January 2006 arXiv papers — page 4

Nikolai A. Krylov

We consider two pairs: the standard unknotted $n$-sphere in $S^{n+2}$, and the product of two $p$-spheres trivially embedded in $S^{2p+2}$, and study orientation preserving diffeomorphisms of these pairs. Pseudo-isotopy classes of such diffeomorphisms form subgroups of the mapping class groups of $S^n$ and $S^p\times S^p$ respectively and we determine the al

Jeffrey C. Lagarias

This paper studies the local spacings of deformations of the Riemann zeta function under certain averaging and differencing operations. For real h it considers A_h(s)= 1/2(xi(s+h)+ xi(s-h)) and B_h(s)=1/(2i)(xi(s+h)-xi(s-h)), where xi(s) is the Riemann xi-function. For |h|\ge 1/2 all zeros of these functions lie on the critical line and are simple zeros. Ass

Rostislav Grigorchuk, Zoran Sunik

We present relations between growth, growth of diameters and the rate of vanishing of the spectral gap in Schreier graphs of automaton groups. In particular, we introduce a series of examples, called Hanoi Towers groups since they model the well known Hanoi Towers Problem, that illustrate some of the possible types of behavior.

R. Sena-Dias

In this paper, we address a question of Donaldson's on the best estimate that can be achieved for the transversality of an asymptotically holomorphic sequence of sections of increasing powers of a line bundle over an integral symplectic manifold. More specifically, we find an upper bound for the transversality of n such sequences of sections over a 2n-di

Benno van den Berg, Federico De Marchi

The paper uses the formalism of indexed categories to recover the proof of a standard final coalgebra theorem, thus showing existence of final coalgebras for a special class of functors on categories with finite limits and colimits. As an instance of this result, we build the final coalgebra for the powerclass functor, in the context of a Heyting pretopos wi

Yon-Seo Kim, Kefeng Liu

We obtain a system of relations between linear Hodge integrals. As an application, we show that its first non-trivial relation implies the Witten's Conjecture/Kontsevich Theorem.

Gabriel Herz

We compare two constructions that associate to a semistable vector bundle on a Mumford curve a representation of the Schottky group and the algebraic fundamental group respectively.

I. D. Chipchakov

The paper establishes a relationship between finite separable extensions and norm groups of strictly quasilocal fields with Henselian discrete valuations, which yields a generally nonabelian one-dimensional local class field theory.

Clara Loeh

Measure homology is a variation of singular homology designed by Thurston in his discussion of simplicial volume. Zastrow and Hansen showed independently that singular homology (with real coefficients) and measure homology coincide algebraically on the category of CW-complexes. It is the aim of this paper to prove that this isomorphism is isometric with resp

Andrew Hone

The Somos 5 sequences are a family of sequences defined by a fifth order bilinear recurrence relation with constant coefficients. For particular choices of coefficients and initial data, integer sequences arise. By making the connection with a second order nonlinear mapping with a first integral, we prove that the two subsequences of odd/even index terms eac

Isabel M. C. Salavessa, Ana Pereira do Vale

We compute explicit transgression forms for the Euler and Pontrjagin classes of a Riemannian manifold $M$ of dimension 4 under a conformal change of the metric, or a change to a Riemannian connection with torsion. These formulae describe the singular set of some connections with singularities on compact manifolds as a residue formula in terms of a polynomial

Isabel M. C. Salavessa, Ana Pereira do Vale

Our main results are: (1) The complex a Lagrangian points of a non-complex Lagrangian $2n$-dimensional submanifold $F:M\ra N$, immersed with parallel mean curvature and with equal Kaehler angles into a Kaehler-Einstein manifold $(N,J,g)$ of complex dimension $2n$, are zeros of finite order of $\sin^2θ$ and $\cos^2θ$ respectively, where $θ$ is the common $J$-

Fernando T. Brandt, Ashok Das, Olivier Espinosa, Josif Frenkel

We extend our previous analysis of gauge and Dirac fields in the presence of a chemical potential. We consider an alternate thermal operator which relates in a simple way the Feynman graphs in QED at finite temperature and charge density to those at zero temperature but non-zero chemical potential. Several interesting features of such a factorization are dis

