June 2000 arXiv papers — page 10

A. Gokalp, O. Yilmaz

We study the radiative decay $ρ^{0}\toπ^{0}π^{0}γ$ within the framework of a phenomenological approach in which the contributions of $σ$-meson and $ω$-meson intermediate states and of the pion-loops are considered. We conclude that the $σ$-meson amplitude provides the dominant contribution.

Xin Zhou, Hu Chen, Jianjun Zhou, Ou-Yang Zhong-can

A simple macroscopic continuum elasticity theory (CET) is used to calculate the structure relaxation of single-wall carbon nanotube (SWNT), an analytic formula is obtained. We also expand an atomic scale three-parameter empirical model [ T. Lenosky {\emph et al.} Nature 355, 333(1992)] in order to correctly describe the bond-length change effects. The struct

UKQCD Collaboration, C. McNeile, C. Michael

We study the flavour singlet pseudoscalar mesons from first principles using lattice QCD. We explore the quark content of the $η$ and $η'$ mesons and we discuss their decay constants.

T. Kugo, K. Ohashi

Supergravity tensor calculus in five spacetime dimensions is derived by dimensional reduction from the d=6 superconformal tensor calculus. In particular, we obtain an off-shell hypermultiplet in 5D from the on-shell hypermultiplet in 6D. Our tensor calculus still retains the dilatation gauge symmetry so that it becomes a trivial gauge fixing to make the Eins

S. F. King, N. Nimai Singh

We perform a renormalisation group (RG) analysis of neutrino masses and mixing angles in the see-saw mechanism in the minimal supersymmetric standard model with three right-handed neutrinos, including the effects of the heavy neutrino thresholds. We focus on the case that one of the right-handed neutrinos provides the dominant contribution to the 23 block of

Klaus Altmann, Jan Arthur Christophersen

Simplicial complexes X provide commutative rings A(X) via the Stanley-Reisner construction. We calculated the cotangent cohomology, i.e., T1 and T2 of A(X) in terms of X. These modules provide information about the deformation theory of the algebro geometric objects assigned to X.

Piero Madau, Martin J. Rees

Recent observations of high-redshift galaxies and quasars indicate that the hydrogen component of the intergalactic medium (IGM) must have been reionized at some redshift z>6. Prior to complete reionization, sources of ultraviolet radiation will be seen behind intervening gas that is still neutral, and their spectra should show the red damping wing of the Gu

Oliver Muelken, Peter Borrmann, Jens Harting, Heinrich Stamerjohanns

We present a detailed description of a classification scheme for phase transitions in finite systems based on the distribution of Fisher zeros of the canonical partition function in the complex temperature plane. We apply this scheme to finite Bose-systems in power law traps within a semi-analytic approach with a continuous one-particle density of states $Ω(

Michail P. Rekalo, Egle Tomasi-Gustafsson

We calculate the cross section and the beam asymmetry for exclusive photoproduction of charmed particles near threshold ($γ+p\to Λ_c^+ +\bar{D^0}$), in the framework of an effective Lagrangian model. We discuss the sensitivity of these observables to the magnetic moment of the $Λ_c$ baryon and of the coupling constant in the $pΛ_c D$ vertex. We show that exc

Y. F. Zhou, Y. L. Wu, J. N. Ng, C. Q. Geng

We present a general analysis on charmless B-meson decays $B\to ππ$ and $πK$. It is noticed that the final state interactions and inelastic rescattering effects must be significant in order to understand the consistency of the current data. By using general isospin decompositions, the isospin amplitudes and the corresponding strong phases could be extracted

A. Corichi, J. M. Reyes

Remarkable efforts in the study of the semi-classical regime of kinematical loop quantum gravity are currently underway. In this note, we construct a ``quasi-coherent'' weave state using Gaussian factors. In a similar fashion to some other proposals, this state is peaked in both the connection and the spin network basis. However, the state constructe

Hyok-Jon Kwon, Alan T. Dorsey, P. J. Hirschfeld

We study the order parameter phase fluctuation effects in cuprate superconductors near T=0, using a quasi-two-dimensional d-wave BCS model. An effective phason theory is obtained which is used to estimate the strength of the fluctuations, the fluctuation correction to the in-plane penetration depth, and the pair-field susceptibility. We find that while the p

