May 2002 arXiv papers — page 3

R. Srianand, P. Petitjean, C. Ledoux, C. Hazard

High velocity outflows from quasars are revealed by the absorption signatures they produce in the spectrum of the quasar. Clues on the nature and origin of these flows are important for our understanding of the dynamics of gas in the central regions of the Active Galactic Nucleus (AGNs) but also of the metal enrichment of the intergalactic space. Line radiat

Olivier Guyon, Francois Roddier

We present a solution to obtain a high-resolution image of a wide field with the central source removed by destructive interference. The wide-field image is created by aperture synthesis with a rotating sparse array of telescopes in space. Nulling of the central source is achieved using a phase-mask coronagraph. The full (u,v) plane coverage delivered by the

M. Mouhcine, A. Lancon

In this paper, we discuss how the integrated properties of intermediate-age single burst population, especially in the near-infrared, behave as a function of age and metallicity. Our models take into account all stellar evolutionary phases that affect the evolution of the integrated optical and near-infrared spectrum of such a population. Particular care was

M. Mouhcine, A. Lancon, C. Leitherer, S. Silva

We present near-IR spectroscopy of the massive intermediate age star cluster W3 in the merger remnant galaxy NGC 7252, obtained with the NTT telescope. This cluster has an age when the integrated near-IR properties of a stellar population are dominated by the cool and luminous AGB stars. We compare the data with instantaneous curst model predictions from new

Yancy L. Shirley, Kaisa E. Mueller, Chadwick H. Young, Neal J. Evans

Studying the physical environments of low mass and high mass cores using dust continuum emission provides important observational constraints on theoretical models of star formation. The motivation and procedure for modeling dust continuum emission is reviewed and the results of recent surveys towards low mass and high mass star forming regions are compared.

Omar Lopez-Cruz, David Schade, L. Felipe Barrientos, Michael D. Gladders

Recent observations have revealed that early-type galaxies (ETG) in clusters comprise an old galaxy population that is evolving passively. We review some recent observations from the ground and from HST that show that ETG have undergone a significant amount of luminosity evolution. This evolution is traced by two projections of the fundamental plane (FP): th

Ryan Scranton

We present halo model predictions for the expected angular clustering and associated errors from the completed Sloan Digital Sky Survey (SDSS) photometric galaxy sample. These results are used to constrain halo model parameters under the assumption of a fixed LCDM cosmology using standard Fisher matrix techniques. Given the ability of the five-color SDSS pho

J. Bland-Hawthorn

In July/August last year, a group of 50 galactic astronomers convened at Dunk Island, Australia to celebrate Prof. Ken Freeman's 60th birthday. The overarching theme of the meeting reflected Ken's wish to understand ``the chain of events that occurred during the formation of the Galaxy", to quote from his Annual Reviews article in 1987. The works

Lam Hui, Jun Zhang

We compute both extrinsic (lensing) and intrinsic contributions to the (galaxy-)density-ellipticity correlation function, the latter done using current analytic theories of tidal alignment. The gravitational lensing contribution has two components: one is analogous to galaxy-galaxy lensing and the other arises from magnification bias -- that gravitational le

J. Richard Bond, Marcelo I. Ruetalo, James W. Wadsley, Michael D. Gladders

The huge worldwide investment in CMB experiments should make the Sunyaev-Zeldovich (SZ) effect a key probe of the cosmic web in the near future. For the promise to be realized, substantial development of simulation and analysis tools to relate observation to theory is needed. The high nonlinearity and dissipative/feedback gas physics lead to highly non-Gauss

Marc Postman, Tod R. Lauer, William Oegerle, Megan Donahue

We have conducted an automated search for galaxy clusters within a contiguous 16 square degree I-band survey in the north Galactic hemisphere. A matched filter detection algorithm identifies 444 cluster candidates in the range 0.2 <= z <= 1.2. The full catalog is presented along with the results from a follow-up spectroscopic survey. The estimated redshift d

A. D. Lahiff, I. R. Afnan

We investigate the relation between different three-dimensional reductions of the Bethe-Salpeter equation and the analytic structure of the resultant amplitudes in the energy plane. This correlation is studied for both the $ϕ^2σ$ interaction Lagrangian and the $πN$ system with $s$-, $u$-, and $t$-channel pole diagrams as driving terms. We observe that the eq

