June 1999 arXiv papers — page 5

S. Tsujikawa, K. Maeda, T. Torii

In higher-curvature inflation models ($R+α_n R^n$), we study a parametric preheating of a scalar field $χ$ coupled non-minimally to a spacetime curvature $R$ ($ξR χ^2$). In the case of $R^2$-inflation model, efficient preheating becomes possible for rather small values of $ξ$, i.e. $|ξ|< several. Although the maximal fluctuation $\sqrt{< χ^2 >}_{max} \approx

O. Utyuzh, G. Wilk, Z. Wlodarczyk

We investigate the effect of nonextensive statistics as applied to the chemical fluctuations in high-energy nuclear collisions discussed recently using the event-by-event analysis of data. It turns out that very minuite nonextensitivity changes drastically the expected experimental output for the fluctuation measure. This results is in agreement with similar

Jun-ichiro Kishine, Kenji Yonemitsu

We have studied spin density wave (SDW) phase transitions in dimerized quarter-filled Hubbard chains weakly coupled via interchain one-particle hopping, $t_{b0}$. It is shown that there exists a critical value of $t_{b0}$, $t_{b}^\ast$, between the incoherent metal regime ($t_{b0}<t_{b}^\ast$) and the Fermi liquid regime ($t_{b0}>t_{b}^\ast$) in the metallic

Y. F. Huang, Z. G. Dai, T. Lu

Conventional dynamic model of gamma-ray burst remnants is found to be incorrect for adiabatic blastwaves during the non-relativistic phase. A new model is derived, which is shown to be correct for both radiative and adiabatic blastwaves during both ultra-relativistic and non-relativistic phase. Our model also takes the evolution of the radiative efficiency i

K. Kajantie, M. Laine, T. Neuhaus, A. Rajantie

We study with lattice Monte Carlo simulations the interactions and macroscopic behaviour of a large number of vortices in the 3-dimensional U(1) gauge+Higgs field theory, in an external magnetic field. We determine non-perturbatively the (attractive or repelling) interaction energy between two or more vortices, as well as the critical field strength H_c, the

Eyvind Aker, Knut Jorgen Maloy, Alex Hansen

We investigate the stabilization mechanisms due to viscous forces in the invasion front during drainage displacement in two-dimensional porous media using a network simulator. We find that in horizontal displacement the capillary pressure difference between two different points along the front varies almost linearly as function of height separation in the di

Eyvind Aker, Knut Jorgen Maloy, Alex Hansen

We investigate the stabilization mechanisms of the invasion front in two-dimensional drainage displacement in porous media by using a network simulator. We focus on the process when the front stabilizes due to the viscous forces in the liquids. We find that the capillary pressure difference between two different points along the front varies almost linearly

D. B. Leinweber, A. W. Thomas, K. Tsushima, S. V. Wright

Consideration of the analytic properties of pion-induced baryon self-energies leads to new functional forms for the extrapolation of light baryon masses. These functional forms reproduce the leading non-analytic behavior of chiral perturbation theory, the correct non-analytic behavior at the $N π$ threshold and the appropriate heavy-quark limit. They involve

Y. M. Cho, D. G. Pak

We present a strong evidence for the magnetic confinement in QCD by demonstrating that the one loop effective action of SU(2) QCD induces a dynamical symmetry breaking thorugh the monopole condensation, which could induce the dual Meissner effect and guarantee the confinement of color in the non-Abelian gauge theory. The result is obtained by separating the

Neil J. Cornish, David N. Spergel

The cosmic microwave background radiation allows us to measure both the geometry and topology of the universe. It has been argued that the COBE-DMR data already rule out models that are multiply connected on scales smaller than the particle horizon. Here we show the opposite is true: compact (small) hyperbolic universes are favoured over their infinite count

Dong Lai, Peter Goldreich

When a self-gravitating spherical gas cloud collapses or accretes onto a central mass, the inner region of the cloud develops a density profile $ρ\propto r^{-3/2}$ and the velocity approaches free-fall. We show that in this region, nonspherical perturbations grow with decreasing radius. In the linear regime, the tangential velocity perturbation increases as

M. Hotta, I. Joichi

We address in this paper how tightly the composability nature of systems: $S_{A+B} =Ω(S_A, S_B)$ constrains definition of generalized entropies and investigate explicitly the composability in some ansatz of the entropy form.

