating wall. Parametric resonances emerge when the oscillation frequency is equal to the energy difference between two eigenstates of the static cavity. Whereas an analytic calculation based on a two-level system approximation reproduces the numerical results at low driving amplitudes

Y. Hatsugai, K. Ishibashi, Y. Morita

The Hall conductance $σ_{xy}$ of two-dimensional {\it lattice} electrons with random potential is investigated. The change of $σ_{xy}$ due to randomness is focused on. It is a quantum phase transition where the {\it sum rule} of $σ_{xy}$ plays an important role. By the {\it string} (anyon) gauge, numerical study becomes possible in sufficiently weak magnetic

Yuji Sugawara

We study the proposed duality between the 5-dimensional supergravity/superstring on $AdS_3\times S^2$ and the 2-dimensional N=(0,4) SCFT defined on the boundary of AdS-space. We construct explicitly the N=(0,4) SCFT by imposing the `quiver projection' developed by Douglas-Moore on the N=(4,4) SCFT of symmetric orbifold, which is proposed to be the dual of th

T. P. Li, Y. X. Feng, L. Chen

Temporal and spectral properties of X-ray rapid variability of Cyg X-1 are studied by an approach of correlation analysis in the time domain on different time scales. The correlation coefficients between the total intensity in 2-60 keV and the hardness ratio of 13-60 keV to 2-6 keV band on the time scale of about 1 ms are always negative in all states. For s

Ulrich Mohrhoff

This article presents a novel interpretation of quantum mechanics. It extends the meaning of ``measurement'' to include all property-indicating facts. Intrinsically space is undifferentiated: there are no points on which a world of locally instantiated physical properties could be built. Instead, reality is built on facts, in the sense that the prope

Vladimir G. Pestov

We establish a close link between the amenability of a unitary representation $π$ of a group $G$ (in the sense of Bekka) and the concentration property (in the sense of V. Milman) of the corresponding dynamical system $(\s_π,G)$, where $\s_\H$ is the unit sphere the Hilbert space of representation. We prove that $π$ is amenable if and only if either $π$ cont

Frans Pretorius

The quantum interest conjecture of Ford and Roman states that any negative energy flux in a free quantum field must be preceded or followed by a positive flux of greater magnitude, and the surplus of positive energy grows the further the positive and negative fluxes are apart. In addition, the maximum possible separation between the positive and negative ene

T. K. Kopeć, J. V. José

We have studied a quantum Hamiltonian that models an array of ultrasmall Josephson junctions with short range Josephson couplings, $E_J$, and charging energies, $E_C$, due to the small capacitance of the junctions. We derive a new effective quantum spherical model for the array Hamiltonian. As an application we start by approximating the capacitance matrix b

Daisuke Takahashi, Kenji Kajiwara

We consider an integrability test for ultradiscrete equations based on the singularity confinement analysis for discrete equations. We show how singularity pattern of the test is transformed into that of ultradiscrete equation. The ultradiscrete solution pattern can be interpreted as a perturbed solution. We can also check an integrability of a given equatio

A. T. Sornborger, E. D. Stewart

To efficiently implement many-qubit gates for use in quantum simulations on quantum computers we develop and present methods reexpressing exp[-i (H_1 + H_2 + ...) Δt] as a product of factors exp[-i H_1 Δt], exp[-i H_2 Δt], ... which is accurate to 3rd or 4th order in Δt. The methods we derive are an extended form of symplectic method and can also be used for

J. Lacki, H. Ruegg, V. Telegdi

We review the history of the road to a manifestly covariant perturbative calculus within quantum electrodynamics from the early semi-classical results of the mid-twenties to the complete formalism of Stueckelberg in 1934. We chose as our case study the calculation of the cross-section of the Compton effect. We analyse Stueckelberg's paper extensively. Th

E. Caurier, K. Langanke, G. Martinez-Pinedo, F. Nowacki

Electron capture and beta-decay rates on nuclei in the mass range A=45-65 play an important role in many astrophysical environments. The determination of these rates by large-scale shell model calculations is desirable, but it requires to reproduce the Gamow-Teller strength distributions and spectra of the pf shell nuclei. We show in this paper that large-sc

Hungchong Kim

In this comment, we propose possible errors in constructing the continuum contribution in the sum rule studied by M. C. Birse and B. Krippa, Phys. Rev. C. {\bf 54} (1996) 3240.

