March 2004 arXiv papers — page 6

Roger Guimera, Marta Sales-Pardo, Luis A. N. Amaral

The mechanisms by which modularity emerges in complex networks are not well understood but recent reports have suggested that modularity may arise from evolutionary selection. We show that finding the modularity of a network is analogous to finding the ground-state energy of a spin system. Moreover, we demonstrate that, due to fluctuations, stochastic networ

Sean Matt, Ralph E. Pudritz

We critically examine the theory of disk locking, which assumes that the angular momentum deposited on an accreting protostar is exactly removed by torques carried along magnetic field lines connecting the star to the disk. In this letter, we consider that the differential rotation between the star and disk naturally leads to an opening (i.e., disconnecting)

Masamune Oguri, Charles R. Keeton

We study the statistics of large-separation gravitational lens systems produced by non-spherical halos in the Cold Dark Matter (CDM) model. Specifically, we examine how the triaxiality of CDM halos affects the overall lensing probabilities and the relative numbers of different image configurations (double, quadruple, and naked cusp lenses). We find that tria

Sergey V. Malinin, Thomas Nattermann, Bernd Rosenow

The variable range hopping results for noninteracting electrons of Mott and Shklovskii are generalized to 1D disordered charge density waves and Luttinger liquids using an instanton approach. Following a recent paper by Nattermann, Giamarchi and Le Doussal [Phys. Rev. Lett. {\bf 91}, 56603 (2003)] we calculate the quantum creep of charges at zero temperature

Marc Freitag, Willy Benz

We report on a very large set of simulations of collisions between two main sequence (MS) stars. These computations were done with the ``Smoothed Particle Hydrodynamics'' method. Realistic stellar structure models for evolved MS stars were used. In order to sample an extended domain of initial parameters space (masses of the stars, relative velocity and impa

K. Hasegawa

We find the condition that the primordial baryon asymmetry is not washed out in the $SU(2)_{L}$ triplet Higgs model by solving the Boltzmann equation. We further require that the model is compatible with the recent results of the neutrino oscillation experiments and WMAP, and the constraints on the $ρ$ parameter imposed by the LEP. We finally obtain the allo

A. Romanelli, R. Siri, G. Abal, A. Auyuanet

We investigate the quantum walk on the line when decoherences are introduced either through simultaneous measurements of the chirality and particle position, or as a result of broken links. Both mechanisms drive the system to a classical diffusive behavior. In the case of measurements, we show that the diffusion coefficient is proportional to the variance of

G. Aldazabal, E. C. Andrés, J. E. Juknevich

We consider configurations of stacks of orientifold planes and D-branes wrapped on a non trivial internal space of the structure {(Gepner model)^{c=3n} x T^{2(3-n)}}/Z_N, for n=1,2,3. By performing simple moddings by discrete symmetries of Gepner models at orienti fold points, consistent with a Z_N orbifold action, we show that projection on D-brane configur

M. Arik, M. C. Calik

The basic motivation of this work is to attempt to explain the rapid primordial inflation and the observed slow late-time inflation by using the Brans-Dicke theory of gravity. We show that the ratio of these two inflation parameters is proportional to the square root of the Brans-Dicke parameter $% ω$ $(ω\gg1) $. We also calculate the Hubble parameter $% H$

Ivan Petrakiev

We consider the problem of bounding the dimension of the linear system of curves in ${\bf P}^2$ of degree $d$ with prescribed multiplicities $m_1,...,m_n$ at $n$ general points (\cite{Hir1},\cite{Hir2}). We propose a new method, based on the work of Ciliberto and Miranda (\cite {CM1}, \cite {CM2}), by specializing the general points to an elliptic curve in $

Shin'ichi Nojiri, Sergei D. Odintsov

It is proposed that dark energy may become dominant over standard matter due to universe expansion (curvature decrease). Two models: non-linear gravity-matter system and modified gravity may provide the effective phantom or effective quintessence dark energy which complies with the conjecture. It is interesting that future of such universe is not necessary f

Etienne Caurier, Frederic Nowacki, Alfredo Poves

The evolution of the N=28 neutron shell closure is studied in the N=28 isotones from neutron drip line's $^{40}$Mg to N=Z doubly magic $^{56}$Ni. It is found that the N=28 closure vanishes at Z=12 in favor of a deformed ground state. For Z=14 and Z=16 closed shell and intruder configurations are almost degenerate, leading to highly mixed ground states an

