May 1998 arXiv papers — page 17

M. Anselmino, M. Bertini, F. Murgia, B. Pire

Final state interactions in quark fragmentation may give origin to non zero values of the off-diagonal element rho_(1,-1) of the helicity density matrix of vector mesons V produced in current jets, with a large energy fraction x_E; the value of rho_(1,-1)(V) is related to the hard constituent dynamics and tests unusual properties of it. Some recent data on p

J. Geiss, W. Cassing, C. Greiner

We study systematically the production of strangeness in nuclear reactions from SIS to SPS energies within the covariant hadronic transport approach HSD. Whereas the proton and pion rapidity distributions as well as pion transverse momentum spectra are well described in the hadronic transport model from 2-200 AGeV, the $K^+$ and $K^-$ spectra are noticeably

S. Kretzer, I. Schienbein

We present O(alpha_s^1) corrections to deep inelastic scattering amplitudes on massive quarks obtained within the scheme of Aivazis, Collins, Olness and Tung (ACOT). After identifying the correct subtraction term the convergence of these contributions towards the analogous coefficient functions for massless quarks, obtained within the modified minimal subtra

C. Kiefer, D. Polarski

We clarify the way in which cosmological perturbations of quantum origin, produced during inflation, assume classical properties. Two features play an important role in this process: First, the dynamics of fluctuations which are presently on large cosmological scales leads to a very peculiar state (highly squeezed) that is indistinguishable, in a precise sen

Sergei V. Shabanov, John R. Klauder

We develop a mathematically well-defined path integral formalism for general symplectic manifolds. We argue that in order to make a path integral quantization covariant under general coordinate transformations on the phase space and involve a genuine functional measure that is both finite and countably additive, the phase space manifold should be equipped wi

B. G. Sidharth

We consider a recent successful model of leptons as Kerr-Newman type Black Holes in a Quantum Mechanical context. The model leads to a cosmology which predicts an ever expanding accelerating universe with decreasing density and to the conclusion that at Compton wavelength scales, electrons would exhibit low dimensionality, both of which conclusions have been

J. Brose, G. Dahlinger, K. R. Schubert

A photomultiplier setup for precise relative CsI(Tl) crystal light yield and uniformity measurements is described. It is used for wrapping material studies to optimize the uniformity and the yield of the light output of 36 cm long crystals. The uniformity is an important property in high energy photon calorimetry. Results of an optimization of photodiode cou

J. Haidenbauer, W. Melnitchouk, J. Speth

We report on progress in the development of a microscopic model for the hyperon-nucleon interaction within the meson-exchange framework, which incorporates both one-meson as well as correlated two-meson exchange contributions. The main new feature of the model is the exchange of two correlated pions or kaons, both in the scalar-isoscalar and the vector-isove

C. G. Bao, Y. X. Liu

The inherent nodal structures of the wavefunctions of 6-nucleon systems have been investigated. The existence of a group of six low-lying states dominated by L=0 has been deduced. The spatial symmetries of these six states are found to be mainly {4,2} and {2,2,2}.

Elliott H. Lieb, Jakob Yngvason

This article is a short version of a longer article to appear in Physics Reports (cond-mat/9708200). The essential postulates of classical thermodynamics are formulated, from which the second law is deduced as the principle of increase of entropy in irreversible adiabatic processes that take one equilibrium state to another. The entropy constructed here is d

Ki-Bong Nam, Moon Ok Wang

Wawamoto generalized the Witt algebra using Laurent extension of polynomial ring. We construct the generalized Witt algebra $W(g_p,n)$ by using an additive map $g_p$ from a set of integers into a field of characteristic zero where $1\leq p \leq n.$

Christopher Beattie

Eigenvalue estimates that are optimal in some sense have self-evident appeal and leave estimators with a sense of virtue and economy. So, it is natural that ongoing searches for effective strategies for difficult tasks such as estimating matrix eigenvalues that are situated well into the interior of the spectrum revisit from time to time methods that are kno

B. M. Brown, M. S. P. Eastham, D. K. R. McCormack

We consider the spectral function $ρ(μ)$ $(μ\geq 0)$ for the Sturm-Liouville equation $y^{''}+(λ-q)y =0$ on $[0,\infty)$ with the boundary condition $y(0)=0$ and where $q$ has slow decay $O(x^{-α})$ $(a>0)$ as $x\to \infty$. We develop our previous methods of locating spectral concentration for $q$ with rapid exponential decay (JCAM 81 (1997) 333-348

