October 1995 arXiv papers — page 4

Ulf-G. Meißner

I summarize the results of the complete one--loop chiral perturbation theory calculation performed recently. It is shown that it allows to accurately pin down the isospin two, S--wave $ππ$ scattering length $a_0^2$. On the other hand, interesting resonance physics makes a precise determination of $a_0^0$ very difficult.

Ulf-G. Meißner

I review the results of a recent dispersion--theoretical analysis of the nucleon electromagnetic form factors and comment on the strangeness form factors. The need for a better data basis at low, intermediate and large momentum transfer is stressed.

Ulf-G. Meißner

I review the interesting tale of the electric dipole amplitude in neutral pion photoproduction and the resulting consequences. I also discuss why there is new life related to P--wave multipoles. Electroproduction is briefly touched upon.

Y. Hosotani

The multi-flavor Schwinger model on $R^1$ at finite temperature $T$ is mathematically equivalent to the model on $S^1$ at $T=0$. The latter is reduced to a quantum mechanical system of $N-1$ degrees of freedom. Physics sensitively depends on the parameter $m/T$. Finite temperature behavior of the massive Schwinger model is quite different from that of the ma

R. J. Rivers

We present a model for the formation of relativistic vortices (strings) at a quench, and calculate their density and correlations. The significance of these to early universe and condensed-matter physics is discussed.

Ulrich Nierste

I present the QCD short distance coefficient $η_3$ of the $ΔS=2$ hamiltonian in the \emph{next-to-leading order} (NLO) of renormalization group improved perturbation theory. Since now all QCD-factors $η_1$, $η_2$ and $η_3$ are known with NLO accuracy, a much higher precision in the analysis of $\varepsilon_K$ can be achieved. The CKM phase $δ$, $|V_{td}|$ an

U. Zückert

In the Nambu--Jona-Lasinio (NJL-) model baryons are considered either as quark-diquark-composites or as soliton configurations of mesons. The construction of a hybrid model, which possesses a dynamical interplay between both pictures, is presented. The Bethe-Salpeter equation for diquarks and the Faddeev equation for diquark-quark bound states in the backgro

Antonio Ferrera

One possible way in which phase transitions in the early universe may have ocurred is via nucleation of bubbles of the new phase (true vacuum) in the old phase (false vacuum). The technique most widely used to compute the probability of bubble nucleation is based on instanton methods in the context of the semiclassical approximation. At zero temperature in (

James Daniel Wells, G. L. Kane

If the reported excess (over the standard model prediction) for Z->bb from LEP persists, and is explained by supersymmetric particles in loops, then we show that (1) a superpartner (chargino and/or stop) will be detected at LEP2, and probably at LEP1.5 in 1995, (2) the basic parameter tan(beta) is at its lower perturbative limit, (3) BR(t->t1+chi0) is at or

D. Henty, C. Parrinello, C. Pittori

We compute the QCD running coupling on the lattice as defined from the 3-gluon vertex. We present the results of an exploratory study at $β=6.0$ on a $16^4$ lattice, which show that for momenta larger than 2 \Gev, the coupling runs according to the 2-loop asymptotic formula, allowing a precise determination of the $Λ$ parameter. Our renormalization procedure

R. Enomoto

The TRISTAN results from 1994 to 1995 are reviewed in this report. The physics results dominated the $γγ$ physics. Therefore, only these are selected in this article. We have systematically investigated jet productions, the $γ$-structure function, and charm pair productions in $γγ$ processes. The results, discussions, and future prospects are presented.

Carlos Barcelo, Luis J. Garay, Pedro F. Gonzalez-Diaz, Guillermo A. Mena Marugan

Starting with a procedure for dealing with general asymptotic behaviors, we construct a quantum theory for asymptotically anti-de Sitter wormholes. We follow both the path integral formalism and the algebraic quantization program proposed by Ashtekar. By adding suitable surface terms, the Euclidean action of the asymptoically anti-de Sitter wormholes can be

Oleg A. Starykh, George F. Reiter

We study hole motion in the Ising antiferromagnet using the recursion method. Using the retraceable path approximation we find the hole's Green's function as well as its wavefunction for arbitrary values of $t/J_z$. The effect of small transverse interaction also is taken into account. Our results provide some additional insight into the self-consist