Sangmin Lee, Soo-Jong Rey

We obtain a simple expression for the triangle `t Hooft anomalies in quiver gauge theories that are dual to toric Sasaki-Einstein manifolds. We utilize the result and simplify considerably the proof concerning the equivalence of a-maximization and Z-minimization. We also resolve the ambiguity in defining the flavor charges in quiver gauge theories. We then c

Henry C. D. Cove, Richard J. Szabo

We compute the two-loop contributions to the free energy in the null compactification of perturbative string theory at finite temperature. The cases of bosonic, Type II and heterotic strings are all treated. The calculation exploits an explicit reductive parametrization of the moduli space of infinite-momentum frame string worldsheets in terms of branched co

T. D. Palev

A system of $N$ non-canonical dynamically free 3D harmonic oscillators is studied. The position and the momentum operators (PM-operators) of the system do not satisfy the canonical commutation relations (CCRs). Instead they obey the weaker postulates for the oscillator to be a Wigner quantum system. In particular the PM-operators fulfil the main postulate, w

Sean Fleming

In this talk I review soft collinear effective theory. After a discussion of the formalism and properties of the effective field theory, I turn to phenomenology. I present results on color-suppressed B to D decays, and on the Upsilon radiative decay spectrum.

T. Binoth, M. Ciccolini, G. Heinrich

A precise understanding of LHC phenomenology requires the inclusion of one-loop corrections for multi-particle final states. In this talk we describe a semi-numerical method to compute one-loop amplitudes with many external particles and present first applications.

T. Fernandez-Carames, A. Valcarce, H. Garcilazo, P. Gonzalez

We use two-body potentials derived from a constituent quark cluster model to analyze the bound-state problem of the $ΣNN$ system. The observables of the two-body subsystems, $NN$ and $ΣN$, are well reproduced. We do not find $ΣNN$ bound states, but there are two attractive channels with a resonance close above the three-body threshold. These channels are the

B. L. Ioffe

The visible universe - it is the universe of nucleons and electrons. The appearance of nucleon mass is caused by the violation of chiral symmetry in quantum chromodynamics (QCD). For this reason, the experiments on high energy accelerators cannot shed light on the origin of the matter in the visible universe. The origin of the mass of matter will be clarifie

T. Hahn, M. Rauch

The FormCalc package automates the computation of FeynArts amplitudes up to one loop including the generation of a Fortran code for the numerical evaluation of the squared matrix element. Major new or enhanced features in Version 5 are: iterative build-up of essentially arbitrary phase-spaces including cuts, convolution with density functions, and uniform tr

R. Bonciani, A. Ferroglia

Recent developments in the calculation of the NNLO corrections to the Bhabha scattering differential cross section in pure QED are briefly reviewed and discussed.

R. J. Crewther, S. D. Bass, F. M. Steffens, A. W. Thomas

The renormalization group is extended to cases where several heavy particles are decoupled at the same time. This involves large logarithms which are scale-invariant and so cannot be eliminated by a change of renormalization scheme. A set of scale-invariant running couplings, one for each heavy particle, is constructed without reference to intermediate thres

G. L. Alberghi, R. Casadio, D. Galli, D. Gregori

We study modifications of the Hawking emission in the evaporation of miniature black holes possibly produced in accelerators when their mass approaches the fundamental scale of gravity, set to 1 TeV according to some extra dimension models. Back-reaction and quantum gravity corrections are modelled by employing modified relations between the black hole mass

Salvatore Mele

The study of low-angle and large-angle Bhabha scattering at LEP gives access to the running of the electromagnetic coupling. Two recent measurements of the OPAL and L3 collaborations probe the running of alpha in the regions 1.8GeV^2<-Q^2<6.1GeV^2 and 1800GeV^2 <-Q^2 <21600GeV^2, respectively. The strategies and the results of these studies are presented. A

Tamas Novak

Bose-Einstein correlations of identical charged-pion pairs produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using Levy stable distributions. The source function is reconstructed with the help of the tau-model.

Dan N. Vollick

In this paper I examine black hole and cosmological space-times in Born-Infeld-Einstein theory with electric and magnetic charges. The field equations are derived and written in the form $G_{μν}=-κT_{μν}$ for spherically symmetric space-times. The energy-momentum tensor is not the Born-Infeld energy-momentum tensor, but can be obtained from Born-Infeld theor

Rodrigo Aros, Mauricio Contreras

In this work the Poincare-Chern Simons and Anti de Sitter Chern Simons gravities are studied. For both a solution that can be casted as a black hole with manifest torsion is found. Those solutions resemble Schwarzschild and Schwarzschild-AdS solutions respectively.

