November 2001 arXiv papers — page 6

Felix Naef, Daniel A. Lim, Nila Patil, Marcelo Magnasco

High-density oligonucleotide arrays are among the most rapidly expanding technologies in biology today. In the {\sl GeneChip} system, the reconstruction of the target concentration depends upon the differential signal generated from hybridizing the target RNA to two nearly identical templates: a perfect match (PM) and a single mismatch (MM) probe. It has bee

Oscar Bolina

We solve a difficult problem involving velocity and acceleration components along oblique axes, and propose two problems of central force motion to be solved using oblique axes.

Giuliano Buceti, Luigi Fortuna, Alessandro Rizzo, Maria Gabriella Xibilia

In this paper, an automatic sensor validation strategy for the measurements of plasma line density in the ENEA-FTU tokamak is presented. Density measurements are performed by a 5-channel DCN interferometer. The approach proposed is based on the design of a neural model of the observed system., i.e. a model able to emulate the behavior of a fault-free sensor

D. Mugnai, A. Ranfagni, L. Ronchi

The tunneling time is here investigated by means of an electromagnetic model, for a system where a gap, between two parallel planes, acts as a classically-forbidden region for an impinging pulse with incidence angle larger than the critical angle. In all cases of frustrated total reflection we obtain a superluminal behavior both for phase and group delays.

M. O. Oktel, L. S. Levitov

Exchange in a Boltzmann gas of bosons with several internal states leads to collective transport of internal polarization. The internal dynamics can be understood as Larmor precession in the presence of a torque induced by atoms on each other via exchange coupling. A generalized Bloch equation that includes interatomic exchange effects as well as orbital mot

P. Olbratowski, J. Dobaczewski, J. Dudek, T. Rzaca-Urban

We report on the first Skyrme-Hartree-Fock calculations with the tilted-axis cranking in the context of magnetic rotation. The mean field symmetries, differences between phenomenological and self-consistent methods and the generation of shears-like structures in the mean field are discussed. Significant role of the time-odd spin-spin effective interaction is

Klaus Morawetz

The numerical solution of the nonlocal kinetic equation allows to simulate heavy ion reactions around Fermi energy. The expansion velocity and density profile show specific radial dependence which can be described with a Tsallis exponent of $q=5/3$. This might be considered as an indication of a phase transition.

M. M. Giannini, E. Santopinto, A. Vassallo

The constituent quark model based on a hypercentral approach takes into account three-body force effects and standard two-body potential contributions. The quark potential contains a hypercentral interaction, to which a hyperfine term is added. While the hypercentral potential supplies good values for the centroid energies of the resonance multiplets and a r

A. V. Avdeenkov, S. P. Kamerdzhiev

In order to analyse the role of the quasiparticle-phonon interaction in the origin of nuclear gap, we applied an approach which is similar to the Eliashberg theory for usual superconductors. We obtained that the averaged contribution of the quasiparticle-phonon mechanism to the observed value of the pairing gap for $^{120}$Sn is 26% and the BCS-type mechanis

A. Bhattacharyay

The amplitude equation of Gierer-Mainhardt model has been actually derived near the boundary abuot which Turing and Hopf modes exist. In a parameter region where Hopf-Turing mixed mode solution is stable, a chaotic state that generally results from interaction between mixed modes, is observed. This chaotic region follows a strong selection of a spatially per

Nadia Bel Baraka

Comparing the star product defined by Takhtajan on the Poisson-Lie group GL(2) and any star product calculated from the Kontsevich's graphs (any ''K-star product'') on the same group, we show, by direct computation, that the Takhtajan star product on GL(2) can't be written as a K-star product.

Daniel Dugger, Daniel C. Isaksen

We show that if U is a hypercover of a topological space X then the natural map from hocolim U to X is a weak equivalence. This fact is used to construct topological realization functors for the A^1-homotopy theory of schemes over real and complex fields.

