September 1999 arXiv papers — page 6

V. Buat, D. Burgarella

The FIR(60 microns) and UV (0.2 microns) emissions of individual star forming galaxies are compared to the mean properties of the local Universe. Almost all the galaxies exhibit a FIR to UV flux ratio larger than the ratio of the FIR and UV luminosity densities. It is likely to be due to the contribution of low luminosity galaxies to the UV luminosity densit

D. L. Clements

We use host galaxy imaging studies of the PG Quasar survey to compare the far-infrared (FIR) properties of quasars with disturbed and undisturbed host galaxies. By using survival analysis, we show that the quasars with disturbed host galaxies, with morphologies classified from a homogenous data set, have a 60 micron luminosity distribution that is different

R. Schneider, A. Ferrara, B. Ciardi, V. Ferrari

We study the gravitational wave emission from the first stars which are assumed to be Very Massive Objects (VMOs). We take into account various feedback (both radiative and stellar) effects regulating the collapse of objects in the early universe and thus derive the VMO initial mass function and formation rate. If the final fate of VMOs is to collapse, leavi

E. Mediavilla, V. Motta, ; S. Arribas, ; E. E. Falco

2D spectroscopy of Q0957+561 in the CIII]lambda1909 emission line reveals a rich variety of spatially extended features. We point out: (i) a blueshifted region apparently connecting the A and B compact images; (ii) an almost complete arc in the West side which fits well with the infrared arc detected by the Hubble Space Telescope and (iii) traces of extended

Vincenzo Testa, Francesco R. Ferraro, Alessandro Chieffi, Oscar Straniero

We present a new deep (down to V ~ 24) photometry of a wide region (6'x 6') around the LMC globular cluster NGC1866: our sample is complete, down to 3 mag below the brightest MS star. Detailed comparisons with various theoretical scenarios using models computed with the evolutionary code FRANEC have been done reaching the following conclusions: both

Jacco Th. van Loon, M. A. T. Groenewegen, A. de Koter, Norman R. Trams

A radiative transfer code is used to model the spectral energy distributions of 57 mass-losing Asymptotic Giant Branch (AGB) stars and red supergiants (RSGs) in the Large Magellanic Cloud (LMC) for which ISO spectroscopic and photometric data are available. As a result we derive mass-loss rates and bolometric luminosities. A gap in the luminosity distributio

Bernd Aschenbach, Anatoli F. Iyudin, Volker Schoenfelder

The discovery of the nearest young supernova remnant RXJ0852-4622/GROJ0852-4642 in the Galaxy by ROSAT and COMPTEL has been reported recently. Age and distance are determined to ~680 years and ~200 pc by the X-ray diameter and the gamma-ray line flux of radioactive 44Ti. Here we discuss the implications of the X-ray spectra and of the fact that 1.8 MeV gamma

Robert E. Lopez

Neutrinos that decay leave their imprint on the cosmic microwave background. We calculate the CMB anisotropy for the full range of decaying neutrino parameter space, and investigate the ability of future experiments like MAP and Planck to probe decaying neutrino physics. MAP and Planck should be able to distinguish from $Λ$CDM, eV-scale neutrinos that decay

J. G. Greenhill, D. K. Galloway, J. R. Murray

We describe three presentations relating to the X-ray pulsar GX 1+4 at a workshop on magnetic fields and accretion at the Astrophysical Theory Centre, Australian National University on 1998, November 12-13. Optical and X-ray spectroscopy indicate that GX 1+4 is seen through a cloud of gravitationaly bound matter. We discuss an unstable negative feedback mech

A. B. Giles, D. K. Galloway, J. G. Greenhill, M. C. Storey

The Rossi X-ray Timing Explorer (RXTE) spacecraft observed the X-ray pulsar GX 1+4 for a period of 34 hours on July 19/20 1996. The source faded from an intensity of ~20 mCrab to a minimum of <~0.7 mCrab and then partially recovered towards the end of the observation. This extended minimum lasted ~40,000 seconds. Phase folded light curves at a barycentric ro

Robert F. Coker, Fulvio Melia

The compact, nonthermal radio source Sgr A* at the Galactic Center appears to be coincident with a 2.6 million solar mass point-like object. Its energy source may be the release of gravitational energy as gas from the interstellar medium descends into its potential well. Simple attempts at calculating the spectrum and flux based on this picture have come clo

