December 2005 arXiv papers — page 25

V. P. Belavkin

A new notion of stochastic germs for quantum processes is introduced and a characterisation of the stochastic differentials for positive definite (PD) processes is found in terms of their germs for arbitrary Ito algebra. A representation theorem, giving the pseudo-Hilbert dilation for the germ-matrix of the differential, is proved. This suggests the general

V. P. Belavkin

A simple axiomatic characterization of the general (infinite dimensional, noncommutative) Ito algebra is given and a pseudo-Euclidean fundamental representation for such algebra is described. The notion of Ito B*-algebra, generalizing the C*-algebra is defined to include the Banach infinite dimensional Ito algebras of quantum Brownian and quantum Levy motion

Pavel Etingof, Ching-Hwa Eu

The goal of this paper is to prove that if Q is a connected non-Dynkin quiver then the preprojective algebra of Q over any field k is Koszul, and has Hilbert series 1/(1-Ct+t^2), where C is the adjacency matrix of the double of Q. (This result, in somewhat less general formulations, was previously obtained by Martinez-Villa and Malkin-Ostrik-Vybornov). We al

Diego Ruano

From a rational convex polytope of dimension $r\ge 2$ J.P. Hansen constructed an error correcting code of length $n=(q-1)^r$ over the finite field $\fq$. A rational convex polytope is the same datum as a normal toric variety and a Cartier divisor. The code is obtained evaluating rational functions of the toric variety defined by the polytope at the algebraic

Aldo Conca, Serkan Hosten, Rekha R. Thomas

This is a survey article on Gorenstein initial complexes of extensively studied ideals in commutative algebra and algebraic geometry. These include defining ideals of Segre and Veronese varieties, toric deformations of flag varieties known as Hibi ideals, determinantal ideals of generic matrices of indeterminates, and ideals generated by Pfaffians of generic

Sergei Ovchinnikov

In this paper we develop a representational approach to media theory. We construct representations of media by well graded families of sets and partial cubes and establish the uniqueness of these representations. Two particular examples of media are also described in detail.

S. F. Yashkov

We give some representation about recent achievements in analysis of the M/G/1 queue with egalitarian processor sharing discipline (EPS). The new formmulas are derived for the j-th moments (j=1,2,...) of the (conditional) stationary sojourn time in the M/G/1--EPS queue with K (K=0,1,2,...) permanent jobs of infinite size. We discuss also how to simplify the

Jim Brown

Let f be a newform of weight 2k-2 and level 1. In this paper we provide evidence for the Bloch-Kato conjecture for modular forms. We demonstrate an implication that under suitable hypothesis if a prime divides the algebraic part of L(k,f), then the prime divides the order of the Selmer group associated to f. We demonstrate this by establishing a congruence b

francesco fidaleo

Let $U$ be a unitary operator acting on the Hilbert space H, and $α:\{1,..., m\}\mapsto\{1,..., k\}$ a partition of the set $\{1,..., m\}$. We show that the ergodic average $$ \frac{1}{N^{k}}\sum_{n_{1},...,n_{k}=0}^{N-1} U^{n_{α(1)}}A_{1}U^{n_{α(2)}}... U^{n_{α(m-1)}}A_{m-1}U^{n_{α(m)}} $$ converges in the weak operator topology if the $A_{j}$ belong to the

J. F. Le Borgne

Let $M$ be a closed oriented $d$-dimensionnal manifold and let $LM$ be the space of free loops on $M$. In this paper, we give a geometrical interpretation of the loop coproduct and we study it's compatibility with the Serre spectral sequence associated to the fibration $ΩM \to LM \to M$. Then, we show that the spectral sequence associated to the free loo

Boaz Tsaban

CONTENTS: On Selective screenability and examples of R. Pol. Workshops and conferences: The Oxford Conference on Topology and Computer Science in Honour of Peter Collins and Mike Reed; Boise Extravaganza In Set Theory (BEST2006). Research announcements: The isometry group of the Urysohn space as a Levy group; Chasing Silver; Disjoint Non-Free Subgoups of Abe

Weiping Yin, An Wang

In this paper we study the complete invariant metrics on Cartan-Hartogs domains which are the special types of Hua domains. Firstly, we introduce a class of new complete invariant metrics on these domains, and prove that these metrics are equivalent to the Bergman metric. Secondly, the Ricci curvatures under these new metrics are bounded from above and below

Roumen Anguelov, Svetoslav Markov, Blagovest Sendov

We show that the operations addition and multiplication on the set $C(Ω)$ of all real continuous functions on $Ω\subseteq\mathbb{R}^n$ can be extended to the set $\mathbb{H}(Ω)$ of all Hausdorff continuous interval functions on $Ω$ in such a way that the algebraic structure of $C(Ω)$ is preserved, namely, $\mathbb{H}(Ω)$ is a commutative ring with identity.

