May 2000 arXiv papers — page 3

Yi-Ping Qin

Bidirectional relativistic proper motions of radio components of nearby extragalactic sources give a strong constraint on the determination of the Hubble constant $H_0$. Under the assumption that the real velocity of radio components of extragalactic sources is not less than that of Galactic sources, the value of $H_0$ can be estimated at a high level of acc

Paola Grandi

BeppoSAX observations of Broad Line Radio Galaxies (BLRGs) have shown that they have a considerable variety of spectral properties and important differences with respect to their radio-quiet counter-part Seyfert 1s. In radio galaxies the soft photons are often absorbed by cold material. In contrast, in Seyfert 1s the soft photons are generally absorbed by wa

Yi-Ping Qin, G. Z. Xie, Xue-Tang Zheng

We investigate quantitatively how the peak emission frequency of the overall energy spectrum is at work in distinguishing RBL-like and XBL-like objects. We employ the sample of Giommi et al. (1995) to study the distribution of BL Lacertae objects with various locations of the cutoff of the overall energy spectrum. We find that the sources with the cutoff loc

Chris Simpson, Steve Rawlings

We present JHKL&#39; photometry of a complete sample of steep-spectrum radio-loud quasars from the revised 3CR catalogue in the redshift range 0.65 < z < 1.20. After correcting for contributions from emission lines and the host galaxies, we investigate their spectral energy distributions (SEDs) around 1 micron. About 75% of the quasars are tightly grouped in

Laura Baudis, Alexander Dietz, Gerd Heusser, Hans Volker Klapdor-Kleingrothaus

GENIUS is a proposal for a large volume detector to search for rare events. An array of 40-400 &#39;naked&#39; HPGe detectors will be operated in a tank filled with ultra-pure liquid nitrogen. After a description of performed technical studies of detector operation in liquid nitrogen and of Monte Carlo simulations of expected background components, the poten

T. Mineo, F. Fiore, A. Laor, E. Costantini

We present results from BeppoSAX observations of 10 low redshift quasars. The quasars are part of the Laor et al. (1997) sample of 23 optically selected PG quasars with redshift <0.4 and low Galactic absorption along the line of sight. Significant spectral curvature is detected for the 6 quasars with the highest signal to noise ratio in their low energy spec

A. N. Parmar, T. Belloni, M. Orlandini, D. Dal Fiume

We report on BeppoSAX observations of the X-ray transient XTE J0421+560 in quiescence 156, 541, and ~690 days after the maximum of the 1998 April outburst. In the first observation the source was soft with a power-law photon index of 4.0 (+1.9 -0.9) and absorption, NH, of (1.1 +4.9 -1.1) X 10^21 atom/cm2. In the second observation, the source brightened by a

M. Juvela, K. Mattila, D. Lemke

Far-infrared maps obtained with ISOPHOT have been searched for point-like sources. The majority of the 55 sources is believed to be extragalactic and in most cases no previously known sources can be associated with them. Based on the far-infrared spectral energy distributions it is likely that dust-enshrouded, distant galaxies form a significant fraction of

M. Juvela, K. Mattila, D. Lemke

We have studied the galactic cirrus in low surface brightness regions using ISOPHOT raster maps at 90, 150 and 180um. Observations are used to determine dust emission spectra and dust temperatures. The data extend to longer wavelengths than IRAS observation. Compared with DIRBE data the resolution and the sensitivity are better and this makes it possible to

Roberto De Propris

We calculate the contribution to Balmer line indices from far ultraviolet component sources. We find that this is significant, and may lead to identification of spurious age differences of the order of a total span of $\sim 6$ Gyrs or $\sim 15%$ size bursts observed a few Gyrs after star formation stops. We suggest that claims for intermediate age population

N. Wang, R. N. Manchester, R. T. Pace, M. Bailes

Timing observations of 40 mostly young pulsars using the ATNF Parkes radio telescope between 1990 January and 1998 December are reported. In total, 20 previously unreported glitches and ten other glitches were detected in 11 pulsars. These included 12 glitches in PSR J1341$- $6220, corresponding to a glitch rate of 1.5 glitches per year. We also detected the

Mu-Chun Chen, K. T. Mahanthappa

We construct a realistic model based on SUSY SO(10) with U(2) flavor symmetry. In contrast to the commonly used effective operator approach, $126-$dimensional Higgses are used to construct the Yukawa sector. R-parity symmetry is thus preserved at low energies. The Dirac and right-handed Majorana mass matrices in our model have very small mixing, and they com

