January 2006 arXiv papers — page 6

François Lucas, James Madden, Daniel Schaub, Mark Spivakovsky

Let R be a real closed field. The Pierce-Birkhoff conjecture says that any piecewise polynomial function f on R^n can be obtained from the polynomial ring R[x_1,...,x_n] by iterating the operations of maximum and minimum. The purpose of this paper is twofold. First, we state a new conjecture, called the Connectedness conjecture, which asserts the existence o

Jan Stevens

We give explicit examples of Gorenstein surface singularities with integral homology sphere link, which are not complete intersections. Their existence was shown by Luengo-Velasco, Melle-Hernandez and Nemethi, thereby providing counterexamples to the Universal abelian covering conjecture of Neumann and Wahl.

Naokazu Shibata, Daijiro Yoshioka

The ground-state wave function and the energy gap are calculated for various layer separations d and for up to 24 electrons by the density matrix renormalization group (DMRG) method. Two-particle distribution function and excitonic correlation function are calculated from the ground-state wave function, and the evolution of the ground state with increasing d

Giovanni Alessandrini, Antonino Morassi, Edi Rosset

We investigate the character of the linear constraints which are needed for Poincaré and Korn type inequalities to hold. We especially analyze constraints which depend on restriction on subsets of positive measure and on the trace on a portion of the boundary.

Joan Rojo

We construct a parametrization of the lepton energy spectrum in inclusive semileptonic decays of B mesons, based on the available experimental information: moments of the spectrum with cuts, their errors and their correlations, together with kinematical constraints. The result is obtained in the form of a Monte Carlo sample of neural networks trained on repl

Georg Feulner, Armin Gabasch, Yuliana Goranova, Ulrich Hopp

We use the optical and near-infrared galaxy samples from the Munich Near-Infrared Cluster Survey (MUNICS), the FORS Deep Field (FDF) and GOODS-S to probe the stellar mass assembly history of field galaxies out to z ~ 5. Combining information on the galaxies' stellar mass with their star-formation rate and the age of the stellar population, we can draw im

Bernd A. Kniehl

We review recent results on the inclusive electroproduction of light hadrons at next-to-leading order in the parton model of quantum chromodynamics implemented with fragmentation functions and present updated predictions for HERA experiments based on the new AKK set. We also discuss phenomenological implications of these results.

V. I. Nazaruk

The complicated processes in the medium (decays, reactions and $n\bar{n}$ conversion) involving final state absorption are considered. The calculations in the framework of field and phenomenological approaches are compared. The reasons for disagreement are studied. The field approach can tend to increase of total process probability as well as probability of

Satyabrata Adhikari, B. S. Choudhury, Indranil Chakrabarty

Suppose we are given an entangled pair and then one can ask how well we can produce two entangled pairs starting from a given entangled pair using only local operations. To give response of the above asked question, we study broadcasting of entanglement using state dependent quantum cloning machine as a local copier. We show that the length of the interval f

S. K. Y. Lee, C. K. Law

Faraday rotation based on AC Stark shifts is a mechanism that can entangle the polarization variables of photons and atoms. We analyze the structure of such entanglement by using the Schmidt decomposition method. The time-dependence of entanglement entropy and the effective Schmidt number are derived for Gaussian amplitudes. In particular we show how the ent

Myeong-Gu Park

Radiation interacts with matter via exchange of energy and momentum. When matter is moving with a relativistic velocity or when the background spacetime is strongly curved, rigorous relativistic treatment of hydrodynamics and radiative transfer is required. Here, we derive fully general relativistic radiation hydrodynamic equations from a covariant tensor fo

Shou-hua Zhu

In the standard model, the weak gauge bosons and fermions obtain mass after spontaneous electro-weak symmetry breaking, which is realized through one fundamental scalar field, namely Higgs field. In this paper we study the simplest scalar cold dark matter model in which the scalar cold dark matter also obtains mass through interaction with the weak-doublet H

Rik J. Williams, Smita Mathur, Fabrizio Nicastro, Martin Elvis

The recent detection with Chandra of two warm-hot intergalactic medium (WHIM) filaments toward Mrk 421 by Nicastro et al. provides a measurement of the bulk of the "missing baryons" in the nearby universe. Since Mrk 421 is a bright X-ray source, it is also frequently observed by the XMM-Newton Reflection Grating Spectrometer (RGS) for calibration pur

