December 2006 arXiv papers — page 24

Henrik Svensmark

It has been proposed that galactic cosmic rays may influence the Earth's climate by affecting cloud formation. If changes in cloudiness play a part in climate change, their effect changes sign in Antarctica. Satellite data from the Earth Radiation Budget Experiment (ERBE) are here used to calculate the changes in surface temperatures at all latitudes, du

I. B. Konovalov, M. Beekmann, A. Richter, J. P. Burrows

We explore possibilities of improving the spatial structure of NOx emissions employed in a continental scale chemistry transport model (CTM) by using satellite measurements of nitrogen dioxide and ground-based observations of near surface ozone. In this study, we combine the tropospheric NO2 columns derived from SCIAMACHY measurements, the data from the EMEP

Amit K Chattopadhyay, Nigel J Burroughs

We analyse the size and density of thermally induced regions of close contact in cell:cell contact interfaces within a harmonic potential approximation, estimating these regions to be below one-tenth of a micron across. Our calculations indicate that as the distance between the close contact threshold depth and the mean membrane-membrane separation increases

Alexei V. Finkelstein, Dmitry N. Ivankov, Alexander M. Dykhne

We present a simple approximate analytical estimate for self-energy of a charge in the middle of cylindrical channel of a high permittivity epsilon_1 in a media of a low permittivity epsilon_2 (for the cases of infinitely long and comparatively short channels) and show that this estimate is in a good quantitative agreement with exact solution of Poisson equa

Yuri A. Rylov

The third modification of the space-time geometry is considered. (The first modification is the spacial relativity, the second one is the general relativity.) After the third modification of the space-time geometry the motion of free particles become to be primordially stochastic (multivariant). This circumstance forces one to construct a multivariant dynami

J. D. Holt, N. Pietralla, J. W. Holt, T. T. S. Kuo

Starting from the microscopic low-momentum nucleon-nucleon interaction V{low k}, we present the first systematic shell model study of magnetic moments and magnetic dipole transition strengths of the basic low-energy one-quadrupole phonon excitations in nearly-spherical nuclei. Studying in particular the even-even N=52 isotones from 92Zr to 100Cd, we find the

M. S. Bhagwat, P. Maris

The electromagnetic form factors of vector mesons are calculated in an explicitly Poincaré covariant formulation, based on the Dyson--Schwinger equations of QCD, that respects electromagnetic current conservation, and unambiguously incorporates effects from vector meson poles in the quark-photon vertex. This method incorporates a 2-parameter effective intera

Dmitry Anchishkin

The pion and quark annihilation mechanisms of dilepton production during relativistic nuclear collisions are studied. We focus on the modifications caused by the specific features of in-medium pion and quark states rather than by medium modification of the $ρ$-meson spectral density. The main ingredient emerging in our approach is a form-factor of the multi-

E. N. E. van Dalen, C. Fuchs, Amand Faessler

We present Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric nuclear matter which are based on improved approximations schemes. The potential matrix elements have been adapted for isospin asymmetric nuclear matter in order to account for the proton-neutron mass splitting in a more consistent way. The proton properties are particularly sensitiv

M. De Napoli, G. Raciti, E. Rapisarda, C. Sfienti

Silicon carbide (SiC) Schottky diodes 21 mum thick with small surfaces and high N-dopant concentration have been used to detect alpha particles and low energy light ions. In particular 12C and 16O beams at incident energies between 5 and 18 MeV were used. The diode active-region depletion-thickness, the linearity of the response, energy resolution and signal

Fabio Ramos, Ricardo Rosa, Roger Temam

We present rigorous estimates for some physical quantities related to turbulent and non-turbulent channel flows driven by a uniform pressure gradient. Such results are based on the concept of stationary statistical solution, which is related to the notion of ensemble average for flows in statistical equilibrium. We provide a lower bound estimate for the mean

A. Stolin, J. Yermolova-Magnusson

In this paper we describe all Lie bialgebra structures on the polynomial Lie algebra $\mathbf{g}[u]$, where $\mathbf{g}$ is a simple, finite dimensional, complex Lie algebra. The results are based on an unpublished paper Montaner and Zelmanov. Further, we introduce quasi-rational solutions of the CYBE and describe all quasi-rational $r$-matrices for $\mathbf

