February 2006 arXiv papers — page 2

Jason Michael Starr

This short, expository note proves the existence of the maximal quotient of a variety by free rational curves.

Jason Michael Starr

Mondromy and deformation-and-specialization arguments are used to produce a pencil of Enriques surfaces with no section and index one. The same technique completes the proof that the witness curves in "Rational connectivity ..." depend on the relative dimension.

Claus Gerhardt

We consider the problem $F=f(ν)$ for strictly convex, closed hypersurfaces in hyperbolic space and solve it for curvature functions $F$ the inverses of which are of class $(K^*)$.

J. Szabados

This is a survey on discrete linear operators which, besides approximating in Jackson or near-best order, possess some interpolatory property at some nodes. Such operators can be useful in numerical analysis.

R. Balasubramanian, Gautami Bhowmik

We prove that for all but a certain number of abelian groups of order n its Davenport constant is atmost n/k+k-1 for k=1,2,..,7. For groups of order three we improve on the existing bound involving the Alon-Dubiner constant.

Friedrich Wehrung

For a distributive join-semilattice S with zero, a S-valued poset measure on a poset P is a map m:PxP->S such that m(x,z) <= m(x,y)vm(y,z), and x <= y implies that m(x,y)=0, for all x,y,z in P. In relation with congruence lattice representation problems, we consider the problem whether such a measure can be extended to a poset measure m*:P*xP*->S, for a larg

P. W. Ng

The corona factorization property is a property with connections to extension theory, K-theory and the structure of C*algebras. This paper is a short survey of the subject, together with some new results and open questions.

Thomas Fleming, Blake Mellor

Chord diagrams on circles and their intersection graphs (also known as circle graphs) have been intensively studied, and have many applications to the study of knots and knot invariants, among others. However, chord diagrams on more general graphs have not been studied, and are potentially equally valuable in the study of spatial graphs. We will define chord

Janko Gravner, David Griffeath

We consider discrete-time random perturbations of monotone cellular automata (CA) in two dimensions. Under general conditions, we prove the existence of half-space velocities, and then establish the validity of the Wulff construction for asymptotic shapes arising from finite initial seeds. Such a shape converges to the polygonal invariant shape of the corres

Yue He

In this paper, we study the well-posedness of boundary value problems for a special class of degenerate elliptic equations coming from geometry. Such problems is intimately tied to rigidity problem arising in infinitesimal isometric deformation, The characteristic form of this class of equations is changing its signs in the domain. Therefore the well-posedne

Margherita Barile

We describe a class of toric varieties in the $N$-dimensional affine space which are minimally defined by no less than $N-2$ binomial equations.

Sam Evens, Jiang-Hua Lu

When ${\frak g}$ is a complex semisimple Lie algebra, we study the variety ${\mathcal L}$ of subalgebras of ${\frak g}\oplus{\frak g}$ that are maximally isotropic with respect to $K_1 - K_2$, where $K_i$ is the Killing form on the ith factor. We show the irreducible components of ${\mathcal L}$ are smooth, classify them in terms of the generalized Belavin-D

Joshua N. Cooper

We introduce a permutation analogue of the celebrated Szemeredi Regularity Lemma, and derive a number of consequences. This tool allows us to provide a structural description of permutations which avoid a specified pattern, a result that permutations which scatter small intervals contain all possible patterns of a given size, a proof that every permutation a

Joshua N. Cooper

Previously, the author introduced quasirandom permutations, permutations of $\mathbb{Z}_n$ which map intervals to sets with low discrepancy. Here we show that several natural number-theoretic permutations are quasirandom, some very strongly so. Quasirandomness is established via discrete Fourier analysis and the Erdos-Turan inequality, as well as by other me

Joshua N. Cooper

We ask, for which $n$ does there exists a $k$, $1 \leq k < n$ and $(k,n)=1$, so that $k/n$ has a continued fraction whose partial quotients are bounded in average by a constant $B$? This question is intimately connected with several other well-known problems, and we provide a lower bound in the case of B=2.

