May 2000 arXiv papers — page 13

Benedict W. Ritchie, Peter A. Thomas

We adapt the Smoothed-Particle Hydrodynamics technique to allow a multiphase fluid in which SPH particles of widely differing density may be freely intermixed. Applications include modelling of galaxy formation and cooling flows.

Paolo Carta

We consider a Callan-Symanzik and a Wilson Renormalization Group approach to the infrared problem for interacting fermions in one dimension with backscattering. We compute the third order (two-loop) approximation of the beta function using both methods and compare it with the well known multiplicative Gell-Mann Low approach. We point out a previously unnotic

Chien-Wen Hwang

The charge and transition form factors of pion ($F_π$, $F_{πγ}$, and $F_{πγ^*}$) are studied with the light-front quark model. We find that our results for $F_π$ and $F_{πγ}$ agree very well with experimental data. Furthermore, the decay constants of $η$ and $η'$ are evaluated. We also calculate $F_{ηγ}$ and $F_{η'γ}$ and compare with the experimenta

R. J. Protheroe, H. Meyer

We consider the implications of the recent determination of the universal infrared background for the propagation of photons up to 20 TeV from the active galaxy Markarian 501 as observed by HEGRA. At 20 TeV the mean free path for photon-photon collisions on the infrared background would be much shorter than the distance to Markarian 501, implying absorption

N. N. Achasov, G. N. Shestakov

A simple model for the exotic waves with $I^G(J^{PC})=1^-(1^{-+})$ in the reactions $VP\to VP$, $VP\to PP$, and $PP\to PP$ is constructed beyond the scope of the quark-gluon approach. The model satisfies unitarity and analyticity and uses as a "priming" the "anomalous" nondiagonal $VPPP$ interaction which couples together the four channels $ρ

Nobuyuki Ishibashi, Kazumi Okuyama, Yuji Satoh

Using the path integral approach, we discuss the correlation functions of the $SL(2,\bfC)/SU(2)$ WZW model, which corresponds to the string theory on the Euclidean $AdS_3$. We obtain the two- and three-point functions for generic primary fields in closed forms. By an appropriate change of the normalization of the primary fields, our results coincide with tho

Yehuda Sharf, Timothy F. Havel, David G. Cory

Quantum information processing by liquid-state NMR spectroscopy uses pseudo-pure states to mimic the evolution and observations on true pure states. A new method of preparing pseudo-pure states is described, which involves the selection of the spatially labeled states of an ancilla spin with which the spin system of interest is correlated. This permits a gen

Bo-Sture K Skagerstam, Bjorn A Bergsjordet, Per K. Rekdal

We investigate the possibility of interference effects induced by macroscopic quantum-mechanical superpositions of almost othogonal coherent states - a Schroedinger cats state - in a resonant microcavity. Despite the fact that a single atom, used as a probe of the cat state, on the average only change the mean number of photons by one unit, we show that this

M. Bachmann, H. Kleinert, A. Pelster

Extending the Feynman-Kleinert variational approach, we calculate the temperature-dependent effective classical potential governing the quantum statistics of a hydrogen atom in a uniform magnetic at all temperatures. The zero-temperature limit yields the binding energy of the electron which is quite accurate for all magnetic field strengths and exhibits, in

Roberto Laura, Mario Castagnino, Rodolfo M. Id Betan

Imposing analytic properties to states and observables we construct a perturbative method to obtain a generalized biorthogonal system of eigenvalues and eigenvectors for quantum unstable systems. A decay process can be described using this generalized spectral decomposition, and the final generalized state is obtained.

Zhao-Yang Tong, Le-Man Kuang

We introduce entanglement measures to describe entanglement in a three-particle system and apply it to studying broadcasting of entanglement in three-particle GHZ state. We show that entanglement of three-qubit GHZ state can be partially broadcasted with the help of local or non-local copying processes. It is found that non-local cloning is much more efficie

Giuseppe Castagnoli

We introduce a local concept of speed-up applicable to intermediate stages of a quantum algorithm. We use it to analyse the complementary roles played by quantum parallel computation and quantum measurement in yielding the speed-up. A severe conflict between there being a speed-up and the many worlds interpretation is highlighted.

