January 1994 arXiv papers — page 5

E. Elizalde, S. D. Odintsov

The renormalization group (RG) is used in order to obtain the RG improved effective potential in curved spacetime. This potential is explicitly calculated for the Yukawa model and for scalar electrodynamics, i.e. theories with several (namely, more than one) mass scales, in a space of constant curvature. Using the $λφ^4$-theory on a general curved spacetime

E. Elizalde, S. D. Odintsov, Yu. I. Shil'nov

The phase structure of the $d=3$ Nambu-Jona-Lasinio model in curved spacetime is considered to leading order in the $1/N$--expansion and in the linear curvature approximation. The possibility of a curvature-induced first-order phase transition is investigated numerically. The dynamically generated fermionic mass is calculated for some values of the curvature

Bernd Bruegmann

We present a formal but simple calculational scheme to relate the expectation value of Wilson loops in Chern-Simons theory to the Jones polynomial. We consider the exponential of the generator of homotopy transformations which produces the finite loop deformations that define the crossing change formulas of knot polynomials. Applying this operator to the exp

Vu B Ho

When a hydrogen-like atom is treated as a two dimensional system whose configuration space is multiply connected, then in order to obtain the same energy spectrum as in the Bohr model the angular momentum must be half-integral.

R. Foot, X. -G. He, H. Lew, R. R. Volkas

A model of a light $Z'$ boson is constructed and phenomenological bounds are derived. This $Z'$ boson arises from a very simple extension to the Standard Model, and it is constrained to be light because the vacuum expectation values which generate its mass also break the electroweak gauge group. It is difficult to detect experimentally because it cou

Kyungsik Kang

This is an overview of the electroweak physics achieved at LEP. After a brief review of the standard model and the calculation of the radiative corrections both in the MS and on-shell schemes, we introduce the Z decay parameters around the resonance energy and discuss the status of the standard model fits for them, along with some selected highlights of the

Susmita Bhowmik Duari, U. A. Yajnik

If cosmic strings are present at the electroweak phase transition, they can act as seeds on which bubbles of true vacuum nucleate. We explore the nature of such a phase transition, in particular the wall velocity and thickness of the bubbles. {}From the viewpoint of electroweak baryogenesis, adiabatic conditions exist in the expanding bubble walls, and such

Zoltan Ligeti, Yosef Nir

Combining the experimental data on the inclusive decays $D\to X\,e\,\nu$, $B\to X\,e\,\nu$ and $B\to X\,\tau\,\nu$, we find severe constraints on the $\bar\Lambda$ and $\lambda_1$ parameters of the Heavy Quark Effective Theory. In particular, we get $\bar\Lambda<0.7\,$GeV. Our constraints further imply $m_c\geq1.43\,$GeV and $m_b\geq4.66\,$GeV. We discuss fu

Terrence Draper, Craig McNeile

We present a new method for the study of heavy-light mesons in the static approximation of lattice QCD which is optimally effective in isolating ground and excited states. With ``MOST&#39;&#39; (Maximal Operator Smearing Technique), the heavy quark is smeared at all possible positions relative to the light quark, subject to the constraint of cubic symmetry.

A. Ali Khan, M. Goeckeler, R. Horsley, P. E. L. Rakow

We investigate a lattice Nambu--Jona-Lasinio model both by the Monte Carlo method and Schwinger-Dyson equations. A comparison allows the discussion of finite size effects and the extrapolation to infinite volume. We pay special attention to the identification of particles and resonances. This enables us to discuss renormalisation group flows in the neighbour

H A Marales-Tecotl, C Rovelli

We study the quantum fermions+gravity system, that is, the gravitational counterpart of QED. We start from the standard Einstein-Weyl theory, reformulated in terms of Ashtekar variables; and we construct its non- perturbative quantum theory by extending the loop representation of general relativity. We construct the fermion equivalent to the loop variables.

