November 2006 arXiv papers — page 2

Chang-shui Yu, He-shan Song

In this paper, an intuitive approach is employed to generalize the full separability criterion of tripartite quantum states of qubits to the higher-dimensional systems (Phys. Rev. A \textbf{72}, 022333 (2005)). A distinct characteristic of the present generalization is that less restrictive conditions are needed to characterize the properties of full separab

Luis E. E. de Araujo, Silvania A. Carvalho, Luciano S. Soares, Antonio A. Soares

Electromagnetically induced transparency and coherent population trapping were observed in a hot (1000 K) calcium vapor embedded into an electrical gas discharge. Unexpectedly large transparencies (of up to 70%) were observed under very unfavorable conditions: probe wavelength shorter than the coupling wavelength, and coupling Rabi frequency significantly sm

Hiroshi Nagaoka

We prove the converse part of the theorem for quantum Hoeffding bound on the asymptotics of quantum hypothesis testing, essentially based on an argument developed by Nussbaum and Szkola in proving the converse part of the quantum Chernoff bound. Our result complements Hayashi's proof of the direct (achievability) part of the theorem, so that the quantum

Omar Mustafa, S. Habib Mazharimousavi

Jia and Dutra (J. Phys. A: Math. Gen. 39 (2006) 11877) have considered the one-dimensional non-Hermitian complexified potentials with real spectra in the context of position-dependent mass in Dirac equation. In their second example, a smooth step shape mass distribution is considered and a non-Hermitian non - PT- symmetric Lorentz vector potential is obtaine

Samuel Colin, Thomas Durt, Roderich Tumulka

The meaning of superselection rules in Bohm-Bell theories (i.e., quantum theories with particle trajectories) is different from that in orthodox quantum theory. More precisely, there are two concepts of superselection rule, a weak and a strong one. Weak superselection rules exist both in orthodox quantum theory and in Bohm-Bell theories and represent the con

Jonathan Barrett

I introduce a framework in which a variety of probabilistic theories can be defined, including classical and quantum theories, and many others. From two simple assumptions, a tensor product rule for combining separate systems can be derived. Certain features, usually thought of as specifically quantum, turn out to be generic in this framework, meaning that t

N. Nayak

We analyze possible hurdles in generating a Fock state of the radiation field in a micromaser cavity.

Jason E Donald, William W Chen, Eugene I Shakhnovich

Protein-DNA interactions are vital for many processes in living cells, especially transcriptional regulation and DNA modification. To further our understanding of these important processes on the microscopic level, it is necessary that theoretical models describe the macromolecular interaction energetics accurately. While several methods have been proposed,

Daniel G. M. Silvestre, Jose F. Fontanari

The coexistence of distinct templates is a common feature of the diverse proposals advanced to resolve the information crisis of prebiotic evolution. However, achieving robust template coexistence turned out to be such a difficult demand that only a class of models, the so-called package models, seems to have met it so far. Here we apply Wright's Island

Jie Zhang, Robert P. Behringer, Alexander Oron

Marangoni instabilities in binary mixtures are different from those in pure liquids. In contrast to a large amount of experimental work on Marangoni convection in pure liquids, such experiments in binary mixtures are not available in the literature, to our knowledge. Using binary mixtures of sodium chloride/water, we have systematically investigated the patt

F. Kalkum, G. Gay, O. Alloschery, J. Weiner

We apply the technique of far-field interferometry to measure the properties of surface waves generated by two-dimensional (2D) single subwavelength slit-groove structures on gold films. The effective surface index of refraction measured for the surface wave propagating over a distance of more than 12 microns is determined to be 1.016 with a measurement unce

Ilya Fushman, Edo Waks, Dirk Englund, Nick Stoltz

We demonstrate fast (up to 20 GHz), low power (5 $μW$) modulation of photonic crystal (PC) cavities in GaAs containing InAs quantum dots. Rapid modulation through blue-shifting of the cavity resonance is achieved via free carrier injection by an above-band picosecond laser pulse. Slow tuning by several linewidths due to laser-induced heating is also demonstr

Claude M. Dion, Peder Sjolund, Stefan J. H. Petra, Svante Jonsell

We study a Brownian motor, based on cold atoms in optical lattices, where atomic motion can be induced in a controlled manner in an arbitrary direction, by rectification of isotropic random fluctuations. In contrast with ratchet mechanisms, our Brownian motor operates in a potential that is spatially and temporally symmetric, in apparent contradiction to the

Lei Shi, Xianfeng Chen

Based on the basic theory of the microfiber loop resonator, we exploit the application of microfiber loop resonators in biochemical sensing. We set up a reliable theoretical model and optimize the structural parameters of microfiber loop resonators including the radius of the microrfiber, the radius of the loop and the length of the coupling region for highe

Jean-Paul Auffray

Samuel Preston's 1875 postulates concerning the nature ether are reviewed.