G. Lopez

The quantization of a constant of motion for the harmonic oscillator with a time-explicitly depending external force is carried out. This quantization approach is compared with the normal Hamiltonian quantization approach. Numerical results show that there are qualitative and quantitative differences for both approaches, suggesting that the quantization of t

Tad Hogg, Dmitriy Portnov

We present a quantum algorithm for combinatorial optimization using the cost structure of the search states. Its behavior is illustrated for overconstrained satisfiability and asymmetric traveling salesman problems. Simulations with randomly generated problem instances show each step of the algorithm shifts amplitude preferentially towards lower cost states,

Arun K. Pati

If a measurement process is regarded as an irreversible process, then by Second law of thermodynamics the entropy should increase after any measurement process. By the same spirit a quantum system undergoing repeated measurement should show strong irreversibility leading to entropy production. On the contrary we show that in quantum Zeno effect setting the e

E. Knill, R. Laflamme, G. Milburn

We investigate the computational power of passive and active linear optical elements and photo-detectors. We show that single photon sources, passive linear optics and photo-detectors are sufficient for implementing reliable quantum algorithms. Feedback from the detectors to the optical elements is required for this implementation. Without feedback, non-dete

Karl Svozil

In the information interpretation of quantum mechanics, information is the most fundamental, basic entity. Every quantized system is associated with a definite discrete amount of information (cf. Zeilinger). This information content remains constant at all times and is permutated one-to-one throughout the system evolution. What is interpreted as measurement

A. Mazur

What is time? Why does it "flow" and why are we sure that it flows from past towards future? Why is there such a gigantic distinction between the Past of our world, which we believe to be fixed, and the Future, which we consider undetermined? And this is in spite of the fact that almost all physical laws are time-symmetric! Why does previously undete

Sven Bilke

A new method to sort gene expression patterns into functional groups is presented. The method is based on a sorting algorithm using a non-local similarity score, which takes all other patterns in the dataset into account. The method is therefore very robust with respect to noise. Using the expression data for yeast, we extract information about functional gr

Afsar Abbas

It is shown that in the Standard Model, the property of charge quantization holds for a Higgs with arbitrary isospin and hypercharge. These defining quantum numbers of the Higgs remain unconstrained while the whole basic and fundamental structure of the Standard Model remains intact. Hence it is shown that the Higgs cannot be a physical particle. Higgs is th

B. G. Sidharth

In recent years, the picture of discrete space time has been studied in the context of stochastic theory. There are a number of ramifications, which are briefly examined. We argue that the causality of physiics has its roots in the analyticity within the two dimensons of a fractal quantum path and further show how this picture has convergence wth quantum sup

E. Garrido, D. V. Fedorov, A. S. Jensen

We investigate dissociation reactions of loosely bound and spatially extended three-body systems. We formulate a practical method for simultaneous treatment of long-range Coulomb and short-range nuclear interactions. We use $^6$He (n+n+$α$) and $^{11}$Li (n+n+$^{9}$Li) as examples and study the two-neutron separation cross sections as functions of target and

U. van Kolck, J. A. Niskanen, G. A. Miller

Chiral effective field theory predicts a specific charge symmetry violating amplitude for pion production. This term is shown to provide the dominant contribution to the forward-backward asymmetry in the angular distribution for the reaction $pn\to dπ^0$, for reasonable values of the mass difference between down and up quarks, $δm_N$. Using a value $δm_N\app

V. A. Karmanov, K. V. Protasov, A. Yu. Voronin

Recent experimental studies of the antiproton-deuteron system at low energies have shown that the imaginary part of the antiproton-deuteron scattering length is smaller than the antiproton-proton one. Two- and three-body systems with strong annihilation are investigated and a mechanism explaining this unexpected relation between the imaginary parts of the sc

Harold W. Fearing

Nucleon-nucleon bremsstrahlung has long been considered a way of getting information about the off-shell nucleon-nucleon amplitude which would allow one to distinguish among nucleon-nucleon potentials based on their off-shell properties. There have been many calculations and many experiments devoted to this aim. We show here, in contrast to this standard vie

Mark Welsh, Harold W. Fearing

We respond to the accompanying Comment on our paper, 'Validity of certain soft photon amplitudes'. While we hope the discussion here clarifies the issues, we have found nothing which leads to a change in the original conclusions of our paper.