A. K. H. Bengtsson

A comprehensive approach to the theory of higher spin gauge fields is proposed. By explicitly separating out details of implementation from general principles, it becomes possible to focus on the bare minimum of requirements that such a theory must satisfy. The abstraction is based on a survey of the progress that has been achieved since relativistic wave eq

Gaetano Fiore

We show that the complicated *-structure characterizing for positive q the U_qso(N)-covariant differential calculus on the non-commutative manifold R_q^N boils down to similarity transformations involving the ribbon element of a central extension of U_qso(N) and its formal square root v. Subspaces of the spaces of functions and of p-forms on R_q^N are made i

J. Reinisch, A. Heuer

Though the existence of two-level systems (TLS) is widely accepted to explain low temperature anomalies in the sound absorption, heat capacity, thermal conductivity and other quantities, an exact description of their microscopic nature is still lacking. We performed computer simulations for a binary Lennard-Jones system, using a newly developed algorithm to

Guido Carlet

We construct the tri-Hamiltonian structure of the two-dimensional Toda hierarchy using the R-matrix theory.

Vladimir Turaev

We relate the author's Lie cobracket in the module additively generated by loops on a surface with the Connes-Kreimer Lie bracket in the module additively generated by trees. To this end we introduce a pre-Lie coalgebra and a (commutative) Hopf algebra of pointed loops on a surface. In the last version I added sections on Wilson loops and knot diagrams.

P. A. Grassi, A. Quadri

The background field method (BFM) for the Poisson Sigma Model (PSM) is studied as an example of the application of the BFM technique to open gauge algebras. The relationship with Seiberg-Witten maps arising in non-commutative gauge theories is clarified. It is shown that the implementation of the BFM for the PSM in the Batalin-Vilkovisky formalism is equival

Gianluca Allemandi, Andrzej Borowiec, Mauro Francaviglia

The evidence of the acceleration of universe at present time has lead to investigate modified theories of gravity and alternative theories of gravity, which are able to explain acceleration from a theoretical viewpoint without the need of introducing dark energy. In this paper we study alternative gravitational theories defined by Lagrangians which depend on

Kenjiro Yanagi, Shigeru Furuichi, Ken Kuriyama

Certain trace inequalities related to matrix logarithm are shown. These results enable us to give a partial answer of the open problem conjectured by A.S.Holevo. That is, concavity of the auxiliary function which appears in the random coding exponent as the lower bound of the quantum reliability function for general quantum states is proven in the case of $0

J. H. Field

Observations of the apparent times and positions of moving clocks as predicted by both `non-local' and `local' Lorentz Transformations are considered. Only local transformations respect translational invariance. Such transformations change temporal but not spatial intervals, so breaking space time exchange symmetry and forbidding relativity of simultaneity a

R. Catena, N. Fornengo, A. Masiero, M. Pietroni

Scalar-tensor theories of gravity provide a consistent framework to accommodate an ultra-light quintessence scalar field. While the equivalence principle is respected by construction, deviations from General Relativity and standard cosmology may show up at nucleosynthesis, CMB, and solar system tests of gravity. After imposing all the bounds coming from thes

L. P. Rokhinson, V. Larkina, Y. B. Lyanda-Geller, L. N. Pfeiffer

Charged carriers with different spin states are spatially separated in a two-dimensional hole gas. Due to strong spin-orbit interaction holes at the Fermi energy have different momenta for two possible spin states travelling in the same direction and, correspondingly, different cyclotron orbits in a weak magnetic field. Two point contacts, acting as a monoch

Stacy S. McGaugh

The mass discrepancy in disk galaxies is shown to be well correlated with acceleration, increasing systematically with decreasing acceleration below a critical scale a0 = 3700 km^2/s^2/kpc = 1.2E-10 m/s/s. For each galaxy, there is an optimal choice of stellar mass-to-light ratio which minimizes the scatter in this mass discrepancy-acceleration relation. The

John N. Bahcall, Aldo M. Serenelli, Marc Pinsonneault

We evaluate the logarithmic derivative of the depth of the solar convective zone with respect to the logarithm of the radiative opacity. We use this expression to show that the radiative opacity near the base of the solar convective zone (CZ) must be known to an accuracy of +- 1% in order to calculate the CZ depth to the accuracy of the helioseismological me