M. Wing, M. Warren, P. D. Dauncey, J. M. Butterworth

This note describes R&D to be carried out on the data acquisition system for a calorimeter at the future International Linear Collider. A generic calorimeter and data acquisition system is described. Within this framework modified designs and potential bottlenecks within the current system are described. Solutions leading up to a technical design report will

Hervé Herbin, Robert Farrenq, Guy Guelachvili, Nathalie Picqué

Velocity-modulation Fourier transform emission spectra from a N_2O/He discharge plasma recorded between 1 and 5.5 $μ$m are described. Surprisingly, they show Doppler-shifted lines for the E ^2 Σ^+ - D ^2 Σ^+, C ^2 Π- A ^2 Σ^+, and D ^2 Σ^+ - A ^2 Σ^+ Rydberg-Rydberg rovibronic transitions of the nitric oxide neutral molecule. These polarity-dependent Doppler

M. L. Glasser

In a medium where a photoreactive species produces N equally photoreactive radicals, by combining the Lambert-Beer law for the decay of light intensity, as a beam propagates into the medium, with the kinetic equation, one obtains a generalization of the Wegscheider equation from photobleaching theory. It is shown that this equation can be solved exactly, but

Dan Braha, Yaneer Bar-Yam

We develop a new approach to the study of the dynamics of link utilization in complex networks using records of communication in a large social network. Counter to the perspective that nodes have particular roles, we find roles change dramatically from day to day. "Local hubs" have a power law degree distribution over time, with no characteristic deg

S. Gandolfi, F. Pederiva, S. Fantoni, K. E. Schmidt

We present an accurate numerical study of the equation of state of nuclear matter based on realistic nucleon--nucleon interactions by means of Auxiliary Field Diffusion Monte Carlo (AFDMC) calculations. The AFDMC method samples the spin and isospin degrees of freedom allowing for quantum simulations of large nucleonic systems and represents an important step

Jean-Paul Blaizot

I give a brief overview of our present understanding of the high temperature phase of QCD, trying to clarify some of the theoretical issues involved in the current discussions that emphasize the strongly coupled character of the quark-gluon plasma produced at RHIC.

Y. G. Ma

Anisotropic flows ($v_2$ and $v_4$) of hadrons and light nuclear clusters are studied by a partonic transport model and nucleonic transport model, respectively, in ultra-relativistic and intermediate energy heavy ion collisions. Both number-of-constituent-quark scaling of hadrons, especially for $ϕ$ meson which is composed of strange quarks, and number-of-nu

E. Jurcisinova, M. Jurcisin, R. Remecky, M. Scholtz

Influence of uniaxial small-scale anisotropy and compressibility on the stability of scaling regime and on the anomalous scaling of structure functions of a scalar field is investigated in the model of a passive scalar field advected by the compressible Gaussian strongly anisotropic velocity field with the covariance $\propto δ(t-t^{\prime})|{\bf x}-{\bf x^{

E. Jurcisinova, M. Jurcisin, R. Remecky, M. Scholtz

Influence of weak uniaxial small-scale anisotropy on the stability of inertial-range scaling regimes in a model of a passive transverse vector field advected by an incompressible turbulent flow is investigated by means of the field theoretic renormalization group. Weak anisotropy means that parameters which describe anisotropy are chosen to be close to zero,

N. I. Stoilova, J. Van der Jeugt

Generalized quantum statistics (GQS) associated to a Lie algebra or Lie superalgebra extends the notion of para-Bose or para-Fermi statistics. Such GQS have been classified for all classical simple Lie algebras and basic classical Lie superalgebras. In the current paper we finalize this classification for all exceptional Lie algebras and superalgebras. Since

A. I. Machavariani

Starting with the conformal transformations in the momentum space, the nonlinear $σ$-model and the standard model with the spontaneous broken $SU(2)\times U(1)$ symmetry are reproduced. The corresponding chiral Lagrangians are given in the five dimensional form because for the conformal transformations of the four-momentum $q_μ$ ($q'_μ=q_μ+h_μ$, $q'_

