April 2000 arXiv papers — page 7

Emmanuel Etievent, Frank Lebourgeois, Jean-Michel Jolion

This work deals with content-based video indexing. Our viewpoint is semi-automatic analysis of compressed video. We consider the possible applications of motion analysis and moving object detection : assisting moving object indexing, summarising videos, and allowing image and motion queries. We propose an approach based on interest points. As first results,

A. Scala, L. A. N. Amaral, M. Barthelemy

We map the conformation space of a simple lattice polymer chain to a network, where (i) the vertices of the network have a one-to-one correspondence to the conformations of the chain, and (ii) a link between two vertices indicates the possibility of switching from one conformation to the other by a single Monte Carlo move of the chain. We find that the geome

Dirk K. Morr, David Pines

Recent inelastic neutron scattering (INS) experiments on La$_{2-x}$Sr$_x$CuO$_4$ have established the existence of a {\it magnetic coherence effect}, i.e., strong frequency and momentum dependent changes of the spin susceptibility, $χ''$, in the superconducting phase. We show, using the spin-fermion model for incommensurate antiferromagnetic spin flu

V. F. Gantmakher, M. V. Golubkov, V. T. Dolgopolov, A. A. Shashkin

We study the response of a thin superconducting amorphous InO film with variable oxygen content to a parallel magnetic field. A field-induced superconductor-insulator transition (SIT) is observed that is very similar to the one in normal magnetic fields. As the boson-vortex duality, which is the key-stone of the theory of the field-induced SIT, is obviously

Hsuan-Yi Chen, David Jasnow

In this Letter we discuss theoretically the instabilities of thermotropic freely standing smectic-A films under shear flow\cite{re:wu}. We show that, in Couette geometry, the centrifugal force pushes the liquid crystal toward the outer boundary and induces smectic layer dilation close to the outer boundary. Under strong shear, this effect induces a layer buc

L. I. Korovin, I. G. Lang, S. T. Pavlov

It has been shown, that a magnetopolaron discrete energy spectrum is realized in the optical experiments where exciting light is directed perpendicularly to a quantum well (QW) plane. The phonon dispersion as well as Coulomb attraction can only shift the magnetopolaron discrete energy levels and broad some of them.

Na Sai, David Vanderbilt

We carry out first-principles density-functional calculations of the antiferrodistortive (AFD) and ferroelectric (FE) soft-mode instabilities in tetragonal SrTiO3, with the structural degrees of freedom treated in a classical, zero-temperature framework. In particular, we use frozen-phonon calculations to make a careful study of the anisotropy of the AFD and

L. Bellaiche, A. Garcia, David Vanderbilt

A first-principles-derived approach is developed to study finite-temperature properties of PbZr{1-x}Ti{x}O3 (PZT) solid solutions near the morphotropic phase boundary (MPB). Structural and piezoelectric predictions are in excellent agreement with experimental data and direct first-principles results. A low-temperature monoclinic phase is confirmed to exist,

Masaru Kato, Kazumi Maki

Making use of the Bogoliubov-de Gennes equation, we study the quasi-particle spectrum and the vortex core structure of a single vortex in quasi 2D s-wave superconductors for small p_F xi_0, where p_F is the Fermi momentum and xi_0=v_F/Delta_0 is the coherence length (hbar=1). During our numerical calculation the particle number is conserved for each p_F xi_0

M. Itoh, G. R. Bell, B. A. Joyce, D. D. Vvedensky

By carrying out Monte Carlo simulations based on the two-species atomic-scale kinetic growth model of GaAs(001) homoepitaxy and comparing the results with scanning tunneling microscope images, we show that initial growing islands undergo the structural transformation before adopting the proper beta2(2x4) reconstruction.

J. Takeya, I. Tsukada, Yoichi Ando, T. Masuda

Thermal conductivity κis measured at very low temperatures down to 0.28 K for pure and Mg-doped CuGeO_3 single crystals. The doped samples carry larger amount of heat than the pure sample at the lowest temperature. This is because antiferromagnetic magnons appear in the doped samples and are responsible for the additional heat conductivity, while κof the pur

M. Damnjanovic

The general form of the operators commuting with the ground representation (appearing in many physical problems within single particle approximation) of the group is found. With help of the modified group projector technique, this result is applied to the system of identical particles with spin independent interaction, to derive the Dirac-Heisenberg hamilton