S. A. Janowsky

We consider the asymptotic behavior of the (one dimensional) two-species annihilation reaction A + B --> 0, where both species have a uniform drift in the same direction and like species have a hard core exclusion. Extensive numerical simulations show that starting with an initially random distribution of A&#39;s and B&#39;s at equal concentration the densit

M. Korotin, A. Postnikov, T. Neumann, G. Borstel

The electronic structure of Fe impurity in MgO was calculated by the linear muffin-tin orbital--full-potential method within the conventional local-density approximation (LDA) and making use of the LDA+$U$ formalism. The importance of introducing different potentials, depending on the screened Coulomb integral $U$, is emphasized for obtaining a physically re

R. Dominguez-Tenreiro, A. Campos, M. A. Gómez-Flechoso, G. Yepes

We present the results of an exhaustive analysis of the morphological segregation of galaxies in the CfA and SSRS catalogs through the scaling formalism. Morphological segregation between ellipticals and spirals has been detected at scales up to 15-20 h$^{-1}$ Mpc in the CfA catalog, and up to 20-30 h$^{-1}$ Mpc in the SSRS catalog. Moreover, it is present n

H. N. Chehime, D. Zeppenfeld

The $t$-channel exchange of two gluons in a color singlet state represents the lowest order approximation to the Pomeron. This exchange mechanism is thought to also explain the formation of rapidity gaps in dijet events at the Tevatron. At the perturbative level this requires suppressed gluon emission in the rapidity interval between widely separated jets, a

Peter A. Clarkson, Elizabeth L. Mansfield

In this article we present first an algorithm for calculating the determining equations associated with so-called ``nonclassical method&#39;&#39; of symmetry reductions (a la Bluman and Cole) for systems of partial differentail equations. This algorithm requires significantly less computation time than that standardly used, and avoids many of the difficultie

Denis Juriev

This paper is devoted to an interaction of 2 objects: the 1st of them is octonions, the classical structure of pure mathematics, the 2nd one is Mobilevision, the recently developped technique of computer graphics. Namely, it is shown that the binocular Mobilevision maybe elaborated by use of the octonionic colour space - the 7-dimensional extension of the cl

G. M. Zhang, S. Feng, L. Yu

Using the fermion-spin transformation to implement spin-charge separation of constrained electrons, a model of two $t-J$ chains with interchain single-electron hopping is studied by abelian bosonization. After spin-charge decoupling the charge dynamics can be trivially solved, while the spin dynamics is determined by a strong-coupling fixed point where the c

Youichi Yamada

We obtain the one- and two-loop renormalization group equations for soft SUSY breaking scalar interactions in general, semi-simple SUSY gauge model, by using the supergraph method. We find that the method simplifies the calculation significantly because of the non-renormalization theorem and also because of the property that the relevant divergences are deri

A. de la Macorra

We study some phenomenological consequences of having moduli fields with large vacuum expectation values (v.e.v.). The v.e.vs of the moduli are dynamically determined once supersymmetry is broken in 4D string theories. The study constraints the possible Yukawa interactions and modular weights for matter fields.

A. de la Macorra

We study the unification scale and gauge coupling constant in 4D string theory. We show that the fine structure constant is determined by the dimension of the hidden gauge group and only $SU(6)$ and $SO(9)$ are consistent with minimal string unification while the unification scale can be of order of $10^{16}\,GeV$.

A. de la Macorra, G. G. Ross

We consider the predictions for the hierarchy of mass scales, the fine structure constant, the radii of compactification and the soft SUSY breaking terms which follow if SUSY breaking is triggered by a gaugino condensate.

M. S. Fayache, L. Zamick

We consider negative-parity excitations in $^4\mbox{He}$, $J^π$=$0^-$ and $1^-$ with isospin $T$=$0$ and $T$=$1$. We show tha t, in contrast to one-particle one-hole results, in a shell model diagonalization none of the above collapses to zero energy as the strength of the tensor interaction is increased.

M. Schäfer, H. C. Dönges, A. Engel, U. Mosel

Starting from a realistic one--boson--exchange--model fitted to the amplitudes of elastic nucleon--nucleon scattering and the process $NN\rightarrow NΔ$ we perform a fully relativistic and gauge invariant calculation for the dilepton production in nucleon--nucleon collisions, including the important effect of propagating the $Δ$--resonance. We compare the re

John Hubbard, Ralph W. Oberste-Vorth

Let H: C^2 -> C^2 be the Henon mapping given by (x,y) --> (p(x) - ay,x). The key invariant subsets are K_+/-, the sets of points with bounded forward images, J_+/- = the boundary of K_+/-, J = the union of J_+ and J_-, and K = the union of K_+ and K_-. In this paper we identify the topological structure of these sets when p is hyperbolic and |a| is sufficien

A. N. Kapustin, P. I. Pronin

We prove that $\be$-function of the gauge coupling in $2+1D$ gauge theory coupled to any renormalizable system of spinor and scalar fields is zero. This result holds both when the gauge field action is the Chern-Simons action and when it is the topologically massive action.

