August 2003 arXiv papers — page 2

Isabella Bierenbaum, Stefan Weinzierl

We consider the massless two-loop two-point function with arbitrary powers of the propagators and derive a representation, from which we can obtain the Laurent expansion to any desired order in the dimensional regularization parameter eps. As a side product, we show that in the Laurent expansion of the two-loop integral only rational numbers and multiple zet

Henryk Czyz, Agnieszka Grzelinska, Johann H. Kuhn, German Rodrigo

The measurement of the pion form factor and, more generally, of the cross section for electron--positron annihilation into hadrons through the radiative return has become an important task for high luminosity colliders such as the $Φ$- or $B$-meson factories. For detailed understanding and analysis of this reaction, the construction of a Monte Carlo program,

Juha J. Vartiainen, Antti O. Niskanen, Mikio Nakahara, Martti M. Salomaa

We investigate the physical implementation of Shor's factorization algorithm on a Josephson charge qubit register. While we pursue a universal method to factor a composite integer of any size, the scheme is demonstrated for the number 21. We consider both the physical and algorithmic requirements for an optimal implementation when only a small number of

P. Habdas, D. Schaar, Andrew C. Levitt, Eric R. Weeks

We use confocal microscopy to study the motion of a magnetic bead in a dense colloidal suspension, near the colloidal glass transition volume fraction $ϕ_g$. For dense liquid-like samples near $ϕ_g$, below a threshold force the magnetic bead exhibits only localized caged motion. Above this force, the bead is pulled with a fluctuating velocity. The relationsh

S. I. Nam, A. Hosaka, H. -Ch. Kim

We study photoproduction reactions for Theta^+, which was recently observed as a candidate of an exotic five quark state uudd(bar s). We employ effective lagrangian interactions in the linear and non-linear formalism of chiral symmetry and investigate two cases of spin and parity of Theta^+, J^P = 1/2^+ and 1/2^-. We calculate cross sections and discuss poss

P. M. C. de Oliveira, J. S. Sa' Martins, D. Stauffer, S. Moss de Oliveira

We introduce a population dynamics model, where individual genomes are represented by bit-strings. Selection is described by death probabilities which depend on these genomes, and new individuals continuously replace the ones that die, keeping the population constant. An offspring has the same genome as its (randomly chosen) parent, except for a small amount

L. M. Pretorius, K. J. Swanepoel

We classify all finite linear spaces on at most 15 points admitting a blocking set. There are no such spaces on 11 or fewer points, one on 12 points, one on 13 points, two on 14 points, and five on 15 points. The proof makes extensive use of the notion of the weight of a point in a 2-coloured finite linear space, as well as the distinction between minimal an

Takashi Shirahata, Tota Nakamura

We have modeled magneto-dielectric phase transitions in ABX$_3$-type layered triangular lattice compounds. The model consists of a spin system (magnetic transition) and a lattice system (dielectric transition). Magnetic exchange interactions are supposed to change with a relative positionbetween two spins. This assumption produces an effective coupling betwe

Andrew P. Hines, G. J. Milburn, Ross H. McKenzie

How does the classical phase space structure for a composite system relate to the entanglement characteristics of the corresponding quantum system? We demonstrate how the entanglement in nonlinear bipartite systems can be associated with a fixed point bifurcation in the classical dynamics. Using the example of coupled giant spins we show that when a fixed po

Rainer Kaltenbaek, Markus Aspelmeyer, Thomas Jennewein, Caslav Brukner

Quantum physics experiments in space using entangled photons and satellites are within reach of current technology. We propose a series of fundamental quantum physics experiments that make advantageous use of the space infrastructure with specific emphasis on the satellite-based distribution of entangled photon pairs. The experiments are feasible already tod

Fu-Guo Deng, Gui Lu Long, Xiao-Shu Liu

A protocol for quantum secure direct communication using blocks of EPR pairs is proposed. A set of ordered $N$ EPR pairs is used as a data block for sending secret message directly. The ordered $N$ EPR set is divided into two particle sequences, a checking sequence and a message-coding sequence. After transmitting the checking sequence, the two parties of co

Fe-Guo Deng, Gui Lu Long

A novel technique is devised to perform orthogonal state quantum key distribution. In this scheme, entangled parts of a quantum information carrier are sent from Alice to Bob through two quantum channels. However before the transmission, the orders of the quantum information carrier in one channel is reordered so that Eve can not steal useful information. At

Pierre Roussel

The EPR (Einstein, Podolsky, Rosen) argument and the Schrodinger cat paradox are revisited in relation with modern quantum optics and atomic physics and with the concept of decoherence. It is shown that the questions raised fifty years ago are still at the heart of our understanding of quantum physics today.