I. Bozovic, N. Bozovic, M. Damnjanovic

Utilizing the line-group symmetry of single-wall nanotubes, we have assigned their electron-energy bands by the symmetry-based quantum numbers. The selection rules for optical absorption are presented in terms of these quantum numbers. Different interband transitions become allowed as the polarization of incident light is varied, and we predict a substantial

D. V. Averin

The problem of continuous quantum measurement of coherent oscillations in an individual quantum two-state system is studied for a generic model of the measuring device. It is shown that for a symmetric detector, the signal-to-noise ratio of the measurement, defined as the ratio of the amplitude of the oscillation line in the output spectrum to background noi

T. H. Jarrett, T. Chester, R. Cutri, S. Schneider

The 2 Micron All-Sky Survey (2MASS) will observe over one-million galaxies and extended Galactic sources covering the entire sky at wavelengths between 1 and 2 microns. The survey catalog will have both high completeness and reliability down to J = 15.0 and Ks = 13.5 mag, equivalent to 1.6 mJy and 2.9 mJy, respectively. This paper describes the basic algorit

Altan Baykal

We present new X-ray observations of the high mass X-ray binary (HMXRB) pulsar OAO 1657-415, obtained during one orbital period (10.44 days) with the Rossi X-Ray Timing Explorer (RXTE). Using the binary orbital parameters, obtained from Burst and Transient Source Experiment (BATSE) observations, we resolve the fluctuations in the pulse frequency at time scal

David C. Knauth, Steven R. Federman, David L. Lambert, Phillipe Crane

As a part of a study on the variation in the 7Li/6Li ratio, high signal to noise, high resolution spectroscopy of Li I (6708 Angstroms) and K I (4044 Angstroms) were obtained toward zeta and o Per. The lithium isotope shift is approximately the same as its fine structure splitting (0.158 Angstroms), resulting in a blend of the 7Li and 6Li lines. Use of the K

Tamas Budavari, Alexander S. Szalay, Andrew J. Connolly, Istvan Csabai

Understanding how the physical properties of galaxies (e.g. their spectral type or age) evolve as a function of redshift relies on having an accurate representation of galaxy spectral energy distributions. While it has been known for some time that galaxy spectra can be reconstructed from a handful of orthogonal basis templates, the underlying basis is poorl

G. Duchene, J. Silber, F. Menard, T. Gledhill

We have obtained new near-infrared images of both GG Tau and UY Aur circumbinary disks with the polarimetric modes of NICMOS aboard the Hubble Space Telescope. The 1 micron intensity map of GG Tau reveals a more complete elliptical shape than in previous ground-based images. Its eastern and western sides are definitely asymmetric. Our image strongly supports

G. Á. Bakos, J. Jurcsik

We present new multicolour CCD photometry of the central part of the globular cluster M3, mapping the precise position of ~120 RR Lyrae stars (RRab, RRd, RRc) on the horizontal branch (HB). The location of the double-mode variables (RRd) is in perfect agreement with recent theoretical results. We find a significant internal spread of metallicity amongst the

I. Baraffe, U. Kolb

We investigate why the spectral type of most cataclysmic variable (CV) secondaries is significantly later than that of a ZAMS star with the same mean density. Using improved stellar input physics, tested against observations of low-mass stars at the bottom of the main sequence, we calculate the secular evolution of CVs with low-mass donors. We consider seque

Benjamin F. Mathiesen, August E. Evrard

We employ an ensemble of hydrodynamic cluster simulations to create spatially and spectrally resolved images of quality comparable to Chandra's expected performance. Emission from simulation mass elements is represented using the XSPEC mekal program assuming 0.3 solar metallicity, and the resulting spectra are fit with a single-temperature model. Despite

P. Di Stefano, L. Berge, B. Chambon, M. Chapellier

The discrimination capabilities of a 70 g heat and ionization Ge bolometer are studied. This first prototype has been used by the EDELWEISS Dark Matter experiment, installed in the Laboratoire Souterrain de Modane, for direct detection of WIMPs. Gamma and neutron calibrations demonstrate that this type of detector is able to reject more than 99.6% of the bac

Niruj R. Mohan, K. R. Anantharamaiah, W. M. Goss

A search for radio recombination lines near 20 cm at z=0.193 and z=0.886 towards the gravitational lens system PKS 1830-211 has yielded upper limits on the line optical depth of 5 x 10^{-5} and 5 x10^{-4} at the two redshifts respectively. Based on the non-detections, we derive upper limits to the emission measure of the ionized gas in the absorbing systems.

