June 1998 arXiv papers — page 2

W. Pych

We present CCD photometry of the long period asteroid 1689 Floris-Jan. On the light curve from nights 1997.02.10/11 and 1997.02.11/12 we detected sine-like oscillations with the period P=4.98 ${\pm}$ 0.01 minutes and full amplitude about 0.11 mag. Observations from night 1997.03.07/08 show no light variations at this period.

S. A. Rinehart, T. L. Hayward, J. R. Houck

We have imaged the M2Iab supergiant star Alpha Ori at 11.7 micron and 17.9 micron using the Hale 5-m telescope and an array camera with sub-arcsecond angular resolution. Our images reveal the circumstellar dust shell extending out to approximately 5" from the star. By fitting two multi-parameter models to the data, we find values for the dust shell inner

W. Becker, J. Trümper

Until now X-radiation from nine millisecond pulsars has been detected. In the present paper we summarize the observations and show the results of a re-analysis of archival ROSAT data. In addition we present the results of recent observations of PSR J0437-4715 with the ROSAT PSPC and HRI detectors. We show that the pulsed fraction is independent of energy in

H. Hirashita, T. T. Takeuchi, N. Tamura

We discuss a physical interpretation of the relation between $M_{\rm vir}/L$ and $M_{\rm vir}$ of dwarf spheroidal galaxies (dSphs), where $M_{\rm vir}$ and $L$ are the virial mass and the total luminosity of a dSph, respectively. We used 11 dSphs in the Local Group as the sample. We find two distinct sequences on the $M_{\rm vir}/L$--$M_{\rm vir}$ plane: $M

Dan Edidin, Robert Laterveer

This paper has been withdrawn. Theorem 2.1 of the paper is false, as it contradicts a result of Srinvas (Crelle's J. v.381, 1987). The error in our proof is in the construction of a functor in Claim 2. What we construct does not preserve composition of functions, so it is not a functor.

A. Ino, T. Mizokawa, K. Kobayashi, A. Fujimori

We have made a high-resolution photoemission study of La2-xSrxCuO4 in a wide hole concentration (x) range from a heavily overdoped metal to an undoped insulator. As x decreases, the spectral density of states at the chemical potential (μ) is suppressed with an x-dependence similar to the suppression of the electronic specific heat coefficient. In the underdo

Y. Naveh

Using the 'drift-diffusion-Langevin' equation, we have recently shown that finite-frequency shot noise in diffusive mesoscopic conductors is very sensitive to the ratio $γ\equiv L/\lee$ between the sample length $L$ and the electron-electron mean free path $\lee$. In this work we present numerical calculations of the noise at arbitrary value of $γ$.

Jeferson J. Arenzon, Juergen F. Stilck, Yan Levin

We present a simple model for the possible mechanism of appearance of attraction between like charged polyions inside a polyelectrolyte solution. The attraction is found to be short ranged, and exists only in presence of multivalent counterions. The attraction is produced by the correlations in the condensed layers of counterions surrounding each polyion, an

Viqar Husain

In recent work on black hole entropy in non-perturbative quantum gravity, an action for the black hole sector of the phase space is introduced and (partially) quantized. We give a number of observations on this and related works. In particular we show that (I) the entropy calculation applies without change to generally covariant theories having no black hole

Changhai Lu

We study the energy density of two distinct fundamental monopoles in SU(3) and Sp(4) theories with an arbitrary mass ratio. Several special limits of the general result are checked and verified. Based on the analytic expression of energy density the coefficient of the internal part of the moduli space metric is also computed, which gives it a nice "mecha

Dong Lai

Gravitational radiation tends to drive gravity modes in rotating neutron stars unstable. For an inviscid star, the instability sets in when the rotation frequency is about 0.7 times the corresponding mode frequency of the nonrotating star. Neutron stars with spin frequencies $\go 100$ Hz are susceptible to this instability, with growth time of order years. H

Andrey M. Shirokov, N. A. Smirnova, Yu. F. Smirnov

We discuss the symmetry of the parameter space of the interacting boson model (IBM). It is shown that for any set of the IBM Hamiltonian parameters (with the only exception of the U(5) dynamical symmetry limit) one can always find another set that generates the equivalent spectrum. We discuss the origin of the symmetry and its relevance for physical applicat

