March 1998 arXiv papers — page 3

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

We introduce a set of scalar fields as test fields to study the dynamical behaviors of the BTZ (Banados-Teitelboim-Zanelli) black hole. These include minimally coupled scalar, conformally coupled scalar, dilaton, and tachyon. To calculate the decay rate of the BTZ black hole, we consider both the Dirichlet boundary condition at spatial infinity and the stabi

Walter T Strunz, Lajos Diosi, Nicolas Gisin

A non-Markovian stochastic Schroedinger equation for a quantum system coupled to an environment of harmonic oscillators is presented. Its solutions, when averaged over the noise, reproduce the standard reduced density operator without any approximation. We illustrate the power of this approach with several examples, including exponentially decaying bath corr

Adonai S. Sant'Anna

We have recently showed that it is possible to deal with collections of indistinguishable elementary particles (in the context of quantum mechanics) in a set-theoretical framework by using hidden variables, in a sense. In the present paper we use such a formalism as a model for quasi-set theory. Quasi-set theory, based on Zermelo-Fraenkel set theory, was dev

Petr A. Braun, Daniel Braun, Fritz Haake, Joachim Weber

A well known description of superradiance from pointlike collections of many atoms involves the dissipative motion of a large spin. The pertinent ``superradiance master equation'' allows for a formally exact solution which we subject to a semiclassical evaluation. The clue is a saddle-point approximation for an inverse Laplace transform. All previous

S. Esposito, M. W. Evans, E. Recami

The Dirac equation is solved for two novel terms which describe the interaction energy between the half integral spin of a fermion and the classical, circularly polarized, electromagnetic field. A simple experiment is suggested to test the new terms and the existence of radiation induced fermion resonance.

N. Pietralla, P. von Brentano, T. Otsuka, R. F. Casten

The wavefunctions of the lowest odd spin positive parity yrast states in the IBA are shown to be nearly pure multiple quadrupole-phonon excitations even outside the three dynamical symmetries. The empirical data for collective nuclei with 30 < Z < 80 confirm these predictions. The quadrupole-phonon purity of the 2^+_1 state can be measured from E2-branching

Ryszard Nest, Boris Tsygan

We define for an associative algebra an $A_{\infty}$ category whose objects are automorphisms of this algebra. This construction has some resemblance with Fukaya&#39;a categories related to Floer cohomology.

Kevin P. Knudson

We show that if R is an integral domain with many units, then the inclusion E_2(R) --> E_2(R[t]) induces an isomorphism in integral homology. This is a consequence of the existence of an amalgamated free product decomposition for E_2(R[t]). We also use this decomposition to study the homology of E_2(Z[t]). We show that H_i(E_2(Z[t]),Z) contains a countable r

H. R. Morton

A simple multivariable version of the reduced Burau matrix is constructed for any braid. It is shown how the multivariable Alexander polynomial for the closure of the braid can be found directly from this matrix.

Michael Farber, Eugenii Shustin

As is well-known, the Witten deformation of the De Rham complex computes the De Rham cohomology. In this paper we study the Witten deformation on a noncompact manifold and restrict it to differential forms which behave polynomially near infinity. Such polynomial differential forms naturally appear on manifolds with a cylindrical structure. We prove that the

F. Bagarello

In this paper we discuss some physical applications of topological *-algebras of unbounded operators. Our first example is a simple system of free bosons. Then we analyze different models which are related to this one. We also discuss the time evolution of two interacting models of matter and bosons. We show that for all these systems it is possible to build

Pyszard Nest, Boris Tsygan

We define several versions of the cohomology ring of an associative algebra. These ring structures unify some well known operations from homological algebra and differential geometry. They have some formal resemblance with the quantum multiplication on Floer cohomology of free loop spaces. We discuss some examples, as well as applications to index theorems,

E B Davies

We propose a method for obtaining rigorous and accurate upper and lower bounds on the eigenvalues of ordinary and partial differential operators in bounded regions of Euclidean space. It uses a boundary condition homotopy method starting from a decomposition of the region into several simpler regions for which the eigenvalues can already be computed accurate

J. F. Gomes, G. M. Sotkov, A. H. Zimerman

We investigate a class of conformal Non-Abelian-Toda models representing a noncompact $SL(2,R)/U(1)$ parafermionions (PF) interacting with a specific abelian Toda theories and having a global U(1) symmetry. A systematic derivation of the conserved currents, their algebras and the exact solution of these models is presented. An important property of this clas

