November 1999 arXiv papers — page 17

David Crampton, Simon Lilly

A method for searching for emission-line objects in "windows" between atmospheric emission lines using multislits is described. A search for Ly alpha emitters at z = 6.5 in the 9130A window using this technique is being carried out with the multi-object spectrograph on CFHT. This technique could be extended to similar windows at longer wavelengths, a

Simon Casassus, Patrick F. Roche, Mike J. Barlow

We report on advances in the study of the cores of NGC6302 and NGC6537 using infrared grating and echelle spectroscopy. In NGC6302, emission lines from species spanning a large range of ionization potential, and in particular [SiIX]3.934um, are interpreted using photoionization models (including CLOUDY), which allow us to reestimate the central star's te

H. Krawczynski, P. S. Coppi, T. Maccarone, F. A. Aharonian

During more than 6 months in 1997, the BL Lac object Mkn 501 was in an exceptionally bright state, both in the X-ray band and in the Very High Energy (VHE) band. In this paper we present a multiwavelength study of Mkn 501 during this extraordinary outburst. We describe the analysis of a data base of X-ray observations acquired with the pointed X-ray telescop

Sebastien Blais-Ouellette, Claude Carignan, Philippe Amram, Stephanie Cote

Using the example of the Sd galaxy NGC 5585, it is shown that high resolution 2-D HII kinematical data are necessary to determine accurately the parameters of the mass distribution in spirals. New CFHT Fabry-Perot Halpha observations are combined with low resolution (20") Westerbork HI data to study its mass distribution. Using the combined rotation curv

A. Somer

We report the discovery of 3 pulsars, PSR J0030+0451, PSR J0711+09, and PSR J1313+09 that were found in a three dimensional (DM, period, position) search at 430 MHz using the 305m Arecibo telescope. PSR J0030+0451 is a nearby 4.8-millisecond solitary pulsar. Spin and astrometric parameters are presented for the three new pulsars. We have measured significant

Kunegunda E. Belle, Geraint F. Lewis

Roughly 10% of all quasars exhibit Broad Absorption Line (BAL) features which appear to arise in material outflowing at high velocity from the active galactic nucleus (AGN). The details of this outflow are, however, very poorly constrained and the particular nature of the BAL material is essentially unknown. Recently, new clues have become available through

Sisir Roy, Menas Kafatos, Suman Datta

The frequency shift of spectral lines from astronomical objects is most often explained by the Doppler Effect arising in relative motion and the broadening of a particular line is supposed to depend on the absolute temperature, pressure or the different line of sight velocities. The Wolf effect on the other hand deals with correlation induced spectral change

Z. Chacko, Markus A. Luty, Ann E. Nelson, Eduardo Ponton

We consider supersymmetric theories where the standard-model quark and lepton fields are localized on a "3-brane" in extra dimensions, while the gauge and Higgs fields propagate in the bulk. If supersymmetry is broken on another 3-brane, supersymmetry breaking is communicated to gauge and Higgs fields by direct higher-dimension interactions, and to q

Sean M. Carroll, Simeon Hellerman, Mark Trodden

We consider models of scalar fields coupled to gravity which are higher-dimensional generalizations of four dimensional supergravity. We use these models to describe domain wall junctions in an anti-de Sitter background. We derive Bogomolnyi equations for the scalar fields from which the walls are constructed and for the metric. From these equations a BPS-li

Xiaofeng Guo, Xiaofei Zhang, Wei Zhu

We analyze $x_F$ dependence of Drell-Yan transverse momentum broadening in hadron-nucleus collisions. In terms of generalized factorization theorem, we show that the $x_F$ dependence of transverse momentum broadening, $ Δ< q_T^2 > (x_F) $, can be calculated in perturbative QCD. We demonstrate that $Δ< q_T^2 > (x_F)$ is a good observable for studying the effe

S. A. Fulling

This is a pedagogical article cited in the foregoing research note, quant-ph/9911050

E. Balkovsky, A. Fouxon, V. Lebedev

We study properties of dilute polymer solutions which are known to depend strongly on polymer elongation. The probability density function (PDF) of polymer end-to-end extensions $R$ in turbulent flows is examined. We demonstrate that if the value of the Lyapunov exponent $λ$ is smaller than the inverse molecular relaxation time $1/τ$ then the PDF has a stron