Jorge Sotomayor, Luis Fernando Mello, Denis de Carvalho Braga

In this paper we study the Lyapunov stability and the Hopf bifurcation in a system coupling an hexagonal centrifugal governor with a steam engine. Here are given sufficient conditions for the stability of the equilibrium state and of the bifurcating periodic orbit. These conditions are expressed in terms of the physical parameters of the system, and hold for

Ciprian Borcea, Xavier Goaoc, Sylvain Petitjean

We prove that the set of directions of lines intersecting three disjoint balls in $R^3$ in a given order is a strictly convex subset of $S^2$. We then generalize this result to $n$ disjoint balls in $R^d$. As a consequence, we can improve upon several old and new results on line transversals to disjoint balls in arbitrary dimension, such as bounds on the num

Alexander Samokhin

In this paper we prove a cohomology vanishing result for quadrics of low dimension in positive characteristic. This vanishing is a necessary condition for the D-affinity of these varieties.

K. D. Elworthy, Xue-Mei Li

An L2 theory of differential forms is proposed for the Banach manifold of continuous paths on Riemannian manifolds M furnished with its Brownian motion measure. Differentiation must be restricted to certain Hilbert space directions, the H-tangent vectors. To obtain a closed exterior differential operator the relevant spaces of differential forms, the H-forms

Rafe Jones

We consider integer recurrences of the form a_n = f(a_{n-1}), where f is a quadratic polynomial with integer coefficients. We show, for four infinite families of f, that the set of primes dividing at least one term of such a sequence must have density zero, regardless of choice of a_0. The proof relies on tools from group theory and probability theory to dev

Sébastien Darses, Ivan Nourdin

We study the dynamical properties of the Brownian diffusions having $σ{\rm Id}$ as diffusion coefficient matrix and $b=\nabla U$ as drift vector. We characterize this class through the equality $D^2_+=D^2_-$, where $D_{+}$ (resp. $D_-$) denotes the forward (resp. backward) stochastic derivative of Nelson's type. Our proof is based on a remarkable identit

Carlo R. Laing, Ioannis G. Kevrekidis

We study a network of 500 coupled modified van der Pol oscillators. The value of a parameter associated with each oscillator is drawn from a normal distribution, giving a heterogeneous network. For strong enough coupling the oscillators all have the same period, and we consider periodic forcing of the network when it is in this state. By exploiting the corre

M. Kapranov

We argue that there should exist a "noncommutative Fourier transform" which should identify functions of noncommutative variables (say, of matrices of indeterminate size) and ordinary functions or measures on the space of paths. Some examples are considered.

Laurent Bartholdi, Serge Cantat, Tullio Ceccherini-Silberstein, Pierre de la Harpe

Numerical estimates are given for the spectral radius of simple random walks on Cayley graphs. Emphasis is on the case of the fundamental group of a closed surface, for the usual system of generators.

Anna Cima, Armengol Gasull, Victor Manosa

This paper studies the iterates of the third order Lyness' recurrence $x_{k+3}=(a+x_{k+1}+x_{k+2})/x_k,$ with positive initial conditions, being $a$ also a positive parameter. It is known that for $a=1$ all the sequences generated by this recurrence are 8-periodic. We prove that for each $a\ne1$ there are infinitely many initial conditions giving rise to

Paul Wright

We study a heavy piston of mass $M$ that separates finitely many ideal, unit mass gas particles moving in two or three dimensions. Neishtadt and Sinai previously determined a method for finding this system's averaged equation and showed that its solutions oscillate periodically. Using averaging techniques, we prove that the actual motions of the piston c

Jeffrey S. Geronimo, Hugo Woerdeman

We consider bivariate polynomials orthogonal on the bicircle with respect to a positive linear functional. The lexicographical and reverse lexicographical orderings are used to order the monomials. Recurrence formulas are derived between the polynomials of different degrees. These formulas link the orthogonal polynomials constructed using the lexicographical

Yves de Cornulier, Romain Tessera, Alain Valette

Our main result is that the simple Lie group $G=Sp(n,1)$ acts properly isometrically on $L^p(G)$ if $p>4n+2$. To prove this, we introduce property $({\BP}_0^V)$, for $V$ be a Banach space: a locally compact group $G$ has property $({\BP}_0^V)$ if every affine isometric action of $G$ on $V$, such that the linear part is a $C_0$-representation of $G$, either h

A. Mudrov, V. Ostapenko

Let $G$ be the complex general linear group and $g$ its Lie algebra equipped with a factorizable Lie bialgebra structure; let $U_h$ be the corresponding quantum group. We construct explicit $U_h$-equivariant quantization of Poisson orbit bundles $O_λ\to O_μ$ in $gl(n)*$.