Christian Jaekel

We study the cluster properties of thermal equilibrium states in theories with a maximal propagation velocity (such as relativistic QFT). Our analysis, carried out in the setting of algebraic quantum field theory, shows that there is a tight relation between spectral properties of the generator of time translations and the decay of spatial correlations in th

Silvia Penati, Andrea Refolli, Alexander Sevrin, Daniela Zanon

We study renormalizable nonlinear sigma-models in two dimensions with N=2 supersymmetry described in superspace in terms of chiral and complex linear superfields. The geometrical structure of the underlying manifold is investigated and the one-loop divergent contribution to the effective action is computed. The condition of vanishing beta-function allows to

S. Ansoldi, A. Aurilia, E. Spallucci

We discuss the relation between string quantization based on the Schild path integral and the Nambu-Goto path integral. The equivalence between the two approaches at the classical level is extended to the quantum level by a saddle--point evaluation of the corresponding path integrals. A possible relationship between M-Theory and the quantum mechanics of stri

V. Barger

Muon colliders offer special opportunities to discover and study new physics. With the high intensity source of muons at the front end, orders of magnitude improvements would be realized in searches for rare muon processes, in deep inelastic muon and neutrino scattering experiments, and in long-baseline neutrino oscillation experiments. At a 100 to 500 GeV m

H. Arthur Weldon

By employing retarded and advanced propagators, Aurenche and Becherrawy showed how to rewrite the real-time thermal Feynman rules so that the temperature dependence is removed from the free propagators and transferred to the vertices. The present paper introduces retarded and advanced field operators and incorporates all temperature dependence into the inter

R. Baier, Yu. L. Dokshitzer, A. H. Mueller, D. Schiff

We study analytically the medium-induced energy loss of a high energy parton passing through a finite size QCD plasma, which is expanding longitudinally according to Bjorken&#39;s model. We extend the BDMPS formalism already applied to static media to the case of a quark which hits successive layers of matter of decreasing temperature, and we show that the r

S. Esposito, N. Tancredi

From a phenomenological point of view, we study active-active and active-sterile flavour-changing (and flavour-conserving) oscillations of Dirac-Majorana neutrinos both in vacuum and in matter. The general expressions for the transition probabilities in vacuum are reported. We then investigate some interesting consequences following from particular simple fo

F. Iddir, S. Safir O. Pène

Hybrid $ c \bar c g$ of quantum numbers $1^{--}$ are considered in a quark model with constituant quarks and gluon. The lowest $J^P=1^-$ states may be built in two ways, $l_g=1$ (gluon excited) corresponding to an angular momentum between the gluon and the $c \bar c$ system, while $l_{c\bar c}=1$ (quark excited) corresponds to an angular momentum between the

C. A. Dominguez, C. van Gend, M. Loewe

The pion nucleon vertex function at finite temperature is studied in the framework of: (a) the thermal (linear) sigma model to leading (one-loop) order, and (b) a thermal QCD-Finite Energy Sum Rule. Results from both methods indicate that the strength of the pion-nucleon coupling decreases with increasing T, vanishing at a critical temperature. The associate

Pushpalatha Bhat, Estia Eichten

New strong dynamics at the energy scale ~ 1 TeV is an attractive and elegant theoretical ansatz for the origin of electroweak symmetry breaking. We review here the theoretical models for strong dynamics, particularly, technicolor theories and their low energy signatures. We emphasize that the fantastic beam energy resolution (sigma_E/E ~10^{-4}) expected at

M. H. R. Khan, A. Murakami, T. Sumiyoshi, T. Kuniya

We report on a design and performances of a monitoring system developed for the aerogel Cherenkov counters (ACC) of the BELLE detector. The system consists of blue LEDs, a diffuser box, and optical distributors which distribute the LED light to the ACC modules. The employed LED (NSPB series) has been observed to have high reliability on the long term stabili

Diego F Torres, Franz E Schunck, Andrew R Liddle

We make a detailed study of boson star configurations in Jordan--Brans--Dicke theory, studying both equilibrium properties and stability, and considering boson stars existing at different cosmic epochs. We show that boson stars can be stable at any time of cosmic history and that equilibrium stars are denser in the past. We analyze three different proposed m