Zoltan Haiman, Lloyd Knox

We compute the expected angular power spectrum of the cosmic Far Infrared Background (FIRB). We find that the signal due to source correlations dominates the shot--noise for $\ell \la 1000$ and results in anisotropies with rms amplitudes $(\sqrt{\ell(\ell+1)C_\ell/2π})$ between 5% and 10% of the mean for $l \ga 150$. The angular power spectrum depends on sev

Jin Young Kim

We find the absorption probability of dilaton field in type 0B string theory. Since the background solutions are of the form $AdS_5 \times S^5$ on both regions, we use the semiclassical formalism adopted in type IIB theory to find the absorption cross section. The background tachyon field solution was used as a reference to relate the solutions of the two re

Rennan Barkana, Abraham Loeb

Direct observations of the first generation of luminous objects will likely become feasible over the next decade. The advent of the Next Generation Space Telescope (NGST) will allow imaging of numerous galaxies and mini-quasars at redshifts z>5. We apply semi-analytic models of structure formation to estimate the rate of multiple imaging of these sources by

D. K. Hong, V. A. Miransky, I. A. Shovkovy, L. C. R. Wijewardhana

The problem of color superconductivity in dense QCD is reconsidered in the improved rainbow approximation to the Schwinger-Dyson equation. The effect of the unscreened magnetic modes of gluons on the value of the color condensate is studied. In particular, it is shown that, at sufficiently large values of the chemical potential, these modes lead to the enhan

S. Parker, S. Bose, M. B. Plenio

We develop theoretical and numerical tools for the quantification of entanglement in systems with continuous degrees of freedom. Continuous variable entanglement swapping is introduced and based on this idea we develop methods of entanglement purification for continuous variable systems. The success of these entanglement purification methods is then assessed

Ian C. Percival

Realistic dynamical theories of measurement based on the diffusion of quantum states are nonunitary, whereas quantum field theory and its generalizations are unitary. This problem in the quantum field theory of quantum state diffusion (QSD) appears already in the Lagrangian formulation of QSD as a classical equation of motion, where Liouville&#39;s theorem d

Asher Yahalom

The variational principle of barotropic Eulerian fluid dynamics is known to be quite cumbersome containing as much as eleven independent functions. This is much more than the the four functions (density and velocity) appearing in the Eulerian equations of motion. This fact may have discouraged applications of the variational method. In this paper a four func

Z. Mei, A. J. Roberts, Zhenquan Li

Consider the dynamics of turbulent flow in rivers, estuaries and floods. Based on the widely used k-epsilon model for turbulence, we use the techniques of centre manifold theory to derive dynamical models for the evolution of the water depth and of vertically averaged flow velocity and turbulent parameters. This new model for the shallow water dynamics of tu

Dinesh Kumar Srivastava, Klaus Geiger

In view of the recent WA98 data of $π^0$ spectra from central Pb+Pb collisions at the CERN SPS, we analyze the production of neutral pions for A+A collisions across the periodic table at $\sqrt{s}=17$ AGeV and 200 AGeV within the framework of the parton-cascade model for relativistic heavy ion collisions. The multiplicity of the pions (having $p_T > 0.5$ GeV

A. B. Larionov, A. S. Botvina, M. Colonna, M. Di Toro

The multifragmentation of excited spherical nuclear sources with various N/Z ratios and fixed mass number is studied within dynamical and statistical models. The dynamical model treats the multifragmentation process as a final stage of the growth of density fluctuations in unstable expanding nuclear matter. The statistical model makes a choice of the final m

H. S. Zong, X. F. Lu, J. Z. Gu, C. H. Chang

Based on the quark propagator in the instanton dilute liquid approximation, we calculate analytically the quark condensate $<\bar{q}q>$, the mixed quark gluon condensate $g_{s}<\bar{q}G_{μν}σ^{μν}q>$ and the four quark condensate $<\bar{q} Γq\bar{q} Γq>$ at the mean field level in the framework of global color symmetry model. The numerical calculation shows

G. Rupak, N. Shoresh

I outline the effective field theory (EFT) calculation of nucleon-nucleon scattering which was recently carried out to next-to-next-to-leading order (NNLO) by Noam Shoresh and myself. In this calculation only potential pion contributions are included. These are the leading contributions from pions. A toy model was also considered in which potential pions are

