May 1998 arXiv papers — page 9

A. Zheludev, S. Maslov, I. Zaliznyak, L. P. Regnault

New neutron diffraction and inelastic neutron scattering experiments on Ba2CuGe2O7 suggest that the previously suggested model for the magnetism of this material (an ideal sinusoidal spin spiral, stabilized by isotropic exchange and Dzyaloshinskii-Moriya interactions) needs to be refined. Both new and previously published experimental results can be quantita

Sadhan K. Adhikari, T. Frederico

It is shown that the appearance of a fixed-point singularity in the kernel of the two-electron Cooper problem is responsible for the formation of the Cooper pair for an arbitrarily weak attractive interaction between two electrons. This singularity is absent in the problem of three and few superconducting electrons at zero temperature on the full Fermi sea.

Angsula Ghosh, Sadhan K. Adhikari

We establish universal behavior in temperature dependencies of some observables in $(s+id)$-wave BCS superconductivity in the presence of a weak $s$ wave. There also could appear a second second-order phase transition. As temperature is lowered past the usual critical temperature $T_c$, a less ordered superconducting phase is created in $d$ wave, which chang

M. Stoytchev, A. Z. Genack

We report measurements of intensity distributions of transmitted microwave radiation in quasi-1D samples with lengths L as large as the localization length $ξ$. In contrast to negative exponential statistics found in the diffusive limit, the distribution falls as a stretched exponential of power 1/2 and becomes nearly log-normal as L approaches $ξ$. We confi

P. Bouwknegt, K. Schoutens

We analyze critical and massive SO(5) superspin regimes for correlated electrons on a two-chain ladder. We identify fundamental low energy excitations, which carry the quantum numbers of a free electron, and can be probed in (inverse) photo-emission experiments. These excitations do not obey the usual Pauli Principle, but are governed by specific forms of so

P. Raychaudhuri, P. Taneja, S. Sarkar, A. K. Nigam

It has been observed that the low temperature magnetoresistance behaviour in polycrystalline colossal magnetoresistive (CMR) manganites differ significantly from the single crystals. The polycrystalline samples show large magnetoresistance at temperatures much below the ferromagnetic transition temperature where the magnetoresistance of single crystals is ve

M. Stoytchev, A. Z. Genack

Measurements have been made of the probability distribution of total transmission of microwave radiation in waveguides filled with randomly positioned scatterers which would have values of the dimensionless conductance g near unity. The distributions are markedly non-Gaussian and have exponential tails. The measured distributions are accurately described by

H. K. Janssen

The influence of long-range interactions decaying in d dimensions as 1/R^{d+σ} on the critical behavior of systems with Fisher&#39;s correlation-function exponent for short-range interactions η_{SR}<0, is re-examined. Such systems, typically described by Φ^{3}-field theories, are e.g. the Potts-model in the percolation-limit, the Edwards-Anderson spin-glass,

Andreas Erb, Alfred A. Manuel, Marc Dhalle, Frank Marti

We report on three different and complementary measurements, namely magnetisation measurements, positron annihilation spectroscopy and NMR measurements, which give evidence that the formation of oxygen vacancy clusters is on the origin of the fishtail anomaly in YBa2Cu3O7-d. While in the case of YBa2Cu3O7.0 the anomaly is intrinsically absent, it can be supp

A. Rebei, W. N. G. Hitchon

At finite temperature, a Fermi gas can have sates that hold simultaneously a particle and a hole with a finite probability. This gives rise to a new set of diagrams that are absent at zero temperature. The so called &#34;anomalous&#34; diagram is just one of the new diagrams. We have already studied the contribution of these new diagrams to the thermodynamic

A. B. Sushkov, E. A. Tishchenko

Development of an ellipsometry to the case of a coherent far infrared irradiation, low temperatures and small samples is described, including a decision of the direct and inverse problems of the convergent beam ellipsometry for an arbitrary wavelength, measurement technique and a compensating orientation of cryostat windows. Experimental results are presente

D. A. Dimitrov, G. M. Wysin

We report numerical simulation results for free-vortex lifetimes in the critical region of classical two-dimensional easy-plane ferro- and antiferromagnets having three-component order parameters. The fluctuations in the vortex number density in a spin dynamics simulation were used to estimate the lifetimes. The observed lifetimes are of the same order of ma