Alfredo B. Henriques

We present some results concerning the large volume limit of loop quantum cosmology in the flat homogeneous and isotropic case. We derive the Wheeler-De Witt equation in this limit. Looking for the action from which this equation can also be obtained, we then address the problem of the modifications to be brought to the Friedman&#39;s equation of motion and

Johann Kronthaler

The Cauchy problem is considered for the scalar wave equation in the Schwarzschild geometry. We derive an integral spectral representation for the solution and prove pointwise decay in time.

J. Podolsky, J. B. Griffiths

A class of exact solutions of the Einstein-Maxwell equations is presented which describes an accelerating and rotating charged black hole in an asymptotically de Sitter or anti-de Sitter universe. The metric is presented in a new and convenient form in which the meaning of the parameters is clearly identified, and from which the physical properties of the so

G. G. Karapetyan

We investigate novel approach, which improves the sensitivity of gravitational wave (GW) interferometer due to stochastic resonance (SR) phenomenon, performing in additional nonlinear cavity (NC). The NC is installed in the output of interferometer before photodetector, so that optical signal emerging interferometer incidents on the NC and passes through it.

Joe Henson

The ideas of spacetime discreteness and causality are important in several of the popular approaches to quantum gravity. But if discreteness is accepted as an initial assumption, conflict with Lorentz invariance can be a consequence. The causal set is a discrete structure which avoids this problem and provides a possible history space on which to build a ``p

Mauricio Mondragon, Merced Montesinos

The various phase spaces involved in the dynamics of parametrized nonrelativistic Hamiltonian systems are displayed by using Crnkovic and Witten&#39;s covariant canonical formalism. It is also pointed out that in Dirac&#39;s canonical formalism there exists a freedom in the choice of the symplectic structure on the extended phase space and in the choice of t

Abhilash Ponnath

This paper presents a review of instantaneously trained neural networks (ITNNs). These networks trade learning time for size and, in the basic model, a new hidden node is created for each training sample. Various versions of the corner-classification family of ITNNs, which have found applications in artificial intelligence (AI), are described. Implementation

Amos Fiat, Manor Mendel

The competitive analysis fails to model locality of reference in the online paging problem. To deal with it, Borodin et. al. introduced the access graph model, which attempts to capture the locality of reference. However, the access graph model has a number of troubling aspects. The access graph has to be known in advance to the paging algorithm and the memo

K. Murali Krishnan, Priti Shankar

A linear time approximate maximum likelihood decoding algorithm on tail-biting trellises is prsented, that requires exactly two rounds on the trellis. This is an adaptation of an algorithm proposed earlier with the advantage that it reduces the time complexity from O(mlogm) to O(m) where m is the number of nodes in the tail-biting trellis. A necessary condit

Carl Lagoze, Dean Krafft, Tim Cornwell, Naomi Dushay

Over three years ago, the Core Integration team of the National Science Digital Library (NSDL) implemented a digital library based on metadata aggregation using Dublin Core and OAI-PMH. The initial expectation was that such low-barrier technologies would be relatively easy to automate and administer. While this architectural choice permitted rapid deployment

Onur Kaya, Sennur Ulukus

For a fading Gaussian multiple access channel with user cooperation, we obtain the optimal power allocation policies that maximize the rates achievable by block Markov superposition coding. The optimal policies result in a coding scheme that is simpler than the one for a general multiple access channel with generalized feedback. This simpler coding scheme al

Emin Martinian, Martin J. Wainwright

We propose a new construction for low-density source codes with multiple parameters that can be tuned to optimize the performance of the code. In addition, we introduce a set of analysis techniques for deriving upper bounds for the expected distortion of our construction, as well as more general low-density constructions. We show that (with an optimal encodi

Robert Brijder, Hendrik Jan Hoogeboom, Grzegorz Rozenberg

Gene assembly in ciliates is one of the most involved DNA processings going on in any organism. This process transforms one nucleus (the micronucleus) into another functionally different nucleus (the macronucleus). We continue the development of the theoretical models of gene assembly, and in particular we demonstrate the use of the concept of the breakpoint

