May 1998 arXiv papers — page 14

E. Adelberger, S. Austin, J. Bahcall, A. Balantekin

We review and analyze the available information for nuclear fusion cross sections that are most important for solar energy generation and solar neutrino production. We provide best values for the low-energy cross-section factors and, wherever possible, estimates of the uncertainties. We also describe the most important experiments and calculations that are r

D. I. Kosenko, K. A. Postnov

We calculate stochastic gravitational wave background produced by extragalactic merging binary white dwarfs at the LISA frequencies $10^{-3}-10^{-2}$ Hz with account of a strong evolution of global star formation rate in the Universe recently established observationally. We show that for the observed global star formation history and modern cosmological mode

Ivone F. M. Albuquerque, Glennys R. Farrar, Edward W. Kolb

We investigate the proposal that primary cosmic rays of energy above the Greisen-Zatsepin-Kuzmin cutoff are exotic massive strongly interacting particles (uhecrons). We study the properties of air showers produced by uhecrons and find that masses in excess of about 50 GeV are inconsistent with the highest energy event observed. We also estimate that with suf

J. Nevalainen, M. Roos

This study combines data from a set of seven Cepheid-calibrated galaxies in Virgo, Leo I and Fornax and four supernovae with known metallicities, including metallicity corrections to the Cepheid distances, in order to determine a consistent mean value for the Hubble constant. We derive Virgo and Coma distances over different paths, starting from the metallic

Frank Göhmann, Shuichi Murakami

We develop a general scheme for the use of Fermi operators within the framework of integrable systems. This enables us to read off a fermionic Hamiltonian from a given solution of the Yang-Baxter equation and to express the corresponding $L$-matrix and the generators of symmetries in terms of Fermi operators. We illustrate our approach through a number of ex

Jeremy S. Heyl, Lars Hernquist

We examine the propagation of electromagnetic radiation through a strong magnetic field using the method of characteristics. Owing to nonlinear effects associated with vacuum polarization, such waves can develop discontinuities analogous to hydrodynamical shocks. We derive shock jump conditions and discuss the physical nature of these non-linear waves

Andrea Brignole, Ferruccio Feruglio, Fabio Zwirner

We discuss the role of the effective interactions among four matter fermions in supersymmetric models with a very light gravitino. We show that, from a field-theoretical viewpoint, no model-independent bound on the gravitino mass can be derived from such interactions. Making use of a naturalness criterion, however, we are able to derive some interesting but

E. R. Takano Natti, Chi-Yong Lin, A. F. R de Toledo Piza, P. L. Natti

Using many-body techniques we obtain the time-dependent Gaussian approximation for interacting fermion-scalar field models. This method is applied to an uniform system of relativistic spin-1/2 fermion field coupled, through a Yukawa term, to a scalar field in 3+1 dimensions, the so-called quantum scalar plasma model. The renormalization for the resulting Gau

Paul Langacker

Efficient oscillations between ordinary (active) and sterile neutrinos can occur only if Dirac and Majorana mass terms exist which are both small and comparable. It is shown that this can occur naturally in a class of string models, in which higher-dimensional operators in the superpotential lead to an intermediate scale expectation value for a scalar field

Katsuyuki Sugiyama

We study topological A-model disk amplitudes with Calabi-Yau target spaces by mirror symmetries. This allows us to calculate holomorphic instantons of Riemann surfaces with boundaries that are mapped into susy cycles in Calabi-Yau d-folds. Also we analyse disk amplitudes in Fano manifold cases by considering fusion relations between A-model operators.

S. Liberati, F. Belgiorno, Matt Visser, D. W. Sciama

Several years ago Schwinger proposed a physical mechanism for sonoluminescence in terms of photon production due to changes in the properties of the quantum-electrodynamic (QED) vacuum arising from a collapsing dielectric bubble. This mechanism can be re-phrased in terms of the Casimir effect and has recently been the subject of considerable controversy. The

K. Pohlmeyer

A relevant part of the quantum algebra of observables for the closed bosonic strings moving in 1+3-dimensional Minkowski space is presented in the form of generating relations involving still one, as yet undetermined, real free parameter.

H. G. Ballesteros, L. A. Fernandez, V. Martin-Mayor, G. Parisi

Using Finite-Size Scaling techniques we obtain accurate results for critical quantities of the Ising model and the site percolation, in three dimensions. We pay special attention in parameterizing the corrections-to-scaling, what is necessary to put the systematic errors below the statistical ones.

