August 2001 arXiv papers — page 24

CDF Collaboration

We present a search for new heavy particles, $X$, which decay via $X rightarrow WZ \to eν+jj$ in $p{\bar p}$ collisions at $\sqrt{s} = 1.8$ TeV. No evidence is found for production of $X$ in 110 pb$^{-1}$ of data collected by the Collider Detector at Fermilab. Limits are set at the 95% C.L. on the mass and the production of new heavy charged vector bosons wh

Barbara M. Terhal, David P. DiVincenzo

We show that a class of quantum computations that was recently shown to be efficiently simulatable on a classical computer by Valiant corresponds to a physical model of noninteracting fermions in one dimension. We give an alternative proof of his result using the language of fermions and extend the result to noninteracting fermions with arbitrary pairwise in

O. Prus, M. Reznikov, U. Sivan, V. Pudalov

The cooling of two-dimensional electrons in silicon-metal-oxide semiconductor field effect transistors is studied experimentally. Cooling to the lattice is found to be more effective than expected from the bulk electron-phonon coupling in silicon. Unexpectedly, the extracted heat transfer rate to phonons at low temperatures depends cubically on electron temp

J. Sacanell, P. Levy, L. Ghivelder, G. Polla

The effect of low magnetic fields on the magnetic and electrical transport properties of polycrystalline samples of the phase separated compound La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ is studied. The results are interpreted in the framework of the field induced ferromagnetic fraction enlargement mechanism. A fraction expansion coefficient af, which relates the ferrom

Shrihari Gopalakrishna, James Wells

Motivated by recent studies of supersymmetry in higher-dimensional spaces, we discuss the experimental signatures of a superlight gravitino, mass < 0.001 eV. We concentrate on the process (e- gamma -> selectronR gravitino) as a probe of supersymmetry, where a single heavy superpartner and a superlight gravitino are produced. The fact that there is only one h

Stefan Antusch, Manuel Drees, Jörn Kersten, Manfred Lindner

We re-derive the renormalization group equation for the effective coupling of the dimension five operator which corresponds to a Majorana mass matrix for the Standard Model neutrinos. We find a result which differs somewhat from earlier calculations, leading to modifications in the evolution of leptonic mixing angles and CP phases. We also present a general

Ali Javan, Olga Kocharovskaya, Hwang Lee, Marlan O. Scully

We derive an analytic expression for the linewidth of EIT resonance in a Doppler broadened system. It is shown here that for relatively low intensity of the driving field the EIT linewidth is proportional to the square root of intensity and is independent of the Doppler width, similar to the laser induced line narrowing effect by Feld and Javan. In the limit

Mohsen Shadmehri, Jamshid Ghanbari

We obtain self-similar solutions that describe the dynamics of a self-gravitating, rotating, viscous system. We use simplifying assumptions; but explicitly include viscosity and the cooling due to the dissipation of energy. By assuming that the turbulent dissipation of energy is as power law of the density and the speed v_{rms} and for a power-law dependence

B. Knuteson, H. Miettinen, L. Holmstrom

We present alphaPDE, a new multivariate analysis technique for parameter estimation. The method is based on a direct construction of joint probability densities of known variables and the parameters to be estimated. We show how posterior densities and best-value estimates are then obtained for the parameters of interest by a straightforward manipulation of t

Stefano Mancini, David Vitali, Paolo Tombesi, Rodolfo Bonifacio

The application of a random modulation of a system parameter usually increases decoherence effects. Here we show how, employing an appropriate stochastic modulation, it is instead possible to preserve the quantum coherence of a system.

L. Trache, F. Carstoiu, C. A. Gagliardi, R. E. Tribble

We show that asymptotic normalization coefficients (ANC) can be extracted from one nucleon breakup reactions of loosely bound nuclei at 30-300 MeV/u. In particular, the breakup of ^{8}B is described in terms of an extended Glauber model. The 8B ANC extracted for the ground state of this nucleus from breakup data at several energies and on different targets,

G. Khaliullin

A theory of the anisotropic superexchange and low energy spin excitations in a Mott insulator with t_{2g} orbital degeneracy is presented. We observe that the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the spin Hamiltonian, which invalidate noninteracting spin wave theory. The frustration of classical states is resolved by an orde

Y. Gallais, A. Sacuto, P. Bourges, Y. Sidis

We report low energy electronic Raman scattering from Ni-substituted YBa2Cu3O6.95 single crystals with Tc ranging from 92.5 K to 78 K. The fully symmetrical A1g channel and the B1g channel which is sensitive to the dx2-y2 gap maximum have been explored. The energy of the B1g pair-breaking peak remains constant under Ni doping while the energy of the A1g peak

