May 2000 arXiv papers — page 12

Kenzo Inoue, Nao-aki Yamashita

The new mechanism for the generation of the chiral generations is proposed based on the SU(1,1) horizontal gauge symmetry. The appearance of the chiral generations is controlled by the coupling constant s of the model. This is crucial in the grand unification scheme. The resulting chiral generations naturally acquire the hierarchal Yukawa coupli ng matrices.

Hongya Liu, Bahram Mashhoon

We extend the classical general relativistic theory of measurement to include the possibility of existence of higher dimensions. The intrusion of these dimensions in the spacetime interval implies that the inertial mass of a particle in general varies along its worldline if the observations are analyzed assuming the existence of only the four spacetime dimen

J. Beckers, N. Debergh, F. H. Szafraniec

Generalizing a recent proposal leading to one-parameter families of Hamiltonians and to new sets of squeezed states, we construct larger classes of physically admissible Hamiltonians permitting new developments in squeezing. Coherence is also discussed.

Nguyen Vien Tho, Phu Chi Hoa

The chiral symmetry-breaking term of the Skyrme model with massive pion is modified to obtain the hedgehog profile function which is in best coincidence with the kink-like profile function. For the modified Lagrangian, the minimum of the energy of the B=2 twisty skyrmion configuration is lower than the values for both the cases of the Skyrme Lagrangian with

Mario Castagnino, Edgard Gunzig

An axiomatic formalism for a minimal irreversible quantum mechanics is introduced. It is shown that a quantum equilibrium and the decoherence phenomenon are consequences of the axioms and that Lyapunov variables, exponential survival probabilities, and a classisal conditional never-decreasing entropy can be defined.

Mario A. Castagnino

The importance of the global nature of the arrow of time is shown. Classical Reichenbach diagram and quantum Bohm-Reichenbach diagram, for the universe are introduced. They are used to show the increase of entropy in closed systems, the global nature of the quantum measurement, and the relation among the different arrows of time.

Peter Sheridan Dodds, Daniel H. Rothman

River networks serve as a paradigmatic example of all branching networks. Essential to understanding the overall structure of river networks is a knowledge of their detailed architecture. Here we show that sub-branches are distributed exponentially in size and that they are randomly distributed in space, thereby completely characterizing the most basic level

Peter Sheridan Dodds, Daniel H. Rothman

The structure of a river network may be seen as a discrete set of nested sub-networks built out of individual stream segments. These network components are assigned an integral stream order via a hierarchical and discrete ordering method. Exponential relationships, known as Horton's laws, between stream order and ensemble-averaged quantities pertaining t

Peter Sheridan Dodds, Daniel H. Rothman

This article is the first in a series of three papers investigating the detailed geometry of river networks. Large-scale river networks mark an important class of two-dimensional branching networks, being not only of intrinsic interest but also a pervasive natural phenomenon. In the description of river network structure, scaling laws are uniformly observed.

Erel Levine, Eytan Domany

We introduce a method for validation of results obtained by clustering analysis of data. The method is based on resampling the available data. A figure of merit that measures the stability of clustering solutions against resampling is introduced. Clusters which are stable against resampling give rise to local maxima of this figure of merit. This is presented

Andrés Aguado

The melting-like transition in disordered sodium clusters Na_N, with N=92 and 142 is studied by using a first-principles constant-energy molecular dynamics simulation method. Na_142, whose atoms are distributed in two (surface and inner) main shells with different radial distances to the center of mass of the cluster, melts in two steps: the first one, at ap

G. W. Wei, R. F. Snider

A proposal is made for reducing the solution of the N-particle Lippmann-Schwinger equation to that of smaller sets of particles. This consists of first writing the N-particle equation in terms of all possible $N/2$-particle Lippmann-Schwinger equations. (If N is odd this needs a minor modification.) The second step requires a decoupling of the resolvents for

Silas R. Beane, Paulo F. Bedaque

We discuss two technical issues related to the gap equation in high-density QCD: i) how to obtain the asymptotic solution with well controlled approximations, and ii) the renormalization of four-quark operators in the high-density effective field theory.