Oron Zachar

For stripes in doped antiferromagnets, we find that the ratio of spin and charge correlation lenghts, $ξ_{s}/ξ_{c}$, provide a sharp criterion for determining the dominant form of disorder in the system. If stripes disorder is controlled by topological defects then $ξ_{s}/ξ_{c}\lesssim 1$. In contast, if stripes correlations are disordered primarily by non-t

Jordi Miralda-Escude

Several emerging links between high-redshift observational cosmology and the Galactic fossil evidence found in the kinematics, metallicities and ages of Milky Way stars are discussed. In a flat Cold Dark Matter model with $Ω\simeq 0.3$ that agrees with present large-scale structure observations, the oldest stars in the Milky Way should have formed in the fir

S. Davidson, M. Losada, N. Rius

We analyse the neutral scalar sector of the MSSM without R-parity. Our analysis is performed for a one-generation model in terms of ``basis-independent&#39;&#39; parameters, and includes one-loop corrections due to large yukawa couplings. We concentrate on the consequences of large $R_p$ violating masses in the soft sector, which mix the Higgses with the sle

Mrinal Dasgupta, Lorenzo Magnea, Graham Smye

We provide an exact analytical calculation at the two-loop level in the abelian limit of the leading power correction for the C parameter in e+e- annihilation. We compare our results to the numerical value obtained employing the soft approximation, the abelian part of the Milan factor. We demonstrate that a simple proportionality holds between the leading po

Riccardo Barbieri, Paolo Creminelli, Alessandro Strumia, Nikolaos Tetradis

Baryogenesis by heavy-neutrino decay and sphaleron reprocessing of both baryon and lepton number is reconsidered, paying special attention to the flavour structure of the general evolution equations and developing an approximate but sufficiently accurate analytic solution to the prototype evolution equation. Two different models of neutrino masses are examin

Yoav Achiman, Carsten Merten

Right Handed (RH) rotations are not observable in the standard model (SM). The freedom is used to give the phenomenologically correct mass matrices all kind of different forms and this is one of the reasons for the proliferation of models for the fermionic masses. The SM must be however extended and in most extensions, RH currents appear at higher energy sca

Heng Fan, Miki Wadati

We apply the nested algebraic Bethe ansatz method to solve the eigenvalue problem for the SU(4) extension of the Hubbard model. The Hamiltonian is equivalent to the SU(4) graded permutation operator. The graded Yang-Baxter equation and the graded Quantum Inverse Scattering Method are used to obtain the eigenvalue of the SU(4) extension of the Hubbard model.

O. N. Pakhomova, V. A. Saleev

We consider spin effects in two-particle hadronic decays of B_c and B_c^* mesons into J/psi plus ρ(π) in the frame work of hard gluon exchange model. It is shown that polarization of the J/psi meson is very different in decays of B_c and B_c^* mesons as well as their decay widths into J/psi plus ρ(π).

G. A. Alekseev

A monodromy transform approach, presented in this communication, provides a general base for solution of space-time symmetry reductions of Einstein equations in all known integrable cases, which include vacuum, electrovacuum, massless Weyl spinor field and stiff matter fluid, as well as some string theory induced gravity models. It was found a special finite

C. Sochichiu

A consistent definition of high dimensional compactified quantum field theory without breaking the Kaluza-Klein tower is proposed. It is possible in the limit when the size of compact dimensions is of the order of the cut off. This limit is nontrivial and depends on the geometry of compact dimensions. Possible consequences are discussed for the scalar model.

Shoichi Ichinose

We formulate the renormalization procedure using the domain wall regularization that is based on the heat-kernel method. The quantum effects of both fermions and bosons (gauge fields) are taken into account. The background field method is quite naturally introduced. With regard to the treatment of the loop-momentum integrals, an interesting contrast between

Kosta Dosen, Zoran Petric

From the analogue of Boehm&#39;s Theorem proved for the typed lambda calculus, without product types and with them, it is inferred that every cartesian closed category that satisfies an equality between arrows not satisfied in free cartesian closed categories must be a preorder. A new proof is given here of these results, which were obtained previously by Ri

Tao Huang, Zuohong Li, Haidong Zhang

We propose a new estimate of the process $B \to (ρ, ω)+ γ$ by using the light-cone QCD sum rule. The aim is to choose the chiral quark current operators in order to eliminate the uncertainty arising from the chiral-even operators in the correlator. In the case of neglecting the corrections from $ρ$-meson mass, the sum rules for form factors are obtained, whi

