October 1999 arXiv papers — page 4

Michael E. Peskin

I describe an new event generator, pandora, which uses the C++ class structure to allow a modular treatment of beams and particle production and decay. (Talk presented at the 1999 International Workshop on Linear Colliders, Sitges, Barcelona, Spain.)

S. Hesselbach, H. Fraas

We study the possibility to measure the masses of the selectrons in neutralino production at an e^+ e^- linear collider with polarized beams. The cross sections and polarization asymmetries of neutralinos with gaugino character strongly depend on the masses of the exchanged selectrons. If the usual GUT relations of the selectron masses in the MSSM are relaxe

J. Kwiecinski, B. Ziaja

We estimate the cross-section and asymmetry relevant for the production of forward jets in polarised deep inelastic scattering in the region of small values of $x$ which can be probed at possible polarised HERA measurements. The kinematical cuts implemented in our analysis are the same as those which were used in the unpolarised deep inelastic scattering at

C. F. Berger, W. Schweiger

We calculate the differential cross section and single-polarization observables for the reaction $γp \to Φp$ within perturbative QCD, treating the proton as a quark-diquark system. The phenomenological couplings of gauge bosons to (spatially extended) diquarks and the quark-diquark distribution amplitude of the proton are adopted from previous investigations

F. Benatti, R. Floreanini

In relation with experiments on correlated kaons at phi-factories, it is shown that the request of complete positivity is necessary in any physically consistent description of neutral kaons as open quantum systems.

A. A. Pankov

The sensitivity to the $Z^\prime$ couplings of the processes $e^+e^-\to l^+l^-,\bar{b}b$ and $\bar{c}c$ at the linear collider with $\sqrt{s}=500 GeV$ with initial beam polarization, for typical extended model examples are studied. To this aim, the suitable integrated, polarized, observables directly related to the helicity cross sections that carry informat

M. Bastero-Gil, G. L. Kane, S. F. King

We discuss fine-tuning constraints on supergravity models. The tightest constraints come from the experimental mass limits on two key particles: the lightest CP even Higgs boson and the gluino. We also include the lightest chargino which is relevant when universal gaugino masses are assumed. For each of these particles we show how fine-tuning increases with

M. Beneke

Exclusive, non-leptonic, two-body decays of B mesons simplify greatly in the heavy quark limit. In this talk I discuss the factorized structure that holds in this limit and some of its consequences: (a) naive factorization is recovered in a certain limit; (b) `non-factorizable' effects are hard and can be calculated; (c) strong interaction phases vanish

K. Huitu, P. N. Pandita, K. Puolamaki

We review the phenomenology of light Higgs scalars in supersymmetric left-right models. We consider models with minimal particle content (with and without non-renormalizable higher-dimensional terms) and with additional Higgs superfields. The upper bound on the lightest CP-even neutral Higgs boson in these models is larger than in the minimal supersymmetric

Nemanja Kaloper, Andrew R. Liddle

On compactification from higher dimensions, a single free massive scalar field gives rise to a set of effective four-dimensional scalar fields, each with a different mass. These can cooperate to drive a period of inflation known as assisted inflation. We analyze the dynamics of the simplest implementation of this idea, paying particular attention to the deco

A. Manashov

The recent progress in solution of the evolution equations of three particle hadron distribution amplitudes is reviewed.

R. N. Mohapatra

Recent developments in our understanding of neutrino masses and their implications for physics beyond the standard model are reviewed.

F. Berruto, E. Coletti, G. Grignani, P. Sodano

We study the strongly coupled 2-flavor lattice Schwinger model and the SU(2)-color QCD_2. The strong coupling limit, even with its inherent nonuniversality, makes accurate predictions of the spectrum of the continuum models and provides an intuitive picture of the gauge theory vacuum. The massive excitations of the gauge model are computable in terms of spin

Roger Forty

A novel concept for the detection of tau neutrinos is presented, potentially suitable for use in a long-baseline neutrino oscillation experiment. It relies on the direct identification of the tau leptons produced in charged-current interactions, by imaging the Cherenkov light that the tau generates in C6F14 liquid. In a simple simulation about half of the ta

S. Ahmed, CLEO Collaboration

We present an update of the search for the lepton family number violating decay tau -> mu gamma using 12.6 million tau+tau- pairs collected with the CLEO detector. No evidence of a signal has been found and the corresponding upper limit is BR(tau -> mu gamma) < 1.1x10^{-6} at 90% CL, significantly smaller than previous experimental limits.