R. Garcia-Patron Sanchez, J. Fiurasek, N. J. Cerf, J. Wenger

We propose a feasible optical setup allowing for a loophole-free Bell test with efficient homodyne detection. A non-gaussian entangled state is generated from a two-mode squeezed vacuum by subtracting a single photon from each mode, using beamsplitters and standard low-efficiency single-photon detectors. A Bell violation exceeding 1% is achievable with 6-dB

Shay Mozes, Benni Reznik, Jonathan Oppenheim

The utilization of a $d$-level partially entangled state, shared by two parties wishing to communicate classical information without errors over a noiseless quantum channel, is discussed. We analytically construct deterministic dense coding schemes for certain classes of non-maximally entangled states, and numerically obtain schemes in the general case. We s

Rex A. C. Medeiros, Francisco M. de Assis

We define the quantum zero-error capacity, a new kind of classical capacity of a noisy quantum channel. Moreover, the necessary requirement for which a quantum channel has zero-error capacity greater than zero is also given.

Zhanjun Zhang

In this letter a deterministic secure direct bidirectional communication protocol is proposed by using the quantum entanglement and local unitary operations on one photon of the Einstein-Podolsky-Rosen (EPR) photon pair.

Wentian Li, Fengzhu Sun, Ivo Grosse

One important issue commonly encountered in the analysis of microarray data is to decide which and how many genes should be selected for further studies. For discriminant microarray data analyses based on statistical models, such as the logistic regression models, gene selection can be accomplished by a comparison of the maximum likelihood of the model given

M. D. Nielsen, C. Jacobsen, N. A. Mortensen, J. R. Folkenberg

We report on a single-mode photonic crystal fiber with attenuation and effective area at 1550 nm of 0.48 dB/km and 130 square-micron, respectively. This is, to our knowledge, the lowest loss reported for a PCF not made from VAD prepared silica and at the same time the largest effective area for a low-loss (< 1 dB/km) PCF. We briefly discuss the future applic

D. Yafaev

We consider the Schrödinger operator ${\bf H}=(i\nabla+A)^2 $ in the space $L_2({\mathbb R}^3)$ with a magnetic potential $A $ created by an infinite straight current. We perform a spectral analysis of the operator ${\bf H}$ almost explicitly. In particular, we show that the operator ${\bf H}$ is absolutely continuous, its spectrum has infinite multiplicity

Bernhard Rothenstein, Corina Nafornita

After having shown that the formula which describes the Doppler effect in the general case holds only in the case of the &#34;very high&#34; frequency assumption, we derive free of assumptions Doppler formulas for two scenarios presented in the revisited paper.

Volker Naulin

The turbulent transport of impurity or minority species, as for example Tritium, is investigated in drift-Alfvén edge turbulence. The full effects of perpendicular and parallel convection are kept for the impurity species. The impurity density develops a granular structure with steep gradients and locally exceeds its initial values due to the compressibility

Miguel C. Brito, Jorge Maia Alves, Joao M. Serra, Antonio Vallera

Nonlinear effects were observed in a forced vibrating string. The motion of the string becomes elliptic as the amplitude of the vibration increases. The fundamental resonance frequency depends on the amplitude of the vibration. At sufficient high amplitudes the system exhibits hysterisis: the resonance frequency is different when measured increasing the driv

J. R. Bochinski, Eric R. Hudson, H. J. Lewandowski, Jun Ye

A special class of molecules that are important to many subfields in molecular dynamics and chemical physics, namely free radical molecules, now enjoy a significant degree of center-of-mass motion control in the laboratory frame. The example reported in this paper concerns hydroxyl radical (OH), which, after the internal degrees of freedom are cooled in a su

G. F. Bertsch, A. Bulgac, R. A. Broglia

Formulas are derived for the coupled quadrupolar and monopolar oscillations of a fermion condensate trapped in a axially symmetric harmonic potential. We consider two-component condensates with a large particle-particle scattering length and in the limits of frequencies either small (adiabatic) or large (diabatic) compared to the pairing gap. Using the metho

S. V. Akkelin, M. S. Borysova, Yu. M. Sinyukov

The problem of spectra formation in hydrodynamic approach to A+A collisions is discussed. It is analyzed in terms of the two different objects: distribution and emission functions. We show that though the process of particle liberation, described by the emission function, is, usually, continuous in time, the observable spectra can be also expressed by means