Marco M. Caldarelli

We review the issue of chronology protection and show how string theory can solve it in the half BPS sector of AdS/CFT. According to the LLM prescription, half BPS excitations of AdS_5 x S^5 geometries in type IIB string theory can be mapped into free fermion configurations. We show that unitarity of the theory describing these fermions is intimately related

R. E. Browne, D. Dudal, J. A. Gracey, V. E. R. Lemes

We review the current status of the application of the local composite operator technique to the condensation of dimension two operators in quantum chromodynamics (QCD). We pay particular attention to the renormalization group aspects of the formalism and the renormalization of QCD in various gauges.

J. Arnlind, M. Bordemann, L. Hofer, J. Hoppe

We introduce C-Algebras (quantum analogues of compact Riemann surfaces), defined by polynomial relations in non-commutative variables and containing a real parameter that, when taken to zero, provides a classical non-linear, Poisson-bracket, obtainable from a single polynomial C(onstraint) function. For a continuous class of quartic constraints, we explicitl

Branko Dragovich, Zoran Rakic

Classical and quantum mechanics for an extended Heisenberg algebra with canonical commutation relations for position and momentum coordinates are considered. In this approach additional noncommutativity is removed from the algebra by linear transformation of phase space coordinates and transmitted to the Hamiltonian (Lagrangian). This transformation does not

Umida Khodjaeva

The simple examples of spontaneous breaking of various symmetries for the scalar theory with fundamental mass have been considered. Higgs generalizations on &#34;fundamental mass&#34; were introduced into the theory on a basis of the five-dimensional de Sitter space.

J. L. F. Barbon, C. Hoyos

We consider one-loop effective potentials for adjoint Higgs fields that originate from flat holonomies in toroidal compactification of gauge theories. We show that such potentials are &#34;landscape-like&#34; for large gauge groups and generic non-supersymmetric matter representations. In particular, there is a large number of vacua with similar local proper

L. Ludovici, K. S. McFarland, M. Shiozawa, G. P. Zeller

We summarize the discussion and presentation of new experimental results in low energy neutrino scattering at the NuInt05 workshop. In addition, we comment on several investigations that should be targeted in preparation for the next NuInt workshop.

G. P. Zeller

This paper summarizes new experimental results in low energy neutrino cross sections as presented in the neutrino scattering working group at the NuFact05 workshop. Several questions and directives for future NuFact workshops are also outlined.

Agustin Sabio Vera

Azimuthal angle decorrelation in inclusive dijet cross sections is studied analytically to take into account the next-to-leading corrections to the BFKL kernel while keeping the jet vertices at leading order. The spectral representation on the basis of leading order eigenfunctions is generalized to include the dependence on conformal spins. With this procedu

Eef van Beveren

Recoupling matrix elements are evaluated, in the harmonic oscillator approximation, for all possible angular and radial excitations in processes where quarks recombine. A diagrammatic representation is given. Their use is demonstrated in calculating the transition potential for rho to two pions in a pair creation model.

Eef van Beveren

Within the independent-harmonic-oscillator model for quarks inside a hadron, a rigorous method is presented for the calculation of coupling constants and transition potentials for hadronic decay, as needed in a multi-channel description of mesons.

Helmut Satz

We discuss the spectral analysis of quarkonium states in a hot medium of deconfined quarks and gluons, and we show that such an analysis provides a way to determine the thermal properties of the quark-gluon plasma.

Xiangdong Ji, Jian-Wei Qiu, Werner Vogelsang, Feng Yuan

Using Drell-Yan pair production as an example, we explore the relation between two well-known mechanisms for single transverse-spin asymmetries in hard processes: twist-three quark-gluon correlations when the pair&#39;s transverse momentum is large, $q_\perp \gg Λ_{\rm QCD}$, and time-reversal-odd and transverse-momentum-dependent parton distributions when $

A. Cordero-Cid, J. L. Garcia-Luna, F. Ramirez-Zavaleta, G. Tavares-Velasco

A complete calculation of the rare three-body decay t --> c h gamma is presented in the framework of the standard model. In the unitary gauge, such a calculation involves about 20 Feynman diagrams. We also calculate this decay in the general two-Higgs doublet model (model III), in which it arises at the tree-level. While in the standard model the decay t -->

B. Alles, M. D&#39;Elia

We review the method developed in Pisa to determine the topological susceptibility in lattice QCD and present a collection of new and old results obtained by the method.

