July 2000 arXiv papers — page 22

V. P. Ruban

An ideal compressible fluid is considered, with an equilibrium density being a given function of coordinates due to presence of some static external forces. The slow flows in such system, which do not disturb the density, are investigated with the help of the Hamiltonian formalism. The equations of motion of the system are derived for an arbitrary given topo

S. Fortunato, H. Satz

For the Ising model, the spin magnetization transition is equivalent to the percolation transition of Fortuin-Kasteleyn clusters; this result remains valid also for the conventional continuous spin Ising model. The investigation of more general continuous spin models may help to obtain a percolation formulation for the critical behaviour in SU(2) gauge theor

S. J. Mitchell, G. Brown, P. A. Rikvold

We study the static and dynamic properties of bromine electrosorption onto single-crystal silver (100) electrodes by Monte Carlo simulation. At room temperature the system displays a second-order phase transition between a low-coverage disordered phase at more negative electrode potentials and a c(2x2) ordered phase with bromine coverage 1/2 at more positive

H. B. Weber, R. Häussler, H. v. Löhneysen, J. Kroha

We have observed interaction effects in the differential conductance $G$ of short, disordered metal bridges in a well-controlled non-equilibrium situation, where the distribution function has a double Fermi step. A logarithmic scaling law is found both for the temperature and for the voltage dependence of $G$ in all samples. The absence of magnetic field dep

Martin Cederwall, Ulf Gran, Mikkel Nielsen, Bengt EW Nilsson

In this paper, the low-energy effective dynamics of M-theory, eleven-dimensional supergravity, is taken off-shell in a manifestly supersymmetric formulation. We show that a previously proposed relaxation of the superspace torsion constraints does indeed accommodate a current supermultiplet which lifts the equations of motion corresponding to the ordinary sec

Sumiyoshi Abe, S. Martinez, F. Pennini, A. Plastino

For the power-law quantum wave packet in configuration space, the variance of the position observable may be divergent. Accordingly, the information-entropic formulation of the uncertainty principle becomes more appropriate than the Heisenberg-type formulation, since it involves only the finite quantities. It is found that the total amount of entropic uncert

A. B. Henriques, R. G. Moorhouse

In many theories of reheating starting from the classical spatially homogeneous inflaton field, its accompanying inhomogeneous part (which arises from primordial quantum fluctuations) is treated as a first order perturbation. We examine some consequences of treating it non-perturbatively in a model where a first order treatment is invalid. In particular we c

R. Mathieu, P. Jönsson, D. N. H. Nam, P. Nordblad

Non-equilibrium dynamics in a Ag(Mn) spin glass are investigated by measurements of the temperature dependence of the remanent magnetisation. Using specific cooling protocols before recording the thermo- or isothermal remanent magnetisations on re-heating, it is found that the measured curves effectively disclose non-equilibrium spin glass characteristics su

Mao-Zhi Yang, Ya-Dong Yang

Motivated by recent CELO measurements and the progress of the theory of B decays, we investigate $B\to P V(P=π,K. V= K^{*},ρ,ω)$ decay modes in the framework of QCD improved factorization. We find that all the measured branching ratios are well accommodated in the reasonable parameter space and predictions for the other decay modes are well below the experim

Jason K. Perry, Jamil Tahir-Kheli, William A. Goddard

Using the Becke-3-LYP functional, we have performed band structure calculations on the high temperature superconductor parent compound, La2CuO4. Under the restricted spin formalism (rho(alpha) equal to rho(beta)), the R-B3LYP band structure agrees well with the standard LDA band structure. It is metallic with a single Cu x2-y2/O p(sigma) band crossing the Fe

Daniel A. Lidar, Dave Bacon, Julia Kempe, K. B. Whaley

Decoherence-free subspaces (DFSs) shield quantum information from errors induced by the interaction with an uncontrollable environment. Here we study a model of correlated errors forming an Abelian subgroup (stabilizer) of the Pauli group (the group of tensor products of Pauli matrices). Unlike previous studies of DFSs, this type of errors does not involve a

H. Pu, P. Meystre

We present a scheme for creating quantum entangled atomic states through the coherent spin-exchange collision of a spinor Bose-Einstein condensate. The state generated possesses macroscopic Einstein-Podolsky-Roson correlation and the fluctuation in one of its quasi-spin components vanishes. We show that an elongated condensate with large aspect ratio is most

