May 2006 arXiv papers — page 43

Chris Good, Lylah Haynes

One possible natural monotone version of countable paracompactness, MCP, turns out to have some interesting properties. We investigate various other possible monotonizations of countable paracompactness and how they are related.

Vladimir Nikiforov

We give inequalities relating the eigenvalues of the adjacency matrix and the Laplacian of a graph, and its minimum and maximum degrees. The results are applied to derive new conditions for quasi-randomness of graphs.

Pedro G. Massey

We study refinements between spectral resolutions in an arbitrary II$_1$ factor $\M$ and obtain diffuse (maximal) refinements of spectral resolutions. We construct models of operators with respect to diffuse spectral resolutions. As an application we obtain new characterizations of sub-majorization and spectral preorder between positive operators in $\M$ and

Xiaojun Huang, Shanyu Ji, Dekang Xu

In this paper (Math. Res. Lett. 13 (2006). No 4, 509-523), the authors established a pseudo-normal form for proper holomoprhic mappings between balls in complex spaces with degenerate rank. This then was used to give a complete characterization for all proper holomorphic maps with geometric rank one, which, in particular, includes the following as an immedia

David Marin, Jorge Vitorio Pereira, Luc Pirio

We investigate the space of abelian relations of planar webs admitting infinitesimal automorphisms. As an application, we construct 4k-14 new algebraic families of global exceptionnal k-webs on the projective plane, for each k >4.

Alexander S. Cherny, Dilip B. Madan

The paper has 2 main goals: 1. We propose a variant of the CAPM based on coherent risk. 2. In addition to the real-world measure and the risk-neutral measure, we propose the third one: the extreme measure. The introduction of this measure provides a powerful tool for investigating the relation between the first two measures. In particular, this gives us - a

Alexander S. Cherny, Dilip B. Madan

We propose a pricing technique based on coherent risk measures, which enables one to get finer price intervals than in the No Good Deals pricing. The main idea consists in splitting a liability into several parts and selling these parts to different agents. The technique is closely connected with the convolution of coherent risk measures and equilibrium cons

Alexander S. Cherny, Dilip B. Madan

We propose a new procedure for the risk measurement of large portfolios. It employs the following objects as the building blocks: - coherent risk measures introduced by Artzner, Delbaen, Eber, and Heath; - factor risk measures introduced in this paper, which assess the risks driven by particular factors like the price of oil, S&P500 index, or the credit spre

J. -C. Novelli, J. -Y. Thibon

We realize several combinatorial Hopf algebras based on set compositions, plane trees and segmented compositions in terms of noncommutative polynomials in infinitely many variables. For each of them, we describe a trialgebra structure, an internal product, and several bases.

Andrei Agrachev, Igor Zelenko

As was shown recently by P. Nurowski, to any rank 2 maximally nonholonomic vector distribution on a 5-dimensional manifold M one can assign the canonical conformal structure of signature (3,2). His construction is based on the properties of the special 12-dimensional coframe bundle over M, which was distinguished by E. Cartan during his famous construction o

Clement Rau

In this article, we consider random walk on the infinite cluster of bond percolation on $\Z^d (d \geq 2)$. We show that the Laplace transformation of the number of visited points $N\_n$, has a behaviour as the random walk was on $\Z^d$. More precisely, for all $0<α<1$, we proved that there exist constants $C\_i$ and $C\_s$ such that for all infinite cluster

Ernesto Mordecki, Paavo Salminen

The optimal stopping problem for a Hunt processes on $\R$ is considered via the representation theory of excessive functions. In particular, we focus on infinite horizon (or perpetual) problems with one-sided structure, that is, there exists a point $x^*$ such that the stopping region is of the form $[x^*,+\infty)$. Corresponding results for two-sided proble

Anton Baranov, Alexander Borichev, Victor Havin

Let $B$ be a meromorphic Blaschke product in the upper half-plane with zeros $z_n$ and let $K_B=H^2\ominus BH^2$ be the associated model subspace of the Hardy class. In other words, $K_B$ is the space of square summable meromorphic functions with the poles at the points $\bar z_n$. A nonnegative function $w$ on the real line is said to be an admissible major