N. N. Nikolaev, B. G. Zakharov, V. R. Zoller

The colour dipole cross section is the principal quantity in the lightcone $s$-channel description of the diffractive scattering. Recently we have shown that the dipole cross section satisfies the generalized BFKL equation. In this paper we discuss properties and solutions of our generalized BFKL equation with allowance for the finite gluon correlation radiu

N. Brambilla, P. Consoli, G. M. Prosperi

In this paper we give a new derivation of the quark-antiquark potential in the Wilson loop context. This makes more explicit the approximations involved and enables an immediate extension to the three-quark case. In the $q\overline{q}$ case we find the same semirelativistic potential obtained in preceding papers but for a question of ordering. In the $3q$ ca

A. Kundu, P. Truini

The aim of the paper is to build a universal R-matrix for the multiparameter deformation of any reductive Lie algebra. Such deformations, formulated in the recent past by Truini and Varadarajan, have the property of universality in a certain class and are shown by the present paper to be quasitriangular Hopf algebras. In order to build the R-matrix we exploi

Tomasz Brzezinski

A generalisation of the classical Calogero-Moser model obtained by coupling it to the Gaudin model is considered. The recently found classical dynamical r-matrix [E. Billey, J. Avan and O. Babelon, PAR LPTHE 93-55] for the Euler-Calogero-Moser model is used to separate variables for this generalised Calogero-Moser model in the case in which there are two Cal

Bruno Iochum, Thomas Schucker

We present a left-right symmetric model with gauge group $U(@)_L\times U(@)_R$ in the Connes-Lott non-commutative frame work. Its gauge symmetry is broken spontaneously, parity remains unbroken.

Y. Frishman, A. Hanany, J. Sonnenschein

It is shown that in a formulation of Yang-Mills theory in two dimensions in terms of $A=if^{-1}\pa f$, $\bar A=i\bar f\bpa\bar f^{-1}$ with $f(z,\bar z)$, $\bar f(z,\bar z)\in[SU(N_C)]^c$ the complexification of $SU(N_C)$ , reveals certain subtleties. ``Physical&#34; massive color singlet states seem to exist. When coupled to $N_F$ quarks the coupling consta

G. K. Savvidy, R. Schneider

We prove inequality (1) for the modified Steiner functional A(M), which extends the notion of the integral of mean curvature for convex surfaces.We also establish an exression for A(M) in terms of an integral over all hyperplanes intersecting the polyhedralral surface M.

V. A. Rubakov, D. T. Son

We consider classical Minkowskian solutions to the field equation in the (1+1) dimensional scalar model with the exponential interaction that describe the unsuppressed false vacuum decay induced by $n$ initial particles. We find that there is a critical value of $n$ below which there are no such solutions, i.e., the vacuum decay is always suppressed. For the

Bernd A. Kniehl, Alberto Sirlin

We discuss a recent analysis of $t\bar{t}$ threshold effects and its implications for the determination of electroweak parameters. We show that the new formulation, when applied to the $ρ$ parameter for $m_t\approx158$~GeV, gives a result of similar magnitude to those previously obtained. In fact, it is quite close to our ``resonance&#39;&#39; calculation. W

Elena Accomando, Silvano Petrarca

The production of a single exotic Higgs particle is studied at Hera. Within the present limits on the Yukawa couplings this doubly charged particle, suggested by the left-right symmetric models, can be observed at Hera up to values of its mass of about 150 GeV.