Vasilii Nomokonov

The analyses of recent LEP data provide us with a rich ground for pQCD and LPHD tests. A number of non-trivial effects predicted in the framework of MLLA are experimentally verified. Recent measurements also enrich our knowledge about the hadronization process.

Sergey Serednyakov

The results of the experimental study of the reactions e+e-->ππγ, ηπγ, η&#39;γ, ωπ,... at VEPP-2M collider with CMD-2 and SND detectors are presented. The branching ratios of ϕ, ρ, ωrare decays were measured. The problem of the possible exotic nature of f0(980), a(980) scalar mesons is discussed.

Ulrich H. Gerlach

The canonical evolution and symmetry generators are exhibited for a Klein-Gordon (K-G) system which has been partitioned by an accelerated coordinate frame into a pair of subsystems. This partitioning of the K-G system is conveyed to the canonical generators by the eigenfunction property of the Minkowski Bessel (M-B) modes. In terms of the M-B degrees of fre

Murat Özer

If gravitation and electromagnetism are both described in terms of a symmetric metric tensor, then the deflection of an electron beam by a charged sphere should be different from its deflection according to the Reissner-Nordström solution of General Relativity. If such a unified description is true, the equivalence principle for the electric field implies th

Manvir S. Kushwaha

A theoretical investigation is made of the dispersion characteristics of plasmons in a two-dimensional periodic system of semiconductor (dielectric) cylinders embedded in a dielectric (semiconductor) background. We consider both square and hexagonal arrangements and calculate extensive band structures for plasmons using a plane-wave method within the framewo

A. V. Moroz, C. H. W. Barnes

We discuss the effect of the spin-orbit interaction on the band structure, wave functions and low temperature conductance of long quasi-one-dimensional electron systems patterned in two-dimensional electron gases (2DEG). Our model for these systems consists of a linear (Rashba) potential confinement in the direction perpendicular to the 2DEG and a parabolic

J. P. de Lima, L. L. Goncalves

The XY model (s=1/2) on the one-dimensional alternating superlattice (closed chain) is solved exactly by using a generalized Jordan-Wigner transformation and the Green function method. Closed expressions are obtained for the excitation spectrum, the internal energy, the specific heat, the average magnetization per site, the static transverse susceptibility a

G. Fagas, Vladimir I. Fal&#39;ko, C. J. Lambert, Yuval Gefen

Spectral correlations in the optical phonon spectrum of a solid with a complex unit cell are analysed using the Wigner-Dyson statistical approach. Despite the fact that all force constants are real, we find that the statistics are predominantly of the GUE type depending on the location within the Brillouin zone of a crystal and the unit cell symmetry. Analyt

F. Mancini, D. Villani

A new theoretical analysis of the current-charge and charge-charge propagators is presented for the Hubbard model, using the static approximation for the Composite Operator Method. This approximation manifestly preserves a sum rule which governs the single-site dynamics. We compare our results with those obtained by numerical analysis.

A. Politi, S. Ruffo, L. Tessieri

We have investigated numerically the quantum evolution of a wave-packet in a quenched disordered medium described by a tight-binding Hamiltonian with long-range hopping (band random matrix approach). We have obtained clean data for the scaling properties in time and in the bandwidth b of the packet width and its fluctuations with respect to disorder realizat

B. Lake, D. A. Tennant, S. E. Nagler

Inelastic neutron scattering measurements are reported that show a new longitudinal mode in the antiferromagnetically ordered phase of the spin-1/2 quasi-one-dimensional antiferromagnet KCuF3. This mode signals the cross-over from one-dimensional to three-dimensional behavior and indicates a reduction in the ordered spin moment of a spin-1/2 antiferromagnet.