Alexander S. Cherny

This paper is the continuation of &#34;Pricing with coherent risk&#34; and deals with further applications of coherent risk measures to problems of finance. First, we study the optimization problem. Three forms of this problem are considered. Furthermore, the results obtained are applied to the optimality pricing. Again three forms of this technique are cons

Itai Benjamini, Roey Izkovsky, Harry Kesten

Let G be a vertex transitive graph. A study of the range of simple random walk on G and of its bridge is proposed. While it is expected that on a graph of polynomial growth the sizes of the range of the unrestricted random walk and of its bridge are the same in first order, this is not the case on some larger graphs such as regular trees. Of particular inter

Alexander S. Cherny

This paper deals with applications of coherent risk measures to pricing in incomplete markets. Namely, we study the No Good Deals pricing technique based on coherent risk. Two forms of this technique are presented: one defines a good deal as a trade with negative risk; the other one defines a good deal as a trade with unusually high RAROC. For each technique

Anton Deitmar, Mark Pavey

A prime geodesic theorem is proven for singular geodesics in quotients of SL(4). This is a case where regularity assumptions of previous papers fail. As a consequence, the analysis becomes much more involved. For applications in number theory (class number asymptotics) it is, however, necessary to consider this case, too.

Margherita Barile

We determine sets of elements which, under certain conditions, generate an intersection of ideals up to radical.

Bruno Schapira

Under the assumption of positive multiplicity, we obtain basic estimates of the hypergeometric functions F\_\la and G\_\la of Heckman and Opdam, and sharp estimates of the particular functions F\_0 and G\_0. Next we prove the Paley-Wiener theorem for the Schwartz class, solve the heat equation and estimate the heat kernel.

Vesselin Drensky, Jie-Tai Yu

We study automorphisms of the free associative algebra K<x,y,z> over a field K which fix the variable z. We describe the structure of the group of z-tame automorphisms and derive algorithms which recognize z-tame automorphisms and z-tame coordinates.

Maarten Solleveld

We show that the inclusion of an affine Hecke algebra in its Schwartz completion induces an isomorphism on periodic cyclic homology.

Vladimir Guletskii

We prove 2-out-of-3 property for rationality of motivic zeta function in distinguished triangles in Voevodsky&#39;s category DM. As an application, we show rationality of motivic zeta functions for all varieties whose motives are in the thick triangulated monoidal subcategory generated by motives of quasi-projective curves in DM. Joint with a result of P.O&#

E. Mukhin, V. Tarasov, A. Varchenko

Under certain conditions, we give an estimate from above on the number of differential equations of order $r+1$ with prescribed regular singular points, prescribed exponents at singular points, and having a quasi-polynomial flag of solutions. The estimate is given in terms of a suitable weight subspace of the tensor power $U(\n_-)^{\otimes (n-1)}$, where $n$

E. Mukhin, V. Tarasov, A. Varchenko

We prove the B. and M. Shapiro conjecture that says that if the Wronskian of a set of polynomials has real roots only, then the complex span of this set of polynomials has a basis consisting of polynomials with real coefficients. This in particular implies the following result: If all ramification points of a parametrized rational curve $ f : CP^1 \to CP^r $

Vladimir Nikiforov

We give upper and lower bounds on the spectral radius of a graph in terms of the number of walks. We generalize a number of known results.

William Crawley-Boevey, Bernt Tore Jensen

It is easy to imagine that a subvariety of a vector bundle, whose intersection with every fibre is a vector subspace of constant dimension, must necessarily be a sub-bundle. We give two examples to show that this is not true, and several situations in which the implication does hold. For example it is true if the base is normal and the field has characterist

R. C. Penner

A classical combinatorial fact is that the simplicial complex consisting of disjointly embedded chords in a convex planar polygon is a sphere. For any surface F with non-empty boundary, there is an analogous complex Arc(F) consisting of suitable equivalence classes of arcs in F connecting its boundary components. The main result of this paper is the determin

O. P. Santillan

The main results presented in this dissertation are the following - We have shown that in $d=4$ weak hyperkahler torsion structures are the same that hypercomplex structures and the same that the Plebanski-Finley conformally invariant heavens. With the help of this identification we have found the most general local form of an hyperkahler torsion space in fo

Urko Reinosa, Julien Serreau

We discuss the application of two-particle-irreducible (2PI) functional techniques to gauge theories, focusing on the issue of non-perturbative renormalization. In particular, we show how to renormalize the photon and fermion propagators of QED obtained from a systematic loop expansion of the 2PI effective action. At any finite order, this implies introducin

