March 2000 arXiv papers — page 17

I. L. Egusquiza, J. G. Muga

We present a decomposition of the general quantum mechanical evolution operator, that corresponds to the path decomposition expansion, and interpret its constituents in terms of the quantum Zeno effect (QZE). This decomposition is applied to a finite dimensional example and to the case of a free particle in the real line, where the possibility of boundary co

Michal Horodecki, Pawel Horodecki, Ryszard Horodecki

Basing on unified approach to {\it all} kinds of quantum capacities we show that the rate of quantum information transmission is bounded by the maximal attainable rate of coherent information. Moreover, we show that, if for any bipartite state the one-way distillable entanglement is no less than coherent information, then one obtains Shannon-like formulas fo

Zhifan Chen, Alfred Z Msezane

Generalized oscillator strengths (GOS's) for the Na $3s -3p$ transition have been investigated using the spin-polarized technique of the random phase approximation with exchange (RPAE) and the first Born approximation (FBA), focussing our attention on the position of the minimum. Intershell correlations are found to influence the position of the minimum

J. Piekarewicz

We calculate the longitudinal response of 208Pb using a relativistic random-phase approximation to three different parameterizations of the Walecka model with scalar self-interactions. From a nonspectral calculation of the response-that automatically includes the mixing between positive- and negative-energy states-we extract the distribution of strength for

M. Modarres, H. R. Moshfegh

The method of lowest-order constrained variational, which predicts reasonably the nuclear matter semi-empirical data is used to calculate the equation of state of beta-stable matter at finite temperature. The Reid soft-core with and without the N-$Δ$ interactions which fits the N-N scattering data as well as the $UV_{14}$ potential plus the three-nucleon int

Tamas S. Biro

Using the method of prolongation we generate new solutions from a simple particular solution for relativistic transverse flow with cylindrical symmetry in 1+3 dimensions. This is an extension of the longitudinal Bjorken flow ansatz and can be applied among others during first order phase transition in an expanding system. The prolongated solution allows for

Dmitry Pelinovsky

Dispersion-managed solitons are reviewed within a Gaussian variational approximation and an integral evolution model. In the normal regime of the dispersion map (when the averaged path dispersion is negative), there are two solitons of different pulse duration and energy at a fixed propagation constant. We show that the short soliton with a larger energy is

Boris Gutkin

We consider classical billiards on surfaces of constant curvature, where the charged billiard ball is exposed to a homogeneous, stationary magnetic field perpendicular to the surface. We establish sufficient conditions for hyperbolicity of the billiard dynamics, and give lower estimation for the Lyapunov exponent. This extends our recent results for non-magn

Jan Wiersig

The pseudo-integrable barrier billiard invented by Hannay and McCraw [J. Phys. A 23, 887 (1990)] -- rectangular billiard with line-segment barrier placed on a symmetry axis -- is generalized. It is proven that the flow on invariant surfaces of genus two exhibits a singular continuous spectral component.

M. A. Jafarizadeh, A. Rostami

A general algorithm has been given for the generation of Coherent and Squeezed states, in one-dimensional hamiltonians with shape invariant potential, obtained from the master function. The minimum uncertainty states of these potentials are expressed in terms of the well-known special functions.

T. A. Larsson

Dzhumadil'daev has classified all tensor module extensions of $diff(N)$, the diffeomorphism algebra in $N$ dimensions, and its subalgebras of divergence free, Hamiltonian, and contact vector fields. I review his results using explicit tensor notation. All of his generic cocycles are limits of trivial cocycles, and many arise from the Mickelsson-Faddeev a

Sangtae Jeong

In this paper we compare several properties and constructions of the Carlitz polynomials and digit derivatives for continuous functions on $\F_q[[T]].$ In particular, we show a close relation between them as orthonormal bases. Moreover, parallel to Carlitz's coefficient formula, we give the closed formula for the expansion coefficients in terms of the di

Davide Franco, Steven L. Kleiman, Alexandru T. Lascu

Our main theorem characterizes the complete intersections of codimension 2 in a projective space of dimension 3 or more over an algebraically closed field of characteristic 0 as the subcanonical and self-linked subschemes. In order to prove this theorem, we'll prove the Gherardelli linkage theorem, which asserts that a partial intersection of two hypersu

