April 2004 arXiv papers — page 9

R. Leidl, W. Selke

A classical variant of the two-dimensional anisotropic Heisenberg model reproducing inelastic neutron scattering experiments on La_5 Ca_9 Cu_24 O_41 [M. Matsuda et al., Phys.Rev. B 68, 060406(R) (2003)] is analysed using mostly Monte Carlo techniques. Phase diagrams with external fields parallel and perpendicular to the easy axis of the anisotropic interacti

H. L. Haroutyunyan, G. Nienhuis

When a single two-level atom interacts with a pair of Laguerre-Gaussian beams with opposite helicity, this leads to an efficient exchange of angular momentum between the light field and the atom. When the radial motion is trapped by an additional potential, the wave function of a single localized atom can be split into components that rotate in opposite dire

Steven T. Flammia, Andrew Silberfarb, Carlton M. Caves

We consider measurements, described by a positive-operator-valued measure (POVM), whose outcome probabilities determine an arbitrary pure state of a D-dimensional quantum system. We call such a measurement a pure-state informationally complete (PSI-complete) POVM. We show that a measurement with 2D-1 outcomes cannot be PSI-complete, and then we construct a P

Bruno Galvan

If the quantum mechanical description of reality is not complete and a hidden variable theory is possible, what arises is the problem to explain where the rates of the outcomes of statistical experiments come from, as already noticed by Landé and Popper. In this paper this problem is investigated, and a new "paradigm" about the nature of dynamical an

Rukmini Kumar, Gilles Clermont, Yoram Vodovotz, Carson Chow

When the body is infected, it mounts an acute inflammatory response to rid itself of the pathogens and restore health. Uncontrolled acute inflammation due to infection is defined clinically as Sepsis and can culminate in organ failure and death. We consider a three dimensional ordinary differential equation model of inflammation consisting of a pathogen, and

David R. Bickel

Motivation: The reconstruction of gene networks from gene expression microarrays is gaining popularity as methods improve and as more data become available. The reliability of such networks could be judged by the probability that a connection between genes is spurious, resulting from chance fluctuations rather than from a true biological relationship. Result

David R. Bickel

A previously proved theorem gives sufficient conditions for an estimator of the false discovery rate (FDR) to conservatively converge to the FDR with probability 1 as the number of hypothesis tests increases, even for small sample sizes. It does not follow that several thousand tests ensure that the estimator has moderate variance under those conditions. In

Cendrine Hudelot, Vivek Gowri-Shankar, Howsun Jow, Magnus Rattray

The PHASE software package allows phylogenetic tree construction with a number of evolutionary models designed specifically for use with RNA sequences that have conserved secondary structure. Evolution in the paired regions of RNAs occurs via compensatory substitutions, hence changes on either side of a pair are correlated. Accounting for this correlation is

Bin Tang, Philippe Boisvert, Paul G. Higgs

The current picture of bacterial evolution is based largely on studies of 16S rRNA. However, this is just one gene. It is known that horizontal gene transfer can occur between bacterial species, although the frequency and implications of this are not fully understood. If horizontal transfer were frequent, there would be no single evolutionary tree for bacter

Bruce R. Pearson, Tarek A. Yousef, Nils Erland L. Haugen, Axel Brandenburg

The dimensionless kinetic energy dissipation rate C_epsilon is estimated from numerical simulations of statistically stationary isotropic box turbulence that is slightly compressible. The Taylor microscale Reynolds number Re_lambda range is 20 < Re_lambda < 220 and the statistical stationarity is achieved with a random phase forcing method. The strong Re_lam

James D. Brownridge, Stephen M. Shafroth

Static charge in and on the surface of pyroelectric crystals of LiNbO3 and LiTaO3 in a dilute gas has been shown to ionize gas molecules via electron tunneling. The released electrons and positive ions are focused and accelerated according to the sign of the static uncompensated charge. The uncompensated charge is produced when the temperature of the crystal

Ferenc Sikler

An experimental report on the construction and operation of a lead-glass calorimeter at the CERN-NA49 experiment is presented.