S. H. Djah, H. Gottschalk, H. Ouerdiane

Partition- and moment functions for a general (not necessarily Gaussian) functional measure that is perturbed by a Gibbs factor are calculated using generalized Feynman graphs. From the graphical calculus, a new notion of Wick ordering arises, that coincides with orthogonal decompositions of Wiener-Itô type only if the measure is Gaussian. Proving a generali

M. Cenkci, Y. Simsek, V. Kurt

This object of this paper to give several properties and applications of multiple p-adic q-L-function of two variables.

Olivier Bernardi

For any graph G with n edges, the spanning subgraphs and the orientations of G are both counted by the evaluation T_G(2,2)=2^n of its Tutte polynomial. We define a bijection $Φ$ between spanning subgraphs and orientations and explore its enumerative consequences regarding the Tutte polynomial. The bijection $Φ$ is closely related to a recent characterization

Emmanuel Candes, Justin Romberg

We consider the problem of reconstructing a sparse signal $x^0\in\R^n$ from a limited number of linear measurements. Given $m$ randomly selected samples of $U x^0$, where $U$ is an orthonormal matrix, we show that $\ell_1$ minimization recovers $x^0$ exactly when the number of measurements exceeds \[ m\geq \mathrm{Const}\cdotμ^2(U)\cdot S\cdot\log n, \] wher

Ivan Horozov

We define iteration over a two dimensional manifold as analog of iteration over a path defined by Chen. We give several applications. Some of them include constructions of non-abelian modular symbol for $SL(3,\Z)$ and for $SL_{2/K}$, where $K$ is a real quadratic field. We construct the latter as generating series of iterated integrals over a two-dimensional

Robin Hartshorne, Juan Migliore, Uwe Nagel

We study the concept of liaison addition for codimension two subschemes of an arithmetically Gorenstein projective scheme. We show how it relates to liaison and biliaison classes of subschemes and use it to investigate the structure of Gorenstein liaison equivalence classes, extending the known theory for complete intersection liaison of codimension two subs

Georges Maltsiniotis

The aim of this paper is to present a very simple original, purely formal, proof of Quillen's adjunction theorem for derived functors, and of some more recent variations and generalizations of this theorem. This is obtained by proving an abstract adjunction theorem for "absolute" derived functors. In contrast with all known proofs, the explicit c

Helena Albuquerque, Florin Panaite

We analyze some relations between quasi-Hopf smash products and certain twisted tensor products of quasialgebras. Along the way we obtain also some results of independent interest, such as a duality theorem for finite dimensional quasi-Hopf algebras and a universal property for generalized diagonal crossed products.

Weiqiang Wang

We introduce the spin Hecke algebra, which is a q-deformation of the spin symmetric group algebra, and its affine generalization. We establish an algebra isomorphism which relates our spin (affine) Hecke algebras to the (affine) Hecke-Clifford algebras of Olshanski and Jones-Nazarov. Relation between the spin (affine) Hecke algebra and a nonstandard presenta

Mate Matolcsi

The open problem of determining the exact value of the $n$-th linear polarization constant $c_n$ of $\R^n$ has received considerable attention over the past few years. This paper makes a contribution to the subject by providing a new lower bound on the value of $\sup_{\|{\bf{y}}\|=1}| {\bf{x}}_1,{\bf{y}} ... {\bf{x}}_n,{\bf{y}} |$, where ${\bf{x}}_1, ... ,{\

Mate Matolcsi

The present work contributes to the determination of the $n$-th linear polarization constant $c_n(H)$ of an $n$-dimensional real Hilbert space $H$. We provide some new lower bounds on the value of $\sup_{\|y\|=1}| x_1,y >... x_n,y |$, where $x_1, ..., x_n$ are unit vectors in $H$. In particular, the results improve an earlier estimate of Marcus. However, the

Lothar Göttsche, Hiraku Nakajima, Kota Yoshioka

In this paper we study the holomorphic Euler characteristics of determinant line bundles on moduli spaces of rank 2 semistable sheaves on an algebraic surface X, which can be viewed as $K$-theoretic versions of the Donaldson invariants. In particular, if X is a smooth projective toric surface, we determine these invariants and their wallcrossing in terms of

Guang'ai Song, Yucai Su, Yuezhu Wu

In a recent paper by the authors, Lie bialgebras structures of generalized Virasoro-like type were considered. In this paper, the explicit formula of the quantization of generalized Virasoro-like algebras is presented.