Chris Stewart, Roman Koniuk

We present the results from a series of lattice simulations of the charmonium system using a highly-improved NRQCD action, both in the quenched approximation, and with n_f = 2 light dynamical quarks. The spectra show some evidence for quenching effects of roughly 10% in the S- and P-hyperfine spin splittings---probably too small to account for the severe und

Marco Matone

We suggest that quantum mechanics and gravity are intimately related. In particular, we investigate the quantum Hamilton-Jacobi equation in the case of two free particles and show that the quantum potential, which is attractive, may generate the gravitational potential. The investigation, related to the formulation of quantum mechanics based on the equivalen

B. Julia, S. Silva

The conserved charges associated to gauge symmetries are defined at a boundary component of space-time because the corresponding Noether current can be rewritten on-shell as the divergence of a superpotential. However, the latter is afflicted by ambiguities. Regge and Teitelboim found a procedure to lift the arbitrariness in the Hamiltonian framework. An alt

Todd A. Brun, Oliver Cohen

There is an ongoing effort to quantify entanglement of quantum pure states for systems with more than two subsystems. We consider three approaches to this problem for three-qubit states: choosing a basis which puts the state into a standard form, enumerating ``local invariants,&#39;&#39; and using operational quantities such as the number of maximally entang

Stephan J. Huber, Qaisar Shafi

Assuming the breaking of gauge symmetries by the Higgs mechanism, we consider the associated bulk gauge boson masses in the Randall-Sundrum background. With the Higgs field confined on the TeV-brane, the W and Z boson masses can naturally be an order of magnitude smaller than their Kaluza-Klein excitation masses. Current electroweak precision data requires t

Harald Grosse, John Madore, Harold Steinacker

We study the q-deformed fuzzy sphere, which is related to D-branes on SU(2) WZW models, for both real q and q a root of unity. We construct for both cases a differential calculus which is compatible with the star structure, study the integral, and find a canonical frame of one-forms. We then consider actions for scalar field theory, as well as for Yang-Mills

Tin-Lun Ho, C. V. Ciobanu

We show that the density profile of a Fermi gas in rapidly rotating potential will develop prominent features reflecting the underlying Landau level like energy spectrum. Depending on the aspect ratio of the trap, these features can be a sequence of ellipsoidal volumes or a sequence of quantized steps.

H. O. Girotti, M. Gomes, V. O. Rivelles, A. J. da Silva

We show that the noncommutative Wess-Zumino model is renormalizable to all orders of perturbation theory. The noncommutative scalar potential by itself is non-renormalizable but the Yukawa terms demanded by supersymmetry improve the situation turning the theory into a renormalizable one. As in the commutative case, there are neither quadratic nor linear dive

Tak Shing Lo, Alain Karma, Mathis Plapp

During the directional solidification of peritectic alloys, two stable solid phases (parent and peritectic) grow competitively into a metastable liquid phase of larger impurity content than either solid phase. When the parent or both solid phases are morphologically unstable, i.e., for a small temperature gradient/growth rate ratio ($G/v_p$), one solid phase

A. S. Majumdar, N. Nayak

We investigate a Bell-type inequality for probabilities of detected atoms formulated using atom-photon interactions in a cavity. We consider decoherence brought about by both atomic decay, as well as cavity photon loss, and study its quantitative action in diminishing the atom-field and the resultant atom-atom secondary correlations. We show that the effects

Laurence S. Littenberg, Robert Shrock

We discuss implications of improved upper bounds on the $|ΔL|=2$ processes (i) $K^+ \to π^- μ^+ μ^+$, from an experiment at BNL, and (ii) $μ^- \to e^+$ conversion, from an experiment at PSI. In particular, we address the issue of constraints on neutrino masses and mixing, and on supersymmetric models with R-parity violation.

