September 2006 arXiv papers — page 24

Kazuhiro Oyamatsu, Kei Iida

We examine how the properties of inhomogeneous nuclear matter at subnuclear densities depend on the density dependence of the symmetry energy. Using a macroscopic nuclear model we calculate the size and shape of nuclei in neutron star matter at zero temperature in a way dependent on the density dependence of the symmetry energy. We find that for smaller symm

Konstantin Glaum, Axel Pelster

We consider a dilute gas of dipole moments in an arbitrary harmonic trap and treat both the short-range, isotropic delta-interaction and the long-range, anisotropic dipole-dipole interaction perturbatively. With this we calculate the leading shift of the critical temperature with respect to that of an ideal gas as a function of the relative orientation of th

J. Maíz Apellániz

I have recently combined HST/STIS spectrophotometry with existing photometric data to analyze the calibration of three standard optical photometry systems: Tycho-2 B_TV_T, Stromgren uvby, and Johnson UBV. In this contribution I summarize those results, present new ones for 2MASS JHK_s, and combine them with recent literature results to generate a uniform set

Morio Hatakeyama, Hideyuki Sawanaka, Hiroto So

To obtain a light mode in two-dimensional staggered fermions, we introduce four new local operators keeping the rotational invariance for a staggered Dirac operator. To split masses of tastes, three cases are considered. The mass matrix and the propagator for free theories are analyzed. We find that one of three cases is a good candidate for taking a single

Mao-Bin Hu, Wen-Xu Wang, Rui Jiang, Qing-Song Wu

We model information traffic on scale-free networks by introducing the node queue length L proportional to the node degree and its delivering ability C proportional to L. The simulation gives the overall capacity of the traffic system, which is quantified by a phase transition from free flow to congestion. It is found that the maximal capacity of the system

Claire Debord, Jean-Marie Lescure, Victor Nistor

We define an analytical index map and a topological index map for conical pseudomanifolds. These constructions generalize the analogous constructions used by Atiyah and Singer in the proof of their topological index theorem for a smooth, compact manifold $M$. A main ingredient is a non-commutative algebra that plays in our setting the role of $C_0(T^*M)$. We

K. Y. Michael Wong, D. Saad

Inference and optimization of real-value edge variables in sparse graphs are studied using the Bethe approximation and replica method of statistical physics. Equilibrium states of general energy functions involving a large set of real edge-variables that interact at the network nodes are obtained in various cases. When applied to the representative problem o

Arnaud Debussche, Eric Gautier

We consider the problem of the error in soliton transmission in long-haul optical fibers caused by the spontaneous emission of noise inherent to amplification. We study two types of noises driving the stochastic focusing cubic one dimensional nonlinear Schrödinger equation which appears in physics in that context. We focus on the fluctuations of the mass and

M. Bate, B. M. S. Martin, G. E. Roehrle

Let G be a reductive linear algebraic group over an algebraically closed field of characteristic p. We study J.-P. Serre's notion of G-complete reducibility for subgroups of G. In particular, for a subgroup H and a normal subgroup N of H, we look at the relationship between G-complete reducibility of N and of H, and show that these properties are equival

Philip Bille, Rolf Fagerberg, Inge Li Goertz

We study the approximate string matching and regular expression matching problem for the case when the text to be searched is compressed with the Ziv-Lempel adaptive dictionary compression schemes. We present a time-space trade-off that leads to algorithms improving the previously known complexities for both problems. In particular, we significantly improve

Rodrigo Bañuelos, Krzysztof Bogdan

We study Fourier multipliers which result from modulating jumps of Lévy processes. Using the theory of martingale transforms we prove that these operators are bounded in $L^p(\Rd)$ for $1<p<\infty$ and we obtain the same explicit bound for their norm as the one known for the second order Riesz transforms.

