July 2002 arXiv papers — page 22

M. Dasgupta, G. P. Salam

We present results from a recently completed project to calculate next-to-leading logarithmic resummed distributions for a variety of event shapes in the 1+1-jet limit of DIS. This allows fits for the strong coupling and for non-perturbative effects using the large amount of data on these observables from HERA. Spin-offs include the discovery of a new class

Felipe C. Mena, Reza Tavakol, Marco Bruni

We summarize recent results concerning the evolution of second order perturbations in flat dust irrotational FLRW models with $Λ\ne 0$. We show that asymptotically these perturbations tend to constants in time, in agreement with the cosmic no-hair conjecture. We solve numerically the second order scalar perturbation equation, and very briefly discuss its all

David Langlois

Recent theoretical developments have generated a strong interest in the ``brane-world'' picture, which assumes that ordinary matter is trapped in a three-dimensional submanifold, usually called brane, embedded in a higher dimensional space. The purpose of this review is to introduce some basic results concerning gravity in these models and then to pr

Carl E. Dolby, Stephen F. Gull

In a recent paper (hep-th/0103228) a new initial value formulation of fermionic QFT was presented that is applicable to an arbitrary observer in any electromagnetic background. This approach suggests a consistent particle interpretation at all times, with the concept of `radar time' used to generalise this interpretation to an arbitrarily moving observer

L. C. Garcia de Andrade

Riemannian Killing conserved currents are used to find the energy spectra of classical spinning particles moving around a spinning string in Einstein-Cartan (EC) theory of gravity. It is shown that a continuos spectrum is obtained for planar open orbits the energy shift between the upper and lower bounds obtained for circular planar orbits. A spin-spin effec

Sergiu I. Vacaru, Panayiotis Stavrinos, Denis Gontsa

We study new classes three dimensional black hole solutions of Einstein equations written in two holonomic and one anholonomic variables with respect to anholonomic frames Thermodynamic properties of such (2+1)-black holes with generic local anisotropy (having elliptitic horizons) are studied by applying geometric methods. The corresponding thermodynamic sys

Sergiu I. Vacaru, Panayiotis Stavrinos, Evghenii Gaburov

We apply the method of moving anholonomic frames in order to construct new classes of solutions of the Einstein equations on (2+1)-dimensional pseudo-Riemannian spaces. There are investigated black holes with deformed horizons and renormalized locally anisotropic constants. We speculate on properties of such anisotropic black holes with characteristics defin

Adnan Darwiche, Pierre Marquis

In this paper, we investigate the extent to which knowledge compilation can be used to improve inference from propositional weighted bases. We present a general notion of compilation of a weighted base that is parametrized by any equivalence--preserving compilation function. Both negative and positive results are presented. On the one hand, complexity result

W. Chen, M. Tanaka

Based on the radial basis function (RBF), non-singular general solution and dual reciprocity method (DRM), this paper presents an inherently meshless, integration-free, boundary-only RBF collocation techniques for numerical solution of various partial differential equation systems. The basic ideas behind this methodology are very mathematically simple. In th

Gerhard Brewka

Logic programs with ordered disjunction (LPODs) combine ideas underlying Qualitative Choice Logic (Brewka et al. KR 2002) and answer set programming. Logic programming under answer set semantics is extended with a new connective called ordered disjunction. The new connective allows us to represent alternative, ranked options for problem solutions in the head

Michael Plischke, D. C. Vernon, Bela Joos

We study a two-component model for gelation consisting of $f$-functional monomers (the gel) and inert particles (the solvent). After equilibration as a simple liquid, the gel particles are gradually crosslinked to each other until the desired number of crosslinks has been attained. At a critical crosslink density the largest gel cluster percolates and an amo

Andreas Voigt

I study the order/disorder transition due to singlet formation in a quantum spin system by means of exact diagonalization. The systems is build by spin 1/2 on a two-dimensional square lattice with two different kinds of antiferromagnetic Heisenberg interactions. The interaction J_p connects 4 nearest neighbor spins on a plaquette. The interaction J_n connect

Sumiyoshi Abe, Norikazu Suzuki

The Gutenberg-Richter law is identified in the Internet time series. This demonstrates the scale free nature of the Internet.

