May 2006 arXiv papers — page 41

Craig Westerland

From an operad C with an action of a group G, we construct new operads using the homotopy fixed point and orbit spectra. These new operads are shown to be equivalent when the generalized G-Tate cohomology of C is trivial. Applying this theory to the little disk operad C_2 (which is an S^1 operad) we obtain variations on Getzler's gravity operad, which we

Dominic W. Berry, A. I. Lvovsky, Barry C. Sanders

We analyze the problem of increasing the efficiency of single-photon sources or single-rail photonic qubits via linear optical processing and destructive conditional measurements. In contrast to previous work we allow for the use of coherent states and do not limit to photon-counting measurements. We conjecture that it is not possible to increase the efficie

Sara Pellegrini, Ryan E. Warburton, Lionel J. J. Tan, Jo Shien Ng

This paper describes the design, fabrication, and performance of planar-geometry InGaAs-InP devices which were specifically developed for single-photon detection at a wavelength of 1550 nm. General performance issues such as dark count rate, single-photon detection efficiency, afterpulsing, and jitter are described.

K. Choy, G. Passante, D. Ahrensmeier, M. E. Carrington

The goal of this paper is to study the effect of entanglement on the running time of a quantum computation. Adiabatic quantum computation is suited to this kind of study, since it allows us to explicitly calculate the time evolution of the entanglement throughout the calculation. On the other hand however, the adiabatic formalism makes it impossible to study

Michael Silberstein, Michael Cifone, W. M. Stuckey

We use a new distinctly "geometrical" interpretation of non-relativistic quantum mechanics (NRQM) to argue for the fundamentality of the 4D blockworld ontology. Our interpretation rests on two formal results: Kaiser, Bohr & Ulfbeck and Anandan showed independently that the Heisenberg commutation relations of NRQM follow from the relativity of simulta

T. Gaebel, M. Domhan, I. Popa, C. Wittmann

Coherent coupling between single quantum objects is at the heart of modern quantum physics. When coupling is strong enough to prevail over decoherence, it can be used for the engineering of correlated quantum states. Especially for solid-state systems, control of quantum correlations has attracted widespread attention because of applications in quantum compu

M. V. S. Bonanca, M. A. M. de Aguiar

We study the effects of dissipation and decoherence induced on a harmonic oscillator by the coupling to a chaotic system with two degrees of freedom. Using the Feynman-Vernon approach and treating the chaotic system semiclassically we show that the effects of the low dimensional chaotic environment are in many ways similar to those produced by thermal baths.

Sangchul Oh, Jaewan Kim

We study a system of two qubits interacting with a common environment, described by a two-spin boson model. We demonstrate two competing roles of the environment: inducing entanglement between the two qubits and making them decoherent. For the environment of a single harmonic oscillator, if its frequency is commensurate with the induced two-qubit coupling st

Jorge F. Mejias, Joaquin J. Torres

Using a realistic model of activity dependent dynamical synapses and a standard integrate and fire neuron model we study, both analytically and numerically, the conditions in which a postsynaptic neuron efficiently detects temporal coincidences of spikes arriving at certain frequency from N different afferents. We extend a previous work that only considers s

Willy Valdivia-Granda, Christopher Dwan

The extraction of information form high-throughput experiments is a key aspect of modern biology. Early in the development of microarray technology, researchers recognized that the size of the datasets and the limitations of both computational and visualization techniques restricted their ability to find the biological meaning hidden in the data. In addition

Neil F. Johnson, Mike Spagat, Jorge A. Restrepo, Oscar Becerra

We report a remarkable universality in the patterns of violence arising in three high-profile ongoing wars, and in global terrorism. Our results suggest that these quite different conflict arenas currently feature a common type of enemy, i.e. the various insurgent forces are beginning to operate in a similar way regardless of their underlying ideologies, mot

T. M. Fortier, Y. Le Coq, J. E. Stalnaker, D. Ortega

We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is pred

S. Pittalis, S. Kurth, E. K. U. Gross

The problem of degenerate ground states of open-shell atoms is investigated in spin-restricted and unrestricted density functional theory using the exact exchange energy functional. For the spin-unrestricted case, spurious energy splittings of the order of 2 to 3 kcal/mol are found for atoms of the second and third period which is larger than the splittings

