April 2000 arXiv papers — page 14

Sergey Fomin

We consider matrices whose elements enumerate weights of walks in planar directed weighted graphs (not necessarily acyclic). These matrices are totally nonnegative; more precisely, all their minors are formal power series in edge weights with nonnegative coefficients. A combinatorial explanation of this phenomenon involves loop-erased walks. Applications inc

Spencer Bloch, Hélène Esnault

We give an explicit formula for the determinant of the Gauß-Manin connection for an irregular connection on a Zariski open set of the projective line $¶^1_K$ over a function field $K$ over a field $k$ of characteristic zero.

Sergey Neshveyev, Erling Stormer

Let (A,α) be a C*-dynamical system. We introduce the notion of pressure P_α(H) of the automorphism αat a self-adjoint operator H\in A. Then we consider the class of AF-systems satisfying the following condition: there exists a dense α-invariant *-subalgebra \A of A such that for all pairs a,b\in\A the C*-algebra they generate is finite dimensional, and there

Rossella Bartolo, Anna Germinario, Miguel Sanchez

In this paper we analyze the problem of the geodesic connectedness of subsets of Riemannian manifolds. By using variational methods, the geodesic connectedness of open domains (whose boundaries can be not differentiable and not convex) of a smooth Riemannian manifold is proved. In some cases also the convexity of the domain is obtained. Moreover we present e

Kai Xu

Let D_n be the Dickson invariant ring of F_2[X_1,...,X_n] acted by the general linear group GL(n,\F_2). In this paper, we provide an elementary proof of the conjecture by [Hung]: each element in D_n is in the image of the Steenrod square in F_2[X_1,...,X_n], where n>3.

Gabriele Vezzosi

We characterize ring spectra morphisms from the algebraic cobordism spectrum $\QTR{Bbb}{MGL}$ (\QCITE{cite}{}{Vo1}) to an oriented spectrum $\QTR{Bbb}{E}$ (in the sense of Morel \QCITE{cite}{}{Mo}) via formal group laws on the ''topological'' subring $E^{*}=\oplus_iE^{2i,i}$ of $E^{**}$. This result is then used to construct for any prime $p$

S. Ferrara, E. Sokatchev

We consider the harmonic superspaces associated to SU(2,2/N) superconformal algebras. For arbitrary N, we show that massless representations, other than the chiral ones, correspond to [N/2] ``elementary'' ultrashort analytic superfields whose first component is a scalar in the k antisymmetric irrep of SU(N) (k=1... [N/2]) with top spin $J_{\rm\script

Bo Feng, Amihay Hanany

We construct the three dimensional mirror theory of SO(2k) and SO(2k+1) gauge groups by using O3-planes. An essential ingredient in constructing the mirror is the splitting of a physical brane (NS-brane or D5-brane) on O3-planes. In particular, matching the dimensions of moduli spaces of mirror pair (for example, the SO(2k+1) and its mirror) there is a D3-br

Emili Bagan, Robin Horan, Martin Lavelle, David McMullan

This talk will summarise the progress we have made in our programme to both characterise and construct charges in gauge theories. As an application of these ideas we will see how the dominant glue surrounding quarks, which is responsible for asymptotic freedom, emerges from a constituent description of the interquark potential.

O. A. Castro-Alvaredo, A. Fring, C. Korff

We provide general determinant formulae for all n-particle form factors related to the trace of the energy momentum tensor and the analogue of the order and disorder operator in the $SU(3)_2$-homogeneous Sine-Gordon model. We employ the form factors related to the trace of the energy momentum tensor in the application of the c-theorem and find perfect agreem

U. D'Alesio

We calculate target fragmentation in $p p \to n X$ and $γp \to n X $ reactions in the meson cloud picture of the nucleon. The $p p \to n X$ reaction is used to fix the $pnπ^+$ form factor for two different models. We take into account the possible destruction of the residual neutron by the projectile. Using the form factor from the hadronic reaction we calcu

K. S. Babu, S. M. Barr

A generalization of the well-known Georgi-Jarlskog relation m_μ/m_τ = 3 (m_s/m_b) to neutrinos is found in the context of SO(10). This new relation is m_{ν_μ}/m_{ν_τ} = 16 (m_c/m_t), which is consistent with present data, assuming the small-angle MSW solution to the solar neutrino problem.

