February 2005 arXiv papers — page 8

Rajiv V. Gavai, Sourendu Gupta

The Wroblewski parameter is a convenient indicator of strangeness production and can be employed to monitor a signal of quark-gluon plasma production : enhancement of strangeness production. It has been shown to be about a factor two higher in heavy ion collisions than in hadronic collisions. Using a method proposed by us earlier, we obtained lattice QCD res

Jorge Zanelli

This is intended as a broad introduction to Chern-Simons gravity and supergravity. The motivation for these theories lies in the desire to have a gauge invariant system --with a fiber bundle formulation-- in more than three dimensions, which could provide a firm ground for constructing a quantum theory of the gravitational field. The starting point is a grav

Subir Ghosh, Probir Pal

We have proposed a generally covariant non-relativistic particle model that can represent the $κ$-Minkowski noncommutative spacetime. The idea is similar in spirit to the noncommutative particle coordinates in the lowest Landau level. Physically our model yields a novel type of dynamical system, (termed here as Exotic "Oscillator"), that obeys a Harm

Shao-You Zhao, Wen-Li Yang, Yao-Zhong Zhang

We construct the Drinfeld twists (factorizing $F$-matrices) of the $gl(m|n)$-invariant fermion model. Completely symmetric representation of the pseudo-particle creation operators of the model are obtained in the basis provided by the $F$-matrix (the $F$-basis). We resolve the hierarchy of the nested Bethe vectors in the $F$-basis for the $gl(m|n)$ supersymm

L. Fang, Y. Wang, P. Y. Zou, L. Tang

In this paper we report the growth and superconductivity of $Na_xTaS_2$ crystals. The structural data deduced from X-ray diffraction pattern shows that the sample has the same structure as $2H-TaS_2$. A series of crystals with different superconducting transition temperatures ($T_c$) ranging from 2.5 K to 4.4 K were obtained. It is found that the $T_c$ rises

D. C. Hannikainen, J. Rodriguez, O. Vilhu, L. Hjalmarsdotter

We report on the analysis of 100 ks INTEGRAL observations of the Galactic microquasar GRS 1915+105. We focus on INTEGRAL Revolution number 48 when the source was found to exhibit a new type of variability as preliminarily reported in Hannikainen et al. (2003). The variability pattern, which we name $ξ$, is characterized by a pulsing behaviour, consisting of

S. Krasnikov

Recently the structure of the Letelier-Gal'tsov spacetime has become a matter of some controversy. I show that the metric proposed in \cite{letgal} is defined only on a dense subset of the whole manifold. In the case when it can be defined on the remainder by continuity, the resulting spacetime corresponds to a system of parallel cosmic strings at rest w

Ely Kerman

We use Floer homology to study the Hofer-Zehnder capacity of neighborhoods near a closed symplectic submanifold M of a geometrically bounded and symplectically aspherical ambient manifold. We prove that, when the unit normal bundle of M is homologically trivial in degree dim(M) (for example, if codim(M) > dim(M)), a refined version of the Hofer-Zehnder capac

Alan M. Kadin

A simple real-space model for the electron wavefunction is suggested, based on a transverse wave with helicity, rotating at mc^2/h. The mapping of the real two-dimensional vector phasor to the complex plane permits this to satisfy the standard time-dependent Schroedinger equation. This model is extended to provide an intuitive physical picture of electron sp

Andreas Klappenecker, Martin Roetteler

The Mean King's problem asks to determine the outcome of a measurement that is randomly selected from a set of complementary observables. We review this problem and offer a combinatorial solution. More generally, we show that whenever an affine resolvable design exists, then a state reconstruction problem similar to the Mean King's problem can be def

Ken Loo

The goals of this paper are to show the following. First, Grover's algorithm can be viewed as a digital approximation to the analog quantum algorithm proposed in "An Analog Analogue of a Digital Quantum Computation", by E. Farhi and S. Gutmann, Phys.Rev. A 57, 2403 - 2406 (1998), quant-ph/9612026. We will call the above analog algorithm the Grove

