March 2006 arXiv papers — page 26

Tomasz Maszczyk

A Poisson geometry arising from maximal commutative subalgebras is studied. A spectral sequence convergent to Hochschild homology with coefficients in a bimodule is presented. It depends on the choice of a maximal commutative subalgebra inducing appropriate filtrations. Its E^{2}_{p,q}-groups are computed in terms of canonical homology with values in a Poiss

M. Graña, J. A. Guccione, J. J. Guccione

Every finite dimensional Hopf algebra is a Frobenius algebra, with Frobenius homomorphism given by an integral. The Nakayama automorphism determined by it yields a decomposition with degrees in a cyclic group. For a family of pointed Hopf algebras, we determine necessary and sufficient conditions for this decomposition to be strongly graded.

Rouchdi Bahloul

This is the second part of a work dedicated to the study of Bernstein-Sato polynomials for several analytic functions depending on parameters. In this part, we give constructive results generalizing previous ones obtained by the author in the case of one function. We also make an extensive study of an example for which we give an expression of a generic (and

Riviere Tristan

We succeed in writing 2-dimensional conformally invariant non-linear elliptic PDE (harmonic map equation, prescribed mean curvature equations...etc) in divergence form. This divergence free quantities generalize to target manifolds without symmetries the well known conservation laws for harmonic maps into homogeneous spaces. From this form we can recover, wi

Tomislav Došlić, Darko Veljan

Two general methods for establishing the logarithmic behavior of recursively defined sequences of real numbers are presented. One is the interlacing method, and the other one is based on calculus. Both methods are used to prove logarithmic behavior of some combinatorially relevant sequences, such as Motzkin and Schröder numbers, sequences of values of some c

Daciberg Lima Gonçalves, John Guaschi

Let n be greater than or equal to 3. We prove that the quaternion group of order 8 is realised as a subgroup of the sphere braid group B\_n(S^2) if and only if n is even. If n is divisible by 4 then the commutator subgroup of B\_n(S^2) contains such a subgroup. Further, for all n greater than or equal to 3, B\_n(S^2) contains a subgroup isomorphic to the dic

S Launois, T H Lenagan

We show that the quantum coordinate ring of a semisimple group is a unique factorisation domain in the sense of Chatters and Jordan in the case where the deformation parameter q is a transcendental element.

Leonid A. Bunimovich, Carl P. Dettmann

We consider open circular billiards with one and with two holes. The exact formulas for escape are obtained which involve the Riemann zeta function and Dirichlet L-functions. It is shown that the problem of finding the exact asymptotics in the small hole limit for escape in some of these billiards is equivalent to the Riemann hypothesis.

Ivan Penkov, Gregg Zuckerman

Let g be a semisimple complex Lie algebra and k in g be any algebraic subalgebra reductive in g. For any simple finite dimensional k-module V, we construct simple (g; k)-modules M with finite dimensional k-isotypic components such that V is a k-submodule of M and the Vogan norm of any simple k-submodule V' of M; V' not isomorphic to V, is greater tha

Maria A. Avino-Diaz, Edward Green, Oscar Moreno

We present a mathematical model: dynamical systems over finite sets (DSF), and we show that Boolean and discrete genetic models are special cases of DFS. In this paper, we prove that a function defined over finite sets with different number of elements can be represented as a polynomial function over a finite field. Given the data of a function defined over

Ildefonso Castro, Bang-yen Chen

We present a method to construct a large family of Lagrangian surfaces in complex Euclidean plane by using Legendre curves in the 3-sphere and in the anti de Sitter 3-space or, equivalently, by using spherical and hyperbolic curves, respectively. Among this family, we characterize minimal, constant mean curvature, Hamiltonian-minimal and Willmore surfaces in

Ruslan Sharipov

The Dirac equation for massive free electrically neutral spin 1/2 particles in a gravitation field is considered. The secondary quantization procedure is applied to it and the Hilbert space of multiparticle quantum states is constructed.