Florin Panaite

We find a relation between two Hopf algebras built on rooted trees. The first is the Connes-Kreimer Hopf algebra H_R which describes a certain type of renormalization in quantum field theory; the second is the Grossman-Larson Hopf algebra A introduced ten years ago by some "differential" and combinatorial reasons. Roughly, the relation is the followi

Alberto S. Cattaneo, Paolo Cotta-Ramusino, Carlo A. Rossi

A generalization of Wilson loop observables for BF theories in any dimension is introduced in the Batalin-Vilkovisky framework. The expectation values of these observables are cohomology classes of the space of imbeddings of a circle. One of the resulting theories discussed in the paper has only trivalent interactions and, irrespective of the actual dimensio

Claude LeBrun

We derive new, sharp lower bounds for certain curvature functionals on the space of Riemannian metrics of a smooth compact 4-manifold with a non-trivial Seiberg-Witten invariant. These allow one, for example, to exactly compute the infimum of the L2-norm of Ricci curvature for all complex surfaces of general type. We are also able to show that the standard m

Bert Schroer

The present state of QFT is analysed from a new viewpoint whose mathematical basis is the modular theory of von Neumann algebras. Its physical consequences suggest new ways of dealing with interactions, symmetries, Hawking-Unruh thermal properties and possibly also extensions of the scheme of renormalized perturbation theory. Interactions are incorporated by

Itzhak Bars

A field theory formulation of two-time physics in d+2 dimensions is obtained from the covariant quantization of the constraint system associated with the OSp(n|2) worldline gauge symmetries of two-time physics. Interactions among fields can then be included consistently with the underlying gauge symmetries. Through this process a relation between Dirac's

M. Bertola, J. Bros, V. Gorini, U. Moschella

We provide a method to decompose the two-point function of a quantum field on a warped manifold in terms of fields living on a lower-dimensional manifold. We discuss explicit applications to Minkowski, de Sitter and anti-de Sitter quantum field theories. This decomposition presents a remarkable analogy with the holography principle, in the sense that physics

L. Bergamin, P. Minkowski

From a supersymmetry covariant source extension of N=2 SYM we study non-trivial thermodynamical limits thereof. Using an argument by one of us about the solution of the strong CP problem and the uniqueness of the QCD ground state we find that the dependence of the effective potential on the defining field operators is severely restricted. In contrast to the

B. Eden, C. Schubert, E. Sokatchev

We explicitly compute the complete three-loop (O(g^4)) contribution to the four-point function of chiral primary current-like operators <(q)^2 q^2 (q)^2 q^2> in any finite N=2 SYM theory. The computation uses N=2 harmonic supergraphs in coordinate space. Dramatic simplifications are achieved by a double insertion of the N=2 SYM linearized action, and applica

Luca Lusanna, D. Nowak-Szczepaniak

For perfect fluids with equation of state $ρ= ρ(n,s)$, Brown gave an action principle depending only on their Lagrange coordinates $α^i(x)$ without Clebsch potentials. After a reformulation on arbitrary spacelike hypersurfaces in Minkowski spacetime, the Wigner-covariant rest-frame instant form of these perfect fluids is given. Their Hamiltonian invariant ma

R. Banerjee, Subir Ghosh

We show that the recently developed soldering formalism in the Lagrangian approach and canonical transformations in the Hamiltonian approach are complementary. The examples of gauged chiral bosons in two dimensions and self-dual models in three dimensions are discussed in details.

O. Abe

We present the new basis functions to investigate the &#39;t Hooft equation, the lowest order mesonic Light-Front Tamm-Dancoff equation for $\rm SU(N_C)$ gauge theories. We find the wave function can be well approximated by new basis functions and obtain an analytic formula for the mass of the lightest bound state. Its value is consistent with the precedent

Uwe Trittmann

The SDLCQ regularization is known to explicitly preserve supersymmetry in 1+1 dimensions. To test this property in higher dimensions, we consider supersymmetric Yang-Mills theory on R x S^1 x S^1. In particular, we choose one of the compact directions to be light-like and another to be space-like. This theory is totally finite, and thus we can solve for boun

V. Antonelli, A. Gall, J. Gasser, A. Rusetsky

In order to investigate specific aspects of bound state calculations in a non-relativistic framework, we consider the energy-levels of a massive scalar particle, which moves in an external field and interacts in addition with a massless scalar particle. The discussion includes the following topics: dimensionally regularized bound-state calculations, ultravio

T. Csorgo

The formulas in the above Erratum are corrected.

