February 2001 arXiv papers — page 13

Tarun Kanti Ghosh, Subhasis Sinha

We consider quadrupole excitations of quasi-two dimensional interacting quantum gas in an anisotropic harmonic oscillator potential at zero temperature. Using the time-dependent variational approach, we calculate a few low-lying collective excitation frequencies of a two dimensional anisotropic Bose gas. Within the energy weighted sum-rule approach, we deriv

M. Marsili, D. Challet

We discuss in detail the derivation of stochastic differential equations for the continuum time limit of the Minority Game. We show that all properties of the Minority Game can be understood by a careful theoretical analysis of such equations. In particular, i) we confirm that the stationary state properties are given by the ground state configurations of a

Anupam Mazumdar, A. Pérez-Lorenzana

Large extra dimensional theories attempt to solve the hierarchy problem by assuming that the fundamental scale of the theory is at the electroweak scale. This requires the size of the extra dimensions to be stabilized at a scale which is determined by the effective four dimensional Planck mass and the number of extra dimensions. In this paper we concentrate

Soumitra SenGupta, Aninda Sinha

The helicity flip of a spin-1/2 Dirac fermion interacting with a torsion- field endowed with a pseudo-tensorial extension is analysed. Taking the torsion to be represented by a Kalb-Ramond field, we show that there is a finite amplitude for helicity flip for massive fermions. The lowest order contribution is proportional to the pseudo-tensor term.

Cosima Schuster, Rudolf A. Roemer, Michael Schreiber

We study the influence of many-particle interaction in a system which, in the single particle case, exhibits a metal-insulator transition induced by a finite amount of onsite pontential fluctuations. Thereby, we consider the problem of interacting particles in the one-dimensional quasiperiodic Aubry-Andre chain. We employ the density-matrix renormalization s

Goutam Tripathy, Andrea Rocco, Jaume Casademunt, Wim van Saarloos

It has recently been proposed that fluctuating ``pulled'' fronts propagating into an unstable state should not be in the standard KPZ universality class for rough interface growth. We introduce an effective field equation for this class of problems, and show on the basis of it that noisy pulled fronts in {\em d+1} bulk dimensions should be in the uni

Mayumi Aoki, Gi-Chol Cho, Makiko Nagashima, Noriyuki Oshimo

We calculate the contributions of the vector-like quark model to $\BsBs$ mixing, taking into account the constraints from the decay $B\to X_sγ$. In this model the neutral bosons mediate flavor-changing interactions at the tree level. However, $\BsBs$ mixing is dominated by contributions from the box diagrams with the top quark and the extra up-type quark. In

W. de Boer, M. Huber, A. V. Gladyshev, D. I. Kazakov

New NLO b->sgamma calculations have become available using resummed radiative corrections. Using these calculations we perform a global fit of the supergravity inspired constrained minimal supersymmetric model (CMSSM). We find that the resummed calculations show similar constraints as the LO calculations, namely that only with a relatively heavy supersymmetr

P. Ghose, A. S. Majumdar, S. Guha, J. Sau

The first examples of Bohmian trajectories for photons have been worked out for simple situations, using the Kemmer-Duffin-Harishchandra formalism.

Andrei V. Frolov

Anisotropic generalization of Randall and Sundrum brane-world model is considered. A new class of exact solutions for brane and bulk geometry is found; it is related to anisotropic Kasner solution. In view of this, the old question of isotropy of initial conditions in cosmology rises once again in the brane-world context.

Arie Bodek, Ulrich Baur

Recent analyses of precision low energy electroweak data indicate that the deviation from the Standard Model predictions of the measurement of atomic parity violation (2.3σ), the effective number of massless neutrinos (2σ), and A_b (2.7σ) could be better described if the existence of an extra Z' neutral gauge boson is assumed. We investigate the implicat

M. Franca Santos, E. Solano, R. L. de Matos Filho

We propose a scheme for producing large Fock states in Cavity QED via the implementation of a highly selective atom-field interaction. It is based on Raman excitation of a three-level atom by a classical field and a quantized field mode. Selectivity appears when one tunes to resonance a specific transition inside a chosen atom-field subspace, while other tra

Xiaoguang Wang

We study the thermal entanglement in the two-qubit anisotropic XXZ model and the Heisenberg model with Dzyaloshinski-Moriya (DM) interactions. The DM interaction is another kind of anisotropic antisymmetric exchange interaction. The effects of these two kinds of anisotropies on the thermal entanglement are studied in detail for both the antiferromagnetic and