J. A. Plascak, W. Figueiredo, B. C. S. Grandi

Some renormalization group approaches have been proposed during the last few years which are close in spirit to the Nightingale phenomenological procedure. In essence, by exploiting the finite size scaling hypothesis, the approximate critical behavior of the model on infinite lattice is obtained through the exact computation of some thermal quantities of the

M. Muller, J. P. Wittmer, M. E. Cates

The interplay of topological constraints and persistence length of ring polymers in their own melt is investigated by means of dynamical Monte Carlo simulations of a three dimensional lattice model. We ask if the results are consistent with an asymptotically regime where the rings behave like (compact) {\em lattice animals} in a self-consistent network of to

R. Pentcheva, M. Scheffler

We report results of density-functional theory calculations on the structural, magnetic, and electronic properties of (1x1)-structures of Co on Cu(001) for coverages up to two monolayers. In particular we discuss the tendency towards phase separation in Co islands and the possibility of segregation of Cu on top of the Co-film. A sandwich structure consisting

M. A. Garcia-Bach

For w-legged antiferromagnetic spin-1/2 Heisenberg ladders, a long-range spin-pairing order can be identified which enables the separation of the space spanned by finite-range (covalent) valence-bond configurations into w+1 subspaces. Since every subspace has an equivalent counter subspace connected by translational symmetry, twofold degeneracy, breaking tra

Klaus Krebs

The possibility of a matrix product representation for eigenstates with energy and momentum zero of a general m-state quantum spin Hamiltonian with nearest neighbour interaction and periodic boundary condition is considered. The quadratic algebra used for this representation is generated by 2m operators which fulfil m^2 quadratic relations and is endowed wit

Dorothea K. Stillinger, Frank H. Stillinger, Salvatore Torquato, Thomas M. Truskett

The triangle distribution function f^(3) for three mutual nearest neighbors in the plane describes basic aspects of short-range order and statistical thermodynamics in two-dimensional many-particle systems. This paper examines prospects for constructing a self-consistent calculation for the rigid-disk system f^(3). We present several identities obeyed by f^(

I. L. Drichko, A. M. Diakonov, A. M. Kreshchuk, T. A. Polyanskaya

The absorption coefficient for surface acoustic waves in a piezoelectric insulator in contact with a GaAs/AlGaAs heterostructure (with two-dimensional electron mobility $μ= 1.3\times 10^5 cm^2/V\cdot s)$ at T=4.2K) via a small gap has been investigated experimentally as a function of the frequency of the wave, the width of the vacuum gap, the magnetic field,

A. Mourachkine

Since the introduction of a MCS (Magnetic Coupling between Stripes) phenomenological model [cond-mat/9902355, to be published in J. Superconductivity] for hole-doped cuprates many new experimental data have been presented in the literature as evidence in support of the MCS model. We consider here recent data and the MCS model which is based upon experimental

Fan Zhong, Z. D. Wang

The order parameters of the magnetic, charge and structural orders at half-doped manganites are identified. A corresponding Landau theory of the phase transitions is formulated. Many structural and thermodynamical behaviors are accounted for and clarified within the framework. In particular, the theory provides a unified picture for the scenario of the phase

Fan Zhong, Z. D. Wang

We analyze the symmetry changes of the paramagnetic to the A-type antiferromagnetic and to the ferromagnetic phase transitions in undoped and moderately doped LaMnO$_3$, respectively. We show that in the orthorhombic-distorted perovskite manganites the phase separation at low doping is associated with the noncollinear nature of the magnetic orders permitted

Fan Zhong, Jinming Dong, Z. D. Wang

We propose that a specific spatial configuration of lattice sites that energetically favor {\it 3+} or {\it 4+} Mn ions in moderately doped manganites constitutes approximately a spatially random two-energy-level system. Such an effect results in a mechanism of metal-insulator transitions that appears to be different from both the Anderson transition and the

Jurgen Horbach, Walter Kob, Kurt Binder

We present the results of extensive molecular dynamics computer simulations in which the high frequency dynamics of silica, nu>0.5 THz, is investigated in the viscous liquid state as well as in the glass state. We characterize the properties of high frequency sound modes by analyzing J_l(q,nu) and J_t(q,nu), the longitudinal and transverse current correlatio

Xiao-hui Wang, Tobias Junno, Sven-Bertil Carlsson, Claes Thelander

We investigate the transport properties of a new class of ratchets. The device is constructed by applying an ac voltage to the metallic single electron tunneling transistor, and a net transport current is induced by the time-dependent bias-voltage, although the voltage value is on the average zero. The mechanism underlying this phenomenon is the Coulomb bloc