A. Taranenko, A. Kugler, R. Pleskac, P. Tlusty

Azimuthal distributions of $η$ and $π^{0}$ mesons emitted at midrapidity in collisions of 1.9 AGeV $^{58}$Ni+$^{58}$Ni and 2 AGeV $^{40}$Ca+$^{nat}$Ca are studied as a function of the number of projectile-like spectator nucleons. The observed anisotropy corresponds to a negative elliptic flow signal for $η$ mesons, indicating a preferred emission perpendicul

Peter Bouwknegt, Nick Halmagyi

In a previous paper we defined the concept of an affinized projective variety and its associated Hilbert series. We computed the Hilbert series for varieties associated to quadratic monomial ideals. In this paper we show how to apply these results to affinized flag varieties. We discuss various examples and conjecture a correspondence between the Hilbert ser

Yan Guo, Gerhard Rein

We prove the existence and nonlinear stability of Camm type steady states of the Vlasov-Poisson system in the gravitational case. The paper demonstrates the effectiveness of an approach to the existence and stability problem for steady states, which was used in previous work by the authors: The steady states are obtained as minimizers of an energy-Casimir fu

Boris M. Doubrov, Boris P. Komrakov

The paper is devoted to the complete classification of all real Lie algebras of contact vector fields on the first jet space of one-dimensional submanifolds in the plane. This completes Sophus Lie's classification of all possible Lie algebras of contact symmetries for ordinary differential equations. As a main tool we use the abstract theory of filtered

Felix Schlenk

We study the rigidity and flexibility of symplectic embeddings of simple shapes. It is first proved that under the condition $r_n^2 \le 2 r_1^2$ the symplectic ellipsoid $E(r_1, ..., r_n)$ with radii $r_1 \le ... \le r_n$ does not embed in a ball of radius strictly smaller than $r_n$. We then use symplectic folding to see that this condition is sharp and to

Michael B. Green

These lecture notes begin with a review of the first nonleading contributions to the derivative expansion of the M theory effective action compactified on a two-torus. The form of these higher-derivative interactions is shown to follow from ten-dimensional type IIB supersymmetry as well as from one-loop quantum corrections to classical eleven-dimensional sup

R. P. Malik

We discuss the BRST cohomology and exhibit a connection between the Hodge decomposition theorem and the topological properties of a two dimensional free non-Abelian gauge theory having no interaction with matter fields. The topological nature of this theory is encoded in the vanishing of the Laplacian operator when equations of motion are exploited. We obtai

Will Loinaz, Tatsu Takeuchi

We discuss the choice of gauge field basis in multiple-U(1) gauge theories. We find that there is a preferred basis, specified by the charge orthogonality condition, in which the U(1) gauge fields do not mix under one-loop renormalization group running.

William B. Kilgore, Walter T. Giele

We report preliminary results for a next-to-leading order event generator for hadronic three jet production. We demonstrate the stability of the calculation and present preliminary results for the jet transverse energy spectra. This is the first calculation of three jet production at this order to include all parton sub-processes.

S. Dawson, L. Reina

We investigate the inclusive production of the Higgs boson with a heavy quark pair, $t {\bar t}$ or $b {\bar b}$, in e^+e^- collisions at high energy. The ${\cal O}(α_s)$ QCD corrections are included.

F. Sannino, J. Schechter

We study the chiral phase transition for vector-like SU(N) gauge theories as a function of the number of quark flavors N_f by making use of an anomaly-induced effective potential. We modify an effective potential of a previous work, suggested for N_f < N, and apply it to larger values of N_f where the phase transition is expected to occur. The new effective

Edward Boos, Thorsten Ohl

We describe the explicit construction of groves, the smallest gauge invariant classes of tree Feynman diagrams in gauge theories. The construction is valid for gauge theories with any number of group factors which may be mixed. It requires no summation over a complete gauge group multiplet of external matter fields. The method is therefore suitable for defin

X. Y. Pham

Neutrino physics is used as an illustrative example for an elementary introduction to the computational method of Feynman loop-diagrams and decay rates. If the neutrinos are as massive as recently reported by the Super-Kamiokande results, the heaviest neutrino $ν_H$ would not be stable. Although chargeless, it could decay -- by quantum loop effect -- into a

N. Brambilla, A. Pineda, J. Soto, A. Vairo

The definition of the quark-antiquark static potential is given within an effective field theory framework. The leading infrared divergences of the static singlet potential in perturbation theory are explicitly calculated.