Joshua Goodman

The inside-outside probabilities are typically used for reestimating Probabilistic Context Free Grammars (PCFGs), just as the forward-backward probabilities are typically used for reestimating HMMs. I show several novel uses, including improving parser accuracy by matching parsing algorithms to evaluation criteria; speeding up DOP parsing by 500 times; and 3

Y. N. Efremov, B. G. Elmegreen

The average age difference between pairs of star clusters in the Large Magellanic Clouds increases with their separation as the ~0.35 power. This suggests that star formation is hierarchical in space and time. Small regions form stars quickly and large regions, which often contain the small regions, form stars over a longer period. A similar result found pre

Zoltan Haiman, Piero Madau, Abraham Loeb

High resolution, deep imaging surveys are instrumental in setting constraints on semi-analytical structure formation models in Cold Dark Matter (CDM) cosmologies. We show here that the lack of unresolved B-band ``dropouts&#39;&#39; with V > 25 mag in the Hubble Deep Field (HDF) appears to be inconsistent with the expected number of quasars if massive black h

J. E. Grove, M. S. Strickman, S. M. Matz, X. -M. Hua

OSSE observed the transient black hole candidate GRO J0422+32 (XN Per 92) between 1992 Aug 11 and 1992 Sep 17. High time resolution data were obtained in several energy bands over the 35-600 keV range with a sampling rate of 8 ms. Power spectra at energies below 175 keV show substantial low-frequency red noise with a shoulder at a few tens of mHz, peaked noi

Jon Loveday

I review the current observational status of the faint end of the optical luminosity function of field galaxies at low redshift. There is growing evidence for an excess number of dwarf galaxies that is not well fit by a single Schechter function. These dwarf galaxies tend to be of late morphological and spectral type, blue in colour, of low surface brightnes

G. I. Ogilvie, S. H. Lubow

We extend our analysis of the three-dimensional response of a vertically polytropic disk to tidal forcing at Lindblad resonances by including the effects of a disk atmosphere. The atmosphere is modeled as an isothermal layer that joins smoothly on to an underlying polytropic layer. The launched wave progressively enters the atmosphere as it propagates away f

A. Cappi, G. Zamorani, E. Zucca, G. Vettolani

We present a detailed discussion of the redshift errors associated to the ESO Slice Project measurements. For a subsample of 742 galaxies with redshifts determined both from the absorption lines (V_{abs}) and from the emission lines (V_{emi}), we find an average difference <V_{abs} - V_{emi}> ~ +100$ km/s. We find that a similar effect is present in another,

I. I. Romanyuk, D. O. Kudryavtsev

The magnetic field of the CP star HD 14437 was discovered by Glagolevskij et al. (1985) using the 6-m telescope of the Special Astrophysical Observatory. No polarity changes have been found during 2 years of observations. A very long (> 3-4 years) period of rotation was proposed to explain the measurements. To check this hypothesis, we made a new series of m

N. Piskunov, H. C. Stempels, T. A. Ryabchikova, V. Malanushenko

kappa Psc (HD 220825) is a typical Chromium Ap star that happens to have optimal parameters for Doppler imaging (DI). Its short rotational period of less then 2 days, rotational velocity of ~40 km/s, and a moderate inclination of the rotational axis put modest requirements on spectroscopic observations. Anomalies of iron peak elements are clearly present, bu

N. Brynildsen, P. Maltby, P. Brekke, T. Fredvik

Bright EUV sunspot plumes have been observed in eight out of eleven different sunspot regions with the Coronal Diagnostic Spectrometer -- CDS on SOHO. From wavelength shifts we derive the line-of-sight velocity, relative to the average velocity in the rastered area, 120 arcsec x 120 arcsec. In sunspot plumes we find that the motion is directed away from the

C. M. Baugh, C. G. Lacey, S. Cole, C. S. Frenk

The high redshift observations of galaxies now becoming available from the Hubble Space Telescope and from large ground based telescopes are opening fresh windows on galaxy formation. Semianalytic models of galaxy formation provide us with a powerful tool to interpret and understand these exciting new data. In this review, we explain the philosophy behind th

E. Paunzen

Using the Hipparcos data, absolute magnitudes and thus the evolutionary status for the group of lambda Bootis stars were derived. The origin of this small group of non-magnetic, chemically peculiar stars, still remains a matter of debate. Using new evolutionary tracks, an age determination could be provided to distinguish between the two competing theories -