Shailesh Chandrasekharan, Fu-Jiun Jiang

We study thermodynamics of strongly coupled lattice QCD with two colors of massless staggered fermions as a function of the baryon chemical potential $μ$ in 3+1 dimensions using a new cluster algorithm. We find evidence that the model undergoes a weak first order phase transition at $μ=0$ which becomes second order at a finite $μ$. Symmetry considerations su

M. O. Wascko

MiniBooNE began running in antineutrino mode on 19 January, 2006. We describe the sensitivity of MiniBooNE to LSND-like nuebar oscillations and outline a program of antineutrino cross-section measurements necessary for the next generation of neutrino oscillation experiments. We describe three independent methods of constraining wrong-sign (neutrino) backgrou

M. O. Wascko

We present MiniBooNE&#39;s preliminary numu charged-current single pion (CC1pi) cross section measurement, calculated using the ratio to charge current quasi-elastic (CCQE) events. We find the inclusive CC1pi cross section to be below the predcition of the NUANCE and NEUGEN Monte Carlos.

Christian Schwanenberger

In this report a new search for a narrow-width heavy resonance decaying into top quark pairs (X -> ttbar) in ppbar collisions at sqrt(s)=1.96 TeV has been performed using data collected by the D0 detector at the Fermilab Tevatron collider. The analysis considers ttbar candidate events in the lepton+jets channel using a lifetime tag to identify b-jets and the

G. A. Benesh, Anzhong Wang

All homothetic self-similar solutions of the Brans-Dicke scalar field in three-dimensional spacetime with circular symmetry are found in closed form.

Jorge Pullin

GGR News: GGR program at the APS April meeting in Dallas We hear that..., 100 years ago, by Jorge Pullin Research Briefs: What&#39;s new in LIGO, by David Shoemaker LISA Pathfinder, by Paul McNamara Recent progress in binary black hole simulations, by Thomas Baumgarte Conference reports: Workshop on Emergence of Spacetime, by Olaf Dreyer Quantum gravity subp

Federico Mattei, Carlo Rovelli, Simone Speziale, Massimo Testa

In various background independent approaches, quantum gravity is defined in terms of a field propagation kernel: a sum over paths interpreted as a transition amplitude between 3-geometries, expected to project quantum states of the geometry on the solutions of the Wheeler-DeWitt equation. We study the relation between this formalism and conventional quantum

Qi Cheng

Let $k$ and $n$ be positive integers, $n>k$. Define $r(n,k)$ to be the minimum positive value of $$ |\sqrt{a_1} + ... + \sqrt{a_k} - \sqrt{b_1} - >... -\sqrt{b_k} | $$ where $ a_1, a_2, ..., a_k, b_1, b_2, ..., b_k $ are positive integers no larger than $n$. It is an important problem in computational geometry to determine a good upper bound of $-\log r(n,k)

H. Ibrahim, M. H. van Emden

Functional programming comes in two flavours: one where ``functions are first-class citizens&#39;&#39; (we call this applicative) and one which is based on equations (we call this declarative). In relational programming clauses play the role of equations. Hence Prolog is declarative. The purpose of this paper is to provide in relational programming a mathema

Israel Klich, Gil Refael, Alessandro Silva

We explore the relation between entanglement entropy of quantum many body systems and the distribution of corresponding, properly selected, observables. Such a relation is necessary to actually measure the entanglement entropy. We show that in general, the Shannon entropy of the probability distribution of certain symmetry observables gives a lower bound to

Peter B. Weichman

An experiment is proposed to test a previously developed theory of the hydrodynamics of a nonequilibrium heat current-induced superfluid-normal interface. It is shown that the interfacial ``trapped&#39;&#39; second sound mode predicted by the theory leads to a sharp resonant dip in the reflected signal from an external second sound pulse propagated towards t

Anton Knigavko, J. P. Carbotte

The concepts, which have traditionally been useful in understanding the effects of the electron--phonon interaction in optical spectroscopy, are based on insights obtained within the infinite electronic band approximation and no longer apply in finite band metals. Impurity and phonon contributions to electron scattering are not additive and the apparent stre

Jian-Ge Zhou, Frank Hagelberg, Chuanyun Xiao

The geometric, electronic, energetic, and dynamic properties of 1-propanol adsorbed on the Si(001)-2x1 surface are studied from first principles by use of a slab approach. The 1-propanol molecule initially interacts with the Si surface through formation of a dative bond, subsequently the physisorbed 1-propanol molecule reacts with the surface by cleavage of