Andrea Baronchelli, Emanuele Caglioti, Vittorio Loreto

Physics concepts have often been borrowed and independently developed by other fields of science. In this perspective a significant example is that of entropy in Information Theory. The aim of this paper is to provide a short and pedagogical introduction to the use of data compression techniques for the estimate of entropy and other relevant quantities in In

Tomislav Ivezic

In this paper we present a new geometric formulation (Clifford algebra formalism) of the field equations, which is independent of the reference frame and of the chosen system of coordinates in it. This formulation deals with the complex 1-vector $Ψ=E-icB$ ($i$ is the unit imaginary), which is four-dimensional (4D) geometric generalization of Majorana's c

Petter Holme

The surrounding of a vertex in a network can be more or less symmetric. We derive measures of a specific kind of symmetry of a vertex which we call degree symmetry -- the property that many paths going out from a vertex have overlapping degree sequences. These measures are evaluated on artificial and real networks. Specifically we consider vertices in the hu

Daniel B. Stouffer, R. Dean Malmgren, Luis A. N. Amaral

Following up on Barabasi's recent letter to Nature [435, 207--211 (2005)], we systematically investigate the time series of e-mail usage for 3,188 users at a university. We focus on two quantities for each user: the time interval between consecutively sent e-mails (interevent time), and the time interval between when a user sends an e-mail and when a rec

Yan Zhao, Pavel A. Belov, Yang Hao

In this paper, a spatially dispersive finite-difference time-domain (FDTD) method to model wire media is developed and validated. Sub-wavelength imaging properties of the finite wire medium slabs are examined. It is demonstrated that the slab with its thickness equal to an integer number of half-wavelengths is capable of transporting images with sub-waveleng

Hyung-Su Chon, Gisung Park, Sang-Bum Lee, Seokchan Yoon

We studied both theoretically and experimentally the intensity distribution of a Gaussian laser beam when it was focussed by an objective lens with its numerical-aperture (NA) up to 0.95. Approximate formulae for full widths at half maximum (FWHM) of the intensity distribution at focus were derived for very large and very small initial beam waists with respe

Filippo Caruso, Sergio Vinciguerra, Vito Latora, Andrea Rapisarda

We present a multifractal analysis of Mount St. Helens seismic activity during 1980-2002. The seismic time distribution is studied in relation to the eruptive activity, mainly marked by the 1980 major explosive eruptions and by the 1980-1986 dome building eruptions. The spectrum of the generalized fractal dimensions, i.e. Dq vs q, extracted from the data, al

M. Baldo, E. E. Saperstein, S. V. Tolokonnikov

The influence of the boundary conditions used in the Wigner-Seitz (WS) approximation applied to the neutron star inner crust is examined. The generalized energy functional method which includes the neutron and proton pairing correlations is used. Predictions of two versions of the boundary conditions are compared with each other. The uncertainties in the equ

N. Angelov, F. Balestra, Yu. Batusov, A. Bianconi

During the runs of the PS 179 experiment at LEAR of CERN, we photographed an event of antiproton-Ne absorption, with a complete pi+ -> mu+ ->e+ chain. From the vertex of the reaction a very slow energy pi+ was emitted. The pi+ decays into a mu+ and subsequently the mu+ decays into a positron. At the first decay vertex a muon neutrino was emitted and at the s

Antonio Politi, Francesco Ginelli, Serhiy Yanchuk, Yuri Maistrenko

The goal of this paper is twofold. In the first part we discuss a general approach to determine Lyapunov exponents from ensemble- rather than time-averages. The approach passes through the identification of locally stable and unstable manifolds (the Lyapunov vectors), thereby revealing an analogy with generalized synchronization. The method is then applied t

Walter Riofrio, Luis Angel Aguilar

It is reported a great variety of functional actions of GABA in auditory system. Although many studies reports the presence and distribution of GABA receptors; nevertheless, the studies about the inhibitory GABA-dependent neurons distribution in the Inferior Culliculus are scarce. We are interested in studies on the role played by GABAergic neurons in the ac

Rodislav Driben, Boris A Malomed, Pak L Chu

We consider dynamics of spatial beams in a dual-channel waveguide with competing cubic and quintic (CQ) nonlinearities. Gradually increasing the power in the input channel, we identify four different regimes of the pulses coupling into the cross channel, which alternate three times between full pass and full stop, thus suggesting three realizations of switch