R. Laiho, S. N. Molotkov, S. S. Nazin

The process of teleportation of a completely unknown single-photon relativistic state is considered. Analysis of the relativistic case reveals that the teleportation as it is understood in the non-relativistic quantum mechanics is impossible if no {\it a priori} information on the state to be teleported is available. It is only possible to speak of the ampli

R. Laiho, S. N. Molotkov, S. S. Nazin

The process of teleportation of a completely unknown one-particle state of a free relativistic quantum field is considered. In contrast to the non-relativistic quantum mechanics, the teleportation of an unknown state of the quantum field cannot be in principle described in terms of a measurement in a tensor product of two Hilbert spaces to which the unknown

V. Giovannetti, S. Mancini, P. Tombesi

We demonstrate the appearance of Einstein-Podolsky-Rosen (EPR) paradox when a radiation field impinges on a movable mirror. The, the possibility of a local realism test within a pendular Fabry-Perot cavity is shown to be feasible.

Bao-Sen Shi, Yun-Kun Jiang, Guang-Can Guo

In this paper, we describe how to realize conditional frequency entanglement swapping and to produce probabilisticly a three-photon frequency entangled state from two pairs of frequency entangled states by using an Acoustic-Optical-Modulator. Both schemes are very simple and may be implementable in practice.

Filippo Troiani, Ulrich Hohenester, Elisa Molinari

We propose an all-optical implementation of quantum-information processing in semiconductor quantum dots, where electron-hole excitations (excitons) serve as the computational degrees of freedom (qubits). We show that the strong dot confinement leads to an overall enhancement of Coulomb correlations and to a strong renormalization of the excitonic states, wh

K. V. Bhagwat, D. C. Khandekar, S. V. G. Menon, R. R. Puri

The argument used, in a recent letter to Nature (Nature 130 vol 404, 2000) to arrive at the `quantum-no-deleting principle' is erroneous. It is pointed out here that there may not be anything like such a principle. In any case, the claims made in the letter are beyond its working premise.

D. O. Riska, G. E. Brown

Recent heavy ion experiments indicate modifications of the $ρ-$meson mass in medium. In the CERES experiments $ρ-$mesons are produced at $\sim$ normal nuclear matter density, where hadrons are more appropriate constituents than quarks. A collective "nuclear $ρ$", in which every nucleon is excited to the N(1520) state, with equal amplitude, enters in

V. S. Vasilevsky, F. Arickx

The convergence problem for scattering states is studied in detail within the framework of the Algebraic Model, a representation of the Schrodinger equation in an L^2 basis. The dynamical equations of this model are reformulated featuring new "Dynamical Coefficients", which explicitly reveal the potential effects. A general analysis of the Dynamical

Alexander Groisman, Victor Steinberg

Behavior of a dilute polymer solution in a random three-dimensional flow with an average shear is studied experimentally. Polymer contribution to the shear stress is found to be more than two orders of magnitude higher than in a laminar shear flow. The results indicate that the polymer molecules get strongly stretched by the random motion of the fluid.

Joan S. Birman, Nancy C. Wrinkle

Let $f:S^1\to R$ be a generic map. We may use $f$ to define a new map $\tilde{f}:S^1\to R^3$ by $\tilde{f}(t) = (-f(t),f'(t),-f''(t))$, and if $f$ is an embedding then the image of $\tilde{f}$ will be a knot. Knots defined by such parametrizations are called holonomic knots. They were introduced in 1997 by Vassiliev, who proved that every knot ty

Benson Farb, Lee Mosher

A finitely presented, torsion free, abelian-by-cyclic group can always be written as an ascending HNN extension Gamma_M of Z^n, determined by an n x n integer matrix M with det(M) \ne 0. The group Gamma_M is polycyclic if and only if |det(M)|=1. We give a complete classification of the nonpolycyclic groups Gamma_M up to quasi-isometry: given n x n integer ma

Robert G. Rieper, Melkamu Zeleke

Valleyless sequences of finite length $n$ and maximum entry $k$ occur in tree enumeration problems and provide an interesting correspondence between permutations and compositions. In this paper we introduce the notion of \emph {valleyless} sequences, explore the correspondence and enumerate them using the method of generating functions.

Carmi Merimovich

We give an application of our extender based Radin forcing to cardinal arithmetic. Using a preparation forcing and interleaving of Cohen and Levy forcings in the normal Radin sequence we get a model with a power function having a fixed finite gap on all cardinals.