Fabio Giannoni, Antonio Masiello, Paolo Piccione

In this paper we use a general version of Fermat&#39;s principle for light rays in General Relativity and a curve shortening method to write the Morse relations for light rays joining an event with a smooth timelike curve in a Lorentzian manifold with boundary. As a physical meaning, one can apply the Morse relations to have a mathematical description of the

Jean-Pierre Aubin

This mini-course provides a presentation of the method of characteristics to initial/boundary-value problems for systems of first-order partial differential equations and to Hamilton-Jacobi variational inequalities. In particular, these results are indeed useful for the treatment of hybrid systems of control theory. We rely on tools forged by set-valued anal

Michael C Sullivan

A Smale flow is a structurally stable flow with one dimensional invariant sets. We use information from homology and template theory to construct, visualize and in some cases, classify, nonsingular Smale flows in the 3-sphere.

D. O. Gunter, H. G. Kaper, G. K. Leaf

This article is concerned with the integration of the time-dependent Ginzburg-Landau (TDGL) equations of superconductivity. Four algorithms, ranging from fully explicit to fully implicit, are presented and evaluated for stability, accuracy, and compute time. The benchmark problem for the evaluation is the equilibration of a vortex configuration in a supercon

Anthony C. Kable, Akihiko Yukie

This is the second part of a two part paper. In this part, we evaluate the previously unevaluated local densities at dyadic places which appear in the density theorem stated in the first part. For this part, we introduce an invariant, the level, attaced to a pair of ramified quadratic extensions of a dyadic local field. This invariant measures how close two

Anthony C. Kable, Akihiko Yukie

Let $k$ be a number field and $\tilde k$ a fixed quadratic extension of $k$. In this paper and its companion, we find the mean value of the product of class numbers and regulators of two quadratic extensions $F,F^*\not=\tilde k$ contained in the biquadratic extensions of $k$ containing $\tilde k$.

Hans G. Kaper, Peter Takac

It is shown that the complex Ginzburg-Landau (CGL) equation on the real line admits nontrivial $2π$-periodic vortex solutions that have $2n$ simple zeros (``vortices&#39;&#39;) per period. The vortex solutions bifurcate from the trivial solution and inherit their zeros from the solution of the linearized equation. This result rules out the possibility that t

David Eisenbud, Sorin Popescu, Charles Walter

We give examples of subcanonical subvarieties of codimension 3 in projective n-space which are not Pfaffian, i.e. defined by the ideal sheaf of submaximal Pfaffians of an alternating map of vector bundles. This gives a negative answer to a question asked by Okonek. Walter had previously shown that a very large majority of subcanonical subschemes of codimensi

Arupkumar Pal

A regular operator T on a Hilbert C^*-module is defined just like a closed operator on a Hilbert space, with the extra condition that the range of (I+T^*T) is dense. Semiregular operators are a slightly larger class of operators that may not have this property. It is shown that, like in the case of regular operators, one can, without any loss in generality,

Thomas Friedrich, Eui Chul Kim

We generalize the well-known lower estimates for the first eigenvalue of the Dirac operator on a compact Riemannian spin manifold proved by Th. Friedrich (1980) and O. Hijazi (1986, 1992). The special solutions of the Einstein-Dirac equation constructed recently by Friedrich/Kim are examples for the limiting case of these inequalities. The discussion of the

A. Kehagias

We examine how a d-dimensional mass hierarchy can be generated from a d+1-dimensional set up. We consider a d+1--dimensional scalar, the hierarchon, which has a potential as in gauged supergravities. We find that when it is in its minimum, there exist solutions of Horava-Witten topology R^d X S^1/Z^2 with domain walls at the fixed points and anti-de Sitter g

M. E. Carrington, R. Kobes, G. Kunstatter

We consider a 1+1 dimensional field theory constrained to a finite box of length L. Traditionally, calculations in a box are done by replacing the integrals over the spatial momenta by discrete sums and then evaluating sums and doing analytic continuations. We show that it is also possible to do such calculations using an analogy to finite temperature field

Ji Sun

The well-known physical equivalence drawn from hole theory is applied in this article. The author suggests to replace, in the part of Feynman diagram which cannot be fixed by experiments, each fermion field operator, and hence fermion propagator, by pairs of equivalent fermion field operators and propagators. The formulation of this article thus yields addit

Phillial Oh

We consider Chern-Simons gauged nonlinear sigma model with boundary which has a manifest bulk diffeomorphism invariance. We find that the Gauss&#39;s law can be solved explicitly when the nonlinear sigma model is defined on the Hermitian symmetric space, and the original bulk theory completely reduces to a boundary nonlinear sigma model with the target space