Bart Jongejan

EPR correlations exist and can be observed independently of any a priori given frame of reference. We can even construct a frame of reference that is based on these correlations. This observation-based frame of reference is equivalent to the customary a priori given frame of reference of the laboratory when describing real EPR experiments. J.S. Bell has argu

Gary R. Goldstein

The recently published book, ``Lise Meitner and the Dawn of the Nuclear Age'', by Patricia Rife (Boston: Birkhäuser, 1999) is reviewed in an essay for the lay audience. Meitner was a leading nuclear physicist at the time that the nucleus was the most exciting frontier of science. To establish her career, she had to overcome daunting prejudices agains

G. Parzen

This paper studies the possibility of using the survival function to predict long term stability by extrapolation. The survival function is a function of the initial coordinates and is the number of turns a particle will survive for a given set of initial coordinates. To determine the difficulties in extrapolating the survival function, tracking studies were

M. Rieutord, B. Georgeot, L. Valdettaro

We investigate the asymptotic properties of inertial modes confined in a spherical shell when viscosity tends to zero. We first consider the mapping made by the characteristics of the hyperbolic equation (Poincaré's equation) satisfied by inviscid solutions. Characteristics are straight lines in a meridional section of the shell, and the mapping shows th

E. L. Afraimovich, E. A. Kosogorov, L. A. Leonovich, O. S. Lesyuta

We developed a new technology for global detection of atmospheric disturbances, on the basis of phase measurements of the total electron content (TEC) using an international GPS networks. Temporal dependencies of TEC are obtained for a set of spaced receivers of the GPS network simultaneously for the entire set of visible satellites. These series are subject

Russell K. Standish

In the {\em Many Worlds Interpretation} of quantum mechanics, the range of possible worlds (or histories) provides variation, and the Anthropic Principle is a selective principle analogous to natural selection. When looked on in this way, the ``process'' by which the laws and constants of physics is determined not too different from the process that

Egle Tomasi-Gustafsson, Michail P. Rekalo

The purpose of this contribution is to stress the great importance of polarization observables for the study of nucleon resonances, in particular in the case of deuteron and proton probes. Polarization observables play a unique role in signing the reaction mechanism and bring new information in the microscopic description of baryon resonances. We will calcul

D. G. Jenkins, R. Wadsworth, J. A. Cameron, M. P. Carpenter

High spin states of the nucleus 104Cd have been studied using the Gammapshere array. The level scheme for 104Cd has been revised and evidence for a structure consisting of magnetic dipole transitions is presented. Shell model calculations, published previously, are invoked to support an interpretation of this structure as an incpient case of magnetic rotatio

P. Mohr, K. Vogt, M. Babilon, J. Enders

The nucleosynthesis of heavy proton-rich nuclei in a stellar photon bath at temperatures of the astrophysical $γ$-process was investigated where the photon bath was simulated by the superposition of bremsstrahlung spectra with different endpoint energies. The method was applied to derive ($γ$,n) cross sections and reaction rates for several platinum isotopes

Russell K. Standish

This paper discusses dynamic evolutionary economics, and introduces a model of such.

Bernhard Baumgartner, Robert Seiringer

We study the ground state properties of an atom with nuclear charge $Z$ and $N$ bosonic ``electrons'' in the presence of a homogeneous magnetic field $B$. We investigate the mean field limit $N\to\infty$ with $N/Z$ fixed, and identify three different asymptotic regions, according to $B\ll Z^2$, $B\sim Z^2$, and $B\gg Z^2$. In Region 1 standard Hartre

K. C. Shin

We consider the non-Hermitian Hamiltonian H= -\frac{d^2}{dx^2}+P(x^2)-(ix)^{2n+1} on the real line, where P(x) is a polynomial of degree at most n \geq 1 with all nonnegative real coefficients (possibly P\equiv 0). It is proved that the eigenvalues λmust be in the sector | arg λ| \leq \fracπ{2n+3}. Also for the case H=-\frac{d^2}{dx^2}-(ix)^3, we establish a