B. M. Terhal, I. L. Chuang, D. P. DiVincenzo, M. Grassl

We study the physical resources required to implement general quantum operations, and provide new bounds on the minimum possible size which an environment must be in order to perform certain quantum operations. We prove that contrary to a previous conjecture, not all quantum operations on a single-qubit can be implemented with a single-qubit environment, eve

Sergey Prokushkin, Mikhail Vasiliev

A remarkable feature of the models with interactions exhibiting higher-spin (HS) gauge symmetries in $d>2$ is that their most symmetric vacua require (anti)-de Sitter (AdS) geometry rather than the flat one. In striking parallelism to what might be expected of M theory HS gauge theories describe infinite towers of fields of all spins and possess naturally sp

J. Greensite, P. Olesen

We point out certain unexpected features of the planar QCD3 confining potential, as computed from a classical worldsheet action in an AdS metric via the Maldacena conjecture. We show that there is no Luscher c/R term in the static-quark potential, which is contrary to both the prediction of various effective string models, and the results of some recent latt

Philip C. Argyres, Alex Buchel

We argue that the topology of the quantum coupling space and the low energy effective action on the Coulomb branch of scale invariant N=2 SU(n) gauge theories pick out a preferred nonperturbative definition of the gauge coupling up to non-singular holomorphic reparametrizations.

A. Ghosh, G. Pollifrone, G. Veneziano

We solve exactly the (linear order) equations for tensor and scalar perturbations over the homogeneous, isotropic, open pre-big bang model recently discussed by several authors. We find that the parametric amplification of vacuum fluctuations (i.e. particle production) remains negligible throughout the perturbative pre-big bang phase.

S. Dalley, B. van de Sande

We describe a non-perturbative procedure for solving from first principles the light-front Hamiltonian problem of SU(N) pure gauge theory in D spacetime dimensions (D>2), based on enforcing Lorentz covariance of observables. A transverse lattice regulator and colour-dielectric link fields are employed, together with an associated effective potential. We argu

Stephen L. Adler

We construct extensions of the standard model based on the hypothesis that the Higgs bosons also exhibit a family structure, and that the flavor weak eigenstates in the three families are distinguished by a discrete $Z_6$ chiral symmetry that is spontaneously broken by the Higgs sector. We study in detail at the tree level models with three Higgs doublets, a

Mary K. Gaillard

It is shown that the one-loop coefficients of on-shell operators of standard supergravity with canonical gauge kinetic energy can be regulated by the introduction of Pauli-Villars chiral and abelian gauge multiplets, subject to a condition on the matter representations of the gauge group. Aspects of the anomaly structure of these theories under global nonlin

Yoshio Koide, Hideo Fusaoka

A universal seesaw mass matrix model, which gives successful description of quark mass matrix in terms of lepton masses, yields three "sterile" neutrinos ν^s_{i}, which compose pseudo-Dirac neutrinos ν_{i\pm}^{ps}\simeq (ν_{i} \pm ν^s_{i})/\sqrt{2} together with the active neutrinos ν_{i} (i=e,μ,τ). The solar and atmospheric neutrino data are explain

A. T. Banin, I. F. Ginzburg, I. P. Ivanov

We discuss the potentialities of the non-standard interaction study via the Higgs boson production at photon ($\ggam$ and $eγ$) colliders. We estimate the scale of New Physics phenomena beyond the standard model that can be seen in the experiments with Higgs boson production. In particular, the effect of new heavy particles within the standard model is shown

S. Frauendorf, J. A. Sheikh

The effects of the residual proton-neutron interactions on bandcrossing features are studied by means of shell model calculations for nucleons in a high-j intruder orbital. The presence of an odd-nucleon shifts the frequency of the alignment of two nucleons of the other kind along the axis of rotation. It is shown that the anomalous delayed crossing observed

David Vitali, Paolo Grigolini

We address the issue of the quantum-classical correspondence in chaotic systems using, as recently done by Zurek [e-print quant-ph/9802054], the solar system as a whole as a case study: this author shows that the classicality of the planetary motion is ensured by the environment-induced decoherence. We show that equivalent results are provided by the theorie