Elias Gravanis, Nick E. Mavromatos

In the context of a toy model we discuss the phenomenon of colliding five-branes, with two of the extra space dimensions compactified on tori. In one of the branes (hidden world) the torus is magnetised. Assuming opposite-tension branes, we argue that the collision results eventually in a (time-dependent) cosmological vacuum energy, whose value today is tiny

Hirosi Ooguri, Cumrun Vafa

We give a worldsheet proof of the equivalence between the U(N) Chern-Simons gauge theory on S^3 and the topological closed string theory on the resolved conifold geometry. When the `t Hooft coupling of the gauge theory is small, the dual closed string worldsheet develops a new branch. We show that the fluctuations of the worldsheet into this branch effective

Alessandra Buonanno, Yanbei Chen, Michele Vallisneri

We investigate the problem of detecting gravitational waves from binaries of nonspinning black holes with masses m = 5--20 Msun, moving on quasicircular orbits, which are arguably the most promising sources for first-generation ground-based detectors. We analyze and compare all the currently available post--Newtonian approximations for the relativistic two-b

F. Bigazzi, A. L. Cotrone, L. Girardello, A. Zaffaroni

We extend the pp-wave correspondence to a non supersymmetric example. The model is the type 0B string theory on the pp-wave R-R background. We explicitly solve the model and give the spectrum of physical states. The field theory counterpart is given by a sector of the large N SU(N) x SU(N) CFT living on a stack of N electric and N magnetic D3-branes. The rel

A. A. Ovchinnikov

We verify the functional form of the asymptotics of the spin - spin equal - time correlation function for the XX-chain, predicted by the hypothesis of conformal invariance at large distances and by the bosonization procedure. We point out that bosonization also predicts the functional form of the correlators for the chains of finite length. We found the exac

Stephan J. Huber, Qaisar Shafi

We consider neutrino oscillations and neutrinoless double beta decay in a five dimensional standard model with warped geometry. Although the see-saw mechanism in its simplest form cannot be implemented because of the warped geometry, the bulk standard model neutrinos can acquire the desired (Majorana) masses from dimension five interactions. We discuss how l

H. Baer, C. Balazs, A. Belyaev, J. Mizukoshi

Recently, refinements have been made on both the theoretical and experimental determinations of the i.) mass of the lightest Higgs scalar (m_h), ii.) relic density of cold dark matter in the universe (Omega_CDM h^2), iii.) branching fraction for radiative B decay BF(b \to s γ), iv.) muon anomalous magnetic moment (a_μ), and v.) flavor violating decay B_s \to

J. R. Simpson, H. D. Drew, S. R. Shinde, R. J. Choudhary

We report on the optical properties of magnetic cobalt-doped anatase phase titanium dioxide Ti_{1-x}Co_{x}O_{2-d} films for low doping concentrations, 0 <= x <= 0.02, in the spectral range 0.2 to 5 eV. For well oxygenated films (d << 1) the optical conductivity is characterized by an absence of optical absorption below an onset of interband transitions at 3.

L. D. Carr, Y. Castin

The stability regimes and nonlinear dynamics of bright solitons created in a harmonic potential which is transversely attractive and longitudinally expulsive are presented. This choice of potential is motivated by the recent creation of a matter-wave bright soliton from an attractive Bose-Einstein condensate (L. Khaykovich {\it et al.}, Science 296, 1290 (20

Lars Egil Helseth

Focusing of atoms with light potentials is studied. In particular, we consider strongly confined, cylindrical symmetric potential, and demonstrate their applications in both red and blue-detuned focusing of atoms. We also study the influence of aberrations, and find that a resolution of 1 nm should in principle be possible.

T. Cerquetelli, N. Ciccoli, M. C. Nucci

Realizations of four dimensional Lie algebras as vector fields in the plane are explicitly constructed. Fourth order ordinary differential equations which admit such Lie symmetry algebras are derived. The route to their integration is described.

