April 2001 arXiv papers — page 8

Merced Montesinos

The canonical analysis of the (anti-) self-dual action for gravity supplemented with the (anti-) self-dual Pontrjagin term is carried out. The effect of the topological term is to add a `magnetic' term to the original momentum variable associated with the self-dual action leaving the Ashtekar connection unmodified. In the new variables, the Gauss constra

W. Chen

This paper is concerned with a few novel RBF-based numerical schemes discretizing partial differential equations. For boundary-type methods, we derive the indirect and direct symmetric boundary knot methods (BKM). The resulting interpolation matrix of both is always symmetric irrespective of boundary geometry and conditions. In particular, the direct BKM app

J. R. Feller, C. -C. Tsai, J. B. Ketterson, J. L. Smith

We present results of a microwave surface impedance study of the heavy fermion superconductor UBe13. We clearly observe an absorption peak whose frequency- and temperature-dependence scales with the BCS gap function. Resonant absorption into a collective mode, with energy approximately proportional to the superconducting gap, is proposed as a possible explan

S. Inouye, S. Gupta, T. Rosenband, A. P. Chikkatur

We have observed phase singularities due to vortex excitation in Bose-Einstein condensates. Vortices were created by moving a laser beam through a condensate. They were observed as dislocations in the interference fringes formed by the stirred condensate and a second unperturbed condensate. The velocity dependence for vortex excitation and the time scale for

B. A. Green, M. D. Scadron

Directional coupling of Thornber-Feynman polarization with the high-Tc ARPES distribution specifies the optimum flatband pseudogap Δand mobile localized quasiparticle. This coupling peaks by tuning the statistics and interaction energy to produce stable short-ranged directional pairing that reflects the lattice asymmetry. Analogous energy gap and BCS ratio p

C. Reichhardt, C. J. Olson, R. T. Scalettar, G. T. Zimanyi

We examine the melting of commensurate and incommensurate vortex lattices interacting with square pinning arrays through the use of numerical simulations. For weak pinning strength in the commensurate case we observe an order-order transition from a commensurate square vortex lattice to a triangular floating solid phase as a function of temperature. This flo

M-T. Kechadi, R. G. Reilly, K. A. Dawson, Yu. A. Kuznetsov

In this paper we present a method to study the folding structure of a simple model consisting of two kinds of monomers, hydrophobic and hydrophilic. This method has three main steps: an efficient simulation method to bring an open sequence of homopolymer to a folded state, the application of a painting method called (regular hull) to the folded globule and t

Stefan Schlagowski, Karin Jacobs, Stephan Herminghaus

A transient surface instability is reported in thin nematic films of 5CB and 8CB, occurring near the nematic-isotropic phase transition. Although this instability leads to patterns reminiscent of spinodal dewetting, we show that it is actually based on a nucleation mechanism. Its characteristic wavelength does not depend markedly on film thickness, but stron

J. P. Huang, K. W. Yu, Jun Lei, Hong Sun

Recent experiments revealed that the dielectric dispersion spectrum of fission yeast cells in a suspension was mainly composed of two sub-dispersions. The low-frequency sub-dispersion depended on the cell length, while the high-frequency one was independent of it. The cell shape effect was simulated by an ellipsoidal cell model but the comparison between the

E. W. Piotrowski, J. Sladkowski

We argue that the recently published by Przystawa and Wolf model of the Bagsik financial oscillator is oversimplified and unrealistic. We propose and analyze a refined explanation of this rare financial phenomenon. We have found an example that results in profitability about 45 000 times bigger than that of the Przystawa and Wolf model.

T. Brandes, F. Renzoni, R. H. Blick

We propose a scheme to prepare arbitrary superpositions of quantum states in double quantum--dots irradiated by coherent microwave pulses. Solving the equations of motion for the dot density matrix, we find that dephasing rates for such superpositions can be quantitatively infered from additional electron current pulses that appear due to a controllable brea

S. Hofmann, A. Rar, D. W. Moon, K. Yoshihara

Application of the so called mxing-roughness-information depth (MRI)-model to the quantitative reconstruction of the in-depth distribution of composition is demonstrated by comparing SIMS and AES depth profiles. A GaAs/AlAs reference sample consisting of two layers of AlAs (1 ML and 36 ML) separated by 44 ML of a GaAs matrix was depth profiled using almost i