Marc Bienert, Wolfgang Merkel, Giovanna Morigi

We investigate theoretically the spectrum of resonance fluorescence of a harmonically trapped atom, whose internal transitions are $Λ$--shaped and driven at two-photon resonance by a pair of lasers, which cool the center--of--mass motion. For this configuration, photons are scattered only due to the mechanical effects of the quantum interaction between light

M. E. Shirokov

Recently Shor proved equivalence of several open (sub)additivity problems related to the Holevo capacity and the entanglement of formation [15]. In our previous note [6] equivalence of these to the additivity of the Holevo capacity for channels with arbitrary linear constraints was shown. This note is the development of the previous one in the direction of c

Jun Zhang, Jiri Vala, Shankar Sastry, K. Birgitta Whaley

From a geometric approach, we derive the minimum number of applications needed for an arbitrary Controlled-Unitary gate to construct a universal quantum circuit. A new analytic construction procedure is presented and shown to be either optimal or close to optimal. This result can be extended to improve the efficiency of universal quantum circuit construction

Andrei Khrennikov

In spite of the very common opinion we show that QM is not complete and that it is possible to create prequantum models providing finer description of physical reality than QM. There exists (at least in theoretical models) dispersion free states and the Heisenberg uncertainty principle can be violated. Thus in spite of all ``No-Go'' theorems (e.g., v

Joseph Emerson, Seth Lloyd, David Poulin, David Cory

We report an efficient quantum algorithm for estimating the local density of states (LDOS) on a quantum computer. The LDOS describes the redistribution of energy levels of a quantum system under the influence of a perturbation. Sometimes known as the ``strength function'' from nuclear spectroscopy experiments, the shape of the LDOS is directly relate

Paolo Giorda, Paolo Zanardi, Seth Lloyd

This paper has been withdrawn by the authors because it was just an early submission of quant-ph/0308133 with the wrong title. Sorry.

P. Zhang, C. P. Sun

The two photon interference phenomenon is theoretically investigated for the general situations with an arbitrary input two photon state with and without photon polarization. For the case without polarization, the necessary-sufficient condition for the destructive interference of coincidence counting is given as the symmetric pairing of photons in the light

Daniele C. E. Bortolotti, John L. Bohn

We consider the problem of an atomic beam propagating quantum mechanically through an atom beam splitter. Casting the problem in an adiabatic representation (in the spirit of the Born-Oppenheimer approximation in molecular physics) sheds light on explicit effects due to non-adiabatic passage of the atoms through the splitter region. We are thus able to probe

C. J. McKinstrie, P. J. Winzer

This report contains a tutorial introduction to the method of importance sampling. The use of this method is illustrated for simulations of the noise-induced energy jitter of return-to-zero pulses in optical communication systems.

Peter W. Milonni, Robert W. Boyd

Motivated by recent discussions concerning the manner in which damping appears in the electric polarizability, we show that (a) there is a dependence of the nonresonant contribution on the damping and that (b) the damping enters according to the "opposite sign prescription." We also discuss the related question of how the damping rates in the polariz

S. Cht. Mavrodiev

This paper is an attempt for arguing the possibility for short time when, where and how Earthquakes prediction. The local when Earthquake prediction is based on the connection between geomagnetic quakes and the next incoming minimum or maximum of tidal gravitational potential. The probability time window for the predicted earthquake is +/-1 day for the minim

Michael Small, Chi K. Tse

Reconstruction of a dynamical system from a time series requires the selection of two parameters, the embedding dimension $d_e$ and the embedding lag $τ$. Many competing criteria to select these parameters exist, and all are heuristic. Within the context of modeling the evolution operator of the underlying dynamical system, we show that one only need be conc