Y. Yang, R. F. Mushotzky, A. J. Barger, L. L. Cowie

We present the spatial correlation function analysis of non-stellar X-ray point sources in the Chandra Large Area Synoptic X-ray Survey of Lockman Hole Northwest (CLASXS). Our 9 ACIS-I fields cover a contiguous solid angle of 0.4 deg^2 and reach a depth of 3x10^-15 c.g.s in the 2-8 keV band. We supplement our analysis with data from the Chandra Deep Field No

Yun-Song Piao

Recently, the early superinflation driven by phantom field has been proposed and studied. The detection of primordial gravitational wave is an important means to know the state of very early universe. In this brief report we discuss in detail the gravitational wave background excited during the phantom superinflation.

Michael Chertkov, Mikhail G. Stepanov

In Linear Programming (LP) decoding of a Low-Density-Parity-Check (LDPC) code one minimizes a linear functional, with coefficients related to log-likelihood ratios, over a relaxation of the polytope spanned by the codewords \cite{03FWK}. In order to quantify LP decoding, and thus to describe performance of the error-correction scheme at moderate and large Si

J. C. Gómez-Izquierdo, A. Pérez-Lorenzana

Neutrino mixing matrix appears to be close to bimaximal mixing, but for the solar mixing angle which is definitively smaller than forty five degrees. Whereas it seems quite easy to understand bimaximal mixing with the use of new global symmetries, as in models using $L_e - L_μ- L_τ$, understanding the about to eleven degrees of deviation in the observed sola

Philip F. Hopkins, Kevin Bundy, Lars Hernquist, Richard S. Ellis

We compile a number of observations to estimate the time-averaged rate of formation or buildup of red sequence galaxies, as a function of mass and redshift. Comparing this with the mass functions of mergers and quasar hosts, and independently comparing their clustering properties as a function of redshift, we find that these populations trace the same mass d

M. Chiaberge, R. Gilli, F. D. Macchetto, W. B. Sparks

We derive the spectral energy distribution (SED) of the nucleus of the Seyfert galaxy NGC4565. Despite its classification as a Seyfert2, the nuclear source is substantially unabsorbed. The absorption we find from Chandra data (N_H=2.5 X 10^21 cm^-2) is consistent with that produced by material in the galactic disk of the host galaxy. HST images show a nuclea

Jacob Sherson, Brian Julsgaard, E. S. Polzik

The notion of an atom-light quantum interface has been developed in the past decade, to a large extent due to demands within the new field of quantum information processing and communication. A promising type of such interface using large atomic ensembles has emerged in the past several years. In this article we review this area of research with a special em

Ramon Lapiedra

Some new temporal Bell inequalities are deduced under joint realism assumption, using some perfect correlation property. No locality condition is needed. When the measured system is a macroscopic system, joint realism assumption substitutes the non-invasive measurabilioty hypothesis advantegeously, provided that the system satisfies the perfect correlation p

R. Garcia-Maraver, K. Eckert, R. Corbalan, J. Mompart

We present two cavity quantum electrodynamics proposals that, sharing the same basic elements, allow for the deterministic generation of entangled photons pairs by means of a three-level atom successively coupled to two single longitudinal mode high-Q optical resonators presenting polarization degeneracy. In the faster proposal, the three-level atom yields a

X. Lacour, N. Sangouard, S. Guerin, H. R. Jauslin

We propose a robust scheme involving atoms fixed in an optical cavity to directly implement the universal controlled-unitary gate. The present technique based on adiabatic passage uses novel dark states well suited for the controlled-rotation operation. We show that these dark states allow the robust implementation of a gate that is a generalisation of the c

Harvey R. Brown, Christopher G. Timpson

In a comparison of the principles of special relativity and of quantum mechanics, the former theory is marked by its relative economy and apparent explanatory simplicity. A number of theorists have thus been led to search for a small number of postulates - essentially information theoretic in nature - that would play the role in quantum mechanics that the re