Sanjay Jain, Sandeep Krishna

Evolution produces complex and structured networks of interacting components in chemical, biological, and social systems. We describe a simple mathematical model for the evolution of an idealized chemical system to study how a network of cooperative molecular species arises and evolves to become more complex and structured. The network is modeled by a direct

Itzhack Dana

A renormalization scheme is introduced to study quantum Anosov maps (QAMs) on a torus for general boundary conditions (BCs), whose number ($k$) is always finite. It is shown that the quasienergy eigenvalue problem of a QAM for {\em all} $k$ BCs is exactly equivalent to that of the renormalized QAM (with Planck's constant $\hbar ^{\prime}=\hbar /k$) at so

Bidhan Chandra Bag, Deb Shankar Ray

We examine the interplay of nonlinearity of a dynamical system and thermal fluctuation of its environment in the ``physical limit'' of small damping and slow diffusion in a semiclassical context and show that the trajectories of c-number variables exhibit dynamical chaos due to the thermal fluctuations of the bath.

Lutz Brusch, Martin G. Zimmermann, Martin van Hecke, Markus Baer

The mechanism for transitions from phase to defect chaos in the one-dimensional complex Ginzburg-Landau equation (CGLE) is presented. We introduce and describe periodic coherent structures of the CGLE, called Modulated Amplitude Waves (MAWs). MAWs of various period P occur naturally in phase chaotic states. A bifurcation study of the MAWs reveals that for su

Pavel Etingof, Olivier Schiffmann

This paper contains a systematic and elementary introduction to a new area of the theory of quantum groups -- the theory of the classical and quantum dynamical Yang-Baxter equations. It arose from a minicourse given by the first author at MIT in the Spring of 1999, when the second author extended and improved his lecture notes of this minicourse. The quantum

Meng Chen

This note mainly studies the generic finiteness of ϕ_m of a complex projective 3-fold of general type. A new result on the classification to bicanonical pencil for Gorenstein 3-folds is attached in the last section.

John Etnyre

In this paper we develop a method for studying tight contact structures on lens spaces. We then derive uniqueness and non-existence statements for tight contact structures with certain (half) Euler classes on lens spaces. We also prove that any lens space admits only finitely many tight contact structures.

Tomasz Brzezinski, Shahn Majid

We develop the noncommutative geometry (bundles, connections etc.) associated to algebras that factorise into two subalgebras. An example is the factorisation of matrices $M_2(\C)=\C\Z_2\cdot\C\Z_2$. We also further extend the coalgebra version of theory introduced previously, to include frame resolutions and corresponding covariant derivatives and torsions.

Dino Lorenzini, Thomas J. Tucker

In this paper, we prove that a Thue equation F(x,y) = h, where h is an integer and F is a polynomial of degree n with integer coefficients and without repeated roots, has at most 2n^3 - 2n - 3 solutions provided that the Mordell-Weil rank of the Jacboian of the corresponding curve is less than (n-1)(n-2)/2. The proof uses the method of Coleman-Chabauty, exte

Giovanna Carnovale

Using equivalences of categories we provide isomorphisms between the Brauer groups of different Hopf algebras. As an example, we show that when k is a field of characteristic different from 2 the Brauer groups BC(k,H_4,r_t) for every dual quasitriangular structure r_t on Sweedler's Hopf algebra H_4 are all isomorphic to the direct sum of (k,+) and the Br

Yuri I. Manin

This talk is dedicated to various aspects of Mirror Symmetry. It summarizes some of the mathematical developments that took place since M. Kontsevich's report at the Zürich ICM and provides an extensive, although not exhaustive, bibliography.

Do Ngoc Diep

In this paper we construct quantum analogs of strata of coadjoint orbits and describe their representations. This kind objects play an important role in describing quantum groups as repeated extensions of quantum strata.

Changrim Ahn, Rafael I. Nepomechie

The boundary supersymmetric sinh-Gordon model is an integrable quantum field theory in 1+1 dimensions with bulk N=1 supersymmetry, whose bulk and boundary S matrices are not diagonal. We present an exact solution of this model. In particular, we derive an exact inversion identity and the corresponding thermodynamic Bethe Ansatz equations. We also compute the

Yuji Satoh

We discuss the string theory on AdS_3. In the first half of this talk, we review the SL(2,R) and the SL(2,C)/SU(2) WZW models which describe the strings on the Lorentzian and Euclidean AdS_3 without RR backgrounds, respectively. An emphasis is put on the fundamental issues such as the unitarity, the modular invariance and the closure of the OPE. In the secon

Murat Gunaydin

I review the relationship between AdS/CFT (anti-de Sitter / conformal field theory) dualities and the general theory of positive energy unitary representations of non-compact space-time groups and supergroups. I show, in particular, how one can go from the manifestly unitary compact basis of the lowest weight (positive energy) representations of the conforma

Jiro Hashiba, Kazuo Hosomichi, Seiji Terashima

It has been recently shown that F-theory on K3 with background B fields (NSNS and RR 2-forms) is dual to the CHL string in 8 dimensions. In this paper, we reexamine this duality in terms of string junctions in type IIB string theory. It is in particular stressed that certain 7-brane configurations produce Sp gauge groups in a novel way.

