January 1998 arXiv papers — page 5

Stephen P. Martin, James D. Wells

We study supersymmetric QCD with N_f<N_c in the limit of small supersymmetry-breaking masses and smaller quark masses using the weak-coupling Kahler potential. We calculate the full spectrum of this theory, which manifests a chiral symmetry breaking pattern similar to that caused by the strong interactions of the standard model. We derive the chiral effectiv

Marcel Demarteau, Tao Han

The potential for the Higgs boson and Z-pole physics at the first muon collider is summarized, based on the discussions at the ``Workshop on the Physics at the First Muon Collider and at the Front End of a Muon Collider&#39;&#39; .

S. Capitani, M. Goeckeler, R. Horsley, B. Klaus

We briefly describe some of our recent results for the mass spectrum and matrix elements using $O(a)$ improved fermions for quenched QCD. Where possible a comparison is made between improved and Wilson fermions.

L. L. Bonilla, M. Kindelan, P. J. Hernando

We present and numerically solve a model of the photorefractive Gunn effect. We find that high field domains can be triggered by phase-locked interference fringes, as it has been recently predicted on the basis of linear stability considerations. Since the Gunn effect is intrinsically nonlinear, we find that such considerations give at best order-of-magnitud

Zh. S. Gevorkian, Th. M. Nieuwenhuizen

The contribution of interference effects to the radiation of a charged particle moving in a medium of randomly spaced plates is considered. In the angular dependent radiation intensity a peak appears at angles $θ\simπ-γ^{-1}$, where $γ$ is the Lorentz factor of the charged particle.

T. Shahbaz, J. R. Thorstensen, P. A. Charles, N. D. Sherman

We have obtained I-band photometry of the neutron star X-ray transient Aql X--1 during quiescence. We find a periodicity at 2.487 cd-1, which we interpret as twice the orbital frequency (19.30+/-0.05 h). Folding the data on the orbital period, we model the light curve variations as the ellipsoidal modulation of the secondary star. We determine the binary inc

X. -Y. Xia, Th. Boller, H. Wu, Z. -G. Deng

We report the discovery of the brightest X-ray source hosted by a faint (M_B=-16) dwarf galaxy in the immediate vicinity of the ultraluminous IRAS merging galaxy Mrk 273. The dwarf galaxy, 1.3 arcmin away from Mrk 273, is at the tip of a faint northeast plume of Mrk 273. Its spectrum exhibits strong [OIII], Halpha, [NII] emission lines, which establish the r

K. Otterbein, M. J. Hardcastle, S. J. Wagner, D. M. Worrall

The BL Lac object S5 0716+714 was monitored during a multifrequency campaign in 1996. Preliminary analysis of the optical, ROSAT and RXTE data are presented. Strong variability on short time scales was observed. The data suggest an interpretation within a multi-component model.

Marek Kutschera

A short introduction is given to astrophysics of neutron stars and to physics of dense matter in neutron stars. Observed properties of astrophysical objects containing neutron stars are discussed. Current scenarios regarding formation and evolution of neutron stars in those objects are presented. Physical principles governing the internal structure of neutro

Shuichi Tasaki, Thomas Gilbert, J. R. Dorfman

For a class of dynamical systems, called the axiom-A systems, Sinai, Ruelle and Bowen showed the existence of an invariant measure (SRB measure) weakly attracting the temporal average of any initial distribution that is absolutely continuous with respect to the Lebesgue measure. Recently, the SRB measures were found to be related to the nonequilibrium statio

R. Bijker, F. Iachello, E. Santopinto

A completely algebraic treatment of the six-dimensional hypercoulomb problem is discussed in terms of an oscillator realization of the dynamical algebra of SO(7,2). Closed expressions are derived for the energy spectrum and form factors.

Nick Evans

A set of non-supersymmetric minimal area embeddings of an M-theory 5-brane are considered. The field theories on the surface of the 5-brane have the field content of N=2 SQCD with fundamental representation matter fields. By suitable choice of curve parameters the N=2 and N=1 superpartners may be decoupled leaving a semi-classical approximation to QCD with m

Alexander Kusenko, Vadim Kuzmin, Igor I. Tkachev

The trilinear couplings of squarks and sleptons to the Higgs bosons can give rise to a spectrum of bound states with exotic quantum numbers, for example, those of a leptoquark.

