June 2002 arXiv papers — page 18

Akira Ishida, Shozo Uehara

We study the rolling tachyon including the gauge fields in boundary string field theory. We show that there are no plane wave solutions for the gauge fields for large time. The disappearance of the plane wave solutions indicates that there are no excitations of the gauge fields on the tachyon matter, which is consistent with the Sen's conjecture.

G. S. Agarwal, Shubhrangshu Dasgupta

We show how a medium, under the influece of a coherent control field which is resonant or close to resonance to an appropriate atomic transition, can lead to very strong asymmetries in the propagation of unpolarized light when the direction of the magnetic field is reversed. We show how EIT can be used to mimic effects occuring in natural systems and that EI

Bao-Xi Sun, Xiao-Fu Lu, Peng-Nian Shen, En-Guang Zhao

The Debye screening masses of the $σ$, $ω$ and neutral $ρ$ mesons and the photon are calculated in the relativistic mean-field approximation. As the density of the nucleon increases, all the screening masses of mesons increase. It shows a different result with Brown-Rho scaling, which implies a reduction in the mass of all the mesons in the nuclear matter ex

J. -F. Muzy, E. Bacry

We define a large class of continuous time multifractal random measures and processes with arbitrary log-infinitely divisible exact or asymptotic scaling law. These processes generalize within a unified framework both the recently defined log-normal Multifractal Random Walk (MRW) [Bacry-Delour-Muzy] and the log-Poisson "product of cynlindrical pulses&#34

G. Giacomelli, A. Margiotta

In this 2001 status report of the MACRO experiment, results are presented on atmospheric neutrinos and neutrino oscillations, high energy neutrino astronomy, searches for WIMPs, search for low energy stellar gravitational collapse neutrinos, stringent upper limits on GUT magnetic monopoles, nuclearites and lightly ionizing particles, high energy downgoing mu

Martin Z. Bazant

A generalization of the Renormalization Group, which describes order-parameter fluctuations in finite systems, is developed in the specific context of percolation. This ``Stochastic Renormalization Group'' (SRG) expresses statistical self-similarity through a non-stationary branching process. The SRG provides a theoretical basis for analytical or num

Dan Margalit

We show that in the mapping class group of a surface any relation between Dehn twists of the form T_x^j T_y^k = M (M a multitwist) is the lantern relation, and any relation of the form (T_x T_y)^k = M (where T_x commutes with M) is the 2-chain relation.

Kang-Sin Choi, Jihn E. Kim

A Z_2 orbifold compactification of the heterotic string is considered. The resulting 6D GUT groups can be SO(16) or E_7 times SU(2) plus some hidden sector groups. The N=4 supersymmetry is reduced to N=2. In particular, the SO(16) 6D model with one spinor representation 128 can reduce to the previous 5D SO(16) or SO(14) family unification models after compac

Vadim Borokhov, Steven S. Gubser

We introduce a computational technique for studying non-supersymmetric deformations of domain wall solutions of interest in AdS/CFT. We focus on the Klebanov-Strassler solution, which is dual to a confining gauge theory. From an analysis of asymptotics we find that there are three deformations that leave the ten-dimensional supergravity solution regular and

Pieter Kok, Ulvi Yurtsever, Samuel L. Braunstein, Jonathan P. Dowling

Simultaneity is a well-defined notion in special relativity once a Minkowski metric structure is fixed on the spacetime continuum (manifold) of events. In quantum gravity, however, the metric is not expected to be a fixed, classical structure, but a fluctuating quantum operator which may assume a coherent superposition of two classically-distinguishable valu

Wilhelm I. Fushchych, A. L. Grishchenko

The paper presents a detailed theoretical-group analysis of three types of two-component equations of motion which describe the particle with zero mass and spin 1/2. There are studied P-, T- and C-propertias of the equations obtained.

Wilhelm I. Fushchych, A. L. Grishchenko

One of us quant-ph/0206077 (Nucl. Phys. B, 1970, 21, 321) has shown that for the particle with zero mass and spin s=1/2 there are three types of two-component equations (or one four-component equation with three different subsidiary conditions) which differ from one another by P, T and C properties. One of these equations is the two-component Weyl equation.

Wilhelm I. Fushchych

The relativistic two-component equation describing the free motion of particles with zero mass and spin 1/2, which is P- and T-non-invariant but C-invariant, is found. The representation of the Poincare group for zero mass and discrete spin is constructed. The position operator for such a particle is defined.