E. J. Ferrer, V. de la Incera

The influence of scalar field interactions in the magnetic catalysis phenomenom is studied in a gauge theory with scalar and fermion fields. It is shown that the external magnetic field catalyzes the appearance of a fermion-antifermion condensate along with a non-zero scalar vev, hence generating a fermion dynamical mass and breaking the discrete chiral symm

Elvio Di Salvo, Michail P. Rekalo, Egle Tomasi-Gustafsson

The Dalitz distribution and the effective mass spectrum of the lepton pair produced in the decay $η_c\to γ\ell^+ \ell^-$, as well as the differential cross sections for the crossed channels $γe^-\to η_c e^- $ and $e^+ e^-\to η_c γ$, are calculated in terms of the sole electromagnetic transition form factor for the vertex $η_c\toγγ^*$, where $γ^*$ is a virtua

J. Kwiecinski, A. D. Martin, A. M. Stasto

We discuss a problem concerning the ultrahigh energy neutrino propagation through the Earth. We present calculation of the neutrino-nucleon cross section at high energies, based on the unifed evolution equation at small x. We also show the solution of the transport equation for different neutrino fluxes originating from active galactic nuclei, gamma ray burs

E. Leader, A. V. Sidorov, D. B. Stamenov

Motivated by the possibility that it may be misleading to assume SU(3) symmetry in the analysis of hyperon β-decays, we study the sensitivity of the polarized parton densities, derived from the world data on inclusive polarized deep inelastic lepton-nucleon scattering, to variation of the value of the nonsinglet axial charge a_8 from its SU(3) value of 3F-D.

O. Mogilevsky

The new method of nonperturbative calculation of the beta function in the lattice gauge theory is proposed. The method is based on the finite size scaling hypothesis.

Yuichi Oyama

The K2K (KEK to Kamioka) long-baseline neutrino-oscillation experiment was successfully started in early 1999. A total intensity of 7.20 x 10^18 protons on target, which is about 7% of the goal of the experiment, was accumulated in 39.4 days of data-taking in 1999. We obtained 3 neutrino events in the fiducial volume of the Super-Kamiokande detector, whereas

C. C. Briggs

A possible theoretical basis is given for propulsive force generation by both conventional and unconventional means.

Adam T. Kruger, John W. Norbury

A new closed-form inflationary solution is given for a hyperbolic interaction potential. The method used to arrive at this solution is outlined as it appears possible to generate additional sets of equations which satisfy the model. In addition a new form of decaying cosmological constant is presented.

Sean A. Hayward

A homothetic, static, spherically symmetric solution to the massless Einstein- Klein-Gordon equations is described. There is a curvature singularity which is central, null, bifurcate and marginally trapped. The space-time is therefore extreme in the sense of lying at the threshold between black holes and naked singularities, just avoiding both. A linear pert

Simon D. Hern

In this work numerical methods for solving Einstein's equations are developed and applied to the study of inhomogeneous cosmological models. A two-dimensional computer code is described which implements two advanced numerical methods: LeVeque's multi-dimensional high-resolution integration scheme which allows accurate evolution of solutions containin

Cristovao Correia da Silva, Ruth M. Williams

Using simplicial minisuperspace techniques we obtain a wormhole configuration, capable of modelling both a throat between two equal Euclidean and Lorentzian universes. Computing the wavefunction associated to such configuration we conclude that for Planck-size Euclidean wormholes there is a prediction of a finite non-vanishing radius of their throat, even in

Prabal K. Maiti, Kurt Kremer, Oliver Flimm, Debashish Chowdhury

We investigate the effects of gemini surfactants, telechelic chain and lipids on the nature of micelles formed by conventional single-tail surfactants in water by carrying out Monte Carlo simulations. In a mixture of gemini and single-tail surfactants in water we find direct evidence of micelles of predominantly single-tail surfactants some of which are dyna

I. L. Kurland, I. L. Aleiner, B. L. Altshuler

The paper is devoted to the magnetic properties of isolated mesoscopic grains. We demonstrate that under very general conditions the electron - electron interactions in such grains can be taken into account by a simple interaction Hamiltonian. This Hamiltonian involves only three coupling constants which correspond to charging, exchange interaction, and supe

Debdeep Jena, Arthur. C. Gossard, Umesh. K. Mishra

Unusually large spontaneous and piezoelectric fields in the III-V nitrides have led to the making of an entirely new class of two-dimensional electron gas. Fluctuation from a perfectly periodic binary structure in highly polar semiconductor alloys present the same physical situation as a random distribution of microscopic dipoles. The excess dipole distribut