Massimiliano Esposito, Shaul Mukamel

A quantum fluctuation theorem for a driven quantum subsystem interacting with its environment is derived based solely on the assumption that its reduced density matrix obeys a closed evolution equation i.e. a quantum master equation (QME). Quantum trajectories and their associated entropy, heat and work appear naturally by transforming the QME to a time depe

D. V. Zakharov, J. Deisenhofer, H. -A. Krug von Nidda, P. Lunkenheimer

We present detailed ESR investigations on single crystals of the low-dimensional quantum magnet TiOCl. The anisotropy of the g-factor indicates a stable orbital configuration below room temperature, and allows to estimate the energy of the first excited state as 0.3(1) eV ruling out a possible degeneracy of the orbital ground state. Moreover, we discuss the

V. L. Gurtovoi, S. V. Dubonos, A. V. Nikulov, N. N. Osipov

The current-voltage curves and magnetic dependence of the critical current of asymmetric superconducting loops are measured. It was found that sign and value of the asymmetry of the current-voltage curves changes with value of magnetic field, periodically for single loop and system of identical loops. The obtained results allow to explain the quantum oscilla

S. Bravina, N. Morozovsky, R. Boukroub

The results of the investigation of changes of parameters of dynamic bipolar charge-voltage and bipolar and unipolar dynamic current-voltage characteristics and transient currents connected with the pulse change of humidity for the samples of por-Si are presented. The view of high voltage current-voltage curves is characteristic for poling processes in the s

Vassilios Yannopapas

We study the blackbody spectrum from slabs of three-dimensional metallodielectric photonic crystals consisting of gold nanoparticles using an ab initio multiple-scattering method. The spectra are calculated for different photonic-crystal slab thicknesses, particle radii and hosting materials. We find in particular that such crystals exhibit a broadband emiss

F. Castellano, R. C. Iotti, F. Rossi

We present modeling and simulation of prototypical multi bound state quantum well infrared photodetectors and show that such a detection design may overcome the problems arising when the operation frequency is pushed down into the far infrared spectral region. In particular, after a simplified analysis on a parabolic-potential design, we propose a fully thre

Charles Simon, Alain Pautrat, Christophe Goupil, Joseph Scola

The existence of a peak effect in transport properties (a maximum of the critical current as function of magnetic field) is a well-known but still intriguing feature of type II superconductors such as NbSe2 and Bi-2212. Using a model of pinning by surface irregularities in anisotropic superconductors, we have developed a calculation of the critical current w

Kedar Damle, T. Senthil

We study S=1 kagome antiferromagnets with isotropic Heisenberg exchange $J$ and strong easy axis single-ion anisotropy $D$. For $D \gg J$, the low-energy physics can be described by an effective $S=1/2$ $XXZ$ model with antiferromagnetic $J_z \sim J$ and ferromagnetic $J_\perp \sim J^2/D$. Exploiting this connection, we argue that non-trivial ordering into a

Luca Salasnich

We study a dilute gas of attractive bosons confined in a harmonic cylinder, i.e. under cylindric confinement due to a transverse harmonic potential. We introduce a many-body wave function which extends the Bethe ansatz proposed by McGuire (J. Math. Phys. {\bf 5}, 622 (1964)) by including a variational transverse Gaussian shape. We investigate the ground stat

Damien Saurel, Annie Brulet, Andre Heinemann, Christine Martin

Transport properties of manganese oxides suggest that their colossal magnetoresistance (CMR) is due to percolation between ferromagnetic metallic (FM) clusters in an antiferromagnetic insulating (AFI) matrix. We have studied small-angle neutron scattering under applied magnetic field in CMR Pr1-xCaxMnO3 crystals for x around 0.33. Quantitative analysis of th

Ounsi El Daïf, Augustin Baas, Thierry Guillet, Jean-Philippe Brantut

We report on the realization of polariton quantum boxes in a semiconductor microcavity under strong coupling regime. The quantum boxes consist of mesas that confine the cavity photon, etched on top of the spacer of a microcavity. For mesas with sizes of the order of a few micron in width and nm in depth, we observe quantization, caused by the lateral confine