Claude LeBrun

Seiberg-Witten theory leads to a delicate interplay between Riemannian geometry and smooth topology in dimension four. In particular, the scalar curvature of any metric must satisfy certain non-trivial estimates if the manifold in question has a non-trivial Seiberg-Witten invariant. However, it has recently been discovered that similar statements also apply

Amir Leshem

In this paper we prove that if k is a cardinal in L[0^#], then there is an inner model M such that M |= (V_k,E) has no elementary end extension. In particular if 0^# exists then weak compactness is never downwards absolute. We complement the result with a lemma stating that any cardinal greater than aleph_1 of uncountable cofinality in L[0^#] is Mahlo in eve

Leonid G. Fel, Boris Y. Rubinstein

A new recursive procedure of the calculation of partition numbers function $W(s,{\bf d}^m)$ is suggested. We find its zeroes and prove a lemma on the function parity properties. The explicit formulas of $W(s,{\bf d}^m)$ and their periods $τ(G)$ for the irreducible Coxeter groups and a list for the first ten symmetric group ${\cal S}_m$ are presented. A {\it

Dolores Bazan, Emilia Mezzetti

We study the degeneracy loci of general bundle morphisms from the direct sum of m copies of the structural sheaf on $P^n$ to $Ω(2)$, also from the point of view of the classical geometrical interpretation of the sections of $Ω(2)$ as linear line complexes. We consider in particular the case of $P^5$ with m=2, 3. For n=5 and m=3 we give an explicit descriptio

Mitsuo Hoshino, Yoshiaki Kato, Jun-ichi Miyachi

First, we show that a compact object $C$ in a triangulated category, which satisfies suitable conditions, induces a $t$-structure. Second, in an abelian category we show that a complex $P^{\centerdot}$ of small projective objects of term length two, which satisfies suitable conditions, induces a torsion theory. In the case of module categories, using a torsi

Alberto Collino, Najmuddin Fakhruddin

We construct some natural cycles with trivial regulator in the higher Chow groups of Jacobians. For hyperelliptic curves we use a criterion due to J. Lewis to prove that the cycles we construct are indecomposable, and then use a specialization argument to prove indecomposability for more general curves. Please note that math.AG/9909062 has become an obsolete

Lajos Molnar

The aim of this paper is to show that between standard operator algebras every bijective map with a certain multiplicativity property related to Jordan triple isomorphisms of associative rings is automatically additive.

Lajos Molnar, Peter Semrl

We prove that every 2-local automorphism of the unitary group or the general linear group on a complex infinite-dimensional separable Hilbert space is an automorphism. Thus these types of transformations are completely determined by their local actions on the two-points subsets of the groups in question.

Lajos Molnar

The set of all efects on a Hilbert space has an affine structure (it is a convex set) as well as a multiplicative structure (it can be equipped with the so-called Jordan triple product). In this paper we describe the corresponding automorphisms of that set.

Lajos Molnar

Let H be a complex infinite dimensional Hilbert space. We describe the form of all *-semigroup endomorphisms $ϕ$ of B(H) which are uniformly continuous on every commutative C*-subalgebra. In particular, we obtain that if $ϕ$ satisfies $ϕ(0)=0$, then $ϕ$ is additive.

Lajos Molnar

We present a generalization of Wigner's unitary-antiunitary theorem for pairs of ray transformations. As a particular case, we get a new Wigner-type theorem for non-Hermitian indefinite inner product spaces.

Mark Haskins

We study special Lagrangian cones in $\C^n$ with isolated singularities. Our main result constructs an infinite family of special Lagrangian cones in $\C^3$ each of which has a toroidal link. We obtain a detailed geometric description of these tori. We prove a regularity result for special Lagrangian cones in $\C^3$ with a spherical link -- any such cone mus

A. Hanany, B. Pioline

The Atiyah-Hitchin manifold arises in many different contexts, ranging from its original occurrence as the moduli space of two SU(2) 't Hooft-Polyakov monopoles in 3+1 dimensions, to supersymmetric backgrounds of string theory. In all these settings, (super)symmetries require the metric to be hyperkähler and have an SO(3) transitive isometry, which in th

L. M. Baker

A proof is given for the observation that the equations of motion for the companion Lagrangian without a square root, subject to some constraints, just reduce to the equations of motion for the companion Lagrangian with a square root in one less dimension. The companion Lagrangian is just an extension of the Klein-Gordon Lagrangian to more fields in order to