S. Groote, J. G. Körner

We discuss various topics in the theory of heavy baryon decays. Among these are recent applications of the Relativistic Three Quark Model to semileptonic, nonleptonic, one-pion and one-photon transitions among heavy baryons, new higher order perturbative results on the correlator of two heavy baryon currents and on the semi-inclusive decay $Λ_b \to X_c + D_s

A. V. Anisovich, V. V. Anisovich, A. V. Sarantsev

In the mass region up to M < 2400 MeV we systematise mesons on the plots (n,M^2) and (J,M^2), thus setting their classification in terms of n^{2S+1}L_J q anti-q states. The trajectories on the (n,M^2)-plots are drawn for the following (IJ^{PC})-states: a_0(10^{++}), a_1(11^{++}), a_2(12^{++}), a_3(13^{++}), a_4(14^{++}), pi(10^{-+}), pi_2(12^{-+}), eta(00^{-

Ruth Durrer, Mairi Sakellariadou

We compute the energy spectra for massless Kalb-Ramond axions in four-dimensional anisotropic string cosmological models. We show that, when integrated over directions, the four-dimensional anisotropic model leads to infra-red divergent spectra similar to the one found in the isotropic case.

E. A. Kuraev, J. Manjavidze, A. Sissakian

The idea that the hard channels may dominate in the very high multiplicity processes is investigated. Quantitative realization of the `hard Pomeron&#39;, deep inelastic scattering and large-angle annihilation mechanism combinations are considered in the pQCD frame for this purpose.

The OPAL collaboration, G. Abbiendi

A study of Z boson pair production in e+e- annihilation at center-of-mass energies near 183 GeV and 189 GeV is reported. Final states containing only leptons, (l+l-l+l- and l+l-nu nubar), quark and lepton pairs, (q qbar l+l-, q qbar nu nubar) and the all-hadronic final state (q qbar q qbar) are considered. In all states with at least one Z boson decaying had

M. L. Ter-Mikayelyan

The review is devoted to the modern investigations of electromagnetic radiation by relativistic charged particles propagating with constant velocity through the periodic media. Two examples of radiation are considered in this review, the first corresponds to the Bragg scattering of charged particles pseudophotons in crystals, the second one to the Fresnel sc

R. Lazkoz, J. A. Valiente Kroon

The asymptotic properties of the solutions to the Einstein-Maxwell equations with boost-rotation symmetry and Petrov type D are studied. We find series solutions to the pertinent set of equations which are suitable for a late time descriptions in coordinates which are well adapted for the description of the radiative properties of spacetimes (Bondi coordinat

S. Capozziello, G. Lambiase

We investigate homogeneous and isotropic cosmological models in scalar-tensor theories of gravity where two scalar fields are nonminimally coupled to the geometry. Exact solutions are found, by Noether symmetries, depending on the form of couplings and self-interaction potentials. An interesting feature is that we deal with the Brans-Dicke field and the infl

Arthur G. Wasserman

It is shown analytically that every static, spherically symmetric solution to the Einstein Yang Mills equations with SU(2) gauge group that is defined in the far field has finite ADM mass. Moreover, there can be at most two horizons for such solutions. The three types of solutions possible, Bartnik-McKinnon particle-like solutions, Reissner-Nordstrom-like so

Joseph Y. Halpern

Knowledge-based program are programs with explicit tests for knowledge. They have been used successfully in a number of applications. Sanders has pointed out what seem to be a counterintuitive property of knowledge-based programs. Roughly speaking, they do not satisfy a certain monotonicity property, while standard programs (ones without tests for knowledge)

L. Castro, D. Warren

XNMR is a system designed to explore the results of combining the well-founded semantics system XSB with the stable-models evaluator SMODELS. Its main goal is to work as a tool for fast and interactive exploration of knowledge bases.