Piet Claus, Renata Kallosh, J. Rahmfeld

We perform the quantization of a massive particle propagating on AdS_5. We use the twistor formulation in which the action can be brought into a quadratic form. We construct the BRST operator which commutes with AdS_5 isometries forming SU(2,2). The condition of a consistent BRST quantization requires that the AdS energy E is quantized in units of the AdS_5

Christos Kokorelis

We consider solutions to the $μ$-problem originating in the effective low energy theories, of N=1 orbifold compactifications of the heterotic string, after supersymmetry breaking. They are consistent with the invariance of the one loop corrected effective action in the linear representation of the dilaton. The proposed $μ$-terms naturally generalize solution

Hung-Jung Lu, Rodrigo Rivera, Ivan Schmidt

We show that a peripheral meson model can explain the large deep inelastic electron-proton scattering rapidity gap events observed at HERA.

Ivan Schmidt, Jian-Jun Yang

The electric screening mass of the gluon at finite temperature is estimated by considering the gluon condensate above the critical temperature. We find that the thermal gluons acquire an electric mass of order T due to the gluon condensate.

R. D. Peccei

These lectures describe some aspects of the physics of massive neutrinos. After a brief introduction of neutrinos in the Standard Model, I discuss possible patterns for their masses. In particular, I show how the presence of a large Majorana mass term for the right-handed neutrinos can engender tiny neutrino masses for the observed neutrinos. If neutrinos ha

M. C. Gonzalez-Garcia, S. M. Lietti, S. F. Novaes

We investigate the potentiality of CERN LEP and Fermilab Tevatron colliders to establish bounds on new couplings involving the bosonic sector of the standard model. A combined exclusion plot for the coefficients of different dimension-6 anomalous operators is presented. We also discuss the sensitivity that can be achieved at the upgraded Tevatron.

M. Ahmed, T. Gehrmann

The distribution of hadrons produced in deeply inelastic electron-proton collisions depends on the azimuthal angle between lepton scattering plane and hadron production plane in the photon-proton centre-of-mass frame. In addition to the well known up-down asymmetry induced by the azimuthal dependence of the Born level subprocess, there is also a non-vanishin

E. O. Iltan, G. Turan

The radiative B ->τ^+ τ^- γdecay is investigated in the framework of the two Higgs doublet model . The dependence of the differential branching ratio on the photon energy and the branching ratio on the two Higgs doublet model parameters, m_{H^\pm} and \tan β, are studied. It is shown that there is an enhancement in the predictions of the two Higgs doublet mo

J. Kwiecinski, B. Ziaja

We argue that the production of forward jets in polarised deep inelastic scattering can be a useful tool for probing the double $ln^2(1/x)$ resummation effects which control the polarised deep inelastic scattering for small values of the Bjorken parameter $x$. We solve the corresponding integral equations generating the double $ln^2(1/x)$ resummation and cal

Anjan S. Joshipura, Emmanuel A. Paschos

The presently available information on neutrino oscillations can be used to tightly constrain the light neutrino mass matrix $m_\n$ under the assumption that the three known neutrinos provide explanation of the solar and atmospheric anomalies. We exploit left right symmetry and the seesaw model to establish direct correlation between this constrained $m_\n$

M. Peloso

Leptogenesis constitues a very simple scenario to achieve the baryon asymmetry that we observe today. It requires only the presence of right handed neutrinos (which arise very naturally in many extensions of the Standard Model) and depends crucially on the mechanism responsible for their production. In particular, when their mass exceeds the inflaton mass (1

D. V. Shirkov, I. L. Solovtsov

We begin with short review of the analytic approach (AA) to QCD recently developed and applied to the process of $e^+e^-$ annihilation into hadrons at low energies. Besides summary of the theoretical description of smeared experimental data for the $R$ cross-section ratio we give fresh analogous result for the corresponding Adler function, $D(Q^2)$, and demo

Tao Huang, Hongying Jin, Ailin Zhang

The spectrum of the $0^{++}$, $0^{--}$, $1^{-+}$ and $1^{+-}$ heavy-light hybrids have been calculated in HQET. The interpolated current of the hybrid is chosen as $g\bar qγ_αG_{αμ}^aT^ah_{\it v}(x)$, $g\bar qγ_αγ_{5}G_{αμ}^aT^ah_{\it v}(x)$ and $g\bar qσ_{μα}G_{αμ}^aT^ah_{\it v}(x)$. Some strong couplings and decay widths of the heavy-light hybrids to $B(D)