Liangyi Zhao

In this paper, we present an improvement of a large sieve type inequality in high dimensions and discuss its implications on a related problem.

Viorel Barbu, Vladimir I. Bogachev, Giuseppe Da Prato, Michael Röckner

A stochastic version of the porous medium equation with coloured noise is studied. The corresponding Kolmogorov equation is solved in the space $L^2(H,ν)$ where $ν$ is an infinitesimally excessive measure. Then a weak solution is constructed.

V. P. Belavkin

Quantum chaotic states over a noncommutative monoid, a unitalization of a noncommutative Ito algebra parametrizing a quantum stochastic Levy process, are described in terms of their infinitely divisible generating functionals over the monoid-valued processes on an atomless `space-time' set. A canonical decomposition of the logarithmic conditionally posiv

Vladimir I. Bogachev, Michael Röckner, Stanislav V. Shaposhnikov

Given a second order parabolic operator $$ Lu(t,x) :=\frac{\partial u(t,x)}{\partial t} + a^{ij}(t,x)\partial_{x_i}\partial_{x_j}u(t,x) + b^i(t,x)\partial_{x_i}u(t,x), $$ we consider the weak parabolic equation $L^{*}μ=0$ for Borel probability measures on $(0,1)\times\mathbb{R}^d$. The equation is understood as the equality $$ \int_{(0,1)\times\mathbb{R}^d}

Enrico De Micheli, Giovanni Alberto Viano

The problem of evaluating the information associated with Fredholm integral equations of the first kind, when the integral operator is self-adjoint and compact, is considered here. The data function is assumed to be perturbed gently by an additive noise so that it still belongs to the range of the operator. First we estimate upper and lower bounds for the ep

Olga Bershtein

In the framework of quantum group theory we obtain a noncommutative analog for the algebra of functions in a bounded symmetric domain, endowed with a whole symmetry. Also we provide a construction for its faithfull irreducible representation and an invariant integral over the bounded symmetric domain.

Jürgen Klüners

We study the asymptotics conjecture of Malle for dihedral groups $D_\ell$ of order $2\ell$, where $\ell$ is an odd prime. We prove the expected lower bound for those groups. For the upper bounds we show that there is a connection to class groups of quadratic number fields. The asymptotic behavior of those class groups is predicted by the Cohen--Lenstra heuri

Giuseppe Da Prato, Boris L. Rozovskii, Michael Röckner, Feng-Yu Wang

Explicit conditions are presented for the existence, uniqueness and ergodicity of the strong solution to a class of generalized stochastic porous media equations. Our estimate of the convergence rate is sharp according to the known optimal decay for the solution of the classical (deterministic) porous medium equation.

Jelena Grbic, Stephen Theriault

The complement of the codimension 2 complex coordinate subspace arrangement is shown to be homotopy equivalent to a wedge of spheres.

Irina Gheorghiciuc

Let $A_q$ be a $q$-letter alphabet and $w$ be a right infinite word on this alphabet. A subword of $w$ is a block of consecutive letters of $w$. The subword complexity function of $w$ assigns to each positive integer $n$ the number $f_w(n)$ of distinct subwords of length $n$ of $w$. The gap function of an infinite word over the binary alphabet $\{0,1 \}$ giv

Atsushi Fujioka, Jun-ichi Inoguchi

In this paper we study Moebius applicable surfaces, i.e., conformally immersed surfaces in Moebius 3-space which admit deformations preserving the Moebius metric. We show new characterizations of Willmore surfaces, Bonnet surfaces and Harmonic inverse mean curvature surfaces in terms of Moebius or similarity invariants.