M. E. J. Friese, T. A. Nieminen, N. R. Heckenberg, H. Rubinsztein-Dunlop

Light-induced rotation of absorbing microscopic particles by transfer of angular momentum from light to the material raises the possibility of optically driven micromachines. The phenomenon has been observed using elliptically polarized laser beams or beams with helical phase structure. But it is difficult to develop high power in such experiments because of

T. A. Nieminen, H. Rubinsztein-Dunlop, N. R. Heckenberg

The T-matrix method is widely used for the calculation of scattering by particles of sizes on the order of the illuminating wavelength. Although the extended boundary condition method (EBCM) is the most commonly used technique for calculating the T-matrix, a variety of methods can be used. We consider some general principles of calculating T-matrices, and ap

T. A. Nieminen, H. Rubinsztein-Dunlop, N. R. Heckenberg

Multipole expansion of an incident radiation field - that is, representation of the fields as sums of vector spherical wavefunctions - is essential for theoretical light scattering methods such as the T-matrix method and generalised Lorenz-Mie theory (GLMT). In general, it is theoretically straightforward to find a vector spherical wavefunction representatio

T. A. Nieminen, H. Rubinsztein-Dunlop, N. R. Heckenberg

Optical trapping, where microscopic particles are trapped and manipulated by light is a powerful and widespread technique, with the single-beam gradient trap (also known as optical tweezers) in use for a large number of biological and other applications. The forces and torques acting on a trapped particle result from the transfer of momentum and angular mome

D. J. Dean, M. Hjorth-Jensen

Using many-body perturbation theory and coupled-cluster theory, we calculate the ground-state energy of He-4 and O-16. We perform these calculations using a no-core G-matrix interaction derived from a realistic nucleon-nucleon potential. Our calculations employ up to two-particle-two-hole coupled-cluster amplitudes.

Scott Pratt, Wolfgang Bauer

Recent measurements of the pi^+pi^- invariant mass distribution at RHIC show a shifted peak for the rho meson in 100A GeV in peripheral Au + Au and even in p + p collisions. A recent theoretical study based on a picture of in-medium production rates of pions, showed that a large shift could result from a combination of the Boltzmann factor and the collisiona

B. Julia-Diaz, A. Valcarce, F. Fernandez

We make use of a $NN \to NN^*(1440)$ transition potential derived from a quark-model in a parameter-free way, to study the Roper excitation diagram contributing to the reaction $p(d,d^{\prime})$. We also determine the $πNN^*(1440)$ and $σNN^*(1440)$ coupling constants.

Silas R. Beane

Recent attempts to make direct contact between QCD and simple nuclear systems are reviewed.

D. B. Leinweber, A. W. Thomas, A. G. Williams, R. D. Young

First results from lattice QCD revealing the chiral nonanalytic behavior of nucleon and Delta baryon magnetic moments are presented. Numerical simulations in the light quark mass regime employing the nonperturbatively O(a)-improved conserved vector current are enabled via FLIC fermions. Quenched chiral perturbation theory for the nucleon and Delta magnetic m

Elton S. Smith

Generalized parton distributions provide a unifying framework for the interpretation of exclusive reactions at high $Q^2$. The most promising reaction for the investigation of these distributions is the hard production of photons using Deeply Virtual Compton Scattering (DVCS). This reaction can be accessed experimentally by determining the production asymmet

Giuseppe Pucacco, Kjell Rosquist

The geometric approach to mechanics based on the Jacobi metric allows to easily construct natural mechanical systems which are integrable (actually separable) at a fixed value of the energy. The aim of the present paper is to investigate the dynamics of a simple prototype system outside the zero-energy hypersurface. We find that the general situation is that

Michael Small

Dynamic invariants are often estimated from experimental time series with the aim of differentiating between different physical states in the underlying system. The most popular schemes for estimating dynamic invariants are capable of estimating confidence intervals, however such confidence intervals do not reflect variability in the underlying dynamics. In

Goce Chadzitaskos, Maciej Horowski, Anatol Odzijewicz, Agnieszka Tereszkiewicz

The eigenproblem for a class of Hamiltonians of the parametric down conversion process in the Kerr medium is solved. Some physical characteristics of the system are calculated.

