February 1994 arXiv papers — page 7

K. Langanke, T. D. Shoppa

We have calculated the E1 and E2 contributions to the low-energy B-8 + Pb-208 -> p + Be-7 + Pb-208 Coulomb dissociation cross sections using the kinematics of a recent experiment at RIKEN. Using a potential model description of the Be-7 (p,gamma) B-8 reaction, we find that the E2 contributions cannot a priori be ignored in the analysis of the data. Its inclu

A. Wierling, B. G. Giraud, F. Mekideche, H. Horiuchi

The usual definition of the prior(post) interaction $V(V^\prime )$ between projectile and target (resp. ejectile and residual target) being contradictory with full antisymmetrization between nucleons, an explicit antisymmetrization projector ${\cal A}$ must be included in the definition of the transition operator, $ T\equiv V^\prime{\cal A}+V^\prime{\cal A}G

Giovanni Felder, V. Pasquier

We show that Belavin's solutions of the quantum Yang--Baxter equation can be obtained by restricting an infinite $R$-matrix to suitable finite dimensional subspaces. This infinite $R$-matrix is a modified version of the Shibukawa--Ueno $R$-matrix acting on functions of two variables.

R. Kirschner, L. N. Lipatov, L. Szymanowski

We construct the effective Lagrangian describing QCD in the multi-Regge kinematics. It is obtained from the original QCD Lagrangian by eliminating modes of gluon and quark fields not appearing in this underlying kinematics.

Jacobus Verbaarschot

Using Selberg's integral formula we derive all Leutwyler-Smilga type sum rules for one and two flavors, and for each of the three chiral random matrix ensembles. In agreement with arguments from effective field theory, all sum rules for $N_f = 1$ coincide for the three ensembles. The connection between spectral correlations and the low-energy effective p

J. -P. Derendinger, F. Quevedo, M. Quiros

In 4-D heterotic superstrings, the dilaton and antisymmetric tensor fields belong to a linear N=1 supersymmetric multiplet L. We study the lagrangian describing the coupling of one linear multiplet to chiral and gauge multiplets in global and local supersymmetry, with particular emphasis on string tree-level and loop-corrected effective actions. This theory

I. J. R. Aitchison, M. Klein-Kreisler

A recent study of dynamical chiral symmetry breaking in N-flavour QED$_3$ at finite temperature is extended to include the effect of fermion wavefunction renormalisation in the Schwinger-Dyson equations. The simple ``zero-frequency'' truncation previously used is found to lead to unphysical results, especially as $T \to 0$. A modified set of equation

Andrzej Czarnecki, James L. Pinfold

We compute the energy spectrum of charged leptons in the decay $H^+\to \bar b+(t\to blν_l)$. The shape of the lepton spectrum obtained, and also the mean lepton energy, are sensitive to the handedness of the intermediate top quark. This sensitivity can be used to precisely determine $\tanβ$, a fundamental parameter of two Higgs doublet models.

M. Drees

The Lightest Supersymmetric Particle (LSP) makes a good Dark Matter (DM) candidate, since its relic density quite naturally comes out close to the cosmologically required value. This is true even in minimal Supergravity models with radiative symmetry breaking, which have a rather small number of free parameters. On the other hand, the experimental detection

Estia J. Eichten, Chris Quigg

Applying knowledge of the interaction between heavy quarks derived from the study of $c\overline{c}$ and $b\overline{b}$ bound states, we calculate the spectrum of $c\overline{b}$ mesons. We compute transition rates for the electromagnetic and hadronic cascades that lead from excited states to the $^1\text{S}_0$ ground state, and briefly consider the prospec

N. N. Nikolaev, B. G. Zakharov

We present a BFKL phenomenology of structure functions in the framework of the generalized BFKL equation for the dipole cross section proposed by us recently. We show that the HERA measurements of excitation of charm at $Q^{2} \lsim $10 GeV$^{2}$ allow determination of the intercept of the BFKL pomeron. A comparison with the experimental data suggests a larg

Costas G. Papadopoulos

This paper is a study of the single-$W$ and $W$-pair production at LEP~II. I show that the sensitivity of the single-$W$ production channel on the anomalous trilinear couplings of $W$ is essentially the same as the sensitivity of the channel $e^+e^-\to W^+W^-$. Therefore, even without the reconstruction of the $W$ boson, deviations form the SM predictions on

F. R. Klinkhamer, P. Olesen

The vortex solution (Z-string) of the electroweak interactions can be interpreted as the 2-dimensional sphaleron at the top of a non-contractible sphere. The same holds for another type of solution, the W-string.

