April 2000 arXiv papers — page 9

M. R. Schreiber, B. T. Gaensicke, F. V. Hessman

We present simulations of dwarf nova outbursts taking into account realistic variations of the mass loss rate from the secondary. The mass transfer variation has been derived from 20 years of visual monitoring and from X-ray observations covering various accretion states of the discless cataclysmic variable AM Herculis. We find that the outburst behaviour of

J. L. Zdunik, T. Bulik, W. Kluźniak, P. Haensel

We compute the maximum mass of moderately rotating strange stars as a function of the strange quark mass, of the QCD coupling constant, $α_c$, and of the bag constant (vacuum energy density), $B$, in the MIT bag model of quark matter with lowest order quark-gluon interactions. For a fixed value of $B$, the maximum stellar mass depends only weakly on $α_c$, a

Andrew R. King

BeppoSAX has detected a population of faint transient X-ray sources in the Galactic Centre. I show that a simple irradiated-disc picture gives a consistent fit to the properties of this population, and that it probably consists of low-mass X-ray binaries which have evolved beyond their minimum periods ~80 min. Since all post-minimum systems are transient, an

E. Lastennet, D. Valls-Gabaud, E. Oblak

Which sample of objects can give strong constraints on single-star evolution theory ? Whilst star cluster members share the same age and the same metallicity, many questions (e.g. field stars contamination, stellar rotation, presence of unresolved binaries) are difficult to clarify properly when using their colour-magnitude diagram to compare with theoretica

E. Kuulkers, J. J. M. in 't Zand, R. Cornelisse, J. Heise

During the 1996/1997 outburst of the X-ray transient GRO J1655-40 the Wide Field Cameras onboard BeppoSAX observed the system with nearly continuous coverage during some stages of this outburst. On two occasions we find clear evidence for frequent dipping behaviour, characterized by several absorption dips occurring within one binary orbit. However, during p

H. C. Spruit, F. Daigne, G. Drenkhahn

We consider possible geometries of magnetic fields in GRB outflows, and their evolution with distance from the source. For magnetically driven outflows, with an assumed ratio of magnetic to kinetic energy density of order unity, the field strengths are sufficient for efficient production of gamma-rays by synchrotron emission in the standard internal shock sc

B. M. Gaensler, B. W. Stappers, D. A. Frail, D. A. Moffett

We report on a sensitive survey for radio pulsar wind nebulae (PWN) towards 27 energetic and/or high velocity pulsars. Observations were carried out at 1.4 GHz using the Very Large Array and the Australia Telescope Compact Array, and utilised pulsar-gating to search for off-pulse emission. These observing parameters resulted in a considerably more sensitive

M. Waugh, R. L. Webster, M. J. Drinkwater

The Multibeam survey at the Parkes Radio Telescope has provided a wealth of 21 cm HI data. We have mosaicked ten standard HIPASS cubes to produce a datacube approximately 25 deg x 25 deg in size, centred on NGC1399, the optical centre of the Fornax Cluster. Some properties of the initial approx. 80 galaxies identified in HI are described. In the optical, Fer

M. J. Drinkwater, M. Waugh, R. L. Webster, D. G. Barnes

We are using the Multibeam 21cm receiver on the Parkes Telescope combined with the optical Two degree Field spectrograph (2dF) of the Anglo-Australian Telescope to obtain the first complete spectroscopic sample of the Fornax cluster. In the optical the survey is unique in that all objects (both ``stars'' and ``galaxies'') within our magnitude

B. Scott Gaudi, M. D. Albrow, Jin H. An, J. -P. Beaulieu

Microlensing is the only technique likely, within the next 5 years, to constrain the frequency of Jupiter-analogs. The PLANET collaboration has monitored nearly 100 microlensing events of which more than 20 have sensitivity to the perturbations that would be caused by a Jovian-mass companion to the primary lens. No clear signatures of such planets have been

Csaba Csaki, Joshua Erlich, Christophe Grojean, Timothy Hollowood

We study the dynamics of brane worlds coupled to a scalar field and gravity, and find that self-tuning of the cosmological constant is generic in theories with at most two branes or a single brane with orbifold boundary conditions. We demonstrate that singularities are generic in the self-tuned solutions compatible with localized gravity on the brane: we sho

Feryal Ozel, Tiziana Di Matteo

We consider the X-ray emission due to bremsstrahlung processes from hot, low radiative-efficiency accretion flows around supermassive and galactic black holes. We calculate surface brightness profiles and Michelson visibility functions for a range of density profiles, rho ~ r^(-3/2+p), with 0 < p < 1, to allow for the presence of outflows. We find that altho