Bertfried Fauser, P. D. Jarvis

An analysis of symmetric function theory is given from the perspective of the underlying Hopf and bi-algebraic structures. These are presented explicitly in terms of standard symmetric function operations. Particular attention is focussed on Laplace pairing, Sweedler cohomology for 1- and 2-cochains, and twisted products (Rota cliffordizations) induced by br

Anatoly N. Kochubei, Mustafa R. Sait-Ametov

We construct measures on the space $\mathcal D'(Q_p^n)$, $n\le 4$, of Bruhat-Schwartz distributions over the field of $p$-adic numbers, corresponding to finite volume polynomial interactions in a $p$-adic analog of the Euclidean quantum field theory. In contrast to earlier results in this direction, our choice of the free measure is the Gaussian measure

Vishvajit V. S. Gautam

In this paper we propose a naive construction of 2-dimensional extended topological quantum field theories (TQFTs), which can be further generalized to the higher-dimension extended TQFTs.

David Bachman, Saul Schleimer

J. Hempel's definition of the distance of a Heegaard surface generalizes to a complexity for a knot which is in bridge position with respect to a Heegaard surface. Our main result is that the distance of a knot in bridge position is bounded above by twice the genus, plus the number of boundary components, of an essential surface in the knot complement. A

Stephen S. Kudla

This article describes results of joint work with Michael Rapoport and Tonghai Yang. First, we construct an modular form ϕ(τ) of weight 3/2 valued in the arithmetic Chow group of the arithmetic surface M attached toa Shimura curve over Q. The q-expansion of this function is an analogue of the Hirzebruch-Zagier generating function for the cohomology classes o

Stephen S. Kudla

This article sketches relations among algebraic cycles for the Shimura varieties defined by arithmetic quotients of symmetric domains for O(n,2), theta functions, values and derivatives of Eisenstein series and values and derivatives of certain L-functions. In the geometric case, results of joint work with John Millson imply that the generating functions for

David Richeson, Jim Wiseman

We give a new and elementary proof showing that a homeomorphism of a compact metric space is positively expansive if and only if the space is finite.

I. Biswas, L. Brambila-Paz, P. E. Newstead

Let X be a non-singular algebraic curve of genus at least 3 and let M denote the moduli space of stable vector bundles of rank n and fixed determinant of degree d with n and d coprime. For any semistable bundle E over X, we can pull E back to XxM, tensor with a universal bundle and take the direct image W(E) on M. If the degree of E is sufficiently large, th

D. D. Porosniuc

We obtain a locally symmetric Kaehler Einstein structure on a tube in the nonzero cotangent bundle of a Riemannian manifold of positive constant sectional curvature. The obtained Kaehler Einstein structure cannot have constant holomorphic sectional curvature.

M. Domokos, T. H. Lenagan

Generators and relations are given for the subalgebra of cocommutative elements in the quantized coordinate rings of the classical groups, where the deformation parameter q is transcendental. This is a ring theoretic formulation of the well known fact that the representation theory of the quantized group is completely analogous to its classical counterpart.

Christian Blohmann

A small and unsystematic selection of my favorite appearances of mathematicians and mathematics in German literature. It includes classic and romantic (Lessing, Goethe, Wezel, F. Schlegel, Kleist, Novalis, Grillparzer, Heine), modern (Wedekind, Doeblin, Morgenstern, Musil, Brecht, Eich), as well as post-modern authors (Hans-Magnus Enzensberger, Volker Braun,

Alan T. Huckleberry, Joseph A. Wolf

The basic setup consists of a complex flag manifold $Z=G/Q$ where $G$ is a complex semisimple Lie group and $Q$ is a parabolic subgroup, an open orbit $D = G_0(z) \subset Z$ where $G_0$ is a real form of $G$, and a $G_0$--homogeneous holomorphic vector bundle $\mathbb E \to D$. The topic here is the double fibration transform ${\cal P}: H^q(D;{\cal O}(\mathb

Kefeng Liu, Andrey Todorov, Shing-Tung Yau, Kang Zuo

In this paper we first study the moduli spaces related to Calabi-Yau manifolds. We then apply the results to the following problem. Let $C$ be a fixed Riemann surface with fixed finite number of points on it. Given a CY manifold with fixed topological type, we consider the set of all families of CY manifolds of the fixed topological type over $C$ with degene