Tomek Bartoszynski, Andrzej Nowik, Tomasz Weiss

The paper contains two results pointing to the lack of symmetry between measure and category. Assume CH. There exists a strongly meager subset of the Cantor set that can be mapped onto the Cantor set by a uniformly continuous function. (It is well known that uniformly continuous image of a strongly null set is strongly null). A ZFC version of this result is

Warren Dicks, Peter H. Kropholler, Ian J. Leary, Simon Thomas

For each finite ordinal n, and each locally-finite group G of cardinality aleph-sub-n, we construct an (n+1)-dimensional, contractible CW-complex on which G acts with finite stabilizers. We use the complex to obtain information about cohomology with induced coefficients. Our techniques also give information about the location of some large free abelian group

Martin Goldstern, Miroslav Ploscica

We show that all balanced d-lattices must be complemented, answering a question of Chajda and Eigenthaler. (A bounded lattice is balanced if any two congruences agree on their 1-classes iff they agree on their 0-classes.) Our main tool is the characterization of d-lattices (a class of bounded lattices including the bounded distributive lattices, originally d

S. Birauas, D. Opris

We study the steady uniphase and multiphase solutions of the discretized nonlinear damped wave equation.Conditions for the stability abd instability of the steady solutions are given;in the instability case the linear stable and unstable associated manifolds are described.

Matthieu Picantin

Birman, Ko and Lee have introduced a new monoid ${\cal B}^{*}_{n}$--with an explicit presentation--whose group of fractions is the $n$-strand braid group ${\cal B}_{n}$. Building on a new approach by Digne, Michel and himself, Bessis has defined a {\it dual} braid monoid for every finite Coxeter type Artin-Tits group extending the type A case. Here, we give

Patrick Dehornoy

A number of properties of spherical Artin groups extend to Garside groups, defined as the groups of fractions of monoids where least common multiples exist, there is no nontrivial unit, and some additional finiteness conditions are satisfied \cite{Dgk}. Here we investigate a wider class of groups of fractions, called {\it thin}, which are those associated wi

S. A. Kudryavtsev

In this paper we prove the existence of purely log terminal blow-up for Kawamata log terminal singularity and obtain the criterion for a singularity to be weakly exceptional in terms of the exceptional divisor of plt blow-up.

Yat Sun Poon, Andrew Swann

The geometry arising from Michelson & Strominger's study of N=4B supersymmetric quantum mechanics with superconformal D(2,1;alpha)-symmetry is a hyperKaehler manifold with torsion (HKT) together with a special homothety. It is shown that different parameters alpha are related via changes in potentials for the HKT target spaces. For alpha not 0 or -1, we

Patrick Dehornoy

A combinatorial property of prositive group presentations, called completeness, is introduced, with an effective criterion for recognizing complete presentations, and an iterative method for completing an incomplete presentation. We show how to directly read several properties of the associated monoid and group from a complete presentation: cancellativity or

M. Campanino, D. Ioffe, Y. Velenik

We derive precise Ornstein-Zernike asymptotic formula for the decay of the two-point function in the general context of finite range Ising type models on Z^d. The proof relies in an essential way on the a-priori knowledge of the strict exponential decay of the two-point function and, by the sharp characterization of phase transition due to Aizenman, Barsky a

Yossi Lonke

The $L^p$-cosine transform of an even, continuous function $f\in C_e(\Sn)$ is defined by: $$H(x)=\int_{\Sn}|\ip{x}ξ|^pf(ξ) dξ,\quad x\in {\R}^n.$$ It is shown that if $p$ is not an even integer then all partial derivatives of even order of $H(x)$ up to order $p+1$ (including $p+1$ if $p$ is an odd integer) exist and are continuous everywhere in ${\R}^n\backs

Tyler J. Evans, Dmitry Fuchs

We show that the p-operator in the Witt algebra (the restricted Lie algebra of derivations of the quotient of the polynomial algebra over a field of characteristic p by the ideal generated by the p-th power of the indeterminant) is given by multiplication by a scalar.

Erik Pedersen, Frank Quinn, Andrew Ranicki

We provide a proof of the controlled surgery sequence, including stability, in the special case that the local fundamental groups are trivial. Stability is a key ingredient in the construction of exotic homology manifolds by Bryant, Ferry, Mio and Weinberger, but no proof has been available. The development given here is based on work of M. Yamasaki.

E. Bedos, R. Conti, L. Tuset

We introduce and study several amenability properties for unitary corepresentations and *-representations of algebraic quantum groups, which may be used to characterize amenability or co-amenability of such groups. As a background for this study, we also investigate the involved tensor C*-categories.