Charles Reichhardt, Niels Gronbech-Jensen

We examine the vortex states in a 2D superconductor interacting with a square array of pinning sites. As a function of pinning size or strength we find a series of novel phases including multi-vortex and composite superlattice states such as aligned dimer and trimer configurations at individual pinning sites. Interactions of the vortices give rise to an orie

Nelson A. Alves, J. R. Drugowich de Felicio, Ulrich H. E. Hansmann

The density of states for the three-dimensional Ising model is calculated with high-precision from multicanonical simulations. This allows us to estimate the leading partition function zeros for lattice sizes up to L=32. Combining previous statistics for smaller lattice sizes, we have evaluated the correction to scaling and the critical exponent $ν$ through

P. Samuelsson, H. Schomerus

We present a theory for the nonequilibrium current in a mesoscopic Josephson junction which is coupled to a normal electron reservoir, and apply it to a chaotic junction. Large sample-to-sample fluctuations of the critical current $I_{\rm c}$ are found, with ${rms} I_{\rm c} \simeq \sqrt{N}eΔ/\hbar$, when the voltage difference eV between the electron reserv

Damien Challet, Matteo Marsili

By considering diffusion on De Bruijn graphs, we study in details the dynamics of the histories in the Minority Game, a model of competition between adaptative agents. Such graphs describe the structure of temporal evolution of $M$ bits strings, each node standing for a given string, i.e. a history in the Minority Game. We show that the frequency of visit of

M. C. Gordillo, J. Boronat, J. Casulleras

We have studied molecular hydrogen in a pure 1D geometry and inside a narrow carbon nanotube by means of the diffusion Monte Carlo method. The one-dimensionality of H2 in the nanotube is well maintained in a large density range, this system being closer to an ideal 1D fluid than liquid 4He in the same setup. H2 shares with 4He the existence of a stable liqui

R. Burioni, D. Cassi, C. Destri

Statistical models on infinite graphs may exhibit inhomogeneous thermodynamic behaviour at macroscopic scales. This phenomenon is of geometrical origin and may be properly described in terms of spectral partitions into subgraphs with well defined spectral dimensions and spectral weights. These subgraphs are shown to be thermodynamically homogeneous and effec

Oded Agam, Boris L. Altshuler

We consider the Faraday surface waves of a fluid in a container with a non-integrable boundary shape. We show that, at sufficiently low frequencies, the wave patterns are ``scars'' selected by the instability of the corresponding periodic orbits, the dissipation at the container side walls, and interaction effects which reflect the nonlinear nature o

L. Brey, F. Guinea

The phase diagram of diluted magnetic semiconductor quantum wells is investigated. The interaction between the carriers in the hole gas can lead to first order ferromagnetic transitions, which remain abrupt in applied fields. These transitions can be induced by magnetic fields or, in double-layer systems by electric fields. We make a number of precise experi

R. Burioni, D. Cassi, A. Vezzani

When averages over all starting points are considered, the Type Problem for the recurrence or transience of a simple random walk on an inhomogeneous network in general differs from the usual "local" Type Problem. This difference leads to a new classification of inhomogeneous discrete structures in terms of {\it recurrence} and {\it transience} {\it o

C. J. Pethick, L. P. Pitaevskii

We consider the criterion for Bose condensation for particles in a harmonic trap. For a fixed angular momentum, the lowest energy state for a cloud of bosons with attractive interactions is the ground state of the cloud with all the angular momentum in the center-of-mass motion, and the one-particle reduced density matrix generally does not have a single lar

Douglas P. Finkbeiner, Marc Davis, David J. Schlegel

From analysis of the DIRBE weekly averaged sky maps, we have detected substantial flux in the 60 and 100 micron channels in excess of expected zodiacal and Galactic emission. Two methods are used to separate zodiacal light from more distant emission. Method I makes use of the time-dependence of the North-South annual variation observed at the ecliptic poles.

E. L. Martin, W. Brandner, J. Bouvier, K. L. Luhman

We present near-infrared photometry and optical spectroscopy of very low-mass stars and brown dwarf candidates in the Pleiades open cluster. The membership status of these objects is assessed. Eight objects out of 45 appear to be non-members. A search for companions among 34 very low-mass Pleiades members (M$\le$0.09 M$_\odot$) in high-spatial resolution ima

Xingzhi Zhang

Point sources in the atmosphere are surrounded by aureole because of atmospheric scattering. The properties of the time-dependent aureole radiance are calculated by use of a Monte Carlo approach and an iterative method. Since the aureole is particularly important in the ultraviolet, which is the region the Ultra-High-Energy (UHE) cosmic ray experiment using