T. -K. Ng, Jizhong Lou, Zhao-Bin Su

In this paper we study the effect of substituting R (rare-earth ion) by non-magnetic ions in the spin-1 chain material $R_2BaNiO_5$. Using a strong-coupling expansion and numerical density matrix renormalization group calculations, we show that spin-wave bound states are formed at the impurity site. Experimental consequences of the bound states are pointed o

Brian C. Hall

This paper explains some of the ideas behind a prior joint work of the author with Bruce Driver on the canonical quantization of Yang-Mills theory on a spacetime cylinder. The idea is that the generalized Segal-Bargmann transform for a compact group can be obtained from the ordinary Segal-Bargmann transform by imposing gauge symmetry.

S. A. Fulling

Residue arithmetic is an elegant and convenient way of computing with integers that exceed the natural word size of a computer. The algorithms are highly parallel and hence naturally adapted to quantum computation. The process differs from most quantum algorithms currently under discussion in that the output would presumably be obtained by classical superpos

A. Gersten

Maxwell equations (Faraday and Ampere-Maxwell laws) can be presented as a three component equation in a way similar to the two component neutrino equation. However, in this case, the electric and magnetic Gauss&#39;s laws can not be derived from first principles. We have shown how all Maxwell equations can be derived simultaneously from first principles, sim

V. M. Tkachuk, P. Roy

We study the motion of a spin 1/2 particle in a scalar as well as a magnetic field within the framework of supersymmetric quantum mechanics(SUSYQM). We also introduce the concept of shape invariant scalar and magnetic fields and it is shown that the problem admits exact analytical solutions when such fields are considered.

G. Chen, S. A. Fulling, M. O. Scully

L. K. Grover&#39;s search algorithm in quantum computing gives an optimal, square-root speedup in the search for a single object in a large unsorted database. In this paper, we expound Grover&#39;s algorithm in a Hilbert-space framework that isolates its geometrical essence, and we generalize it to the case where more than one object satisfies the search cri

A. Gersten

We generalize previous results and demonstrate that the Dirac representation theory can be effectively adjusted and applied to continuous or discrete signals of infinite time duration. The role of the identity and projection operators is emphasized. The sampling theorem is viewed from the point of view of orthogonal physical states. An orthogonal basis which

A. Gersten

We demonstrate that the Dirac representation theory can be effectively adjusted and applied to signal theory. The main emphasis is on orthogonality as the principal physical requirement. The particular role of the identity and projection operators is stressed. A Dirac space is defined, which is spanned by an orthonormal basis labeled with the time points. An

A. Gersten, O. Gersten, A. Ronen, Y. Cassuto

A reliable spectral analysis requires sampling rate at least twice as large as the frequency bound, otherwise the analysis will be unreliable and plagued with aliasing distortions. The RR samplings do not satisfy the above requirements and therefore their spectral analysis might be unreliable. In order to demonstrate the feasibility of aliasing in RR spectra

Ruhi Gurcan

Researchers of seismic waves may construct a new seismographic recording adding one seismometer to each component of a conventional seismic station. The two identical conventional seismometers are set up in position of perpendicular and are connected in parallel feeding one recording device (digital or analog). This use of the seismometers (which they may be

Lev Kaplan, Thomas Papenbrock

We study the structure of eigenstates in two-body interaction random matrix ensembles and find significant deviations from random matrix theory expectations. The deviations are most prominent in the tails of the spectral density and indicate localization of the eigenstates in Fock space. Using ideas related to scar theory we derive an analytical formula that

Gabor Papp, George Fai, Peter Levai

We study the mechanism of the $γ$ and $π^0$ enhancement at large transverse momenta in proton-nucleus collisions. A proposed mechanism suggests an increase in the width of the transverse momentum distribution of partons in a semihard process.