B. Cessac

It has been rigorously shown in [Ruelle, 2005] that the complex susceptibility of chaotic maps of the interval can have a pole in the upper-half complex plane. We develop a numerical procedure allowing to exhibit this pole from time series. We then apply the same analysis to the Henon map and conjecture that the complex susceptibility has also a pole in the

Georg K. H. Madsen

A new functional form for the exchange enhancement in the generalized gradient approximation within density functional theory is given. The functional form satisfies the constraints used to construct the Perdew-Burke-Ernzerhof (PBE) functional but can be systematically varied using one parameter. This gives the possibility to estimate the reliability of a co

Ashok Palaniappan, Eric Jakobsson

Excitability is an attribute of life, and is a driving force in the descent of complexity. Cellular electrical activity as realized by membrane proteins that act as either channels or transporters is the basis of excitability. Electrical signaling is mediated by a wave of action potentials, which consist of synchronous redistribution of ionic gradients down

C. M. Chandrashekar

In most widely discussed discrete time quantum walk model, after every unitary shift operator, the particle evolves into the superposition of position space and settles down in one of its basis states, loosing entanglement in the coin space in the new position. The Hadamard operation is applied to let the particle to evolve into the superposition in the coin

Y. Qiang, J. Annand, J. Arrington, Ya. I. Azimov

A high-resolution (sigma_instr. = 1.5 MeV) search for narrow states (Gamma < 10 MeV) with masses of M_x approx 1500-1850 MeV in ep -> e&#39;K^+ X, e&#39;K^- X and e&#39; pi^+ X electroproduction at small angles and low Q^2 was performed. These states would be candidate partner states of the reported Theta^+(1540) pentaquark. No statistically significant sign

Wen-ge Wang, G. Casati, Baowen Li

We study the stability of quantum motion of classically regular systems in presence of small perturbations. Onthe base of a uniform semiclassical theory we derive the fidelity decay which displays a quite complexbehaviour, from Gaussian to power law decay $t^{-α}$ with $1 \le α\le 2$. Semiclassical estimates are given for the time scales separating the diffe

Tomohiro Harada

Applying the first and generalised second laws of thermodynamics for a realistic process of near critical black hole formation, we derive an entropy bound, which is identical to Bekenstein&#39;s one for radiation. Relying upon this bound, we derive an absolute minimum mass $\sim0.04 \sqrt{g_{*}}m_{\rm Pl}$, where $g_{*}$ and $m_{\rm Pl}$ is the effective deg

James M. Cline

Pedagogical lectures on baryogenesis, with emphasis on the electroweak phase transition and electroweak baryogenesis. Contents: (1) Observational evidence for the BAU; (2) Sakharov&#39;s conditions for baryogenesis; (3) Example: GUT baryogenesis; (4) B and CP violation in the standard model; (5) Electroweak phase transition and electroweak baryogenesis; (6)

E. Mukhin, V. Schechtman, V. Tarasov, A. Varchenko

A new form of Bethe ansatz equations is introduced. A version of a separation of variables for the quantum $sl_3$ Gaudin model is presented.

M. Cristina Diamantini, Carlo A. Trugenberger

Qubit networks with long-range interactions inspired by the Hebb rule can be used as quantum associative memories. Starting from a uniform superposition, the unitary evolution generated by these interactions drives the network through a quantum phase transition at a critical computation time, after which ferromagnetic order guarantees that a measurement retr

Ken-ichiroh Yoshino, Takao Aoki, Akira Furusawa

Continuous-wave light beams with broadband Einstein-Podolsky-Rosen correlation (Einstein-Podolsky-Rosen beams) are created with two independent squeezed vacua generated by two periodically-poled lithium niobate waveguides and a half beam splitter.

T. Jana, P. Roy

Using the shape invariance property we obtain exact solutions of the (1+1)dimensional Klein-Gordon equation for certain types of scalar and vector potentials. We also discuss the possibility of obtaining real energy spectrum with non-Hermitian interaction within this framework.