Alberto J. Castro-Tirado

GRBs have remained a puzzle for many high-energy astrophysicists since their discovery in 1967. With the advent of the X-ray satellites BeppoSAX and RossiXTE, it has been possible to carry out deep multi-wavelength observations of the counterparts associated with the GRBs just within a few hours of occurence, thanks to the observation of the fading X-ray emi

M. J. Harris, D. M. Palmer, J. E. Naya, B. J. Teegarden

The TGRS experiment on board the Wind spacecraft has many advantages as a sky monitor --- broad field of view (~2 pi) centered on the south ecliptic pole), long life (1994-present), and stable low background and continuous coverage due to Wind's high altitude high eccentricity orbit. The Ge detector has sufficient energy resolution (3-4 keV at 511 keV) t

M. J. Harris, B. J. Teegarden, T. L. Cline, N. Gehrels

The good energy resolution (3--4 keV FWHM) of the Transient Gamma Ray Spectrometer (TGRS) on board the WIND spacecraft makes it sensitive to Doppler-shifted outbursts of 511 keV electron-positron annihilation radiation, the reason being that the Doppler shift causes the cosmic line to be slightly offset from a strong instrumental background 511 keV line at r

R. E. Lingenfelter, J. C. Higdon, R. Ramaty

We review the evidence for cosmic ray acceleration in the superbubble/hot phase of the interstellar medium, and discuss the implications for the composition of cosmic rays and the structure and evolution of the interstellar medium. We show that the bulk of the galactic supernovae, their expanding remnants, together with their metal-rich grain and gas ejecta,

J. K. Cannizzo

We examine a new paradigm to account for the exponential decay seen in the light curves of some of the bright X-ray novae. These systems show an exponential decay in soft X-rays with an e-folding time constant of ~30 d. We investigate a scenario in which evaporation of matter into a corona is the dominant mass removal mechanism from the accretion disk. We ut

M. J. Harris, J. E. Naya, B. J. Teegarden, T. L. Cline

The Transient Gamma Ray Spectrometer (TGRS) on board the WIND spacecraft has spent most of the interval 1995-1997 in a high-altitude orbit where gamma-ray backgrounds are low. Its high-resolution Ge spectrometer is thus able to detect weak lines which are slightly offset from stronger background features. One such line is predicted from nucleosynthesis in cl

A. D. Erlykin, S. J. Fatemi, A. W. Wolfendale

The recently published precise spectrum of cosmic ray protons from the Alpha Magnetic Spectrometer has been examined in some detail from the standpoint of a search for deviations from a smooth, simple, power law. We find a significant excess ($\simeq$ 10% over $\sim$ 0.3 interval in logE) centered on 50 GeV in the published data. It is possible that the &#39

L. Wisotzki, N. Christlieb, N. Bade, V. Beckmann

We present a new sample of 415 bright QSOs and Seyfert~1 nuclei drawn from the Hamburg/ESO survey (HES). The sample is spectroscopically 99 % complete and well-defined in terms of flux and redshift limits. Optical magnitudes are in the interval 13 < B_J < 17.5, redshifts range within 0< z < 3.2. More than 50 % of the objects in the sample are new discoveries

D. Raimann, T. Storchi-Bergmann, E. Bica, J. Melnick

We study the gas emission of galaxies with active star formation, consisting mostly of HII galaxies and Starbursts, as well as some Seyfert 2s, and determine chemical and physical parameters. The data consist of 19 high signal-to-noise ratio optical templates, a result of grouping 185 emission line galaxy spectra. Underlying stellar population models were su

Matt A. Wood, Michele M. Montgomery, James C. Simpson

In recent years a handful of systems have been observed to show &#34;negative&#34; (nodal) superhumps, with periods slightly shorter than the orbital period. It has been suggested that these modes are a consequence of the slow retrograde precession of the line of nodes in a disk tilted with respect to the orbital plane. Our simulations confirm and refine thi

Raffaele Gratton, Eugenio Carretta, Francesca Matteucci, Chris Sneden

The accurate O, Mg and Fe abundances derived in previous papers of this series from a homogenous reanalysis of high quality data for a large sample of stars are combined with stellar kinematics in order to discuss the history of star formation in the solar neighborhood. We found that the Fe/O and Fe/Mg abundance ratios are roughly constant in the (inner) hal