A1 Collaboration, A. Liesenfeld

The reaction p(e,e&#39;pi+)n was measured at the Mainz Microtron MAMI at an invariant mass of W=1125 MeV and four-momentum transfers of Q^2=0.117, 0.195 and 0.273 (GeV/c)^2. For each value of Q^2, a Rosenbluth separation of the transverse and longitudinal cross sections was performed. An effective Lagrangian model was used to extract the `axial mass&#39; fro

Palle E. T. Jorgensen

In this paper we provide a quantitative comparison of two obstructions for a given symmetric operator S with dense domain in Hilbert space ${\cal H}$ to be selfadjoint. The first one is the pair of deficiency spaces of von Neumann, and the second one is of more recent vintage: Let P be a projection in ${\cal H}$. We say that it is smooth relative to S if its

Maurice Kibler

The genesis and impact of the M.Sc. thesis by Moshé Flato is analysed. In this connection, the fruitful passage of Moshé in Lyon, capitale mondiale de la gastronomie, is evoked. Finally, some basic elements for a model in crystal- field theory are given as a important step on the way opened by Moshé.

Louis H. Kauffman, David E. Radford

This paper has two purposes. The first is to explicate the diagrammatic approach to Hopf algebras due to Kuperberg, and to examine his proof of the existence and uniqueness of integrals in both the diagrammatic and purely algebraic contexts. The second purpose of the paper is to show that the theory of integrals for a finite dimensional Hopf algebra A can be

Oliver Baues, Vicente Cortés

We prove that any simply connected special Kaehler manifold admits a canonical immersion as a parabolic affine hypersphere. As an application, we associate a parabolic affine hypersphere to any nondegenerate holomorphic function. Also we show that a classical result of Calabi and Pogorelov on parabolic spheres implies Lu&#39;s theorem on complete special Kae

M. Farber, S. Weinberger

We prove that the answer to the &#34;zero-in-the-spectrum&#34; conjecture, in its form, suggested by J. Lott, is negative. Namely, we show that for any n > 5 there exists a closed n-dimensional manifold M, so that zero does not belong to the spectrum of the Laplace-Beltrami operator acting on the L^2 forms of all degrees on the universal covering of M.

Anatoly N. Kochubei

We study certain classes of equations for $F_q$-linear functions, which are the natural function field counterparts of linear ordinary differential equations. It is shown that, in contrast to both classical and $p$-adic cases, formal power series solutions have positive radii of convergence near a singular point of an equation. Algebraic properties of the ri

Jin Hong, Seok-Jin Kang

We give a realization of crystal graphs for basic representations of the quantum affine algebra $U_q(C_2^{(1)})$ in terms of new combinatorial objects called the Young walls.

Michael Baake, Uwe Grimm, Dieter Joseph, Przemyslaw Repetowicz

The shelling of crystals is concerned with counting the number of atoms on spherical shells of a given radius and a fixed centre. Its straight-forward generalization to quasicrystals, the so-called central shelling, leads to non-universal answers. As one way to cope with this situation, we consider shelling averages over all quasicrystal points. We express t

Chris M. Hull, Ramzi R. Khuri

Duality transformations involving compactifications on timelike as well as spacelike circles link M-theory, the 10+1-dimensional strong coupling limit of IIA string theory, to other 11-dimensional theories in signatures 9+2 and 6+5 and to type II string theories in all 10-dimensional signatures. These theories have BPS branes of various world-volume signatur

C. Angelantonj, I. Antoniadis, G. D&#39;Appollonio, E. Dudas

We show how chiral type I models whose tadpole conditions have no supersymmetric solution can be consistently defined introducing antibranes with non-supersymmetric world volumes. At tree level, the resulting stable non-BPS configurations correspond to tachyon-free spectra, where supersymmetry is broken at the string scale on some (anti)branes but is exact i

C. M. Hull

Duality symmetries in M--theory and string theory are reviewed, with particular emphasis on the way in which string winding modes and brane wrapping modes can lead to new spatial dimensions. Brane world-volumes wrapping around Lorentzian tori can give rise to extra time dimensions and in this way dualities can change the number of time dimensions as well as

German Sierra

We propose a connection between conformal field theory (CFT) and the exact solution and integrability of the reduced BCS model of superconductivity. The relevant CFT is given by the $SU(2)_k$-WZW model in the singular limit when the level k goes to -2. This theory has to be perturbed by an operator proportional to the inverse of the BCS coupling constant. Us

O. B. Zaslavskii

It is shown that static solutions with a finite curvature at the horizon may exist in dilaton gravity at temperatures $T\neq T_{H}$ (including T=0) where $T_{H} $is the Hawking one. Hawking radiation is absent and the state of a system represents thermal excitation over the Boulware vacuum. The horizon remains unattainable for a observer because of thermal d