Hung-Liang Lai, Hsiang-nan Li

We investigate effects of threshold resummation of logarithmic corrections $\ln N$ in Mellin space quantitatively. Threshold resummation leads to enhancement of next-to-leading-order QCD predictions for jet production at large jet transverse energy, which is in the trend indicated by experimental data. We show that this enhancement is completely determined b

C. Alexandrou, Ph. de Forcrand, M. D&#39;Elia, H. Panagopoulos

We study the efficiency of an improved Multiboson algorithm with two flavours of Wilson fermions in a realistic physical situation ($β= 5.60$, $κ= 0.156$ on a $16^3 \times 24$ lattice). The performance of this exact algorithm is compared with that of a state-of-the-art HMC algorithm: a considerable improvement is obtained for the plaquette auto-correlation t

Yorick Wilks, Roberta Catizone

The article surveys a little of the history of the technology, sets out the main current theoretical approaches in brief, and discusses the on-going opposition between theoretical and empirical approaches. It illustrates the situation with some discussion of CONVERSE, a system that won the Loebner prize in 1997 and which displays features of both approaches.

Gertjan van Noord, Gosse Bouma, Rob Koeling, Mark-Jan Nederhof

We argue that grammatical analysis is a viable alternative to concept spotting for processing spoken input in a practical spoken dialogue system. We discuss the structure of the grammar, and a model for robust parsing which combines linguistic sources of information and statistical sources of information. We discuss test results suggesting that grammatical p

E. Del Giudice, G. Preparata, M. Buzzacchi

Faced with the Kauzmann paradox, glasses have always been a puzzle for condensed matter theorists. We show that in a new picture of condensed matter, which takes into account the coherent interaction mechanisms of QED, glasses are nothing but liquids, whose non coherent fraction is highly depleted, very close to zero near T$_g$, the temperature of glass form

D. F. Agterberg, Victor Barzykin, Lev. P. Gor&#39;kov

We consider the pairing state due to the usual BCS mechanism in substances of cubic and hexagonal symmetry where the Fermi surface forms pockets around several points of high symmetry. We find that the symmetry imposed on the multiple pocket positions could give rise to a multidimensional nontrivial superconducting order parameter. The time reversal symmetry

Georg M. Bruun, Charles W. Clark

We investigate theoretically the properties of a trapped gas of fermionic atoms in both the normal and the superfluid phases. Our analysis, which accounts for the shell structure of the normal phase spectrum, identifies two observables which are sensitive to the presence of the superfluid: the response of the gas to a modulation of the trapping frequency, an

N. P. Rapapa

The effect of shear on the ordering-kinetics of a conserved order-parameter system with O(n) symmetry and order-parameter-dependent mobility Γ({\vecϕ}) \propto (1- {\vecϕ} ^2/n)^αis studied analytically within the large-n limit. In the late stage, the structure factor becomes anisotropic and exhibits multiscaling behavior with characteristic length scales (t

Leonid A. Openov

An interaction of electromagnetic field with a nanostructure composed of two quantum dots is studied theoretically. An effect of a resonant electron transfer between the localized low-lying states of quantum dots is predicted. A necessary condition for such an effect is the existence of an excited bound state whose energy lies close to the top of the barrier

Vladimir Kolevzon

The temperature dependence of surface tension γ(T) at liquid gallium is studied theoretically and experimentally using light scattering from capillary waves. The theoretical model based on the Gibbs thermodynamics relates the temperature derivative of γto the surface excess entropy -ΔS. Although capillary waves contribute to the surface entropy with a positi

Markus Buttiker

In the presence of shot noise the charge on a mesoscopic conductor fluctuates. We are interested in the charge fluctuations which arise if the conductor is in the proximity of a gate to which it is coupled by long range Coulomb forces only. Specifically we consider a gate coupled to the edge of a Hall bar subject to a quantizing magnetic field which contains

I. Chaplygin, R. Hayn, K. Koepernik

Bandstructure calculations with different spin arrangement for the spin-chain compound MgVO_3 have been performed, and paramagnetic as well as magnetic solutions with ferro- and antiferromagnetically ordered chains are found, the magnetic solutions being by 0.22 eV per formula unit lower than the paramagnetic one. The orbital analysis of the narrow band cros