G. N. Parfionov, R. R. Zapatrin

The Connes formula giving the dual description for the distance between points of a Riemannian manifold is extended to the Lorentzian case. It resulted that its validity essentially depends on the global structure of spacetime. The duality principle classifying spacetimes is introduced. The algebraic account of the theory is suggested as a framework for quan

Hideo Kodama

This is a summary report of the workshop D2 in GR15. In this workshop rather diverging problems related to quantum gravity and quantum cosmology were discussed. Since it is almost impossible to summarize all these discussions in coherent and integrated expressions, in this report, I give a brief description of the content of each paper in order, with some ad

Anton Yu. Alekseev, Vadim V. Cheianov, Juerg Froehlich

We study transport in a class of physical systems possessing two conserved chiral charges. We describe a relation between universality of transport properties of such systems and the chiral anomaly. We show that the non-vanishing of a current expectation value implies the presence of gapless modes, in analogy to the Goldstone theorem. Our main tool is a new

D. Das, S. Doniach

In this paper, we argue that, in 2-d, the weak localisation of bosons, which occurs on the insulating side of the superconductor-insulator transition, is characterised by $ρ\sim ln(1/T)$, as compared to $σ\sim lnT$ for fermions. Such an unconventional behaviour is tied to the diffusion pole of the delocalised (uncondensed) vortices.

David Wales, Jonathan Doye

We describe a global optimization technique using `basin-hopping&#39; in which the potential energy surface is transformed into a collection of interpenetrating staircases. This method has been designed to exploit the features which recent work suggests must be present in an energy landscape for efficient relaxation to the global minimum. The transformation

Rainer Merkt, Martin Janssen, Bodo Huckestein

We introduce a network model to describe two-dimensional disordered electron systems with spin-orbit scattering. The network model is defined by a discrete unitary time evolution operator. We establish by numerical transfer matrix calculations that the model exhibits a localization-delocalization transition. We determine the corresponding phase diagram in th

Tomaz Prosen

Berry-Robnik level spacing distribution is demonstrated clearly in a generic quantized plane billiard for the first time. However, this ultimate semi-classical distribution is found to be valid only for extremely small semi-classical parameter (effective Planck&#39;s constant) where the assumption of statistical independence of regular and irregular levels i

Giulio Casati, Tomaz Prosen

We study the quantum behaviour of the stadium billiard. We discuss how the interplay between quantum localization and the rich structure of the classical phase space influences the quantum dynamics. The analysis of this model leads to new insight in the understanding of quantum properties of classically chaotic systems.

V. N. Antonov, H. Takayanagi, F. K. Wilhelm, A. D. Zaikin

Interference of proximity induced superconducting correlations in mesoscopic metallic rings is sensitive to the magnetic flux $Φ$ inside these rings. This is the reason for magnetoconductance oscillations in such systems. We detected experimentally and explained theoretically a novel effect: the phase of these oscillations can switch between 0 and $π$ depend

Daniel A. Lidar

The Sudden Approximation (SA) for scattering of atoms from surfaces is generalized to allow for double collision events and scattering from time-dependent quantum liquid surfaces. The resulting new schemes retain the simplicity of the original SA, while requiring little extra computational effort. The results suggest that inert atom (and in particular He) sc

Y. Naveh, D. V. Averin, K. K. Likharev

Using the &#39;drift-diffusion-Langevin&#39; equation, we have quantitatively analyzed the effects of electron energy relaxation via their interaction with phonons, generally in presence of electron-electron interaction, on shot noise in diffusive conductors. We have found that the noise power $ S_I(ω)$ (both at low and high observation frequencies $ω$) drop

Kihong Kim

We develop a novel and powerful method of exactly calculating various transport characteristics of waves in one-dimensional random media with (or without) coherent absorption or amplification. Using the method, we compute the probability densities of the reflectance and of the phase of the reflection coefficient, together with the localization length, of ele

J. H. Oaknin, B. Paredes, C. Tejedor

A microscopic description of (baby)skyrmions in quantum Hall ferromagnets is derived from a scattering theory of collective (neutral) spin modes by a bare quasiparticle. We start by mapping the low lying spectrum of spin waves in the uniform ferromagnet onto that of free moving spin excitons, and then we study their scattering by the defect of charge. In the