David Pask, Iain Raeburn, Mikael Rordam, Aidan Sims

We describe a class of rank-2 graphs whose C^*-algebras are AT algebras. For a subclass which we call rank-2 Bratteli diagrams, we compute the K-theory of the C*-algebra. We identify rank-2 Bratteli diagrams whose C*-algebras are simple and have real-rank zero, and characterise the K-invariants achieved by such algebras. We give examples of rank-2 Bratteli d

F. Maucourant

We show that Haar measures of connected semisimple groups, embedded via a representation into a matrix space, have a homogeneous asymptotic limit when viewed from far away and appropriately rescaled. This is still true if the Haar measure of the semisimple group is replaced by the Haar measure of a irreducible lattice of the group, and the asymptotic measure

Junhao Shen

In the paper, we study the generator problem of II$_1$ factors. By defining a new concept related to the number of generators of a von Neumann algebra, we are able to show that a large class of II$_1$ factors are singly generated, i.e., generated by two self-adjoint elements. In particular, this shows that most of II$_1$ factors, whose free entropy dimension

Sergey Zlobin

We study integrals over the triangle with vertices (1,0), (0,1), (1,1) that give linear combinations of multiple zeta values.

Robert L. Benedetto

Let K be a function field in one variable over an arbitrary field F. Given a rational function f(z) in K(z) of degree at least two, the associated canonical height on the projective line was defined by Call and Silverman. The preperiodic points of f all have canonical height zero; conversely, if F is a finite field, then every point of canonical height zero

Olga Bershtein

In this paper a quantum analog of the $*$-algebra of regular functions on the Shilov boundary $S(\mathbb D)$ of bounded symmetric domain $\mathbb D$ is constructed. The algebras of regular functions on $S(\mathbb D)$ are described in terms of generators and relations for two particular series of bounded symmetric domains. Also, the degenerate principal serie

L. Winther Christensen, A. Frankild, H. Holm

Gorenstein homological dimensions are refinements of the classical homological dimensions, and finiteness singles out modules with amenable properties reflecting those of modules over Gorenstein rings. As opposed to their classical counterparts, these dimensions do not immediately come with practical and robust criteria for finiteness, not even over commutat

Nadav Drukker, Shoichi Kawamoto

We use the conformal group to study non-local operators in conformal field theories. A plane or a sphere (of any dimension) is mapped to itself by some subgroup of the conformal group, hence operators confined to that submanifold may be classified in representations of this subgroup. For local operators this gives the usual definition of conformal dimension

Sean M. Carroll

It goes without saying that we are stuck with the universe we have. Nevertheless, we would like to go beyond simply describing our observed universe, and try to understand why it is that way rather than some other way. Physicists and cosmologists have been exploring increasingly ambitious ideas that attempt to explain why certain features of our universe are

Kiyoshi Kamimura, Toni Ramirez

We analyze brane dualities in the non-relativistic limit of the worldvolume actions. In particular we have analyzed how the non-relativistic M2-brane is related via these dualities to non-relativistic D2-brane, non-relativistic IIA fundamental string and also, by using T-duality, to non-relativistic D1-string. These actions coincide with ones obtained from r

S. McNamara, C. Papageorgakis, S. Ramgoolam, B. Spence

Finite N effects on the time evolution of fuzzy 2-spheres moving in flat spacetime are studied using the non-Abelian DBI action for N D0-branes. Constancy of the speed of light leads to a definition of the physical radius in terms of symmetrised traces of large powers of Lie algebra generators. These traces, which determine the dynamics at finite N, have a s

F. Bloore, P. A. Horvathy

The 'dyon' system of D'Hoker and Vinet consisting of a spin 1/2 particle with anomalous gyromagnetic ratio 4 in the combined field of a Dirac monopole plus a Coulomb plus a suitable $1/r^2$ potential (which arises in the long-range limit of a self-dual monopole) is studied following Biedenharn's approach to the Dirac-Coulomb problem: the expl

F. Bezrukov, Y. Burnier, M. Shaposhnikov

We describe a possibility of creation of an odd number of fractionally charged fermions in 1+1 dimensional Abelian Higgs model. We point out that for 1+1 dimensions this process does not violate any symmetries of the theory, nor makes it mathematically inconsistent. We construct the proper definition of the fermionic determinant in this model and underline i

Arsen Khvedelidze, Alex Kovner, David McMullan

We address the question of defining the second quantised monopole creation operator in the 3+1 dimensional Georgi-Glashow model, and calculating its expectation value in the confining phase. Our calculation is performed directly in the continuum theory within the framework of perturbation theory. We find that, although it is possible to define the "coher

T. Banks, M. Johnson

We present an interpretation of the physics of space-times undergoing eternal inflation by repeated nucleation of bubbles. In many cases the physics can be interpreted in terms of the quantum mechanics of a system with a finite number of states. If this interpretation is correct, the conventional picture of these space-times is misleading.