V. Barger, S. Pakvasa, T. J. Weiler, K. Whisnant

We consider the consequences for future neutrino factory experiments of small CPT-odd interactions in neutrino oscillations. The ν_μ\toν_μand \barν_μ\to\barν_μsurvival probabilities at a baseline L=732 km can test for CPT-odd contributions at orders of magnitude better sensitivity than present limits. Interference between the CPT-violating interaction and CP

Edmond L. Berger, Michael Klasen, Tim M. P. Tait

We present complete results of a next-to-leading order calculation of the production of gaugino-like charginos ($\chargino$) and neutralinos ($\neutralino$) in association with gluinos ($\gluino$) at hadron colliders, including the strong corrections from the exchange of colored particles and sparticles. Adopting a variety of models for the sparticle mass sp

Edmond Iancu

The high energy limit of QCD is controlled by the small-$x$ part of a hadron wavefunction. We argue that this part is universal to all hadrons and is composed of a new form of matter: a Colored Glass Condensate. This matter is weakly interacting at very small $x$, but is non-perturbative because of the highly occupied boson states which compose the condensat

T. Binoth

The search for an intermediate mass Higgs boson at the LHC needs the quantitative understanding of the two-photon background. A calculation of two-photon production in hadronic collisions at full next-to-leading order is described. It includes photons originating from the hadronization of QCD partons which play an important role at the LHC. A prediction for

W. S. Carvalho, A. S. de Castro, A. C. B. Antunes

A quarkonium-gluonium mixing scheme previously developed to describe the characteristic of the pseudoscalar mesons is applied to axial and tensor mesons. The parameters of the model are determined by fitting the eigenvalues of a mass matrix. The corresponding eigenvectors give the proportion of light quarks, strange quarks and glueball in each meson. However

A. Erdas, C. Isola

We calculate the one-loop neutrino self-energy in a magnetized plasma to all orders in the magnetic field. The calculation is done in a general gauge. We obtain the dispersion relation and effective potential for neutrinos in a CP-symmetric plasma under various conditions, and show that, while the self-energy depends on the gauge parameter $ξ$, the dispersio

Irina Mocioiu, Maxim Pospelov, Radu Roiban

A non-vanishing vacuum expectation value for an antisymmetric tensor field leads to the violation of Lorentz invariance on the brane. This violation is controlled by the $θ_{μν}$ parameter, which has a dimension of inverse mass squared. We assume that the zeroth order term in theta-expansion represents the Standard Model and study the effects induced by line

Shin Ishida, Muneyuki Ishida, Tomohito Maeda

Assuming the spin-independence for confining force, we give a covariant quark representation of general composite meson systems with definite Lorentz transformation properties. For benefit of this representation we are able to deduce automatically the transformation rules of composite mesons for general symmetry operations from those of constituent (exciton)

Johan Bijnens, Joaquim Prades

The $K\toππ$ system is analyzed in the chiral limit within the Standard Model. We discuss how to connect the short-distance running in the $|ΔS|=1$ case to the matrix-elements calculated in a low-energy approximation in a scheme-independent fashion. We calculate this correction and the resulting Wilson Coefficients. The matrix elements are calculated to next

Francesco Terranova

It has been shown in the past that the real part of the e'/e ratio is particularly sensitive to anomalous gauge couplings that modify the Standard Model Lagrangian. Due to the loose bounds on these couplings coming from low energy processes and to the poor sensitivity of hadron colliders to couplings such as $Δg_Z$, it has been argued that anomalous coup

Xiao-Jun Wang, Mu-Lin Yan

We study $e^+e^-\toπ^+π^-$ cross section and phase shift of $I=l=1$ $π-π$ scattering below 1GeV in framework of chiral constituent quark model. The results including all order contribution of the chiral perturbation expansion and all one-loop effects of pseudoscalar mesons, but without any adjust parameters. Width of $ρ$ predicted by the model strongly depen

Sven Bergmann, Yuval Grossman, Zoltan Ligeti, Yosef Nir

If the true values of the D0-anti-D0 mixing parameters lie within the one sigma ranges of recent measurements, then there is strong evidence for a large width difference, y > 0.01, and large SU(3) breaking effects in strong phases, δ> pi/4. These constraints are model independent, and would become stronger if M_{12}/Gamma_{12} << 1 in the D0-anti-D0 system.