Y. Aharonov, L. Vaidman

It is shown that a quantum shutter, pre- and post-selected in particular quantum states, can close simultaneously arbitrary number of slits preventing the passage of a single photon in an arbitrary state. A set of K pre- and post-selected shutters can close the slits preventing the passage of K or less photons. This result indicates that the surprising prope

Sahin Kaya Ozdemir, Adam Miranowicz, Masato Koashi, Nobuyuki Imoto

Quantum projection synthesis can be used for phase-probability-distribution measurement, optical-state truncation and preparation. The method relies on interfering optical lights, which is a major challenge in experiments performed by pulsed light sources. In the pulsed regime, the time frequency overlap of the interfering lights plays a crucial role on the

D. Alonso, R. Sala Mayato, C. R. Leavens

For the special case of freely evolving Dirac electrons in $1 + 1$ dimensions, Feynman checkerboard paths have previously been used to derive Wigner's arrival-time distribution which includes all arrivals. Here, an attempt is made to use these paths to determine the corresponding distribution of first-arrival times. Simple analytic expressions are obtain

Jiannis Pachos, Enrique Solano

The generation of entangled states and their degree of entanglement is studied ab initio in a relativistic formulation for the case of two interacting spin-1/2 charged particles. In the realm of quantum electrodynamics we derive the interaction that produces entanglement between the spin components of covariant Dirac spinors describing the two particles. Fol

Reginald J. Hill

Equations that follow from the Navier-Stokes equation and incompressibility but with no other approximations are called "exact" here. Exact equations relating 2nd and 3rd-order structure functions are obtained, as is an exact incompressibility condition on the 2nd-order velocity structure function. Ensemble, temporal, and spatial averages are all con

Timothy H. Boyer

A new thermodynamic analysis is presented for the intimate connections between blackbody radiation and zero-point radiation within classical physics. First, using the thermodynamic behavior of an oscillator under an adiabatic change of frequency, we show that the thermodynamic functions can all be derived from a single function of w/T, analogous to Wien'

Chris Wiggins, Ilya Nemenman

Motivated by recent experimental developments in functional genomics, we construct and test a numerical technique for inferring it process pathways, in which one process calls another process, from time series data. We validate using a case in which data are readily available and formulate an extension, appropriate for genetic regulatory networks, which expl

Hourong Pang, Jialun Ping, Fan Wang, T. Goldman

The Omega-Omega (SIJ=-6,0,0) dibaryon state is studied with the extended quark-delocalization color-screening model including a pi meson exchange tail, which reproduces the properties of the deuteron quantitatively. We find the mass of the di-Omega to be about 45 MeV lower than the Omega-Omega threshold. The effect of channel coupling due to the tensor force

Ju. M. Gavriljuk, A. M. Gangapshev, V. V. Kuzminov, N. Ya. Osetrova

In this article the measurement results of proportional counter working characteristics filled with CF$_4$ and Xe ($0\div5$% Xe) additions at different pressures ($0.8\div14.8$ $at$) are presented. We have found that a bit of Xe addition reduces working voltage necessary to get the same gas amplification by two times against pure CF$_4$, it improves as well

Hiroaki Takagi, Kunihiko Kaneko

Dynamics maintaining diversity of cell types in a multi-cellular system are studied in relationship with the plasticity of cellular states. First, we introduce a new theoretical framework, reaction-diffusion system on `chemical species space' to model intra-cellular chemical reaction dynamics. Then, by considering the cell division and death of such cell

R. P. Malik

We discuss the integrability properties of the Boussinesq equations in the language of geometrical quantities defined on an appropriately chosen coset manifold connected with the $W_{3}$ algebra of Zamolodchikov. We provide a geometrical interpretation to the commuting conserved quantities, Lax-pair formulation, zero-curvature representation, Miura maps, etc

M. El Baz, Y. Hassouni, F. Madouri

A relation between the $Z_3$-graded Grassmann variables and parafermions is established. Coherent states are constructed as a direct consequence of such a relationship. We also give the analog of the Bargmann-Fock representation in terms of these Grassmann variables.