Daniel M. Bikel, Scott Miller, Richard Schwartz, Ralph Weischedel

This paper presents a statistical, learned approach to finding names and other non-recursive entities in text (as per the MUC-6 definition of the NE task), using a variant of the standard hidden Markov model. We present our justification for the problem and our approach, a detailed discussion of the model itself and finally the successful results of this new

P. Castiglione, A. Crisanti, A. Mazzino, M. Vergassola

Explicit examples of scalar enhanced diffusion due to resonances between different transport mechanisms are presented. Their signature is provided by the sharp and narrow peaks observed in the effective diffusivity coefficients and, in the absence of molecular diffusion, by anomalous transport. For the time-dependent flow considered here, resonances arise be

Ramandeep S. Johal

The purpose of this letter is to define a distance on the underlying phase space of a chaotic map, based on natural invariant density of the map. It is observed that for logistic map this distance is equivalent to Wootters&#39; statistical distance. This distance becomes the Euclidean distance for a map with constant invariant density.

Jean-Pierre Eckmann, Claude-Alain Pillet, Luc Rey-Bellet

We study the statistical mechanics of a finite-dimensional non-linear Hamiltonian system (a chain of anharmonic oscillators) coupled to two heat baths (described by wave equations). Assuming that the initial conditions of the heat baths are distributed according to the Gibbs measures at two different temperatures we study the dynamics of the oscillators. Und

Krzysztof Gawedzki

The paper reviews some of the recent progress in the understanding of anomalous scaling and intermittency in a simple hydrodynamical model. It is directed to a non-specialized audience.

Wolfgang Brandner, Rainer Koehler

We have carried out K-band speckle observations of a sample of 114 X-ray selected weak-line T Tauri stars in the nearby Scorpius-Centaurus OB association. We find that for binary T Tauri stars closely associated to the early type stars in Upper Scorpius, the youngest subgroup of the OB association, the peak in the distribution of binary separations is at 90

D. Galli, F. Palla

The process of molecule formation in the primordial gas is considered in the framework of Friedmann cosmological models from redshift z=1e4 to z=0. First, a comprehensive analysis of 87 gas phase reaction rates (both collisional and radiative) relevant in the physical environment of the expanding universe is presented and critically discussed. On this basis,

D. Lutz, D. Kunze, H. W. W. Spoon, M. D. Thornley

We report the detection of faint emission in the high-excitation [OIV] 25.90um line in a number of starburst galaxies, from observations obtained with the Short Wavelength Spectrometer (SWS) on board ISO. Further observations of M82 spatially resolve the [OIV] emitting region. Detection of this line in starbursts is surprising since it is not produced in mea

S. Moehler, W. Landsman, R. Napiwotzki

We have obtained medium-resolution spectra of seven UV-bright stars discovered on images of four southern globular clusters obtained with the Ultraviolet Imaging Telescope (UIT). Effective temperatures, surface gravities and helium abundances are derived from LTE and non-LTE model atmosphere fits. Three of the stars have sdO spectra, including M4-Y453 (Teff

Palash B. Pal

In this talk, I have discussed some issues of recent interest and activity in the field of neutrino astrophysics and cosmology. The topics are: (1)~The origin of high peculiar velocities of pulsars; (2)~Energization of the supernova shock wave; (3)~Ultra-high energy neutrino astronomy; (4)~Possible implications of the recent measurements of low deuterium abu

Andrea Cimatti, Sperello di Serego Alighieri, Joël Vernet, Marshall H. Cohen

We present the results of deep spectropolarimetry of two powerful radio galaxies at $z\sim2.5$ (4C 00.54 and 4C 23.56) obtained with the W.M. Keck II 10m telescope, aimed at studying the relative contribution of the stellar and non-stellar components to the ultraviolet continuum. Both galaxies show strong linear polarization of the continuum between rest-fra

R. A. E. Fosbury, J. Vernet, M. Villar-Martin, M. H. Cohen

As a prerequisite for interpreting new observations of the most distant radio galaxies, we make an optical study of the closest powerful radio source, Cygnus A. Using Keck imaging- and spectro-polarimetry in conjunction with HST, WFPC2 broad and narrow band imaging, we are able to identify specific geometrical structures in the galaxy with optical continuum