C. D. Fassnacht, E. Xanthopoulos, L. V. E. Koopmans, T. J. Pearson

The four-component gravitational lens CLASS B1608+656 has been monitored with the VLA for two seasons in order to search for time delays between the components. These time delays can be combined with mass models of the lens system to yield a measurement of H_0. The component light curves show significantly different behavior in the two observing seasons. In

A. B. Lahanas, D. V. Nanopoulos, V. C. Spanos

We discuss the relic density of the lightest of the supersymmetric particles in view of new cosmological data, which favour the concept of an accelerating Universe with a non-vanishing cosmological constant. Recent astrophysical observations provide us with very precise values of the relevant cosmological parameters. Certain of these parameters have direct i

J. Cline, C. Grojean, G. Servant

We generalize solutions of Einstein&#39;s equations for intersecting branes in higher dimensional spacetimes to the nonstatic case, modeling an expanding universe. The relation between the Hubble rate, the brane tensions, and the bulk cosmological constant is similar to the case of a single 3-brane in a 5-dimensional spacetime. However, because the bulk infl

J. G. Naeini, J. C. Irwin, T. Sasagawa, Y. Togawa

We report the results of Raman scattering experiments on single crystals of La(2-x)Sr(x)CuO(4) [La214] as a function of temperature and doping. In underdoped compounds low-energy B1g spectral weight is depleted in association with the opening of a pseudogap on regions of the Fermi surface located near (pi, 0) and (0, pi). The magnitude of the depletion incre

A. H. Hoang, P. Labelle, S. M. Zebarjad

A detailed presentation is given of the analytic calculation of the single-photon annihilation contributions to the positronium ground state hyperfine splitting to order $m_eα^6$ in the framework of non-relativistic effective theories. The current status of the theoretical description of the positronium ground state hyperfine splitting is reviewed.

L. Mersini

We examine the issue of the cosmological constant in the $many$ $inflating$ branes scenario, extending on two recent models by I.Oda and Randall-Sundrum. The exact solution in a closed form is found in the slow roll approximation of the radion. Defining an effective expansion rate, which depends on the location of each brane in the fifth dimension and demand

B. L. Altshuler, D. L. Maslov, V. M. Pudalov

A generalization of the single-parameter scaling theory of localization is proposed for the case when the random potential depends on temperature. The scaling equation describing the behavior of the resistance is derived. It is shown that the competition between the metallic-like temperature dependence of the Drude resistivity and localization leads to a max

G. Aldazabal, L. E. Ibanez, F. Quevedo

We construct D=4 Type I vacua with massless content remarkably close to that of the standard model of particle physics. They are tachyon-free non-supersymmetric models which are obtained starting with a standard D=4, N=1 compact Type IIB orientifold and adding the same number of Dp-branes and anti-Dp-branes distributed at different points of the underlying o

B. Georgeot, D. L. Shepelyansky

We study a generic model of quantum computer, composed of many qubits coupled by short-range interaction. Above a critical interqubit coupling strength, quantum chaos sets in, leading to quantum ergodicity of the computer eigenstates. In this regime the noninteracting qubit structure disappears, the eigenstates become complex and the operability of the compu

J. Z. Bai

BES data on $J/ψ\to γ(π^{+} π^{-} π^{+} π^{-})$ have been analyzed into partial waves. We fit with resonances having $J^{PC}=2^{++}$ at 1275 MeV, $0^{++}$ at 1500 MeV, $2^{++}$ at 1565 MeV, $0^{++}$ at 1740 MeV, $2^{++}$ at 1940 MeV and $0^{++}$ at 2104 MeV, plus a broad $0^-$ component. The $0^{++}$ resonances decay dominantly to $σσ$, while $2^{++}$ resona

K. Tsutsui, T. Tohyama, S. Maekawa

The Cu K-edge resonant inelastic x-ray scattering (RIXS) spectrum in one-dimensional insulating cuprates is theoretically examined by using the exact diagonalization technique for the extended one-dimensional Hubbard model with nearest neighbor Coulomb interaction. We find the following characteristic features that can be detectable by RIXS experiments: (i)

D. S. Petrov, M. Holzmann, G. V. Shlyapnikov

We discuss BEC in (quasi)2D trapped gases and find that well below the transition temperature $T_c$ the equilibrium state is a true condensate, whereas at intermediate temperatures $T<T_c$ one has a quasicondensate (condensate with fluctuating phase). The mean-field interaction in a quasi2D gas is sensitive to the frequency $ω_0$ of the (tight) confinement i