Yu. M. Sinyukov, S. V. Akkelin

We propose a method to estimate the entropy of thermal pions in A+A collisions irrespective of unknown form of freeze-out (isothermal) hypersurface and transverse flows developed. We analyse the average phase-space densities and entropies of the thermal pions vs their multiplicities and collision energies. The behaviour of these values apparently indicates t

Jamal Jalilian-Marian

The Color Glass Condensate formalism and its application to high energy heavy ion collisions at RHIC are discussed. We argue that the RHIC data supports the view that the Color Glass Condensate provides the initial conditions for gold-gold collisions at RHIC while final state (Quark Gluon Plasma) effects are responsible for the high $p_t$ suppression in mid

C. P. Achenbach, J. H. Cobb

We report on the prototyping of a plastic scintillator hodoscope with wavelength-shifting fibre read-out by a multi-anode photomultiplier as part of the development of a detector for cosmic ray muons to be carried aboard an aircraft. Light yield and light attenuation measurements on single- and double-clad wavelength-shifting fibres were performed. Low power

A. M. Dikande

Radial solitons are investigated in armchair carbon nanotubes using a generalized Lennard-Jones potential. The radial solitons are found in terms of moving kink defects whose velocity obeys a dispersion relation. Effects of lattice discreteness on the shape of kink defects are examined by estimating the Peierls stress. Results suggest that the typical size f

Alain M. Dikande, J. P. Nguenang

A parametrized spin model was recently introduced and intended for one-dimensional ferromagnets with a deformable Zeeman energy. This model is revisited and given more realistic interpretation in terms of a model for ferromagnetic systems with nonconvex anisotropies. A main virtue of the improved form is its exact reduction to the discrete Remoissenet-Peyrar

H. Makino, S. Tasaki

Along the line of thoughts of Berry and Robnik{\cite{Ber}}, the limiting gap distribution function of classically integrable quantum systems is derived in the limit of infinitely many independent components. The limiting gap distribution function is characterized by a single monotonically increasing function $\barμ(S)$ of the level spacing $S$, and the corre

Klaus Kirsten, Alan J. McKane

Simple and analytically tractable expressions for functional determinants are known to exist for many cases of interest. We extend the range of situations for which these hold to cover systems of self-adjoint operators of the Sturm-Liouville type with arbitrary linear boundary conditions. The results hold whether or not the operators have negative eigenvalue

Christian Gerard, Christian Jaekel

We construct interacting quantum fields in 1+1 dimensional Minkowski space, representing neutral scalar bosons at positive temperature. Our work is based on prior work by Klein and Landau and Hoegh-Krohn

Detlef Mueller, Christoph Thiele

Let L be the distinguished Laplacian on certain semidirect products of R by R^n which are of ax+b type. We prove pointwise estimates for the convolution kernels of spectrally localized wave operators for arbitrary time and scaling parameter.

Jozef H. Przytycki, Witold Rosicki

We give a topological interpretation of the core group invariant of a surface embedded in S^4. We show that the group is isomorphic to the free product of the fundamental group of the double branch cover of S^4 with the surface as a branched set, and the infinite cyclic group. We present a generalization for unoriented surfaces, for other cyclic branched cov

S. Denisov, S. Kupin

Let p be a trigonometric polynomial, nonnegative on the unit circle $\mathbb{T}$. We say that a measure $σ$ on $\mathbb{T}$ belongs to the polynomial Szego class, if $dσ=sigma&#39;_{ac}dθ+dσ_s$, $σ_s$ is singular, and $p\ln σ&#39;_{ac}$ is summable on $\mathbb{T}$. For the associated orthogonal polynomials, we obtain pointwise asymptotics inside the unit dis

Ivan Dimitrov, Ivan Penkov

The purpose of the present paper is twofold: to introduce the notion of a generalized flag in an infinite dimensional vector space $V$ (extending the notion of a flag of subspaces in a vector space), and to give a geometric realization of homogeneous spaces of the ind--groups $SL(\infty)$, $SO(\infty)$ and $Sp(\infty)$ in terms of generalized flags. Generali

C M Doria

It is shown that the non-homogeneous Dirichlet and Neuman problems for the $2^{nd}$-order Seiberg-Witten equation admit a regular solution once the $\mathcal{H}$-condition (described in the article) is satisfied. The approach consist in applying the elliptic techniques to the variational setting of the Seiberg-Witten equation.