Marc Denecker

This paper analyses the declarative readings of logic programming. Logic programming - and negation as failure - has no unique declarative reading. One common view is that logic programming is a logic for default reasoning, a sub-formalism of default logic or autoepistemic logic. In this view, negation as failure is a modal operator. In an alternative view,

Thorsten Brants

Trigrams&#39;n&#39;Tags (TnT) is an efficient statistical part-of-speech tagger. Contrary to claims found elsewhere in the literature, we argue that a tagger based on Markov models performs at least as well as other current approaches, including the Maximum Entropy framework. A recent comparison has even shown that TnT performs significantly better for the t

A. Zheludev, Y. Chen, C. L. Broholm, Z. Honda

Inelastic neutron scattering on deuterated single-crystal samples is used to study Haldane-gap excitations in the new S=1 one-dimensional quantum antiferromagnet NDMAP, that was recently recognized as an ideal model system for high-field studies. The Haldane gap energies $Δ_x=0.42$ meV, $Δ_y=0.52$ meV and $Δ_z=1.86$ meV, for excitations polarized along the a

Jung Hoon Han, Dung-Hai Lee

We study the single-vortex solution of the t-J model within resonating-valence-bond (RVB) mean-field theory. We find two types of vortex cores, insulating and metallic, depending on the parameters of the model. The pairing order parameter near both cores have $d_{x^2 -y^2}+iηd_{xy}$ symmetry. For some range of $t/J$ the calculated tunneling spectrum of the m

G. K. Savvidy

I suggest and examine artificial material which has exponentially degenerate vacuum state. The corresponding Hamiltonian contains only exotic four-spin interaction term. Each vacuum state is realized as a particular spin configuration separated from others by potential barriers. The benefit of such system in practical applications is that it can be used as h

A. V. Moroz, K. V. Samokhin, C. H. W. Barnes

We present a new model for the study of spin-orbit coupling in interacting quasi-one-dimensional systems and solve it exactly to find the spectral properties of such systems. We show that the combination of spin-orbit coupling and electron-electron interactions results in: the replacement of separate spin and charge excitations with two new kinds of bosonic

Andrea Montanari

Turbo codes are a very efficient method for communicating reliably through a noisy channel. There is no theoretical understanding of their effectiveness. In [1] they are mapped onto a class of disordered spin models. The analytical calculations concerning these models are reported here. We prove the existence of a no-error phase and compute its local stabili

Niurka R. Quintero, Angel Sanchez, Franz G. Mertens

We analyze the diffusive motion of kink solitons governed by the thermal sine-Gordon equation. We analytically calculate the correlation function of the position of the kink center as well as the diffusion coefficient, both up to second-order in temperature. We find that the kink behavior is very similar to that obtained in the overdamped limit: There is a q

L. Shlyk, P. Estrela, J. C. Waerenborgh, L. E. De Long

Heat capacity experiments, crystal structure determination and transmission electron microscopy have been carried out on U3Cu3Sn4 single-crystals. U3Cu3Sn4 was confirmed to be a heavy-fermion antiferromagnet (TN=13(1) K) with a low temperature electronic heat capacity coefficient gamma=390 mJ/molUK2. Low temperature heat capacity experiments on a U3Ni3Sn4 si

R. S. Decca, H. D. Drew, E. Osquiguil, B. Maiorov

Josephson junctions were photogenerated in underdoped thin films of the YBa$_2$Cu$_3$O$_{6+x}$ family using a near-field scanning optical microscope. The observation of the Josephson effect for separations as large as 100 nm between two wires indicates the existence of an anomalously large proximity effect and show that the underdoped insulating material in

Debashish Chowdhury, Rashmi C. Desai

A Bus Route Model (BRM) can be defined on a one-dimensional lattice, where buses are represented by &#34;particles&#34; that are driven forward from one site to the next with each site representing a bus stop. We replace the random sequential updating rules in an earlier BRM by parallel updating rules. In order to elucidate the connection between the BRM wit

Mahito Kohmoto, Masatoshi Sato

Superconductive properties of the two-leg ladder compounds are studied theoretically. The antiferromagnetic fluctuations are considered because of the good nesting of the Fermi surfaces. The attractive interaction which is most likely due to the electron-phonon coupling is also taken into account. Under this circumstance, it is shown that the superconductivi

J. Kopu, R. Hänninen, E. V. Thuneberg

We study theoretically the stability of flow in superfluid 3He-A. The calculations are done using a one-dimensional model where the order parameter depends only on the coordinate in the direction of the superfluid velocity v_s. We concentrate on the case that the external magnetic field H is perpendicular to v_s, where only few results are available analytic