T. Aspelmeier, A. J. Bray, M. A. Moore

The overlap length of a three-dimensional Ising spin glass on a cubic lattice with Gaussian interactions has been estimated numerically by transfer matrix methods and within a Migdal-Kadanoff renormalization group scheme. We find that the overlap length is large, explaining why it has been difficult to observe spin glass chaos in numerical simulations and ex

A. V. Pronin, K. Pucher, P. Lunkenheimer, A. Krimmel

LiBC, a semiconducting ternary borocarbide constituted of the lightest elements only, has been synthesized and characterized by x-ray powder diffraction, dielectric spectroscopy, and conductivity measurements. Utilizing an infrared microscope the phonon spectrum has been investigated in single crystals. The in-plane B-C stretching mode has been detected at 1

Fabio L. Toninelli

We consider the Sherrington-Kirkpatrick model and we prove that the thermodynamic limit of the quenched free energy per site is strictly greater than the corresponding replica symmetric approximation, for all values of the temperature and of the magnetic field below the Almeida-Thouless line. This is based on recent rigorous bounds by F. Guerra, relating the

K-V Pham, F. Piechon, K-I Imura, P. Lederer

We propose a formalism which uses boundary conditions imposed on the Luttinger liquid (LL) to describe the transport properties of a LL coupled to reservoirs. The various boundary conditions completely determine linear transport in the joint system reservoirs+LL. As an illustration we consider an exactly solvable microscopic model in a multi-terminal geometr

Richard P. Sear

George and Wilson [Acta. Cryst. D 50, 361 (1994)] looked at the distribution of values of the second virial coefficient of globular proteins, under the conditions at which they crystallise. They found the values to lie within a fairly narrow range. We have defined a simple model of a generic globular protein. We then generate a set of proteins by picking val

Donavan Hall, S. W. Tozer, E. C. Palm, T. P. Murphy

Measurements of the de Haas - van Alphen effect have been carried out on the heavy fermion anti-ferromagnet CeRhIn5 at temperatures between 25 mK and 500 mK under pressure. We present some preliminary results of our measurements to track the evolution of the Fermi surface as the pressure induced superconducting transition is approached.

Alberto Rosso, Alexander K. Hartmann, Werner Krauth

We compute roughness exponents of elastic d-dimensional manifolds in (d+1)-dimensional embedding spaces at the depinning transition for d=1,...,4. Our numerical method is rigorously based on a Hamiltonian formulation; it allows to determine the critical manifold in finite samples for an arbitrary convex elastic energy. For a harmonic elastic energy, we find

M. P. López-Sancho, M. C. Muñoz, L. Brey

We study the properties of heterostructures formed by two layers of diluted magnetic semiconductor separated by a nonmagnetic semiconductor layer. We find that there is a RKKY-type exchange coupling between the magnetic layers that oscilles between ferromagnetic and antiferromagnetic as a function of the different parameters in the problem. The different tra

S. J. C. Yates, G. Santi, S. M. Hayden, P. J. Meeson

We report a study of the de Haas-van Alphen effect in the normal state of the ferromagnetic superconductor ZrZn2. Our results are generally consistent with an LMTO band structure calculation which predicts four exchange-split Fermi surface sheets. Quasiparticle effective masses are enhanced by a factor of about 4.9 implying a strong coupling to magnetic exci

M. Lopez de Haro, S. B. Yuste, A. Santos

A detailed analysis of two different theoretical equations of state for a binary mixture of additive hard disks [C. Barrio and J. R. Solana, Phys. Rev. E 63, 011201 (2001); A. Santos, S. B. Yuste and M. Lopez de Haro, Mol. Phys. 96, 1 (1999)], including their comparison with Monte Carlo results, is carried out. It is found that both proposals, which require

Ramon Aguado, David C. Langreth

The out-of-equilibrium transport properties of a double quantum dot system in the Kondo regime are studied theoretically by means of a two-impurity Anderson Hamiltonian with inter-impurity hopping. The Hamiltonian, formulated in slave-boson language, is solved by means of a generalization of the non-crossing approximation (NCA) to the present problem. We pro

P. M. Echenique, J. M. Pitarke, E. V. Chulkov, V. M. Silkin

The unequivocal observation in the early 1980s of a new class of unnocupied surface states that are bound to the vacuum level of a variety of metal surfaces has led over the last two decades to an active area of research in condensed-matter and surface physics. We discuss the key ingredients of the theory of these so-called image states, which have their ori