V. P. Maslov

We give a risk-minimizing formula for government investments taking into account the zero intelligence law for financial markets.

V. P. Maslov

The notion of density of a finite set is discussed. We proof a general theorem of set theory which refines Bose-Einstein distribution.

Mark Adler, Pierre van Moerbeke

This paper is a step in the direction of understanding the behavior of non-intersecting Brownian motions on the real line, when the number of particles becomes large. Consider 2k non-intersecting Brownian motions, all starting at the origin, such that the k left paths end up at -a and the k right paths end up at +a at time t=1. The Karlin-McGregor formula en

Anton S. Galaev

The problem of classification of connected holonomy groups (equivalently of holonomy algebras) for pseudo-Riemannian manifolds is open. The classification of Riemannian holonomy algebras is a classical result. The classification of Lorentzian holonomy algebras was obtained recently. In the present paper weakly-irreducible not irreducible subalgebras of $\su(

Hamed Hatami, Michael Molloy

We determine under which conditions certain natural models of random constraint satisfaction problems have sharp thresholds of satisfiability. These models include graph and hypergraph homomorphism, the $(d,k,t)$-model, and binary constraint satisfaction problems with domain size 3.

Yichuan Ding, Nathan Krislock, Jiawei Qian, Henry Wolkowicz

We study Semidefinite Programming, \SDPc relaxations for Sensor Network Localization, \SNLc with anchors and with noisy distance information. The main point of the paper is to view \SNL as a (nearest) Euclidean Distance Matrix, \EDM, completion problem and to show the advantages for using this latter, well studied model. We first show that the current popula

Mihai Damian

Let X be a finite CW-complex of dimension q. If its fundamental group $π_{1}(X)$ is polycyclic of Hirsch number h>q we show that at least one of the homotopy groups $π_{i}(X)$ is not finitely generated. If h=q or h=q-1 the same conclusion holds unless X is an Eilenberg-McLane space $K(π_{1}(X),1)$.

Jean-Philippe Anker, Bruno Schapira, Bartosz Trojan

We obtain a global estimate of the transition density $p^n(0,x)$ associated to a nearest neighbor random walk, called here "simple", on affine buildings of type $\widetilde{A}_r$. Then we deduce a global estimate of the Green function. This is the analogue of a result on Riemannian symmetric spaces of the noncompact type.

Osamu Ikawa, Takashi Sakai, Hiroyuki Tasaki

We introduce the notion of a weakly reflective submanifold, which is an austere submanifold with a certain global condition, and study its fundamental properties. Using these, we determine weakly reflective orbits and austere orbits of s-representations.

Lei Yang

In the present paper, we will show that three apparently disjoint objects: Galois representations arising from twenty-seven lines on a cubic surface (number theory and arithmetic algebraic geometry), Picard modular forms (automorphic forms), rigid Calabi-Yau threefolds and their arithmetic (Diophantine geometry) are intimately related to Hessian polyhedra an

Ivan Tyukin, Erik Steur, Henk Nijmeijer, Cees van Leeuwen

We consider the problem of asymptotic convergence to invariant sets in interconnected nonlinear dynamic systems. Standard approaches often require that the invariant sets be uniformly attracting. e.g. stable in the Lyapunov sense. This, however, is neither a necessary requirement, nor is it always useful. Systems may, for instance, be inherently unstable (e.

Toshiyuki Akita, Nariya Kawazumi

The first author conjectured certain relations for Morita-Mumford classes and Newton classes in the integral cohomology of mapping class groups (integral Riemann-Roch formulae). In this paper, the conjecture is verified for cyclic subgroups of mapping class groups.

Mahya Ghandehari, Hamed Hatami

For constant $r$ and arbitrary $n$, it was known that in the graph $K_r^n$ any independent set of size close to the maximum is close to some independent set of maximum size. We prove that this statement holds for arbitrary $r$ and $n$.