C. L. Emmott

A perturbation expansion is considered about the Ohta-Jasnow-Kawasaki theory of phase-ordering dynamics; the non-linear terms neglected in the OJK calculation are reinstated and treated as a perturbation to the linearised equation. The first order correction term to the pair correlation function is calculated in the large-d limit and found to be of order 1/(

J. M. Isidro

A wide class of Seiberg-Witten models constructed by M-theory techniques and described by non-hyperelliptic Riemann surfaces are shown to possess an associative algebra of holomorphic differentials. This is a first step towards proving that also these models satisfy the Witten-Dijkgraaf-Verlinde-Verlinde equation. In this way, similar results known for simpl

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

A 5D black hole(M$_5$) is investigated in the type IIB superstring theory compactified on S$^1 \times $T$^4$. This corresponds to AdS$_3 \times $S$^3 \times $T$^4$ in the near horizon with asymptotically flat space. Here the harmonic gauge is introduced to decouple the mixing between the dilaton and others. On the other hand we obtain the BTZ balck hole(AdS$

V. V. Dmitriev, V. B. Eltsov, M. Krusius, J. J. Ruohio

Nonlinear spin precession has been observed in 3He-B in large counterflow of the normal and superfluid fractions. The new precessing state is stabilized at high rf excitation level and displays frequency-locked precession over a large range of frequency shifts, with the magnetization at its equilibrium value. Comparison to analytical and numerical calculatio

Clifford V. Johnson

The four six-dimensional ``little string'' theories are all described in the infinite momentum frame (IMF) as matrix theories by non-trivial 1+1 dimensional infra-red fixed points. We characterize these fixed points using supergravity. Starting from the matrix theory definition of M5-branes, we derive an associated dual supergravity description of th

Q. P. Liu, M. Manas

The vectorial fundamental transformation for the Darboux equations is reduced to the symmetric case. This is combined with the orthogonal reduction of Lame type to obtain those vectorial Ribaucour transformations which preserve the Egoroff reduction. We also show that a permutability property holds for all these transformations. Finally, as an example, we ap

G. M. D'Ariano, L. Maccone

We show how recent state-reconstruction techniques can be used to determine the Hamiltonian of an optical device that evolves the quantum state of radiation. A simple experimental setup is proposed for measuring the Liouvillian of phase-insensitive devices. The feasibility of the method with current technology is demonstrated on the basis of Monte Carlo simu

Marco Toller

The present paper deals with the quantum coordinates of an event in space-time, individuated by a quantum object. It is known that these observables cannot be described by self-adjoint operators or by the corresponding spectral projection-valued measure. We describe them by means of a positive-operator-valued (POV) measure in the Minkowski space-time, satisf

Tarso B. L. Kist, M. Orszag, T. A. Brun, L. Davidovich

We propose physical interpretations for stochastic methods which have been developed recently to describe the evolution of a quantum system interacting with a reservoir. As opposed to the usual reduced density operator approach, which refers to ensemble averages, these methods deal with the dynamics of single realizations, and involve the solution of stochas

St. Hollinger, M. Luecke

Convection in horizontal layers of binary fluids heated from below and in particular the influence of the Soret effect on the bifurcation properties of extended stationary and traveling patterns that occur for negative Soret coupling is investigated theoretically. The fixed points corresponding to these two convection structures are determined for realistic

A. Sibirtsev, W. Cassing

We calculate the momentum-dependent potentials for $K^+$ and $K^-$ mesons in a dispersion approach at nuclear density $ρ_0$ using the information from the vacuum $K^+ N$ and $K^- N$ scattering amplitudes, however, leaving out the resonance contributions for the in-medium analysis. Whereas the $K^+$ potential is found to be repulsive ($\approx$ + 30 MeV) and

A. van Hameren, R. Kleiss

The concept of discrepancy plays an important role in the study of uniformity properties of point sets. For sets of random points, the discrepancy is a random variable. We apply techniques from quantum field theory to translate the problem of calculating the probability density of (quadratic) discrepancies into that of evaluating certain path integrals. Both

David Gabai, William H. Kazez

We show that if a closed atoroidal 3-manifold M contains a genuine lamination, then it is group negatively curved in the sense of Gromov. Specifically, we exploit the structure of the non-product complementary regions of the genuine lamination and then apply the first author's Ubiquity Theorem to show that M satisfies a linear isoperimetric inequality.