M. El Baz, Y. Hassouni

We give a general approach for the construction of deformed oscillators. These ones could be seen as describing deformed bosons. Basing on new definitions of certain quantum series, we demonstrate that they are nothing but the ordinary exponential functions in the limit when the deformation parameters goes to one. We also prove that these series converge to

Alexander E. Holroyd

In the bootstrap percolation model, sites in an $L$ by $L$ square are initially independently declared active with probability $p$. At each time step, an inactive site becomes active if at least two of its four neighbours are active. We study the behaviour as $p \to 0$ and $L \to \infty$ simultaneously of the probability $I(L,p)$ that the entire square is ev

Omer Angel, Itai Benjamini, Noam Berger, Yuval Peres

We study random walks on supercritical percolation clusters on wedges in $\Z^3$, and show that the infinite percolation cluster is (a.s.) transient whenever the wedge is transient. This solves a question raised by O. Haggstrom and E. Mossel. We also show that for convex gauge functions satisfying a mild regularity condition, the existence of a finite energy

P. Gilkey, R. Ivanova, T. Zhang

Let E be a natural operator associated to the curvature tensor of a pseudo-Riemannian manifold. This survey article studies when the spectrum, or more generally the real Jordan normal form, of E is constant on the natural domain of definition. It deals with results for the Jacobi operator, the higher order Jacobi operator, the Szabo operator, and the skew-sy

David J. Green

We establish a weak form of Carlson's conjecture on the depth of the mod-p cohomology ring of a p-group. In particular, Duflot's lower bound for the depth is tight if and only if the cohomology ring is not detected on a certain family of subgroups. The proofs use the structure of the cohomology ring as a comodule over the cohomology of the centre via

Ulrich Betke

We consider the homogenized linear feasibility problem, to find an $x$ on the unit sphere, satisfying $n$ line ar inequalities $a_i^Tx\ge 0$. To solve this problem we consider the centers of the insphere of spherical simpl ices, whose facets are determined by a subset of the constraints. As a result we find a new combinatorial algor ithm for the linear feasi

Vishvajit V S Gautam

We give some equivalent characterizations of exremally disconnected spaces

Vijay Kodiyalam, K. N. Raghavan

We prove a recent conjecture of Kreiman and Lakshmibai about Hilbert functions of points on Schubert varieties in Grassmannians.

Volker Runde

We prove that the measure algebra $M(G)$ of a locally compact group $G$ is Connes-amenable if and only if $G$ is amenable.

Noam D. Elkies

For any field k and any integers m,n with 0 <= 2m <= n+1, let W_n be the k-vector space of sequences (x_0,...,x_n), and let H_m be the subset of W_n consisting of the sequences that satisfy a degree-m linear recursion, that is, for which there exist a_0,...,a_m in k, not all zero, such that sum(a_i x_{i+j}, i=0..m) = 0 holds for each j=0,1,...,n-m. Equivalen

Oleg Lunin, Samir D. Mathur

We construct an exact metric which at short distances is the metric of massless particles in 5+1 spacetime (moving along a diameter of the sphere) and is AdS_3\times S^3 at infinity. We also consider a set of a conical defect spacetimes which are locally AdS_3\times S^3 and have the masses and charges of a special set of chiral primaries of the dual orbifold

David Kastor, Jennie Traschen

We construct a set of conserved charges for asymptotically deSitter spacetimes that correspond to asymptotic conformal isometries. The charges are given by boundary integrals at spatial infinity in the flat cosmological slicing of deSitter. Using a spinor construction, we show that the charge associated with conformal time translations is necessarilly positi

Paolo Aschieri, Igor Bakovic, Branislav Jurco, Peter Schupp

We define noncommutative gerbes using the language of star products. Quantized twisted Poisson structures are discussed as an explicit realization in the sense of deformation quantization. Our motivation is the noncommutative description of D-branes in the presence of topologically non-trivial background fields.

J. Hwang, H. Noh

We present unified ways of handling the cosmological perturbations in a class of gravity theory covered by a general action in eq. (1). This gravity includes our previous generalized $f(ϕ,R)$ gravity and the gravity theory motivated by the tachyonic condensation. We present general prescription to derive the power spectra generated from vacuum quantum fluctu

Artem Starodubtsev

The issue of non-perturbative background independent quantization of matrix models is addressed. The analysis is carried out by considering a simple matrix model which is a matrix extension of ordinary mechanics reduced to 0 dimension. It is shown that this model has an ordinary mechanical system evolving in time as a classical solution. But in this treatmen

T. Banks, W. Fischler, A. Kashani-Poor, R. McNees

We analyze the properties of stars whose interior is described by the stiffest equation of state consistent with causality. We note the remarkable fact that the entropy of such stars scales like the area.