A. Soffer, C. Stucchio

We present a new algorithm, the Time Dependent Phase Space Filter (TDPSF) which is used to solve time dependent Nonlinear Schrodinger Equations (NLS). The algorithm consists of solving the NLS on a box with periodic boundary conditions (by any algorithm). Periodically in time we decompose the solution into a family of coherent states. Coherent states which a

Haidong Feng, Yu-tin Huang, Warren Siegel

We combine two partons on a random lattice as a vector state. In the ladder approximation, we find that such states have 1/p^2 propagators (after tuning the mass to vanish). We also construct some diagrams which are very similar to 3-string vertices in string field theory for the first oscillator mode. Attaching 3 such lattice states to these vertices, we ge

Forough Nasseri

In this Reply, using G.de.A.Marques' comment, we correct calculations and results presented in [Phys.Lett.B 632(2006) 151-154] about corrections to the fine structure constant in the spacetime of a cosmic string from the generalized uncertainty principle.

U. Gran, J. Gutowski, G. Papadopoulos, D. Roest

We review some aspects of the spinorial geometry approach to the classification of supersymmetric solutions of supergravity theories. In particular, we explain how spinorial geometry can be used to express the Killing spinor equations in terms of a linear system for the fluxes and the geometry of spacetime. The solutions of this linear system express some of

T. E. Clark, S. T. Love, Muneto Nitta, T. ter Veldhuis

Coset methods are used to construct the action describing the dynamics associated with the spontaneous breaking of the local Poincare symmetries of D dimensional space-time due to the embedding of a p-brane with codimension N=D-p-1. The resulting action is an ISO(1,p+N) invariant form of the Einstein-Hilbert action, which, in addition to the gravitational vi

O. Ogetbil

After reviewing the existing results we give an extensive analysis of the critical points of the potentials of the gauged N=2 Yang-Mills/Einstein Supergravity theories coupled to tensor- and hyper multiplets. Our analysis includes all the possible gaugings of all N=2 Maxwell-Einstein supergravity theories whose scalar manifolds are symmetric spaces. In gener

Raffaele Punzi, Frederic P. Schuller, Mattias N. R. Wohlfarth

Area metric manifolds emerge as effective classical backgrounds in quantum string theory and quantum gauge theory, and present a true generalization of metric geometry. Here, we consider area metric manifolds in their own right, and develop in detail the foundations of area metric differential geometry. Based on the construction of an area metric curvature s

Burak Himmetoglu, Marco Peloso

We study a recently proposed model, where a codimension one brane is wrapped around the axis of symmetry of an internal two dimensional space compactified by a flux. This construction is free from the problems which plague delta-like, codimension two branes, where only tension can be present. In contrast, arbitrary fields can be localized on this extended br

Don N. Page

Unless our universe is decaying at an astronomical rate (i.e., on the present cosmological timescale of Gigayears, rather than on the quantum recurrence timescale of googolplexes), it would apparently produce an infinite number of observers per comoving volume by thermal or vacuum fluctuations (Boltzmann brains). If the number of ordinary observers per comov

Mathias Butenschoen, Frank Fugel, Bernd A. Kniehl

In most of the mass range encompassed by the limits from the direct search and the electroweak precision tests, the Higgs boson of the standard model preferably decays to bottom quarks. We present, in analytic form, the dominant two-loop electroweak correction, of O(G_F^2 m_t^4), to the partial width of this decay. It amplifies the familiar enhancement due t

Andreas Gerhold, Thomas Schaefer, Andrei Kryjevski

We study the stability of the kaon condensed color-flavor locked (CFL) phase of dense quark matter with regard to the formation of a non-zero Goldstone boson current. In the kaon condensed phase there is an electrically charged fermion which becomes gapless near μ_s^(1) \simeq 1.35Δand a neutral fermion which becomes gapless near μ_s^(2)\simeq 1.61Δ. Here, μ

Alexander Lenz

We review the theoretical status of the lifetime ratios $τ_{B^+} / τ_{B_d}$ and $τ_{B_s} / τ_{B_d}$ and of the mixing quantities $ΔM_s$, $ΔΓ_s$ and $ϕ_s$. We show that the ratio $ΔΓ_s / ΔM_s$ can be determined with almost no non-perturbative uncertainties. Finally we explain how this precise determination of the standard model values can be used to find poss

M. P. Lombardo

I describe the results for the critical line and the thermodynamics of different phases of QCD which have been obtained by lattice simulations with an imaginary chemical potential, and review motivations and merits of the different strategies -- Taylor expansion, Fourier analysis and Pade' approximants -- for analytic continuation from imaginary to real