Masoud Khalkhali

A classical result of Loday-Quillen and Tsygan states that the Lie algebra homology of the algebra of stable matrices over an associative algebra is isomorphic, as a Hopf algebra, to the exterior algebra of the cyclic homology of the algebra. In this paper we develop the necessary tools needed to extend extend this result to the category of L_{\infty} algebr

Masoud Khalkhali

We present an approach to cyclic homology of A_{\infty} algebras. Our main technical tool is the concept of X-complex due to Cuntz and Quillen. This, in particular, enables us to compute the periodic cyclic homology of an A_{\infty} algebra in terms of the periodic cyclic homology of its homology.

Swanhild Bernstein

Monotonicity principles can be used to get informations about nonlinear singular integral equations. These results are based on a theorem of Browder and Minty. We consider a family of monotone singular integral operators and associated nonlinear singular integral equations with Nemickii operator in Clifford analysis which has an application to the nonlinear

Peter Gloessner

We propose a reduction procedure that leads to a reduced star product on the reduced phase space of a `First Class'-constrained system, where no symmetries, group actions or the like are present. For the case that the coisotropic submanifold has codimension 1, we establish a constructive method to compute the reduced star product explicitly. Concluding e

M. Havlíček, A. U. Klimyk, S. Pošta

An algebra homomorphism $ψ$ from the nonstandard q-deformed (cyclically symmetric) algebra $U_q(so_3)$ to the extension ${\hat U}_q(sl_2)$ of the Hopf algebra $U_q(sl_2)$ is constructed. Not all irreducible representations of $U_q(sl_2)$ can be extended to representations of ${\hat U}_q(sl_2)$. Composing the homomorphism $ψ$ with irreducible representations

E. Bergshoeff, D. Sorokin, P. K. Townsend

We obtain the Hamiltonian form of the worldvolume action for the M5-brane in a general D=11 supergravity background. We use this result to obtain a new version of the covariant M5-brane Lagrangian in which the tension appears as a dynamical variable, although this Lagrangian has some unsatisfactory features which we trace to peculiarities of the null limit.

HoSeong La

We propose a systematic way of introducing the (nongravitational) low energy dilaton and a scheme for spontaneous breaking of scale symmetry (SBSS) is explained.

Arthur K. Kerman, Chi-Yong Lin

The Gaussian-time-dependent variational equations are used to explored the physics of $(ϕ^4)_{3+1}$ field theory. We have investigated the static solutions and discussed the conditions of renormalization. Using these results and stability analysis we show that there are two viable non-trivial versions of $(ϕ^4)_{3+1}$. In the continuum limit the bare couplin

Y. Brihaye, B. Kleihaus, D. H. Tchrakian

We make a numerical study of the classical solutions of the combined system consisting of the Georgi-Glashow model and the SO(3) gauged Skyrme model. Both monopole-Skyrmion and dyon-Skyrmion solutions are found. A new bifurcation is shown to occur in the gauged Skyrmion solution sector.

P. C. West

In these lectures we discuss the supersymmetry algebra and its irreducible representations. We construct the theories of rigid supersymmetry and gave their superspace formulations. The perturbative quantum properties of the extended supersymmetric theories are derived, including the superconformal invariance of a large class of these theories. We also discus

S. Gonorazky, C. Núñez, F. A. Schaposnik, G. Silva

We study N=2 supersymmetric Born-Infeld-Higgs theory in 3 dimensions and derive Bogomol'nyi relations in its bosonic sector. A peculiar coupling between the Higgs and the gauge field (with dynamics determined by the Born-Infeld action) is forced by supersymmetry. The resulting equations coincide with those arising in the Maxwell-Higgs model. Concerning B

Heinrich Saller

In analogy to the class structure $\GL(\R^4)/Ø(1,3)$ for general relativity with a local Lorentz group as stabilizer and a basic tetrad field for the parametrization, a corresponding class structure $\GL(\C^2)/\U(2)$ is investigated for the standard model with a local hyperisospin group $\U(2)$. The lepton, quark, Higgs and gauge fields, used in the standard