Takahiro Miura, Eiichi Takasugi, Masaki Yoshimura

We consider the democratic-type neutrino mass matrix and show that this matrix predicts the atmospheric neutrino mixing to be almost maximal, $\sin^2 2θ_{atm}>0.999$ as well as the large CP violation (the CP violation phase in the standard form is maximal $δ=π/2$). We construct the $Z_3$ symmetric dimension five effective Lagrangian with two up-type Higgs do

Wu-Sheng Dai, Xin-Heng Guo, Hong-Ying Jin, Xue-Qian Li

The two heavy quarks in a baryon which contains two heavy quarks and a light one, can constitute a scalar or axial vector diquark. We study electromagnetic radiations of such baryons, (i) Ξ_{(bc)_1} -> Ξ_{(bc)_0}+γ, (ii) Ξ_{(bc)_1}^* -> Ξ_{(bc)_0}+γ, (iii) Ξ_{(bc)_0}^{**}(1/2, l=1) -> Ξ_{(bc)_0}+γ, (iv) Ξ_{(bc)_0}^{**}(3/2, l=1) -> Ξ_{(bc)_0}+γand (v) Ξ_{(bc

Thomas A. Trainor

Correlation data from high-energy p-p collisions indicate substantial anticorrelation of like-sign pions and correlation of unlike-sign pions on rapidity and azimuth at small length scale suggesting approach to a 1D lattice structure during string hadronization. I generalize this result to propose that an {\em incipient} 3D pion lattice structure may be form

Chris Van Den Broeck

Various objections against Alcubierre&#39;s warp drive geometry are reviewed. Superluminal warp bubbles seem an unlikey possibility within the framework of general relativity and quantum field theory, although subluminal bubbles may still be possible.

R. B. Mann, D. Robbins, T. Ohta, M. R. Trott

We extend the canonical formalism for the motion of $N$-particles in lineal gravity to include charges. Under suitable coordinate conditions and boundary conditions the determining equation of the Hamiltonian (a kind of transcendental equation) is derived from the matching conditions for the dilaton field at the particles&#39; position. The canonical equatio

Pankaj Joshi, Naresh Dadhich, Roy Maartens

The origin of cosmic gamma-ray bursts remains one of the most intriguing puzzles in astronomy. We suggest that purely general relativistic effects in the collapse of massive stars could account for these bursts. The late formation of closed trapped surfaces can occur naturally, allowing the escape of huge energy from curvature-generated fireballs, before the

Chen-Shan Chin, Marcel den Nijs

Flat surface phases are unstable during growth and known to become rough. This does not exclude the possibility that surface reconstruction order persists in rough growing surfaces, in analogy with so-called equilibrium reconstructed rough phases. We investigate this in the context of KPZ type dynamics, using the restricted solid on solid model with negative

S. Tsonchev, R. D. Coalson, S. -S. Chern, A. Duncan

The reliability of the mean-field approach to polymer statistical mechanics is investigated by comparing results from a recently developed lattice mean-field theory (LMFT) method to statistically exact results from two independent numerical Monte Carlo simulations for the problems of a polymer chain moving in a spherical cavity and a polymer chain partitioni

I. Borukhov, D. Andelman, R. Borrega, M. Cloitre

Titration of methacrylic acid / ethyl-acrylate copolymers is studied experimentally and theoretically. At low salt concentrations, this polyacid exhibits a plateau in the titration curve below the neutralization point. The plateau has been often attributed to a first-order phase transition associated with polymer conformational changes. We argue that the spe

R. Gaudoin, M. Nekovee, W. M. C. Foulkes, R. J. Needs

Quantum Monte Carlo simulations of interacting electrons in solids often use Slater-Jastrow trial wave functions with Jastrow factors containing one- and two-body terms. In uniform systems the long-range behavior of the two-body term may be deduced from the random-phase approximation (RPA) of Bohm and Pines. Here we generalize the RPA to nonuniform systems.