Zora Thomova, Pavel Winternitz

Maximal abelian subalgebras of one of the classical real inhomogeneous Lie algebras are constructed, namely those of the pseudoeuclidean Lie algebra e(p,q). Use is made of the semidirect sum structure of e(p,q) with the translations T(p+q) as an abelian ideal. We first construct splitting MASAs that are themselves direct sums of abelian subalgebras of o(p,q)

Nicola Ciccoli, Erik Koelink, Tom H. Koornwinder

The q-Laguerre polynomials correspond to an indetermined moment problem. For explicit discrete non-N-extremal measures corresponding to Ramanujan's ${}_1ψ_1$-summation we complement the orthogonal q-Laguerre polynomials into an explicit orthogonal basis for the corresponding L^2-space. The dual orthogonal system consists of so-called big q-Bessel functio

Yanlin Yu

This paper deals with a semi-classical limit (Theorem 1) by using traditional mathematical methods, and shows a Hopf theorem as a corollary. A formal discussion of it may be found in [7].

Ryoshi Hotta

The first part of these notes is devoted to an introduction to algebraic $D$-modules. Several basic notions are introduced. In the second part, $D$-modules with group action are treated. Several important examples in this situation are discussed in details. Particularly, the Harish-Chandra systems for group characters and the Gelfand generalized hypergeometr

B. M. Brown, W. D. Evans, D. K. R. McCormack, M. Plum

The Weyl-Sims classification for a second-order ordinary differential equation with general complex coefficients is investigated. Connections are then established between the associated m-function and the spectral properties of maximal-accretive realisations of the differential expression.

Jaemo Park

We study M5-brane configuration of the chiral gauge theory whose Type IIA brane configuration with orientifold 6-plane(O6) is studied by various authors. Much of the paper is devoted to studying M-theory picture of SO/Sp gauge theory with fundamental flavors realized in Type IIA setup with O6-plane. The Higgs branch of N=2 SO/Sp gauge theory is studied and t

Christopher Kolda, Nir Polonsky

It is demonstrated how the hierarchy between the gauge coupling unification scale of minimal supersymmetry and the Planck (or string) scale, which resembles in order of magnitude a loop factor, can actually be explained as such in supergravity-coupled supersymmetry. A gauge and global singlet field acquires a linear potential term due to its one-loop supergr

Xiao-Xia Yao, Wei-Qin Chao, Yang Pang

Using the General Cascade Program(GCP), the production and absorption of $J/ψ$ in p-A and A-A collisions have been studied. Nucleon absorption mechanism and comover absorption mechanism are considered to investigate the $J/ψ$ suppression. The results agree well with experimental data of $J/ψ$ production, except for the data in Pb-Pb collision.

K. G. Chetyrkin, A. Kwiatkowski

In this note radiative corrections to the total hadronic decay rate of the $τ$-lepton are studied employing perturbative QCD and the operator product expansion. We calculate quadratic quark mass corrections to the decay rate ration $R_τ$ to the order ${\cal O}(α_s^2 m^2)$ and find that they contribute appreciably to the Cabbibo supressed decay modes of the $

V. N. Baier, V. M. Katkov

Effect of radiation of many photons by a single electron traversing a target is discussed. When the summary energy of emitted photons (the energy losses spectrum) is measured only, the photon spectrum is distorted comparing with the photon spectrum in one interaction. Influence of this effect is discussed for the cases (1) bremsstrahlung (described by Bethe-

Shahin S. Agaev

The pion and kaon electromagnetic form factors $F_M(Q^2)$ are calculated at the leading order of pQCD using the running coupling constant method. In calculations a dependence of the mesons distribution amplitudes on the hard scale $Q^2$ is taken into account. The Borel transform and resummed expression for $F_M(Q^2)$ are found.

Luis E. Ibanez

After a review of some topics concerning the phenomenological applications of perturbative string theory, I discuss to what extent all of it is affected by the recent developements in string dualities.