Brendan Hassett, Yuri Tschinkel

We compute the effective cone for the moduli space of stable rational curves with at most six marked points.

Geoffrey F. Chew, Henry P. Stapp

A 6-component "wave function" (not field, but S-matrix interpretable) for a massive spin-1 particle parallels the Dirac "chirality-doubled" 4-component wave function for a spin-1/2 particle, by pairing two wave functions for same spin but opposite "handedness". The correlated "opposite-parity" pair of complex 3-vectors defines

U. Trittmann

The evaluation of field theoretic correlators at strong couplings is especially interesting in the light of recently discovered string/field theory correspondences. We present a calculation of the stress-tensor correlator in N=1 SYM theory in 2+1 dimensions. We calculate this object numerically with the method of supersymmetric discrete light-cone quantizati

Peter Rajan

We compute RR charges of D2-branes on a background with H-field which belongs to a nontrivial cohomology class. We discover that the RR charge depends on the configuration of the background `electric' RR field. This result explains the ambiguity in the definition of the RR charge previously observed in the SU(2) WZW model.

M. P. Fry

The current status of bounds on and limits of fermion determinants in two, three and four dimensions in QED and QCD is reviewed. A new lower bound on the two-dimensional QED determinant is derived. An outline of the demonstration of the continuity of this determinant at zero mass when the background magnetic field flux is zero is also given.

Henrik Aratyn, Johan van de Leur

An integrable structure behind Witten--Dijkgraaf--Verlinde--Verlinde (WDVV) equations is identified with reduction of a Riemann-Hilbert problem for a homogeneous GL(N, C) loop group. Reduction requires the dressing matrices to be fixed points of a loop group automorphism of order two resulting in a sub-hierarchy of gl(N,C) hierarchy containing only odd symme

V. V. Nesterenko, G. Lambiase, G. Scarpetta

The basic results in calculations of the thermodynamic functions of electromagnetic field in the background of a dilute dielectric ball at zero and finite temperature are presented. Summation over the angular momentum values is accomplished in a closed form by making use of the addition theorem for the relevant Bessel functions. The behavior of the thermodyn

Stanley J. Brodsky

Heisenberg's matrix formulation of quantum mechanics can be generalized to relativistic systems by evolving in light-front time tau = t+z/c. The spectrum and wavefunctions of bound states, such as hadrons in quantum chromodynamics, can be obtained from matrix diagonalization of the light-front Hamiltonian on a finite dimensional light-front Fock basis de

Holger B. Nielsen, Masao Ninomiya

We propose a new way of second quantizing string theory. The method is based on considering the Fock space of strings described by constituents which make up the $X^μ_R$ and the $X^μ_L$ i.e. the right and left mover modes separately. A state with any number of strings get represented by the Cartesian product of two free particle Fock spaces, one for right mo

A. J. M. Medved

We consider a brane universe in a Reissner-Nordstrom-de Sitter background spacetime of arbitrary dimensionality. It is shown that the brane evolution is described by generalized Friedmann equations for radiative matter along with a stiff-matter contribution. On the basis of the (conjectured) dS/CFT correspondence, we identify various thermodynamic properties

Marcus Spradlin, Andrew Strominger, Anastasia Volovich

These lectures present an elementary discussion of some background material relevant to the problem of de Sitter quantum gravity. The first two lectures discuss the classical geometry of de Sitter space and properties of quantum field theory on de Sitter space, especially the temperature and entropy of de Sitter space. The final lecture contains a pedagogica

The CDF collaboration

We present measurements of the B+ meson total cross section and differential cross section $dσ/ dp_T$. The measurements use a $98\pm 4$ pb^{-1} sample of $p \bar p$ collisions at $\sqrt{s}=1.8$ TeV collected by the CDF detector. Charged $B$ meson candidates are reconstructed through the decay $B^{\pm} \to J/ψK^{\pm}$ with $J/ψ\to μ^+ μ^-$. The total cross se