Kazuto Oshima, Masanobu Yahiro

The spontaneous symmetry breaking in (1+1)-dimensional $ϕ^{4}$ theory is studied with discretized light-front quantization, that is, by solving the zero-mode constraint equation. The symmetric ordering is assumed for the operator-valued constraint equation. The commutation relation between the zero mode and each oscillator mode is calculated with $\hbar$ exp

Washington Taylor

These notes give a pedagogical introduction to D-branes and Matrix theory. The development of the material is based on super Yang-Mills theory, which is the low-energy field theory describing multiple D-branes. The main goal of these notes is to describe physical properties of D-branes in the language of Yang-Mills theory, without recourse to string theory m

Stephen P. Martin, James D. Wells

There are many theoretical reasons why heavy quasi-stable charged particles might exist. Pair production of such particles at the Tevatron can produce highly ionizing tracks (HITs) or fake muons. In gauge-mediated supersymmetry breaking, sparticle production can lead to events with a pair of quasi-stable sleptons, a significant fraction of which will have th

Isard Dunietz

The branching ratio B(Lambda_c -> p K- pi+) normalizes the production and decay of charmed and bottom baryons. At present, this crucial branching ratio is extracted dominantly from B.bar -> baryons analyses. This note questions several of the underlying assumptions and predicts sizable B.bar -> D(*) N N'.bar X transitions, which were traditionally neglec

L. Burakovsky

We show that linear Regge trajectories for mesons and baryons, and the cubic mass spectrum associated with them, determine expressions for the hadron masses in terms of the universal Regge slope α' alone. The ground state hadron masses as calculated from these expressions are in excellent agreement with experiment for α'=0.85 GeV^{-2}.

C. P. Burgess, A. de la Macorra, I. Maksymyk, F. Quevedo

We briefly discuss the differences between considering the gauge coupling as a constant or as a field, the dilaton, in N=1 supersymmetric theories. We emphasize the differences regarding supersymmetry breaking. Recent developments on the nonperturbative dynamics of these theories provide new ideas on the induced dilaton potential and its stabilization.

A. Bassetto, G. Heinrich, Z. Kunszt, W. Vogelsang

We present calculations of next-to-leading order QCD splitting functions, employing the light-cone gauge method of Curci, Furmanski, and Petronzio (CFP). In contrast to the `principal-value' prescription used in the original CFP paper for dealing with the poles of the light-cone gauge gluon propagator, we adopt the Mandelstam-Leibbrandt prescription whic

C. Helminen, D. O. Riska

The interaction mediated by irreducible pion and gluon exchange between constituent quarks is calculated and shown to have a strong tensor component, which tends to cancel the pion exchange tensor interaction between quarks. Its spin-spin component is somewhat weaker than the pion exchange spin-spin interaction, while its central and spin-orbit components ar

Nikolaos Kidonakis, Gianluca Oderda, George Sterman

We discuss threshold resummation for dijet production in hadronic collisions. Resummation to next-to-leading logarithmic (NLL) accuracy is given in terms of an anomalous dimension matrix for each partonic subprocess involved.

Shahin S. Agaev

The pion and kaon electromagnetic form factors $F_M(Q^2)$ are calculated at the leading order of pQCD using the running coupling constant method. In calculations the leading and next-to-leading order terms in $α_S((1-x)(1-y)Q^2)$ expansion in terms of $α_S(Q^2)$ are taken into account. The resummed expression for $F_M(Q^2)$ is found. Results of numerical cal

Hui-Shi Dong, Xin-Heng Guo, Xue-Qian Li, Rui Zhang

Data show that τ_{B^{\pm}}\simτ_{B^0}, but τ_{D^{\pm}}\sim 2τ_{D^0}. The naive interpretation which attributes τ_{D^{\pm}}\sim 2τ_{D^0} to a destructive interference between two quark diagrams for D^{\pm} decays, definitely fails in the B-case. We investigate Close and Lipkin's suggestion that the phases for producing radially excited states ψ_{2s} in th

U. A. Yajnik, Hatem Widyan, Shobhit Mahajan, Amitabha Mukherjee

It is shown that the minimal Left-Right symmetric model admits cosmic string, domain wall and conditionally, monopole solutions. The strings arise when the $SU(2)_R$ is broken and can either be destabilized at the electroweak scale or remain stable through the subsequent breakdown to $U(1)_{EM}$. The monopoles and domain wall configurations exist in the $SU(

M. Maltoni, M. I. Vysotsky

We show that recently announced strong bound on $μ_{ν_τ}$ can not be justified, and confirm original L3 result.