Giuliano Benenti, Xavier Waintal, Jean-Louis Pichard, Dima Shepelyansky

Using Hartree-Fock orbitals with residual Coulomb repulsion, we study spinless fermions in a two dimensional random potential. When we increase the system size $L$ at fixed particle density, the size dependence of the average inverse compressibility exhibits a smooth crossover from a $1/L^2$ towards a 1/L decay when the Coulomb energy to Fermi energy ratio $

Andreas Voigt, Johannes Richter

We consider the frustrated antiferromagnetic s=1 Heisenberg quantum spin chain with regard to the Marshall-Peierls sign rule (MPSR). By using exact diagonalization data we investigate the breakdown of the MPSR in dependence on frustration and compare our findings with data for s=1/2. We calculate a critical value of frustration J_2(crit) where the MPSR is vi

Subhradip Ghosh, Chhanda Basu Chaudhuri, Biplab Sanyal, Abhijit Mookerjee

We here study electronic structure and magnetic properties of disordered CoPd and CoPt alloys using Augmented Space Recursion technique coupled with the tight-binding linearized muffin tin orbital (TB-LMTO) method. Effect of short range ordering present in disordered phase of alloys on electronic and magnetic properties has been discussed. We present results

Giorgio Parisi, Frantisek Slanina

We investigate a toy model of liquid, based on simplified HNC equations in very large spatial dimension D. The model does not exhibit a phase transition, but several regimes of the behavior when D\to\infty can be observed in different intervals of the density.

Bosiljka Tadic

We show that the temporal fluctuations $ΔH(t)$ of the threshold driving field $H(t)$, which triggers an avalanche in slowly driven disordered ferromagnets with many domains, exhibit long-range correlations in space and time. The probability distribution of the distance between {\it successive} avalanches as well as the distribution of trapping times of domai

G. Manoj, P. Ray

We study the distribution of persistent sites (sites unvisited by particles $A$) in one dimensional $A+A\to\emptyset$ reaction-diffusion model. We define the {\it empty intervals} as the separations between adjacent persistent sites, and study their size distribution $n(k,t)$ as a function of interval length $k$ and time $t$. The decay of persistence is the

Debdeep Jena, Arthur. C. Gossard, Umesh K. Mishra

A theory of scattering by charged dislocation lines in a two-dimensional electron gas (2DEG) is developed. The theory is directed towards understanding transport in AlGaN/GaN high-electron-mobility transistors (HEMT), which have a large number of line dislocations piercing through the 2DEG. The scattering time due to dislocations is derived for a 2DEG in clo

A. Bezryadin, C. N. Lau, M. Tinkham

We report measurements on ultrathin (<10 nm) nanowires produced by coating carbon nanotubes with a superconducting amorphous MoGe alloy. We find that nanowires can be superconducting or insulating depending on their normal state resistance $R_{N}$ compared to $R_{q}=h/(2e)^{2}$ -- the quantum resistance for Cooper pairs. If $R_{N}< R_{q}$ the tunneling of qu

J. Merino, Ross H. McKenzie

Many layered metals such as quasi-two-dimensional organic molecular crystals show properties consistent with a Fermi liquid description at low temperatures. The effective masses extracted from the temperature dependence of the magnetic oscillations observed in these materials are in the range, m^*_c/m_e \sim 1-7, suggesting that these systems are strongly co

W. Barford, R. J. Bursill, M. Yu Lavrentiev

We solve a model of interacting electrons coupled to longitudinal phonons using the density matrix renormalisation group method. The model is parametrised for polyenes. We calculate the ground state, and first excited odd-parity singlet and triplet states; and we investigate their energies, and bond length changes and fluctuations for up to 30 sites. The tra

Kevin S. Bedell, Krastan B. Blagoev

We derive the quantum spin hydrodynamic equations in a ferromagnetic metal. From these equations we show the existence of a new massive spin-current mode. This mode can be observed in neutron scattering experiments and we discuss the difficulties in seeing it. At the end we discuss the existence of this mode in localized ferromagnets.