F. Verstraete, M. M. Wolf, D. Perez-Garcia, J. I. Cirac

The projected entangled pair state (PEPS) representation of quantum states on two-dimensional lattices induces an entanglement based hierarchy in state space. We show that the lowest levels of this hierarchy exhibit an enormously rich structure including states with critical and topological properties as well as resonating valence bond states. We prove, in p

Heinz-Peter Breuer, Jochen Gemmer, Mathias Michel

The time-convolutionless (TCL) projection operator technique allows a systematic analysis of the non-Markovian quantum dynamics of open systems. We introduce a class of projection superoperators which project the states of the total system onto certain correlated system-environment states. It is shown that the application of the TCL technique to this class o

Washington Barbosa da Silva, Luiz Roncaratti, Geraldo Magela e Silva, Paulo Hora Acioli

In this article we present a caracterization of the vibrational spectrum of the H5+ molecule using the correlation function quantum Monte Carlo (CFQMC) method and a genetic algorithm study of the topology of the potential energy surface used in this work. The vibrational modes associated with the H3+ - H2 torsion and stretching posses very flat minima. As a

C. R. Doering, B. Eckhardt, J. Schumacher

Energy theory for incompressible Newtonian fluids is, in many cases, capable of producing strong absolute stability criteria for steady flows. In those fluids the kinetic energy naturally defines a norm in which perturbations decay monotonically in time at sufficiently low (but non-zero) Reynolds numbers. There are, however, at least two obstructions to the

Wei-Long She

Very recently we present a theory to discuss the nature of light and show that the quantization of light energy in vacuum can be derived directly from classical electromagnetic theory. In the theory a key concept of stability of statistical distribution and a variational procedure searching for those of relatively stable statistical distributions were introd

J. Dukelsky, V. G. Gueorguiev, P. Van Isacker, S. Dimitrova

The complete exact solution of the T=1 neutron-proton pairing Hamiltonian is presented in the context of the SO(5) Richardson-Gaudin model with non-degenerate single-particle levels and including isospin-symmetry breaking terms. The power of the method is illustrated with a numerical calculation for $^{64}$Ge for a $pf+g_{9/2}$ model space which is out of re

Amir H. Rezaeian, Hans-Juergen Pirner

We study the stability of the nuclear matter in a non-local Nambu-Jona-Lasinio model. We work out the equation of state in a relativistic Faddeev approach where we take into account the internal structure of nucleon. We show that the binding energy saturates when the nucleon as a composite particle made of quarks is incorporated. After truncation of the two-

Partha Sharathi Dutta, Bitihotra Routroy, Soumitro Banerjee, S. S. Alam

In this paper we report some important results that help in analizing the border collision bifurcations that occur in n-dimensional discontinuous maps. For this purpose, we use the piecewise linear approximation in the neighborhood of the plane of discontinuity. Earlier, Feigin had made a similar analysis for general n-dimensional piecewise smooth continuous

Wolodymyr Skrypnik

A class of general spin 1/2 lattice models on hyper-cubic lattice $Z^d$, whose Hamiltonians are sums of two functions depending on the Pauli matrices $S^1$, $S^2$ and $S^3$, respectively, are found, which have Gibbsian eigen (ground) states and two order parameters for two spin components $x$, $z$ simultaneously for large values of the parameter $α$ playing

Kazunari Shima, Motomu Tsuda

We show explicitly that a free Lagrangian expressed in terms of scalar, spinor, vector and Rarita-Schwinger (RS) fields is invariant under linear supersymmetry transformations generated by a global spinor-vector parameter. A (generalized) gauge invariance of the Lagrangian for the RS field is also discussed.

Aaron Levin

We study the S-integral points on the complement of a union of hyperplanes in projective space, where S is a finite set of places of a number field k. In the classical case where S consists of the set of archimedean places of k, we completely characterize, in terms of the hyperplanes and the field k, when the (S-)integral points are not Zariski-dense.

Aaron Levin

In this article we completely determine the possible dimensions of integral points and holomorphic curves on the complement of a union of hyperplanes in projective space. Our main theorems generalize a result of Evertse and Gyory, who determined when all sets of integral points (over all number fields) on the complement of a union of hyperplanes are finite,

Martin Niepel

We construct a new family {K_n} of simply connected symplectic 4-manifolds with the property c_1^2(K_n)/chi(K_n) -> 9 (as n goes to infinity).