C. Menotti, J. R. Anglin, J. I. Cirac, P. Zoller

We study the dynamic process of splitting a condensate by raising a potential barrier in the center of a harmonic trap. We use a two-mode model to describe the phase coherence between the two halves of the condensate. Furthermore, we explicitly consider the spatial dependence of the mode funtions, which varies depending on the potential barrier. This allows

L. D. Carlos, R. A. Sa Ferreira, V. De Zea Bermudez, Sidney J. L. Ribeiro

White light tunable phosphors are obtained from a sol-gel derived siliceous network to which oxyethylene units are covalently grafted by means of urea or urethane cross-linkages. The bright photoluminescence is ascribed to an unusual convolution of distinct emissions originated in the NH groups of the urea or urethane bridges and in the siliceous nanodomains

Franco Ferrari, Hagen Kleinert, Ignazio Lazzizzera

We formulate a field theory capable of describing the entanglement in a canonical ensemble of N polymers in terms of Feynman diagrams.

A. Matulis, F. M. Peeters

Wigner crystallization can be induced in a quantum dot by increasing the effective electron-electron interaction through a decrease of the electron density or by the application of a strong magnetic field. We show that the ground state in both cases is very similar but the energy scales are very different and therefore also the dynamics.

N. A. Slavnov

The six-vertex model with domain wall boundary conditions is considered. A Fredholm determinant representation for the partition function of the model is obtained. The kernel of the corrtesponding integral operator depends on Laguerre polynomials.

Bidhan Chandra Bag, Deb Shankar Ray

We examine the weak noise limit of an overdamped dissipative system within a semiclassical description and show how quantization influences the growth and decay of fluctuations of the thermally equilibrated systems. We trace its origin in a semiclassical counterpart of the generalized potential for the dissipative system.

K. N. Altmann, D. Y. Petrovykh, G. J. Mankey, Nic Shannon

The spin-split Fermi level crossings of the conduction band in Ni are mapped out by high-resolution photoemission and compared to the equivalent crossing in Cu. The area of the quasiparticle peak decreases rapidly below Ef in Ni, but not in Cu. Majority spins have larger spectral weight at Ef than minority spins, thereby enhancing the spin-polarization beyon

Alfonso Romano, Julius Ranninger

We examine the normal-state temperature and doping dependence of the Hall coefficient in the context of a pair-fluctuation scenario, based on a model where itinerant electrons are hybridized with localized electron pairs via a charge exchange term. We show that an anomalous behavior of the Hall effect, qualitatively similar to that observed in high-Tc superc

Cristobal Lopez, Pedro L. Garrido, Francisco de los Santos

We study the influence of the bulk dynamics of a growing cluster of particles on the properties of its interface. First, we define a {\it general bulk growth model} by means of a continuum Master equation for the evolution of the bulk density field. This general model just considers arbitrary addition of particles (though it can be easily generalized to cons

B. G. L. Jager, S. Wimmer, A. Lorke, J. P. Kotthaus

We investigate the Terahertz(THz)-response of a square antidot superlattice by means of photoconductivity measurements using a Fourier-transform-spectrometer. We detect, spectrally resolved, the cyclotron resonance and the fundamental magnetoplasmon mode of the periodic superlattice. In the dissipative transport regime both resonances are observed in the pho

S. Brosig, K. Ensslin, A. G. Jansen, C. Nguyen

InAs-AlSb quantum wells are investigated by transport experiments in magnetic fields tilted with respect to the sample normal. Using the coincidence method we find for magnetic fields up to 28 T that the spin splitting can be as large as 5 times the Landau splitting. We find a value of the g-factor of about 13. For small even-integer filling factors the corr

Yoichi Ando, A. N. Lavrov, Kouji Segawa

Authors&#39; Reply to the Comment by Janossy et al. [cond-mat/0005275] on our article, &#34;Magnetoresistance Anomalies in Antiferromagnetic YBa_{2}Cu_{3}O_{6+x}: Fingerprints of Charged Stripes&#34; [cond-mat/9905071, Phys. Rev. Lett. 83, 2813 (1999)].