Adan Cabello, John Calsamiglia

The absent-minded driver's problem illustrates that probabilistic strategies can give higher pay-offs than deterministic ones. We show that there are strategies using quantum entangled states that give even higher pay-offs, both for the original problem and for the generalized version with an arbitrary number of intersections and any possible set of pay-

L. J. Boya, J. Casahorran

We deduce Levinson\'{}s theorem in non-relativistic quantum mechanics in one dimension as a sum rule for the spectral density constructed from asymptotic data. We assume a self-adjoint hamiltonian which guarantees completeness; the potential needs not to be isotropic and a zero-energy resonance is automatically taken into account. Peculiarities of this o

Alioscia Hamma, Radu Ionicioiu, Paolo Zanardi

We investigate bipartite entanglement in spin-1/2 systems on a generic lattice. For states that are an equal superposition of elements of a group $G$ of spin flips acting on the fully polarized state $\ket{0}^{\otimes n}$, we find that the von Neumann entropy depends only on the boundary between the two subsystems $A$ and $B$. These states are stabilized by

Veit Schwämmle, Suzana M. de Oliveira

The Penna model is a strategy to simulate the genetic dynamics of age-structured populations, in which the individuals genomes are represented by bit-strings. It provides a simple metaphor for the evolutionary process in terms of the mutation accumulation theory. In its original version, an individual dies due to inherited diseases when its current number of

Martin Gander, Christian Mazza, Hansklaus Rummler

We study a stochastic model proposed recently in the genetic literature to explain the heterogeneity of cell populations or of gene products. Cells are located in two colonies, whose sizes fluctuate as birth and migration processes in switching environments. We prove that there is a range of parameters where heterogeneity induces a larger mean fitness

Pablo Balenzuela Jordi Garcia-Ojalvo

We examine the behavior in the presence of noise of an array of Morris-Lecar neurons coupled via chemical synapses. Special attention is devoted to comparing this behavior with the better known case of electrical coupling arising via gap junctions. In particular, our numerical simulations show that chemical synapses are more efficient than gap junctions in e

Stefan Klumpp, Theo M. Nieuwenhuizen, Reinhard Lipowsky

The stationary states of systems with many molecular motors are studied theoretically for uniaxial and centered (aster-like) arrangements of cytoskeletal filaments using Monte Carlo simulations and a two-state model. Mutual exclusion of motors from binding sites of the filaments is taken into account. For small overall motor concentration, the density profil

Gianluca Geloni, Evgeni Saldin, Evgeni Schneidmiller, Mikhail Yurkov

This work contains a systematic treatment of single particle Synchrotron Radiation and some application to realistic beams with given cross section area, divergence and energy spread. Standard theory relies on several approximations whose applicability limits and accuracy are often forgotten. We begin remarking that on the one hand, a paraxial approximation

C. Anteneodo, R. Riera

We investigate a generalized stochastic model with the property known as mean reversion, that is, the tendency to relax towards a historical reference level. Besides this property, the dynamics is driven by multiplicative and additive Wiener processes. While the former is modulated by the internal behavior of the system, the latter is purely exogenous. We fo

S. Bize, P. Laurent, M. Abgrall, H. Marion

This paper describes advances in microwave frequency standards using laser-cooled atoms at BNM-SYRTE. First, recent improvements of the $^{133}$Cs and $^{87}$Rb atomic fountains are described. Thanks to the routine use of a cryogenic sapphire oscillator as an ultra-stable local frequency reference, a fountain frequency instability of $1.6\times 10^{-14}τ^{-1

F. F. Valiev

A simulation of electric current pulses formed by a packet of gamma-quanta moving through an absorptive medium is presented. The electromagnetic fields of the current pulse moving along the straight line with super light velocity are obtained

J. A. Sherman, T. W. Koerber, A. Markhotok, W. Nagourney

Using a single trapped barium ion we have developed an rf spectroscopy technique to measure the ratio of the off-resonant vector ac Stark effect (or light shift) in the 6S_{1/2} and 5D_{3/2} states to 0.1% precision. We find R = Delta_S / Delta_D = -11.494(13) at 514.531 nm where Delta_{S,D} are the light shifts of the m = +/- 1/2 splittings due to circularl

M. Bender, P. -H. Heenen

Starting from successful self-consistent mean-field models, this paper discusses why and how to go beyond the mean field approximation. To include long-range correlations from fluctuations in collective degrees of freedom, one has to consider symmetry restoration and configuration mixing, which give access to ground-state correlations and spectroscopy.