Rossella Falcone, Roberto Fiore, Mario Gravina, Alessandro Papa

We consider the mass spectrum of the 3$d$ 3-state Potts model in the broken phase (a) near the second order Ising critical point in the temperature - magnetic field plane and (b) near the weakly first order transition point at zero magnetic field. In the case (a), we compare the mass spectrum with the prediction from universality of mass ratios in the 3$d$ I

R. G. Campos, J. L. Lopez-Lopez, R. Vera

We present a matrix technique to obtain the spectrum and the analytical index of some elliptic operators defined on compact Riemannian manifolds. The method uses matrix representations of the derivative which yield exact values for the derivative of a trigonometric polynomial. These matrices can be used to find the exact spectrum of an elliptic operator in p

J. Balewski

Measurement of the transverse spin dependence of the di-jet opening angle in pp collisions at sqrt{s}=200 GeV has been performed by the STAR collaboration. An analyzing power consistent with zero has been observed over a broad range in pseudorapidity sum of the two jets with respect to the polarized beam direction. A non-zero (Sivers) correlation between tra

J. Kowalski-Glikman, A. Starodubtsev

In this paper, by making use of the perturbative expansion around topological field theory we are trying to understand why the standard perturbation theory for General Relativity, which starts with linearized gravity does not see gravitational collapse. We start with investigating classical equations of motion. For zero Immirzi parameter the ambiguity of the

German Izquierdo, Diego Pavon

The generalized second law of gravitational thermodynamics is examined in scenarios where the dark energy dominates the cosmic expansion. For quintessence and phantom fields this law is fulfilled but it may fail when the dark energy is in the form of a Chaplygin gas. However, if a black hole is allowed in the picture, the law can be violated if the field is

S. Jalalzadeh

The geodesic equation in induced matter theory is redefined. It is shown that the extra forces do not change the four-impulse of massive particles. We show that the 4D space-time is non-integrable and find the relation between non-integrability and the Mach's principal.

Francis Heylighen

The explosive development of "free" or "open source" information goods contravenes the conventional wisdom that markets and commercial organizations are necessary to efficiently supply products. This paper proposes a theoretical explanation for this phenomenon, using concepts from economics and theories of self-organization. Once available on

V. N. Zavaritsky

In a recent letter, henceforth referred to as Ref.[1], You et al postulate that Bi2212 factually represents a series array of SIS junctions and claim that the nonlinear current-voltage characteristics (IVC) of their bridge are free of heating. Earlier experiments cast serious doubt upon the accuracy of the principal postulate (of this letter), see Ref.[2] an

Philippe Colomban, Véronique Milande, Lionel Le Bihan

On site Raman analyses were performed at the Musée national de Céramique, Sèvres, France, on rare Iznik (former Nicaea) pottery produced from ~1480 to ~1620. A comparison is made with a series of shards. The town of production of these potteries was highly disputed in the 80's and many questions still remain. The potential of glaze on-site analyses as a

Alberto Cortijo, María A. H. Vozmediano

A formalism is proposed to study the electronic and transport properties of graphene sheets with corrugations as the one recently synthesized. The formalism is based on coupling the Dirac equation that models the low energy electronic excitations of clean flat graphene samples to a curved space. A cosmic string analogy allows to treat an arbitrary number of

Heitor C. Marques Fernandes, Jeferson J. Arenzon, Yan Levin

Monte Carlo simulations are used to study lattice gases of particles with extended hard cores on a two dimensional square lattice. Exclusions of one and up to five nearest neighbors (NN) are considered. These can be mapped onto hard squares of varying side length, $λ$ (in lattice units), tilted by some angle with respect to the original lattice. In agreement

Pierluigi Contucci, Joel Lebowitz

We prove a correlation type inequality for spin systems with quenched symmetric random interactions. This gives monotonicity of the pressure with respect to the strength of the interaction for a class of spin glass models. Consequences include existence of the thermodynamic limit for the pressure and bounds on the surface pressure. We also describe other con

V. Ahufinger, A. Mebrahtu, R. Corbalan, A. Sanpera

We study the possibility of implementing a quantum switch and a quantum memory for matter wave lattice solitons by making them interact with "effective" potentials (barrier/well) corresponding to defects of the optical lattice. In the case of interaction with an "effective" potential barrier, the bright lattice soliton experiences an abrupt t