Tomoya Isoshima, Tetsuo Ohmi, Kazushige Machida

It is investigated theoretically that magnetized Bose-Einstein condensation (BEC) with the internal (spin) degrees of freedom exhibits a rich variety of phase transitions, depending on the sign of the interaction in the spin channel. In the antiferromagnetic interaction case there exist always double BEC transitions from single component BEC to multiple comp

J. Kuraszkiewicz, B. J. Wilkes, W. N. Brandt, M. Vestergaard

We present supportive evidence that the Boroson and Green eigenvector 1 is not driven by source orientation. Until recently it was generally accepted that eigenvector 1 does not depend on orientation as it strongly correlates with [OIII]5007 emission, thought to be an isotropic property. However, recent studies of radio-loud AGN have questioned the isotropy

Rupert A. C. Croft, Chris Metzler

We explore the possibility that an intrinsic correlation between galaxy ellipticities arising during the galaxy formation process may account for part of the shear signal recently reported by several groups engaged in weak lensing surveys. Using high resolution N-body simulations we measure the projected ellipticities of dark matter halos and their correlati

Heino Falcke, Neil M. Nagar, Andrew S. Wilson, James S. Ulvestad

We have used the VLBA at 5 GHz to observe all galaxies with nuclear radio flux densities above 3.5 mJy found in a VLA survey at 15 GHz of a sample of nearby LINER galaxies. All galaxies were detected revealing high brightness temperature ($T_{b} \ga 10^8$ K) radio sources. Free-free emission is unlikely since it greatly overpredicts the soft X-ray luminositi

Neil M. Nagar, Heino Falcke, Andrew S. Wilson, Luis C. Ho

We report a 0.2&#34; resolution, 15 GHz survey of a sample of 48 low-luminosity active galactic nuclei with the Very Large Array. Compact radio emission has been detected in 57% (17 of 30) of LINERs and low-luminosity Seyferts, at least 15 of which have a flat to inverted radio spectrum (alpha > -0.3). The compact radio cores are found in both type 1 (i.e. w

G. B. Taylor, J. S. Bloom, D. A. Frail, S. R. Kulkarni

We report on the discovery of the radio afterglow from the gamma-ray burst (GRB) of 1999 May 6 (GRB 990506) using the Very Large Array (VLA). The radio afterglow was detected at early times (1.5 days), but began to fade rapidly sometime between 1 and 5 days after the burst. If we attribute the radio emission to the forward shock from an expanding fireball, t

Masaru Shibata, Thomas W. Baumgarte, Stuart L. Shapiro

We study the dynamical stability against bar-mode deformation of rapidly spinning neutron stars with differential rotation. We perform fully relativistic 3D simulations of compact stars with $M/R \geq 0.1$, where $M$ is the total gravitational mass and $R$ the equatorial circumferential radius. We adopt an adiabatic equation of state with adiabatic index $Γ=

O. Laurent, I. F. Mirabel, V. Charmandaris, P. Gallais

We present the effects of limited spatial resolution to the observed mid-infrared (MIR) spectrum of an active galactic nucleus (AGN) surrounded by a disk with massive star forming regions. Using MIR observations of the face-on nearby Seyfert 1 galaxy NGC 6814, we vary the observing aperture and examine the evolution of the observed AGN/starburst fraction wit

O. Laurent, I. F. Mirabel, V. Charmandaris, P. Gallais

We present new mid-infrared (MIR) diagnostics to distinguish emission of active galactic nuclei (AGN) from that originating in starburst regions. Our method uses empirical spectroscopic criteria based on the fact that MIR emission from star forming or active galaxies arises mostly from HII regions, photo-dissociation regions (PDRs) and AGNs. The analysis of

Lev Titarchuk, Vladimir Osherovich

The recently formulated Two Oscillator (TO) model interprets the lowest of the kilohertz frequencies of the twin peak quasi-periodic oscillations in X -ray binaries as the Keplerian frequency nu_K. The high twin frequency nu_h in this model holds the upper hybrid frequency relation to the rotational frequency of the neutron star&#39;s magnetosphere Omega: nu

M. Franqueira, M. Tagger, A. I. Gomez de Castro

We present the results of a 2-D, two fluid (ions and neutrals) simulation of the ambipolar filamentation process, in which a magnetized, weakly ionized plasma is stirred by turbulence in the ambipolar frequency range. The higher turbulent velocity of the neutrals in the most ionized regions gives rise to a non-linear force driving them out of these regions,

Patrick Petitjean, Bastien Aracil, R. Srianand, Rodrigo Ibata

A study of the absorption systems toward the gravitationally lensed quasar APM 08279+5255 is presented. Most of the MgII systems in the redshift range 1.2-2.07, although saturated, show large residuals at the bottom of the lines. The most likely interpretation is that individual clouds within MgII halos do cover only one of the two brightest QSO images. This