Anatoly E. Shabad, Vladimir V. Usov

A maximum value for the magnetic field is determined, which provides the full compensation of the positronium rest mass by the binding energy in the maximum symmetry state and disappearance of the energy gap separating the electron-positron system from the vacuum. The compensation becomes possible owing to the falling to the center phenomenon. The maximum ma

S. N. Vergeles

It is shown that in the theory of discrete quantum gravity the cosmological constant problem can be solved due to the phenomena of elliptic operators spectrum &#34;loosening&#34; and universe inflation.

Michael Lublinsky

The high energy/density QCD has been widely used for DIS phenomenology with a projectile particle considered as perturbative and dilute. We review some recent attempts to derive a high energy evolution kernel which treats targets and projectiles in a symmetric manner. From theoretical point of view the problem is tightly related to inclusion of Pomeron loops

D. Chang, C. S. Chen, H. Hatanaka, C. S. Kim

We study the decay processes $B \to K π$ by using generalized decay amplitudes with both the final state re-scattering strong phases and the topological quark diagrammatic strong phases included together as part of fitting parameters. Using a generalized approach, so called ``isospin phased topological approach&#39;&#39;, for all the currently available data

The BaBar Collaboration, B. Aubert

We describe searches for decays of B mesons to the charmless final states eta&#39; eta&#39; K. The data consist of 228 million B Bbar pairs produced in e+ e- annihilation, collected with the BaBar detector at the Stanford Linear Accelerator Center. The 90% confidence level upper limits for the branching fractions are Br(B0->eta&#39; eta&#39; K0)<31 10^{-6} a

Carlos F. Sopuerta, Ulrich Sperhake, Pablo Laguna

We introduce a computational framework which avoids solving explicitly hydrodynamic equations and is suitable to study the pre-merger evolution of black hole-neutron star binary systems. The essence of the method consists of constructing a neutron star model with a black hole companion and freezing the internal degrees of freedom of the neutron star during t

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

We study the global structure of Lorentzian manifolds with partial sectional curvature bounds. In particular, we prove completeness theorems for homogeneous and isotropic cosmologies as well as static spherically symmetric spacetimes. The latter result is used to rigorously prove the absence of static spherically symmetric black holes in more than three dime

V H Satheesh Kumar, P K Suresh

This is a pedagogical introduction to original Kaluza-Klein theory and its salient features. Most of the technical calculations are given in detail and the nature of gravitons is discussed.

B. Vakili, S. Jalalzadeh, H. R. Sepangi

We study the classical and quantum cosmology of a 4+1-dimensional space-time with a non-zero cosmological constant coupled to a self interacting massive spinor field. We consider a spatially flat Robertson-Walker universe with the usual scale factor $R(t)$ and an internal scale factor $a(t)$ associated with the extra dimension. For a free spinor field the re

Arnaud Durand, Etienne Grandjean

In this paper, we consider first-order logic over unary functions and study the complexity of the evaluation problem for conjunctive queries described by such kind of formulas. A natural notion of query acyclicity for this language is introduced and we study the complexity of a large number of variants or generalizations of acyclic query problems in that con

Shengtian Yang, Peiliang Qiu

An information-spectrum approach is applied to solve the multiterminal source coding problem for correlated general sources, where sources may be nonstationary and/or nonergodic, and the distortion measure is arbitrary and may be nonadditive. A general formula for the rate-distortion region of the multiterminal source coding problem with the maximum distorti

Paolo Messina, Matteo Mannini, Andrea Caneschi, Dante Gatteschi

The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. An ensemble of spins can produce a coherent signal at the frequency of a static magnetic field, known as spin noise, an effect due to the statistical polarization of small ensembles. The difficulty of these measurements is that the signal is extremely small, even

Limei Xu, Sergey V. Buldyrev, C. Austen Angell, H. Eugene Stanley

Using molecular dynamics simulations, we study a liquid model which consists of particles interacting via a spherically-symmetric two-scale Jagla ramp potential with both repulsive and attractive ramps. The Jagla potential displays anomalies similar to those found in liquid water, namely expansion upon cooling and an increase of diffusivity upon compression,