M. J. Cantero, L. Moral, L. Velazquez

In this paper we prove some characterizations of the matrix orthogonal polynomials whose derivatives are also orthogonal, which generalize other known ones in the scalar case. In particular, we prove that the corresponding orthogonality matrix functional is characterized by a Pearson-type equation with two matrix polynomials of degree not greater than 2 and

Nick Gill

Given polar spaces $(V,β)$ and $(V,Q)$ where $V$ is a vector space over a field $K$, $β$ a reflexive sesquilinear form and $Q$ a quadratic form, we have associated classical isometry groups. Given a subfield $F$ of $K$ and an $F$-linear function $L:K\to F$ we can define new spaces $(V,Lβ)$ and $(V,LQ)$ which are polar spaces over $F$. The construction so des

Yueyun Hu, Zhan Shi

We are interested in the random walk in random environment on an infinite tree. Lyons and Pemantle [11] give a precise recurrence/transience criterion. Our paper focuses on the almost sure asymptotic behaviours of a recurrent random walk $(X\_n)$ in random environment on a regular tree, which is closely related to Mandelbrot [13]'s multiplicative cascade

Ari Laptev, Alexander V. Sobolev

In 1986 A. Ancona showed, using the Koebe one-quarter Theorem, that for a simply-connected planar domain the constant in the Hardy inequality with the distance to the boundary is greater than or equal to 1/16. In this paper we consider classes of domains for which there is a stronger version of the Koebe Theorem. This implies better estimates for the constan

Antonin Pottier

We study the stability of Koszul and Gorentein properties for the semi-cross product of homogeneous algebras. Nous étudions la conservation des propriétés de Koszul et de Gorenstein pour le produit semi-croisé des algèbres homogènes.

N. Chernov, N. Simanyi

This work results from our attempts to solve Boltzmann-Sinai's hypothesis about the ergodicity of hard ball gases. A crucial element in the studies of the dynamics of hard balls is the analysis of special hypersurfaces in the phase space consisting of degenerate trajectories (which lack complete hyperbolicity). We prove that if a flow-invariant hypersurf

Raphael Rouquier

We discuss the homological algebra of representation theory of finite dimensional algebras and finite groups. We present various methods for the construction and the study of equivalences of derived categories: local group theory, geometry and categorifications.

Andreas Thom

We study L^2-Betti numbers for von Neumann algebras, as defined by D. Shlyakhtenko and A. Connes. We give a definition of L^2-cohomology and show how the study of the first L^2-Betti number can be related with the study of derivations with values in a bi-module of affiliated operators. We show several results about the possibility of extending derivations fr

L. Berezansky, L. Idels

We study the combined effects of periodically varying carrying capacity and survival rates on the fish population in the ocean (sea). We introduce the Getz type delay differential equation model with a control parameter which describes how fish are harvested. We will modify and extend harvesting model of an exploited fish population to include periodic and r

Philippe Nuss, Marc Wambst

We introduce non-abelian cohomology sets of Hopf algebras with coefficients in Hopf modules. We prove that these sets generalize Serre's non-abelian group cohomology theory. Using descent techniques, we establish that our construction enables to classify as well twisted forms for modules over Hopf-Galois extensions as torsors over Hopf-modules.

Nicola Ciccoli, Fabio Gavarini

We develop a quantum duality principle for coisotropic subgroups of a (formal) Poisson group and its dual. Namely, starting from a quantum coisotropic subgroup (for a quantization of a given Poisson group) we provide functorial recipes to produce quantizations of the dual coisotropic subgroup (in the dual formal Poisson group). By the natural link between su

V. Chernousov, Ph. Gille, Z. Reichstein

Let G be a linear algebraic group defined over a field k. We prove that, under mild assumptions on k and G, there exists a finite k-subgroup S of G such that the natural map H^1(K, S) -> H^1(K, G) is surjective for every field extension K/k. We give several applications of this result in the case where k an algebraically closed field of characteristic zero a

Dominic Joyce

This is the first in a series of papers math.AG/0503029, math.AG/0410267, math.AG/0410268 on &#34;configurations&#34; in an abelian category A. Given a finite partially ordered set (I,<), an (I,<)-configuration (σ,ι,π) is a finite collection of objects σ(J) and morphisms ι(J,K) or π(J,K) : σ(J) --> σ(K) satisfying some axioms, where J,K are subsets of I. Con

Rouchdi Bahloul

This is the first part of a work dedicated to the study of Bernstein-Sato polynomials for several analytic functions depending on parameters. The main result of this part is a constructibility result for the analytic Gröbner fan of a parametric ideal in the ring of analytic differential operators. In this part, the main tool is the notion of generic reduced

Bert Schroer

Based on past contributions by Robert Schrader and Michael Karowski I review the problem of existence of interacting quantum field theory and present recent ideas and results on rigorous constructions.

Alexander Vilenkin

I review recent progress in defining probability distributions in the inflationary multiverse.