Satya N. Majumdar, Supriya Krishnamurthy, Mustansir Barma

We study nonequilibrium phase transitions in a mass-aggregation model which allows for diffusion, aggregation on contact, dissociation, adsorption and desorption of unit masses. We analyse two limits explicitly. In the first case mass is locally conserved whereas in the second case local conservation is violated. In both cases the system undergoes a dynamica

S. V. Chekanov

Multiplicity correlations between the current and target regions of the Breit frame in deep-inelastic scattering processes are studied. It is shown that the correlations are sensitive to the first-order perturbative QCD effects and can be used to extract the behavior of the boson-gluon fusion rates as a function of the Bjorken variable. The behavior of the c

T. Horibata, M. Oi, N. Onishi

We solved the constrained Hill-Wheeler Equation, and found several signatures of multi-band crossing in 182 Os.

Elena Caceres, Pirjo Pasanen

We study the M-theory five-brane wrapped around the Seiberg-Witten curves for pure classical and exceptional groups given by an integrable system. Generically, the D4-branes arise as cuts that collapse to points after compactifying the eleventh dimension and going to the semiclassical limit, producing brane configurations of NS5- and D4-branes with N=2 gauge

Andrei V. Frolov

This paper constructs continuously self-similar solution of a spherically symmetric gravitational collapse of a scalar field in n dimensions. The qualitative behavior of these solutions is explained, and closed-form answers are provided where possible. Equivalence of scalar field couplings is used to show a way to generalize minimally coupled scalar field so

Guifre Vidal, Rolf Tarrach

In the quest of completely describing entanglement in the general case of a finite number of parties sharing a physical system of finite dimensional Hilbert space a new entanglement magnitude is introduced for its pure and mixed states: robustness. It corresponds to the minimal amount of mixing with locally prepared states which washes out all entanglement.

Vladimir Buzek

We show how to determine (reconstruct) a master equation governing the time evolution of an open quantum system. We present a general algorithm for the reconstruction of the corresponding Liouvillian superoperators. Dynamics of a two-level atom in various environments is discussed in detail.

Noah Linden, Sandu Popescu

We argue that the halting problem for quantum computers which was first raised by Myers, is by no means solved, as has been claimed recently. We explicitly demonstrate the difficulties that arise in a quantum computer when different branches of the computation halt at different, unknown, times.

M. Strikman, M. G. Tverskoy, M. B. Zhalov

Recently E-665 reported the first measurement of soft ($E_n \le 10 $MeV) neutron production in deep inelastic scattering (DIS) off nuclei. We report the first theoretical analysis of the data. We find that the observed cross section can be quantitatively explained as due to the final state interactions (FSI) of low energy nucleons ($E_N \sim 200-400 MeV$) pr

M. Baldo, O. Elgaroey, L. Engvik, M. Hjorth-Jensen

We present results for the $^3P_2 - ^3F_2$ pairing gap in neutron matter with several realistic nucleon-nucleon potentials, in particular with recent, phase-shift equivalent potentials. We find that their predictions for the gap cannot be trusted at densities above $ρ\approx 1.7ρ_0$, where $ρ_0$ is the saturation density for symmetric nuclear matter. In orde

J. Edelmann, N. Kaiser, G. Piller, W. Weise

We generalize the sum rules for the nucleon electric plus magnetic polarizability $Σ=α+β$ and for the nucleon spin-polarizability $γ$, to virtual photons with $Q^2>0$. The dominant low energy cross sections are represented in our calculation by one-pion-loop graphs of relativistic baryon chiral perturbation theory and the $Δ(1232)$-resonance excitation. For

H. Shen, H. Toki, K. Oyamatsu, K. Sumiyoshi

We construct the equation of state (EOS) of nuclear matter at finite temperature and density with various proton fractions within the relativistic mean field (RMF) theory for the use in the supernova simulations. The Thomas-Fermi approximation is adopted to describe the non-uniform matter where we consider nucleus, alpha-particle, proton and neutron in equil

Atsushi Kajiyama, Kimikazu Taniguchi, Yoshinao Miyanishi

We discuss about the Hermitian treatment of Dyson-type boson expansion theory. We show that the basic assumption of the conventional treatment does not hold in general and the method is only approximately valid. We also show that the approximation is the same order as that of truncation of the expansion usually done in the Hermitian type boson expansion theo