Wei Liu, Hanqing Zheng, Xiao-Lin Chen

A numerical analysis to the scalar form-factor in the $ππ$ and KK coupled--channel system is made by solving the coupled-channel dispersive integral equations, using the iteration method. The solutions are found not unique. Physical application to the $ππ$ central production in the $pp\to ppππ$ process is discussed based upon the numerical solutions we found

D. Anselmi

I study a class of interacting conformal field theories and conformal windows in three dimensions, formulated using the Parisi large-N approach and a modified dimensional-regularization technique. Bosons are associated with composite operators and their propagators are dynamically generated by fermion bubbles. Renormalization-group flows between pairs of int

Toshifumi Yagi, Kazuhiro Kuboki

We study the effect of magnetic impurities in the d_{x^2-y^2}-wave superconducting (SC) state of the two dimensional t-J model.The spin-orbit and the spin-exchange interactions are examined by treating the impurity as a classical spin. The Bogoliubov de Gennes equation derived within a slave-boson mean-field approximation is solved numerically at T = 0. The

Chunglee Kim, Heon-Young Chang, Insu Yi

We study the effects of the beaming-induced luminosity function on statistics of observed GRBs, assuming the cosmological scenario. We select and divide the BATSE 4B data into 588 long bursts (T$_{90}>2.5$ sec) and 149 short bursts (T$_{90}<2.5$ sec), and compare the statistics calculated in each subgroup. The $<V/V_{\rm max}>$ of the long bursts is $ 0.2901

Giulio Biroli, Jorge Kurchan

Truly stable metastable states are an artifact of the mean-field approximation or the zero temperature limit. If such appealing concepts in glass theory as configurational entropy are to have a meaning beyond these approximations, one needs to cast them in a form involving states with finite lifetimes. Starting from elementary examples and using results of G

P. West

The bosonic sectors of the eleven dimensional and IIA supergravity theories are derived as non-linear realisations. The underlying group includes the conformal group, the general linear group and as well as automorphisms of the supersymmetry algebra. We discuss the supersymmetric extension and argue that Osp(1/64) is a symmetry of M theory. We also derive th

R. Kajimoto, H. Yoshizawa, H. Kawano-Furukawa, H. Kuwahara

Spin wave excitations were measured in the ferromagnetic phase of Nd$_{1/2}$Sr$_{1/2}$MnO$_{3}$ by neutron scattering. This compound is located in proximity to the A-type antiferromagnetic state, and it shows a clear anisotropy and anomalous softening of the spin wave excitations. The softening in the ferromagnetic phase is induced by the orbital ordering.

Kazuo Fujikawa

We comment on a formulation of quantum statistical mechanics, which incorporates the statistical inference of Shannon. Our basic idea is to distinguish the dynamical entropy of von Neumann, $H = -k Tr \hatρ\ln\hatρ$, in terms of the density matrix $\hatρ(t)$, and the statistical amount of uncertainty of Shannon, $S= -k \sum_{n}p_{n}\ln p_{n}$, with $p_{n}=<

Martin Goldstern, Saharon Shelah

We investigate the structure of the lattice of clones on an infinite set X. We first observe that ultrafilters naturally induce clones; this yields a simple proof of Rosenberg&#39;s theorem: &#34;there are 2^2^kappa many maximal (=precomplete) clones on a set of size kappa.&#34; The clones we construct here do not contain all unary functions. We then investi

Kazuo Hida

Low energy spectrum of the S=1 kagomé Heisenberg antiferromagnet (KHAF) is studied by means of exact diagonalization and the cluster expansion. The magnitude of the energy gap of the magnetic excitation is consistent with the recent experimental observation for \mpynn. In contrast to the $S=1/2$ KHAF, the non-magnetic excitations have finite energy gap compa

Akifumi Sako, Toru Sasaki

We show that a partition function of topological twisted N=4 Yang-Mills theory is given by Seiberg-Witten invariants on a Riemannian four manifolds under the condition that the sum of Euler number and signature of the four manifolds vanish. The partition function is the sum of Euler number of instanton moduli space when it is possible to apply the vanishing

Andrei Parnachev, Laurence G. Yaffe

We discuss a simple procedure for computing one-loop quantum energies of any static field configuration that depends non-trivially on only a single spatial coordinate. We specifically focus on domain wall-type field configurations that connect two distinct minima of the effective potential, and may or may not be the solutions of classical field equations. We

V. Dzhunushaliev, D. Singleton

In this article we investigate the metric signature as a non-differentiable ({\it i.e.} discrete as opposed to continuous) degree of freedom. The specific model is a vacuum 7D Universe on the principal bundle with an SU(2) structural group. An analytical solution is found which to a 4D observer appears as a flat Universe with a fluctuating metric signature,