I. P. Zois

We make some remarks on the group of symmetries in gravity; we believe that K-theory and noncommutative geometry inescepably have to play an important role. Furthermore we make some comments and questions on the recent work of Connes and Kreimer on renormalisation, the Riemann-Hilbert correspondence and their relevance to quantum gravity.

Naoyuki Haba, Atsushi Watanabe, Koichi Yoshioka

A new framework for handling flavor symmetry breaking in the neutrino sector is discussed where the source of symmetry breaking is traced to the global property of right-handed neutrinos in extra-dimensional space. Light neutrino phenomenology has rich and robust predictions such as the tri/bi-maximal form of generation mixing, controlled mass spectrum, and

S. Dawson, C. B. Jackson, L. Reina, D. Wackeroth

We review the status of the QCD corrected cross sections and kinematic distributions for the production of a Higgs boson in association with top quark or bottom quark pairs at the Fermilab Tevatron and at the LHC. Results for b-bbar-H production are presented in the Minimal Supersymmetric Model, where the rates can be greatly enhanced relative to the Standar

Phung Van Dong, Hoang Ngoc Long, Dang Van Soa

Interactions among the standard model gauge bosons and scalar fields in the framework of SU(3)_C X SU(3)_L X U(1)_X gauge model with minimal (economical) Higgs content are presented. From these couplings, all scalar fields including the neutral scalar $h$ and the Goldstone bosons can be identified and their couplings with the usual gauge bosons such as the p

Hiroyuki Nishiura

The normal muon decay $μ^{+} \to e^{+}ν_{e}\bar{ν_μ}$ is studied as a tool to discriminate between the Dirac and Majorana type neutrinos. For the purpose to do this, we propose a new parameterization in place of the Michel parameters for the energy spectrum of $e^{+}$. The $χ^2$-fitting is used by noticing different energy spectra between the Dirac and Major

Atsushi Watanabe, Koichi Yoshioka

The origin of the observed masses and mixing angles of quarks and leptons is one of imperative subjects in and beyond the standard model. Toward a deeper understanding of flavor structure, we investigate in this paper the minimality of fermion mass (Yukawa) matrices in unified theory. That is, the simplest matrix form is explored in light of the current expe

Wei Liu, Ying Chen, Ming Gong, Xin Li

Static quark potential is studied using a tadpole improved gauge lattice action. The scale is set using the potential for a wide range of bare parameters. The renormalized anisotropy of the lattice is also measured.

Werner M. Sun

Due to the presence of the quantum correlation between the pair-produced D0 and D0bar from the decay of the psi(3770), the time-integrated single and double tag decay rates depend on charm mixing amplitudes, doubly-Cabibbo-suppressed amplitudes, and the relative strong phase, delta, between D0 and D0bar decays to identical final states. Using 281 pb^-1 of in

Werner M. Sun

Using e+e- collisions recorded at the psi(3770) resonance with the CLEO-c detector at the Cornell Electron Storage Ring, we determine absolute hadronic branching fractions of charged and neutral D mesons. Among measurements for both Cabibbo-favored and Cabibbo-suppressed modes, we obtain reference branching fractions B(D0 -> K-pi+)=(3.91 +- 0.08 +- 0.09)% an

Sergei Kopeikin, Pavel Korobkov, Alexander Polnarev

Extremely high precision of near-future radio/optical interferometric observatories like SKA, Gaia, SIM and the unparalleled sensitivity of LIGO/LISA gravitational-wave detectors demands more deep theoretical treatment of relativistic effects in the propagation of electromagnetic signals through variable gravitational fields of the solar system, oscillating

Charles H. -T. Wang

A new canonical transformation is found that enables the direct canonical treatment of the conformal factor in general relativity. The resulting formulation significantly simplifies the previously presented conformal geometrodynamics. It provides a further theoretical basis for the conformal approach to loop quantum gravity and offers a generic framework for

S. Krasnikov

The possibility is discussed of superluminal motion of non-tachyonic (i.e. moving with the instantaneous speed v<c) bodies within general relativity. It is shown that in some occasions quantum field theory apparently prohibits such motion, but not - to all appearance - in the general case.

