August 1997 arXiv papers — page 10

Claudio G. Parazzoli, Benjamin E. C. Koltenbah

Electron bunches with charge densities $ρ$ of the order of $10^2$ to $10^3$ [nC/cm$^3$], energies between $20.$ and $100.$ [MeV], peak current $>100$ [A], bunch lengths between 0.3 and 1.8 [cm], and bunch charge of 2.0 to $20.$ [nC] are relevant to the design of Free Electron Lasers and future linear colliders. In this paper we present the results of numeric

Xiao-jun Li, Hao-wen Xi, J. D. Gunton

We investigate the nature of the parallel-roll to spiral-defect-chaos (SDC) transition in Rayleigh-Benard convection, based on the generalized Swift-Hohenberg model. We carry out extensive, systematic numerical studies by, on one branch, increasing the control parameter gradually from the parallel roll regime to the SDC regime and, on the other branch, decre

P. Olesen

I review the properties of a matrix action of relevance for IIB superstrings. This model generalizes the action proposed by Ishibashi, Kawai, Kitazawa, and Tsuchiya by introducing an auxillary field Y, which is the matrix version of the auxillary field g in the Schild action.

Joachim Kupsch, Oleg G. Smolyanov

The Fock space of bosons and fermions and its underlying superalgebra are represented by algebras of functions on a superspace. We define Gaussian integration on infinite dimensional superspaces, and construct superanalogs of the classical function spaces with a reproducing kernel -- including the Bargmann-Fock representation -- and of the Wiener-Segal repre

M. B. Voloshin

A supersymmetric theory with several scalar superfields generically has several domain wall type classical configurations which interpolate between various supersymmetric vacua of the scalar fields. Depending on the couplings, some of these configurations develop instability and decay into multiple domain walls, others can form intersections in space. These

A. Abbasabadi, D. Bowser-Chao, D. A. Dicus, W. W. Repko

We present cross sections for the reaction $μ\barμ\to Hγ$ over a range of $μ\barμ$ collider energies. The amplitudes for this process receive tree level contributions and one-loop contributions, which are of comparable magnitude. The tree level amplitudes are dominated by helicity non-flip terms and the one-loop amplitudes are dominated by helicity flip term

Adam F. Falk, Michael Luke

We compute the first two moments of the final hadronic invariant mass in inclusive semileptonic B decay, in the presence of a cut on the charged lepton energy. These moments may be measured directly by experiments at the Upsilon(4S) using the neutrino reconstruction technique, which requires such a cut. Measurement of these moments will place constraints on

G. D'Ambrosio, G. Isidori, J. Portoles

A new analysis of the long-distance two-photon dispersive amplitude of K_L -> mu^+ mu^- is presented. We introduce a phenomenological parameterization of the K_L -> gamma^* gamma^* form factor, constrained at low energies by K_L -> gamma l^+ l^- (l = e,mu) data and at high energies by perturbative QCD. Using this form factor we provide a reliable estimate of

Nir Polonsky

The importance of Yukawa contributions to the renormalization of the spectrum in non-minimal supersymmetric models is illustrated in the cases of explicit lepton number violation (leading to the possibility of singly produced sneutrinos at LEP energies), an intermediate scale singlet neutrino and negative mass squared parameters (possibly modifying fine-tuni

D. Yu. Peressounko

It is shown that due to contribution of the hadrons, emitted directly from the inner hot region of central heavy ion collision, radial flow of the final state hadrons is rather sensitive to the creation of quark-gluon plasma with mixed phase.

Frank X. Lee

A complete set of QCD sum rules for the magnetic moments of decuplet baryons are derived using the external field method. They are analyzed thoroughly using a Monte-Carlo based procedure. Valid sum rules are identified under the criteria of OPE convergence and ground state dominance and their predictions are obtained. The performances of these sum rules are

Michael G. Schmidt

We first review why a strongly first-order phase transition needed for baryogenesis is excluded in the electroweak standard model. We also comment on some intriguing effects in the strongly interacting hot phase. In the MSSM with a light stop a strongly first-order phase transition can be achieved. It possibly proceeds in two stages.