Satish D. Joglekar

We establish a finite field-dependent BRS transformation that connects the Yang-Mills path-integrals with Faddeev-Popov effective actions for an arbitrary pair of gauges F and F'. We establish a result that relates an arbitrary Green's function [either a primary one or one that of an operator] in an arbitrary gauge F' to those in gauge F that are

B. Stefanski

The D-brane spectrum of a $\Zop_2\times\Zop_2$ Calabi-Yau three-fold orbifold of toroidally compactified Type IIA and Type IIB string theory is analysed systematically. The corresponding K-theory groups are determined and complete agreement is found. New kinds of stable non-BPS D-branes are found, whose stability regions are far more complicated than the pre

Kimball A. Milton, Igor L. Solovtsov

A relativistic Coulomb-like resummation factor in QCD is suggested, based on the solution of the quasipotential equation.

E. Kh. Akhmedov, J. Pulido

Assuming that the solar neutrino deficit observed in the Homestake, SAGE, Gallex, Kamiokande and Super-Kamiokande experiments is due to the interaction of the neutrino transition magnetic moment with the solar magnetic field, we calculate the expected values of a number of observables to be measured by SNO. For three model solar magnetic field profiles that

Chun-xiu Liu, Zuo-tang Liang

Longitudinal polarizations of different kinds of hyperons produced in e+e- annihilation at LEP I and LEP II energies in different event samples are calculated using two different pictures for the spin structure of hyperon: that drawn from polarized deep inelastic lepton-nucleon scattering data or that using SU(6) symmetric wave functions. The result shows th

Paolo Gondolo

Neutralino dark matter may be incompatible with current cold dark matter models with cuspy dark halos, because excessive synchrotron radiation may originate from neutralino annihilations close to the black hole at the galactic center.

Bohdan Grzadkowski, John F. Gunion, Jacek Pliszka

We study the possibility of measuring the muon Yukawa couplings in s-channel Higgs boson production at a muon collider with transversely polarized beams. We investigate sensitivity to the relative size of the CP-odd and CP-even muon Yukawa couplings. Provided the event rate observed justifies the operation of the mu+mu- Higgs boson factory, we find that 40%

Carl E. Carlson

We consider some of the things that we understand about the theoretical underpinnings of duality, including items such as why the resonance peak/background ratio is constant in general, why it falls for the $Δ(1232)$, what we might expect for scaling and duality with longitudinal or spin-dependent structure functions, and what kind of scaling or duality we m

R. Sekhar Chivukula

We discuss the bound on the mass of the Higgs boson arising from precision electroweak measurements in the context of the triviality of the scalar Higgs model. We show that, including possible effects from the underlying nontrivial dynamics, a Higgs boson mass of up to 500 GeV is consistent with current data.

M. Czakon, J. Studnik, M. Zralek, J. Gluza

The neutrinoless double beta decay as well as any other laboratory experiment has not been able to answer the question of the neutrino's nature. Hints on the answer are available when neutrino oscillations and $(ββ)_{0 ν}$ are considered simultaneously. In this case phenomenologically interesting neutrino mass schemes can lead to non-vanishing and large

Nick van Eijndhoven

Transverse momentum spectra of the reaction products from proton-proton and nucleus-nucleus collisions are discussed within the phenomenological frameworks of statistical phase-space and string fragmentation models. It will be shown that a string fragmentation model can accommodate all of the observations discussed here and consequently it is claimed that no

V. E. Markushin

A coupled channel model is used to study the nature of the scalar mesons produced in the decay phi - gamma pi pi. The KKbar molecular picture of f0(980) is found to be in a good agreement with the recent experimental data from SND and CMD-2. The structure of the light scalar mesons is elucidated by investigating the S-matrix poles and the qqbar spectral dens

Tuomas Multamaki, Iiro Vilja

Collisions of non-topological solitons, Q-balls, are considered in the Minimal Supersymmetric Standard Model where supersymmetry has been broken at a low energy scale via a gauge mediated mechanism. Q-ball collisions are studied numerically on a two dimensional lattice for a range of Q-ball charges. Total cross-sections, as well as fusion and geometrical cro

K. E. Lassila, E. N. Magar, V. A. Nikolaev, V. Yu. Novozhilov

Nucleon electromagnetic form factors are considered in the framework of the generalized Skyrme model with dilaton-quarkonium field. In our recent publication we have got big discrepancies between calculated form factors and dipole approximation formula. Here we have reasonably good accordance between them in finite impulse region after vector meson dominance