Thushari Jayasekera, Kieran Mullen, Michael A. Morrison

We discuss the theory of cooling electrons in solid-state devices via ``evaporative emission.&#39;&#39; Our model is based on filtering electron subbands in a quantum-wire device. When incident electrons in a higher-energy subband scatter out of the initial electron distribution, the system equilibrates to a different chemical potential and temperature than

A. B. Dzyubenko, D. A. Cosma, T. D. Kelly, A. R. Todd

We theoretically study localization of quasi-two-dimensional negatively charged excitons X^- on isolated charged donors in magnetic fields. We consider donors located in a barrier at various distances L from the heteroboundary as well as donors in the quantum well. We establish how many different singlet X_s^- and triplet X_t^- bound states a donor ion D^+ c

Paolo Visco

We explicitly determine the large deviation function of the energy flow of a Brownian particle coupled to two heat baths at different temperatures. This toy model, initially introduced by Derrida and Brunet [B. Derrida and E. Brunet, in &#34;Einstein aujourd&#39;hui&#34;, EDP Sciences, 2005], allows not only to sort out the influence of initial conditions on

Bahman Roostaei, Kieran Mullen

Periodic nanostructures can display the dynamics of arrays of atoms while enabling the tuning of interactions in ways not normally possible in Nature. We examine one dimensional arrays of a ``synthetic atom,&#39;&#39; a one dimensional ring with a nearest neighbor Coulomb interaction. We consider the classical limit first, finding that the singly charged rin

N. L. Abraham, M. I. J. Probert

A novel Genetic Algorithm is described that is suitable for determining the global minimum energy configurations of crystal structures and which can also be used as a polymorph search technique. This algorithm requires no prior assumptions about unit cell size, shape or symmetry, nor about the ionic configuration within the unit cell. This therefore enables

S. Wolfsheimer, C. Tanase, K. Shundyak, R. van Roij

We present a study of the isotropic-nematic interface in a system of hard spherocylinders. First we compare results from Monte Carlo simulations and Onsager density functional theory for the interfacial profiles of the orientational order parameter and the density. Those interfacial properties that are not affected by capillary waves are in good agreement, d

Martin Valldor

The Y_0.5Ca_0.5BaCo_4O_7 compound exhibits four magnetic anomalies at the temperatures 387, 281, 52, and 14 K; all anomalies show characteristics typical for spin freezing into disordered states: frequency dependent transition temperature in the AC magnetic susceptibility together with relaxation of thermoremnant magnetization. Y_0.5Ca_0.5BaCo_4O_7 is a semi

N. Boulant, G. Ithier, F. Nguyen, P. Bertet

Bloch oscillations predicted to occur in current-biased single Josephson junctions have eluded direct observation up to now. Here, we demonstrate similar Bloch oscillations in a slightly richer Josephson circuit, the quantronium. The quantronium is a Bloch transistor with two small junctions in series, defining an island, in parallel with a larger junction.

Lorenzo Malavasi, Maria Cristina Mozzati, Vladimir Pomjakushin, Cristina Tealdi

In this work we studied, by means of high-resolution neutron diffraction as a function of temperature, the La1.4Sr0.8Ca0.8Mn2O7 bilayered manganite for two different annealing treatments. Out data allowed us to shown, for the first time, the absence of long-range magnetic order in this optimally doped bilayered manganite where the A-site of the structure is

Marco Polin, David G. Grier, Yilong Han

Charge-stabilized colloidal spheres dispersed in deionized water are supposed to repel each other. Instead, artifact-corrected video microscopy measurements reveal an anomalous long-ranged like-charge attraction in the interparticle pair potential when the spheres are confined to a layer by even a single charged glass surface. These attractions can be masked

Robert A. Nyman, Gael Varoquaux, Fabien Lienhart, Damien Chambon

We present our the construction of an atom interferometer for inertial sensing in microgravity, as part of the I.C.E. (\textit{Interférométrie Cohérente pour l&#39;Espace}) collaboration. On-board laser systems have been developed based on fibre-optic components, which are insensitive to mechanical vibrations and acoustic noise, have sub-MHz linewidth, and r

E. Diaz, F. Dominguez-Adame, Yu. A. Kosevich, V. A. Malyshev

We study numerically the linear optical response of a quasiparticle moving on a one-dimensional disordered lattice in the presence of a linear bias. The random site potential is assumed to be long-range-correlated with a power-law spectral density $S(k) \sim 1/k^α$, $α> 0$. This type of correlations results in a phase of extended states at the band center, p