T. Strohm, F. Guinea

Mesoscopic capacitances, in the quantum regime, are described as a quantum rotor coupled to a dissipative bath. We analyze the phase diagram of this model, as function of the capacitance, the coupling to the bath (that is, the conductance of the device), and the decay of the correlation functions in the bath, i.\ e., the strength of the many body effects wit

C. Balland, A. Blanchard

We study the uncertainty in galaxy cluster mass estimates derived from X-ray data assuming hydrostatic equilibrium (HE) for the intra cluster gas. Using a Monte-Carlo procedure we generate a general class of mass models allowing very massive clusters. We then compute the corresponding temperature profiles via the HE equation and compare them to observational

Max Tegmark, Dieter Hartmann, Michael Briggs, Charles Meegan

We compute the angular power spectrum C_l from the BATSE 3B catalog of 1122 gamma-ray bursts, and find no evidence for clustering on any scale. These constraints bridge the entire range from small scales (which probe source clustering and burst repetition) to the largest scales (which constrain possible anisotropies from the Galactic halo or from nearby cosm

Cristina C. Popescu, Ulrich Hopp, Hans J. Hagen, Hans Elsaesser

We present the observational results of our search for emission-line galaxies (ELG) towards nearby voids. In order to find ELG, we started a survey using the IIIa-J objective prism plates from the Hamburg QSO Survey. The plates are digitized and an automatic procedure was applied to select the candidates. Digitized direct plates were used to determine coordi

Roy Maartens, George Ellis, William Stoeger

A recent paper (Martinez--Gonzalez & Sanz 1995) showed that if the universe is homogeneous but anisotropic, then the small quadrupole anisotropy in the cosmic microwave background radiation implies that the spacetime anisotropy is very small. We point out that more general results may be established, without assuming a priori homogeneity. We have proved that

Frederic A. Rasio

The hydrodynamics of stellar collisions and mergers is discussed in the context of blue straggler formation. Emphasis is placed on the very important question of hydrodynamic mixing during the merger process. Recent results of three-dimensional hydrodynamic calculations suggest that the merger remnants produced by stellar collisions are typically {\em not\/}

H. Aratyn, E. Nissimov, S. Pacheva

We present an elementary discussion of the Calogero-Moser model. This gives us an opportunity to illustrate basic concepts of the dynamical integrable models. Some ideas are also presented regarding interconnections between integrable models based on the relation established between the Calogero-Moser model and the truncated KP hierarchy of Burgers-Hopf type

G. Buchalla, G. Burdman, C. T. Hill, D. Kominis

In strong dynamical schemes for electroweak symmetry breaking the third generation must be treated in a special manner, owing to the heavy top quark. This potentially leads to new flavor physics involving the members of the third generation in concert with the adjoining generations, with potential novel effects in beauty and charm physics. We give a general

Joe Ginocchio, Wick Haxton

We show that the introduction of a more general closed-shell operator allows one to extend Laughlin's wave function to account for the richer hierarchies (1/3, 2/5, 3/7 ...; 1/5, 2/9, 3/13, ..., etc.) found experimentally. The construction identifies the special hierarchy states with condensates of correlated electron clusters. This clustering implies a sing

The ZEUS Collaboration

We report on a measurement of the proton structure function $F_2$ in the range $3.5\times10^{-5}\leq x \leq 4\times10^{-3}$ and 1.5 ${\rm GeV^2} \leq Q^2 \leq15$ ${\rm GeV^2}$ at the $ep$ collider HERA operating at a centre-of-mass energy of $\sqrt{s} = 300$ ${\rm GeV}$. The rise of $F_2$ with decreasing $x$ observed in the previous HERA measurements persist

Anne Schilling

We give explicit expressions for the q-multinomial generalizations of the q-binomials and Andrews' and Baxter's q-trinomials. We show that the configuration sums for the generalized RSOS models in regime III studied by Date et al. can be expressed in terms of these multinomials. This generalizes the work of ABF and AB where configuration sums of stat

She-Sheng Xue

Analyzing an $SU_L(2)$-chiral gauge theory with external multifermion couplings, we find a possible scaling region where doublers decouple by acquiring chiral-invariant masses and $ψ_R$ is free mode owing to the $ψ_R$-shift-symmetry, the chiral continuum theory of $ψ^i_L$ can be defined. This is not in agreement with the general belief of the failure of theo

P. B. Price

For electromagnetic cascades induced by electron-neutrinos in South Pole ice, the effective volume per detector element (phototube, radio antenna, or acoustic transducer) as a function of cascade energy is estimated, taking absorption and scattering into account. A comparison of the three techniques shows that the optical technique is most effective for ener

G. E. Arutyunov

By applying the Hamiltonian reduction method to the cotangent bundle over loop groups we recover the well-known classical trigonometric $r$-matrices of the periodic Toda lattice.

