December 1998 arXiv papers — page 4

Herbert Kroemer

A simple one-dimensional model for SNS weak links in the ballistic limit is presented. In the presence of a bias voltage, the quasiparticle state at any given instant of time is described as a superposition of that particular set of phase-dependent Andreev bound states that belongs to the specific phase difference present at this instant between the supercon

Christos Panagopoulos, Jeffery L Tallon, Tao Xiang

The temperatuer dependence of the magnetic penetration depth of grain aligned YBa2Cu4O8 has been measured along the ab plane and c-axis. Both $λ_ab$ and $λ_c$ vary as \sqrt{T} up to 0.4Tc implying a square root density of states at low energy. The results are discussed in terms of a proximity model of alternating stacked superconducting and normal layers

C. W. J. Beenakker

A theory is presented for the universal reduction of shot noise by Coulomb repulsion, which was observed in computer simulations of a disordered non-degenerate electron gas by Gonzalez et al. (cond-mat/9803372). The universality of the reduction below the uncorrelated value is explained as a feature of the high-voltage regime of space-charge limited conducti

Matthew B. Kennel, Alistair I. Mees

We construct a statistic and null test for examining the stationarity of time-series of discrete symbols: whether two data streams appear to originate from the same underlying unknown dynamical system, and if any difference is statistically significant. Using principles and computational techniques from the theory of data compression, the method intelligentl

J. D. Law-Green, A. Zezas, M. J. Ward, C. Boisson

Mid-infrared photometry of the hosts of Narrow-Line X-ray Galaxies at 6 microns and 12 microns has been attempted with ISOCAM. No conclusive detections have been made. This implies that these are quiescent objects with little or no active star-formation. Neither X-ray binaries nor starburst-driven superwinds are consistent explanations for the X-ray emission

T. Shahbaz, E. Kuulkers, P. A. Charles, F. van der Hooft

We have obtained high resolution optical spectroscopy of the accretion disc corona source 2S0921--630 (=V395 Car) that constrains the spectral type of the companion star to be most probably K0III. At 6500A the secondary star is found to contribute ~25% to the observed flux. The absorption line spectrum of the K0III companion star is broadened (compared to te

O. K. Sil'chenko, A. N. Burenkov, V. V. Vlasyuk

By using bidimensional spectral data obtained at the 6m telescope for the Virgo spirals NGC 4216 and NGC 4501, we have found chemically distinct metal-rich nuclei in these galaxies. Under the assumption of equal ages for the nuclear and bulge stellar populations, the metallicity difference between the nuclei and their environments in the galaxies is estimate

F. Combes

In the last years, progress has been very rapid in the domain of molecules at high redshift, and we know in better detail now the molecular and dust content in several systems beyond z=1 and up to z = 5. The first discovery in 1992 by Brown and van den Bout of CO lines at z=2.28 in a gravitationally lensed starburst galaxy, strongly stimulated searches of ot

H. Baumgardt, C. Dettbarn, B. Fuchs, J. Rockmann

The statistical test described by Wielen et al.(1994) is used to derive new zero-points of ground-based Cepheid period-luminosity (PL) and period-luminosity-colour (PLC) relations. Eleven relations are compared with the Hipparcos data. Our results argue for a typical increase of the adopted distance scale by about 8% +- 8%. Our zero-point for the PL relation

Ralph Neuhaeuser, Cesar Briceno, Fernando Comeron, Thomas Hearty

Following the recent classification of the X-ray detected object V410 x-ray 3 with a young brown dwarf candidate (Briceno et al. 1998) and the identification of an X-ray source in Chamaeleon as young bona-fide brown dwarf (Neuhaeuser & Comeron 1998), we investigate all ROSAT All-Sky Survey and archived ROSAT PSPC and HRI pointed observations with bona-fide o

T. R. Marsh

We present time-resolved spectra of the double-degenerate binary star, GP Com. The spectra confirm the presence and period (46.5 min) of the `S'-wave feature found by Nather, Robinson and Stover. GP Com is erratically variable at X-ray and UV wavelengths. We have found the equivalent variability in our data, which, as also seen in UV data, is mostly conf