Z. Sullivan, P. M. Nadolsky

We investigate the uncertainties of the heavy-quark parton distribution functions in the variable flavor number scheme. Because the charm- and bottom-quark parton distribution functions (PDFs) are constructed predominantly from the gluon PDF, it is a common practice to assume that the heavy-quark and gluon uncertainties are the same. We show that this approx

S. V. Molodtsov, G. M. Zinovjev

The interaction of light quarks and instanton liquid in the phase of nonzero values of chiral condensate is studied at finite quark/baryon density. Calculating the generating functional in the tadpole approximation we investigate the behaviour of dynamical quark mass and chiral condensate together with instanton liquid density (which shows insignificant incr

Minos Axenides

Semitopological Vortices (Q-Rings) are identified to be classical soliton configurations whose stability is attributed to both topological and nontopological charges. We discuss some recent work on the simplest possible realization of such a configuration in a scalar field theory with an unbroken U(1) global symmetry. We show that Q-Rings correspond to local

G. W. Carter

If quark matter exists in the cores of neutron stars, it is most likely color superconducting. Thus a phase transition from free to paired quark matter might occur during the first minute of proto-neutron star evolution. In this talk I discuss how critical behavior of the medium will modify neutrino diffusion, possibly leading to a short temporal variation i

E. V. Shuryak, A. R. Zhitnitsky

It has been recently shown that meta-stable domain walls exist in high-density QCD ($μ\neq 0$) as well as in QCD with large number of colors ($N_c\to\infty$), with the lifetime being exponentially long in both cases. Such metastable domain walls may exist in our world as well, especially in hot hadronic matter with temperature close to critical. In this pape

A. Widom, Y. N. Srivastava

The electric field corrections to the recently measured muon magnetic moment g-2 anomaly are considered from both the classical (BMT) and the quantum mechanical (Dirac) viewpoints. In both views, we prove that the electric field inducing the horizontal betatron tune does not renormalize the anomaly frequency. With this result kept in mind, the experimental m

M. Laine

We review briefly the current status of thermal phase transitions within the Standard Model and its simplest extensions. We start with an update on QCD thermodynamics, then discuss the electroweak phase transition, particularly in supersymmetric extensions of the Standard Model, and end with a few remarks on the cosmological constraints that thermal phase tr

K. Enqvist, A. Jokinen, T. Multamaki, I. Vilja

We consider different types of Q-balls as self-interacting dark matter. For the Q-balls to act as the dark matter of the universe they should not evaporate, which requires them to carry very large charges; depending on the type, the minimum charge could be as high as Q \sim 10^{33} or the Q-ball coupling to ordinary matter as small as \sim 10^{-35}. The cros

Matthew Mewes

Spectropolarimetry of distant sources of electromagnetic radiation at wavelengths ranging from infrared to ultraviolet are used to constrain Lorentz violation. A bound of 3x10^{-32} is placed on coefficients for Lorentz violation.

W. Bernreuther, A. Brandenburg, Z. G. Si, P. Uwer

Top quark-antiquark ($t\bar t$) pairs will be produced copiously at the Tevatron collider and in huge numbers at the LHC. This will make possible detailed investigations of the properties and interactions of this quark flavor. The analysis and interpretation of future data requires precise predictions of the hadronic production of $t\bar t$ pairs and of thei

Yu. A. Simonov, J. A. Tjon, J. Weda

An effective quark Lagrangian is derived from first principles through bilocal gluon field correlators. It is used to write down equations for baryons, containing both perturbative and nonperturbative fields. As a result one obtains magnetic moments of octet and decuplet baryons without introduction of constituent quark masses and using only string tension a

Robert J. Geller, Tatsuhiko Hara

Several proposed experiments will send beams of neutrinos through the Earth along paths with a source-receiver distance of hundreds or thousands of kilometers. Knowledge of the physical properties of the medium traversed by these beams, in particular the density, will be necessary in order to properly interpret the experimental data. Present geophysical know

A. Rebhan

These lectures give an introduction to thermal perturbation theory, hard thermal loops, and their use in a nonperturbative, approximately self-consistent resummation of the thermodynamical potentials of quantum chromodynamics.