A. J. Baltz

The delta function gauge of the electromagnetic potential allows semiclassical formulas to be obtained for the probability of exciting a single electron out of the ground state in an ultrarelativistic heavy ion reaction. Exact formulas have been obtained in the limits of zero impact parameter and large, perturbative, impact parameter. The perturbative impact

Dimitri Gilis, Serge Massar, Nicolas Cerf, Marianne Rooman

How robust is the natural genetic code with respect to mistranslation errors? It has long been known that the genetic code is very efficient in limiting the effect of point mutation. A misread codon will commonly code either for the same amino acid or for a similar one in terms of its biochemical properties, so the structure and function of the coded protein

Sujay Chattopadhyay, William A. Kanner, Jayprokas Chakrabarti

The evolution in coding DNA sequences brings new flexibility and freedom to the codon words, even as the underlying nucleotides get significantly ordered. These curious contra-rules of gene organisation are observed from the distribution of words and the second moments of the nucleotide letters. These statistical data give us the physics behind the classific

A. I. Titov, B. Kampfer, B. L. Reznik

Results of a combined analysis are presented for the production of $ω$ and $ϕ$ mesons in $πN$ reactions in the near-threshold region using throughoutly a conventional ''non-strange'' dynamics based on such processes which are allowed by the non-ideal $ω-ϕ$ mixing. We show that strong interferences of the $t$ (meson exchange) and $s$ and $u$ (

Denes Molnar, Miklos Gyulassy

Differential elliptic flow out to p_t ~ 5 GeV/c is calculated using the MPC elastic parton cascade model for Au+Au at Ecm ~ 130A GeV. The results are compared to recent STAR/RHIC elliptic flow data. An elliptic flow pattern comparable to the data seems to require initial parton densities at least twice higher than predicted by the HIJING model. Elliptic flow

R. Anni

A simple recipe for revealing classical-like contributions in optical potential cross sections is proposed. The recipe is based on the fact that the classical-like properties are not expected to depend on the actual value of $\hbar$. This allows us to identify the classical-like characteristics of an optical potential cross section by simply repeating the ca

T. J. Stocki, D. F. Measday, E. Gete, M. A. Saliba

The hyperfine (hf) transition rates for muonic atoms have been re-measured for select light nuclei, using neutron detectors to evaluate the time dependence of muon capture. For $^{19}$F $Λ$$_{h}$ = 5.6 (2) $μ$s$^{-1}$ for the hf transition rate, a value which is considerably more accurate than previous measurements. Results are also reported for Na, Al, P, C

Aline Bonami, Bruno Demange, Philippe Jaming

We extend an uncertainty principle due to Beurling into a characterization of Hermite functions. More precisely, all functions $f$ on $\R^d$ which may be written as $P(x)\exp (Ax,x)$, with $A$ a real symmetric definite positive matrix, are characterized by integrability conditions on the product $f(x)\hat{f}(y)$. We also give the best constant in uncertainty

Harold Steinacker

This is a short summary of the paper hep-th/9910037. An algebra of functions on q-deformed Anti-de Sitter space AdS_q^D is defined for q a root of unity, which is covariant under U_q(so(2,D-1)). The scalar fields have an intrinsic high- energy cutoff, and arise most naturally on products of the quantum AdS space with a classical sphere. Hilbert spaces of sca

Sergei Buyalo, Viktor Schroeder

We introduce a new quasi-isometry invariant $\subcorank X$ of a metric space $X$ called {\it subexponential corank}. A metric space $X$ has subexponential corank $k$ if roughly speaking there exists a continuous map $g:X\to T$ such that for each $t\in T$ the set $g^{-1}(t)$ has subexponential growth rate in $X$ and the topological dimension $\dim T=k$ is min

Thomas Foertsch, Viktor Schroeder

We introduce a notion of the Euclidean- and the Minkowski rank for arbitrary metric spaces and we study their behaviour with respect to products. We show that the Minkowski rank is additive with respect to metric products, while additivity of the Euclidean rank only holds under additional assumptions, e.g. for Riemannian manifolds. We also study products wit

A. Berkovich, A. Riese

In this paper we give a computer proof of a new polynomial identity, which extends a recent result of Alladi and the first author. In addition, we provide computer proofs for new finite analogs of Jacobi and Euler formulas. All computer proofs are done with the aid of the new computer algebra package qMultiSum developed by the second author. qMultiSum implem

Richard Randell

Through the study of Morse theory on the associated Milnor fiber, we show that complex hyperplane arrangement complements are minimal. That is, the complement of a complex hyperplane arrangement has the homotopy type of a CW complex in which the number of p-cells equals the p-th betti number.