Sourav Sarkar, B. K. Patra, V. J. Menon, S. Mallik

This is a short review on the thermal, spectral representation in the real-time version of the finite temperature quantum field theory. After presenting a clear derivation of the spectral representation, we discuss the properties of its spectral function. Two applications of this representation are then considered. One is the solution of the Dyson equation f

J. D. Bjorken, S. Pakvasa, S. F. Tuan

We have searched for conceptually simple extensions of the standard model, and describe here a candidate model which we find attractive. Our starting point is the assumption that off-diagonal CKM mixing matrix elements are directly related by lowest order perturbation theory to the quark mass matrices. This appears to be most easily and naturally implemented

Wu-Ki Tung

A new generation of parton distribution functions with increased precision and quantitative estimates of uncertainties is presented. This work includes a full treatment of available experimental correlated systematic errors for both new and old data sets and a systematic and pragmatic treatment of uncertainties of the parton distributions and their physical

Hans-Joachim Drescher, Glennys R. Farrar

In hadron induced air showers of highest energies (E> 1e18 eV), the lateral distribution functions of electrons and muons are a superposition of many separate electromagnetic sub-showers, initiated by meson decay at different altitudes and energies. The lateral distribution function is the primary tool for reconstructing the energy of the primary in a UHE co

K. Werner

An event generator for nuclear collisions is a microscopic model, obtained from extrapolating elementary interactions -- as electron-positron annihilation, deep inelastic scattering, and proton-proton interactions -- towards proton-nucleus and nucleus-nucleus scattering, by using Monte Carlo techniques. In this paper, we will discuss the physical concepts be

Eric Braaten, Eugeniu Radescu

The linear delta expansion is applied to the 3-dimensional O(N) scalar field theory at its critical point in a way that is compatible with the large-N limit. For a range of the arbitrary mass parameter, the linear delta expansion for <phi^2> converges, with errors decreasing like a power of the order n in delta. If the principal of minimal sensitivity is use

M. Ciafaloni, S. Munier

We point out that canonical quantization of the two-body problem in 2+1-Gravity is related to the high-energy equation in Yang-Mills theory by a proper ordering of the relevant operators. This feature arises from expanding the Hamiltonian around its conformal limit - or treating running coupling effects in the Yang-Mills case - and yields a peculiar short di

Claude Amsler

We argue that the experimental decay rates of the f0(1500) meson into two pseudoscalar mesons and into two photons are incompatible with a quark-antiquark state and that the f0(1710) meson is dominantly an ssbar state.

H1 Collaboration, C. Adloff

A measurement of inclusive jet cross-sections in deep-inelastic ep scattering at HERA is presented based on data with an integrated luminosity of 21.1 pb^-1. The measurement is performed for photon virtualities Q^2 between 5 and 100 GeV^2, differentially in Q^2, in the jet transverse energy E_T, in E_T^2/Q^2 and in the pseudorapidity eta_lab. With the renorm

Emilio Radicioni

Hadron production is a key ingredient in many aspects of neutrino physics. Precise prediction of atmospheric neutrino fluxes, characterization of accelerator neutrino beams, quantification of pion production and capture for neutrino factory designs, all of these would profit of high-statistics, high-precision hadron production measurements. In addition, such

Martin Weber

With center of mass energies up to 209 GeV of LEP II, massive W and Z bosons can be produced in pairs and jointly with photons. This allows to study boson-boson couplings. Since the W and Z bosons are unstable and decay into fermions, two- and four-fermion final states, accompanied possibly by photons, play an important role for these measurements. The coupl

Golam Mortuza Hossain, Parthasarathi Majumdar

Assuming a flat Friedmann-Robertson-Walker cosmology with a single perfect fluid, we propose a pressure-density ratio that evolves as a specific universal function of the scale parameter. We show that such a ratio can indeed be consistent with several observational constraints including those pertaining to late-time accelerated expansion. Generic dynamical s

Richard E. Livine

We study the generalised constrained BF theory described in gr-qc/0102073 in order to introduce the Immirzi parameter in spin foam models. We show that the resulting spin foam model is still based on simple representations and that the generalised BF action is simply a deformation of the Barrett-Crane model. The Immirzi parameter doesn&#39;t change the repre