David McMahon, Paul M. Alsing, Pedro Embid

A pedagogical introduction to the Dirac equation for massive particles in Rindler space is presented. The spin connection coefficients are explicitly derived using techniques from general relativity. We then apply the Lagrange-Green identity to greatly simplify calculation of the inner products needed to normalize the states. Finally, the Bogolubov coefficie

Tomasz Stachowiak, Marek Szydlowski, Andrzej J. Maciejewski

We investigate the evolution equation of linear density perturbations in the Friedmann-Robertson-Walker universe with matter, radiation and the cosmological constant. The concept of solvability by quadratures is defined and used to prove that there are no &#34;closed form&#34; solutions except for the known Chernin, Heath, Meszaros and simple degenerate ones

S. I. Denisov, E. S. Denisova, P. Hänggi

We study analytically and numerically the overdamped, deterministic dynamics of a chain of {\it charged}, interacting particles driven by a longitudinal alternating electric field and additionally interacting with a smooth ratchet potential. We derive the equations of motion, analyze the general properties of their solutions and find the drift criterion for

Jeromos Vukov, György Szabó, Attila Szolnoki

We have studied an evolutionary prisoner&#39;s dilemma game with players located on two types of random regular graphs with a degree of 4. The analysis is focused on the effects of payoffs and noise (temperature) on the maintenance of cooperation. When varying the noise level and/or the highest payoff, the system exhibits a second order phase transition from

K. Wagner, D. Neumaier, M. Reinwald, W. Wegscheider

To understand quantum mechanical transport in ferromagnetic semiconductor the knowledge of basic material properties like phase coherence length and corresponding dephasing mechanism are indispensable ingredients. The lack of observable quantum phenomena prevented experimental access to these quantities so far. Here we report about the observations of univer

S. I. Denisov, P. Hänggi

We present a comprehensive study for the statistical properties of random variables that describe the domain structure of a finite Ising chain with nearest-neighbor exchange interactions and free boundary conditions. By use of extensive combinatorics we succeed in obtaining the one-variable probability functions for (i) the number of domain walls, (ii) the n

Ernst Helmut Brandt

The complex impedance, currents, and electric and magnetic fields are calculated as functions of resistivity and frequency or London depth for a long thin strip with applied ac current. Both Ohmic and superconducting strips are considered. While the inductance per unit length of the strip depends on the strip length logarithmically, the sheet current, magnet

Mikael C. Rechtsman, Salvatore Torquato, Frank H. Stillinger

We formulate statistical-mechanical inverse methods in order to determine optimized interparticle interactions that spontaneously produce target many-particle configurations. Motivated by advances that give experimentalists greater and greater control over colloidal interaction potentials, we propose and discuss two computational algorithms that search for o

Holly M. Kokstein, Paul V. Quinn

A one dimensional experiment in granular dynamics is carried out to test the thermodynamic theory of weakly excited granular systems [Hayakawa and Hong, Phys. Rev. Lett. 78, 2764(1997)] where granular particles are treated as spinless Fermions. The density profile is measured and then fit to the Fermi distribution function, from which the global temperature

F. Pesty, P. Garoche

The surface of an insulating material irradiated by a beam of low energy electrons charges positively if the yield of secondary electron is greater than unity. For such a dynamical equilibrium, the thermodynamic properties have been investigated by measuring the surface potential in response to a temperature oscillation of the material. It is shown that an o

Fenghua Li, Oleksandr Buchnev, Chae Il Cheon, Anatoliy Glushchenko

We investigated the physical properties of low concentration ferroelectric nematic colloids, using calorimetry, optical methods, infra-red spectroscopy and capacitance studies. The resulting colloids normally remain homogeneous, but the nematic orientational coupling is significantly amplified. In particular cases, the nematic orientation coupling increases

Brian C. Sales, Rongying Jin, David Mandrus, Peter Khalifah

The Hall resistivity (Rho_xy), resistivity (Rho_xx), and magnetization of three metallic ferromagnets are investigated as a function of magnetic field and temperature. The three ferromagnets, EuFe4Sb12 (Tc = 84 K), Yb14MnSb11 (Tc = 53 K), and Eu8Ga16Ge30 (Tc = 36 K) are Zintl compounds with carrier concentrations between 1 x 10^21 cm^-3 and 3.5 x 10^21 cm^-3

Pedro M. Reis, Rohit A. Ingale, Mark D. Shattuck

We experimentally investigate the crystallization of a uniformly heated quasi-2D granular fluid as a function of filling fraction. Our experimental results for the Lindemann melting criterion, the radial distribution function, the bond order parameter and the statistics of topological changes at the particle level are the same as those found in simulations o

A. L. Owczarek, T. Prellberg

The collapse transition of an isolated polymer has been modelled by many different approaches, including lattice models based on self-avoiding walks and self-avoiding trails. In two dimensions, previous simulations of kinetic growth trails, which map to a particular temperature of interacting self-avoiding trails, showed markedly different behaviour for what