M. Yu. Kuchiev, V. V. Flambaum

The Coulomb problem for vector bosons W incorporates a well known difficulty; the charge of the boson localized in a close vicinity of the attractive Coulomb center proves be infinite. This fact contradicts the renormalizability of the Standard Model, which presumes that at small distances all physical quantities are well defined. The paradox is shown to be

S. N. Vergeles

Some variant of discrete quantum theory of gravity having "naive" continuum limit is constructed. It is shown that in a highly compressed state of universe a sort of "high-temperature expansion" is valid and, thus, the confinement of "color" takes place at early stage of universe expansion. In the considered theory any nontrivial repr

A. Lewis Licht

A noncommutative geometry that preserves lorentz covariance was introduced by Hartland Snyder in 1947. We show that this geometry has unusual properties under momentum translation, and derive for it a form of star product.

Bhaskar Dutta, Yukihiro Mimura

We consider the Yukawa couplings for quarks and leptons in the context of Pati-Salam model using intersecting D-brane models where the Yukawa coupling matrices are rank one in a simple choice of family replication. The CKM mixings can be explained by perturbing the rank 1 matrix using higher order terms involving new Higgs fields available in the model. We s

V. N. Senoguz, Q. Shafi

A gauged U(1)_B-L symmetry predicts three right handed handed neutrinos and its spontaneous breaking automatically yields the seesaw mechanism. In a supersymmetric setting this breaking can be nicely linked with inflation to yield deltaT/ T proportional to (M_B-L / M_P)^2, where M_B-L (M_P) denote the B-L breaking (Planck) scale. Thus M_B-L is estimated to b

Andre Hoang, Pedro Ruiz-Femenia

We present an effective field theory suitable to describe a non-relativistic particle-antiparticle pair of heavy scalars based on the gauge group SU(3). Its formulation is analogous to that of "velocity NRQCD" (vNRQCD), a non-relativistic effective theory for heavy quark pairs. The matching conditions with scalar QCD and the renormalization group evo

V. I. Mokeev, V. D. Burkert, L. Elouadrhiri, A. A. Boluchevsky

First comprehensive data on the evolution of nucleon resonance photocouplings with photon virtuality Q^2 are presented for excited proton states in the mass range from 1.4 to 2.0 GeV. N^* photocouplings were determined in phenomenological analysis of CLAS data on 2 pi photo and electroproduction within the framework of the JLAB-MSU phenomenological model.

E. Meggiolaro

After a brief review, in the first part, of some relevant analyticity properties of the loop-loop scattering amplitudes in gauge theories, when going from Minkowskian to Euclidean theory, in the second part we shall see how they can be related to the still unsolved problem of the s-dependence of the hadron-hadron total cross-sections.

S. De Curtis

In the linear moose framework, which naturally emerges in deconstruction models, we discuss the effect of direct couplings between the left-handed fermions living on the boundary of the chain and the gauge fields in the internal sites. This is realized by means of a product of nonlinear sigma-model scalar fields which, in the continuum limit, is equivalent t

Agnes Mocsy, Peter Petreczky

We study the quarkonia correlators above deconfinement using the potential model with screened temperature-dependent potentials. We find that while the qualitative features of the spectral functions, such as the survival of the 1S state, can be reproduced by potential models, the temperature dependence of the correlators disagree with the recent lattice data

Timo A. Lahde, Johan Bijnens, Niclas Danielsson

This paper summarizes the recent calculations of the masses and decay constants of the pseudoscalar mesons at the two-loop level, or NNLO, in Partially Quenched Chiral Perturbation Theory (PQxPT). Possible applications include chiral extrapolations of Lattice QCD, as well as the determination of the low-energy constants (LEC:s) of QCD.

Michael Creutz

It is popular to discuss low energy physics in lattice gauge theory in terms of the small eigenvalues of the lattice Dirac operator. I play with some ensuing pitfalls in the interpretation of these eigenvalue spectra.