Alex Kumjian, David Pask

Building on recent work of Robertson and Steger, we associate a C*-algebra to a combinatorial object which may be thought of as a higher rank graph. This C*-algebra is shown to be isomorphic to that of the associated path groupoid. Sufficient conditions on the higher rank graph are found for the associated C*-algebra to be simple, purely infinite and AF. Res

Wei-Dong Ruan

In this paper we give a construction of Lagrangian torus fibration for Calabi-Yau hypersurface in toric variety via the method of gradient flow. Using our construction of Lagrangian torus fibration, we are able to prove the symplectic topological version of SYZ mirror conjecture for generic Calabi-Yau hypersurface in toric variety. We will also be able to gi

Steve Shkoller

We present a very simple proof of the global existence of a $C^\infty$ Lagrangian flow map for the 2D Euler and second-grade fluid equations (on a compact Riemannian manifold with boundary) which has $C^\infty$ dependence on initial data $u_0$ in the class of $H^s$ divergence-free vector fields for $s>2$.

Wlodzimierz Bryc

In a previous paper we determined one dimensional distributions of a stationary field with linear regressions and quadratic conditional variances under a linear constraint on the coefficients of the quadratic expression. In this paper we show that for stationary Markov chains with linear regressions and quadratic conditional variances the coefficients of the

Steven Dale Cutkosky, Lawrence Ein, Robert Lazarsfeld

The problem of bounding the "complexity" of a polynomial ideal in terms of the degrees of its generators has attracted considerable interest, brought into focus by the influential survey of Bayer and Mumford. The present paper examines some of these results and questions from a geometric perspective. Specifically, motivated by work of Paoletti we int

Tatiana Bandman, Leonid Makar-Limanov

In this paper we give a description of hypersurfaces with trivial ring $AK(S)$, introduced by the second author as following. Let $X$ be an affine variety and let $G(X)$ be the group generated by all $\Bbb {C}^+$-actions on $X$. Then $AK(X)$ is the subring of all regular $G(X)-$ invariant functions on $X.$ We show that a smooth affine surface $S$ with $AK(S)

Moti Gitik

Our aim is to show that it is impossible to find a bound for the power of the first fixed point of the aleph function.

A. Ballesteros, F. J. Herranz, J. Negro, L. M. Nieto

The minimal twist map introduced by B. Abdesselam, A. Chakrabarti, R. Chakrabarti and J. Segar (Mod. Phys. Lett. A 14 (1999) 765) for the non-standard (Jordanian) quantum sl(2,R) algebra is used to construct the twist maps for two different non-standard quantum deformations of the (1+1) Schrodinger algebra. Such deformations are, respectively, the symmetry a

S. Kharchev, D. Lebedev

The integral representations for the eigenfunctions of $N$ particle quantum open and periodic Toda chains are constructed in the framework of Quantum Inverse Scattering Method (QISM). Both periodic and open $N$-particle solutions have essentially the same structure being written as a generalized Fourier transform over the eigenfunctions of the $N-1$ particle

Erick J. Weinberg

Duality arguments suggest the existence of massless magnetic monopoles in gauge theories with the symmetry broken to a non-Abelian subgroup. I discuss how these arise and show how they are manifested as clouds of massless fields surrounding massive monopoles. The dynamics of these clouds is discussed, and the scattering of massless monopole clouds and massiv

Jeffrey A. Harvey, Oleg Ruchayskiy

Anomaly cancellation for M-theory fivebranes requires the introduction of a "bump-form" which smoothes out the five-brane source. We discuss the physical origin of this bump-form in the simpler case of axion strings in 3+1 dimensions and construct it in terms of the radial profile of the fermion zero modes. Our treatment allows for a clearer understanding of

M. Eliashvili, G. Tsitsishvili

We consider the parity invariant (2+1)-dimensional QED where the matter is represented as a mixture of fermions with opposite spins. It is argued that the perturbative ground state of the system is unstable with respect to the formation of magnetized ground state. Carrying out the finite temperature analysis we show that the magnetic instability disappears i

M. Eliashvili, G. Tsitsishvili

By considering the area preserving geometric transformations in the configuration space of electrons moving in the lowest Landau level (LLL) we arrive at the Chern-Simons type Lagrangian. Imposing the LLL condition, we get a scheme with the complex gauge fields and transformations. Quantum theory for the matter field in LLL is considered and formal expressio