G. A. Baramidze, G. A. Kharadze

The orbitally isotropic Equal Spin Pairing (ESP) state has been proposed in Ref. [1] as a candidate of an A-like phase of superfluid $^3He$ in aerogel environment. In order to preserve an exact isotropy of the state in the presence of the magnetic field the condensate with equal values of the amplitudes $Δ_{\uparrow\uparrow}$ and $Δ_{\downarrow\downarrow}$ w

M. A. Yurishchev

The temperature dependence of the zero-field susceptibilities of 2D and 3D Ising lattices with anisotropic coupling is analyzed. Infinite 2D and 3D lattices are approximated, respectively, by ensembles of independent L x oo and L x L x oo chain clusters that are infinitely long in the strong-coupling (J) direction. This approach is used as a basis for a quan

S. M. Reimann, M. Koskinen, Y. Yu, M. Manninen

Finite quantal systems at high angular momenta may exhibit vortex formation and localization. These phenomena occur independent of the statistics of the repulsively interacting particles, which may be of bosonic or fermionic nature. We analyze the relation between vortex localization and formation of stable Wigner molecules at high angular momenta in the vie

A. O. Anokhin, A. V. Zarubin, V. Yu. Irkhin

The problem of motion of a single electron interacting with a periodic lattice of two-level systems is investigated within a spinless fermion model. The Green&#39;s function is calculated in a single-site dynamical coherent potential approximation which is equivalent to DMFT. The picture of one-electron density of states is obtained for various values of the

H. J. Xiang, Zhenyu Li, W. Z. Liang, Jinlong Yang

We have developed a linear scaling algorithm for calculating maximally-localized Wannier functions (MLWFs) using atomic orbital basis. An O(N) ground state calculation is carried out to get the density matrix (DM). Through a projection of the DM onto atomic orbitals and a subsequent O(N) orthogonalization, we obtain initial orthogonal localized orbitals. The

Chisa Hotta, Nobuo Furukawa

We propose a new type of charge liquid state in the spinless fermion system on a triangular lattice under strong inter-site Coulomb interactions, $V$. In the strong coupling limit ($t=0$), the ground state is classical and disordered due to geometrical frustration. The introduction of small t will drive the system to a partially ordered phase which we call a

A. Yamasaki, M. Feldbacher, Y. -F. Yang, O. K. Andersen

Calculations employing the local density approximation combined with static and dynamical mean-field theories (LDA+U and LDA+DMFT) indicate that the metal-insulator transition observed at 32 GPa in paramagnetic LaMnO3 at room temperature is not a Mott-Hubbard transition, but is caused by orbital splitting of the majority-spin eg bands. For LaMnO3 to be insul

Takahiro Murashima, Kiyohide Nomura

Commensurate-incommensurate change on the one-dimensional S=1 bilinear-biquadratic model (${\cal H}(α)=\sum_i \{{\bf S}_i\cdot {\bf S}_{i+1} +α({\bf S}_i\cdot{\bf S}_{i+1})^2\}$) is examined. The gapped Haldane phase has two subphases (the commensurate Haldane subphase and the incommensurate Haldane subphase) and the commensurate-incommensurate change point

Clemens J. Foerst, Jan Slycke, Krystyn J. Van Vliet, Sidney Yip

Point defect species and concentrations in metastable Fe-C alloys are determined using density functional theory and a constrained free-energy functional. Carbon interstitials dominate unless iron vacancies are in significant excess, whereas excess carbon causes greatly enhances vacancy concentration. Our predictions are amenable to experimental verification

Valentin S. Rychkov, Markus Buttiker

We investigate the current shot noise at a three terminal node in which one of the branches contains a noise generating source and the correlations are measured between the currents flowing through the other two branches. Interestingly, if the node is macroscopic, the current correlations are positive, whereas for a quantum coherent mesoscopic node anti-bunc

C. Goldenberg, A. P. F. Atman, P. Claudin, G. Combe

It is demonstrated, by numerical simulations of a 2D assembly of polydisperse disks, that there exists a range (plateau) of coarse graining scales for which the stress tensor field in a granular solid is nearly resolution independent, thereby enabling an `objective&#39; definition of this field. Expectedly, it is not the mere size of the the system but the (