C. Erten, S. G. Kobourov

Traditional representations of graphs and their duals suggest the requirement that the dual vertices be placed inside their corresponding primal faces, and the edges of the dual graph cross only their corresponding primal edges. We consider the problem of simultaneously embedding a planar graph and its dual into a small integer grid such that the edges are d

E. W. Carlson, V. J. Emery, S. A. Kivelson, D. Orgad

It is the purpose of this paper to explore the theory of high temperature superconductivity. Much of the motivation for this comes from the study of the cuprate high temperature superconductors. However, our primary focus is on the core theoretical issues associated with the mechanism of high temperature superconductivity more generally. We concentrate on ph

Harry Suhl

An extension of the original Overhauser effect to a more general nonequilibrium state was proposed by G. Feher, and demonstrated by Clark and Feher some forty years ago. It is suggested here that it might be possible to produce excess electron spin polarization by allowing the role of the nuclei to be played by other magnetic entities, such as paramagnetic i

P. Keblinski, M. Z. Bazant, R. K. Dash, M. M. Treacy

Using molecular dynamics simulations we study the thermodynamic behavior of a single-component covalent material described by the recently proposed Environment-Dependent Interatomic Potential (EDIP). The parameterization of EDIP for silicon exhibits a range of unusual properties typically found in more complex materials, such as the existence of two structur

R. Mislovaty, Y. Perchenok, Ido Kanter, Wolfgang Kinzel

The security of neural cryptography is investigated. A key-exchange protocol over a public channel is studied where the parties exchanging secret messages use multilayer neural networks which are trained by their mutual output bits and synchronize to a time dependent secret key. The weights of the networks have integer values between $\pm L$. Recently an alg

Karel Vyborny, Ludvik Smrcka, Rainer A. Deutschmann

The linear response theory is used to describe magnetoresistance oscillations of short-period unilateral superlattices with strong modulation (or alternatively arrays of coupled quantum wires). The semiclassical description of this system fails for strong magnetic fields (magnetic breakdown) and we employ a simple fully-quantum-mechanical tight-binding model

F. Venturini, M. Opel, T. P. Devereaux, J. K. Freericks

The electron dynamics in the normal state of Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ is studied by inelastic light scattering over a wide range of doping. A strong anisotropy of the electron relaxation is found which cannot be explained by single-particle properties alone. The results strongly indicate the presence of an unconventional quantum-critical metal-insulator

M. I. Molina

We examine some new DNLS-like equations that arise when considering strongly-coupled electron-vibration systems, where the local oscillator potential is anharmonic. In particular, we focus on a single, rather general nonlinear vibrational impurity and determine its bound state(s) and its dynamical selftrapping properties.

D. -J. Kang, N. H. Peng, R. Webb, C. Jeynes

Ion beam damage combined with nanoscale focused ion beam direct milling was used to create manufacturable SNS type Josephson junctions in 100 nm thick MgB$_{2}$ with T$_{C}$ of 38 K. The junctions show non-hysteretic current - voltage characteristics between 36 and 4.2 K. Experimental evidence for the dc and ac Josephson effects in MgB$_{2}$ metal masked ion

M. K. Hassan, N. Wessel, J. Kurths

We formulate a model for a cooperative ballistic deposition (CBD) process whereby the incoming particles are correlated with the ones already adsorbed via attractive force. The strength of the correlation is controlled by a tunable parameter $a$ that interpolates the classical car parking problem at $a=0$, the ballistic deposition at $a=1$ and the CBD model

Kazuhiko Kuroki, Takashi Kimura, Ryotaro Arita

Superconductivity in the Hubbard model is studied on a series of lattices in which dimers are coupled in various types of arrays. Using fluctuation exchange method and solving the linearized Eliashberg equation, the transition temperature $T_c$ of these systems is estimated to be much higher than that of the Hubbard model on a simple square lattice, which is

D. W. Wang, A. J. Millis, S. Das Sarma

We show that claims, presented in Phys. Rev. B {\bf 65}, 125109 (2002) concerning the threshold behavior of dynamical correlations of a Coulomb Luttinger liquid, are based on an inconsistent mathematical analysis. Physical arguments are also presented, indicating that the claimed behavior is unlikely to be correct.