S. Khakshournia, R. Mansouri

Applying the distributional formalism to study the dynamics of thin shells in general relativity, we regain the junction equations for matching of two spherically symmetric spacetimes separated by a singular hypersurface. In particular, we have shown how to define and insert the relevant sign functions in the junction equations corresponding to the signs of

N. D. Hari Dass, V. Soni

In this paper we construct non-Abelian gauge theories with fermions and scalars that nevertheless possess asymptotic freedom.The scalars are taken to be in a chiral multiplet transforming as $(2,2)$ under $SU(2)_L\otimes SU(2)_R$ and transforming as singlets under the colour SU(3) group. We consider two distinct scenarios, one in which the additional scalars

V. Dmitrasinovic, F. Myhrer

A modified linear sigma model that allows for $g_A = 1.26$ by addition of vector and pseudovector $πN$ coupling terms was discussed by Bjorken and Nauenberg and by Lee. In this extended linear sigma model the elastic $π$N scattering amplitudes satisfy the relevant chiral low-energy theorems, such as the Weinberg-Tomozawa relation for the isovector scattering

Cetin Savkli, Franz Gross

The quark-antiquark bound states are discussed using the relativistic spectator (Gross) equations. A relativistic covariant framework for analyzing confined bound states is developed. The relativistic linear potential developed in an earlier work is proven to give vanishing meson$\to$ $q+\bar{q}$ decay amplitudes, as required by confinement. The regularizati

Alessandro Ballestrero

Helicity amplitudes calculations with the program PHACT are explained. Some examples of their application in WPHACT and SIXPHACT MC&#39;s are given.

S. Kanemura, T. Kasai, Y. Okada

By imposing validity of the perturbation and stability of vacuum up to an energy scale $Λ$ ($\leq 10^{19}$ GeV), we evaluate mass bounds of the lightest CP-even Higgs-boson mass ($m_h$) in the two-Higgs-doublet model (2HDM) with a softly-broken discrete symmetry. The most general bounds are obtained as a function of $Λ$ vering all the free parameters under t

J. G. Koerner, F. Krajewski, A. A. Pivovarov

In a previous paper we performed an analysis of asymptotic structure of perturbation theory series for semileptonic $τ$-lepton decays in massless limit. We extend our analysis to the Cabibbo suppressed $ΔS=1$ decay modes of the $τ$ lepton. In particular we address the problem of $m_s^2$ corrections to theoretical formulas. The properties of the asymptotic be

G. Passarino

A condensed survey of various aspects of LEP 1 physics is presented with a critical examination of the ingredients that are available for theoretical predictions. A prototype of comparisons for 2f calculations can be found in hep-ph/9902452.

John F. Donoghue, Eugene Golowich

We show how the isospin vector and axialvector current spectral functions rho_V and rho_A can be used to determine in leading chiral order the low energy constants B_7^{3/2} and B_8^{3/2}. This is accomplished by matching the Operator Product Expansion to the dispersive analysis of vacuum polarization functions. The data for the evaluation of these dispersiv

Keith A. Olive

These lectures contain an introduction to supersymmetric theories and the minimal supersymmetric standard model. Phenomenological and cosmological consequences of supersymmetry are also discussed.

Shinya Kanemura, Takashi Kasai, Yasuhiro Okada

The upper and the lower bounds of the lightest CP-even Higgs-boson mass ($m_h$) are discussed in the two-Higgs-doublet model (2HDM) with a softly-broken discrete symmetry. They are obtained as a function of a cut-off scale $Λ$ ($\leq 10^{19}$ GeV) by imposing the conditions in which the running coupling constants neither blow up nor fall down below $Λ$. In c

W. Bietenholz

We perform renormalization group transformations to construct optimally local perfect lattice actions for free scalar fields of any mass. Their couplings decay exponentially. The spectrum is identical to the continuum spectrum, while thermodynamic quantities have tiny lattice artifacts. To make such actions applicable in simulations, we truncate the coupling

I. Montvay

Least-squares optimized polynomials are discussed which are needed in the two-step multi-bosonic algorithm for Monte Carlo simulations of quantum field theories with fermions. A recurrence scheme for the calculation of necessary coefficients in the recursion and for the evaluation of these polynomials is introduced.