G. P. Vacca

The Regge limit in perturbative QCD for processes as DIS (low x) and photon or onia-particles scattering is considered. In the first part a phenomenological approach for the inclusion of the running coupling, preserving the gluon reggeization property, is analyzed. In particular the spectrum of the hard pomeron equation and the asymptotic form of the solutio

Kostas Orginos, Doug Toussaint

We extend tests of "Naik" and "fat link" improvements of the Kogut-Susskind quark action to full QCD simulations, and verify that the improvements previously demonstrated in the quenched approximation apply also to dynamical quark simulations. We extend the study of flavor symmetry improvement to the complete set of pions, and find that the n

Samim Erhan

CP-violation is one of the least understood phenomena in our field. There are major experimental programs in all high energy laboratories around the world which will hopefully remedy this within the next decade. The study of CP-violating effects in B meson decays will allow stringent tests of the Standard Model to be made and may point the way to New Physics

Michael John Pfenning, L. H. Ford

In quantum field theory, there exist states in which the expectation value of the energy density for a quantized field is negative. These negative energy densities lead to many problems. Although quantum field theory introduces negative energies, it also provides constraints in the form of quantum inequalities (QI's). These uncertainty principle-type rel

L. Herrera, J. Martinez

A relativistic model of a heat conducting collapsing star, which includes thermal pre-relaxation processes, is presented. Particular attention is paid to the influence of a given parameter defined in terms of thermodynamic variables, on the outcome of evolution. Evaluation of the system when passing through a critical value of the aforesaid parameter, does n

A. Feoli, W. R. Wood, G. Papini

The dynamical process following the breaking of Weyl geometry to Riemannian geometry is considered by studying the motion of de Sitter bubbles in a Weyl vacuum. The bubbles are given in terms of an exact, spherically symmetric thin shell solution to the Einstein equations in a Weyl-Dirac theory with a time-dependent scalar field of the form beta = f(t)/r. Th

N. Barros e Sa, I. Bengtsson

It has been proposed to study the theory resulting from setting the gravitational constant to zero in the first order formalism for general relativity. In this letter we investigate this theory in the presence of matter fields, establish its equivalence with parametrized field theory on a flat background, and relate it to previous results in topological fiel

Toshiharu Kawai, Eisaku Sakane, Takashi Tojo

In Poincaré gauge theory of gravity and in $\overline{\mbox{Poincaré}}$ gauge theory of gravity, we give the necessary and sufficient condition in order that the Schwarzschild space-time expressed in terms of the Schwarzschild coordinates is obtainable as a torsionless exact solution of gravitational field equations with a spinless point-like source having t

J. W. Lynn, L. Vasiliu-Doloc, M. A. Subramanian

Neutron scattering has been used to study the magnetic order and spin dynamics of the colossal magnetoresistive pyrochlore Tl_2Mn_2O_7. On cooling from the paramagnetic state, magnetic correlations develop and appear to diverge at T_C (123 K). In the ferromagnetic phase well defined spin waves are observed, with a gapless ($Δ<0.04$ meV) dispersion relation E

Anupam Garg

Field-dependent maxima in the relaxation rate of the magnetic molecules Mn_12-Ac and Fe_8-tacn have commonly been ascribed to some resonant tunneling phenomenon. We argue instead that the relaxation can be understood as purely due to phonons. The rate maxima arise because of a Jahn-Teller-like distortion caused by the coupling of lattice phonons to degenerat

Daniel Loss, Herbert Schoeller, Paul M. Goldbart

In a recent preprint (cond-mat/9803170), van~Langen, Knops, Paasschens and Beenakker attempt to re-analyze the proposal of Loss, Schoeller and Goldbart (LSG) [Phys. Rev. B~48, 15218 (1993)] concerning Berry phase effects in the magnetoconductance of diffusive systems. Van Langen et al. claim that the adiabatic approximation for the Cooperon previously derive

A. Chattopadhyay, M. Jarrell, H. R. Krishnamurthy, H. K. Ng

We compare the magnetoresistance of UCu$_{3.5}$Pd$_{1.5}$ with calculations done within the disordered heavy fermion framework of Miranda et al. using a phenomenological spectral function for the Anderson model, calibrated against Bethe ansatz and quantum Monte Carlo results. Both in experiment and theory, we find a weak negative magnetoresistance. In contra

Gregory Brown, Per Arne Rikvold, S. J. Mitchell, M. A. Novotny

We present a tutorial discussion of Monte Carlo methods for equilibrium and nonequilibrium problems in interfacial electrochemistry. The discussion is illustrated with results from simulations of three specific systems: bromine adsorption on silver (100), underpotential deposition of copper on gold (111), and electrodeposition of urea on platinum (100).