M Bertola

We consider the biorthogonal polynomials associated to the two-matrix model where the eigenvalue distribution has potentials V_1,V_2 with arbitrary rational derivative and whose supports are constrained on an arbitrary union of intervals (hard-edges). We show that these polynomials satisfy certain recurrence relations with a number of terms d_i depending on

Eldad Bettelheim, Oded Agam, Anton Zabrodin, Paul Wiegmann

We study a family of solutions to the Saffman-Taylor problem with zero surface tension at a critical regime. In this regime, the interface develops a thin singular finger. The flow of an isolated finger is given by the Whitham equations for the KdV integrable hierarchy. We show that the flow describing bubble break-off is identical to the Gurevich-Pitaevsky

Roldao da Rocha, Jayme Vaz

Z2-gradings of Clifford algebras are reviewed and we shall be concerned with an alpha-grading based on the structure of inner automorphisms, which is closely related to the spacetime splitting, if we consider the standard conjugation map automorphism by an arbitrary, but fixed, splitting vector. After briefly sketching the orthogonal and parallel components

Robert Sims

We consider compactly supported perturbations of periodic Sturm-Liouville equations. In this context, one can use the Floquet solutions of the periodic background to define scattering coefficients. We prove that if the reflection coefficient is identically zero, then the operators corresponding to the periodic and perturbed equations, respectively, are unita

Rowan Killip, Robert Sims

We consider solutions of the one-dimensional equation $-u'' +(Q+ λV) u = 0$ where $Q: \mathbb{R} \to \mathbb{R}$ is locally integrable, $V : \mathbb{R} \to \mathbb{R}$ is integrable with supp$(V) \subset [0,1]$, and $λ\in \mathbb{R}$ is a coupling constant. Given a family of solutions $\{u_λ \}_{λ\in \mathbb{R}}$ which satisfy $u_λ(x) = u_0(x)$ for a

Antonio Laface

Let S be a smooth algebraic surface satisfying the following property: H^i(\oc_S(C))=0 (i=1,2) for any irreducible and reduced curve C of S. The aim of this paper is to provide a characterization of special linear systems on S which are singular along a set of double points in general position. As an application, the dimension of such systems is evaluated in

Antonio Laface, Luca Ugaglia

In this note we deal with rational curves in P^3 which are images of a line by means of a finite sequence of cubo-cubic Cremona transformations. We prove that these curves can always be obtained applying to the line a sequence of such transformations increasing at each step the degree of the curve. As a corollary we get a result about curves that can give sp

Daniel J. Bates, Andrew J. Sommese, Charles W. Wampler

A path tracking algorithm that adaptively adjusts precision is presented. By adjusting the level of precision in accordance with the numerical conditioning of the path, the algorithm achieves high reliability with less computational cost than would be incurred by raising precision across the board. We develop simple rules for adjusting precision and show how

Vladimir Potapov, Denis Krotov

The asymptotic form of the number of n-quasigroups of order 4 is $3^{n+1} 2^{2^n +1} (1+o(1))$. Keywords: n-quasigroups, MDS codes, decomposability, reducibility.

Catharina Stroppel

We study projective functors (i.e. direct summands of compositions of translations through walls) for parabolic versions of $\cO$ as well as for integral regular blocks outside the critical hyperplanes in the symmetrizable Kac-Moody case. It turns out that in both situations the functors are completely determined by their restriction to the additive category

Sixin Zeng

In this note we will study the Hilbert 12th problem for a primitive CM field, and the corresponding Stark conjectures. Using the idea of Mirror Symmetry, we will show how to generate all the class fields of a given primitive CM field, thus complete the work of Shimura- Taniyama-Weil.

Alina Marian, Dragos Oprea

We prove that the strange duality conjecture of Beauville-Donagi-Tu holds for all curves. We establish first a more extended rank-level duality, interesting in its own right, from which the standard rank-level duality follows by restriction.

Laurent Charles, San Vu Ngoc

This article gives a simple treatment of the quantum Birkhoff normal form for semiclassical pseudo-differential operators with smooth coefficients. The normal form is applied to describe the discrete spectrum in a generalised non-degenerate potential well, yielding uniform estimates in the energy $E$. This permits a detailed study of the spectrum in various

Valery A. Lunts, Dmitri Orlov

We develop a general deformation theory of objects in homotopy and derived categories of DG categories. The main result is a general pro-representability theorem for the corresponding deformation functor.