Xiaotong Song

We developed a new and unified scheme for describing both quark spin and orbital angular momenta in symmetry-breaking chiral quark model. The loss of quark spin in the chiral splitting processes is compensated by the gain of the orbital angular momentum carried by quarks and antiquarks. The sum of both spin and orbital angular momenta carried by quarks and a

H. B. Dreis, F. Eisele, M. Hildebrandt, B. Schmidt

A fibre detector with multianode PM readout for high rate applications was developed for the HERA-B spectometer to cover the area near the beampipe. Such a detector has to operate at particle rates up to 2*10**4 mm**(-2) s**(-1) and has to tolerate a radiation dosis up to 1 Mrad/y. The light output of test detectors with different scintillating fibres was me

G. Fodor, M. Marklund, Z. Perjés

Stationary axisymmetric perfect fluid space-times are investigated using the curvature description of geometries. Attention is focused on space-times with a vanishing electric part of the Weyl tensor. It is shown that the only incompressible axistationary magnetic perfect fluid is the interior Schwarzschild solution. The existence of a rigidly rotating perfe

A. Dimitropoulos

Since the discovery of the large angular scale anisotropies in the microwave background radiation, the behaviour of cosmological perturbations (especially, density perturbations and gravitational waves) has been of great interest. In this study, after a detailed and rigorous treatment of the behaviour of gravitational waves in viscous cosmic media, we conclu

J. Kowalski - Glikman

We present a spherically symmetric and static exact solution of Quantum Einstein Equations. This solution is asymptotically (for large $r$) identical with the black hole solution on the anti--De Sitter background and, for some range of values of the mass possesses two horizons. We investigate thermodynamical properties of this solution.

Dongsu Bak, Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh

We show that the quantum dynamics of a real scalar field for a large class of potentials in the symmetric Gaussian state, where the nonperturbative quantum contributions are taken into account, can be described equivalently by a two-dimensional nonlinear dynamical system with a definite angular momentum (U(1) charge of a complex theory). It is found that the

A. During, A. C. C. Coolen, D. Sherrington

We solve the dynamics of Hopfield-type neural networks which store sequences of patterns, close to saturation. The asymmetry of the interaction matrix in such models leads to violation of detailed balance, ruling out an equilibrium statistical mechanical analysis. Using generating functional methods we derive exact closed equations for dynamical order parame

K. Manabe, H. Ishimoto, N. Koide, Y. Sasago

We have measured the magnetic susceptibilities of single crystals of Cu_{1-x}Zn_xGeO_3 with extremely low Zn concentration (x) lower than x=5x10^{-3} at very low temperatures to investigate the spin-Peierls and antiferromagnetic transitions. The results show that the undoped CuGeO_3 has no antiferromagnetic phase down to 12 mK and there exists an antiferroma

G. N. Nugmanova

We study the solitonic excitations in the compressible ferromagnetic Heisenberg chain(in the continuum limit).

Th. M. Nieuwenhuizen

A system is glassy when the observation time is much smaller than the equilibration time. A unifying thermodynamic picture of the glassy state is presented. Slow configurational modes are in quasi-equilibrium at an effective temperature. It enters thermodynamic relations with the configurational entropy as conjugate variable. Slow fluctuations contribute to

Francesca Zambelli, Sandro Stringari

Using a sum rule approach we calculate the frequency shifts of the quadrupole oscillations of a harmonically trapped Bose gas due to the presence of a quantized vortex. Analytic results are obtained for positive scattering lengths and large N where the shift relative to excitations of opposite angular momentum is found to be proportional to the quantum circu

Wataru Izumida, Osamu Sakai, Yukihiro Shimizu

The tunneling conductance is calculated as a function of the gate voltage in wide temperature range for the single quantum dot systems with Coulomb interaction. We assume that two orbitals are active for the tunneling process. We show that the Kondo temperature for each orbital channel can be largely different. The tunneling through the Kondo resonance almos

K. A. Kikoin, M. N. Kiselev

A theory is proposed for kinetic effects in isotropic Heisenberg antiferromagnets at temperatures above the Neel point. A metod based on the analysis of a set of Feynman diagrams for the kinetic coefficients is developed for studying the critical dynamics. The scaling behavior of the generalized coefficient of spin diffusion and relaxation constant in the pa