W. Broniowski

The large-$N_c$ consistency conditions for axial vector and isovector magnetic couplings of pions to baryons are discussed from the point of view of low-energy current-algebra sum rules (Adler-Weisberger, Cabibbo-Radicati). In particular, we show how the result that ratios of axial vector and isovector magnetic coupling constants get corrections only at the

Yongseok Oh, Byung-Yoon Park, Dong-Pil Min

We take into account the $1/m_Q$ corrections upto $1/N_c$ order in the heavy-meson-soliton bound state approach for heavy baryons. With these corrections, the mass spectra of baryons with $c$-quark as well as of those with $b$-quark are well reproduced. For charmed baryons, however, the correction to the mass spectra amounts to about 300 MeV, which is not sm

Tonatiuh Matos

We find a new class of exact solutions of the five-dimensional Einstein equations whose corresponding four-dimensional spacetime possesses a Schwarzschild-like behavior. The electromagnetic potential depends on a harmonic function and can be choosen to be of a monopole, dipole, etc. field. The solutions are asymptotically flat and for vanishing magnetic fiel

Juan Pablo Paz

We examine the dependence of decoherence on the spectral density of the environment as well as on the initial state of the system. We use two simple examples to illustrate some important effects. The simplest derivation of the general form of the master equation for a general quantum Brownian motion is outlined in an Appendix.

L. B. Szabados

The recently constructed two dimensional Sen connection is applied in the problem of quasi-local energy-momentum in general relativity. First it is shown that, because of one of the two 2 dimensional Sen--Witten identities, Penrose's quasi-local charge integral can be expressed as a Nester--Witten integral.Then, to find the appropriate spinor propagation

Giorgio Immirzi

Spacetime discretized in simplexes, as proposed in the pioneer work of Regge, is described in terms of selfdual variables. In particular, we elucidate the "kinematic" structure of the initial value problem, in which 3--space is divided into flat tetrahedra, paying particular attention to the role played by the reality condition for the Ashtekar varia

Bryan M. Gorman, Per Arne Rikvold, M. A. Novotny

We apply both a scalar field theory and a recently developed transfer-matrix method to study the stationary properties of metastability in a two-state model with weak, long-range interactions: the $N$$\times$$\infty$ quasi-one-dimensional Ising model. Using the field theory, we find the analytic continuation $\tilde f$ of the free energy across the first-ord

Andrey V. Chubukov, Subir Sachdev, T. Senthil

We study frustrated, two-dimensional, quantum antiferromagnets in the vicinity of a quantum transition from a non-collinear, magnetically-ordered ground state to a quantum disordered phase. The general scaling properties of this transition are described. A detailed study of a particular field-theoretic model of the transition, with bosonic spin-1/2 spinon fi

F. A. Rasio

The unusually large eccentricity ($e_1=0.025$) of the low-mass binary millisecond pulsar PSR B1620-26 can be explained naturally as arising from the secular perturbation of a second, more distant companion. Such a triple configuration has been proposed recently as the most likely cause of the anomalous second period derivative of the pulsar. The current timi

A. Kogut, A. J. Banday, C. L. Bennett, G. Hinshaw

We have searched the temperature maps from the COBE Differential Microwave Radiometers (DMR) first two years of data for evidence of unresolved sources. The high-latitude sky (|b| > 30°) contains no sources brighter than 192 uK thermodynamic temperature (322 Jy at 53 GHz). The cumulative count of sources brighter than threshold T, N(> T), is consistent with

K. Subramanian, T. Padmanabhan

Models for structure formation attempt to predict the power spectrum of density perturbations in the present universe from the initial power spectrum and the nature of dark matter. Observational constraints on the power spectrum at different scales in the present epoch can, therefore, be used to eliminate (or choose between) different theoretical models. Suc

P. Mazzei, G. De Zotti

We have investigated the IRAS colours and the far-IR to optical luminosity ratios of a complete sample of elliptical's and S0's brighter than $B_T = 12$. On the average, elliptical galaxies emit in the far-IR less than 1\% of their bolometric luminosity, while S0's are about a factor of three brighter in the far-IR. On the average, the photospher