P. Busch

A quantum state can be understood in a loose sense as a map that assigns a value to every observable. Formalizing this characterization of states in terms of generalized probability distributions on the set of effects, we obtain a simple proof of the result, analogous to Gleason&#39;s theorem, that any quantum state is given by a density operator. As a corol

Apostolos Pilaftsis

The complete set of Higgs-boson two-loop contributions to electric dipole moments of the electron and neutron is calculated in the minimal supersymmetric standard model. The electric dipole moments are induced by CP-violating trilinear couplings of the `CP-odd&#39; and charged Higgs bosons to the scalar top and bottom quarks. Numerical estimates of the indiv

H. Ita, K. Landsteiner, T. Pisar, J. Rant

We establish the existence of the topological vector supersymmetry in the six dimensional topological field theory for two-form fields introduced by Baulieu and West. We investigate the relation of these symmetries to the twist operation for the (2,0) supersymmetry and comment on their resemblance to the analogous symmetries in topological Yang-Mills theory.

Taizo Muta, Mao-Zhi Yang

We study the $η&#39;-g^*-g$ transition form factor by using the $η&#39;$ wave function constrained by the experimental data on the $η&#39;-γ^*-γ$ transition form factor provided by CLEO and L3 . We also take into account the contribution of the possible gluonic content of the $η&#39;$ meson.

T. Matsuki, M. Shiotani

Assuming dynamical spontaneous breakdown of chiral symmetry for massless gauge theory without scalar fields, we find a method how to construct an effective action of the dynamical Nambu-Goldstone bosons and elemetary fermions by using auxiliary fields. Here dynamical particles are asssumed to be composed of elementary fermions. Various quantities including d

David N. Spergel, Paul J. Steinhardt

Cosmological models with cold dark matter composed of weakly interacting particles predict overly dense cores in the centers of galaxies and clusters and an overly large number of halos within the Local Group compared to actual observations. We propose that the conflict can be resolved if the cold dark matter particles are self-interacting with a large scatt

Y. Aharonov, L. Vaidman

Various aspects of nonlocality of a quantum wave are discussed. In particular, the question of the possibility of extracting information about the relative phase in a quantum wave is analyzed. It is argued that there is a profound difference in the nonlocal properties of the quantum wave between fermion and boson particles. The phase of the boson quantum sta

Rob Clifton, Bradley Monton

In a previous article (cf. quant-ph/9905065) we argued that, while Lewis is correct that the enumeration principle fails in dynamical wavepacket reduction theories, one need not following Lewis in rejecting these theories. Because the dynamical reduction process itself prevents the failure of enumeration from ever becoming manifest, and because one can treat

A. Zh. Muradyan, H. L. Haroutyunyan

It is shown that a two-level atom, being initially in general superposition state of ground and excited energy levels with mutually different momentum distributions there, gets a large scale evolution in the energy levels momentum distribution. As a consequence the mean momentum of each individual energy level also gets large scale changes, more than the own

Christoph Best, Hans-Christian Hege

The Monte Carlo simulation of the dynamics of complex molecules produces trajectories with a large number of different configurations to sample configuration space. It is expected that these configurations can be classified into a small number of conformations representing essential changes in the shape of the molecule. We present a method to visualize these

Charles Francis

We take the view that physical quantities are values generated by processes in measurement, not pre-existent objective quantities, and that a measurement result is strictly a product of the apparatus and the subject of the measurement. We habitually make an inaccurate statements when we speak of the measurement of a quantity by an apparatus. These statements

M. Sambataro

We discuss a multistep variational approach for the study of many-body correlations. The approach is developed in a boson formalism (bosons representing particle-hole excitations) and based on an iterative sequence of diagonalizations in subspaces of the full boson space. Purpose of these diagonalizations is that of searching for the best approximation of th

S. A. Sofianos, G. Ellerkmann, W. Sandhas

The two-fragment electrodisintegration of 4He into proton and triton is calculated in Plane Wave Impulse Approximation (PWIA). The three- and four-nucleon wave functions involved are obtained by solving the Alt-Grassberger-Sandhas (AGS) integral equations, with the Malfliet-Tjon potential as the underlying NN-interaction. Our results are in remarkable agreem