S. Plueschke, R. Diehl, D. H. Hartmann, U. G. Oberlack

Recent observations of the diffuse Galactic gamma-ray glow at 1.809 MeV, attributed to the radioactive decay of 26Al, point towards a massive star origin of this radioactive isotope. Wolf Rayet stars and core-collapse supernovae appear to dominate the production of this isotope. Massive stars are commonly located in clusters and OB associations, regions of r

S. Refsdal, R. Stabell, J. Pelt, R. Schild

From regular monitoring of the Double Quasar QSO 0957+561 A,B there is now general agreement on a time delay of about 416 days. This has made it possible to determine the microlensing residual in the light-curve, see Pelt et al. (1998). We have used two significant microlensing features: 1) A ``quiet&#39;&#39; period with a variability less than 0.05 mag las

F. Bocchino, J. Vink, F. Favata, A. Maggio

We present a spectral analysis of the Northern and Southwestern rim of the RCW86 X-ray shell, pointing out the remarkable differences between these two parts of the same object. In the North, a single temperature Non Equilibrium of Ionization emission model describes the data well, and the derived abundances of O, Ne, Mg, Si, S, Ar and Fe are in agreement wi

B. J. Boyle, T. Shanks, S. M. Croom, R. J. Smith

We present a determination of the optical QSO luminosity function and its cosmological evolution with redshift for a sample of over 6000 QSOs identified primarily from the first observations of the 2dF QSO Redshift Survey (2QZ). For QSOs with -26 < M_B < -23 and 0.35 < z < 2.3, we find that pure luminosity evolution (PLE) models provide an acceptable fit to

Ruth C. Peterson, Carolus J. Schrijver

We have obtained echelle spectra with the Hubble Space Telescope (HST) of the MgII 2800A region of ten stars whose metallicities range from 1/300 to 1/3 that of the Sun, and whose space velocities suggest a halo or old thick-disk origin. Spectra of all ten show double-peaked emission in the MgII core, very much like the quiet Sun. A half-dozen non-rotating s

Anthony Mezzacappa, Matthias Liebendoerfer, O. E. Bronson Messer, W. Raphael Hix

With exact three-flavor Boltzmann neutrino transport, we simulate the stellar core collapse, bounce, and postbounce evolution of a 13 solar mass star in spherical symmetry, the Newtonian limit, without invoking convection. In the absence of convection, prior spherically symmetric models, which implemented approximations to Boltzmann transport, failed to prod

R. Sankaranarayanan, A. Lakshminarayan, V. B. Sheorey

A discontinuous generalization of the standard map, which arises naturally as the dynamics of a periodically kicked particle in a one dimensional infinite square well potential, is examined. Existence of competing length scales, namely the width of the well and the wavelength of the external field, introduce novel dynamical behaviour. Deterministic chaos ind

Iosif Bena, Aleksey Nudelman

We use dielectric branes to find non singular string theory duals of a perturbed 2+1 dimensional gauge theory living on D2 branes. By adding fermion masses we obtain theories with reduced supersymmetry. The Higgs vacua of the perturbed theory correspond to polarization of the D2 branes into D4 branes. The confining vacua correspond to polarization of the D2

P. Berglund, T. Hubsch, D. Minic

It is shown that non-supersymmetric spacetime varying string vacua can lead to an exponential hierarchy between the electroweak and the gravitational scales. The hierarchy is naturally generated by a string coupling of O(1).

P. Baseilhac

We propose exact vacuum expectation values of local fields for a quantum group restriction of the $C_2^{(1)}$ affine Toda theory which corresponds to two coupled minimal models. The central charge of the unperturbed models ranges from $c=1$ to $c=2$, where the perturbed models correspond to two magnetically coupled Ising models and Heisenberg spin ladders, r

T. W. Allen, W. H. Klink, W. N. Polyzou

Point-form relativistic quantum mechanics is applied to elastic electron-deuteron scattering. The deuteron is modeled using relativistic interactions that are scattering-equivalent to the nonrelativistic Argonne $v_{18}$ and Reid &#39;93 interactions. A point-form spectator approximation (PFSA) is introduced to define a conserved covariant current in terms o

Y. G. Yi

The Lagrangian approach of Dirac is presented in a complete form. This suggests to identify the Schrödinger equation as the Euler-Lagrange equation rather than the Hamiltonian operator equation.