P. S. Spencer, C. Michael

We investigate the {\it topography\/} of the \o3 vacuum after various degrees of under-relaxed cooling, using the na\&#34;ıve action density and geometric and field theoretical definitions of the topological charge density. The results are presented graphically. (This is a cutdown version of the full paper which is available via anonymous ftp to suna.amtp.li

Deniz Ertas, Mehran Kardar

The depinning of a contact line is studied as a dynamical critical phenomenon by a functional renormalization group technique. In $D=2-ε$ interface dimensions, the roughness exponent is $ζ=ε/3$ to all orders in perturbation theory. Thus, $ζ=1/3$ for the contact line, equal to the Imry-Ma estimate of Huse for the equilibrium roughness. The dynamical exponent

A. A. Nersesyan, A. M. Tsvelik, F. Wenger

Influence of weak nonmagnetic impurities on the single-particle density of states $ρ(ω)$ of two-dimensional electron systems with a conical spectrum is studied. We use a nonperturbative approach, based on replica trick with subsequent mapping of the effective action onto a one-dimensional model of interacting fermions, the latter being treated by Abelian and

J. Lorenzana, A. Dobry

Exact diagonalization calculations show a continuous transition from delocalized to small polaron behavior as a function of intersite electron-lattice coupling. A transition, found previously at Hartree-Fock level [Yonemitsu et al., Phys. Rev. Lett. {\bf 69}, 965 (1992)], between a magnetic and a non magnetic state does not subsist when fluctuations are incl

X. Y. Zhang, G. M. Zhang

We present an asymptotically exact solution of the $\infty-d$ Hubbard model at a special interaction strength $U_T$ corresponding to the strong-coupling Fermi-liquid fixed point. This solution is intimately related to the Toulouse limit of the single-impurity Kondo model and the symmetric Anderson model in its strong-coupling limit.

Imre Varga, János Pipek

The scaling properties of the wave functions in finite samples of the one dimensional Anderson model are analyzed. The states have been characterized using a new form of the information or entropic length, and compared with analytical results obtained by assuming an exponential envelope function. A perfect agreement is obtained already for systems of $10^3$-

Dan Maoz, Andrew Gould

A Massive Compact Halo Object (Macho) that lenses a background star will magnify different parts of the rotating stellar disk by varying amounts. The differential magnification will cause a shift in the centroid of the star&#39;s spectral lines during the lensing event. The shift is proportional to the ratio of the stellar radius to the projected separation

Eric Woods, Abraham Loeb

We place empirical constraints on the physical properties of $γ-$ray burst events at cosmological distances. In particular we derive probability distributions for the radiation energy $E_γ$, the minimum Lorentz factor $γ_{\rm min}$, the maximum baryonic mass $M_{\rm max}$ and the upper bound on the surrounding gas density $n_{\rm max}$ in the events, based o

Dan Kiselman

The formation of the resonance lines of neutral boron in solar-type stellar atmospheres is investigated taking into account effects of departures from local thermodynamic equilibrium (NLTE effects). The latter are due to a combination of overionisation and optical pumping in resonance lines, both caused by the hot, non-local, ultraviolet radiation fields in

Enzo Branchini, Luigi Guzzo, Riccardo Valdarnini

We show how, based on considerations on the observed form of the galaxy 2-point spatial correlation function xi(r), a very simplified -- yet surprisingly effective -- model for the linear density fluctuations power spectrum can be constructed. We first relate the observed large-scale shape of xi(r) to a power-law form for the power spectrum, P(k)\propto k^{-

W. Cai, T. C. Lubensky, P. Nelson, T. Powers

We study two geometrical factors needed for the correct construction of statistical ensembles of surfaces. Such ensembles appear in the study of fluid bilayer membranes, though our results are more generally applicable. The naive functional measure over height fluctuations must be corrected by these factors in order to give correct, self-consistent formulas

Stanley Myint, Claudio Rebbi

We evaluate the coefficients of the effective chiral Lagrangian to $O(p^4)$ in the strong coupling, large-N expansion. In this limit we explicitly perform the functional integral over fundamental degrees of freedom and obtain the effective chiral Lagrangian. We perform this calculation on the Body Centered Hypercubical lattice which preserves Euclidean invar

Daniel J. Eisenstein, Abraham Loeb

We show that seeds for quasar black holes could have originated from the initial cosmological collapse of overdense regions with unusually small rotation. The gas in these rare regions collapses into a compact disk that shrinks on a short viscous time scale. Using an analytical model, we calculate the low-spin tail of the probability distribution of angular