Viviane Baladi, Enrique R. Pujals, Martin Sambarino

We study the Ruelle dynamical determinant of a real analytic diffeomorphism on a compact surface, assuming that the tangent space over the nonwandering set admits a dominated splitting. Combining previous work of Pujals and Sambarino with methods introduced by Rugh, we show that the determinant is either entire or holomorphic in a (possibly multiply) slit pl

Stefan Fredenhagen, Volker Schomerus

In this note we reconsider the minisuperspace toy models for rolling and bouncing tachyons. We show that the theories require to choose boundary conditions at infinity since particles in an exponentially unbounded potential fall to infinity in finite world-sheet time. Using standard techniques from operator theory, we determine the possible boundary conditio

B. M. Zupnik

It is shown that the N=3 harmonic-superfield equations of motion are invariant with respect to the 4-th supersymmetry. The SU(3) harmonics are also used to analyze a more flexible form of superfield constraints for the Abelian N=4 vector multiplet and its N=3 decomposition. An alternative unusual representation of the N=4 supersymmetry is realized on infinit

Takeshi Sato

A quantum-mechanical technique is used within the framework of U(2) super-Yang-Mills theory to investigate processes after recombination of two D-p-branes at one angle. Two types of initial conditions are considered, one of which with $p=4$ is a candidate of inflation mechanism. It is shown that the branes' shapes come to have three extremes due to local

Zdzislaw Burda, Bengt Petersson, Marc Wattenberg

We derive analytically one-loop corrections to the effective Polyakov-line operator in the branched-polymer approximation of the reduced four-dimensional supersymmetric Yang-Mills integrals.

Paul K. Townsend

The status of accelerating four-dimensional universes obtained by time-dependent compactifications of 10 or 11 dimensional supergravity is reviewed, as is the `no-go' theorem that they evade. All flat cosmologies for a simple exponential potential are found explicitly. It is noted that transient acceleration is generic, and unavoidable for `flux' com

A. A. Arkhipov

In this note we propose to search new strange $a_2^s(1520)$-meson which is a strange partner of the $a_2(1311)$-meson observed in a three-pion system.

M. A. Braun

By direct numerical calculations the influence of a physically relevant infrared cutoff and running coupling on the gluon density and structure function of a large nucleus is studied in the perturbative QCD approach. It is found that the infrared cutoff changes the solutions very little. Running of the coupling produces a bigger change, considerably lowering

Stefan W. Bosch

We apply Soft-Collinear Effective Theory to prove at leading power in Lambda_QCD/m_b a factorization formula for the radiative leptonic decay B -> gamma l nu. Large logarithms entering the hard-scattering kernel are systematically resummed by a two-step perturbative matching procedure.

I. Marfin, V. Mossolov, T. Shishkina

The production of several vector bosons in $γγ$-interactions is the best place to search directly for any anomalous behavior of triple and quartic couplings. A few anomalous quartic boson operators are considered in the paper. A high precision of anomalous effects can be achieved by calculation of the lowest order electroweak corrections: one-loop correction

Giulia Zanderighi

We present a master formula, with applicability conditions, which allows us to automate the resummation of infrared and collinear logarithms appearing in distributions of jet observables in QCD at next-to-leading logarithmic accuracy.

E. Iancu, A. H. Mueller

Within the Color Glass formalism, we construct the wavefunction of a high energy onium in the BFKL and large-N_c approximations, and demonstrate the equivalence with the corresponding result in the Color Dipole picture. We propose a simple factorization formula for the elastic scattering between two non-saturated ``color glasses'' in the center-of-ma

Muneyuki Ishida, Shin Ishida

In the covariant level-classification scheme of hadrons based on U(12)SF * O(3,1)L symmetry, the ground state baryons and antibaryons are assigned to the (12 * 12 * 12)Sym = 364-multiplet in the spin-flavor U(12)SF symmetry. This multiplet includes, in addition to the ordinary 56-multiplet of the static SU(6)SF, the extra chiral 56' and 70-multiplets, ca

Muneyuki Ishida, Shin Ishida

In our talk at Nihon university symposium, we have argued that the pipi / Kpi production amplitudes F generally have different structures from those of the pipi / Kpi scattering amplitudes T from a viewpoint of generalized S matrix on the right bases, reflecting the quark-physical picture of strong interactions, and that F should be analyzed independently fr