C. Fuchs, D. S. Kosov, Amand Faessler, Z. S. Wang

The influence of the chiral mean field on the kaon dynamics in heavy ion reactions is investigated. Inside the nuclear medium the kaons are described as dressed quasi-particles carrying effective masses and momenta. A momentum dependent part of the interaction which resembles a Lorentz force originates from spatial components of the vector field and provides

J. H. Field

A model independent analysis has been performed on the LEP and SLD data on Z decays. Using only very weak theoretical assumptions, the effective vector and axial-vector couplings of leptons, c quarks and b quarks have been extracted. Although the lepton and c quark couplings agree well with Standard Model predictions, those of the b quark show deviations of

U. Leonhardt, T. Kiss, P. Piwnicki

Impressive pictures of moving Bose-Einstein condensates have been taken using phase-contrast imaging M. R. Andrews et al., Science 273, 84 (1996). We calculate the quantum backaction of this measurement technique. We find that phase-contrast imaging is not a quantum nondemolition measurement of the atomic density. Instead, the condensate gets gradually deple

Marco Cavaglia, Lorenzo Fatibene, Mauro Francaviglia

We apply a global and geometrically well-defined formalism for spinor-dilaton-gravity to two-dimensional manifolds. We discuss the general formalism and focus attention on some particular choices of the dilatonic potential. For constant dilatonic potential the model turns out to be completely solvable and the general solution is found. For linear and exponen

S. M. Catterall, M. Hasenbusch, R. R. Horgan, R. L. Renken

The RP(2) gauge model is studied in 2D. We use Monte-Carlo renormalization techniques for blocking the mean spin-spin interaction, <A>, and the mean gauge field plaquette, <P>. The presence of the O(3) renormalized trajectory is verified and is consistent with the known three-loop beta-function. The first-order `vorticity&#39; transition observed by Solomon

A. De Pace

Many-body techniques for the calculation of quasielastic nuclear matter response functions in the fully antisymmetrized random phase approximation on a Hartree-Fock basis are discussed in detail. The methods presented here allow for an accurate evaluation of the response functions with little numerical effort. Formulae are given for a generic non-relativisti

Kristian Ranestad, Frank-Olaf Schreyer

The variety of sums of powers of a homogeneous polynomial of degree d in n variables is defined and investigated in some examples, old and new. These varieties are studied via apolarity and syzygies. Classical results of Sylvester (1851), Hilbert (1888), Dixon and Stuart (1906) and some more recent results of Mukai (1992) are presented together with new resu

M. O. Katanaev, I. V. Volovich

We consider scattering of elastic waves on parallel wedge dislocations in the geometric theory of defects or, equivalently, scattering of point particles and light rays on cosmic strings. Dislocations are described as torsion singularities located on parallel lines, and trajectories of phonons are assumed to be the corresponding extremals. Extremals are foun

I. Dadic

We analyze ill-defined pinch singularities characteristic of out of equilibrium thermal field theories. We identify two mechanisms that eliminate pinching even at the single self-energy insertion approximation to the propagator: the first is based on the vanishing of phase space at the singular point (threshold effect). It is effective in QED with a massive

Romesh K. Kaul, Parthasarathi Majumdar

We derive an exact formula for the dimensionality of the Hilbert space of the boundary states of SU(2) Chern-Simons theory, which, according to the recent work of Ashtekar et al, leads to the Bekenstein-Hawking entropy of a four dimensional Schwarzschild black hole. Our result stems from the relation between the (boundary) Hilbert space of the Chern-Simons t

H. W. Lee, N. J. Kim, Y. S. Myung, Jin Young Kim

It is shown that all string fields except dilaton are non-propagating in the (2+1)-dimensional black string. One finds that the perturbation around the black string reveals a mixing between the dilaton and other fields. Under the new gauge(dilaton gauge), we disentangle this mixing and obtain one decoupled dilaton equation. It turns out that this black strin

G. M. Moy, J. J. Hope, C. M. Savage

We discuss the use of the Born and Markov approximations in describing the dynamics of an atom laser. In particular, we investigate the applicability of the quantum optical Born-Markov master equation for describing output coupling. We derive conditions based on the atomic reservoir, and atom dispersion relations for when the Born-Markov approximations are v

Henry P. Stapp

Unruh has commented upon my recent proof that certain predictions of quantum theory are incompatible with the assertion that no influence of any kind acts backward in time in any Lorentz frame. Unruh fails to make a necessary distinction between statements that assert the existence of values, and statements that assert the existence merely of correlations be

A. Lambrecht, M. -T. Jaekel, S. Reynaud

We show that the Casimir force between mirrors with arbitrary frequency dependent reflectivities obeys bounds due to causality and passivity properties. The force is always smaller than the Casimir force between two perfectly reflecting mirrors. For narrow-band mirrors in particular, the force is found to decrease with the mirrors bandwidth.