Stanley J. Brodsky

A natural calculus for describing the bound-state structure of relativistic composite systems in quantum field theory is the light-front Fock expansion which encodes the properties of a hadrons in terms of a set of frame-independent n-particle wavefunctions. Light-front quantization in the doubly-transverse light-cone gauge has a number of remarkable advanta

G. Kramer, H. S. Song, Chaehyun Yu

The joint angular distribution of the decay B \to J/ΨV, where V is an axial vector or vector resonance, followed by the subsequent decay processes of the J/Ψand V is calculated using the covariant density method. In particular, the case where V is the axial vector meson K_1(1270) which decays into K ρis considered as well as the case that V is the vector mes

E. Jenkins

The 1/N_c expansion provides a theoretical method for analyzing the spin-flavor symmetry properties of baryons in QCD that is quantitative, systematic and predictive. An exact spin-flavor symmetry exists for large-N_c baryons, whereas for QCD baryons, the spin-flavor symmetry is approximate and is broken by corrections proportional to the symmetry-breaking p

Ira Z. Rothstein

In this talk I review recent progress made in extracting V_{ub} from the cut electron energy and hadronic mass spectra of inclusive B meson decays utilizing the data from radiative decays. It is shown that an extraction is possible without modeling the B meson structure function. I discuss the issues involving the assumptions of local duality in various extr

B. Nicolescu, J. R. Cudell, V. V. Ezhela, P. Gauron

We consider several classes of analytic parametrizations of hadronic scattering amplitudes, and compare their predictions to all available forward data (proton- proton, antiproton-proton, pion-proton, kaon-proton, photon-proton, photon- photon, sigma-proton). Although these parametrizations are very close for energy larger than 9 GeV, it turns out that they

Barbara Mele

Theoretical predictions for the top quark rare decays are reviewed within and beyond the standard model. Expectations at the CERN Large Hadron Collider are discussed.

A. Duncan, E. Eichten, H. Thacker

A truncated determinant algorithm is used to study the physical effects of the quark eigenmodes associated with eigenvalues below 420 MeV. This initial high statistics study focuses on coarse ($6^4$) lattices (with O($a^2$) improved gauge action), light internal quark masses and large physical volumes. Three features of full QCD are examined: topological cha

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

The extraction of quantities from lattice QCD calculations at realistic quark masses is of considerable importance. Whilst physical quark masses are some way off, the recent advances in the calculation of hadron masses within full QCD now invite improved extrapolation methods. We show that, provided the correct chiral behaviour of QCD is respected in the ext

Noriyoshi Ishii, Hideo Suganuma, Hideo Matsufuru

We study the glueball properties at finite temperature below T_c using SU(3) anisotropic quenched lattice QCD with beta=6.25, the renormalized anisotropy gamma = a_s/a_t = 4 and 20^3 \times N_t (N_t = 35, 36, 37, 38, 40, 43, 45, 50, 72). From the temporal correlation analysis with the smearing method, we observe the mass reduction of about 20 % for the lowes

Doug Toussaint

I summarize recent developments in spectrum calculations using Kogut-Susskind quarks. Theoretical developments include one-loop computations with improved actions. I present some recent simulation results, mostly from a MILC collaboration project using three flavors. Effects of dynamical quarks are clearly seen in the isovector 0++ meson propagator and in th

The BABAR Collaboration, B. Aubert

We search for direct CP violation in charmless hadronic B decays observed in a sample of about 22.7 million $B\bar{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $e^+e^-$ collider. We measure the following charge asymmetries: ${\cal A}_{CP} (B^{\pm}\toη^\prime K^{\pm}) = -0.11\pm 0.11\pm 0.02$, ${\cal A}_{CP} (B^{\pm}\toωπ^{\pm})

J. Chen, M. Laznovsky, R. MacKenzie

It has been the goal of SLAC Controls Software to offload processing from the aging Alpha/VMS based control system onto machines that are more widely accepted and used. An additional goal has been to provide more modern software tools to our user community. This paper presents two software products which satisfy those goals.

David E Hutchcroft

The results of searches for several type of physics beyond the Standard Model using data from the four LEP experiments are presented. In the absence of any excess signal events seen in the data limits are placed on the existence of extra-dimensions, gauge mediated supersymmetry and some exotic states.