Yi Zhou, Rong Lu, Jia-Lin Zhu, Lee Chang

The phenomenon of quantum nucleation is studied in a ferromagnet in the presence of a magnetic field at an arbitrary angle. We consider the magnetocrystalline anisotropy with tetragonal symmetry and that with hexagonal symmetry, respectively. By applying the instanton method in the spin-coherent-state path-integral representation, we calculate the dependence

J. C. Lemm, J. Uhlig, A. Weiguny

The paper discusses the reconstruction of potentials for quantum systems at finite temperatures from observational data. A nonparametric approach is developed, based on the framework of Bayesian statistics, to solve such inverse problems. Besides the specific model of quantum statistics giving the probability of observational data, a Bayesian approach is ess

G. M. D&#39;Ariano, P. Lo Presti, M. F. Sacchi

A general matrix approach to study entangled states is presented, based on operator completeness relations. Bases of unitary operators are considered, with focus on irreducible representations of groups. Bell measurements for teleportation are considered, and robustness of teleportation to various kinds of non idealities is shown.

Jaromir Fiurasek

We investigate exponential phase moments of the s-parametrized quasidistributions (smoothed Wigner functions). We show that the knowledge of these moments as functions of s provides, together with photon-number statistics, a complete description of the quantum state. We demonstrate that the exponential phase moments can be directly sampled from the data reco

Bruno Eckhardt, Krzysztof Sacha

Recent high resolution measurements of the momenta of two electrons emitted from Argon atoms in a strong laser field show a strong preference for the outgoing electrons to have similar momenta and to be ejected in the same direction along the field. We discuss the final stages of this process in a classical model in the spirit of Wanniers approach to double

B. Dubetsky, P. R. Berman

Atom density profile arising in the atomic beam after passing through the one or two microfabricated structures (MS) is considered. Two limiting cases the beam with large and small angular divergence are considered. An equivalence of the considerations based on the Fresnel-Kirchhoff theory of diffraction and on the atomic recoil-effect is established. Higher

F. Kleefeld

The onshell description of Initial- and Final-State-Interactions (ISI and FSI) of threshold meson production reactions is reviewed. Existing onshell models and their offshell extension are discussed. Unitarity constraints on enhancement factors are formulated. A strategy for the treatment of essential singularities connected to Coulomb-like FSI is given.

T. Gilbert, J. R. Dorfman

We consider a one-dimensional persisent random walk viewed as a deterministic process with a form of time reversal symmetry. Particle reservoirs placed at both ends of the system induce a density current which drives the system out of equilibrium. The phase space distribution is singular in the stationary state and has a cumulative form expressed in terms of

Gregorio Falqui, Cesare Reina, Alessandro Zampa

We consider the geometrical aspects of the Krichever map in the context of Jacobian Super KP hierarchy. We use the representation of the hierarchy based on the Faa` di bruno recursion relations, considered as the cocycle condition for the natural double complex associated with the deformations of super Krichever data. Our approach is based on the constructio

Yan V. Fyodorov, H. -J. Sommmers

Random contractions (sub-unitary random matrices) appear naturally when considering quantized chaotic maps within a general theory of open linear stationary systems with discrete time. We analyze statistical properties of complex eigenvalues of generic $N\times N$ random matrices $\hat{A}$ of such a type, corresponding to systems with broken time-reversal in

Bambi Hu, Changsong Zhou

Previous studies have shown that noise can induce coherence resonance in some nonlinear dynamical systems close to a bifurcation of a periodic motion, such as in excitable systems. We demonstrate that coherence resonance can be observed in systems close to a {\sl blowout bifurcation}. It is shown that for dynamical systems with an invariant subspace in which

Denis V. Juriev

The article is devoted to new mathematical methods for psychophysical filtering of experimental data and their processing.

Shun-Jen Cheng, Ngau Lam

In this paper we continue the study of representation theory of formal distribution Lie superalgebras initiated in q-alg/9706030. We study finite Verma-type conformal modules over the N=2, N=3 and the two N=4 superconformal algebras and also find explicitly all singular vectors in these modules. From our analysis of these modules we obtain a complete list of

Jin-Hwan Cho, Mikiya Masuda

We calculate the R(G)-algebra structure on the reduced equivariant K-groups of two-dimensional spheres on which a compact Lie group G acts as involutions. In particular, the reduced equivariant K-groups are trivial if G is abelian, which shows that the previous Y. Yang&#39;s calculation in [Yan95] is not true.