G. Weiglein

Recent results for higher-order corrections to the relation between the vector-boson masses in the Standard Model and Supersymmetry are summarized. In the Standard Model, the Higgs-mass dependence of the two-loop contributions to Delta r is studied. Exact results are given for the Higgs-dependent two-loop corrections associated with the fermions, i.e. no exp

P. Olesen

In this talk I discuss the non-linear development of magnetic fields in the early universe. I very briefly mention a number of particle physics mechanisms for generating magnetic fields in the early universe, but the emphasis is on a review of the field theoretic aspects of the developments of these fields, mainly on the occurence of inverse cascades, i.e. g

Yu. S. Kalashnikova, A. V. Nefediev

The canonical description of the straight-line string is given in the einbein field formalism. The system is quantized and Regge spectrum is reproduced. The covariant analogue of the Newton-Wigner coordinate is found, and peculiarities of the gauge fixing in τ-reparametrization group are discussed.

Daniele Dominici

The phenomenology at future hadron colliders of a model with strong interacting vector and axial vector bosons possessing a discrete symmetry demanding mass degeneracy is presented.

H. G. Dosch, A. Laser, M. G. Schmidt

The corelation masses of the 3-dimensional SU(2)-Higgs-model are calculated from the bound state Green's function. For a heavy-light and a light-light system the results are reported. We compare with lattice data and find good agreement.

K. -I. Izawa

We consider dynamical models of supersymmetry breaking which naturally incorporate cosmological inflation. The inflaton plays an inevitable role in dynamical SUSY breaking and the hierarchical scales of inflation and SUSY breaking are simultaneously realized through a single dynamics.

Wei-Shu Hou, Cheng-Ying Ko

The heaviness of the glueball mass scale is suggested as the source of the OZI rule at low energy. The $J/ψ\to ρπ$ decay "anomaly" implies the vector glueball $O$ has mass $m_O \approx m_{J/ψ}$. Such a heavy mass is supported by other glueball studies. Glueball-meson matrix elements turn out to be not suppressed at all at the 1 GeV scale, and a simpl

John Ellis, Douglas Ross

We have calculated the one-loop supersymmetric corrections to the 2 to 2 parton scattering subprocesses antiq q to antiq q, antiq q to g g, g q to g q and g g to g g, including form-factor corrections and box diagrams with internal squarks and gluinos of arbitrary mass. In general, these exhibit cusps at the corresponding direct-channel sparticle thresholds.

R. Loll

We show that the algebra of discretized spatial diffeomorphism constraints in Hamiltonian lattice quantum gravity closes without anomalies in the limit of small lattice spacing. The result holds for arbitrary factor-ordering and for a variety of different discretizations of the continuum constraints, and thus generalizes an earlier calculation by Renteln.

B. L. Hu, K. Shiokawa

Here we study novel effects associated with electromagnetic wave propagation in a Robertson-Walker universe and the Schwarzschild spacetime with a small amount of metric stochasticity. We find that localization of electromagnetic waves occurs in a Robertson-Walker universe with time-independent metric stochasticity, while time-dependent metric stochasticity

Boris Shapiro

We give a criterion when a planar tree-like curve, i.e. a generic immersed plane curve each double point of which cuts it into two disjoint parts, can be send by a diffeomorphism of the plane onto a curve with no inflection points. We also present some upper and lower bounds for the minimal number of inflection points on such curves unremovable by diffeomorp

V. N. Zhuravlev, T. Maniv, I. D. Vagner, P. Wyder

The effect of quasi-particle (QP) 'scattering' by the vortex lattice on the de-Haas van-Alphen oscillations in a pure type-II superconductor is investigated within mean field,asymptotic perturbation theory. Using a 2D electron gas model it is shown that, due to a strict phase coherence in the many-particle correlation functions, the 'scattering&#

Minoru Takahashi

The basics of the thermodynamic Bethe ansatz equation are given. The simplest case is repulsive delta function bosons, the thermodynamic equation contains only one unknown function. We also treat the XXX model with spin 1/2 and the XXZ model and the XYZ model. This method is very useful for the investigation of the low temperature thermodynamics of solvable

A. M. Martin, J. F. Annett

We develop a method to solve the Bogoliubov de Gennes equation for superconductors self-consistently, using the recursion method. The method allows the pairing interaction to be either local or non-local corresponding to s and d-wave superconductivity, respectively. Using this method we examine the properties of various S-N and S-S interfaces. In particular