Roland Wielen, Christian Dettbarn, Hartmut Jahreiss, Helmut Lenhardt

The comparison of quasi-instantaneously measured HIPPARCOS proper motions with long-term averaged proper motions, derived from ground-based data, allows the identification of many stellar objects as Delta_mu binaries (Wielen et al., 1999, A&A 346, 675). We have used this method to find Delta_mu binaries among the fundamental stars, among the GC stars, and am

H. Sudou, Y. Taniguchi, Y. Ohyama, S. Kameno

Mapping the central 5 pc region of the nearby radio galaxy NGC 6251 with a 0.2 pc resolution using VLBI at two radio frequencies, 5 GHz and 15 GHz, we have found the sub-pc-scale counter jet for the first time in this radio galaxy. This discovery allows us to investigate the jet acceleration based on the relativistic beaming model (Ghisellini et al. 1993).

David H. Hughes, Enrique Gaztanaga

Current submillimetre surveys are hindered in their ability to reveal detailed information on the epoch of galaxy formation and the evolutionary history of a high-redshift starburst galaxy population. The difficulties are due to the small primary apertures (D < 15 m) of existing submillimetre telescopes and the limited sensitivities of their first generation

Massimo Di Pierro

We present a set of programming tools (classes and functions written in C++ and based on Message Passing Interface) for fast development of generic parallel (and non-parallel) lattice simulations. They are collectively called MDP 1.2. These programming tools include classes and algorithms for matrices, random number generators, distributed lattices (with arb

Clifford V. Johnson

We study the `enhancon', a spherical hypersurface apparently made of D-branes, which arises in string theory studies of large N SU(N) pure gauge theories with eight supercharges. When the gauge theory is 2+1 dimensional, the enhancon is an S^2. A relation to charge N BPS multi-monopoles is exploited to uncover many of its detailed properties. It is simply a

P. Castelo Ferreira, Ian I. Kogan, Bayram Tekin

A detailed study of the charge spectrum of three dimensional Abelian Topological Massive Gauge Theory (TMGT) is given. When this theory is defined on a manifold with two disconnected boundaries there are induced chiral Conformal Field Theories (CFT&#39;s) on the boundaries which can be interpreted as the left and right sectors of closed strings. We show that

C. M. Hull

BPS representations of 5-dimensional supersymmetry algebras are classified. For BPS states preserving 1/2 the supersymmetry, there are two distinct classes of multiplets for N=4 supersymmetry and three classes for N=8 supersymmetry. For N=4 matter theories, the two 1/2 supersymmetric BPS multiplets are the massive vector multiplet and the massive self-dual 2

Frederic Zamora

Motivated by the mixing of UV and IR effects, we test the OPE formula in noncommutative field theory. First we look at the renormalization of local composite operators, identifying some of their characteristic IR/UV singularities. Then we find that the product of two fields in general cannot be described by a series expansion of single local operator inserti

Shu-Chiuan Chang, Robert Shrock

We present exact solutions for the zero-temperature partition function (chromatic polynomial $P$) and the ground state degeneracy per site $W$ (= exponent of the ground-state entropy) for the $q$-state Potts antiferromagnet on strips of the square lattice of width $L_y$ vertices and arbitrarily great length $L_x$ vertices. The specific solutions are for (a)

J. Scott, J. Bechtold, A. Dobrzycki, V. Kulkarni

A homogeneous sample of 99 moderate resolution QSO spectra at z > 1.7 were presented in Paper I, including 39 previously unpublished spectra from the Multiple Mirror Telescope. The statistics of the Lyman alpha forest were discussed. In this analysis, we demonstrate that a proximity effect is present in the data, ie. there exists a significant (5.5$σ$) defic

J. Scott, J. Bechtold, A. Dobrzycki

We present moderate resolution data for 39 QSOs at z $\approx$ 2 obtained at the Multiple Mirror Telescope. These data are combined with spectra of comparable resolution of 60 QSOs with redshifts greater than 1.7 found in the literature to investigate the distribution of Ly-alpha forest lines in redshift and equivalent width. We find a value for $γ$, the par

R. Jackiw, V. P. Nair, So-Young Pi

We propose a non-Abelian generalization of the Clebsch parameterization for a vector in three dimensions. The construction is based on a group-theoretical reduction of the Chern-Simons form on a symmetric space. The formalism is then used to give a canonical (symplectic) discussion of non-Abelian fluid mechanics, analogous to the way the Abelian Clebsch para