Wayne Hu, Naoshi Sugiyama

Through analytic techniques verified by numerical calculations, we establish general relations between the matter and cosmic microwave background (CMB) power spectra and their dependence on cosmological parameters on small scales. Fluctuations in the CMB, baryons, cold dark matter (CDM), and neutrinos receive a boost at horizon crossing. Baryon drag on the p

Karim Benakli

Known mechanisms for breaking of supersymmetry at the level of string theory imply that at least one of the internal dimensions has a very large size. Experimental detection of the associated light Kaluza-Klein (KK) excitations would be a strong hint for the existence of string like elementary objects, as no consistent field theory describing them is known.

V. E. Zavlin, G. G. Pavlov, Yu. A. Shibanov, F. J. Rogers

We present first results of modeling convective photospheres of neutron stars. We show that in photospheres composed of the light elements convection arises only at relatively low effective temperatures (< 3-5*10^4 K), whereas in the case of iron compositon it arises at < 3*10^ K. Convection changes the depth dependence of the photosphere temperature and the

I. Montvay

Lüscher&#39;s local bosonic algorithm for Monte Carlo simulations of quantum field theories with fermions is applied to the simulation of a possibly supersymmetric Yang-Mills theory with a Majorana fermion in the adjoint representation. Combined with a correction step in a two-step polynomial approximation scheme, the obtained algorithm seems to be promising

Tony Gherghetta, Chris Kolda, Stephen P. Martin

The scalar potential of the Minimal Supersymmetric Standard Model (MSSM) is nearly flat along many directions in field space. We provide a catalog of the flat directions of the renormalizable and supersymmetry-preserving part of the scalar potential of the MSSM, using the correspondence between flat directions and gauge-invariant polynomials of chiral superf

B. V. de Bakker, J. Smit

We study correlations on the euclidean spacetimes generated in Monte Carlo simulations of the model. In the elongated phase, curvature correlations appear to fall off like a fractional power. Near the transition to the crumpled phase this power is consistent with 4. We also present improved data of our computations of the binding energy of test particles.

S. E. Massen, V. P. Garistov, M. E. Grypeos

We investigate the effects of fluctuations of the nuclear surface on the harmonic oscillator elastic charge form factor of light nuclei, while simultaneously approximating the short-range correlations through a Jastrow correlation ~factor. Inclusion of surface-fluctuation effects within this description, by truncating the cluster expansion at the two-body pa

Petro Holod, Sergey Kondratiuk

A construction of integrable hamiltonian systems associated with different graded realizations of untwisted loop algebras is proposed. Such systems have the form of Euler - Arnold equations on orbits of loop algebras. The proof of completeness of the integrals of motion is carried out independently of the realization of the loop algebra. The hamiltonian syst

Yuri B. Suris

Four integrable symplectic maps approximating two Hamiltonian flows from the relativistic Toda hierarchy are introduced. They are demostrated to belong to the same hierarchy and to examplify the general scheme for symplectic maps on groups equiped with quadratic Poisson brackets. The initial value problem for the difference equations is solved in terms of a

Saburo Kakei

In this letter, we show that certain Fredholm determinant $D(λ;t)$, introduced by Zamolodchikov in his study of 2D polymers, is a continuum limit of soliton solution for the Toda lattice hierarchy with 2-periodic reduction condition.

Robert Bluhm, Alan Kostelecky, Bogdan Tudose

We construct minimum-uncertainty solutions of the three-dimensional Schrödinger equation with a Coulomb potential. These wave packets are localized in radial and angular coordinates and are squeezed states in three dimensions. They move on elliptical keplerian trajectories and are appropriate for the description of the corresponding Rydberg wave packets, the

Bogdan Mielnik, Marco A. Reyes

A non perturbative numerical method for determining the discrete spectra is deduced from the classical analogue of the Schrodinger&#39;s equation. The energy eigenvalues coincide with the bifurcation parameters for the classical orbits.