M. S Fayache, L. Zamick

We perform shell model calculations in odd-odd nuclei using a quadrupole-quadrupole interaction and single-particle splittings chosen so as to obtain the SU(3) results. Elliott had shown that such an interaction gives rotational bands for which the energies go as I(I+1). This is certainly true for eve-even and for odd-even or even-odd nuclei with $K\neq 1/2$

J. Paetzold, R. Bilger, H. Clement, K. Foehl

The reaction 7Li(pi+,pi-)7B has been measured at incident pion energies of 30-90 MeV. 7Li constitutes the lightest target nucleus, where the pionic charge exchange may proceed as a binary reaction to a discrete final state. Like in the Delta-resonance region the observed cross sections are much smaller than expected from the systematics found for heavier nuc

J. J. P. Veerman, M. M. Peixoto, A. C. Rocha, S. Sutherland

Brillouin zones were introduced by Brillouin in the thirties to describe quantum mechanical properties of crystals, that is, in a lattice in $\R^n$. They play an important role in solid-state physics. It was shown by Bieberbach that Brillouin zones tile the underlying space and that each zone has the same area. We generalize the notion of Brillouin Zones to

Thomas Bauer, Sandra Di Rocco, Tomasz Szemberg

An algebraic variety X is embedded to the order k via a line bundle L if the global sections of L generate all (simultaneous) jets of order k on X or if they separate all zero-dimensional subschemes of length at most k+1. Even though we refer to both situations as "higher order embeddings", the first notion (in which case L is said to be k-jet ample)

N. Andruskiewitsch, H-J. Schneider

In a previous work \cite{AS2} we showed how to attach to a pointed Hopf algebra A with coradical $\kΓ$, a braided strictly graded Hopf algebra R in the category $_Γ^Γ\Cal{YD}$ of Yetter-Drinfeld modules over $Γ$. In this paper, we consider a further invariant of A, namely the subalgebra R' of R generated by the space V of primitive elements. Algebras of

G. Bini, C. De Concini, M. Polito, C. Procesi

These are the informal notes of two seminars held at the Universita` di Roma "La Sapienza", and at the Scuola Normale Superiore in Pisa in Spring and Autumn 1997. We discuss in detail the content of the parts of Givental's paper dealing with mirror symmetry for projective complete intersections.

Shlomo Gelaki

In this paper we construct and study two new families of finite dimensional pointed Hopf algebras which generalize Radford&#39;s families. We show that over any infinite field which contains a primitive nth root of unity, one of the families contains infinitely many non-isomorphic Hopf algebras of any dimension of the form Nn^2, where 2<n<N are integers so t

L. M. Morato, L. Viola

We construct a relativistically covariant stochastic model for systems of non-interacting spinless particles whose number undergoes random fluctuations. The model is compared with the canonical quantization of the free scalar field in the limit of infinite volume.

A. Buonanno, T. Damour, G. Veneziano

We formulate the basic postulate of pre-big bang cosmology as one of ``asymptotic past triviality&#39;&#39;, by which we mean that the initial state is a generic perturbative solution of the tree-level low-energy effective action. Such a past-trivial ``string vacuum&#39;&#39; is made of an arbitrary ensemble of incoming gravitational and dilatonic waves, and

Francesco Sannino

We present a ``toy&#39;&#39; model for breaking supersymmetric gauge theories at the effective Lagrangian level. We show that it is possible to achieve the decoupling of gluinos and squarks, below a given supersymmetry breaking scale m, in the fundamental theory for super QCD once a suitable choice of supersymmetry breaking terms is made. A key feature of th

Frank Wilczek

In quantum mechanics, symmetry groups can be realized by projective, as well as by ordinary unitary, representations. For the permutation symmetry relevant to quantum statistics of N indistinguishable particles, the simplest properly projective representation is highly non-trivial, of dimension $2^{(N-1)/2}$, and is most easily realized starting with spinor

Eric G. Gimon

We obtain an M--theory interpretation of different IIA orientifold planes by compactifying them on a circle and use a chain of dualities to get a new IIA limit of these objects using this circle as the eleventh dimension. Using the combination of the two IIA description, we give an interpretation for all orientifold four-planes in M-theory, including a mecha

S. Kalyana Rama

We study the description of Schwarzschild black holes, of entropy S, within matrix theory in the regime $N \ge S \gg 1$. We obtain the most general matrix theory equation of state by requiring that black holes admit a description within this theory. It has a recognisable form in various cases. In some cases a D dimensional black hole can plausibly be thought

A. I. Davydychev, P. Osland

The two-loop three-gluon vertex is calculated in an arbitrary covariant gauge, in the limit when two of the gluons are on the mass shell. The corresponding two-loop results for the ghost-gluon vertex are also obtained. It is shown that the results are consistent with the Ward-Slavnov-Taylor identities.