T. S. Grigera, V. Martin-Mayor, G. Parisi, P. Verrocchio

The findings of X-ray and neutron scattering experiments on amorphous systems are interpreted within the framework of the theory of Euclidean random matrices. This allows to take into account the topological nature of the disorder, a key ingredient which strongly affects the vibrational spectra of those systems. We present a resummation scheme for a perturba

L. Tewordt, D. Fay

We calculate the thermal conductivity kappa in magnetic fields near H_c2 for spin-triplet superconducting states with line nodes vertical and horizontal relative to the RuO_2-planes. The method for calculating the Green's functions takes into account the spatial variation of the order parameter and superconducting flow for the Abrikosov vortex lattice. F

M. Reichenstein, H. Stark, J. Stelzer, H. -R. Trebin

We study dynamical processes in a multi-domain (MD) structured nematic liquid crystal cell with a particular emphasis on the motion, creation and annihilation of disclinations. In the MD cell right- and left-handed director helices alternate due to a special choice of the director pretilt angles at the surfaces. As a result, a net of twist disclinations occu

R. Rajesh, Satya N. Majumdar

We study analytically the correlations between the positions of tagged particles in the random average process, an interacting particle system in one dimension. We show that in the steady state the mean squared auto-fluctuation of a tracer particle grows subdiffusively as $sigma^2(t) ~ t^{1/2}$ for large time t in the absence of external bias, but grows diff

V. T. Dolgopolov, A. A. Shashkin, J. M. Broto, H. Rakoto

We measure the Hall conductivity, $σ_{xy}$, on a Corbino geometry sample of a high-mobility AlGaAs/GaAs heterostructure in a pulsed magnetic field. At a bath temperature about 80 mK, we observe well expressed plateaux in $σ_{xy}$ at integer filling factors. In the pulsed magnetic field, the Laughlin condition of the phase coherence of the electron wave funct

O. C. Martin, R. Monasson, R. Zecchina

Recently, it has been recognized that phase transitions play an important role in the probabilistic analysis of combinatorial optimization problems. However, there are in fact many other relations that lead to close ties between computer science and statistical physics. This review aims at presenting the tools and concepts designed by physicists to deal with

Stephan Herminghaus, Karin Jacobs, Ralf Seemann

A simple and predictive model is put forward explaining the experimentally observed substantial shift of the glass transition temperature, Tg, of sufficiently thin polymer films. It focuses on the limit of small molecular weight, where geometrical `finite size' effects on the chain conformation can be ruled out. The model is based on the idea that the po

Frank Mack, Peter Horsch

The optical conductivity of the double exchange and the orbital degenerate Kondo lattice Hamiltonian (orbital t-J model) are invetigated by means of finite temperature diagonalization for different doping concentrations. The temperature dependence of sum rules, kinetic energy and Drude weight are studied. In particular it is shown that the double exchange mo

J. K. Hoogland, C. D. D. Neumann, D. Bloch

We give a simple algorithm to incorporate the effects of resets in convertible bond prices, without having to add an extra factor to take into account the value of the reset. Furthermore we show that the effect of a notice period, and additional make-whole features, can be treated in a straightforward and simple manner. Although we present these results with

Yoshiyuki Ono, Tetsuya Hamano

The Peierls distortions in a two-dimensional electron-lattice system described by a Su-Schrieffer-Heeger type model extended to two-dimensions are numerically studied for a square lattice. The electronic band is just half-filled and the nesting vector is ($π/a$, $π/a$) with $a$ the lattice constant. In contrast to the previous understanding on the Peierls tr

V. I. Yukalov, E. P. Yukalova, V. S. Bagnato

The population dynamics of a trapped Bose-Einstein condensate, subject to the action of an oscillatory field, is studied. This field produces a modulation of the trapping potential with the frequency close to the transition frequency between the ground state and an excited energy level. Unusual critical effects are found exhibiting sharp qualitative changes

Gabriel A. Cwilich, Fredy R. Zypman

Waves propagate through disordered systems in a variety of regimes. There is a threshold of disorder beyond which waves become localized and transport becomes restricted. The intensity I of the wave transmitted through a system has a dependence on the length L of the sample that is characteristic of the regime. For example, I decays as 1/L in the diffusive r

Jian-Sheng Wang, Robert H. Swendsen

We present a formalism of the transition matrix Monte Carlo method. A stochastic matrix in the space of energy can be estimated from Monte Carlo simulation. This matrix is used to compute the density of states, as well as to construct multi-canonical and equal-hit algorithms. We discuss the performance of the methods. The results are compared with single his