Daniel G. Davis

Let us take for granted that L_{K(n)}S^0 --> E_n is some kind of a G_n-Galois extension. Of course, this is in the setting of continuous G_n-spectra. How much structure does this continuous G-Galois extension have? How much structure does one want to build into this notion to obtain useful conclusions? If the author's conjecture that ``E_n/I, for a cofin

Oleg Karpenkov

Recently V.I.Arnold have formulated a geometrical concept of monads and apply it to the study of difference operators on the sets of $\{0,1\}$-valued sequences of length $n$. In the present note we show particular examples of these monads and indicate one question arising here.

Andreas Cap, A. Rod Gover

We prove that Fefferman spaces, associated to non--degenerate CR structures of hypersurface type, are characterised, up to local conformal isometry, by the existence of a parallel orthogonal complex structure on the standard tractor bundle. This condition can be equivalently expressed in terms of conformal holonomy. Extracting from this picture the essential

Mate Matolcsi

In this note we give an example of a set $\W\subset \R^4$ such that $L^2(\W)$ admits an orthonormal basis of exponentials $\{\frac{1}{|\W |^{1/2}}e^{2πi x, ξ}\}_{ξ\inŁ}$ for some set $Ł\subset\R^4$, but which does not tile $\R^4$ by translations. This improves Tao's recent 5-dimensional example, and shows that one direction of Fuglede's conjecture fa

Mate Matolcsi

A basic result in semigroup theory states that every $C_0$-semigroup is quasi-contractive with respect to some appropriately chosen equivalent norm. This paper contains a counterpart of this well-known fact. Namely, by examining the convergence of the Trotter-type formula $(e^{\frac{t}{n}A}P)^n$ (where $P$ denotes a bounded projection), we prove that wheneve

R. Husseini, M. Kassmann

Markov chain approximations of symmetric jump processes are investigated. Tightness results and a central limit theorem are established. Moreover, given the generator of a symmetric jump process with state space $\mathbbm{R}^d$ the approximating Markov chains are constructed explicitly. As a byproduct we obtain a definition of the Sobolev space $H^{α/2}(\mat

Mate Matolcsi

The aim of this paper is to give a characterization in Hilbert spaces of the generators of $C_0$-semigroups associated with closed, sectorial forms in terms of the convergence of a generalized Trotter's product formula. In the course of the proof of the main result we also present a similarity result which can be of independent interest: for any unbounde

Feng Xiao, Long Wang

In this paper, we study asynchronous consensus problems of continuous-time multi-agent systems with discontinuous information transmission. The proposed consensus control strategy is implemented only based on the state information at some discrete times of each agent's neighbors. The asynchronization means that each agent's update times, at which the

C. Robin Graham, Kengo Hirachi

An extension of the ambient metric construction of Fefferman-Graham to infinite order in even dimensions is described. The main ingredients are the introduction of "inhomogeneous ambient metrics" with asymptotic expansions involving the logarithm of a defining function homogeneous of degree 2, and an invariant procedure for taking the smooth part of

Kari Ragnarsson

In this paper we explore the possibility of defining p-local finite groups in terms of transfer properties of their classifying spaces. More precisely, we consider the question posed by Haynes Miller, whether an equivalent theory can be obtained by studying triples (f,t,X), where X is a p-complete, nilpotent space with finite fundamental group, f is a map fr

Anca Mustata, Andrei Mustata

We describe the Chow ring with rational coefficients of the moduli space of stable maps with marked points Mbar_{0,m}(n,d) as the subring of invariants of a ring B, relative to the action of the group of symmetries of d elements. B is computed by following a sequence of intermediate spaces for Mbar_{0,m}(n,d) and relating them to substrata of Mbar_{0,1}(n,d+

L. A. Barreiro, R. Medina

In this work we report on recent progress in the calculation of open superstring scattering amplitudes, at tree level, with more than four external massless states. We also report on the corresponding terms in the low energy effective lagrangian.