Adan Cabello

It is shown that the correlations between two qubits selected from a trio prepared in a W state violate the Clauser-Horne-Shimony-Holt inequality more than the correlations between two qubits in any quantum state. Such a violation beyond Cirel&#39;son&#39;s bound is smaller than the one achieved by two qubits selected from a trio in a Greenberger-Horne-Zeili

D. Cabrera, M. J. Vicente Vacas

The $ϕ$ meson spectrum, which in vacuum is dominated by its coupling to the $\bar{K} K$ system, is modified in nuclear matter. Following a model based on chiral SU(3) dynamics we calculate the $ϕ$ meson selfenergy in nuclear matter considering the $K$ and $\bar{K}$ in-medium properties. For the latter we use the results of previous calculations which account

Michael Gronau, Jonathan L. Rosner

CP-violating asymmetries in the decay $B^0(t)\to π^+ π^-$ are a potentially rich source of information about both strong and weak phases. In a previous treatment by the present authors use was made of an assumption about the relative magnitude of tree and penguin amplitudes contributing to this process. This assumption involved an ambiguity in relating the t

A. Amato, B. Roessli, P. Fischer, N. Bernhoeft

We report muon spin relaxation and inelastic neutron measurements on the Heusler system YbPd$_2$Sn. Localised anisotropic and quasi-elastic Yb magnetic fluctuations are observed below $T = 150$K. Both $μ$SR and neutron data indicate a slowing-down of the spin-fluctuations, upon lowering the temperature, similar to that observed in Kondo lattices. The tempera

M. Bender, P. -H. Heenen

Starting from constrained Skyrme-mean-field calculations, the low-energy excitation spectrum of 16O is calculated by configuration mixing of particle-number and angular-momentum projected mean-field states in the framework of the Generator Coordinate Method. Without any adjustable parameters, this approach gives a very good description of those states and th

G Alvarez, F Finkel, A Gonzalez-Lopez, M A Rodriguez

We study a large class of models with an arbitrary (finite) number of degrees of freedom, described by Hamiltonians which are polynomial in bosonic creation and annihilation operators, and including as particular cases n-th harmonic generation and photon cascades. For each model, we construct a complete set of commuting integrals of motion of the Hamiltonian

Jean-Marc Schlenker

Let $(M, \partial M)$ be a compact 3-manifold with boundary, which admits a convex co-compact hyperbolic metric. We consider the hyperbolic metrics on $M$ such that the boundary is smooth and strictly convex. We show that the induced metrics on the boundary are exactly the metrics with curvature $K>-1$, and that the third fundamental forms of $\dr M$ are exa

Aalok Misra

Following the work of Lima et al on the exact evaluation of the nonperturbative contribution to the superpotential from open-membrane instanton in Heterotic M-Theory, we evaluate systematically the contribution to the superpotential of a membrane instanton obtained by wrapping of a single M2 brane, once, on an isolated supersymmetric 3-cycle in a G_2-holonom

Jonivar Skullerud, Ayse Kizilersu

The quark-gluon vertex in Landau gauge is studied in the quenched approximation using the Sheikholeslami-Wohlert (SW) fermion action with mean-field improvement coefficients in the action and for the quark fields. We see that the form factor that includes the running coupling is substantially enhanced in the infrared, over and above the enhancement arising f

Kenji Kajiwara

Rational solutions for a $q$-difference analogue of the Painlevé III equation are considered. A Determinant formula of Jacobi-Trudi type for the solutions is constructed.

Jingfu Zhang, Zhiheng Lu, Lu Shan, Zhiwei Deng

By designing a proper unitary operator U, we synthesize NMR analogues of Einstein-Podolsky-Rosen states (pseudo-EPR states) using generalized Grover&#39;s algorithm on a nuclear magnetic resonance (NMR) quantum computer. Experiments also demonstrate generalized Grover&#39;s algorithm for the case in which there are multiple marked states.

Neta A. Bahcall, Feng Dong, Paul Bode, Rita Kim

The mass function of clusters of galaxies is determined from 400 deg^2 of early commissioning imaging data of the Sloan Digital Sky Survey; ~300 clusters in the redshift range z = 0.1 - 0.2 are used. Clusters are selected using two independent selection methods: a Matched Filter and a red-sequence color magnitude technique. The two methods yield consistent r

T. Xiang, Y. H. Su, C. Panagopoulos, Z. B. Su

We have derived the effective low energy Hamiltonian for Zn or Ni substituted high-T_c cuprates from microscopic three-band models consisting of the most relevant Cu or impurity 3d and O 2p orbitals. We find that both scattering potential and hopping integral induced by impurities have a finite range but decay very fast with distance from the impurity. The Z