R. Jin, M. Paranthaman, H. Y. Zhai, H. M. Christen

We have investigated the temperature and magnetic field dependence of the Hall coefficient of two well-characterized superconducting MgB$_2$ films (T$_{c0}$=38.0 K) in both the normal and superconducting states. Our results show that the normal-state Hall coefficient R$_H$ is positive and increases with decreasing temperature, independent of the applied magn

Geza Toth, Craig S. Lent

Quantum-dot Cellular Automata (QCA) may offer a viable alternative of traditional transistor-based technology at the nanoscale. When modeling a QCA circuit, the number of degrees of freedom necessary to describe the quantum mechanical state increases exponentially making modeling even modest size cell arrays difficult. The intercellular Hartree approximation

W. N. Brandt, S. C. Gallagher, S. Kaspi

We briefly review X-ray studies of ionized AGN outflows and high-redshift AGN. We discuss recent progress with Chandra and XMM-Newton as well as prospects and requirements for future X-ray missions.

Laura Ferrarese, Richard W. Pogge, Bradley M. Peterson, David Merritt

We report the first results of a program to measure accurate stellar velocity dispersions in the bulges of the host galaxies of active galactic nuclei (AGNs) for which accurate black hole (BH) masses have been determined via reverberation mapping. We find good agreement between BH masses obtained from reverberation mapping, and from the M(BH) - sigma relatio

S. V. Vadawale, A. R. Rao, S. K. Chakrabarti

The Galactic microquasar GRS 1915+105 exhibits several episodes of steady X-ray emission characterized by a hard power-law spectrum and intense Quasi Periodic Oscillations. It is known that there are two types of such low-hard states, one with steady radio emission and the other without any significant radio emission. We present the results of a detailed X-r

E. L. Martin, M. R. Zapatero Osorio, H. J. Lehto

We report CCD photometric monitoring of the nonemission ultracool dwarf BRI 0021-0214 (M9.5) obtained during 10 nights in 1995 November and 4 nights in 1996 August, with CCD cameras at 1 m class telescopes on the observatories of the Canary Islands. We present differential photometry of BRI 0021-0214, and we report significant variability in the I-band light

C. Trigilio, C. S. Buemi, G. Umana, M. Rodono`

We present multifrequency VLA and VLBA observations at 8.4 GHz of the RS CVn system AR Lac, that were performed in autumn 1997 simultaneously with X-ray observations obtained from Rodono` et al. (1999). Our VLBA data indicate a resolved source with dimension close to the system separation, while the study of the flux density curve evidences a small amplitude

W. V. Dixon, S. Sallmen, M. Hurwitz, R. Lieu

We report the detection of diffuse O VI 1032, 1038 A emission in a 29-ksec observation centered on the Coma Cluster (l = 57.6, b = +88.0) and an 11-ksec observation toward Virgo (l = 284.2, b = +74.5) through the low-resolution (30"x30") aperture of the Far Ultraviolet Spectroscopic Explorer (FUSE). The emission lines have a redshift near zero and ar

Eve C. Ostriker, Chin-Fei Lee, James M. Stone, Lee G. Mundy

We analyze the dynamics of the shell produced when a bow shock from a collimated jet propagates into the surrounding medium. Under interstellar conditions, the shock is radiative, and a ballistic approximation for the shell flow is appropriate beyond the working surface where the jet impacts its surroundings. The solution is then determined by the ambient an

Chin-Fei Lee, James M. Stone, Eve C. Ostriker, Lee G. Mundy

We present two-dimensional hydrodynamical simulations of both jet- and wind-driven models for protostellar outflows in order to make detailed comparisons to the kinematics of observed molecular outflows. Comparing the different simulations with observations, we find that some outflows, e.g., HH 212, show features consistent with the jet-driven model, while o

K. Benabed, F. Bernardeau

We explore the possibility of putting constraints on quintessence models with large-scale structure observations. In particular we compute the linear and second order growth rate of the fluctuations in different flavors of quintessence scenarios. We show that effective models of quintessence (e.g. with a constant equation of state) do not account of the resu

Paolo Conconi, Sergio Campana

Grazing incidence mirrors for X-ray astronomy are usually designed in the parabola-hyperbola (Wolter I) configuration. This design allows for optimal images on-axis, which however degrade rapidly with the off-axis angle. Mirror surfaces described by polynomia (with terms higher than order two), have been put forward to improve the performances over the field

F. W. Stecker, M. H. Salamon

The COMPTEL and EGRET detectors aboard the Compton Gamma-Ray Observatory measured an extragalactic gamma-ray background extending from MeV energies up to about 100 GeV. Calculations performed making reasonable assumptions indicate that blazars can account for the background between about 10 MeV and at least 10 GeV. Below 30 MeV, the background flux and spect