Ricardo A. Flores, Joel R. Primack

The distribution of dark matter around galactic or cluster halos has usually been assumed to be approximately isothermal with a non-zero core radius, which is expected to be of the order of the size of the visible matter distribution. Recently, the possibility has been raised that dark matter halos might be singular in the sense that the dark matter density

Rien van de Weygaert, Arif Babul

We present preliminary results of our investigation into the influence of shear fields on the evolution of galactic scale fluctuations in a primordial Gaussian random density field. Specifically, we study how the matter associated with a galaxy-scale peak evolves, to determine whether the shear can affect the peak's ability to form a virialized structure

M. B. Cakir, G. R. Farrar

Given a resonance of known mass, width, and J^{PC}, we can determine its gluonic branching fraction, b(R->gg), from data on its production in radiative vector quarkonium decay, V -> gamma+R. For most resonances b(R->gg) is found to be O(10%), consistent with being q-qbar states, but we find that both pseudoscalars observed in the 1440 MeV region have b(R->gg

J. L. F. Barbon

General arguments based on curved space-time thermodynamics show that any extensive quantity, like the free energy or the entropy of thermal matter, always has a divergent boundary contribution in the presence of event horizons, and this boundary term comes with the Hawking-Bekenstein form. Although the coefficients depend on the particular geometry we show

V. Kaplunovsky, J. Louis

We investigate the field dependence of the gauge couplings of locally supersymmetric effective quantum field theories. We find that the Weyl rescaling of supergravity gives rise to Wess-Zumino terms that affect the gauge couplings at the one-loop level. These Wess-Zumino terms are crucial in assuring supersymmetric consistency of both perturbative and non-pe

Ashoke Sen

We present several pieces of evidence for strong-weak coupling duality symmetry in the heterotic string theory, compactified on a six dimensional torus. These include symmetry of the 1) low energy effective action, 2) allowed spectrum of electric and magnetic charges in the theory, 3) allowed mass spectrum of particles saturating the Bogomol'nyi bound, a

N. Bilić, J. Cleymans, M. D. Scadron

We review the relationship between the pion decay constant $f_π$, the chiral symmetry restoration temperature $T_c$ and the phenomenology of low energy chiral symmetry breaking in view of the recent confirmation of the existence of a sigma meson with a mass of 600-700 MeV.

S. V. Akulinichev

We argue that nuclei are not transparent for fast projectile partons. Color transparency is effective for final state interactions in heavy particle production, though nuclear filtering of initial partons can reduce the cross sections. We show that short-ranged initial state interactions, which have been neglected so far, can be important in hadroproduction

Carsten Schütt

In [K--S 1] it was shown that $$ \underset π \to {\text{Ave}} (\sum_{i=1}^{n}|x_i a_{π(i)}|^2)^{\frac {1}{2}} $$ is equivalent to an Orlicz norm whose Orlicz function is 2-concave. Here we give a formula for the sequence $a_1, a_2,....,a_n$ so that the above expression is equivalent to a given Orlicz norm.

Sean Dineen

We lift upper and lower estimates from linear functionals to $n$-homogeneous polynomials and using this result show that $l_\infty$ is finitely represented in the space of $n$-homogeneous polynomials, $n\ge2$, for any infinite dimensional Banach space. Refinements are also given.

F. D. T. Smith

The Lagrangian action for the D4-D5-E6 model of hep-th/9306011 has 8-dim spacetime V8 of the vector representation of Spin(0,8); 8-dim fermion fields S8+ = S8- of the half-spinor reps of Spin(0,8); and 28 gauge boson fields of the bivector adjoint rep of Spin(0,8). In this paper, the structure of the positive definite Clifford algebra Cl(0,8) of Spin(0,8), a

H. Awata, M. Fukuma, Y. Matsuo, S. Odake

We calculate the Kac determinant for the quasi-finite representation of \Winf algebra up to level 8. It vanishes only when the central charge is integer. We give an algebraic construction of null states and propose the character formulae. The character of the Verma module is related to free fields in three dimensions which has rather exotic modular propertie

D. Tommasini

In the Supersymmetric extension of the Standard Model with minimal particle content the three neutrinos can have non trivial masses and mixings, generated at 1 loop due to renormalizable lepton number violating interactions. We show that the resulting mass matrix can provide simultaneously a significant amount of the Dark Matter of the Universe and solve the