D. L. Groep, M. F. van Batenburg, Th. S. Bauer, H. P. Blok

Cross sections for the 3He(e,e&#39;pp)n reaction were measured at an energy transfer of 220 MeV and three-momentum transfers q of 305, 375, and 445 MeV/c. Results are presented as a function of q and the final-state neutron momentum for slices in specific kinematic variables. At low neutron momenta, comparison of the data to results of continuum Faddeev calc

Andrei Starinets

We study solutions of the equations $(\triangle -λ)ϕ= 0$ and $(\triangle -λ)^2ϕ= 0$ in global coordinates on the covering space $CAdS_d$ of the $d$-dimensional Anti de-Sitter space subject to various boundary conditions and their connection to the unitary irreducible representations of $\widetilde{SO}(d-1,2)$. The ``vanishing flux&#39;&#39; boundary conditio

Yakov Varshavsky

In this paper we show that certain Shimura varieties, uniformized by the product of complex unit balls, can be p-adically uniformized by the product (of equivariant coverings) of Drinfeld upper half-spaces. We also extend a p-adic uniformization to automorphic vector bundles. It is a continuation of our previous work [V], and contains all cases (up to a cent

Yakov Varshavsky

In this paper we generalize Cherednik&#39;s method and prove that certain Shimura varieties corresponding to groups of unitary similitudes and automorphic vector bundles over them have p-adic uniformization. This is proved for Shimura varieties, uniformized by the complex unit ball, when the central simple algebra over a CM-field defining the group of unitar

Yakov Varshavsky

In this paper we recall the construction and basic properties of complex Shimura varieties and show that these properties actually characterize them. This characterization immediately implies the explicit form of Kazhdan&#39;s theorem on the conjugation of Shimura varieties. As a further corollary, we show that each Shimura variety corresponding to an adjoin

Manuel Pedreira-Perez, Luis-Eduardo Sola-Conde

We study second order focal loci of nondegenerate plane congruences in P4(C) with degenerate focal conic. We show the projective generation of such congruences when the second order focal locus fills a component of the focal conic, improving a result of Corrado Segre

Yakar Kannai

The fundamental solution for the wave equation in n variables is built from the simple one-dimensional formula, via an integral representation of the cosine of the sum of squares of self-adjoint operators. Representation formulas are given both in the commutative and non-commutative case. The formulas are illustrated for the wave equation as well as for the

Manuel Pedreira-Perez, Luis-Eduardo Sola-Conde

Nondegenerate plane congruences in the four-dimensional complex projective space with degenerate general focal conic are classified by using the focal method due to Corrado Segre.

Philippe Ellia, Davide Franco

We prove the following: (a) Let X be a smooth, codimension two subvariety of P6. If X lies on a hyperquintic or if deg(X)<74, then X is a complete intersection. (b) Let X be a smooth, subcanonical threefold in P5. If X lies on a hyperquartic, then X is a complete intersection.

Marian Aprodu, Vasile Brinzanescu, Matei Toma

It is in general unknown which topological complex vector bundles on a non-algebraic surface admit holomorphic structures. We solve this problem for primary Kodaira surfaces by using results of Kani on curves of genus two with elliptic differentials. Some of the corresponding moduli spaces will be smooth compact and holomorphically symplectic.

I. Dolgachev, D. -Q. Zhang

A smooth rational surface X is a Coble surface if the anti-canonical linear system is empty while the anti-bicanonical linear system is non-empty. In this note we shall classify these X and consider the finiteness problem of the number of negative curves on X modulo automorphisms.

A. P. C. Malbouisson, R. Portugal, N. F. Svaiter

We have done a study of the zero-dimensional $λϕ^{4}$ model. Firstly, we exhibit the partition function as a simple exact expression in terms of the Macdonald&#39;s function for $Re(λ)>0$. Secondly, an analytic continuation of the partition function for $Re(λ)<0$ is performed, and we obtain an expression defined in the complex coupling constant plane $λ$, fo

P. Bowcock, M. Perkins

In this paper we study various aspects of classical solutions to the affine Toda equations on a half-line with integrable boundary conditions. We begin by finding conditions that the theory has a stable vacuum by finding a Bogomolny bound on the energy, and analysing the possible singularities of the field at the boundary. Using these constraints and extensi