Pierre Le Doussal, Thierry Giamarchi

We study periodic structures, such as vortex lattices, moving in a random potential. As predicted in [T. Giamarchi, P. Le Doussal Phys. Rev. Lett. 76 3408 (1996)] the periodicity in the direction transverse to motion leads to a new class of driven systems: the Moving Glasses. We analyse using several RG techniques the properties at T=0 and $T>0$: (i) decay o

Jai Sam Kim, J. C. Toledano, P. Toledano

We propose a Monte Carlo algorithm to search for the boundary points of the orbit space which is important in determining the symmetry breaking directions in the Higgs potential and the Landau potential. Our algorithm is robust, efficient and generally applicable. We apply the method to the Landau potential of the $d-$wave abnormal superconductor.

David Clarke, Steven Strong, Paul Chaikin, Ekaterina Chashechkina

In a normal Fermi liquid, Landau's theory precludes the loss of single fermion, quantum coherence in the low energy/temperature limit. For highly anisotropic, strongly correlated metals there is no proof that this remains the case: we propose that quantum coherence for transport in some directions may be lost intrinsically. This should stabilize a novel,

R. Sadat, A. Blanchard, J. Oukbir

Properties of high redshift clusters are a fundamental source of information for cosmology. It has been shown by Oukbir and Blanchard (1997) that the combined knowledge of the redshift distribution of X-ray clusters of galaxies and the luminosity-temperature correlation, $L_X-T_X$, provides a powerful test of the mean density of the Universe. In this paper,

Max Pettini, Charles C. Steidel, Kurt L. Adelberger, . Melinda Kellogg

We review the steps which have led to the discovery of a widespread population of objects at z = 3 with many of the characteristics which we expect for primeval galaxies, and emphasize in particular the advantages of a colour selection technique which targets the Lyman discontinuity at 912 Angstroms. Star forming galaxies at z = 3 resemble local starbursts,

M. J. Way, R. A. Flores, H. Quintana

Using spectrophotometry of a large sample of galaxies in 19 Abell Clusters, we have selected 42 candidate AGN by the criteria used by Dressler et.al. 1985 (DTS) in their analysis of the statistics of 22 AGN in 14 rich cluster fields, which are based on the equivalent width of [OII]3727, Hbeta, and [OIII]5007 emission. We have then discriminated AGN from HII

Jing Wang, Timothy M. Heckman, Matthew D. Lehnert

We have analyzed deep narrow-band H$α$ images and high-resolution long-slit spectra for a sample of the nearest and brightest late-type galaxies to study the morphology, physical state, and kinematics of the `Diffuse Ionized Medium' (`DIM'). We find that the DIM covers most of the star-forming disk, and is morphologically related to the presence of t

T. Belloni, M. Mendez, A. R. King, M. van der Klis

We have analyzed the spectral variations of the superluminal black-hole X-ray binary GRS 1915+105 by using data obtained with the PCA on the Rossi XTE. We find that, despite the marked differences in the structure and the time scale of variability, all spectral changes can be attributed to the rapid disappearing of the inner region of an accretion disk, foll

Karen M. Leighly, Richard F. Mushotzky, Kirpal Nandra, Karl Forster

We report the observation of features near 1 keV in the ASCA spectra from three ``Narrow Line Seyfert 1'' (NLS1) galaxies. We interpret these as oxygen absorption in a highly relativistic outflow. If interpreted as absorption edges, the implied velocities are 0.2--0.3c, near the limit predicted by ``line-locking'' radiative acceleration. If i

S. Mao, A. O. Petters, H. J. Witt

We study the critical curves, caustics, and multiple imaging due to one of the simplest many-body gravitational lens configurations: equal-mass point masses on the vertices of a regular polygon. Some examples of the critical curves and caustics are also displayed. We pose the problem of determining the maximum number of lensed images due to regular-polygon a

Rainer W. Kuhne

Recently, Nodland and Ralston reported to have discovered a cosmic axis. We argue that their axis is supported by an earlier independent observation on the spin axes of galaxies in the Perseus-Pisces supercluster and explainable within the framework of Godel's cosmology.