A. Lambrecht, E. Giacobino, J. M. Courty

This paper presents the nonlinear dynamics of laser cooled and trapped cesium atoms placed inside an optical cavity and interacting with a probe light beam slightly detuned from the 6S1/2(F=4) to 6P3/2(F=5) transition. The system exhibits very strong bistability and instabilities. The origin of the latter is found to be a competition between optical pumping

J. M. Courty, A. Lambrecht

We analyze nonlinear transverse mode coupling in a Kerr medium placed in an optical cavity and its influence on bistability and different kinds of quantum noise reduction. Even for an input beam that is perfectly matched to a cavity mode, the nonlinear coupling produces an excess noise in the fluctuations of the output beam. Intensity squeezing seems to be p

A. Lambrecht, J. M. Courty, S. Reynaud

We evaluate the squeezing of a probe beam with a transverse Gaussian profile interacting with an ensemble of two-level atoms in a cavity. We use the linear input-output formalism where the effect of atoms is described by susceptibility and noise functions. The transverse structure is accounted for by averaging atomic functions over the intensity profile. The

A. Lambrecht, T. Coudreau, A. M. Steinberg, E. Giacobino

Cold atoms from a magneto-optic trap have been used as a nonlinear medium in a nearly resonant cavity. Squeezing in a probe beam passing through the cavity was demonstrated. The measured noise reduction is 40% for free atoms and 20% for weakly trapped atoms.

A. Lambrecht, E. Giacobino, S. Reynaud

We evaluate the effective number of atoms in experiments where a probe laser beam with a Gaussian profile passes through an atomic medium consisting of a cold atom cloud released from a magneto-optical trap. Considering the case where the initial distribution is a Gaussian function of position and velocity, we give a quantitative description of the time vari

A. Lambrecht, J. M. Courty, S. Reynaud, E. Giacobino

Laser-cooled and trapped cesium atoms have been used as a nonlinear medium in a nearly resonant cavity. A study of the semiclassical dynamics of the system was performed, showing bistability and instabilities. In the quantum domain, squeezing in a probe beam having interacted with this system was demonstrated.

Andre Martin

We discuss the stability of three- and four-particle system interacting by pure Coulomb interactions, as a function of the masses and charges of the particles. We present a certain number of general properties which allow to answer a certain number of questions without or with less numerical calculations.

Christian Ohn

We study and classify almost all quantum SL(3,C)&#39;s whose representation theory is ``similar&#39;&#39; to that of the (ordinary) group SL(3,C). Only one case, related to smooth elliptic curves, could not be treated completely.

L. Frappat, A. Sciarrino, P. Sorba

The quantum enveloping algebra U_q(sl(2) \oplus sl(2)) in the limit q \to 0 is proposed as a symmetry algebra for the genetic code. In this approach the triplets of nucleotids or codons in the DNA chain are classified in crystal bases, tensor product of U_{q \to 0}(sl(2) \oplus sl(2)) representations. Such a construction might be compared to the baryon class

Wim van Saarloos

These are lecture notes of a course given at the 9th International Summer School on Fundamental Problems in Statistical Mechanics, held in Altenberg, Germany, in August 1997. In these notes, we discuss at an elementary level three themes concerning interface dynamics that play a role in pattern forming systems: (i) We briefly review three examples of systems

Ulrich Heinz

I present highlights from the parallel sessions on the theory of hadronic observables in e^+ e^-, hadronic and nuclear reactions.

Bao-An Li, C. M. Ko

Using an isospin-dependent transport model, we have studied the isospin and momentum relaxation times in the heavy residues formed in heavy-ion collisions at intermediate energies. It is found that only at incident energies below the Fermi energy, chemical or thermal equilibrium can be reached before dynamical instability is developed in the heavy residues.