H. B. Thacker

Monte Carlo studies of pure glue SU(3) gauge theory using the overlap-based topological charge operator have revealed a laminar structure in the QCD vacuum consisting of extended, thin, coherent, locally 3-dimensional sheets of topological charge embedded in 4D space, with opposite sign sheets interleaved. In this talk I discuss the interpretation of these M

Amihay Hanany, Christian Romelsberger

This note is presenting the generating functions which count the BPS operators in the chiral ring of a N=2 quiver gauge theory that lives on N D3 branes probing an ALE singularity. The difficulty in this computation arises from the fact that this quiver gauge theory has a moduli space of vacua that splits into many branches -- the Higgs, the Coulomb and mixe

Camillo Imbimbo

We present a level (10,30) numerical computation of the spectrum of quadratic fluctuations of Open String Field Theory around the tachyonic vacuum, both in the scalar and in the vector sector. Our results are consistent with Sen's conjecture about gauge-triviality of the small excitations. The computation is sufficiently accurate to provide robust eviden

Alexander A. Chernitskii

The field nature of spin in the framework of the field electromagnetic particle concept is considered. A mathematical character of the fine structure constant is discussed. Three topologically different field models for charged particle with spin are investigated in the scope of the linear electrodynamics. A using of these field configurations as an initial

Roman V. Buniy, Thomas W. Kephart

It is well known that for a field theory with the Chern-Simons action, expectation values of Wilson line operators are topological invariants. The standard result is expressed in terms of the Gaussian linkings of closed curves defining the operators. We show how judicious choice of Wilson lines leads to higher order topological linkings.

Alex E. Bernardini, Marcelo M. Guzzo, Fernando R. Torres

We report about an analytic study involving the {\em intermediate} wave packet formalism for quantifying the physically relevant information which appear in the neutrino two-flavor conversion formula and help us to obtain more precise limits and ranges for neutrino flavor oscillation. By following the sequence of analytic approximations where we assume a str

Verena Werth, Michael Buballa, Micaela Oertel

We study pseudoscalar meson excitations in the color-flavor locked phase within a Nambu-Jona-Lasinio-type model by calculating diquark loops.

M. Salvatori

We analyze a SU(N) gauge theory on $\mathcal{M}_4 \times T^2$. We find and catalogue all possible degenerate zero-energy stable configurations in the case of trivial or non-trivial 't Hooft non abelian flux. We describe the residual symmetries of each vacua and the 4-dimensional effective spectrum in terms of continous and discrete parameters, respective

Fabio L. Braghin

Some consequences of a classical vector field (chromo-electromagnetic field) coupled to quarks, which undergo to superfluid and/or superconductive states with diquark / diantiquark condensation, are investigated. For this, one scalar field exchange is considered in the lines investigated by Pisarski and Rischke \cite{PISARSKI-RISCHKE} in the mean field appro

Howard Baer, Azar Mustafayev, Eun-Kyung Park, Xerxes Tata

In the post-LEP2 era, and in light of recent measurements of the cosmic abundance of cold dark matter (CDM) in the universe from WMAP, many supersymmetric models tend to predict 1. an overabundance of CDM and 2. pessimistically low rates for direct detection of neutralino dark matter. However, in models with a ``well-tempered neutralino'', where the

V. M. Braun, D. Yu. Ivanov, A. Lenz, A. Peters

We consider the cross section of the deep inelastic pion electroproduction on a proton target at threshold for Q^2 in the region 5-10 GeV^2. The corresponding amplitudes are described in terms of two form factors which we calculate using light cone sum rules (LCSR) to leading order in QCD and including higher twist corrections. Our results suggest a consider

A. V. Lipatov, N. P. Zotov

We consider the prompt photon production at modern high energy colliders in the framework of $k_T-$factorization approach. We compare our theoretical predictions with recent experimental data at HERA and Tevatron, empahasizing the distinction between our theoretical predictions and the results of NLO QCD calculations. Finally, we extrapolate our predictions

Asmita Mukherjee

We report on a calculation to show that the Fourier transform of the Deeply Virtual Compton Scattering (DVCS) amplitude with respect to the skewness variable ζat fixed invariant momentum transfer squared t gives results that are analogous to the diffractive scattering of a wave in optics. As a specific example, we utilize the quantum fluctuations of a fermio

M. Ablikim

Using the data sample of about 33 pb-1 collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied inclusive K0~/K0 and K*(892)+- decays of D0 and D+ mesons. The branching fractions for the inclusive K0~/K0 and K*(892)- decays are measured to be BF(D0 to K0~/K0 X)=(47.6+-4.8+-3.0)%, BF(D+ to K0~/K0 X)=(60.5+-5.5+-3.3)%, B