Sh. Zh. Akhmadaliev, G. Ya. Kezerashvili, S. G. Klimenko, R. N. Lee

The new data analysis of the experiment, where the photon splitting in the atomic fields has been observed for the first time, is presented. This experiment was performed at the tagged photon beam of the ROKK-1M facility at the VEPP-4M collider. In the energy region of 120-450 MeV, the statistics of $1.6\cdot 10^9$ photons incident on the BGO target was coll

Florian Siebel, Jose A. Font, Ewald Mueller, Philippos Papadopoulos

We present new numerical algorithms for the coupled Einstein-perfect fluid system in axisymmetry. Our framework uses a foliation based on a family of light cones, emanating from a regular center, and terminating at future null infinity. This coordinate system is well adapted to the study of the dynamical spacetimes associated with isolated relativistic compa

G. S. Khadekar, Avinash R. Nagpure

We study the Robertson-Walker type model in the Lyttleton-Bondi universe in five dimensional general theory of relativity. Some exact and physical properties of solutions are discussed.

G. S. Khadekar, Shilpa Samdurkar

Higher dimensional solutions are obtained for a homogeneous, spatially isotropic cosmological model in Wesson theory of gravitation. Some cosmological parameter are also calculated for this model.

Yann Loyer, Nicolas Spyratos, Daniel Stamate

We address the problem of integrating information coming from different sources. The information consists of facts that a central server collects and tries to combine using (a) a set of logical rules, i.e. a logic program, and (b) a hypothesis representing the server's own estimates. In such a setting incomplete information from a source or contradictory

Gustavo A. Ospina, Baudouin Le Charlier

Environments for systematic construction of logic programs are needed in the academy as well as in the industry. Such environments should support well defined construction methods and should be able to be extended and interact with other programming tools like debuggers and compilers. We present a variant of the Deville methodology for logic program developm

P. Allegrini, J. Bellazzini, G. Bramanti, M. Ignaccolo

We show that the dynamic approach to Lévy statistics is characterized by aging and multifractality, induced by an ultra-slow transition to anomalous scaling. We argue that these aspects make it a protoptype of complex systems.

E. V. Tsiper

Using Darling's theorem on products of generalized hypergeometric series an analytic expression is obtained for the Coulomb matrix elements in the lowest Landau level in the representation of angular momentum. The result is important in the studies of Fractional Quantum Hall effect (FQHE) in disk geometry. Matrix elements are expressed as simple finite s

M. Katori, H. Tanemura

We study systems of interacting Brownian particles in one dimension constructed as the diffusion scaling limits of Fisher's vicious walk models. We define two types of nonintersecting Brownian motions, in which we impose no condition (resp. nonintersecting condition forever) in the future for the first-type (resp. second-type). It is shown that, when all

Kok-Kiong Loh, Avadh Saxena, Turab Lookman, Atul N. Parikh

We propose a model to understand periodic oscillations relevant to the origin of mesoscopic channels formed during a Langmuir-Blodgett deposition observed in recent experiments \{M. Gleiche, L.F. Chi, and H. Fuchs, Nature {\bf 403}, 173 (2000)\}. We numerically study one-dimensional flow of a van der Waals fluid near its discontinuous liquid-gas transition a

Pasquale Calabrese, Andrea Pelissetto, Ettore Vicari

We consider ring polymers in good solvents in the dilute limit. We determine the structure factor and the monomer-monomer distribution function. We compute accurately the asymptotic behavior of these functions for small and large momenta and distances by using field-theoretical methods. Phenomenological expressions with the correct asymptotic behaviors are a

D. Alfe`, M. J. Gillan, G. D. Price

Several research groups have recently reported {\em ab initio} calculations of the melting properties of metals based on density functional theory, but there have been unexpectedly large disagreements between results obtained by different approaches. We analyze the relations between the two main approaches, based on calculation of the free energies of solid

Miroslav Kotrla, Joachim Krug

We discuss effects of the different chemical bondings on the island morphology and on the island density scaling in two-component submonolayer growth. Different regimes depending on the strength of the mutual interactions and on the relative mobility of species are described and studied by kinetic Monte Carlo simulations using a two-component solid-on-solid

Huijie Yang, Fangcui Zhao, Xizhen Wu, Zhuxia Li

An analytical formula for the contributions of the trend leftovers in DFA method is presented, based upon which the crossovers in DFA are investigated in detail. This general formula can explain the calculated results with DFA method for some examples in literature very well.