Friedrich Wagner

Stock markets can be characterized by fat tails in the volatility distribution, clustering of volatilities and slow decay of their time correlations. For an explanation models with several mechanisms and consequently many parameters as the Lux-Marchesi model have been used. We show that a simple herding model with only four parameters leads to a quantitative

F. Capraro, C. Gros

Using the density matrix renormalization group technique, we evaluate the low-energy spectrum (ground state and first excited states) of the anisotropic antiferromagnetic spin-one-half chain under magnetic fields. We study both homogeneous longitudinal and transversal fields as well as the influence of a transversal staggered field on opening of a spin-gap.

Yu. M. Tsipenyuk, R. P. May

The small angle neutron scattering from liquid helium at saturated vapour pressure in the temperature range from 1.5 to 4.2 K was measured with the instrument D22 of the ILL Grenoble at a wavelength of 4.6 angstrom. The zero angle cross section is monotonically decreasing with decreasing temperature and does not show any singularity at the lambda-point. On t

K. A. Matveev, A. I. Larkin, L. I. Glazman

The superconductivity in very thin rings is suppressed by quantum phase slips. As a result the amplitude of the persistent current oscillations with flux becomes exponentially small, and their shape changes from sawtooth to a sinusoidal one. We reduce the problem of low-energy properties of a superconducting nanoring to that of a quantum particle in a sinuso

Congjun Wu, W. Vincent Liu

We solve a popular effective Hamiltonian of competing $d$-density wave and d-wave superconductivity orders self-consistently at the mean-field level for a wide range of doping and temperature. The theory predicts a temperature dependence of the $d$-density wave order parameter seemingly inconsistent with the neutron scattering and $μ$SR experiments of the cu

P. Brune, G. I. Japaridze, A. P. Kampf, M. Sekania

We investigate the ground state phase diagram of the one-dimensional ionic Hubbard model with an alternating potential at half-filling by the bosonization technique as well as by numerical diagonalization of finite systems with the Lanczos and DMRG methods. Our results support the existence of a single "metallic" transition point from a band to a cor

John C. Hayes, Michael L. Norman

This paper presents a new code for performing multidimensional radiation hydrodynamic (RHD) simulations on parallel computers involving anisotropic radiation fields and nonequilibrium effects. The radiation evolution modules described here encapsulate the physics provided by the serial algorithm of Stone et. al (ApJSupp, vol 80, pp. 819-845), but add new fun

Peter O. Vandervoort

This paper describes a general investigation of stationary oscillations of galaxies. It begins with a linear analysis of modes of oscillation with continuous spectra of real frequencies. Such modes are gravitational analogues of the van Kampen modes of oscillation in plasmas. The characteristic value problem governing modes of the van Kampen type in a galaxy

J. H. Knapen, D. Perez-Ramirez, S. Laine

We present optical broad- and narrow-band imaging of a sample of a dozen barred galaxies. These images are analyzed in conjunction with our previously published near-infrared imaging of their central regions and with literature values for, e.g., bar strengths and the total star formation activity of the galaxies. We present B, I and H alpha images, and radia

John K. Cannizzo, Neil Gehrels, Janet A. Mattei

We examine the AAVSO light curve of U Geminorum from 1908 to 2002, with particular focus on the October 1985 outburst. This outburst was longer than any other seen in U Gem by about a factor of 2, and appears to be unique among all dwarf nova outbursts seen in systems with orbital periods longer than 3 hr in that one can measure the decay time scale during t

Curtis Struck, Babak E. Cohanim, Lee Anne Willson

We present numerical hydrodynamical models of the effects of planets or brown dwarfs orbiting within the extended atmosphere and wind formation zone of Mira variables. We find time-dependent wake dynamics and episodic accretion phenomena which may give rise to observable optical events and affect SiO maser emission.