Alessandra Frabetti, Friedrich Wagemann

I. M. Gelfand and D. B. Fuks have studied the cohomology of the Lie algebra of vector fields on a manifold. In this article, we generalize their main tools to compute the Leibniz cohomology, by extending the two spectral sequences associated to the diagonal and the order filtration. In particular, we determine some new generators for the diagonal Leibniz coh

Jaya N. Iyer

We show that polarisations of type (1,...,1,2g+2) on g-dimensional abelian varieties are $\it{never}$ very ample, if $g\geq 3$. This disproves a conjecture of Debarre, Hulek and Spandaw. We also give a criterion for non-embeddings of abelian varieties into 2g+1-dimensional linear systems.

Costas Kounnas

We consider a conformal system of a string and a particle defined in D=10+2 space-time dimensions. The extra time-like dimension is a gauge artifact and can be eliminated by choosing a gauge in which the SO(10,1) Lorentz symmetry is manifest. The effective theory of string observables is the 11d supergravity. The same theory compactified on T^2 provides a no

Pei-Ming Ho, Miao Li

We study the quantum analogue of primary fields and their descendants on fuzzy AdS_2, proposed in hep-th/0004072. Three-point vertices are calculated and shown to exhibit the conventional 1/N expansion as well as nonperturtive effects in large N, thus providing a strong consistency check of the fuzzy AdS_2 model. A few new physical motivations for this model

Kirill Krasnov

We study holography for asymptotically AdS spaces with an arbitrary genus compact Riemann surface as the conformal boundary. Such spaces can be constructed from the Euclidean AdS_3 by discrete identifications; the discrete groups one uses are the so-called classical Schottky groups. As we show, the spaces so constructed have an appealing interpretation of ``

Alex Pomarol

We present a Grand Unified Theory (GUT) that has GUT fields with masses of the order of a TeV, but at the same time preserves (at the one-loop level) the success of gauge-coupling unification of the MSSM and the smallness of proton decay operators. This scenario is based on a five-dimensional theory with the extra dimension compactified as in the Randall-Sun

Fayyazuddin

The time-dependent analysis of the decays $Λ_b\to Λ+D^0(t)$ and $Λ_b\to Λ+\bar{D}^0(t)$ is discussed. The effect of particle mixing due to time evolution of $D^0$ and $\bar{D}^0$ on the observables for these decays viz the branching ratio of decay widths and the asymmetry parameters $α,β$ and $γ$ are analysed. It is shown that it is possible to extract infor

Yu. F. Pirogov

Neutrino mixing in the standard model extensions, both renormalizable and effective, with arbitrary numbers of the singlet and left-handed doublet neutrinos is investigated in a systematic fashion. The charged and neutral (the Z and Higgs mediated)lepton currents are written under general Majorana condition, and the odservable independence of the choice of t

H. Ciftci, H. Koru

Leptonic decay widths and leptonic decay constants of light vector mesons and weak leptonic decay widths and weak decay constants of light and heavy pseudoscalar mesons have been studied in a field- theoretic framework based on the independent quark model with a scalar- vector power-law potential. The results are in very good agreement with the experimental

D. A. Demir, Ernest Ma, Utpal Sarkar

We extend the recently proposed gluino axion model to include neutrino masses. We discuss how the canonical seesaw model and the Higgs triplet model may be realized in this framework. In the former case, the heavy singlet neutrinos are contained in superfields which do not have any vacuum expectation value, whereas the gluino axion is contained in one which

C. Avila, J. Magnin, J. C. Sanabria

We study the low $Q^2$ wave-functions of pions and kaons as an expansion in terms of hadron-like Fock state fluctuations. In this formalism, pion and kaon wave-functions are related one another. Consequently, the knowledge of the pion structure allows the determination of parton distributions in kaons. In addition, we show that the intrinsic (low $Q^2$) sea

Stefan Weinzierl

A next-to-leading order calculation for single top production including spin-dependent observables requires efficient techniques for the calculation of the relevant loop amplitudes. We discuss the adaption of dimensional regularization, the spinor helicity method and of tensor integral reduction algorithms to these needs.