Muneyuki Ishida, Shin Ishida

Our method of analysis, which led to existence of sigma and kappa mesons, is reviewed and examined from a viewpoint of general S-matrix. It is shown that the method is consistent with the constraints from chiral symmetry and unitarity. Accordingly the long-believed common analyses of pipi (Kpi) scattering and production processes, based on elastic unitarity,

Shin Ishida, Muneyuki Ishida

The essential points and physical backgrounds of the covariant level-classification scheme, recently proposed by us, are reviewed: In this scheme the general composite hadrons are classified as the multiplets with the U(12)SF * O(3,1) symmetry, where U(12)SF supset U(4)D.S. * SU(3)F, and U(4)D.S. is a homogeneous Lorentz transformation group for Dirac spinor

Q. H. Zhang, J. Barrette, C. Gale

We derive the phase space density of bosons from a general boson interferometry formula. We find that the phase space density is connected with the two-particles and the single particle density distribution functions. If the boson density is large, the two particles density distribution function can not be expressed as a product of two single particle densit

James D. Wells

From a theoretical point of view it is not hard to imagine gaugino masses being much lighter than scalar masses. The dominant contributions to gaugino masses are then their anomaly-mediated values. Given current lower bounds on gauginos, which are near the W-mass scale, considering a little hierarchy between weak-scale gauginos and much heavier scalars requi

F. Berruto, R. Narayanan, H. Neuberger

Let B be the largest spacing between adjacent eigenvalues of the Polyakov loop. We propose to employ the distribution of B as an order parameter for the finite temperature phase transition in SU(N) lattice gauge theories. Using smeared links to reduce ultraviolet fluctuations, we carry out a test for the gauge group SU(3).

Julian Rautenberg

Single and double differential cross sections ds/dQ^2, ds/dx, ds/dy and d^2s/dQ^2dx of the inclusive neutral current (NC) measurement from the 98/99 e^-p and the charged current (CC) measurement from the 99/00 e^+p data sets are presented. With the previously published e^+p NC ZEUS measurement xF_3 and xG_3, and with the e^-p CC ZEUS measurement F_2^CC are e

Matthew Wing

The production of charm and beauty quarks in $γγ$ collisions at LEP, $ep$ collisions at HERA and $p \bar{p}$ collisions at the Tevatron is discussed. The comparison with predictions of next-to-leading-order QCD and the issues it raises are detailed. In particular, the strengths and weaknesses of the measurements and predictions are discussed.

Alain Romeyer, Juan De Dios Zornoza Gomez, Ronald Bruijn

The European collaboration ANTARES aims to operate a large neutrino telescope in the Mediterranean Sea, 2400 m deep, 40 km from Toulon (France). Muon neutrinos are detected through the muon produced in charged current interactions in the medium surrounding the detector. The Cherenkov light emitted by the muon is registered by a 3D photomultiplier array. Muon

J. Z. Bai

In a sample of 58 million $J/ψ$ events collected with the BES II detector, the process J/$ψ\toγη_c$ is observed in five decay channels: $η_c \to K^+K^-π^+π^-$, $π^+π^-π^+π^-$, $K^\pm K^0_S π^\mp$ (with $K^0_S\toπ^+π^-$), $ϕϕ$ (with $ϕ\to K^+K^-$) and $p\bar{p}$. From these signals, we determine $Br(J/ψ\toγη_c)\times Br(η_c\to K^+K^-π^+π^-)$ $=(1.5\pm0.2\pm0.

Kazuo Abe

Recent results from BaBar and Belle experiments on $B \bar B$ mixing and $\sin 2ϕ_1$ are presented. Accuracy of $Δm_d$ measurements has reached 1.2%. Higher order effects within the Standard Model or possible new physics effect that might appear in the $B \bar B$ mixing through non-zero $ΔΓ/Γ$, CP violation, or $CPT$ violation have been explored. The BaBar a

K. Mazumdar

The LHC potential for observing a light Higgs boson produced through Weak Boson Fusion mode, ${\rm qq}\to {\rm qqH}$, is presented. For non-hadronic decays modes of the Higgs boson the process is identified with a final state containing two energetic forward-backward jets, separated with a large rapidity and a hadronically quiet central region. The use of th