I. M. Abu-Shiekah, O. O. Bernal, H. B. Brom, M. L. de Kok

Charge and spin ordering in La2NiO4.17 has been studied by 139La NMR using the field and temperature dependence of the linewidth and relaxation rates. The stripes are site centered and the domain spins freeze at ~ 180 K, followed by a second transition at ~ 50 K, where the spins on the domain walls freeze. Although consistent with the neutron measurements, t

G. Bedürftig, B. Brendel, H. Frahm, R. M. Noack

Using the Density Matrix Renormalization Group (DMRG), we calculate critical exponents for the one-dimensional Hubbard model with open boundary conditions with and without additional boundary potentials at both ends. A direct comparison with open boundary condition Bethe Ansatz calculations provides a good check for the DMRG calculations on large system size

P. Delsing, C. D. Chen, D. B. Haviland, Tobias Bergsten

We describe transport properties of two-dimensional arrays of low capacitance tunnel junctions, such as the current voltage characteristic and its dependence on external magnetic field and temperature. We discuss several experiments in which the small capacitance of the junctions plays an important role. In arrays where the junctions have a relatively large

R. Eder, A. Dorneich, M. G. Zacher, W. Hanke

We discuss properties of an exactly SO(5) symmetric ladder model. In the strong coupling limit we demonstrate how the SO(3)-symmetric description of spin ladders in terms of bond Bosons can be upgraded to an SO(5)-symmetric bond-Boson model, which provides a particularly simple example for the concept of SO(5) symmetry. Based on this representation we show t

H. Kawamura, K. Hukushima

Spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin glasses are studied both by equilibrium and off-equilibrium Monte Carlo simulations. Fully isotropic model is found to exhibit a finite-temperature chiral-glass transition without the conventional spin-glass order. Although chirality is an Ising-like quantity from symmetry, universali

Hikaru Kawamura

Spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin glasses are studied with and without randaom magnetic anisotropy by dynamical Monte Carlo simulations. In isotropic case, clear evidence of a finite-temperature chiral-glass transition is presented. While the spin autocorrelation exhibits only an interrupted aging, the chirality autoc

H. J. Kaufmann, E. G. Maksimov, E. K. H. Salje

Observed optical reflectivity in the infrared spectral region is compared with theoretical predictions in a strongly coupled electron-phonon system. Starting from a Froehlich Hamiltonian, the spectral functions and their temperature dependence are derived. A full analysis including vertex corrections leads to an expression for the optical conductivity σ(ω) w

I. Dan Melamed

Parallel texts (bitexts) have properties that distinguish them from other kinds of parallel data. First, most words translate to only one other word. Second, bitext correspondence is noisy. This article presents methods for biasing statistical translation models to reflect these properties. Analysis of the expected behavior of these biases in the presence of

I. Dan Melamed

Bilingual annotators were paid to link roughly sixteen thousand corresponding words between on-line versions of the Bible in modern French and modern English. These annotations are freely available to the research community from http://www.cis.upenn.edu/~melamed . The annotations can be used for several purposes. First, they can be used as a standard data se

Tatsuo Shibata, Kunihiko Kaneko

An algorithm to characterize collective motion is presented, with the introduction of ``collective Lyapunov exponent&#39;&#39;, as the orbital instability at a macroscopic level. By applying the algorithm to a globally coupled map, existence of low-dimensional collective chaos is confirmed, where the scale of (high-dimensional) microscopic chaos is separated

Ole M. Grimsrud, Ira Wasserman

We consider an ultra-relativistic wind consisting of electron-positron pairs and photons with the principal goal of finding the asymptotic Lorentz factor $γ_{\infty}$ for zero baryon number. The wind is assumed to originate at radius $r_i$ where it has a Lorentz factor $γ_i$ and a temperature $T_i$ sufficiently high to maintain pair equilibrium. As $r$ incre