J. U. Fynbo, P. Moller, S. J. Warren

The number of damped Ly-alpha absorbers (DLAs) currently known is about 100, but our knowledge of their sizes and morphologies is still very sparse as very few have been detected in emission. Here we present narrow-band and broad-band observations of a DLA in the field of the quasar pair Q0151+048A (qA) and Q0151+048B (qB). These two quasars have very simila

M. Ostrowski

The particle acceleration process at a shock wave, in the presence of the second-order Fermi acceleration in the turbulent medium near the shock, is discussed as an alternative explanation for the observed flat synchrotron spectra of supernova remnants (SNRs) in molecular clouds. We argue that medium Alfvén Mach number shocks considered by Chevalier (1999, A

G. C. Anupama, J. Mikolajewska

Spectroscopic and photometric behaviour of the class of recurrent novae with giant secondaries (T Coronae Borealis, RS Ophiuchi, V3890 Sagittarii and V745 Scorpii) at quiescence are presented in this study. The hot component in these systems is variable, with the variability manifesting as variability in the ultraviolet luminosity, the ultraviolet and optica

Atsushi Kawai, Junichiro Makino

We present the pseudo-particle multipole method (P2M2), a new method to handle multipole expansion in fast multipole method and treecode. This method uses a small number of pseudo-particles to express multipole expansion. With this method, the implementation of FMM and treecode with high-order multipole terms is greatly simplified. We applied P2M2 to treecod

N. A. Zabotin, E. S. Kovalenko

Computer simulations of radio energy transfer in the ionospheric layer with random small-scale irregularities for the case of a point ground-based source and total reflection have been carried out using specially designed algorithm based on Monte Carlo method ideas. The model demonstrates redistribution of the reflected radiation power on the Earth's sur

J. S. Greaves, W. S. Holland, P. Friberg, W. R. F. Dent

Linearly polarized, non-masing, rotational lines have been detected for the first time in the interstellar medium. This effect occurs in molecular clouds with a magnetic field, and traces the field direction, offering an alternative technique to dust emission polarimetry. The line polarization mechanism is similar to that in masers, but with lower degrees of

L. Kaper, H. F. Henrichs, J. S. Nichols, J. H. Telting

A quantitative analysis of time series of ultraviolet spectra from a sample of 10 bright O-type stars (cf. Kaper et al. 1996, Paper I) is presented. The migrating discrete absorption components (DACs), responsible for the observed variability in the UV resonance doublets, are modeled. It turns out that the column density of a DAC first increases and subseque

E. Ramirez-Ruiz, E. E. Fenimore

Many cosmological models of GRBs envision the energy source to be a cataclysmic stellar event leading to a relativistically expanding fireball. Particles are thought to be accelerated at shocks and produce nonthermal radiation. The highly variable temporal structure observed in most GRBs has significantly constrained models. By using different methods of sta

P. Traat

We have studied the spectral evolution of stellar populations in function of their heavy element content and star formation, using Geneva and Padova stellar track sets, both covering a number of metallicities, and Kurucz grid of stellar atmospheres. The general trend is the progressive growth of absorption and decline of flux towards shorter, UV-wavelengths,

Asantha R. Cooray

The submillimeter universe has now been explored with the Submillimeter Common User Bolometer Array (SCUBA) camera on the James Clerk Maxwell Telescope, and a claim has been made to the presence of a new population of optically unidentified starforming galaxies at high redshifts (z \gtrsim 3). Such a population dramatically alters current views on the star f

S. De Grandi, L. Guzzo, H. Böhringer, S. Molendi

We present the X-ray luminosity function (XLF) for clusters of galaxies derived from the RASS1 Bright Sample. The sample, selected from the ROSAT All-Sky Survey in a region of 2.5 sr within the southern Galactic cap, contains 130 clusters with flux limits in the range ~ 3-4 x 10^-12 ergs/cm^2/s in the 0.5-2.0 keV band. A maximum-likelihood fit with a Schecht

G. Chalmers, M. Rocek, S. Wiles

Beginning with the Legendre transform construction of hyperkähler metrics, we analyze the ALF version of the D_n metrics. We determine the constraint equation obtained from extremizing the $w$ coordinate of the generating function F(z,\bar{z},u,\bar{u},w) and study its behavior as we send two of the mass parameters of the $D_n$ metric to zero. We find that t