Jeremy Kepner, Rita Kim

Clusters of galaxies are the most massive objects in the Universe and mapping their location is an important astronomical problem. This paper describes an algorithm (based on statistical signal processing methods), a software architecture (based on a hybrid layered approach) and a parallelization scheme (based on a client/server model) for finding clusters o

Hajime Susa, Tetsu Kitayama

The collapse of marginally Jeans unstable primordial gas clouds in the presence of UV radiation field is discussed. Assuming that the dynamical collapse proceeds approximately in an isothermal self-similar fashion, we investigate the thermal evolution of collapsing central core until H$_2$ cooling dominates photoheating and the temperature drops to below $10

Yongge Ma, Yi Ling

We construct a weave state which approximates a degenerate 3-metric of rank 2 at large scales. It turns out that a non-degenerate metric region can be evolved from this degenerate metric by the classical Ashtekar equations, hence the degeneracy of 3-metrics is not preserved by the evolution of Ashtekar's equations. As the s-knot state corresponding to th

David Elazzar Kaplan, Tim M. P. Tait

We present a supersymmetric model in which the observed fermion masses and mixings are generated by localizing the three generations of matter and the two Higgs fields at different locations in a compact extra dimension. Supersymmetry is broken by the shining method and the breaking is communicated to standard model fields via gaugino mediation. Quark masses

Isaac Shlosman, Reynier F. Peletier, Johan H. Knapen

Using all available major samples of Seyfert galaxies and their corresponding control samples of closely matched non-active galaxies, we find that the bar ellipticities (or axial ratios) in Seyfert galaxies are systematically different from those in non-active galaxies. Overall, there is a deficiency of bars with large ellipticities (i.e., `fat' or `weak

Eliot Quataert, Andrei Gruzinov

Two possible explanations for the low luminosity of the supermassive black hole at the center of our galaxy are (1) an accretion rate of order the canonical Bondi value (roughly 10^{-5} solar masses per year), but a very low radiative efficiency for the accreting gas or (2) an accretion rate much less than the Bondi rate. Both models can explain the broad-ba

Tomas Novotny, Petr Chvosta

We consider a generalization of the model by Doering and Gadoua to non-Markovian potential-switching generated by arbitrary renewal processes. For the Markovian switching process, we extend the original results by Doering and Gadoua by giving a complete description of the absorption process. For all non-Markovian processes having the first moment of the wait

A. V. Efremov, K. Goeke, P. V. Pobylitsa

We present the QCD analysis of the behavior of quark and gluon distributions in the limit of a large number of colors N_c. We show that the results agree qualitatively with the phenomenological data. In particular we draw attention to the fact that the polarized gluon distribution is suppressed at large N_c compared to the unpolarized one.

Donam Youm

By carefully analyzing the geodesic motion of a test particle in the bulk of brane worlds, we identify an extra force which is recognized in spacetime of one lower dimensions as a non-gravitational force acting on the particle. Such extra force acts on the particle in such a way that the conventional particle mechanics in one lower dimensions is violated, th

Martin Goliath, Ulf S. Nilsson

We consider the problem of late-time isotropization in spatially homogeneous but anisotropic cosmological models when the source of the gravitational field consists of two non-interacting perfect fluids -- one tilted and one non-tilted. In particular, we study irrotational Bianchi type V models. By introducing appropriate dimensionless variables, a full glob

Ulises Nucamendi, Daniel Sudarsky

We consider the spacetimes corresponding to static Global Monopoles with interior boundaries corresponding to a Black Hole Horizon and analyze the behavior of the appropriate ADM mass as a function of the horizon radius r_H. We find that for small enough r_H, this mass is negative as in the case of the regular global monopoles, but that for large enough r_H

Samuel M Leach, Ian J Grivell, Andrew R Liddle

The running-mass inflation model, which has strong motivation from particle physics, predicts density perturbations whose spectral index is strongly scale-dependent. For a large part of parameter space the spectrum rises sharply to short scales. In this paper we compute the production of primordial black holes, using both analytic and numerical calculation o

E. E. Boos, V. A. Ilyin, A. N. Skachkova

A serious computational problem in the evaluation of hadronic collision processes is connected with the large number of partonic subprocesses included in the calculation. These are from the quark and gluon content of the initial hadrons, and from CKM quark mixing. For example, there are 180 subprocesses which contribute to the $W$+2jets process, and 292 subp

R. Mélin, D. Denaro

We consider spin accumulation at a ferromagnet--normal metal interface in the presence of magnetic scattering in the normal metal. In the classical regime, we discuss the inverse Drude scaling of the conductance as a function of the interface transparencies. We present a treatment based on an exact solution of the Boltzmann equation. In the quantum regime, w

Luca Marinatto, Tullio Weber

We extend the concept of a classical two-person static game to the quantum domain, by giving an Hilbert structure to the space of classical strategies and studying the Battle of the Sexes game. We show that the introduction of entangled strategies leads to a unique solution of this game.