Christof Gattringer, Meinulf Göckeler, C. B. Lang, P. E. L. Rakow

We compare the behavior of different lattice Dirac operators in gauge backgrounds which are lattice discretizations of a classical instanton. In particular we analyze the standard Wilson operator, a chirally improved Dirac operator and the overlap operators constructed from these two operators. We discuss the flow of real eigenvalues as a function of the ins

Kazuya Koyama, Jiro Soda

We investigate the effect of the bulk gravitational field on the cosmological perturbations on a brane embedded in the 5D Anti-de Sitter (AdS) spacetime. The effective 4D Einstein equations for the scalar cosmological perturbations on the brane are obtained by solving the perturbations in the bulk. Then the behaviour of the corrections induced by the bulk gr

D. Vitali, P. Tombesi

We study the application of decoupling techniques to the case of a damped vibrational mode of a chain of trapped ions, which can be used as a quantum bus in linear ion trap quantum computers. We show that vibrational heating could be efficiently suppressed using appropriate ``parity kicks&#39;&#39;. We also show that vibrational decoherence can be suppressed

I. Antoniadis, K. Benakli, M. Quiros

We identify a class of chiral models where the one-loop effective potential for Higgs scalar fields is finite without any requirement of supersymmetry. It corresponds to the case where the Higgs fields are identified with the components of a gauge field along compactified extra dimensions. We present a six dimensional model with gauge group U(3)xU(3) and qua

I. V. Tokatly, R. Stubner, O. Pankratov

A diagrammatic expansion for the dynamic exchange-correlation kernel f_xc of time dependent density functional theory is formulated. It is shown that f_xc has no singularities at Kohn-Sham transition energies in every order of the perturbation theory. However, it may diverge with the system size in extended systems. This signifies that any approximate pertur

N. Haba, T. Kondo, Y. Shimizu, Tomoharu Suzuki

We suggest a simple grand unified theory where the fifth dimensional coordinate is compactified on an $S^1/(Z_2 \times Z_2&#39;)$ orbifold. This model contains additional ${\bf 10 + \overline{10}}$, (${\bf 15 + \overline{15}}$) and two ${\bf 24}$ Higgs multiplets in the non-supersymmetric SU(5) grand unified theory. Although this model is non-supersymmetric

Kajsa Dahlstedt, Henrik Jeldtoft Jensen

We study the effect of long range algebraic correlations on extreme value statistics and demonstrate that correlations can produce a limit distribution which is indistinguishable from the ubiquitous Bramwell-Holdsworth-Pinton distribution. We also consider the square-width fluctuations of the avalanche signal. We find, as recently predicted by T. Antal, M. D

Lev Shchur, Paolo Butera, Bertrand Berche

We analyze Monte Carlo simulation and series-expansion data for the susceptibility of the three-state Potts model in the critical region. The amplitudes of the susceptibility on the high- and the low-temperature sides of the critical point as extracted from the Monte Carlo data are in good agreement with those obtained from the series expansions and their (u

Nobuhito Maru

We consider the doublet-triplet splitting problem in supersymmetric SU(5) grand unified theory in five dimensions where the fifth dimension is non-compact. We point out that an unnatural fine-tuning of parameters in order to obtain the light Higgs doublets is not required due to the exponential suppression of the overlap of the wave functions.

Naoki Seto, Seiji Kawamura, Takashi Nakamura

It may be possible to construct a laser interferometer gravitational wave antenna in space with $h_{rms}\sim 10^{-27}$ at $ f\sim 0.1{\rm Hz}$ in this century. We show possible specification of this antenna which we call DECIGO. Using this antenna we show that 1) typically $ 10^5$ ($10^4\sim 10^6$) chirp signals of coalescing binary neutron stars per year ma

Stoytcho S. Yazadjiev

We present a method for generating solutions in some scalar-tensor theories with a minimally coupled massless scalar field or irrotational stiff perfect fluid as a source. The method is based on the group of symmetries of the dilaton-matter sector in the Einstein frame. In the case of Barker&#39;s theory the dilaton-matter sector possesses SU(2) group of sym

A. J. Daley, A. S. Parkins, R. Leonhardt, S. M. Tan

We numerically investigate momentum diffusion rates for the pulse kicked rotor across the quantum to classical transition as the dynamics are made more macroscopic by increasing the total system action. For initial and late time rates we observe an enhanced diffusion peak which shifts and scales with changing kick strength, and we also observe distinctive pe

Jens O. Andersen

We discuss corrections to the Casimir effect at finite temperature and effective field theory. Recently, it has been shown that effective field theories can reproduce radiative corrections to the Casimir energy calculated in full QED. We apply effective field theory methods at finite temperature and reproduce the Casimir free energy. We show that the system

Marie Ericsson, Erik Sjoqvist

An atomic analogue of Landau quantization based on the Aharonov-Casher (AC) interaction is developed. The effect provides a first step towards an atomic quantum Hall system using electric fields, which may be realized in a Bose-Einstein condensate.