Stefan Scherer, Horst Stocker

Nuclear collisions at intermediate, relativistic, and ultra-relativistic energies offer unique opportunities to study in detail manifold fragmentation and clustering phenomena in dense nuclear matter. At intermediate energies, the well known processes of nuclear multifragmentation -- the disintegration of bulk nuclear matter in clusters of a wide range of si

M. Papa, G. Giuliani, A. Bonasera

In this work we illustrate the basic development of the constrained molecular dynamics applied to the N-body problem in nuclear physics. The heavy computational taskes related to quantum effects, to the presence of the "hard core" repulsive interaction have been worked out by defining a set of transformations based on the concept of impulsive forces.

Klaus Reygers

Direct photons are an important tool for the detection of the quark-gluon plasma in ultra-relativistic nucleus-nucleus collisions. Direct-photon measurements were made in Pb+Pb collisions at sqrt{s_NN}=17.2 GeV and in Au+Au collisions at sqrt{s_NN}=200 GeV. These results are reviewed and compared with model calculations.

C. M. Casciola, P. Gualtieri, B. Jacob, R. Piva

Recent developments in turbulence are focused on the effect of large scale anisotropy on the small scale statistics of velocity increments. According to Kolmogorov, isotropy is recovered in the large Reynolds number limit as the scale is reduced and, in the so-called inertial range, universal features -namely the scaling exponents of structure functions - em

Won-Ho Kye, Muhan Choi, Chil-Min Kim, Young-Jai Park

We propose a new communication scheme that uses time-delayed chaotic systems with delay time modulation. In this method, the transmitter encodes a message as an additional modulation of the delay timeand then the receiver decodes the message by tracking the delay time.We demonstrate our communication scheme in a system of coupled logistic maps.Also we discus

David Damanik, Serguei Tcheremchantsev

We develop a general method to bound the spreading of an entire wavepacket under Schrödinger dynamics from above. This method derives upper bounds on time-averaged moments of the position operator from lower bounds on norms of transfer matrices at complex energies. This general result is applied to the Fibonacci operator. We find that at sufficiently large c

Daniel Bump, Alex Gamburd

We provide an elementary and self-contained derivation of formulae for products and ratios of characteristic polynomials from classical groups using classical results due to Weyl and Littlewood.

Sara Billey, Ravi Vakil

Using a blend of combinatorics and geometry, we give an algorithm for algebraically finding all flags in any zero-dimensional intersection of Schubert varieties with respect to three transverse flags, and more generally, any number of flags. In particular, the number of flags in a triple intersection is also a structure constant for the cohomology ring of th

Elie Feder

The braid group has recently attracted much attention. This is primarily based upon the discovery of its usage in various cryptosystems [AAG],[KLCHKP]. One major focus of current research has been in solving decision problems in braid groups and analyzing their complexity. Among the decision problems which have been investigated are: the word problem, the co

Ser Peow Tan, Yan Loi Wong, Ying Zhang

We study general representations of the free group on two generators into $SL(2,C)$, and the connection with generalized Markoff maps, following Bowditch. We show that Bowditch's Q-conditions for generalized Markoff maps are sufficient for the generalized McShane identity to hold for the corresponding representations and that the subset of representation

Yona Cherniavsky, Eli Bagno

A product formula for the parity generating function of the number of 1's in invertible matrices over Z_2 is given. The computation is based on algebraic tools such as the Bruhat decomposition. The same technique is used to obtain a parity generating function also for symplectic matrices over Z_2. We present also a generating function for the sum of entr

Yi Hu

In this paper, we prove that any two birational projective varieties with finite quotient singularities can be realized as two geometric GIT quotients of a non-singular projective variety by a reductive algebraic group. Then, by applying the theory of Variation of Geometric Invariant Theory Quotients ([3]), we show that they are related by a sequence of GIT

Taekyun Kim

We construct the q-extension of the Hurwitz's type L-function which interpolates the q-extension of generalized Bernoulli polynomials attached to $chi$.