Till D. Kuehner, Steven R. White

The density matrix renormalization group (DMRG) method allows for very precise calculations of ground state properties in low-dimensional strongly correlated systems. We investigate two methods to expand the DMRG to calculations of dynamical properties. In the Lanczos vector method the DMRG basis is optimized to represent Lanczos vectors, which are then used

H. D. Trottier

The first observation is made of hadronic string breaking due to dynamical fermions in zero temperature lattice QCD. The simulations are done for SU(2) color in three dimensions, with two flavors of staggered fermions. The results have clear implications for the large scale simulations that are being done to search (so far, without success) for string breaki

Stefano Forte, Lorenzo Magnea

We derive evolution equations satisfied by moments of parton distributions when the integration over the Bjorken variable is restricted to a subset (x_0 <= x <= 1) of the allowed kinematical range 0<= x<= 1. The corresponding anomalous dimensions turn out to be given by a triangular matrix which couples the N--th truncated moment with all (N + K)--th truncat

Danny Birmingham, Conall Kennedy, Siddhartha Sen, Andy Wilkins

We show how a theorem of Sullivan provides a precise mathematical statement of a 3d holographic principle, that is, the hyperbolic structure of a certain class of 3d manifolds is completely determined in terms of the corresponding Teichmuller space of the boundary. We explore the consequences of this theorem in the context of the Euclidean BTZ black hole in

Andrew W. Blain, Jean-Paul Kneib, R. J. Ivison, Ian Smail

We present the counts of luminous submillimeter (sub-mm) galaxies from an analysis of our survey of the distant Universe through lensing clusters, which uses massive cluster lenses with well-constrained mass models to magnify the background sky. This both increases the sensitivity and reduces the effects of source confusion. Accurate lens models are used to

E. O. Alt, T. Csörgö, B. Lörstad, J. Schmidt-Sørensen

Starting from an asymptotically correct three-body Coulomb wave-function, we determine the effect of Coulomb final state interaction on the three-particle Bose-Einstein correlation function of similarly charged particles. We numerically estimate that the Riverside approximation is not precise enough to determine the three-body Coulomb correction factor in th

Guido Altarelli, Ferruccio Feruglio

Assuming three light neutrinos and the see-saw mechanism we present a semiquantitative model of fermion masses based on (SUSY) SU(5) and abelian horizontal charges. A good description of the observed pattern of quark and lepton masses is obtained. For neutrinos we naturally obtain widely split masses and large atmospheric neutrino mixing as a consequence of

J. S. Dowker

The effective actions of a scalar and massless spin-half field are determined as functions of the deformation of a symmetrically squashed three-sphere. The extreme oblate case is particularly examined as pertinant to a high temperature statistical mechanical interpretation that may be relevant for the holographic principle. Interpreting the squashing paramet

Jonathan Rosenberg

In a strengthening of the G-Signature Theorem of Atiyah and Singer, we compute, at least in principle (modulo certain torsion of exponent dividing a power of the order of G), the class in equivariant K-homology of the signature operator on a G-manifold, localized at a prime idea of R(G), in terms of the classes in non-equivariant K-homology of the signature

Karl Mannheim

Three independent predictions follow from postulating the existence of protons co-accelerated with electrons in extragalactic jets (i) multi-TeV gamma ray emission from nearby blazars, (ii) extragalactic cosmic ray protons up to 10^20 eV, and (iii) extragalactic neutrinos up to 5 10^18 eV. Recent gamma ray observations of Mrk 421 and Mrk 501 employing the ai

Johan Holmberg, Chris Flynn

We determine the velocity distribution and space density of a volume complete sample of A and F stars, using parallaxes and proper motions from the Hipparcos satellite. We use these data to solve for the gravitational potential vertically in the local Galactic disc, by comparing the Hipparcos measured space density with predictions from various disc models.