D. E. Mkrtichian, A. V. Kusakin, V. P. Malanushenko, M. Paparo

The preliminary results of a 1996 multisite campaign on the pulsating lambda Bootis star 29 Cyg are presented. This campaign, initiated by the Central Asian Network (CAN), allowed to collect data during 48 photometric and 2 spectroscopic nights at observatories of Ukraine, Kazakhstan, Turkey, Hungary, Canada and USA. The multiplicity of excited modes is conf

Ravi Subrahmanyan, Michael J. Kesteven, Ronald D. Ekers, Malcolm Sinclair

We have made an 8.7 GHz image of a sky region with a resolution of 8 arcmin and high brightness sensitivity using the Australia Telescope Compact Array (ATCA). in an ultra compact configuration. The foreground discrete-source confusion was estimated from observations with higher resolution at the same frequency and in a scaled array at a lower frequency. Fol

T. Lueftinger, R. Kuschnig, W. W. Weiss

The surface distribution of five elements: iron, chromium, titanium, magnesium and manganese on the magnetic A0pCr star epsilon UMa, have been calculated using the Doppler imaging technique. We found that iron, chromium and manganese are correlated with the assumed dipole magnetic field geometry of this star, which is apparently not the case of magnesium and

R. Kuschnig, G. A. Wade, G. M. Hill, N. Piskunov

In order to clarify the role of the magnetic field in generating abundance inhomogeneities in the atmospheres of Ap stars, we present new abundance Doppler images and an approximate magnetic field geometry for the Ap star iota Cas.

M. Toscano, M. Bailes, R. N. Manchester, J. S. Sandhu

We compare the spectral properties of the millisecond and slow pulsars detected in the Parkes 70 cm survey. The mean spectral index for the millisecond pulsars (MSPs) is -1.9 +/- 0.1 whereas the mean spectral index for the slow pulsars is a surprisingly steep -1.72 +/- 0.04. A Kolmogorov-Smirnov test indicates that there is only a 72% probability that the tw

Amiel Sternberg

I use recent photometric and stellar velocity dispersion measurements of the super-star-clusters (SSCs) NGC 1569A and NGC 1705-1 to determine their present-day luminosity/mass (L_V/M) ratios. I then use the inferred L_V/M ratios, together with population synthesis models of evolving star-clusters, to constrain the initial-mass-functions (IMFs) in these objec

Daniel J. Eisenstein, Wayne Hu, Max Tegmark

We show that upcoming CMB satellite experiments and large redshift surveys can be used together to yield 5% determinations of H_0 and Omega_m, an order of magnitude improvement over CMB data alone. CMB anisotropies provide the sound horizon at recombination as a standard ruler. For reasonable baryon fractions, this scale is imprinted on the galaxy power spec

Sascha Hilgenfeldt, Detlef Lohse, Michael Zomack

The scattering of ultrasound from bubbles of micrometer-sized radius, such as used in contrast enhancers for ultrasound diagnostics, is studied. We show that sound scattering and ``active&#39;&#39; emission of sound from oscillating bubbles are not contradictory, but are just two different aspects derived from the same physics. Treating the bubble as a nonli

Sascha Hilgenfeldt, Michael P. Brenner, Siegfried Grossmann, Detlef Lohse

Recent work on single bubble sonoluminescence (SBSL) has shown that many features of this phenomenon, especially the dependence of SBSL intensity and stability on experimental parameters, can be explained within a hydrodynamic approach. More specifically, many important properties can already be derived from an analysis of bubble wall dynamics. This dynamics

M. A. Grebeniuk, V. D. Ivashchuk

A family of Majumdar-Papapetrou type solutions in sigma-model of p-brane origin is obtained for all direct sums of finite-dimensional simple Lie algebras. Several examples of p-brane dyonic configurations in D=10 (IIA) and D=11 supergravities corresponding to the Lie algebra sl(3,C) are considered.

Lev N. Shchur, Paolo Butera

Using a recently proposed directed random walk test, we systematically investigate the popular random number generator RANLUX developed by Luescher and implemented by James. We confirm the good quality of this generator with the recommended luxury level. At a smaller luxury level (for instance equal to 1) resonances are observed in the random walk test. We a

Pushan Majumdar, H. S. Sharatchandra

Dual form of 3+1 dimensional Yang-Mills theory is obtained as another SO(3) gauge theory. Duality transformation is realized as a canonical transformation. The The non-abelian Gauss law implies the corresponding Gauss law for the dual theory. The dual theory is non-local. There is a non-local version of Yang-Mills theory which is self dual.