José Carlos Corrêa Eidam, Paolo Piccione

In this article, we give a simple and direct proof of the Yoshida-Nicolaescu Theorem in a more general context by using the theory of partial signatures. We do not impose the usual condition of non-degeneracy at the endpoints and use a natural definition of the Maslov index.

Sebastien Gouezel

We prove that solutions $u$ of the equation $f=u-u\circ T$ are automatically Holder continuous when $f$ is Holder continuous, and $T$ is non uniformly expanding and Markov. This result applies in particular to Young towers and to intermittent maps.

F. Hivert, J. -C. Novelli, J. -Y. Thibon

We propose several constructions of commutative or cocommutative Hopf algebras based on various combinatorial structures, and investigate the relations between them. A commutative Hopf algebra of permutations is obtained by a general construction based on graphs, and its non-commutative dual is realized in three different ways, in particular as the Grossman-

John Lindsay Orr

We continue the study of the rich family of norm-closed, automorphism invariant ideals of a continuous nest algebra. First we present a unified framework which captures all stable ideals as the kernels of limits of diagonal compressions. We then characterize when two such limits give rise to the same ideal, and we obtain detailed information of the structure

Ivan K. Babenko, Florent N. Balacheff

For a Riemannian polyhedra, we study the geometry of the unit ball for the unidimensional stable norm (stable ball). In the case of a unidimensional Riemannian polyhedra (graph), we show that the stable ball is a polytope whose vertices are completely described by combinatorial properties of the graph. We study then the realizable forms as stable ball of Rie

Peter Balint, Sebastien Gouezel

We prove that the Birkhoff sums for ``almost every'' relevant observable in the stadium billiard obey a non-standard limit law. More precisely, the usual central limit theorem holds for an observable if and only if its integral along a one-codimensional invariant set vanishes, otherwise a $\sqrt{n\log n}$ normalization is needed. As one of the two ke

Victorita Dolean, Frédéric Nataf

In this work we design a new domain decomposition method for the Euler equations in 2 dimensions. The basis is the equivalence via the Smith factorization with a third order scalar equation to whom we can apply an algorithm inspired from the Robin-Robin preconditioner for the convection-diffusion equation. Afterwards we translate it into an algorithm for the

M. Sadowski

The results of the paper concern the topological structure of complete riemannian manifolds with cyclic holonomy groups and low-dimensional orientable complete flat manifolds. We also discuss related results such as the affine classification of orientable complete flat 4-manifolds, an algebraic criterion of an affine equivalence, the relationship between hol

Eric Mourre

From the method of realization of bialgebras developped in a preceding paper, we obtain the Duality Theorem and apply it to the study of the ideal of relations for each realized bialgebra. This is detailed in the english version of the abstract of this paper.

Volker Heiermann

The result in theorem 2.1 has been strengthened (see theorem 2.3) and the remarks in the introduction and the text adapted to this new result. Also some misprints in the previous version have been corrected.

Ira M. Gessel, Guoce Xin

We give a formal Laurent series proof of Andrews's $q$-Dyson Conjecture, first proved by Zeilberger and Bressoud.

Alfonso Gracia-Saz

We give an explicit formula for the symbol of a function of an operator. Given an operator {\hat A} on L^2(R^N) with symbol A, and a function f, we obtain the symbol of f(\hat A) in terms of A. As an application, Bohr-Sommerfeld quantization rules are explicitely calculated at order 4 in hbar.

Guoce Xin

In this paper, we establish a residue theorem for Malcev-Neumann series that requires few constraints, and includes previously known combinatorial residue theorems as special cases. Our residue theorem identifies the residues of two formal series that are related by a change of variables. We obtain simple conditions for when a change of variables is possible

Steven F. Bellenot

Necessary and sufficient conditions are given for when a sequence of finite dimensional subspaces (X_n) can be blocked to be a skipped blocking decompositon (SBD). These are very similar to known results about blocking of biorthogonal sequences. A separable space $X$ has PCP, if and only if, every norming decomposition (X_n) can be blocked to be a boundedly

A. B. Goncharov

We discuss several approaches to motivic complexes and explicit constructions of the regulator maps from the motivic complexes to Deligne complexes.