Markus H. Thoma

Using the effective Lagrangian for the low energy photon-photon interaction the lowest order photon self energy at finite temperature and in non-equilibrium is calculated within the real time formalism. The Debye mass, the dispersion relation, the dielectric tensor, and the velocity of light following from the photon self energy are discussed. As an applicat

C. W. Bauer, S. Fleming, M. Luke

We construct an effective field theory valid for processes in which highly energetic light-like particles interact with collinear and soft degrees of freedom, using the decay B -> X_s + gamma near the endpoint of the photon spectrum, x = 2 E_gamma / m_b -> 1, as an example. Below the scale mu=m_b both soft and collinear degrees of freedom are included in the

L3 Collaboration

We present results obtained from a study of the structure of hadronic events recorded by the L3 detector at various centre-of-mass energies. The distributions of event shape variables and the energy dependence of their mean values are measured from 30GeV to 189GeV and compared with various QCD models. The energy dependence of the moments of event shape varia

Hwanbae Park

Current status of charm mixing search, lifetime difference measurement and rare decay search are reported. The best upper limit at 95% CL for mixing is reported from the CLEO collaboration. E791 has reported lifetime difference measurement and results of rare decay searches. Rare decay searches of the FOCUS collaboration are in progress and their sensitiviti

ALEPH Collaboration

The production of W-pairs is analysed in a data sample collected by ALEPH at a mean centre-of-mass energy of 188.6 GeV, corresponding to an integrated luminosity of 174.2 pb^-1. Cross sections are given for different topologies of W decays into leptons or hadrons. Combining all final states and assuming Standard Model branching fractions, the total W-pair cr

M. R. Convery, K. T. McDonald

We present a scheme for noncontact measurement of the tension of a wire, such as that in a drift chamber or straw tube detector.

A. Ashtekar, J. Baez, K. Krasnov

Using the earlier developed classical Hamiltonian framework as the point of departure, we carry out a non-perturbative quantization of the sector of general relativity, coupled to matter, admitting non-rotating isolated horizons as inner boundaries. The emphasis is on the quantum geometry of the horizon. Polymer excitations of the bulk quantum geometry pierc

Valeria Ferrari, Massimo Pauri, Federico Piazza

In this paper we study the perturbations of the charged, dilaton black hole, described by the solution of the low energy limit of the superstring action found by Garfinkle, Horowitz and Strominger. We compute the complex frequencies of the quasi-normal modes of this black hole, and compare the results with those obtained for a Reissner-Nordström and a Schwar

V. Bozza, A. Feoli, G. Papini, G. Scarpetta

The dynamics of a relativistic particle in a Reissner-Nordstrom background is studied using Caianiello model with maximal acceleration. The behaviour of the particle, embedded in a new effective geometry, changes with respect to the classical scenario because of the formation of repulsive potential barriers near the horizon. Black hole formation by accretion

Yurii V. Dumin

Evading formation of the domain walls in cosmological phase transitions is one of the key problems to be solved for getting agreement with the observed large-scale homogeneity of the Universe. The previous attempts to get around this obstacle led to imposing severe observational constraints on the parameters of the fields involved. Our aim is to show that ye

Hae-Young Kee, Yong Baek Kim, Kazumi Maki

Assuming that the superconductivity in Sr$_2$RuO$_4$ is described by a planar p-wave order parameter, we consider possible topological defects in Sr$_2$RuO$_4$. In particular, it is shown that both of the ${\hat d}$-soliton and half-quantum vortex can be created in the presence of the magnetic field parallel to the $a$-$b$ plane. We discuss how one can detec

L. Bureau, T. Baumberger, C. Caroli

We study the shear response of a sliding multicontact interface submitted to a harmonically modulated normal load, without loss of contact. We measure, at low velocities ($V<100 μ$m.s$^{-1}$), the average value $\bar{F}$ of the friction force and the amplitude of its first and second harmonic components. The excitation frequency ($f=120$ Hz) is chosen much l

F. Mila, R. Shiina, F. -C. Zhang, A. Joshi

Motivated by recent neutron, X-ray absorption and resonant scattering experiments, we revisit the electronic structure of V2O3. We propose a model in which S=1 V3+ ions are coupled in the vertical V-V pairs forming two-fold orbitally degenerate configurations with S=2. Ferro-orbital ordering of the V-V pairs gives a description which is consistent with all e

Z. Ropka, R. J. Radwanski

We argue that in LaCoO3 exists the fine electronic structure associated with the atomic-like states of the Co3+ ions and caused by the crystal-field and intra-atomic spin-orbit interactions. This low-energy fine electronic structure has to be taken into account for any meaningful analysis of electronic and magnetic properties of LaCoO3.