M. Battaglia, R. Orava, K. Tammi, K. Osterberg

In order to fully exploit the physics potential of a future high energy e+e- linear collider, a Vertex Tracker, providing high resolution track reconstruction, is required. Hybrid Silicon pixel sensors are an attractive option, for the sensor technology, due to their read-out speed and radiation hardness, favoured in the high rate environment of the TESLA e+

Sally Seidel

Results are presented for the inclusive jet cross section versus jet transverse energy in proton-antiproton collisions at center of mass energy 1.8 TeV as measured by the CDF and D0 detectors at Fermilab&#39;s Tevatron collider. The data are compared to next-to-leading order QCD predictions using different input parton distribution functions. The ratio of in

G. J. Mathews, J. R. Wilson

We report on numerical results from a revised hydrodynamic simulation of binary neutron-star orbits near merger. We find that the correction recently identified by Flanagan significantly reduces but does not eliminate the neutron-star compression effect. Although results of the revised simulations show that the compression is reduced for a given total orbita

Eloy Ayón-Beato, Alberto García

The first regular exact black hole solution in General Relativity is presented. The source is a nonlinear electrodynamic field satisfying the weak energy condition, which in the limit of weak field becomes the Maxwell field. The solution corresponds to a charged black hole with |q| \leq 2 s_c m \approx 0.6 m, having the metric, the curvature invariants, and

Giovanni Losurdo

The VIRGO superattenuator (SA) is effective in depressing the seismic noise below the thermal noise level above 4 Hz. On the other hand, the residual mirror motion associated to the SA normal modes can saturate the dynamics of the interferometer locking system. This motion is reduced implementing a wideband (DC-5 Hz) multidimensional control (the so called i

Jim Gray

Charles Babbage&#39;s vision of computing has largely been realized. We are on the verge of realizing Vannevar Bush&#39;s Memex. But, we are some distance from passing the Turing Test. These three visions and their associated problems have provided long-range research goals for many of us. For example, the scalability problem has motivated me for several dec

Stefan V. Mashkevich, Stanislav I. Vilchynskyy

We study the possibility of existence of bound states for two interacting He-4 atoms. It is shown that for some potentials, there exist not only discrete levels but also bands akin to those in the Kronig--Penney model.

Boris Spivak, Fei Zhou

We propose a model which explains the experimental observation of spontaneous spin polarization of conducting electrons in quasi- one-dimensional GaAs/AlGaAs channels. We show that a ferromagnetic order is a generic property of a quasi-one-dimensional conducting channel embedded in a Wigner crystal. We also discuss gate voltage, magnetic field and temperatur

Jeferson J. Arenzon, Yan Levin, Juergen F. Stilck

A mean-field theory based on Gibbs-Bogoliubov inequality is constructed to study the interactions between two like-charged polyions. It is shown that contrary to the previously established paradigm, a properly constructed mean-field theory can quantitatively account for the attractive interactions between two like-charged rods.

Geza Toth, Alexei O. Orlov, Islamshah Amlani, Craig S. Lent

The electrostatic interaction between two capacitively-coupled metal double-dots is studied at low temperatures. Experiments show that when the Coulomb blockade is lifted by applying appropriate gate biases to both double-dots, the conductance through each double-dot becomes significantly lower than when only one double-dot is conducting. A master equation i

E. Goldobin, B. A. Malomed, A. V. Ustinov

Dynamics of a fluxon in a stack of inductively coupled long Josephson junctions is studied analytically and numerically. We demonstrate that the fluxon has a maximum velocity, which does not necessarily coincide with any of the characteristic Josephson plasma wave velocities. The maximum fluxon velocity is found by means of numerical simulations of the quasi

Kun Yang, R. A. Hyman

In a recent Letter (PRL 83, 3297 (1999)), Hida presented numerical results indicating that the Haldane phase of the Heisenberg antiferromagnetic spin-1 chain is stable against bond randomness, for box distributions of the bond strength, even when the box distribution stretches to zero bond strength. The author thus concluded that the Haldane phase is stable

D. V. Efremov, M. S. Mar&#39;enko, M. A. Baranov, M. Yu. Kagan

The critical temperature of a superfluid phase transition in a Fermi gas with repulsive interaction is found. The influence of a magnetic field on the transition is analyzed. The estimates for the critical temperature for a trapped gas of $^6$Li atoms and $^3$He--$^4$He mixtures are presented.