A. La Barbera, L. Burderi, T. Di Salvo, R. Iaria

We report on the spectral analysis of the X-ray pulsar LMC X-4 in its high state out of eclipse observed by BeppoSAX. During this observation no coherent pulsations are detected. The primary continuum is well described by a power law with a high energy cutoff (E_cutoff ~ E_fold ~ 18 keV). The addition of a cyclotron absorption line at ~100 keV improves the f

M. Douspis, J. G. Bartlett, A. Blanchard, M. Le Dour

Most parameter constraints obtained from cosmic microwave background (CMB) anisotropy data are based on power estimates and rely on approximate likelihood functions; computational difficulties generally preclude an exact analysis based on pixel values. With the specific goal of testing this kind of approach, we have performed a complete (un-approximated) lik

J. C. Guirado, E. Ros, D. L. Jones, J. F. Lestrade

We present 5 GHz space-VLBI observations of the quasar pair B1342+662/B1342+663 that demonstrate the feasibility of phase-reference techniques using an antenna in space. The space-based data were taken by the satellite HALCA, of the space-VLBI mission VSOP. From residual (referenced) phases we derive an upper bound of 10 meters to the uncertainty of the spac

N. G. Kantharia, K. R. Anantharamaiah

We present results of a search for carbon recombination lines in the Galaxy at 34.5 MHz (C$575α$) made using the dipole array at Gauribidanur near Bangalore. Observations made towards 32 directions, led to detections of lines in absorption at nine positions. Followup observations at 328 MHz (C$272α$) using the Ooty Radio Telescope detected these lines in emi

Kohji Yoshikawa, Atsushi Taruya, Y. P. Jing, Yasushi Suto

We perform an extensive analysis of nonlinear and stochastic biasing of galaxies and dark halos in spatially flat low-density CDM universe using cosmological hydrodynamic simulations. We compare their biasing properties with the predictions of an analytic halo biasing model. Dark halos in our simulations exhibit reasonable agreement with the predictions only

W. D. Watson, D. S. Wiebe

Calculations are performed for the circular polarization of maser radiation from a turbulent, Keplerian disk that is intended to represent the sub-parsec disk at the nucleus of the galaxy NGC4258. The polarization in the calculations is a result of the Zeeman effect in the regime in which the Zeeman splitting is much less than the spectral linebreadth. Plaus

M. Arnould, S. Goriely

Critical views are presented on some nucleo-cosmochronological questions. Progress has been made recently in the development of the 187Re-187Os cosmochronometry. From this, there is good hope for this clock to become of the highest quality for the nuclear dating of the Universe. The simultaneous observation of Th and U in ultra-metal-poor stars would also be

Hongsong Chou, George B. Field

Dynamical studies of MHD turbulence on the one hand, and arguments based upon magnetic helicity on the other, have yielded seemingly contradictory estimates for the $α$ parameter in turbulent dynamo theory. Here we show, with direct numerical simulation of three-dimensional magnetohydrodynamic turbulence with a mean magnetic field, $\OB$, that the constraint

Eugene Demler, Fei Zhou

We study superfluid and Mott insulator phases of cold spin-1 Bose atoms with antiferromagnetic interactions in an optical lattice, including a usual polar condensate phase, a condensate of singlet pairs, a crystal spin nematic phase, and a spin singlet crystal phase. We suggest a possibility of exotic fractionalized phases of spinor BEC and discuss them in t

Ivan Vitev, Miklos Gyulassy

PHENIX data on Au+Au at root(s)_= 130 AGeV suggest that p-bar yields may exceed pi- at high p_T > 2 GeV/c. We propose that jet quenching in central collisions suppresses the hard PQCD component of the spectra in central A+A reactions, thereby exposing a novel component of baryon dynamics that we attribute to (gluonic) baryon junctions. We predict that the ob

Peter G. Jonker, Michiel van der Klis

We report the discovery of 0.59 s X-ray pulsations from the low-mass X-ray binary, 5.57 hr dipping and eclipsing ADC source 2A 1822-371. Pulse arrival time analysis indicates a circular orbit with e < 0.03 (95% confidence) and an asini for the neutron star of 1.006(5) lightseconds, implying a mass function of (2.03+-0.03) x 10^-2 M_sun. The barycentric pulse