G. Molchan

This paper presents an analysis of the distribution of the time $τ$ between two consecutive events in a stationary point process. The study is motivated by the discovery of a unified scaling law for $τ$ for the case of seismic events. It is shown that the unified law must necessarily be exponential. We discuss the parameterization of the empirical unified la

V. I. Balykin, K. Hakuta, Fam Le Kien, J. Q. Liang

We suggest using an evanescent wave around a thin fiber to trap atoms. We show that the gradient force of a red-detuned evanescent-wave field in the fundamental mode of a silica fiber can balance the centrifugal force when the fiber diameter is about two times smaller than the wavelength of the light and the component of the angular momentum of the atoms alo

Henry Chen, Michael P. Brenner

The production of small fluid droplets relies on an instability of solutions to the Young-Laplace equation. We ask whether smaller droplets can be produced by changing the shape of the nozzle. At a given critical pressure, the circular nozzle actually produces the largest droplet. The droplet volume can be decreased by up to 18% using a triangular nozzle wit

Kevin L. Haglin

We study spectral properties of the phi meson at finite temperature using an effective Lagrangian together with finite-temperature field theory as a basis for modeling. General field-theoretic arguments are then used to establish the lifetime of the phi in hot hadronic matter. We find from the model, and we therefore propose a scenario in which, the phi deca

Cetin Savkli, Franz Gross, John Tjon

In this paper we present a summary of results obtained for scalar field theories using the Feynman-Schwinger (FSR) approach. Specifically, scalar QED and chi^2phi theories are considered. The motivation behind the applications discussed in this paper is to use the FSR method as a rigorous tool for testing the quality of commonly used approximations in field

David A. Brown, Pawel Danielewicz, Mike Heffner, Ron Soltz

We report an extension of the source imaging method for imaging full three-dimensional sources from three-dimensional like-pair correlations. Our technique consists of expanding the correlation data and the underlying source function in spherical harmonics and inverting the resulting system of one-dimensional integral equations. With this method of attack, w

Ladislav Šándor

Recent results on hyperon production in Pb--Pb collisions from the NA57 experiment are reported. Strangeness enhancement and the transverse mass spectra properties at 158 GeV per nucleon are described.

An Tai

We present the first comprehensive measurement of $D^{0}, D^{+}, D^{*+}$ and their charge conjugate states at mid-rapidity in $d$+Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV using the STAR TPC. The directly measured open charm multiplicity distribution covers a broad transverse momentum region of 0$<p_{T}<11$ GeV/$c$. The measured $dN/dy$ at mid-rapidity for

V. A. Khitrov, Li Chol, A. M. Sukhovoj

Systematic error in determination of the absolute intensities of the two-step gamma-cascades after the thermal neutron capture and its influence on the value and localization of extracted from (n,2gamma)-reaction probable level densities and radiative strength functions of dipole gamma-transitions have been analysed. It was found that this error in limits of

L. S. Azhgirey, M. Janek, A. N. Khrenov, V. P. Ladygin

The results of the measurements of the vector polarization of the extracted deuteron beam at Nuclotron are presented. The intensity of the polarized deuteron beam during the measurements was 2.5*10^7 particles/spill. The measurements were made at the initial deuteron momenta of 5 and 3.5 GeV/c. The averaged polarizations of the beam were 0.606 +/- 0.014 and

Paul Kersten, Iosif Krasil&#39;shchik, Alexander Verbovetsky

Using methods of math.DG/0304245 and [I.S.Krasil&#39;shchik and P.H.M.Kersten, Symmetries and recursion operators for classical and supersymmetric differential equations, Kluwer, 2000], we accomplish an extensive study of the N=1 supersymmetric Korteweg-de Vries equation. The results include: a description of local and nonlocal Hamiltonian and symplectic str

Kanehisa Takasaki

For some integrable systems, such as the open Toda molecule, the spectral curve of the Lax representation becomes the graph $C = \{(λ,z) \mid z = A(λ)\}$ of a function $A(λ)$. Those integrable systems provide an interesting ``toy model&#39;&#39; of separation of variables. Examples of this type of integrable systems are presented along with generalizations f

A. G. Ramm, O. L. Weaver

In Feynman&#39;s lectures there is a remark about the limiting value of the impedance of an n-section ladder consisting of purely reactive elements (capacitances and inductances). The remark is that this limiting impedance $z=\lim_{n\to\infty}z_n$ has a positive real part. He notes that this is surprising since the real part of each $z_n$ is zero, therefore

M. A. Jafarizadeh, H. Goudarzi

Using the irreducible representations of the group $SO(d+1)$, we discuss the degeneracy symmetry of hydrogen atom in $d$-dimensions and calculate its energy spectrum as well as the correspouding degeneracy. We show that $SO(d+1)$ is the energy spectrum generating group

Hernan Cendra, Alberto Ibort, Manuel de Leon, David Martin de Diego

The constraint distribution in non-holonomic mechanics has a double role. On one hand, it is a kinematic constraint, that is, it is a restriction on the motion itself. On the other hand, it is also a restriction on the allowed variations when using D&#39;Alembert&#39;s Principle to derive the equations of motion. We will show that many systems of physical in

W. A. Zuniga-Galindo

We show the existence of fundamental solutions for p-adic pseudo-differential operators with polynomial symbols.