Ye. M. Smagina

The present book is the first publication in English considered the modern problems of control theory and analysis connected with a concept of system zeros. The previous book by Ye.M. Smagina (1990) had been written in Russian and it is inaccessible to English speaking researchers. The purpose of the offered book is to systematize and consistently to state b

Alice Fialowski, Marc de Montigny

In this contributed presentation, we discuss and compare the mutually opposite procedures of deformations and contractions of Lie algebras. We suggest that with appropriate combinations of both procedures one may construct new Lie algebras. We first discuss low-dimensional Lie algebras and illustrate thereby that whereas for every contraction there exists a

K. D. Elworthy, Xue-Mei Li

We consider versions of Malliavin calculus on path spaces of compact manifolds with diffusion measures, defining Gross-Sobolev spaces of differentiable functions and proving their intertwining with solution maps, I, of certain stochastic differential equations. This is shown to shed light on fundamental uniqueness questions for this calculus including unique

A. Campillo, F. Delgado, S. M. Gusein-Zade

Let a finite group $G$ act on the complex plane $({\Bbb C}^2, 0)$. We consider multi-index filtrations on the spaces of germs of holomorphic functions of two variables equivariant with respect to 1-dimensional representations of the group $G$ defined by components of a modification of the complex plane ${\Bbb C}^2$ at the origin or by branches of a $G$-invar

Kieran G. O'Grady

A locally complete family of projective symplectic 4-folds is provided by natural double covers of Eisenbud-Popescu-Walter (EPW) sextic hypersurfaces in projective 5-space. The dual of an EPW sextic is another EPW sextic, thus to a double EPW sextic X we may associate a "dual" double EPW sextic X^{\vee}. We show how to obtain the Hodge structure on H

Daniel Cranston, I. Hal Sudborough, Douglas B. West

We consider the problem of determining the maximum number of moves required to sort a permutation of $[n]$ using cut-and-paste operations, in which a segment is cut out and then pasted into the remaining string, possibly reversed. We give short proofs that every permutation of $[n]$ can be transformed to the identity in at most $\flr{2n/3}$ such moves and th

Georgi Ganchev, Vesselka Mihova

Using as an underlying manifold an alpha-Sasakian manifold we introduce warped product Kaehler manifolds. We prove that if the underlying manifold is an alpha-Sasakian space form, then the corresponding Kaehler manifold is of quasi-constant holomorphic sectional curvatures with special distribution. Conversely, we prove that any Kaehler manifold of quasi-con

A. M. Grundland, M. Y. Mo

The objective of this paper is to present some geometric aspects of surfaces associated with theta function solutions of the periodic 2D-Toda lattice. For this purpose we identify the $(N^2-1)$-dimensional Euclidean space with the ${\frak su}(N)$ algebra which allows us to construct the generalized Weierstrass formula for immersion for such surfaces. The ele

Karsten Grove, Krishnan Shankar, Wolfgang Ziller

The known manifolds of positive sectional curvature are either homogeneous spaces or biquotients, i.e. quotients of a compact Lie group by a group acting on the left and right simultaneously. The full isometry group of the homogeneous metrics of positive curvature were determined by K.Shankar. Here we determine the isometry group of some of the biquotients d

A. Degtyarev, T. Ekedahl, I. Itenberg, B. Shapiro

We show that if a meromorphic function of degree at most four on a real algebraic curve of an arbitrary genus has only real critical points then it is conjugate to a real meromorphic function after a suitable projective automorphism of the image.

Martin Dyer, Leslie Ann Goldberg, Mark Jerrum, Russell Martin

This is an expository paper, focussing on the following scenario. We have two Markov chains, $\mathcal {M}$ and $\mathcal {M}'$. By some means, we have obtained a bound on the mixing time of $\mathcal {M}'$. We wish to compare $\mathcal {M}$ with $\mathcal {M}'$ in order to derive a corresponding bound on the mixing time of $\mathcal {M}$. We inv

Guangcun Lu

In this paper we give concrete estimations for the pseudo symplectic capacities of toric manifolds in combinatorial data. Some examples are given to show that our estimates can compute their pseudo symplectic capacities. As applications we also estimate the symplectic capacities of the polygon spaces. Other related results are impacts of symplectic blow-up o