Tomonori Totani, Yuzuru Yoshii

(Abridged) We present a detailed analysis of the number count and photometric redshift distribution of faint galaxies in the Hubble Deep Field (HDF), paying a special attention to the selection effects including the cosmological dimming of surface brightness of galaxies. We find a considerably different result from previous studies ignoring the selection eff

Raphael Bousso, Joseph Polchinski

A four-form gauge flux makes a variable contribution to the cosmological constant. This has often been assumed to take continuous values, but we argue that it has a generalized Dirac quantization condition. For a single flux the steps are much larger than the observational limit, but we show that with multiple fluxes the allowed values can form a sufficientl

Jairo Sinova, A. H. MacDonald, S. M. Girvin

We report on a finite-size Hartree-Fock study of the competition between disorder and interactions in a two-dimensional electron gas near Landau level filling factor $ν=1$. The ground state at $ν=1$ evolves with increasing disorder from a fully spin-polarized ferromagnet with a charge gap, to a partially spin-polarized ferromagnetic Anderson insulator, to a

Darwin Chang, We-Fu Chang, Mariana Frank, Wai-Yee Keung

We analyze the neutron electric dipole moment (EDM) in the Minimal Supersymmetric Model with explicit R-parity violating terms. The leading contribution to the EDM occurs at the 2-loop level and is dominated by the chromoelectric dipole moments of quarks, assuming there is no tree-level mixings between sleptons and Higgs bosons or between leptons and gaugino

H. -W. Hammer, R. J. Furnstahl

The virtues of an effective field theory (EFT) approach to many-body problems are illustrated by deriving the expansion for the energy of an homogeneous, interacting Fermi gas at low density and zero temperature. A renormalization scheme based on dimensional regularization with minimal subtraction leads to a more transparent power-counting procedure and diag

Marion Wirschins, Abha Sood, Jutta Kunz

We construct regular and black hole solutions in SU(2) Einstein-Born-Infeld theory. These solutions have many features in common with the corresponding SU(2) Einstein-Yang-Mills solutions. In particular, sequences of neutral non-abelian solutions tend to magnetically charged limiting solutions, related to embedded abelian solutions. Thermodynamic properties

Sergei A. Voloshin

It was recently argued that in heavy ion collision the parity could be broken. This Note addresses the question of possibility of the experimental detection of the effect. We discuss how parity violating effects would modify the final particle distributions and how one could construct variables sensitive to the effect, and which measurement would be the (mos

V. Senz, T. Ihn, T. Heinzel, K. Ensslin

We find that temperature dependent screening can quantitatively explain the metallic behaviour of the resistivity on the metallic side of the so-called metal-insulator transition in p-SiGe. Interference and interaction effects exhibit the usual insulating behaviour which is expected to overpower the metallic background at sufficiently low temperatures. We fi

Y. J. Kim, R. J. Birgeneau

We present a quantum Monte Carlo study of a Heisenberg antiferromagnet on a spatially anisotropic square lattice, where the coupling strength in the x-direction ($J_x$) is different from that in the y-direction ($J_y$). By varying the anisotropy $α$ from 0 to 1, we interpolate between the one-dimensional chain and the two-dimensional isotropic square lattice

Sibasish Ghosh, Anirban Roy, Ujjwal Sen

We show that the Bloch vectors lying on any great circle is the largest set S(L) for which the parallel states |n,n> can always be transformed into the anti-parallel states |n,-n>. Thus more information about the Bloch vector is not extractable from |n,-n> than from |n,n> by any measuring strategy, for the Bloch vector belonging to S(L). Surprisingly, the la

D. Challet, M. Marsili, R. Zecchina

We show that the dynamical equations describing the collective behavior of the model introduced by Cavagna et al. i) are not their Eqs. (5,6) but rather ii) are the same as those of the minority game (MG). As a consequence the analytic solution of the MG presented in [PRL, 84, 1824 (2000)] holds also for this model. Finally we show that iii) the the large te

Rodrigo Ibata, Michael Irwin, Geraint Lewis, Andrea Stolte

Two studies have recently reported the discovery of pronounced Halo substructure in the Sloan Digital Sky Survey (SDSS) commissioning data. Here we show that this Halo substructure is almost in its entirety due to the expected tidal stream torn off the Sagittarius dwarf galaxy during the course of its many close encounters with the Milky Way. This interpreta