Elchanan Mossel, Yuval Peres, Alistair Sinclair

In the cyclic-to-random shuffle, we are given n cards arranged in a circle. At step k, we exchange the k&#39;th card along the circle with a uniformly chosen random card. The problem of determining the mixing time of the cyclic-to-random shuffle was raised by Aldous and Diaconis in 1986. Recently, Mironov used this shuffle as a model for the cryptographic sy

A. G. Ramm

Consider an operator equation (*) $B(u)+\ep u=0$ in a real Hilbert space, where $\ep>0$ is a small constant. The DSM (dynamical systems method) for solving equation (*) consists of a construction of a Cauchy problem, which has the following properties: 1) it has a global solution for an arbitrary initial data, 2) this solution tends to a limit as time tends

A. G. Ramm

Let $L$ be an unbounded linear operator in a real Hilbert space $H$, a generator of $C_0$ semigroup, and $g:H\to H$ be a $C^2_{loc}$ nonlinear map. The DSM (dynamical systems method) for solving equ$ $F(v):=Lv+gv=0$ consists of solving the Cauchy problem $\dot {u}=Φ(t,u)$, $u(0)=u_0$, where $Φ$ is a suitable operator, and proving that i) $\exists u(t) \quad

A. G. Ramm, S. Gutman

This paper contains a self-contained brief presentation of the scattering theory for periodic structures. Its main result is a theorem (the Modified Rayleigh Conjecture, or MRC), which gives a rigorous foundation for a numerical method for solving the direct scattering problem for periodic structures. A numerical example illustrating the procedure is present

Ruy Tojeiro

We prove conformal versions of the local decomposition theorems of de Rham and Hiepko of a Riemannian manifold as a Riemannian or a warped product of Riemannian manifolds. Namely, we give necessary and sufficient conditions for a Riemannian manifold to be locally conformal to either a Riemannian or a warped product. We also obtain other related de Rham-type

Yitwah Cheung

It is known that nonergodic directions in a rational billiard form a subset of the unit circle with Hausdorff dimension at most 1/2. Explicit examples realizing the dimension 1/2 are constructed using Diophantine numbers and continued fractions. A lower estimate on the number of primitive lattice points in certain subsets of the plane is used in the construc

Margaret M. Bayer

Ordinary polytopes were introduced by Bisztriczky as a (nonsimplicial) generalization of cyclic polytopes. We show that the colex order of facets of the ordinary polytope is a shelling order. This shelling shares many nice properties with the shellings of simplicial polytopes. We also give a shallow triangulation of the ordinary polytope, and show how the sh

Frank Neumann, Ulrich Stuhler

We describe the action of the different Frobenius morphisms on the cohomology ring of the moduli stack of algebraic vector bundles of fixed rank and determinant on an algebraic curve over a finite field in characteristic p and analyse special situations like vector bundles on the projective line and relations with infinite Grassmannians.

T. Suzuki

In this paper, we discuss characterizations of common fixed points of commutative semigroups of nonexpansive mappings. We next prove convergence theorems to a common fixed point. We finally discuss nonexpansive retractions onto the set of common fixed points. In our discussion, we may not assume the strict convexity of the Banach space.

Jan Hendrik Bruinier

We give an introduction to the theory of Borcherds products and to some number theoretic and geometric applications. In particular, we discuss how the theory can be used to study the geometry of Hilbert modular surfaces.

Anton S. Galaev

Weakly-irreducible not irreducible subalgebras of $\so(1,n+1)$ were classified by L. Berard Bergery and A. Ikemakhen. In the present paper a geometrical proof of this result is given. Transitively acting isometry groups of Lobachevskian spaces and transitively acting similarity transformation groups of Euclidean spaces are classified.