Luca Biferale, Detlef Lohse, Irene M. Mazzitelli, Federico Toschi

SO(3) and SO(2) decompositions of numerical channel flow turbulence are performed. The decompositions are used to probe, characterize, and quantify anisotropic structures in the flow. Close to the wall the anisotropic modes are dominant and reveal the flow structures. The SO(3) decomposition does not converge for large scales as expected. However, in the she

S. Majid

We discuss some of the issues to be addressed in arriving at a definitive noncommutative Riemannian geometry that generalises conventional geometry both to the quantum domain and to the discrete domain. This also provides an introduction to our 1997 formulation based on quantum group frame bundles. We outline now the local formulae with general differential

S. Majid

We outline the recent classification of differential structures for all main classes of quantum groups. We also outline the algebraic notion of `quantum manifold' and `quantum Riemannian manifold' based on quantum group principal bundles, a formulation that works over general unital algebras.

Joachim Kock

Let X be a smooth projective variety. Using modified psi classes on the stack of genus zero stable maps to X, a new associative quantum product is constructed on the cohomology space of X. When X is a homogeneous variety, this structure encodes the characteristic numbers of rational curves in X, and specialises to the usual quantum product upon resetting the

Ettore Aldrovandi, Leon A. Takhtajan

We revisit and generalize our previous algebraic construction of the chiral effective action for Conformal Field Theory on higher genus Riemann surfaces. We show that the action functional can be obtained by evaluating a certain Deligne cohomology class over the fundamental class of the underlying topological surface. This Deligne class is constructed by app

Svante Linusson, Johan Waestlund

We give a conjecture for the expected value of the optimal k-assignment in an m x n-matrix, where the entries are all exp(1)-distributed random variables or zeros. We prove this conjecture in the case there is a zero-cost $k-1$-assignment. Assuming our conjecture, we determine some limits, as $k=m=n\to \infty$, of the expected cost of an optimal n -assignmen

Kenneth S. Brown

We analyze random walks on a class of semigroups called ``left-regular bands''. These walks include the hyperplane chamber walks of Bidigare, Hanlon, and Rockmore. Using methods of ring theory, we show that the transition matrices are diagonalizable and we calculate the eigenvalues and multiplicities. The methods lead to explicit formulas for the pro

Roger Bielawski

We prove the existence of a (unique) S^1-invariant Ricci-flat Kaehler metric on a neighbourhood of the zero section in the canonical bundle of a real-analytic Kaehler manifold X, extending the metric on X.

Roger Bielawski

We generalize the hyperkaehler quotient construction to the situation where there is no group action preserving the hyperkaehler structure but for each complex structure there is an action of a complex group preserving the corresponding complex symplectic structure. Many (known and new) hyperkaehler manifolds arise as quotients in this setting. For example,

Mikhail Borovoi

Let $f$ be an indefinite ternary quadratic form, and let $q$ be an integer such that $-q det(f)$ is not a square. Let $N(T,f,q)$ denote the number of integral solutions of the equation $f(x)=q$ where $x$ lies in the ball of radius $T$ centered at the origin. We are interested in the asymptotic behavior of $N(T,f,q)$ as $T$ tends to infinity. We deduce from t

Gunther Cornelissen, Karim Zahidi

We show that Mazur's conjecture on the real topology of rational points on varieties implies that there is no diophantine model of the rational integers in the rational numbers. We also prove that there is a diophantine model of the polynomial ring over a finite field in the ring of rational functions over that finite field. Both proofs depend upon Matij

H. Collins, B. Holdom

We use the Israel condition to treat carefully the weak-field perturbations due to the presence of matter on a 3-brane embedded between two regions of anti-de Sitter (AdS) space with different curvature lengths. A four dimensional Newton's Law only emerges at distances that are large compared to the AdS lengths. When a scalar curvature is included in the