Peter Horak, Peter Domokos, Helmut Ritsch

Atoms coupled to optical fields confined in one and two spatial dimensions in solid state microstructures can experience very large light shifts if the driving frequencies are close to a resonance of the microstructures and an atomic transition. Using the simple example of a quasi one-dimensional waveguide structure we can analytically calculate the atomic A

Young-Tak Chough, Hyunchul Nha, Sang Wook Kim, Sun-Hyun Youn

We provide an intuitive interpretation of the optical Stern-Gerlach effect (OSGE) in the dressed-state point of view. We also analyze the effect of atomic damping in an experiment on the OSGE. We show that the atomic damping also causes the wave packet splitting, in a non-mechanical fashion, as opposed to the coherent process that is mechanical.

Ulrich Mohrhoff

Theories of decoherence come in two flavors---Platonic and Aristotelian. Platonists grant ontological primacy to the concepts and mathematical symbols by which we describe or comprehend the physical world. Aristotelians grant it to the physical world. The significance one attaches to the phenomenon of decoherence depends on the school to which one belongs. T

D. J. Summers

Two 2200m radius hybrid rings of fixed superconducting magnets and iron magnets ramping at 200 Hz and 330 Hz are used to accelerate muons. Muons are given 25 GeV of RF energy per orbit. Acceleration is from 250 GeV/c to 2400 GeV/c and requires a total of 86 orbits in both rings; 82% of the muons survive. The total power consumption of the iron dipoles is 4 m

Ben-Hao Sa, A. Bonasera, An Tai, Dai-Mei Zhou

Using a hadron and string cascade model, JPCIAE, the energy and centrality dependences of charged particle pseudorapidity density in relativistic nuclear collisions were studied. Within the framework of this model, both the relativistic $p+\bar p$ experimental data and the PHOBOS and PHENIX $Au+Au$ data at $\sqrt s_{nn}$=130 GeV could be reproduced fairly we

E. J. V. de Passos, M. S. Hussein, L. F. Canto, B. V. Carlson

We investigate the mean energy, strength and width of the triple giant dipole resonance using sum rules.

D. Gupta, C. Samanta

The proton-inelastic scattering from $^{6,8}$He and $^{7,11}$Li nuclei are studied in a folding model approach. A finite-range, momentum, density and isospin dependent nucleon-nucleon interaction (SBM) is folded with realistic density distributions of the above nuclei. The renormalization factors N$_R$ and N$_I$ on the real and volume imaginary part of the f

Adam Bernstein, Yifang Wang, Giorgio Gratta, Todd West

Cubic-meter-sized antineutrino detectors can be used to non-intrusively, robustly and automatically monitor and safeguard a wide variety of nuclear reactor types, including power reactors, research reactors, and plutonium production reactors. Since the antineutrino spectra and relative yields of fissioning isotopes depend on the isotopic composition of the c

A. A. Kapaev

The isomonodromy deformation equation for a 2x2 matrix linear ODE with a large parameter can be locally reduced to a (hyper)elliptic equation. To globalize this result, we apply the isomonodromy deformation method and obtain the modulation equations for the asymptotic algebraic curve. The method is applied to the degenerate solution of the Painleve first equ

M. A. Castagnino, A. R. Ordoniez

An algebraic formalism for quantum decoherence in systems with continuous evolution spectrum is introduced. A certain subalgebra, dense in the characteristic algebra of the system, is defined in such a way that Riemann-Lebesgue theorem can be used to explain decoherence in a well defined final pointer basis.