M. Boglione, P. J. Mulders

We present some estimates of T-odd fragmentation and distribution functions, $H_1^\perp$ and $f_{1T}^{\perp}$, evaluated on the basis of a fit on experimental data in p$^\uparrow$p. Assuming the T-odd fragmentation function to be responsible for the single spin asymmetry in pion production in p$^\uparrow$p, we find the ratio $H_1^{\perp}/D_1$ to be in good a

Stefan Olejnik, Peter Presnajder

This WWW page contains links to contributions that appear in the Festschrift issue of the journal Acta Physica Slovaca dedicated to Professor Jan Pisut on the occasion of his 60th birthday. Where available, links are given also to e-prints in xxx archives.

Jie-Jie Zhu, Mu-Lin Yan

We show how to construct covariant amplitudes for processes involving higher spins in this paper. First we give the explicit expressions of Rarita-Schwinger wave functions and propagators for bosons with spins, then kinematic singularity free 3-leg effective vertexes are derived and given in a list. Equivalence relations are worked out to get these independe

Zhenjun Xiao, Chongsheng Li, Kuangta Chao

We calculate the new contributions to the rare decays $K^+ \to π^+ ν\bar ν$, $K_L \to π^0 ν\bar ν$ and $K_L \to μ^+ μ^-$ from new $Z^0$-penguin and box diagrams induced by the unit-charged scalars $(\tildeπ^\pm, \tilde{H}^\pm, π_1^\pm, π_8^\pm)$ appeared in the Topcolor-assisted technicolor (TC2) models. We find that: (a) the unit-charged top-pion $\tildeπ^\

Zhenjun Xiao, Linxia Lü, Hongkai Guo, Gongru Lu

We calculate the one-loop $Z^0$-penguin contributions to the rare K-decays, $K^+ \to π^+ ν\bar ν$, $K_L \to π^0 ν\bar ν$ and $K_L \to μ^+ μ^-$, from the unit-charged technipions $π_1$ and $π_8$ in the framework of the Multiscale Walking Technicolor Model. We find that: (a) the $π_1$ and $π_8$ can provide one to two orders enhancements to the branching ratios

Xiao Zhenjun, Jia Liqun, Lü Linxia, Lu Gongru

We calculate the contributions to the rare decays $B \to X_{s,d} ν\bar ν$ and $B_{s,d} \to l^+l^-$ from one-loop $Z^0$-penguin diagrams in the framework of Topcolor-assisted Technicolor Model. Within the parameter space, we find that: (a) the new contribution from technipions is less than 2% of the standard model prediction; (b) the top-pions can provide a f

Xiao Zhenjun, Lü Linxia, Guo Hongkai, Lu Gongru

We calculate the contributions to the rare B-decays, $B \to X_{s,d} ν\bar ν$, $B_{s,d} \to l^+l^- $ from the unit-charged technipions. Within the considered parameter space we find that: (a) the enhancements to the branching ratios in question can be as large as three orders of magnitude; (b) the ALEPH data of $B \to X_s ν\bar ν$ lead to strong mass bounds o

D. Pekurovsky, G. Kilcup

We have gained enough statistical precision to distinguish signal from noise in matrix elements of all operators relevant for the Delta I=1/2 rule in kaon decays and for the direct CP violation parameter epsilon-prime. We confirm significant enhancement of Delta I=1/2 transitions observed in experiments, although a few large systematic uncertainties remain i

Martino Margoni

The inclusive direct and cascade semileptonic branching ratios of the b quark were measured from a fit to the lepton momentum spectrum in the B-hadron rest frame, exploiting the charge correlation between the lepton and the heavy meson. The value of the Vcb element in the CKM quark mixing matrix was computed from the differential decay width of the process B

The OPAL Collaboration, G. Abbiendi et al

Gluon jets are identified in hadronic Z0 decays as all the particles in a hemisphere opposite to a hemisphere containing two tagged quark jets. Gluon jets defined in this manner are equivalent to gluon jets produced from a color singlet point source and thus correspond to the definition employed for most theoretical calculations. In a separate stage of the a

John Belz

We present new results on the related rare KL decay modes KL -> pi+ pi- gamma and KL -> pi+ pi- e+ e-. KTeV has performed the first direct measurement of the form factor for the &#34;direct emission&#34; component of KL -> pi+ pi- gamma decays, a quantity with ramifications for particular chiral models. In addition, the form factor and direct emission/inner

Filipe Bonjour, Christos Charmousis, Ruth Gregory

We investigate a self-gravitating thick domain wall for a $λΦ^4$ potential. The system of scalar and Einstein equations admits two types of non-trivial solutions: domain wall solutions and false vacuum-de Sitter solutions. The existence and stability of these solutions depends on the strength of the gravitational interaction of the scalar field, which is cha