Jaegwan Chung, Junghwan Park, J. G. Park, Byung-Hee Choi

We studied the electronic structure of rare-earth ditelluride (ReTe_2 : Re = La, Pr, Sm, and Gd) using photoemission spectroscopy. From the x-ray photoelectron spectroscopy (XPS) study of the 3d core levels of rare-earth elements, we found that all the rare earth elements are trivalent. We have also made theoretical calculations using the Gunnarsson and Scho

Jens Schneider, Axel Schenzle

Atom lasers based on rf-outcoupling from a trapped Bose-Einstein condensate can be described by a set of generalized, coupled Gross-Pitaevskii equations (GPE). If not only one but two radio frequencies are used for outcoupling, the atoms emerging from the trap have two different energies and the total wavefunction of the untrapped spin-state is a coherent su

H. T. C. Stoof

In this course we give a selfcontained introduction to the quantum field theory for trapped atomic gases, using functional methods throughout. We consider both equilibrium and nonequilibrium phenomena. In the equilibrium case, we first derive the appropriate Hartree-Fock theory for the properties of the gas in the normal phase. We then turn our attention to

S. Prestipino, E. A. Jagla, E. Tosatti

We discuss the possibility that, besides roughening, a vicinal surface could display preroughening (PR), and consider the possible mechanisms for its promotion. Within the framework of a terrace-step-kink model, it turns out that a PR transition is possible, and could be induced by a short-range repulsion between parallel kinks along the same step or on adja

N. M. Bogoliubov, R. K. Bullough, V. S. Kapitonov, C. Malyshev

Previous functional integral methods for translationally invariant systems have been extended to the case of a confining trap potential. Essentially all finite-temperature properties of the repulsive Bose gas in a paraboloidal trap can be determined this way. New analytical results reported here are for the finite-temperature two-point correlation functions

P. Chaddah, S. B. Roy

Hysteresis in cycling through first-order phase transitions in vortex matter, akin to the well-studied phenomenon of supercooling of water, has been discussed in literature. Hysteresis can be seen while varying either temperature T or magnetic field H (and thus the density of vortices). Our recent work on phase transitions with two control variables shows th

P. E. Kornilovitch

A path-integral representation is constructed for the Jahn-Teller polaron (JTP). It leads to a perturbation series that can be summed exactly by the diagrammatic Quantum Monte Carlo technique. The ground-state energy, effective mass, spectrum and density of states of the three-dimensional JTP are calculated with no systematic errors. The band structure of JT

R. Klages, Chr. Dellago

We study the deterministic diffusion coefficient of the two-dimensional periodic Lorentz gas as a function of the density of scatterers. Results obtained from computer simulations are compared to the analytical approximation of Machta and Zwanzig [Phys.Rev.Lett. 50, 1959 (1983)] showing that their argument is only correct in the limit of high densities. We d

Laura Ferrarese, Holland C. Ford, John Huchra, Robert C. Kennicutt,

We present a compilation of Cepheid distance moduli and data for four secondary distance indicators that employ stars in the old stellar populations: the planetary nebula luminosity function (PNLF), the globular cluster luminosity function (GCLF), the tip of the red giant branch (TRGB), and the surface brightness fluctuation (SBF) method. The database includ

Cesar A. Caretta, Marcio A. G. Maia, Christopher N. A. Willmer

We have carried out an independent quantitative evaluation of the galaxy component of the &#34;COSMOS/UKST Southern Sky Object Catalogue&#34; (SSC) and the &#34;APM/UKST J Catalogue&#34; (APM). Using CCD observations our results corroborate the accuracy of the photometry of both catalogs, which have an overall dispersion of about 0.2 mag in the range 17 <= b

Wesley N. Colley, Rudolph E. Schild

We have continued our effort to re-reduce archival Q0957+561 brightness monitoring data and present results for 1629 R-band images using the methods for galaxy subtraction and seeing correction reported previously. The new dataset comes from 4 observing runs, several nights apiece, with sampling of typically 5 minutes, which allows the first measurement of t

W. J. Maciel

The O/H metallicity distribution of different samples of planetary nebulae in the bulge of the Milky Way and M31 are compared. O/H abundances are converted into [Fe/H] metallicity by the use of theoretical [O/Fe] x [Fe/H] relationships both for the bulge and the solar neighbourhood. It is found that these relationships imply an offset of [Fe/H] abundances by