M. Knecht, S. Peris, E. de Rafael

It is shown that the K -> pi pi matrix elements of the four-quark operator Q_7, generated by the electroweak penguin-like diagrams of the Standard Model, can be calculated to first non-trivial order in the chiral expansion and in the 1/Nc expansion. Although the resulting B factors B_7^(1/2) and B_7^(3/2) are found to depend only logarithmically on the match

B. Ludoph, J. M. van Ruitenbeek

The thermopower and conductance of atomic-size metallic contacts have been simultaneously measured using a mechanically controllable break junction. For contacts approaching atomic dimensions, abrupt steps in the thermopower are observed which coincide with jumps in the conductance. The measured thermopower for a large number of atomic-size contacts is rando

George Jorjadze, Włodzimierz Piechocki

We consider dynamics of massless particle in 2d spacetimes with constant curvature. We analyze different examples of spacetime. Dynamical integrals are constructed from spacetime symmetry related to $sl(2.{\bf R})$ algebra. Mass-shell condition restricts dynamical integrals to a cone (without vertex) which defines physical-phase space. We parametrize the con

Hagen Kleinert

Using strong-coupling quantum field theory we calculate highly accurate critical exponents nu, eta from new seven-loop expansions in three dimensions. Our theoretical value for the critical exponent alpha of the specific heat near the lambda-point of superfluid helium is alpha =-0.01294+-0.00060, in excellent agreement with the space shuttle experimental val

Y. F. Gu, X. H. Li

Recent data on branching ratios for ψ(2S) decays to J/ψπ^+π^-, J/ψπ^0π^0 and J/ψηare reviewed. An alternative treatment of data is proposed to get rid of the logical inconsistency which occurs in original computational procedure.

Masahide Sasaki, Stephen M. Barnett, Richard Jozsa, Masao Osaki

We study the problem of optimizing the Shannon mutual information for sources of real quantum states i.e. sources for which there is a basis in which all the states have only real components. We consider in detail the sources ${\cal E}_M$ of $M$ equiprobable qubit states lying symmetrically around the great circle of real states on the Bloch sphere and give

Shi-Lin Zhu

We have calculated the binding energy of the hybrid quarkonium up to the order of ${\cal O}(1/m_Q)$ and found their decay constants scale like $m_Q^{5/4}$ as $m_Q\to \infty$. The $0^{--}$ and $0^{++}$ hybrid quarkonium is exactly degenerate in the limit of $m_Q\to\infty$ while the ${\cal O}(1/m_Q)$ correction renders the $0^{--}$ mass lower than that for $0^

M. A. Ivanov, Yu. L. Kalinovsky, C. D. Roberts

We employ a Dyson-Schwinger equation model to effect a unified and uniformly accurate description of light- and heavy-meson observables, which we characterise by heavy-meson leptonic decays, semileptonic heavy-to-heavy and heavy-to-light transitions - B -> D*, D, rho, pi; D -> K*, K, pi, radiative and strong decays - B(s)* -> B(s) gamma; D(s)* -> D(s) gamma,

A. Balan

This text has been withdrawn by the author.

Gérard Cohen, Sylvia Encheva, Simon Litsyn

Using the notion of generalized weight we improve estimates on the parameters of quantum codes obtained by Steane&#39;s construction from binary codes. This yields several new families of quantum codes.

Guihua Zeng

A simplified eavesdropping-strategy for BB84 protocol in quantum cryptography (refer to quant-ph/9812022) is proposed. This scheme implements by the `indirect copying&#39; technology. Under this scheme, eavesdropper can exactly obtain the exchanged information between the legitimate users without being detected.

M. Bachmann, H. Kleinert, A. Pelster

We develop convergent variational perturbation theory for quantum statistical density matrices. The theory is applicable to polynomial as well as nonpolynomial interactions. Illustrating the power of the theory, we calculate the temperature-dependent density of a particle in a double-well and of the electron in a hydrogen atom.

L. Frappat, A. Sciarrino, P. Sorba

The ratios of the codon usage in the quartets and sextets for the vertebrate series exhibit a correlated behaviour which fits naturally in the framework of the crystal basis model of the genetic code. Moreover the observed universal behaviour of these suitably normalized ratios can be easily explained.