Samanta Piano, Fabrizio Bobba, Adele De Santis, Filippo Giubileo

We present conductance characteristics of point contact junctions realized between a normal Pt-Ir tip and YBa$_2$Cu$_3$O$_{7-x}$/La$_{0.7}$Ca$_{0.3}$MnO$_3$ (YBCO/LCMO) bilayers. The point contact characteristics show a zero bias conductance peak, as a consequence of the formation of Andreev bound states at the YBCO Fermi level. The temperature evolution of

M. Georgiev

We review the basic theoretical background for working out a variational band solution for vibronic polarons in crystals. It is based on the Lee-Low-Pines proposal as extended by Thomas et al. for describing Jahn-Teller polarons along a linear chain of atoms. The variational properties of antiadiabatic itinerant polarons are also discussed.

P. Jiji Thomas Joseph, Prabhakar P. Singh

Using density-functional-based method, we study the k-resolved sigma- and pi-band holes in Mg_{1-x}Al_{x}B_{2} and Mg(B_{1-y}C_{y})_{2} alloys. We find that the calculated profiles of the loss of sigma- and pi-band holes in these two systems as a function of impurity concentration are in qualitative agreement with experiments, as expected. We also describe i

Dana Levanony, Dov Levine

We consider a simple dissipative system with spatial structure in contact with a heat bath. The system always exhibits correlations except in the cases of zero and maximal dissipation. We explicitly calculate the correlation function and the nonlocal response function of the system and show that they have the same spatial dependence. Finally, we examine heat

Hem Chandra Kandpal, Gerhard H. Fecher, Claudia Felser, Gerd Schönhense

Half-metallic ferromagnets like the full Heusler compounds with formula X$_2$YZ are supposed to show an integer value of the spin magnetic moment. Calculations reveal in certain cases of X = Co based compounds non-integer values, in contrast to experiments. In order to explain deviations of the magnetic moment calculated for such compounds, the dependency of

Sabine Wurmehl, Gerhard H. Fecher, Kristian Kroth, Florian Kronast

Quaternary Heusler alloys Co$_2$Cr$_{1-x}$Fe$_{x}$Al with varying Cr to Fe ratio $x$ were investigated experimentally and theoretically. The electronic structure and spectroscopic properties were calculated using the full relativistic Korringa-Kohn-Rostocker method with coherent potential approximation to account for the random distribution of Cr and Fe atom

Brian H. Moeckly, Ward S. Ruby

We report a new in-situ reactive deposition thin film growth technique for the production of MgB2 thin films which offers several advantages over all existing methods and is the first deposition method to enable the production of high-quality MgB2 films for real-world applications. We have used this growth method, which incorporates a rotating pocket heater,

Nicola M. Pugno

In this paper different deterministic and statistical models, based on new quantized theories proposed by the author, are presented to estimate the strength of a real, thus defective, space elevator cable. The cable, of ~100 megameters in length, is composed by carbon nanotubes, ~100 nanometers long: thus, its design involves from the nano- to the mega-mecha

Z. Korczak, T. Kwapinski

The electrical conductance and RHEED intensities as a function of the coverage have been measured during Pb depositions at 105 K on Si(111)-(6x6)Au with up to 4.2 ML of annealed Pb. The experiments show the strong influence of used substrates on the behavior of the conductance during the epitaxy of Pb atoms, especially for very initial stage of growth. Oscil

Andrea Pelissetto, Ettore Vicari

We calculate the correction-to-scaling exponent $ω_T$ that characterizes the approach to the scaling limit in multicomponent polymer solutions. A direct Monte Carlo determination of $ω_T$ in a system of interacting self-avoiding walks gives $ω_T = 0.415(20)$. A field-theory analysis based on five- and six-loop perturbative series leads to $ω_T = 0.41(4)$. We

Simon L. Cornish, Sarah T. Thompson, Carl E. Wieman

We observe bright matter-wave solitons form during the collapse of 85Rb condensates in a three-dimensional magnetic trap. The collapse is induced by using a Feshbach resonance to suddenly switch the atomic interactions from repulsive to attractive. Remnant condensates containing several times the critical number of atoms for the onset of instability are obse