Marc Barthelemy

We study strongly nonlinear disordered media using a functional method. We solve exactly the problem of a nonlinear impurity in a linear host and we obtain a Bruggeman-like formula for the effective nonlinear susceptibility. This formula reduces to the usual Bruggeman effective medium approximation in the linear case and has the following features: (i) It re

Z. Ropka, R. Michalski, R. J. Radwanski

Electronic and magnetic (e-m) properties of FeBr2 have been surprisingly well described as originating from the Fe2+ ions and their fine electronic structure. The fine electronic structure have been evaluated taking into account the spin-orbit (s-o) coupling, crystal-field and inter-site spin-dependent interactions. The required magnetic doublet ground state

Evgeny E. Pestov, Yury N. Nozdrin, Vladislav V. Kurin

We report a set of experimental data on local third-harmonic generation at microwave frequencies (0.5 GHz) in $YBa_2Cu_3O_7$ and Nb films. For local investigations of the nonlinear response a probe with inductive coupling was elaborated. The map of the nonlinear microwave response of a $YBa_2Cu_3O_7$ thin film is plotted below $T_c$ with high resolution. The

M. Ahr, M. Biehl, M. Kinne, W. Kinzel

We report the results of computer simulations of epitaxial growth in the presence of a large Schwoebel barrier on different crystal surfaces: simple cubic(001), bcc(001), simple hexagonal(001) and hcp(001). We find, that mounds coarse by a step edge diffusion driven process, if adatoms can diffuse relatively far along step edges without being hindered by kin

V. F. Radantsev, A. M. Yafyasov, V. B. Bogevolnov, I. M. Ivankiv

The first study of two-dimensional electron gas in surface layers on HgMnTe with inverted bands is carried out experimentally and theoretically. It is shown that the structure of investigated capacitance magnetooscillations in HgMnTe MOS structures is fully similar to the one in the non-magnetic narrow-gap semiconductor HgCdTe and the sole effect due to exch

T. Fujii, N. Kawakami

We study how the multi-channel Kondo effect is dynamically induced to affect the photoemission and the inverse photoemission spectrum when an electron is emitted from (or added to) the completely screened Kondo impurity with spin $S>1/2$. The spectrum thereby shows a power-law edge singularity characteristic of the multi-channel Kondo model. We discuss this

Yashwant Singh, Debaprasad Giri, Sanjay Kumar

A phase diagram for a surface-interacting long flexible polymer chain in a two-dimensional poor solvent where the possibility of collapse exists is determined using exact enumeration method. A model of a self-attracting self avoiding walk (SASAW) on a square lattice was considered and up to 28 steps in series were evaluated. A new adsorbed state having the c

Igor F. Herbut, Anand Yethiraj, John Bechhoefer

We show that order-parameter fluctuations in a good type-I superconductor or a liquid crystal always increase the size of the first-order transition. This behavior is eventually changed when the system crosses over to inverted-XY critical behavior, with the size of the first-order transition vanishing as a power law with a crossover exponent. We find a good

D. A. Garanin, E. M. Chudnovsky

We study quantum-classical escape-rate transitions for uniaxial and biaxial models with finite spins S=10 (such as Mn_12Ac and Fe_8) and S=100 by a direct numerical approach. At second-order transitions the level making a dominant contribution into thermally assisted tunneling changes gradually with temperature whereas at first-order transitions a group of l

Una Hwang, Stephen S. Holt, Robert Petre

We present X-ray emission line equivalent width images of the bright Galactic supernova remnant Cassiopeia A for the elements Si, S, Ar, Ca, and Fe using a 50,000 s observation with the Advanced CCD Imaging Spectrometer on the Chandra X-ray Observatory. The images essentially identify the bulk of detectable ejecta of these elements over a wide range of surfa

Robert E. Rutledge, Gibor Basri, Eduardo Martin, Lars Bildsten

We have detected a bright X-ray flare from the nearby brown dwarf LP 944-20 with the Chandra/ACIS-S. This is an old (500 Myr), rapidly rotating, lithium-bearing M9 object, with a bolometric luminosity of 6e29 ergs cm-2 s-1. It was only detected by Chandra during an X-ray flare of duration 1-2 hours near the end of a 12.1 hour observation. The peak X-ray lumi