Ioan Kosztin, Qijin Chen, Boldizsar Janko, K. Levin

The existence of a normal state spectral gap in underdoped cuprates raises important questions about the associated superconducting phase. For example, how does this pseudogap evolve into its below Tc counterpart? In this paper we characterize this unusual superconductor by investigating the nature of the ``residual'' pseudogap below Tc and, find tha

A. K. McMahan, C. Huscroft, R. T. Scalettar, E. L. Pollock

We describe current experimental and theoretical understanding of the pressure-induced volume collapse transitions occurring in the early trivalent rare earth metals. General features of orbitally realistic mean-field based theories used to calculate these transitions are discussed. Potential deficiencies of these methods are assessed by comparing mean field

Andreas Weymer, Martin Janssen

We study hierarchical network models which have recently been introduced to approximate the Chalker-Coddington model for the integer quantum Hall effect (A.G. Galstyan and M.E. Raikh, PRB 56 1422 (1997); Arovas et al., PRB 56, 4751 (1997)). The hierarchical structure is due to a recursive method starting from a finite elementary cell. The localization-deloca

H. Alt, C. Dembowski, H. -D. Graef, R. Hofferbert

High resolution eigenvalue spectra of several two- and three-dimensional superconducting microwave cavities have been measured in the frequency range below 20 GHz and analyzed using a statistical measure which is given by the distribution of the normalized mode fluctuations. For chaotic systems the limit distribution is conjectured to show a universal Gaussi

D. Psaltis, M. Mendez, R. Wijnands, J. Homan

Pairs of quasi-periodic oscillations (QPOs) at kilohertz frequencies are a common phenomenon in several neutron-star low-mass X-ray binaries. The frequency separation of the QPO peaks in the pair appears to be constant in many sources and directly related to the neutron star spin frequency. However, in Sco X-1 and possibly in 4U 1608-52, the frequency separa

A. R. Thakar, B. S. Ryden

We present the results of Smoothed Particle Hydrodynamics (SPH) simulations of the formation of a massive counterrotating disk in a spiral galaxy. The current study revisits and extends (with SPH) previous work carried out with sticky particle gas dynamics, in which adiabatic gas infall and a retrograde gas-rich dwarf merger were tested as the two most likel

C. Marinoni, P. Monaco, G. Giuricin, B. Costantini

By correcting the redshift--dependent distances for peculiar motions through a number of peculiar velocity field models, we recover the true distances of a wide, all-sky sample of nearby galaxies (~ 6400 galaxies with velocities cz<5500 km/s), which is complete up to the blue magnitude B=14 mag. Relying on catalogs of galaxy groups, we treat ~2700 objects as

S. Campana, M. Colpi, S. Mereghetti, L. Stella

Soft X-ray Transients (SXRTs) have long been suspected to contain old, weakly magnetic neutron stars that have been spun up by accretion torques. After reviewing their observational properties, we analyse the different regimes that likely characterise the neutron stars in these systems across the very large range of mass inflow rates, from the peak of the ou

J. M. Colberg, S. D. M. White, T. J. MacFarland, A. Jenkins

We investigate the peculiar velocities predicted for galaxy clusters by theories in the cold dark matter family. A widely used hypothesis identifies rich clusters with high peaks of a suitably smoothed version of the linear density fluctuation field. Their peculiar velocities are then obtained by extrapolating the similarly smoothed linear peculiar velocitie

A. K. H. Kong, P. A. Charles, E. Kuulkers

We report for the first time the detection of long-term X-ray variability in the bright bulge source GX 354-0 (=4U 1728-34) observed with the All Sky Monitor (ASM) on board the Rossi X-Ray Timing Explorer (RXTE). The 2-year RXTE ASM database reveals significant power at ~72 days. Similar behaviour was seen in the 6-year Ariel 5 ASM database, but at a period

M. Rode, H. M. Maitzen, E. Paunzen

A number of about 1500 spectroscopically classified CP2 stars in the southern sky (delta =-90 to -12 degrees) was extracted from the Michigan Catalogue (Vols. I - IV). This sample was compared with the classification from Bidelman & Mc Connell (1973). We confirmed the spectral classification with the known photometric peculiarity indices in the Geneva system