Antonio Politi, Segio Ciliberto, Riccardo Scorretti

The average time for the onset of macroscopic fractures is analytically and numerically investigated in the fiber-bundle model with quenched disorder and thermal noise under a constant load. We find an implicit exact expression for the failure time in the low-temperature limit that is accurately confirmed by direct simulations. The effect of the disorder is

Shiping Feng, Feng Yuan, Zhao-Bin Su, Lu Yu

The recently discovered coexistence of incommensurate antiferromagnetic neutron scattering peaks and commensurate resonance in underdoped YBa$_2$Cu$_3$O$_{6+x}$ is calling for an explanation. Within the t-J model, the doping and energy dependence of the spin dynamics of the underdoped bilayer cuprates in the normal state is studied based on the fermion-spin

Y. Itoh, S. Adachi, T. Machi, Y. Ohashi

We report Cu nuclear quadrupole resonance experiment on magnetic impurity Ni-substituted YBa$_2$Cu$_{3-x}$Ni$_x$O$_{7-δ}$. The distribution of Ni-substituted sites and its effect on the Cu electron spin dynamics are investigated. Two samples with the same Ni concentration $x$=0.10 and nearly the same oxygen content but different $T_c$&#39;s were prepared: On

Shi-Dong Liang, T. K. Lee

The magnetic polarization induced by nonmagnetic impurities such as Zn in high Tc cuprate compounds is studied by the variational Monte Carlo simulation. The variational wave function is constructed from the eigenstates obtained from Bogoliubov de Gennes mean field Hamiltonian for the two-dimensional t-J model. A Jastrow factor is introduced to account for t

W. Wernsdorfer, S. Bhaduri, R. Tiron, D. N. Hendrickson

It is shown that dipolar and weak superexchange interactions between the spin systems of single-molecule magnets (SMM) play an important role in the relaxation of magnetization. These interactions can reduce or increase resonant tunneling. The one-body tunnel picture of SMMs is not always sufficient to explain the measured tunnel transitions. We propose to i

Scott A Hill

In a recent paper (Physica A 296, 320 (2001)), T. Nagatani proposes a time-headway model for buses on a bus route, and studies the stability of that model&#39;s homogeneous solutions. While investigating the phase diagram gotten by varying the rate of passenger arrival and the initial spacing of buses, he discovers a discrepancy between the results of simula

Alán Aspuru-Guzik, William A. Lester

This is a book chapter soon to appear (2002) in the &#34;Handbook for Numerical Analysis&#34; volume dedicated to &#34;Computational Chemistry&#34; edited by Claude Le Bris. The series editors are P.G. Ciarlet and J. L. Lions. [North Holland/Elservier]. This review deals with some of the methods known under the umbrella term quantum Monte Carlo (QMC), specif

David Burstein, George Blumenthal

Most spiral galaxies are found in galaxy groups with low velocity dispersions; most E/S0 galaxies are found in galaxy groups with relatively high velocity dispersions. The mass of the hot gas we can observe in the E/S0 groups via their thermal X-ray emission is, on average, as much as the baryonic mass of the galaxies in these groups. By comparison, galaxy c

Orsola De Marco, M. J. Barlow, M. Cohen

We present Hubble Space Telescope ultraviolet and optical STIS spectroscopy of the [WCL] planetary nebula central star CPD-568032, obtained during its latest lightcurve minimum. The UV spectrum shows the central star&#39;s continuum light distribution to be split into two bright peaks separated by 0.10 arcsec. We interpret this finding as due to an edge-on d

C. Sanchez Contreras, R. Sahai, A. Gil de Paz

In this paper (paper I) we present optical long-slit spectroscopy and imaging of the protoplanetary nebula CRL618. The optical lobes of CRL618 consist of shock-excited gas, which emits many recombination and forbidden lines, and dust, which scatters light from the innermost regions. From the analysis of the scattered Halpha emission, we derive a nebular incl

Andrew A. Cole, Martin D. Weinberg

Using data from the Two Micron All-Sky Survey (2MASS), we identify a population of infrared carbon (IR C) stars with J-K >= 2 in the Milky Way. These stars are shown to trace the stellar bar previously identified in IR and optical surveys. The properties of C stars strongly suggest that they are of intermediate age. We conclude that the bar is likely to have