A. G. Abanov, P. B. Wiegmann

We study the mechanism of topological superconductivity in a hierarchical chain of chiral non-linear sigma-models (models of current algebra) in one, two, and three spatial dimensions. The models have roots in the 1D Peierls-Frohlich model and illustrate how the 1D Frohlich's ideal conductivity extends to a genuine superconductivity in dimensions higher

L. D. Faddeev, R. M. Kashaev, A. Yu. Volkov

The quantum discrete Liouville model in the strongly coupled regime, 1<c<25, is formulated as a well defined quantum mechanical problem with unitary evolution operator. The theory is self-dual: there are two exponential fields related by Hermitean conjugation, satisfying two discrete quantum Liouville equations, and living in mutually commuting subalgebras o

R. J. Finkelstein

The q-field theories are constructed by substituting quantum groups for the usual Lie groups. In earlier papers this construction was carried out for the quantum group SU_q(2). Here the investigation is extended to SL_q(3). The resulting theory describes two sectors, one sector lying close to the standard theory and accessible by perturbation theory, while t

A. Pelster, H. Kleinert

Extending recent work on QED and the symmetric phase of the euclidean multicomponent scalar ϕ^4-theory, we construct the vacuum diagrams of the free energy and the effective energy in the ordered phase of ϕ^4-theory. By regarding them as functionals of the free correlation function and the interaction vertices, we graphically solve nonlinear functional diffe

Jean-Bernard Zuber

These pedagogical lectures present some material, classical or more recent, on (Rational) Conformal Field Theories and their general setting ``in the bulk&#39;&#39; or in the presence of a boundary. Two well posed problems are the classification of modular invariant partition functions and the determination of boundary conditions consistent with conformal in

Juan Fernando Ospina Giraldo

The Wess-Zumino action for y deformed and generalized orientifold planes (yGOp-planes) is presented and one power expantion is realized from which processes that involves yGOp-planes, RR-forms, gravitons and gaugeons, are obtained. Finally non-standard yGOp-planes are showed.

B. Kleihaus, J. Kunz

We construct static axially symmetric solutions of SU(2) Einstein-Yang-Mills-Higgs theory in the topologically trivial sector, representing gravitating monopole--antimonopole pairs, linked to the Bartnik-McKinnon solutions.

C. E. Aguiar, T. Kodama, T. Osada, Y. Hama

The method of smoothed particle hydrodynamics (SPH) is developped appropriately for the study of relativistic heavy ion collision processes. In order to describe the flow of a high energy but low baryon number density fluid, the entropy is taken as the SPH base. We formulate the method in terms of the variational principle. Several examples show that the met

Yu. A. Simonov, J. A. Tjon

Dynamics of a light quark in the field of static source (heavy-light meson) is studied using the nonlinear Dirac equation, derived recently. Special attention is paid to the contribution of magnetic correlators and it is found that it yields a significant increase of string tension at intermediate distances. The spectrum of heavy-light mesons is computed wit

Marek Gazdzicki, Mark I. Gorenstein, Dieter Roehrich

A recent paper on energy dependence of strangeness production in A+A and p+p interactions written by Dunlop and Ogilvie (Phys. ReV. C61 031901(R) (2000) indicates that there is a significant misunderstanding about the concept of strangeness enhancement and its role as a signal of Quark Gluon Plasma creation. In this comment we will try to clarify some essent

V. Barger, K. Whisnant

A revolution in our understanding of the neutrino sector is underway, driven by observations that are interpreted in terms of changes in neutrino flavors as they propagate. Since neutrino oscillations occur only if neutrinos are massive, these phenomena indicate physics beyond the Standard Model. With the present evidence for oscillations from atmospheric, s

A. Hebecker, T. Teubner

New developments in the theory and phenomenology of high-energy scattering and diffraction that were presented and discussed at DIS2000 are reviewed.