S. Zaroubi, M. Bernardi, L. N. da Costa, Y. Hoffman

We estimate the mass density fluctuations power spectrum (PS) on large scales by applying a maximum likelihood technique to the peculiarvelocity data of the recently completed redshift-distance survey of early-type galaxies (ENEAR). The general results are in agreement with the high amplitude power spectra found from similar analysis of other independent all

G. Chabrier, I. Baraffe, F. Allard, P. Hauschildt

We present evolutionary calculations for very-low-mass stars and brown dwarfs based on synthetic spectra and non-grey atmosphere models which include dust formation and opacity, i.e. objects with $\te\simle 2800$ K. The interior of the most massive brown dwarfs is shown to develop a conductive core after $\sim 2$ Gyr which slows down their cooling. Compariso

Giovanni Vladilo, Piercarlo Bonifacio, Miriam Centurion, Paolo Molaro

Zinc is a good indicator of metallicity in Damped Lyman alpha (DLA) systems because it is almost unaffected by dust depletion. However, the use of zinc as a tracer of metallicity evolution has been hampered by the difficulty of detecting the Zn II resonance lines at high redshift. The measurement of zinc abundance in a DLA system at z_abs > 3 obtained by mea

Patrick McDonald, Jordi Miralda-Escude, Michael Rauch, Wallace L. W. Sargent

The evolution of the temperature in the intergalactic medium is related to the reionization of hydrogen and helium, and has important consequences for our understanding of the Lya forest and of galaxy formation in gravitational models of large-scale structure. We measure the temperature-density relation of intergalactic gas from Lya forest observations of ei

L. Hanlon, R. J. Laureijs, L. Metcalfe, B. McBreen

The Infrared Space Observatory observed the field of the $γ$--ray burst GRB 970508 with the CAM and PHT instruments on May 21 and 24, 1997 and with PHT in three filters in November 1997. A source at 60 $μ$m (flux in May of $66\pm 10$ mJy) was detected near the position of the host galaxy of this $γ$--ray burst. The source was detected again in November 1997,

S. Rosswog, M. B. Davies, F. -K. Thielemann, T. Piran

Results of 3D, Newtonian hydrodynamic calculations of the last stages of the inspiral and the final coalescence of neutron star binary systems are described. The focus is on sligthly asymmetric systems with the asymmetry stemming either from different spins or different masses of the binary components. Implications for nucleosynthesis and gamma ray bursts ar

Matts Roos, S. M. Harun-or-Rashid

We combine the two balloon experiments BOOMERANG and MAXIMA-1 with our previous fit which used 9 constraints and concluded that the Universe is flat. The result is that the flatness is robust, $Ω_0 = 0.97 \pm 0.05$.

R. Q. Mao, C. Henkel, A. Schulz, M. Zielinsky

12CO 1-0,2-1,4-3,7-6, and 13CO 1-0, 2-1, and 3-2 line was mapped with angular resolutions of 13&#34; - 22&#34; toward the nuclear region of starburst galaxy M82. The difference of lobe spacings in submillimeter (~15&#34;) and millimeter (~26&#34;) lines indicates the presence of a `low&#39; and a `high&#39; CO excitation component. An LVG excitation analysis

N. Hasselmann, A. H. Castro Neto, C. Morais Smith

We propose that the spin glass phase of cuprates is due to the proliferation of topological defects of a spiral distortion of the antiferromagnet order. Our theory explains straightforwardly the simultaneous existence of short range incommensurate magnetic correlations and complete a-b symmetry breaking in this phase. We show via a renormalization group calc

David Nolland

We discuss the gauge invariance and &#34;mass&#34; of the Rarita-Schwinger field in a background spacetime which is assumed to be Einstein but not necessarily Ricci-flat.

George Kastrinakis

This paper treats a number of issues of the cuprates, ranging from the spin resonance peak and the linear one-particle scattering rate to the superconducting transition, in the frame of a Fermi liquid model. Recent ARPES expts. by Valla et al., Science vol. 285, 2110 (1999), and e-print cond-mat/0003407, directly support the linearity of the one-particle sca

Robert R. Tucci

We give necessary and sufficient conditions under which a density matrix acting on a two-fold tensor product space is separable. Our conditions are given in terms of quantum conditional information transmission.

D. M. Snyder

Einstein&#39;s argument on the relativity of simultaneity itself is the first result of the special theory of relativity. The nature of this result is explored, and implications of this result for the structure and functioning of the physical world found in the special theory are discussed.