Alexandru Tamasan

In this paper we reconstruct convection terms from boundary measurements.We reduce the Beals and Coifman inverse scattering scattering formalism from a first order system to a formalism for the $\bar{\partial}$ equation.

Christopher King, Michael Nathanson

Suppose that A and B are real stable matrices, and that their difference A-B is rank one. Then A and B have a common quadratic Lyapunov function if and only if the product AB has no real negative eigenvalue. This result is due to Shorten and Narendra, who showed that it follows as a consequence of the Kalman-Yacubovich-Popov solution of the Lur&#39;e problem

Joao Jose de Farias Neto

It is shown that in the multivariate case the orders p, of the AR part, and q, of the MA part, are not invariants of the time series. Thus, it is concluded that it only makes sense to define the class of ARMA(p,p)- irreducible models, where p is the biggest of the system&#39;s Kronecker indices. This class is shown not to be a differentiable manifold, but to

Daniel Azagra, Juan Ferrera

We introduce a proximal subdifferential and develop a calculus for nonsmooth functions defined on any Riemannian manifold $M$. We give several applications of this theory, concerning: 1) differentiability and geometrical properties of the distance function to a closed subset $C$ of $M$; 2) solvability and implicit function theorems for nonsmooth functions on

Rakib Feyruz Efendiev

In this paper the complete spectral analysis of the operators is carried out and also with help of generalized normalizing numbers the inverse problem is solved.

H. Hakopian

We derive two consequences of the multivariate fundamental theorem of algebra (MFTA). The first one is the Bezout theorem for $n$ polynomials. Notably the intersection multiplicities, as in MFTA, are characterized just by means of partial differential operators given by polynomials from $D$-invariant linear spaces. The second consequence provides a solution

H. Hakopian, M. Tonoyan

We study a class of overdetermined algebraic systems of equations. We prove that the number of distinct solutions equals to the maximal possible if and only if certain matrices are commuting and semisimple. This gives a characterization of correct systems of points for multivariate Lagrange interpolation.

Sinya Kitani, Eiki Sawada, Kimio Ueno

The theory of finite automata applies to the study on relations of multiple zeta values.

Michitomo Nishizawa, Kimio Ueno

The functional relation of the Hurwitz zeta function is proved by using the connection problem of the confluent hypergeometric equation.

Sarah J. Campbell, Graham A. Niblo

We show that the Hilbert space compression of any finite dimensional CAT(0) cube complex is 1 and deduce that any discrete group acting properly, co-compactly on a CAT(0) cube complex is exact. The class of groups covered by this theorem includes free groups, finitely generated Coxeter groups, finitely generated right angled Artin groups, finitely presented

Nikos Frantzikinakis, Bryna Kra

We answer a question posed by Vitaly Bergelson, showing that in a totally ergodic system, the average of a product of functions evaluated along polynomial times, with polynomials of pairwise differing degrees, converges in $L^{2}$ to the product of the integrals. Such averages are characterized by nilsystems and so we reduce the problem to one of uniform dis

Nikos Frantzikinakis

Motivated by a problem in ergodic Ramsey theory, Furstenberg and Katznelson introduced the notion of strong stationarity, showing that certain recurrence properties hold for arbitrary measure preserving systems if they are valid for strongly stationary ones. We construct some new examples and prove a structure theorem for strongly stationary systems. The bui

D. Arcara

We produce a lower bound for the dimension of the base locus of the generalized theta divisor on the moduli space SU_C(r) of semistable vector bundles of rank r and trivial determinant on a smooth curve C of genus g > 1.