Franco Ferrari, Jan Sobczyk

In this paper we investigate massless scalar field theory on non-degenerate algebraic curves. The propagator is written in terms of the parameters appearing in the polynomial defining the curve. This provides an alternative to the language of theta functions. The main result is a derivation of the third kind differential normalized in such a way that its per

C. Bachas, B. Pioline

We consider the elastic scattering of two open strings living on two D-branes separated by a distance $r$. We compute the high-energy behavior of the amplitude, to leading order in string coupling, as a function of the scattering angle $ϕ$ and of the dimensionless parameter $v= r/(πα^\prime\sqrt{s})$ with $\sqrt{s}$ the center-of-mass energy. The result exhi

Norma Mankoc Borstnik, Holger Bech Nielsen

One of us got spins and charges of not only scalars and vectors but also of spinors out of fields, which are antisymmetric tensor fields. Kahler got spins of spinors out of differential forms, which again are antisymmetric tensor fields. Using our simple Grassmann formulation of spins and charges of either spinors or vectors and comparing it to the Dirac-Kah

C. J. Houghton, N. S. Manton, N. M. Romão

We discuss the explicit formulation of the transcendental constraints defining spectral curves of SU(2) BPS monopoles in the twistor approach of Hitchin, following Ercolani and Sinha. We obtain an improved version of the Ercolani-Sinha constraints, and show that the Corrigan-Goddard conditions for constructing monopoles of arbitrary charge can be regarded as

H. Arfaei, D. Kamani

Interaction of branes in presence of internal gauge fields is considered by using the boundary state formalism. This approach enables us to consider the problems that are not easily accessible to the canonical approach via open strings. The effects of compactification of some of the dimensions on tori are also discussed. Also we study the massless state cont

R. A. Alanakyan

We consider positronium-like bound states of doubly charged fermions.We consider also $P(CP)$-parity violation in positronium like system (including quarkonium and lepton antilepton bound states and mesoatoms) which take place due to $Z^0$-bosons or Higgs bosons exchange.By model independent way we consider also vector bosons bound states in the Coulomb and

M. Ladisa, G. Nardulli, T. N. Pham, P. Santorelli

In the framework of a QCD relativistic potential model we evaluate the form factors describing the exclusive decay B => ππ\ell ν. The calculation is performed in a phase space region far away from the resonances and therefore is complementary to other decay mechanisms where the pions are produced by intermediate particles, e.g. in the chiral approach. We giv

Thomas Hadig, Gavin McCance

In this article we present a generic interface to several next-to-leading order cross-section programs. This enables the user to implement his/her code once and make cross-checks with different programs.

N. V. Krasnikov, V. A. Matveev

We review the standard Higgs boson physics and the search for higgs boson at LEP and LHC supercolliders

M. Penttinen, M. V. Polyakov, K. Goeke

We compute the helicity skewed quark distributions $\widetilde{H}$ and $\widetilde{E}$ in the chiral quark-soliton model of the nucleon. This model emphasizes correctly the role of spontaneously broken chiral symmetry in structure of nucleon. It is based on the large-N_c picture of the nucleon as a soliton of the effective chiral lagrangian and allows to cal

M. B. Gay Ducati, V. P. Gonçalves

In this contribution we discuss distinct approaches for the high density QCD (hdQCD) and the demonstration of the equivalence between the AGL approach and the K approach is presented. Our conclusion is that the AGL equation is a good candidate for an unitarized evolution equation at high densities in the DLA limit.

Edward Boos, Thorsten Ohl

We describe the explicit construction of groves, the smallest gauge invariant classes of tree Feynman diagrams in gauge theories

Stephan Paul

This paper reviews different aspects of hadronic systems with strange quarks. It reviews production, spectroscopy and decay of baryons and hypernuclei with emphasis on recent results obtained in this field. It includes a comparison of different systems doped with strange (or heavy) quarks, emphasizing the single particle nature which can be observed in baryo

K. Schilling

Considerable progress has been achieved recently in the observation of string breaking within non-Abelian Higgs models, by use of multi-channel methods allowing for broken string states. Similarly, in pure gauge theory this approach has been shown to reveal string breaking for color charges in the adjoint represaentation. For QCD with dynmical fermions, one

Christoph Best

The scale hierarchy of wavelets provides a natural frame for renormalization. Expanding the order parameter of the Landau-Ginzburg/$Φ^4$ model in a basis of compact orthonormal wavelets explicitly exhibits the coupling between scales that leads to non-trivial behavior. The locality properties of Daubechies&#39; wavelets enable us to derive the qualitative re

Martin Lüscher

A recently proposed formulation of chiral lattice gauge theories is reviewed, in which the locality and gauge invariance of the theory can be preserved if the fermion representation of the gauge group is anomaly-free.