D. L. Zhou, C. P. Sun

The second order quantum decoherence (SOQDC)is proposed as a novel description for the loss of quantum coherence only reflected by second order quantum correlations. By calculating the two-time correlation function, the phenomenon of SOQDC is studied in details for a simple model, a two boson system interacting with a reservoir composed of one or many bosons

S. Sugimoto, K. Sumiyoshi, H. Toki

We investigate the pairing property of nuclear matter with Relativistic Hartree-Bogoliubov(RHB) approach. Recently, the RHB approach has been widely applied to nuclear matter and finite nuclei. We have extended the RHB approach to be able to include non-linear coupling terms of mesons. In this paper we apply it to nuclear matter and observe the effect of non

O. A. Ponkratenko, V. I. Tretyak, Yu. G. Zdesenko

The computer code DECAY4 is developed to generate initial energy, time and angular distributions of particles emitted in radioactive decays of nuclides and nuclear (atomic) deexcitations. Data for description of nuclear and atomic decay schemes are taken from the ENSDF and EADL database libraries. The examples of use of the DECAY4 code in several underground

Alexander Groisman, Victor Steinberg

Turbulence is one of the most fascinating phenomena in nature and one of the biggest challenges for modern physics. It is common knowledge that a flow of a simple, Newtonian fluid is likely to be turbulent, when velocity is high, viscosity is low and size of the tank is large\cite{Landau,Tritt}. Solutions of flexible long-chain polymers are known as visco-el

David M. J. Calderbank, Maciej Dunajski

We find all three-dimensional Einstein--Weyl spaces with the vanishing scalar curvature

Rupert W. T. Yu

In this paper, by establishing an explicit and combinatorial description of the centralizer of a distinguished nilpotent pair in a classical simple Lie algebra, we solve in the classical case Panyushev&#39;s Conjecture which says that distinguished nilpotent pairs are wonderful, and the classification problem on almost principal nilpotent pairs. More precise

Michael L. Schmid

In general relativity and electrodynamics fields are always generated from static monopoles (like mass or electric charge) or their corresponding currents by surrounding them in a spherical configuration. We investigate a generation of fields from primary fields by a scalar coupling. The generated secondary fields fulfill the condition of source-freedom and

A. N. Mitra, B. M. Sodermark

The baryon-$qqq$ vertex function governed by the Markov-Yukawa Transversality Principle ($MYTP$), is formulated via the Covariant Null-Plane Ansatz ($CNPA$) as a 3-body generalization of the corresponding $q{\bar q}$ problem, and employed to calculate the proton e.m. form factor and baryon octet magnetic moments.The e.m. coupling scheme is specified by letti

Dilip Kumar Ghosh, Anirban Kundu, Probir Roy, Sourov Roy

Though the minimal model of anomaly mediated supersymmetry breaking has been significantly constrained by recent experimental and theoretical work, there are still allowed regions of the parameter space for moderate to large values of $\tanβ$. We show that these regions will be comprehensively probed in a ${\sqrt s} =1$ TeV $e^+e^-$ linear collider. Diagnost

Tibor Torma

In Randall-Sundrum type scenarios the effective size of the extra dimension remains unconstrained. A TeV-scale brane tension without orbifold boundary conditions would allow phenomenologically observable processes at high energy colliders. Among others, the brane could fragment into bubbles that fly away for good or return within a time <O(1 mm)/c. Particles

Peter Hrasko

A local conception is proposed to reconcile quantum theory with general relativity, which allows one to avoid some difficulties --- as e.g. vacuum catastrophe --- of the global approach.

D. G. Polyakov, F. Evers, A. D. Mirlin, P. Woelfle

We study theoretically the magnetoresistance $ρ_{xx}(B)$ of a two-dimensional electron gas scattered by a random ensemble of impenetrable discs in the presence of a long-range correlated random potential. We believe that this model describes a high-mobility semiconductor heterostructure with a random array of antidots. We show that the interplay of scatterin

Igor Zutic, Jaroslav Fabian, S. Das Sarma

A solar cell illuminated by circularly-polarized light generates charge and spin currents. We show that the spin polarization of the current significantly exceeds the spin polarization of the carrier density for the majority carriers. Based on this principle we propose a semiconductor spin-polarized solar battery and substantiate our proposal using analytica

E. A. Pashitskii, S. V. Mashkevich, S. I. Vilchynskyy

One considers the superfluid (SF) state of a Bose liquid with a strong repulsion between bosons, in which at T=0, along with a weak single-particle Bose-Einstein condensate (BEC), there exists an intensive pair coherent condensate (PCC), analogous to the Cooper condensate in a Fermi liquid with an attraction between the fermions. Such a PCC emerges in a syst