Alison Sills, Charles D. Bailyn

A primary production mechanism for blue stragglers in globular clusters is thought to be collisionally-induced mergers, perhaps mediated by dynamical encounters involving binary stars. We model the formation and evolution of such blue stragglers, and produce theoretical distributions of them in the colour-magnitude diagram. We use a crude representation of c

Patricia M. Knezek, Joel N. Bregman

The detection of resonance absorption lines against known objects such as individual galaxies and clusters of galaxies is a powerful approach for studying the gas content of these systems. We describe an efficient method of identifying background quasars suitable for absorption line studies. In this finding technique, we identify serendipitous X-ray sources,

Philip J. Armitage

The global development of magnetohydrodynamic turbulence in an accretion disk is studied within a simplified disk model that omits vertical stratification. Starting with a weak vertical seed field, a saturated state is obtained after a few tens of orbits in which the energy in the predominantly toroidal magnetic field is still subthermal. The efficiency of a

Alice K. Harding, Alexander G. Muslimov

We investigate self-consistent particle acceleration near a pulsar polar cap (PC) by the electrostatic field due to the effect of inertial frame dragging. Test particles gain energy from the electric field parallel to the open magnetic field lines and lose energy by both curvature radiation (CR) and resonant and non-resonant inverse Compton scattering (ICS)

R. G. Carlberg, H. K. C. Yee, S. L Morris, H. Lin

The CNOC2 field galaxy redshift survey is designed to provide measurements of the evolution of galaxies and their clustering over the redshift range 0 to 0.7. The sample is spread over four sky patches with a total area of about 1.5 square degrees. Here we report preliminary results based on two of the sky patches, and the redshift range of 0.15 to 0.55. We

S. Ronen, A. Aragon-Salamanca, O. Lahav

We analyse synthetic galaxy spectra from the evolutionary models of Bruzual&Charlot and Fioc&Rocca-Volmerange using the method of Principal Component Analysis (PCA). We explore synthetic spectra with different ages, star formation histories and metalicities, and identify the Principal Components (PCs) of variance in the spectra due to these different model p

Claudia Mendes de Oliveira, Henri Plana, Philippe Amram, Mike Bolte

We report on kinematic observations of Ha emission line from four late-type galaxies of Hickson Compact Group 16 (H16a,b,c and d) obtained with a scanning Fabry-Perot interferometer and samplings of 16 km/s and 1&#34;. The velocity fields show kinematic peculiarities for three of the four galaxies: H16b, c and d. Misalignments between the kinematic and photo

P. G. Niarchos, Luciano Mantegazza, Ennio Poretti, V. Manimanis

New V photoelectric observations of the eclipsing system YY CMi, obtained at La Silla, Chile, and Merate Observatory, Italy, are presented. New times of minima and ephemeris based on our observations are also given. The V light curve was analysed by using the WD code to derive the geometrical and physical parameters of the system. Since no spectroscopic mass

L. Girardi, M. A. T. Groenewegen, A. Weiss, M. Salaris

The I-band brightness of clump stars has been used recently to determine the distance to the bulge, the LMC and SMC, and to M31. It was assumed to be a standard candle based on the observational fact that it is independent of (V-I)-colour in all observed populations. The calibration was done using nearby clump stars with HIPPARCOS-parallaxes. The most surpri

Ralf S. Klessen, Andreas Burkert, Matthew R. Bate

The isothermal gravitational collapse and fragmentation of a region within a molecular cloud and the subsequent formation of a protostellar cluster is investigated numerically. The clump mass spectrum which forms during the fragmentation phase can be well approximated by a power law distribution dN/dM ~ M^(-1.5). In contrast, the mass spectrum of protostella

Henrik P. Nordberg, George F. Smoot

This work presents a detailed analysis of Cosmic Microwave Background (CMB) radiation intensity observations. The CMB is a relic of the Big Bang and its study greatly enhances our knowledge of cosmology. This work has led to new values for the best fit temperature $2.7356 \pm 0.0038$ K (95% CL) and the speed of our solar system relative to the CMB, and limit

Tom Theuns, Anthony Leonard, George Efstathiou, F. R. Pearce

(Abridged) We investigate the importance of several numerical artifacts such as lack of resolution on spectral properties of the Lyman alpha forest as computed from cosmological hydrodynamic simulations in a standard cold dark matter universe. We assume an ionising background produced by quasars as computed by Haardt & Madau. We use a new simulation code bas