Christophe Kapoudjian

We build actions of Thompson group V (related to the Cantor set) and of the so-called "spheromorphism" group of Neretin, on "towers" of moduli spaces of genus zero real stable curves. The latter consist of inductive limits of spaces which are the real parts of the Grothendieck-Knudsen compactification of the usual moduli spaces of punctured R

Alexander Schmitt

To every oriented tree, we associate a moduli problem for sheaves over a projective manifold $X$. We define the corresponding notion of semistability and establish the existence of moduli spaces. Applying the results to the tree *->*, we obtain a GIT construction for the moduli space of holomorphic triples of Bradlow and Garcia-Prada.

T. Banks, W. Fischler

We discuss the construction of the analog of an S-matrix for space-times that begin with a Big-Bang and asymptote to an FRW universe with nonnegative cosmological constant. When the cosmological constant is positive there are many such S-matrices, related mathematically by gauge transformations and physically by an analog of the principle of black hole compl

Jeffrey A. Harvey

These lectures provide an introduction to noncommutative geometry and its origins in quantum mechanics and to the construction of solitons in noncommutative field theory. These ideas are applied to the construction of D-branes as solitons of the tachyon field in noncommutative open string theory. A brief discussion is given of the K-theory classification of

Laurent Baulieu, Marc Bellon

The progress brought to the study of chiral fermions and gauge theories by quantization methods with a bulk time suggests their usefulness in supersymmetric theories. Using superspace methods, we show how an explicitly supersymmetric version of such quantization methods may be given.

Harold Steinacker

These notes are a short review of the q-deformed fuzzy sphere S^2_{q,N}, which is a ``finite'' noncommutative 2-sphere covariant under the quantum group U_q(su(2)). We discuss its real structure, differential calculus and integration for both real q and q a phase, and show how actions for Yang-Mills and Chern- Simons-like gauge theories arise natural

Hang Bae Kim

There are many interesting issues in the brane world with a large/warped extra dimension. We focus on the cosmological aspects. We review the cosmological solutions of the brane world and how the conventional four-dimensional cosmology is recovered by including the effect of stabilization. Its implications on the mass hierarchy and the cosmological constant

Debrupa Chakraverty, Debajyoti Choudhury, Anindya Datta

The recent result from the E821 experiment at BNL on the anomalous magnetic moment of the muon shows a distinct discrepancy with the Standard Model predictions. We calculate the additional correction that the anomalous magnetic moment receives in a model with scalar leptoquarks. We find that such models can account for the deviation from the SM value even fo

S. I. Bityukov, N. V. Krasnikov

We investigate squark and gluino pair production at LHC (CMS) with subsequent decays into quarks, leptons and LSP in models with effective supersymmetry where third generation of squarks is relatively light while the first two generations of squarks are heavy. We consider the general case of nonuniversal gaugino masses. Visibility of signal by an excess over

A. V. Kotikov

We discuss a progress in calculation of Feynman integrals which has been done with help of the Differential Equation Method and demonstrate the results for a class of two-point two-loop diagrams.

A. V. Kotikov

We discuss a progress in calculation of Feynman integrals which has been done with help of the Gegenbauer Polynomial Technique and demonstrate the results for most complicated parts of O(1/N^3) contributions to critical exponents of ϕ^4 -theory, for any spacetime dimensionality D.