Grigorii Pivovarov, Sergei Trunov

A new method of hierarchical clustering of graph vertexes is suggested. In the method, the graph partition is determined with an equivalence relation satisfying a recursive definition stating that vertexes are equivalent if the vertexes they point to (or vertexes pointing to them) are equivalent. Iterative application of the partitioning yields a hierarchica

Hong Ma, Tao Pang

Two-species hard-core bosons trapped in a three-dimensional isotropic harmonic potential are studied with the path-integral quantum Monte Carlo simulation. The double condensates show two distinct structures depending on how the external potentials are set. Contrary to the mean-field results, we find that the heavier particles form an outer shell under an id

K. P. Hewaparakrama, N. Mukolobwiez, L. M. Smith, H. E. Jackson

We study the excitonic structure of CdSe/ZnSe self assembled quantum dots (SAQD) by magneto-photoluminescence (PL) spectroscopy. Using fixed 200 nm apertures through a metal film, we are able to probe single narrow (200 micro-eV) spectroscopic lines emitted from CdSe quantum dots at 2K. Using linear polarization analysis of these lines, we find that approxim

A. Mobius, U. K. Roessler

One- to three-dimensional hypercubic lattices half-filled with localized particles interacting via the long-range Coulomb potential are investigated numerically. The temperature dependences of specific heat, mean staggered occupation, and of a generalized susceptibility indicate order-disorder phase transitions in two- and three-dimensional systems. The crit

A. T. Boothroyd, P. G. Freeman, D. Prabhakaran, M. Enderle

We have studied magnetic correlations in several compositions of stripe-ordered La2-xSrxNiO4. In this paper we show how polarized-neutron scattering has helped uncover important features of the magnetic ordering and spin dynamics. In particular, polarization analysis has enabled us (1) to characterize a spin reorientation transition, (2) to identify anisotro

A. T. Boothroyd, P. G. Freeman, D. Prabhakaran, H. Woo

We report neutron scattering measurements of the spectrum of magnetic excitations in the stripe-ordered phase of La2-xSrxNiO4 (x=0.275 and 1/3). The propagating spin excitations follow a similar dispersion relation for the two compositions, but the line widths are broader for x=0.275 than for x=1/3.

Agata Fronczak, Piotr Fronczak, Janusz A. Holyst

The poster presents an analytic formalism describing metric properties of undirected random graphs with arbitrary degree distributions and statistically uncorrelated (i.e. randomly connected) vertices. The formalism allows to calculate the main network characteristics like: the position of the phase transition at which a giant component first forms, the mean

Jesús Casado-Pascual, José Gómez-Ordóñez, Manuel Morillo, Peter Hänggi

An amenable, analytical two-state description of the nonlinear population dynamics of a noisy bistable system driven by a rectangular subthreshold signal is put forward. Explicit expressions for the driven population dynamics, the correlation function (its coherent and incoherent part), the signal-to-noise ratio (SNR) and the Stochastic Resonance (SR) gain a

J. -P. Martikainen, H. Stoof

We examine the effect of the transverse breathing mode on the longitudinal sound propagation in a Bose-Einstein condensate in a one-dimensional optical lattice. In particular, we discuss how the coupling with the transverse breathing mode influences the sound velocity in an optical lattice. Using a variational approach we calculate the dispersion relations f

O. V. Gendelman, A. V. Savin

Heat conduction of one-dimensional chain of equivalent rigid particles in the field of external on-site potential is considered. Zero diameters of the particles correspond to exactly integrable case with divergent heat conduction coefficient. By means of simple analytical model it is demonstrated that for any nonzero particle size the integrability is violat

Christopher R. Ashman, Clemens J. Foerst, Karlheinz Schwarz, Peter E. Bloechl

This paper reports state-of-the-art electronic structure calculations on the deposition of strontium on the technologically relevant, (001) orientated silicon surface. We identified the surface reconstructions from zero to four thirds monolayers and relate them to experimentally reported data. A phase diagram is proposed. We predict phases at 1/6, 1/4, 1/2,

P. F. Gora

We discuss the role of spatial correlations of the noise in the array enhanced stochastic resonance. We show numerically that the noises with negative correlations between different sites lead to significantly larger values of the signal-to-noise ratio than the uncorrelated noises or noises with positive correlations. If the noise is global, the system displ