G. Auberson, ; G. Mahoux, ; S. M. Roy, Virendra Singh

We address the classical and quantum marginal problems, namely the question of simultaneous realizability through a common probability density in phase space of a given set of compatible probability distributions. We consider only distributions authorized by quantum mechanics, i.e. those corresponding to complete commuting sets of observables. For four-dimen

Avshalom C. Elitzur, Shahar Dolev, Anton Zeilinger

When a single photon is split by a beam splitter, its two `halves&#39; can entangle two distant atoms into an EPR pair. We discuss a time-reversed analogue of this experiment where two distant sources cooperate so as to emit a single photon. The two `half photons,&#39; having interacted with two atoms, can entangle these atoms into an EPR pair once they are

L. M. Castellano, H. Vinck

In this paper we show how to control the quantum laser atoms instability using IR radiation. The control can be achieved by controlling the scattering length constant via the infrared coupling constant. This method is applied in the scheme of a continuous CW laser and involves three occupation levels in the condensed atoms.This atoms in Lambda configuration

Sameen Ahmed Khan

A new formalism of beam-optics and polarization has been recently presented, based on an exact matrix representation of the Maxwell equations. This is described in Part-I and Part-II. In this Part, we present the application of the above formalism to the specific example of the axially symmetric graded index fiber. This formalism leads to the wavelength-depe

Sameen Ahmed Khan

We present a formalism for light optics starting with the Maxwell equations and casting them into an exact matrix form taking into account the spatial and temporal variations of the permittivity and permeability. This $8 \times 8$ matrix representation is used to construct the optical Hamiltonian. This has a close analogy with the algebraic structure of the

Sameen Ahmed Khan

Matrix representations of the Maxwell equations are well-known. However, all these representations lack an exactness or/and are given in terms of a {\em pair} of matrix equations. We present a matrix representation of the Maxwell equation in presence of sources in a medium with varying permittivity and permeability. It is shown that such a representation nec

A. N. Ageev, A. G. Chirkov

A theoretical analysis of the excitation of an infinitely long solenoid by oscillating current has revealed the existence of specific potentials in the space outside the solenoid, which can affect electron diffraction in an experiment similar to the Aharonov-Bohm effect. Thus, these time-dependent potentials are physical fields possessing a number of specifi

R. Bijker, A. Frank

We study the origin of the regular features obtained in numerical studies of the IBM with random interactions, in particular the dominance of L=0 ground states and the occurrence of vibrational and rotational band structures. It is shown that the geometric shapes associated with IBM Hamiltonians play a crucial role in understanding these regular properties.

PHOBOS Collaboration, B. B. Back

This paper describes the measurement of collective flow for charged particles in Au+Au collisions at sqrt{s_NN}} = 130 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). An azimuthal anisotropy is observed in the charged particle hit distribution in the PHOBOS multiplicity detector. This anisotropy is presented over a wide range of

Steven Tomsovic, Eric J. Heller

In a recent Phys. Rev. E Rapid Communication, the authors, Silvestrov and Beenakker, introduce a way to lengthen the Ehrenfest time, $τ$, for fully chaotic systems. We disagree with several statements made in their paper, and address the following points essential to their conclusions: 1) it is not true that all semiclassical approximations for chaotic syste

Jose Fernandez Nunez, Wifredo Garcia Fuertes, Askold Perelomov

We solve perturbatively the quantum elliptic Calogero-Sutherland model in the regime in which the quotient between the real and imaginary semiperiods of the Weierstrass ${\cal P}$ function is small

Alexey V. Bolsinov, Bozidar Jovanovic

The purpose of this paper is to discuss the relationship between commutative and non-commutative integrability of Hamiltonian systems and to construct new examples of integrable geodesic flows on Riemannian manifolds. In particular, we prove that the geodesic flow of the bi-invariant metric on any bi-quotient of a compact Lie group is integrable in non-commu

Alexander Varchenko

This paper is a set of lecture notes of my course &#34;Special functions, KZ type equations, and representation theory&#34; given at MIT during the spring semester of 2002. The notes do not contain new results, and are an exposition (mostly without proofs) of various published results in this area, illustrated by the simplest nontrivial examples. Some refere

Vyjayanthi Chari, Thang Le

We study representations of the double affine Lie algebra associated to a simple Lie algebra. We construct a family of indecomposable integrable representations and identify their irreducible quotients. We also give a condition for the indecomposable modules to be irreducible, this is analogous to a result in the representation theory of quantum affine algeb

Markus Perling

In this note we derive a formalism for describing equivariant sheaves over toric varieties. This formalism is a generalization of a correspondence due to Klyachko, which states that equivariant vector bundles on toric varieties are equivalent to certain sets of filtrations of vector spaces. We systematically construct the theory from the point of view of gra

John B. Etnyre, Ko Honda

We study the behavior of Legendrian and transverse knots under the operation of connected sums. As a consequence we show that there exist Legendrian knots that are not distinguished by any known invariant. Moreover, we classify Legendrian knots in some non-Legendrian simple knot types.