Kazushi Mimura, Masato Okada

Statistical mechanics is applied to lossy compression using multilayer perceptrons for unbiased Boolean messages. We utilize a tree-like committee machine (committee tree) and tree-like parity machine (parity tree) whose transfer functions are monotonic. For compression using committee tree, a lower bound of achievable distortion becomes small as the number

A. Huebsch, K. W. Becker

A very rich phase diagram has recently been found in CeCu$_{2}$Si$_{2}$ from high pressure experiments where, in particular, a transition between an intermediate valence configuration and an integral valent heavy fermion state has been observed. We show that such a valence transition can be understood in the framework of the periodic Anderson model. In parti

A. Petric, C. L. Carilli, F. Bertoldi, A. Beelen

We present Very Large Array observations at 1.4 and 5 GHz of a sample of 16 quasi-stellar objects (QSOs) at z = 1.78 to 2.71. Half of the chosen quasars are bright at mm wavelengths (250 or 350 GHz) while the other half were not detected at mm wavelengths; the former QSOs were detected at 1.4 GHz, in most cases at high significance (S/N > ~7), but only three

M. Angela Osterman, H. Richard Miller, Amy M. Campbell, Kevin Marshall

PG 1553+11 was the target of a coordinated three week multiwavelength campaign during 2003 April and May. A significant X-ray flare was observed during the second half of this campaign. Although no optical flare was recorded during the X-ray campaign, optical observations obtained immediately prior to the campaign displayed a higher flux than that recorded d

W. J. Maciel, L. G. Lago, R. D. D. Costa

New results on the time variation of the radial abundance gradients in the galactic disk are presented on the basis of four different samples of planetary nebulae. These comprise both smaller, homogeneous sets of data, and larger but non-homogeneous samples. Four different chemical elements are considered, namely, O, S, Ar, and Ne. Other objects such as open

C. Firmani, G. Ghisellini, V. Avila-Reese, G. Ghirlanda

We report the discovery of a correlation among three prompt emission properties of GRBs. These are the isotropic peak luminosity L_iso, the peak energy of the time-integrated prompt emission spectrum E_pk, and the ``high signal&#34; timescale T_0.45, previously used to characterize the variability behavior of bursts. In the rest frame of the source the found

Pavel Kroupa

Star clusters are observed to form in a highly compact state and with low star-formation efficiencies. If the residual gas is expelled on a dynamical time the clusters disrupt thereby (i) feeding a hot kinematical stellar component into their host-galaxy&#39;s field population, and (ii) if the gas-evacuation time-scale depends on cluster mass, then a power-l

Christopher M. Hirata, Kris Sigurdson

The 21-cm hyperfine line of atomic hydrogen (HI) is a promising probe of the cosmic dark ages. In past treatments of 21-cm radiation it was assumed the hyperfine level populations of HI could be characterized by a velocity-independent ``spin temperature&#39;&#39; T_s determined by a competition between 21-cm radiative transitions, spin-changing collisions, a

David Merritt

Recent work on the dynamical evolution of galactic nuclei containing supermassive black holes is reviewed. Topics include galaxy structural properties; collisionless and collisional equilibria; loss-cone dynamics; and dynamics of binary and multiple supermassive black holes.

R. Coniglione, the NEMO Collaboration

Simulation results showing the comparison between the performance of different km3 detector geometries are reported. Effective neutrino areas and angular resolutions are reported for three different geometries based on NEMO-towers and strings. The results show that the NEMO-tower based detector has the best performance concerning both the effective area and

C. Distefano, the NEMO Collaboration

n this paper we present the results of Monte Carlo simulation studies on the capability of the proposed NEMO km3 telescope to detect high energy neutrinos. We calculated the detector sensitivity to muon neutrinos coming from a generic point-like source. We also simulated the lack of atmospheric muons in correspondence to the Moon disk in order to determine t

J. B. Milingo, K. B. Kwitter, R. B. C. Henry, S. P. Souza

Planetary Nebulae (PNe) abundance patterns have long been used to note signatures of nuclear processing and to trace the distribution of metals throughout galaxies. We present abundance gradients and heavy element ratios based upon newly acquired spectrophotometry of a sample of >120 Galactic PNe. This new data set is extracted from spectra that extend from