S. L. Tufte, J. D. Wilson, G. J. Madsen, L. M. Haffner

It has been suggested that high velocity clouds may be distributed throughout the Local Group and are therefore not in general associated with the Milky Way galaxy. With the aim of testing this hypothesis, we have made observations in the H-alpha line of high velocity clouds selected as the most likely candidates for being at larger than average distances. W

Renee C. Kraan-Korteweg, Patricia A. Henning, Anja C. Schroeder

As part of our program to map the large-scale distribution of galaxies behind the Milky Way, we used the Parkes 210 ft (64 m) radio telescope for pointed HI observations of a sample of low surface-brightness (due to heavy obscuration) spiral galaxies selected from the deep optical Zone of Avoidance (ZOA) galaxy catalog in the Hydra/Antlia region (Kraan-Korte

Allan Sacha Brun, Juri Toomre

The intense turbulence present in the solar convection zone is a major challenge to both theory and simulation as one tries to understand the origins of the striking differential rotation profile with radius and latitude that has been revealed by helioseismology. The differential rotation must be an essential element in the operation of the solar magnetic dy

D. Sanwal, G. G. Pavlov, V. E. Zavlin, M. A. Teter

We observed 1E 1207.4--5209, a neutron star in the center of the supernova remnant PKS 1209--51/52, with the ACIS detector aboard the Chandra X-ray observatory and detected two absorption features in the source spectrum. The features are centered near 0.7 keV and 1.4 keV, their equivalent widths are about 0.1 keV. We discuss various possible interpretations

J. A. Collins, R. A. Benjamin, R. J. Rand

To better understand diffuse ionized gas kinematics and halo rotation in spiral galaxies, we have developed a model in which clouds are ejected from the disk and follow ballistic trajectories through the halo. The behavior of clouds in this model has been investigated thoroughly through a parameter space search and a study of individual cloud orbits. Synthet

Christopher H. De Vries, Gopal Narayanan, Ronald L. Snell

We present the results of the first detailed millimeter and submillimeter molecular line survey of bright rimmed clouds, observed at FCRAO in the CO (J=1-0), C18O (J=1-0), HCO+ (J=1-0), H13CO+ (J=1-0), and N2H+ (J=1-0) transitions, and at the HHT in the CO (J=2-1), HCO+ (J=3-2), HCO+ (J=4-3), H13CO+ (J=3-2), and H13CO+ (J=4-3) molecular line transitions. The

H. Meusinger, J. Brunzendorf

We study a sample of 23 narrow-emission line galaxies (NELGs) which were selected by their strong variability as QSO candidates in the framework of a variability-and-proper motion QSO survey on digitised Schmidt plates. In previous work, we have shown that variability is an efficient method to find AGNs. The variability properties of the NELGs are however si

M. Gliozzi, W. Brinkmann, C. Raeth, I. E. Papadakis

We use data from a recent long ASCA observation of the Narrow Line Seyfert 1 Ark 564 to investigate in detail its timing properties. We show that a thorough analysis of the time series, employing techniques not generally applied to AGN light curves, can provide useful information to characterize the engines of these powerful sources.We searched for signs of

Alexander B. Men&#39;shchikov, Dieter Schertl, Peter Tuthill, Gerd Weigelt

New diffraction-limited speckle images of the Red Rectangle in the wavelength range 2.1--3.3 microns with angular resolutions of 44--68 mas and previous speckle images at 0.7--2.2 microns revealed well-resolved bright bipolar outflow lobes and long X-shaped spikes originating deep inside the outflow cavities. This set of high-resolution images stimulated us

A. R. King, E. M. Puchnarewicz

Many black-hole sources emit a substantial fraction of their luminosities in blackbody-like spectral components. It is usual to assume that these are produced in regions at least comparable in size to the hole&#39;s Schwarzschild radius, so that a measure of the emitting area provides an estimate of the black hole mass M. However there is then no guarantee t

Andrew M. Read, Ian R. Stevens

We present results from XMM-Newton Reflection Grating Spectrometer observations of the prototypical starburst galaxy M82. These high resolution spectra represent the best X-ray spectra to date of a starburst galaxy. A complex array of lines from species over a wide range of temperatures is seen, the most prominent being due to Lyman-alpha emission from abund