Valeri V. Dvoeglazov

This talk presents the review of forgotten but attractive formalism proposed by Joos and Weinberg in the sixties for description of high-spin particles. Problems raised in the recent works [Ahluwalia {\it et al.}] are discussed. New results obtained by the author in his preceding papers [&#34;Hadronic J.&#34;, 1993, v. 16, No. 5, pp. 423-428; No. 6, pp. 459-

Francois Englert, Benni Reznik

The tunneling approach, for entropy generation in quantum gravity, is shown to be valid when applied to 3-D general relativity. The entropy of de Sitter and Reissner-Nordström external event horizons and of the 3-D black hole obtained by Bañados et. al. is rederived from tunneling of the metric to these spacetimes. The analysis for spacetimes with an externa

E. L. Wright, G. F. Smoot, C. L. Bennett, P. M. Lubin

The angular power spectrum estimator developed by Peebles (1973) and Hauser & Peebles (1973) has been modified and applied to the 2 year maps produced by the COBE DMR. The power spectrum of the real sky has been compared to the power spectra of a large number of simulated random skies produced with noise equal to the observed noise and primordial density flu

Andrew R Liddle, David H Lyth

We address the possibility of bounding the spectral index $n$ of primordial density fluctuations, using both the cosmic microwave background (cmb) anisotropy and data on galaxies and clusters. Each piece of galaxy and cluster data is reduced to a value of $σ(R)$ (the linearly evolved {\em rms} density contrast with top hat smoothing on scale $R$) which allow

I. Sarcevic, H. C. Eggers, H. Th. Elze

We present an effective field theory of multiparticle correlations based on analogy with Ginzburg-Landau theory of superconductivity. We assume that the field represents particle density fluctuations, and show that in the case of gaussian-type effective action there are no higher-order correlations, in agreement with the recent data. We predict that two-part

Ken Yee

We examine in pure SU(3) the dependence of extended monopole current k and cross-species extended monopole current k^{cross} on temperature t, monopole size L, and fractional monopole charge 1/q. We find that features of both k and k^{cross} are sensitive to t for a range of L and q. In particular, the spatial-temporal asymmetry ratios of both k and k^{cross

J. Baez, W. Taylor

Minor corrections made and several references changed.

T. Gisiger, M. B. Paranjape

We study the scattering of two Skyrmions at low energy and large separation. We use the method proposed by Manton for truncating the degrees of freedom of the system from infinite to a manageable finite number. This corresponds to identifying the manifold consisting of the union of the low energy critical points of the potential along with the gradient flow

R. P. Lano, V. G. J. Rodgers

Fermions on a cylinder coupled to gravity and gauge fields are examined by studying the geometric action associated with the symmetries of such a system. The gauge coupling constant is shown to be constrained and the effect of gravity on the masses is discussed. Furthermore, we introduce a new gravitational theory which couples to the fermions by promoting t

Attila Csoto

Using the complex scaling method, the low-lying three-body resonances of $^6$He, $^6$Li, and $^6$Be are investigated in a parameter-free microscopic three-cluster model. In $^6$He a 2$^+$, in $^6$Li a 2$^+$ and a 1$^+$, and in $^6$Be the 0$^+$ ground state and a 2$^+$ excited state is found. The other experimentally known 2$^+$ state of $^6$Li cannot be loca

I. Juhász, Lajos Soukup, Z. Szentmiklóssy

We formulate several conditions (two of them are necessary and sufficient) which imply that a space of small character has large weight. In section 3 we construct a ZFC example of a first countable 0-dimensional space X of size 2^omega with w(X)=2^omega and nw(X)=omega, we show that CH implies the existence of a 0-dimensional space Y of size omega_1 with w(Y

Joshua Boorstein, David Kutasov

Two dimensional QCD coupled to fermions in the adjoint representation of the gauge group $SU(N)$, a useful toy model of QCD strings, is supersymmetric for a certain ratio of quark mass and gauge coupling constant. Here we study the theory in the vicinity of the supersymmetric point; in particular we exhibit the algebraic structure of the model and show that