Thomas H. Geisser

We calculate the total derived functor for the map from the Weil-etale site introduced by Lichtenbaum to the etale site for varieties over finite fields. In particular, there is a long exact sequence relating Weil-etale cohomology and etale cohomology. In the second half of the paper, we apply this to study the Weil-etale cohomology of the motivic complex fo

I. Blank, P. Smith

Convergence of Rothe&#39;s method for the fully nonlinear parabolic equation u_t + F(D^2 u, Du, u, x, t) = 0 is considered under some continuity assumptions on F. We show that the Rothe solutions are Lipschitz in time, Holder in space, and they solve the equation in the viscosity sense. As an immediate corollary we get Lipschitz behavior in time of the visco

Scott Contini, Ernie Croot, Igor Shparlinski

We present an algorithm to invert the Euler function $ϕ(m)$. The algorithm, for a given $n \geq 1$, in polynomial time ``on average&#39;&#39;, finds the set $Ψ(n)$ of all solutions $m$ to $ϕ(m) = n$. In fact, in the worst case, $Ψ(n)$ is exponentially large, and cannot be computed in polynomial time. In the opposite direction, we show, under a widely accepte

Paul Kersten, Iosif Krasil&#39;shchik, Alexander Verbovetsky

Using the result by D.Gessler (Differential Geom. Appl. 7 (1997) 303-324, DIPS-9/98, http://diffiety.ac.ru/preprint/98/09_98abs.htm), we show that any invariant variational bivector (resp., variational 2-form) on an evolution equation with nondegenerate right-hand side is Hamiltonian (resp., symplectic).

Andreas Cap

For a semisimple Lie group $G$ with parabolic subgroups $Q\subset P\subset G$, we associate to a parabolic geometry of type $(G,P)$ on a smooth manifold $N$ the correspondence space $\Cal CN$, which is the total space of a fiber bundle over $N$ with fiber a generalized flag manifold, and construct a canonical parabolic geometry of type $(G,Q)$ on $\Cal CN$.

C. A. S. Almeida, R. R. Landim, D. M. Medeiros

In this work we show a dualization process of a non-Abelian model with an antisymmetric tensor gauge field in a three-dimensional space-time. We have constructed a non-Abelian gauge invariant Stückelberg-like master action, and a duality between a non-Abelian topologically massive $B\wedgeϕ$ model and a non-Abelian massive scalar action, which leads us to a

M. Khovanov, L. Rozansky

We define topological Landau-Ginzburg models on a world-sheet foam, that is, on a collection of 2-dimensional surfaces whose boundaries are sewn together along the edges of a graph. We use matrix factorizations in order to formulate the boundary conditions at these edges and produce a formula for the correlators. Finally, we present the gluing formulas, whic

J. L. F. Barbon

This is a rendering of a review talk on the state of String Theory, given at the EPS-2003 Conference, intended for a wide audience of experimental and theoretical physicists. It emphasizes general ideas rather than technical aspects.

Manfred Herbst, C. I. Lazaroiu

We reconsider the issue of localization in open-closed B-twisted Landau-Ginzburg models with arbitrary Calabi-Yau target. Through careful analsysis of zero-mode reduction, we show that the closed model allows for a one-parameter family of localization pictures, which generalize the standard residue representation. The parameter $λ$ which indexes these pictur

M. Movshev, A. Schwarz

In the present paper we analyze algebraic structures arising in Yang-Mills theory. The paper should be considered as a part of a project started with a paper &#34;On maximally supersymmetric Yang-Mills theories&#34; devoted to maximally supersymmetric Yang-Mills theories. In this paper we collected those of our results which are correct without assumption of

Jihn E. Kim, Gary B. Tupper, Raoul D. Viollier

We present a general framework for nonparallel brane worlds and use it to discuss the nonlinear radion problem. By imposing the Einstein frame as a gauge condition we are able to give the effective action for both Minkowski and (A)dS$_{4}$ branes. In particular we find the nonlinear radion does not disappear in the second Randall-Sundrum model.

Wolfgang Bietenholz, Frank Hofheinz, Jun Nishimura

It is well-known that non-commutative (NC) field theories at theta = infinity are ``equivalent&#39;&#39; to large N matrix field theories to all orders in perturbation theory, due to the dominance of planar diagrams. By formulating a NC field theory on the lattice non-perturbatively and mapping it onto a twisted reduced model, we point out that the above equ

Riccardo Capovilla, Jemal Guven, Efrain Rojas

We consider a relativistic extended object described by a reparametrization invariant local action that depends on the extrinsic curvature of the worldvolume swept out by the object as it evolves. We provide a Hamiltonian formulation of the dynamics of such higher derivative models which is motivated by the ADM formulation of general relativity. The canonica

Dirk Kreimer

We discuss in an introductory manner structural similarities between the polylogarithm and Green functions in quantum field theory.