Oliver Baues, Vicente Cortés

We show that the natural S^1-bundle over a projective special Kaehler manifold carries the geometry of a proper affine hypersphere endowed with a Sasakian structure. The construction generalizes the geometry of the Hopf-fibration $\Sr^{2n+1} \longrightarrow \CP^n$ in the context of projective special Kaehler manifolds. As an application we have that a natura

Massimiliano Berti, Luca Biasco, Philippe Bolle

We consider non-isochronous, nearly integrable, a-priori unstable Hamiltonian systems with a (trigonometric polynomial) $O(μ)$-perturbation which does not preserve the unperturbed tori. We prove the existence of Arnold diffusion with diffusion time $ T_d = O((1/ μ) \log (1/ μ))$ by a variational method which does not require the existence of ``transition cha

Howard Kleiman

The algorithm reduces the running time of an algorithm of Frieze from O(n^{1.5)) to O(n^(4/3 + o)). It also introduces the concept of admissible permutations that is used in algorithms for obtaining solutions to the AP and the TSP.

Blake Mellor

We show that the adjacency matrices of the intersection graphs of chord diagrams satisfy the 2-term relations of Bar-Natan and Garoufalides [bg], and hence give rise to weight systems. Among these weight systems are those associated with the Conway and HOMFLYPT polynomials. We extend these ideas to looking at a space of {\it marked} chord diagrams modulo an

Dehbia Achab, Frank Betten, Bernhard Kroetz

This paper deals with the analytic continuation of holomorphic automorphic forms on a Lie group $G$. We prove that for any discrete subgroup $Γ$ of $G$ there always exists a non-trivial holomorphic automorphic form, i.e., there exists a $Γ$-spherical unitary highest weight representation of $G$. Holomorphic automorphic forms have the property that they analy

Nick E. Mavromatos, John Rizos

In this article we extend previous work by the authors, and elaborate further on the structure of the general solution to the graviton and dilaton equations of motion in brane world scenaria, in the context of five-dimensional effective actions with O(α&#39;)$ higher-curvature corrections, compatible with bulk string-amplitude calculations. We consider (mult

Riccardo Argurio, Vanicson L. Campos, Gabriele Ferretti, Rainer Heise

We study warped compactifications to three dimensions, realized as an orientifold of type IIA string theory on T^7. By turning on 3- and 4-form fluxes on the torus in a supersymmetric way, we generate a potential for the moduli fields. We present various flux configurations with N=1,2,3,4,5,6 supersymmetries and count the number of moduli in each case. In pa

J. Kluson

We present example of exact solution to Witten&#39;s open bosonic string field theory. We will analyse the new BRST operator and we will argue that the new solution describes the flow from zero slope limit to the tensionless limit in the string world-sheet action.

Konstantin Savvidy

In this note we investigate a new type of non-commutative field theory based on a constant skew-symmetric three-form parameter. In 3+1 dimensions such a three-form parameter can be viewed as a short-distance regulator which nevertheless preserves spatial-rotation and at long range preserves Lorentz invariance approximately. For a scalar field theory with qua

Y. Hoshino

We examine the Dyson-Schwinger equation for the fermion propagator in quenched QED in three and four dimension based on spectral representation with vertex ansatz which preserves Ward-Takahashi Identity.An appropriate renormalization within dispersion integral smoothes the threshold behaviour of the fermion self energy in three dimension.Thus we avoid the in

Gustavo Burdman

We derive constraints on the Randall-Sundrum scenario with the standard model fields in the bulk. These result from tree level effects associated with the deformation of the zero mode wave-functions of the W and the Z once electroweak symmetry is broken. Recently Csáki, Erlich and Terning pointed out that this implies large contributions to electroweak obliq

Matteo Cacciari

We review the state-of-the-art of our understanding of heavy quark fragmentation. Recent e^+e^- data for B mesons are compared to the most up-to-date theoretical predictions, and the need for inclusion of a non-perturbative component is discussed. Experimental analyses in moments space are suggested, and it is pointed out how perturbative and non-perturbativ

S. V. Goloskokov

We consider double spin asymmetries for longitudinally polarized leptons and transversally polarized protons in diffractive vector meson and $Q \bar Q$ production at high energy range on the basis of two-gluon model. The asymmetry predicted for meson production is quite small. Large asymmetry is expected for $Q \bar Q$ production.