D. M. Appleby

The analytic properties of a class of generalized Husimi functions are discussed, with particular reference to the problem of state reconstruction. The class consists of the subset of Wodkiewicz&#39;s operational probability distributions for which the filter reference state is a squeezed vacuum state. The fact that the function is analytic means that perfec

Goran Senjanovic

Rochelle salt has a remarkable characteristic of becoming more ordered for a range of high temperatures before melting. In the particle physics language this means more symmetry breaking for high T. In many realistic field theories this is a perfectly consistent scenario which has profound consequences in the early universe. In particular it implies that the

Jacek Dziarmaga

Production of Bloch waves during a rapid quench is studied by analytical and numerical methods. The density of Bloch waves decays exponentially with the quench time. It also strongly depends on temperature. Very few textures are produced for temperatures lower than a characteristic temperature proportional to the square of the magnetic field.

M. N. Chernodub, F. V. Gubarev, E. -M. Ilgenfritz, A. Schiller

We study the properties of Nambu monopoles and Z-vortices in the 3D lattice SU(2) Higgs theory which represents the Standard Model at high temperature. We show that the densities of the Nambu monopoles and the Z-vortices are O(1) in the symmetric phase and generically small in the Higgs phase. Near to the critical Higgs mass and in the vicinity of the phase

Alexey Maznytsia, Christian Preitschopf, Dmitri Sorokin

Using examples of a D=2 chiral scalar and a duality-symmetric formulation of D=4 Maxwell theory we study duality properties of actions for describing chiral bosons. In particular, in the D=4 case, upon performing a duality transform of an auxiliary scalar field, which ensures Lorentz covariance of the action, we arrive at a new covariant duality-symmetric Ma

Xinwei Kong, Finn Ravndal

We construct an effective Lagrangian for interacting pions with non-relativistic energies. The coupling constants can be expressed in terms of the different scattering lengths and slopes. When used in the calculation of the pionium decay rate, the scattering slope contribution gives a correction of about 8% compared with the lowest order contribution coming

Jochen Biebel, Tord Riemann

The differential cross-sections for processes of the type e+ e- to W+ W- to l nu q anti-q are determined with account of background contributions and of anomalous triple gauge boson couplings. Analytic expressions for dsigma/ds1 ds2 dcostheta, where theta is the production angle of the W boson, are numerically integrated with the Fortran package GENTLE. QED

Arne Neumayr, Walter Metzner

We derive explicit results for fermion loops with an arbitrary number of density vertices in two dimensions at zero temperature. The 3-loop is an elementary function of the three external momenta and frequencies, and the N-loop can be expressed as a linear combination of 3-loops with coefficients that are rational functions of momenta and frequencies. We sho

Mu-Lin Yan, Yi Wei, Ting-Liang Zhuang

We make comments on ref.[Z.Phys. C73, 541 (1997)], and provide partial wave analysis to the decays of excited heavy S-wave $1^-$ quarkonia into the basic $1^-$ quarkonia state plus $ππ$. It is revealed that there exist contributions of D-wave transition in $ψ&#39;\longrightarrow J/ψππ$, $Υ(2S)\longrightarrow Υ(1S) ππ$ and $Υ(3S)\longrightarrow Υ(1S) ππ$ by u

P. P. N. de Groen

The method of ``Total Least Squares'' is proposed as a more natural way (than ordinary least squares) to approximate the data if both the matrix and and the right-hand side are contaminated by ``errors''. In this tutorial note, we give a elementary unified view of ordinary and total least squares problems and their solution. As the geometry underlying the pr

Mihai Tibar

We consider an equisingularity problem for polynomial families of affine hypersurfaces $X_\tau \subset \mathbb C^n$ with (at worst) isolated singularities. We show that the constancy of the global polar invariants $\gamma^* (X_\tau)$ is equivalent to the $t$-equisingularity at infinity, an asymptotic-type equisingularity that we introduce. We prove that $\ga

A. J. Bordner, E. Corrigan, R. Sasaki

A new formulation of Calogero-Moser models based on root systems and their Weyl group is presented. The general construction of the Lax pairs applicable to all models based on the simply-laced algebras (ADE) are given for two types which we call `root&#39; and `minimal&#39;. The root type Lax pair is new; the matrices used in its construction bear a resembla