Yu. L. Dokshitzer, D. E. Kharzeev

A major contribution to the quest of constructing quantum dynamics of non-Abelian fieds is due to V.N. Gribov. Perturbative approach to the colour confinement, both in gluodynamics and the real world, was long considered heretic but is gaining ground. We discuss Gribov&#39;s approach to the confinement problem, centered around the role played by light quarks

Mark Alford, Gerald Good

We study reflection and transmission of light at the interface between different phases of a U(1) x U(1) gauge theory. On each side of the interface, one can choose a basis so that one generator is free (allowing propagation of light), and the orthogonal one may be free, Higgsed, or confined. However, the basis on one side will in general be rotated relative

F. Jegerlehner, M. Yu. Kalmykov

Recent progress in the calculation of the two-loop on-shell mass counterterms within the electroweak Standard Model (SM) for the massive particles are discussed. We are in progress of developing a package for full two-loop SM calculations of 2 -> 2 fermion processes, with emphasis on the analytical approach where feasible. The complete two-loop on-shell reno

M. Luszczak, A. Szczurek

Correlation of charm quark - charm antiquark in $γp$ scattering are calculated in the $k_t$-factorization approach. We apply different unintegrated gluon distributions (uGDF) used in the literature. The results of our calculations are compared with very recent experimental results from the FOCUS collaboration. The CCFM uGDF developed recently by Kwieciński e

A. Djouadi, S. Heinemeyer, M. Mondragon, G. Zoupanos

Finite Unified Theories (FUTs) are N=1 supersymmetric Grand Unified Theories, which can be made all-loop finite, both in the dimensionless (gauge and Yukawa couplings) and dimensionful (soft supersymmetry breaking terms) sectors. This remarkable property provides a drastic reduction in the number of free parameters, which in turn leads to an accurate predict

F. Gastineau, E. Blanquier, J. Aichelin

The Nambu Jona-Lasinio Lagrangian offers an explication of the seemingly contradictory observations that a) the energy loss in the entrance channel of heavy ion reactions is not sufficient to thermalize the system and that b) the observed hadron cross sections are in almost perfect agreement with hydrodynamical calculations. According to this scenario, a cri

M. Gorchtein, P. A. M. Guichon, M. Vanderhaeghen

We discuss the two-photon exchange contribution to observables which involve lepton helicity flip in elastic lepton-nucleon scattering. This contribution is accessed through the spin asymmetry for a lepton beam polarized normal to the scattering plane. We estimate this beam normal spin asymmetry at large momentum transfer using a parton model and we express

U. Harbach, S. Hossenfelder, M. Bleicher, H. Stoecker

We discuss modifications of the gyromagnetic moment of electrons and muons due to a minimal length scale combined with a modified fundamental scale $M_f$. First-order deviations from the theoretical standard model value for $g-2$ due to these String Theory-motivated effects are derived. A constraint of $M_f>577 GeV$ for the new fundamental scale is given.

F. J. Yndurain

We show that a generalized Regge behaviour, $$Im F(s,t)\simeq Φ(t)(\log s/\hat{s})^{ν(t)}(s/\hat{s})^{α_P(t)},\quad{\rm for} |t|<|t_0|, s\to\infty$$ where $Φ(t)\simeq e^{bt}$, $α_P(t)\simeq α_P(0)+α&#39;_P(0)t$, and $t_0$ is the first zero of $α_P(t)$, $α_P(t_0)=0$, implies that the corresponding cross section is bounded by $$σ_{\rm tot}(s)<({\rm Const.})\ti

B. F. Irgaziev, B. A. Fayzullaev

The pi- d atom strong energy-level shift in the 1s state is derived by using the effective field theory. Taking into account the large value of radius of pionic deuterium and short radius of strong interaction between pion and deuteron we have considered deuteron as particle described by vector field. Pion is described by scalar field. To obtain non-relativi

I. M. Dremin

A brief survey of theoretical approaches to description of multiplicity distributions in high energy processes is given. It is argued that the multicomponent nature of these processes leads to some peculiar characteristics observed experimentally. Predictions for LHC energies are presented. It is shown that similarity of the energy dependence of average mult

Aiichi Iwazaki, Osamu Morimatsu, Munehisa Ohtani, Tetsuo Nishikawa

We have recently shown that dense quark matter possesses a color ferromagnetic phase in which a stable color magnetic field arises spontaneously. This ferromagnetic state has been known to be Savvidy vacuum in the vacuum sector. Although the Savvidy vacuum is unstable, the state is stabilized in the quark matter. The stabilization is achieved by the formatio

Maury Goodman

New experiments at accelerators and reactors are being designed to search for a possible non-zero value of the MNS matrix parameter theta_{13}.