N. Kolachevsky, M. Haas, U. D. Jentschura, M. Herrmann

We consider the excitation dynamics of the two-photon \sts transition in a beam of atomic hydrogen by 243 nm laser radiation. Specifically, we study the impact of ionization damping on the transition line shape, caused by the possibility of ionization of the 2S level by the same laser field. Using a Monte-Carlo simulation, we calculate the line shape of the

Hai-Jhun Wanng

Using path integrals we express the quantum nonlocality of AB-effect type in the form of singularity. The gauge-fixing term in path integrals induce the AB effect in ordinary scattering processes. This means that all scattering processes are accompanied by nonlocal effect. The formulae are then extended to theory of fields that additionally include a scalar

Vincenzo Carnevale, Simone Raugei, Cristian Micheletti, Paolo Carloni

Proteases regulate various aspects of the life cycle in all organisms by cleaving specific peptide bonds. Their action is so central for biochemical processes that at least 2% of any known genome encodes for proteolytic enzymes. Here we show that selected proteases pairs, despite differences in oligomeric state, catalytic residues and fold, share a common st

Pierre Mahé, Jean-Philippe Vert

Motivated by chemical applications, we revisit and extend a family of positive definite kernels for graphs based on the detection of common subtrees, initially proposed by Ramon et al. (2003). We propose new kernels with a parameter to control the complexity of the subtrees used as features to represent the graphs. This parameter allows to smoothly interpola

Yan Levin, Felipe B. Rizzato

Motivated by a beautiful demonstration of the Faraday&#39;s and Lenz&#39;s law in which a small neodymium magnet falls slowly through a conducting non-ferromagnetic tube, we consider the dynamics of a magnet falling through a superconducting pipe. Unlike the case of normal conducting pipes, in which the magnet quickly reaches the terminal velocity, inside a

Vadim A. Markel, Andrey K. Sarychev

We report a numerical investigation of surface plasmon (SP) propagation in ordered and disordered linear chains of metal nanospheres. In our simulations, SPs are excited at one end of a chain by a near-field tip. We then find numerically the SP amplitude as a function of propagation distance. Two types of SPs are discovered. The first SP, which we call the o

S. Esposito

We give an accurate historical and scientific account of a previously unknown manuscript written by Ettore Majorana in French. The retrieved text deals with Quantum Electrodynamics by using the formalism of field quantization, and it is here reported, for the first time, in translation. It is likely related to an invited talk for a conference at Leningrad (o

Bernd Burghardt, Alexander K. Hartmann

We consider the inverse-folding problem for RNA secondary structures: for a given (pseudo-knot-free) secondary structure find a sequence that has that structure as its ground state. If such a sequence exists, the structure is called designable. We implemented a branch-and-bound algorithm that is able to do an exhaustive search within the sequence space, i.e.

John T. A. Ely

Evidence from skeletal remains and pictorial records for the past several millennia established that humans have had a very inadequate ascorbic acid intake and commonly exhibited signs of frank scurvy, as well as the invisible signs of subclinical scurvy (absence of AA in scorbutic urine is universal). They suffered scurvy&#39;s mortality, being a major caus

F. Sorrentino, G. Ferrari, N. Poli, R. Drullinger

This review describes the production of atomic strontium samples at ultra-low temperature and at high phase-space density, and their possible use for physical studies and applications. We describe the process of loading a magneto-optical trap from an atomic beam and preparing the sample for high precision measurements. Particular emphasis is given to the app

Stefan Hippler, Felix Hormuth, David J. Butler, Wolfgang Brandner

We built and characterized an optical system that emulates the optical characteristics of an 8m-class telescope like the Very Large Telescope. The system contains rotating glass phase-screens to generate realistic atmosphere-like optical turbulence, as needed for testing multi-conjugate adaptive optics systems. In this paper we present an investigation of th

Dan Christensen, Brian Neyenhuis, Dallin S. Durfee

We present a numerical exercise in which classical and non-classical electrostatic potentials were calculated. The non-classical fields take into account effects due to a possible non-zero photon rest mass. We show that in the limit of small photon rest mass, both the classical and non-classical potential can be found by solving Poisson&#39;s equation twice,

I. C. Arsene, L. V. Bravina, W. Cassing, Yu. B. Ivanov

Central collisions of gold nuclei are simulated by several existing models and the central net baryon density rho and the energy density eps are extracted at successive times, for beam kinetic energies of 5-40 GeV per nucleon. The resulting trajectories in the (rho,eps) phase plane are discussed from the perspective of experimentally exploring the expected f

P. Papakonstantinou, R. Roth, N. Paar

We examine to which extent correlated realistic nucleon-nucleon interactions, derived within the Unitary Correlation Operator Method (UCOM), can describe nuclear collective motion in the framework of first-order random-phase approximation (RPA). To this end we employ the correlated Argonne V18 interaction in calculations within the so-called &#34;Extended&#3

Steven R. Elliott

This document gives an overview of the technical issues and goals facing future double-beta decay experiments.