J. A. S. Lima, J. S. Alcaniz

We investigate the influence of an exotic fluid component (&#34;quintessence&#34;) on the angular size-redshift relation for distant extragalactic sources. Particular emphasis is given for the redshif $z_{m}$ at which the angular size takes its minimal value. We derive an analytical closed form which determines how $z_m$ depends on the parameter of the equat

Donald C. Ellison, Evgeny G. Berezhko, Matthew G. Baring

We have extended a simple model of nonlinear diffusive shock acceleration (Berezhko and Ellison 1999) to include the injection and acceleration of electrons and the production of photons from bremsstrahlung, synchrotron, inverse-Compton, and pion-decay processes. We argue that the results of this model, which is simpler to use than more elaborate ones, offer

Li-Xin Li, Bohdan Paczynski

The highest efficiency of converting rest mass into energy by accreting matter into a Kerr black hole is ~ 31% (Thorne 1974). We propose a new process in which periods of accretion from a thin disk, and the associated spin-up of the black hole, alternate with the periods of no accretion and magnetic transfer of energy from the black hole to the disk. These c

Vasso Agapitou, John C. B. Papaloizou

We calculate the structure of a force-free magnetosphere which is assumed to corotate with a central star and which interacts with an embedded differentially rotating accretion disc. The magnetic and rotation axes are aligned and the stellar field is assumed to be a dipole. We concentrate on the case when the amount of field line twisting through the disc-ma

A. Burrows, T. Guillot, W. B. Hubbard, M. S. Marley

The recent discovery that the close-in extrasolar giant planet, HD209458b, transits its star has provided a first-of-its-kind measurement of the planet&#39;s radius and mass. In addition, there is a provocative detection of the light reflected off of the giant planet, $τ$ Boo b. Including the effects of stellar irradiation, we estimate the general behavior o

Kurt Roettiger, Ricardo Flores

We present a numerical Hydro+N-body model of A3266 whose X-ray surface brightness, temperature distribution, and galaxy spatial and velocity distribution data are consistent with the A3266 data. The model is an old (~3 Gyr), off-axis merger having a mass ratio of ~2.5:1. The less massive subcluster in the model is moving on a trajectory from southwest to nor

F. Aharonian, The HEGRA Collaboration

The Crab Nebula has been observed by the HEGRA (High-Energy Gamma-Ray Astronomy) stereoscopic system of imaging air Cherenkov telescopes (IACTs) for a total of about 200 hrs during two observational campaigns: from September 1997 to March 1998 and from August 1998 to April 1999. The recent detailed studies of system performance give an energy threshold and a

Erik Kuulkers, Michiel van der Klis

During several observations in 1999 August with RXTE of the low-mass X-ray binary GX 3+1, we found a single short and strong X-ray burst. This is the first burst from GX 3+1 which clearly shows evidence for radius expansion of the neutron-star photosphere during the thermo-nuclear runaway. We show that the cooling phase of the neutron star photosphere starts

M. Coleman Miller

Many lines of evidence suggest that nonbaryonic dark matter constitutes roughly 30% of the critical closure density, but the composition of this dark matter is unknown. One class of candidates for the dark matter is compact objects formed in the early universe, with typical masses M between 0.1 and 1 solar masses to correspond to the mass scale of objects fo

V. Charmandaris, F. Combes, J. M. van der Hulst

Shells are faint arc-like stellar structures, which have been observed around early type galaxies and are thought to be the result of an interaction. HI gas has recently been detected in shells, a surprising result in view of the theoretical predictions that most of the gas should decouple from stars and fall into the nucleus in such interactions. Here we re

J. R. Walsh, N. Ageorges

High resolution near-infrared adaptive optics imaging and polarimetry have been obtained of the Homunculus Nebula and its central star Eta Carinae (HD 93308). Maps of the linear polarization at a resolution of <0.2&#39;&#39; have been made in the J, H and K bands and in a narrow 2.15micron continuum band (K_c). The overall appearance of the nebula in the nea

D. N. Voskresensky, V. A. Khodel, M. V. Zverev, J. W. Clark

It is proposed that a rearrangement of single-particle degrees of freedom may occur in a portion of the quantum fluid interior of a neutron star. Such a rearrangement is associated with the pronounced softening of the spin-isospin collective mode which, under increasing density, leads to pion condensation. Arguments and estimates based on fundamental relatio

H. Mouri, Y. Taniguchi

By using the flux ratio [FeII]8617/[OI]6300, we demonstrate that most of the interstellar dust grains survive in shocks associated with supernova remnants and Herbig-Haro objects. The [FeII]/[OI] flux ratio is sensitive to the gas-phase Fe/O abundance ratio, but is insensitive to the ionization state, temperature, and density of the gas. We calculate the [Fe