G. Parisi, F. Zamponi

We discuss the high density behavior of a system of hard spheres of diameter d on the hypercubic lattice of dimension n, in the limit n -> oo, d -> oo, d/n=delta. The problem is relevant for coding theory. We find a solution to the equations describing the liquid up to very large values of the density, but we show that this solution gives a negative entropy

A. Saichev, D. Sornette

We find that multifractal scaling is a robust property of a large class of continuous stochastic processes, constructed as exponentials of long-memory processes. The long memory is characterized by a power law kernel with tail exponent $ϕ+1/2$, where $ϕ>0$. This generalizes previous studies performed only with $ϕ=0$ (with a truncation at an integral scale),

Cun-Xi Zhang, Y. -H. Nie, J. -Q. Liang

Using the effective-mass approximation and Floquet theory, we study the electron transmission over a quantum well in semiconductor heterostructures with Dresselhaus spin-orbit coupling and an applied oscillation field. It is demonstrated by the numerical evaluations that Dresselhaus spin-orbit coupling eliminates the spin degeneracy and leads to the splittin

V. L. Gurtovoi, S. V. Dubonos, R. V. Kholin, A. V. Nikulov

The quantum rectification effect observed on asymmetric superconducting loops is proposed to use as a basic of a noise detector with maximum sensitivity. The measurements show that a critical amplitude of noise or ac current decreases down to zero near superconducting transition, Tc, just as superconducting critical current. Therefore any how weak noise, rig

Daniel Ruhl, Florian Gebhard

We use Brueckner-Goldstone perturbation theory to calculate the ground-state energy of the half-filled Hubbard model in infinite dimensions up to fourth order in the Hubbard interaction. We obtain the momentum distribution as a functional derivative of the ground-state energy with respect to the bare dispersion relation. The resulting expressions agree with

A. M. M. Pruisken, I. S. Burmistrov, R. Shankar

We study the instanton vacuum of the $CP^{N-1}$ model with large values of $N$ in 1+1 space-time dimensions. Unlike the longstanding claims which state that the theory always has a mass gap, we for the first time establish a complete {\em critical} theory for the transition at $θ= π$ obtained from a mapping onto the low temperature phase of the 1D Ising mode

J. P. Rodriguez, M. P. Maley

The critical current density shown by a superconductor at the extreme type-II limit is predicted to follow an inverse square-root power law with external magnetic field if the vortex lattice is weakly pinned by material line defects. It acquires an additional inverse dependence with thickness along the line direction once pinning of the interstitial vortex l

I. S. Burmistrov

We present the renormalization group analysis for the problem of a spin-S impurity in nearly ferromagnetic Fermi liquid. We evaluate the renormalization group function that governs the temperature behavior of the invariant charge to the second order of both weak and strong coupling expansions. It allows us to determine behavior of the zero field magnetic sus

Y. Zhang, Z. Jiang, J. P. Small, M. S. Purewal

The quantum Hall (QH) effect in two-dimensional (2D) electrons and holes in high quality graphene samples is studied in strong magnetic fields up to 45 T. QH plateaus at filling factors $ν=0,\pm 1,\pm 4$ are discovered at magnetic fields $B>$20 T, indicating the lifting of the four-fold degeneracy of the previously observed QH states at $ν=\pm(|n|+1/2)$, whe

P. Jiang, I. Yang, W. Kang, L. N. Pfeiffer

Tunneling characteristics of a two-dimensional lateral tunnel junction (2DLTJ) are reported. A pseudogap on the order of Coulomb energy is detected in the tunneling density of states (TDOS) when two identical two-dimensional electron systems are laterally separated by a thin energy barrier. The Coulombic pseudogap remains robust well into the quantum Hall re

Ken-ichi Sasaki, Shuichi Murakami, Riichiro Saito

By considering the continuous model for graphene, we analytically study a special gauge field for the edge state. The gauge field explains the properties of the edge state such as the existence only on the zigzag edge, the partial appearance in the $k$-space, and the energy position around the Fermi energy. It is demonstrated utilizing the gauge field that t

O. Bakharev, D. Bono, H. B. Brom, A. Schnepf

Compelling evidence for band-type conductivity and even bulk superconductivity below $T\_{\text{c}}\approx 8$ K has been found in $^{69,71}$Ga-NMR experiments in crystalline ordered, giant Ga$\_{84}$ cluster-compounds. This material appears to represent the first realization of a theoretical model proposed by Friedel in 1992 for superconductivity in ordered