B. C. Ngo

We prove a conjecture of Frenkel-Gaitsgory-Kazhdan-Vilonen on some exponential sums related to the geometric Langlands correspondence. Our main ingredients are the resolution of Lusztig scheme of lattices introduced by Laumon and the decomposition theorem of Beilinson-Bernstein-Deligne-Gabber.

Pavel Etingof, Olivier Schiffmann

We construct a fully faithful functor from the category C_F of finite-dimensional representations of Felder&#39;s (dynamical) elliptic quantum group E_{tau,gamma}(gl(n)) to a cretain category D_B of (infinite-dimensional) representations of Belavin&#39;s quantum elliptic algebra B by difference operators, and a fully faithful functor from the category C_B of

A. H. Chamseddine, W. A. Sabra

BPS black hole configurations which break half of supersymmetry in the theory of N=2, d=5 supergravity coupled to an arbitrary number of abelian vector multiplets are discussed. A general class of solutions comprising all known BPS rotating black hole solutions is obtained.

D. V. Gal'tsov, O. A. Rytchkov

Starting with the D-dimensional Einstein-dilaton-antisymmetric form equations and assuming a block-diagonal form of a metric we derive a $(D-d)$-dimensional $\sigma$-model with the target space $SL(d,R)/SO(d) \times SL(2,R)/SO(2) \times R$ or its non-compact form. Various solution-generating techniques are developed and applied to construct some known and so

Eric Bergshoeff, George Papadopoulos, Jan Pieter van der Schaar

We show that all branes admit worldvolume domain wall solutions. We find one class of solutions for which the tension of the brane changes discontinuously along the domain wall. These solutions are not supersymmetric. We argue that there is another class of domain wall solutions which is supersymmetric. A particular case concerns supersymmetric domain wall s

Ilka Brunner, Andreas Karch

We review the construction of six dimensional N=1 fixed points in a brane picture involving D6 branes stretching between NS 5 branes.

Ilka Brunner, Andreas Karch

We review the problems associated with Matrix compactifications on T^6.

T. S. Evans, T. W. B. Kibble, D. A. Steer

We consider arbitrary splits of field operators into two parts, and use the corresponding definition of normal ordering introduced by Evans and Steer. In this case the normal ordered products and contractions have none of the special symmetry properties assumed in existing proofs of Wick&#39;s theorem. Despite this, we prove that Wick&#39;s theorem still hol

N. V. Mikheev, O. S. Ovchinnikov, L. A. Vassilevskaya

The process of electron-positron pair production by axion propagating in an external magnetic field is investigated in a model with only induced axion coupling to leptons. Contributions of the lowest and higher Landau levels are analyzed. The results we have obtained demonstrate a strong catalyzing influence of the field.

Prasanta. K. Panigrahi, C. Nagaraja

We derive travelling soliton solutions of the $σ$ model, relevant for the description of dynamics of pions, in the high-energy, heavy-ion collisions. These extended objects are analogs of Ne$\grave{e}$l and Bloch type defects in ferromagnetic systems and could possibly describe the disoriented chiral condensates. It is shown that these solutions are metastab

K. J. Abraham, B. Lampe

We study NLO QCD corrections as relevant to hadronic W decay in W pair production at a future 500 GeV electron-positron linac, with particular emphasis on the determination of triple gauge boson vertices. We find that hard gluon bremstrahlung may mimic signatures of anomalous triple gauge boson vertices in certain distributions. The size of these effects can

Han-Ying Guo, Ke Wu, Chi Xiong

Based on the differential calculus and the gauge theory on discrete groups, we reconstruct two physics models with spontaneous CP violation: (1) The Georgi-Glashow-Lee model with two Higgs triplets; (2) The Weinberg-Salam-Branco model with three Higgs doublets and the natural flavor conservation (NFC). We focus on the Lagrangian terms containing the Higgs pa

A. H. Hoang, T. Teubner

The complete next-to-next-to-leading order (i.e. $O(v^2)$, $O(v α_s)$ and $O(α_s^2)$) relativistic corrections to the total photon mediated $t\bar t$ production cross section at threshold are presented in the framework of nonrelativistic quantum chromodynamics. The results are obtained using semi-analytic methods and ``direct matching&#39;&#39;. The size of