B. Altschul

We analyze Lorentz violations in the bosonic sector of a Yukawa-type quantum field theory. The nonrelativistic potential may be determined to all orders in the Lorentz violation, and we find that only specific types of modifications to the normal Yukawa potential can be generated. The influence of this modified potential on scattering and bounds states is ca

Alberto Enciso, Alexios P. Polychronakos

We derive the phase space particle density operator in the 'droplet' picture of bosonization in terms of the boundary operator. We demonstrate that it satisfies the correct algebra and acts on the proper Hilbert space describing the underlying fermion system, and therefore it can be used to bosonize any hamiltonian or related operator. As a demonstra

Dmitriy Belov, Gregory W. Moore

We revisit the construction of self-dual field theory in 4l+2 dimensions using Chern-Simons theory in 4l+3 dimensions, building on the work of Witten. Careful quantization of the Chern-Simons theory reveals all the topological subtleties associated with the self-dual partition function, including the generalization of the choice of spin structure needed to d

J. A. Gracey

We review the techniques used to renormalize quantum field theories at several loop orders. This includes the techniques to systematically extract the infinities in a Feynman integral and the implementation of the algorithm within computer algebra. To illustrate the method we discuss the renormalization of phi^4 theory and QCD including the application of th

B. Bellazzini, M. Mintchev

We construct canonical quantum fields which propagate on a star graph modeling a quantum wire. The construction uses a deformation of the algebra of canonical commutation relations, encoding the interaction in the vertex of the graph. We discuss in this framework the Casimir effect and derive the correction to the Stefan-Boltzmann law induced by the vertex i

Olaf Lechtenfeld

These lectures deal mainly with solitons in three-dimensional Moyal-deformed sigma models. The topics are: static and moving (multi-)solitons of the (integrable) Ward sigma model, with space-space and time-space noncommutativity, their scattering, moduli space dynamics, stability and dimensional reduction, including an integrable deformation of the sine-Gord

Enrique Álvarez, Antón F. Faedo

The contents of this paper have been incorporated in the new version of hep-th/0602150.

Andrew G. Cohen, Sheldon L. Glashow

We explore implications for neutrino physics of Very Special Relativity (VSR), wherein the symmetry group of nature includes only a 4-parameter subgroup of the Lorentz group. VSR can provide a natural origin to lepton-number conserving neutrino masses without need for sterile (right-handed) states. Neutrinoless double beta decay is forbidden if VSR is solely

B. M. Waugh, H. Jung, A. Buckley, L. Lonnblad

A common problem in particle physics is the requirement to reproduce comparisons between data and theory when the theory is a (general purpose) Monte Carlo simulation and the data are measurements of final state observables in high energy collisions. The complexity of the experiments, the obervables and the models all contribute to making this a highly non-t

D0 Collaboration, V. Abazov

We present a search for supersymmetry in the R-parity violating resonant production and decay of smuons and muon-sneutrinos in the channels smuon->neutralino_1 muon, smuon->neutralino_2 muon, and muon-sneutrino->chargino muon. We analyzed 0.38 fb^-1 of integrated luminosity collected between April 2002 and August 2004 with the D0 detector at the Fermilab Tev

A. López-Ortega

We extensively study the exact solutions of the massless Dirac equation in 3D de Sitter spacetime that we published recently. Using the Newman-Penrose formalism, we find exact solutions of the equations of motion for the massless classical fields of spin s=1/2,1,2 and to the massive Dirac equation in 4D de Sitter metric. Employing these solutions, we analyze

Di Wu, Predrag Spasojevic

Motivated by the problem of reducing the peak to average power ratio (PAPR) of transmitted signals, we consider a design of complementary set matrices whose column sequences satisfy a correlation constraint. The design algorithm recursively builds a collection of $2^{t+1}$ mutually orthogonal (MO) complementary set matrices starting from a companion pair of

Marcus Hutter

Solomonoff completed the Bayesian framework by providing a rigorous, unique, formal, and universal choice for the model class and the prior. We discuss in breadth how and in which sense universal (non-i.i.d.) sequence prediction solves various (philosophical) problems of traditional Bayesian sequence prediction. We show that Solomonoff's model possesses