Eurico Covas, Reza Tavakol

We investigate the detailed dynamics of a truncated $αω$ dynamo model with a dynamic $α$ effect. We find the presence of multiple attractors, including two chaotic attractors with a fractal basin boundary which merge to form a single attractor as the control parameter is increased. By considering phase portraits and the scaling of averaged times of transitio

M. A. Malkov

The efficiency and uniqueness of the diffusive shock acceleration is studied on the basis of the novel kinetic solutions. These solutions obtained earlier (paper I, astro-ph/9707152) selfconsistently describe a strong coupling of cosmic rays with the gas flow. They show that the dependence of the acceleration efficiency upon physical parameters is critical i

M. S. Oey, R. C. Kennicutt,

We estimate the total predicted Lyc emission rates of OB associations for which the complete census of O star spectral types exists. The results are compared to the observed H-alpha luminosities of the host H II regions. We find evidence for substantial leakage of ionizing photons from some H II regions, while others appear to be radiation bounded. We estima

Stefan J. Wagner, Corinna von Montigny, Martin Herter

The largest group of sources identified by EGRET are Blazars. This sub-class of AGN is well known to vary in flux in all energy bands on time-scales ranging from a few minutes (in the optical and X-ray bands) up to decades (radio and optical regimes). In addition to variations of the gamma-ray flux between different viewing periods, the brightest of these so

Jian Ge, Jill Bechtold, Constance Walker, John

We have obtained a moderate resolution spectrum of the quasar PKS 0528-250 with the Red Channel Spectrograph on the Multiple Mirror Telescope (MMT) in order to study a damped Lyman alpha absorption line system at z = 2.8115. We obtain a new upper limit for the CO column density for the z = 2.8108 velocity component in the z = 2.8115 damped Lyman alpha system

Jian Ge, Roger Angel, David Sandler, Chris Shelton

We have done theoretical calculations and simulations for infrared spectroscopy at the MMT 6.5 m with laser guide star AO, which provides almost full sky coverage. The results show we can expect 40-60% of the photons from a unresolved source within 0.2 arcsec diameter circle for J, H, K, L and M bands under typical atmospheric seeing condition at 2.2 micron.

Uffe Hellsten, Lars Hernquist, Neal Katz, David Weinberg

We develop a prescription for characterizing the strengths of metal lines associated with Lyman-alpha forest absorbers (LYFAs) of a given neutral hydrogen column density N_HI and metallicity [Fe/H]. This Line Observability Index (LOX) is line-specific and translates, for weak lines, into a measure of the equivalent width. It can be evaluated quickly for thou

W. Vincent Liu

We study the damping of low-lying collective excitations of condensates in a weakly interacting Bose gas model within the framework of imaginary time path integral. A general expression of the damping rate has been obtained in the low momentum limit for both the very low temperature regime and the higher temperature regime. For the latter, the result is new

E. Boos, H. -J. He, W. Kilian, A. Pukhov

In the absence of light Higgs bosons, the W and Z bosons become strongly interacting particles at energies of about 1 TeV. If the longitudinal W,Z components are generated by Goldstone modes associated with spontaneous symmetry breaking in a new strong interaction theory, the quasi-elastic W,Z scattering amplitudes can be predicted as a systematic chiral exp

Klaus Behrndt, Dieter Lust, Wafic A. Sabra

In this paper we discuss compactifications of type II superstrings where the moduli of the internal Calabi-Yau space vary over four-dimensional space time. The corresponding solutions of four-dimensional N=2 supergravity are given by charged, extremal BPS black hole configurations with non-constant scalar field values. In particular we investigate the behavi

P. Berglund, D. Minic

We study the relation between the effective Lagrangian in Matrix Theory and eleven dimensional supergravity. In particular, we provide a relationship between supergravity operators and the corresponding terms in the post-Newtonian approximation of Matrix Theory.

Jihn E. Kim, Bookyung Sul

In this paper, we construct a supersymmetric composite axion (c-axion) model based on the gauge group $SU(N)\times SU(M)$, which is one possible physical application of the N=1 duality. The dual of SU(M) is interpreted as the color gauge group. We illustrate the existence of c-axion for the case of one dual quark in the dual gauge group $SU(\tilde M)$.

Yuli B. Rudyak

We prove the Arnold conjecture for closed symplectic manifolds with $π_2(M)=0$ and $\cat M=\dim M$. Furthermore, we prove an analog of the Lusternik-Schnirelmann theorem for functions with ``generalized hyperbolicity'' property.