Sandhya Choubey, Srubabati Goswami, Debasish Majumdar

We re-examine the neutrino decay solution to the solar neutrino problem in the light of the SuperKamiokande (SK) data. For the decay solution the SK spectrum data by its own can provide a fit comparable to the fit obtained from the MSW solution. However when one combines the results from the total rates of the $^{37}{Cl}$ and $^{71}{Ga}$ experiments the fit

E. Harikumar, R. P. Malik, M. Sivakumar

We show that the BRST/anti-BRST invariant 3+1 dimensional 2-form gauge theory has further nilpotent symmetries (dual BRST /anti-dual BRST) that leave the gauge fixing term invariant. The generator for the dual BRST symmetry is analogous to the co-exterior derivative of differential geometry. There exists a bosonic symmetry which keeps the ghost terms invaria

Mikhail A. Braun, Claudio Ciofi degli Atti, Daniele Treleani

The problem of the final state interaction in quasi-elastic $(e,e')$ scattering at large $Q^2$, is investigated by exploiting the idea that the ejected nucleon needs a finite amount of time to assume its asymptotic form. It is shown that when the dependence of the scattering amplitude of the ejected nucleon on its virtuality is taken into account, the fi

J. A. Aguilar-Saavedra, G. C. Branco

Top decays into a light Higgs boson and an up or charm quark can reach detectable levels in Standard Model extensions with two Higgs doublets or with new exotic quarks, and in the Minimal Supersymmetric Standard Model. Using both a standard and a neural network analysis we show that the CERN Large Hadron Collider will give 3 sigma evidence of decays with Br(

Weimin Chen, Yongbin Ruan

Motivated by orbifold string theory, we introduce orbifold cohomology group for any almost complex orbifold and orbifold Dolbeault cohomology for any complex orbifold. Then, we show that our new cohomology group satisfies Poincare duality and has a natural ring structure. Some examples of orbifold cohomology ring are computed.

M. G. Moore, P. Meystre

We propose using spontaneous Raman scattering from an optically driven Bose-Einstein condensate as a source of atom-photon pairs whose internal states are maximally entangled. Generating entanglement between a particle which is easily transmitted (the photon) and one which is easily trapped and coherently manipulated (an ultracold atom) will prove useful for

J. Witters

This is a theory for the fundamental structure of nature based on spinors as unique building blocks. Confinement of the spinors in particles is due uniquely to the dynamics of the collisions between them. The interaction operator contains only spin and momentum operators. The eigenfunctions of the interaction operator have negative as well as positive eigenv

S. Mancini, H. Moya-Cessa, P. Tombesi

We propose a scheme to generate superpositions of coherent states for the vibrational motion of a laser cooled trapped-ion. It is based on the interaction with a standing wave making use of the counter-rotating terms, i.e. not applying the rotating wave approximation. We also show that the same scheme can be exploited for quantum state measurement, i.e. with

C. L. Foden, V. I. Talyanskii, G. J. Milburn, M. L. Leadbeater

We propose a single optical photon source for quantum cryptography based on the acousto-electric effect. Surface acoustic waves (SAWs) propagating through a quasi-one-dimensional channel have been shown to produce packets of electrons which reside in the SAW minima and travel at the velocity of sound. In our scheme these electron packets are injected into a

Luca Marinatto, Tullio Weber

The use of a three-particle quantum channel to teleport entangled states through a slight modification of the standard teleportation procedure is studied. It is shown that it is not possible to perform successful teleportation of an arbitrary and unknown two-particle entangled state, following our version of the standard teleportation procedure. On the contr

B. G. Sidharth

In this paper it is shown that a recent formulation of the electron in terms of a Kerr-Newman type metric, exhibits a short range magnetic effect, as indeed has been observed at Cornell, and also an Aharonov-Bohm type of an effect.