K. Holland, U. -J. Wiese

In cylindrical volumes with C-periodic boundary conditions in the long direction, static quarks are confined even in the gluon plasma phase due to the presence of interfaces separating the three distinct high-temperature phases. An effective &#34;string tension&#34; is computed analytically using a dilute gas of interfaces. At T_c, the deconfined-deconfined

The OPAL Collaboration, K. Ackerstaff et al

An investigation of CP violation was performed using a total of 24 candidates for B^0 -> J/psi K^0_S decay, with a purity of about 60%. These events were selected from 4.4 million hadronic Z^0 decays recorded by the OPAL detector at LEP. An analysis procedure, involving techniques to reconstruct the proper decay times and tag the produced b-flavours, B^0 or

V. Avati, K. Eggert, C. Taylor

The FELIX collaboration has proposed the construction of a full acceptance detector for the LHC, to be located at Intersection Region 4, and to be commissioned concurrently with the LHC. The primary mission of FELIX is QCD: to provide comprehensive and definitive observations of a very broad range of strong-interaction processes. This paper reviews the detec

A. Yu. Kamenshchik, I. M. Khalatnikov, A. V. Toporensky

Continuing the investigation of the simplest cosmological model with the massive real scalar non-interacting inflaton field minimally coupled to gravity we study an influence of the cosmological constant on the behaviour of trajectories in closed minisuperspace Friedmann-Robertson-Walker model. The transition from chaotic to regular behaviour for large value

D. E. Angelescu, M. C. Cross, M. L. Roukes

Phonon heat transport in mesoscopic systems is investigated using methods analogous to the Landauer description of electrical conductance. A &#34;universal heat conductance&#34; expression that depends on the properties of the conducting pathway only through the mode cutoff frequencies is derived. Corrections due to reflections at the junction between the th

R. J. P. Keijsers, O. I. Shklyarevskii, H. van Kempen

Answer to the Comment on ``Point-Contact Study of Fast and Slow Two-Level Fluctuators in Metallic Glasses&#39;&#39; by Jan von Delft et al.

W. Schirmacher, G Diezemann, C. Ganter

We consider a system of coupled classical harmonic oscillators with spatially fluctuating nearest-neighbor force constants on a simple cubic lattice. The model is solved both by numerically diagonalizing the Hamiltonian and by applying the single-bond coherent potential approximation. The results for the density of states $g(ω)$ are in excellent agreement wi

Matteo Buzzacchi, Emilio Del Giudice, Giuliano Preparata

We comment some recent unexpected experimental results on proton/deuteron deep inelastic scattering off water molecules in H2O-D2O mixtures (C.A. Chatzidimitrou-Dreismann et al. Phys. Rev. Lett. 79, 2839 (1997)) where a strong dependence of the ratio of proton/deuteron cross sections on the composition of the mixture was observed. We propose an explanation o

G. Ravikumar

A study of path dependent effects in single crystals of CeRu2 and 2H-NbSe2 show that critical current density Jc of the vortex state depends on its thermomagnetic history over a very large part of (H,T) parameter space. The path dependence in Jc is absent above the peak position (i.e., H > Hp) of the peak effect region, which we believe identifies the comple

G. Zarand, Jan von Delft, A. Zawadowski

We point out that a recent experiment by Keijsers, Shklyarevskii and van Kempen [Phys. Rev. Lett. 77, 3411 (1996)] on metallic glass point contacts containing two-level systems (TLS) effectively measures for the first time the conductance contributions of individual TLSs (previous experiments averaged over a distribution of TLSs). For this case the predictio

S. Djordjevic, L. A. de Vaulchier, N. Bontemps, J. P. Vieren

Measurement of the penetration depth as a function of temperature using millimeter wave transmission in the range 130-500GHz are reported for three YBCO thin films. The experiment provides the absolute value for the penetration depth at low temperature: the derivation from the transmission data and the experimental uncertainty are discussed. We find a zero t

Gang Su, Masuo Suzuki

It is rigorously shown that the two-dimensional Hubbard model with narrow bands (including next nearest-neighbor hopping, etc.) does not exhibit $d_{x^2 -y^2}$-wave pairing long-range order at any nonzero temperature. This kind of pairing long-range order will also be excluded at zero temperature if an excited energy gap opens in the charge excitation spectr