Antonio Riotto

We show that stable local cosmic strings are a generic prediction of supersymmetric models where supersymmetry is broken at scales within a few orders of magnitude of the weak scale and is fed down to the observable sector by gauge interactions. The typical energy scale of these strings is about $10^2$ TeV. Since in the most general and natural scenario ther

M. Leibundgut, P. Minkowski

We show that in supersymmetric pure Yang Mills theories with arbitrary simple gauge group, the spontaneous breaking of chiral fermionic and bosonic charge by the associated gaugino and gauge boson condensates implies the spontaneous breaking of supersymmetry by the condensate of the underlying Lagrangian density. The explicit breaking of the restricted fermi

Alexei Nurmagambetov

We construct a manifestly dual formulation of Dirichlet three-brane in the framework of Pasti-Sorokin-Tonin approach.

You-Quan Li, Pierre-Antoine Bares

An one dimensional model of a Kondo impurity with arbitrary spin in the presence of electronic correlations is solved exactly. The Bethe ansatz equations are obtained for the case of quadratic dispersion. The ground state is studied in the thermodynamic limit, and the magnetic susceptibility at zero temperature is calculated.

Uwe R. Fischer

We demonstrate the way in which vortex rings in neutral superfluids are equivalent to massive, charged, elastic strings in an electromagnetic field defined locally on the string from a Kalb-Ramond gauge field. We argue that the action thus obtained describes an intermediate scale of vortex motion with phonon fluctuations of the line between the incompressibl

Bo Qin, Xiang-Ping Wu, Ming-Chung Chu, Li-Zhi Fang

The energy source has remained to be the great mystery in understanding of the gamma-ray bursts (GRBs) if the events are placed at cosmological distances as indicated by a number of recent observations. The currently popular models include (1)the merger of two neutron stars or a neutron star and a black hole binary and (2)the hypernova scenario of the collap

A. M. Sintes

A brief summary of results on kinematic self-similarities in general relativity is given. Attention is focussed on locally rotationally symmetric models admitting kinematic self-similar vectors. Coordinate expressions for the metric and the kinematic self-similar vector are provided. Einstein's field equations for perfect fluid models are investigated an

M. Kachkachi, M. Nazah

We prove the Polyakov conjecture on the supertorus $(ST_2)$: we dermine an iterative solution at any order of the superconformal Ward identity and we show that this solution is resumed by the Wess-Zumino-Polyakov (WZP) action that describes the $(1,0)$ 2D-supergravity. The resolution of the superBeltrami equation for the Wess-Zumino (WZ) field is done by usi

H. Lu, C. N. Pope, T. R. Tran, K. -W. Xu

We give a full classification of the multi-charge supersymmetric $p$-brane solutions in the massless and massive maximal supergravities in dimensions $D\ge2$ obtained from the toroidal reduction of eleven-dimensional supergravity. We derive simple universal rules for determining the fractions of supersymmetry that they preserve. By reversing the steps of dim

C. S. Kim, T. Morozumi, A. I. Sanda

We propose a new method to extract |Vtd/Vts| from the ratio of the decay distributions dR/ds = dB(B->Xdl+l-)/ds/dB(B->Xsl+l-)/ds. This ratio depends only on the KM ratio |Vtd/Vts| with 15% theoretical uncertainties, if dilepton invariant mass-squared s is away from the peaks of the possible resonance states, J/psi, psiprime, and etc. We also give a detailed

Richard Cleve, Wim van Dam, Michael Nielsen, Alain Tapp

We consider the communication complexity of the binary inner product function in a variation of the two-party scenario where the parties have an a priori supply of particles in an entangled quantum state. We prove linear lower bounds for both exact protocols, as well as for protocols that determine the answer with bounded-error probability. Our proofs employ

E. H. Saidi, M. B. Sedra

The $6 = 3\times 2$ huge Lie algebra $Ξ$ of all local and non local differential operators on a circle is applied to the standard Adler-Kostant-Symes (AKS) R-bracket sckeme. It is shown in particular that there exist three additional Lie structures, associated to three graded modified classical Yang-Baxter(GMCYB) equations. As we know from the standard case,

Alan Kostelecky, Neil Russell

For isotropic confining Ioffe-Pritchard or TOP potentials, a valence fermion trapped with a closed core of other fermions can be described by an analytical effective one-particle model with a physical eigenspectrum. Related constructions exist for Paul and Penning traps. The analytical models arise from quantum-mechanical supersymmetry.