Alexey K. Mazur

The macroscopic curvature induced in the double helical B-DNA by regularly repeated adenine tracts (A-tracts) plays an exceptional role in structural studies of DNA because this effect presents the most well-documented example of sequence specific conformational modulations. Recently, a new hypothesis of its physical origin has been put forward, based upon t

A. G. Khachatryan

It is shown that an undesirable curvature of the wave front of two-dimensional nonlinear wake wave excited in uniform plasma by a relativistic charged bunch or laser pulse may be compensated by radial change of the equilibrium plasma density.

V. P. Ladygin

In recent time the deuteron structure at short distances is often treated from the point of view nonnucleonic degrees of freedom. In this paper the measurements of T-odd polarization observables using tensor polarized deuteron beam and polarized proton target or proton polarimeter are proposed to search the quark configurations inside the deuteron.

Andrea Vanossi, K. Ø. Rasmussen, A. R. Bishop, B. A. Malomed

We demonstrate the spontaneous formation of spatial patterns in a damped, ac-driven cubic Klein-Gordon lattice. These patterns are composed of arrays of intrinsic localized modes characteristic for nonlinear lattices. We analyze the modulation instability leading to this spontaneous pattern formation. Our calculation of the modulational instability is applic

T. Barakat

The semi-relativistic equation is cast into a second-order Schrodinger-like equation with the inclusion of relativistic corrections up to order (v/c)^2. The resulting equation is solved via the shifted-l expansion technique, which has been recently developed to get eigenvalues of relativistic and non-relativistic wave equations. The Coulomb, Oscillator, and

Tamas Hausel, Endre Makai, Andras Szucs

First, we prove a special case of Knaster's problem, implying that each symmetric convex body in R^3 admits an inscribed cube. We deduce it from a theorem in equivariant topology, which says that there is no S_4-equivariant map from SO(3) to S^2, where S_4 acts on SO(3) as the rotation group of the cube and on S^2 as the symmetry group of the regular tet

Artur Elezi

We prove the Aspinwall-Morrison formula by relating their calculation to Gromov-Witten theory.

V. V. Uspenskij

Let f:X -> Y be an onto map between compact spaces such that all point-inverses of f are zero-dimensional. Let A be the set of all functions u:X -> I=[0,1] such that $u[f^\leftarrow(y)]$ is zero-dimensional for all y in Y. Do almost all maps u:X -> I, in the sense of Baire category, belong to A? H. Toruńczyk proved that the answer is yes if Y is countable-di

A. Degtyarev, V. Kharlamov

The survey gives an overview of the achievements in topology of real algebraic varieties in the direction initiated in the early 70th by V.I.Arnold and V.A.Rokhlin. We make an attempt to systematize the principal results in the subject. After an exposition of general tools and results, special attention is paid to surfaces and curves on surfaces.

John C. Baez, James Dolan

`Categorification' is the process of replacing equations by isomorphisms. We describe some of the ways a thoroughgoing emphasis on categorification can simplify and unify mathematics. We begin with elementary arithmetic, where the category of finite sets serves as a categorified version of the set of natural numbers, with disjoint union and Cartesian pro

Chongying Dong, Geoffrey Mason, Kiyokazu Nagatomo

We study graded traces of vectors in free bosonic vertex operator algebras and lattice vertex operator algebras. We show in particular that trace functions in these two theories always have the shape f(q)/η(q)^d where f(q) is quasi-modular in the case of d free bosons, and modular (i.e., a sum of holomorphic modular forms of various weights) in the case of t

F. Flamini

For a linear system $|C|$ on a smooth projective surface $S$, whose general element is a smooth, irreducible curve, the Severi variety $V_{|C|, δ}$ is the locally closed subscheme of $|C|$ which parametrizes irreducible curves with only $δ$ nodes as singularities. In this paper we give numerical conditions on the class of divisors and upper-bounds on $δ$ ens

Michel Lassalle

We obtain the specialization of monomial symmetric functions on the alphabet (a-b)/(1-q). This gives a remarkable algebraic identity, and four new developments for the Macdonald polynomial associated with a row. The proofs are given in the framework of $λ$-ring theory.