M. Bartels, G. Mack, G. Palma

In this paper we show the Wilson effective action for the 2-dimensional O(N+1)-symmetric lattice nonlinear sigma-model computed in the 1-loop approximation for the nonlinear choice of blockspin $Φ(x)$, $Φ(x)= \Cavϕ(x)/{|\Cavϕ(x)|}$,where $\Cav$ is averaging of the fundamental field $ϕ(z)$ over a square $x$ of side $\tilde a$. The result for $S_{eff}$ is comp

G. M. de Divitiis, L. Del Debbio, M. Di Pierro, J. M. Flynn

The coupling $g_{B^\ast B π}$ is related to the form factor at zero momentum of the axial current between $B^\ast$ and $B$ states. Moreover it is related to the effective coupling between heavy mesons and pions that appear the heavy meson chiral Lagrangian. This coupling has been evaluated on the lattice using static heavy quarks and light quark propagators

L. Del Debbio, M. Di Pierro, A. Dougall, C. Sachrajda

We present preliminary results for the second moment of the pion&#39;s distribution amplitude. The lattice formulation and the phenomenological implications are briefly reviewed, with special emphasis on some subtleties that arise when the Lorentz group is replaced by the hypercubic group. Having analysed more than half of the available configurations, the r

T. Bhattacharya, R. Gupta, W. Lee, S. Sharpe

We describe how the improvement of quark bilinears generalizes from quenched to unquenched QCD, and discuss which of the additional improvement constants can be determined using Ward Identities.

CDF Collaboration, T. Affolder

We use the transverse momentum spectrum of leptons in the decay chain t-->bW with W-->l nu to measure the helicity of the W bosons in the top quark rest frame. Our measurement uses a ttbar sample isolated in 106 +/- 4 inverse picobarns of data collected in ppbar collisions at sqrt(s)=1.8 TeV with the CDF detector at the Fermilab Tevatron. Assuming a standard

NuTeV Collaboration, T. Adams, A. Alton, T. Bolton

We present evidence for the diffractive processes nu_mu Fe -> mu^- D_s^+ (D_s^*+) Fe and nubar_mu Fe -> mu^+ D_s^- (D_s^*-) Fe using the Fermilab SSQT neutrino beam and the Lab E neutrino detector. We observe the neutrino trident reactions nu_mu Fe -> nu_mu mu^- mu^+ Fe and nubar_mu Fe -> nubar_mu mu^+ mu^- Fe at rates consistent with Standard Model expectat

J. H. Vossebeld

New measurements of dijet photoproduction at HERA provide information on the gluon density in the photon and on its quark densities at high x_gamma and high factorisation scales.

J. Z. Bai

Using a sample of 3.8 M psi(2S) events accumulated with the BES detector, the process psi(2S) -> pi^+ pi^- J/psi is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D-wave, as well as S-wave. On the other hand, the J/psi-(pi pi) relative angular momentum is consist

E. Ben-Naim, S. Y. Chen, G. D. Doolen, S. Redner

We provide a simple physical picture which suggests that the asymptotic dynamics of inelastic gases in one dimension is independent of the degree of inelasticity. Statistical characteristics, including velocity fluctuations and the velocity distribution are identical to those of a perfectly inelastic sticky gas, which in turn is described by the inviscid Bur

A. Dorneich, M. G. Zacher, C. Groeber, R. Eder

We reanalyze the Hubbard-I approximation by showing that it is equivalent to an effective Hamiltonian describing Fermionic charge fluctuations, which can be solved by Bogoliubov transformation. As the most important correction in the limit of large U and weak spin correlations we augment this Hamiltonian by further effective particles, which describe composi

M. -H. Julien, P. Carretta, F. Borsa

NQR 139La and 63Cu spin-lattice relaxation rate (1/T_1) measurements in a La1.94Sr0.06CuO4 single crystal are described. Slowing-down of Cu2+ spin fluctuations is evidenced through a dramatic increase of 139La 1/T_1 on cooling. While the onset of diamagnetism occurs at Tc=8 K, 1/^{139}T_1 has a peak at Tg~5 K, when the characteristic frequency of magnetic fl