G. Barenboim, K. Huitu, M. Raidal

We study flavour violation in the minimal SUSY SU(5) GUT assuming all the third generation Yukawa couplings to be due to the renormalizable physics above GUT scale. At large $\tanβ,$ as suggested by Yukawa unification in SU(5), sizable flavour violation in the left (right) slepton (down squark) sector is induced due to renormalization effects of down type Yu

Jean-Michel Levy

Forsaking the traditionnal hand-waving in the treatment of the motion, we show that the ultra-relativistic approximation and the equality of kinematical variables are unnecessary ingredients in the derivation of the oscillation length using plane waves, at least in a two flavor world. It ensues that the formula is valid as it is in the non relativistic regim

J. M. Carmona, A. Di Giacomo, B. Lucini

Lattice studies of monopole condensation in QCD are based on the construction of a disorder parameter, a creation operator of monopoles which is written in terms of the gauge fields. This procedure is expected to work for any system which presents duality. We check it on the Ising model in 2d, which is exactly solvable. The output is an amusing exercise in s

Levan Babukhadia

We report on a new measurement of the rapidity dependence of the inclusive jet production cross section in pbar p collisions at sqrt(s)=1.8 TeV using 92 pb^-1 of data collected by the DZero detector at the Tevatron collider. The differential cross sections, d^2sigma/(dEt deta), are presented as a function of jet transverse energy (Et) in five pseudorapidity

Supriya Jain, Ambreesh K. Gupta, Naba K. Mondal

We make a Monte Carlo study on compositeness of first generation quarks and leptons using the Drell-Yan distribution in the high dielectron mass region at the Tevatron and LHC energies. The current experimental lower limits on the compositeness scale, Λ, vary from 2.5 to 6.1 TeV. In the present analysis, we assume that there will be no deviation of the diele

Robert Beig

We describe recent work due to Niall Ó Murchadha and the author (Phys. Rev. D57, 4728 (1998)) on the late time behaviour of the maximal foliation of the extended Schwarzschild geometry which results from evolving a time symmetric slice into the past and future, with time running equally fast at both spatial ends of the manifold. We study the lapse function o

M. V. Takook

A covariant quantization of the free spinor fields (s=1/2) in 4-dimensional de Sitter (dS) space-time based on analyticity in the complexified pseudo-Riemanian manifold is presented. We define the Wigthman two-point function ${\cal W}(x,y)$, which satisfies the conditions of: a) positivity, b) locality, c) covariance, and d) normal analyticity. Then the Hilb

Takashi Okamura

In a gedankenexperiment about the generalized second law (GSL) of black hole thermodynamics, the buoyant force by black hole atmosphere (the acceleration radiation) plays an important role, and then it is significant to understand the nature of the buoyant force. Recently, Bekenstein criticizes that the fluid approximation of the acceleration radiation which

Yungui Gong

Brane cosmology takes the unconventional form $H\sim \sqrtρ$. To recover the standard cosmology, we have to assume that the matter density is much less than the brane tension. We show that the assumption can be justified even near the end of inflation if we fine-tune the coupling constant of the inflaton potential. As a consequence, the standard cosmology is

A. Bille, R. A. Klemm, K. Scharnberg

We calculate the critical current density $J^J_c$ for c-axis Josephson tunneling between identical high temperature superconductors twisted an angle $ϕ_0$ about the c-axis. We model the tunneling matrix element squared as a Gaussian in the change of wavevector q parallel to the junction, $<|t({\bf q})|^2>\propto\exp(-{\bf q}^2a^2/2π^2σ^2)$. The $J^J_c(ϕ_0)/J

Ian Affleck

Using previous results from boundary conformal field theory and integrability, a phase diagram is derived for the 2 dimensional Ising model at its bulk tri-critical point as a function of boundary magnetic field and boundary spin-coupling constant. A boundary tri-critical point separates phases where the spins on the boundary are ordered or disordered. In th

V. A. Stephanovich

We show that in strong (quantizing) magnetic fields &#34;ordinary&#34; free magnetic polaron in diluted magnetic semiconductors (of type $A^2MeB^6$, where Me=Fe, Mn) exists in the form of vortex lattice quite similar to that in type II superconductors (Abricosov vortex lattice). The region of external parameters (like external magnetic field and temperature)