Michel Talagrand

We construct an exhaustive submeasure that is not equivalent to a measure. This solves problems of J. von Neumann (1937) and D. Maharam (1947).

Claude Dellacherie, Servet Martinez, Jaime San Martin

We prove that the class of GUM matrices is the largest class of bi-potential matrices stable under Hadamard increasing functions. We also show that any power greater than 1, in the sense of Hadamard functions, of an inverse M-matrix is also inverse M-matrix showing a conjecture stated in Neumann 1998. We study the class of filtered matrices, which include na

Jon McCammond

Certain mathematical structures make a habit of reoccuring in the most diverse list of settings. Some obvious examples exhibiting this intrusive type of behavior include the Fibonacci numbers, the Catalan numbers, the quaternions, and the modular group. In this article, the focus is on a lesser known example: the noncrossing partition lattice. The focus of t

Aaron Levin

Let C in C_1xC_2 be a curve of type (d_1,d_2) in the product of the two curves C_1 and C_2. Let d be a positive integer. We prove that if a certain inequality involving d_1, d_2, d, and the genera of the curves C_1, C_2, and C is satisfied, then the set of points P in C(\kbar) with [k(P):k]<=d is finite for any number field k. We prove a similar result for i

Aaron Levin

We study one-parameter families of S-unit equations of the form f(t)u+g(t)v=h(t), where f, g, and h are univariate polynomials over a number field, t is an S-integer, and u and v are S-units. For many possible choices of f, g, and h, we are able to determine all but finitely many solutions to the corresponding one-parameter family of S-unit equations. The re

Olivier Bernardi

The number of tree-rooted maps, that is, rooted planar maps with a distinguished spanning tree, of size $n$ is C(n)C(n+1) where C(n)=binomial(2n,n)/(n+1) is the nth Catalan number. We present a (long awaited) simple bijection which explains this result. We prove that our bijection is isomorphic to a former recursive construction on shuffles of parenthesis sy

Pavel Shvartsman

We give an intrinsic characterization of the restrictions of Sobolev, Triebel-Lizorkin and Besov spaces to regular subsets of $R^n$ via sharp maximal functions and local approximations.

Vladimir Andrievskii

This is a survey of some recent results concerning polynomial inequalities and polynomial approximation of functions in the complex plane. The results are achieved by the application of methods and techniques of modern geometric function theory and potential theory.

Pavel Shvartsman

We characterize the restrictions of first order Sobolev functions to regular subsets of a homogeneous metric space and prove the existence of the corresponding linear extension operator.

Olivier Bernardi

We solve three enumerative problems concerning families of planar maps. More precisely, we establish algebraic equations for the generating function of non-separable triangulations in which all vertices have degree at least d, for a certain value d chosen in {3, 4, 5}. The originality of the problem lies in the fact that degree restrictions are placed both o

Boris Tsirelson

A random dense countable set is characterized (in distribution) by independence and stationarity. Two examples are `Brownian local minima&#39; and `unordered infinite sample&#39;. They are identically distributed. A framework for such concepts, proposed here, includes a wide class of random equivalence classes.

Stefano Galatolo, Dong Han Kim, Kyewon Koh Park

We investigate quantitative recurrence in systems having an infinite measure. We extend the Ornstein-Weiss theorem for a general class of infinite systems estimating return time in decreasing sequences of cylinders. Then we restrict to a class of one dimensional maps with indifferent fixed points and calculate quantitative recurrence in sequences of balls, o

Margherita Barile

We show that for all $n\geq 3$ and all primes $p$ there are infinitely many simplicial toric varieties of codimension $n$ in the $2n$-dimensional affine space whose minimum number of defining equations is equal to $n$ in characteristic $p$, and lies between $2n-2$ and $2n$ in all other characteristics. In particular, these are new examples of varieties which

Kirill Zainoulline

Let A and B be two central simple algebras of a prime degree n over a field F generating the same subgroup in the Brauer group. We show that the Chow motive of a Severi-Brauer variety SB(A) is a direct summand of the motive of a generalized Severi-Brauer variety SB_d(B) if and only if [A]=d[B] or [A]=-d[B] in the Brauer group. The proof uses methods of Schub