Mehul M. Khimasia, Peter V. Coveney

Protein structure prediction can be shown to be an NP-hard problem; the number of conformations grows exponentially with the number of residues. The native conformations of proteins occupy a very small subset of these, hence an exploratory, robust search algorithm, such as a genetic algorithm (GA), is required. The dynamics of GAs tend to be complicated and

S. Kondratyuk, G. Martinus, O. Scholten

We study the influence of the off-shell structure of the nucleon electromagnetic vertex on proton-proton bremsstrahlung observables. Realistic choices for these off-shell effects are found to have considerable influences on observables such as cross sections and analyzing powers. The rescattering contribution diminishes the effects of off-shell modifications

Manoelito M. de Souza

We introduce a classical field theory based on a concept of extended causality that mimics the causality of a point-particle Classical Mechanics by imposing constraints that are equivalent to a particle initial position and velocity. It results on a description of discrete (pointwise) interactions in terms of localized particle-like fields. We find the propa

Hitoshi Nishino

We present supersymmetric Yang-Mills theories in arbitrary even dimensions with the signature (9+m,1+m) where $m=0,1,2,...$ beyond ten-dimensions up to infinity. This formulation utilizes null-vectors and is a generalization of our previous work in 10+2 dimensions to arbitrary even dimensions with the above signature. We have overcome the previously-observed

A. Gregori, E. Kiritsis, C. Kounnas, N. A. Obers

We compute and analyse a variety of four-derivative gravitational terms in the effective action of six- and four-dimensional type II string ground states with N=4 supersymmetry. In six dimensions, we compute the relevant perturbative corrections for the type II string compactified on K3. In four dimensions we do analogous computations for several models with

M. Shifman

In a wide class of supersymmetric theories degenerate families of the BPS-saturated domain walls exist. The internal structure of these walls can continuously vary, without changing the wall tension. This is described by hidden parameters (collective coordinates). Differentiating with respect to the collective coordinates one gets a set of the bosonic zero m

Dieter Mayer, Alexander Ushveridze, Zbigniew Walczak

In this paper we propose a simple method for building exactly solvable multi-parameter spectral equations which in turn can be used for constructing completely integrable and exactly solvable quantum systems. The method is based on the use of a special functional relation which we call the scalar triangle equation because of its similarity to the classical Y

Dieter Mayer, Alexander Ushveridze

In this paper we formulate a general method for building completely integrable quantum systems. The method is based on the use of the so-called multi-parameter spectral equations, i.e. equations with several spectral parameters. We show that any such equation, after eliminating some spectral parameters by means of the so-called inverse procedure of separatio

A. D. Dolgov, I. B. Khriplovich

The propagation of a massless field in attractive and repulsive potentials is considered. It is shown that though the group velocity in such potentials can be larger than one, the wave front propagates with the speed of light. A larger-than-one group velocity leads only to a strong deformation of the wave packet. The results obtained are applied to the light

O. Philipsen

The mass spectrum of the 3d SU(2) Higgs model for states with quantum numbers $0^{++}$, $2^{++}$ and $1^{--}$ as obtained from lattice simulations is presented in the Higgs and confinement regions, both for a small and a large scalar coupling. In the latter case it is possible to continuously connect the spectra and observe the transition from confining to H

Qiu-Yu Liu

Assuming three flavour neutrino mixing takes place in vacuum, we investigate the possibility that the solar $ν_e$ take part in MSW transitions in the Sun due to $Δm^2_{31} \sim (10^{-7} - 10^{-4})~eV^2$, followed by long wave length vacuum oscillations on the way to the Earth, triggered by $Δm^2_{21}$ (or $Δm^2_{32}$) $\sim (10^{-12} - 10^{-10})~eV^2$. The s

Christian Bauer, Aneesh V. Manohar

The operator mixing matrix for the dimension six operators in the heavy quark effective theory Lagrangian is computed at one loop. The results are shown to be consistent with constraints from the equations of motion, and from reparametrization invariance.