Lee Rudolph

Murasugi sums can be defined as readily for Morse maps to the circle of (arbitrary) link complements in the 3-sphere as for fibrations over the circle of (fibered) link complements in the 3-sphere. As one application, I show that if a knot K has free genus m, then there is a Morse map from its complement to the circle (representing the relative homology clas

Stefan Wewers

In this paper we investigate the cohomological obstruction for the field of moduli of a $G$-cover to be a field of definition, in the case of local fields and covers with tame admissible reduction. This applies in particular to $p$-adic fields where $p$ does not divide the order of the group $G$. We give examples of $G$-covers with field of moduli $\QQ_p$ th

Marina Prokhorova

There was proposed the method of a factorization of PDE. The method is based on reduction of complicated systems to more easy ones (for example, due to dimension decrease). This concept is proposed in general case for the arbitrary PDE systems, and its concrete investigation is developing for the heat equation case. There is considered the category of second

Mourad E. H. Ismail, Nicholas S. Witte

We derive raising and lowering operators for orthogonal polynomials on the unit circle and find second order differential and $q$-difference equations for these polynomials. A general functional equation is found which allows one to relate the zeros of the orthogonal polynomials to the stationary values of an explicit quasi-energy and implies recurrences on

Dominic Joyce

This is the third in a series of papers constructing explicit examples of special Lagrangian submanifolds in C^m. The previous paper in the series, math.DG/0008155, defined the idea of evolution data, which includes an (m-1)-submanifold P in R^n, and constructed a family of special Lagrangian m-folds N in C^m, which are swept out by the image of P under a 1-

Vladimir Dergachev

We present a new method of analysis of associative algebras. This method bears a certain resemblance to the famous analysis of commutative $C^*$-algebras in which an important role is played by multiplicative functionals over the algebra. These functionals can be considered as &#34;rank 1&#34; in the framework of our method. In our approach a special positio

Klaus Kirsten

Special case calculations are presented, which can be used to put restrictions on the general form of heat kernel coefficients for transmittal boundary conditions and for generalized bag boundary conditions.

Subrata Bal, Hiroyuki Takata

We have calculated interactions between two fuzzy spheres in 3 dimension. It depends on the distance r between the spheres and the radii rho_1, rho_2. There is no force between the spheres when they are far from each other (long distance case). We have also studied the interaction for r=0 case. We find that an attractive force exists between two fuzzy sphere

Arvind Rajaraman, Moshe Rozali

We construct boundary states representing D-strings in $AdS_3$. These wrap twisted conjugacy classes of SL(2,R), and the boundary states are therefore based on continuous representations only. We check Cardy&#39;s condition and find a consistent open string spectrum. The open string spectrum on all the D-branes is the same.

W. F. Kao

The possible existence of a complex metric tensor field is studied. We show that an effective scalar field is induced by an overall phase component of the complex metric tensor. The corresponding gauge field is shown to be a tachyon. Possible implications of this scalar field to the no hair theorem in a spherically symmetric space is also analyzed. We also s

J. P. Zibin

I demonstrate that instability in a system of homogeneous scalar fields leads to the growth of super-Hubble metric perturbations. This generalizes the result that parametric resonance can lead to the growth of cosmological perturbations. Since dynamical chaos is common in multi-field quartically coupled systems, I argue that the evolution of the fields after

M. R. Ahmady, M. Nagashima, A. Sugamoto

We extend the standard model by adding an extra generation of isosinglet up- and down-type quark pair which engage in weak interactions only via mixing with the three ordinary quark families. It is shown that the generalized $4\times 4$ quark mixing matrix, which is necessarily nonunitary, leads to nonvanishing flavor changing neutral currents. We then proce

C. S. Kim, Y. Kwon, Jake Lee, W. Namgung

We investigate the possibility of testing factorization hypothesis in non-leptonic exclusive decays of B-meson. In particular, we considered the non factorizable \bar{B^0} -> D^{(*)+} D_s^{(*)-} modes and \bar{B^0} -> D^{(*)+} (π^-, ρ^-) known as well-factorizable modes. By taking the ratios BR(\bar{B^0}-> D^{(*)+}D_s^{(*)-})/BR(\bar{B^0}-> D^{(*)+}(π^-,ρ^-)

Yongsheng Gao

Recent CLEO results on beauty and charm meson decays presented at the International Conference on Flavor Physics (ICFP2001) are discussed. The results include exclusive rare B decays (B to PP, PV, VV, \phiK^(*), l^+l^-K^(*)), inclusive b to s γ, and CP violation measurements in beauty and charm mesons. Preliminary results on rare B decays using CLEO III data

K. Abe

We present measurements of the Cabibbo-suppressed decays $Λ_c^+ \to Λ^0 K^+$ and $Λ_c^+ \to Σ^0 K^+$ (both first observations), $Λ_c^+ \to Σ^+ K^+π^-$ (seen with large statistics for the first time), $Λ_c^+ \to p K^+ K^-$ and $Λ_c^+ \to p ϕ$ (measured with improved accuracy). Improved branching ratio measurements for the decays $Λ_c^+ \to Σ^0 K^+ K^-$ and $Λ