A. A. Golovin, A. A. Nepomnyashchy, L. M. Pismen, H. Riecke

The stability of Marangoni roll convection in a liquid-gas system with deformable interface is studied in the case when there is a nonlinear interaction between two modes of Marangoni instability: long-scale surface deformations and short-scale convection. Within the framework of a model derived previously, it is shown that the nonlinear interaction between

Barry R. Holstein

Because of Pauli suppression effects the $Nπ$ decay of the free $Λ$ is not of importance in hypernuclei with $A\geq 10$. Rather the decay of such hypernuclei proceeds via the nucleon-stimulated mode $ΛN\rightarrow NN$, analysis of which presents a considerable theoretical challenge and about which there exists only a limited amount of experimental informatio

W. K. Baskerville

A new method for approximating Skyrme solutions is developed. It consists of cutting sections out of the Skyrme crystal and smoothly interpolating between the boundary and spatial infinity. Several field configurations are constructed, and their energies calculated. The surface energy (per unit area) of an infinite flat plane of the crystal is also calculate

O. Elgaroy, L. Engvik, E. Osnes, F. V. De Blasio

In this work we consider the role of muons in various URCA processes relevant for neutrino emissions in the core region of neutron stars. The calculations are done for $β$--stable nuclear matter with and without muons. We find muons to appear at densities $ρ= 0.15$ fm$^{-3}$, slightly around the saturation density for nuclear matter $ρ_0 =0.16$ fm$^{-3}$. Th

Jie Wu

We give some formulas of the James-Hopf maps by using combinatorial methods. An application is to give a product decomposition of the spaces $ΩΣ^2(X)$.

S. Varma, E. C. G. Sudarshan

We present an exactly solvable quantum field theory which allows rearrangement collisions. We solve the model in the relevant sectors and demonstrate the orthonormality and completeness of the solutions, and construct the S-matrix. In the light of the exact solutions constructed, we discuss various issues and assumptions in quantum scattering theory, includi

Joseph Polchinski, Edward Witten

A study is made of the implications of heterotic string $T$-duality and extended gauge symmetry for the conjectured equivalence of heterotic and Type I superstrings. While at first sight heterotic string world-sheet dynamics appears to conflict with Type I perturbation theory, a closer look shows that Type I perturbation theory ``miraculously&#39;&#39; break

Jan de Boer, Kostas Skenderis, Peter van Nieuwenhuizen, Andrew Waldron

We prove the renormalizability of the Curci-Ferrari model with and without auxiliary fields using BRST methods. In both cases we find 5 $Z$ factors instead of 3. We verify our results by explicit one loop calculations. We determine a set of generators for the ``physical states&#39;&#39;, many of which have negative norm. Supersymmetrization is considered.

Jean Avan, Genevieve Rollet

We compute the classical $r$-matrix for the relativistic generalization of the Calogero-Moser model, or Ruijsenaars-Schneider model, at all values of the speed-of-light parameter $λ$. We connect it with the non-relativistic Calogero-Moser $r$-matrix $(λ\rightarrow -1)$ and the $λ= 1$ sine-Gordon soliton limit.

G. Sartori, G. Valente

Covariant or invariant functions under a compact linear group can be expressed in terms of functions defined in the orbit space of the group. The semialgebraic relations defining the orbit spaces of all finite coregular real linear groups with at most 4 basic invariants are determined. For each group $G$ acting in $\real^n$, the results are obtained through

M. Shifman

A pedagogical introduction to the heavy quark theory is given. It is explained that various expansions in the inverse heavy quark mass $1/m_Q$ present a version of the Wilson operator product expansion in QCD. A systematic approach is developed and many practically interesting problems are considered. I show how the $1/m_Q$ expansions can be built using the

Robert D. Pisarski

In a constituent quark model at nonzero temperature, the amplitude for $π^0 \rightarrow 2 γ$ vanishes in a chirally symmetric phase, while that for $π^0 σ\rightarrow 2 γ$ does not.

G. Knoechlein, S. Scherer, D. Drechsel

We investigate the rare radiative eta decay modes eta -> pi+ pi- gamma gamma and eta -> pi0 pi0 gamma gamma within the framework of chiral lagrangians at o(p^4) and present photon spectra for both processes.