Thomas P. Sotiriou

The way one chooses to couple gravity to matter is an essential characteristic of any gravitational theory. In theories where the gravitational field is allowed to have more degrees of freedom than those of General Relativity (e.g. scalar-tensor theory, f(R) gravity) this issue often becomes even more important. We concentrate here on f(R) gravity treated wi

Zdenek Stuchlik, Jiri Kovar

Equilibrium conditions and spin dynamics of spinning test particles are discussed in the stationary and axially symmetric Kerr-de Sitter black-hole or naked-singularity spacetimes. The general equilibrium conditions are established, but due to their great complexity, the detailed discussion of the equilibrium conditions and spin dynamics is presented only in

Jiri Kovar, Zdenek Stuchlik

Forces defined in the framework of optical reference geometry are introduced in the case of stationary and axially symmetric Kerr black-hole and naked-singularity spacetimes with a repulsive cosmological constant. Properties of the forces acting on test particles moving along circular orbits in the equatorial plane are discussed, whereas it is shown where th

Willemien Visser

An observational study was conducted on a professional designer working on a design project in aerospace industry. The protocol data were analyzed in order to gain insight into the actions the designer used for the development of a solution to the corresponding problem. Different processes are described: from the "simple" evocation of a solution exis

Willemien Visser, Brigitte Trousse

This text analyses the papers accepted for the workshop "Reuse of designs: an interdisciplinary cognitive approach". Several dimensions and questions considered as important (by the authors and/or by us) are addressed: What about the "interdisciplinary cognitive" character of the approaches adopted by the authors? Is design indeed a domain wh

Ricardo C. Correa, Valmir C. Barbosa

Asynchronous executions of a distributed algorithm differ from each other due to the nondeterminism in the order in which the messages exchanged are handled. In many situations of interest, the asynchronous executions induced by restricting nondeterminism are more efficient, in an application-specific sense, than the others. In this work, we define partially

Dimitris Kalles

In this paper we experiment with a 2-player strategy board game where playing models are evolved using reinforcement learning and neural networks. The models are evolved to speed up automatic game development based on human involvement at varying levels of sophistication and density when compared to fully autonomous playing. The experimental results suggest

Dimitris Kalles

We investigate systematically the impact of human intervention in the training of computer players in a strategy board game. In that game, computer players utilise reinforcement learning with neural networks for evolving their playing strategies and demonstrate a slow learning speed. Human intervention can significantly enhance learning performance, but carr

Kai-Uwe Schmidt

The use of error-correcting codes for tight control of the peak-to-mean envelope power ratio (PMEPR) in orthogonal frequency-division multiplexing (OFDM) transmission is considered in this correspondence. By generalizing a result by Paterson, it is shown that each q-phase (q is even) sequence of length 2^m lies in a complementary set of size 2^{k+1}, where k

Reuven Cohen, Mira Gonen, Avishai Wool

It is widely believed that the Internet's AS-graph degree distribution obeys a power-law form. Most of the evidence showing the power-law distribution is based on BGP data. However, it was recently argued that since BGP collects data in a tree-like fashion, it only produces a sample of the degree distribution, and this sample may be biased. This argument

Petros Elia, K. Vinodh, M. Anand, P. Vijay Kumar

We consider cooperative relay communication in a fading channel environment under the Orthogonal Amplify and Forward (OAF) and Orthogonal and Non-Orthogonal Selection Decode and Forward (OSDF and NSDF) protocols. For all these protocols, we compute the Diversity-Multiplexing Gain Tradeoff (DMT). We construct DMT optimal codes for the protocols which are sphe

T. Kunimatsu, T. Sato, K. Izumina, A. Matsubara

We report on orientation of the order parameter in the 3He-A and 3He-B phases caused by aerogel anisotropy. In 3He-A we have observed relatively homogeneous NMR line with an anomalously large negative frequency shift. We can attribute this effect to an orientation of orbital momentum along the axis of density anisotropy. The similar orientation effect we hav

Stefan Grosskinsky, Gunter M. Schutz, Richard D. Willmann

We study spontaneous symmetry breaking in a one-dimensional driven two-species stochastic cellular automaton with parallel sublattice update and open boundaries. The dynamics are symmetric with respect to interchange of particles. Starting from an empty initial lattice, the system enters a symmetry broken state after some time T_1 through an amplification lo