M P Das, F Green

Isakov, Martin, and Ouvry [PRL 83, 580 (1999)] have recently proposed a fresh approach to the potential observation of fractional exclusion statistics. According to their argument, a clear signature of fractional statistics should exist in the shot noise of a Luttinger fluid, an ideal system postulated by some to underlie the well-founded Laughlin quasiparti

T. A. Costi

The effect of a magnetic field on the spectral density of a $\rm{S=1/2}$ Kondo impurity is investigated at zero and finite temperatures by using Wilson&#39;s numerical renormalization group method. A splitting of the total spectral density is found for fields larger than a critical value $H_{c}(T=0)\approx 0.5 T_{K}$, where $T_{K}$ is the Kondo scale. The sp

U. Becciani, V. Antonuccio-Delogu, M. Gambera

N-body codes to perform simulations of the origin and evolution of the Large Scale Structure of the Universe have improved significantly over the past decade both in terms of the resolution achieved and of reduction of the CPU time. However, state-of-the-art N-body codes hardly allow one to deal with particle numbers larger than a few 10^7, even on the large

Kanehisa Takasaki

We extend the work of Fuchs, Painlevé and Manin on a Calogero-like expression of the sixth Painlevé equation (the ``Painlevé-Calogero correspondence&#39;&#39;) to the other five Painlevé equations. The Calogero side of the sixth Painlevé equation is known to be a non-autonomous version of the (rank one) elliptic model of Inozemtsev&#39;s extended Calogero sy

Xianglin Ke, Feng Yuan, Shiping Feng

The influence of the additional second neighbor hopping t&#39; on the spin response of the t-J model in the underdoped and optimally doped regimes is studied within the fermion-spin theory. Although the additional second neighbor hopping t&#39; is systematically accompanied with the reduction of the dynamical spin structure factor and susceptibility, the qua

R. Kuriki, A. Sugamoto

We propose a geometrized Higgs mechanism based on the gravitational sector in the Connes-Lott formulation of the standard model, which has been constructed by Chamseddine, Fr$\ddot{o}$hlic and Grandjean. The point of our idea is that Higgs-like couplings depend on the local coordinates of the four-dimensional continuum,$M_4$. The localized couplings can be c

Ambar Ghosal

We propose a texture of three generation Majorana-type neutrino mass matrix in terms of only two parameters which gives rise to nearly bi-maximal mixing angles. We also demonstrate an explicit realization of such type of neutrino mass-matrix in the context of an $SU(2)_L$$\times$$U(1)_Y$ model due to higher dimensional mass terms through the inclusion of dis

A. Gokalp, O. Yilmaz

The experimental branching ratio for the radiative decay $ρ^{0}\toπ^{+}+π^{-}+γ$ is used to estimate the coupling constant $g_{ρσγ}$ for a set of values of $σ$-meson parameters M$_σ$ and $Γ_σ$. Our results are quite different than the values of this constant used in the literature.

A. I. Akhiezer, A. A. Isayev, S. V. Peletminsky, A. A. Yatsenko

Influence of asymmetry on superfluidity of nuclear matter with triplet-singlet pairing of nucleons (in spin and isospin spaces) is considered within the framework of a Fermi-liquid theory. Solutions of self-consistent equations for the critical temperature and the energy gap at T=0 are obtained. It is shown, that the backward influence of pairing correlation

M. D. Albrow, J. An, J. -P. Beaulieu, J. A. R. Caldwell

We present PLANET observations of OGLE-1999-BUL-23, a binary-lens microlensing event towards the Galactic bulge. PLANET observations in the I and V bands cover the event from just before the first caustic crossing until the end of the event. In particular, a densely-sampled second caustic crossing enables us to derive the linear limb-darkening coefficients o

Joseph J. Mohr, Erik D. Reese, E. Ellingson, Aaron D. Lewis

We present the first measurements of the X-ray size-temperature (ST) relation in intermediate redshift (z~0.30) galaxy clusters. We interpret the local ST relation (z~0.06) in terms of underlying scaling relations in the cluster dark matter properties, and then we use standard models for the redshift evolution of those dark matter properties to show that the

Viacheslav P Belavkin, Masanori Ohya

The mathematical structure of quantum entanglement is studied and classified from the point of view of quantum compound states. We show that t he classical-quantum correspondences such as encodings can be treated as dia gonal (d-) entanglements. The mutual entropy of the d-compound and entangled states lead to two different types of entropies for a given qua