Pedro Teixeira-Dias

During the run in the year 2000, with data collected at collision energies up to 209 GeV, the LEP experiments have possibly unearthed the first evidence of a Higgs boson signal at mh=115 GeV/c2. The preliminary combined results prepared immediately after the end of the data-taking, in November 2000, are presented here. Overall, a 2.9 sigma excess over the ba

Pedro Teixeira-Dias

The ALEPH search for the Standard Model Higgs boson in the year 2000 revealed an excess of signal-like events, consistent with a signal hypothesis mh=115 GeV/c2. Here we present the first results after the analysis of all of the data collected during the year 2000, at collision energies up to 209 GeV, and which were published in November 2000.

Oliver Henkel

A theorem about local in time existence of spacelike foliations with prescribed mean curvature in cosmological spacetimes will be proved. The time function of the foliation is geometrically defined and fixes the diffeomorphism invariance inherent in general foliations of spacetimes. Moreover, in contrast to the situation of the more special constant mean cur

Wolfgang Hasse, Volker Perlick

In Schwarzschild spacetime the value $r=3m$ of the radius coordinate is characterized by three different properties: (a) there is a ``light sphere&#39;&#39;, (b) there is ``centrifugal force reversal&#39;&#39;, (c) it is the upper limiting radius for a non-transparent Schwarschild source to act as a gravitational lens that produces infinitely many images. In

Gabrielle Allen, David Angulo, Ian Foster, Gerd Lanfermann

The ability to harness heterogeneous, dynamically available &#34;Grid&#34; resources is attractive to typically resource-starved computational scientists and engineers, as in principle it can increase, by significant factors, the number of cycles that can be delivered to applications. However, new adaptive application structures and dynamic runtime system me

Gonzalo Usaj, Harold U. Baranger

We calculate the Coulomb Blockade peak spacing distribution at finite temperature using the recently introduced ``universal Hamiltonian&#39;&#39; to describe the e-e interactions. We show that the temperature effect is important even at kT~0.1Δ(Δis the single-particle mean level spacing). This sensitivity arises because: (1) exchange reduces the minimum ener

G. Chiappe, M. J. Sánchez

The effect of disorder on confined metallic cavities with an Aharonov-Bohm flux line is addressed. We find that, even deep in the diffusive regime, large values of persistent currents may arise for a wide variety of geometries. We present numerical results supporting an anomalous scaling law of the average typical current $< I_{typ}>$ with the strength of di

Eli Barkai

The foundations of the fractional diffusion equation are investigated based on coupled and decoupled continuous time random walks (CTRW). For this aim we find an exact solution of the decoupled CTRW, in terms of an infinite sum of stable probability densities. This exact solution is then used to understand the meaning and domain of validity of the fractional

V. Plerou, P. Gopikrishnan, B. Rosenow, L. A. N. Amaral

We analyze cross-correlations between price fluctuations of different stocks using methods of random matrix theory (RMT). Using two large databases, we calculate cross-correlation matrices C of returns constructed from (i) 30-min returns of 1000 US stocks for the 2-yr period 1994--95 (ii) 30-min returns of 881 US stocks for the 2-yr period 1996--97, and (iii

M. Clincy, M. R. Evans, D. Mukamel

In this work we study a two species driven diffusive system with open boundaries that exhibits spontaneous symmetry breaking in one dimension. In a symmetry broken state the currents of the two species are not equal, although the dynamics is symmetric. A mean field theory predicts a sequence of two transitions from a strongly symmetry broken state through an

G. Feve, W. D. Oliver, M. Aranzana, Y. Yamamoto

The influence of spin-orbit coupling in two-dimensional systems is investigated within the framework of the Landauer-Buettiker coherent scattering formalism. This formalism usually deals with spin-independent stationary states and, therefore, it does not include a spin-orbit contribution to the current. In this article, we will rederive the coherent scatteri

Jesper Nygard, David H. Cobden

We present a simple technique which uses a self-aligned oxide etch to suspend individual single-wall carbon nanotubes between metallic electrodes. This enables one to compare the properties of a particular nanotube before and after suspension, as well as to study transport in suspended tubes. As an example of the utility of the technique, we study quantum do