R. Mazumder, S. Ghosh, P. Mondal, Dipten Bhattacharya

We report results of a comprehensive study of the phase transition at T_N (~643 K) as a function of particle size in multiferroic BiFeO3 system. We employed electrical, thermal, and temperature dependent X-ray diffraction (XRD) studies in order to characterize the transition in a host of samples. We also carried out detailed magnetic measurements over a temp

J. D. Burton, R. F. Sabirianov, S. S. Jaswal, E. Y. Tsymbal

Magnetic moments in atomic scale domain walls formed in nanoconstrictions and nanowires are softened which affects dramatically the domain wall resistance. We perform ab initio calculations of the electronic structure and conductance of atomic-size Ni nanowires with domain walls only a few atomic lattice constants wide. We show that the hybridization between

A. V. Akimov, A. V. Scherbakov, D. R. Yakovlev, I. A. Merkulov

The magnetization kinetics in (Zn,Mn)Se/(Zn,Be)Se quantum wells has been studied on a ps-time scale after pulsed laser excitation. The magnetization induced by an external magnetic field is reduced by up to 30% during ~100 ps due to spin and energy transfer from photocarriers to Mn spin system. The giant Zeeman splitting leads to a complete spin polarization

C. Michioka, H. Ohta, Y. Itoh, K. Yoshimura

We report 59Co nuclear quadrupole resonance (NQR) studies of bilayer water intercalated sodium cobalt oxides NaxCoO2.yH2O (BLH) with the superconducting transition temperatures, 2 K < T_c <= 4.6 K, as well as a magnetic BLH sample without superconductivity. We obtained a magnetic phase diagram of T_c and the magnetic ordering temperature T_M against the peak

Simone S. Alexandre, Eduardo Anglada, Jose M. Soler, Felix Yndurain

Careful first-principles density functional calculations reveal the importance of hexagonal versus cubic stacking of closed packed planes of Pd as far as local magnetic properties are concerned. We find that, contrary to the stable face centered cubic phase, which is paramagnetic, the hexagonal close-packed phase of Pd is ferromagnetic with a magnetic moment

V. I. Yukalov

Thermodynamic stability of statistical systems requires that susceptibilities be semipositive and finite. Susceptibilities are known to be related to the fluctuations of extensive observable quantities. This relation becomes nontrivial, when the operator of an observable quantity is represented as a sum of operators corresponding to the extensive system part

G. Campi, E. Cappelluti, Th. Proffen, X. Qiu

We have studied the evolution with temperature of the local as well as the average crystal structure of MgB$_2$ using the real-space atomic pair distribution function (PDF) measured by high resolution neutron powder diffraction. We have investigated the correlations of the B-B and B-Mg nearest neighbor pair motion by comparing, in the wide temperature range

A. Fukuda, A. Sawada, S. Kozumi, D. Terasawa

Magnetotransport properties are investigated in the bilayer quantum Hall state at the total filling factor $ν=2$. We measured the activation energy elaborately as a function of the total electron density and the density difference between the two layers. Our experimental data demonstrate clearly the emergence of the canted antiferromagnetic (CAF) phase betwe

Mukul Gupta, Ajay Gupta, Sujoy Chakravarty, Rachana Gupta

Iron self-diffusion in nano-composite FeZr alloy has been investigated using neutron reflectometry technique as a function of applied compressive stress. A composite target of (Fe+Zr) and (57Fe+Zr) was alternatively sputtered to deposit chemically homogeneous multilayer (CHM) structure, [Fe75Zr25/57Fe75Zr25]10. The multilayers were deposited on to a bent Si

Carlos S. O. Yokoi, Francisco A. da Costa

We study the stability of the replica-symmetric solution of a two-sublattice infinite-range spin-glass model, which can describe the transition from antiferromagnetic to spin glass state. The eigenvalues associated with replica-symmetric perturbations are in general complex. The natural generalization of the usual stability condition is to require the real p

Daniel Dantchev, H. W. Diehl, Daniel Grüneberg

We consider systems confined to a $d$-dimensional slab of macroscopic lateral extension and finite thickness $L$ that undergo a continuous bulk phase transition in the limit $L\to\infty$ and are describable by an O(n) symmetrical Hamiltonian. Periodic boundary conditions are applied across the slab. We study the effects of long-range pair interactions whose

Jörg Lehmann, Daniel Loss

We consider cotunneling through a quantum dot in the presence of spin-flip processes induced by the coupling to acoustic phonons of the surrounding. An expression for the phonon-assisted cotunneling current is derived by means of a generalized Schrieffer-Wolff transformation. The influence of the spin-phonon coupling on the heating of the dot is considered.