V. Rotger, A. Skorobogatov, A. Yafaev

We show how to construct counter-examples to the Hasse principle over the field of rational numbers on Atkin-Lehner quotients of Shimura curves and on twisted forms of Shimura curves by Atkin-Lehner involutions. A particular example is the quotient of the Shimura curve X attached to the indefinite rational quaternion algebra of discriminant 23*107 by the Atk

Sebastien Gouezel, Carlangelo Liverani

We study the spectral properties of the Ruelle-Perron-Frobenius operator associated to an Anosov map on classes of functions with high smoothness. To this end we construct anisotropic Banach spaces of distributions on which the transfer operator has a small essential spectrum. In the C^\infty case, the essential spectral radius is arbitrarily small, which yi

Brian Conrey, Alex Gamburd

We compute integral moments of partial sums of the Riemann zeta function on the critical line and obtain an expression for the leading coefficient as a product of the standard arithmetic factor and a geometric factor. The geometric factor is equal to the volume of the convex polytope of substochastic matrices and is equal to the leading coefficient in the ex

Reza Javaherdashti

After certain subsets of Natural numbers called Range and Row are defined, we assume (1) there is a function that can produce prime numbers and (2) each even number greater than 2, like A, can be represented as the sum of n prime numbers. We show this by DC(A)less than or equal to n. Each Row is similar to each other in properties,(so is each Range). It is p

Ioannis Giannakis

In this paper we discuss symmetry breaking in string theory. Spacetime symmetries are implemented as inner automorphisms of the underlying superconformal algebra. Conserved currents generate unbroken spacetime symmetries. As we deform the classical solutions of the string equations of motion, the deformed currents continue to generate spontaneously broken sy

P. Merlatti, F. Sannino, G. Vallone, F. Vian

We investigate the vacuum structure of pure SU(N) N=1 super Yang-Mills. The theory is expected to possess N vacua with associated domain walls. We show that the newly extended version of the low energy effective Lagrangian for super Yang-Mills supports the BPS domain wall solutions associated with any two vacua aligned with the origin of the moduli space. Fo

David Alba, Luca Lusanna

We introduce a family of relativistic non-rigid non-inertial frames as a gauge fixing of the description of N positive energy particles in the framework of parametrized Minkowski theories. Then we define a multi-temporal quantization scheme in which the particles are quantized, but not the gauge variables describing the non-inertial frames: {\it they are con

M. Göckeler, R. Horsley, A. C. Irving, D. Pleiter

We present a determination of the QCD parameter Lambda in the quenched approximation (n_f=0) and for two flavours (n_f=2) of light dynamical quarks. The calculations are performed on the lattice using O(a) improved Wilson fermions and include taking the continuum limit. We find Lambda_{n_f=0} = 259(1)(20) MeV and Lambda_{n_f=2} = 261(17)(26) MeV}, using r_0

Alexander Grigoriev, Alexander Studenikin, Alexei Ternov

We consider propagation of a massive neutrino in matter within the quantum approach based on the two equations for the neutrino field: the first one is the Dirac-Pauli equation for a massive neutrino in an external magnetic field generalized on the inclusion of effects of the background matter; the second one is the modified Dirac equation derived directly f

R. Casalbuoni, S. De Curtis, D. Dolce, D. Dominici

We discuss the fermion couplings in a four dimensional SU(2) linear moose model by allowing for direct couplings between the left-handed fermions on the boundary and the gauge fields in the internal sites. This is realized by means of a product of non linear $σ$-model scalar fields which, in the continuum limit, is equivalent to a Wilson line. The effect of

Paul Hoyer

The phenomenological success of PQCD is based on processes where the effects of the color field environment on parton propagation can be eliminated or is universal. In hard diffraction and quarkonium production the PQCD subprocess is the same as in fully inclusive scattering, but the sensitivity to reinteractions is different. I discuss how this may be explo

Tor Jacobsen

The mass of some hadrons are reproduced in terms of the mass of the nucleon. A possible reason for emission of soft gammas is proposed.