Lee Anne Willson, Curt Struck

Short time scale variations have been reported for a few Miras, including sudden 0.2 magnitude or more brightening in the visual lasting from a few hours to a few days. Are these flashes real? Are they hot? What are they? Almost all the natural time scales for variation in the atmosphere and wind of a Mira variable are months to years long. What could cause

S. Fabrika, T. Irsmambetova

Mean orbital light curves of SS433 in different precessional phases are analysed for active and passive states separately. In passive states the mean brightness depends strongly on the disk orientation, the star is fainter by a factor about 2.2 in the disk edge-on positions. In active states the brightness does not depend significantly on the precessional ph

Vasiliki Pavlidou, Brian D. Fields

The diffuse extragalactic gamma-ray background (EGRB) above 100 MeV encodes unique information about high-energy processes in the universe. Numerous sources for the EGRB have been proposed, but the two systems which are certain to make some contribution are active galaxies (blazars) as well as normal galaxies. In this paper, we evaluate the contribution to t

Ph. Jetzer, L. Mancini, G. Scarpetta

The nature and the location of the lenses discovered in the microlensing surveys done so far towards the LMC remain unclear. Motivated by these questions we compute the optical depth and particularly the number of expected events for self-lensing for both the MACHO and EROS2 observations. We calculate these quantities also for other possible lens populations

Joshua Kempner, Craig Sarazin, Paul Ricker

We present an analysis of a highly asymmetric cluster merger from a Chandra observation of Abell 85. The merger shows significant disruption of the less massive subcluster from ram pressure effects. Nevertheless, a cold core, coincident with the cD galaxy, is observed to persist in the subcluster. We derive dynamical information from the motion of the cold c

Paul L. Schechter, Greg Burley, Charles L. Hull, Matt Johns

The Magellan active optics system has been operating continuously on the Baade 6.5-m since the start of science operations in February 2001. The active optical elements include the primary mirror, with 104 actuators, and the secondary mirror, with 5 positional degrees of freedom. Shack-Hartmann (SH) wavefront sensors are an integral part of the dual probe gu

Jong-Hak Woo, C. Megan Urry

Black hole mass, along with mass accretion rate, is a fundamental property of active galactic nuclei. Black hole mass sets an approximate upper limit to AGN energetics via the Eddington limit. We collect and compare all AGN black hole mass estimates from the literature; these 177 masses are mostly based on the virial assumption for the broad emission lines,

A. C. Calder, A. Alexakis, L. J. Dursi, R. Rosner

We present the results of a simulation of a wind-driven non-linear gravity wave breaking on the surface of a white dwarf. The ``wind'' consists of H/He from an accreted envelope, and the simulation demonstrates that this breaking wave mechanism can produce a well-mixed layer of H/He with C/O from the white dwarf above the surface. Material from this

Richard de Grijs, Gerry Gilmore, Rachel Johnson

We present the detailed analysis of Hubble Space Telescope observations of the spatial distributions of different stellar species in two young compact star clusters in the Large Magellanic Cloud, NGC 1805 and NGC 1818. Based on a comparison of the characteristic relaxation times in their cores and at their half-mass radii with the observed degree of mass seg

Richard de Grijs, Uta Fritze-v. Alvensleben

The cluster luminosity function (CLF) is one of the most important diagnostics in the study of old globular and young compact star cluster populations. We are currently using ASTROVIRTEL to obtain CLFs in several optical and/or near-infrared passbands, and colour distributions. This will provide us with a powerful analytical tool for the determination of the

C. Abia, I. Dominguez, R. Gallino, M. Busso

We present the first detailed and homogeneous analysis of the s-element content in Galactic carbon stars of N-type. Abundances of Sr,Y, Zr (low-mass s-elements, or ls) and of Ba, La, Nd, Sm and Ce (high-mass s-elements, hs) are derived using the spectral synthesis technique from high-resolution spectra. The N-stars analyzed are of nearly solar metallicity an

L. Sorriso-Valvo, V. Carbone, V. Abramenko, V. Yurchyshyn

The observations of magnetic field variations as a signature of flaring activity is one of the main goal in solar physics. Some efforts in the past give apparently no unambiguous observations of changes. We observed that the scaling laws of the current helicity inside a given flaring active region change clearly and abruptly in correspondence with the erupti

Anthony H. Gonzalez, Dennis Zaritsky, Luc Simard, Doug Clowe

The ESO Distant Cluster Survey (EDisCS) is a photometric and spectroscopic study of the galaxy cluster population at two epochs, z~0.5 and z~0.8, drawn from the Las Campanas Distant Cluster Survey (LCDCS). We report results from the initial candidate confirmation stage of the program and use these results to probe the properties of the LCDCS. Of the 30 candi