G. Chalmers, H. Nastase, K. Schalm, R. Siebelink

We test the conjectured relationship between N=4 super Yang-Mills theory in four dimensions and IIB supergravity compactified on $AdS_5\times S_5$ by computing the two- and three-point functions of R-symmetry currents. We observe that the integral expressions describing the general three-point correlator on the supergravity side have a structure similar to o

Z. Hradil, R. Myska

The data of the experiment of Schiller et al., Phys. Rev. Lett. 77 (1996) 2933, are alternatively evaluated using the maximum likelihood estimation. The given data are fitted better than by the standard deterministic approach. Nevertheless, the data are fitted equally well by a whole family of states. Standard deterministic predictions correspond approximate

Felix M. Lev

The structure of representations describing systems of free particles in the theory with the invariance group SO(1,4) is investigated. The property of the particles to be free means as usual that the representation describing a many-particle system is the tensor product of the corresponding single-particle representations (i.e. no interaction is introduced).

Boris F. Samsonov

Transformations of coherent states of the free particle by bounded and semibounded symmetry operators are considered. Resolution of the identity operator in terms of the transformed states is analyzed. A generalized identity resolution is formulated. Darboux transformation operators are analyzed as operators defined in a Hilbert space. Coherent states of mul

Jochen Rau

I give a concise introduction to some essential concepts of statistical mechanics: 1. Probability theory (constrained distributions, concentration theorem, frequency estimation, hypothesis testing); 2. Macroscopic systems in equilibrium (macrostate, thermodynamic variables, entropy, first law, thermodynamic potentials, correlations); 3. Linear response (Kubo

H. Yamada, T. Nakagaki, M. Ito

The amoeboid organism, the plasmodium of Physarum polycephalum, behaves on the basis of spatio-temporal pattern formation by local contraction-oscillators. This biological system can be regarded as a reaction-diffusion system which has spatial interaction by active flow of protoplasmic sol in the cell. Paying attention to the physiological evidence that the

R. Albrecht

New results on transverse mass spectra of neutral pions measured at central rapidity are presented for impact parameter selected 200 AGeV S + S and S + Au collisions. The spectra from all systems show a clear power-law like shape with similar curvature. Collisions of S + Au exhibit a larger mean transverse momentum than pp increasing with centrality. Predict

Valeri V. Dvoeglazov

We proceed to derive equations for the symmetric tensor of the second rank on the basis of the Bargmann-Wigner formalism in a straightforward way. The symmetric multispinor of the fourth rank is used. It is constructed out of the Dirac 4-spinors. Due to serious problems with the interpretation of the results obtained on using the standard procedure we genera

Oscar Arratia, Miguel A. Martin, Mariano A. Olmo

We review several procedures of quantization formulated in the framework of (classical) phase space M. These quantization methods consider Quantum Mechanics as a &#34;deformation&#34; of Classical Mechanics by means of the &#34;transformation&#34; of the commutative algebra of smooth functions on M in a new non-commutative algebra. These ideas lead in a natu

Eric Bedford, Mattias Jonsson

We study the dynamics of polynomial mappings f:C^k to C^k of degree at least 2 that extend continuously to projective space P^k. Our approach is to study the dynamics near the hyperplane at infinity and then making a descent to K --- the set of points with bounded orbits --- via external rays.

Francesco Brenti, Sergey Fomin, Alexander Postnikov

We introduce and study a family of operators which act in the span of a Weyl group $W$ and provide a multi-parameter solution to the quantum Yang-Baxter equations of the corresponding type. Our operators generalize the &#34;quantum Bruhat operators&#34; that appear in the explicit description of the multiplicative structure of the (small) quantum cohomology

Claude Sabbah

We analyse the Gauss-Manin system of differential equations---and its Fourier transform---attached to regular functions satisfying a tameness assupmption on a smooth affine variety over C (e.g. tame polynomials on C^{n+1}). We give a solution to the Birkhoff problem and prove Hodge-type results analogous to those existing for germs of isolated hypersurface s

Chuu-Lian Terng, Karen Uhlenbeck

We construct a local action of the group of rational maps from $S^2$ to $GL(n,C)$ on local solutions of flows of the ZS-AKNS $sl(n,C)$-hierarchy. We show that the actions of simple elements (linear fractional transformations) give local Bäcklund transformations, and we derive a permutability formula from different factorizations of a quadratic element. We pr