O. P. Yushchenko, S. A. Akimenko, G. I. Britvich, K. V. Datsko

The decay K- -> pi0 e- nu is studied using in-flight decays detected with the ISTRA+ spectrometer. About 920K events are collected for the analysis. The lambda+ slope parameter of the decay form-factor f+(t) in the linear approximation (average slope) is measured: lambda+(lin)= 0.02774 +- 0.00047(stat) +- 0.00032(syst). The quadratic contribution to the form

Stergos D. Afantenos, Irene Doura, Eleni Kapellou, Vangelis Karkaletsis

This paper presents a methodology for summarization from multiple documents which are about a specific topic. It is based on the specification and identification of the cross-document relations that occur among textual elements within those documents. Our methodology involves the specification of the topic-specific entities, the messages conveyed for the spe

Matthew Pelton, David Grier, Philippe Guyot-Sionnest

Fluctuations in the fluorescence from macroscopic ensembles of colloidal semiconductor quantum dots have the spectral form of 1/f noise. The measured power spectral density reflects the fluorescence intermittency of individual dots with power-law distributions of &#34;on&#34; and &#34;off&#34; times, and can thus serve as a simple method for characterizing s

Aldemar Torres, Gabriel Tellez

We study the statistical mechanics of classical Coulomb systems in a low coupling regime (Debye-Huckel regime) in a confined geometry with Dirichlet boundary conditions. We use a method recently developed by the authors which relates the grand partition function of a Coulomb system in a confined geometry with a certain regularization of the determinant of th

M. Mikulis, C. J. Olson Reichhardt, C. Reichhardt, R. T. Scalettar

We study colloidal ordering and disordering on two-dimensional periodic substrates where the number of colloids per substrate minima is two or three. The colloids form dimer or trimer states with orientational ordering, referred to as colloidal molecular crystals. At a fixed temperature such that, in the absence of a substrate, the colloids are in a triangul

E. Rasanen, J. Konemann, R. J. Haug, M. J. Puska

We have studied the single-electron transport spectrum of a quantum dot in GaAs/AlGaAs resonant tunneling device. The measured spectrum has irregularities indicating a broken circular symmetry. We model the system with an external potential consisting of a parabolic confinement and a negatively charged Coulombic impurity placed in the vicinity of the quantum

R. Puzniak, M. Angst, A. Szewczyk, J. Jun

The upper critical field Hc2||c(0) of 85 kOe in Mg(B0.94C0.06)2 single crystals, determined from torque measurements, is more than twice as large as that one of 31 kOe in unsubstituted MgB2. Anisotropy of Hc2 increases from about 3.4 near Tc, the value close to that in MgB2, to about 4 at low temperature, the value considerably lower than that in MgB2. The c

D. Alfe`, M. J. Gillan

We have reformulated the quantum Monte Carlo (QMC) technique so that a large part of the calculation scales linearly with the number of atoms. The reformulation is related to a recent alternative proposal for achieving linear-scaling QMC, based on maximally localized Wannier orbitals (MLWO), but has the advantage of greater simplicity. The technique we propo

C. Schroll, Florian Marquardt, C. Bruder

We study the Mott-insulator transition of bosonic atoms in optical lattices. Using perturbation theory, we analyze the deviations from the mean-field Gutzwiller ansatz, which become appreciable for intermediate values of the ratio between hopping amplitude and interaction energy. We discuss corrections to number fluctuations, order parameter, and compressibi

F. Amblard, G. Deffuant

In (Deffuant et al., 2002), we proposed a simple model of opinion dynamics, which we used to simulate the influence of extremists in a population. Simulations were run without any specific interaction structure and varying the simulation parameters, we observed different attractors such as predominance of centrism or of extremism. We even observed in certain

Iacopo Carusotto, Cristiano Ciuti

We investigate the two-dimensional motion of polaritons injected into a planar microcavity by a continuous wave optical pump in presence of a static perturbation, e.g. a point defect. By finding the stationary solutions of the nonlinear mean-field equations (away from any parametric instability), we show how the spectrum of the polariton Bogoliubov-like exci