Daniel Gottesman

Quantum states are very delicate, so it is likely some sort of quantum error correction will be necessary to build reliable quantum computers. The theory of quantum error-correcting codes has some close ties to and some striking differences from the theory of classical error-correcting codes. Many quantum codes can be described in terms of the stabilizer of

Ladislav Mista,, Jiri Herec, Viktor Jelinek, Jaroslav Rehacek

In the framework of Heisenberg-Langevin theory the dynamical and statistical effects arising from the linear interaction of two nondegenerate down-conversion processes are investigated. Using the strong-pumping approximation the analytical solution of equations of motion is calculated. The phenomena reminiscent of Zeno and anti-Zeno effects are examined. The

Viacheslav P Belavkin, Masanori Ohya

Quantum entanglements, describing truly quantum couplings, are stu died and classified from the point of view of quantum compound states. We show that c lassical-quantum correspondences such as quantum encodings can be treated as d-entanglements leading to a special class of the separable compound states. The mutual information of the d-compound and entangle

X. X. Yi, D. L. Zhou, C. P. Sun

The decoherence in trapped ion induced by coupling the ion to the engineered reservoir is studied in this paper. The engineered reservoir is simulated by random variations in the trap frequency, and the trapped ion is treated as a two-level system driven by a far off-resonant plane wave laser field. The dependence of the decoherence rate on the amplitude of

Xijia Miao

Any unitary transformation of quantum computational networks is explicitly decomposed, in an exact and unified form, into a sequence of a limited number of one-qubit quantum gates and the two-qubit diagonal gates that have diagonal unitary representation in usual computational basis. This decomposition may be simplified greatly with the help of the propertie

Massimo Casu, Christoph Keitel

Small parts of the electronic wavepacket of a multiple charged ion may still tunnel through the high Coulomb barrier for a sufficiently intense laser field of $10^{15}W/cm^2$ and higher. Solving numerically the corresponding Schrödinger equation we find that the periodic recollisions of such a wavepacket in the oscillating high power laser field will give ri

B. G. Sidharth

It is shown that a collection of photons with nearly the same frequency exhibits a &#34;condensation&#34; type of phenomenon corresponding to a peak intensity. The observed cosmic background radiation can be explained from this standpoint in terms of the radiation due to fluctuations in interstellar Hydrogen.

Richard A. Arndt, Igor I. Strakovsky, Ron L. Workman

A partial-wave analysis (PWA) of NN elastic scattering data has been completed. This analysis covers an expanded energy range, from threshold to a laboratory kinetic energy of 3 GeV, in order to include recent elastic pp polarized scattering measurements performed at SATURNE II. Results of the energy-dependent fit are compared with single-energy solutions an

Nevio Grion

The pion-production $π^+ A \to π^+π^{\pm} A&#39;$ reactions were studied on nuclei $^{2}H$, $^{12}C$, $^{40}Ca$ and $^{208}Pb$ at a pion energy of $T_{π^{+}}$=283 MeV using the CHAOS spectrometer. The experimental results are reduced to differential cross sections and compared to both theoretical predictions and reaction phase space. Near the $2m_π$ threshol

A. Loskutov, D. Andrievsky, V. Ivanov, K. Vasiliev

A theoretical model for fractal growth of DLA-clusters in two- and three-dimensional Euclidean space is proposed. This model allows to study some statistical properties of growing clusters in two different situations: in the static case (the cluster is fixed), and in the case when the growing structure has a nonzero rotation around its germ. By the direct co

Bidhan Chandra Bag, Deb Shankar Ray

We consider a general N-degree-of-freedom dissipative system which admits of chaotic behaviour. Based on a Fokker-Planck description associated with the dynamics we establish that the drift and the diffusion coefficients can be related through a set of stochastic parameters which characterize the steady state of the dynamical system in a way similar to fluct

Danny Stevenson

This thesis reviews the theory of bundle gerbes and then examines the higher dimensional notion of a bundle 2-gerbe. The notion of a bundle 2-gerbe connection and 2-curving are introduced and it is shown that there is a class in $H^{4}(M;\Z)$ associated to any bundle 2-gerbe.

Sergei V. Shabanov

A path integral description of an effective action of monopoles in Abelian projections of Yang-Mills theories is discussed and used to establish a projection independence of the effective action. A dynamic regime in which the effective dynamics may contain massive solitonic excitations is described.