Dmitry Rinberg, Victor Steinberg

We report the experimental studies of a parametric excitation of a second sound (SS) by a first sound (FS) in a superfluid helium in a resonance cavity. The results on several topics in this system are presented: (i) The linear properties of the instability, namely, the threshold, its temperature and geometrical dependencies, and the spectra of SS just above

A. S. Alexandrov

The Fermi energy, Ef of newly discovered high-Tc superconductor MgB2 and cuprates is estimated from the measured London penetration depth using a parameter-free expression. Ef of MgB2 and more than 30 lanthanum, yttrium and mercury-based cuprates appears to be about or below 100 meV, depending on doping. There is every evidence that the remarkable low value

E. Canessa

We address the issue of stock market fluctuations within Langevin Dynamics (LD) and the thermodynamics definitions of multifractality in order to study its second-order characterization given by the analogous specific heat C_{q}, where q is an analogous temperature relating the moments of the generating partition function for the financial data signals. Due

Sung Jong Lee, Jong-Rim Lee, Bongsoo Kim

We obtain via Monte Carlo simulations the low temperature charge configurations in the lattice Coulomb gas on square lattices for charge filling ratio $f$ in the range $1/3 < f < 1/2 $. We find a simple regularity in the low temperature charge configurations which consist of a suitable periodic combination of a few basic striped patterns characterized by the

O. Entin-Wohlman, Y. Levinson, P. Wolfle

The acoustoelectric current, J, induced in a ballistic point contact (PC) by a surface acoustic wave is calculated in the presence of a perpendicular magnetic field, B. It is found that the dependence of the current on the Fermi energy in the terminals is strongly correlated with that of the PC conductance: J is small at the conductance plateaus, and is larg

Avishay Efrat

Random bond Ising systems on a general hierarchical lattice are considered. The inequality between the specific heat exponent of the pure system, $α_p$, and the crossover exponent $ϕ$, $α_p<=ϕ$, gives rise to a possibility of a negative $α_p$ along with a positive $ϕ$, leading to random criticality in disagreement with the Harris criterion. An explicit examp

R. de Grijs, R. W. O&#39;Connell, J. S. Gallagher

Using new HST imaging, we identify a large, evolved system of super star clusters in a disk region just outside the starburst core in the prototypical starburst galaxy M82, ``M82 B.&#39;&#39; This region has been suspected to be a fossil starburst site in which an intense episode of star formation occurred over 100 Myr ago, which is now confirmed by our deri

R. Cayrel, V. Hill, T. Beers, B. Barbuy

The ages of the oldest stars in the Galaxy indicate when star formation began, and provide a minimum age for the Universe. Radioactive dating of meteoritic material and stars relies on comparing the present abundance ratios of radioactive and stable nuclear species to the theoretically predicted ratios of their production. The radioisotope $^{232}$Th (half-l

J. Vinko, B. Csak, Sz. Csizmadia, G. Furesz

CCD-photometry and low-resolution spectroscopy of the bright supernova SN 2000E in NGC 6951 are presented. Both the light curve extending up to 150 days past maximum and the spectra obtained at 1 month past maximum confirm that SN 2000E is of Type Ia. The reddening of SN 2000E is determined as E(B-V)=0.36+/-0.15, its error is mainly due to uncertainties in t

Azwinndini Muronga

The Müller-Israel-Stewart second order theory of relativistic imperfect fluids based on Grad&#39;s moment method is used to study the expansion of hot matter produced in ultra-relativistic heavy ion collisions. The temperature evolution is investigated in the framework of the Bjorken boost-invariant scaling limit. The results of these second-order theories a

Diego F. Torres, M. E. Pessah, Gustavo E. Romero

We present a Monte Carlo analysis of the recently introduced variability indices $τ$ (Tompkins 1999) and $I$ (Zhang et al. 2000 & Torres et al. 2001) for $γ$-ray sources. We explore different variability criteria and prove that these two indices, despite the very different approaches used to compute them, are statistically correlated (5 to 7$σ$). This conclu

Tamara M. Davis, Charles H. Lineweaver, John K. Webb

We use the dynamics of a galaxy, set up initially at a constant proper distance from an observer, to derive and illustrate two counter-intuitive general relativistic results. Although the galaxy does gradually join the expansion of the universe (Hubble flow), it does not necessarily recede from us. In particular, in the currently favored cosmological model,