A. Tsukada, H. Shibata, M. Noda, H. Yamamoto

T&#39;-RE2CuO4 (RE: rare-earth element), after appropriate &#34;reduction&#34;, has fairly high conductivity and also exhibits clear Fermi edge in photoemission spectroscopy. To clarify the origin of conductivity in the T&#39; mother compounds, we evaluated the unscreened charge-transfer gap for T&#39;-RE2CuO4 and T-La2CuO4. The value of charge-transfer gap

Vesa Apaja, Olav F. Syljuasen

Boson lattices are theoretically well described by the Hubbard model. The basic model and its variants can be effectively simulated using Monte Carlo techniques. We describe two newly developed approaches, the Stochastic Series Expansion (SSE) with directed loop updates and continuous--time Diffusion Monte Carlo (CTDMC). SSE is a formulation of the finite te

Igor Goychuk, Jesus Casado-Pascual, Manuel Morillo, Joerg Lehmann

We study within the spin-boson dynamics the synchronization of quantum tunneling with an external periodic driving signal. As a main result we find that at a sufficiently large system-bath coupling strength (Kondo parameter a>1) the thermal noise plays a constructive role in yielding both a frequency and a phase synchronization in a symmetric two-level syste

Shidong Wang, Milena Grifoni, Stephan Roche

We explore the nature of anomalous diffusion of wave packets in disorder-free incommensurate multi-walled carbon nanotubes. The spectrum-averaged diffusion exponent is obtained by calculating the multifractal dimension of the energy spectrum. Depending on the shell chirality, the exponent is found to lie within the range $1/2 \leq η< 1$. For large unit cell

A. A. Bykov, A. V. Goran, D. R. Islamov, A. K. Bakarov

The influence of microwave radiation (1.2-140 GHz) on resistance of high-mobility two-dimensional electron gas in GaAs quantum wells is studied. Two series of microwave-induced magnetoresistance oscillations periodic in 1/B were observed under microwave radiation. The periods of oscillations are determined by the microwave frequency and power, correspondingl

P. G. Kevrekidis, J. Gagnon, D. J. Frantzeskakis, B. A. Malomed

Motivated by recent experimental and theoretical results on optical X-waves, we propose a new type of waveforms in 2D and 3D discrete media -- multi-legged extended nonlinear structures (ENS), built as arrays of lattice solitons (tiles or stones, in the 2D and 3D cases, respectively). First, we study the stability of the tiles and stones analytically, and th

D. R. Paula, A. D. Araujo, J. S. Andrade, H. J. Herrmann

We study a model for neural activity on the small-world topology of Watts and Strogatz and on the scale-free topology of Barabási and Albert. We find that the topology of the network connections may spontaneously induce periodic neural activity, contrasting with chaotic neural activities exhibited by regular topologies. Periodic activity exists only for rela

Nicolas Laflorencie, Erik S. Sorensen, Ming-Shyang Chang, Ian Affleck

We present exact diagonalization and density matrix renormalization group results for the entanglement entropy of critical spin-1/2 XXZ chains. We find that open boundary conditions induce an alternating term in both the energy density and the entanglement entropy which are approximately proportional, decaying away from the boundary with a power-law. The pow

Volkan Sevim, Per Arne Rikvold

We study the growth of a directed network, in which the growth is constrained by the cost of adding links to the existing nodes. We propose a new preferential-attachment scheme, in which a new node attaches to an existing node i with probability proportional to 1/k_i, where k_i is the number of outgoing links at i. We calculate the degree distribution for th

A. P. Micolich, E. Tavenner, B. J. Powell, A. R. Hamilton

Ion-implantation of normally insulating polymers offers an alternative to depositing conjugated organics onto plastic films to make electronic circuits. We used a 50 keV nitrogen ion beam to mix a thin 10 nm Sn/Sb alloy film into the sub-surface of polyetheretherketone (PEEK) and report the low temperature properties of this material. We observed metallic be

Thomas Kissinger, Andreas Kotowicz, Oliver Kurz, Francesco Ginelli

As a canonical model for wetting far from thermal equilibrium we study a Kardar-Parisi-Zhang interface growing on top of a hard-core substrate. Depending on the average growth velocity the model exhibits a non-equilibrium wetting transition which is characterized by an additional surface critical exponent theta. Simulating the single-step model in one spatia