Bertfried Fauser

A combinatorial formula of G.-C. Rota and J.A. Stein is taken to perform Wick re-ordering in quantum field theory. Wick's theorem becomes a Hopf algebraic identity called Cliffordization. The combinatorial method relying on Hopf algebras is highly efficient in computations and yields closed algebraic expressions. AMS Subject Classifications 2000: 81R50;

M. H. Seymour

We discuss recent progress and open questions in QCD jet physics, with particular emphasis on two areas: jet definitions and jet substructure.

Z. Merebashvili, A. P. Contogouris, G. Grispos

A complete next-to-leading order calculation of longitudinally polarized heavy quark photoproduction is presented. All results of the purturbative calculation are given in detail. For reactions and energies of interest cross sections differential in the transverse momentum and rapidity of the heavy quark, total cross sections and the corresponding asymmetrie

Daniel Boer

Transversely polarized Lambda production in hard scattering processes is discussed in terms of a leading twist T-odd fragmentation function which describes the fragmentation of an unpolarized quark into a transversely polarized Lambda. We focus on the properties of this function and its relevance for the RHIC and HERMES experiments.

M. Jack, A. Hoefer, A. Leike, T. Riemann

We discuss the status and some ongoing upgrades of the ZFITTER program for applications at e+e- colliders LEP1/SLC, LEP2, GigaZ, and TESLA. The inclusion of top quark pair production is under work.

Levon Pogosian, Tanmay Vachaspati

We consider the Grand Unified SU(5) model with a small or vanishing cubic term in the adjoint scalar field in the potential. This gives the model an approximate or exact Z$_2$ symmetry whose breaking leads to domain walls. The simplest domain wall has the structure of a kink across which the Higgs field changes sign ($Φ\to -Φ$) and inside which the full SU(5

R. N. Faustov, A. P. Martynenko

The contribution of the proton polarizability to the hydrogen hyperfine splitting is evaluated on the basis of modern experimental and theoretical results on the proton polarized structure functions. The value of this correction is equal to 1.4 ppm.

Dorota Kotlorz

The review of the nucleon spin structure functions problems is presented. The perturbative QCD predictions for the small x behaviour of the nucleon spin structure functions are discussed. The role of the resummation of the ln^2 1/x terms is emphasized. Predictions for the nonsinglet structure function g_1 in case of a flat as well as a dynamical input are gi

Asmaa Abada, Marta Losada

We consider neutrino masses generated at tree level and at one loop, through fermion--sfermion loop diagrams, in the MSSM with R-parity violation. Using the $(3\times 3)$ mass and mixing matrices for three generations of neutrinos and the present experimental results on neutrinos from laboratories and astrophysics simultaneously, we put bounds on both trilin

Francesco Vissani

We introduce the standard model of elementary particles and discuss the reasons why we have to modify it. Emphasis is put on the indications from the neutrinos and on the role of the Higgs particle; some promising theoretical ideas, like quark-lepton symmetry, existence of super-heavy ``right-handed'' neutrinos, grand unification and supersymmetry at

E. O. Iltan

We study the decay width of the inclusive process b --> s g g in the two Higgs doublet model with three level flavor changing neutral currents (model III). We analyse the dependencies of the differential decay width to the s quark energy E_s and model III parameters, charged Higgs mass m_{H^{\pm}} and Yukawa coupling \barξ_{N,bb}^D. We observe that there exi

A. Niégawa

We establish from first principles a perturbative framework that allows us to compute reaction rates for processes taking place in nonequilibrium $O (N)$ linear-sigma systems in broken phase. The system of our concern is quasiuniform system near equilibrium or nonequilibrium quasistationary system. We employ the closed-time-path formalism and use the so-call

J. M. Cline, H. Firouzjahi

A complete calculation of the radion mass has been given by Tanaka and Montes, hep-th/0001092, and also by Csaki, Graesser and Kribs (in preparation), which both obtain the TeV-scale. It seems likely that the problem with our computation was neglect of the back-reaction of the scalar field on the graviton zero mode, and consequent contributions to the radion