Zhi-zhong Xing

Unitarity triangles and characteristic measurables of the $3\times 3$ Cabibbo-Kobayashi-Maskawa (CKM) matrix are discussed. Beyond the $3\times 3$ CKM scheme we make a rephasing-invariant generalization of the Gronau-Wyler-Dunietz approach to determine the weak phase shift in $B^{\pm}_u\rightarrow D K^{\pm}$ or $B^0_d\rightarrow D K^{*0}$ vs $\bar{B}^0_d\rig

Yu. S. Kalashnikova

Theoretical arguments are given in favour of existence of gluonic degrees of freedom at the constituent level. Models for hybrid mesons are discussed, and the predictions are compared with the data on meson spectroscopy in the light quark sector. It is demonstrated that the $q\bar q g$ content might be responsible for the properties of some recently found me

Subir Sarkar

The temperature fluctuations in the cosmic microwave background observed by COBE provide strong support for an inflationary phase in the early universe, below the GUT scale. We argue that a singlet field in a hidden sector of an effective supergravity theory yields the required inflationary potential without fine tuning. Reheating occurs to a temperature low

Takeo Inami, C. S. Lim, B. Takeuchi, M. Tanabashi

Non-decoupling effects of heavy particles present in beyond-the-standard models are studied for the triple gauge boson vertices $γW^+W^-$ and $Z^0W^+W^-$. We show from a general argument that the non-decoupling effects are described by four independent parameters, in comparison with the three parameters $S$, $T$ and $U$ in the oblique corrections. These four

P. I. Krastev, S. T. Petcov

We study the stability of the two--neutrino vacuum oscillation solution of the solar neutrino problem with respect to changes of the total fluxes of boron and beryllium neutrinos. For any value of $Φ_{\rm Be}$ from the interval $0.7Φ^{\rm BP}_{\rm Be}\leq Φ_{\rm Be} \leq 1.3Φ^{\rm BP}_{\rm Be}$ the solar $ν_e$ oscillations into an active neutrino provide at

Kazuyuki Kanaya

Recent progress in lattice QCD at finite temperature is reviewed.

K. Kanaya

The finite temperature QCD phase transition is studied on the lattice with degenerate two flavors of Wilson quarks. Motivated by reported strange behaviors with the standard action on lattices with the temporal extention $N_t=4$ and 6, a renormalization group improved gauge action is applied. On an $N_t=4$ lattice, the strange behaviors observed with the sta

Herbert Nachbagauer, Anton K. Rebhan, Dominik J. Schwarz

Using a recent thermal-field-theory approach to cosmological perturbations, the exact solutions that were found for collisionless ultrarelativistic matter are generalized to include the effects from weak self-interactions in a $λϕ^4$ model through order $λ^{3/2}$. This includes the effects of a resummation of thermal masses and associated nonlocal gravitatio

Pierre Teyssandier, Robin W Tucker

We discuss the definitions of standard clocks in theories of gravitation. These definitions are motivated by the invariance of actions under different gauge symmetries. We contrast the definition of a standard Weyl clock with that of a clock in general relativity and argue that the historical criticisms of theories based on non-metric compatible connections

Henk van Elst, George F R Ellis

The dynamics of perfect fluid spacetime geometries which exhibit {\em Local Rotational Symmetry} (LRS) are reformulated in the language of a $1+\,3$ &#34;threading&#34; decomposition of the spacetime manifold, where covariant fluid and curvature variables are used. This approach presents a neat alternative to the orthonormal frame formalism. The dynamical eq

Koichi Hayashi, Toshiharu Samura

First order perturbations for the fields with spin on the background metric of the gravitational shock waves are discussed. Applying the Newman -- Penrose formalism, exact solutions of the perturbation equations are obtained. For particle physics, this would be one approach to the problem of scattering paticle at Planck energy.