R. Roldan, M. P. Lopez-Sancho, F. Guinea, S. -W. Tsai

The electron-electron interactions affect the low-energy excitations of an electronic system and induce deformations of the Fermi surface. These effects are especially important in anisotropic materials with strong correlations, such as copper oxides superconductors or ruthenates. Here we analyze the deformations produced by electronic correlations in the Fe

P. M. C. de Oliveira, C. A. F. Leite, C. V. Chianca, J. S. Sá Martins

The experiment consists of counting and measuring the size of the many fragments observed after the fall of a mercury drop on the floor. The size distribution follows a power-law for large enough fragments. We address the question of a possible crossover to a second, different power-law for small enough fragments. Two series of experiments were performed. Th

M. Ondracek, J. Kudrnovsky, F. Maca

We investigate theoretically the ground state of the FeMn binary alloy monolayer on the W(001) surface, the stability of different magnetic configurations (ferro/antiferromagnetic, disordered local moments, etc.) and estimate concentrations at which a transition occurs between different magnetic orders. The tight-binding linear muffin-tin orbital method comb

Luca Dell'Anna, Michele Fabrizio, Claudio Castellani

We analyze how the range of disorder affects the localization properties of quasiparticles in a two-dimensional d-wave superconductor within the standard non-linear sigma-model approach to disordered systems. We show that for purely long-range disorder, which only induces intra-node scattering processes, the approach is free from the ambiguities which often

C. Brügger, C. P. Hofmann, F. Kämpfer, M. Moser

In contrast to hole-doped systems which have hole pockets centered at $(\pm \fracπ{2a},\pm \fracπ{2a})$, in lightly electron-doped antiferromagnets the charged quasiparticles reside in momentum space pockets centered at $(\fracπ{a},0)$ or $(0,\fracπ{a})$. This has important consequences for the corresponding low-energy effective field theory of magnons and e

Akira Oguri

We reexamine basic aspects of a nonequilibrium steady state in the Kondo problem for a quantum dot under a bias voltage using a reduced density matrix, which is obtained in the Fock space by integrating out one of the two conduction channels. The integration has been carried out by discretizing the conduction channels preserving the two-fold degeneracy due t

M. Bejas, A. Greco, A. Foussats

Several experimental and theoretical studies in cobaltates suggest the proximity of the system to charge ordering (CO). We show, qualitatively, in the frame of a $t-V$ model coupled to phonons that optical phonon modes at the $K$ and $M$ points of the Brillouin zone, which involves only $O$-ions displacement around a $Co$-ion, are good candidates to display

Shengqiang Zhou, K. Potzger, H. Reuther, K. Kuepper

The structural and magnetic properties of V doped ZnO are presented. V ions were introduced into hydrothermal ZnO single crystals by ion implantation with fluences of 1.2*10^16 to 6*10^16 cm^-2. Post-implantation annealing was performed in high vacuum from 823 K to 1023 K. The ZnO host material still partly remains in a crystalline state after irradiation, a

Chun Zou, Zhi-Wei Tian, Hong-Juan Liu, Chu-Guang Zheng

The collision consistency between the BGK collision model equation and lattice-BGK (LBGK) model is proposed by researching the physical significance of the relaxation factor tau in LBGK model. For microscalar flow in which the continuum hypothesis is not still satisfied, the collision consistency tau=1.0 should be ensured when using the LBGK model for simula

R. S. Liu, H. Pettersson, L. Michalak, C. M. Canali

We have investigated spin accumulation in Ni/Au/Ni single-electron transistors assembled by atomic force microscopy. The fabrication technique is unique in that unconventional hybrid devices can be realized with unprecedented control, including real-time tunable tunnel resistances. A grid of Au discs, 30 nm in diameter and 30 nm thick, is prepared on a SiO2

N. Baer, S. Schulz, P. Gartner, S. Schumacher

The electronic and optical properties of self-assembled InN/GaN quantum dots (QDs) are investigated by means of a tight-binding model combined with configuration interaction calculations. Tight-binding single particle wave functions are used as a basis for computing Coulomb and dipole matrix elements. Within this framework, we analyze multi-exciton emission