Sh. Farhangfar, R. S. Poikolainen, J. P. Pekola, D. S. Golubev

Properties of one-dimensional (1D) arrays of low Ohmic tunnel junctions (i.e. junctions with resistances comparable to, or less than, the quantum resistance $R_{\rm q}\equiv h/e^2\approx 25.8$ k$Ω$) have been studied experimentally and theoretically. Our experimental data demonstrate that -- in agreement with previous results on single- and double-junction s

I. Perez-Castillo, A. Perez-Madrid, J. M. Rubi, G. Bossis

We discuss the effect of an homogeneous flow in the aggregation process of colloidal magnetic particles at moderate concentration. Situations in which the presence of flow acts in favor of the chaining process: particles assemble into chains larger than the ones emerging in the absence of flow, under the only influence of an externnaly imposed field, have be

Kazuhiro Sano, Ken&#39;ichi Takano

We study the spin gap of the S=1/2 Heisenberg model on the distorted diamond chain, which is recently proposed to represent magnetic properties of Cu_3 Cl_6 (H_2 O)_2 2H_8 C_4 SO_2. This model is composed of stacked trimers and has three kinds of exchange interactions J_1, J_2 and J_3. Using the numerical diagonalization, we obtain a contour map of the spin

E. Zipper, M. Lisowski

A mesoscopic system of cylindrical geometry made of a metal or a semiconductor is shown to exhibit features of a quantum coherent state. It is shown that magnetostatic interaction can play an important role in mesoscopic systems leading to an ordered ground state. The temperature $T^{*}$ below the system exhibits long-range order is determined. The self-cons

E. Louis, J. A. Verges

The magnetoconductance G in chaotic quantum dots at medium/high magnetic fluxes Phi is calculated by means of a tight binding Hamiltonian on a square lattice. Chaotic dots are simulated by introducing diagonal disorder on surface sites of L x L clusters. It is shown that when the ratio W/L is sufficiently large, W being the leads width, G increases steadily

J. Stepanic, G. Bilalbegovic

Molecular dynamics computer simulations which employ the embedded-atom potential show that nanowires of gold exist as multishelled structures. We simulate double-walled gold nanowires and calculate the capacitance of a finite nanometer-size cylindrical capacitor. For the sizes for which multishelled nanowires appear in simulations we find the capacitances be

Andras Janossy, Ferenc Simon, Titusz Feher

In a recent Letter Ando et al (cond-mat/9905071) discovered an anomalous magnetoresistance(MR) in hole doped antiferromagnetic YBa$_2$Cu$_3$O$_{6+x}$, which they attributed to charged stripes, i.e., to segregation of holes into lines. In this Comment we show that the experiments, albeit being interesting, do not prove the existence of stripes. In our view th

Bernard Nienhuis

Tiling models are classical statistical models in which different geometric shapes, the tiles, are packed together such that they cover space completely. In this paper we discuss a class of two-dimensional tiling models in which the tiles are rectangles and isosceles triangles. Some of these models have been solved recently by means of Bethe Ansatz. We discu

R. Melzi, P. Carretta, A. Lascialfari, M. Mambrini

NMR and magnetization measurements in Li$_2$VOSiO$_4$ and Li$_2$VOGeO$_4$ are reported. The analysis of the susceptibility shows that both compounds are two-dimensional $S=1/2$ Heisenberg antiferromagnets on a square lattice with a sizeable frustration induced by the competition between the superexchange couplings $J_1$ along the sides of the square and $J_2

S. B. Roy, P. Chaddah, Sujeet Chaudhary

We present experimental results on single crystal CeRu$_2$ showing that the extent of history dependence of peak-effect depends on the path followed in the space of field (H) and temperature (T). The (H,T) regime over which history effect is observed is larger if the vortex lattice is prepared by lowering T from above T$_C$ in constant H i.e. by field coolin

Hideo Hasegawa

The mean-field theory with the use of the slave-boson functional method is generalized to take account of the spin- and orbital-ordered state in the doubly degenerate Hubbard model. Some numerical calculations are presented of the antiferromagnetic orbital-ordered state in the half-filled simple-cubic model. The orbital order in the present theory is much re