S. Capitani, M. Goeckeler, R. Horsley, H. Perlt

We discuss the improvement of flavour non-singlet point and one-link lattice quark operators, which describe the quark currents and the first moment of the DIS structure functions respectively. Suitable bases of improved operators are given, and the corresponding renormalisation factors and improvement coefficients are calculated in one-loop lattice perturba

L. Schuelke

An introductory review to short-time critical dynamics is given. From the scaling relation valid already in the early stage of the evolution of a system at or near the critical point, one derives power law behaviour for various quantities. By a numerical simulation of the system one can measure the critical exponents and, by searching for the best power law

A. K. Ciftci, S. Sultansoy, O. Yavas

Main parameters and physics search potential of gamma-p and gamma-A colliders, which will be available due to constructing the TESLA linear electron-positron collider tangentially to the HERA proton ring, are discussed.

S. Mikocki

Preliminary H1 results on dedicated searches for QCD instanton induced processes in DIS are presented. The investigations are based on the expected characteristics of their hadronic final state. Searches were performed in the kinematical region x > 0.001, 0.1 < y < 0.6 and the polar angle of scattered positron greater than 156 degrees.

Sergei M. Kopeikin, N. V. Shuygina, M. V. Vasilyev, E. I. Yagudina

The accuracy of astrometric observations conducted via a space-borne optical interferometer orbiting the Earth is expected to approach a few microarcseconds. Data processing of such extremely high-precision measurements requires access to a rigorous relativistic model of light ray propagation developed in the framework of General Relativity. The data-process

P. A. Zizzi

In a previous paper (gr-qc/9907063) we described the early inflationary universe in terms of quantum information. In this paper, we analize those results in more detail, and we stress the fact that, during inflation, the universe can be described as a superposed state of quantum registers. The self-reduction of the superposed quantum state is consistent with

Hans G. Kaper, Sever Tipei, Elizabeth Wiebel

This article describes a collaborative project between researchers in the Mathematics and Computer Science Division at Argonne National Laboratory and the Computer Music Project of the University of Illinois at Urbana-Champaign. The project focuses on the use of sound for the exploration and analysis of complex data sets in scientific computing. The article

Hans G. Kaper, Sever Tipei, Jeff M. Wright

This paper describes an object-oriented approach to music composition and sound design. The approach unifies the processes of music making and instrument building by using similar logic, objects, and procedures. The composition modules use an abstract representation of musical data, which can be easily mapped onto different synthesis languages or a tradition

R. R. P. Singh, W. E. Pickett, D. W. Hone, D. J. Scalapino

Summary of Quantum Magnetism Conference, Institute for Theoretical Physics, University of California, Santa Barbara, California, August 16-20, 1999.

Clare C. Yu

At low temperatures electron hopping in a three dimensional Coulomb glass produces fluctuations in the single particle density of states and hence in the resistivity. This results in a low frequency resisitivity noise spectrum which goes as (1/f)^(alpha) where alpha is very close to 1. This holds down to extremely low frequencies.

Nikolay V. Dokholyan, Leonid A. Mirny, Eugene I. Shakhnovich

It has been conjectured that evolution exerted pressure to preserve amino acids bearing thermodynamic, kinetic, and functional roles. In this letter we show that the physical requirement to maintain protein stability gives rise to a sequence conservatism pattern that is in remarkable agreement with that found in natural proteins. Based on the physical proper

D. B. Romero, Y. Moritomo, J. F. Mitchell, H. D. Drew

The competition of charge, orbital, and ferromagnetic interactions in layered manganites is investigated by magneto-Raman scattering spectroscopy. We find that the colossal magnetoresistance effect in the layered compounds results from the interplay of the orbital and ferromagnetic double-exchange correlations. Inelastic scattering by charge-order fluctuatio

Roberto Soldati, Alberto Zannoni

The behavior of a Bose-Einstein ideal gas of particles in a three dimensional space in the presence of a uniform field, such as gravity, and of contact interaction, describing the presence of one impurity, is investigated. It is shown that Bose-Einstein condensation can not occur.