Karen L. van der Molen, Allard P. Mosk, Ad Lagendijk

We prescribe the minimal set of experimental data and parameters that should be reported for random-laser experiments and models. This prescript allows for a quantitative comparison between different experiments, and for a criterion whether a model predicts the outcome of an experiment correctly. In none of more than 150 papers on random lasers that we found

V. E. Sinitsyn, I. G. Bostrem, A. S. Ovchinnikov

We present a quantum cluster solver for spin-$S$ Heisenberg model on a two-dimensional lattice. The formalism is based on the real-space renormalization procedure and uses the lattice point group-theoretical analysis and nonabelian SU(2) spin symmetry technique. The exact diagonalization procedure is used twice at each renormalization group step. The method

Alberto Cortijo, María A. H. Vozmediano

In this work we will focus on the effects produced by topological disorder on the electronic properties of a graphene plane. The presence of this type of disorder induces curvature in the samples of this material, making quite difficult the application of standard techniques of many body quantum theory. Once we understand the nature of these defects, we can

S. S. McGaugh, W. J. G. de Blok, J. M. Schombert, R. Kuzio de Naray

We examine the amplitude of the rotation velocity that can be attributed to the dark matter halos of disk galaxies, focusing on well measured intermediate radii. The data for 60 galaxies spanning a large range of mass and Hubble types, taken together, are consistent with a dark halo velocity log(Vh) = C + B log(r) with C = 1.47 (+0.15, -0.19) and B = 1/2 ove

V. Luridiana, M. Cervino

For a number of reasons, the properties of integrated stellar populations are distributed. Traditional synthesis models usually return the mean value of such distribution, and a perfect fitting to observational data is sought for to infer the age and metallicity of observed stellar populations. We show here that, while this is correct on average, it is not i

S. Pilling, D. P. P. Andrade, R. Neves, A. M. Ferreira-Rodrigues

We present experimental results obtained from photoionization and photodissociation processes of abundant interstellar CH$_3$-X type organic molecules like methanol (CH$_3$OH), methylamine (CH$_3$NH$_2$) and acetonitrile (CH$_3$CN) as alternative route for the production of H$_3^+$ in interstellar and star forming environments. The measurements were taken at

J. da Angela, T. Shanks, S. M. Croom, P. Weilbacher

We combine the QSO samples from the 2dF QSO Redshift Survey (2QZ) and the 2dF-SDSS LRG and QSO Survey (2SLAQ) in order to investigate the clustering of z~1.4 QSOs and measure the correlation function. The clustering signal in z-space, projected along the sky direction, is similar to that previously obtained from 2QZ alone. By fitting the z-space correlation

Emre Isik, Manfred Schuessler, Sami K. Solanki

We carry out numerical simulations of the surface evolution of bipolar magnetic regions (BMRs) and magnetic spots on stars, which have radii and surface rotational shears of AB Doradus, the Sun, and the HR 1099 primary. The surface flux transport model is based on the magnetic induction equation for radial fields under the effects of surface differential rot

C. C. Cheung, A. Springmann

A small number of double-lobed radio galaxies are found with an additional pair of extended low surface brightness `wings' of emission giving them a distinctive `X'-shaped appearance. One popular explanation for the unusual morphologies posits that the central supermassive black hole (SMBH)/accretion disk system underwent a recent realignment; in a m

V. Strokov

We show that hydrodynamical and field approaches in theory of cosmological scalar perturbations are equivalent for a single medium. We also give relations between notations introduced by V. Lukash, J. Bardeen, J. Bardeen et al. and G. Chibisov and V. Mukhanov.

Jonathan Irwin, Mike Irwin, Suzanne Aigrain, Simon Hodgkin

We have begun a large-scale photometric survey of nearby open clusters and star-forming regions, the Monitor project, aiming to measure time-series photometry for >10,000 cluster members over >10 sq.deg of sky, to find low-mass eclipsing binary and planet systems. We describe the software pipeline we have developed for this project, showing that we can achie

E. R. Seaquist, M. Stankovic

The compact non-thermal sources in M82 and other starburst galaxies are generally thought to be supernova remnants (SNRs). We consider an alternative hypothesis that most are wind driven bubbles (WDBs) associated with very young super star clusters (SSCs). In this scenario, the synchrotron emitting particles are produced at the site of the shock transition b