Yuval Grossman, Gino Isidori, Mihir P. Worah

The difference in the time dependent CP asymmetries between the modes $B --> psi K_S$ and $B --> phi K_S$ is a clean signal for physics beyond the Standard Model. This interpretation could fail if there is a large enhancement of the matrix element of the $b --> u ubar s$ operator between the $B_d$ initial state and the $phi K_S$ final state. We argue against

M. Giovannini, M. E. Shaposhnikov

We show that the presence of primordial stochastic (hypercharge) magnetic fields before the electroweak (EW) phase transition induces isocurvature fluctuations (baryon number inhomogeneities). Depending on the details of the magnetic field spectrum and on the particle physics parameters (such as the strength of the EW phase transition and electron Yukawa cou

Robert S. Thorne

Recently the H1 collaboration has published a ``determination'' of the structure function F_L(x,Q^2) at low x. I address the question of how reliable this determination really is. I argue that it is in fact a consistency check of a given theoretical approach rather than a real determination of the value of F_L(x,Q^2), but potentially a very useful on

G. Conforto, A. Marchionni, F. Martelli, F. Vetrano

All existing measurements of the solar neutrino flux are compared with the predictions of the most recent solar model by Bahcall and Pinsonneault, modified by introducing the hypothesis of neutrino oscillations with mass differences large enough to render energy-independent any quantity observable on earth. It is concluded that the data are consistent with t

F. J. Yndurain

We consider bounds on light quark masses that follow from positivity of the pseudoscalar correlator spectral function plus the assumption that perturbative QCD is valid for the correlator and its derivatives up to order $N$ for momenta $t\geq\hat{t}$. We find that the bounds vary a lot depending on the assumed value of $\hat{t}$ and even, if it is too small

A. Donini, M. Guagnelli, P. Hernandez, A. Vladikas

We present results for the Quenched SU(2) N=1 Super-Yang-Mills spectrum at $β=2.6$, on a $V=16^3 \times 32$ lattice, in the OZI approximation. This is a first step towards the understanding of the chiral limit of lattice N=1 SUSY.

Carlos O. Lousto, Richard H. Price

Numerical relativity codes now being developed will evolve initial data representing colliding black holes at a relatively late stage in the collision. The choice of initial data used for code development has been made on the basis of mathematical definitiveness and usefulness for computational implementation. By using the ``particle limit'' (the lim

D. A. Kalinin

The quantization of a single particle without spin in an appropriate curved space-time is considered. The Hamilton formalism on reduced space for a particle in a curved space-time is constructed and the main aspects of quantization scheme are developed. These investigations are applied to quantization of the particle Hamiltonian in an appropriate curved spac

A. M. Sintes, A. A. Coley, J. Carot

Space-times admitting a 3-dimensional Lie group of conformal motions $C_3$ acting on null orbits are studied. Coordinate expressions for the metric and the conformal Killing vectors (CKV) are provided (irrespectively of the matter content) and then all possible perfect fluid solutions are found, although none of these verify the weak and dominant energy cond

Yuli B. Rudyak, John Oprea

We prove that the Lusternik-Schnirelmann category $cat(M)$ of a closed symplectic manifold $(M, ω)$ equals the dimension $dim(M)$ provided that the symplectic cohomology class vanishes on the image of the Hurewicz homomorphism. This holds, in particular, when $π_2(M)=0$. The Arnold conjecture asserts that the number of fixed points of a Hamiltonian symplecto

D. Chang, C. -Y. Mou, B. Rosenstein, C. L. Wu

Small angle neutron diffraction experiments are analyzed using recently developed and properly generalized one-field effective free energy method. In the case of experiment of Keimer et al on YBCO, we show that the fourfold symmetry of the underlying crystal is explicitly broken, but the reflection with respect to the [110] and [1\={1}0] axes remains a symme

Alan Tennant, Stephen Nagler, Ted Barnes, Andrew Garrett

Magnetic excitations in an array of (VO)2P2O7 single crystals have been measured using inelastic neutron scattering. Until now, (VO)2P2O7 has been thought of as a two-leg antiferromagnetic Heisenberg spin ladder with chains running in the a-direction. The present results show unequivocally that (VO)2P2O7 is best described as an alternating spin-chain directe

W. C. Wu, J. P. Carbotte

It is known that for an unconventional superconductor with nodes in the gap, the in-plane microwave or dc conductivity saturates at low temperatures to a universal value independent of the impurity concentration. We demonstrate that a similar feature can be accessed using channel-dependent Raman scattering. It is found that, for a $d_{x^2-y^2}$-wave supercon