D. L. Feder, C. W. Clark

The properties of a rotating Bose-Einstein condensate confined in a prolate cylindrically symmetric trap are explored both analytically and numerically. As the rotation frequency increases, an ever greater number of vortices are energetically favored. Though the cloud anisotropy and moment of inertia approach those of a classical fluid at high frequencies, t

Fredrick Michael, M. D. Johnson

Distributions derived from non-extensive Tsallis statistics are closely connected with dynamics described by a nonlinear Fokker-Planck equation. The combination shows promise in describing stochastic processes with power-law distributions and superdiffusive dynamics. We investigate intra-day price changes in the S&P500 stock index within this framework by di

Christophe Chatelain, Bertrand Berche, Lev N. Shchur

We report a numerical study of the bond-diluted 2-dimensional Potts model using transfer matrix calculations. For different numbers of states per spin, we show that the critical exponents at the random fixed point are the same as in self-dual random-bond cases. In addition, we determine the multifractal spectrum associated with the scaling dimensions of the

M. Ausloos, K. Ivanova

Specialized topics on financial data analysis from a numerical and physical point of view are discussed. They pertain to the analysis of crash prediction in stock market indices and to the persistence or not of coherent and random sequences in fluctuations of foreign exchange currency rates. A brief historical introduction to crashes is given, including rece

Guido Caldarelli, Raffaella Frondoni, Andrea Gabrielli, Marco Montuori

This paper focuses on the statistical properties of wild-land fires and, in particular, investigates if spread dynamics relates to simple invasion model. The fractal dimension and lacunarity of three fire scars classified from satellite imagery are analysed. Results indicate that the burned clusters behave similarly to percolation clusters on boundaries and

D. A. Johnston, R. P. K. C. Malmini

On various regular lattices (simple cubic, body centred cubic..) decorating an edge with an Ising spin coupled by bonds of strength L to the original vertex spins and competing with a direct anti-ferromagnetic bond of strength alpha L can give rise to three transition temperatures for suitable alpha. The system passes through ferromagnetic, paramagnetic, ant

M. Gutowski, K. Piotrowski, M. Gutowska, A. Szewczyk

We report experimental observations of magnetic bubble domain arrays with no apparent translational symmetry. Additionally the results of comparative numerical studies are discussed. Our goal is to present experimental evidence for natural occurence of conformal structures.

A. Bernert, P. Thalmeier, P. Fulde

We present a microscopic model for alpha&#39;-NaV2O5. Using an extended Hubbard model for the vanadium layers we derive an effective low-energy model consisting of pseudospin Ising chains and Heisenberg chains coupled to each other. We find a ``spin-Peierls-Ising&#39;&#39; phase transition which causes charge ordering on every second ladder and superexchange

M. K. Hassan, J. Kurths

We revisit the scaling theory of the Smoluchowski equation with special emphasis on the dimensional analysis to derive the scaling ansatz and to give an insightful foundation to it. It has long been argued that the homogeneity exponent $λ$ of the aggregation kernel divides the aggregation process into two regimes (i) $λ\leq 1$ nongelling and (ii) $λ>1$ gelli

P. Pedri, L. Pitaevskii, S. Stringari, C. Fort

We investigate the properties of a coherent array containing about 200 Bose-Einstein condensates produced in a far detuned 1D optical lattice. The density profile of the gas, imaged after releasing the trap, provides information about the coherence of the ground-state wavefunction. The measured atomic distribution is characterized by interference peaks. The

Maged Elhajal, Benjamin Canals, Claudine Lacroix

The kagomé lattice exhibits peculiar magnetic properties due to its strongly frustated cristallographic structure, based on corner sharing triangles. For nearest neighbour antiferromagnetic Heisenberg interactions there is no Neel ordering at zero temperature both for quantum and classical s pins. We show that, due to the peculiar structure, antisymmetric Dz

M. A. Yurishchev

An analysis is made of various methods of phenomenological renormalization based on finite-size scaling equations for inverse correlation lengths, the singular part of the free energy density, and their derivatives. The analysis is made using two-dimensional Ising and Potts lattices and the three-dimensional Ising model. Variants of equations for the phenome

P. Coleman, C. Hooley, Y. Avishai, Y. Goldin

We consider a `quantum dot&#39; in the Coulomb blockade regime, subject to an arbitrarily large source-drain voltage V. When V is small, quantum dots with odd electron occupation display the Kondo effect, giving rise to enhanced conductance. Here we investigate the regime where V is increased beyond the Kondo temperature and the Kondo resonance splits into t