M. Sean O&#39;Brien

One of the least understood aspects of white dwarf evolution is the process by which they are formed. We are aided, however, by the fact that many H- and He-deficient pre-white dwarfs (PWDs) are multiperiodic g-mode pulsators. Pulsations in PWDs provide a unique opportunity to probe their interiors, which are otherwise inaccesible to direct observation. Unti

D. Konenkov, U. Geppert

We consider the expulsion of the magnetic field from the super-conducting core of a neutron star and its subsequent decay in the crust. Particular attention is paid to a strong feedback of the distortion of magnetic field lines in the crust on the expulsion of the flux from the core. This causes a considerable delay of the core flux expulsion if the initial

M. Ostrowski

We consider effects on an (ultra-) relativistic jet and its ambient medium caused by high energy cosmic rays accelerated at the jet side boundary. As illustrated by simple models, during the acceleration process a flat cosmic ray distribution can be created, with gyroradia for highest particles&#39; energies reaching the scales comparable to the jet radius o

M. Jahan-Miri

Models for the evolution of magnetic fields of neutron stars are constructed, assuming the field is embedded in the proton superconducting core of the star. The rate of expulsion of the magnetic flux out of the core, or equivalently the velocity of outward motion of flux-carrying proton-vortices is determined from a solution of the Magnus equation of motion

R. Della Ceca, R. Scaramella, I. M. Gioia, P. Rosati

We present X-ray observations of two high redshift clusters of galaxies carried out with the BeppoSAX satellite. One cluster, RXJ0152.7-1357 at z = 0.83, was selected from the ROSAT Deep Cluster Survey sample, as one of the most X-ray luminous systems known at z>0.5. The optical and ROSAT-PSPC data show a complex morphology with at least two cores. Our SAX o

H. Hoekstra, M. Franx, K. Kuijken

We have measured the weak gravitational lensing signal of MS 1054-03, a rich and X-ray luminous cluster of galaxies at a redshift of z=0.83, using a two-colour mosaic of deep WFPC2 images. The small corrections for the size of the PSF and the high number density of background galaxies obtained in these observations result in an accurate and well calibrated m

Kulinder Pal Singh, Laurence R. Jones

Two optical candidates - a galaxy and a star, are found within the error circle of the X-ray source position of an ultra-soft X-ray source discovered with ROSAT. Optical spectroscopy of the two candidates reveals that a) the galaxy is a narrow-line Seyfert type 1 galaxy, and b) the star is a late A-type or an early F-type. The Fx/Fopt ratio is too high for t

S. F. Sanchez, J. I. Gonzalez-Serrano

We have conducted an optical study of the environments of seven radio-loud quasars at redshifts 1<z<1.6. In this paper we describe deep B and R band images obtained for fields of $\sim6\times$6 arcmin around these quasars with 3$σ$ limiting magnitudes of $B\sim26$ and $R\sim25.4$. We found an statistically significant excess of {\it faint} (B>22.5 and R>22.0

A. Malizia, L. Bassani, A. J. Dean, M. McCollough

BATSE/OSSE observations of the high redshift quasar 4C 71.07 indicate that this is the brightest and furthest AGN so far detected above 20 keV. BATSE Earth occultation data have been used to search for emission from 4C 71.07 from nearly 3 years of observation. The mean source flux over the whole period in the BATSE energy range 20-100 keV is (13.2 +/- 1.06)

Winfried Zimdahl

Combining the equivalence between cosmological particle creation and an effective viscous fluid pressure with the fact that the latter represents a dynamical degree of freedom within the second-order Israel-Stewart theory for imperfect fluids, we reconsider the possibility of accelerated expansion in fluid cosmology. We find an inherent self-limitation for t

Uros Seljak, Daniel E. Holz

Due to the effects of gravitational lensing, the magnification distribution of high redshift supenovae can be a powerful discriminator between smooth dark matter and dark matter consisting of compact objects. We use high resolution N-body simulations in combination with the results of simulations with compact objects to determine the magnification distributi

Myung Gyoon Lee, Sang Chul Kim

We present deep BVRI CCD photometry of the stars in the dwarf irregular galaxy SagDIG. The color-magnitude diagrams of the measured stars in SagDIG show a blue plume which consists mostly of young stellar populations, and a well-defined red giant branch (RGB). The foreground reddening of SagDIG is estimated to be E(B-V)=0.06. The tip of the RGB is found to b