Audun Bakk, Johan S. Hoye, Alex Hansen, Kim Sneppen

We refine a protein model that reproduces fundamental aspects of protein thermodynamics. The model exhibits two transitions, hot and cold unfolding. The number of relevant parameters is reduced to three: 1) binding energy of folding relative to the orientational energy of bound water, 2) ratio of degrees of freedom between the folded and unfolded protein cha

A. Priel, I. Kanter

We study the capability to learn and to generate long-range, power-law correlated sequences by a fully connected asymmetric network. The focus is set on the ability of neural networks to extract statistical features from a sequence. We demonstrate that the average power-law behavior is learnable, namely, the sequence generated by the trained network obeys th

A. Priel, I. Kanter

The properties of time series generated by a perceptron with monotonic and non-monotonic transfer function, where the next input vector is determined from past output values, are examined. Analysis of the parameter space reveals the following main finding: a perceptron with a monotonic function can produce fragile chaos only whereas a non-monotonic function

Pi-Gang Luan, Zhen Ye

In this paper we comment the results of ``Statistics of the Lyapunov Exponent in 1D random periodic-on-Average Systems&#34; [Phys. Rev. Lett. {\bf 81}, 5390, 1998].

M. J. W. Dodgson, V. B. Geshkenbein, M. V. Feigel&#39;man, G. Blatter

We consider the thermal softening of crystals due to anharmonicity. Self-consistent methods find a maximum temperature for a stable crystal, which gives an upper bound to the melting temperature. Previous workers have shown that the self-consistent harmonic approximation (SCHA) gives misleading results for the thermal stability of crystals. The reason is tha

M. D. Glinchuk, E. A. Eliseev, V. A. Stephanovich, B. Hilczer

We suggest a random field based model for calculation of physical properties of mixed ferroelectric relaxors. Our model naturally incorporates the different orientations of electric dipoles (related to different solid solution components) as well as the contribution of nonlinear and correlation effects of random field. We calculate the transition temperature

V. Fiorentino, F. Mancini, E. Zasinas, A. F. Barabanov

The p-d model which well describes the CuO_2 planes of the high-Tc superconductors is studied by means of the Composite Operator Method (COM). The relevant quasi-particle excitations are represented by composite operators. As a result of taking into account spin excitations we find a p- like band near the Fermi level. The dispersion of this band gives a Ferm

P. W. Leung

We study the relevance of the staggered-flux phase in the t-J model using a system with two holes on a 32-site lattice with periodic boundary conditions. We find a staggered-flux pattern in the current-current correlation in the lowest energy d-wave state where there is mutual attraction between the holes. This staggered correlation decays faster with distan

Y. Morita, Y. Hatsugai

A single-parameter family of lattice-fermion model is constructed. It is a deformation of the Azbel-Hofstadter problem by a parameter $h={$B%((BDelta}/t$ (quantum parameter). A topological number is attached to each energy band. A duality between the classical limit ($h=+0$) and the quantum limit ($h=1$) is revealed in the energy spectrum and the topological

M. Martinez, P. A. Mello

We extend previous studies on transport through ballistic chaotic cavities with spatial left-right (LR) reflection symmetry to include the presence of direct processes. We first analyze fully LR-symmetric systems in the presence of direct processes and compare the distribution w(T) of the transmission coefficient T with that for an asymmetric cavity with the

Peter J. Klinko, Bruce N. Miller

Important gaps remain in our understanding of the thermodynamics and statistical physics of self-gravitating systems. Using mean field theory, here we investigate the equilibrium properties of several spherically symmetric model systems confined in a finite domain consisting of either point masses, or rotating mass shells of different dimension. We establish

C. J. Hamer

Energy eigenvalues and order parameters are calculated by exact diagonalization for the transverse Ising model on square lattices of up to 6x6 sites. Finite-size scaling is used to estimate the critical parameters of the model, confirming universality with the three-dimensional classical Ising model. Critical amplitudes are also estimated for both the energy

J. D. Naud, Leonid P. Pryadko, S. L. Sondhi

Stacked two dimensional electron systems in transverse magnetic fields exhibit three dimensional fractional quantum Hall phases. We analyze the simplest such phases and find novel bulk properties, e.g., irrational braiding. These phases host ``one and a half&#39;&#39; dimensional surface phases in which motion in one direction is chiral. We offer a general a