K. Hasebe, A. Nakayama, Y. Sugiyama

The exact solutions of the first order differential equation with delay are derived. The equation has been introduced as a model of traffic flow. The solution describes the traveling cluster of jam, which is characterized by Jacobi&#39;s elliptic function. We also obtain the family of solutions of such type of equations.

W. Poeschl, B. Mueller

The Yang Mills equations provide a classical mean field description of gauge fields. In view of developing a coherent description of the formation of the quark gluon plasma in high energetic nucleus-nucleus collisions we study pure gauge field dynamics in 3+1 dimensions. In collisions of wave packets, numerically simulated on a SU(2) gauge lattice, we study

A. Mengoni

We show how to derive nuclear structure information on loosely bound nuclei far from the beta stability line from their Coulomb dissociation into the continuum. The 19C -> 18C + n process is taken as an example and it is shown that basic properties such as ground-state spin and parity and the neutron binding energy of the halo nucleus 19C can be derived from

L. P. Kaptari, B. Kaempfer, S. M. Dorkin, S. S. Semikh

The elastic backward proton-deuteron scattering is analyzed within a covariant approach based on the Bethe-Salpeter equation with realistic meson-exchange interaction. Contributions of the one-nucleon and one-pion exchange mechanisms to the cross section and polarization observables are investigated in explicit form. Results of numerical calculations for the

Christof Kuelske

We consider the Gibbs-measures of continuous-valued height configurations on the $d$-dimensional integer lattice in the presence a weakly disordered potential. The potential is composed of Gaussians having random location and random depth; it becomes periodic under shift of the interface perpendicular to the base-plane for zero disorder. We prove that there

Christophe Soulé

Let p be an odd prime, n an odd positive integer and C the p-Sylow subgroup the class group of the p-cyclotomic extension of the rationals. When log(p) is bigger than n**(224n**4), we prove that the eigenspace on C attached to the (p-n)-th power of the Teichmuller character is trivial. The proof uses the K-theory of the integers and the Voronoi reduction the

Alejandro Adem, Dikran Karagueuzian, Jan Minac

Let F denote a field of characteristic different from two. In this paper we describe the mod 2 cohomology of a Galois group which is determined by the Witt ring WF.

Alejandro Adem, Ergün Yalçin

We study and relate certain actions and extensions involving 2-groups.

Todd Eisworth, Peter Nyikos, Saharon Shelah

We produce a model of ZFC in which there are no locally compact first countable S-spaces, and in which 2^{aleph_0}<2^{aleph_1}. A consequence of this is that in this model there are no locally compact, separable, hereditarily normal spaces of size aleph_1, answering a question of the second author.

Ronald Brown, A. Razak Salleh

We give formulae for a module presentation of the module of identities among relations for a presentation of a group, in terms of information on 0- and 1-combings of the Cayley graph. This is seen as a special case of extending a partial free crossed resolution of a group given a partial contracting homotopy of its universal cover.

Francisco J. Lopez, Francisco Martin

We construct complete nonorientable minimal surfaces whose Gauss map omits two points of the projective plane. This result proves that Fujimoto&#39;s theorem is sharp in nonorientable case.

Wilberd van der Kallen

We show that the integers in the HMM LLL HNF algorithm have bit length O(m.log(m.B)), where m is the number of rows and B is the maximum square length of a row of the input matrix. This is only a little worse than the estimate O(m.log(B)) in the LLL algorithm.

J. -M. Drézet

In this paper, some particular rational maps P_n ---> P_n+1, called quadratic congruences, are studied. They appear in the theory of exceptional vector bundles on projective spaces.

Ezra Miller, Bernd Sturmfels, Kohji Yanagawa

Monomial ideals which are generic with respect to either their generators or irreducible components have minimal free resolutions derived from simplicial complexes. For a generic monomial ideal, the associated primes satisfy a saturated chain condition, and the Cohen-Macaulay property implies shellability for both the Scarf complex and the Stanley-Reisner co

Christina W. Tønnesen-Friedman

It is shown that if a minimal ruled surface admits a Kähler Yamabe minimizer, then this metric must be generalized Kähler-Einstein and the underlying holomorphic vector bundle of the ruled surface must be quasi-stable.