Chris Shrader, Lev Titarchuk

We discuss the emergent spectra from accreting black holes, considering in particular the case where the accretion is characterized by relativistic bulk motion. We suggest that such accretion is likely to occur in a wide variety of black hole enviroments, where the strong gravitational field is expected to dominate the pressure forces, and this likely to lea

W. J. G. de Blok, J. M. van der Hulst

We present measurements of the oxygen abundances in 64 HII regions in 12 LSB galaxies. We find that oxygen abundances are low. No regions with solar abundance have been found, and most have oxygen abundances $\sim 0.5$ to 0.1 solar. The oxygen abundance appears to be constant as a function of radius, supporting the picture of quiescently and sporadically evo

Efrain J. Ferrer, Vivian de la Incera

We derive the Ward-Takahashi identity obeyed by the fermion-antifermion-gauge boson vertex in ladder QED in the presence of a constant magnetic field. The general structure in momentum space of the fermion mass operator with external electromagnetic field is discussed. Using it we find the solutions of the ladder WT identity with magnetic field. The consiste

Norman H. Shakespeare, Howard D. Trottier

A comprehensive analysis of tadpole-improved SU(2) lattice gauge theory is made. Simulations are done on isotropic and anisotropic lattices, with and without improvement. Two tadpole renormalization schemes are employed, one using average plaquettes, the other using mean links in Landau gauge. Simulations are done with spatial lattice spacings $a_s$ in the r

Jerome P. Gauntlett, Neil D. Lambert, Peter C. West

The fivebrane worldvolume theory in eleven dimensions is known to contain BPS threebrane solitons which can also be interpreted as a fivebrane whose worldvolume is wrapped around a Riemann surface. By considering configurations of intersecting fivebranes and hence intersecting threebrane solitons, we determine the Bogomol&#39;nyi equations for more general B

Pierre Leroux, Etienne Rassart, Ariane Robitaille

This paper concerns the enumeration of rotation-type and congruence-type convex polyominoes on the square lattice. These can be defined as orbits of the groups C4, of rotations, and D4, of symmetries of the square acting on (translation- type) polyominoes. In virtue of Burnside&#39;s Lemma, it is sufficient to enumerate the various symmetry classes (fixed po

Keith R. Dienes, Emilian Dudas, Tony Gherghetta

We study the effects of extra spacetime dimensions at intermediate mass scales, as expected in string theories with large-radius compactifications, and focus on the gauge and Yukawa couplings within the Minimal Supersymmetric Standard Model. We find that extra spacetime dimensions naturally lead to the appearance of grand unified theories at scales substanti

G. Curio

In the framework of N=1 supersymmetric string models given by the heterotic string on an elliptic Calabi-Yau $π:Z\ra B$ together with a SU(n) bundle we compute the chiral matter content of the massless spectrum. For this purpose the net generation number, i.e. half the third Chern class, is computed from data related to the heterotic vector bundle in the spe

K. Golec-Biernat, J. Kwiecinski, A. D. Martin

We propose exclusive diffractive dijet photoproduction as an ideal measure of the off-diagonal gluon distribution at high scales. We solve the off-diagonal evolution equations for the gluon and quark singlet over the full kinematic domain. We discuss the nature of the solutions of these equations, which embody both DGLAP and ERBL evolution. We give predictio

A. Diercks, E. W. Deutsch, F. J. Castander, C. Corson

We present an R-band and J-band photometry of an optical transient which is likely to be associated with the gamma-ray burst event GRB 971214. Our first measurement took place 13 hours after the gamma-ray event. The brightness decayed with a power-law exponent alpha = -1.20 +- 0.02, which is similar to those of GRB 970228 and GRB 970508 which had exponents o

W. Bietenholz

We discuss a number of lattice fermion actions solving the Ginsparg-Wilson relation. We also consider short ranged approximate solutions. In particular, we are interested in reducing the lattice artifacts, while avoiding (or suppressing) additive mass renormalization. In this context, we also arrive at a formulation of improved domain wall fermions.