Franco Bagnoli, Duccio Fanelli, Luca Sguanci

The interaction between a fluid and a granular material plays a crucial role in a large class of phenomena such as landscape morphology and transport of sediments, aeolian sand dunes formation and ripples dynamics. Standard models involve deterministic continuum equations or, alternatively, Lattice Boltzmann and Lattice Gas Cellular Automata. We here introdu

Bas Zoetekouw, Rene van Roij

We present a study of thermodynamic properties of suspensions of charged colloids on the basis of linear Poisson-Boltzmann theory. We calculate the effective Hamiltonian of the colloids by integrating out the ionic degrees of freedom grand-canonically. This procedure not only yields the well-known pairwise screened-Coulomb interaction between the colloids, b

M. Mariantoni, M. J. Storcz, F. K. Wilhelm, W. D. Oliver

We propose a method to couple metastable flux-based qubits to superconductive resonators based on a quantum-optical Raman excitation scheme that allows for the deterministic generation of stationary and propagating microwave Fock states and other weak quantum fields. Moreover, we introduce a suitable microwave quantum homodyne technique, with no optical coun

Teemu Hynninen, Hannes Raebiger, Andres Ayuela, J. von Boehm

The effect of microscopic Mn cluster distribution on the Curie temperature (Tc) is studied using density-functional calculations. We find that the calculated Tc depends crucially on the microscopic cluster distribution, which can explain the abnormally large variations in experimental Tc values from a few K to well above room temperature. The partially dimer

Flavio S. Nogueira, Hagen Kleinert

We show that roton-like excitations are thermally induced in a two-dimensional dilute Bose gas as a consequence of the strong phase fluctuations in two dimensions. At low momentum, the roton-like excitations lead for small enough temperatures to an anomalous phonon spectrum with a temperature dependent exponent reminiscent of the Kosterlitz-Thouless transiti

Michael Endl, William D. Cochran, Robert A. Wittenmyer, Artie P. Hatzes

We present the precise radial velocity (RV) data for the metal-rich star HD 45350 collected with the Harlan J. Smith (HJS) 2.7 m telescope and the Hobby-Eberly Telescope (HET) at McDonald Observatory. This star was noticed by us as a candidate for having a giant planetary companion in a highly eccentric orbit, but the lack of data close to periastron left th

Peter A. Milne

The SPI instrument on-board the ESA/INTEGRAL satellite is engaged in a mission-long study of positron annihilation radiation from the Galaxy. Early results suggest that the disk component is only weakly detected at 511 keV by SPI. We review CGRO/OSSE, TGRS and SMM studies of 511 keV line and positronium continuum emission from the Galaxy in light of the earl

Francis T. O&#39;Donovan, David Charbonneau, Guillermo Torres, Georgi Mandushev

Ground-based wide-field surveys for nearby transiting gas giants are yielding far fewer true planets than astrophysical false positives, of which some are difficult to reject. Recent experience has highlighted the need for careful analysis to eliminate astronomical systems where light from a faint eclipsing binary is blended with that from a bright star. Dur

G. Duchene, E. Delgado-Donate, K. Haisch, L. Loinard

It has now been known for over a decade that low-mass stars located in star-forming regions are very frequently members of binary and multiple systems, even more so than main sequence stars in the solar neighborhood. This high multiplicity rate has been interpreted as the consequence of the fragmentation of small molecular cores into a few seed objects that

W. H. T. Vlemmings, P. J. Diamond, H. Imai

Planetary nebulae often have asymmetric shapes, which could arise due to collimated jets from evolved stars before evolution to the planetary nebula phase. The source of jet collimation in these stars is unknown. Magnetic fields are thought to collimate outflows that are observed in many other astrophysical sources, such as active galactic nuclei and proto-s

C. del Burgo, L. Cambresy

We present ISOPHOT observations between 60 and 200 microns and a near-infrared extinction map of LDN 1780. We have used the ISOPHOT data together with the 25, 60 and 100 microns IRIS maps to disentangle the warm and cold components of large dust grains that are observed in translucent and dense clouds. The warm and cold components in LDN 1780 have different