John L. Tonry, Christopher S. Kochanek

The redshifts of the gravitational lens galaxies in MG1131+0456 and B1938+666 are 0.844 and 0.881 respectively. Both are early-type galaxies lying at the redshifts predicted by assuming that they are early-type galaxies with old stellar populations lying on the fundamental plane. We also find evidence for a foreground group of galaxies at z=0.343 near MG1131

Eanna E. Flanagan, S. -H. Henry Tye, Ira Wasserman

The cosmology of the Randall-Sundrum scenario for a positive tension brane in a 5-D Universe with localized gravity has been studied previously. In the radiation-dominated Universe, it was suggested that there are two solutions for the cosmic scale factor a(t) : the standard solution $a\sim t^{1/2}$, and a solution $a\sim t^{1/4}$, which is incompatible with

Kaustubh Agashe

We investigate whether multi-TeV (1-3 TeV) squarks can be natural in models of gauge mediated SUSY breaking. The idea is that for some boundary condition of the scalar (Higgs and stop) masses, the Higgs (mass)$^2$, evaluated at the renormalization scale $\sim O(100)$ GeV, is not very sensitive to (boundary values of) the scalar masses (this has been called `

David W. Hogg, Gerry Neugebauer, Judith G. Cohen, Mark Dickinson

Images of the Hubble Deep Field at 3.2 um, taken with the 10-m Keck Telescope, are presented. The images cover a total area of ~2.5 arcmin^2. To a 5-sigma limit of [3.2](total)=17.5 mag (Vega-relative), 11 sources are detected, 9 of which are extragalactic. The integrated galaxy number counts are therefore ~1.3x10^4 deg^{-2} to this depth. The galaxies detec

Boris Podobnik, Plamen Ch. Ivanov, Youngki Lee, Alessandro Chessa

We study how the presence of correlations in physical variables contributes to the form of probability distributions. We investigate a process with correlations in the variance generated by (i) a Gaussian or (ii) a truncated Lévy distribution. For both (i) and (ii), we find that due to the correlations in the variance, the process ``dynamically&#39;&#39; gen

Nadav Drukker

In the framework of Matrix theory we show that Wilson loops can serve as interpolating fields to define string scattering amplitudes as gauge theory observables.

J. Mesot, M. Randeria, M. R. Norman, A. Kaminski

We study the normal state electronic excitations probed by angle resolved photoemission spectroscopy (ARPES) in Bi2201 and Bi2212. Our main goal is to establish explicit criteria for determining the Fermi surface from ARPES data on strongly interacting systems where sharply defined quasiparticles do not exist and the dispersion is very weak in parts of the B

Scott A. Hughes

A major focus of much current research in gravitation theory is on understanding how radiation reaction drives the evolution of a binary system, particularly in the extreme mass ratio limit. Such research is of direct relevance to gravitational-wave sources for space-based detectors (such as LISA). We present here a study of the radiative evolution of circul

J. S. Sa&#39; Martins

The bit-string Penna Model is used to simulate the competition between an asexual parthenogenetic and a sexual population sharing the same environment. A new-born of either population can mutate and become a part of the other with some probability. In a stable environment the sexual population soon dies out. When an infestation by fastly mutating genetically

Nathan F. Lepora

We calculate the gauge couplings in the dual standard model. These values are consistent with an associated GeV mass scale, and predict the weak mixing angle to be ${\sin^2 θ_w} (M_Z) \sim 0.22$.

Takeo Hoshi, Takeo Fujiwara

From the order-N electronic-structure formulation, a Hamiltonian is derived, of which lowest eigen state is the generalized or composite-band Wannier state. This Hamiltonian maps the locality of the Wannier state to that of a virtual impurity state and to a perturbation from a bonding orbital. These theories are demonstrated in the diamond-structure solids,

Alberto S. Cattaneo, Paolo Cotta-Ramusino, Riccardo Longoni

The real cohomology of the space of imbeddings of S^1 into R^n, n>3, is studied by using configuration space integrals. Nontrivial classes are explicitly constructed. As a by-product, we prove the nontriviality of certain cycles of imbeddings obtained by blowing up transversal double points in immersions. These cohomology classes generalize in a nontrivial w