Filippo Giubileo, Marco Aprili, Fabrizio Bobba, Samanta Piano

Superconducting micro-constrictions between Nb tips and high quality MgB$_{2}$ pellets have been realized by means of a point-contact inset, driven by a micrometric screw. Measurements of the current-voltage characteristics and of the dynamical conductance versus bias have been performed in the temperature range between 4.2 K and 500 K. Above the Nb critical

Junchao Xia, Harvey Gould, W. Klein, J. B. Rundle

Simple models of earthquake faults are important for understanding the mechanisms for their observed behavior, such as Gutenberg-Richter scaling and the relation between large and small events, which is the basis for various forecasting methods. Although cellular automaton models have been studied extensively in the long-range stress transfer limit, this lim

Reza Mansouri

Within the recently proposed structured FRW model universe the averaged Einstein equations are derived. The backreaction turns out to have an interesting behavior. Its equivalent density and pressure, being proportional, are negative at early times of the dark ages of the universe, and change sign near our present time in our local patch. In addition to expl

Peter Berczik, David Merritt, Rainer Spurzem, Hans-Peter Bischof

Binary supermassive black holes form naturally in galaxy mergers, but their long-term evolution is uncertain. In spherical galaxies, N-body simulations show that binary evolution stalls at separations much too large for significant emission of gravitational waves (the &#34;final parsec problem&#34;). Here, we follow the long-term evolution of a massive binar

E. S. Levine, Leo Blitz, Carl Heiles

We examine the outer Galactic HI disk for deviations from the b=0 plane by constructing maps of disk surface density, mean height, and thickness. We find that the Galactic warp is well described by a vertical offset plus two Fourier modes of frequency 1 and 2, all of which grow with Galactocentric radius. Adding the m=2 mode accounts for the large asymmetry

Roman R. Rafikov, Fabio De Colle

Structure and spectral energy distributions (SEDs) of externally irradiated circumstellar disks are often computed on the basis of the two-temperature model of Chiang & Goldreich. We refine these calculations by using a more realistic temperature profile which is continuous at all optical depths and thus goes beyond the two-temperature model. It is based on

Martin D. Weinberg, Leo Blitz

We show that a Magellanic Cloud origin for the warp of the Milky Way can explain most quantitative features of the outer HI layer recently identified by Levine, Blitz & Heiles (2005). We construct a model similar to that of Weinberg (1998) that produces distortions in the dark matter halo, and we calculate the combined effect of these dark-halo distortions a

A. M. Soderberg

Over the last few years our understanding of local Type Ibc supernovae and their connection to long-duration gamma-ray bursts has been revolutionized. Recent discoveries have shown that the emerging picture for core-collapse explosions is one of diversity. Compiling data from our dedicated radio survey of SNe Ibc and our comprehensive HST survey of GRB-SNe t

Naomi A. Ridge, Scott L. Schnee, Alyssa A. Goodman, Jonathan B. Foster

The Perseus molecular cloud complex is a ~30pc long chain of molecular clouds most well-known for the two star-forming clusters NGC1333 and IC348 and the well-studied outflow source in B5. However, when studied at mid- to far-infrared wavelengths the region is dominated by a ~10pc diameter shell of warm dust, likely generated by an HII region caused by the e

Ivan Zolotukhin, Sergey Koposov, Elena Glushkova

Current catalogues of open clusters are rather heterogeneous and incomplete lists of clusters than true catalogues. Before there has been no attempts of automatic search for open clusters in huge photometric catalogues using homogeneous all-sky approach. We have developed such a method based on extraction from catalogue and successive analysis of stellar den

Ari Laor

A high quality Keck spectrum of the Halpha line in NGC 4395 reveals symmetric exponential wings, fv\propto e^{-v/sigma}, with sigma~500km/s. The wings extend out to >2500km/s from the line core, and down to a flux density of <10^-3 of the peak flux density. Numerical and analytic calculations indicate that exponential wings are expected for optically thin, i