D. Khomskii

Phase separation and a tendency to form inhomogeneous structures seems to be a generic property of systems with strongly correlated electrons. After shortly summarising the existing theoretical results in this direction, I concentrate on the phenomena in doped manganites. I discuss general theoretical results on the phase separation at small doping and close

Eugene V. Sukhorukov, Daniel Loss, Guido Burkard

We consider a scattering set-up with an entangler and beam splitter where the current noise exhibits bunching behavior for electronic singlet states and antibunching behavior for triplet states. We show that the entanglement of two electrons in the double-dot can be detected in mesoscopic transport measurements. In the cotunneling regime the singlet and trip

Ronald Dickman

A detailed study of critical spreading in the one-dimensional pair contact process is performed using a recently devised reweighting method. The results confirm the validity of a generalized hyperscaling relation among the (nonuniversal) spreading exponents, and support the assertion that the critical point location does not depend on the particle density ϕ.

A. Gammal, T. Frederico, Lauro Tomio, Ph. Chomaz

We study the effects of a repulsive three-body interaction on a system of trapped ultra-cold atoms in Bose-Einstein condensed state. The stationary solutions of the corresponding $s-$wave non-linear Schrödinger equation suggest a scenario of first-order liquid-gas phase transition in the condensed state up to a critical strength of the effective three-body f

M. M. Tsypin, H. W. J. Blöte

We study the probability distribution P(M) of the order parameter (average magnetization) M, for the finite-size systems at the critical point. The systems under consideration are the 3-dimensional Ising model on a simple cubic lattice, and its 3-state generalization known to have remarkably small corrections to scaling. Both models are studied in a cubic bo

R. R. Rey-Gonzalez, P. A. Schulz

In the present work the problem of coupled disordered quantum wells is addressed in a random matrix theory framework. The quantum wells are short repulsive binary alloys embeded by ordered barriers and show well defined quantized levels as a consequence of spatial confinement. Finite disordered superlattices may show both diffusive-like and localized miniban

S. Luescher, A. Fuhrer, R. Held, T. Heinzel

A single-electron transistor has been realized in a Ga[Al]As heterostructure by oxidizing lines in the GaAs cap layer with an atomic force microscope. The oxide lines define the boundaries of the quantum dot, the in-plane gate electrodes, and the contacts of the dot to source and drain. Both the number of electrons in the dot as well as its coupling to the l

I. Pagonabarraga, M. E. Cates, G. J. Ackland

The structure of polydisperse hard sphere fluids, in the presence of a wall, is studied by the Rosenfeld density functional theory. Within this approach, the local excess free energy depends on only four combinations of the full set of density fields. The case of continuous polydispersity thereby becomes tractable. We predict, generically, an oscillatory siz

P. S. Kuhn, Y. Levin, M. C. Barbosa

We study a complex formation between the DNA and cationic amphiphilic molecules. As the amphiphile is added to the solution containing DNA, a cooperative binding of surfactants to the DNA molecules is found. This binding transition occurs at specific density of amphiphile, which is strongly dependent on the concentration of the salt and on the hydrophobicity

T. Heinzel, G. Salis, R. Held, S. Luescher

A quantum wire is spatially displaced by suitable electric fields with respect to the scatterers inside a semiconductor crystal. As a function of the wire position, the low-temperature resistance shows reproducible fluctuations. Their characteristic temperature scale is a few hundred millikelvin, indicating a phase-coherent effect. Each fluctuation correspon

Y. Moreno, J. B. Gomez, A. F. Pacheco

Following the Renormalization Group scheme recently developed by Pietronero {\it et al}, we introduce a simplifying strategy for the renormalization of the relaxation dynamics of sandpile models. In our scheme, five sub-cells at a generic scale $b$ form the renormalized cell at the next larger scale. Now the fixed point has a unique nonzero dynamical compone

G. G. Kozlov

A method is proposed for manipulating with diagrammatic expansion of Green&#39;s function of Frenkel&#39;s exciton random walks on the perfect lattice. The method allows one to select diagrams, to supply diagrams with factors containing information about the number of sites the diagram has passed through, etc. Simple problems related to the defect lattices a