Gernot Alber, Georgios Metikas

The renormalization group is not only a powerful method for describing universal properties of phase transitions but it is also useful for evaluating non- universal properties beyond mean-field theory. In this contribution we concentrate on these latter aspects of the renormalization group approach. We introduce its main underlying ideas in the familiar cont

A. E. Muryshev, G. V. Shlyapnikov, W. Ertmer, K. Sengstock

We find two types of moving dark soliton textures in elongated Bose-Einstein condensates: non-stationary kinks and proper dark solitons. The former have a curved notch region and rapidly decay by emitting phonons and/or proper dark solitons. The proper moving solitons are characterized by a flat notch region and we obtain the diagram of their dynamical stabi

C. W. J. Beenakker, H. van Houten

We calculate the DC Josephson current through a semiconducting quantum dot which is weakly coupled by tunnel barriers to two superconducting reservoirs. A Breit-Wigner resonance in the conductance corresponds to a resonance in the critical current, but with a different (non-lorentzian) lineshape.

C. Timm, F. Schäfer, F. von Oppen

In a recent Letter, Berciu and Bhatt have presented a mean-field theory of ferromagnetism in III-V semiconductors doped with manganese, starting from an impurity band model. We show that this approach gives an unphysically broad impurity band and is thus not appropriate for (Ga,Mn)As containing 1-5% Mn. We also point out a microscopically unmotivated sign ch

Szilard Pafka, Imre Kondor

According to recent findings [1,2], empirical covariance matrices deduced from financial return series contain such a high amount of noise that, apart from a few large eigenvalues and the corresponding eigenvectors, their structure can essentially be regarded as random. In [1], e.g., it is reported that about 94% of the spectrum of these matrices can be fitt

D. J. Priour, H. A. Fertig

At the nucleus of a superconducting vortex is a small, circular region where superconductivity is destroyed. Like an atomic nucleus, this core may become deformed, and such distortions can have important consequences in non-equilibrium situations. Using Ginzburg-Landau theory, we have investigated this phenomenon for vortices in the presence of artificial de

Caryl Gronwall, Vicki Sarajedini, John Salzer

Objective-prism surveys for UV-excess and emission-line objects, especially the First and Second Byurakan Surveys, have been central to the study of active galactic nuclei (AGNs). We review previous line-selected surveys for AGNs and discuss their contribution to our understanding of the AGN phenomena. In addition, we present results from the KPNO Internatio

M. Bureau, C. Carignan

Neutral hydrogen VLA D-array observations of the dwarf irregular galaxy HoII, a prototype galaxy for studies of shell formation, are presented. The large-scale HI morphology is reminiscent of ram pressure and is unlikely caused by interactions. A case is made for intragroup gas in poor and compact groups like the M81 group, to which HoII belongs. Numerous sh

Henry E. Kandrup, Ioannis V. Sideris

This paper summarises an investigation of chaos in a toy potential which mimics much of the behaviour observed for the more realistic triaxial generalisations of the Dehnen potentials, which have been used to model cuspy triaxial galaxies both with and without a supermassive black hole. The potential is the sum of an anisotropic harmonic oscillator potential

A. E. Broderick, M. Prakash, J. M. Lattimer

We investigate the effects of very strong magnetic fields upon the equation of state of dense bayonic matter in which hyperons are present. In the presence of a magnetic field, the equation of state above nuclear density is significantly affected both by Landau quantization and magnetic moment interactions, but only for field strengths $B>5\times10^{18}$ G.