Ryotaro Arita, Yukihiro Shimoi, Kazuhiko Kuroki, Hideo Aoki

Density matrix renormalization group method is used to analyze how the nearest-neighbor repulsion V added to the Hubbard model on 1D triangular lattice and a railway trestle (t-t&#39;) model will affect the electron-correlation dominated ferromagnetism arising from the interference (frustration). Obtained phase diagram shows that there is a region in smaller

Peter Nordlander, Ned S. Wingreen, Yigal Meir, David C. Langreth

Using a time-dependent Anderson Hamiltonian, a quantum dot with an ac voltage applied to a nearby gate is investigated. A rich dependence of the linear response conductance on the external frequency and driving amplitude is demonstrated. At low frequencies the ac potential produces sidebands of the Kondo peak in the spectral density of the dot, resulting in

Sergei Maslov, Yi-Cheng Zhang

We design an optimal strategy for investment in a portfolio of assets subject to a multiplicative Brownian motion. The strategy provides the maximal typical long-term growth rate of investor&#39;s capital. We determine the optimal fraction of capital that an investor should keep in risky assets as well as weights of different assets in an optimal portfolio.

Matteo Marsili, Sergei Maslov, Yi-Cheng Zhang

We propose and study a simple model of dynamical redistribution of capital in a diversified portfolio. We consider a hypothetical situation of a portfolio composed of N uncorrelated stocks. Each stock price follows a multiplicative random walk with identical drift and dispersion. The rules of our model naturally give rise to power law tails in the distributi

M. J. Calderon, E. Bascones

A grain boundary which separates domains with different orientation along the c-axis is analyzed. The coupling of two parallel superconducting planes whose order parameters are rotated leads to interesting properties which are expected to be common to other kinds of grain boundary. The density of states is enhanced at low energies. The number of localized st

Austin B. Tomaney

The principles of difference imaging outlined and the technique of Alard and Lupton (1997) is generalised to generate the best possible difference images to within the limits of measurement error. It is shown how for a large database of images we can approach diffraction-limited spatial resolution to within measurement error of a combined image. This is achi

Piotr Zycki, Chris Done, David Smith

We identify the X-Ray reflected component in the Ginga spectra of Nova Muscae 1991, a Black Hole transient system used as the prototype for the recent model of Esin, McClintock & Narayan (1997) based on advection dominated disk solutions. We see that the reflected spectrum is generally significantly relativistically smeared, and use this, together with the a

D. Friedli

Various large-scale processes induced by triaxial potentials and able to alter stellar and gaseous abundance profiles are reviewed. In particular, strong bars can quickly and efficiently blend stars through chaotic mixing, and entail intricate inflows/outflows of gas. Bar-generated abundance features include flattenings, breaks, and plateaus in radial gradie

Eric L. Sandquist, Ronald E. Taam, Xingming Chen, Peter Bodenheimer

The evolution of binary systems consisting of an asymptotic giant branch star of mass equal to 3 M_sun or 5 M_sun, and a main sequence star of mass equal to 0.4 M_sun or 0.6 M_sun with orbital periods > 200 days has been followed from the onset through the late stages of the common envelope phase. Using a nested grid technique, the three-dimensional hydrodyn

Dimitar D. Sasselov

Gravitational microlensing is a new technique for studying the surfaces of distant stars. A point mass lens, usually a low-mass star from the disk, will typically resolve the surface of a red giant in the Galactic bulge, as well as amplify its brightness by a factor of 10 or more. Such events are now detected in real time and can be followed up with precisio

Henry C. Ferguson, Nial R. Tanvir, Ted von Hippel

It has been suspected for nearly 50 years that clusters of galaxies contain a population of intergalactic stars, ripped from galaxies during cluster formation or when the galaxies&#39; orbits take them through the cluster center. Support for the existence of such a population of free-floating stars comes from measurements of the diffuse light in clusters, an

J. H. Knapen

(Abridged) From a new H alpha mosaic image of the complete disc of the spiral galaxy M100, a catalogue is composed listing 1948 individual HII regions. I give details of the data collection and reduction procedure, and of the production of the HII region catalogue. For each HII region, the catalogue gives its position relative to the centre of the galaxy, it

K. Iwasawa, A. C. Fabian, W. N. Brandt, H. Kunieda

We report the detection of a 58 ks (16 hr) periodicity in the 0.5-10 keV X-ray light curve of the Seyfert galaxy IRAS18325-5926 (Fairall49), obtained from a 5-day ASCA observation. Nearly 9 cycles of the periodic variation are seen; it shows no strong energy dependence and has an amplitude of about 15 per cent. Unlike most other well-studied Seyfert galaxies

Boudewijn F. Roukema

Several recent large length scale methods of detecting the topology of the Universe are briefly reviewed. Three-dimensional methods include those of Lehoucq, Luminet & Lachièze-Rey (1996), Roukema (1996) and Roukema & Edge (1997). The two-dimensional ``circles&#39;&#39; method of Cornish, Spergel & Starkman (1996b) is also mentioned.