Marianne Akian, Stephane Gaubert, Vassili Kolokoltsov

We consider equations of the form Bf=g, where B is a Galois connection between lattices of functions. This includes the case where B is the Legendre-Fenchel transform, or more generally a Moreau conjugacy. We characterise the existence and uniqueness of a solution f in terms of generalised subdifferentials. This extends a theorem of Vorobyev and Zimmermann,

Elias Katsoulis, David W. Kribs

Based on a Wold decomposition for families of partial isometries and projections of Cuntz-Krieger-Toeplitz-type, we extend several fundamental theorems from the case of single vertex graphs to the general case of countable directed graphs with no sinks. We prove a Szego-type factorization theorem for CKT families, which leads to information on the structure

Al Vitter

We study the restrictions of rank 2 semistable vector bundles E on P^2 to conics. A Grauert-Mulich type theorem on the generic splitting is proven. The jumping conics are shown to have the scheme structure of a hypersurface J_{2} in P^5 of degree c_{2}(E) when c_{1}(E)=0 and of degree c_{2}(E)-1 when c_{1}(E)=-1. Some examples of jumping conics and jumping l

Elchanan Mossel

We apply the theory of markov random fields on trees to derive a phase transition in the number of samples needed in order to reconstruct phylogenies. We consider the Cavender-Farris-Neyman model of evolution on trees, where all the inner nodes have degree at least 3, and the net transition on each edge is bounded by e. Motivated by a conjecture by M. Steel,

Elliott H. Lieb, Robert Seiringer, Jakob Yngvason

The classic Poincare inequality bounds the $L^q$-norm of a function $f$ in a bounded domain $Ω\subset \R^n$ in terms of some $L^p$-norm of its gradient in $Ω$. We generalize this in two ways: In the first generalization we remove a set $Γ$ from $Ω$ and concentrate our attention on $Λ= Ω\setminus Γ$. This new domain might not even be connected and hence no Po

Alex Eskin, Howard Masur, Anton Zorich

A holomorphic 1-form on a compact Riemann surface S naturally defines a flat metric on S with cone-type singularities. We present the following surprising phenomenon: having found a geodesic segment (saddle connection) joining a pair of conical points one can find with a nonzero probability another saddle connection on S having the same direction and the sam

Mark Laidlaw, Madoka Nishimura

We consider the open string tachyon action in a world-sheet sigma model approach. We present explicit calculations up to order 8 in derivatives for the bosonic string, and mimic these to order 6 for the superstring, including terms with multiple derivatives acting on the tachyon field. We reproduce lower derivative terms obtained elsewhere, and speculate on

J. L. F. Barbon, E. Rabinovici

We discuss the various scales determining the temporal behaviour of correlation functions in the presence of eternal black holes. We point out the origins of the failure of the semiclassical gravity approximation to respect a unitarity-based bound suggested by Maldacena. We find that the presence of a subleading (in the large-N approximation involved) master

D. Bashkirov

Covariant (polysymplectic)Hamiltonian field theory is the Hamiltonian counterpart of classical Lagrangian field theory. They are quasi-equivalent in the case of almost-regular Lagrangians. This work addresses BV quantization of polysymplectic Hamiltonian field theory. We compare BV quantizations of associated Lagrangian and polysymplectic Hamiltonian field s

Dmitri Kharzeev, Eugene Levin, Larry McLerran

We consider the influence of parton saturation in the Color Glass Condensate on the back-to-back azimuthal correlations of high $p_T$ hadrons in $pA$ (or $dA$) collisions. When both near--side and away--side hadrons are detected at mid-rapidity at RHIC energy, the effects of parton saturation are constrained to transverse momenta below the saturation scale $

D. N. Argyriou, C. J. Milne, N. Aliouane, P. G. Radaelli

We have used electron and neutron powder diffraction to elucidate the structural properties of superconducting \NaD. Our measurements show that our superconducting sample exhbits a number of supercells ranging from ${1/3}a^{*}$ to ${1/15}a^{*}$, but the most predominant one, observed also in the neutron data, is a double hexagonal cell with dimensions \dhx.

F. S. Bergeret, A. F. Volkov, K. B. Efetov

We consider ferromagnetic particles embedded into a superconductor and study the screening of their magnetic moments by the spins of the Cooper pairs in the superconductor. It is shown that a magnetic moment opposite to the one of the ferromagnetic particle is induced in the superconductor. In the case of a small itinerant ferromagnet grain and low temperatu

Garin F. J. Ananos, Fulvio Baldovin, Constantino Tsallis

We perform a throughout numerical study of the average sensitivity to initial conditions and entropy production for two symplectically coupled standard maps focusing on the control-parameter region close to regularity. Although the system is ultimately strongly chaotic (positive Lyapunov exponents), it first stays lengthily in weak-chaotic regions (zero Lyap