S. P. Gavrilov, D. M. Gitman, A. E. Goncalves

We study exact solutions of Dirac and Klein-Gordon equations and Green functions in d-dimensional QED and in an external electromagnetic field with constant and homogeneous field invariants. The cases of even and odd dimensions are considered separately, they are essentially different. We direct attention to the asymmetry of the quasienergy spectrum, which a

Nadav Drukker, David J. Gross, N. Itzhaki

We construct unstable classical solutions of Yang-Mills theories and their dual unstable states of type IIB on AdS_5. An example is the unstable D0-brane of type IIB located at the center of AdS. This has a field theory dual which is a sphaleron in gauge theories on S^3 x R. We argue that the two are dual because both are sphalerons associated to the topolog

Charles B. Thorn

I describe renewed efforts to establish a string description of large N_c QCD by summing large ``fishnet&#39;&#39; diagrams. Earlier work on fishnets indicated that the usual relativistic (zero thickness) string theory can arise at strong &#39;t Hooft coupling, at best yielding a highly idealized description, which fails to incorporate such salient features

Anirban Basu, Satish D. Joglekar

We study the nonlocal regularization for the non-abelian gauge theories for an arbitrary value of the gauge parameter (ξ). We show that the procedure for the nonlocalization of field theories established earlier by the original authors, when applied in that form to the Faddeev-Popov effective action in a linear gauge cannot lead to a (ξ)-independent result f

G. Corcella, M. L. Mangano, M. H. Seymour

We analyse the impact of matrix-element corrections to top decays in HERWIG on several observables related to the jet activity in t-tbar events at the Tevatron and at the LHC. In particular, we study the effects induced by the higher-order corrections to top decays on the top mass reconstruction using the recently proposed J/psi+lepton final states.

B. Krippa, B. L. G. Bakker

We consider the effective field theory of the NN system in a separable representation. The pionic part of the effective potential is included nonperturbatively and approximated by a separable potential. The use of a separable representation allows for the explicit solution of the Lippmann-Schwinger equation and a consistent renormalization procedure. The pha

Yoshiaki Koma, Hiroshi Toki

The flux-tube solution in the dual Ginzburg-Landau (DGL) theory in the Bogomol&#39;nyi limit is studied by using the manifestly Weyl invariant form of the DGL Lagrangian. The dual gauge symmetry is extended to $[U(1)]_m^3$, and accordingly, there appear three different types of the flux-tube. The string tension for each flux-tube is calculated analytically a

I. P. Lokhtin, A. M. Snigirev

The most suitable way to study the jet quenching as a function of distance traversed is varying the impact parameter b of ultrarelativistic nucleus-nucleus collision (initial energy density in nuclear overlapping zone is almost independent of b up to b R_A). It is shown that b-dependences of medium-induced radiative and collisional energy losses of a hard pa

Tatsuo Kobayashi, Koichi Yoshioka

We study new renormalization-group invariant quantities of soft supersymmetry breaking parameters other than the ratio of gaugino mass to gauge coupling squared by using the spurion method. The obtained invariants are useful to probe supersymmetry breaking and mu-term generation mechanisms at high-energy scale. We also discuss the convergence behavior of fix

S. Munier

We show that a forward jet with large transverse momentum in an onium-onium collision is a hard probe which can be effectively characterized by a colour- dipole distribution at the time of the interaction. The dipole distribution is computed, and compared to its counterpart for a virtual photon in the initial state. We find that while in the photon case, the

Y. -Y. Keum, H. -n. Li, A. I. Sanda

We compute branching ratios of $B\to Kπ$ decays in the framework of perturbative QCD factorization theorem. Decay amplitudes are classified into the topologies of tree, penguin and annihilation, all of which contain both factorizable and nonfactorizable contributions. These contributions are expressed as the convolutions of hard $b$ quark decay amplitudes wi

J. Blümlein, V. Ravindran, W. L. van Neerven

We study the validity of a relation by Drell, Levy and Yan (DLY) connecting the deep inelastic structure (DIS) functions and the single-particle fragmentation functions in e^+e^- annihilation which are defined in the spacelike (q^2<0) and timelike (q^2>0) regions respectively. Here q denotes the momentum of the virtual photon exchanged in the deep inelastic

John Ellis, Toby Falk, Gerardo Ganis, Keith A. Olive

We analyze the accelerator constraints on the parameter space of the Minimal Supersymmetric extension of the Standard Model, comparing those now available from LEP II and anticipating the likely sensitivity of Tevatron Run II. The most important limits are those from searches for charginos, neutralinos and Higgs bosons at LEP, and searches for stop squarks,