Gilles Esposito-Farese

This talk is based on my work in collaboration with Thibault Damour. We compare the probing power of different classes of gravity experiments: solar-system tests (weak-field regime), binary-pulsar tests (strong-field regime), and future gravitational-wave observations of inspiralling binaries (strong-field effects detected in our weak-gravitational-field con

Tamath Rainsford, Peter Szekeres

Newtonian Cosmology is commonly used in astrophysical problems, because of its obvious simplicity when compared with general relativity. However it has inherent difficulties, the most obvious of which is the non-existence of a well-posed initial value problem. In this paper we investigate how far these problems are met by using the post-Newtonian approximati

Peter Nordlander, Michael Pustilnik, Yigal Meir, Ned S. Wingreen

The time-development of the Kondo effect is theoretically investigated by studying a quantum dot suddenly shifted into the Kondo regime by a change of voltage on a nearby gate. Using time-dependent versions of both the Anderson and Kondo Hamiltonians, it is shown that after a time $t$ following the voltage shift, the form of the Kondo resonance matches the {

B. N. Narozhny, I. L. Aleiner, B. L. Altshuler

We consider a normal metal - superconductor (N-S) junction in the regime, when electrons in the normal metal are driven out of equilibrium. We show that the non-equilibrium fluctuations of the electron density in the N-layer cause the fluctuations of the phase of the order parameter in the S-layer. As a result, the density of states in the superconductor dev

V. T. Petrashov, I. A. Sosnin, I. Cox, A. Parsons

A strong mutual influence of superconductors (S) and ferromagnetic (F) conductors in hybrid F/S (Ni/Al) nanostructures is observed. The magnitude of a proximity-induced conductance on the F-side is more than two orders larger than that predicted by theory. Re-entrance of the superconductors to the normal state reciprocated by changes on the F-side has been f

A. V. Bobylev, Alex Hansen, J. Piasecki, E. H. Hauge

We consider a system of non-interacting charged particles moving in two dimensions among fixed hard scatterers, and acted upon by a perpendicular magnetic field. Recollisions between charged particles and scatterers are unavoidable in this case. We derive from the Liouville equation for this system a generalized Boltzmann equation with infinitely long memory

Haranath Ghosh, S. Sil, S. N. Behera

A model study for the coexistence of the spin density wave and superconductivity is presented. With reference to the recent angle resolved photo emmission experimental data in high T_c cuprates, presence of the nested pieces of bands is assumed. The single band Hubbard model, therefore, when treated within the Hatree-Fock mean field theory leads to a spin de

Robert Shrock, Shan-Ho Tsai

We present exact calculations of the zero-temperature partition function (chromatic polynomial) and the (exponent of the) ground-state entropy $S_0$ for the $q$-state Potts antiferromagnet on families of cyclic and twisted cyclic (Möbius) strip graphs composed of $p$-sided polygons. Our results suggest a general rule concerning the maximal region in the comp

T. Blasius, Ch. Niedermayer, J. L. Tallon, D. M. Pooke

From muon spin rotation measurements on under- to overdoped Bi-2212 crystals we obtain evidence for a two-stage transition of the vortex matter as a function of temperature. The first transition is well known and related to the irreversibility line (IL). The second one is located below the IL and has not been previously observed. It occurs for all three sets

X. H. Wang, K. A. Chao

We have used the method of generating functional in imaginary time to derive the current-voltage characteristics of a tunnel junction with arbitrary tunneling conductance, connected in series with an external impedance and a voltage source. We have shown that via the renormalized charging energy and the renormalized environment conductance, our nonperturbati

H. G. Ballesteros, G. Parisi

We study two different versions of the site-diluted Ising model in three dimensions with long-range spatially correlated disorder by Monte Carlo means. We use finite-size scaling techniques to compute the critical exponents of these systems, taking into account the strong scaling-corrections. We find a $ν$ value that is compatible with the analytical predict

Andrzej Pawlak

The nonasymptotic critical behavior of sound attenuation coefficient has been studied in an elastically isotropic Ising system above the critical point on the basis of a complete stochastic model including both spin-energy and lattice-energy modes linearly coupled to the longitudinal sound mode. The effect of spin-lattice relaxation on the ultrasonic attenua