B. C. Allanach, A. J. Barr, L. Drage, C. G. Lester

The measurement of sparticle masses in the Minimal Supersymmetric Standard Model at the LHC is analysed, in the scenario where the lightest neutralino decays into three quarks. Such decays, occurring through the baryon-number violating coupling lambda"\_ijk, pose a severe challenge to the capability of the LHC detectors since the final state has no missi

M. Carena, A. Delgado, J. Lykken, S. Pokorski

We analyze the propagation of a scalar field in multidimensional theories which include kinetic corrections in the brane, as a prototype for gravitational interactions in a four dimensional brane located in a (nearly) flat extra dimensional bulk. We regularize the theory by introducing an infrared cutoff given by the size of the extra dimensions and a physic

Stanislav Dubnicka, Anna Zuzana Dubnickova, Peter Weisenpacher

A behaviour of strange nucleon form factors is predicted by means of Jaffe's idea about the relations of $ω$ and $ϕ$ vector-meson coupling constant ratios. Its application to a specific eight-resonance unitary and analytic model of nucleon electromagnetic structure, describing also the time-like nucleon electromagnetic form factor data, explains the posi

Marco Battaglia

Recent analyses of the LEP and Upsilon(4S) data have better outlined the picture of semileptonic B decays. Results on inclusive and exclusive decay branching fractions and on the extraction of the |Vub| and |Vcb| elements of the CKM mixing matrix are discussed, together with some of the still open questions and the sources of model systematics.

H. E. Haber, M. J. Herrero, H. E. Logan, S. Penaranda

We study the supersymmetric (SUSY) QCD radiative corrections, at the one-loop level, to $h^0$, $H^{\pm}$ and t quark decays, in the context of the Minimal Supersymmetric Standard Model (MSSM) and in the decoupling limit. The decoupling behaviour of the various MSSM sectors is analyzed in some special cases, where some or all of the SUSY mass parameters becom

C. S. Kim, Yeong Gyun Kim, Cai-Dian Lu

We investigate the angular distributions of the rare B decay, $B \to K^* (\to K π) \ell^+ \ell^-$, in general supersymmetric extensions of the standard model. We consider the new physics contributions from the operators $O_{7,8,9,10}$ in small invariant mass region of lepton pair. We show that the azimuthal angle distribution of the decay can tell us the new

Osamu Yasuda

Various solutions of the atmospheric neutrino data are reviewed. Apart from orthodox two flavor $ν_μ\leftrightarrowν_τ$ oscillations and three flavor oscillations, there are still possibilities, such as four flavor oscillations with the (2+2)- and (3+1)- schemes, a neutrino decay scenario and decoherence, which give a good fit to the data.

Osamu Yasuda

Recent status of neutrino oscillation phenomenology with four neutrinos is reviewed. It is emphasized that the so-called (2+2)-scheme as well as the (3+1)-scheme are still consistent with the recent solar and atmospheric neutrino data.

Claudio Coriano

Using a recursive algorithm to solve the renormalization group equations of N=1 QCD (DGLAP), we describe the most general supersymmetric evolution of the parton distributions. The analysis involves the regular DGLAP evolution, a partial supersymmetric intermediate evolution and a final supersymmetric evolution combined at various matching scales. We use a mo

Hiroyuki Kawamura

In processes at the energy much higher than electroweak scale, weak boson mass act as the infrared cutoff in weak boson loops and resulting Sudakov log corrections can be as large as 10%. Since electroweak theory is off-diagonally broken gauge theory, its IR structure is quite different from that of QCD. We briefly review recent developments on electroweak S

Dirk Lehmann, Gary Prezeau

A Lorentz-covariant regularization scheme for effective field theories with an arbitrary number of propagating heavy and light particles is given. This regularization scheme leaves the low-energy analytic structure of Greens functions intact and preserves all the symmetries of the underlying Lagrangian. The power divergences of regularized loop integrals are

Tobias Hurth, Choong Sun Kim, Claire Shepherd-Themistocleous, Fergus Wilson

We review theoretical and experimental results on CP violation summarizing the discussions in the working group on CP violation at the UK phenomenology workshop 2000 in Durham.

Alejandro Cabo, Marcos Rigol

A recently proposed modified perturbation expansion for QCD is employed to evaluate the quark self-energies. Results of the order of 1/3 of the nucleon mass are obtained for the effective masses of the up and down quarks in a first approximation. Also, the predicted flavor dependence of the calculated quarks masses turns out to be the appropriate to well rep

Jian Dai, Xing-Chang Song

A generalized anti-hermitian staggered Dirac operator is formulated. Its relation with noncommutative geometry is briefly reviewed. Once this anti-hermitian operator is modified to be ``$γ^5$-hermitian'', it will provide a new solution to Ginsparg-Wilson relation, basing on an abstract algebraic analysis of Neuberger's overlap construction and a

Howard S. Budd

We present a description of the CMS central hadron calorimeter. We describe the production of the 1996 CMS hadron testbeam module. We show the results of the quality control tests of the testbeam module. We present some results of the 1995 CMS hadron testbeam.