Arup Banerjee, Manoj K. Harbola

Performing electronic structure calculations for large systems, such as nanoparticles or metal clusters, via orbital based Hartree-Fock or Kohn-Sham theories is computationaly demanding. To study such systems, therefore, we have taken recourse to the hydrodynaic approach to time-dependent density functonal theory. In this paper we develop variation-perturbat

Megan Donahue, Jennifer Mack, G. Mark Voit, William Sparks

We report new HST NICMOS and WFPC2 imaging of emission-line nebulae in the central galaxies of 3 clusters of galaxies purported to host massive cooling flows, NGC1275, A2597, and PKS0745. The spectral signature of vibrationally- excited molecular hydrogen (VEMH) has been seen in every galaxy searched so far in a cluster cooling flow with an optical emission

Nicole M. Lloyd-Ronning, Vahe&#39; Petrosian

We investigate synchrotron emission models as the source of gamma-ray burst spectra. We show that including the possibility for synchrotron self-absorption, a ``smooth cutoff&#39;&#39; to the electron energy distribution, and an anisotropic distribution for the electron pitch angles produces a whole range of low energy spectral behavior. In addition, we show

Tsvi Piran, Hagai El-Ad, Hugo Martel, Myron Lecar

We introduce a set of four new publicly available N-body simulations, the most recent additions to the Texas P^3M Database. Our models probe the less studied parameter space region of moderate volume (100/h Mpc box) combined with fine mass resolution (~10^12 M_Sol, roughly comparable to a L_* galaxy), making these simulations especially suitable for study of

K. L. Luhman

By combining deep optical imaging and infrared spectroscopy with data from the Two-Micron All-Sky Survey (2MASS) and from previous studies (e.g., Briceno et al.), I have measured the Initial Mass Function (IMF) for a reddening-limited sample in four fields in the Taurus star forming region. This IMF is representative of the young populations within these fie

Roman R. Rafikov

Purely gravitational perturbations are considered in a thin rotating disk composed of several gas and stellar components. The dispersion relation for the axisymmetric density waves propagating through the disk is found and the criterion for the local axisymmetric stability of the whole system is formulated. In the appropriate limit of two-component gas we co

Sean G. Ryan

The lithium abundances of planet-harbouring stars have been compared with those of open clusters and field stars. Young (chromospherically active) and subgiant stars have been eliminated from the comparison because they are at different stages of evolution and Li processing to the planet-harbouring stars, and hence have systematically higher Li abundances. T

R. X. Xu, G. J. Qiao

The Orthogonal Polarization Modes (OPM) have been reported observationally and accepted widely by pulsar researchers. However, no acceptable theory can show the origin of the OPM, which becomes a mystery in pulsar research field. Here a possible way to solve this mystery is presented. We ask a question: Does there exist any real so-called OPM in pulsar radia

Ronald E. Taam, Andrew R. King, Hans Ritter

We reexamine evolutionary channels for the formation of binary millisecond pulsars in order to understand their observed orbital period distribution. The available paths provide a natural division into systems characterized by long orbital periods (> 60 d) and short orbital periods (< 30 d). Systems with initial periods 1 - 2 d ultimately produce low mass He

W. K. Gear, S. J. Lilly, J. A. Stevens, D. L. Clements

We present a high-resolution millimetre interferometric image of the brightest SCUBA-selected galaxy from the Canada-UK deep SCUBA survey (CUDSS). We make a very clear detection at 1.3 mm, but fail to resolve any structure in the source. The interferometric position is within 1.5 arcsec of the SCUBA 850 $μ$m centroid, and also within 1.5 arcsec of a 44 $μ$Jy

P. Cea, G. L. Fogli, L. Tedesco

We investigate the scattering of fermions off domain walls at the electroweak phase transition in presence of a magnetic field. We consider both the bubble wall and the kink domain wall. We derive and solve the Dirac equation for fermions with momentum perpendicular to the walls, and compute the transmission and reflection coefficients. In the case of kink d

G. Fritz Benedict

This article describes astrometric science that can be done with the Hubble Space Telescope Fine Guidance Sensors and presents some recent science results. We outline how these data are modeled, acquired, and calibrated. We next show how the astrometer, FGS 3, works as an interferometer. Finally, we present a guide to the literature that provides additional