H. J. de Vega, N. Sánchez, F. Combes

While the universe becomes more and more homogeneous at large scales, statistical analysis of galaxy catalogs have revealed a fractal structure at small-scales (λ< 100 h^{-1} Mpc), with a fractal dimension D=1.5-2 (Sylos Labini et al 1996). We study the thermodynamics of a self-gravitating system with the theory of critical phenomena and finite-size scaling

J. S. Bagla

Large inhomogeneities in neutral hydrogen in the universe can be detected at redshifts $z \leq 10$ using the redshifted 21cm line emission from atomic hydrogen. This paper reviews the expected evolution of neutral hydrogen and presents estimates for future surveys of HI at $z \approx 3$. We also discuss the possibility of detecting neutral hydrogen at higher

P. Giommi, F. Fiore, D. Ricci, S. Molendi

We present the preliminary results of a survey that makes use of several deep exposures obtained with the X-Ray telescopes of the BeppoSAX satellite. The survey limiting sensitivity is 5 x 10^-14 cgs in the 2-10 keV band and 7 x 10^-14 cgs in the harder 5-10 keV band. We find that the 2-10 keV LogN-LogS is consistent with that determined in ASCA surveys. The

B. E. J. Pagel, G. Tautvaisiene

We have extended our analytical chemical evolution modelling ideas for the Galaxy to the Magellanic Clouds. Unlike previous authors, we assume neither a steepened IMF nor selective galactic winds, since among the alpha-particle elements only oxygen shows a large deficit relative to iron and a similar deficit is also found in Galactic supergiants. Thus we ass

Jean Swank, Xingming Chen, Craig Markwardt, Ronald Taam

We present time-resolved GRS 1915+105 energy and power spectra observed by RXTE, during an episode where the X-ray intensity makes an extreme dip. If the spectra are modeled in terms of disk and power law components, both have large variations. When the inner disk is disrupted, the power law dominates, exhibiting quasi-periodic oscillations with varying freq

T. E. Strohmayer, J. H. Swank, W. Zhang

Oscillations in the X-ray flux of thermonuclear X-ray bursts have been observed with RXTE from at least 6 low-mass binaries, at frequencies from 330 Hz to 589 Hz. There appear to be preferred relations between the frequencies present during the bursts and those seen in the persistent flux. The amplitude of the oscillations can exceed 50 % near burst onset. E

J. H. Swank

The Rossi X-Ray Timing Explorer (RXTE) has found that the neutron stars in low-mass X-ray binaries exhibit oscillations in the range 300-1200 Hz. Persistent emission may exhibit one or both of two features. In bursts a nearly coherent pulsation is seen, which may be the rotation period of the neutron star. For some the frequency equals the difference between

Felix Finster, Joel Smoller, Shing-Tung Yau

The coupled Einstein-Dirac equations for a static, spherically symmetric system of two fermions in a singlet spinor state are derived. Using numerical methods, we construct an infinite number of soliton-like solutions of these equations. The stability of the solutions is analyzed. For weak coupling (i.e., small rest mass of the fermions), all the solutions a

Pei-Ming Ho, Yong-Shi Wu

We present a general framework for Matrix theory compactified on a quotient space R^n/G, with G a discrete group of Euclidean motions in R^n. The general solution to the quotient conditions gives a gauge theory on a noncommutative space. We characterize the resulting noncommutative gauge theory in terms of the twisted group algebra of G associated with a pro

Luis G. C. Rego, George Kirczenow

Using the Landauer formulation of transport theory, we predict that dielectric quantum wires should exhibit quantized thermal conductance at low temperatures in a ballistic phonon regime. The quantum of thermal conductance is universal, independent of the characteristics of the material, and equal to $π^2 k^2_B T /3h$ where $k_B$ is the Boltzmann constant, h