Max Tegmark, Daniel J. Eisenstein, Wayne Hu, Richard Kron

We assess the accuracy with which Omega and Lambda can be measured by combining various types of upcoming experiments. Useful expressions for the Fisher information matrix are derived for classical cosmological tests involving luminosity (eg, SN Ia), angular size, age and number counts. These geometric probes are found to be quite complementary both to each

Konstantin T. Matchev, Damien M. Pierce

We present new upper limits on the light Higgs boson mass mh in supersymmetric models. We consider two gravity-mediated models (with and without universal scalar masses) and two gauge-mediated models (with a 5+5 or 10+10 messenger sector). We impose standard phenomenological constraints, as well as SU(5) Yukawa coupling unification. Requiring that the bottom

D. M. Appleby

In a previous paper it was shown that the distribution of measured values for a retrodictively optimal simultaneous measurement of position and momentum is always given by the initial state Husimi function. This result is now generalised to retrodictively optimal simultaneous measurements of an arbitrary pair of rotated quadratures x_theta1 and x_theta2. It

Dafne Guetta

A detailed analysis of the effects of supersymmetric models without R-parity on various CP asymmetries in neutral $B$ decays is given. We concentrate on models with Abelian horizontal symmetries that allow us to estimate the order of magnitude of the new effects. We focus on channels where the Standard Model gives clean predictions: $ B_{d}\toψK_{S} $ and $B

E. Kh. Akhmedov

We present an exact analytic solution to the neutrino evolution equation in matter with periodic step-function density profile and discuss in detail the parametric resonance of neutrino oscillations that can occur in such a system. Solar and atmospheric neutrinos traversing the earth pass through layers of alternating density and can therefore experience par

Y. Hanein, D. Shahar, J. Yoon, C. C. Li

The low-temperature conductivity of low-density, high-mobility, two-dimensional hole systems in GaAs was studied. We explicitly show that the metal-insulator transition, observed in these systems, is characterized by a well-defined critical density, p_0c. We also observe that the low-temperature conductivity of these systems depends linearly on the hole dens

Juan J. G. Ripoll, Victor M. Perez-Garcia

We study the dynamics of a forced condensed atom cloud and relate the behavior to a classical Mathieu oscillator in a singular potential. It is found that there are wide resonances which can strongly affect the dynamics even when dissipation is present. The behavior is characteristic of condensed clouds of any shape and has experimental relevance.

Bernard d&#39;Espagnat

While philosophy of science is the study of problems of knowledge concerning science in general, there also exists - or should exist - a &#39;&#39; philosophy in science&#39;&#39; directed at finding out in what ways our actual scientific knowledge may validly contribute to the basic philosophical quest. Contrary to philosophy of science, which is a subject

Andrew E. Chubykalo

In virtue of the Chubykalo - Smirnov-Rueda generalized form of the Maxwell-Lorentz equation a new form of the energy density of the electromagnetic field was obtained. This result allows us to explain a physical origin of the Oppenheimer-Ahluwalia zero-energy solutions of the Maxwell equations.

Nick Evans

The field theories on the surface of non-supersymmetric D-brane constructions are identified. By moving to M-theory a semi-classical, strong coupling expansion to the IR non-supersymmetric gauge dynamics is obtained. The solution is consistent with the formation of a quark condensate but there is evidence that in moving to strong coupling scalar degrees of f

Robert Carroll

A number of formulas are displayed concerning Whitham theory for a simple example of pure N=2 susy YM with gauge group SU(2). In particular this serves to illuminate the role of Lambda and T derivatives and the interaction with prepotentials F based on Seiberg-Witten and Whitham theory.

Darwin Chang, Ernest Ma

Precision measurements at the $Z$ resonance agree well with the standard model. However, there is still a hint of a discrepancy, not so much in $R_b$ by itself (which has received a great deal of attention in the past several years) but in the forward-backward asymmetry $A^b_{FB}$ together with $R_b$. The two are of course correlated. We explore the possibil

B. G. Zakharov

The recent data of the SLAC E-146 collaboration on the Landau-Pomeranchuk-Migdal effect for bremsstrahlung from 8 and 25 GeV electrons are analyzed within a rigorous light-cone path integral approach. Numerical calculations have been carried out treating rigorously the Coulomb effects and including the inelastic processes. Comparison with the experimental da