D. A. Sokolov, M. C. Aronson, C. Henderson, J. W. Kampf

We have succeeded in synthesizing of single crystals of a new intermetallic compound, Ce$_{3}$Rh$_{4}$Pb$_{13}$. Magnetic susceptibility measurements indicate that the Ce moments are highly localized, despite the metallic character of the electrical resistivity. Heat capacity measurements reveal that the cubic crystal electric field lifts the six-fold degene

Yucel Yildirim, Gonzalo Alvarez, Adriana Moreo, Elbio Dagotto

The properties of Mn-doped GaAs are studied at several doping levels and hole compensations, using a real-space Hamiltonian on an fcc lattice that reproduces the valence bands of undoped GaAs. Large-scale Monte Carlo (MC) simulations on a Cray XT3 supercomputer, using up to a thousand nodes, were needed to make this effort possible. Our analysis considers bo

Doron Bergman, Jason Alicea, Emanuel Gull, Simon Trebst

Frustration refers to competition between different interactions that cannot be simultaneously satisfied, a familiar feature in many magnetic solids. Strong frustration results in highly degenerate ground states, and a large suppression of ordering by fluctuations. Key challenges in frustrated magnetism are characterizing the fluctuating spin-liquid regime a

Ping Chu, D. L. Mills

We develop the theory of Brillouin light scattering (BLS) from spin wave modes in ferromagnetic nanospheres, within a framework that incorporates the spatial variation of the optical fields within the sphere. Our recent theory of exchange dipole spin wave modes of the sphere provides us with eigenvectors. When properly normalized, these eigenvectors allow ca

E. G. Maksimov, S. V. Ebert, M. V. Magnitskaya, A. E. Karakozov

Ab initio linear-response calculations are reported of the phonon spectra and the electron-phonon interaction for several transition metal carbides and nitrides in a NaCl-type structure. For NbC, the kinetic, optical, and superconducting properties are calculated in detail at various pressures and the normal-pressure results are found to well agree with the

H. G. Roberts, S. Crampin, S. J. Bending

We demonstrate the presence of an important anisotropic magnetoresistance contribution to the domain wall resistance recently measured in thin-film (Ga,Mn)As with in-plane magnetic anisotropy. Analytic results for simple domain wall orientations supplemented by numerical results for more general cases show this previously omitted contribution can largely exp

A. D. Rata, H. Braak, D. E. Buergler, C. M. Schneider

Magnetic tunnel junctions with the layer sequence Co$_2$Cr$_{0.6}$Fe$_{0.4}$Al/MgO/CoFe were fabricated by magnetron sputtering at room temperature (RT). The samples exhibit a large inverse tunneling magnetoresistance (TMR) effect of up to -66% at RT. The largest value of -84% at 20 K reflects a rather weak influence of temperature. The dependence on the vol

D. Ivaneyko, B. Berche, Yu. Holovatch, Ja. Ilnytskyi

In this Monte Carlo study we concentrated on the influence of non-magnetic impurities arranged as the lines with random orientation on paramagnetic-to-ferromagnetic phase transition in the 3D Ising model. Special emphasize is given to the long-distance decay of the impurity-impurity pair correlation function. It is shown that for the lattice sizes considered

K. Ozdogan, I. Galanakis, B. Aktas, E. Sasioglu

In a recent publication [Galanakis I et al 2006 \PR B \textbf{74} 140408(R)] we have shown that in the case of CrAs and related transition-metal chalcogenides and pnictides, crystallizing in the zinc-blende structure, the excess of the transition-metal atoms leads to half-metallic ferrimagnetism. The latter property is crucial for spintronic applications wit

C. Battaglia, H. Cercellier, C. Monney, M. G. Garnier

The atomic structure of self-assembled quasi-one-dimensional Gd chains on Si(111) has been investigated by low-energy electron diffraction and scanning tunneling microscopy. Based on comparison between Gd and Ca chains we show that this Gd induced surface reconstruction belongs to the class of honeycomb chain-channel structures. This clearly demonstrates tha

Daisuke Yamamoto, Susumu Kurihara

We discuss a pseudospin representation of the two-dimensional t-J model. We introduce pseudospins associated with empty sites, deriving a new representation of the t-J model that consists of local spins and spinless fermions. We show, within a mean-field approximation, that our representation of t-J model corresponds to the {\it isotropic} antiferromagnetic