Robert Geroch, Gabriel Nagy, Oscar Reula

It is well-known that the equations for a simple fluid can be cast into what is called their Lagrange formulation. We introduce a notion of a generalized Lagrange formulation, which is applicable to a wide variety of systems of partial differential equations. These include numerous systems of physical interest, in particular, those for various material media

J. G. Pereira, T. Vargas, C. M. Zhang

In the context of the teleparallel equivalent of general relativity, we obtain the tetrad and the torsion fields of the stationary axisymmetric Kerr spacetime. It is shown that, in the slow rotation and weak field approximations, the axial-vector torsion plays the role of the gravitomagnetic component of the gravitational field, and is thus the responsible f

Martin Bojowald

It is shown that the cosmological singularity in isotropic minisuperspaces is naturally removed by quantum geometry. Already at the kinematical level, this is indicated by the fact that the inverse scale factor is represented by a bounded operator even though the classical quantity diverges at the initial singularity. The full demonstation comes from an anal

V. Bozza, S. Capozziello, G. Iovane, G. Scarpetta

We give the formulation of the gravitational lensing theory in the strong field limit for a Schwarzschild black hole as a counterpart to the weak field approach. It is possible to expand the full black hole lens equation to work a simple analytical theory that describes at a high accuracy degree the physics in the strong field limit. In this way, we derive c

Amos Ori

We construct a dilatonic two-dimensional model of a charged black hole. The classical solution is a static charged black hole, characterized by two parameters, $m$ and $q$, representing the black hole's mass and charge. Then we study the semiclassical effects, and calculate the evaporation rate of both $m$ and $q$, as a function of these two quantities.

Spiros Cotsakis, Peter Leach

An introductory guide to mathematical cosmology is given focusing on the issue of the genericity of various important results which have been obtained during the last thirty or so years. Some of the unsolved problems along with certain new and potentially powerful methods which may be used for future progress are also given from a unified perspective.

Pietro Menotti

A summary is given of some results and perspectives of the hamiltonian ADM approach to 2+1 dimensional gravity. After recalling the classical results for closed universes in absence of matter we go over the the case in which matter is present in the form of point spinless particles. Here the maximally slicing gauge proves most effective by relating 2+1 dimen

Uwe R. Fischer, Grigori E. Volovik

We give an account of the physical behaviour of a quasiparticle horizon due to non-Lorentz invariant modifications of the effective space-time experienced by the quasiparticles (``matter'') for high momenta. By introducing a ``relativistic'' conserved energy-momentum tensor, we derive quasi-equilibrium states of the fluid across the ``Landau&

J. S. Slusky, N. Rogado, K. A. Regan, M. A. Hayward

The basic magnetic and electronic properties of most binary compounds have been well known for decades. Therefore the recent announcement of superconductivity at 39 K in the simple binary ceramic compound MgB2 is surprising. This compound, available from common chemical suppliers, and used as a starting material for chemical metathesis reactions, has been kn

A. Ossipov, M. Weiss, Tsampikos Kottos, T. Geisel

We study the time evolution of the survival probability $P(t)$ in open one-dimensional quasiperiodic tight-binding samples of size $L$, at critical conditions. We show that it decays algebraically as $P(t)\sim t^{-α}$ up to times $t^*\sim L^γ$, where $α= 1-D_0^E$, $γ=1/D_0^E$ and $D_0^E$ is the fractal dimension of the spectrum of the closed system. We verif

A. E. Allahverdyan, R. Balian, Th. M. Nieuwenhuizen

We investigate a mean-field approach to a quantum brownian particle interacting with a quantum thermal bath at temperature $T$, and subjected to a non-linear potential. An exact, partially classical description of quantum brownian motion is proposed, which uses negative probabilities in its intermediate steps. It is shown that properties of the quantum parti

L. Bellaiche, A. Garcia, David Vanderbilt

A first-principles-derived approach is used to study structural, piezoelectric and dielectric properties of Pb(Zr_{1-x}Ti_{x})O_{3} (PZT) solid solutions near the morphotropic phase boundary at low temperature. Three ferroelectric phases are found to exist: a tetragonal phase for larger x compositions, a rhombohedral phase for smaller x compositions, and the