Firooz Arash, Ali Naghi Khorramian

We calculate the partonic structure of constituent quark in the Next-to-Leading Order for the first time. The structure of any hadron can be obtained thereafter using a convolution method. Such a procedure is used to generate the structure function of proton and pion in NLO. It is shown that while the constituent quark structure is generated purely perturbat

C. D. Fosco, M. Teper

We show that, under certain general assumptions, any sensible lattice Dirac operator satisfies a generalized form of the Ginsparg-Wilson relation (GWR). Those assumptions, on the other hand, are mostly dictated by large momentum behaviour considerations. We also show that all the desirable properties often deduced from the standard GWR hold true of the gener

Michael Engelhardt

A definition of the Pontryagin index for SU(2) center vortex world-surfaces composed of plaquettes on a hypercubic lattice is constructed. It is used to evaluate the topological susceptibility in a previously defined random surface model for vortices, the parameters of which have been fixed such as to reproduce the confinement properties of SU(2) Yang-Mills

D. B. Cline, Y. Fukui, A. Garren

We briefly discuss the physics motivation for a neutrino factory with varying baseline distances of about 1000 to 9000 km. We describe the amount of non planarity of the storage ring required to service three or four detectors at once. A novel bowtie storage ring is described that could in part provide these beams; a preliminary lattice design is given. We g

D. Bakari, S. Cecchini, H. Dekhissi, J. Derkaoui

We present qualitative pictures of the structures of magnetic monopoles (MMs), nuclearites (nuggets of strange quark matter, strangelets, surrounded by electrons) and Q-balls (supersymmetric states of squarks, sleptons and Higgs fields). In particular we discuss the relation between their mass and size. MMs, nuclearites and Q-balls could be part of the cold

Mauricio Bellini

I consider the COBE data coarse-grained field that characterize the now observable universe for a model of warm inflation which takes into account the thermal coupled fluctuations of the scalar field with the thermal bath. The power spectrum for both, matter and metric fluctuations are analyzed. I find that the amplitude for the fluctuations of the metric wh

Yasufumi Kojima, Masayasu Hosonuma

Axial oscillations relevant to the r-mode instability are studied with slow rotation formalism in general relativity. The approximate equation governing the oscillations is derived with second-order rotational corrections. The equation contains an effective &#39;viscosity-like&#39; term, which originates from coupling to the polar g-mode displacements. The t

Lex Weaver

Multicomputers have traditionally been viewed as powerful compute engines. It is from this perspective that they have been applied to various problems in order to achieve significant performance gains. There are many applications for which this compute intensive approach is only a partial solution. CAD, virtual reality, simulation, document management and an

V. Celli, J. S. Frasier

Laser experiments with optically excited frozen gases entail the excitation of polarization waves. In a continuum approximation the waves are dispersionless, but their frequency depends on the direction of the propagation vector. An outline is given of the theory of transient phenomena that involve the excitation of these waves by a resonant dipole-dipole tr

K. Ziegler

Consequences of different discretizations of the two-dimensional Dirac operator on low energy properties (e.g., the number of nodes) and their relations to gauge properties are discussed. Breaking of the gauge invariance was suggested in a recent work by M. Bocquet, D. Serban, and M.R. Zirnbauer [cond-mat/9910480] in order to destroy an intermediate metallic

Raymond J. Hawkins, Michael R. Arnold

We show how a novel application of the theory of anelasticity unifies the observed dynamics and proposed models of administered-rate products. This theory yields a straightforward approach to rate model construction that we illustrate by simulating the observed relaxation dynamics of two administered rate products. We also demonstrate how the use of this for

G. B. Martins, C. Gazza, J. C. Xavier, A. Feiguin

The extended and standard t-J models are computationally studied on ladders and planes, with emphasis on the small J/t region. At couplings compatible with photoemission results for undoped cuprates, half-doped stripes separating $π$-shifted antiferromagnetic (AF) domains are found, as in Tranquada&#39;s interpretation of neutron experiments. Our main result

J. Gopalakrishnan, A. Chattopadhyay, S. B. Ogale, T. Venkatesan

We have investigated the structure and electronic properties of ferrimagnetic double perovskites, A2FeReO6 (A= Ca, Sr, Ba). The A=Ba phase is cubic (Fm3m) and metallic, while the A=Ca phase is monoclinic (P21/n) and nonmetallic. 57Fe Mossbauer spectroscopy shows that iron is present mainly in the high-spin (S=5/2) Fe3+ state in the Ca compound, while it occu