Alexandra Pope, Douglas Scott, Mark Dickinson, Ranga-Ram Chary

How does the submm galaxy population detected by SCUBA fit into galaxy evolution? How do these rare starbursting systems, which contribute significantly to high redshift star-formation, relate to other galaxy populations? Deep radio observations have been most useful for studying these systems, but still leave a significant fraction of the population unident

B. J. Smith, C. Struck, M. Hancock, P. Appleton

We present Spitzer mid-infrared images from a survey of three dozen pre-merger strongly interacting galaxy pairs selected from the Arp Atlas. The global mid-infrared colors of these galaxies and their tidal tails and bridges are similar to those of normal spiral galaxies, thus this optically selected sample of interacting galaxies does not have strongly enha

Jose Luis Prieto, Armin Rest, Nicholas B. Suntzeff

We present a new empirical method for fitting multicolor light curves of Type Ia supernovae. Our method combines elements from two widely used techniques in the literature: the delta_m15 template fitting method and the Multicolor Light-Curve Shape method. An advantage of our technique is the ease of adding new colors, templates, or parameters to the fitting

Desika Narayanan, Thomas J. Cox, Brant Robertson, Romeel Dave

We investigate the effect of embedded active galactic nuclei (AGN) in galaxy mergers on the CO molecular line emission by combining non-local thermodynamic equilibrium (LTE) radiative transfer calculations with hydrodynamic simulations. We find that AGN feedback energy in gas rich galaxy mergers can contribute to large molecular outflows which may be detecta

Howard A. Smith, J. L. Hora, M. Marengo, Judith L. Pipher

The bipolar outflow from the massive star forming cluster in DR21 is one of the most powerful known, and in IRAC images the outflow stands out by virtue of its brightness at 4.5 um (Band 2). Indeed, IRAC images of many galactic and extragalactic star formation regions feature prominent Band 2 morphologies. We have analyzed archival ISOSWS spectra of the DR21

E. J. Murphy, G. Helou, L. Armus, R. Braun

We present an analysis of the far-infrared (FIR)-radio correlation within a group of nearby star-forming galaxy disks observed as part of the {\it Spitzer} Infrared Nearby Galaxies Survey (SINGS). In our study we critically test a phenomenological model for the FIR-radio correlation which describes the radio image as a smeared version of the infrared image.

Edward A. Laag, Gabriela Canalizo, Wil van Breugel, Elinor L. Gates

We present high resolution imaging observations of a sample of previously unidentified far-infrared galaxies at z < 0.3. The objects were selected by cross-correlating the IRAS Faint Source Catalog with the VLA FIRST catalog and the HST Guide Star Catalog to allow for adaptive optics observations. We found two new ULIGs (with L_FIR equal to or greater than 1

M. Hancock, B. J. Smith, C. Struck, M. Giroux

To help understand the effects of galaxy interactions on star formation, we analyze Spitzer infrared and GALEX ultraviolet images of the interacting galaxy pair Arp 82 (NGC 2535/6), and compare to a numerical simulation of the interaction. We investigate the UV and IR properties of several star forming regions (clumps). Using the FUV/NUV colors of the clumps

E. Costa, R. Bellazzini, P. Soffitta, G. di Persio

An extensive theoretical literature predicts that X-ray Polarimetry can directly determine relevant physical and geometrical parameters of astrophysical sources, and discriminate between models further than allowed by spectral and timing data only. X-ray Polarimetry can also provide tests of Fundamental Physics. A high sensitivity polarimeter in the focal pl

Gennady S. Bisnovatyi-Kogan, Marco Merafina

We derive a variational principle for the dynamical stability of a cluster as a gas sphere in a box. Newtonian clusters are always dynamically stable and, for relativistic clusters, the relation between dynamical and thermodynamical instabilities is analyzed. The boundaries between dynamically and thermodynamically stable and unstable models are found numeri

I. Plauchu-Frayn, R. Coziol, H. Bravo-Alfaro

Images of 7 Compact groups of galaxies (CG) were obtained using the 2.1m telescope in San Pedro Martir (B.C. Mexico) equipped with the NIR camera CAMILA. The NIR images trace the mass of the galaxies, through the oldest and more evolved stellar populations. The goal of this project is to search for evidence of morphological perturbations correlated with the

B. W. Holwerda, R. A. Gonzalez, D. Calzetti, R. J. Allen

Dust emission in the far-infrared (FIR) characterizes the temperature and quantity of interstellar dust in a spiral disk. The three Spitzer/MIPS bands are well suited to measuring the gradient in temperature and the total optical depth in the disk of a spiral galaxy. Another way to estimate the quantity of dust in a spiral disk is the &#34;Synthetic Field Me