A. Capella, E. G. Ferreiro, A. B. Kaidalov, C. A. Salgado

We investigate the role of unitarization effects in virtual photon-proton (γ^*p) interactions at small x. The q\bar{q}-fluctuation of the initial photon is separated into a small distance and a large distance component and a model for the unitarization of each component is proposed. The Born approximation for the small size component is calculated using QCD

Jiri Chyla

QCD corrections to the QED formula for parton distribution functions of the longitudinal virtual photon are derived in the leading--logarithmic approximation. It is shown that the resulting PDF satisfy the same homogeneous evolution equations as those of hadrons, but contrary to the latter are perturbatively calculable. Properties of these distribution funct

W. L. van Neerven, A. Vogt

We briefly discuss recent results on the evolution of unpolarized parton densities and structure functions in massless perturbative QCD. Present partial results on the next-to-next-to-leading order (NNLO) evolution kernels prove sufficient for reliable calculations at not too small values of the Bjorken variable, x > 10^-3. One order more can be taken into a

Eduard Masso, Francesc Rota

We show that neutrino-photon reactions above $m_e$ are dominated by the reaction $νγ\to νe^+ e^-$. We calculate its cross-section and see that it is larger by several orders of magnitude than the cross-sections of other neutrino-photon processes, for energies above $m_e$. We also discuss potential astrophysical and cosmological consequences.

N. Timneanu, G. Ingelman

Soft colour exchange models give a unified description of both diffractive and non-diffractive events, such that e-p and p-pbar collider data with and without rapidity gaps are well reproduced. We show that these models also describe the new Tevatron data on diffraction based on observed leading antiprotons, which provide new information on how to treat the

M. A. Ivanov, Yu. L. Kalinovsky, C. D. Roberts

We summarise a Dyson-Schwinger-equation-based calculation of an extensive range of light- and heavy-meson observables, characterised by heavy-meson leptonic decays, semileptonic heavy-to-heavy and heavy-to-light transitions, radiative and strong decays, and the rare flavour-changing neutral-current process. In the calculation the heavy-quark mass functions a

A. Kappes

Measurements of differential cross sections for deep inelastic ep neutral-current (NC) and charged-current (CC) reactions are presented using data taken during the 1994-97 e^+p and the 1998-99 e^-p running periods. The structure function xF_3 has been extracted combining NC e^-p and e^+p data sets. Both the measured cross sections and xF_3 are well described

Erast B. Gliner

The controversy between relativistic causality and quantum non-locality can be resolved by establishing the general relativistic background of quantum non-locality.

Beverly K. Berger, Vincent Moncrief

Previous studies \cite{berger98a} have provided strong support for a local, oscillatory approach to the singularity in U(1) symmetric, spatially inhomogeneous vacuum cosmologies on $T^3 \times R$. The description of a vacuum Bianchi type IX, spatially homogeneous Mixmaster cosmology (on $S^3 \times R$) in terms of the variables used to describe the U(1) symm

J. Makela, P. Repo

We consider the quantum mechanics of a system consisting of two identical, Planck-size Schwarzschild black holes revolving around their common center of mass. We find that even in a very highly-excited state such a system has very sharp, discrete energy eigenstates, and the system performs very rapid transitions from a one stationary state to another. For in

Milan Stefanik, Jan Horsky

For stationary cylindrically symmetric solutions of the Einstein-Maxwell equation we have shown that the &#34;charged&#34; solutions of McCrea, Chitre et al.(CGN), Van den Bergh and Wils (VW) can be obtained from the seed metrics using generating conjecture. The McCrea &#34;charged&#34; solution has as a seed vacuum metric the Van Stockum solution with a Kil

Miroslav Sukenik, Jozef Sima, Julius Vanko

Introduction of Vaidya metrics into the Expansive Nondecelerative Universe model allows to localize the energy of gravitational field. On the assumption that there is an interaction of long-range gravitational and electromagnetic fields, the localization might be verified experimentally. In this contribution some details on such an experiment are given.