V. A. Novikov

The latest electroweak precision data are analyzed assuming the existence of the fourth generation of leptons ($N, E$) and quarks ($U, D$), which are not mixed with the known three generations. If all four new particles are heavier than $Z$ boson, quality of the fit for the one new generation is as good as for the Standard Model. In the case of neutral lepto

S. Munier

We illustrate geometric scaling for the photon-proton cross section with a very simple saturation model. We describe the proton structure function F2 at small x in a wide kinematical range with an elementary functional form and a small number of free parameters. We speculate that the symmetry between low and high Q2 recently discovered in the data could be r

Zoltan Ligeti

The main challenge in the Standard Model calculation of the mass and width difference in $D^0 - \bar D^0$ mixing is to estimate the size of SU(3) breaking. We prove that mixing occurs in the Standard Model only at second order in SU(3) violation. We calculate SU(3) breaking due to phase space effects, and find that it can naturally give rise to a width diffe

John Zhou

We present some new results on searches for new physics at the Tevatron Run 1 (1992 -- 1996). The topics covered are searches for R-Parity violating and conserving mSUGRA, large extra dimensions in di-photon and monojet channels, leptoquark in jets + missing Et channel, and two model independent searches. All results were finalized during the past year.

Katja Klein

Searches for neutralinos and sleptons with arbitrary lifetimes, as predicted in the framework of the Gauge Mediated Supersymmetry Breaking (GMSB) model, have been performed by the four LEP collaborations. No evidence for these particles has been found in the data recorded at center-of-mass energies up to sqrt(s)=209GeV. Therefore constraints on the productio

F. Cerutti

The combined results of the search for the Standard Model Higgs boson from the four LEP experiments are given. These results are based on the full data sample collected by ALEPH, DELPHI, L3 and OPAL at centre-of-mass energies up to 209GeV, corresponding to a total integrated luminosity of about 2.5fb-1. A slight excess of events over the background expectati

S. D. Robins

Inclusive production of D*+/- (2010) mesons in deep inelastic scattering has been measured using e+p and e-p data obtained with the ZEUS detector at HERA using integrated luminosities of 16.7 and 65.2 pb-1, respectively. The decay channel D*+/- -> D0 pi+ with D0 -> K- pi+ and corresponding antiparticle decays were used to identify D*+/- mesons. The D*+/- cro

Giovanni Amelino-Camelia

I analyze the deformation of Lorentz symmetry that holds in certain noncommutative spacetimes and the way in which Lorentz symmetry is broken in other noncommutative spacetimes. I also observe that discretization of areas does not necessarily require departures from Lorentz symmetry. This is due to the fact that Lorentz symmetry has no implications for exclu

R. G. Beausoleil, E. D&#39;Ambrosio, W. Kells, J. Camp

We develop a steady-state analytical and numerical model of the optical response of power-recycled Fabry-Perot Michelson laser gravitational-wave detectors to thermal focusing in optical substrates. We assume that the thermal distortions are small enough that we can represent the unperturbed intracavity field anywhere in the detector as a linear combination

Cayetano Di Bartolo, Rodolfo Gambini, Jorge Pullin

We discuss the canonical quantization of systems formulated on discrete space-times. We start by analyzing the quantization of simple mechanical systems with discrete time. The quantization becomes challenging when the systems have anholonomic constraints. We propose a new canonical formulation and quantization for such systems in terms of discrete canonical

D. V. Ahluwalia

The talk centers around the question: Can general-relativistic description of physical reality be considered complete? On the way I argue how -- unknown to many a physicists, even today -- the ``forty orders of magnitude argument&#39;&#39; against quantum gravity phenomenology was defeated more than a quarter of a century ago, and how we now stand at the pos