C. Bonatto, E. Bica, S. Ortolani, B. Barbuy

We derive the structure, distribution of MS and PMS stars and dynamical state of the young open cluster NGC 4755. We explore the possibility that, at the cluster age, some MS and PMS stars still present infrared excesses related to dust envelopes and proto-planetary discs. The radial density profile follows King&#39;s law with a core radius $\rm\rc=0.7\pm0.1

A. V. Smith Castelli, L. P. Bassino, S. A. Cellone, T. Richtler

We present the first results of a project aimed to study the galaxy population of the Antlia cluster, the third nearest galaxy cluster after Virgo and Fornax. The observations for the Antlia project consist of Washington wide-field images taken with the MOSAIC camera mounted at the prime focus of the CTIO 4-m Blanco telescope. Our preliminary results corresp

Sergei Fabrika

(abridged) The review describes observations of SS433. The main difference between SS433 and other X-ray binaries is the supercritical regime for the gas accretion onto the relativistic star (most likely a black hole), which has lead to the formation of collimated relativistic jets. The properties of the jets are determined by their interaction with the disk

G. Bernardi, E. Carretti, R. J. Sault, S. Cortiglioni

We present results of polarization observations at 1.4 GHz of the two fields imaged by the DASI experiment ($α= 23^{\rm h} 30^{\rm m}$, $δ= -55^{\circ}$ and $α= 00^{\rm h} 30^{\rm m}$, $δ= -55^{\circ}$, respectively). Data were taken with the Australia Telescope Compact Array with 3.4 arcmin resolution and $\sim 0.18$ mJy beam$^{-1}$ sensitivity. The emissio

D. Lorenzetti, T. Giannini, L. Calzoletti, S. Puccetti

We present a near-IR study of the EXor variable V1118 Ori, performed by following a slightly declining phase after a recent outburst. In particular, the near-IR (0.8 - 2.3 micron) spectrum, obtained for the first time, shows a large variety of emission features of the HI and HeI recombination and CO overtone. By comparing the observed spectrum with a wind mo

Pierre Brun

In the quest for indirect signals from dark matter annihilation, powerful computation codes are required. I report here a new code based on micrOMEGAs devoted to the analysis of such signals in term of Supersymmetry. It computes gamma rays and positrons fluxes in a general SuSy model, as well as the other charged cosmic rays and neutrinos source terms. This

Y. Momany, S. Zaggia, G. Gilmore, G. Piotto

(Abridged) We derive the structure of the Galactic stellar Warp and Flare using 2MASS RC and RGB stars, selected at mean heliocentric distances of 3, 7 and 17 kpc. Our results are: (i) a clear stellar warp signature is derived for the 3 selected rings; (ii) the derived stellar warp is consistent (both in amplitude and phase-angle) with that for the Galactic

N. Ryde, M. J. Richter, G. M. Harper, K. Eriksson

Several recent papers have argued for warm, semi-detached, molecular layers surrounding red giant and supergiant stars, a concept known as a MOLsphere. Spectroscopic and interferometric analyses have often corroborated this general picture. Here, we present high-resolution spectroscopic data of pure rotational lines of water vapor at 12 microns for the super

S. Ettori, A. C. Fabian

In this Letter, we consider the role played by the sedimentation of helium nuclei on the emissivity and metallicity distribution of the X-ray emitting plasma in the cores of relaxed galaxy clusters. We model the gas density and temperature profiles of nearby cooling core clusters to estimate the gravitational acceleration acting on the helium and show that i

Adam J. Burgasser, J. Davy Kirkpatrick

We report the discovery of LEHPM 2-59 as the coolest extreme M subdwarf (esdM) found to date. Optical and near infrared spectroscopy demonstrate that this source is of later spectral type than the esdM7 APMPM 0559-2903, with the presence of strong alkali lines (including Rb I), VO absorption at 7400 A and H2O absorption at 1.4 microns. Current optical classi

G. Hobbs, R. Edwards, R. Manchester

Contemporary pulsar timing experiments have reached a sensitivity level where systematic errors introduced by existing analysis procedures are limiting the achievable science. We have developed tempo2, a new pulsar timing package that contains propagation and other relevant effects implemented at the 1ns level of precision (a factor of ~100 more precise than