H. Fujii, F. Gelis, R. Venugopalan

In this note, we discuss the problem of quark-antiquark pair production in the framework of the color glass condensate. The cross-section can be calculated in closed form for the case of proton-nucleus collisions, where the proton can be considered to be a dilute object. We find that kt-factorization is broken by rescattering effects.

Matteo Cacciari, Paolo Nason, Ramona Vogt

We make up-to-date QCD predictions for open charm and bottom production at RHIC in nucleon-nucleon collisions at \sqrt{S} = 200 GeV. We also calculate the electron spectrum resulting from heavy flavor decays to allow direct comparison to the data. A rigorous benchmark, including the theoretical uncertainties, is established against which nuclear collision da

R. Kirschner

Integral kernels describing the pair interaction of reggeized gluons and quarks are reconstructed in terms of conformal symmetric 4-point functions in the transverse plane of impact parameters.

Z. G. Xiao, H. Q. Zheng

By studying $ππ$ scattering amplitudes in the large $N_c$ limit, we clarify the $N_c$ dependence of the $S$ matrix pole position. It is demonstrated that analyticity and the $N_c$ counting rule exclude the existence of $S$ matrix poles with ${\cal M}, Γ\sim O(1)$. Especially the properties of $σ$ and $f_0(980)$ with respect to the $1/N_c$ expansion are discu

B. Field

We study the production of a pseudoscalar Higgs boson A^0 in association with a Z^0 boson at a future international linear collider (ILC). We consider the contributions to this process at the one loop level in the Minimal Supersymmetric Standard Model (MSSM) from top and bottom quarks as well as stop and sbottom squarks. We also study the squark contribution

M. N. Rebelo

The observation of neutrino masses leads to the possibility of leptonic mixing and CP violation. One of the simplest extensions of the Standard Model giving rise to neutrino masses consists of the introduction of one righthanded neutrino field per generation, singlet of SU(2). In the context of the seesaw mechanism this leads to three light and three heavy n

Zhi-guang Xiao, Hanqing Zheng

This paper is withdrawn due to a mistake. The revised version with a new tiltle can be found in hep-ph/0502199.

Pavel Krtous, Jiri Podolsky

The directional behavior of dominant components of algebraically special spin-s fields near a spacelike, timelike or null conformal infinity is studied. By extending our previous general investigations we concentrate on fields which admit a pair of equivalent algebraically special null directions, such as the Petrov type D gravitational fields or algebraical

Pavel Krtous, Jiri Podolsky

We analyze the directional properties of general gravitational, electromagnetic, and spin-s fields near conformal infinity I. The fields are evaluated in normalized tetrads which are parallelly propagated along null geodesics which approach a point P of I. The standard peeling-off property is recovered and its meaning is discussed and refined. When the (loca

Emanuele Alesci, Giovanni Montani

The main issue of the present letter is to fix specific features (which turn out being independent of extradimension size) of gravitational waves generated before a dimensional compactification process. Valuable is the possibility to detect our prediction from gravitational wave experiment without high energy laboratory investigation. In particular we show h

H. Vucetich

Much research has been done in the latter years on the subject of Lorentz violation induced by Quantum Gravity effects. On the theoretical side it has been shown that both Loop Quantum Gravity and String Theory predict that Lorentz violation can be induced at an energy near to the Planck scale. On the other hand, most of the experimental results in the latte

Sanjay B. Sarwe, R. V. Saraykar

We study five dimensional(5D) spherically symmetric self-similar perfect fluid space-time with adiabatic equation of state, considering all the families of future directed non-spacelike geodesics. The space-time admits globally strong curvature naked singularities in the sense of Tipler and thus violates the cosmic censorship conjecture provided a certain al

Hakan Andreasson

The main purpose of this article is to provide a guide to theorems on global properties of solutions to the Einstein-Vlasov system. This system couples Einstein's equations to a kinetic matter model. Kinetic theory has been an important field of research during several decades in which the main focus has been on nonrelativistic and special relativistic p

Steven Willison

A theory of gravity in higher dimensions is considered. The usual Einstein-Hilbert action is supplemented with Lovelock terms, of higher order in the curvature tensor. These terms are important for the low energy action of string theories. The intersection of hypersurfaces is studied in the Lovelock theory. The study is restricted to hypersurfaces of co-dime