Zhi-Feng Huang

A self-organized model with social percolation process is proposed to describe the propagations of information for different trading ways across a social system and the automatic formation of various groups within market traders. Based on the market structure of this model, some stylized observations of real market can be reproduced, including the slow decay

N. Kirova, S. Brazovskii

The rich order parameter of Spin Density Waves allows for unusual object of a complex topological nature: a half-integer dislocation combined with a semi-vortex of a staggered magnetization. It becomes energetically preferable to ordinary dislocation due to enhanced Coulomb interactions in the semiconducting regime. Generation of these objects changes e.g. t

O. N. Makarovskii, L. Smrcka, P. Vasek, T. Jungwirth

Bilayer two-dimensional electron systems formed by a thin barrier in the GaAs buffer of a standard heterostructure were investigated by magnetotransport measurements. In magnetic fields oriented parallel to the electron layers, the magnetoresistance exhibits an oscillation associated with the depopulation of the higher occupied subband and the field-induced

A. D. Jackson, G. M. Kavoulakis, B. Mottelson, S. M. Reimann

We consider a weakly-interacting, harmonically-trapped Bose-Einstein condensed gas under rotation and investigate the connection between the energies obtained from mean-field calculations and from exact diagonalizations in a subspace of degenerate states. From the latter we derive an approximation scheme valid in the thermodynamic limit of many particles. Me

G. M. Kavoulakis, B. Mottelson, C. J. Pethick

We investigate the ground and low excited states of a rotating, weakly interacting Bose-Einstein condensed gas in a harmonic trap for a given angular momentum. Analytical results in various limits, as well as numerical results are presented, and these are compared with those of previous studies. Within the mean-field approximation and for repulsive interacti

Serge Galam

The concept and technics of real space renormalization group are applied to study majority rule voting in hierarchical structures. It is found that democratic voting can lead to totalitarianism by keeping in power a small minority. Conditions of this paradox are analyzed and singled out. Indeed majority rule produces critical thresholds to absolute power. Va

S. Huegle, R. Egger, H. Grabert

We study electron tunneling from a tip or a lead into an interacting quantum wire described by Luttinger liquid theory. Within a WKB-type approach, the Coulomb interaction between the wire and the tunneling electrons, as well as the finite traversal time are taken into account. Although the static image potential is only logarithmically suppressed against th

marco zoli

This study details the conditions under which strong-coupling perturbation theory can be applied to the molecular crystal model, a fundamental theoretical tool for analysis of the polaron properties. I show that lattice dimensionality and intermolecular forces play a key role in imposing constraints on the applicability of the perturbative approach. The pola

I. E. Psarobas, N. Stefanou, A. Modinos

We develop a formalism for the calculation of the frequency band structure of a phononic crystal consisting of non-overlapping elastic spheres, characterized by Lamé coefficients which may be complex and frequency dependent, arranged periodically in a host medium with different mass density and Lamé coefficients. We view the crystal as a sequence of planes o

Gerald H. Ristow

The settling dynamics of spherical and elliptical particles in a viscous Newtonian fluid are investigated numerically using a finite difference technique. The terminal velocity for spherical particles is calculated for different system sizes and the extrapolated value for an infinite system size is compared to the Oseen approximation. Special attention is gi

V. Ya. Pokrovskii, S. V. Zaitsev-Zotov

In the Peierls state very thin samples of TaS_3 (cross-section area \sim 10^{-3} mkm^2) are found to demonstrate smearing of the I-V curves near the threshold field. With approaching the Peierls transition temperature, T_P, the smearing evolves into smooth growth of conductance from zero voltage interpreted by us as the contribution of fluctuations to the no

Feng Yuan, Xianglin Ke, Shiping Feng

The momentum and doping dependence of the electron spectrum of copper oxide materials in the underdoped regime is studied within the t-J model. It is shown that the pseudogap opens near ($π$,0) point in the Brillouin zone, and the electron dispersion exhibits the flat band around ($π$,0), which are consistent with the experiments.