D. John Hillier, T. Gull, K. Nielsen, G. Sonneborn

We have made an extensive study of the UV spectrum of Eta Carinae, and find that we do not directly observe the star and its wind in the UV. Because of dust along our line of sight, the UV light that we observe arises from bound-bound scattering at large impact parameters. We obtain a reasonable fit to the UV spectrum by using only the flux that originates o

Mark M. Phillips, Kevin Krisciunas, Nicholas B. Suntzeff, R. G. Abraham

We present 39 nights of optical photometry, 34 nights of infrared photometry, and 4 nights of optical spectroscopy of the Type Ia SN 1999ac. This supernova was discovered two weeks before maximum light, and observations were begun shortly thereafter. At early times its spectra resembled the unusual SN 1999aa and were characterized by very high velocities in

Dipak Munshi, Patrick Valageas

We show that as many as 4000 SNeIa may be required to detect the effect of weak lensing on their flux distribution with a high level of significance. However, if the intrinsic SNeIa magnitude dispersion is unknown one needs an even higher number of SNeIa (an order of magnitude more) to reach a similar level of statistical significance. Moreover, the ability

M. Röllig, V. Ossenkopf, S. Jeyakumar, J. Stutzki

We study the effects of a metallicity variation on the thermal balance and [CII] fine-structure line strengths in interstellar photon dominated regions (PDRs). We find that a reduction in the dust-to-gas ratio and the abundance of heavy elements in the gas phase changes the heat balance of the gas in PDRs. The surface temperature of PDRs decreases as the met

S. Bilir, T. Guver, M. Aslan

136 stars which were known to be the members of open cluster NGC 752 were observed at R band with ROTSE-IIId telescope located at the Turkish National Observatory (TUG) site. The data had been evaluated together with BV and 2MASS photometric data. A new practical method for separating dwarf and giant was described and applied. Evaluating the colour magnitude

F. Combes

The bulk of the molecular component in galaxies is made of cold H2, which is not observed directly, but which abundance is derived from indirect tracers such as CO emission. The CO to H2 conversion ratio remains uncertain, and may vary by large factors in special environments with different excitation or metallicity. Recent cold gas discoveries (through gamm

P. Englmaier, O. Gerhard, ;

The Milky Way is made up of a central bar, a disk with embedded spiral arms, and a dark matter halo. Observational and theoretical constraints for the characteristic parameters of these components will be presented, with emphasis on the constraints from the dynamics of the Milky Way gas. In particular, the fraction of dark matter inside the solar radius, the

V. R. Khalack, G. A. Wade

The surface magnetic field configuration of the Ap star HD 118022 (78 Vir) has been reconstructed in the framework of the magnetic charge distribution (MCD) method from the analysis of Stokes $IQUV$ spectra obtained using the MuSiCoS spectropolarimeter at Pic du Midi Observatory. Magnetically-sensitive Fe~{\sc ii} lines were primarily employed in the analysi

G. A. Shields, S. Salviander, E. W. Bonning

QSOs allow study of the evolution of the relationship between black holes in galactic nuclei and their host galaxies. The black hole mass can be derived from the widths of the broad emission lines, and the stellar velocity dispersion (sigma_*) of the host galaxy can be inferred from the narrow emission lines. Results based on [OIII] and [OII] line widths ind

L. Clewley, Matt J. Jarvis

We present 2-degree field spectroscopic observations of a sample of 96 A-type stars selected from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Our aim is to identify blue horizontal branch (BHB) stars in order to measure the kinematic properties of the tidal tails of the Sagittarius dwarf spheroidal galaxy. We confine our attention to the 44 class

G. Weidenspointner, C. R. Shrader, J. Knoedlseder, P. Jean

We present a measurement of the sky distribution of positronium (Ps) annihilation continuum emission obtained with the SPI spectrometer on board ESA&#39;s INTEGRAL observatory. The only sky region from which significant Ps continuum emission is detected is the Galactic bulge. The Ps continuum emission is circularly symmetric about the Galactic centre, with a

Anne J. Metevier, David C. Koo, Luc Simard, Andrew C. Phillips

Using moderate-resolution Keck spectra, we have examined the velocity profiles of 15 members of cluster Cl0024+1654 at z=0.4. WFPC2 images of the cluster members have been used to determine structural parameters, including disk sizes, orientations, and inclinations. We compare two methods of optical rotation curve analysis for kinematic measurements. Both me