Chao-Shang Huang, Wei Liao, Qi-Shu Yan

It is shown that in supersymmetric models (SUSYMs) the large supersymmetric contributions to $B \to X_s{\mu}^{+}{\mu}^{-}$ come from the Feynman diagrams which consist of exchanging neutral Higgs bosons (NHBs) and the chargino-stop loop and are proportional to $m_b m_{\mu}$tan$^3\beta/m_{h}^2$ when tan$\beta$ is large and the mass of the lightest neutral Hig

T. M. Aliev, E. O. Iltan

We calculate the leading logarithmic QCD corrections to the decay B_{s} -->γγin the two Higgs doublet model with tree level flavor changing currents (model III) including O_7 type long distance effects. Further, we analyse the dependencies of the branching ratio Br(B_{s} --> γγ)$ and the ratio of CP-even and CP-odd amplitude squares, R=|A^{+}|^2/|A^{-}|^2, o

Kanehisa Takasaki

The $u$-plane integrals of topologically twisted $N = 2$ supersymmetric gauge theories generally contain contact terms of nonlocal topological observables. This paper proposes an interpretation of these contact terms from the point of view of integrable hierarchies and their Whitham deformations. This is inspired by Mariño and Moore&#39;s remark that the blo

Pradip Roy, Sourav Sarkar, Jan-e Alam, Bikash Sinha

The modifications of hadronic masses and decay widths at finite temperature and baryon density are investigated using a phenomenological model of hadronic interactions in the Relativistic Hartree Approximation. We consider an exhaustive set of hadronic reactions and vector meson decays to estimate the photon emission from hot and dense hadronic matter. The r

Masaru Shibata

We present relativistic hydrostatic equations for obtaining irrotational binary neutron stars in quasi equilibrium states in 3+1 formalism. Equations derived here are different from those previously given by Bonazzola, Gourgoulhon, and Marck, and have a simpler and more tractable form for computation in numerical relativity. We also present hydrostatic equat

T. Boyadjiev, P. Fiziev, S. Yazadjiev

We develop the general theory of stars in Saa&#39;s model of gravity with propagating torsion and study the basic stationary state of neutron star. Our numerical results show that the torsion force decreases the role of the gravity in the star configuration leading to significant changes in the neutron star masses depending on the equation of state of star m

Hai-Yang Cheng, B. Tseng

Nonfactorizable effects in hadronic charmless B -> PP, VP decays can be parametrized in terms of the effective number of colors N_c in the effective parameters $a_i^{eff}$ that are linear combinations of Wilson coefficients. It is shown that N_c(V+A) in the penguin amplitudes induced by the (V-A)(V+A) four-quark operators is different from N_c(V-A) in the de

Bambi Hu, Baowen Li, Jie Liu, Ji-Lin Zhou

We study kicked quantum systems by using the squeezed state approach. Taking the kicked quantum harmonic oscillator as an example, we demonstrate that chaos in an underlying classical system can be enhanced as well as suppressed by quantum fluctuations. Three different energy diffusions are observed in the kicked quantum harmonic oscillator, namely, localiza

Raymond R. Volkas, Yvonne Y. Y. Wong

Energy-dependent solar neutrino flux reduction caused by the Mikheyev-Smirnov-Wolfenstein (MSW) effect is applied to the Exact Parity Model. Several scenarios are possible, depending on the region of parameter space chosen. The interplay between intergenerational MSW transitions and vacuum ``intragenerational&#39;&#39; ordinary-mirror neutrino oscillations i

Rainer Dietrich, Manfred Opper

Using methods of statistical mechanics, we analyse the effect of outliers on the supervised learning of a classification problem. The learning strategy aims at selecting informative examples and discarding outliers. We compare two algorithms which perform the selection either in a soft or a hard way. When the fraction of outliers grows large, the estimation

Jens Erler

I calculate the QED coupling, alpha, directly in the MS-bar scheme using an unsubtracted dispersion relation for the three light quarks, and perturbative QCD for charm and bottom quarks. Compact analytical expressions are presented, making this approach particularly suitable for electroweak fits. After alpha^(-1) (m_tau) = 133.513 +- 0.025 is obtained in a f

C. Gazza, G. Martins, J. Riera, E. Dagotto

The stability of hole bound states in the t-J model including short-range Coulomb interactions is analyzed using computational techniques on ladders with up to $2 \times 30$ sites. For a nearest-neighbors (NN) hole-hole repulsion, the two-holes bound state is surprisingly robust and breaks only when the repulsion is several times the exchange $J$. At $\sim 1

L. Hlavaty

The equations that define the Lax pairs for generalized principal chiral models can be solved for any nondegenerate bilinear form on $su(2)$. The solution is dependent on one free variable that can serve as the spectral parameter.