Patrick Dorey, Roberto Tateo

The spectral determinant $D(E)$ of the quartic oscillator is known to satisfy a functional equation. This is mapped onto the $A_3$-related $Y$-system emerging in the treatment of a certain perturbed conformal field theory, allowing us to give an alternative integral expression for $D(E)$. Generalising this result, we conjecture a relationship between the $x^

C. M. Hull

The SO(32) heterotic string can be obtained from the type IIB string by gauging a discrete symmetry that acts as $(-1)^{F_L}$ on the perturbative string states and reverses the parity of the D-string. Consistency requires the presence of 32 NS 9-branes -- the S-duals of D9-branes -- which give SO(32) Chan-Paton factors to open D-strings. At finite string cou

T. D. Bakeyev

A simplified version of Higher Covariant Derivative regularization for Yang-Mills theory is constructed. This may make Higher Covariant Derivative method more attractive for practical calculations.

J. De Jaegher, J. Raeymaekers, A. Sevrin, W. Troost

We present a convenient method for deriving the transformation of the dilaton under T-duality in the path-integral approach. Subtleties arising in performing the integral over the gauge fields are carefully analysed using Pauli-Villars regularization, thereby clarifying existing ambiguities in the literature. The formalism can not only be applied to the abel

M. Rudolph

This is the written version of a short talk given at the University of Leipzig in December 1998. It reviews some general aspects of string theory from the viewpoint of the search for an unifying theory. Here, special emphasis lies on the motivation to consider string theory not only as the leading candidate for the unification of gravity and the other fundam

M. Billo, R. Russo

The description of D-branes as boundary states for type II string theories (in the covariant formulation) requires particular care in the R-R sector. Also the vertices for R-R potentials that can couple to D-branes need a careful handling. As an illustration of this, the example of the D0-D8 system is reviewed, where a ``microscopic&#39;&#39; description of

A. Kuiroukidis, K. Kleidis, D. B. Papadopoulos

A generic ansatz is introduced which provides families of exact solutions to the equations of motion and constraints for null-strings in Bianchi type I cosmological models. This is achieved irrespective of the form of the metric. Within classes of dilaton cosmologies a backreaction mapping relation is established where the null string leads to more or less a

Clifford V. Johnson

This is a short arrangement of notes on D-branes, offered as an embellishment of five lectures which were presented at the 1998 Trieste Spring School entitled ``Non-Perturbative Aspects of String Theory and Supersymmetric Gauge Theory&#39;&#39;. There is a good number of collections of pedagogical notes on D-branes in the literature, and since space here is

Monika Lynker, Rolf Schimmrigk, Andreas Wisskirchen

Theories in more than ten dimensions play an important role in understanding nonperturbative aspects of string theory. Consistent compactifications of such theories can be constructed via Calabi-Yau fourfolds. These models can be analyzed particularly efficiently in the Landau-Ginzburg phase of the linear sigma model, when available. In the present paper we

Carlos Castro

Several quantum mechanical wave equations for $p$-branes are proposed based on the role that the volume-preserving diffeomorphisms group has on the physics of extended objects. The $p$-brane quantum mechanical wave equations determine the quantum dynamics involving the creation/destruction of $p$-branes in a $D$ dimensional spacetime background with a given

Dmitri V. Fursaev

It is pointed out that the entanglement entropy of quantum fields near the horizon of a two-dimensional black hole can be derived by means of the conformal field theory. This can be done in a way analogous to the computation of the entropy of BTZ black holes. The important feature of the considered case is that the degrees of freedom of the conformal theory

Gia Dvali, S. -H. Henry Tye

We present a novel inflationary scenario in theories with low scale (TeV) quantum gravity, in which the standard model particles are localized on the branes whereas gravity propagates in the bulk of large extra dimensions. This inflationary scenario is natural in the brane world picture. In the lowest energy state, a number of branes sit on top of each other

E. V. Shuryak

In the lecture we review several issues related to recent development in non-perturbative QCD. The ``instanton liquid model&#39;&#39; reproduces not only the basic vacuum parameters (the condensates), but even hadronic correlators. New information obtained from lattice simulations also confirm it. Meanwhile the model itself was developed into a self-consiste