K. Kornet, M. Rozyczka

We numerically test the mode-coupling model (Lubow 1991a) of tidal instability in SU UMa systems. So far, all numercial models confirming it have been based on SPH codes and isothermal equation of state. In our paper we present Eulerian models, using both isothermal approximation and the full energy equation. We also investigate influence of different ways o

M. Mouchet, A. Abrassart, D. Porquet, A. -M. Dumont

Seyfert galaxies have been shown to exhibit a large variety of features in their X-ray spectra from which the environment of the central engine can be deduced. We focus on the two following aspects: the Warm Absorber, mainly responsible of the soft X-ray properties, and the reprocessing/reflecting plasma medium at the origin of the iron Kalpha fluorescent li

Eric Emsellem, Pierre Ferruit

We present the results of new 3D TIGER spectroscopic observations and archived HST/WFPC2 and NICMOS images of the central region of M 104. The [NII]+Ha images reveal the presence of a nuclear spiral structure, and the gaseous kinematics in the central arcsecond shows evidence for kinematical decoupling of the central peak. A straight nuclear dust lane, with

Alain Coc, Margarita Hernanz, Jordi Jose, Jean-Pierre Thibaud

Gamma-ray emission from classical novae is dominated, during the first hours, by positron annihilation resulting from the beta decay of radioactive nuclei. The main contribution comes from the decay of 18F and hence is directly related to 18F formation during the outburst. A good knowledge of the nuclear reaction rates of production and destruction of 18F is

W. E. Schaap, R. Sancisi, R. A. Swaters

The neutral hydrogen line profiles along the major axis of the nearby spiral galaxy NGC 2403 show a wing towards the sytemic velocity. This asymmetry can be explained with the presence of an abnormally thick HI disk (FWHM ~ 5 kpc) or with a two-component structure: a thin disk and a slowly rotating, thicker (1-3 kpc) HI layer. The latter model gives a better

Volker Springel, Naoki Yoshida, Simon D. M. White

We describe the newly written code GADGET which is suitable both for cosmological simulations of structure formation and for the simulation of interacting galaxies. GADGET evolves self-gravitating collisionless fluids with the traditional N-body approach, and a collisional gas by smoothed particle hydrodynamics. Along with the serial version of the code, we

Pierre-Yves Gaillard

The Vogan Conjectures (sometimes called Kazhdan-Lusztig Conjectures) say that a certain algorithm works both on the category of BGG modules and on the category of Harish-Chandra modules. The Alexandru Conjecture tries to uncover the general property common to these two categories which makes Vogan&#39;s algorithm work.

Pierre-Yves Gaillard

Is a Verma module transformed into another Verma module by a selfequivalence? The answer is affirmative and the proof suggests a notion of standard object in the category of Harish-Chandra modules that coincides often, but not always, with the usual one.

F. Darabi, P. S. Wesson

We introduce a generalized gravitational conformal invariance in the context of non-compactified 5D Kaluza-Klein theory. It is done by assuming the 4D metric to be dependent on the extra non-compactified dimension. It is then shown that the conformal invariance in 5D is broken by taking an absolute cosmological scale $R_0$ over which the 4D metric is assumed

Bernd Rosenow, Stefan Scheidl

We develop a Chern-Simons theory to describe a two-dimensional electron gas in intermediate magnetic fields. Within this approach, inhomogeneous states emerge in analogy to the intermediate state of a superconductor. At half filling of the highest Landau level we find unidirectional charge-density-wave (CDW) solutions. With a semiclassical calculation we giv

R. Singh, M. P. Bora

Instabilities of ion-acoustic waves in a dusty plasma with electron-drift, collisional, and dust charge fluctuations effects, have been investigated. The regimes are clearly marked out where the theory is applicable. The critical electron-drift velocity required to drive the instability is predicted. It is also shown that electron thermal conductivity and ch

Steven Moszkowski, Sonia Fleck, Ali Krikeb, Lukas Theußl

We estimate the ratio $R=g_{3}/g_{2}$ of the critical coupling constants $g_{2}$ and $g_{3}$ which are required to achieve binding of 2 or 3 bosons, respectively, with a short-range interaction, and examine how this ratio depends on the shape of the potential. Simple monotonous potentials give $R\simeq 0.8$. A wide repulsive core pushes this ratio close to R