Gloria Andreuzzi, Harvey B. Richer, Marco Limongi, Michael Bolte

We develop the white dwarf luminosity function (LF) of the old open cluster NGC 188 in order to determine a lower limit to the age of the cluster by using the faint end of the cooling sequence. To produce an extensive sequence of the cooling white dwarfs we imaged four contiguous HST-WFPC2 fields in the center of the cluster in the F555W and F814W filters. A

A. Brunthaler, M. Reid, H. Falcke, L. J. Greenhill

Key and still largely missing parameters for measuring the mass content and distribution of the Local Group are the proper motion vectors of its member galaxies. The problem when trying to derive the gravitational potential of the Local Group is that usually only radial velocities are known, and hence statistical approaches have to be used. The expected prop

Ryoko Ishioka, Taichi Kato, Makoto Uemura, Gary W. Billings

We report the first time-series observations of the short outburst of the proposed intermediate polar HT Cam (=RX J0757.0+6306). On 2001 December 29, we detected the object was undergoing a bright outburst at the magnitude of $m_{vis}=12.2$. Following this detection, we started international joint observations through VSNET. The light curve showed a gradual

E. Berger, S. R. Kulkarni, R. A. Chevalier

We report the discovery and monitoring of radio emission from the Type Ic SN 2002ap ranging in frequency from 1.43 to 22.5 GHz, and in time from 4 to 50 days after the SN explosion. As in most other radio SNe, the radio spectrum of SN 2002ap shows evidence for absorption at low frequencies, usually attributed to synchrotron self-absorption or free-free absor

Peter Schneider, Ludovic van Waerbeke, Martin Kilbinger, Yannick Mellier

We derive in this paper expressions for the covariance matrix of the cosmic shear two-point correlation functions which are readily applied to any survey geometry. Furthermore, we consider the more special case of a simple survey geometry which allows us to obtain approximations for the covariance matrix in terms of integrals which are readily evaluated nume

M. A. Jimenez-Garate, C. J. Hailey, J. W. den Herder, S. Zane

We analyze the high-resolution X-ray spectrum of Hercules X-1, an intermediate-mass X-ray binary, which was observed with the XMM-Newton Reflection Grating Spectrometer. We measure the elemental abundance ratios by use of spectral models, and we detect material processed through the CNO-cycle. The CNO abundances, and in particular the ratio N/O > 4.0 times s

A. S. Brun, H. M. Antia, S. M. Chitre, J. -P. Zahn

We have computed accurate 1-D solar models including both a macroscopic mixing process in the solar tachocline as well as up-to-date microscopic physical ingredients. Using sound speed and density profiles inferred through primary inversion of the solar oscillation frequencies coupled with the equation of thermal equilibrium, we have extracted the temperatur

Saleem Zaroubi

I review the recent developments in the analysis of cosmic flow data, in particular, latest results of bulk flow measurements, comparison between redshift and peculiar velocity catalogs with emphasis on the measured value of the $β(=Ω_m^{0.6}/b)$ parameter, and matter power spectrum estimates from galaxy peculiar velocity catalogs. Based on these development

A. Pinzul, A. Stern

We examine Chern-Simons theory written on a noncommutative plane with a `hole&#39;, and show that the algebra of observables is a nonlinear deformation of the $w_\infty$ algebra. The deformation depends on the level (the coefficient in the Chern-Simons action), and the noncommutativity parameter, which were identified, respectively, with the inverse filling

Y. Aoki, T. Namiki, S. Ohsaki, S. R. Saha

We report measurements of low-temperature specific heat on the 4f^2-based heavy-fermion superconductor PrOs4Sb12. In magnetic fields above 4.5 T in the normal state, distinct anomalies are found which demonstrate the existence of a field-induced ordered phase (FIOP). The Pr nuclear specific heat indicates an enhancement of the 4f magnetic moment in the FIOP.

Lev Kofman, Andrei Linde, V. Mukhanov

Recently Hollands and Wald argued that inflation does not solve any of the major cosmological problems. We explain why we disagree with their arguments. They also proposed a new speculative mechanism of generation of density perturbations. We show that in their scenario the inhomogeneities responsible for the large scale structure observed today were generat

Mina Nozar

The reaction pim p --> omega pim p, omega --> pip pim pi0 has been studied at 18 GeV/c. The omega pim mass spectrum is found to be dominated by the b1(1235). Partial Wave Analysis shows that b1 production is dominated by natural parity exchange. The S-wave and D-wave amplitudes for b1(1235) --> omega pi have been determined, and it is found that the amplitud