Hyungju Park

Let $k$ be an arbitrary field, and C be a curve in A^n defined parametrically by x_1=f_1(t),...,x_n=f_n(t), where f_1,...,f_n\in k[t]. A necessary and sufficient condition for the two function fields k(t) and k(f_1,...,f_n) to be same is developed in terms of zero-dimensionality of a derived ideal in the bivariate polynomial ring k[s,t]. Since zero-dimension

E. Javier Elizondo, Paulo Lima-Filho

Given a projective algebraic variety $X$, let $Π_p(X)$ denote the monoid of effective algebraic equivalence classes of effective algebraic cycles on $X$. The $p$-th Euler-Chow series of $X$ is an element in the formal monoid-ring $Z[[Π_p(X)]]$ defined in terms of Euler characteristics of the Chow varieties $\cvpd{p}α{X}$ of $X$, with $α\inΠ_p(X)$. We provide

Edward Witten

In the mapping from four-dimensional gauge theories to string theory in $AdS$ space, many features of gauge theory can be described by branes wrapped in different ways on $§^5$, $\RP^5$, or subspaces thereof. These include a baryon vertex coupling N external charges in the fundamental representation of SU(N), a bound state of $k$ gluons in SO(2k) gauge theor

D. Bailin, G. V. Kraniotis, A. Love

The picture of CP-violation in orbifold compactifications in which the $T$-modulus is at a complex fixed point of the modular group is studied. CP-violation in the neutral kaon system and in the neutron electric dipole moment are both discussed. The situation where the $T$-modulus takes complex values on the unit circle which are not at a fixed point is also

R. Banerjee, C. Wotzasek

We develop a technique that solders the dual aspects of some symmetry. Using this technique it is possible to combine two theories with such symmetries to yield a new effective theory. Some applications in two and three dimensional bosonisation are discussed. In particular, it is shown that two apparently independent three dimensional massive Thirring models

J. Ambjorn, R. Loll

We formulate a non-perturbative lattice model of two-dimensional Lorentzian quantum gravity by performing the path integral over geometries with a causal structure. The model can be solved exactly at the discretized level. Its continuum limit coincides with the theory obtained by quantizing 2d continuum gravity in proper-time gauge, but it disagrees with 2d

T. Nakatsu

We review M-theory description of 4d N=2 SQCD. Configurations of M-theory fivebranes relevant to describe the moduli spaces of the Coulomb and Higgs branches are studied using the Taub-NUT geometry. Minimal area membranes related with the BPS states of N=2 SQCD are given explicitly. They almost saturate the BPS bounds. The deviation from the bounds is due to

J. A. Minahan, N. P. Warner

We compute, in the large N limit, the quark potential for ${\cal N}=4$ supersymmetric SU(N) Yang-Mills theory broken to $SU(N_1) \times SU(N_2)$. At short distances the quarks see only the unbroken gauge symmetry and have an attractive potential that falls off as 1/L. At longer distances the interquark interaction is sensitive to the symmetry breaking, and o

Karim Benakli

We suggest that compactifications on Anti-de-Sitter (AdS) spaces of type IIA, IIB, heterotic strings and eleven dimensional vacuua of M-theory are related by a combination of $T$ and strong/weak dualities. Maldacena conjecture relates then all these vacuua to a conformal theory on the boundaries. Furthermore acting with discrete groups on part of the interna

Mirjam Cvetic, Finn Larsen

We interpret the general rotating black holes in five dimensions as rotating black strings in six dimensions. In the near horizon limit the geometry is locally AdS_3 x S_3, as in the nonrotating case. However, the global structure couples the AdS_3 and the S_3, giving angular velocity to the S_3. The asymptotic geometry is exploited to count the microstates

R. Brout, F. Englert

The personal and scientific history of the discovery of spontaneous symmetry breaking in gauge theories is outlined and its scientific content is reviewed

G. Sanchez-Colon, J. Wudka

We present a model and process independent study of the contributions from non-Standard Model physics to the oblique parameters S, T and U. We show that within an effective lagrangian parameterization the expressions for the oblique parameters in terms of observables are consistent, while those in terms of the vector-boson vacuum polarization tensors are amb