M. Bardeen, E. Gilbert, T. Jordan, P. Neywoda

We describe a case study that uses grid computing techniques to support the collaborative learning of high school students investigating cosmic rays. Students gather and upload science data to our e-Lab portal. They explore those data using techniques from the GriPhyN collaboration. These techniques include virtual data transformations, workflows, metadata c

Pascal Hitzler

In [Hitzler and Wendt 2002, 2005], a new methodology has been proposed which allows to derive uniform characterizations of different declarative semantics for logic programs with negation. One result from this work is that the well-founded semantics can formally be understood as a stratified version of the Fitting (or Kripke-Kleene) semantics. The constructi

Robert Ewaschuk, Peter Turney

It has been argued that a central objective of nanotechnology is to make products inexpensively, and that self-replication is an effective approach to very low-cost manufacturing. The research presented here is intended to be a step towards this vision. In previous work (JohnnyVon 1.0), we simulated machines that bonded together to form self-replicating stra

Pierre-Yves Oudeyer

The speech code is a vehicle of language: it defines a set of forms used by a community to carry information. Such a code is necessary to support the linguistic interactions that allow humans to communicate. How then may a speech code be formed prior to the existence of linguistic interactions? Moreover, the human speech code is discrete and compositional, s

Fabien Viger, Matthieu Latapy

We address here the problem of generating random graphs uniformly from the set of simple connected graphs having a prescribed degree sequence. Our goal is to provide an algorithm designed for practical use both because of its ability to generate very large graphs (efficiency) and because it is easy to implement (simplicity). We focus on a family of heuristic

Chih-Chun Wang, H. Vincent Poor, Sanjeev R. Kulkarni

Density evolution (DE) is one of the most powerful analytical tools for low-density parity-check (LDPC) codes on memoryless binary-input/symmetric-output channels. The case of non-symmetric channels is tackled either by the LDPC coset code ensemble (a channel symmetrizing argument) or by the generalized DE for linear codes on non-symmetric channels. Existing

Sinan Gezici, Zafer Sahinoglu, Hisashi Kobayashi, H. Vincent Poor

Spectral properties and performance of multi-pulse impulse radio ultra-wideband systems with pulse-based polarity randomization are analyzed. Instead of a single type of pulse transmitted in each frame, multiple types of pulses are considered, which is shown to reduce the effects of multiple-access interference. First, the spectral properties of a multi-puls

Guangyong Xu, P. M. Gehring, G. Shirane

The response of polar nanoregions (PNR) in the relaxor compound Pb[(Zn$_{1/3}$Nb$_{2/3}$)$_{0.92}$Ti$_{0.08}$]O$_3$ subject to a [111]-oriented electric field has been studied by neutron diffuse scattering. Contrary to classical expectations, the diffuse scattering associated with the PNR persists, and is even partially enhanced by field cooling. The effect

Markus Greiner, Cindy A. Regal, Deborah S. Jin

Ultracold atomic gases have proven to be remarkable model systems for exploring quantum mechanical phenomena. Experimental work on gases of fermionic atoms in particular has seen large recent progress including the attainment of so-called Fermi condensates. In this article we will discuss this recent development and the unique control over interparticle inte

Jing Wang, Eric Polizzi, Avik Ghosh, Supriyo Datta

In this letter, we report a three-dimensional (3D) quantum mechanical simulation to investigate the effects of surface roughness scattering (SRS) on the device characteristics of Si nanowire transistors (SNWTs). We treat the microscopic structure of the Si/SiO2 interface roughness directly by using a 3D finite element technique. The results show that 1) SRS

C. Bell, R. Loloee, G. Burnell, M. G. Blamire

We present the measurement of superconductor / ferromagnetic Josephson junctions, based on an epitaxial Nb bottom electrode and epitaxial Fe20Ni80 barrier. Uniform junctions have been fabricated with a barrier thicknesses in the range 2-12 nm. The maximum critical current density ~ 2.4 \pm 0.2 * 10^9 Am^-2 was found for a devices with a 3 nm thick barrier at