K. S. D. Beach, A. W. Sandvik

In a system with an even number of SU(2) spins, there is an overcomplete set of states--consisting of all possible pairings of the spins into valence bonds--that spans the S=0 Hilbert subspace. Operator expectation values in this basis are related to the properties of the closed loops that are formed by the overlap of valence bond states. We construct a gene

D. V. Evtushinsky, A. A. Kordyuk, S. V. Borisenko, V. B. Zabolotnyy

Fitting the momentum distribution photoemission spectra to the Voigt profile appears to be a robust procedure to purify the interaction effects from the experimental resolution. In application to Bi-2212 high-Tc cuprates, the procedure reveals the true scattering rate at low binding energies and temperatures, and, consequently, the true value of the elastic

Michael Köhl, Kenneth Günter, Thilo Stöferle, Henning Moritz

We report on the realization of a strongly interacting quantum degenerate gas of fermionic atoms in a three-dimensional optical lattice. We prepare a band-insulating state for a two-component Fermi gas with one atom per spin state per lattice site. Using a Feshbach resonance, we induce strong interactions between the atoms. When sweeping the magnetic field f

F. P. M. dos Santos, R. Donangelo, S. R. Souza

Stochastic models for the development of cracks in 1 and 2 dimensional objects are presented. In one dimension, we focus on particular scenarios for interacting and non-interacting fragments during the breakup process. For two dimensional objects, we consider only non-interacting fragments, but analyze isotropic and anisotropic development of fissures. Analy

Nikolay Prokof'ev, Philip Stamp

The common perception is that strong coupling to the environment will always render the evolution of the system density matrix quasi-classical (in fact, diffusive) in the long time limit. We present here a counter-example, in which a particle makes quantum transitions between the sites of a d-dimensional hypercubic lattice whilst strongly coupled to a bath o

A. Emperador, E. Lipparini, Ll. Serra

We calculate ground state energies in the Brueckner-Hartree-Fock theory for $N$ electrons (with $N\le 20$) confined to a circular quantum dot and in presence of a static magnetic field. Comparison with the predictions of Hartree-Fock, local-spin-density and exact configuration-interaction theories is made. We find that the correlations taken into account in

Marini Bettolo Marconi Umberto, Tarazona Pedro

We consider the properties of a one dimensional fluid of brownian inertial hard-core particles, whose microscopic dynamics is partially damped by a heat-bath. Direct interactions among the particles are represented as binary, instantaneous elastic collisions. Collisions with the heath bath are accounted for by a Fokker-Planck collision operator, whereas dire

Jing-Dong Bao, Yi-Zhong Zhuo, Fernando A. Oliveira, Peter Hänggi

Nonergodic Brownian motion is elucidated within the framework of the generalized Langevin equation. For thermal noise yielding either a vanishing or a divergent zero-frequency friction strength, the non-Markovian Browninan dynamics exhibits a riveting, anomalous diffusion behavior being characterized by a ballistic or possibly also a localized dynamics. As a

Samuele Bissola, Alberto Parola

We investigate the nature of the ground state of the one-dimensional t-J model coupled to adiabatic phonons by use of the Lanczos technique at quarter filling. Due to the interplay between electron-electron and electron-phonon interactions, the model undergoes instabilities toward the formation of lattice and charge modulations. Moderate on-site and intra-si

Cyril Falvo, Vincent Pouthier, J. C. Eilbeck

By using a Generalized Hubbard model for bosons, the energy transfer in a nonlinear quantum lattice is studied, with special emphasis on the interplay between local and nonlocal nonlinearity. For a strong local nonlinearity, it is shown that the creation of v quanta on one site excites a soliton band formed by bound states involving v quanta trapped on the s

Alan R. Denton

The phase behavior of charge-stabilized colloidal suspensions is modeled by a combination of response theory for electrostatic interparticle interactions and variational theory for free energies. Integrating out degrees of freedom of the microions (counterions, salt ions), the macroion-microion mixture is mapped onto a one-component system governed by effect

Massimo Campostrini, Martin Hasenbusch, Andrea Pelissetto, Ettore Vicari

We improve the theoretical estimates of the critical exponents for the three-dimensional XY universality class, which apply to the superfluid transition in He4 along the lambda-line of its phase diagram. We obtain the estimates alpha=-0.0151(3), nu=0.6717(1), eta=0.0381(2), gamma=1.3178(2), beta=0.3486(1), and delta=4.780(1). Our results are obtained by fini