The BABAR Collaboration, B. Aubert et al

We have searched for the decays $B^0 \rightarrow D_s^{+}a_0^-$, $B^0 \rightarrow D_s^{*+}a_0^-$, $B^0 \rightarrow D_s^{+}a_2^-$ and $B^0 \rightarrow D_s^{*+}a_2^-$ in a sample of about 230 million $Υ(4S) \rightarrow B{\bar B}$ decays collected with the {\sl BaBar} detector at the PEP-II asymmetric-energy $B$-factory at SLAC. We find no evidence for these dec

B collaboration

The mid-rapidity (dsigma_(pN)/dy at y=0) and total sigma_(pN) production cross sections of J/Psi mesons are measured in proton-nucleus interactions. Data collected by the HERA-B experiment in interactions of 920 GeV/c protons with carbon, titanium and tungsten targets are used for this analysis. The J/Psi mesons are reconstructed by their decay into lepton p

The BABAR Collaboration, B. Aubert

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, these decays are expected to be highly suppressed since they proceed through annihilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BABAR detector at SLAC. We find no eviden

Ezra T. Newman

We first review asymptotic twistor theory with its real subspace of null asymptotic twistors. This is followed by a description of an asymptotic version of the Kerr theorem that produces regular asymptotically shear free null geodesic congruences in arbitrary asymptotically flat Einstein or Einstein-Maxwell spacetimes.

Jorma Louko

I discuss group averaging as a method for quantising constrained systems whose gauge group is a noncompact Lie group. Focussing on three case studies, I address the convergence of the averaging, possible indefiniteness of the prospective physical inner product and the emergence of superselection sectors.

Yasusada Nambu, Yohei Araki

We investigate the evolution of the non-linear long wavelength fluctuations during preheating after inflation. By using the separate universe approach, the temporal evolution of the power spectrum of the scalar fields and the curvature variable is obtained numerically. We found that the amplitude of the large scale fluctuations is suppressed after non-linear

Raluca Ilie, Gregory B. Thompson, David D. Reid

This paper presents the results of a computational study related to the path-geodesic correspondence in causal sets. For intervals in flat spacetimes, and in selected curved spacetimes, we present evidence that the longest maximal chains (the longest paths) in the corresponding causal set intervals statistically approach the geodesic for that interval in the

Gennady P. Berman, Vyacheslav N. Gorshkov, Xidi Wang

Irreducible frequent patters (IFPs) are introduced for transactional databases. An IFP is such a frequent pattern (FP),(x1,x2,...xn), the probability of which, P(x1,x2,...xn), cannot be represented as a product of the probabilities of two (or more) other FPs of the smaller lengths. We have developed an algorithm for searching IFPs in transactional databases.

John M. Hitchcock

We establish a relationship between the online mistake-bound model of learning and resource-bounded dimension. This connection is combined with the Winnow algorithm to obtain new results about the density of hard sets under adaptive reductions. This improves previous work of Fu (1995) and Lutz and Zhao (2000), and solves one of Lutz and Mayordomo's "

Gwénaël Richomme, Francis Wlazinski

A challenging problem is to find an algorithm to decide whether a morphism is k-power-free. We provide such an algorithm when k >= 3 for uniform morphisms showing that in such a case, contrarily to the general case, there exist finite test-sets for k-power-freeness.

Jérôme Azé, Mathieu Roche, Yves Kodratoff, Michèle Sebag

A key data preparation step in Text Mining, Term Extraction selects the terms, or collocation of words, attached to specific concepts. In this paper, the task of extracting relevant collocations is achieved through a supervised learning algorithm, exploiting a few collocations manually labelled as relevant/irrelevant. The candidate terms are described along

Jeff Stuckman, Guo-Qiang Zhang

In this paper we show that the Mastermind Satisfiability Problem (MSP) is NP-complete. The Mastermind is a popular game which can be turned into a logical puzzle called Mastermind Satisfiability Problem in a similar spirit to the Minesweeper puzzle. By proving that MSP is NP-complete, we reveal its intrinsic computational property that makes it challenging a

Tharaka A. Lamahewa, Rodney A. Kennedy, Thushara D. Abhayapala, Van K. Nguyen

In this paper, we introduce the novel use of linear spatial precoding based on fixed and known parameters of multiple-input multiple-output (MIMO) channels to improve the performance of space-time coded MIMO systems. We derive linear spatial precoding schemes for both coherent (channel is known at the receiver) and non-coherent (channel is un-known at the re