Wojciech Broniowski, Wojciech Florkowski

We analyze the light-flavor particle mass spectra and show that in the region up to ~1.8GeV the Hagedorn temperature for baryons is about 30% smaller than for mesons, reflecting the fact that the number of baryon states grows more rapidly with the mass. We also show that the spectra are well reproduced in a model where hadrons are compound objects of quanta,

R. Jackiw, A. P. Polychronakos

When anticommuting Grassmann variables are introduced into a fluid dynamical model with irrotational velocity and no vorticity, the velocity acquires a nonvanishing curl and the resultant vorticity is described by Gaussian potentials formed from the Grassmann variables. Upon adding a further specific interaction with the Grassmann degrees of freedom, the mod

Christian Hilmoine, Rune Niclasen

The microscopic spectral correlations of the Dirac operator in Yang-Mills theories coupled to fermions in (2+1) dimensions can be related to three universality classes of Random Matrix Theory. In the microscopic limit the Orthogonal Ensemble (OE) corresponds to a theory with 2 colors and fermions in the fundamental representation and the Symplectic Ensemble

H. T. Cho, R. Kantowski

We evaluate the divergent part of the Vilkovisky-DeWitt effective action for Einstein gravity on even-dimensional Kaluza-Klein spacetimes of the form $M^{4}\times S^{N}$. Explicit results are given for $N$=2, 4, and 6. Trace anomalies for gravitons are also given for these cases. Stable Kaluza-Klein configurations are sought, unsuccessfully, assuming the div

M. Girardi, G. Giuricin, ;

We analyze the three catalogs of nearby loose groups identified by Garcia (1993). She used a percolation and a hierarchical method, and proposed a third group catalog defined as a combination of the two. Each catalog contains almost 500 groups. In agreement with previous works on earlier catalogs, we find that groups can be described as collapsing systems. T

Guido Burkard, Hans-Andreas Engel, Daniel Loss

Control over electron-spin states, such as coherent manipulation, filtering and measurement promises access to new technologies in conventional as well as in quantum computation and quantum communication. We review our proposal of using electron spins in quantum confined structures as qubits and discuss the requirements for implementing a quantum computer. W

S. Cacciatori, D. Klemm, W. A. Sabra, D. Zanon

We consider general black holes in D=5, N=2 supergravity coupled to vector multiplets, and discuss the issue of microstate counting from various viewpoints. The statistical entropy is computed for the near-extremal case using the central charge of the $AdS_2$ factor appearing in the near-horizon geometry. Furthermore, we explicitly construct the duality tran

Hans J. Briegel, Robert Raussendorf

We study the entanglement properties of a class of $N$ qubit quantum states that are generated in arrays of qubits with an Ising-type interaction. These states contain a large amount of entanglement as given by their Schmidt measure. They have also a high {\em persistency of entanglement} which means that $\sim N/2$ qubits have to be measured to disentangle

Piotr T. Chrusciel, Walter Simon

We present a systematic study of static solutions of the vacuum Einstein equations with negative cosmological constant which asymptotically approach the generalized Kottler (``Schwarzschild--anti-de Sitter&#39;&#39;) solution, within (mainly) a conformal framework. We show connectedness of conformal infinity for appropriately regular such space-times. We giv

Tamiaki Yoneya

The notion of a space-time uncertainty principle in string theory is clarified and further developed. The motivation and the derivation of the principle are first reviewed in a reasonably self-contained way. It is then shown that the nonperturbative (Borel summed) high-energy and high-momentum transfer behavior of string scattering is consistent with the spa

Tamiaki Yoneya

This is a brief overview on the current status of string theory for non-specialists. The purpose is to give an aspect on the nature of string theory as a unified theory of all interactions including quantum gravity and to discuss future perspectives. Particular emphases are put on the mysteries why string theory contains gravity and why it resolves the ultra

Pei-Ming Ho, Miao Li

We show that the existent fuzzy S^2 and S^4 models are natural candidates for the quantum geometry on the corresponding spheres in AdS/CFT correspondence. These models fit nicely the data from the dipole mechanism for the stringy exclusion principle. In the AdS_2 X S^2 case, we show that a wrapped fractional membrane can be used to count for the large ground

Arjan Keurentjes

It is argued that the T-dual of a crosscap is a combination of an O+ and an O- orientifold plane. Various theories with crosscaps and D-branes are interpreted as gauge-theories on tori obeying twisted boundary conditions. Their duals live on orientifolds where the various orientifold planes are of different types. We derive how to read off the holonomies fro