M. N. Kiselev, K. Kikoin, L. W. Molenkamp

It is shown that the resonance Kondo tunneling through a double quantum dot (DQD) with even occupation and singlet ground state may arise at a strong bias, which compensates the energy of singlet/triplet excitation. Using the renormalization group technique we derive scaling equations and calculate the differential conductance as a function of an auxiliary d

A. Koeder, W. Limmer, S. Frank, W. Schoch

We report on an enhancement of the Curie temperature in GaMnAs/InGaMnAs superlattices grown by low-temperature molecular beam epitaxy, which is due to thin InGaMnAs or InGaAs films embedded into the GaMnAs layers. The pronounced increase of the Curie temperature is strongly correlated to the In concentration in the embedded layers. Curie temperatures up to 1

Maria K. Koleva, L. A. Petrov

It is found out that there are physical effects, typical of small metal clusters deposited on a non-adsorbing support, that cause a difference between the adsorption properties of sites at the metal cluster surface and those of sites at the boundary of metal-support. This difference gives rise to an extra band in the IR spectra of the adsorbate whose major p

M. D. Haw

We study the flow of model experimental hard sphere colloidal suspensions at high volume fraction $Φ$ driven through a constriction by a pressure gradient. Above a particle-size dependent limit $Φ_0$, direct microscopic observations demonstrate jamming and unjamming--conversion of fluid to solid and vice versa--during flow. We show that such a jamming flow p

Michael W. Deem, Ha Youn Lee

We introduce a model of protein evolution to explain limitations in the immune system response to vaccination and disease. The phenomenon of original antigenic sin, wherein vaccination creates memory sequences that can \emph{increase} susceptibility to future exposures to the same disease, is explained as stemming from localization of the immune system respo

Ligang Chen, Michael W. Deem

How topological defects affect the dynamics of particles hopping between lattice sites of a distorted, two-dimensional crystal is addressed. Perturbation theory and numerical simulations show that weak, short-ranged topological disorder leads to a finite reduction of the diffusion coefficient. Renormalization group theory and numerical simulations suggest th

A. L. Efros, A. L. Pokrovsky

We show that a two-dimensional photonic crystal (PC) made from a non-magnetic dielectric is a left-handed material in the sense defined by Veselago. Namely, it has negative values of both the electric permittivity $ε$ and the magnetic permeability $μ$ in some frequency range. This follows from a recently proven general theorem. The negative values of $ε$ and

Hoang Nam Nhat

This paper presents the bond valence calculation for several perovskite systems and describes the evidences for a valence charge transfer process in these compounds. The reviewing of the crystal structures of La1-xPbxMnO3 (x=0.1-0.5), La0.6Sr0.4-xTixMnO3 (x=0.0-0.25) and La1-xSrxCoO3 (x=0.1-0.5) is also presented. On the basis of testing samples, the distrib

P. Amengual, A. Allison, R. Toral, D. Abbott

Parrondo's games manifest the apparent paradox where losing strategies can be combined to win and have generated significant multidisciplinary interest in the literature. Here we review two recent approaches, based on the Fokker-Planck equation, that rigorously establish the connection between Parrondo's games and a physical model known as the flashi

A. B. Harris, Amnon Aharony, O. Entin-Wohlman, I. Ya. Korenblit

The Kugel-Khomskii (KK) Hamiltonian for the titanates describes spin and orbital superexchange interactions between $d^1$ ions in an ideal perovskite structure in which the three $t_{2g}$ orbitals are degenerate in energy and electron hopping is constrained by cubic site symmetry. In this paper we implement a variational approach to mean-field theory in whic

C. A. Regal, M. Greiner, D. S. Jin

We report a dramatic magnetic field dependence in the lifetime of trapped, ultracold diatomic molecules created through an s-wave Feshbach resonance in 40K. The molecule lifetime increases from less than 1 ms away from the Feshbach resonance to greater than 100 ms near resonance. We also have measured the trapped atom lifetime as a function of magnetic field

Wlodzimierz Kozlowski

One reports computational study revealing a set of general requirements, fulfilling of which would allow employing changes in ambient conditions to regulate accomplishing the collective outcome of emerging active network patterns in an ensemble of a moderate number of finite discrete systems. The patterns within all these component systems emerge out of rand