Shaffique Adam, Markus Kindermann, Saar Rahav, Piet W. Brouwer

The conductance of a ferromagnetic particle depends on the relative orientation of the magnetization with respect to the direction of current flow. This phenomenon is known as "anisotropic magnetoresistance". Quantum interference leads to an additional, random dependence of the conductance on the magnetization direction. These "anisotropic magnet

Paul H. Barsic, Oriol T. Valls, Klaus Halterman

We study the thermodynamics of clean structures composed of superconductor (S) and ferromagnet (F) layers and consisting of one or more SFS junctions. We use fully self consistent numerical methods to compute the condensation free energies of the possible order parameter configurations as a function of temperature $T$. As $T$ varies, we find that there are p

Vladimir I. Fal'ko, Boris N. Narozhny

We propose a microscopic mechanism for triplet pairing due to spin-orbit-assisted electron interaction with optical phonons in a crystal with a complex unit cell. Using two examples of electrons with symmetric Fermi surfaces in crystals with either a cubic or a layered square lattice, we show that spin-orbit-assisted electron-phonon coupling can, indeed, gen

T. Zykova-Timan, D. Ceresoli, U. Tartaglino, E. Tosatti

This paper presents a broad theoretical and simulation study of the high temperature behavior of crystalline alkali halide surfaces typified by NaCl(100), of the liquid NaCl surface near freezing, and of the very unusual partial wetting of the solid surface by the melt. Simulations are conducted using two-body rigid ion BMHFT potentials, with full treatment

R. G. Mani

We examine the microwave-photoexcited magnetoresistance oscillations in a tilted magnetic field in the high mobility two-dimensional electron system. In analogy to the 2D Shubnikov-de Haas effect, the characteristic field, $B_{f}$, and the period of the radiation-induced magnetoresistance oscillations appears dependent upon the component of the applied magne

G. Metalidis P. Bruno

Phase randomizing processes in mesoscopic systems can be described in a phenomenological way within the Landauer-Büttiker formalism by attaching extra voltage probes to the sample. In this paper, it is shown that a perturbation treatment of this idea allows for the incorporation of such effects without the need of giving up the efficiency of recursive techni

M. Lezaic, Ph. Mavropoulos, J. Enkovaara, G. Bihlmayer

The temperature dependence of the magnetization and spin-polarization at the Fermi level is investigated for half-metallic ferromagnets. We reveal a new mechanism, where the hybridization of states forming the half-metallic gap depends on thermal spin fluctuations and the polarization can drop abruptly at temperatures much lower than the Curie point. We veri

G. Fiori, G. Iannaccone, G. Klimeck

In this work, we simulate the expected device performance and the scaling perspectives of Carbon nanotube Field Effect Transistors (CNT-FETs), with doped source and drain extensions. The simulations are based on the self-consistent solution of the 3D Poisson-Schroedinger equation with open boundary conditions, within the Non-Equilibrium Green's Function

Joachim Mathiesen, Itamar Procaccia, Harry L. Swinney, Matthew Thrasher

We investigate whether fractal viscous fingering and diffusion limited aggregates are in the same scaling universality class. We bring together the largest available viscous fingering patterns and a novel technique for obtaining the conformal map from the unit circle to an arbitrary singly connected domain in two dimensions. These two Laplacian fractals appe

Mohammad Hadi Ghatee, Mahmod Sanchooli

The structural property of liquid cesium is investigated in the temperature range 900 K to 1900 K by application of semiempirical effective Lennard-Jones (8.5-4) pair potential function and employing Gillan s algorithm to solve Percus-Yevick equation. The potential function has been derived accurately by application of cohesive energy density in a wide range

Leonardo Spanu, Federico Becca, Sandro Sorella

From general arguments, that are valid for spin models with sufficiently short-range interactions, we derive strong constraints on the excitation spectrum across a continuous phase transition at zero temperature between a magnetic and a dimerized phase, that breaks the translational symmetry. From the different symmetries of the two phases, it is possible to

C. Micheletti, D. Marenduzzo, E. Orlandini, D. W. Sumners

Stochastic simulations are used to characterize the knotting distributions of random ring polymers confined in spheres of various radii. The approach is based on the use of multiple Markov chains and reweighting techniques, combined with effective strategies for simplifying the geometrical complexity of ring conformations without altering their knot type. By

Örs Legeza, Florian Gebhard, Jörg Rissler

For the one-dimensional Hubbard model subject to periodic boundary conditions we construct a unitary transformation between basis states so that open boundary conditions apply for the transformed Hamiltonian. Despite the fact that the one-particle and two-particle interaction matrices link nearest and next-nearest neighbors only, the performance of the densi