L. Eyer, C. Aerts, M. Van Loon, F. Bouckaert

We report on the results from a large photometric campaign on thirty five gamma Dor star candidates undertaken at the Institute of Astronomy of the University of Leuven in the framework of the Flanders -- South-Africa grant. An overview of the data, as well as the results of the analysis of the obtained time series are presented, the main conclusion being th

T. J. Turner, P. Romano, S. B. Kraemer, I. M. George

We present spectral results from a multi-satellite, broad-band campaign on the Narrow-line Seyfert 1 galaxy Ton S180 performed at the end of 1999. We discuss the spectral-energy distribution of the source, combining simultaneous Chandra, ASCA and EUVE data with contemporaneous FUSE, HST, and ground-based optical and infra-red data. The resulting SED shows th

Daniel Stern, Edward C. Moran, Alison L. Coil, Andrew Connolly

We report on observations of a TypeII quasar at redshift z=3.288, identified as a hard X-ray source in a 185 ks observation with the Chandra X-ray Observatory and as a high-redshift photometric candidate from deep, multiband optical imaging. CXOJ084837.9+445352 (hereinafter CXO52) shows an unusually hard X-ray spectrum from which we infer an absorbing column

Andrew Gould, Samir Salim

Stars in the mass range 8 Msun<M<30 Msun are thought to end their lives as luminous supernovae that leave behind a neutron star. However, if a substantial fraction of these stars instead ended as black-hole remnants, without producing a supernova (a `failed&#39; supernova), how would one know? We show that, under plausible assumptions, the Hipparcos catalog

D. K. Strickland, T. M. Heckman, K. A. Weaver, C. G. Hoopes

We present a detailed case study of the diffuse X-ray and H-alpha emission in the halo of NGC 253, a nearby edge-on starburst galaxy driving a galactic superwind. The arcsecond spatial resolution of the Chandra ACIS instrument allows us to study the spatial and spectral properties of the diffuse X-ray emitting plasma with greatly superior spatial and spectra

J. D. Monnier, L. J. Greenhill, P. G. Tuthill, W. C. Danchi

A small number of dusty Wolf-Rayet stars have been resolved into pinwheel nebulae, defined by their ``rotating&#39;&#39; spiral dust shells observed in the infrared. This morphology is naturally explained by dust formation associated with colliding winds in a binary system. In order to confirm and further explore this hypothesis, we have observed the known p

J. S. B. Wyithe, E. L. Turner

It is conventional to calculate the probability of microlensing for a cosmologically distant source based on the Press-Gunn approximation that the lensing objects are uniformly and randomly distributed in the intervening space with a constant comoving density. Here we investigate more realistic cosmological microlensing statistics by considering the strong s

Itziar Aretxaga, David H. Hughes, Edward Chapin, Enrique Gaztanaga

More than 150 galaxies have been detected in blank-field millimetre and sub-millimetre surveys. However the redshift distribution of sub-mm galaxies remains uncertain due to the difficulty in identifying their optical-IR counterparts, and subsequently obtaining their spectroscopic emission-line redshifts. In this paper we discuss results from a Monte-Carlo a

Adrienne M. Juett, Herman L. Marshall, Deepto Chakrabarty, Claude R. Canizares

We report on a 25 ks observation of the anomalous X-ray pulsar 4U 0142+61 with the High Energy Transmission Grating Spectrometer (HETGS) on the Chandra X-ray Observatory. The continuum spectrum is consistent with previous measurements and is well fit by an absorbed power-law + blackbody model with photon index Gamma=3.3+/-0.4 and blackbody temperature kT=0.4

Nazar R. Ikhsanov

The condition for the subsonic propeller - accretor state transition of neutron stars in wind-fed mass-exchange binary systems is discussed. I show that the value of the break period, at which the neutron star change its state to accretor, presented by Davies & Pringle (1981) is underestimated by a factor of 7.5. The correct value is P_{\rm br} = 450 μ_{30}^

T. Treu, M. Stiavelli, S. Casertano, P. Møller

We have measured the Fundamental Plane (FP) parameters for a sample of 30 field early-type galaxies (E/S0) in the redshift range 0.1<z<0.66. We find that: i) the FP is defined and tight out to the highest redshift bin; ii) the intercept γevolves as dγ/dz=0.58+0.09-0.13 (for Ω=0.3, Ω_Λ=0.7), or, in terms of average effective mass to light ratio, as d\log(M/L_

L. Fuhrmann, T. P. Krichbaum, G. Cimò, T. Beckert

There is new evidence which identifies seasonal changes of the variability time scale in intraday variable sources with refractive interstellar scintillation effects. Such a RISS-model takes the annual change of the Earth velocity relative to the scattering medium into account. In September 1998 we found a remarkable prolongation of the variability time scal