Filippo Bracci, Manuel D. Contreras, Santiago Diaz-Madrigal

We characterize the infinitesimal generator of a semigroup of linear fractional self-maps of the unit ball in $\mathbb C^n$, $n\geq 1$. For the case $n=1$ we also completely describe the associated Koenigs function and we solve the embedding problem from a dynamical point of view, proving, among other things, that a generic semigroup of holomorphic self-maps

A. Dimca, Ph. Maisonobe, M. Saito, T. Torrelli

We show that the restriction to a smooth transversal section commutes to the computation of multiplier ideals and V-filtrations. As an application we prove the constancy of the spectrum along any stratum of a Whitney regular stratification.

Nicole Lemire, Jan Minac, Andrew Schultz, John Swallow

Assuming the Bloch-Kato Conjecture, we determine precise conditions under which Hilbert 90 is valid for Milnor k-theory and Galois cohomology. In particular, Hilbert 90 holds for degree n when the cohomological dimension of the Galois group of the maximal p-extension of F is at most n.

Dongho Chae

In this brief note we show that the author&#39;s previous result in \cite{cha} on the nonexistence of self-similar singularities for the 3D incompressible Euler equations implies actually the nonexistence of `locally self-similar&#39; singular solution, which has been sought by many physicists.

Chongying Dong, Cuipo Jiang

Let V be a vertex operator algebra and m,n be nonnegative integers. We construct an A_n(V)-A_m(V)-bimodule A_{n,m}(V) which determines the action of V from the level m subspace to level n subspace of an admissible V-module. We show how to use A_{n,m}(V) to construct naturally admissible V-modules from A_m(V)-modules. We also determine the structure of A_{n,m

Enrique Pardo, Friedrich Wehrung

We give an elementary characterization of those (abelian) semigroups $M$ that are direct limits of countable sequences of finite direct products of monoids of the form $C\cup\{0\}$ for monogenic groups $C$. This characterization involves the Riesz refinement property together with lattice-theoretical properties of the collection of subgroups of $M$, and it m

Andrew S. Toms

An unital C*-algebra A is said to have cancellation of projections if the semigroup D(A) of Murray-von Neumann equivalence classes of projections in matrices over A is cancellative. It has long been known that stable rank one implies cancellation, and some partial convereses have been established. We prove that cancellation does not imply stable rank one for

Kouichi Takemura

Eigenvalues of the Lamé operator are studied as complex-analytic functions in period $τ$ of an elliptic function. We investigate the branching of eigenvalues numerically and clarify the relationship between the branching of eigenvalues and the convergent radius of a perturbation series.

Akira Ishida, Yoonbai Kim, Seyen Kouwn

We study decay of a flat unstable D$p$-brane in the context of boundary string field theory action. Three types of homogeneous rolling tachyons are obtained without and with Born-Infeld type electromagnetic field.

Chanju Kim, Yoonbai Kim, O-Kab Kwon, Ho-Ung Yee

We study tachyon kinks with and without electromagnetic fields in the context of boundary string field theory. For the case of pure tachyon only an array of kink-antikink is obtained. In the presence of electromagnetic coupling, all possible static codimension-one soliton solutions such as array of kink-antikink, single topological BPS kink, bounce, half kin

Volker Braun, Yang-Hui He, Burt A. Ovrut

In this paper, we present a formalism for computing the Yukawa couplings in heterotic standard models. This is accomplished by calculating the relevant triple products of cohomology groups, leading to terms proportional to Q*H*u, Q*Hbar*d, L*H*nu and L*Hbar*e in the low energy superpotential. These interactions are subject to two very restrictive selection r

James E. Lidsey, David J. Mulryne

Positively-curved, oscillatory universes have recently been shown to have important consequences for the pre-inflationary dynamics of the early universe. In particular, they may allow a self-interacting scalar field to climb up its potential during a very large number of these cycles. The cycles are naturally broken when the potential reaches a critical valu

Ion I. Cotăescu, Mihai Visinescu

We present the properties of new Dirac-type operators generated by real or complex-valued special Killing-Yano tensors that are covariantly constant and represent roots of the metric tensor. In the real case these are just the so called complex or hyper-complex structures of the K\&#34; ahlerian manifolds. Such a Killing-Yano tensor produces simultaneously a