Jayme De Luca

We study numerically the dynamical system of a two-electron atom with the Darwin interaction as a model to investigate scale-dependent effects of the relativistic action-at-a-distance electrodynamics. This dynamical system consists of a small perturbation of the Coulomb dynamics for energies in the atomic range. The key properties of the Coulomb dynamics are

Xiao Wei Zhao, Tian Lun Chen

Based on the LISSOM model and the OFC earthquake model, we introduce a self-organized feature map Neural Network model . It displays a &#34;Self Organized Criticality&#34;(SOC) behavior. It can be seen that the feature area (synchronized area) produced by self-organized process brings about some definite effect on SOC behavior and the system evolves into a &

Dan Abramovich, Angelo Vistoli

We define two equivalent notions of twisted stable map from a curve to a Deligne-Mumford stack with projective moduli space, and we prove that twisted stable maps of fixed degree form a complete Deligne-Mumford stack with projective moduli space.

Bong H. Lian, Chien-Hao Liu, Shing-Tung Yau

We apply the mirror principle of [L-L-Y] to reconstruct the Euler data $Q=\{Q_d\}_{d\in{\tinyBbb N}\cup\{0\}}$ associated to a vector bundle $V$ on ${\smallBbb C}{\rm P}^n$ and a multiplicative class $b$. This gives a direct way to compute the intersection number $K_d$ without referring to any other Euler data linked to $Q$. Here $K_d$ is the integral of the

L. P. Colatto

A matter self-interacting model with N=1-supersymmetry in 3D is discussed in connection with the appearance of a central charge in the algebra of the supersymmetry generators. The result is extended to include gauge fields with a Chern-Simons term. The main result is that, for a simple supersymmetry, only the matter sector contributes to the central charge i

Marcello B. Silva Neto

Using the ideas of effective field theory and dimensional reduction, we relate the parameters of two low energy models of QCD: the O(N) nonlinear sigma model in D=3+1, which describes the dynamics of cool pions, and the O(N) Heisenberg magnet in D=3+0, which is commonly argued to reproduce the correct critical behaviour of the chiral phase transition. As a r

Emili Bagan, Martin Lavelle, David McMullan

The particle Fock space of the matter fields in QED can be constructed using the free creation and annihilation operators. However, these particle operators are not, even at asymptotically large times, the modes of the matter fields that enter the QED Lagrangian. In this letter we construct the fields which do recover such particle modes at large times. We a

M. V. Chizhov, S. T. Petcov

We show that the arguments forming the basis for the claim that the conditions for total neutrino conversion derived and studied in detail in [1,2] ``are just the conditions of the parametric resonance of neutrino oscillations supplemented by the requirement that the parametric enhancement be complete&#39;&#39;, given in [4] have flaws which make the claim p

Rene A. Ong

The field of high energy particle astronomy is exciting and rapidly developing. In the last few years, we have detected extragalactic sources of intense TeV gamma radiation and individual cosmic ray particles with energies exceeding 25 Joules. Understanding the workings of astrophysics under extreme conditions is the primary goal of this field. Also importan

Adriana Iamnitchi, Ian Foster

The idle computers on a local area, campus area, or even wide area network represent a significant computational resource---one that is, however, also unreliable, heterogeneous, and opportunistic. This type of resource has been used effectively for embarrassingly parallel problems but not for more tightly coupled problems. We describe an algorithm that allow

M. D. Glinchuk, I. V. Kondakova

Theory of the first order Raman scattering (FOR) line shape allowing for nonlinear and correlation effects contribution to inhomogeneous broadening as well as dynamic mechanisms of homogeneous broadening is developed. It is shown that in general case FOR line contains two maxima, shape of low frequency one being defined by homogeneous broadening. Our theory

Todd M. Squires, Michael P. Brenner

We demonstrate that the attractive interaction measured between like-charged colloidal spheres near a wall can be accounted for by a nonequilibrium hydrodynamic effect. We present both analytical results and Brownian dynamics simulations which quantitatively capture the one-wall experiments of Larsen and Grier (Nature 385, p. 230, 1997).

Yanqin Wu, Peter Goldreich

ZZ Ceti stars exhibit small amplitude photometric pulsations in multiple gravity-modes. We demonstrate that parametric instability, a form of resonant 3-mode coupling, limits overstable modes to amplitudes similar to those observed. In particular, it reproduces the observed trend that longer period modes have larger amplitudes. Parametric instability involve