Y. Otsuka, Y. Hatsugai

Combined effects of interactions and disorder are investigated using a finite temperature quantum Monte Carlo technique for the three-dimensional Hubbard model with random potentials of a finite range. Temperature dependence of the charge compressibility shows that the Mott gap collapses beyond a finite disorder strength. This is a quantum phase transition f

Eric Gawiser

We combine detections of anisotropy in the Cosmic Microwave Background radiation with observations of inhomogeneity in the large-scale distribution of galaxies to test the predictions of models of cosmological structure formation. This combination probes spatial scales varying by three orders of magnitude, including a significant region where the two types o

L. Bildsten, R. E. Rutledge

We summarize the quiescent X-ray observations of transient low-mass X-ray binaries. These observations show that, in quiescence, binaries containing black holes are fainter than those containing neutron stars. This has triggered a number of theoretical ideas about what causes the quiescent X-ray emission. For black hole binaries, the options are accretion on

Jason D. Fiege, Ralph E. Pudritz

We model the sub-millimetre polarization patterns that are expected for filamentary clouds that are threaded by helical magnetic fields. We previously developed a three parameter model of such clouds (Fiege & Pudritz 2000a), which are described by a concentration parameter $C$, and two flux to mass ratios $\Gz$ and $\Gphi$ to specify the mass loading of the

Motomichi Tashiro, Ryoichi Nishi

We perform linear analysis of thermal instability in a contracting large cloud filled with warm HI gas and investigate the effect of metallicity and radiation flux. When the cloud reaches critical density n_f, the cloud fragments into cool, dense condensations because of thermal instability. For a lower metallicity gas cloud, the value of n_f is high. Collis

C. Alcock, R. Allsman, D. R. Alves, T. Axelrod

More than 1300 variables classified provisionally as first overtone RR Lyrae pulsators in the MACHO variable star database of the Large Magellanic Cloud (LMC) have been subjected to standard frequency analysis. Based on the remnant power in the prewhitened spectra, we found 70% of the total population to be monoperiodic. The remaining 30% (411 stars) are cla

F. L. Schoeier, H. Olofsson

We present observations of circumstellar millimetre-wave 13CO line emission towards a sample of 20 cool carbon stars. Using a detailed radiative transfer model we estimate the circumstellar 12CO/13CO-ratios, which we believe accurately measure the important stellar 12C/13C-ratios. For those optically bright carbon stars where it is possible, our derived 12C/

Amir Leshem, Alle-Jan van der Veen, Albert-Jan Boonstra

Radio-astronomical observations are increasingly corrupted by RF interference, and online detection and filtering algorithms are becoming essential. To facilitate the introduction of such techniques into radio astronomy, we formulate the astronomical problem in an array signal processing language, and give an introduction to some elementary algorithms from t

A. Gardini, S. A. Bonometto, G. Murante, G. Yepes

We evaluate the dependence of the cluster correlation length r_c on the mean intercluster separation D_c, for three models with critical matter density, vanishing vacuum energy (Lambda = 0) and COBE normalized: a tilted CDM (tCDM) model (n=0.8) and two blue mixed models with two light massive neutrinos yielding Omega_h = 0.26 and 0.14 (MDM1 and MDM2, respect

P. A. Denissenkov, A. Weiss

The recent discovery of low-mass red giants with enhanced atmospherical Li abundance in galactic low-metallicity stellar clusters adds to the mysterious phenomenon of the Li-rich giants. We propose a combined scenario for the Li-enrichment: engulfing a giant planet (or brown dwarf) by a red giant (external source) activates inside the giant the &#34;7Be-mech

Klaus Elsaesser

The generalized Helmholtz equations of relativistic multifluid plasmas can be integrated for axisymmetric equilibria in close analogy to the magnetic flux conservation law in ideal magnetohydrodynamics (J. D. Bekenstein and E. Oron, Phys. Rev. D 18, 1809 (1978)). The results are, for each fluid component, two flux functions and a potential equation for the p

M. J. D. Linden-Voernle, H. U. Noergaard-Nielsen, H. E. Joergensen, L. Hansen

We present here the results of a deep survey in a 0.4 sq.deg. blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observatory (ISO) at both 60 um and 90 um. The resulting sky maps have a spatial resolution of 15 x 23 sq.arcsec. per pixel which is much higher than the 90 x 90 sq.arcsec. pixels of the IRAS All Sky S

M. Molla, M. L. Garcia-Vargas

We present a grid of theoretical models where the calculation of absorption line spectral indices in both the blue and red wavelength ranges is done with the same evolutionary synthesis code. We have computed some of these indices: CaT, NaI, MgI in the near infrared and Mgb, Mg2, Fe52, Fe53, NaD and Hbeta, in the blue-visible range, for Single Stellar Popula

Winfried Zimdahl, Diego Pavón

We reveal unifying thermodynamic aspects of so different phenomena as the cosmological electron-positron annihilation, the evaporation of primordial black holes with a narrow mass range, and the ``deflationary&#39;&#39; transition from an initial de Sitter phase to a subsequent standard Friedmann-Lema\^ıtre-Robertson-Walker begin (FLRW) behavior.