Mark Hillery, Vladimir Buzek

We consider several problems that involve finding the eigenvalues and generating the eigenstates of unknown unitary gates. We first examine Controlled-U gates that act on qubits, and assume that we know the eigenvalues. It is then shown how to use singlet states to produce qubits in the eigenstates of the gate. We then remove the assumption that we know the

W. P. Tan, B-A. Li, R. Donangelo, C. K. Gelbke

Calculations predict a connection between the isotopic composition of particles emitted during an energetic nucleus-nucleus collision and the density dependence of the asymmetry term of the nuclear equation of state (EOS). This connection is investigated for central 112Sn+112Sn and 124Sn+124Sn collisions at E/A=50 MeV in the limit of an equilibrated freezeou

A. V. Ivlev, R. Sütterlin, V. Steinberg, M. Zuzic

A new simple method to measure the spatial distribution of the electric field in the plasma sheath is proposed. The method is based on the experimental investigation of vertical oscillations of a single particle in the sheath of a low-pressure radio-frequency discharge. It is shown that the oscillations become strongly nonlinear and secondary harmonics are g

Alexander Groisman, Victor Steinberg

Mixing in fluids is a rapidly developing field of fluid mechanics \cite{Sreen,Shr,War}, being an important industrial and environmental problem. The mixing of liquids at low Reynolds numbers is usually quite weak in simple flows, and it requires special devices to be efficient. Recently, the problem of mixing was solved analytically for a simple case of rand

Teodor Burghelea, Victor Steinberg

The onset of the {\em wave resistance}, via generation of capillary gravity waves, of a small object moving with velocity $V$, is investigated experimentally. Due to the existence of a minimum phase velocity $V_c$ for surface waves, the problem is similar to the generation of rotons in superfluid helium near their minimum. In both cases waves or rotons are p

Sh. Kaliman, St. Venereau, M. Zaidenberg

The Abhyankar-Sathaye Problem asks whether any biregular embedding of affine spaces $A^m_k\to A^n_k$ can be rectified, that is, is equivalent to a linear embedding up to an automorphism of the target space. Here we study this problem for the embeddings $C^3 \to C^4$ whose image $X$ is given in $C^4$ by an equation $p=f(x,y)u+g(x,y,z)=0$, where $f\in C[x,y],$

Xi Chen

We call a log variety (X, D) algebraically hyperbolic if there exists a positive number e such that 2g(C) - 2 + i(C, D) >= e deg(C) for all curves C on X, where i(C, D) is the number of the intersections between D and the normalization of C. Among other things, we proved that (P^2, D) is algebraically hyperbolic for a very general curve D of degree at least

Eyal Markman

Let M be a moduli space of stable sheaves on a K3 or Abelian surface S. We express the class of the diagonal in the cartesian square of M in terms of the Chern classes of a universal sheaf. Consequently, we obtain generators of the cohomology ring of M. When S is a K3 and M is the Hilbert scheme of length n subschemes, this set of generators is sufficiently

Stefan Schroeer

A line bundle with a base-point-free multiple is called semiample. I give a cohomological characterization of semiample line bundles. The result is a common generalization of the Fujita-Zariski criterion for semiampleness and the Grothendieck-Serre characterization of ampleness. Applying the Fujita-Zariski Theorem, I characterize contractible curves in 1-dim

Massimo Giovannini

The evolution of the gauge coupling is modelled using a scalar degree of freedom whose homogeneous and inhomogeneous modes evolve from an ordinary inflationary phase to the subsequent epochs. Depending upon various parameters (scalar mass, curvature scale at the end of inflation and at the onset of the radiation epoch), the two-point function of the magnetic

A. A. Pivovarov

Analytic structure in the strong coupling constant that emerges for some observables in QCD after duality averaging of renormalization group improved amplitudes is discussed. It is shown that perturbation theory calculations are justified for the proper observables related to the two-point correlators of hadronic currents the analytic properties of which are

S. Ansoldi, A. Aurilia, E. Spallucci

Modern particle physics and cosmology support the idea that a background of invisible material pervades the whole universe, and identify in the cosmic vacuum the ultimate source of matter-energy, both seen and unseen. Within the framework of the theory of fundamental relativistic membranes, we suggest a self-consistent, vacuum energy-driven mechanism for dar

Luis M. A. Bettencourt, Karen Pao, J. G. Sanderson

We study the dynamics of a spatially inhomogeneous quantum $λϕ^4$ field theory in 1+1 dimensions in the Hartree approximation. In particular, we investigate the long-time behavior of this approximation in a variety of controlled situations, both at zero and finite temperature. The observed behavior is much richer than that in the spatially homogeneous case.