S. Drozdz, F. Gruemmer, F. Ruf, J. Speth

Detailed study of the financial empirical correlation matrix of the 30 companies comprised by DAX within the period of the last 11 years, using the time-window of 30 trading days, is presented. This allows to clearly identify a nontrivial time-dependence of the resulting correlations. In addition, as a rule, the draw downs are always accompanied by a sizable

D. V. Efremov, M. S. Mar&#39;enko, M. A. Baranov, M. Yu. Kagan

In the framework of a 2D Fermi-gas with short-range repulsive interaction we find the critical temperature of the superfluid phase transition based on Kohn-Luttinger effect, and analyze its dependence on magnetic field. We calculate strong-coupling corrections to the Ginzburg-Landau free energy functional and analyze the staibility of 2D superfluid phases. P

D. Lacoste, B. A. van Tiggelen

This paper describes how coherent backscattering is altered by an external magnetic field. In the theory presented, magneto-optical effects occur inside Mie scatterers embedded in a non-magnetic medium. Unlike previous theories based on point-like scatterers, the decrease of coherent backscattering is obtained in leading order of the magnetic field using rig

G. Allodi, R. De Renzi, M. Solzi, K. Kamenev

The antiferromagnetic manganite Pr$_{0.5}$Sr$_{0.5}$MnO$_3$ was investigated at low temperature by means of magnetometry and $^{55}$Mn NMR. A field-induced transition to a ferromagnetic state is detected by magnetization measurements at a threshold field of a few tesla. NMR shows that the ferromagnetic phase develops from zero field by the nucleation of micr

Sze-Shiang Feng

An inequality of the eigenvalues of the reduced density matrix $ρ_2$ at finite temperature in the Hubbard model is obtained by means of the Bogolyubov inequality. The quasi-average of $\tilde{S}^{+}$ in a simple symmetry-breaking perturbation of the Hamiltonian for a bipartite lattice is shown to be zero.

Sze-Shiang Feng, Ferdinando Mancini

We draw some rigorous conclusions about the functional properties of the $μ-ρ$ relation in the Hubbard model based on symmetry considerations and unitary transformations. It is shown that the charge susceptibility reaches its local extreme at half-filling. Exact expressions are obtained in two limiting cases.

Luca Capriotti, Sandro Sorella

We investigate the non magnetic phase of the spin-half frustrated Heisenberg antiferromagnet on the square lattice using exact diagonalization (up to 36 sites) and quantum Monte Carlo techniques (up to 144 sites). The spin gap and the susceptibilities for the most important crystal symmetry breaking operators are computed. A genuine and somehow unexpected `p

S. Pleutin

Important questions concern the existence of excitonic strings in organic compounds and their signatures in the photophysics of these systems. A model in terms of Hard Core Bosons is proposed to study this problem in one dimension. Mainly the cases with two and three particles are studied for finite and infinite lattices, where analytical results are accessi

Paul M. Goldbart

In many interesting physical settings, such as the vulcanization of rubber, the introduction of permanent random constraints between the constituents of a homogeneous fluid can cause a phase transition to a random solid state. In this random solid state, particles are permanently but randomly localized in space, and a rigidity to shear deformations emerges.

U. Kuhl, F. M. Izrailev, A. A. Krokhin, H. -J. Stoeckmann

The tight-binding model with correlated disorder introduced by Izrailev and Krokhin [PRL 82, 4062 (1999)] has been extended to the Kronig-Penney model. The results of the calculations have been compared with microwave transmission spectra through a single-mode waveguide with inserted correlated scatterers. All predicted bands and mobility edges have been fou

J. L. Tallon, J. W. Loram, G. V. M. Williams, J. R. Cooper

Evidence is presented from the scaling of the Knight shift, entropy and transport properties together with the sharp peaking of condensation energy, critical currents, superfluid density and a variety of other physical properties for the occurrence of a common critical doping point in lightly overdoped high-Tc superconductors (HTS). This critical doping lies

T. Takayanagi, T. Kitajima, T. Takemura, I. Terasaki

The anisotropic dielectric constants of the parent antiferromagnet Bi2Sr2MCu2O8 (M=Dy, Y and Er) single crystals were measured from 80 to 300 K. The in-plane dielectric constant is found to be very huge (10^4-10^5). This suggests a remnant of the Fremi surface of the parent antiferromagnet. The out-of-plane dielectric constant is 50-200, which is three order