Volker Schomerus

It has been discussed earlier that ( weak quasi-) quantum groups allow for conventional interpretation as internal symmetries in local quantum theory. From general arguments and explicit examples their consistency with (braid-) statistics and locality was established. This work addresses to the reconstruction of quantum symmetries and algebras of field opera

Michael G. Sotiropoulos, George Sterman

We calculate the leading twist contribution to near-forward proton-proton (and proton-antiproton) elastic scattering with large momentum transfer, in the multiple scattering (Landshoff) mechanism. The amplitude in the near-forward region is dominated by singlet exchange for all three valence quark-quark scatterings. We assume the existence of a hard singlet

Estia Eichten, Kenneth Lane

Pair-production of heavy top quarks at the Tevatron Collider is significantly enhanced by the color--octet technipion, $η_T$, occurring in multiscale models of walking technicolor. We discuss $\bar tt$ rates for $m_t = 170$ GeV and $M_{η_T} = 400-500$ GeV. Multiscale models also have color--octet technirho states in the mass range 200-600 GeV that appear as

S. A. Abel, K. E. C. Benson

We examine the generation of baryon asymmetry at the weak scale from a primordial lepton asymmetry. If the electroweak phase transition is first order, partial reflection of tau leptons off the bubble walls and the resulting hypercharge transport into the symmetric phase, gives rise to a baryon number consistent with observation.

H. C. Chiang, J. Hüfner, H. J. Pirner

We calculate the corrections to the three-gluon decay widths $Γ_{3g}$ of $c\bar c$ and $b \bar b$ quarkonia due to the finite extension of the $Q\bar Q\to 3g$ vertex function. The widths computed with zero range vertex are reduced by a factor $γ$ where $γ=0.31$ for the $J/ψ$ and $γ=0.69$ for the $Υ$. These large corrections necessitate a redetermination of t

Richard F. Lebed, Markus A. Luty

We analyze the baryon mass differences up to second order in chiral perturbation theory, including the effects of decuplet intermediate states. We show that the Coleman--Glashow relation has computable corrections of order $(m_d - m_u) m_s$. These corrections are numerically small, and in agreement with the data. We also show that corrections to the $Σ$ equa

Noriaki Kitazawa

The extended technicolor theory is a candidate of the physics beyond the standard model. To explain the mass hierarchy of the quarks and leptons, the extended technicolor gauge symmetry must hierarchically break to the technicolor gauge symmetry. Tumbling gauge theory is considered as a candidate of the dynamics of such hierarchical symmetry breaking, since

Stanley Myint, Claudio Rebbi

After a very brief review of the formalism of lattice gauge theories we show how one can calculate the parameters of the continuum chiral Lagrangians proceeding through the derivation of an effective lattice chiral Lagrangian as an intermediary step. The derivation is done in the strong coupling limit. We also discuss how the derivation could be carried out

Frithjof Karsch

We review recent results on QCD at finite temperature. In particular we will discuss the chiral phase transition in two flavour QCD and new results on the excitation spectrum in the plasma phase of QCD.

Lian Zheng, H. A. Fertig

We study a trial wavefunction for an interstitial in a Wigner crystal. We find that the electron correlations, ignored in a conventional Hartree-Fock treatment, dramatically lower the interstitial energy, especially at fillings close to an incompressible liquid state. The correlation between the interstitial electron and the lattice electrons at $ν<1/m$ is i

M. Sigrist, T. M. Rice, F. C. Zhang

The single rung t-J ladder is analyzed in a mean field theory using Gutzwiller renormalization of the matrix elements to account for strong correlation. The spin liquid (RVB) state at half-filling evolves into a superconducting state upon doping. The order parameter has a modified d-wave character. A lattice of weakly coupled ladders should show a supercondu

Y. Yu, Y. M. Li, N. d&#39;Ambrumenil

Non-Fermi liquid behavior is found for the first time in a two-dimensional (2D) system with non-singular interactions using Haldane&#39;s bosonization scheme. The bosonized system is solved exactly by a generalized Bogoliubov transformation. The fermion momentum distribution, calculated using a generalized Mattis-Lieb technique, exhibits a non-universal powe