Kazuhiko Minami, Masuo Suzuki

Two conditions are derived for Ising models to show non-universal critical behaviour, namely conditions concerning 1) logarithmic singularity of the specific heat and 2) degeneracy of the ground state. These conditions are satisfied with the eight-vertex model, the Ashkin-Teller model, some Ising models with short- or long-range interactions and even Ising s

R. Guyon, T. Jonckheere, V. Mujica, A. Crepieux

The transport properties of a simple model for a finite level structure (a molecule or a dot) connected to metal electrodes in an alternating current scanning tunneling microscope (AC-STM) configuration is studied. The finite level structure is assumed to have strong binding properties with the metallic substrate, and the bias between the STM tip and the hyb

G. A. Wigger, C. Beeli, E. Felder, H. R. Ott

Upon substituting Ca for Eu in the local-moment ferromagnet EuB$_6$, the Curie temperature $T_C$ decreases substantially with increasing dilution of the magnetic sublattice and is completely suppressed for $x$ $\leq$ 0.3. The Ca substitution leads to significant changes of the electronic properties across the Eu$_x$Ca$_{1-x}$B$_6$ series. Electron microscopy

R. Martonak, D. Donadio, M. Parrinello

We report results of MD simulations of amorphous ice in the pressure range 0 - 22.5 kbar. The high-density amorphous ice (HDA) prepared by compression of Ih ice at T = 80 K is annealed to T = 170 K at intermediate pressures in order to generate relaxed states. We confirm the existence of recently observed phenomena, the very high-density amorphous ice and a

Mark. H. Ruemmeli, Ewa Borowiak-Palen, Thomas Gemming, Martin Knupfer

A thermally induced templated synthesis for SiC nanotubes and nanofibers using ammonia or nitrogen as a carrier gas, single wall carbon nanotubes (SWCNT) as templates as well as gaseous Si is presented. The bundles of SWCNT act as both the carbon source and as a nanoframe from which SiC structuctures form. Depending on the duration of the thermally induced t

A. S. Moskvin

We suppose that the doping of the 2D hard-core boson system away from half-filling may result in the formation of multi-center topological inhomogeneity (defect) such as charge order (CO) bubble domain(s) with Bose superfluid (BS) and extra bosons both localized in domain wall(s), or a {\it topological} CO+BS {\it phase separation}, rather than an uniform mi

A. S. Moskvin, I. G. Bostrem, A. S. Ovchinnikov

We suppose that the doping of the 2D hard-core boson system away from half-filling may result in the formation of multi-center topological defect such as charge order (CO) bubble domain(s) with Bose superfluid (BS) and extra bosons both localized in domain wall(s), or a {\it topological} CO+BS {\it phase separation}, rather than an uniform mixed CO+BS supers

J. M. Vogels, T. Lahaye, C. Roos, J. Dalibard

In this paper, we report our progress towards the realization of a continuous guided atomic beam in the degenerate regime. So far, we have coupled into a magnetic guide a flux of a few $10^{8}$ atoms/s at 60 cm/s with a propagation in the guide over more than 2 meters. At this stage, the collision rate is not high enough to start an efficient forced evaporat

J. Jung, P. García-González, J. E. Alvarellos, R. W. Godby

The complex nature of electron-electron correlations is made manifest in the very simple but non-trivial problem of two electrons confined within a sphere. The description of highly non-local correlation and self-interaction effects by widely used local and semi-local exchange-correlation energy density functionals is shown to be unsatisfactory in most cases

Anjana Dogra, S. Rayaprol, N. A. Shah, D. G. Kuberkar

The effect of Co-Ga paired substitution on the superconducting properties of YBa2Cu3O7-d (Y-123) has been investigated by X-ray diffraction, ac susceptibility,dc resistivity and oxygen content measurements. We report in this paper the results of our studies on the paired substitution of a magnetic and non-magnetic ion at Cu site in Y-123, while keeping the t

Marco A. Idiart, Yan Levin

We discuss pore dynamics in osmotically stressed vesicles. A set of equations which govern the liposomal size, internal solute concentration, and pore diameter is solved numerically. We find that dependent on the internal solute concentration and vesicle size, liposomes can stay pore-free, nucleate a short lived pore, or nucleate a long-lived pore. The phase