Ryotaro Arita, Kazuhiko Kuroki, Hideo Aoki

Inspired from an experimentally examined organic conductor, a novel mechanism for negative magnetoresistance is proposed for repulsively interacting electrons on a lattice whose band dispersion contains a flat portion (a flat bottom below a dispersive part here). When the Fermi level lies in the flat part, the electron correlation should cause ferromagnetic

I. Terasaki, T. Takemura, T. Takayanagi, T. Kitajima

The resistivity and the thermopower for Bi2Sr2Ca{1-x}RxCu2O8 single crystals are measured and analyzed with a special interest in the parent antiferromagnet insulators. Above room temperature, the parent insulators show an electric conduction confined in the CuO2 plane and a decreasing thermopower with temperature, which are very similar to those for high-$T

Matias Zaldarriaga, Uros Seljak

We extend the cosmological linear perturbation theory code CMBFAST to closed geometries. This completes the implementation of CMBFAST to all types of geometries and allows the user to perform an unlimited search in the parameter space of models. This will be specially useful for placing confidence limits on cosmological parameters from existing and future da

S. Khlebnikov

We study numerically evolution of a self-gravitating nonequilibrium Bose gas contained in a fixed volume. We find that, even when the volume is small enough to prevent collisionless instability, a compact phase-correlated object (a Bose star) can form, by gravity alone, from a disordered initial state. We interpret this effect and the associated growth of th

Pamela Gay, David L. Lambert

Isotopic abundance ratios 24^Mg:25^Mg:26^Mg are derived for 20 stars from high- resolution spectra of the MgH A-X 0-0 band at 5140AA. With the exception of the weak g-band giant HR 1299, the stars are dwarfs that sample the metallicity range -1.8 < [Fe/H] <0.0. The abundance of 25^Mg amd 26^Mg relative to the dominant isotope 24^Mg decreases with decreasing

J. C. Clemens, M. H. van Kerkwijk, Y. Wu

We have used time-resolved spectroscopy to measure the colour dependence of pulsation amplitudes in the DAV white dwarf G 29-38. Model atmospheres predict that mode amplitudes should change with wavelength in a manner that depends on the spherical harmonic degree l of the mode. This dependence arises from the convolution of mode geometry with wavelength-depe

M. H. van Kerkwijk, J. C. Clemens, Y. Wu

We present time-resolved spectrophotometry of the pulsating DA white dwarf G 29-38. As in previous broad-band photometry, the light curve shows the presence of a large number of periodicities. Many of these are combination frequencies, i.e., periodicities occurring at frequencies that are sums or differences of frequencies of stronger, real modes. We identif

S. P. Littlefair, V. S. Dhillon, S. B. Howell, D. R. Ciardi

We present time resolved J-band (1.025 - 1.340 micron) infrared spectra of the short-period dwarf novae (DNe) WZ Sge, VY Aqr and single spectra of the short-period DN EF Peg and the novalike variable PX And. There is some evidence in the spectra of VY Aqr and EF Peg that we have detected the secondary star, both in the continuum slope and also through the po

G. S. Bisnovatyi-Kogan

Standard accretion disk theory is formulated which is based on the local heat balance. The energy produced by a turbulent viscous heating is supposed to be emitted to the sides of the disc. Sources of turbulence in the accretion disc are connected with nonlinear hydrodynamic instability, convection, and magnetic field. In standard theory there are two branch

David Nice, Zaven Arzoumanian, Stephen Thorsett

We present results of long-term timing of eclipsing binaries PSR B1744-24A and PSR B1957+20 at Arecibo, the VLA, and Green Bank. Both pulsars exhibit irregularities in pulsar rotation and orbital motion. Increases and decreases of the orbital period of PSR B1957+20 are of order Delta-P_b/P_b ~ 10^-7, varying on a time scale of a few years. Over a decade of o

M. V. Safonova, D. Lohiya

In non-minimally coupled effective gravity theories one can have non-topological solitonic solutions. A typical solution is a spherical region with $G_{\it eff}=0$ outside and having the canonical Newtonian value inside. Such a spherical domain (gravity-ball) is characterized by an effective index of refraction which causes bending of light incident on it. T