H. M. Antia, Sarbani Basu

The recent downward revision of solar photospheric abundances of Oxygen and other heavy elements has resulted in serious discrepancies between solar models and solar structure as determined through helioseismology. In this work we investigate the possibility of determining the solar heavy-element abundance without reference to spectroscopy by using helioseis

S. Fornasier, I. Belskaya, M. Fulchignoni, M. A. Barucci

We present the first albedo determination of 2867 Steins, the asteroid target o f the Rosetta space mission together with 21 Lutetia. The data were obtained in polarimetric mode at the ESO-VLT telescope with the FORS1 instrument in the V and R filters. Observations were carried out from Jun e to August 2005 covering the phase angle range from 10.3 deg. to 28

Marta Volonteri

Supermassive black holes (SMBHs) are nowadays believed to reside in most local galaxies, and the available data show an empirical correlation between bulge luminosity - or stellar velocity dispersion - and black hole mass, suggesting a single mechanism for assembling black holes and forming spheroids in galaxy halos. The evidence is therefore in favour of a

Thierry Sousbie, Christophe Pichon, Hélène Courtois, Stéphane Colombi

The length of the three-dimensional filaments observed in the fourth public data-release of the SDSS is measured using the {\em local skeleton} method. It consists in defining the set of points where the gradient of the smoothed density field is extremal along its isocontours, with some additional constraints on local curvature to probe actual ridges in the

Juan R. Cortes, Jeffrey D. P. Kenney, Eduardo Hardy

We present the results of the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies. The stellar velocity field are mostly consistent with a rotation pattern, but some of them shows interesting features such as; S-shaped stellar isovelocity contours in NGC 4064, and signatures of kinematical distinct components in NGC 4429, and NGC

William J. Henney

This review covers the dynamic processes that are important in the evolution and structure of galactic HII regions, concentrating on an elementary presentation of the physical concepts and recent numerical simulations of HII region evolution in a non-uniform medium. The contents are as follows: (1) The equations (Euler equations; Radiative transfer; Rate equ

P. G. Jonker, C. G. Bassa, G. Nelemans, A. M. Juett

In this Paper we report on our analysis of a ~25 ksec. Chandra X-ray observation of the neutron star soft X-ray transient (SXT) 1H1905+000 in quiescence. Furthermore, we discuss our findings of the analysis of optical photometric observations which we obtained using the Magellan telescope and photometric and spectroscopic observations which we obtained using

Josefa Perez, Patricia B. Tissera, Diego G. Lambas, Cecilia Scannapieco

We carry out a statistical analysis of galaxy pairs selected from chemical hydrodynamical simulations with the aim at assessing the capability of hierarchical scenarios to reproduce recent observational results for galaxies in pairs. Particularly, we analyse the effects of mergers and interactions on the star formation (SF) activity, the global mean chemical

N. Mauron, P. J. Huggins

We report the results of an exploratory program to image the extended circumstellar envelopes of asymptotic giant branch (AGB) stars in dust-scattered galactic light. The goal is to characterize the morphology of the envelopes as a probe of the mass-loss process. The observations consist of short exposures with the VLT and longer exposures with 1-2m telescop

G. B. Taylor, N. E. Gugliucci, A. C. Fabian, J. S. Sanders

We present Very Long Baseline Array (VLBA) observations of the nucleus of NGC 1275, the central, dominant galaxy in the Perseus cluster of galaxies. These are the first observations to resolve the linearly polarized emission from 3C84, and from them we determine a Faraday rotation measure (RM) ranging from 6500 to 7500 rad/m^2 across the tip of the bright so

P. Serra, S. C. Trager, J. M. van der Hulst, T. A. Oosterloo

We present the result of radio and optical observations of the S0 galaxy IC 4200. We find that the galaxy hosts 8.5 billion solar masses of HI rotating on a ~90 deg warped disk extended out to 60 kpc from the centre of the galaxy. Optical spectroscopy reveals a simple-stellar-population-equivalent age of 1.5 Gyr in the centre of the galaxy and V- and R-band

Natasa Gavrilovic

Here we determine the projected rotational velocity of 10 Be stars using Fourier Transform Method. Also, we discuss the gravity darkening and extend of deviation from solid body rotation for our sample of stars. We found that 7 of considered stars are affected by strong gravity darkening or/and solar differential rotation.