S-L Blyth, M J Horner, T Awes, T Cormier

Standard jet finding techniques used in elementary particle collisions have not been successful in the high track density of heavy-ion collisions. This paper describes a modified cone-type jet finding algorithm developed for the complex environment of heavy-ion collisions. The primary modification to the algorithm is the evaluation and subtraction of the lar

C. Blume

The current experimental situation concerning high pt observables at the CERN SPS is reviewed. Recent data from the NA45, NA49 and NA57 collaborations are discussed and compared to earlier measurements by WA98 and NA45 at the same center-of-mass energies, as well as to measurements at the higher energies by the RHIC experiments. The observables include new p

Vladimir A. Manasson

We have proposed a simple one-dimensional model of internal particle dynamics. The model is based on the assumption that self-interaction can be represented by a nonlinear feedback and described by a quadratic recurrent map. Charge plays the role of a generalized dynamical variable and a feedback coupling parameter. The model suggests that charge and action

D. V. Senthilkumar, M. Lakshmanan, J. Kurths

Though the notion of phase synchronization has been well studied in chaotic dynamical systems without delay, it has not been realized yet in chaotic time-delay systems exhibiting non-phase coherent hyperchaotic attractors. In this article we report the first identification of phase synchronization in coupled time-delay systems exhibiting hyperchaotic attract

B. Cessac, M. Samuelides

This paper presents an overview of some techniques and concepts coming from dynamical system theory and used for the analysis of dynamical neural networks models. In a first section, we describe the dynamics of the neuron, starting from the Hodgkin-Huxley description, which is somehow the canonical description for the ``biological neuron&#39;&#39;. We discus

C. Gerard, R. Tiedra de Aldecoa

We advocate for the systematic use of a symmetrized definition of time delay in scattering theory. In two-body scattering processes, we show that the symmetrized time delay exists for arbitrary dilated spatial regions symmetric with respect to the origin. It is equal to the usual time delay plus a new contribution, which vanishes in the case of spherical spa

Elizabeth Gasparim, Pedro Ontaneda

We use instanton numbers to: (i) stratify moduli of vector bundles, (ii) calculate relative homology of moduli spaces and (iii) distinguish curve singularities.

Matthew D. Blair, Hart F. Smith, Christopher D. Sogge

We prove local Strichartz estimates on compact manifolds with boundary. Our results also apply more generally to compact manifolds with Lipschitz metrics.

Donggao Deng, Xuan Thinh Duong, Adam Sikora, Lixin Yan

Let L be a generator of a semigroup satisfying the Gaussian upper bounds. In this paper, we study further a new BMO_L space associated with L which was introduced recently by Duong and Yan. We discuss applications of the new BMO_L spaces in the theory of singular integration such as BMO_L estimates and interpolation results for fractional powers, purely imag

J. P. C. Greenlees

This is an expository account of completion and local cohomology in brave new commutative algebra, especially as it applies to completion theorems and their duals in equivariant topology. The first part is fairly direct, but the second considers Morita theory and Gorenstein ring spectra. This draws on work of the author with Benson, Dwyer, Iyengar and May, a

J. P. C. Greenlees

The article is designed to explain to commutative algebraists what spectra (in the sense of algebraic topology) are, why they were originally defined, and how they can be useful for commutative algebra.

Jose Seade

Let $(X,0)$ be an isolated complete intersection complex singularity ($X$ can also be smooth at 0). Let $K$ be its link, $\cal X$ its canonical contact structure and $\D_X$ the complex vector bundle associated to $\cal X$. We prove that the bundle $\D_X$ is trivial if and only if the Milnor number of $X$ satisfies $μ(X,0) \equiv (-1)^{n-1}$ modulo $(n-1)!$.