L. Birzan, B. R. McNamara, C. L. Carilli, P. E. J. Nulsen

We present new, high resolution radio images of sources associated with cD galaxies and X-ray cavity systems located in cluster cores. The cavity properties derived from archival Chandra observations give reliable estimates of the total jet power and age independently of the radio synchrotron flux. We combine the X-ray data and VLA radio images taken at mult

Rodrigo S. Nemmen, Richard G. Bower, Arif Babul, Thaisa Storchi-Bergmann

Recently, Allen et al. measured a tight correlation between the Bondi accretion rates and jet powers of the nuclei of nearby X-ray luminous elliptical galaxies. We employ two models of jet powering to understand the above correlation and derive constraints on the spin and accretion rate of the central black holes. The first is the Blandford-Znajek model, in

Maria Kun

This paper reviews the results of studies of star forming regions, carried out at the Konkoly Observatory in the last two decades. The studies involved distance determination of star-forming dark clouds, search for candidate pre-main sequence stars, and determination of the masses and ages of the candidates by spectroscopic follow-up observations. The result

Robert G. Izzard, Brad K. Gibson, Richard J. Stancliffe

Galactic chemical evolution models which include sodium from type II supernovae alone underestimate the abundance of sodium in the interstellar medium by a factor of two to three over about 3 dex in metallicity and predict a flat behaviour in the evolution of [Na/Fe] at super-solar metallicities. Conversely, recent observations of stars with [Fe/H]~+0.4 sugg

A. Asensio Ramos, M. J. Martinez Gonzalez, A. Lopez Ariste, J. Trujillo Bueno

We report on spectropolarimetric observations of a near-IR line of Mn I located at 15262.702 A whose intensity and polarization profiles are very sensitive to the presence of hyperfine structure. A theoretical investigation of the magnetic sensitivity of this line to the magnetic field uncovers several interesting properties. The most important one is that t

H. Socas-Navarro, A. Asensio Ramos, R. Manso Sainz

% context heading (optional) {With the development of new polarimeters for large telescopes, the spectro-polarimetric study of astrophysical bodies is becoming feasible and, indeed, more frequent. In particular, this is permitting the observational study of stellar magnetic fields} % aims heading (mandatory) {With the aim to optimize and interpret this kind

Alejandro M. Leiva, Carlos B. Briozzo

In the framework of the planar CR3BP for mass parameter mu=0.0121505, corresponding to the Earth-Moon system, we identify and describe 80 families of periodic orbits encircling both the Earth and the Moon ("transfer" orbits). All the orbits in these families have very low energies, most of them corresponding to values of the Jacobi constant C for whi

Ujjaini Alam, Varun Sahni, Alexei A. Starobinsky

We reconstruct dark energy properties from two complementary supernova datasets -- the newly released Gold+HST sample and SNLS. The results obtained are consistent with standard $Λ$CDM model within $2σ$ error bars although the Gold+HST data favour evolving dark energy slightly more than SNLS. Using complementary data from baryon acoustic oscillations and the

S. C. Lowry, P. R. Weissman

We present results from CCD observations of comet 2P/Encke acquired at Steward Observatory's 2.3m Bok Telescope on Kitt Peak obtained in Oct. 2002, when the comet was near aphelion. Rotational lightcurves in B, V and R-filters were acquired over two nights of observations, and analysed to study the physical and color properties of the nucleus. The averag

Massimo Giovannini

The main motivations and challenges related with the physics of large-scale magnetic fields are briefly analyzed. The interplay between large-scale magnetic fields and scalar CMB anisotropies is addressed with specific attention on recent progresses.

A. D. Panov, J. H. Adams, H. S. Ahn, G. L. Bashindzhagyan

The results of ATIC-2 baloon experiment (2002-2003) for energy spectra of protons, He, C, O, Ne, Mg, Si, Fe, some groups of nuclei, and all-particle spectrum in primary cosmic rays are presented in energy region 50GeV--200TeV. The conclusion is that the spectra of protons and helium nuclei are essentially different (the spectrum of protons is steeper) and th

M. Nikolajuk, P. Gurynowicz, B. Czerny

We estimate black hole masses in Narrow Line Seyfert 1 (NLS1) galaxies at the basis of their X-ray excess variance. We apply the standard approach appropriate for Broad Line Seyfert 1 (BLS1) galaxies. In general, we find that the obtained masses are by a factor \sim 20 too small to agree with values obtained from other methods (reverberation, stellar dispers