N. F. Johnson, P. M. Hui, Dafang Zheng, C. W. Tai

We study a model of a competing population of N adaptive agents, with similar capabilities, repeatedly deciding whether to attend a bar with an arbitrary cutoff L. Decisions are based upon past outcomes. The agents are only told whether the actual attendance is above or below L. For L-> N/2, the game reproduces the main features of Challet and Zhang&#39;s mi

Masaaki Nakamura

The phase transition between charge- and spin-density-wave (CDW, SDW) phases is studied in the one-dimensional extended Hubbard model at half-filling. We discuss whether the transition can be described by the Gaussian and the spin-gap transitions under charge-spin separation, or by a direct CDW-SDW transition. We determine these phase boundaries by level cro

Frank Mack, Peter Horsch

We investigate a planar model for the ferromagnetic (FM) phase of manganites, which develops orbital order of $e_g$ electrons with x$^2$-y$^2$-symmetry at low temperature. The dynamic structure factor of orbital excitations and the optical conductivity $σ(ω)$ are studied with help of a finite-temperature diagonalization method. Our calculations provide a the

H. C. Lee

The resonant Raman scattering of a quantum wire in a strong magnetic field is studied, focused on the effect of long range Coulomb interaction and the spin-charge separation. The energy-momentum dispersions of charge and spin excitation obtained from Raman cross-section show the characteristc cross-over behaviour induced by inter-edge Coulomb interaction. Th

Jian-Sheng Wang, Lik Wee Lee

We discuss Monte Carlo dynamics based on <N(sigma, Delta E)>_E, the (microcanonical) average number of potential moves which increase the energy by Delta E in a single spin flip. The microcanonical average can be sampled using Monte Carlo dynamics of a single spin flip with a transition rate min(1, <N(sigma&#39;, E-E&#39;)>_E&#39; / <N(sigma, E&#39;-E) >_E)

Yukitoshi Motome, Masatoshi Imada

Roles of orbital and lattice degrees of freedom in strongly correlated systems are investigated to understand electronic properties of perovskite Mn oxides such as La_{1-x}Sr_{x}MnO_{3}. An extended double-exchange model containing Coulomb interaction, doubly degenerate orbitals and Jahn-Teller coupling is derived under full polarization of spins with two-di

A. Mazzino, P. Castiglione

The role played on the scalar transport by a finite, not small, correlation time, $τ_u$, for the noise velocity is investigated, both analytically and numerically. For small $τ_u$&#39;s a mechanism leading to enhancement of transport has recently been identified and shown to be dominating for any type of flow. For finite non-vanishing $τ_u$&#39;s we recogniz

C. Chandre, H. R. Jauslin, G. Benfatto, A. Celletti

We construct an approximate renormalization transformation that combines Kolmogorov-Arnold-Moser (KAM)and renormalization-group techniques, to analyze instabilities in Hamiltonian systems with three degrees of freedom. This scheme is implemented both for isoenergetically nondegenerate and for degenerate Hamiltonians. For the spiral mean frequency vector, we

Joshua E. Barnes

Theoretical considerations and observational data support the idea that mergers were more frequent in the past. At high redshifts, violent interactions and mergers may be implicated in the origin of Lyman-break galaxies, sub-mm starbursts, and active galactic nuclei. Most stars in cluster ellipticals probably formed at redshifts z > 2, as did most of the hal

Martin White

The ten&#39;s of micro-Kelvin variations in the temperature of the cosmic microwave background (CMB) radiation across the sky encode a wealth of information about the Universe. The full-sky, high-resolution maps of the CMB that will be made in the next decade should determine cosmological parameters to unprecedented precision and sharply test inflation and o

Mou Roy, H. J. Crawford, Athena Trattner

In this paper we look at \sim 10^14 eV neutrino bursts which are predicted to be observed in correlation with gamma ray bursts (GRBs). We describe an efficient way of constructing a km^2 effective area detector for these neutrino bursts. The proposed detector will cost <$3M and will operate in the 4-km deep water off St.Croix for at least one year, sufficien

N. Neininger

This contribution presents a short overview about the investigation of the molecular gas content of nearby galaxies using the Plateau de Bure Interferometer. I try to give a rather complete list of recent references, and explicit descriptions are given for objects under study at RAI Bonn. They comprise very different types of galaxies such as Haro 2, Mrk 297

Ronald L. Gilliland, Peter E. Nugent, M. M. Phillips

Two supernovae detected in the Hubble Deep Field using the original December 1995 epoch and data from a shorter (63000 s in F814W) December 1997 visit with HST are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen etal. (1996) and 1.32 (photometric) from the work of Fernandez-Soto, Lanz