Mian Wang

Recent observations confirm that our universe is flat and consists of a dark energy component with negative pressure. This dark energy is responsible for the recent cosmic acceleration as well as determines the feature of future evolution of the universe. In this paper, we discuss the dark energy of the universe in the framework of scalar-tensor cosmology. I

Yidun Wan

Markopoulou and Smolin have argued that the low energy limit of LQG may suffer from a conflict between locality, as defined by the connectivity of spin networks, and an averaged notion of locality that emerges at low energy from a superposition of spin network states. This raises the issue of how much non-locality, relative to the coarse grained metric, can

Kazuyuki Furuuchi

The large $N$ reductions in gauge theories are identified with dimensional reductions with homogeneous distribution of the eigenvalues of the gauge field, and it is used to identify the corresponding closed string descriptions in the Maldacena duality. When one does not take the zero-radii limit, the large $N$ reductions are naturally extended to the equival

Howard E. Haber, Heather E. Logan, Siannah Penaranda, David Temes

We consider the leading one-loop Yukawa-coupling corrections to the h^0 b b-bar coupling at O(m_t^2)in the MSSM in the decoupling limit. The decoupling behavior of the corrections from the various MSSM sectors is analyzed in the case of having some or all of the supersymmetric mass parameters and/or the CP-odd Higgs mass large as compared to the electroweak

Andrew G. Cohen, Sheldon L. Glashow

By Very Special Relativity (VSR) we mean descriptions of nature whose space-time symmetries are certain proper subgroups of the Poincaré group. These subgroups contain space-time translations together with at least a 2-parameter subgroup of the Lorentz group isomorphic to that generated by $K_{x}+J_{y}$ and $K_{y}-J_{x}$. We find that VSR implies special rel

G. Heinrich

A method based on sector decomposition is briefly described which is suitable for the calculation of the double real radiation part of e^+e^- to 3 jets at next-to-next-to-leading order in a fully differential way.

S. Ostapchenko

Contemporary models of hadronic interactions are reviewed. Basic phenomenological approaches are compared, with an emphasizes on the predicted air shower characteristics. Special attention is payed to the remaining discrepancies between present hadronic MC generators and cosmic ray data. Finally, future prospects concerning model improvements are discussed,

C. Royon

In these lectures, we describe some recent results from the DØand CDF experiments at the Tevatron.

C. Royon

We use a Monte Carlo implementation of recently developped models of inclusive and exclusive diffractive $W$, top, Higgs and stop productions to assess the sensitivity of the LHC experiments. We also discuss how the Tevatron experiments could test the models and measure the gluon density in the pomeron, which is needed to make precise predictions at the LHC.

Ernest Ma

A minimal extension of the Standard Model is proposed, where the observed left-handed neutrinos obtain naturally small Majorana masses from a one-loop radiative seesaw mechanism. This model has two candidates (one bosonic and one fermionic) for the dark matter of the Universe. It has a very simple structure and should be verifiable in forthcoming experiments

Francisco del Aguila, Manuel Perez-Victoria, Jose Santiago

We study how theories defined in (extra-dimensional) spaces with localized defects can be described perturbatively by effective field theories in which the width of the defects vanishes. These effective theories must incorporate a ``classical&#39;&#39; renormalization, and we propose a renormalization prescription a la dimensional regularization for codimens

A. Peshier

Emphasizing the importance of renormalization in the context of thermal field theory in general, it is pointed out that the Debye mass in the hot quark gluon plasma is determined by the coupling at the scale $m_D$, not $T$ as commonly presumed. The mended result agrees quantitatively with lattice QCD calculations in the strong coupling regime almost down to

Zhun Lu, Ivan Schmidt

We investigate the exclusive two-pion production at the $Z$-pole through the process $e^+e^-\to Z \to ππγ$. In the kinematical region where the invariant mass of the two pions is much smaller than the mass of the $Z$ boson, the process can be factorized into the convolution of a hard coefficient and a soft matrix element, the generalized distribution amplitu

K. R. Koehler

We use direct products of Einstein Metrics to construct new solutions to Einstein&#39;s Equations with cosmological constant. We illustrate the technique with three families of solutions having the geometries Kerr/de Sitter X de Sitter, Kerr/anti-de Sitter X anti-de Sitter and Kerr X Kerr.