A. A. Bichl, J. M. Grimstrup, V. Putz, M. Schweda

A U(N) Chern-Simons theory on noncommutative $\mathbb{R}^{3}$ is constructed as a $\q$-deformed field theory. The model is characterized by two symmetries: the BRST-symmetry and the topological linear vector supersymmetry. It is shown that the theory is finite and $\q_{\m\n}$-independent at the one loop level and that the calculations respect the restriction

Nicolas Borghini, Mai Dinh, Jean-Yves Ollitrault

Several heavy ion experiments at SPS have measured azimuthal distributions of particles with respect to the reaction plane. These distributions are deduced from two-particle azimuthal correlations under the assumption that they result solely from correlations with the reaction plane. In this paper, we investigate other sources of azimuthal correlations: tran

Andrea Gregori

We consider Z2, freely acting orbifolds of the type IIB string with 16 parallel D5-branes. When the string is compactified on T2 X T4 and the D5-branes are wrapped on T2, these systems possess N=2 supersymmetry, originating from the spontaneous, partial breaking of N=4. Extended supersymmetry allows us to investigate the duality with certain heterotic and ty

Thomas Eckl, Enrico Arrigoni, Werner Hanke, Fakher F. Assaad

We examine the competition and relationship between an antiferromagnetic (AF) Mott insulating state and a d_{x^2-y^2} superconducting (SC) state in two dimensions using semi-analytical, i. e. diagrammatic calculations of the t-U-W model. The AF Mott insulator is described by the ground state of the half-filled Hubbard model on a square lattice with on-site C

D. Bolle&#39;, P. Kozlowski

Ashkin-Teller type perceptron models are introduced. Their maximal capacity per number of couplings is calculated within a first-step replica-symmetry-breaking Gardner approach. The results are compared with extensive numerical simulations using several algorithms.

P. N. Timonin

The mechanism of appearance of exponentially large number of metastable states in magnetic phases of disordered Ising magnets with short-range random exchange is suggested. It is based on the assumption that transitions into inhomogeneous magnetic phases results from the condensation of macroscopically large number of sparse delocalized modes near the locali

Klaus Morawetz

The numerical solutions of nonlocal and local Boltzmann kinetic equations for the simulation of central heavy ion reactions are parameterized in terms of time dependent thermodynamical variables in the Fermi liquid sense. This allows one to discuss dynamical trajectories in phase space. The nonequilibrium state is characterized by non-isobaric, non-isochoric

Sandhya Choubey, Srubabati Goswami, Kamales Kar

In this paper we do a three-generation oscillation analysis of the latest (848 days) Super-Kamiokande (SK) atmospheric neutrino data going beyond the one mass scale dominance (OMSD) approximation. We fix $Δ_{12} = Δ_{13}$ ($Δ_{LSND}$) in the range 0.5 - 2 eV$^2$ as allowed by the results from LSND and other accelerator and reactor experiments on neutrino osc

T. Schmidt, P. König, E. McCann, Vladimir I. Fal&#39;ko

A spectroscopic method is applied to measure the inelastic quasi-particle relaxation rate in a disordered Fermi liquid. The quasi-particle relaxation rate, $γ$ is deduced from the magnitude of fluctuations in the local density of states, which are probed using resonant tunneling through a localized impurity state. We study its dependence on the excitation en

S. C. C. Ng, D. L. Wiltshire

We study observational constraints on cosmological models with a quintessence field in the form of a dynamical pseudo Nambu-Goldstone boson. After reviewing the properties of the solutions, from a dynamical systems phase space analysis, we consider the constraints on parameter values imposed by luminosity distances from the 60 Type Ia supernovae published by

Toyoki Matsuyama, Hideko Nagahiro

We investigate how a dynamical mass of a fermion is affected by a topological mass of a gauge field in a Maxwell-Chern-Simons $QED_3$ coupled with a two-component fermion. The dynamical mass and also a parity condensate are estimated by using a non-perturbative Schwinger-Dyson method. In particular, we study a limit of vanishing the topological mass in detai

Jizhong Lou, Shaojin Qin, Tao Xiang, Changfeng Chen

We report a systematic study of the transition from a band insulator (BI) to a Mott insulator (MI) in a one-dimensional Hubbard model at half-filling with an on-site Coulomb interaction U and an alternating periodic site potential V. We employ both the zero-temperature density matrix renormalization group (DMRG) method to determine the gap and critical behav