I. Negueruela, P. Roche, J. Fabregat, M. J. Coe

We present optical and infrared observations of BQ Cam, the optical counterpart to the Be/X-ray transient system V0332+53. BQ Cam is shown to be an O8-9Ve star, which places V0332+53 at a distance of ~7 kpc. H-alpha spectroscopy and infrared photometry are used to discuss the evolution of the circumstellar envelope. Due to the low inclination of the system,

I. A. G. Snellen, R. T. Schilizzi, M. N. Bremer, G. K. Miley

We present spectroscopic observations of a sample of faint Gigahertz Peaked Spectrum (GPS) radio sources drawn from the Westerbork Northern Sky Survey (WENSS). Redshifts have been determined for 19 (40%) of the objects. The optical spectra of the GPS sources identified with low redshift galaxies show deep stellar absorption features. This confirms previous s

John D. Barrow

We discuss the evolution of radiation and Bekenstein-Hawking entropies in expanding isotropic universes. We establish a general relation which shows why it is inevitable that there is currently a huge difference in the numerical values of these two entropies. Some anthropic constraints on their values are given and other aspects of the cosmological &#39;entr

Frank Verbunt, Peter J. Wheatley, Janet A. Mattei

We have observed YZ Cnc at two day intervals from 6 to 24 April 1998, covering two full outburst cycles. The 0.1-2.4 keV flux is lower during optical outburst than in quiescence, and lowest at the end of the outburst. The decline of the X-ray flux in the quiescent interval appears to be in contrast to prediction of simple models for accretion-disk instabilit

A. W. Jones, A. N. Lasenby, P. Mukherjee, C. M. Gutierrez

We use data from the Tenerife 10, 15 and 33 GHz beamswitching experiments along with the COBE 53 and 90 GHz data to separate the cosmic microwave background (CMB) signal from the Galactic signal and create two maps at high Galactic latitude. The new multi-MEM technique is used to obtain the best reconstruction of the two channels. The two maps are presented

B. L. Ziegler, R. P. Saglia, R. Bender, P. Belloni

We investigate the evolution of early-type galaxies in four clusters at z=0.4 (Abell370, Cl0303+17, Cl0939+47 and Cl1447+26) and in one at z=0.55 (Cl0016+16). The galaxies are selected according to their spectrophotometrically determined spectral types and comprise the morphological classes E, S0 and Sa galaxies. Structural parameters are determined by a two

Andrew W. Blain

This proceeding discusses the potential modifications to the mid-infrared spectral energy distribution (SED) of a high-redshift dusty AGN that is graviationally lensed by a foreground galaxy. The mid-infrared colour of a lensed galaxy would typically be bluer than that of the same galaxy in the absence of magnification. This effect would make it more difficu

G. A. Tammann, B. Reindl

Blue Supernovae of Type Ia (SNe Ia) have become the most important objects in cosmology being of exceptionally uniform luminosity. Used as relative distance indicators they map deviations from pure Hubble flow and determine the cosmological constant Lambda. Once their absolute magnitude is determined they provide the best estimate of the large-scale value of

C. Alcock, R. A. Allsman, D. Alves, T. S. Axelrod

The MACHO collaboration has been carrying out Difference Image Analysis (DIA) since 1996 with the aim of increasing the sensitivity to the detection of gravitational microlensing. This is a preliminary report on the application of DIA to galactic bulge images in one field. We show how the DIA technique significantly increases the number of detected lensing e

V. J. S. Bejar, M. R. Zapatero Osorio, R. Rebolo

We present a CCD-based photometric survey covering 870 sq. arcmin in a young stellar cluster around the young multiple star sigma Orionis. Our survey limiting R, I, and Z magnitudes are 23.2, 21.8, and 21.0, respectively. From our colour-magnitude diagrams, we have selected 49 faint objects, which smoothly extrapolate the photometric sequence defined by more

L. Sriramkumar, T. Padmanabhan

We compare the different approaches presently available in literature to probe the vacuum structure of quantum fields in classical electromagnetic and gravitational backgrounds. We compare the results from the Bogolubov transformations and the effective Lagrangian approach with the response of monopole detectors (of the Unruh-DeWitt type) in non-inertial fra

K. Takahashi, S. Iida

The correlations of the QCD Dirac eigenvalues are studied with use of an extended chiral random matrix model. The inclusion of spatial dependence which the original model lacks enables us to investigate the effects of diffusion modes. We get analytical expressions of level correlation functions with non-universal behavior caused by diffusion modes which is c