Adrian Ghinculov, York-Peng Yao

For Z -> b bbar, we calculate all the two-loop top dependent Feynman graphs, which have mixed QCD and electroweak contributions that are not factorizable. For evaluating the graphs, without resorting to a mass expansion, we apply a two-loop extension of the one-loop Passarino-Veltman reduction. This is an analytic-numerical method, which first converts all d

M. E. Carrington, W. F. Chen, R. Kobes

A complete analysis of dynamical scale symmetry breaking in 2+1-dimensional QED at both zero and finite temperature is presented by looking at solutions to the Schwinger-Dyson equation. In different kinetic energy regimes we use various numerical and analytic techniques (including an expansion in large flavour number). It is confirmed that, contrary to the c

G. Dillon, G. Morpurgo

Due to a new measurement of the Xi(0) mass,the Coleman-Glashow formula for the baryon octet e.m. masses (derived using unbroken SU(3) is satisfied to an extraordinary level of precision.The same unexpected precision exists for the Gell-Mann Okubo formula and for its octet-decuplet extension (G.Morpurgo,Phys.Rev.Lett. 68(1992)139).We show that the old questio

Rathin Adhikari, Ernest Ma, G. Rajasekaran

The mass matrix of three Majorana neutrinos of equal mass is not necessarily proportional to the identity matrix, but expressible in terms of two angles and one phase. We discuss how such a mass matrix may be stable or unstable against radiative corrections. We then propose a model with additional explicit breaking of the threefold degeneracy to account for

F. T. Brandt, Ashok Das, J. Frenkel

We examine the parity violating terms generated by the box diagram in QED_3 at finite temperature. These lead to both extensive as well as non-extensive effective actions, which have very distinct behavior in the long wavelength and static limits. We discuss a large gauge Ward identity for the leading terms in the static limit, whose solution coincides with

N. Brambilla, A. Vairo

The effective field theory approach allows a rigorous disentangling of high and low energy effects in the heavy quarkonium dynamics. Focusing in particular on the spectrum, we describe the nature of the non-perturbative effects and discuss our present knowledge of them.

H. Athar

We study neutrino conversions in a recently envisaged source of high-energy neutrinos (E \geq 10^6 GeV), that is, in the vicinity of cosmological Gamma-Ray Burst fireballs (GRB). We consider the effects of flavor and spin-flavor conversions and point out that in both situations, a some what higher than estimated high energy tau neutrino flux from GRBs is exp

S. Bethke

Theoretical basics and experimental determinations of the coupling parameter of the Strong Interaction, $α_s$, are reviewed. The world average value of $α_s$, expressed at the energy scale of the rest mass of the $Z^0$ boson, is determined from analyses which are based on complete NNLO perturbative QCD. The result is $α_s (M_Z) = 0.1184 \pm 0.0031$. No signi

Miroslav Sukenik, Jozef Sima, Julius Vanko

Applying the Vaidya metrics in the model of Expansive Nondecelerative Universe (ENU) leads to compatibility of the ENU model both with the classic Newton gravitational theory and the general theory of relativity in weak fields

Yury Petrov, Takeshi Egami

The Hamiltonian describing a system of strongly correlated electrons coupled to dispersionless phonons was solved numerically for a ring of 8 atoms using the density matrix renormalization group (DMRG) method. It was found that electron correlation and electron-phonon coupling compete against each other, and strong electron correlations suppress the charge-o

Y. J. Wang, Y. -J. Kim, R. J. Christianson, S. C. LaMarra

The critical fluctuations of CuGeO$_3$ have been measured by synchrotron x-ray scattering, and two length scales are clearly observed. The ratio between the two length scales is found to be significantly different along the $a$ axis, with the $a$ axis along the surface normal direction. We believe that such a directional preference is a clear sign that surfa

H. A. Mook, P. Dai, F. Dogan, R. D. Hunt

There is increasing evidence that inhomogeneous distributions of charge and spin--so-called "striped phases"--play an important role in determining the properties of the high-temperature superconductors. For example, recent neutron-scattering measurements on the YBa$_2$Cu$_3$O$_{7-x}$ family of materials show both spin and charge fluctuations that ar

A. O. Parry, E. D. Macdonald, C. Rascon

Recent work on local functional theories of critical inhomogeneous fluids and Ising-like magnets has shown them to be a potentially exact, or near exact, description of universal finite-size effects associated with the excess free-energy and scaling of one-point functions in critical thin films. This approach is extended to predict the two-point correlation