A. Bergara, J. M. Pitarke, R. H. Ritchie

We present semi-classical and quantized hydrodynamic models to obtain the quadratic electronic response of a plane-bounded electron gas. Explicit expressions for the dynamic image potential experienced by charged particles moving near a jellium surface are derived, up to third order in the projectile charge. These expressions are employed to compute the imag

Hidetoshi Fukuyama, Hitoshi Seo, Hiori Kino

It is known that the ground states of organic conductors have a diversity reflecting the spatial arrangement of the constituent molecules within the unit cell. A systematic theoretical search for the unifying view behind such possible ground states has been made based on the Hartree-Fock mean field approximation not only to the on-site but also to intersite

J. M. Mao, M. E. Zudov, R. R. Du, P. P. Lee

Electrical transport properties of DyAs epitaxial layers grown on GaAs have been investigated at various temperatures and magnetic fields up to 12T. The measured longitudinal resistances show two distinct peaks at fields around 0.2 and 2.5T which are believed to be related to the strong spin-disorder scattering occurring at the phase transition boundaries in

A. N. Tahvildar-Zadeh, M. Jarrell, Th. Pruschke, J. K. Freericks

Monte Carlo-maximum entropy calculations of the conductivity of the infinite-dimensional periodic Anderson model are presented. We show that the optical conductivity displays anomalies associated with the exhaustion of conduction-band states near the Fermi energy including a Drude weight which rises with temperature, with weight transferred from a temperatur

A. Mourachkine

There is a clear discrepancy among the energy-gap values for different 90 K cuprates, inferred from tunneling measurements. By using the phase diagram for hole-doped cuprates we show that tunneling measurements performed on 90 K cuprates, simply, detect two different energy gaps: the pairing gap and the coherent gap, which are identical in conventional super

Peter Sollich, Martin R Evans

We analyse the out of equilibrium behavior of an Ising spin chain with an asymmetric kinetic constraint after a quench to a low temperature T. In the limit T\to 0, we provide an exact solution of the resulting coarsening process. The equilibration time exhibits a `glassy&#39; divergence \teq=\exp(const/T^2) (popular as an alternative to the Vogel-Fulcher law

X. Delfosse, T. Forveille, S. Udry, J. -L Beuzit

We present very accurate orbital parameters and mass measurements (2.4% accuracy) for the well known very low mass triple system Gl 866. We obtain first orbital elements for the short-period orbit and greatly improve the long period orbit. All three stars have masses close to 0.1 solar masses, and the system thus provides the strongest constraints to date on

T. J. Davidge

Images recorded through J, H, Ks, 2.2 micron continuum, and 2.3 micron CO filters are used to investigate the stellar contents of the low Galactic latitude globular clusters NGC 6528, Liller 1, Djorgovski 1, and HP 1, as well as surrounding bulge fields. Metallicities are estimated for the latter three clusters by comparing the colors and CO indices of giant

D. A. Frail, S. R. Kulkarni, J. S. Bloom, S. G. Djorgovski

We report the discovery of a radio transient VLA 232937.2-235553, coincident with the proposed X-ray afterglow for the gamma-ray burst GRB 981226. This GRB has the highest ratio of X-ray to gamma-ray fluence of all the GRBs detected by BeppoSAX so far and yet no corresponding optical transient was detected. The radio light curve of VLA 232937.2-235553 is qua

J. A. Garcia-Barreto, E. Moreno

A remarkable structure is observed in the innermost regions of the barred galaxy NGC 1415 : a small stellar bar, bright circumnuclear ionized gas seen in Halpha, two bright ionized gas sources, seen in Halpha, just beyond the ends of the small bar and a boxy distribution of optical continuum. We have developed a mass distribution model consisting in disk, a

Frank Grundahl

Stromgren uvby CCD photometry can be used in a variety of ways to constrain the absolute and relative ages of globular clusters. The reddening corrected (v-y, c1) diagram offers the means to derive ages that are completely independent of distance. Very precise differential ages for clusters of the same chemical composition may also be determined from such 2-

Allen V. Sweigart, John C. Lattanzio, James P. Gray, Christopher A. Tout

We investigate the gravonuclear instabilities reported by Bono et al. (1997a,b) during the onset of helium-shell burning at the end of the horizontal-branch (HB) phase. These instabilities are characterized by relaxation oscillations within the helium shell which lead to loops in the evolutionary tracks. We find the occurrence of these instabilities depends