Gemunu H. Gunaratne, Chamith S. Rajapaksa, Kevin E. Bassler, Kishore K. Mohanty

Inner porous regions play a critical role in the load bearing capability of large bones.We show that an extension of disordered elastic networks [Chung et. al., Phys. Rev. B, {\bf 54}, 15094 (1996)] exhibits analogs of several known mechanical features of bone. The &#34;stress-backbones&#34; and histograms of stress distributions for healthy and weak network

Jonathan Granot, Re&#39;em Sari

Gamma-Ray Burst (GRB) afterglows are well described by synchrotron emission from relativistic blast waves expanding into an external medium. The blast wave is believed to amplify the magnetic field and accelerate the electrons into a power law distribution of energies promptly behind the shock. These electrons then cool both adiabatically and by emitting syn

Daniel Wolf Savin, J. Martin Laming

We have investigated how the relative elemental abundances inferred from the solar upper atmosphere are affected by uncertainties in the dielectronic recombination (DR) rate coefficients used to analyze the spectra. We find that the inferred relative abundances can be up to a factor of ~5 smaller or ~1.6 times larger than those inferred using the currently r

S. Dib, J. Surdej, J. -F. Claeskens

Microlensing consists in two major effects: (1) variation in the apparent position of the background sources (astrometric component) and (2) flux variations of the background sources (photometric component). While the latter has been extensively used in the search for dark objects in the Galactic disk and halo (projects like MACHO (Alcock et al, 1997), EROS

Christine M. Clement, Adam Muzzin, Quentin Dufton, Thivya Ponnampalam

Based on a search of the literature up to May 2001, the number of known variable stars in Galactic globular clusters is approximately 3000. Of these, more than 2200 have known periods and the majority (approximately 1800) are of the RR Lyrae type. In addition to the RR Lyrae population, there are approximately 100 eclipsing binaries, 120 SX Phe variables, 60

Lee Hartmann, Javier Ballesteros-Paredes, Edwin A. Bergin

Observations of both star-forming regions and young, gas-free stellar associations indicate that most nearby molecular clouds form stars only over a short time span before dispersal; large-scale flows in the diffuse interstellar medium have the potential for forming clouds sufficiently rapidly, and for producing stellar populations with ages much less than t

James Di Francesco, Philip C. Myers, David J. Wilner, Nagayoshi Ohashi

Millimeter wavelength observations are presented of NGC 1333 IRAS 4, a group of highly-embedded young stellar objects in Perseus, that reveal motions of infall, outflow, rotation, and turbulence in the dense gas around its two brightest continuum objects, 4A and 4B. These data have finest angular resolution of approximately 2&#34; (0.0034 pc) and finest velo

J. E. Gallegos, J. F. Macias-Perez, C. M. Gutierrez, R. Rebolo

We describe the first instrument of a Cosmic Microwave Background experiment for mapping cosmological structures on medium angular scales (the COSMOSOMAS experiment) and diffuse Galactic emission. The instrument is located at Teide Observatory (Tenerife) and is based on a circular scanning sky strategy. It consists of a 1 Hz spinning flat mirror directing th

Christopher J. Conselice, John S. Gallagher, Rosemary F. G. Wyse

Sub-arcsecond images, taken in B, R, and H-Alpha filters, and area spectroscopy obtained with the WIYN 3.5-m telescope provide the basis for an investigation of the unusual structures in the stellar body and ionized gas in and around the Perseus cluster central galaxy, NGC 1275. Our H-Alpha filter is tuned to gas at the velocity of NGC 1275, revealing comple

Paul J. Groot, Gijs Nelemans, Danny Steeghs, Tom Marsh

We used the 6.5m MMT to obtain a spectrum of the AM CVn star CP Eri in quiescence. The spectrum is dominated by He I emission lines, which are clearly double peaked with a peak-to-peak separation of ~1900 km/s. The spectrum is similar to that of the longer period AM CVn systems GP Com and CE 315, linking the short and the long period AM CVn systems. In contr

D. S. Baskill, P. J. Wheatley, J. P. Osborne

We present ASCA observations of the dwarf nova Z Camelopardalis during outburst and during a transition from quiescence to another outburst. At the beginning of the transition the X-ray count rate was an order of magnitude higher and the spectrum much harder than during the outburst. As the transition progressed, the spectrum remained hard as the X-ray flux

T. M. Gledhill, M. Takami

The dust shell around the evolved star HD 179821 has been detected in scattered light in near-IR imaging polarimetry observations. Here, we subtract the contribution of the unpolarized stellar light to obtain an intrinsic linear polarization of between 30 and 40 per cent in the shell which seems to increase with radial offset from the star. The J and K band