Maurice H. P. M. van Putten

A torus around a stellar mass Kerr black hole can emit about 10% of the spin-energy of the black hole in gravitational radiation, potentially associated with a gamma-ray burst. Wide tori may develop buckling modes by the Papaloizou-Pringle instability and gravitational radiation-reaction forces in the Burke-Thorne approximation. Gravitational wave experiment

R. Fusco-Femiano, D. Dal Fiume, M. Orlandini, S. De Grandi

We review all the BeppoSAX results relative to the search for additional nonthermal components in the spectra of clusters of galaxies. In particular, our MECS data analysis of A2199 does not confirm the presence of the nonthermal excess reported by Kaastra et al. (1999). A new observation of A2256 seems to indicate quite definitely that the nonthermal fluxes

Lawrence M. Widrow

A variety of observations suggest that magnetic fields are present in all galaxies and galaxy clusters. These fields are characterized by a modest strength (10^{-7}-10^{-5} G) and huge spatial scale (~Mpc). It is generally assumed that magnetic fields in spiral galaxies arise from the combined action of differential rotation and helical turbulence, a process

M. Temmer, A. Veronig, A. Hanslmeier, W. Otruba

A statistical analysis of a large data set of H-alpha flares comprising almost 100000 single events that occurred during the period January 1975 to December 1999 is presented. We analyzed the flares evolution steps, i.e. duration, rise times, decay times and event asymmetries. Moreover, these parameters characterizing the temporal behavior of flares, as well

M. Tucci, E. Carretti, S. Cecchini, L. Nicastro

We study the angular power spectra of the polarized component of the Galactic synchrotron emission in the 28-deg^2 Test Region of the Southern Galactic Plane Survey at 1.4 GHz. These data were obtained by the Australia Telescope Compact Array and allow us to investigate angular power spectra down to arcminute scales. We find that, at this frequency, the pola

V. N. Shalyapin, L. J. Goicoechea, D. Alcalde, E. Mediavilla

From the peak of a gravitational microlensing high-magnification event in the A component of QSO 2237+0305, which was accurately monitored by the GLITP collaboration, we derived new information on the nature and size of the optical V-band and R-band sources in the far quasar. If the microlensing peak is caused by a microcaustic crossing, we firstly obtained

B. Stecklum, B. Brandl, Th. Henning, I. Pascucci

We present results of our diffraction-limited mid-infrared imaging of the massive star-forming region W3(OH) with SpectroCam-10 on the 5-m Hale telescope at wavelengths of 8.8, 11.7, and 17.9 micron. The thermal emission from heated dust grains associated with the ultracompact HII region W3(OH) is resolved and has a spatial extent of ~2 arcsec in the N band.

A. Veronig, M. Temmer, A. Hanslmeier, W. Otruba

A statistical analysis of almost 50000 soft X-ray (SXR) flares observed by GOES during the period 1976-2000 is presented. On the basis of this extensive data set, statistics on temporal properties of soft X-ray flares, such as duration, rise and decay times with regard to the SXR flare classes is presented. Correlations among distinct flare parameters, i.e.

Sebastien Majerowicz, Monique Arnaud, Doris M. Neumann

We present the follow-up of three medium redshift galaxy clusters from the SHARC survey observed with XMM-Newton. We studied RX J0256.5+0006 which shows two components which are very likely in interaction. The smallest component exhibits a comet-like structure indicating ram pressure stripping as it falls onto the main cluster. The second cluster, RX J2237.0

V. V. Flambaum

In a recent paper [1] Lineweaver and Davis performed a statistical analysis to claim that the rapidity of biogenesis on Earth indicates high probability of biogenesis on terrestrial- type planets. We argue that the rapid appearance of life on Earth hardly tells us anything about the probability of life to appear on other planet. The conclusion should be diff

D. Adamova

Results are presented of a two-pion interferometry (HBT) analysis in Pb+Au collisions at 40, 80, and 158 AGeV. A detailed study of the Bertsch-Pratt HBT radius parameters has been performed as function of the mean pair transverse momentum $k_t$ and in bins of the centrality of the collision. From these results we extract model dependent information about the

Theodore J. Allen, Todd Coleman, M. G. Olsson, Sinisa Veseli

We demonstrate that the Nambu-Goto string spectroscopy with massless quarks is replicated in highly excited states of the linear vector confinement potential. For deep radial excitations we observe that the Regge slope, spacing between daughter trajectories, and absolute state energies agree with those of the QCD string.