P. North, D. Erspamer, M. Kuenzli

Using Hipparcos parallaxes, we show that the metallic A-F giants found by Hauck (1986) on the basis of their high Delta m_2 index in Geneva photometry are on average more evolved than their non-metallic counterparts. Their mass distribution, rate of binaries and vsini are shown to be incompatible with those of Am stars, so that they cannot be descendants of

S. Hubrig, P. North, G. Mathys

The positions in the H-R diagram of strongly magnetic Ap and Bp stars are compared with those of normal main sequence stars of types B7 to F2, with a view to investigating possible differences in evolutionary status between magnetic and non-magnetic stars. The normal B7-F2 stars fill the whole width of the main sequence band with some concentration towards t

Marc Hempel, Hartmut Holweger, Inga Kamp

We present preliminary results of our search for circumstellar absorption features in the Ca K lines based on high S/N observations obtained with the ESO CAT/CES system.

F. A. Catalano, F. Leone

Some CP stars have recently been discovered by Catalano et al. (1991) to be variable also in the near infrared, although with smaller amplitudes than in the visible. Hence an observational campaign was started in which the infrared light variability of a number of CP2 and CP4 stars has been investigated at the ESO-La Silla Observatory in the bands J, H, and

J. Katz, D. Lynden-Bell, J. Bicak

Slowly rotating collapsing spherical shells have flat spaces inside and the inertial frames there rotate at omega_s(t) relative to infinity. As first shown by Lindblom & Brill the inertial axes within the shell rotate rigidly without time delays from one point to another. Although the rotation rate of the inertial axes is changing the axes are inertial so, r

I. Kh. Iliev, I. S. Barzova

The hydrogen-line spectrum of eight lambda Boo type stars is studied. The observed H_delta and H_gamma profiles are compared with Kurucz&#39;s theoretical profiles. The existence of weak emission-like details in the cores of five lambda Boo stars is demonstrated. The Inglis-Teller formula is used to calculate the electron densities. It is found that electron

G. A. Wade, J. -F. Donati, G. Mathys, N. Piskunov

We present preliminary results from a programme aimed at acquiring linear spectropolarimetry of magnetic A and B stars. Linear polarization in the spectral lines of these objects is due to the Zeeman effect, and should provide detailed new information regarding the structure of their strong magnetic fields. To illustrate the impact of these new data, we comp

S. Bagnulo

The observations in broadband linear polarization (BBLP) represent a powerful diagnostic tool for detecting the magnetic morphology of CP stars. In several cases, BBLP observations are not consistent with the prediction of the oblique rotator model with a simple dipolar field. Discrepancies between theoretical predictions and observations may partially be as

D. V. Vasil&#39;chenko, V. V. Stepanov, V. L. Khokhlova

An efficient method has been developed for solving the inverse problem of Doppler-Zeeman mapping of magnetic, chemically peculiar stars. A regularized iteration method is used to simultaneously solve the integral equations for the Stokes I, V, Q and U parameters. The validity of analytical fits to the local profiles of the Stokes parameters is substantiated.

R. Kuschnig

Doppler imaging, a technique which inverts spectral line profile variations of an Ap star into a two-dimensional abundance maps, provides new observational constraints on diffusion mechanism in the presence of a global magnetic field. A programme is presented here with the aim to obtain abundance distributions of at least five elements on each star, in order

C. M. Jomaron, M. M. Dworetsky, D. A. Bohlender

We report new results for the elemental and isotopic abundances of the normally rare elements mercury and platinum in HgMn stars. Typical overabundances can be 4 dex or more. The isotopic patterns do not follow the fractionation model of White et al (1976).

T. Ryabchikova

We present a short review of the abundances in the atmospheres of SB2 systems with Mercury-Manganese (HgMn) primaries. Up to now a careful study has been made for both components of 8 out of 17 known SB2 binaries with orbital periods shorter than 100 days and mass ratio ranging from 1.08 to 2.2. For all eight systems we observe a lower Mn abundance in the se

Glenn M. Wahlgren, Linus Dolk

We describe the early results of an investigation into the spectral characteristics of the hottest Am stars (A0 - A2) in an attempt to link the HgMn and Am classes of chemical peculiarity. A limited sample of hot-Am stars was searched for the presence of lines from the very heavy elements platinum and mercury, as well as a search for lines from the rare-eart