Olga K. Silchenko

Central regions of the early-type disk galaxies NGC 524 and NGC 6340 have been investigated with the Multi-Pupil Field Spectrograph at the 6m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. I confirm the existence of chemically distinct stellar nuclei in these galaxies which have been claimed earlier. The metallicity di

F. Nicastro, M. Elvis, F. Fiore, G. Matt

We present photoionization and collisional ionization models, and their application to three important fields: (a) the Warm Absorbers/Emitters in type 1 AGN, (b) the Warm Reflectors in Type 2 AGN, and (c) X-ray absorption of background quasars by intergalactic gas. A number of cases are investigated, and the dependences of the main parameters explored.

Eli Waxman, Abraham Loeb

The shocks produced in the intergalactic medium during large-scale structure formation accelerate a population of highly relativistic electrons which emit synchrotron radiation due to intergalactic magnetic fields. In a previous paper (Loeb & Waxman 2000) we have shown that these electrons cool primarily by inverse-Compton scattering of the microwave backgro

A. N. Taylor, W. E. Ballinger, A. F. Heavens, H. Tadros

We apply a spherical harmonic analysis to the Point Source Redshift Survey (PSCz), to compute the real-space galaxy power spectrum and the degree of redshift distortion caused by peculiar velocities. We employ new parameter eigenvector and hierarchical data compression techniques, allowing a much larger number of harmonic modes to be included, and correspond

Andreas Burkert

The rotational properties of the visible and dark components of low-mass disk galaxies (vrot<=100 km/s) are investigated using the Swaters sample. The rotational parameter lambda&#39;=lambda_DM*(j_d/m_d) is determined, where lambda_DM is the dark halo spin parameter and j_d/m_d is the ratio between the specific angular momentum of the disk and that of the da

L. C. Garcia de Andrade

Riemannian vectorial collineations along with current Killing conservation are shown to lead to tensorial collineations for the energy-stress tensor in general relativity and in Einstein-Cartan Weyssenhoff fluid cosmology.

R. Gispert, G. Lagache, J. L. Puget

The Cosmic Background due to the integrated radiation from galaxies over the whole life of the Universe is reviewed. We find that this background is well constrained by measurements. The total power in the background is in the range 60-93 nW/m2/sr. The data show the existence of a minimum separating the direct stellar radiation from the infrared part due to

K. S. Cheng, C. M. Zhang

Based on the accretion induced magnetic a field decay model, in which a frozen field and an incompressible fluid are assumed, we obtain the following results. (1) An analytic relation between the magnetic field and spin period, if the fastness parameter of the accretion disk is neglected. The evolutionary tracks of accreting neutron stars in the P-B diagram

A. A. Louis, P. G. Bolhuis, J. P. Hansen

We show that the Gaussian core model of particles interacting via a penetrable repulsive Gaussian potential, first considered by Stillinger (J. Chem. Phys. 65, 3968 (1976)), behaves like a weakly correlated ``mean field fluid&#39;&#39; over a surprisingly wide density and temperature range. In the bulk the structure of the fluid phase is accurately described

Philip J. Armitage, Christopher S. Reynolds, James Chiang

We use three dimensional magnetohydrodynamic simulations, in a pseudo-Newtonian potential, to study geometrically thin accretion disc flows crossing the marginally stable circular orbit around black holes. We concentrate on vertically unstratified and isothermal disk models, but also consider a model that includes stratification. In all cases, we find that t

C. Pastorino, Z. Gamba

We analize two anisotropic atom-atom models used to describe the crystalline alpha,beta and gamma phases of S8 crystals, the most stable compound of elemental sulfur in solid phases, at ambient pressure and T<=400 K. The calculations are performed via a series of classical molecular dynamics (MD) simulations, with flexible molecular models and using a consta

E. Elizalde, E. J. Ferrer, V. de la Incera

The Ritus&#39; $E_{p}$ eigenfunction method is extended to the case of spin-1 charged particles in a constant electromagnetic field and used to calculate the one-loop neutrino self-energy in the presence of a strong magnetic field.From the obtained self-energy, the neutrino dispersion relation and index of refraction in the magnetized vacuum are determined w