Isard Dunietz

It was recently pointed out that inclusive B^0(t) decays could show CP violation. The totally inclusive asymmetry is expected to be tiny [O(10^{-3})] because of large cancellations among the asymmetries in the charmless, single charm and double charm final states. Enriching particular final state configurations could significantly increase the CP-asymmetry a

R. N. Mohapatra

Supersymmetric left-right models with the see-saw mechanism for the neutrino masses have the attractive property that they conserve baryon and lepton number exactly in the Lagrangian. In this talk, I review the recent results valid for a large class of minimal versions of the model that supersymmetry combined with the requirement that the ground state of the

Marta Losada

We construct an effective three dimensional theory for the MSSM at high temperatures in the limit of large-$m_{A}$. We analyse the two-loop effective potential of the 3D theory for the case of a light right handed stop to determine the precise region in the $m_{h}$-$m_{\tilde{t}_{R}}$ plane for which the sphaleron constraint for preservation of the baryon as

John Ellis

A personal selection is made of some of the hot topics debated at this conference, including examples of using our knowledge of QCD to make electroweak measurements, structure functions at low x in the light of the corrections to the leading BFKL behaviour recently calculated, diffraction, the existence of one or more Pomerons and whether it/they may have a

D Boedeker, P V Landshoff, O Nachtmann, A Rebhan

We show how the fully resummed thermal pressure is rendered ultraviolet finite by standard zero-temperature renormalisation. The analysis is developed in a 6-dimensional scalar model that mimics QED and has $N$ flavours. The $N\to\infty$ limit of the model can be calculated completely. At a critical temperature, one of the degrees of freedom has vanishing sc

D. de Florian, J. Soffer, M. Stratmann, W. Vogelsang

We study inclusive Lambda hyperon production in pp collisions at BNL RHIC, with just one transversely polarized proton. We show that the measurement of the spin transfer between the initial proton and the produced Lambda is sensitive to the proton transversity distributions and to the corresponding Lambda transversity fragmentation functions. In view of our

Ulrich Heinz

I review recent applications of two-particle intensity interferometry in high energy physics, concentrating on relativistic heavy ion collisions. By measuring hadronic single-particle spectra and two-particle correlations in hadron-hadron or heavy-ion collisions, the size and dynamical state of the collision fireball at freeze-out can be reconstructed. I dis

Andrzej Czarnecki, Kirill Melnikov

We review recent calculations of second order corrections to heavy quark decays. Techniques developed in this context are applicable to many processes involving heavy charged particles, for example the nonabelian dipole radiation. Calculations involving relativistic radiating particles are also discussed.

Susan E. Morrison

The effectiveness of the Glasgow algorithm is explored via implementation in the 3d U(1) Gross-Neveu model and the realisation of the Goldstone mechanism in this model is compared and contrasted with its realisation in QCD.

SH. ZH. Akhmadaliev, G. Ya. Kezerashvili, S. G. Klimenko, V. M. Malyshev

The differential cross section of Delbrück scattering is measured on a bismuth germanate $Bi_4Ge_3O_{12}$ target at photon energies $140 - 450 MeV$ and scattering angles $2.6 - 16.6 mrad$. A good agreement with the theoretical results, obtained exactly in a Coulomb field, is found.