Ehab Malkawi

We discuss the structure of the neutrino mass matrix as derived from a nonuniversal electroweak gauge interaction model. We discuss two interesting patterns of neutrino masses. The first pattern is hierarchal which fits the LMA or LOW solutions of solar neutrino data. The second pattern gives rise to inverted mass spectrum which fits the currently not prefer

G. G. Raffelt

The case for small neutrino mass differences from atmospheric and solar neutrino oscillation experiments has become compelling, but leaves the overall neutrino mass scale m_nu undetermined. The most restrictive limit of m_nu < 0.8 eV arises from the 2dF galaxy redshift survey in conjunction with the standard theory of cosmological structure formation. A rela

Michael Schirber, James S. Bullock

We determine the evolution of the faint, high-redshift, optical luminosity function (LF) of AGN implied by several observationally-motivated models of the ionizing background. Our results depend crucially on whether we use the total ionizing rate measured by the proximity effect technique or the lower determination from the flux decrement distribution of Ly

R. Aldrovandi, V. C. de Andrade, A. L. Barbosa, J. G. Pereira

Applied to the electroweak interactions, the theory of Lie algebra extensions suggests a mechanism by which the boson masses are generated without resource to spontaneous symmetry breaking. It starts from a gauge theory without any additional scalar field. All the couplings predicted by the Weinberg-Salam theory are present, and a few others which are nevert

Marcos Marino

The universal perturbative invariants of rational homology spheres can be extracted from the Chern-Simons partition function by combining perturbative and nonperturbative results. We spell out the general procedure to compute these invariants, and we work out in detail the case of Seifert spaces. By extending some previous results of Lawrence and Rozansky, t

A. M. Childs, D. W. Leung, F. Verstraete, G. Vidal

We compute the asymptotic entanglement capacity of the Ising interaction ZZ, the anisotropic Heisenberg interaction XX + YY, and more generally, any two-qubit Hamiltonian with canonical form K = a XX + b YY. We also describe an entanglement assisted classical communication protocol using the Hamiltonian K with rate equal to the asymptotic entanglement capaci

Hsin-Chia Cheng, Jonathan L. Feng, Konstantin T. Matchev

We propose that cold dark matter is made of Kaluza-Klein particles and explore avenues for its detection. The lightest Kaluza-Klein state is an excellent dark matter candidate if standard model particles propagate in extra dimensions and Kaluza-Klein parity is conserved. We consider Kaluza-Klein gauge bosons. In sharp contrast to the case of supersymmetric d

Marc Sher

The existence of large ν_μ-ν_τmixing suggests the likelihood of large smuon-stau mixing in supersymmetric models, leading to μand τnumber violation. In addition to interesting signatures in slepton and neutralino production and decay, this will lead to rare τdecays, such as τ--> mu γ. Recently, it has been pointed out that the τ--> 3μbranching ratio could be

G. Ramon, A. Mann, E. Cohen

Electron scattering on both neutral ($X$) and charged ($X^-$) excitons in quantum wells is studied theoretically. A microscopic model is presented, taking into account both elastic and dissociating scattering. The model is based on calculating the exciton-electron direct and exchange interaction matrix elements, from which we derive the exciton scattering ra

Mehdi Yahyanejad, Mehran Kardar, Chao Tang

We study the space of all compact structures on a two-dimensional square lattice of size $N=6\times6$. Each structure is mapped onto a vector in $N$-dimensions according to a hydrophobic model. Previous work has shown that the designabilities of structures are closely related to the distribution of the structure vectors in the $N$-dimensional space, with hig

Susan Kurien

We study the isotropic, helical component in homogeneous turbulence using statistical objects which have the correct symmetry and parity properties. Using these objects we derive an analogue of the Kármán-Howarth equation, that arises due to parity violation in isotropic flows. The main equation we obtain is consistent with the results of O. Chkhetiani [JETP

C. Barbot, M. Drees, F. Halzen, D. Hooper

In models where the ultra-high energy cosmic ray problem is solved by top-down scenarios, a significant flux of ultra-high energy neutralinos is predicted. We calculate the number of events expected from such particles in future experiments such as EUSO or OWL. We show that by using the Earth as a filter, showers generated by neutralinos can be separated fro