Shoji Yamamoto

We make a modified spin-wave description of the nuclear spin relaxation in Heisenberg alternating-spin chains with antiferromagnetic exchange coupling. In contrast with the conventional one-dimensional antiferromagnetic spin-wave theory, which is plagued with the divergence of the sublattice magnetization even in the ground state, the present spin-wave descr

K. H. Ahn, A. J. Millis

The effects of uniaxial strain on the structural, orbital, optical, and magnetic properties of LaMnO_3 are calculated using a general elastic energy expression, along with a tight-binding parameterization of the band theory. Tensile uniaxial strain of the order of 2 % (i.e., of the order of magnitude of those induced in thin films by lattice mismatch with su

Namiko Mitarai, Hiizu Nakanishi

The spatio-temporal structure of traffic flow pattern is investigated under the open boundary condition using the optimal velocity (OV) model. The parameter region where the uniform solution is convectively unstable is determined. It is found that a localized perturbation triggers a linearly unstable oscillatory solution out of the linearly unstable uniform

Dmitry Green, Claudio Chamon

We formulate the problem of adsorption onto the surface of a carbon nanotube as a lattice gas on a triangular lattice wrapped around a cylinder. This model is equivalent to an XXZ Heisenberg quantum spin tube. The geometric frustration due to wrapping leads generically to four magnetization plateaus, in contrast to the two on a flat graphite sheet. We obtain

B. A. Bernevig, D. Giuliano, R. B. Laughlin

We propose that the finite-frequency susceptibility of matter near a class of zero-temperature phase transition exhibits distinctive excitonic structure similar to meson resonances. The specific case of a Landau level undergoing a transition to antiferromagnetism is considered as a prototype. A physical analogy is drawn between the behavior calculated for su

Martin Rost

A continuum model for growth of solids is developed, considering adatom deposition, surface diffusion, and configuration dependent incorporation rate. For amorphous solids it is related to surface energy densities. The high adatom density leads to growth enhanced dynamics of (a) Mullins&#39; classical equation [J. Appl. Phys. {\bf 28}, 333 (1957)] without, a

J. J. Garcia-Ripoll, V. M. Perez-Garcia

We study the rotational properties of a Bose-Einstein condensate confined in a rotating harmonic trap for different trap anisotropies. Using simple arguments, we derive expressions for the velocity field of the quantum fluid for condensates with or without vortices. While the condensed gas describes open spiraling trajectories, on the frame of reference of t

Steven M. Anlage, D. E. Steinhauer, B. J. Feenstra, C. P. Vlahacos

Near-field microwave microscopy has created the opportunity for a new class of electrodynamics experiments of materials. Freed from the constraints of traditional microwave optics, experiments can be carried out at high spatial resolution over a broad frequency range. In addition, the measurements can be done quantitatively so that images of microwave materi

T. H. Jarrett, G. Helou, D. Van Buren, E. Valjavec

We report on an infrared 1 to 17 micron study of the nearby (cz = 4600 km/s) interacting spiral galaxy system, UGC 12914/12915, using the ground-based Palomar 200&#34; telescope and PFIRCAM near-infrared detector and space-based mid-infrared imaging and spectral observations using ISOCAM and Phot-S on the Infrared Space Observatory (ISO). Strong line emissio

Simon DeDeo, Dimitrios Psaltis, Ramesh Narayan

Most models of anomalous X-ray pulsars (AXPs) account for the observed X-ray spectra and pulsations by means of radiation processes that occur on the surfaces of neutron stars. For any such model, general relativistic deflection of light severely suppresses the amplitude of the observed pulsations. We calculate the expected pulsation amplitudes of AXPs accor

T. Hearty, M. Fernandez, J. M. Alcala, E. Covino

We present high-resolution spectra (R ~ 49,000) of stars that have parallax measurements from the Hipparcos satellite and are projected along the line of sight to the two nearest known star forming clouds to the Sun: MBM12 and MBM20. The spectra were obtained with the FOCES Echelle Spectrograph at the 2.2 meter telescope in Calar Alto, Spain and the waveleng

Percy L. Gomez, John P. Hughes, Mark Birkinshaw

We present new redshift measurements for 55 galaxies in the vicinity of the rich galaxy cluster Abell 665. When combined with results from the literature, we have good velocity measurements for a sample of 77 confirmed cluster members from which we derive the cluster&#39;s redshift z=0.1829 +/- 0.0005 and line-of-sight velocity dispersion of 1390 +/- 120 km/

Michael R. Corbin

The large scale (~ 100 kpc) environments of Seyfert galaxies are not significantly different from those of non-Seyfert galaxies. In the context of the interaction model of the formation of active galactic nuclei (AGN), it has been proposed that AGN form via &#34;minor mergers&#34; of large disk galaxies with smaller companions. We test this hypothesis by com