A. Hui-Bon-Hoa

Abundances of Mg, Ca, Sc, Cr, Fe, and Ni are derived for A stars of five nearby open clusters of various ages using high resolution spectroscopy. We point out a correlation between the abundance of Ca and that of Sc, suggesting that the abundance anomalies of these elements arise from the same physical process. Pronounced Am patterns are rather found in the

C. Moran, T. R. Marsh, V. S. Dhillon

We have discovered that the white dwarf PG 2329+267 is magnetic, and assuming a centered dipole structure, has a dipole magnetic field strength of approximately 2.3MG. This makes it one of only approximately 4% of isolated white dwarfs with a detectable magnetic field. Linear Zeeman splitting as well as quadratic Zeeman shifts are evident in the hydrogen Bal

B. Smalley, F. Kupka

We present a discussion on the effects of convection on the uvby colours of A and F stars. The mixing-length theory used in ATLAS9 is compared to the turbulent convection theory of Canuto & Mazzitelli (1991, 1992). Comparison with fundamental stars reveals that colours calculated using the Canuto & Mazzitelli convection theory are generally in better agreeme

F. Kupka, N. E. Piskunov

We describe a new method for the computation of opacity distribution functions (ODFs) useful to calculate one-dimensional model atmospheres in local thermal equilibrium (LTE). The new method is fast enough to be applied on current workstations and allows the computation of model atmospheres which deviate significantly from (scaled) solar chemical composition

C. van &#39;t Veer-Menneret, C. Bentolila, D. Katz

We show how previous works (Fuhrmann et al., van &#39;t Veer-Menneret & Megessier) demonstrate the efficiency of the use of Balmer line profiles for effective temperature determination. In agreement with them, we insist on the physical interest of this method based on the behaviour of these lines with the variations of the parameters involved in the treatmen

J. Budaj

A lot of evidence has recently accumulated that physical characteristics of CP stars (delta m_1, Ca/Fe ratio, Li abundance, distribution of orbital periods, vsini, Delta (V1-G), magnetic field) depend on orbital period or eccentricity. Consequently, the &#34;tidal mixing + stabilization&#34; hypothesis has been formulated to account for such features and the

R. Faraggiana, M. Gerbaldi

Since the identification of these stars by Morgan et al. in 1943, various definitions have been proposed for the stars of the Lambda Bootis group. We present here the various definitions which have been given to these objects in order to induce a general discussion on this topic.

I. Kamp, H. Holweger

High-resolution spectra of lambda Bootis stars reveal the presence of circumstellar gas for example in the Ca K line. The example of the normal A star beta Pictoris shows, that the narrow stable absorption component in Ca K can be reproduced using appropriate disk models and a calcium underabundance in the circumstellar gas of a factor of ~30. Similar models

U. Heiter

The results of the abundance analyses of six lambda Bootis stars are presented. For three stars, the impact of individual ODFs and various treatments of convection in the calculactions of the model atmospheres are investigated.

E. Paunzen

In this article the current knowledge of the group of lambda Bootis stars is reviewed. These metal poor objects are quite outstanding compared to other chemically peculiar stars of the upper main sequence. Up to now no theory has been developed which is able to explain the majority of observational results. This article is mainly focused on the work which ne

Martin J. Stift

Certain problems in the field of stellar atmospheres, polarized radiative transfer and magnetic field diagnostics cannot be addressed by means of traditional sequential programming techniques because CPU times become prohibitive on even the fastest single processor machines when realistic physics and accurate numerical methods are employed. This contribution

Stephen A. Drake

Before 1985, attempts to detect radio or X-ray emission from Magnetic CP (MCP) stars were either fruitless or ambiguous. However, more successful results have been obtained in the last dozen years: (i) Radio emission has now been detected from ~35 MCP stars of the Helium-peculiar and Silicon-strong subclasses, with a functional dependence of radio luminosity

N. Piskunov

The modern Doppler Imaging (DI) technique allows the reconstruction of different stellar surface structures based on accurate calculation of spectra of specific intensity. New applications like the mapping of the magnetic field vector put very stringent requirements on the radiative transfer (RT) solver which should be accurate, fast, and robust against nume

F. Castelli

The comparison of the observed and computed energy distributions of beta CrB has shown that a model with the specific chemical composition of the star can account for the visual enery distribution, while it is still unable to reproduce ultraviolet observations shortward of 1700 A. Furthermore, the predicted absorption of strong Fe II and Mg II UV lines is mu

R. R. Metsaev, A. A. Tseytlin

We construct the covariant kappa-symmetric superstring action for a type IIB superstring on AdS_5 x S^5 background. The action is defined as a 2d sigma-model on the coset superspace SU(2,2|4) / SO(4,1) x SO(5) and is shown to be the unique one that has the correct bosonic and flat space limits.