L. P. Bassino, T. Richtler, F. R. Faifer, J. C. Forte

We present the combined results of two investigations: a large-scale study of the globular cluster system (GCS) around NGC 1399, the central galaxy of the Fornax cluster, and a study of the GCSs around NGC 1374, NGC 1379 and NGC 1387, three low-luminosity early-type galaxies located close to the centre of the same cluster. In both cases, the data consist of

Robin Ciardullo

Planetary nebulae (PNe) have the potential to revolutionize our understanding of extragalactic stellar populations. Indeed, in many systems, bright PNe are the only individual objects identifiable from the ground, and, even more often, they are the only stars that are amenable to spectroscopy. We review the ways in which ensembles of PNe can be used to probe

A. Esquivel, R. A. Benjamin, A. Lazarian, J. Cho

We present models of turbulent mixing at the boundaries between hot (T~10^{6-7} K) and warm material (T~10^4 K) in the interstellar medium, using a three-dimensional magnetohydrodynamical code, with radiative cooling. The source of turbulence in our simulations is a Kelvin-Helmholtz instability, produced by shear between the two media. We found, that because

Alan P. Boss

While the recent microlensing discoveries of super-Earths orbiting two M dwarf stars have been taken as support for the core accretion mechanism of giant planet formation, we show here that these planets could also have been formed by the competing mechanism of disk instability, coupled with photoevaporative loss of their gaseous envelopes by a strong extern

Rodger I. Thompson, Daniel Eisenstein, Xiaohui Fan, Mark Dickinson

We use the NICMOS Treasury and ACS HUDF images to measure the extinction corrected star formation history for 4681 galaxies in the region common to both images utilizing the star formation rate distribution function and other techniques similar to those employed with the NICMOS and WFPC2 images in the HDFN. Unlike the HDFN the NICMOS region of the HUDF appea

N. C. Sterling, Harriet L. Dinerstein

We present preliminary results from a large-scale survey of the neutron(n)-capture elements Se and Kr in Galactic planetary nebulae (PNe). These elements may be produced in PN progenitors by s-process nucleosynthesis, and brought to the stellar envelope by third dredge-up (TDU). We have searched for [Kr III] 2.199 and [Se IV] 2.287 $μ$m in 120 PNe, and detec

Aaron J. Romanowsky

I present various projects to study the halo dynamics of elliptical galaxies. This allows one to study the outer mass and orbital distributions of ellipticals in different environments, and the inner distributions of groups and clusters themselves.

M. Spite, R. Cayrel, V. Hill, F. Spite

Extremely metal-poor (EMP) stars preserve a fossil record of the composition of the ISM when the Galaxy formed. It is crucial, however, to verify whether internal mixing has modified their surface. We aim to understand the CNO abundance variations found in some, but not all EMP field giants analysed earlier. Mixing beyond the first dredge-up of standard mode

R. Iaria, T. Di Salvo, G. Lavagetto, N. R. Robba

We present the results of a 50 ks long Chandra observation of the dipping source XB 1916-053. During the observation two X-ray bursts occurred and the dips were not present at each orbital period. From the zero-order image we estimate the precise X-ray coordinates of the source with a 90% uncertainty of 0.6&#39;&#39;. In this work we focus on the spectral st

Seppo Mikkola, David Merritt

Algorithmic regularization uses a transformation of the equations of motion such that the leapfrog algorithm produces exact trajectories for two-body motion as well as regular results in numerical integration of the motion of strongly interacting few-body systems. That algorithm alone is not sufficiently accurate and one must use the extrapolation method for

M. Aldenius, S. Johansson, M. T. Murphy

The most precise method of investigating possible space-time variations of the fine-structure constant, using high-redshift quasar absorption lines, is the many-multiplet (MM) method. For reliable results this method requires very accurate relative laboratory wavelengths for a number of UV resonance transitions from several different ionic species. For this

S. Migliari, J. A. Tomsick, T. J. Maccarone, E. Gallo

Spitzer observations of the neutron star (ultra-compact) X-ray binary (XRB) 4U 0614+091 with the Infrared Array Camera reveal emission of non-thermal origin in the range 3.5-8 um. The mid-infrared spectrum is well fit by a power law with spectral index of alpha=-0.57+/-0.04 (where the flux density is F_nu \propto nu^(alpha)). Given the ultra-compact nature o