W. Aoki, J. E. Norris, S. G. Ryan, T. C. Beers

We report the detection of the Pb I 4057.8A line in the very metal-poor ([Fe/H]=-2.7), carbon-rich star, LP625-44. We determine the abundance of Pb ([Pb/Fe] = 2.65) and 15 other neutron-capture elements. The abundance pattern between Ba and Pb agrees well with a scaled solar system s-process component, while the lighter elements (Sr-Zr) are less abundant tha

D. M. Neumann, M. Arnaud

We reanalyzed the ROSAT/HRI observation of MS1054-03, optimizing the channel HRI selection and including a new exposure of 68 ksec. From a wavelet analysis of the HRI image we identify the main cluster component and find evidence for substructure in the west, which might either be a group of galaxies falling onto the cluster or a foreground source. Our 1-D a

N. Huelamo, R. Neuhaeuser, B. Stelzer, R. Supper

We present a study of the X-ray emission from binary systems extracted from the Lindroos catalogue (Lindroos 1986) based on the ROSAT All-Sky survey as well as ROSAT PSPC and HRI pointings. The studied sample consists of visual binary systems comprised of early-type primaries and late-type secondaries. The ages of the systems were determined by Lindroos (198

Nick N. Gorkavyi, Leonid M. Ozernoy, John C. Mather, Sara R. Heap

We have applied a powerful numerical approach to compute, with a high resolution, the structure of dusty circumstellar disks with embedded planets. We emphasize some testable implications of our simulations which would verify the presence of a planet via thermal emission of one or more dusty clumps which are in mean motion resonances with the planet. In part

Nino Boccara, Henryk Fuks

A necessary and sufficient condition for a one-dimensional q-state n-input cellular automaton rule to be number-conserving is established. Two different forms of simpler and more visual representations of these rules are given, and their flow diagrams are determined. Various examples are presented and applications to car traffic are indicated. Two nontrivial

Bumsoo Kyung

In this paper, from the microscopic Hubbard Hamiltonian we extract the local spin-singlet amplitude due to short-range spin correlations, and quantify its strength near half-filling. As a first application of the present approach, we study a problem of the energy dispersion and its d-wave modulation in the insulating cuprates, Sr$_{2}$CuO$_{2}$Cl$_{2}$ and C

Michal Brhlik, Daniel J. H. Chung, Gordon L. Kane

Suppose the lightest superpartner (LSP) is observed at colliders, and WIMPs are detected in explicit experiments. We point out that one cannot immediately conclude that cold dark matter (CDM) of the universe has been observed, and we determine what measurements are necessary before such a conclusion is meaningful. We discuss the analogous situation for neutr

Benjamin Lange

This paper solves two major problems which have blocked a free-fall Equivalence-Principle (EP) in a satellite for 25 years: a semimajor-axis error between the two proof masses cannot be distinguished from an EP violation and the response to an EP violation only grows as t not t^2. Using the cancellation method described in this paper, the nonobservability pr

Spencer R. Klein, Joakim Nystrand, Ramona Vogt

In relativistic heavy ion collisions, top quarks can be produced by photon-gluon fusion when a photon from the Weizsäcker-Williams virtual photon field of one nucleus interacts with a gluon in the other nucleus. Photoproduction with heavy ions at the Large Hadron Collider (LHC) will be the first accessible non-hadronic top production channel. We calculate th

Alexander G. Abanov

We derive an effective action for Dirac fermions coupled to O(3) non-linear sigma-model (NLSM) through the Yukawa-type interaction. The nonperturbative (global) quantum anomaly of this model results in a Hopf term for the effective NLSM. We obtain this term using the ``embedding&#39;&#39; of the CP$^1$ model into the CP$^M$ generalization of the model which