M. Urban, P. Schuck, X. Vinas

We revise the Thomas-Fermi approximation for describing vortex states in Bose condensates of magnetically trapped atoms. Our approach is based on considering the hbar -> 0 limit rather than the N -> infinity limit as Thomas-Fermi approximation in close analogy with the Fermi systems. Even for relatively small numbers of trapped particles we find good agreeme

L. Gerritzen, R. Holtkamp

Generalizations of the series exp and log to noncommutative non-associative and other types of algebras were considered by M.Lazard, and recently by V.Drensky and L.Gerritzen. There is a unique power series exp(x) in one non-associative variable x such that exp(x)exp(x)=exp(2x), exp&#39;(0)=1. We call the unique series H=H(x,y) in two non-associative variabl

Jan Brugues, Joaquim Gomis, Toni Mateos, Toni Ramirez

We construct the supergravity solution in 11 dimensions describing D6-branes wrapped around a Kahler four-cycle with a B-field along the flat directions of the brane. The configuration is dual to an N=2 noncommutative gauge theory in 2+1 dimensions. We also construct the four associated independent Killing spinors. The phenomenon of supersymmetry without sup

Samuel M Leach, Andrew R Liddle

We use a compilation of cosmic microwave anisotropy data (including the recent VSA, CBI and Archeops results), supplemented with an additional constraint on the expansion rate, to directly constrain the parameters of slow-roll inflation models. We find good agreement with other papers concerning the cosmological parameters, and display constraints on the pow

Thomas Durt, Nicolas J. Cerf, Nicolas Gisin, Marek Zukowski

The study of quantum cryptography and quantum non-locality have traditionnally been based on two-level quantum systems (qubits). In this paper we consider a generalisation of Ekert&#39;s cryptographic protocol [Ekert] where qubits are replaced by qutrits. The security of this protocol is related to non-locality, in analogy with Ekert&#39;s protocol. In order

V. Yershov

A composite model of the fundamental fermions based on colour preons is discussed. It is found that, if endowed with the pairwise (repulsive/attractive) chromoelectric fields, preons would cohere in a series of structures, resembling by their properties the three generations of the fundamental fermions. The model is self-consistent in the sense that it makes

Carlo Rovelli

Hamiltonian mechanics of field theory can be formulated in a generally covariant and background independent manner over a finite dimensional extended configuration space. The physical symplectic structure of the theory can then be defined over a space G of three-dimensional surfaces without boundary, in the extended configuration space. These surfaces provid

Roman R. Zapatrin

With any state of a multipartite quantum system its separability polytope is associated. This is an algebro-topological object (non-trivial only for mixed states) which captures the localisation of entanglement of the state. Particular examples of separability polytopes for 3-partite systems are explicitly provided. It turns out that this characterisation of

G. Savona, D. V. Livanov, R. Raimondi, A. A. Varlamov

This paper has been withdrawn by the author(s),

John E. Wang

Spacelike branes are new time-dependent systems to explore and it has been observed that related supergravity solutions can be obtained by analytically continuing known D-brane solutions. Here we show that analytic continuation of known solutions of the Dirac-Born-Infeld equations also lead to interesting analogs of time dependent gravity solutions. Properti

Yuri A. Shchekinov

Accretion disks with an additional mass input on the disk surface from environment are considered in the limit of low mass input rate, i.e. when the accretion flow remains keplerian. Due to dissipation of kinetic energy of the infalling gas disk temperature increases, and can deviate significantly from standard temperature of reprocessing accretion disks in

S. I. Bityukov

The incorporation of uncertainties to calculations of signal significance in planned experiments is an actual task. Several approaches to this problem are discussed. We present a procedure for taking into account the systematic uncertainty related to nonexact knowledge of signal and background cross sections. A method of a treatment of statistical errors of

I. L. Buchbinder, V. A. Krykhtin

We study the theory of noncommutative U(N) Yang-Mills field interacting with scalar and spinor fields in the fundamental and the adjoint representations. We include in the action both the terms describing interaction between the gauge and the matter fields and the terms which describe interaction among the matter fields only. Some of these interaction terms

Bing Dong, X. L. Lei

In this paper we study the thermopower of a quantum dot connected to two leads in the presence of Kondo correlation by employing a modified second-order perturbation scheme at nonequilibrium. A simple scheme, Ng&#39;s ansatz [Phys. Rev. Lett. {\bf 76}, 487 (1996)], is adopted to calculate nonequilibrium distribution Green&#39;s function and its validity is f