L. Benfatto, A. Perali, C. Castellani, M. Grilli

We evaluate the charge and spin susceptibilities of the 2D attractive Hubbard model and we compare our results with Montecarlo simulations on the same model. We discuss the possibility to include topological Kosterlitz-Thouless superconducting fluctuations in a standard perturbative approach substituting in the fluctuation propagator the Ginzburg-Landau corr

K. Baerwinkel, H. -J. Schmidt, J. Schnack

For the diagonalization of the Hamilton matrix in the Heisenberg model relevant dimensions are determined depending on the applicable symmetries. Results are presented, both, by general formulae in closed form and by the respective numbers for a variety of special systems. In the case of cyclic symmetry, diagonalizations for Heisenberg spin rings are perform

L. Pizzagalli, A. Catellani, G. Galli, F. Gygi

By means of ab initio molecular dynamics and band structure calculations, as well as using calculated STM images, we have singled out one structural model for the (3x2) reconstruction of the Si-terminated (001) surface of cubic SiC, amongst several proposed in the literature. This is an alternate dimer-row model, with an excess Si coverage of 1/3, yielding S

Jun-ichiro Kishine, Kenji Yonemitsu

We study interplay of electronic correlation, randomness and dimensionality effects in half-filled random Hubbard chains weakly coupled via an interchain one-particle hopping. Based on the two-loop renormalization-group approach, phase diagrams are given in terms of temperature vs. strengths of the intrachain electron-electron umklapp scattering, the random

H. Rieger, R. Juhasz, F. Igloi

We study random XY and (dimerized) XX spin-1/2 quantum spin chains at their quantum phase transition driven by the anisotropy and dimerization, respectively. Using exact expressions for magnetization, correlation functions and energy gap, obtained by the free fermion technique, the critical and off-critical (Griffiths-McCoy) singularities are related to pers

C. W. J. Beenakker, M. Patra

A recent theory is reviewed for the shot noise of coherent radiation propagating through a random medium. The Fano factor P/I (the ratio of the noise power and the mean transmitted current) is related to the scattering matrix of the medium. This is the optical analogue of Buttiker&#39;s formula for electronic shot noise. Scattering by itself has no effect on

Myung-Hoon Chung, So-Nam Choi, Jae-Hoon Kwon

A low energy effective Hamiltonian for the fractional quantum Hall effect is obtained by using irreducible representations of the symmetry group. It is found that the model described by the effective Hamiltonian is similar to the Heisenberg spin chain. Symmetries of the effective Hamiltonian are studied in order to decompose the relevant Hilbert space. This

Giuliano Benenti, Xavier Waintal, Jean-Louis Pichard, Dima L. Shepelyansky

For a constant density of spinless fermions in strongly disordered two dimensional clusters, the energy level spacing between the ground state and the first excitation is studied for increasing system sizes. The average indicates a smooth opening of the gap when the Coulomb energy to Fermi energy ratio $r_s$ increases from 0 to 3, while the distribution exhi

A. Garcia, L. Sodre, F. J. Jablonski, R. J. Terlevich

We present an analysis of quasar variability from data collected during a photometric monitoring of 50 objects carried out at CNPq/Laboratorio Nacional de Astrofisica, Brazil, between March 1993 and July 1996. A distinctive feature of this survey is its photometric accuracy, ~ 0.02 V mag, achieved through differential photometry with CCD detectors, what allo

R. Atkins, W. Benbow, D. Berley, M. -L. Chen

The Milagro detector is an air shower array which uses the water Cherenkov technique and is capable of continuously monitoring the sky at energies near 1 TeV. The detector consists of 20000 metric tons of pure water instrumented with 723 photo-multiplier tubes (PMTs). The PMTs are arranged in a two-layer structure on a lattice of 3 m spacing covering 5000 $m

Maxim Markevitch

Using CCD detectors onboard the forthcoming X-ray observatories Chandra and XMM, it is possible to devise a measurement of the absolute density of heavy elements in the hypothetical warm gas filling intercluster space. This gas may be the largest reservoir of baryonic matter in the Universe, but even its existence has not been proven observationally at low r