K. Guruprasad, J. Huebschmann, L. Jeffrey, A. Weinstein

Let $G$ be a Lie group, with an invariant non-degenerate symmetric bilinear form on its Lie algebra, let $π$ be the fundamental group of an orientable (real) surface $M$ with a finite number of punctures, and let $\bold C$ be a family of conjugacy classes in $G$, one for each puncture. A finite-dimensional construction used earlier to obtain a symplectic str

S. M. Quinlan, P. J. Hirschfeld, D. J. Scalapino

Calculations are presented of the in-plane far-infrared conductivity of a d_{x^2-y^2}-wave superconductor, incorporating elastic scattering due to impurities and inelastic scattering due to spin fluctuations. The impurity scattering is modeled by short-range potential scattering with arbitrary phase shift, while scattering due to spin fluctuations is calcula

Claudio Castellano, Marco Zannetti

The Bray-Humayun model for phase ordering dynamics is solved numerically in one and two space dimensions with conserved and non conserved order parameter. The scaling properties are analysed in detail finding the crossover from multiscaling to standard scaling in the conserved case. Both in the nonconserved case and in the conserved case when standard scalin

Chetan Nayak, Frank Wilczek

We consider a correlated wavefunction including particle-hole pairing at half a reciprocal lattice vector for itinerant electrons hopping on a square lattice in two dimensions and subject both to on-site and nearest-neighbor repulsion. We find, within mean field theory, that in a suitable range of parameters there is a tendency toward a novel form of orderin

Oleg A. Starykh, Oziel F. de Alcantara Bonfim, George F. Reiter

The dispersion relation of the single hole in the $CuO_2$ plane is calculated in the self-consistent Born approximation for the three-band Hamiltonian. We find that direct oxygen-oxygen hopping removes the strong anisotropy of the hole spectrum around the band minima. Our results compare well with recent photoemission measurements of the single-hole dispersi

Stefano Lise, Henrik Jeldtoft Jensen

We investigate a random--neighbours version of the two dimensional non-conserving earthquake model of Olami, Feder and Christensen [Phys. Rev. Lett. {\bf 68}, 1244 (1992)]. We show both analytically and numerically that criticality can be expected even in the presence of dissipation. As the critical level of conservation, $α_c$, is approached, the cut--off o

H. Eskes, R. Grimberg, W. van Saarloos, J. Zaanen

The discovery by Tranquada et al. of an ordered phase of charged domain walls in the high-Tc cuprates leads us to consider the possible existence of a quantum domain-wall liquid. We propose minimal models for the quantization, by meandering fluctuations, of isolated charged domain walls. These correspond to lattice string models. The simplest model of this k

I. K. Marmorkos, A. Matulis, F. M. Peeters

The problem of the giant vortex state around a magnetic dot which is embedded in a superconducting film is investigated. The full non-linear, self-consistent Ginzburg-Landau equations are solved numerically in order to calculate the free energy, the order parameter of the host superconductor, the internal magnetic field due to the supercurrents, the correspo

F. Daerden, C. Vanderzande

We calculate time correlation functions in the Bak-Sneppen model (Phys. Rev. Lett. {\bf 71} 4083 (1993)), a model showing self-organised criticality. For a random neighbour version of the model, analytical results are presented, while on a one dimensional lattice we give numerical results. The power spectrum of these correlation functions shows $1/f$- behavi

W. H. Warner, P. R. Sethna, James P. Sethna

Normal forms allow the use of a restricted class of coordinate transformations (typically homogeneous polynomials) to put the bifurcations found in nonlinear dynamical systems into a few standard forms. We investigate here the consequences of relaxing the restrictions of the form of the coordinate transformations. In the Duffing equation, a logarithmic trans

Dong Lai, Edwin E. Salpeter

We study the energy levels of H$_2$ molecules in a superstrong magnetic field ($B\go 10^{12}$ G), typically found on the surfaces of neutron stars. The interatomic interaction potentials are calculated by a Hartree-Fock method with multi-configurations assuming electrons are in the ground Landau state. Both the aligned configurations and arbitrary orientatio

Dong Lai, Edwin E. Salpeter

We study the effects of finite proton mass on the energy levels of hydrogen atoms moving transverse to a superstrong magnetic field $B$ with generalized pseudomomentum $K_\perp$. Field strengths of order $B\sim 10^{12}$ Gauss are typically found on the surfaces of neutron stars, but we also study the regime $B\go B_{crit}= 4.23\times 10^{13}$ Gauss, where th

Eric J. Bakker, L. B. F. M. Waters, Henny J. G. L. M. Lamers, Norman R. Trams

We present the detection of molecular absorption lines in the optical spectrum of the post-AGB star HD56126. The C2 Phillips A^{1}Π_{u}-X^{1}Σ^{+}_{g} (1,0), (2,0), and (3,0); Swan d^{3}Π_{g}-a^{3}Π_{u} (0,0) and (1,0); and CN Red system A^{2}Π-X^{2}Σ^{+} (1,0), (2,0), (3,0), and (4,0) bands have been identified. From the identification of the molecular band