Y. M. Li, N. d&#39;Ambrumenil

An approximate partition functional is derived for the infinite-dimensional Hubbard model. This functional naturally includes the exact solution of the Falicov-Kimball model as a special case, and is exact in the uncorrelated and atomic limits. It explicitly keeps spin-symmetry. For the case of the Lorentzian density of states, we find that the Luttinger the

J. Pelt, W. Hoff, R. Kayser, S. Refsdal

We present a new analysis of previously published optical and radio data sets of the gravitationally lensed quasar 0957+561 A,B with the aim of determining the time delay between its two images. We use a non-parametric estimate of the dispersion of the combined data set where, however, we only make use of alternating neighbours in order to avoid windowing ef

David Eisenbud, Bernd Sturmfels

We investigate the structure of ideals generated by binomials (polynomials with at most two terms) and the schemes and varieties associated to them. The class of binomial ideals contains many classical examples from algebraic geometry, and it has numerous applications within and beyond pure mathematics. The ideals defining toric varieties are precisely the b

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

The first two years of COBE DMR observations of the CMB anisotropy are analyzed and compared with our previously published first year results. The results are consistent, but the addition of the second year of data increases the precision and accuracy of the detected CMB temperature fluctuations. The two-year 53 GHz data are characterized by RMS temperature

A. Hanany, Y. Oz, M. R. Plesser

We construct a topological Landau-Ginzburg formulation of the two-dimensional string at the self-dual radius. The model is an analytic continuation of the $A_{k+1}$ minimal model to $k=-3$. We compute the superpotential and calculate tachyon correlators in the Landau-Ginzburg framework. The results are in complete agreement with matrix model calculations. We

Flora Pempinelli

By introducing generalized Backlund Transformations depending on arbitrary functions, wave and localized soliton solutions of the Davey- Stewartson equations are generated. Moreover explicit soliton solutions of the Hamiltonian DSI and DSIII equations are obtained.

Th. A. Rijken

After a short survey of some topics of interest in the study of baryon-baryon scattering, the recent Nijmegen energy dependent partial wave analysis (PWA) of the nucleon-nucleon data is reviewed. In this PWA the energy range for both pp and np is now 0 < Tlab < 350 MeV and a chi^2_{d.o.f.}=1.08 was reached. The implications for the pion-nucleon coupling cons

Weidong Zhao

By a mapping to the bosonic string theory, we present an exact solution to the O(26) sigma model coupled to 2-D quantum gravity. In particular, we obtain the exact gravitational dressing to the various matter operators classified by the irreducible representations of O(26). We also derive the exact form of the gravitationally modified beta function for the o

D. R. Grigore

A complete list of all transitive symplectic manifolds of the Poincaré and Galilei group in 1+2 dimensions is given.

Mihai Visinescu

The geodesic motion of pseudo-classical spinning particles in the Euclidean Taub-NUT space is analysed. The generalized Killing equations for spinning space are investigated and the constants of motion are derived in terms of the solutions of these equations. A simple exact solution, corresponding to trajectories lying on a cone, is given.

A. Khvedelidze, V. Pervushin

Zero modes of first class secondary constraints in the two-dimensional electrodynamics and the four-dimensional SU(2) Yang-Mills theory are considered by the method of reduced phase space quantization in the context of the problem of a stable vacuum. We compare the description of these modes in the Dirac extended method and reveal their connection with the t

S. Randjbar-Daemi, J. Strathdee

Some aspects and applications of $ σ$-models in particle and condensed matter physics are briefly reviewed.

Andre Roberge

Using a simple model, a new sphaleron solution which incorporates finite fermionic density effects is obtained. The main result is that the height of the potential barrier (sphaleron energy) decreases as the fermion density increases. This suggests that the rate of sphaleron-induced transitions increases when the fermionic density increases. However the rate

R. P. Manvelyan, R. L. Mkrtchyan

The geometric action on a certain orbit of the group of the area-preserving diffeomorphisms is considered, and it is shown, that it coincides with a special reduction of the three-dimensional Chern-Simons theory, under which group and space coordinates are identified.

D. R. Karakhanyan, R. P. Manvelyan, R. L. Mkrtchyan

The effective action for 2d-gravity with manifest area-preserving invariance is obtained in the flat and in the general gravitational background. The cocyclic properties of the last action are proved, and generalizations on higher dimensions are discussed.