Richard P. Sear

If many micelles adsorb onto the same polymer molecule then they are said to form a necklace. A minimal model of such a necklace is proposed and shown to be almost equivalent to a 1-dimensional fluid with nearest-neighbour interactions. The thermodynamic functions of this fluid are obtained and then used to predict the change in the critical micellar concent

J. Hausmann, P. Rujan

We consider the behavior of an Ising ferromagnet obeying the Glauber dynamics under the influence of a fast switching, random external field. Analytic results for the stationary state are presented in mean-field approximation, exhibiting a novel type of first order phase transition related to dynamic freezing. Monte Carlo simulations performed on a quadratic

Boris Neubert, Michel Pleimling, Rolf Siems

Models which allow an explicit application to structurally modulated substances are reviewed within the frame of a symmetry-based approach starting from discrete lattice theory. Focus is set on models formulated in terms of local variables assigned to discrete crystallographic units (unit cells or parts of them). Especially considered are symmetry-based pseu

Marilyn A. Walker

Centering was formulated as a model of the relationship between attentional state, the form of referring expressions, and the coherence of an utterance within a discourse segment (Grosz, Joshi and Weinstein, 1986; Grosz, Joshi and Weinstein, 1995). In this chapter, I argue that the restriction of centering to operating within a discourse segment should be ab

Julyan H. E. Cartwright, Emilio Hernández-García, Oreste Piro

We construct a model of an excitable medium with elastic rather than the usual diffusive coupling. We explore the dynamics of elastic excitable media, which we find to be dominated by low dimensional structures, including global oscillations, period-doubled pacemakers, and propagating fronts. We suggest that examples of elastic excitable media are to be foun

D. Markovic

We study the use of parallax microlensing to separate the effects of the mass function of dark massive halo objects (MHOs or `machos') on the one hand and their spatial distribution and kinematics on the other. This disentanglement is supposed to allow a much better determination of the two than could be achieved entirely on the basis of the durations of

Robert M. Cavallo, Allen V. Sweigart, Roger A. Bell

We follow the static abundance profiles of the C, N, O, Ne, Na, Mg, and Al isotopes around the hydrogen-burning shell (H shell) of globular cluster red-giant-branch (RGB) stellar models in order to study the observed abundance anomolies associated with these elements. We do this by combining four "realistic" stellar evolutionary sequences of differen

David Valls-Gabaud

The detection of microlensing events from stars in the Large Magellanic Cloud and in the Galactic bulge raise important constraints on the distribution of dark matter and on galactic structure, although some events may be due to a new type of intrinsic variability. When lenses are relatively close to the sources, we predict that chromatic and spectroscopic e

J. E. Larkin, L. Armus, R. A. Knop, B. T. Soifer

This paper reports the results of a near infrared spectroscopic survey of LINER galaxies undertaken with a new infrared spectrograph at the 5 m Hale telescope. The galaxy sample includes 11 LINERs with spectra covering the [FeII] (1.2567 microns), PaBeta (1.2818 microns), H2 (1-0 S(1), 2.1218 microns) and BrGamma (2.1655 microns) near infrared emission lines

M. Catelan, J. Borissova, A. V. Sweigart, N. Spassova

The outer-halo globular cluster NGC 6229 has a peculiar horizontal-branch (HB) morphology, with clear indications of a bimodal HB and a ``gap" on the blue HB. In this paper, we present extensive synthetic HB simulations to determine whether peculiar distributions in the underlying physical parameters are needed to explain the observed HB morphology. We f

Eurico Covas, Andrew Tworkowski, Reza Tavakol, Axel Brandenburg

In a recent work (Covas et al. 1997), the behaviour and the robustness of truncated $αΩ$ dynamos with a dynamic $α$ were studied with respect to a number of changes in the driving term of the dynamic $α$ equation, which was considered previously by Schmalz and Stix (1991) to be of the form $\sim A_ϕB_ϕ$. Here we review and extend our previous work and consid

Eurico Covas, Andrew Tworkowski, Axel Brandenburg, Reza Tavakol

We investigate the behaviour of $αΩ$ dynamos with a dynamic $α$, whose evolution is governed by the imbalance between a driving and a damping term. We focus on truncated versions of such dynamo models which are often studied in connection with solar and stellar variability. Given the approximate nature of such models, it is important to study how robust they