Alexander I. Bobenko, Ivan Izmestiev

We present a constructive proof of Alexandrov&#39;s theorem regarding the existence of a convex polytope with a given metric on the boundary. The polytope is obtained as a result of a certain deformation in the class of generalized convex polytopes with the given boundary. We study the space of generalized convex polytopes and discover a relation with the we

Khalid Koufany

These notes were written following lectures I had the pleasure of giving on this subject at Keio University, during November and December 2004. The first part is about new applications of Jordan algebras to the geometry of Hermitian symmetric spaces and to causal semi-simple symmetric spaces of Cayley type. The second part will present new contributions for

Abdelhamid Boussejra, Khalid Koufany

We characterize the $L^p$-range, $1 < p < +\infty$, of the Poisson transform on the Shilov boundary for non-tube bounded symmetric domains. We prove that this range is a Hua-Hardy type space for harmonic functions satisfying a Hua system.

Kathryn Hess, Paul-Eugene Parent, Jonathan Scott

Let EK be the simplicial suspension of a pointed simplicial set K. We construct a chain model of the James map, $α_{K} : CK \to ΩCEK$. We compute the cobar diagonal on $ΩCEK$, not assuming that $EK$ is 1-reduced, and show that $α_{K}$ is comultiplicative. As a result, the natural isomorphism of chain algebras $TCK \cong ΩCK$ preserves diagonals. In an append

Christian Berg, Henrik L. Pedersen

We show that the median $m(x)$ in the gamma distribution with parameter $x$ is a strictly convex function on the positive half-line

I. M. Burban

We present a description of a new kind of the deformed canonical commutation relations, their representations and generated by them Heisenberg-Weyl algebra. This deformed algebra allows us to derive operations of the Hopf algebra structure: comultiplication, counit and antipode. We discuss properties of a discrete spectrum of the Hamiltonian of the deformed

B. Enriquez

Let Phi be the KZ associator and Psi_N be its analogue for N-th roots of 1. We prove a hexagon relation for Psi_4. Similarly to the Broadhurst (for Psi_2) and Okuda (for Psi_4) duality relations, it relies on the &#34;supplementary&#34; (i.e., non-dihedral) symmetries of C^* - mu_4(C) (i.e., the octahedron group S_4). We also derive relations between Phi and

Marco Hien

We define homology groups for flat irregular singular connections on surfaces and a pairing between these and the de Rham cohomology of the connection, generalizing work of S. Bloch and H. Enault in dimension one. Assuming a conjecture of C. Sabbah (known to be true if the rank of the vector bundle is at most 5), we prove perfectness of the pairing. We comme

Marcel Morales

Some results on the Cohen-Macaulayness of the canonical module. We study the $S_2$-fication of rings which are quotients by lattices ideals. Given a simplicial lattice ideal of codimension two $I,$ its Macaulayfication is given explicitly from a system of generators of $I$.

Frédéric Chapoton

A new anticyclic operad Mould is introduced, on spaces of functions in several variables. It is proved that the Dendriform operad is an anticyclic suboperad of this operad. Many operations on the free Mould algebra on one generator are introduced and studied. Under some restrictions, a forgetful map from moulds to formal vector fields is then defined. A conn

Victor Bovdi, Martin Hertweck

We confirm a conjecture of Zassenhaus about rational conjugacy of torsion units in integral group rings for a covering group of the symmetric group $S_{5}$ and for the general linear group $\text{GL}(2,5)$.

Hock Peng Chan, Cheng-Der Fuh, Inchi Hu

Consider the following multi-phase project management problem. Each project is divided into several phases. All projects enter the next phase at the same point chosen by the decision maker based on observations up to that point. Within each phase, one can pursue the projects in any order. When pursuing the project with one unit of resource, the project state

Thierry Coulhon, Adam Sikora

We prove that in presence of $L^2$ Gaussian estimates, so-called Davies-Gaffney estimates, on-diagonal upper bounds imply precise off-diagonal Gaussian upper bounds for the kernels of analytic families of operators on metric measure spaces.