T. Matsushita, E. Perez, R. Rückl

Preliminary results from H1 and ZEUS on Deep Inelastic Scattering (DIS) at high momentum transfer squared $Q^2$ are presented. Used are all available $e^+ p$ data accumulated by the H1 and ZEUS experiments between 1994 and 1997, corresponding to integrated luminosities of $37 {pb}^{-1}$ and $47 {pb}^{-1}$, respectively. The anomalies observed at high $Q^2$ i

Edward Shuryak

This is the full text of the summary talk: copies of transparancies of all talks with Introduction and Summary would be mailed to participants from RIKEN/BNL center

J. Blümlein, A. Tkabladze

The target mass corrections are calculated for all structure functions of neutral and charged current deep inelastic scattering in lowest order in the coupling constant. Representations of the correction to the twist--2 and twist--3 contributions are derived both in Mellin-$n$ and $x$-space. The impact of the target mass corrections on the general relations

H. R. Christiansen, J. Magnin

We derive the nucleon non-perturbative sea-quark distributions coming from a composite model involving quarks and hadronic degrees of freedom. The model predicts a definite structured quark-antiquark asymmetry in the nucleon sea.

D. Cormier, R. Holman

Out-of-equilibrium, non-perturbative, quantum effects significantly modify the standard picture of inflation in a wide class of models including new, natural, and hybrid inflation. We find that the quantum evolution of a single real inflaton field may be modeled by a classical theory of two homogeneous scalar fields. We briefly discuss the important observat

Ashok Goyal

We study the neutrino interaction rates through charged as well as neutral current weak interactions in hot, dense magnetized matter. At densities near the neutrino sphere, matter in the presence of intense magnetic field is polarized and electrons and protons typically occupy the lowest Landau level. The weak interaction rates in such a situation are severa

S. Heinemeyer, W. Hollik, G. Weiglein

We present detailed results of a diagrammatic calculation of the leading two-loop QCD corrections to the masses of the neutral CP-even Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM). The two-loop corrections are incorporated into the full diagrammatic one-loop result and supplemented with refinement terms that take into account leading elec

C. P. Burgess

A brief introduction is given to the methods and spirit of effective lagrangians. The emphasis is on a summary of the overall picture, using a simple model as the vehicle to motivate and illustrate the main points. Powercounting is illustrated by estimating the size of the quantum corrections to the predictions of classical gravity.

Michael C. Birse

Jido, Oka and Hosaka have shown that the p-slash gamma_5 piece of the pion-to-vacuum correlator of two baryon interpolating fields vanishes in the soft-pion limit, as a consequence of chiral transformation properties of those fields. This is a statement about the particular combination of pion-baryon couplings and subtraction terms that corresponds to the ch

V. N. Baier, V. M. Katkov

Transition radiation (TR) from ultrarelativistic particles is considered. It is shown that performing collimation of the TR from the periodic N-foil stack (parameters of which are selected in a appropriate manner) one obtains the spectrum of the TR which has a form of a peak position of which $ω_1$ depends on the plasma frequency and the thickness of the rad

Gabriele Gionti

We study the elongated phase of 4-D Dynamical Triangulations. In the case of the sphere topology by using the Walkup&#39;s theorem we show that the dominating configurations are stacked spheres. These stacked spheres can be mapped into tree-like graphs (branched polymers). By using Baby-Universes arguments and an antsatz on the universality class between the

Shinji Mukohyama

In this thesis properties and the origin of black hole entropy are investigated from various points of view. First, laws of black hole thermodynamics are reviewed. In particular, the first and generalized second laws are investigated in detail. It is in these laws that the black hole entropy plays key roles. Next, three candidates for the origin of the black

Walter Daelemans, Antal van den Bosch, Jakub Zavrel

We show that in language learning, contrary to received wisdom, keeping exceptional training instances in memory can be beneficial for generalization accuracy. We investigate this phenomenon empirically on a selection of benchmark natural language processing tasks: grapheme-to-phoneme conversion, part-of-speech tagging, prepositional-phrase attachment, and b