Shengqiang Zhou, K. Potzger, Gufei Zhang, F. Eichhorn

We report the structural and magnetic properties of ZnO single crystals implanted at 623 K with up to 10 at. % of Ni. As revealed by X-ray diffraction, crystalline fcc-Ni nanoparticles were formed inside ZnO. The magnetic behavior (magnetization with field reversal and with different temperature protocol) of all samples is well explained by a magnetic Ni-nan

V. Kagalovsky, I. Vagner

We study localization-delocalization transition in quantum Hall systems with a random field of nuclear spins acting on two-dimensional (2d) electron spins via hyperfine contact (Fermi) interaction. We use Chalker-Coddington network model, which corresponds to the projection onto the lowest Landau level. The inhomogeneous nuclear polarization acts on the elec

Yoshihiro Nishiyama

Finite-size scaling (FSS) of the five-dimensional (d=5) Ising model is investigated numerically. Because of the hyperscaling violation in d>4, FSS of the d=5 Ising model no longer obeys the conventional scaling relation. Rather, it is expected that the FSS behavior depends on the geometry of the embedding space (boundary condition). In this paper, we conside

Richard A. Shaw, WArren A. Reid, Quentin A. Parker

We present Hubble Space Telescope (HST) images of new planetary nebulae (PNe) that were discovered in the Reid-Parker AAO/UKST H-alpha survey of the Large Magellanic Cloud. These serendipitous observations from various HST programs yield independent confirmations of 6 PNe; one other detected nebula may also be a PN, and one appears to be a region of diffuse

Reba M. Bandyopadhyay, Andrew J. Gosling, Katherine M. Blundell, Philipp Podsiadlowski

We present results of a multi-wavelength program to study the faint discrete X-ray source population discovered by Chandra in the Galactic Centre (GC). From IR imaging obtained with the VLT we identify candidate K-band counterparts to 75% of the X-ray sources in our sample. By combining follow-up VLT K-band spectroscopy of a subset of these candidate counter

Richard J. Stancliffe, C. Simon Jeffery

We investigate the uncertainty in surface abundances and yields of asymptotic giant branch (AGB) stars. We apply three different mass loss laws to a 1.5 solar mass star of metallicity Z=0.008 at the beginning of the thermally pulsing asymptotic giant branch (TP-AGB) phase. Efficient third dredge-up is found even at very low envelope mass, contrary to previou

B. D. Lehmer, W. N. Brandt, D. M. Alexander, E. F. Bell

We investigate the evolution over the last 6.3 Gyr of cosmic time (i.e., since z ~ 0.7) of the average X-ray properties of early-type galaxies within the Extended Chandra Deep Field-South (E-CDF-S). Our early-type galaxy sample includes 539 objects with red-sequence colors and Sersic indices larger than n = 2.5, which were selected jointly from the COMBO-17

Ji Jianghui, Liu Lin, Li Guangyu

We investigate the secular resonances for massless small bodies and Earth-like planets in several planetary systems. We further compare the results with those of Solar System. For example, in the GJ 876 planetary system, we show that the secular resonances $ν_1$ and $ν_2$ (respectively, resulting from the inner and outer giant planets) can excite the eccentr

T. W. B. Muxlow, R. J. Beswick, A. M. S. Richards, H. Thrall

Star-formation and the Starburst phenomenon are presented with respect to a number of nearby star-forming galaxies where our understanding of the process can be calibrated. Methods of estimating star-formation rates are discussed together with the role played in the investigation of the process by multi-wavelength studies of a few selected starburst galaxies

Gabriel B. Brammer, Pieter G. van Dokkum

We use the deep NIR imaging of the FIRES survey to investigate trends with redshift of the properties of galaxies selected to have strong Balmer/4000A breaks at 2<z<4.5. Analagous to the J-K>1.3 (AB) color criterion designed to select red galaxies at z>2, we propose two color criteria, J-H>0.9 and H-K>0.9, to select red galaxies in two redshift bins at 2<z<3

S. F. Hoenig, T. Beckert, K. Ohnaka, G. Weigelt

We present 3-dimensional radiative transfer models for clumpy dust tori around AGN. Our method combines Monte Carlo simulations of individual dust clouds with the actual 3-dimensional distribution of clouds in the torus. The model has been applied to NIR and MIR photometric and interferometric observations of NGC 1068. For the first time, it is possible to s