Klaus Morawetz, Václav Špička, Pavel Lipavský

The finite duration of the collisions in Fermionic systems as expressed by the retardation time in non-Markovian Levinson-type kinetic equations is discussed in the quasiclassical limit. We separate individual contributions included in the memory effect resulting in (i) off-shell tails of the Wigner distribution, (ii) renormalization of scattering rates and

Pei-Ming Ho, Yu-Ting Yeh

We show that when the field strength H of the NS-NS B field does not vanish, the coordinates X and momenta P of an open string endpoints satisfy a set of mixed commutation relations among themselves. Identifying X and P with the coordinates and derivatives of the D-brane world volume, we find a new type of noncommutative spaces which is very different from t

Pedro Bernaola-Galvan, Plamen Ch. Ivanov, Luis A. Nunes Amaral, Ary L. Goldberger

We introduce a segmentation algorithm to probe temporal organization of heterogeneities in human heartbeat interval time series. We find that the lengths of segments with different local values of heart rates follow a power-law distribution. This scale-invariant structure is not a simple consequence of the long-range correlations present in the data. We also

A. Katavolos, I. G. Todorov

The set of normalizers between von Neumann (or, more generally, reflexive) algebras A and B, (that is, the set of all operators x such that xAx* is a subset of B and x*Bx is a subset of A) possesses `local linear structure&#39;: it is a union of reflexive linear spaces. These spaces belong to the interesting class of normalizing linear spaces, namely, those

D. Fioravanti, M. Stanishkov

We present a construction of a Virasoro symmetry of the sine-Gordon (SG) theory. It is a dynamical one and has nothing to do with the space-time Virasoro symmetry of 2D CFT. Although it is clear how it can be realized dyrectly in the SG field theory, we are rather concerned here with the corresponding N-soliton solutions. We present explicit expressions for

Davide Rocchesso

While traditional implementations of variable-length digital delay lines are based on a circular buffer accessed by two pointers, we propose an implementation where a single fractional pointer is used both for read and write operations. On modern general-purpose architectures, the proposed method is nearly as efficient as the popularinterpolated circular buf

S. Horata, H. S. Egawa

The bosonic IIB matrix model is studied using a numerical method. This model contains the bosonic part of the IIB matrix model conjectured to be a non-perturbative definition of the type IIB superstring theory. The large N scaling behavior of the model is shown performing a Monte Carlo simulation. The expectation value of the Wilson loop operator is measured

A. M. Ghezelbash, K. Kaviani, S. Parvizi

Considering the Randall-Sundrum background, we calculate the total cross-section for $ϕϕ^\star \to G γ$ in the framework of the scalar electrodynamics.

Corneliu Sochichiu

We present some arguments showing spectrum doubling of matrix models in the limit $N\to\infty$ which is connected with fermionic determinant behaviour. The problems are similar to ones encountered in the lattice gauge theories with chiral fermions. One may discuss the ``physical meaning&#39;&#39; of the doubling states or ways to eliminate them. We briefly c

L. Feher, B. G. Pusztai

A complete description of the non-dynamical r-matrices of the degenerate Calogero-Moser models based on $gl_n$ is presented. First the most general momentum independent r-matrices are given for the standard Lax representation of these systems and those r-matrices whose coordinate dependence can be gauged away are selected. Then the constant r-matrices result

Erik Sjöqvist, Arun K. Pati, Artur Ekert, Jeeva S. Anandan

We provide a physical prescription based on interferometry for introducing the total phase of a mixed state undergoing unitary evolution, which has been an elusive concept in the past. We define the parallel transport condition that provides a connection-form for obtaining the geometric phase for mixed states. The expression for the geometric phase for mixed

Lajos Diosi, Claus Kiefer

Classical properties of an open quantum system emerge through its interaction with other degrees of freedom (decoherence). We treat the case where this interaction produces a Markovian master equation for the system. We derive the corresponding distinguished local basis (pointer basis) by three methods. The first demands that the pointer states mimic as clos

Makoto Tsubota, Tsunehiko Araki, Sergey K. Nemirovskii

A recent experiment has shown that a tangle of quantized vortices in superfluid $^4$He decayed even at mK temperatures where the normal fluid was negligible and no mutual friction worked. Motivated by this experiment, this work studies numerically the dynamics of the vortex tangle without the mutual friction, thus showing that a self-similar cascade process,