J. E. Aman, Ingemar Bengtsson, Narit Pidokrajt

The Hessian of either the entropy or the energy function can be regarded as a metric on a Gibbs surface. For two parameter families of asymptotically flat black holes in arbitrary dimension one or the other of these metrics are flat, and the state space is a flat wedge. The mathematical reason for this is traced back to the scale invariance of the Einstein-M

T. Clifton, John D. Barrow

We investigate the effect of deviations from general relativity on approach to the initial singularity by finding exact cosmological solutions to a wide class of fourth-order gravity theories. We present new anisotropic vacuum solutions of modified Kasner type and demonstrate the extent to which they are valid in the presence of non-comoving perfect-fluid ma

Joan Josep Ferrando

The basic elements of Coll positioning systems (n clocks broadcasting electromagnetic signals in a n-dimensional space-time) are presented in the two-dimensional case. This simplified approach allows us to explain and to analyze the properties and interest of these relativistic positioning systems. The positioning system defined in flat metric by two geodesi

Kourosh Nozari, A. S. Sefiedgar

There are several approaches to quantum gravitational corrections of black hole thermodynamics. String theory and loop quantum gravity, by direct analysis on the basis of quantum properties of black holes, show that in the entropy-area relation the leading order correction should be of log-area type. On the other hand, generalized uncertainty principle(GUP)

Varqa Abyaneh, Bernard S. Kay

In ``Decoherence of macroscopic closed systems within Newtonian quantum gravity&#39;&#39; (Kay B S 1998 Class. Quantum Grav. 15 L89-L98) it was argued that, given a many-body Schroedinger wave function ψ(x_1,...,x_N) for the centre-of-mass degrees of freedom of a closed system of N identical uniform-mass balls of mass M and radius R, taking account of quantu

Mustafa M. Ozer, James R. Thompson, Hanno H. Weitering

Superconductivity is inevitably suppressed in reduced dimensionality. Questions of how thin superconducting wires or films can be before they lose their superconducting properties have important technological ramifications and go to the heart of understanding coherence and robustness of the superconducting state in quantum-confined geometries. Here, we explo

Luiz O. de Oliveira Filho, Francisco Alexandre da Costa, Carlos S. O. Yokoi

The random-energy model is studied in the presence of random fields. The problem is solved exactly both in the microcanonical ensemble, without recourse to the replica method, and in the canonical ensemble using the replica formalism. The phase diagrams for bimodal and Gaussian random fields are investigated in detail. In contrast to the Gaussian case, the b

C. W. J. Beenakker

The conductance G of a pair of single-channel point contacts in series, one of which is a spin filter, increases from 1/2 to 2/3 x e^2/h with more and more spin-flip scattering. This excess conductance was observed in a quantum dot by Zumbuhl et al., and proposed as a measure for the spin relaxation time T_1. Here we present a quantum mechanical theory for t

K. Lai, T. M. Lu, W. Pan, D. C. Tsui

We have investigated the valley splitting of two-dimensional electrons in high quality Si/Si$_{1-x}$Ge$_x$ heterostructures under tilted magnetic fields. For all the samples in our study, the valley splitting at filling factor $ν=3$ ($Δ_3$) is significantly different before and after the coincidence angle, at which energy levels cross at the Fermi level. On

Tim Schmiedl, Thomas Speck, Udo Seifert

Entropy production along a single stochastic trajectory of a biomolecule is discussed for two different sources of non-equilibrium. For a molecule manipulated mechanically by an AFM or an optical tweezer, entropy production (or annihilation) occurs in the molecular conformation proper or in the surrounding medium. Within a Langevin dynamics, a unique identif

Francesc Malet, Enrico Lipparini, Manuel Barranco, Martí Pi

We have studied the relevance of spin-orbit coupling to the dispersion 00009 relation of the Larmor resonance observed in inelastic light scattering and electron-spin resonance experiments on GaAs quantum wells. We show that the spin-orbit interaction, here described by a sum of Dresselhaus and Bychkov-Rashba terms, couples Zeeman and spin-density excitation