The OPAL Collaboration, K. Ackerstaff et al

Bose-Einstein Correlations (BEC) of three identical charged pions were studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP. The genuine three-pion correlations, corrected for the Coulomb effect, were separated from the known two-pion correlations by a new subtraction procedure. A significant genuine three-pion BEC enhancement near

V. Pravda, A. Pravdova

Electromagnetic field produced by magnetic multipoles in hyperbolic motion is derived and compared with electromagnetic field produced by electric multipoles in hyperbolic motion. The resulting fields are related by duality symmetry. Radiative properties of these solutions are demonstrated. In the second part an analogous, uniformly accelerated source of gra

S. Foster

The global behavior of scalar field cosmological models with very hard potential walls is investigated via the simple example of an exponentially steep potential well. It is found that the solutions exhibit a non-trivial oscillatory behavior in the approach to an initial space-time singularity. This behavior can be interpreted as being due to the inability o

M. Naraschewski, R. J. Glauber

We study first and second order coherence of trapped dilute Bose gases using appropriate correlation functions. Special attention is given to the discussion of second order or density correlations. Except for a small region around the surface of a Bose-Einstein condensate the correlations can be accurately described as those of a locally homogeneous gas with

Shirish M. Chitanvis

We have developed a theory of polymer entanglement using an extended Cahn-Hilliard functional, with two extra terms. One is a nonlocal attractive term, operating over mesoscales, which is interpreted as giving rise to entanglement, and the other a local repulsive term indicative of excluded volume interactions. This functional can be derived using notions fr

David A. Meyer, Thad A. Brown

Decision procedures aggregating the preferences of multiple agents can produce cycles and hence outcomes which have been described heuristically as `chaotic&#39;. We make this description precise by constructing an explicit dynamical system from the agents&#39; preferences and a voting rule. The dynamics form a one dimensional statistical mechanics model; th

Sven Lubeck

We study numerically the dynamical properties of the BTW model on a square lattice for various dimensions. The aim of this investigation is to determine the value of the upper critical dimension where the avalanche distributions are characterized by the mean-field exponents. Our results are consistent with the assumption that the scaling behavior of the four

Fumitaka Matsubara, Takayuki Shirakura, Michinori Siomi

We calculate the naive defect energy $ΔE$ of Ising spin glass(SG) models in two dimensions using conjugate boundary conditions. We predict that, in the $\pm J$ model, the averaged value $\bar{ΔE}$ converges to some non-zero value in the thermodynamic limit in contrast with $\bar{ΔE} = 0$ in the Gaussian model. This prediction is incompatible with previous on

John Cardy

A rigorous theorem due to Aizenman and Wehr asserts that there can be no latent heat heat in a two-dimensional system with quenched random impurities. We examine this result, and its possible extensions to higher dimensions, in the context of several models. For systems whose pure versions undergo a strong first-order transition, we show that there is an asy

B. Starmark, Torsten Henning, A. N. Korotkov, T. Claeson

An extensive investigation of low frequency noise in single electron transistors as a function of gain is presented. Comparing the output noise with gain for a large number of bias points, it is found that the noise is dominated by external charge noise. For low gains we find an additional noise contribution which is compared to a model including resistance

V. V. Harutunyan, T. S. Hakobyan, A. S. Hovhannesian, V. A. Gevorkyan

Optical reflection spectra of corundum single crystals grown by HOC and Verneil methods are investigated before and after irradiated by electrons and neutrons using synchrotron radiation polarization (5-30eV).

Janne Ruostekoski, Dan F. Walls

We propose a method of measuring diffusion of the relative phase between two Bose-Einstein condensates occupying different nuclear or spin hyperfine states coupled by a two-photon transition via an intermediate level. Due to the macroscopic quantum coherence the condensates can be decoupled from the electromagnetic fields. The rate of decoherence and the pha

Mark Leadbeater, Rudolf A. Romer, Michael Schreiber

We study the formation of electron-hole pairs for disordered systems in the limit of weak electron-hole interactions. We find that both attractive and repulsive interactions lead to electron-hole pair states with large localization length $λ_{2}$ even when we are in this non-excitonic limit. Using a numerical decimation method to calculate the decay of the G

Y. Naveh

Using the &#39;drift-diffusion-Langevin&#39; equation we show that, at least in one geometry, finite-frequency shot noise is of the order of the &#39;full&#39; shot noise $2eI$ provided the sample is either short or long enough, $L > L_0(ω)$. Here $L_0(ω) = D&#39;/\lph ω$ with $D&#39;$ the effective diffusion coefficient, $\lph$ the electron-phonon energy re

Matthew Stone, Bonnie Webber

We focus on the production of efficient descriptions of objects, actions and events. We define a type of efficiency, textual economy, that exploits the hearer&#39;s recognition of inferential links to material elsewhere within a sentence. Textual economy leads to efficient descriptions because the material that supports such inferences has been included to s