Hristo Bojinov, Arancha Casal, Tad Hogg

We demonstrate how multiagent systems provide useful control techniques for modular self-reconfigurable (metamorphic) robots. Such robots consist of many modules that can move relative to each other, thereby changing the overall shape of the robot to suit different tasks. Multiagent control is particularly well-suited for tasks involving uncertain and changi

R. N. Costa Filho, M. G. Cottam, G. A. Farias

The linear and nonlinear processes in ferromagnetic films at low temperatures T<< Tc are studied in a microscopic theory. Both the long-range magnetic dipole-dipole and the Heisenberg exchange interactions to nearest and next-nearest neighbors are included. The results obtained for the linearized spin-wave spectrum are compared with previous macroscopic theo

Marcello Acquarone, Canio Noce

For a dimer with a non-degenerate orbital built from atomic wave functions of Gaussian shape we evaluate all the electron-phonon couplings derived from the one-body and two-body electronic interactions, considering both the adiabatic and extreme non-adiabatic limit. Not only the values of the coupling parameters in the two limits, but also the expressions of

Paul G. Dommersnes, Alex Hansen, Mogens H. Jensen, Kim Sneppen

Growing experimental evidence shows that proteins follow one or a few distinct paths when folding. We propose in this paper a procedure to parametrize these observed pathways, and from this parametrization construct effective Hamiltonians for the proteins. We furthermore study the denaturated-native transitions for a wide class of possible effective Hamilton

D. Natelson, R. L. Willett, K. W. West, L. N. Pfeiffer

Temperature dependent weak localization is measured in metallic nanowires in a previously unexplored size regime down to width $w=5$ nm. The dephasing time, $τ_ϕ$, shows a low temperature $T$ dependence close to quasi-1D theoretical expectations ($τ_ϕ \sim T^{-2/3}$) in the narrowest wires, but exhibits a relative saturation as $T \to 0$ for wide samples of

T. Dahm, H. Won, K. Maki

Recent experimental data on purest Sr_2RuO_4 single crystals clearly indicate the presence of nodes in the superconducting order parameter. Here, we consider one special p-wave order parameter symmetry and two two-dimensional f-wave order parameter symmetries having nodes within the RuO_2 plane. These states reasonably describe both specific heat and penetra

J. Riha, K. Svackova, I. Vysin

In this paper we discuss more wide applicability of the Chandrasekhar model of coupled oscillators in the optical rotatory dispersion of the crystals. We solve the problem using the Chandrasekhar model of two coupled oscillators in the case when we include all couplings between adjacent oscillators on the helix that is given by the crystal structure. Further

I. Vysin, K. Svackova

In this paper we generalize the quantum mechanical model of three coupled oscillators because of its usage in the crystal optical activity. Using this model we can include the influence of all essential couplings between single oscillators which represent the molecules or atoms of optically active crystals belonging for example to the space groups of symmetr

I. Vysin, J. Riha

In this paper we present the revised view on the optical activity of crystals based on the model of two dumped coupled oscillators. The results are compared with the results of the same problem solved before and it is presented that the results of the quantum mechanical model are the generalization of the classical model only and they do not introduce the ne

V. Vysin, I. Vysin

It is shown that some formulae describing optical rotatory dispersion of $α$-quartz with the aid of two Drude&#39;s terms reduce to the combined formula containing one Drude&#39;s and one Chandrasekhar&#39;s term. Comparison of various formulae describing the experimental data of $α$-quartz leads to the conclusion that the optical activity of this crystal is

R. Combescot, X. Leyronas

We investigate a simple explanation for the high maximum gap to $T_{c}$ ratio found experimentally in high $T_{c}$ compounds. We ascribe this observation to the lowering of $T_{c}$ by boson scattering of electrons between parts of the Fermi surface with opposite sign for the order parameter. We study the simplest possible model within this picture. Our quant

Z. Honda, K. Katsumata, Y. Nishiyama, I. Harada

We have measured the heat capacity and magnetization of the spin one one-dimensional Heisenberg antiferromagnet NDMAP and constructed a magnetic field versus temperature phase diagram. We found a field induced long-range magnetic ordering. We have been successful in explaining the phase diagram theoretically.