Tamara M. Rogers, Gary A. Glatzmaier

We present numerical simulations of convective overshoot in a two-dimensional model of the solar equatorial plane. The simulated domain extends from 0.001 R_sun to 0.93 R_sun, spanning both convective and radiative regions. We show that convective penetration leads to a slightly extended, mildly subadiabatic temperature gradient beneath the convection zone b

Rodrigo Gil-Merino, Geraint F. Lewis

We qualitatively study the effects of gravitational microlensing on our view of unresolved extragalactic star formation regions. Using a general gravitational microlensing configuration, we perform a number of simulations that reveal that specific imprints of the star forming region are imprinted, both photometrically and spectroscopically, upon observations

Paola Rebusco, Marek A. Abramowicz

There is strong evidence that the observed kHz Quasi Periodic Oscillations (QPOs) in the X-ray flux of neutron star and black hole sources in LMXRBs are linked to Einstein&#39;s General Relativity. Abramowicz&Kluźniak (2001) suggested a non-linear resonance model to explain the QPOs origin: here we summarize their idea and the development of a mathematical t

P. Meszaros

The rapid follow-up of gamma-ray burst (GRB) afterglows made possible by the multi-wavelength satellite Swift, launched in November 2004, has put under a microscope the GRB early post-burst behavior, This is leading to a significant reappraisal and expansion of the standard view of the GRB early afterglow behavior, and its connection to the prompt gamma-ray

G. A. Wade

Magnetic fields play an important role in producing and modifying the photospheric chemical peculiarities of intermediate-mass main sequence stars. This article discusses the basic theory and methods of measurement used to detect and characterise stellar magnetic fields, and reviews our current knowledge of selected characteristics of magnetic fields in inte

G. A. Wade, D. Drouin, S. Bagnulo, J. D. Landstreet

We are investigating the magnetic characteristics of pre-main sequence Herbig Ae/Be stars, with the aim of (1) understanding the origin and evolution of magnetism in intermediate-mass stars, and (2) exploring the influence of magnetic fields on accretion, rotation and mass-loss at the early stages of evolution of A, B and O stars. We have begun by conducting

S. Nojiri, S. D. Odintsov

We review various modified gravities considered as gravitational alternative for dark energy. Specifically, we consider the versions of $f(R)$, $f(G)$ or $f(R,G)$ gravity, model with non-linear gravitational coupling or string-inspired model with Gauss-Bonnet-dilaton coupling in the late universe where they lead to cosmic speed-up. It is shown that some of s

Victor W. Guillemin, Shlomo Sternberg, Jonathan Weitsman

We derive an Ehrhart function for symbols from the Euler-MacLaurin formula with remainder.

Felix Finster

In this short article we introduce the mathematical framework of the principle of the fermionic projector and set up a variational principle in discrete space-time. The underlying physical principles are discussed. We outline the connection to the continuum theory and state recent results. In the last two sections, we speculate on how it might be possible to

D. Arnaudon, A. Chakrabarti, V. K. Dobrev, S. G. Mihov

The exotic bialgebra S03, defined by a solution of the Yang-Baxter equation, which is not a deformation of the trivial, is considered. Its FRT dual algebra $s03_F$ is studied. The Baxterisation of the dual algebra is given in two different parametrisations. The finite-dimensional representations of $s03_F$ are considered. Diagonalisations of the braid matric

Yoshimichi Ueda

With a minor change made in the previous construction we observe that any reduced HNN extension is precisely a compressed algebra of a certain reduced amalgamated free product in both the von Neumann algebra and the $C^*$-algebra settings. It is also pointed out that the same fact holds true even for universal HNN extensions of C$^*$-algebras. We apply the o

A. Marshakov

We consider certain examples of applications of the general methods, based on geometry and integrability of matrix models, described in hep-th/0601212. In particular, the nonlinear differential equations, satisfied by quasiclassical tau-functions are investigated. We also discuss a similar quasiclassical geometric picture, arising in the context of multidime

A. Marshakov

We consider the simplest gauge theories given by one- and two- matrix integrals and concentrate on their stringy and geometric properties. We remind general integrable structure behind the matrix integrals and turn to the geometric properties of planar matrix models, demonstrating that they are universally described in terms of integrable systems directly re