S. Plueschke, M. Cervino, R. Diehl, K. Kretschmer

The COMPTEL observations of the diffuse galactic 1.809 MeV emission attributed to the radioactive decay of 26Al have confirmed the diffuse nature of this interstellar emission line. One of the most significant features of the reconstructed intensity pattern is a flux enhancement in the direction of the Cygnus region. This region is fairly young and contains

Toshiyuki Fukushige, Junichiro Makino

We investigate the structure of the dark matter halo formed in three different cold dark matter scenarios. We performed N-body simulations of formation of 13 cluster-sized halos. In all runs, density cusps proportional to $r^{-1.5}$ developed at the center. This result was independent of the cosmological models we simulated. We could not reproduce the cusp s

Timothy A. McKay, Erin Scott Sheldon, Judith Racusin, Philippe Fischer

We present new measurements of scaling laws relating the luminosity of galaxies to the amplitude and shape of their dark matter halos. Early imaging and spectroscopic data from the Sloan Digital Sky Survey are used to make weak lensing measurements of the surface mass density contrast Delta Sigma_+ around classes of lens objects. This surface mass density co

L. K. Hunt, L. Vanzi, T. X. Thuan

We present 4-micron ISAAC imaging and spectroscopy of the extremely metal-poor dwarf galaxy SBS 0335-052, aimed at a better understanding of the dust in this low-metallicity galaxy. The 4-micron emission turns out to be very compact, confined to the brightest pair of Super Star Clusters (SSCs). The Ks-L$^\prime$ color is extremely red, and the $L^\prime$ emi

R. Enomoto, T. Tanimori, CANGAROO collaboration

We have detected gamma-rays from RXJ1713$-$39 in the energy range between 400 GeV and 5 TeV using a new kind of analysis: likelihood analysis. The statistical significance of the measurement is greater than 8 $σ$. The details of this analysis method are presented.

Andrew Cumming, Sharon M. Morsink, Lars Bildsten, John L. Friedman

We present calculations of the spin-down of a neutron star atmosphere due to hydrostatic expansion during a Type I X-ray burst. We show that (i) Cumming and Bildsten overestimated the spin-down of rigidly-rotating atmospheres by a factor of two, and (ii) general relativity has a small (5-10%) effect on the angular momentum conservation law. We rescale our re

Masami Ouchi, Kazuhiro Shimasaku, Sadanori Okamura, Mamoru Doi

We study the clustering properties of about 1200 z~4 Lyman Break Galaxy (LBG) candidates with i&#39;<26 which are selected by color from deep BRi&#39; imaging data of a 618 arcmin^2 area in the Subaru/XMM-Newton Deep Field taken with Subaru Prime Focus Camera. The contamination and completeness of our LBG sample are evaluated, on the basis of the Hubble Deep

John S. Gallagher, Christopher J. Conselice, Rosemary F. G. Wyse

Despite their apparent fragile appearance, dwarf spheroidals are the most common galaxy type in clusters. In this paper we consider some of the issues associated with two major models for the origin of these dwarfs: primeval galaxies which formed with the cluster and the modification of accreted systems. We argue that the present observational evidence, deri

Matthew Colless, Keith Taylor

We propose a new multi-object spectrograph for the VLT. MAXIMUS (MAXimum MUltiplex Spectrograph) will fully exploit the multiplexing capabilities of the OzPoz fibre positioner in order to extend and complement FLAMES and VIMOS in covering observational parameter space, and to meet the increasing demand for multi-object spectroscopy by ESO users in the next d

Kartik Sheth

We study the molecular gas properties in the central kiloparsec of 29 barred and 15 unbarred spirals from the BIMA Survey of Nearby Galaxies (SONG). We find that the mean nuclear molecular gas surface density of barred spirals (<Sigma_{nuc}>=309 +/- 71 Msun pc^{-2}) is three times higher than that of unbarred spirals (<Sigma_{nuc}>=107 +/- 29 Msun pc^{-2}).

Hale Bradt, Alan M. Levine, Francis E. Marshall, Ronald A. Remillard

The role of the Rossi X-ray Timing Explorer (RXTE) in the study of Gamma-ray Bursts (GRBs) is reviewed. Through April 2001, the All-Sky Monitor (ASM) and the Proportional Counter Array (PCA) instruments have detected 30 GRBs. In 16 cases, an early celestial position was released to the community, sometimes in conjunction with IPN results. The subsequent opti