A. Garcia-Lekue, J. M. Pitarke

Self-consistent calculations of the energy-loss spectra of charged particles moving near a plane-bounded free electron gas are reported. Energy-loss probabilities are obtained, within linear-response theory, from the knowledge of the density-response function of the inhomogeneous electron system. Self-consistent single-particle wave functions and energies ar

Igor Aranson, Victor Steinberg

Nucleation of vortices in rotating superfluid by spin-up and rapid thermal quench is discussed in the framework of the time-dependent Ginzburg--Landau equation (TDGLE). An analysis of the instability in inhomogeneous rotationally-invariant system results in the expression for the critical rotational velocity. A stability analysis of multicharged vortices is

Keith Slevin, Peter Markoš, Tomi Ohtsuki

We reconcile the phenomenon of mesoscopic conductance fluctuations with the single parameter scaling theory of the Anderson transition. We calculate three averages of the conductance distribution: $\exp(<\ln g>)$, $<g>$ and $1/<R>$ where $g$ is the conductance in units of $e^2/h$ and $R=1/g$ is the resistance and demonstrate that these quantities obey single

Siddhartha Lal, Sumathi Rao, Diptiman Sen

We use the technique of bosonization to understand a variety of recent experimental results on the conductivity of a quantum wire. The quantum wire is taken to be a finite-length Luttinger liquid connected on two sides to semi-infinite Fermi liquids through contacts. The contacts are modeled as (short) Luttinger liquids bounded by localized one-body potentia

J. K. Lawrence, A. C. Cadavid, A. Ruzmaikin

Below the scale of supergranules we find that cellular flows are present in the solar photosphere at two distinct size scales, approximately 2 Mm and 4 Mm, with distinct characteristic times. Simultaneously present in the flow is a non-cellular component, with turbulent scaling properties and containing 30% of the flow energy. These results are obtained by m

P. Slane, J. P. Hughes, R. J. Edgar, P. P. Plucinsky

The newly discovered supernova remnant G266.2-1.2 (RX J0852.0-4622), along the line of sight to the Vela SNR, was observed with ASCA for 120 ks. We find that the X-ray spectrum is featureless, and well described by a power law, extending to three the class of shell-type SNRs dominated by nonthermal X-ray emission. Although the presence of the Vela SNR compro

A. Janiuk, B. Czerny, G. M. Madejski

We present the study of the emission properties of the quasar PG1211+143, which belongs to the class of Narrow Line Seyfert 1 galaxies. On the basis of observational data analyzed by us and collected from the literature, we study the temporal and spectral variability of the source in the optical/UV/X-ray bands and we propose a model that explains the spectru

A. D. Karnik, S. K. Ghosh, T. N. Rengarajan, R. P. Verma

High resolution far-infrared observations of a large area of the star forming complex RCW 106 obtained using the TIFR 1-metre balloon-borne telescope are presented. Intensity maps have been obtained simultaneously in two bands centred around 150 & 210 micron. Intensity maps have also been obtained at the 4 IRAS bands using HIRES processed IRAS data. From the

Patrick Slane

Supernova remnants have long been suggested as a class of potential counterparts to unidentified gamma-ray sources. The mechanisms by which such gamma-rays can arise may include emission from a pulsar associated with a remnant, or a variety of processes associated with energetic particles accelerated by the SNR shock. Imaging and spectral observations in the

K. Indulekha, G. V. Vijayagovindan, S. Ramadurai

With a view to understand the galaxy/star formation scenario, we investigate the dissipative collapse of a spherical cluster of gas clouds with an isotropic velocity distribution. The time scale for collapse to one tenth radius is studied as a function of the collision time in the system. The scalar virial equation is used to investigate the evolution of the

C. R. Chen, J. L. Friar, G. L. Payne

A new method for solving the configuration-space Faddeev equations for elastic p-d scattering below the deuteron-breakup threshold is described. Numerical solutions that demonstrate the convergence and accuracy of the method are given. The number of channels and the value of the matching radius required to obtain an accurate solution are also investigated. T

T. M. aliev, A. Ozpineci, M. Savci

Using the general form of the (Sigma^0) and (Lambda) currents, the (Sigma^0-Lambda) transition magnetic moment is calculated in framework of the light cone QCD sum rules. A comparison of our result on this quantity with the existing theoretical results and experimental data is presented.