Michael P. Tuite

We construct the genus two (or two loop) partition function for meromorphic bosonic conformal field theories. We use a sewing procedure involving two genus one tori by exploiting an explicit relationship between the genus two period matrix and pinching modular parameters. We obtain expressions for the partition function for the chiral bosonic string, even ra

K. Baerwinkel, H. -J. Schmidt, J. Schnack

Exact ground state properties of antiferromagnetic Heisenberg spin rings with isotropic next neighbour interaction are presented for various numbers of spin sites and spin quantum numbers. Earlier work by Peierls, Marshall, Lieb, Schultz and Mattis focused on bipartite lattices and is not applicable to rings with an odd number of spins. With the help of exac

C. D. Dermer, M. Boettcher, J. Chiang

Sari, Piran, and Narayan have derived analytic formulas to model the spectra from gamma-ray burst blast waves that are energized by sweeping up material from the surrounding medium. We extend these expressions to apply to general radiative regimes and to include the effects of synchrotron self-absorption. Electron energy losses due to the synchrotron self-Co

S. Fratini, P. Quemerais

The melting of a Wigner Crystal of electrons placed into a host polar material is examined as a function of the density and the temperature. When the coupling to the longitudinal optical modes of the host medium is turned on, the WC is progressively transformed into a polaronic Wigner Crystal. We estimate the critical density for crystal melting at zero temp

Andrzej Czarnecki, Kirill Melnikov, Alexander Yelkhovsky

We present details of our recent calculation of alpha^2 corrections to the parapositronium decay into two photons. These corrections are rather small and our final result for the parapositronium lifetime agrees well with the most recent measurement. Implications for orthopositronium decays are briefly discussed.

Jozef Sima, Miroslav Sukenik, Magdalena Sukenikova

A profound relationship between the ENU (Expansive Nondecelerative Universe) and dimensionless constants of the fundamental physical interactions is presented. The contribution corrects the Dirac presumption on a time decrease of the gravitational constant G and using simple relations it precises the values of the vector bosons x and y.

Kensuke Imanishi, Jun Yokogawa, Masahiro Tsujimoto, Katsuji Koyama

ASCA observed the central region of the Small Magellanic Cloud, and found a hard X-ray source, AX J0051-733, at the position of the ROSAT source RX J0050.8-7316, which has an optical counterpart of a Be star. Coherent X-ray pulsations of 323.1 +/- 0.3 s were discovered from AX J0051-733. The pulse profile shows several sub-peaks in the soft (0.7-2.0 keV) X-r

P. Chiappetta, A. Deandrea, E. Nagy, S. Negroni

We investigate the potential of the LHC to probe the R parity violating couplings involving the third generation by considering single top production. This study is based on particle level event generation for both signal and background, interfaced to a simplified simulation of the ATLAS detector.

Makoto Sakamoto, Hiroyuki Yamashita

We give a very simple proof that the renormalization of the Chern-Simons coupling in the Wilsonian effective action is exhausted at one-loop. Our proof can apply to arbitrary 2+1-dimensional abelian as well as nonabelian gauge theories without a bare Chern-Simons coupling, including any non-renormalizable interactions and non-minimal couplings. Our proof rev

Jeong-Hyuck Park

Three-dimensional N-extended superconformal symmetry is studied within the superspace formalism. A superconformal Killing equation is derived and its solutions are classified in terms of supertranslations, dilations, Lorentz transformations, R-symmetry transformations and special superconformal transformations. Superconformal group is then identified with a

P. Kuusk, M. Saal

The Hamilton-Jacobi equation for the string cosmology is solved using the gradient expansion method. The zeroth order solution is taken to be the standard pre-big bang model and the second order solution is found for the dilaton and the three-metric. It indicates that corrections generated by inhomogeneities of the seed metric are suppressed near the singula

A. Muecke, R. J. Protheroe

The April 1997 giant flare of Mkn 501 is modelled by a stationary Synchrotron-Proton-Blazar model. Our derived model parameters are consistent with X-ray-to-TeV-data in the flare state and diffusive shock acceleration of electron and proton in a Kolmogorov/Kraichnan turbulence sprectrum. While the emerging pair-synchrotron cascade spectra initiated by photon

Bhuvnesh Jain, Ludovic Van Waerbeke

We present a new approach to measure the mass function of dark matter halos and to discriminate models with differing values of Omega through weak gravitational lensing. We measure the distribution of peaks from simulated lensing surveys and show that the lensing signal due to dark matter halos can be detected for a wide range of peak heights. Even when the