I. Krichever, A. Zabrodin

An algebro-geometric approach to representations of Sklyanin algebra is proposed. To each 2 \times 2 quantum L-operator an algebraic curve parametrizing its possible vacuum states is associated. This curve is called the vacuum curve of the L-operator. An explicit description of the vacuum curve for quantum L-operators of the integrable spin chain of XYZ type

P. Ohberg, S. Stenholm

We have studied the elementary excitations in a two-component Bose-Einstein condensate. We concentrate on the breathing modes and find the elementary excitations to possess avoided crossings and regions of coalescing oscillations where both components of the condensates oscillate with same frequency. For large repulsive interactions between the condensates,

Meng Ta-chung, R. Rittel, Zhang Yang

It is proposed, that ``the colorless objects&#39;&#39; which manifest themselves in large-rapidity-gap events are color-singlet gluon-clusters due to self-organized criticality (SOC), and that optical-geometrical concepts and methods are useful in examing the space-time properties of such objects. A simple analytical expression for the $t$-dependence of the

M. Krcmar, Z. Krecak, M. Stipcevic, A. Ljubicic

We have made a search for Fe-57 gamma rays of energy 14.4 keV induced by resonant absorption of monochromatic solar axions, as proposed by Moriyama. The proposed axions are suggested to be emitted from the Sun, in M1 transitions between the first, thermally excited state and the ground state of Fe-57. An upper limit on hadronic axion mass of 745 eV is obtain

W. A. Hofer

The standard solution of the Schroedinger equation for the hydrogen atom is analyzed. Comparing with the recently established internal properties of electrons it is found, that these solutions cannot be seen as physically valid states of the electron wave. The paper therefore proposes a new model of hydrogen based on internal properties of electrons. The gro

Hsin-Chia Cheng, Yael Shadmi

We study Seiberg duality for N=1 supersymmetric QCD with soft supersymmetry-breaking terms. We generate the soft terms through gauge mediation by coupling two theories related by Seiberg duality to the same supersymmetry-breaking sector. In this way, we know what a supersymmetry-breaking perturbation in one theory maps into in its ``dual&#39;&#39;. Assuming

Chong-Sheng Li, Shou-Hua Zhu

We calculate the $O(αm_t^2/m^2_W)$ corrections arising from diagrams involving the top-quark loops to the light neutral Higgs boson production via $q\bar q&#39;\to WH$ at the Fermilab Tevatron in both the standard model and the minimal supersymmetric model. In contrast to the QCD correction which increases the tree-level cross section, the corrections imply

D. Clowe, N. Kaiser, G. Luppino, J. P. Henry

We report the detection of weak gravitational lensing of distant background galaxies by two rich, X-ray luminous clusters of galaxies, MS 1137+66 at z=0.783 and RXJ 1716+67 at z=0.813. We detect a shear signal in each cluster over the radial range 100<r<700 h^-1 kpc. Assuming the background galaxies lie in a sheet at z=2, we measure a mass of 2.45*10^14 h^-1

Unal Goktas, Willy Hereman

An algorithm to compute polynomial conserved densities of polynomial nonlinear lattices is presented. The algorithm is implemented in Mathematica and can be used as an automated integrability test. With the code diffdens.m, conserved densities are obtained for several well-known lattice equations. For systems with parameters, the code allows one to determine

A. Zabrodin

We construct local M-operators for an integrable discrete time version of the classical Heisenberg magnet by convolution of the twisted quantum trigonometric 4$\times$4 R-matrix with certain vectors in its &#34;quantum&#34; space. Components of the vectors are identified with $τ$-functions of the model. Hirota&#39;s bilinear formalism is extensively used. Th

Gennady A. Koganov, Reuben Shuker

Bloch equations for the atomic population and the polarization/coherence and the equation of motion for the photon number in a laser are solved in steady state as a function of the pump rate. Two level atom and two modes of three levels atom are investigated. Close to threshold the usual linear dependence of the intensity on the pump rate in found for all ca

J. Meng, I. Tanihata, S. Yamaji

The interaction cross sections for $^A Na + ^{12}C$ reaction are calculated using Glauber model. The continuum Hartree-Bogoliubov theory has been generalized to treat the odd particle system and take the continuum into account. The theory reproduces the experimental result quite well. The matter distributions from the proton drip line to the neutron drip lin