C. W. Lai, P. Maletinsky, A. Badolato, A. Imamoglu

We demonstrate dynamical nuclear spin polarization in the absence of an external magnetic field, by resonant circularly polarized optical excitation of a single electron or hole charged quantum dot. Optical pumping of the electron spin induces an effective inhomogeneous magnetic (Knight) field that determines the direction along which nuclear spins could pol

J. M. Rubi

Small thermodynamic systems exhibit peculiar behavior different from that observed in long-scale systems. Non-equilibrium processes taking place in those systems are strongly influenced by the presence of fluctuations which can be large. Contributions to the free energy which vanish at the infinite number of particles limit cannot be neglected and may exert

K. Potzger, Shengqiang Zhou, H. Reuther, A. Muecklich

Room-temperature ferromagnetism has been induced within ZnO single crystals by implant-doping with Fe ions. For an implantation temperature of 620 K and an ion fluence of 4x10^16 cm^-2, very tiny Fe particles, formed inside the host matrix, are responsible for the ferromagnetic properties. They were identified using synchrotron X-ray diffraction and Moessbau

D. Collin, F. Ritort, C. Jarzynski, S. B. Smith

The description of nonequilibrium processes in nano-sized objects, where the typical energies involved are a few times, is increasingly becoming central to disciplines as diverse as condensed-matter physics, materials science, and biophysics. Major recent developments towards a unified treatment of arbitrarily large fluctuations in small systems are describe

Phan Van-Nham, Tran Minh-Tien

Doping change and distortion effect on the double-exchange ferromagnetism are studied within a simplified double-exchange model. The presence of distortion is modelled by introducing the Falicov-Kimball interaction between itinerant electrons and classical variables. By employing the dynamical mean-field theory the charge and spin susceptibility are exactly

Tobias Bergsten, Toshiyuki Kobayashi, Yoshiaki Sekine, Junsaku Nitta

We demonstrate the time reversal Aharonov-Casher (AC) effect in small arrays of mesoscopic semiconductor rings. By using an electrostatic gate we can control the spin precession rate and follow the AC phase over several interference periods. We show that we control the precession rate in two different gate voltage ranges; in the lower range the gate voltage

Yu-Pin Luo, Ming-Chang Huang, Yen-Liang Chou, Tsong-Ming Liaw

The effect of different move sets on the folding kinetics of the Monte Carlo simulations is analysed based on the conformation-network and the temperature-dependent folding kinetics. A new scheme of implementing Metropolis algorithm is given. The new method is shown to satisfy the detailed balance and converge efficiently towards thermal equilibrium. A new q

Tsong-Ming Liaw, Ming-Chang Huang, Yen-Liang Chou, Simon C. Lin

The exact closed forms of the partition functions of 2D Ising model on square lattices with twisted boundary conditions are given. The constructions of helical tori are unambiguously related to the twisted boundary conditions by virtue of the SL(2,Z) transforms. Numerical analyses reveal that the finite size effect is irrelevant to the chirality equipped wit

F. Libisch, S. Rotter, J. Burgdoerfer

The validity of the retracing approximation in the semiclassical quantization of Andreev billiards is investigated. The exact energy spectrum and the eigenstates of normal-conducting, ballistic quantum dots in contact with a superconductor are calculated by solving the Bogoliubov-de Gennes equation and compared with the semiclassical Bohr-Sommerfeld quantiza

Claudio Castelnovo, Claudio Chamon, Christopher Mudry, Pierre Pujol

The exotic nature of many strongly correlated materials at reasonably high temperatures, for instance cuprate superconductors in their normal state, has lead to the suggestion that such behavior occurs within a quantum critical region where the physics is controlled by the influence of a phase transition down at zero temperature. Such a scenario can be thoug

D. Kurfess, H. Hinrichsen, I. Zimmermann

Fine powders often tend to agglomerate due to van der Waals forces between the particles. These forces can be reduced significantly by covering the particles with nanoscaled adsorbates, as shown by recent experiments. In the present work a quantitative statistical analysis of the effect of powder flow regulating nanomaterials on the adhesive forces in powder

Gerald H. Moriarty-Schieven, Doug Johnstone, John Bally, Tim Jenness

The L1551 molecular cloud contains two small clusters of Class 0 and I protostars, as well as a halo of more evolved Class II and III YSOs, indicating a current and at least one past burst of star formation. We present here new, sensitive maps of 850 and 450 um dust emission covering most of the L1551 cloud, new CO J=2-1 data of the molecular cloud, and a ne

Christopher J. Greenwood

This was my final paper for the AST 308 Galaxies class at Michigan State University. Using many sources I was able to compile a moderate amount of information concerning the evidence for, and the formation of Supermassive Black Holes.