Antonio Dobado, Antonio Lopez, John Morales

The large N effective action of the non-linear sigma model based in the coset O(N+1)/O(N) is obtained. The renormalization of this effective action requires the introduction of an infinite set of counterterms. However, there exit particular cases where, at some scale, only a finite number of non-zero coupling constants are present. This fact makes possible a

Jamal Jalilian-Marian

We study radiative decay modes of the Z-boson into heavy quark bound states. We find that the widths for these decays are extremely small. We conclude that these decays will not be detectable for the time being unless there is a significant increase in the number of Z-bosons produced at the electron- positron colliders.

James T. Liu, Daniel Ng

By extending the electroweak gauge group to $SU(3)_L\times U(1)_Y$, the 331 model incorporates dilepton gauge bosons $Y$ which do not respect individual lepton family number. We point out that, in addition to family diagonal couplings such as $Y$--$e$--$e$ that change lepton family number by two units, dileptons may also have family non-diagonal couplings su

F. Caravaglios

We investigated the possibility of introducing sizeable negative corrections to the $\varepsilon_{N1}$ ($δρ$) parameter without affecting $\varepsilon_{N3}$. We have found that a proper vector-like family of fermions can imply such corrections. Differently from supersymmetry \cite{bcf}, this can be realized without introducing light particles easily observab

Adam F. Falk, Zoltan Ligeti, Matthias Neubert, Yosef Nir

We calculate the differential decay rate for inclusive $\bar B\toτ\,\barν\,X$ transitions to order $1/m_b^2$ in the heavy quark expansion, for both polarized and unpolarized tau leptons. We show that using a systematic $1/m_b$ expansion significantly reduces the theoretical uncertainties in the calculation. We obtain for the total branching ratio ${\rm BR}(\

Chao-Hsi Chang, Yu-Qi Chen

Under the framework of the Bethe-Salpeter (B.S.) wave functions and the Mandelstam formalism as well, to make ``instantaneous approximation&#39;&#39; to a transition matrix element (a current operator sandwiched between two bound-states of double heavy quarks) is described. By taking the typical concerned decays as examples, such as $B_c$ meson decaying to $

Tonatiuh Matos

We present the complete scheme of the application of the one-and two dimensional subspace and subgroups method to five-dimensional gravity with a $G_{3}$ group of motion. We do so in the space time and in the potential space formalisms. From this method one obtains the Kramer, Belinsky-Ruffini, Dobiasch-Maison, Clément, Gross-Perry-Sorkin solutions etc. as s

Hideo Kodama, Hideki Ishihara, Yoshihisa Fujiwara

The behavior of gravitational wave perturbations on a locally Minkowskian spacetime background containing a planar domain wall is investigated in the gauge-invariant general relativistic framework. It is shown that for this particular background the domain wall does not emit gravitational waves spontaneously by its free oscillation in the first order, althou

Amaral, Barabasi, Buldyrev, Havlin

We report imbibition experiments investigating the effect of evaporation on the interface roughness and mean interface height. We observe a new exponent characterizing the scaling of the saturated surface width. Further, we argue that evaporation can be usefully modeled by introducing a gradient in the strength of the disorder, in analogy with the gradient p

Edmund J Copeland, Andrew R Liddle, David H Lyth, Ewan D Stewart

We investigate chaotic inflation models with two scalar fields, such that one field (the inflaton) rolls while the other is trapped in a false vacuum state. The false vacuum becomes unstable when the inflaton field falls below some critical value, and a first or second order transition to the true vacuum ensues. Particular attention is paid to Linde&#39;s se

A. Ferrara, R. J. Dettmar

We present a study of the radio emission from rotating, charged dust grains immersed in the ionized gas constituting the thick, H$α$-emitting disk of many spiral galaxies. Using up-to-date optical constants, the charge on the grains exposed to the diffuse galactic UV flux has been calculated. An analytical approximation for the grain charge has been derived,

M. Milgrom

We describe a simple derivation of virial relations (VR) for arbitrary action-governed systems. These follow directly from the action with no need to go via the equations of motion. When some of the degrees of freedom are of the same type a tensor virial theorem presents itself. Further generalizations are discussed. Symmetries of the action may lead to iden