Nobuya Maeshima

Vertical density matrix algorithm (VDMA), a tensor product state formulation of the ``higher-dimensional&#39;&#39; density matrix renormalization group, is applied to the spin 1/2 antiferromagnetic XXZ model on the checkerboard lattice. The VDMA was, in the preceding study, applied to the transverse field Ising model on the square lattice and the three-dimen

Kikuo Harigaya

Electronic structures and optical excitations in Moebius conjugated polymers are studied theoretically. Periodic and Moebius boundary conditions are applied to the tight binding model of poly(para-phenylene), taking into account of the exciton effects by long-range Coulomb interactions. We first discuss that oligomers with a few structural units are more eff

E. G. Mishchenko, M. Yu. Reizer, L. I. Glazman

In a ballistic two-dimensional electron gas, the Landau damping does not lead to plasmon attenuation in a broad interval of wave vectors q << k_F. Similarly, it does not contribute to the optical conductivity σ(ω, q) in a wide domain of its arguments, E_F > ω> qv_F, where E_F, k_F and v_F are, respectively, the Fermi energy, wavevector and velocity of the el

M. J. Page, R. Soria, S. Zane, K. Wu

We present spectral and timing results from a long (130 ks) XMM-NEWTON EPIC observation of the nucleus of the Seyfert/LINER galaxy M 81. During the observation the X-ray flux varied by 20%, but there was no significant change in spectral shape. The 2-10 keV spectrum is well described by a power law continuum and three narrow Fe K emission lines at 6.4, 6.7 a

Istvan Szapudi

We explore linear redshift distortions in wide angle surveys from the point of view of symmetries. We show that the redshift space two-point correlation function can be expanded into tripolar spherical harmonics of zero total angular momentum $S_{l_1 l_2 l_3}(\hat x_1, \hat x_2, \hat x)$. The coefficients of the expansion $B_{l_1 l_2 l_3}$ are analogous to t

Istvan Szapudi

Multipole expansion of spatial three-point statistics is introduced as a tool for investigating and displaying configuration dependence. The novel parametrization renders the relation between bi-spectrum and three-point correlation function especially transparent as a set of two-dimensional Hankel transforms. It is expected on theoretical grounds, that three

Eric Emsellem

I briefly report on the work conducted to probe the gravitational potential of active and non-active disk galaxies using two-dimensional gas and stellar kinematics, first emphasizing the need to make a distinction between &#39;&#39;fuelling the nucleus&#39;&#39; and &#39;&#39;building a gas reservoir&#39;&#39;.

S. Toft, V. Mainieri, P. Rosati, C. Lidman

We derive the Ks-band luminosity function (LF) of the z=1.237 massive X-ray luminous cluster of galaxies RDCS J1252.9-2927. Photometric redshifts, derived from deep multi-wavelength BVRIzJKs data, and calibrated using a large subset of galaxies with spectroscopic redshifts, are used to separate the cluster galaxy population from the foreground and background

C. Borys, S. C. Chapman, M. Donahue, G. Fahlman

We present a new SCUBA image of the cluster MS0451.6-0305, which exhibits strong, extended sub-mm flux at 850 microns. The most striking feature in the map is an elongated region of bright sub-mm emission, with a flux density of >10 mJy over several beam-sizes. This region is apparently coincident with a previously known optical arc (which turns out to be a

T. J. Davidge, F. Rigaut

Deep K&#39; images with 0.1 arcsec angular resolution, obtained with ALTAIR+NIRI on Gemini North, are used to investigate photometric variablity among the brightest asymptotic giant branch (AGB) stars in the central regions of M32. Based on a comparison with brightnesses obtained from the K-band data discussed by Davidge et al. (2000, ApJ, 545, L89), it is c

Pieter van Dokkum, Marijn Franx, Natascha Forster Schreiber, Garth Illingworth

We recently identified a substantial population of galaxies at z>2 with red rest-frame optical colors. These distant red galaxies (DRGs) are efficiently selected by the simple observed color criterion J-K>2.3. In this paper we present NIR spectroscopy with Keck/NIRSPEC of six DRGs at 2.4<z<3.2. We detect continuum emission and emission lines of all observed

S. P. Boughn, R. G. Crittenden

We have detected statistically significant correlations between the cosmic microwave background and two tracers of large-scale structure, the HEAO1 A2 full sky hard X-ray map and the NVSS 1.4 GHz, nearly full sky radio galaxy survey. The level of correlations in these maps is consistent with that predicted for the integrated Sachs-Wolfe (ISW) effect in the c