Paolo Aluffi, Carel Faber

The `linear orbit&#39; of a plane curve of degree d is its orbit in the projective space of dimension d(d+3)/2 parametrizing such curves under the natural action of PGL(3). In this paper we compute the degree of the closure of the linear orbits of most curves with positive dimensional stabilizers. Our tool is a nonsingular variety dominating the orbit closur

Sahraoui Chaieb, Sergio Rica

We investigate the instability of a tubular fluid membranes made of a water soluble surfactant. The tubules are obtained at high salinities. The instability is due to the introduction within the vesicle multilayer of an alkane. We measure the wavelength of this instability versus the unperturbed radius of the tubules. To interpretthis dependance we use a mod

David D. Song, Richard J. Szabo

The quantum corrections to the counting of statistical entropy for the 5+1-dimensional extremal black string in type-IIB supergravity with two observers are studied using anomalous Wess-Zumino actions for the corresponding intersecting D-brane description. The electric-magnetic duality symmetry of the anomalous theory implies a new symmetry between D-string

D. J. Broadhurst

In 3 dimensions, the Ising model is in the same universality class as $ϕ^4$-theory, whose massive 3-loop tetrahedral diagram, $C^{Tet}$, was of an unknown analytical nature. In contrast, all single-scale 4-dimensional tetrahedra were reduced, in hep-th/9803091, to special values of exponentially convergent polylogarithms. Combining dispersion relations with

J. P. Rueff, R. M. Galera, Ch. Giorgetti, E. Dartyge

The X-ray magnetic circular dichroism (XMCD) has been measured at the Co K edge in Co-hcp and R-Co compounds (R=La, Tb, Dy). The structure of the experimental XMCD spectra in the near-edge region has been observed to be highly sensitive to the magnetic environment of the absorbing site. Calculations of the XMCD have been carried out at the Co K edge in Co me

J. Fuchs, C. Schweigert

On the bundles of WZW chiral blocks over the moduli space of a punctured rational curve we construct isomorphisms that implement the action of outer automorphisms of the underlying affine Lie algebra. These bundle-isomorphisms respect the Knizhnik-Zamolodchikov connection and have finite order. When all primary fields are fixed points, the isomorphisms are e

Nikolaos Stergioulas

Rotating relativistic stars are receiving significant attention in recent years, because of the information they can yield about the equation of state of matter at extremely high densities and because they are one of the more possible sources of detectable gravitational waves. We review the latest theoretical and numerical methods for modeling rotating relat

Won Jae Chung, Michael W. Deem

We address via numerical simulation the two-dimensional bimolecular annihilation reaction $A + A \to \emptyset$ in the presence of quenched, random impurities. Renormalization group calculations have suggested that this reaction displays anomalous kinetics at long times, $c_{A}(t) \sim at^{δ-1}$, for certain types of topological or charged reactants and impu

D. A. Garanin

The integral relaxation time τ_{int} of thermoactivating noninteracting single-domain ferromagnetic particles is calculated analytically in the geometry with a magnetic field H applied parallel to the easy axis. It is shown that the drastic deviation of τ_{int}^{-1} from the lowest eigenvalue of the Fokker-Planck equation Λ_1 at low temperatures, starting fr

D. A. Garanin

A macroscopic equation of motion for the magnetization of a ferromagnet at elevated temperatures should contain both transverse and longitudinal relaxation terms and interpolate between Landau-Lifshitz equation at low temperatures and the Bloch equation at high temperatures. It is shown that for the classical model where spin-bath interactions are described

Prasad Subramanian, Peter A. Becker, Demosthenes Kazanas

We examine the possibility that the relativistic jets observed in many active galactic nuclei may be powered by the Fermi acceleration of protons in a tenuous corona above a two-temperature accretion disk. In this picture the acceleration arises as a consequence of the shearing motion of the magnetic field in the corona, which is anchored in the underlying K