Richard P. Sear

Starting from a protein solution which is metastable with respect to the crystalline phase, the effect of adding semidilute non-adsorbing polymer is considered. It is found to increase the chemical potential of the protein by a few tenths of kT, which may be enough to lower the barrier to nucleation of the crystalline phase by enough to allow crystallisation

M. Ya. Amusia, V. R. Shaginyan

It is argued that the superconducting and pseudogaps represent different coexisting phenomena, and this observation speaks against the precursor-superconductivity scenario of the pseudogap; see, V.M. Krasnov et al., Phys. Rev. Lett. 84, 5860 (2000). We present brief comments showing that the experimental facts of this paper do not contradict to the observati

Federico Becca, Sandro Sorella

We present different numerical calculations based on variational quantum Monte Carlo simulations supporting a ferromagnetic ground-state for finite and small hole densities in the two-dimensional infinite-$U$ Hubbard model. Moreover, by studying the energies of different total spin sectors, these calculations strongly suggest that the paramagnetic phase is u

M. Picco, F. Ricci-Tersenghi, F. Ritort

We present a detailed study of the scaling behavior of correlations functions and AC susceptibility relaxations in the aging regime in three dimensional spin glasses. The agreement between simulations and experiments is excellent confirming the validity of the full aging scenario with logarithmic corrections which manifests as weak sub-aging effects.

A. V. Razumov, Yu. G. Stroganov

The finite XXZ Heisenberg spin chain with twisted boundary conditions was considered. For the case of even number of sites $N$, anisotropy parameter -1/2 and twisting angle $2 π/3$ the Hamiltonian of the system possesses an eigenvalue $-3N/2$. The explicit form of the corresponding eigenvector was found for $N \le 12$. Conjecturing that this vector is the gr

A. Awazu

Liquid-solid phase transition and the change of the frictional force of a system with two hard spheres in a two-dimensional rectangular box are discussed. Under controlling the pressure or the supply of energy from the wall, the solid like state, the solid-liquid temporal coexistence state, and the liquid like state are alternatively observed. The frictional

G. Daskalakis, G. K. Savvidy

We consider the model of random surfaces with extrinsic curvature term embedded into 3d Euclidean lattice $Z^3$. On a 3d Euclidean lattice it has equivalent representation in terms of transfer matrix $K(Q_{i},Q_{f})$, which describes the propagation of loops $Q$. We study the spectrum of the transfer matrix $K(Q_{i},Q_{f})$ on finite dimensional lattices. Th

J. Pando, L. Feng, L. Z. Fang

We investigate the weakly non-linear evolution of cosmic gravitational clustering in phase space by looking at the Zel'dovich solution in the discrete wavelet transform (DWT) representation. We show that if the initial perturbations are Gaussian, the relation between the evolved DWT mode and the initial perturbations in the weakly non-linear regime is qu

Ceri E. Ashton, Geraint F. Lewis

Recent studies have demonstrated that detailed monitoring of gravitational microlensing events can reveal the presence of planets orbiting the microlensed source stars. With the potential of probing planets in the Galactic Bulge and Magellanic Clouds, such detections greatly increase the volume over which planets can be found. This paper expands on these ori

P. Meszaros

Gamma-ray bursts (GRB) are sudden, intense flashes of gamma-rays which, for a few blinding seconds, light up in an otherwise fairly dark gamma-ray sky. They are detected at the rate of about once a day, and while they are on, they outshine every other gamma-ray source in the sky, including the sun. Major advances have been made in the last three or four year

C. L. Gerardy, R. A. Fesen

Near-infrared spectra (0.95 - 2.4 micron) of the Cassiopeia A and Kepler supernova remnants (SNRs) are presented. Low-dispersion (R = 700) spectra were obtained for five bright fast-moving ejecta knots (FMKs) at two locations on the main shell and for three bright circumstellar knots (QSFs) near the southwest rim of Cas A. The main shell FMKs in Cas A exhibi

Paola Marigo, Leo Girardi, Cesare Chiosi, Peter R. Wood

We present extensive evolutionary models of stars with initial zero-metallicity, covering a large range of initial masses (i.e. 0.7 <= M <= 100 Msun). Calculations are carried out at constant mass, with updated input physics, and applying an overshooting scheme to convective boundaries. The nuclear network includes all the important reactions of the p-p chai