Denis Blackmore, Lu Ting, Omar Knio

It is well known that the dynamics of three point vortices moving in an ideal fluid in the plane can be expressed in Hamiltonian form, where the resulting equations of motion are completely integrable in the sense of Liouville and Arnold. The focus of this investigation is on the persistence of regular behavior (especially periodic motion) associated to comp

S. Deser, A. Waldron

We propose that maximal depth, partially massless, higher spin excitations can mediate charged matter interactions in a de Sitter universe. The proposal is motivated by similarities between these theories and their traditional Maxwell counterpart: their propagation is lightlike and corresponds to the same Laplacian eigenmodes as the de Sitter photon; they ar

Roberto Contino

If the Higgs boson has a composite nature, it might be the 4-dimensional hologram of a gauge field living in a warped extra dimension. In this talk I discuss a minimal, calculable model that passes all electroweak precision tests, included that from Z->bb, and gives a natural account of the electroweak symmetry breaking.

M. Hirsch

Neutrinoless double beta decay violates lepton number by two units, a positive observation therefore necessarily implies physics beyond the standard model. Here, three possible contributions to neutrinoless double beta decay are briefly reviewed: (a) The mass mechanism and its connection to neutrino oscillations; (b) Left-right symmetric models and the lower

M. Ciuchini, M. Pierini, L. Silvestrini

We present a new technique to extract information on the Unitarity Triangle from the study of B -> K pi pi Dalitz plots. Using the sensitivity of Dalitz analyses to the absolute values and the phases of decay amplitudes and isospin symmetry, we obtain a new constraint on the elements of the CKM matrix. We discuss in detail the role of electroweak penguins an

M. Voutilainen

We present a new preliminary measurement of the inclusive jet cross section in pp-bar collisions based on a integrated luminosity of about 0.8 fb-1. The data were acquired using the D0 detector between 2002 and 2005. Jets are reconstructed using an iterative cone algorithm with radius R_cone = 0.7. The inclusive jet cross section is presented as a function o

Martin Bojowald, Hector H. Hernández, Mikhail Kagan, Parampreet Singh

Cosmological perturbation equations are derived systematically in a canonical scheme based on Ashtekar variables. A comparison with the covariant derivation and various subtleties in the calculation and choice of gauges are pointed out. Nevertheless, the treatment is more systematic when correction terms of canonical quantum gravity are to be included. This

J. B. Griffiths, P. Krtous, J. Podolsky

The basic properties of the C-metric are well known. It describes a pair of causally separated black holes which accelerate in opposite directions under the action of forces represented by conical singularities. However, these properties can be demonstrated much more transparently by making use of recently developed coordinate systems for which the metric fu

Keisuke Taniguchi, Thomas W. Baumgarte, Joshua A. Faber, Stuart L. Shapiro

We construct quasiequilibrium sequences of black hole-neutron star binaries for arbitrary mass ratios by solving the constraint equations of general relativity in the conformal thin-sandwich decomposition. We model the neutron star as a stationary polytrope satisfying the relativistic equations of hydrodynamics, and account for the black hole by imposing equ

G. O. Papadopoulos

In the present work the problem of distinguishing between essential and spurious (i.e., absorbable) constants contained in a metric tensor field in a Riemannian geometry is considered. The contribution of the study is the presentation of a sufficient and necessary criterion, in terms of a covariant statement, which enables one to determine whether a constant

Xiaofei Huang, Suquan Ding, Zhixing Yang, Youshou Wu

In this paper, we present a fast min-sum algorithm for decoding LDPC codes over GF(q). Our algorithm is different from the one presented by David Declercq and Marc Fossorier in ISIT 05 only at the way of speeding up the horizontal scan in the min-sum algorithm. The Declercq and Fossorier&#39;s algorithm speeds up the computation by reducing the number of con

Xiaofei Huang

The normalized min-sum algorithm can achieve near-optimal performance at decoding LDPC codes. However, it is a critical question to understand the mathematical principle underlying the algorithm. Traditionally, people thought that the normalized min-sum algorithm is a good approximation to the sum-product algorithm, the best known algorithm for decoding LDPC

Jacek Michalski, Leszek Skoczylas

The paper presents the methodology of modelling tooth flanks of cylindrical gears in the Cad environment. The modelling consists in a computer simulation of gear generation. A model of tooth flanks is an envelope curve of a family of envelopes that originate from the rolling motion of a solid tool model in relation to a solid model of the cylindrical gear. T