Patrik Eden, Gosta Gustafson

We discuss some important issues concerning multiplicities in quark and gluon jets in e+e- annihilation. In QCD the properties of a jet in general depend on two scales, the energy and virtuality of the jet. Frequently theoretical predictions apply to a situation where these scales coincide, while for experimental data they are often different. Thus an analys

R. Nebauer, J. Aichelin

The average transverse energy of nucleons and intermediate mass fragments observed in the heavy ion reaction Xe(50A MeV)+Sn shows the same linear increase as a function of their mass as observed in heavy ion collisions up to the highest ene rgies available today and fits well into the systematics. At higher energies this observation has been interpreted as a

M. De Menech, A. L. Stella, C. Tebaldi

Due to intermittency and conservation, the Abelian sandpile in 2D obeys multifractal, rather than finite size scaling. In the thermodynamic limit, a vanishingly small fraction of large avalanches dominates the statistics and a constant gap scaling is recovered in higher moments of the toppling distribution. Thus, rare events shape most of the scaling pattern

S. Digal, R. Ray, S. Sengupta, A. M. Srivastava

We demonstrate the possibility of forming a single, large domain of disoriented chiral condensate (DCC) in a heavy-ion collision. In our scenario, rapid initial heating of the parton system provides a driving force for the chiral field, moving it away from the true vacuum and forcing it to go to the opposite point on the vacuum manifold. This converts the en

M. S. Cunha

The theoretical work on roAp stars is reviewed, especially in relation with observational facts that still need to be understood: high frequencies of the modes observed, which can be higher than the theoretical critical cutoff frequency for acoustic modes in these stars; their apparent alignment with the magnetic field, and the fact that some modes cannot be

V. M. Braun, S. E. Derkachov, A. N. Manashov

We show that Brodsky-Lepage evolution equation for the leading twist spin 3/2 baryon distribution amplitude is completely integrable and reduces to the three-particle XXX_{s=-1} Heisenberg spin chain. Trajectories of the anomalous dimensions are identified and calculated using the 1/N expansion. Extending this result, we prove integrability of the evolution

Luis J. Garay, Guillermo A. Mena Marugan

The generalised Wick transform discovered by Thiemann provides a well-established relation between the Euclidean and Lorentzian theories of general relativity. We extend this Thiemann transform to the Ashtekar formulation for gravity coupled with spin-1/2 fermions, a non-Abelian Yang-Mills field, and a scalar field. It is proved that, on functions of the gra

S. Groote, J. G. Körner, A. A. Pivovarov

We present a new method to investigate a class of diagrams which generalizes the sunset topology to any number of massive internal lines. Our attention is focused on the computation of the spectral density of these diagrams which is related to many-body phase space in $D$ dimensional space-time. The spectral density is determined by the inverse $K$-transform

Victor M. Eguiluz, Preben Alstrom, Emilio Hernandez-Garcia, Oreste Piro

Chaotic pattern dynamics in many experimental systems show structured time averages. We suggest that simple universal boundary effects underly this phenomenon and exemplify them with the Kuramoto-Sivashinsky equation in a finite domain. As in the experiments, averaged patterns in the equation recover global symmetries locally broken in the chaotic field. Pla

Bodo Huckestein, Rochus Klesse

We study the time evolution of wave packets at the mobility edge of disordered non-interacting electrons in two and three spatial dimensions. The results of numerical calculations are found to agree with the predictions of scaling theory. In particular, we find that the $k$-th moment of the probability density $<r^k >(t)$ scales like $t^{k/d}$ in $d$ dimensi

M. Contini, M. A. Prieto, S. M. Viegas

Simultaneous modeling of the line and continuum emission from the nuclear region of the Circinus galaxy is presented. Composite models which include the combined effect of shocks and photoionization from the active center and from the circumnuclear star forming region are considered. The effects of dust reradiation, bremsstrahlung from the gas and synchrotro

Ryu Takayama, Osamu Sakai

We study how the Kondo effect is affected by the Coulomb interaction between conduction electrons on the basis of a simplified model. The single impurity Anderson model is extended to include the Coulomb interaction on the nearest-neighbour ligand orbital. The excitation spectra are calculated using the numerical renormalization group method. The effective b