A. Soffer, M. I. Weinstein

We present a theory of resonances for a class of non-autonomous Hamiltonians to treat the structural instability of spatially localized and time-periodic solutions associated with an unperturbed autonomous Hamiltonian. The mechanism of instability is radiative decay, due to resonant coupling of the discrete modes to the continuum modes by the time-dependent

A. Soffer, M. I. Weinstein

We consider a class of nonlinear Klein-Gordon equations which are Hamiltonian and are perturbations of linear dispersive equations. The unperturbed dynamical system has a bound state, a spatially localized and time periodic solution. We show that, for generic nonlinear Hamiltonian perturbations, all small amplitude solutions decay to zero as time tends to in

Holger Kantz, Thomas Schreiber

We discuss aspects of randomness and of determinism in electrocardiographic signals. In particular, we take a critical look at attempts to apply methods of nonlinear time series analysis derived from the theory of deterministic dynamical systems. We will argue that deterministic chaos is not a likely explanation for the short time variablity of the inter-bea

D. Downes, P. M. Solomon

New high resolution interferometer data of 10 IR ultraluminous galaxies shows the molecular gas is in rotating nuclear rings or disks with radii 300 to 800 pc. Most of the CO flux comes from a moderate-density, warm, intercloud medium rather than self-gravitating clouds. Gas masses of ~ 5 x 10^9 Msun, 5 times lower than the standard method are derived from a

Andrea Ferrara, Benedetta Ciardi

In this paper we briefly review some of the most recent developments concerning the formation of the first luminous objects in the universe, to which we refer to as Pop III objects, and their observable effects. In particular, we try to critically discuss the possible connection between them and dwarf spheroidal galaxies. We come to the conclusion that, if t

S. Ettori, A. C. Fabian, D. A. White

We present an analysis of four off-axis ROSAT PSPC observations of the Perseus cluster of galaxies (Abell~426). We detect the surface brightness profile to a radius of 80 arcmin ($\sim 2.4 h_{50}^{-1}$ Mpc) from the X-ray peak. The profile is measured in various sectors and in three different energy bands. Firstly, a colour analysis highlights a slight varia

Robert G. Crittenden, Neil G. Turok

We investigate various pixelizations of the sky which allow for fast spherical transforms, for implementation in full sky CMB experiments such as Planck and MAP. We study the effect of varying pixel shape and area on the extraction of the CMB power spectrum. We argue for the benefits of having a truly azimuthal, or `igloo&#39; pixelization. Such pixelization

Pedro G. Ferreira

A scalar field with an exponential potential has the particular property that it is attracted into a solution in which its energy scales as the dominant component (radiation or matter) of the Universe, contributing a fixed fraction of the total energy density. We briefly discuss the dynamics of such a scalar field and its impact on Big Bang nucleosynthesis,

C. L. Sarazin, A. M. Koekemoer, S. A. Baum, C. P. O&#39;Dea

X-ray observations with the ROSAT HRI and with ASCA are presented for the nearby radio quasar B2 1028+313, which is located in the cD galaxy at the center of the Abell cluster A1030. We also analyze archival ROSAT PSPC observations. We find that the X-ray emission is dominated by the quasar. The flux varied by a factor of about two between the ROSAT HRI and

TEP Network, :, H. J. Deeg, L. R. Doyle

Results from a photometric search for extrasolar planetary transits across the eclipsing binary CM Dra are presented. The TEP (Transits of Extrasolar Planets) network has observed this star since 1994, and a lightcurve with 617 hours of coverage has been obtained. The data give a complete phase coverage of the CM Dra system at each of the 3 years of observat

S. Bianchi, P. B. Alton, J. I. Davies, M. Trewhella

We present observations of the spiral galaxy NGC 7331 using the Sub-millimetre Common User Bolometer Array (SCUBA) on the James Clark Maxwell Telescope. We have detected a dust ring of 45 arcsec radius (3.3 kpc) at wavelengths of 450 and 850-micron. The dust ring is in good correspondence with other observations of the ring in the mid-infrared (MIR), CO and