Hervé Rivano, Fabrice Theoleyre, Fabrice Valois

Ad hoc networking specific challenges foster a strong research effort on efficient protocols design. Routing protocols based on a self-organized structure have been studied principally for the robustness and the scalability they provide. On the other hand, self-organization schemes may decrease the network capacity since they concentrate the traffic on privi

A. Sparavigna, B. Montrucchio

The paper describes a new image processing for a non-photorealistic rendering. The algorithm is based on a random generation of gray tones and competing statistical requirements. The gray tone value of each pixel in the starting image is replaced selecting among randomly generated tone values, according to the statistics of nearest-neighbor and next-nearest-

A. M. Lobos, A. A. Aligia

We propose a simple approach to study the conductance through an array of $N$ interacting quantum dots, weakly coupled to metallic leads. Using a mapping to an effective site which describes the low-lying excitations and a slave-boson representation in the saddle-point approximation, we calculated the conductance through the system. Explicit results are pres

H. B. Chan, C. Stambaugh

We explore fluctuation-induced switching in a parametrically-driven micromechanical torsional oscillator. The oscillator possesses one, two or three stable attractors depending on the modulation frequency. Noise induces transitions between the coexisting attractors. Near the bifurcation points, the activation barriers are found to have a power law dependence

Mario G. Silveirinha, Pavel A. Belov, Constantin R. Simovski

We demonstrate that an array of metallic nanorods enables sub-wavelength (near-field) imaging at infrared frequencies. Using an homogenization approach, it is theoretically proved that under certain conditions the incoming radiation can be transmitted by the array of nanorods over a significant distance with fairly low attenuation. The propagation mechanism

Tomaz Rejec, Yigal Meir

A quantum point contact (QPC), a narrow region separating two wider electron reservoirs, is the standard building block of sub-micron devices, such as quantum dots - small boxes of electrons, and qubits - the proposed basic elements of quantum computers. As a function of its width, the conductance through a QPC changes in integer steps of G0 = $2e^2/h$, sign

H. Tabuteau, John R. de Bruyn, P. Coussot

We have investigated the drag on a sphere falling through a clay suspension that has a yield stress and exhibits rheological aging. The drag force increases with both speed and the rest time between preparation of the system and the start of the experiment, but there exists a nonzero minimum speed below which steady motion is not possible. We find that only

Srikanth Sastry, Emilia La Nave, Francesco Sciortino

We study lattice gas models with the imposition of a constraint on the maximum number of bonds (nearest neighbor interactions) that particles can participate in. The critical parameters, as well as the coexistence region are studied using the mean field approximation and the Bethe-Peierls approximation. We find that the reduction of the number of interaction

A. Kadigrobov, S. I. Kulinich, R. I. Shekhter, M. Jonson

We consider the electrical current through a magnetic point contact in the limit of a strong inelastic scattering of electrons. In this limit local Joule heating of the contact region plays a decisive role in determining the transport properties of the point contact. We show that if an applied constant bias voltage exceeds a critical value, the stationary st

R. Khasanov, T. Kondo, J. Schmalian, S. M. Kazakov

The dimensionality of a correlated many-body system has a large impact on its electronic properties. When electrons are confined to one-dimensional chains of atoms their behavior is very different than in higher dimensional systems because they become strongly correlated, even in the case of vanishingly small interactions. The chains consisting of copper and

P. Guardia, B. Batlle-Brugal, A. G. Roca, Oscar Iglesias

Monodisperse magnetite Fe3O4 nanoparticles of controlled size within 6 and 20 nm in diameter were synthesized by thermal decomposition of an iron organic precursor in an organic medium. Particles were coated with oleic acid. For all samples studied, saturation magnetization Ms reaches the expected value for bulk magnetite, in contrast to results in small par

K. V. Emtsev, Th. Seyller, F. Speck, L. Ley

Graphitization of the 6H-SiC(0001) surface as a function of annealing temperature has been studied by ARPES, high resolution XPS, and LEED. For the initial stage of graphitization - the 6root3 reconstructed surface - we observe sigma-bands characteristic of graphitic sp2-bonded carbon. The pi-bands are modified by the interaction with the substrate. C1s core