Fausto Vagnetti, Dario Trevese

Brightness variability of QSOs is associated with variations of the spectral energy distribution in the optical-UV range. The observed change of the spectral shape depends on the contribution of the host galaxy. Simulations, taking into account luminosities and spectra expected for the host galaxies, are compared with the observed spectral variability of a c

Thorsten Naab, Andreas Burkert

Collisionless N-body simulations of merging disk-galaxies with mass ratios ($η$) of 1:1, 2:1, 3:1, and 4:1 have been performed using direct summation with the special purpose hardware GRAPE. The simulations are used to examine whether the formation of elliptical galaxies can be explained in the context of the merger scenario. The photometric, kinematical and

S. Bogovalov, K. Tsinganos

Recent numerical simulations and analytical models of magnetically collimated plasma outflows from a uniformly rotating central gravitating object and/or a Keplerian accretion disk have shown that relatively low mass and magnetic fluxes reside in the produced jet. Observations however indicate that in some cases, as in jets of YSO&#39;s, the collimated outfl

W. Bednarek

We consider the propagation of very high energy (VHE) gamma-rays in the radiation field of the massive star of binary system Cen X-3. VHE gamma-rays or electrons, injected by the compact object close to the surface of a massive companion, develop inverse Compton pair (ICS) cascades. Based on the Monte Carlo simulations, we obtain the fraction of secondary ca

T. Venturi, S. Bardelli, G. Zambelli, R. Morganti

We report and discuss the results of a 22 cm radio survey carried out with the Australia Telescope Compact Array (ATCA) covering the A3528 complex, a chain formed by the merging ACO clusters A3528-A3530-A3532, located in the central region of the Shapley Concentration. Simultaneous 13 cm observations are also presented. Our final catalogue includes a total o

Chiaki Kobayashi, Ken&#39;ichi Nomoto, Takuji Tsujimoto

Adopting a single degenerate scenario for Type Ia supernova progenitors with the metallicity effect, we make a prediction of the cosmic supernova rate history as a composite of the supernova rates in spiral and elliptical galaxies, and compare with the recent observational data up to z ~ 0.55.

Thorsten Naab, Andreas Burkert

We performed N-body/SPH simulations of merging gas rich disk-galaxies with a mass ratio of 3:1. A stellar disk and bulge component and a dark halo is realized with collisionless particles, the gas is simulated using SPH particles. In this paper we focus on the gas dynamics in mergers and its influence on the structure of the final merger remnant, neglecting

G. I. Ogilvie

A new theory of eccentric accretion discs is presented. Starting from the basic fluid-dynamical equations in three dimensions, I derive the fundamental set of one-dimensional equations that describe how the mass, angular momentum and eccentricity vector of a thin disc evolve as a result of internal stresses and external forcing. The analysis is asymptoticall

S. Wellstein, N. Langer, H. Braun

We present evolutionary calculations for 74 close binaries systems with initial primary masses in the range 12...25 M_sun, and initial secondary masses between 6 and 24 M_sun. The initial periods were chosen such that mass overflow starts during the core hydrogen burning phase of the primary (Case A), or shortly thereafter (Case B). We assume conservative ev

C. Gallart, D. Martinez-Delgado, M. A. Gomez-Flechoso, Mario Mateo

We present the first radial velocity measurement of the stellar component of the Local Group dwarf galaxy Phoenix, using FORS1 at the VLT UT1 (ANTU) telescope. From the spectra of 31 RGB stars, we derive an heliocentric optical radial velocity of Phoenix Vo=-52 +/- 6 \kms. On the basis of this velocity, and taking into account the results of a series of semi

Mareki Honma

In this paper we investigate the properties of astrometric microlensing of distant radio sources (QSOs and radio galaxies) due to MACHOs, and discuss their implications for VERA (VLBI Exploration of Radio Astrometry). First we show that in case of astrometric microlensing of distant sources, the event duration is only a function of the lens mass and tangenti

D. V. Bisikalo, A. A. Boyarchuk, A. A. Kilpio, O. A. Kuznetsov

The results of three-dimensional numerical simulations of mass transfer in semidetached binaries after mass transfer termination is presented and the structure of residual accretion disk was investigated. It was shown that after the mass transfer termination the quasi-elliptic accretion disk becomes circular. It was also shown that the cessation of mass tran