Russell K. Standish

In a recent paper, Newman surveys the literature on power law spectra in evolution, self-organised criticality and presents a model of his own to arrive at a conclusion that self-organised criticality is not necessary for evolution. Not only did he miss a key model (Ecolab) that has a clear self-organised critical mechanism, but also Newman&#39;s model exhib

R. Brandenberger, Richard Easther, J. Maia

We study spatially homogeneous and isotropic solutions to the equations of motion derived from dilaton gravity, in the presence of a special combination of higher derivative terms in the gravitational action. All solutions are nonsingular. For initial conditions resembling those in the pre-big-bang scenario, there are solutions corresponding to a spatially f

Christof Gattringer, Ivan Hip

We study the role of the O(a)-improving clover term for the spectrum of the lattice Dirac operator using cooled and thermalized SU(2) gauge field configurations. For cooled configurations we observe improvement of the spectral properties when adding the clover term. For the thermalized case (12^4, beta = 2.4) without clover term we find a rather bad separati

A. I. Smirnov, V. N. Glazkov, L. I. Leonyuk, A. G. Vetkin

ESR of the pure monocrystals of CuGeO3 is studied in the frequency range 9-75 GHz and in the temperature interval 1.2-25 K. The splitting of the ESR line into several spectral components is observed below 5 K, in the temperature range where the magnetic susceptibility is suppressed by the spin-Peierls dimerization. The analysis of the magnetic resonance sign

E. Oset, J. A. Gomez Tejedor, F. Cano, J. C. Nacher

We report on reactions producing two pions induced by real and virtual photons or nucleons. The role of different resonances in these reactions is emphasized. Novel results on coherent two pion photoproduction in nuclei are also reported.

Jonathan Beck, Igor Frenkel, Naihuan Jing

In the basic representation of $U_q(\hat{sl}(2))$ realized via the algebra of symmetric functions we compare the canonical basis with the basis of Macdonald polynomials with $q=t^2$. We show that the Macdonald polynomials are invariant with respect to the bar involution defined abstractly on the representations of quantum groups. We also prove that the Macdo

J. T. Londergan, A. W. Thomas

Recent measurements of the Gottfried sum rule have focused attention on the possibility of substantial flavor symmetry breaking in the proton sea. This is confirmed by pp and pD Drell-Yan processes measured at FNAL. Theoretical models used to `prove' flavor symmetry breaking rely on the assumption of charge symmetric parton distributions. Substantial charge

Yakov Itin

The wave type field equation $\square \vt^a=\la \vt^a$, where $\vt^a$ is a coframe field on a space-time, was recently proposed to describe the gravity field. This equation has a unique static, spherical-symmetric, asymptotically-flat solution, which leads to the viable Yilmaz-Rosen metric. We show that the wave type field equation is satisfied by the pseudo

J. M. Kosterlitz, N. Akino

The XY model with quenched random phase shifts is studied by a T=0 finite size defect energy scaling method in 2d and 3d. The defect energy is defined by a change in the boundary conditions from those compatible with the true ground state configuration for a given realization of disorder. A numerical technique, which is exact in principle, is used to evaluat

Y. V. Ivanenko, N. I. Lebovka, N. V. Vygornitskii

The stochastic Eden model of charged particles aggregation in two-dimensional systems is presented. This model is governed by two parameters: screening length of electrostatic interaction, $λ$, and short range attraction energy, $E$. Different patterns of finite and infinite aggregates are observed. They are of following types of morphologies: linear or line

Shoji Yamamoto, Takahiro Fukui, Klaus Maisinger, Ulrich Schollwöck

We investigate the thermodynamic properties of Heisenberg ferrimagnetic mixed-spin chains both numerically and analytically with particular emphasis on the combination of ferromagnetic and antiferromagnetic features. Employing a new density-matrix renormalization-group technique as well as a quantum Monte Carlo method, we reveal the overall thermal behavior:

Shoji Yamamoto

Based on a symmetry argument we systematically reveal Hartree-Fock broken-symmetry solutions of the one-dimensional two-band extended Peierls-Hubbard model, which covers various materials of interest such as halogen-bridged metal complexes and mixed-stack charge-transfer salts. We find out all the regular-density-wave solutions with an ordering vector $q=0$

V. Kurasov

Some simplifications of the theory of the density profiles of condensation are discussed. The role of the additive effects is outlined.