M. Dakna, L. Knoll, D. -G. Welsch

State preparation via conditional output measurement on a beam splitter is studied, assuming the signal mode is mixed with a mode prepared in a Fock state and photon numbers are measured in one of the output channels. It is shown that the mode in the other output channel is prepared in either a photon-subtracted or a photon-added Jacobi polynomial state, dep

Decio Krause, Adonai S. Sant&#39;Anna, Analice G. Volkov

Quasi-set theory provides a mathematical background for dealing with collections of indistinguishable elementary particles. In this paper, we show how to obtain the quantum statistics into the scope of quasi-set theory and discuss the Helium atom, which represents the simplest example where indistinguishability plays an important role. A brief discussion abo

Luca Salasnich

Bose-Einstein condensation (BEC) in a gas has now been achieved. Alkali atoms ($^{87}Rb$, $^{23}Na$ and $^{7}Li$) have been cooled to the point of condensation (temperature of 100 nK) using laser cooling and trapping, followed by magnetic trapping and evaporative cooling. This important experimental result has also renewed the interest on theoretical studies

S. Chaturvedi, A. K. Kapoor, V. Srinivasan

Various methods of constructing an orthonomal set out of a given set of linearly independent vectors are discussed. Particular attention is paid to the Gram-Schmidt and the Schweinler-Wigner orthogonalization procedures. A new orthogonalization procedure which, like the Schweinler- Wigner procedure, is democratic and is endowed with an extremal property is s

Artur Ekert, Richard Jozsa

We discuss the fundamental role of entanglement as the essential nonclassical feature providing the computational speed-up in the known quantum algorithms. We review the construction of the Fourier transform on an Abelian group and the principles underlying the fast Fourier transform algorithm. We describe the implementation of the FFT algorithm for the grou

J. Fuchs, A. Ch. Ganchev, K. Szlachanyi, P. Vecsernyes

We show that a left-rigid monoidal C^*-category with irreducible monoidal unit is also a sovereign and spherical category. Defining a Frobenius-Schur type indicator we obtain selection rules for the fusion coefficients of irreducible objects. As a main result we prove S_4-invariance of 6j-symbols in such a category.

D. R Bes, O. Civitarese, N. N. Scoccola

A consistent treatment of intrinsic and collective coordinates is applied to the calculation of matrix elements describing nuclear double beta decay transitions. The method, which was developed for the case of nuclear rotations, is adapted to include isospin and number of particles degrees of freedom. It is shown that the uncertainties found in most models,

Zoltan Batiz, Franz Gross

In this paper we reconcile two contradictory statements about deep inelastic scattering (DIS) in manifestly covariant theories: (i) the scattering must be gauge invariant, even in the deep inelastic limit, and (ii) the pole term (which is not gauge invariant in a covariant theory) dominates the scattering amplitude in the deep inelastic limit. An ``intermedi

S Misicu

The work deals with one of the topics of collective motion. In the frame of Nuclear Fluid Dynamics, a model which portrays the nuclear matter as a quantum elastic body, the torus-like motions and their associated energies are computed using the thirteen moment approximation. The spin-dependent collective excitations, with toroidal electromagnetic structure,

S Misicu, A Sandulescu, W Greiner

We predict a molecular vibrational state in the cold binary fission of $^{252}$Cf using a simple decay cluster model. The Hamiltonian of two even-even fragments in the pole-pole configuration is built in the same fashion as that for the dinuclear molecule formed in heavy-ions collisions. The interaction between the two fragments is described by the double-fo

A. Sandulescu, F. Carstoiu, S. Misicu, A. Florescu

A new type of decay corresponding to the neutronless $^{10}$Be-accompanied fragmentation of $^{252}$Cf is studied. We employ a cluster model similar to the model used for the description of cluster radioactivity. No preformation factors were considered. The ternary relative isotopic yields were calculated as the ratio of the penetrability of a given ternary

A. Sandulescu, S. Misicu, F. Carstoiu, A. Florescu

We study the binary cold fission of $^{252}$Cf in the frame of a cluster model where the fragments are born to their respective ground states and interact via a double-folded potential with deformation effects taken into account up to multipolarity $λ=4$. The preformation factors were neglected. In the case when the fragments are assumed to be spherical or w