L. Martin-Moreno, L. Brey, C. Tejedor

We analyze the transitions that a magnetic field provokes in the ground state of an artificial homonuclear diatomic molecule. For that purpose, we have performed numerical diagonalizations for a double quantum dot around the regime of filling factor 2. We present phase diagrams in terms of tunneling and Zeeman couplings, and confinement strength. We identify

Hui Hu, Rong Lü, Jia-Ling Zhu, Jia-Jiong Xiong

The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model. On the basis of instanton technique in the spin-coherent-state path-integral representation, both the rigorous Wentzel-Kramers-Brillouin exponent and preexp

J. E. Bunder, Ross H. McKenzie

We consider the statistical properties of the local density of states of a one-dimensional Dirac equation in the presence of various types of disorder with Gaussian white-noise distribution. It is shown how either the replica trick or supersymmetry can be used to calculate exactly all the moments of the local density of states. Careful attention is paid to h

Richard B. Larson

The overall frequency and other statistical properties of binary systems suggest that star formation is intrinsically a complex and chaotic process, and that most binaries and single stars actually originate from the decay of multiple systems. Interactions between stars forming in close proximity to each other may play an important role in the star formation

Elizabeth J. Barton, Sheila J. Kannappan, Michael J. Kurtz, Margaret J. Geller

Longslit spectroscopy is entering an era of increased spatial and spectral resolution and increased sample size. Improved instruments reveal complex velocity structure that cannot be described with a one-dimensional rotation curve, yet samples are too numerous to examine each galaxy in detail. Therefore, one goal of rotation curve measurement techniques is t

Manuel A. Bautista

Several different approximations and techniques have been developed for the calculation of atomic structure, ionization, and excitation of atoms and ions. These techniques have been used to compute large amounts of spectroscopic data of various levels of accuracy. This paper presents a review of these theoretical methods to help non-experts in atomic physics

M. E. van den Ancker, P. S. Thé, D. de Winter

The spectral and extinction properties of 14 pre-main sequence candidates in the central part of the very young open cluster NGC 6383 were investigated. None of these stars shows evidence for anomalous circumstellar extinction. However, six out of 14 programme stars do show an infrared excess, indicative of the presence of circumstellar dust, heated up by th

T. G. Brainerd, C. O. Wright

We investigate the weak lensing shear due to dark matter galaxy halos whose mass distributions, as projected on the sky, are nearly elliptical. The shear pattern due to these halos is anisotropic about the lens centers and we quantify the level of anisotropy by comparing the mean shear experienced by sources located closest to the major axes of the lenses $<

Corinne Charbonnel, Constantine P. Deliyannis, Marc H. Pinsonneault

The fragile light elements lithium, beryllium, and boron are easily destroyed in stellar interiors, and are thus superb probes of physical processes occuring in the outer stellar layers. The light elements are also excellent tracers of the chemical evolution of the Galaxy, and can test big bang nucleosynthesis (BBN). These inter-related topics are reviewed w

Marc H. Pinsonneault, Corinne Charbonnel, Constantine P. Deliyannis

The fragile light elements lithium, beryllium, and boron are easily destroyed in stellar interiors, and are thus superb probes of physical processes occuring in the outer stellar layers. The light elements are also excellent tracers of the chemical evolution of the Galaxy, and can test big bang nucleosynthesis (BBN). These inter-related topics are reviewed w

R. P. Fender, G. G. Pooley

We report simultaneous millimetre and infrared observations of a sequence of very large amplitude quasi-periodic oscillations from the black hole X-ray binary GRS 1915+105. These oscillations are near the end of a sequence of over 700 repeated events as observed at 15 GHz, and are simultaneous at the mm and infrared wavelengths to within our time resolution

Richard J. Edgar, Ruth Esser

We examine the accuracy of a common FIP effect diagnostic, the ratio of Ne VI to Mg VI lines in the solar transition region. Since the two ions have quite similar contribution functions near their maxima in equilibrium, the ratio of these two ions is often taken to be the abundance ratio of Ne and Mg. First we compute non-equilibrium ionization effects on th

Steven Weinberg

The widely cited formula $\ell_1\simeq 200 Ω_0^{-1/2}$ for the multipole number of the first Doppler peak is not even a crude approximation in the case of greatest current interest, in which the cosmic mass density is less than the vacuum energy density. For instance, with $Ω_M$ fixed at 0.3, the position of any Doppler peak varies as $Ω_0^{-1.58}$ near $Ω_0

Victor P. Debattista, J. A. Sellwood

We show that bars in galaxy models having halos of moderate density and a variety of velocity distributions all experience a strong drag from dynamical friction unless the halo has large angular momentum in the same sense as the disk. The frictional drag decreases the bar pattern speed, driving the corotation point out to distances well in excess of those es