Claudio J. Tessone, Claudio R. Mirasso, Raul Toral, James D. Gunton

We present conclusive evidence showing that different sources of diversity, such as those represented by quenched disorder or noise, can induce a resonant collective behavior in an ensemble of coupled bistable or excitable systems. Our analytical and numerical results show that when such systems are subjected to an external subthreshold signal, their respons

G Kandasamy, C J Wellard, L C L Hollenberg

We theoretically investigate cross-talk in hyperfine gate control of donor-qubit quantum computer architectures, in particular the Kane proposal. By numerically solving the Poisson and Schrödinger equations for the gated donor system, we calculate the change in hyperfine coupling and thus the error in spin-rotation for the donor nuclear-electron spin system,

J. Y. Jo, D. J. Kim, Y. S. Kim, S. -B. Choe

A long standing problem of domain switching process - how domains nucleate - is examined in ultrathin ferroelectric films. We demonstrate that the large depolarization fields in ultrathin films could significantly lower the nucleation energy barrier (U*) to a level comparable to thermal energy (kBT), resulting in power-law like polarization decay behaviors.

I. I. Lyapilin, A. E. Patrakov

The response of an electron system to a DC measurement electric field has been investigated in the case when the system is driven out of the equilibrium by the magnetic ultra-high frequency field that leads to combined transitions. The discussed model includes contributions from Landau quantization and from microwave irradiation. Impurity centers are conside

Nils Hasselmann, Peter Kopietz

We study spin-wave interactions in quantum antiferromagnets by expressing the usual magnon annihilation and creation operators in terms of Hermitian field operators representing transverse staggered and ferromagnetic spin fluctuations. In this parameterization, which was anticipated by Anderson in 1952, the two-body interaction vertex between staggered spin

Steffen Krusch, Paul Sutcliffe

We study the motion of vortices in the planar Ginzburg-Landau model with Schrodinger-Chern-Simons dynamics. We compare the moduli space approximation with the results of numerical simulations of the full field theory and find that there is agreement if the coupling constant is very close to the critical value separating Type I from Type II superconductors. H

Matthias Eschrig

We review recent experimental and theoretical results on the interaction between single-particle excitations and collective spin excitations in the superconducting state of high-Tc cuprates. We concentrate on the traces, that sharp features in the magnetic excitation spectrum imprint in the spectra of single-particle excitations. The review gives in the firs

S. V. Zhukovsky, V. M. Galynsky

Influence of material anisotropy and gyrotropy on optical properties of fractal multilayer nanostructures is theoretically investigated. Gyrotropy is found to uniformly rotate the output polarization for bi-isotropic multilayers of arbitrary geometrical structure without any changes in transmission spectra. When introduced in a polarization splitter based on

Valery V. Kravtsov

Presently unaccounted but quite probable "chemical factor" may be responsible for the formation of old metal-rich globular clusters (MRGCs) in spheroids, as well as of their conterparts, young (intermediate-age) massive star clusters (MSCs) in irregulars. Their formation presumably occurs at the same stage of the host galaxies' chemical evolution

Peter W. A. Roming, Keith O. Mason

The Swift Ultra-Violet/Optical Telescope (UVOT) has performed extensive follow-up on 71 Swift Burst Alert Telescope triggered gamma-ray bursts (GRBs) in its first ten months of operations. In this paper, we discuss some of the UV and optical properties of UVOT detected afterglows such as XRF 050406, the bright GRB 050525A, the high redshift GRB 050730, the e

Jonay I. Gonzalez Hernandez, Rafael Rebolo, Garik Israelian, Emilios T. Harlaftis

We present medium-resolution optical spectra of the secondary star in the high Galactic latitude black hole X-ray binary XTE J1118+480 and determine the abundance of Mg, Al, Ca, Fe, and Ni in its atmosphere. For all the elements investigated we find supersolar abundances; thus, we reject the hypothesis that the black hole came from the direct collapse of an

F. Ozel

The interiors of neutron stars contain matter at very high densities, in a state that differs greatly from those found in the early universe or achieved at terrestrial experiments. Matter in these conditions can only be probed through astrophysical observations that measure the mass and radius of neutron stars with sufficient precision. Here I report for the