L. C. Garcia de Andrade

The motion of spinless particles in Riemann-Cartan (RC) $U_{4}$ and teleparallel spacetimes is revisited on the light of gravitational waves hitting on the spinless test particles. It is shown that in the case Cartan contortion is totally skew-symmetric the spinless particles follow geodesics but if this symmetry is dropped they are able to follow nongeodesi

Vincent Conitzer, Tuomas Sandholm

In multiagent settings where the agents have different preferences, preference aggregation is a central issue. Voting is a general method for preference aggregation, but seminal results have shown that all general voting protocols are manipulable. One could try to avoid manipulation by using voting protocols where determining a beneficial manipulation is har

Vincent Conitzer, Tuomas Sandholm

Preference elicitation is a central problem in AI, and has received significant attention in single-agent settings. It is also a key problem in multiagent systems, but has received little attention here so far. In this setting, the agents may have different preferences that often must be aggregated using voting. This leads to interesting issues because what,

Sylvain Neuvel, Sean A. Fulop

The first morphological learner based upon the theory of Whole Word Morphology Ford et al. (1997) is outlined, and preliminary evaluation results are presented. The program, Whole Word Morphologizer, takes a POS-tagged lexicon as input, induces morphological relationships without attempting to discover or identify morphemes, and is then able to generate new

Akira Kawaguchi, Akihisa Koga, Kouichi Okunishi, Norio Kawakami

Hole-doping effects are investigated on the {\it t-J} ladder model with the linked-tetrahedra structure. We discuss how a metal-insulator transition occurs upon hole doping with particular emphasis on the effects of geometrical frustration. By computing the electron density and the spin correlation function by the density matrix renormalization group, we sho

J. Kuntze, A. Mugarza, J. E. Ortega

The formation of a Ag stabilized regular step lattice on vicinal Si(111) miscut towards [11-2] is reported. The step bunching characteristic of the clean surface is prevented by a single-domain Si(111)-(3x1)-Ag reconstruction. The nanostructured surface is used as a template for growing one-dimensional arrays of 1 nm sized Ag quantum dots with a preferential

Ivo Souza, Jorge Iniguez, David Vanderbilt

We describe a method for computing the response of an insulator to a static, homogeneous electric field. It consists of iteratively minimizing an electric enthalpy functional expressed in terms of occupied Bloch-like states on a uniform grid of k points. The functional has equivalent local minima below a critical field E_c that depends inversely on the densi

P. F. N. Faisca, R. C. Ball

Monte Carlo simulations of protein folding show the emergence of a strong correlation between the relative contact order parameter, CO, and the folding time, t, of two-state folding proteins for longer chains with number of amino acids, N>=54, and higher contact order, CO > 0.17. The correlation is particularly strong for N=80 corresponding to slow and more

Imre Derenyi, Frank Julicher, Jacques Prost

We show that the formation of membrane tubes (or membrane tethers), which is a crucial step in many biological processes, is highly non-trivial and involves first order shape transitions. The force exerted by an emerging tube is a non-monotonic function of its length. We point out that tubes attract each other, which eventually leads to their coalescence. We

Eun-Ah Kim, Eduardo Fradkin

We propose a scenario to understand the puzzling features of the recent experiment by Kang and coworkers on tunneling between laterally coupled quantum Hall liquids by modeling the system as a pair of coupled chiral Luttinger liquid with a point contact tunneling center. We show that for filling factors $ν\sim1$ the effects of the Coulomb interactions move t

V. Dupuis, E. Vincent, F. Bert, D. Herisson

The spin glasses are disordered and frustrated magnetic systems. They show aging phenomena which are also a characteristic feature of structural glasses, polymers, dielectrics, colloids, etc. Under a strong enough magnetic field variation, spin glasses can be &#34;rejuvenated&#34;, in the same way as glasses under a high enough stress. But spin glasses also

F. Corberi, G. Gonnella, E. Lippiello, M. Zannetti

The relation between the autocorrelation $C(t,t_w)$ and the integrated linear response function $χ(t,t_w)$ is studied in the context of the large-N model for phase-ordering systems subjected to a shear flow. In the high temperature phase $T>T_c$ a non-equilibrium stationary state is entered which is characterized by a non-trivial fluctuation-dissipation rela