A. Lupascu, E. F. C. Driessen, L. Roschier, C. J. P. M. Harmans

We demonstrate high-contrast state detection of a superconducting flux qubit. Detection is realized by probing the microwave transmission of a nonlinear resonator, based on a SQUID. Depending on the driving strength of the resonator, the detector can be operated in the monostable or the bistable mode. The bistable operation combines high-sensitivity with int

Y. T. Xing, I. Barb, R. Gerritsma, R. J. C. Spreeuw

We describe the design and fabrication of novel all-magnetic atom chips for use in ultracold atom trapping. The considerations leading to the choice of nanocrystalline exchange coupled FePt as best material are discussed. Using stray field calculations, we designed patterns that function as magnetic atom traps. These patterns were realized by spark erosion o

Xuhui Wang, Gerrit E. W. Bauer, Teruo Ono

The current driven magnetization dynamics of a thin-film, three magnetic terminal device (spin-flip transistor) is investigated theoretically. We consider a magnetization configuration in which all magnetizations are in the device plane, with source-drain magnetizations chosen fixed and antiparallel, whereas the third contact magnetization is allowed to move

Taketo Moyoshi, Yukio Yasui, Minoru Soda, Yoshiaki Kobayashi

Neutron inelastic scattering studies on aligned crystals of NaxCoO2.yD2O have been carried out. Significant scattering has been observed for phonons originating from the vibrations of the short-range ordered D2O molecules. No firm evidence for the magnetic fluctuations has been found for the NaxCoO2.yD2O, while the very weak intensity modulation observed in

Xuhui Wang, Gerrit E. W. Bauer, Axel Hoffmann

A &#34;spin-flip transistor&#34; is a lateral spin valve consisting of ferromagnetic source drain contacts to a thin-film normal-metal island with an electrically floating ferromagnetic base contact on top. We analyze the \emph{dc}-current-driven magnetization dynamics of spin-flip transistors in which the source-drain contacts are magnetized perpendicularly

M. K. Olsen, M. J. Davis

In a recent experiment Campbell et al. [Phys. Rev. Lett. 96, 020406 (2006)] observed degenerate four-wave mixing of matter-waves in a one-dimensional optical lattice, a process with potential for generating entanglement among atoms. We analyse the essential quantum features of the experiment to show that entanglement is created between the quadratures of the

W. Pan, H. L. Stormer, D. C. Tsui, L. N. Pfeiffer

The magnetoresistance, Rxx, at even-denominator fractional fillings, of an ultra high quality two-dimensional electron system at T ~ 35 mK is observed to be strictly linear in magnetic field, B. While at 35mK Rxx is dominated by the integer and fractional quantum Hall states, at T~1.2K an almost perfect linear relationship between Rxx vs B emerges over the w

Daniel E. Gómez, Joel van Embden, Paul Mulvaney

We have explored the influence of different matrices on the emission line shape of individual homogeneously coated CdSe/CdS/ZnS nanocrystals. The results obtained corroborate previous observations of a correlation between blinking events and spectral diffusion but in addition we have found that the extent of spectral diffusion is almost independent of the di

Lachezar S. Georgiev, Michael R. Geller

The nu=5/2 fractional quantum Hall effect state has attracted great interest recently, both as an arena to explore the physics of non-Abelian quasiparticle excitations, and as a possible architecture for topological quantum information processing. Here we use the conformal field theoretic description of the Moore-Read state to provide clear tunneling signatu

Thomas Vojta, Man Young Lee

We show that the interplay between geometric criticality and dynamical fluctuations leads to a novel universality class of the contact process on a randomly diluted lattice. The nonequilibrium phase transition across the percolation threshold of the lattice is characterized by unconventional activated (exponential) dynamical scaling and strong Griffiths effe

Radhakrishnan Nagarajan

Scaling analysis of the magnitude series (volatile series) has been proposed recently to identify possible nonlinear/multifractal signatures in the given data [1-3]. In this letter, correlations of volatile series generated from stationary first-order linear feedback process with Gaussian and non-Gaussian innovations are investigated. While volatile correlat