Latchezar Benatov, Ken Rines, Priyamvada Natarajan, Andrey Kravtsov

In this paper we examine how well galaxies and intra-cluster gas trace the gravitational potential of clusters. Utilizing mass profiles derived from gravitational lensing and X-ray observations, coupled with measured galaxy velocities, we solve for the velocity anisotropy parameter using the anisotropic Jeans equation. This is done for five clusters, three a

D. D. Proctor

Pattern recognition techniques have been used with increasing success for coping with the tremendous amounts of data being generated by automated surveys. Usually this process involves construction of training sets, the typical examples of data with known classifications. Given a feature set, along with the training set, statistical methods can be employed t

J C Jackson, Marina Dodgson

In homogeneous isotropic cosmological models the angular size theta of a standard measuring rod changes with redshift z in a manner that depends upon the parameters of the model. It has been argued that as a population ultracompact (milliarcsecond) radio sources measured by very long-baseline interferometry (VLBI) do not evolve with cosmic epoch, and thus co

F. Sidoli, L. J. Smith, P. A. Crowther

We present new high spectral resolution VLT/UVES spectroscopy and archival HST/STIS imaging and spectroscopy of the giant HII region Tol89 in NGC5398. From optical and UV HST images, we find that the star-forming complex as a whole contains at least seven young compact massive clusters. We resolve the two brightest optical knots, A and B, into five individua

M. D. Johnson, J. S. Levitt, R. B. C. Henry, K. B. Kwitter

We present ELSA, a new modular software package, written in C, to analyze and manage spectroscopic data from emission-line objects. In addition to calculating plasma diagnostics and abundances from nebular emission lines, the software provides a number of convenient features including the ability to ingest logs produced by IRAF's splot task, to semi-auto

Ricardo R. Munoz, Steven R. Majewski, Simone Zaggia, William E. Kunkel

A new large-area Washington M,T_2+DDO51 filter survey of more than 10 deg^2 around the Carina dSph galaxy reveals a spectroscopically confirmed power law radial density "break" population of Carina giant stars extending several degrees beyond the central King profile. Magellan telescope MIKE spectroscopy establishes the existence of Carina stars to a

Albert Zijlstra

Mass loss on the Asymptotic Giant Branch provides the origin of planetary nebulae. This paper reviews several relevant aspects of AGB evolution: pulsation properties, mass loss formalisms and time variable mass loss, evidence for asymmetries on the AGB, binarity, ISM interaction, and mass loss at low metallicity. There is growing evidence that mass loss on t

Scott J. Wolk, Bradley D. Spitzbart, Tyler L. Bourke, Joao Alves

We report on results of a 96.7 ks Chandra observation of one of the youngest, most embedded and massive young stellar clusters studied in X-rays - RCW 38. We detect 460 sources in the field of which 360 are confirmed to be associated with the RCW~38 cluster. The cluster members range in luminosity from ~10^30 ergs s^-1 to 10^33.5 ergs s^-1. Over ten percent

L. J. Smith, M. S. Westmoquette, J. S. Gallagher, R. W. O'Connell

We present optical spectroscopy obtained with the Space Telescope Imaging Spectrograph (STIS) of five young massive star clusters in the starburst galaxy M82. A detailed analysis is performed for one cluster `M82-A1' and its immediate environment in the starburst core. From HST archive images, we find that it is elliptical with an effective radius of 3.0

Zdenek Stuchlik, Petr Slany

Perfect fluid tori with uniform distribution of the specific angular momentum orbiting the Kerr-de Sitter black holes or naked singularities are studied. Closed equipotential surfaces corresponding to stationary toroidal discs are allowed only in the spacetimes admitting stable circular geodesics. The last closed surface crosses itself in the cusp(s) enablin

Zdenek Stuchlik, Petr Slany, Gabriel Torok

We show that in the equatorial plane of marginally stable thick discs (with uniformly distributed specific angular momentum the orbital velocity relative to the locally non-rotating frames (LNRF) has a positive radial gradient in the vicinity of black holes with spin a>0.99979. The change of sign of the velocity gradient occurs just above the center of the t

W. H. T. Vlemmings, P. J. Diamond, H. Imai

We present the first direct measurements of the magnetic field strength and direction in a collimated jet from an evolved star on its way to become a planetary nebula. Very Long Baseline Array (VLBA) observations of the linear and circular polarization of the water masers in the collimated jet of W43A reveal a strong toroidal magnetic field, indicating that