Hiroyasu Tajima, for GLAST Tracker Team

The Large Area Telescope (LAT) on board the Gamma-ray Large-Area Space Telescope (GLAST) is a pair-conversion gamma-ray detector designed to explore the gamma-ray universe in the 20 MeV-300 GeV energy band. The Tracker subsystem of the LAT will perform tracking of electron and positrons to determine the origin of the gamma-ray. The design and performance of

David Pooley, Saul Rappaport

The globular cluster G1 (Mayall II) in M31 is the most massive (~10^7 M_sun) stellar cluster in the Local Group, and it has the highest central velocity dispersion (~28 km/s). It has been claimed to host a central ~20,000 M_sun black hole, but these claims have been controversial. We report here the XMM-Newton detection of X-ray emission from G1 at a level o

David Pooley, Piet Hut

We answer the long-standing question of which production mechanism is responsible for the cataclysmic variables (CVs) in globular clusters. Arguments have been given that range from mostly primordial presence to a significant contribution of later dynamical formation in close stellar encounters. We conclude, based on a thorough analysis of a homogeneous {\it

Steven R. Warren, Eric L. Sandquist, Michael Bolte

We have surveyed the blue straggler star population of the Galactic globular cluster M5 using high-resolution images of the core along with wide-field ground-based images reaching to more than 19 core radii. To gauge M5&#39;s relative efficiency of producing stragglers, we compared our sample to five studies of other globular clusters (mainly Ferraro et al.

Maria Emilia De Rossi, Patricia Beatriz Tissera, Cecilia Scannapieco

In this work, we study the Luminosity-Metallicity relation (LMR) and the Stellar Mass -Metallicity relation (MMR) of galactic systems in a hierarhical clustering scenario. We performed numerical hydrodynamical simulations with the chemical GADGET-2 of Scannapieco et al.(2005) in a LCDM universe. We found that our simulated galactic systems reproduce the obse

Eyal Neistein, Frank C. van den Bosch, Avishai Dekel

Stellar-population analyses of today&#39;s galaxies show &#34;downsizing&#34;, where the stars in more massive galaxies tend to have formed earlier and over a shorter time span. We show that this phenomenon is not necessarily &#34;anti-hierarchical&#34; but rather has its natural roots in the bottom-up clustering process of dark-matter haloes. While the main

Alejandro Corichi, Jacobo Diaz-Polo, Enrique Fernandez-Borja

Quantum black holes within the loop quantum gravity (LQG) framework are considered. The number of microscopic states that are consistent with a black hole of a given horizon area $A_0$ are counted and the statistical entropy, as a function of the area, is obtained for $A_0$ up to $550 l^2_{\rm Pl}$. The results are consistent with an asymptotic linear relati

Ruoheng Liu, Ivana Maric, Roy D. Yates, Predrag Spasojevic

A multiple-access channel is considered in which messages from one encoder are confidential. Confidential messages are to be transmitted with perfect secrecy, as measured by equivocation at the other encoder. The upper bounds and the achievable rates for this communication situation are determined.

Abhay Ashtekar

After a brief introduction, basic ideas of the quantum Riemannian geometry underlying loop quantum gravity are summarized. To illustrate physical ramifications of quantum geometry, the framework is then applied to homogeneous isotropic cosmology. Quantum geometry effects are shown to replace the big bang by a big bounce. Thus, quantum physics does not stop a

Vlad Elgart, Alex Kamenev

Equilibrium phase transitions are associated with rearrangements of minima of a (Lagrangian) potential. Treatment of non-equilibrium systems requires doubling of degrees of freedom, which may be often interpreted as a transition from the ``coordinate&#39;&#39; to the ``phase&#39;&#39; space representation. As a result, one has to deal with the Hamiltonian fo

Karen B. Kwitter, Richard B. C. Henry

We present the Gallery of Planetary Nebula Spectra now available at http://oit.williams.edu/nebulae The website offers high-quality, moderate resolution (~7-10 A FWHM) spectra of 128 Galactic planetary nebulae from 3600-9600 A, obtained by Kwitter, Henry, and colleagues with the Goldcam spectrograph at the KPNO 2.1-m or with the RC spectrograph at the CTIO 1