David Yong, Bruce W. Carney, Luisa de Almeida, Brian L. Pohl

We present metallicities, [Fe/H], and elemental abundance ratios, [X/Fe], for a sample of 24 Cepheids in the outer Galactic disk. The sample have Galactocentric distances covering 12 < R_GC (kpc) < 17.2 making them the most distant Galactic Cepheids upon which detailed abundance analyses have been performed. We find sub-solar ratios of [Fe/H] and overabundan

Bhasker K. Moorthy, Jon A. Holtzman

We present line strengths in the bulges and inner disks of 38 galaxies in the local universe, including several galaxies whose bulges were previously identified as being disk-like in their colors or kinematics, to see if their spectral properties reveal evidence for secular evolution. We find that red bulges of all Hubble types are similar to luminous ellipt

Kelly Holley-Bockelmann, Steinn Sigurdsson, J. Christopher Mihos, John J. Feldmeier

Hypervelocity stars have been recently discovered in the outskirts of galaxies, such as the unbound star in the Milky Way halo, or the three anomalously fast intracluster planetary nebulae (ICPNe) in the Virgo Cluster. These may have been ejected by close 3-body interactions with a binary supermassive black hole (SMBBH), where a star which passes within the

Kate Brand, Michael J. I. Brown, Arjun Dey, Buell T. Jannuzi

The XBootes Survey is a 5-ks Chandra survey of the Bootes Field of the NOAO Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest (9.3 deg^2), contiguous region imaged in X-ray with complementary deep optical and near-IR observations. We present a catalog of the optical counterparts to the 3,213 X-ray point sources detected in the X

Maxim Lyutikov

I describe electromagnetic model of gamma ray bursts and contrast its main properties and predictions with hydrodynamic fireball model and its magnetohydrodynamical extension. The electromagnetic model assumes that rotational energy of a relativistic, stellar-mass central source (black-hole--accretion disk system or fast rotating neutron star) is converted i

H. S. Knight, M. Bailes, R. N. Manchester, S. M. Ord

We have conducted a search for giant pulses from four millisecond pulsars using the 100m Green Bank Telescope. Coherently dedispersed time-series from PSR J0218+4232 were found to contain giant pulses of very short intrinsic duration whose energies follow power-law statistics. The giant pulses are in phase with the two minima of the radio integrated pulse pr

Steve B. Howell, Thomas E. Harrison, Ryan K. Campbell, France A. Cordova

We present phase-resolved low resolution $JHK$ and higher resolution $K$-band spectroscopy of the polar VV Pup. All observations were obtained when VV Pup was in a low accretion state having a K magnitude near 15. The low resolution observations reveal cyclotron emission in the $J$ band during some phases, consistent with an origin near the active 30.5 MG po

Jaime Alvarez-Muñiz, Enrique Marqués, Ricardo A. Vázquez, Enrique Zas

We study the frequency and angular dependences of Cherenkov radio pulses originated by the excess of electrons in electromagnetic showers in different dense media. We develop a simple model to relate the main characteristics of the electric field spectrum to the properties of the shower such as longitudinal and lateral development. This model allows us to es

C. Marois, D. Lafreniere, R. Doyon, B. Macintosh

Angular differential imaging is a high-contrast imaging technique that reduces quasi-static speckle noise and facilitates the detection of nearby companions. A sequence of images is acquired with an altitude/azimuth telescope while the instrument field derotator is switched off. This keeps the instrument and telescope optics aligned and allows the field of v

R. Diehl, H. Halloin, K. Kretschmer, A. W. Strong

We performed a spectroscopic study of the 1809 keV gamma-ray line from 26Al decay in the Galaxy using the SPI imaging spectrometer with its high-resolution Ge detector camera on the INTEGRAL observatory. We analyzed observations of the first two mission years, fitting spectra from all 7130 telescope pointings in narrow energy bins to models of instrumental b