Todd M. Tripp, Blair D. Savage

We report the discovery of an O VI absorption system at z(abs) = 0.14232 in a high resolution FUV spectrum of PG0953+415 obtained with the Space Telescope Imaging Spectrograph (STIS). Both lines of the O VI 1032, 1038 doublet and multicomponent H I Lya absorption are detected, but the N V doublet and the strong lines of C II and Si III are not apparent. We e

P. T. Cochrane, G. J. Milburn, W. J. Munro

We analyse the fidelity of teleportation protocols, as a function of resource entanglement, for three kinds of two mode oscillator states: states with fixed total photon number, number states entangled at a beam splitter, and the two-mode squeezed vacuum state. We define corresponding teleportation protocols for each case including phase noise to model degra

Nobuya Maeshima, Kouichi Okunishi

We study thermodynamic behaviors of the antiferromagnetic zigzag spin chain in magnetic fields, using the density-matrix renormalization group method for the quantum transfer matrix. We focus on the thermodynamics of the system near the critical fields in the ground-state magnetization process($M$-$H$ curve): the saturation field, the lower critical field as

G. Sardanashvily

Time-dependent quantum evolution is described by an algebraic connection on a $C^\infty(R)$-module of sections of a $C^*$-algebra (or Hilbert) fibre bundle.

F. Popescu, A. S. Chirkin

The systematic theory of the formation of the short light pulses in the squeezed state during the propagation in a medium with inertial Kerr nonlinearity is developed. The algebra of time-dependent Bose-operators is elaborated and the normal-ordering theorem for them is formulated. It is established that the spectral region where the quadrature fluctuations

J. Lu, Z. Roller-Lutz, H. O. Lutz

We have performed classical trajectory Monte Carlo (CTMC) studies of electron capture and ionization in multiply charged (Q=8) ion-Rydberg atom collisions at intermediate impact velocities. Impact parallel to the minor and to the major axis, respectively, of the initial Kepler electron ellipse has been investigated. The important role of the initial electron

Hans E. Plesser, Theo Geisel

Noise aids the encoding of continuous signals into pulse sequences by way of stochastic resonance and endows the encoding device with a preferred frequency. We study encoding by a threshold device based on the Ornstein-Uhlenbeck process, equivalent to the leaky integrate-and-fire neuron model. Preferred frequency, optimum noise intensity, and optimum signal-

A. A. Fedyanin, T. V. Dolgova, O. A. Aktsipetrov, D. Schuhmacher

The second-harmonic interferometric spectroscopy (SHIS) which combines both amplitude (intensity) and phase spectra of the second-harmonic (SH) radiation is proposed as a new spectroscopic technique being sensitive to the type of critical points (CP&#39;s) of combined density of states at semiconductor surfaces. The increased sensitivity of SHIS technique is

A. M. Burkhanov, K. B. Vlasov, V. V. Gudkov, B. V. Tarasov

Theory of the acoustic analog of the polar Kerr effect is developed for an inclined incidence of the p-type wave on the interface between isotropic non-magnetic medium and ferromagnetic cubic crystal. Magnetic field dependences of ellipticity and rotation of the polarization plane of the reflected wave under magnon-phonon resonance are analysed in a weak-cou

G. F. Bertsch, Angel Rubio, K. Yabana

Several techniques have appeared in the literatuare to solve the equations of time-dependent density functional theory. We compare the efficiency of different methods based on mesh representations of the wave function (direct and Fourier space), taking as a test case the calculation of the surface plasmon in the cluster Na_8. For smaller systems, the methods

M. Baldo, A. Fiasconaro

In non-relativistic Brueckner calculations of nuclear matter, the self-consistent single particle potential is strongly momentum dependent. To simplify the calculations, a parabolic approximation is often used in the literature. The variation in the binding energy value introduced by the parabolic approximation is quantitatively analyzed in detail. It is fou

J. Cleymans, H. Oeschler, K. Redlich

The excitation functions of $K^+$ and $K^-$ mesons in heavy ion collisions are studied within a statistical model assuming chemical and thermal equilibrium with exact strangeness conservation. At low incident energies the associate production of kaons, i.e. the production of a K+ together with a hyperon and the production of a K- together with a K+, implies

L. Beaulieu, T. Lefort, K. Kwiatkowski, R. T. de Souza

Excitation-energy-gated two-fragment correlation functions have been studied between 2 to 9A MeV of excitation energy for equilibrium-like sources formed in $π^-$ and p + $^{197}$Au reactions at beam momenta of 8,9.2 and 10.2 GeV/c. Comparison of the data to an N-body Coulomb-trajectory code shows a decrease of one order of magnitude in the fragment emission