Dirk-Jan Heijs, Victor A. Malyshev, Jasper Knoester

We theoretically study the trapping time distribution and the efficiency of the excitation energy transport in dendritic systems. Trapping of excitations, created at the periphery of the dendrimer, on a trap located at its core, is used as a probe of the efficiency of the energy transport across the dendrimer. The transport process is treated as incoherent h

M. Kira, S. W. Koch

The build-up of exciton populations in resonantly laser excited semiconductors is studied microscopically. For excitation at the $2s$-exciton resonance, it is shown that polarization with a strict $s$-type radial symmetry can be efficiently converted into an incoherent $p$-type population. As a consequence, inversion between the $2p$ and $1s$ exciton states

Ph. Mavropoulos, I. Galanakis, P. H. Dederichs

We report on first-principles calculations of multilayers of zinc-blende half-metallic ferromagnets CrAs and CrSb with III-V and II-VI semiconductors, in the [001] orientation. We examine the ideal and tetragonalised structures, as well as the case of an intermixed interface. We find that, as a rule, half-metallicity can be conserved throughout the heterostr

A. De Martino, I. Giardina, M. Marsili, A. Tedeschi

We introduce a simple extension of the minority game in which the market rewards contrarian (resp. trend-following) strategies when it is far from (resp. close to) efficiency. The model displays a smooth crossover from a regime where contrarians dominate to one where trend-followers dominate. In the intermediate phase, the stationary state is characterized b

Manabu Kiguchi, Shiro Entani, Genki Yoshikawa, Koichiro Saiki

We have studied atomic structures of a-sexithienyl (6T) films grown on Cu(110) by near-edge x-ray absorption fine structure (NEXAFS). A one-dimensional (1D) ordered structure of 6T with its molecular long axis parallel to the Cu[001] direction could be fabricated by deposition at 300 K and subsequent annealing at 360 K. Polarization and azimuth-dependent NEX

Guillemette Picard, Armand Ajdari, Francois Lequeux, Lyderic Bocquet

With the eventual aim of describing flowing elasto-plastic materials, we focus on the elementary brick of such a flow, a plastic event, and compute the long-range perturbation it elastically induces in a medium submitted to a global shear strain. We characterize the effect of a nearby wall on this perturbation, and quantify the importance of finite size effe

Thorsten Poeschel, Nikolai V. Brilliantov, Alexei Zaikin

We investigate the motion of a hard cylinder rolling down a soft inclined plane. The cylinder is subjected to a viscous drag force and stochastic fluctuations due to the surrounding medium. In a wide range of parameters we observe bistability of the rolling velocity. In dependence on the parameters, increasing noise level may lead to increasing or decreasing

A. E. Patrakov, I. I. Lyapilin

Under microwave irradiation, in 2D electron systems with high filling factors oscillations of longitudinal magnetoresistance appear in the range of magnetic fields where ordinary SdH oscillations are suppressed. An unusual beat-like behaviour of these oscillations in weak magnetic fields (B < 0.02 T) was attributed to the zero spin splitting previously. We p

M. Pustilnik, L. I. Glazman

We review mechanisms of low-temperature electronic transport through a quantum dot weakly coupled to two conducting leads. Transport in this case is dominated by electron-electron interaction. At temperatures moderately lower than the charging energy of the dot, the linear conductance is suppressed by the Coulomb blockade. Upon further lowering of the temper

Steven C. Erwin, Igor Zutic

If magnetic semiconductors are ever to find wide application in real spintronic devices, their magnetic and electronic properties will require tailoring in much the same way that band gaps are engineered in conventional semiconductors. Unfortunately, no systematic understanding yet exists of how, or even whether, properties such as Curie temperatures and ban

Matthias Vojta, Lars Fritz

Impurity moments coupled to fermions with a pseudogap density of states display a quantum phase transition between a screened and a free moment phase upon variation of the Kondo coupling. We describe the universal theory of this transition for the experimentally relevant case of particle-hole asymmetry. The theory takes the form of a crossing between effecti

T. C. Hillwig, D. R. Gies, W. Huang, M. V. McSwain

We present spectroscopy of the microquasar SS 433 obtained near primary eclipse and disk precessional phase Psi = 0.0, when the accretion disk is expected to be most ``face-on&#39;&#39;. The likelihood of observing the spectrum of the mass donor is maximized at this combination of orbital and precessional phases since the donor is in the foreground and above