Leonard Gamberg, George R. Kalbfleisch, Kimball A. Milton

Recently, there have been proposals that the classic Euler-Heisenberg Lagrangian together with duality could be employed to set limits on magnetic monopoles having masses less than 1 TeV. The D0 collaboration at Fermilab has used such a proposal to set mass limits based on the nonobservation of pairs of photons each with high transverse momentum. In this not

Paresh Malde, Robin G. Stuart

The O(N_f alpha^2) electroweak radiative corrections to the Thomson scattering matrix element are calculated for a general renormalization scheme with massless fermions. All integrals can be evaluated exactly in dimensional regularization which in several cases yields new results that are remarkably simple in form. A number of stringent internal consistency

Bing An Li

Effective chiral theory of mesons is applied to study the four decay modes of $τ\toρππν$. Theoretical values of the branching ratios are in agreement with the data. The theory predicts that the $a_{1}$ resonance plays a dominant role in these decays. There is no new parameter in this study.

Mikhail Galynskii, Sergei Sikach

We calculate the number of $e^+ e^-$-pairs produced by a Compton high energy photon in turn formed in the process $e + n γ_0 -> e + γ$ at simultaneous collision with several photons $γ_0$ of the same laser beam $γ+ s γ_0 -> e^+ + e^-$. The case when polarization states of initial electron beam and laser photons are helicity is considered. It is shown that ta

Sergio Lupia

The complete QCD evolution equation for factorial moments in quark and gluon jets is numerically solved with initial conditions at threshold by fully taking into account the energy-momentum conservation law. Within the picture of Local Parton Hadron Duality, the perturbative QCD predictions can successfully describe the available experimental data.

Hong-Yi Zhou

CP violating effects in top quark pair production at the future 2 TeV $p\bar p$ Tevatron and 14 TeV $pp$ LHC colliders are investigated. We study three kinds of CP violating sources:the supersymmetric CP-odd phase of the stop trilinear soft breaking term: $arg(A_t)$, the CP-odd parameter in two-Higgs doublet extensions of the standard model(2HDM), and the mo

M. A. Ivanov, V. E. Lyubovitskij, E. Z. Lipartia, A. G. Rusetsky

Hadronic (Pi+Pi-) atom is studied in the relativistic perturbative approach based on the Bethe-Salpeter equation. The general expression for the atom lifetime is derived. Lowest-order corrections to the relativistic Deser-type formula for the atom lifetime are evaluated within the Chiral Perturbation Theory.

Borut Bajc

I offer some computational details and useful and concise formulae to calculate the effective potential for a general abelian supersymmetric model at high temperature and density. It will be shown that such cases are very good candidates for symmetry nonrestoration at high temperature, providing large densities are present.

Wojciech Broniowski, Maxim Polyakov, Hyun-Chul Kim, Klaus Goeke

We show that the constituent quark model leads to simple expressions for the isoscalar and isovector tensor susceptibilities of the vacuum. The found values are negative and of magnitude compatible with QCD-sum-rule parameterizations of spectral densities in appropriate L=1-meson channels.

M. Grazzini

Fracture functions and their evolution equations are reviewed. Some phenomenological applications are briefly discussed.

M. Carena, P. H. Chankowski, S. Pokorski, C. E. M. Wagner

Recently, the LEP collaborations have reported a lower bound on a Standard Model-like Higgs boson of order 89 GeV. We discuss the implications of this bound for the minimal supersymmetric extension of the Standard Model (MSSM). In particular, we show that the lower bound on $\tanβ$, which can be obtained from the presently allowed Higgs boson mass value, bec

K. Hamaguchi, Yasunori Nomura, T. Yanagida

We show that there are discrete gauge symmetries protect naturally heavy X particles from decaying into the ordinary light particles in the supersymmetric standard model. This makes the proposal very attractive that the superheavy X particles constitute a part of the dark matter in the present universe. It is more interesting that there are a class of discre

Mary K. Gaillard

The weakly coupled vacuum of $E_8\otimes E_8$ heterotic string theory remains an attractive scenario for phenomenolgy and cosmology. The particle spectrum is reviewed and the issues of gauge coupling unification, dilaton stabilization and modular cosmology are discussed. A specific model for condensation and supersymmetry breaking, that respects known constr