J. B. Kogut, M-P Lombardo, D. K. Sinclair

Simulations of quenched $QCD$ at relatively small but {\it nonzero} chemical potential $μ$ on $32 \times 16^3$ lattices indicate that the nucleon screening mass decreases linearly as $μ$ increases predicting a critical chemical potential of one third the nucleon mass, $m_N/3$, by extrapolation. The meson spectrum does not change as $μ$ increases over the sam

Jorge Pullin

Table of contents Editorial Correspondents Gravity News: Open Letter to gravitational physicists, Beverly Berger A Missouri relativist in King Gustav's Court, Clifford Will Gary Horowitz wins the Xanthopoulos award, Abhay Ashtekar Research briefs: Gamma-ray bursts and their possible cosmological implications, Peter Meszaros Current activity and results i

L. B. Szabados

The two dimensional version of the Sen connection for spinors and tensors on spacelike 2-surfaces is constructed. A complex metric $γ_{AB}$ on the spin spaces is found which characterizes both the algebraic and extrinsic geometrical properties of the 2-surface $\$ $. The curvature of the two dimensional Sen operator $Δ_e$ is the pull back to $\$ $ of the ant

M. Koppel, R. Feldman, A. M. Segre

The theory revision problem is the problem of how best to go about revising a deficient domain theory using information contained in examples that expose inaccuracies. In this paper we present our approach to the theory revision problem for propositional domain theories. The approach described here, called PTR, uses probabilities associated with domain theor

D. J. Cook, L. B. Holder

The ability to identify interesting and repetitive substructures is an essential component to discovering knowledge in structural data. We describe a new version of our SUBDUE substructure discovery system based on the minimum description length principle. The SUBDUE system discovers substructures that compress the original data and represent structural conc

C. X. Ling

Learning the past tense of English verbs - a seemingly minor aspect of language acquisition - has generated heated debates since 1986, and has become a landmark task for testing the adequacy of cognitive modeling. Several artificial neural networks (ANNs) have been implemented, and a challenge for better symbolic models has been posed. In this paper, we pres

E. J. Mele, S. C. Erwin

We study the electronic spectrum for doped electronic states in the orientationally disordered M3C60 fullerides. Momentum-resolved Green's functions are calculated within a cluster-Bethe-lattice model, and compared with results from calculations on periodically repeated supercells containing quenched orientational disorder. Despite the relatively strong

S. C. Erwin, E. J. Mele

We derive numerical tight-binding hopping parameters to describe conduction-band dispersion in arbitrary orientational phases of $A_3$C$_{60}$. The parameters are obtained by direct Fourier inversion of the spectra from self-consistent electronic-structure calculations for K$_3$C$_{60}$ using the local-density approximation, including the effects of orientat

P. Ossadnik, C. -H. Lam, L. M. Sander

In analogy to recent results on non-universal roughening in surface growth [Lam and Sander, Phys. Rev. Lett. {\bf 69}, 3338 (1992)], we propose a variant of diffusion-limited aggregation ($DLA$) in which the radii of the particles are chosen from a power law distribution. For very broad distributions, the huge particles dominate and the fractal dimension is

V. Subrahmanyam

The Spin-1/2 Heisenberg Model (HM) is investigated using a block-spin renormalization approach on Kagome and triangular lattices. In both cases, after coarse graining the triangles on original lattice and truncation of the Hilbert space to the triangular ground state subspace, HM reduces to an effective model on a triangular lattice in terms of the triangula

V. Subrahmanyam

The ground state of closed Heisenberg spin chains with an odd number of sites has a chiral degeneracy, in addition to a two-fold Kramers degeneracy. A non-zero chirality implies that the spins are not coplanar, and is a measure of handedness. The chirality operator, which can be treated as a spin-1/2 operator, is explicitly constructed in terms of the spin o

Richard N. Henriksen, Lawrence M. Widrow

We propose that the recently reported MACHO/EROS events correspond to gravitational amplification by dark clouds rather than compact objects. These clouds must be very dense with $M\sim 0.1 ~M_\odot$ and $R\la 10^{14}~{\rm cm}$. In all likelihood, the clouds will be members of a family of objects with different sizes and masses. We therefore expect events of

Alfonso Aragon-Salamanca, Carlos S. Frenk, Julio F. Navarro, Stephen E. Zepf

We present a detailed prescription for how galaxy formation can be modelled in hierarchical theories of structure formation. Our model incorporates the formation and merging of dark matter halos, the shock heating and radiative cooling of baryonic gas gravitationally confined in these halos, the formation of stars regulated by the energy released by evolving