Pramod Kumar, Niraj K. Singh, K. G. Suresh, A. K. Nigam

The effect of Ge substitution on the magnetization, heat capacity, magnetocaloric effect and magnetoresistance of GdMn2Si2-xGex (x=0, 1, and 2) compounds has been studied. The magnetic transition associated with the Gd ordering is found to change from second order to first order on Ge substitution. Magnetic contributions to the total heat capacity and the en

Burkhard Schmidt, Nic Shannon, Peter Thalmeier

We discuss our numerical results on the properties of the S = 1/2 frustrated J1-J2 Heisenberg model on a square lattice as a function of temperature and frustration angle phi = atan(J2/J1) in an applied magnetic field. We cover the full phase diagram of the model in the range -pi <= phi <= pi. The discussion includes the parameter dependence of the saturatio

Alfred Scharff Goldhaber, M. L. Horner

We study spectra for a 2D electron in the lowest Landau level with randomly distributed, repulsively correlated electric impurities. The lowest energy band reflects an effective magnetic field downshifted by an integer multiple of the impurity density. The downshift is precisely half that for the corresponding electron density in the composite-fermion pictur

F. Ritort

I review single-molecule experiments (SME) in biological physics. Recent technological developments have provided the tools to design and build scientific instruments of high enough sensitivity and precision to manipulate and visualize individual molecules and measure microscopic forces. Using SME it is possible to: manipulate molecules one at a time and mea

S. Chadov, J. Minar, H. Ebert, A. Perlov

The magneto-optical spectra of NiMnSb were calculated in the framework of the Local Spin Density Approximation (LSDA) combined with Dynamical Mean-Field Theory (DMFT). Comparing with results based on plain LSDA, an additional account of many-body correlations via DMFT results in a noticably improved agreement of the theoretical Kerr-rotation and ellipticity

Helga M. Böhm, Eckhard Krotscheck, Martin Panholzer

Based on an equations--of--motion approach for time--dependent pair correlations in strongly interacting Fermi liquids, we have developed a theory for describing the excitation spectrum of these systems. Compared to the known ``correlated&#39;&#39; random--phase approximation (CRPA), our approach has the following properties: i) The CRPA is reproduced when p

D. Makogon, V. Juricic, C. Morais Smith

We study the transport properties of a quantum wire, described by the Tomonaga-Luttinger model, in the presence of a backscattering potential provided by several extended time-dependent impurities (barriers). Employing the B\&#34; uttiker-Landauer approach, we first consider the scattering of noninteracting electrons ($g=1$) by a rectangular-like barrier and

A. I. Tartakovskii, T. Wright, A. Russell, V. I. Fal&#39;ko

We show that by illuminating an InGaAs/GaAs self-assembled quantum dot with circularly polarized light, the nuclei of atoms constituting the dot can be driven into a bistable regime, in which either a threshold-like enhancement or reduction of the local nuclear field by up to 3 Tesla can be generated by varying the intensity of light. The excitation power th

Abdullah Alqudami, S. Annapoorni, Subhalakshmi Lamba, P C Kothari

Nanoparticles of iron were prepared in distilled water using very thin iron wires and sheets, by the electro-exploding wire technique. Transmission electron microscopy reveals the size of the nanoparticles to be in the range 10 to 50 nm. However, particles of different sizes can be segregated by using ultrahigh centrifuge. X-ray diffraction studies confirm t

Abdullah Alqudami, S. Annapoorni

The observation of intense visible fluorescence from silver and iron nanoparticles in different solution phases and surface capping is reported here. Metallic silver and iron nanoparticles were obtained by exploding pure silver and iron wires in pure water. Bovine serum albumin protein adsorption on the silver nanoparticles showed an enhanced fluorescence. T

Miron J. Cristea

In this work, an analytical formula that gives the reach-through breakdown voltage of bipolar transistors, asymmetric thyristors, Punch Through-IGBTs and other devices with similar structure is deduced for the first time.

Ashot S. Gevorkyan, Chin-Kun Hu

A dielectric medium consisting of roughly polarized molecules is treated as a 3D disordered spin system (spin glass). A microscopic approach for the study of statistical properties of this system on micrometer space scale and nanosecond time scale of standing electromagnetic wave is developed. Using ergodic hypothesis the initial 3D spin problem is reduced t