Shufang Su

In the minimal anomaly-mediated supersymmetry breaking (AMSB) model, a universal contribution $m_{0}$ to all the scalar masses is introduced in order to avoid the negative slepton mass problem. The Higgs spectrum and couplings are determined by four parameters: $m_{\rm aux}, m_{0}, \tanβ$ and sign ($μ$). The sign of $μ$ affects $m_A$ at large $\tanβ$ and $m_

P. Facchi, S. Pascazio

Van Hove's "\lambda^2 t" limiting procedure is analyzed in some interesting quantum field theoretical cases, both in nonrelativistic and relativistic models. We look at the deviations from a purely exponential behavior in a decay process and discuss the subtle issues of state preparation and initial time.

Per K Rekdal, Bo-Sture K Skagerstam

We investigate, in an exact manner, the phase structure of the micromaser system in terms of the physical parameters at hand like the atom cavity transit time, the atom-photon frequency detuning, the number of thermal photons and the probability for a pump atom to be in its excited state. Phase diagrams are mapped out for various values of the physical param

I. Ya. Aref&#39;eva, I. V. Volovich

An exact general formula for the matrix elements of the evolution operator in quantum theory is established. The formul (&#34;ABC-formula&#34;) has the form <U(t)>=exp(At+B+C(t)). The constants A and B and the decreasing function C(t) are computed in perturbation theory. The ABC-formula is valid for a general class of Hamiltonians used in statistical physics

Chi-Keung Chow

Crater has shown that, for two particles (with masses $m_1$ and $m_2$) in a Coulombic bound state, the charge distribution is equal to the sum of the two charge distributions obtained by taking $m_1\to\infty$ and $m_2\to\infty$ respectively, while keeping the same Coulombic potential. We provide a simple scaling criterion to determine whether an arbitrary Ha

Alexander K. Guts

We constructed a model of five-dimensional Lorentz manifold with foliation of codimension 1 the leaves of which are four-dimensional space-times. The Past of these space-times can interact in macroscopic scale by means of large quantum fluctuations. Hence, it is possible that our Human History consists of &#34;somebody else&#39;s&#34; (alien) events.

Neil Broderick, Graeme Ross, Herman Offerhaus, David Richardson

We report on the fabrication of what we believe is the first example of a two dimensional nonlinear periodic crystal\cite{berger}, where the refractive index is constant but in which the 2nd order nonlinear susceptibility is spatially periodic. Such a crystal allows for efficient quasi-phase matched 2nd harmonic generation using multiple reciprocal lattice v

Saibal Mitra

In this thesis we use renormalization group methods to study the critical behaviour of the staggered F-model. This model is a six vertex model that can be used to calculate the thermodynamic properties of a facet of a BCC crystal in the (100) direction.

Q. B. Li, P. N. Shen

In the framework of RGM, the binding energy of one channel $ΔΔ_{(3,0)}$($d^*$) and $ΔΔ_{(0,3)}$ are studied in the chiral SU(3) quark cluster model. It is shown that the binding energies of the systems are a few tens of MeV. The behavior of the chiral field is also investigated by comparing the results with those in the SU(2) and the extended SU(2) chiral qu

D. Faralli, C. Ciofi degli Atti, G. West

The recent TJLAB experimental data on inclusive electron scattering at high momentum transfer from complex nuclei are analyzed in terms of y-scaling, taking into account the final state interaction (FSI) of the struck, off-shell nucleon. It is shown that at large negative values of y (x>1), the Q^2 dependence of the FSI is mostly driven by the elastic nucleo

E. Epelbaum, W. Glöckle, Ulf-G. Meißner

We employ the chiral nucleon-nucleon potential derived in ref.[1] to study bound and scattering states in the two-nucleon system. At next-to-leading order, this potential is the sum of renormalized one-pion and two-pion exchange and contact interactions. At next-to-next-to-leading order, we have additional chiral two-pion exchange with low-energy constants d

Bila Nicoleta

One considers a special class of PDEs systems and one determines the associated symmetry group. Particulary, for the Blair system, one finds the symmetry group. A solutions of the Blair system gives a conformally flat contact metric structure and also it defines a &#34;force-free&#34; model of solar physics. By using the symmetry groups theory, one shows tha