P. Danielewicz, Roy A. Lacey, P. -B. Gossiaux, C. Pinkenburg

Using a relativistic hadron transport model, we investigate the utility of the elliptic flow excitation function as a probe for the stiffness of nuclear matter and for the onset of a possible quark-gluon-plasma (QGP) phase-transition at AGS energies 1 < E_Beam < 11 AGeV. The excitation function shows a strong dependence on the nuclear equation of state, and

B. Davids, D. W. Anthony, Sam M. Austin, D. Bazin

In an effort to understand the implications of Coulomb dissociation experiments for the determination of the 7Be(p,gamma)8B reaction rate, longitudinal momentum distributions of 7Be fragments produced in the Coulomb dissociation of 44 and 81 MeV/nucleon 8B beams on a Pb target were measured. These distributions are characterized by asymmetries interpreted as

W. Trautmann, ALADIN collaboration

New results for the masses, excitation energies, temperatures, and densities of excited spectator systems at breakup are presented. They were obtained in two recent experiments with the ALADIN spectrometer at SIS in which reactions of Au-197 on Au-197 in the regime of relativistic energies up to 1 GeV per nucleon were studied. The methods used to extract the

E B Davies

We prove that the spectrum of certain non-self-adjoint Schrodinger operators is unstable in the semi-classical limit. Similar results hold for a fixed operator in the high energy limit. The method involves the construction of approximate semi-classical modes of the operator by the JWKB method for energies far from the spectrum.

Aleksandrs Mihailovs

This work develops a methodical approach to counting of walks on cartesian products, biproducts, symmetric and exterior powers and bipowers, Schur operations, coverings and semicoverings of weighted graphs. For weight and root lattices of semisimple Lie algebras, this approach allows us to compute various combinatorial and representation-theoretical constant

P. M. Hajac, R. Matthes

We construct a quantum frame bundle of the quantum plane $C^2_p$ by requiring that a $GL_{q,p}(2)$-covariant differential calculus on $C^2_p$ be isomorphic as a bimodule to the space of sections of the associated quantum cotangent bundle. We also construct the section space of the associated quantum tangent bundle, and show that it is naturally dual to the d

Noriaki Kitazawa, Francesco Sannino

A new method of deriving the Higgs Lagrangian from vector-like gauge theories is explored. After performing a supersymmetric extension of gauge theories we identify the auxiliary field associated with the &#34;meson&#34; superfield, in the low energy effective theory, as the composite Higgs field. The auxiliary field, at tree level, has a &#34;negative squar

Luiz C. de Albuquerque

Some questions were recently raised about the equivalence of two methods commonly used to compute the Casimir energy: the mode summation approach and the one-loop effective potential. In this respect, we argue that the scale dependence induced by renormalization effects, displayed by the effective potential approach, also appears in the MS method.

J. Antonio García, Josep M. Pons

The general conditions for the applicability of the Faddeev-Jackiw approach to gauge theories are studied. When the constraints are effective a new proof in the Lagrangian framework of the equivalence between this method and the Dirac approach is given. We find, however, that the two methods may give different descriptions for the reduced phase space when in

Khazret Nirov, Mikhail Plyushchay

We investigate hidden symmetries of P,T-invariant system of topologically massive U(1) gauge fields. For this purpose, we propose a pseudoclassical model giving rise to this field system at the quantum level. The model contains a parameter, which displays a quantization property at the classical and the quantum levels and demonstrates a nontrivial relationsh

Anastasia Volovich

Within recent Maldacena&#39;s proposal to relate gauge theories in the large N limit to the supergravity in the AdS background and recipe for calculation the Wilson loop, we compute corrections to the energy of quark/anti-quark pair in the large N limit.

I. Brevik, G. E. A. Matsas, E. S. Moreira

We revisit two-point function approaches used to study vacuum fluctuation in wedge-shaped regions and conical backgrounds. Appearance of divergent integrals is discussed and circumvented. The issue is considered in the context of a massless scalar field in cosmic string spacetime.

Ingo Gaida

Repulsive singularities (repulsons) in extended supergravity theories are investigated. These repulsive singularities are related to attractive singularities (black holes) in moduli space of extended supergravity vacua. In order to study these repulsive singularities a scalar test-particle in the background of a repulson is investigated. It is shown, using a