C. J. Miller, D. J. Batuski, K. A. Slinglend, J. M. Hill

An analysis of R >= 1 Abell clusters is presented for samples containing recent redshifts from the MX Northern Abell Cluster Survey. The newly obtained redshifts from the MX Survey as well as those from the ESO Nearby Abell Cluster Survey (ENACS) provide the necessary data for the largest magnitude-limited correlation analysis of rich clusters in the entire

D. J. Batuski, C. J. Miller, K. A. Slinglend, C. Balkowski

We report the discovery of two highly extended filaments and one extremely high density knot within the region of Aquarius. The supercluster candidates were chosen via percolation analysis of the Abell and ACO catalogs and include only the richest clusters (R >= 1). The region examined is a 10x45 degree strip and is now 87% complete in cluster redshift measu

D. L. Clements, S. A. Eales, A. C. Baker

We present the results of colour selection of candidate high redshift galaxies in Hubble Deep Field South (HDF-S) using the Lyman dropout scheme. The HDF-S data we discuss were taken in a number of different filters extending from the near--UV (F300W) to the infrared (F222M) in two different fields. This allows us to select candidates with redshifts from z~3

J. S. Alcaniz, J. A. S. Lima

The limits imposed by the classical cosmological tests on closed and open FRW universes driven by adiabatic matter creation are investigated. Exact expressions for the lookback time, age of the universe, luminosity distance, angular diameter, and galaxy number counts versus redshift are derived and their meaning discussed in detail. An interesting consequenc

G. L. Israel, G. Marconi, S. Covino, D. Lazzati

We present the results of optical observations of the GRB990510 field carried out at different epochs from European Southern Observatory (ESO) telescopes. Deep observations, down to a limiting magnitude of about 27 and 24 in the Bessel-R and Gunn-I band, respectively, were obtained between May 16 and 18 from the ESO NTT-SUSI2 telescope and on May 20 from the

Yogesh Wadadekar, Ajit Kembhavi

Using the most recent (1998) version of the VLA FIRST survey radio catalog, we have searched for radio emission from 1704 quasars taken from the most recent (1993) version of the Hewitt and Burbidge quasar catalog. These quasars lie in the ~5000 square degrees of sky already covered by the VLA FIRST survey. Our work has resulted in positive detection of radi

P. N. Werner, D. M. Worrall, M. Birkinshaw

Redshifts of several galaxies thought to be associated with NGC 326 are determined. The results confirm the presence of a cluster and find a mean redshift of z = 0.0477 +/- 0.0007 and a line-of-sight velocity dispersion sigma_{z} = 599 (+230, -110) km/s. The velocity dispersion and previously measured X-ray gas temperature of kT ~ 1.9 keV are consistent with

Adi Nusser, Martin Haehnelt

The real-space optical depth distribution along the line of sight to the QSO Q1422+231 is recovered from two HIRES spectra. The first two moments of the truncated optical depth distribution are used to constrain the density fluctuation amplitude of the intergalactic medium (IGM). The $rms$ of the IGM density at $z\approx 3.25$ estimated from the first spectr

A. Konopelko, F. Aharonian, M. Hemberger, W. Hofmann

The sensitivity of imaging atmospheric Cherenkov telescopes (IACTs) in TeV gamma-ray observations reachs its maximum at small zenith angles (< 30 degree) which provide the minimum attainable energy threshold of an instrument. However, for a specific telescope site a number of gamma-ray sources, or source candidates, can only be observed at much larger zenith

M. Brüggen

In this paper it is investigated whether torsion, which arises naturally in most theories of quantum gravity, has observable implications for the Big Bang nucleosynthesis. Torsion can lead to spin flips amongst neutrinos thus turning them into sterile neutrinos. In the early Universe they can alter the helium abundance which is tightly constrained by observa

S. Brandt, N. Lund, H. Pedersen, J. Hjorth

The cosmological origin of gamma ray bursts has now been established with reasonable certainty. Many more bursts will need to be studied to establish the typical distance scale, and to map out the large diversity in properties which have been indicated by the first handful of events. We are proposing Ballerina, a small satellite to provide accurate positions

S. C. Trager

Early-type galaxies are not the simple Population II systems they have long been assumed to be. While upwards of 80% of the stellar mass of early-type galaxies likely formed at high redshift, small frostings of intermediate-age stellar populations (a few to 20% percent by mass of 1-2 Gyr old stars) are present in nearly every field and group early-type galax

K. Hulek, I. Nieto, G. K. Sankaran

We continue our study of the geometry of Nieto&#39;s quintic threefold, looking at degenerate surfaces that correspond to certain loci and showing how they arise from a toroidal compactification of a suitable moduli space.