H. Heiselberg, C. J. Pethick, H. Smith, L. Viverit

We calculate the effects of induced interactions on the transition temperature to the BCS state in dilute Fermi gases. For a pure Fermi system with 2 species having equal densities, the transition temperature is suppressed by a factor $(4e)^{1/3}\approx 2.2$, and for $ν$ fermion species, the transition temperature is increased by a factor $(4e)^{ν/3-1} \appr

G. Labeyrie, C. A. Müller, D. S. Wiersma, Ch. Miniatura

Coherent backscattering (CBS) of light waves by a random medium is a signature of interference effects in multiple scattering. This effect has been studied in many systems ranging from white paint to biological tissues. Recently, we have observed CBS from a sample of laser-cooled atoms, a scattering medium with interesting new properties. In this paper we di

D. G. Rowan, J. -P. Hansen, E. Trizac

An effective pair potential for systems of uniformly charged lamellar colloids in the presence of an electrolytic solution of microscopic co- and counterions is derived. The charge distribution on the discs is expressed as a collection of multipole moments, and the tensors which determine the interactions between these multipoles are derived from a screened

Farhad H Jafarpour

In this paper we study an one-dimensional two-species exclusion model with open boundaries. The model consists of two types of particles moving in opposite directions on an open lattice. Two adjacent particles swap their positions with rate p and at the same time they can return to their initial positions with rate q if they belong to the different types. Us

Normand Mousseau

Using the activation-relaxation technique (ART), we study the nature of relaxation events in a binary Lennard-Jones system above and below the glass transition temperature (T_g). ART generates trajectories with almost identical efficiency at all temperature, thus avoiding the exponential slowing down below T_g and providing extensive sampling everywhere. Com

M. Nita, A. Aldea

Statistics of level spacing and magnetization are studied for the phase diagram of the integer quantum Hall effect in a 2D finite lattice model with Anderson disorder.

M. I. Katsnelson, A. V. Trefilov, M. N. Khlopkin, K. Yu. Khromov

The calculations are performed for a broad range of the properties of Ca and Sr in the fcc and bcc phases. A detailed information on the magnitude and character of temperature dependence of anharmonic effects in the lattice dynamics over the entire Brillouin zone (frequency shifts and phonon damping, Gruneisen parameters) is given. A detailed comparison of t

W. Prellier, A. M. Haghiri-Gosnet, B. Mercey, Ph. Lecoeur

An insulator to metal transition below 240K is induced by applying a 7T magnetic field in Pr0.5Ca0.5MnO3 thin films grown by the Pulsed Laser Deposition technique on (100) SrTiO3 substrates. This value of the melting magnetic field, much lower that the one required in bulk (20T), is assumed to be an effect of the tensile stress. These results confirm the imp

Sher Alam, M. O. Rahman, M. Ando, S. B. Mohamed

Following our recent conjecture to model the phenomenona of antiferromagnetism and superconductivity by quantum symmetry groups, we discuss in the present note how to construct a workable scenario using this symmetry. In particular we propose to patch the relevant critical points. This means we identify fixed points, corresponding to various $k$ or $q$ [sinc

P. V. Bogdanov, A. Lanzara, S. A. Kellar, X. J. Zhou

Quasiparticle dispersion in $Bi_{2}Sr_{2}CaCu_{2}O_{8}$ is investigated with improved angular resolution as a function of temperature and doping. Unlike the linear dispersion predicted by the band calculation, the data show a sharp break in dispersion at $50\pm10$ $meV$ binding energy where the velocity changes by a factor of two or more. This change provide

Haye Hinrichsen

Recently it has been shown that the transition of the 1+1-dimensional annihilation-fission process 2X->3X, 2X->0 exhibits an unusual type of nonequilibrium critical behavior. The phenomenological properties of critical clusters are characterized by two different dynamic modes for spreading and diffusion. In order to describe the interplay of these modes, we

M. Damnjanovic, T. Vukovic, I. Milosevic

For the single-wall carbon nanotubes conducting in the simplest tight binding model, the complete set of line group symmetry based quantum numbers for the bands crossing at Fermi level are given. Besides linear (k), helical (k'} and angular momenta, emerging from roto-translational symmetries, the parities of U axis and (in the zig-zag and armchair cases

I. Milosevic, T. Vukovic, M. Damnjanovic, B. Nikolic

The full geometrical symmetry groups (the line groups) of the monolayered, 2Hb and 3R polytypes of the inorganic MoS2 and WS2 micro- and nanotubes of arbitrary chirality are found. This is used to find the coordinates of the representative atoms sufficient to determine completely geometrical structure of tubes. Then some physical properties which can be dedu