Rene D. Oudmaijer, Eric J. Bakker

We have investigated the report of Tamura and Takeuti that the Halpha line of the F-type post-AGB star HD56126 is variable on time scales of minutes. To this end, HD56126 was observed on two occasions with the William Herschel Telescope. Seventeen, respectively thirty spectra were taken within time span of 1.5 hours in order to detect any short term variatio

Eric J. Bakker

In this paper preliminary results are presented based on a study of the low and high resolution ultraviolet spectrum of the peculiar supergiant (post-AGB star) HD101584. By a comparison of the low resolution spectrum (1200-3200ang) with standard stars, the star is classified as an A7I, indicating an effective temperature of 8150 K, where literature quotes sp

Laurent Segretain

The 3-body crystallization diagrams of C/O/Ne ionic mixtures characteristic of white dwarf interiors are examined within the framework of the density-functional theory of freezing. The crystallization process is described more accurately than in former calculations where the three-component system was treated as an effective two-component mixture (Segretain

Adam Frank, T. W. Jones, Dongsu Ryu, Joseph B. Gaalaas

Using a new numerical code we have carried out two-dimensional simulations of the nonlinear evolution of unstable sheared magnetohydrodynamic flows. We considered two cases: a strong magnetic field (Alfven Mach number, M_a = 2.5) and a weak field (M_a =5). Each flow rapidly evolves until it reaches a nearly steady condition, which is fundamentally different

C. D. Wilson, D. L. Welch, I. N. Reid, A. Saha

We have measured the distance to the Local Group dwarf irregular galaxy IC 10 from near-infrared $JHK$ observations of Cepheids. The reddening-corrected distance modulus is $24.57\pm0.21$ mag or $0.82\pm 0.08$ Mpc. This distance lies at the short end of the range of previous estimates, and is significantly more accurate than all prior determinations. At this

Robert W. Nelson, Scott Tremaine

Large-scale warps in the outer parts of spiral galaxy discs have been observed for almost forty years, but their origin remains obscure. We review the dynamics of warped galaxy discs. We identify several mechanisms that could excite warps, all involving the gravitational interaction between the disc and the dark-matter halo.

Ariel R. Zhitnitsky

We discuss two dimensional $QCD (N_c\to\infty)$ with fermions in the fundamental as well as adjoint representation. We find factorial growth $\sim (g^2N_cπ)^{2k}\frac{(2k)!(-1)^{k-1}}{(2 π)^{2k}}$ in the coefficients of the large order perturbative expansion. We argue that this behavior is related to classical solutions of the theory, instantons, thus it has

Dimitra Karabali, V. P. Nair

The Hamiltonian formulation for a non-Abelian gauge theory in two spatial dimensions is carried out in terms of a gauge-invariant matrix parametrization of the fields. The Jacobian for the relevant transformation of variables is given in terms of the WZW-action for a hermitian matrix field. Some gauge-invariant eigenstates of the kinetic term of the Hamilton

N. A. Gromov

The nonsemisimple quantum Cayley-Klein groups $ Fun(SU_{q}(2;\bf j}) $ are realized as Hopf algebra of the noncommutative functions with the dual (or Study) variables. The {\it dual} quantum algebras $ su_q(2;{\bf j}) $ are constructed and their isomorphisms with the corresponding quantum orthogonal algebras $ so_q(3;{\bf j}) $ are established. The possible

Abdellatif Abada, Dominique Vautherin

The description of collective motion in nuclei at finite temperature using the framework of the random phase approximation is discussed. We focus on the special case of the isovector response function of hot nuclear matter using various effective Skyrme interactions.

Miao Li

Polchinski&#39;s recent construction of Dirichlet-branes of R-R charges, together with Witten&#39;s mechanism for forming bound states of both NS-NS charges and R-R charges, provides a rigorous method to treat these dy-branes. We construct the massless sector of boundary states of D-branes, as well as of dy-strings of charge $(p,1)$. As a consequence, the st

Gregory Kilcup, Jeffrey Grandy, Lakshmi Venkataraman

We present a calculation of the mass of the eta-prime meson using quenched and dynamical staggered fermions. We also discuss the effects of &#34;cooling&#34; and suggest its use as a quantitative tool.