J. W. T. Hessels, M. S. E. Roberts, S. M. Ransom, V. M. Kaspi

We present results from X-ray and radio observations of the recently discovered young Vela-like pulsar PSR J2021+3651, which is coincident with the EGRET gamma-ray source GeV 2020+3658. A 19.0-ks Chandra ACIS-S observation has revealed a ~20&#39;&#39; x 10&#39;&#39; pulsar wind nebula that is reminiscent of the equatorial tori seen around some young pulsars,

Antony A. Stark, Youngung Lee

We have used an antenna temperature thresholding algorithm on the Bell Laboratories 13CO Milky Way Survey to create a catalog of 1,400 molecular clouds. Of these, 281 clouds were selected for having well-determined kinematic distances. The scaleheight, luminosity, internal velocity dispersion, and size of the cloud sample are analyzed to show that clouds sma

G. D. Barr, T. K. Gaisser, P. Lipari, S. Robbins

A Monte-Carlo calculation of the atmospheric neutrino fluxes [1,2] has been extended to take account of the three-dimensional (3D) nature of the problem, including the bending of secondary particles in the geomagnetic field. Emphasis has been placed on minimizing the approximations when introducing the 3D considerations. In this paper, we describe the techni

A. Sáiz, R. Domínguez-Tenreiro, A. Serna

We present results of an analysis of the structural and kinematical properties of a sample of elliptical-like objects (ELOs) identified in four hydrodynamical, self-consistent simulations run with the DEVA code (Serna et al. 2003). Star formation has been implemented in the code through a simple phenomenological parameterization, that takes into account stel

O. Le Fevre, G. Vettolani, S. Paltani, L. Tresse

{This paper presents the VIMOS VLT Deep Survey around the Chandra Deep Field South (CDFS). We have measured 1599 new redshifts with VIMOS on the European Observatory Very Large Telescope - UT3, in an area 21x21.6 arcmin^2, including 784 redshifts in the Hubble Space Telescope - Advanced Camera for Surveys GOODS area. 30% of all objects with I_AB=24 have been

M. Boettcher, A. Reimer

BL Lacertae was the target of an extensive multiwavelength monitoring campaign in the second half of 2000. In this paper, we are using leptonic and hadronic jet models to fit the observed broadband spectra and spectral variability patterns. We start out with global spectral models. Subsequently, we investigate various flaring scenarios for comparison with th

F. Meynadier, M. Heydari-Malayeri, L. Deharveng, V. Charmandaris

We study the Large Magellanic Cloud Papillon Nebula (N159-5), a conspicuous High Excitation Blob (HEB) lying in the star forming complex N159. Using JHK near-infrared photometry obtained at the ESO VLT with the ISAAC camera, we examine the stellar populations associated with the Papillon, tracing their history using stellar evolution models. Two populations

M. Still, P. Boyd

RXTE ASM count rates from the X-ray pulsar Her X-1 began falling consistently during the late months of 2003. The source is undergoing another state transition similar to the anomalous low state of 1999. This new event has triggered observations from both space- and ground-based observatories. In order to aid data interpretation and telescope scheduling, and

Mario A. Jimenez-Garate, Toan Khu

We measure the metal abundance ratios in the X-ray photoionized gas located near the narrow line region of a sample of Seyfert 2 AGN. The high-resolution X-ray spectra observed with the Chandra high- and low-energy transmission grating spectrometers are compared with models of the resonant scattering and recombination emission from a plasma in thermal balanc

M. H. Brookes, P. N. Best

The Combined EIS-NVSS Survey Of Radio Sources (CENSORS) has been produced with the primary goal of investigating the cosmological evolution of the radio luminosity function. This 1.4GHz sample, complete to the 7.2 mJy level, contains 150 radio sources. Host galaxies are almost entirely identified in optical and near-IR bands and the sample is now approaching

J. Iglesias-Paramo, A. Boselli, G. Gavazzi, A. Zaccardo

Since the Halpha and UV fluxes from galaxies are sensitive to stellar populations of ages < 10^7 and ~ 10^8 yr respectively, their ratio f(Halpha)/f(UV) provides us with a tool to study the recent t < 10^8 yr star formation history of galaxies, an exercise that we present here applied to 98 galaxies in 4 nearby clusters (Virgo, Coma, Abell 1367 and Cancer).