Vadim I. Puller, Lev G. Mourokh, Norman J. M. Horing, Anatoly Yu. Smirnov

We employ the method of the theory of open quantum systems to analyze spin relaxation and decoherence in semiconductors in the presence of a magnetic field. We derive a set of Bloch equations for electron spin with a fully microscopic determination of longitudinal and transverse relaxation times. Electron scattering from optical and acoustic phonons and rand

Aubrey T. Hanbicki, P. J. Rous, E. W. Plummer

Static and dynamic changes induced by adsorption of atomic hydrogen on the NiAl(110) lattice at 130 K have been examined as a function of adsorbate coverage. Adsorbed hydrogen exists in three distinct phases. At low coverages the hydrogen is itinerant because of quantum tunneling between sites and exhibits no observable vibrational modes. Between 0.4 ML and

Lars Egil Helseth

The interplay between magnetic and superconductive films is studied. The generalized London equation for this system is solved, and the magnetic fields, the energy and the interaction forces are computed. In particular, we focus on how to manipulate vortices using magnetic nanostructures.

Marian Boguna, Romualdo Pastor-Satorras

We study a dynamical model of epidemic spreading on complex networks in which there are explicit correlations among the node&#39;s connectivities. For the case of Markovian complex networks, showing only correlations between pairs of nodes, we find an epidemic threshold inversely proportional to the largest eigenvalue of the connectivity matrix that gives th

O. Trushin, E. Granato, S. C. Ying, P. Salo

We study numerically the minimum energy path and energy barriers for dislocation nucleation in a two-dimensional atomistic model of strained epitaxial layers on a substrate with lattice misfit. Stress relaxation processes from coherent to incoherent states for different transition paths are determined using saddle point search based on a combination of repul

R. Pagnani, U. Marini Bettolo Marconi, A. Puglisi

We study the steady state properties of a 2D granular mixture in the presence of energy driving by employing simple analytical estimates and Direct Simulation Monte Carlo. We adopt two different driving mechanisms: a) a homogeneous heat bath with friction and b) a vibrating boundary (thermal or harmonic) in the presence of gravity. The main findings are: the

F. Radjai, S. Roux

We analyze particle velocity fluctuations in a simulated granular system subjected to homogeneous quasistatic shearing. We show that these fluctuations share the following scaling characteristics of fluid turbulence in spite of their different physical origins: 1) Scale-dependent probability distribution with non-Guassian broadening at small time scales; 2)

T. M. Mishonov, J. P. Wallington, E. S. Penev, J. O. Indekeu

A detailed Linear Combination of Atomic Orbitals (LCAO) tight-binding model is developed for the layered High-Temperature Superconductor cuprates. The band structure of these materials is described using a sigma-band Hamiltonian employing Cu4s, Cu3d_x^2-y^2, O2p_x and O2p_y atomic orbitals. The Fermi level and the shape of the resulting Fermi surface are fit

T. Scopigno, E. Pontecorvo, R. Di Leonardo, M. Krisch

The dynamic structure factor of glassy and liquid glycerol has been measured by inelastic X-ray scattering in the exchanged momentum ($Q$) region $Q$=2$÷$23 nm$^{-1}$ and in the temperature range 80$÷$570 K. Beside the propagating longitudinal excitations modes, at low temperature the spectra show a second non $Q$-dispersing peak at $\hbar Ω_T$$\approx$8.5 m

Katarzyna Sznajd-Weron

We introduce a formula for the disagreement function which is used to control a recently proposed dynamics of the Ising spin system. This leads to four different phases of the Ising spin chain in a zero temperature. One of these phases is doubly degenerated (anti- and ferromagnetic states are equally probable). On the borders between the phases two types of

Alejandro F. Rozenfeld, Reuven Cohen, Daniel ben-Avraham, Shlomo Havlin

We suggest a method for embedding scale-free networks, with degree distribution P(k) k^-lambda, in regular Euclidean lattices. The embedding is driven by a natural constraint of minimization of the total length of the links in the system. We find that all networks with lambda>2 can be successfully embedded up to an (Euclidean) distance xi which can be made a

David A. Kessler, Yitzhak Rabin

We show that when a gradually increasing tensile force is applied to the ends of a helical spring with sufficiently large ratios of radius to pitch and twist to bending rigidity, the end-to-end distance undergoes a sequence of discontinuous stretching transitions. Subsequent decrease of the force leads to step-like contraction and hysteresis is observed. For