O. M. Bulashenko, M. J. Garcia, L. L. Bonilla

Self-sustained time-dependent current oscillations under dc voltage bias have been observed in recent experiments on n-doped semiconductor superlattices with sequential resonant tunneling. The current oscillations are caused by the motion and recycling of the domain wall separating low- and high-electric- field regions of the superlattice, as the analysis of

Manoelito M. de Souza

Classical Electrodynamics is not a consistent theory because of its field inadequate behaviour in the vicinity of their sources. Its problems with the electron equation of motion and with non-integrable singularity of the electron self field and of its stress tensor are well known. These inconsistencies are eliminated if the discrete and localized (classical

N. Hambli, C. P. Burgess

Polchinski has argued that the prediction of Hawking radiation must be independent of the details of unknown high-energy physics because the calculation may be performed using `nice slices&#39;, for which the adiabatic theorem may be used. If this is so, then any calculation using a manifestly covariant --- and so slice-independent --- ultraviolet regulariza

O. Sheinman

A new series of integrable cases of the many-body problem in many-dimensional spaces is found. That series appears as a part of the larger series of integrable problems, which are in 1-1 correspondence with Krichever-Novikov algebras of affine type (that is with pairs each one consisting of some finite root system and some Riemann surface of finite genus wit

V. Frolov

We discuss and compare different definitions of the entropy of a black hole. In particular we show that the thermodynamical entropy defined by the response of the free energy of a black hole to the change of temperature does not coincide with the statistical-mechanical entropy, obtained by counting its dynamical degrees of freedom. The no-boundary wavefuncti

Dennis Bonatsos, C. Daskaloyannis, Harry A. Mavromatis

It is proved that quasi-exactly soluble potentials (QESPs) corresponding to an oscillator with harmonic, quartic and sextic terms, for which the $n+1$ lowest levels of a given parity can be determined exactly, may be approximated by WKB equivalent potentials corresponding to deformed anharmonic oscillators of SU$_q$(1,1) symmetry, which have been used for th

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis, D. Lenis

Various applications of quantum algebraic techniques in nuclear structure physics, such as the su$_q$(2) rotator model and its extensions, the use of deformed bosons in the description of pairing correlations, and the construction of deformed exactly soluble models (Interacting Boson Model, Moszkowski model) are briefly reviewed. Emphasis is put in the study

Chong-Sun Chu, Pei-Ming Ho, Bruno Zumino

The quantum deformation $CP_q(N)$ of complex projective space is discussed. Many of the features present in the case of the quantum sphere can be extended. The differential and integral calculus is studied and $CP_q(N)$ appears as a quantum Kähler manifold. The braiding of several copies of $CP_q(N)$ is introduced and the anharmonic ratios of four collinear

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis, D. Lenis

Various applications of quantum algebraic techniques in nuclear structure physics, such as the su$_q$(2) rotator model and its extensions, the use of deformed bosons in the description of pairing correlations, and the construction of deformed exactly soluble models (Interacting Boson Model, Moszkowski model) are briefly reviewed. Emphasis is put in the study

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis, D. Lenis

Various applications of quantum algebraic techniques in nuclear and molecular physics are briefly reviewed. Emphasis is put in the study of the symmetries of the anisotropic quantum harmonic oscillator with rational ratios of frequencies, which underly the structure of superdeformed and hyperdeformed nuclei, the Bloch--Brink $α$-cluster model and possibly th

Dennis Bonatsos, C. Daskaloyannis, P. Kolokotronis

Several physical systems (two identical particles in two dimensions, isotropic oscillator and Kepler system in a 2-dim curved space) and mathematical structures (quadratic algebra QH(3), finite W algebra $\bar {\rm W}_0$) are shown to posses the structure of a generalized deformed su(2) algebra, the representation theory of which is known. Furthermore, the g

Takashi Kimura, Kazuhiko Kuroki, Hideo Aoki

In a magnetic field an interacting electron gas in one dimension may be described as a Tomonaga-Luttinger model comprising two components with different Fermi velocities due to the Zeeman splitting. This destroys the spin-charge separation, and even the quantities such as the density-density correlation involve spin and charge critical exponents (K). Specifi