K. Hulek, I. Nieto, G. K. Sankaran

We study the geometry of Nieto&#39;s quintic threefold (Barth & Nieto, J. Alg. Geom. 3, 1994) and the Kummer and abelian surfaces that correspond to special loci.

Naoaki Ono, Takashi Ikegami

We construct a simple model of a proto-cell that simulates a stochastic dynamics of abstract chemicals on a two-dimensional lattice. We assume that chemicals catalyze their reproduction through interaction with each other, and that between some chemicals repulsion occurs. We have shown that chemicals organize themselves into a cell-like structure that mainta

V. A. Dzuba, V. V. Flambaum, G. F. Gribakin, C. Harabati

A new relativistic method for calculation of positron binding to atoms is presented. The method combines a configuration interaction treatment of the valence electron and the positron with a many-body perturbation theory description of their interaction with the atomic core. We apply this method to positron binding by the copper atom and obtain the binding e

Yusuke Taniguchi

One loop correction to the SUSY Ward-Takahashi identity is calculated on lattice with Wilson fermion. The supersymmetry on lattice is broken explicitly by the gluino mass and the lattice artifact. We should fine tune parameters in the theory to the point given by the additive mass correction in order to eliminate the breaking effect of lattice artifact. It i

V. V. Dobrovitski, M. I. Katsnelson, B. N. Harmon

Decoherence mechanisms in crystals of weakly anisotropic magnetic molecules, such as V15, are studied. We show that an important decohering factor is the rapid thermal fluctuation of dipolar interactions between magnetic molecules. A model is proposed to describe the influence of this source of decoherence. Based on the exact solution of this model, we show

D. Z. Freedman, S. S. Gubser, K. Pilch, N. P. Warner

States on the Coulomb branch of N=4 super-Yang-Mills theory are studied from the point of view of gauged supergravity in five dimensions. These supersymmetric solutions provide examples of consistent truncation from type IIB supergravity in ten dimensions. A mass gap for states created by local operators and perfect screening for external quarks arise in the

M. Abolfath, Ramin Golestanian, T. Jungwirth

An effective field theoretic description of $ν=1$ bilayer electron systems stabilized by Coulomb repulsion in a single wide quantum well is examined using renormalization group techniques. The system is found to undergo a crossover from a low temperature strongly correlated quantum Hall state to a high temperature compressible state. This picture is used to

G. Chan, E. D&#39;Hoker

Linear recursion relations for the instanton corrections to the effective prepotential of N=2 supersymmetric gauge theories with an arbitrary number of hypermultiplets in the fundamental representation of an arbitrary classical gauge group are dervied. The construction proceeds from the Seiberg-Witten solutions and the renormalization group type equations fo

M. S. Berger

We study the impact of a set of horizontal symmetries on the requirements for producing the baryon asymmetry of the universe via leptogenesis. We find that Abelian horizontal symmetries lead to a simple description of the parameters describing leptogenesis in terms of the small expansion parameter that arises from spontaneous symmetry breaking. If the family

Chong-Sun Chu, Pei-Ming Ho

In a previous paper we provided a consistent quantization of open strings ending on D-branes with a background $B$ field. In this letter, we show that the same result can also be obtained using the more traditional method of Dirac&#39;s constrained quantization. We also extend the discussion to the fermionic sector.

S. A. Voloshin, A. M. Poskanzer

The centrality dependence of elliptic flow and how it is related to the physics of expansion of the system created in high energy nuclear collisions is discussed. Since in the hydro limit the centrality dependence of elliptic flow is mostly defined by the elliptic anisotropy of the overlapping region of the colliding nuclei, and in the low density limit by t

Mathis Plapp, Alain Karma

We present a novel computational method to simulate accurately a wide range of interfacial patterns whose growth is limited by a large scale diffusion field. To illustrate the computational power of this method, we demonstrate that it can be used to simulate three-dimensional dendritic growth in a previously unreachable range of low undercoolings that is of

Maximo Banados, Adam Ritz

We consider bosonic strings propagating on Euclidean adS_3, and study in particular the realization of various worldsheet symmetries. We give a proper definition for the Brown-Henneaux asymptotic target space symmetry, when acting on the string action, and derive the Giveon-Kutasov-Seiberg worldsheet contour integral representation simply by using Noether&#3