Joseph Y. Halpern, Carl Lagoze

We describe the Computing Research Repository (CoRR), a new electronic archive for rapid dissemination and archiving of computer science research results. CoRR was initiated in September 1998 through the cooperation of ACM, LANL (Los Alamos National Laboratory) e-Print archive, and NCSTRL (Networked Computer Science Technical Research Library. Through its im

L. Sheng, C. S. Ting

From a general model of the Mn oxides R_{1-x}A_{x}MnO_3, we derive an effective Hamiltonian in the low-energy subspace using the projection operator method, in which a novel coupling between the spin and orbital degrees of freedom is included. A phase diagram for temperature T versus doping concentration x is computed by means of Monte Carlo simulation. Our

Andrea Cavagna, Juan P. Garrahan, Irene Giardina

We study the energy distribution of maxima and minima of a simple one-dimensional disordered Hamiltonian. We find that in systems with short range correlated disorder there is energy separation between maxima and minima, such that at fixed energy only one kind of stationary points is dominant in number over the other. On the other hand, in the case of system

Z. E. Usatenko, M. P. Kozlovskii

The method of calculating the free energy and thermodynamic characteristics of the classical n-vector three-dimensional (3D) magnetic model at the microscopic level without any adjustable parameters is proposed. Mathematical description is perfomed using the collective variables (CV) method in the framework of the $ρ^4$ model approximation. The exponentially

M. Horvatic, Y. Fagot Revurat, C. Berthier, G. Dhalenne

In the spin-Peierls compound CuGeO$_{3}$, the commensurate-incommensurate transition concerning the modulation of atomic position and the local spin-polarization is fully monitored at T=0 by the application of an external magnetic field ($H$) above a threshold value $H_{c}\simeq $ 13 Tesla. The solitonic profile of the spin-polarization, as well as its absol

J. A. Torres, E. Tosatti, A. Dal Corso, F. Ercolessi

We have examined theoretically the spontaneous thinning process of tip-suspended nanowires, and subsequently studied the structure and stability of the monatomic gold wires recently observed by Transmission Electron Microscopy (TEM). The methods used include thermodynamics, classical many-body force simulations, Local Density (LDA) and Generalized Gradient (

C. Castellani, P. Schwab, M. Grilli

We comment on transport experiments in underdoped LaSrCuO in the non-superconducting phase. The temperature dependence of the resistance strongly resembles what is expected from standard localization theory. However this theory fails, when comparing with experiments in more detail.

N. Macris, Ph. A. Martin, J. V. Pule

We consider an electron in two dimensions submitted to a magnetic field and to the potential of impurities. We show that when the electron is confined to a half-space by a planar wall described by a smooth increasing potential, the total Hamiltonian necessarily has a continuous spectrum in some intervals in-between the Landau levels provided that both the am

P. G. Radaelli, D. E. Cox, L. Capogna, S-W. Cheong

The crystallographic (charge-ordered) and magnetic superstructures of La0.333Ca0.667MnO3 were studied by high-resolution synchrotron x-ray and neutron powder diffraction. In the antiferromagnetic structure, which was refined using a non-collinear model, the a lattice parameter is tripled and the c lattice parameter is doubled with respect to the average crys

R. Mallik, E. V. Sampathkumaran

The behaviour of electrical resistivity ($ρ$) and magnetoresistance in the vicinity of respective magnetic ordering temperatures in a number of Gd alloys is reported. In some compounds, e.g., GdNi_2Sn_2 and GdPt_2Ge_2, there is an enhancement of $ρ$ prior to long range magnetic order over a wide temperature range which can be highlighted by the suppression o

Leonid Didukh

A model for description of materials with narrow energy bands is proposed. It is shown that in narrow-band materials electron-hole symmetry is absent in contrast to the Hubbard model. In this paper metal-insulator transition is studied. The obtained results are compared with experimental data for narrow-band materials. Some specific narrow-band effects are d

S. Stringari

We investigate the thermodynamic stability of quantized vortices in a dilute Bose gas confined by a rotating harmonic trap at finite temperature. Interatomic forces play a crucial role in characterizing the resulting phase diagram, especially in the large $N$ Thomas-Fermi regime. We show that the critical temperature for the creation of stable vortices exhib