D. M. Alexander

An optical spectropolarimetric study has shown that the detectability of polarised broad H-alpha in Seyfert 2 galaxies is correlated to the IRAS f60/f25 flux ratio where only those Seyfert 2s with &#34;warm&#34; IRAS colours show polarised broad line emission. It was suggested that those Seyfert 2s with &#34;cool&#34; IRAS colours have highly inclined tori w

Marie-Noëlle Célérier

Recently collected SNIa data have been used to address the problem of measuring the cosmological parameters of the universe. Analysed in the framework of homogeneous models, they have yielded, as a primary result, a strictly positive cosmological constant. However, a straight reading of the published measurements, conducted with no a priori idea of which mod

S. Turcotte, J. Richer, G. Michaud, J. Christensen-Dalsgaard

Recent dramatic improvements in the modeling of abundance evolution due to diffusion in A stars have been achieved with the help of monochromatic opacity tables from the OPAL group. An important result in the context of stellar pulsations is the substantial helium abundance shown to be left over in the driving region of delta Scuti-type pulsations in chemica

Jian-Min Wang, You-Yuan Zhou, Ye-Fei Yuan, Xin-Wu Cao

Recent observations show strong evidence for the presence of Doppler-shifted emission lines in the spectrum of both black hole candidates and active galactic nuclei. These lines are likely to originate from relativistic outflows (or jets) in the vicinity of the central black hole. Consequently, the profile of such a line should be distorted by strong gravita

S. Boldyrev

The Batchelor passive advection is an advection by a smooth velocity field. If the velocity field is a delta-correlated in time random Gaussian process, then the problem is reduced to quantum mechanics of fluctuating velocity gradient u&#39;(t). For the finite-time correlated velocity field, such a reduction does not exist. To illustrate this point, the seco

W. Kluzniak, D. Kita

An analytic solution is presented to the three-dimensional problem of steady axisymmetric fluid flow through an accretion disk. The solution has been obtained through a systematic expansion in the small parameter epsilon =H/R (the ratio of disk thickness to its radial dimension) of the equations of viscous hydrodynamics. The equation of state was assumed to

Rosalba Perna, Jeremy Heyl, Lars Hernquist

We examine properties of thermal radiation emitted by strongly magnetized neutron stars (NSs). In particular, we show that the pulsation amplitudes of the energy-integrated flux are an increasing function of the absorption column density to the source. This is especially important for the interpretation of the Anomalous $X$-ray Pulsars (AXPs) as cooling neut

V. V. Sokolov, T. A. Fatkhullin, V. N. Komarova

We present photometric multiband spectral energy distributions for the GRB host galaxies: GRB 971214, GRB 970508, GRB 980613, GRB 980703 and GRB 990123 obtained with the 6-m telescope of SAO RAS. Using SEDs for the starburst galaxies, we made estimates of K-correction values and estimated the absolute magnitudes of the GRB host galaxies within the range of c

Steffen Krusch

This paper discusses multi-skyrmions on the 3-sphere with variable radius L using the rational map ansatz. For baryon number B = 3,...,9 this ansatz produces the lowest energy solutions known so far. By considering the geometry of the model we find an approximate analytic formula for the shape function. This provides an insight why skyrmions have a shell-lik

Caslav Brukner, Anton Zeilinger

In a classical measurement the Shannon information is a natural measure of our ignorance about properties of a system. There, observation removes that ignorance in revealing properties of the system which can be considered to preexist prior to and independent of observation. Because of the completely different root of a quantum measurement as compared to a c

A. Ya. Maltsev, S. P. Novikov

We study in this work the important class of nonlocal Poisson Brackets (PB) which we call weakly nonlocal. They appeared recently in some investigations in the Soliton Theory. However there was no theory of such brackets except very special first order case. Even in this case the theory was not developed enough. In particular, we introduce the Physical forms

Shinji Mukohyama

The junction condition across a singular surface in general relativity, formulated by Israel, has double covariance. In this paper, a general perturbation scheme of the junction condition around an arbitrary background is given in a doubly covariant way. After that, as an application of the general scheme, we consider perturbation of the junction condition a