C. P. Dullemond, D. Hollenbach, I. Kamp, P. D&#39;Alessio

We review advances in the modeling of protoplanetary disks. This review will focus on the regions of the disk beyond the dust sublimation radius, i.e. beyond 0.1 - 1 AU, depending on the stellar luminosity. We will be mostly concerned with models that aim to fit spectra of the dust continuum or gas lines, and derive physical parameters from these fits. For o

A. Natta, L. Testi, S. Randich

The aim of this paper is to provide a measurement of the mass accretion rate in a large, complete sample of objects in the core of the star forming region Rho-Oph. The sample includes most of the objects (104 out of 111) with evidence of a circumstellar disk from mid-infrared photometry; it covers a stellar mass range from about 0.03 to 3 Msun and it is comp

C. Dominik, J. Blum, J. Cuzzi, G. Wurm

We discuss the results of laboratory measurements and theoretical models concerning the aggregation of dust in protoplanetary disks, as the initial step toward planet formation. Small particles easily stick when they collide and form aggregates with an open, often fractal structure, depending on the growth process. Larger particles are still expected to grow

S. P. Goodwin, A. P. Whitworth, D. Ward-Thompson

We investigate the effect of the turbulent power spectrum (P(k) \propto k^{-n}, with n=3, 4 or 5) on the fragmentation of low-mass cores, by means of SPH simulations. We adopt initial density profiles and low levels of turbulence based on observation, and for each n-value we conduct an ensemble of simulations with different initial seeds for the turbulent ve

K. Shimasaku, N. Kashikawa, M. Doi, C. Ly

We present the properties of Ly Alpha emitters (LAEs) at z = 5.7 in the Subaru Deep Field. A photometric sample of 89 LAE candidates is constructed from narrow-band (NB816) data down to NB816 = 26.0 (AB) in a continuous 725 arcmin^2 area. Spectra of 39 objects satisfying the photometric selection criteria for LAEs were obtained with Subaru and Keck II Telesc

Prasad Subramanian, Peter A. Becker

We reexamine the energetics of nonthermal electron acceleration in solar noise storms. A new result is obtained for the minimum nonthermal electron number density required to produce a Langmuir wave population of sufficient intensity to power the noise storm emission. We combine this constraint with the stochastic electron acceleration formalism developed by

Ramesh Chandra, Rajmal Jain, Wahab Uddin, Keiji Yoshimura

We present the H$α$ observations from ARIES, Nainital of a compact and impulsive solar flare occurred on March 10, 2001 and associated with a CME. We have also analysed HXT, SXT/Yohkoh observations as well as radio observations from Nobeyama Radio Observatory to derive the energetics and dynamics of this impulsive flare. We co-align the H$α$, SXR, HXR, MW an

K. G. Noeske, D. C. Koo, A. C. Phillips, C. N. A. Willmer

We analyze 26 Luminous Compact Blue Galaxies (LCBGs) in the HST/ACS Ultra Deep Field (UDF) at z ~ 0.2-1.3, to determine whether these are truly small galaxies, or rather bright central starbursts within existing or forming large disk galaxies. Surface brightness profiles from UDF images reach fainter than rest-frame 26.5 B mag/arcsec^2 even for compact objec

K. S. Cheng, Ronald E. Taam, W. Wang

The non-thermal, non-pulsed X-ray emission of MSPs is investigated. As in young pulsars, MSPs emit a relativistic wind, which interacting with the interstellar medium and/or a binary companion can significantly contribute to the non-pulsed emission of these pulsars. An application and extension of a simple model developed for young pulsars is applied to the

J. Ma, R. de Grijs, Y. Yang, X. Zhou

We independently redetermine the reddening and age of the globular cluster 037-B327 in M31 by comparing independently obtained multicolour photometry with theoretical stellar population synthesis models. 037-B327 has long been known to have a very large reddening value, which we confirm to be E(B-V)=1.360+-0.013, in good agreement with the previous results.

H. D. Nissen, M. Gustafsson, J. L. Lemaire, Y. Clenet

Observations are reported of H2 IR emission in the S(1) v=1-0 line at 2.121 microns in the Orion Molecular Cloud, OMC1, using the GriF instrument on the Canada-France-Hawaii Telescope. GriF is a combination of adaptive optics and Fabry-Perot interferometry, yielding a spatial resolution of 0.15&#34; to 0.18&#34; and a velocity discrimination as high as 1 km/