M. Damnjanovic, T. Vukovic, I. Milosevic

Modified group projector technique for induced representations is a powerful tool for calculation and symmetry quantum numbers assignation of a tight binding Hamiltonian energy bands of crystals. Namely, the induced type structure of such a Hamiltonian enables efficient application of the procedure: only the interior representations of the orbit stabilizers

Michael M. Fogler, David A. Huse

We re-examine a long-standing problem of a finite-frequency conductivity of a weakly pinned two-dimensional classical Wigner crystal. In this system an inhomogeneously broadened absorption line (pinning mode) centered at disorder and magnetic field dependent frequency $ω_p$ is known to appear. We show that the relative linewidth $Δω_p / ω_p$ of the pinning m

Y. Y. Xue, B. Lorenz, A. K. Heilman, M. Gospodinov

A field-induced crossover is observed in the resistivity and magnetization (M) of a La(0.7)Pb(0.3)MnO(3) single crystal. The field-dependence of the resistivity and M suggests that a small spin-canted species with mean-field-like interactions dominates at low fields (H), whereas, individual spins and 3D Ising/Heisenberg models describe the high-H behavior ra

W. A. Heindl, W. Coburn, D. E. Gruber, M. Pelling

In this paper, we summarize the RXTE measurements of cyclotron resonance scattering features in 8 accreting pulsars. The wide bandpass and modest resolution of the RXTE instruments make them ideal for measuring these generally broad features. In particular, the high energy response of HEXTE provides a window for discovery of new lines not detectable with pro

R. B. C. Henry, M. G. Edmunds, J. Koeppen

We analyze the behavior of N/O and C/O abundance ratios as a function of metallicity as gauged by O/H in large, extant Galactic and extragalactic H II region abundance samples. Numerical chemical evolution models are computed using published stellar yields implied by comparing analytical models to the observations. Our results suggest that carbon and nitroge

S. Ayala, A. Noriega-Crespo, P. M. Garnavich, S. Curiel

We present images and spectra of the Cepheus E (Cep E) region at both optical and infrared wavelengths. Only the brightest region of the southern lobe of the Cep E outflow reveals optical emission, suggesting that the extinction close to the outflow source plays an important rôle in the observed difference between the optical and IR morphologies. Cep E is a

W. A. Heindl, W. Coburn, D. E. Gruber, M. Pelling

We report phase resolved spectroscopy of the transient accreting pulsar, 4U0115+63. For the first time, more than two cylotron resonance scattering features are detected in the spectrum of an X-ray pulsar. The shape of the fundamental line appears to be complex, and this is in agreement with predictions of Monte-Carlo models. As in other pulsars, the line en

J. Jimenez-Vicente, E. Battaner

We have observed the nearly face-on spiral galaxy NGC 5668 with the TAURUS II Fabry-Perot interferometer at the William Herschel Telescope using the $Hα$ line to study the kinematics of the ionized gas. From the extracted data cube we construct intensity, velocity and velocity dispersion maps. We calculate the rotation curve in the innermost 2 arcmin and we

Niruj R. Mohan, K. R. Anantharamaiah, W. M. Goss

Radio recombination lines (RRL) at 8 GHz and 15 GHz detected from four starburst galaxies are shown to arise in compact high density HII regions, which are undetectable below ~4 GHz. Detection of an RRL at 1.4 GHz towards one galaxy and upper limits in the other three are consistent with the presence of an equal amount of low density diffuse gas. Continuum f

K. R. Anantharamaiah, F. Viallefond, Niruj R. Mohan, W. M. Goss

We present observations of radio recombination lines from the starburst galaxy Arp 220 at 1.4, 8.1, 84, 96 and 207 GHz (sensitive upper limit for the 1.4 GHz line and firm detections at the other frequencies), and the radio continuum spectrum between 330 MHz and 207 GHz. We show that a model with three components of ionized gas with different densities and a

S. Cebrian, N. Coron, G. Dambier, E. Garcia

Rare Objects SEarch with Bolometers UndergrounD) is an experiment which attempts to detect low mass Weak Interacting Massive Particles (WIMPs) through their elastic scattering off Al and O nuclei. It consists of three small sapphire bolometers (of a total mass of 100 g) with NTD-Ge sensors in a dilution refrigerator operating at 20 mK in the Canfranc Undergr