R B Tully, L Rizzi, A E Dolphin, I D Karachentsev

Hubble Space Telescope Advanced Cameras for Surveys has been used to determine accurate distances for 20 galaxies from measurements of the luminosity of the brightest red giant branch stars. Five associations of dwarf galaxies that had originally been identified based on strong correlations on the plane of the sky and in velocity are shown to be equally well

S. L. Skinner, K. R. Briggs, M. Guedel

FU Orionis stars (FUors) are young low-mass eruptive stars that are thought to be accreting at high rates. They could give rise to soft X-ray emission from accretion shocks, but their X-ray properties are largely unknown. We report the first X-ray detection of the prototype star FU Orionis with XMM-Newton. Its X-ray spectrum is unusual compared to those of c

J. Dunkel, J. Chluba, R. A. Sunyaev

Ultraluminous X-ray sources fed by Wolf-Rayet star winds and X-ray bursters in ultracompact binaries with He or C white dwarfs have accretion disks, whose properties may significantly differ from those of pure H alpha-accretion disks. We have therefore included the dependence on charge number Z and mean molecular weights mu_{e/I} into the Shakura and Sunyaev

V. V. Sokolov, V. G. Kurt, G. S. Bisnovatyi-Kogan, Yu. N. Gnedin

Typical observational gamma-ray burst (GRB) spectra are discussed and, in this connection, what is the origin of the compactness problem and how it was solved at first. If the threshold for $e^{-}e^{+}$ pair production depends on an angle between photon momenta, then another solution of the compactness problem is possible. We discuss a possibility of the $γ$

Orfeu Bertolami, Jorge Paramos

The vacuum solutions arising from a spontaneous breaking of Lorentz symmetry due to the acquisition of a vacuum expectation value by a vector field are derived. These include the purely radial Lorentz symmetry breaking (LSB), radial/temporal LSB and axial/temporal LSB scenarios. It is found that the purely radial LSB case gives rise to new black hole solutio

T. D. Browning, R. Dietmann

Let Q be a non-singular quadratic form with integer coefficients. When Q is indefinite we provide new upper bounds for the least non-trivial integral solution to the equation Q=0. When Q is positive definite we provide improved upper bounds for the least positive integer k such that the equation Q=k is insoluble in integers, despite being soluble modulo ever

A. K. H. Kong, C. Bassa, D. Pooley, W. H. G. Lewin

We report on the Chandra X-ray Observatory observations of the globular cluster NGC 288. We detect four X-ray sources within the core radius and seven additional sources within the half-mass radius down to a limiting luminosity of Lx=7e30 erg/s (assuming cluster membership) in the 0.3-7 keV band. We also observed the cluster with the Hubble Space Telescope A

Jacques-Olivier Moussafir

We consider in this paper the problem of computing the entropy of a braid. We recall its definition and construct, for each braid, a sequence of real numbers, whose limit is its entropy. We state one conjecture about the convergence speed, and two about the braids that have high entropy, but are written with few letters.

Ravi Vakil, Aleksey Zinger

We construct a desingularization of the ``main component&#39;&#39; $\bar{\mathfrak M}_{1,k}^0(\Bbb{P}^n,d)$ of the moduli space $\bar{\mathfrak M}_{1,k}(\Bbb{P}^n,d)$ of genus-one stable maps into the complex projective space $\Bbb{P}^n$. As a bonus, we obtain desingularizations of certain natural sheaves over $\bar{\mathfrak M}_{1,k}^0(\Bbb{P}^n,d)$. Such d

Guangyue Han, Brian Marcus

Consider a hidden Markov chain obtained as the observation process of an ordinary Markov chain corrupted by noise. Zuk, et. al. [13], [14] showed how, in principle, one can explicitly compute the derivatives of the entropy rate of at extreme values of the noise. Namely, they showed that the derivatives of standard upper approximations to the entropy rate act

Richard C. Brower, Joseph Polchinski, Matthew J. Strassler, Chung-I Tan

The traditional description of high-energy small-angle scattering in QCD has two components -- a soft Pomeron Regge pole for the tensor glueball, and a hard BFKL Pomeron in leading order at weak coupling. On the basis of gauge/string duality, we present a coherent treatment of the Pomeron. In large-N QCD-like theories, we use curved-space string-theory to de

Denis D. Sheka, Franz G. Mertens

We apply the recently generalized Levinson theorem for potentials with inverse square singularities [Sheka et al, Phys.Rev.A, v.68, 012707 (2003)] to Aharonov-Bohm systems in two-dimensions. By this theorem, the number of bound states in a given m-th partial wave is related to the phase shift and the magnetic flux. The results are applied to 2D soliton-magno