The WA102 Collaboration, D. Barberis et al

The reaction pp to pfps(K+K-K+K-) in which the K+K-K+K- system is centrally produced has been studied at 450 GeV/c. Phi phi production has been found to dominate this reaction and is compatible with being produced by double Pomeron exchange. An angular analysis of the phi phi system favours JPC = 2++ and its dPT dependence is similar to that observed for glu

M. Navarro

We show that the equations of motion of two-dimensional dilaton gravity conformally coupled to a scalar field can be reduced to a single non-linear second-order partial differential equation when the coordinates are chosen to coincide with the two scalar fields, the matter field $f$ and the dilaton $ϕ$, which are present in the theory. This result may help s

Jerome Martin, Dominik J. Schwarz

We reply to L.P. Grishchuk&#39;s comment (gr-qc/9801011) on our paper ``The Influence of Cosmological Transitions on the Evolution of Density Perturbations&#39;&#39; (Phys. Rev. D 57, 3302, 1998). We show that his points of criticism are not correct.

Naresh Dadhich

By resolving the gravitational field into electric and magnetic parts, we define an electrogravity duality transformation and discover an interesting property of the field. Under the duality transformation a vacuum/flat spacetime maps into the original spacetime with a topological defect of global monopole/texture. The elctrogravity-duality is thus a topolog

D. V. Ahluwalia

The local galactic cluster, the Great attractor, embeds us in a dimensionless gravitational potential of about - 3 x 10^{-5}. In the solar system this potential is constant to about 1 part in 10^{11}. Consequently, planetary orbits, which are determined by the gradient in the gravitational potential, remain unaffected. However, this is not so for the recentl

T. P. Singh

This article gives an elementary review of gravitational collapse and the cosmic censorship hypothesis. Known models of collapse resulting in the formation of black holes and naked singularities are summarized. These models, when taken together, suggest that the censorship hypothesis may not hold in classical general relativity. The nature of the quantum pro

Domenico Giulini

We consider Einstein Gravity coupled to dynamical matter consisting of a gauge field with any compact gauge group and minimally coupled scalar fields. We investigate the conditions under which a free specification of a spatial field configuration for the total system and its derivative with respect to coordinate-time determines a solution to the field equati

Hisao Suzuki, Eiichi Takasugi, Hiroshi Umetsu

It is well known that the perturbation equations of massless fields for the Kerr-de Sitter geometry can be written in the form of separable equations. The equations have five definite singularities so that the analysis has been expected to be difficult. We show that these equations can be transformed to Heun&#39;s equations, for which we are able to use know

Giuliano Benenti, Giulio Casati, Dima L. Shepelyansky

The microwave ionization of internally chaotic Rydberg atoms is studied analytically and numerically. The internal chaos is induced by magnetic or static electric fields. This leads to a chaotic enhancement of microwave excitation. The dynamical localization theory gives a detailed description of the excitation process even in a regime where up to few thousa

M. Krech, Alex Bunker, D. P. Landau

We have proposed new algorithms for the numerical integration of the equations of motion for classical spin systems. In close analogy to symplectic integrators for Hamiltonian equations of motion used in Molecular Dynamics these algorithms are based on the Suzuki-Trotter decomposition of exponential operators and unlike more commonly used algorithms exactly

Dirk Helbing

A kind of fluid dynamic description for the collective movement of pedestrians is developed on the basis of a Boltzmann-like gaskinetic model. The differences between these pedestrian specific equations and those for ordinary fluids are worked out, for example concerning the mechanism of relaxation to equilibrium, the role of ``pressure&#39;&#39;, the specia

A. Baldassarri, J. P. Bouchaud, I. Dornic, C. Godrèche

It was recently realized that the persistence exponent appearing in the dynamics of nonequilibrium systems is a special member of a continuously varying family of exponents, describing generalized persistence properties. We propose and solve a simplified model of coarsening, where time intervals between spin flips are independent, and distributed according t

F. de los Santos, P. L. Garrido

We review the critical behaviour of the Driven Lattice Gas (DLG) model. As a result, we obtain a novel Langevin equation for the DLG which depends on the microscopic transition probabilities. We then show how this dependence affects the critical behaviour of the the DLG placing the finite and the infinite driving field cases into different universality class

Tomaso Aste

Topologically stable cellular partitions of D dimensional spaces are studied. A complete statistical description of the average structural properties of such partition is given in term of a sequence of D/2-1 (or (D-1)/2) variables for D even (or odd). These variables are the average coordination numbers of the 2k-dimensional polytopes (2k < D) which make the