Stefano Curtarolo, Aleksey N. Kolmogorov, Franklin Hadley Cocks

Prediction and characterization of crystal structures of alloys are a key problem in materials research. Using high-throughput ab initio calculations we explore the low-temperature phase diagrams for the following systems: {Bi-In, Bi-Mg, Bi-Sb, In-Mg, In-Sb, and Mg-Sb}. For the experimentally observed phases in these systems we provide information about thei

Igor I. Smolyaninov, Quirino Balzano, Christopher C. Davis

Plasmon-polariton behavior on the surfaces of constant negative curvature is considered. Analytical solutions for the eigenfrequencies and eigenfunctions are found, which describe resonant behavior of metal nanotips and nanoholes. These resonances may be used to improve performance of metal tips and nanoapertures in various scanning probe microscopy and surf

Nicolas Giovambattista, H. Eugene Stanley, Francesco Sciortino

We describe the phase diagram of amorphous solid water by performing molecular dynamics simulations. Our simulations follow different paths in the phase diagram: isothermal compression/decompression, isochoric cooling/heating and isobaric cooling/heating. We are able to identify low-density amorphous (LDA), high-density amorphous (HDA), and very-high density

Stefan Klumpp, Theo M. Nieuwenhuizen, Reinhard Lipowsky

Processive molecular motors which drive the traffic of organelles in cells move in a directed way along cytoskeletal filaments. On large time scales, they perform motor walks, i.e., peculiar random walks which arise from the repeated unbinding from and rebinding to filaments. Unbound motors perform Brownian motion in the surrounding fluid. In addition, the t

Rafi Weill, Amir Rosen, Ariel Gordon, Omri Gat

Light is shown to exhibit critical and tricritical behavior in passive mode-locked lasers with externally injected pulses. It is a first and unique example of critical phenomena in a one-dimensional many body light-mode system. The phase diagrams consist of regimes with continuous wave, driven para-pulses, spontaneous pulses via mode condensation, and hetero

Sharat Chandra, S. Mathi Jaya, M. C. Valsakumar

Li2Pd3B is known to be superconducting, while the isotypical Li2Pt3B compound is not. Electronic structures of Li2Pd3B and Li2Pt3B have been calculated in order to obtain an insight into this surprising difference, through an analysis of the differences in the band structures. The electronic structures of these systems were obtained using the Full Potential

L. H. Machtoub, B. Keimer, K. Yamada

We report electronic Raman scattering experiments on a superconducting ${\rm La_{1.88}Sr_{0.12}CuO_{4}}$ single crystal in a magnetic field. At low temperatures, the spectral weight of the high-energy two-magnon peak increases linearly with field and is amplified by a factor of more than two at 14 T. The effect disappears at elevated temperatures and is not

A. V. Goran, A. A. Bykov, A. K. Bakarov, J. C. Portal

We study the transport properties of a 2D electron gas in narrow GaAs quantum wells with AlAs/GaAs superlattice barriers. It is shown that the anisotropic positive magnetoresistance observed in selectively doped semiconductor structures in a parallel magnetic field is caused by the spatial modulation of the 2D electron gas.

Niels Gronbech-Jensen, Matteo Cirillo

We study analytically and numerically the phase-modulation properties of a biased classical Josephson tunnel junction in the zero-voltage state and phase-locked to an external ac field. We show that the phase-locked state is being modulated in the transients, or in response to perturbations, and the modulation frequency is calculated as a function of relevan

Yehuda Snir, Randall D. Kamien

The helix is a ubiquitous motif for biopolymers. We propose a heuristic, entropically based model that predicts helix formation in a system of hard spheres and semiflexible tubes. We find that the entropy of the spheres is maximized when short stretches of the tube form a helix with a geometry close to that found in natural helices. Our model could be direct

W. Q. Chen, Z. Y. Weng

We present a systematic study of spin dynamics in a superconducting ground state, which itself is a doped-Mott-insulator and can correctly reduce to an antiferromagnetic (AF) state at half-filling with an AF long-range order (AFLRO). Such a doped Mott insulator is described by a mean-field theory based on the phase string formulation of the t-J model. We sho