Peter G. Tuthill, John D. Monnier, William C. Danchi

A star forms when a cloud of dust and gas collapses. It is generally believed that this collapse first produces a flattened rotating disk, through which matter is fed onto the embryonic star at the center of the disk. When the temperature and density at the center of the star pass a critical threshold, thermonuclear fusion begins. The remaining disk, which c

A. C. Calder, B. Fryxell, R. Rosner, L. J. Dursi

We present direct numerical simulations of mixing at Rayleigh-Taylor unstable interfaces performed with the FLASH code, developed at the ASCI/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago. We present initial results of single-mode studies in two and three dimensions. Our results indicate that three-dimensional instabil

Sungsoo S. Kim, Mark Morris

Star formation in the inner few hundred pc of the Galactic bulge occurs in a flattened molecular layer called the central molecular zone (CMZ). Serabyn & Morris (1996) suggest that the star formation in the CMZ has been sustained for the lifetime of the Galaxy, and that the resulting agglomeration of stars formed in the CMZ has resulted in the prominent r^-2

V. La Parola, G. Fabbiano, D. W. Kim, G. Peres

We have analysed the spectra and the variability of individual X-ray sources in the M-81 field using data from the available ROSAT-PSPC and ROSAT-HRI observations of this nearby spiral galaxy. Here we present the results on the second brightest source in the field (X-9 - Fabbiano, 1988 ApJ 325 544), whose identification and interpretation is still unclear. O

V. La Parola, G. Fabbiano, D. W. Kim, G. Peres

We analyzed the spectral and temporal features of X-ray sources in M81 using data from the relevant ROSAT-PSPC/HRI observations. We discuss the main features of the point-like nucleus and of the second brightest source in the field (X-9), whose identification is still unclear.

Charles B. Leffert

The current big-bang cosmological model requires re-introduction of Einstein&#39;s &#34;regretted&#34; old cosmological constant to fit the astronomical measurements of supernova Ia magnitude versus redshift. The physical basis of the cosmological constant and the resulting acceleration of the universe are not supported by any other physical evidence and som

Utpal Chattopadhyay, Pran Nath

We analyze the implications of the new physics effect seen in the $g-2$ Brookhaven measurement and show that if the effect arises from supersymmetry, then the sign of the Higgs mixing parameter $μ$ is determined to be positive in the standard sign convention. Further, analyses within the minimal supergravity model show that the Brookhaven result leads to upp

Jennifer Adams, Bevan Cresswell, Richard Easther

We use a numerical code to compute the density perturbations generated during an inflationary epoch which includes a spontaneous symmetry breaking phase transition. A sharp step in the inflaton potential generates $k$ dependent oscillations in the spectrum of primordial density perturbations. The amplitude and extent in wavenumber of these oscillations depen

Howard Baer, Csaba Balazs, Michal Brhlik, Pedro Mercadante

A promising way to reconcile naturalness with a decoupling solution to the SUSY flavor and CP problems is suggested by models with a radiatively driven inverted mass hierarchy (RIMH). The RIMH models arise naturally within the context of SUSY SO(10) grand unified theories. In their original form, RIMH models suffer from two problems: 1.) obtaining the radiat

Rafael Ferraro, Daniel M. Sforza

The Becci-Rouet-Stora-Tyutin (BRST) operator quantization of a finite-dimensional gauge system featuring two quadratic super Hamiltonian and m linear supermomentum constraints is studied as a model for quantizing generally covariant gauge theories. The proposed model ``completely&#39;&#39; mimics the constraint algebra of General Relativity. The Dirac constr

V. B. Mandelzweig, F. Tabakin

The general conditions under which the quadratic, uniform and monotonic convergence in the quasilinearization method of solving nonlinear ordinary differential equations could be proved are formulated and elaborated. The generalization of the proof to partial differential equations is straight forward. The method, whose mathematical basis in physics was disc

Gabino Rubio-Bollinger, Hermann Suderow, Sebastian Vieira

We report on tunneling spectroscopy experiments in small grains of the new binary intermetallic superconductor MgB2. Experiments have been performed at 2.5 K using a low temperature scanning tunneling microscope. Good fit to the BCS model is obtained, with a gap value of 2 meV. In the framework of this model, this value should correspond to a surface critica