A. I. Nikishov

Even if the electromagnetic field does not create pairs, virtual pairs lead to the appearance of a phase in vacuum-vacuum amplitude. This makes it necessary to distinguish the in- and out-solutions even when it is commonly assumed that there is only one complete set of solutions as, for example, in the case of a constant magnetic field. Then in- and out-solu

Doyeol Ahn, Hyuk-jae Lee, Sung Woo Hwang

In this paper, we derived Lorentz covariant quantum Liouville equation for the density operator which describes the relativistic quantum information processing from Tomonaga-Schwinger equation and an exact formal solution for the reduced-density-operator is obtained using the projector operator technique and the functional calculus. When all the members of t

Sohrab Ismail-Beigi Steven G. Louie

We present a new first-principles formalism for calculating forces for optically excited electronic states using the interacting Green&#39;s function approach with the GW-Bethe Salpeter Equation method. This advance allows for efficient computation of gradients of the excited-state Born-Oppenheimer energy, allowing for the study of relaxation, molecular dyna

Chui-Ping Yang, Shih-I Chu, Siyuan Han

A scheme is presented for protecting one-qubit quantum information against decoherence due to a general environment and local exchange interactions. The scheme operates essentially by distributing information over two pairs of qubits and through error prevention procedures. In the scheme, quantum information is encoded through a decoherence-free subspace for

Emilio Santos

I review the relation of the Bell inequalities - characteristic of (classical) probabilities defined on Boolean logics - with noncontextual and local hidden variables theories of quantum mechanics and with quantum information.

A. D. Alhaidari

Given a spatially dependent mass distribution we obtain potential functions for exactly solvable nonrelativistic problems. The energy spectrum of the bound states and their wavefunctions are written down explicitly. This is accomplished by mapping the wave equation for these systems into well-known exactly solvable Schrodinger equations with constant mass us

L. M. K. Vandersypen, R. Hanson, L. H. Willems van Beveren, J. M. Elzerman

We present a set of concrete and realistic ideas for the implementation of a small-scale quantum computer using electron spins in lateral GaAs/AlGaAs quantum dots. Initialization is based on leads in the quantum Hall regime with tunable spin-polarization. Read-out hinges on spin-to-charge conversion via spin-selective tunneling to or from the leads, followed

Matthieu Legre, Mark Wegmuller, Nicolas Gisin

A novel method for the direct measurement of the degree of polarization is described. It is one of the first practical implementations of a coherent quantum measurement, the projection on the singlet state. Our first results demonstrate the successful operation of the method. However, due to the nonlinear crystals used presently, its application is limited t

Afshin Shafiee, Mehdi Golshani, M. Ghasem Mahjani

Chemical potential is a property which involves the effect of interaction between the components of a system, and it results from the whole system. In this paper, we argue that for two particles which have interacted via their spins and are now spatially separated, the so-called Bell&#39;s locality condition implies that the chemical potential of each partic

Kazuyuki Fujii

Geometrical aspects of quantum computing are reviewed elementarily for non-experts and/or graduate students who are interested in both Geometry and Quantum Computation. In the first half we show how to treat Grassmann manifolds which are very important examples of manifolds in Mathematics and Physics. Some of their applications to Quantum Computation and its

Peter W. Shor, John A. Smolin, Ashish V. Thapliyal

We show that, in a multi-party setting, two non-distillable (bound-entangled) states tensored together can make a distillable state. This is an example of true superadditivity of distillable entanglement. We also show that unlockable bound-entangled states cannot be asymptotically unentangled, providing the first proof that some states are truly bound-entang

E B Davies

We discuss the extent to which the visibility of the heavens was a necessary condition for the development of science, with particular reference to the measurement of time. Our conclusion is that while astronomy had significant importance, the growth of most areas of science was more heavily influenced by the accuracy of scientific instruments, and hence by

Michael C. Wittmann

Detailed investigations of student reasoning show that students approach the topic of wave physics using both event-like and object-like descriptions of wavepulses, but primarily focus on object properties in their reasoning. Student responses to interview and written questions are analysed using diSessa and Sherin&#39;s coordination class model which sugges