December 2001 arXiv papers — page 9

D. P. Gurd

Building an accelerator at six geographically dispersed sites is quite mad, but politically expedient. The Spallation Neutron Source (SNS), currently under construction in Oak Ridge, Tennessee, combines a pulsed 1 Gev H- superconducting linac with a compressor ring to deliver 2MW of beam power to a liquid mercury target for neutron production [1]. Accelerato

R. D. Mota, A. Valcarce, F. Fernández, D. R. Entem

We study the possible existence of nonstrange dibaryons and tribaryons by solving the bound-state problem of the two- and three-body systems composed of nucleons and deltas. The two-body systems are $NN$, $NΔ$, and $ΔΔ$, while the three-body systems are $NNN$, $NNΔ$, $NΔΔ$, and $ΔΔΔ$. We use as input the nonlocal $NN$, $NΔ$, and $ΔΔ$ potentials derived from

Al. H. Raduta, Ad. R. Raduta

A general discussion is made concerning the ways in which one can get signatures about a possible liquid-gas phase transition in nuclear matter. Microcanonical temperature, heat capacity and second order derivative of the entropy versus energy formulas have been deduced in a general case. These formulas are {\em exact}, simply applicable and do not depend on

M. Baldo, L. Lo Monaco

The hole spectral function is calculated in nuclear matter to assess the relevance of nucleon-nucleon short range correlations. The calculation is carried out within the Brueckner scheme of many-body theory by using several nucleon-nucleon realistic interactions. Results are compared with other approaches based on variational methods and transport theory. Di

N. Le Neindre, for REVERSE collaboration

Mass and charge identification of charged products detected with Silicon-CsI(Tl) telescopes of the Chimera apparatus is presented. An identification function, based on the Bethe-Bloch formula, is used to fit empirical correlation between Delta E and E ADC readings, in order to determine, event by event, the atomic and mass numbers of the detected charged rea

C. Verhoeven, M. Musette, R. Conte

The generalized Hénon-Heiles Hamiltonian $H=1/2(P_X^2+P_Y^2+c_1X^2+c_2Y^2)+aXY^2-bX^3/3$ with an additional nonpolynomial term $μY^{-2}$ is known to be Liouville integrable for three sets of values of $(b/a,c_1,c_2)$. It has been previously integrated by genus two theta functions only in one of these cases. Defining the separating variables of the Hamilton-J

Anandamohan Ghosh, V. Ravi Kumar, B. D. Kulkarni

Parameter estimation for spatiotemporal dynamics for coupled map lattices and continuous time domain systems is shown using a combination of multiple shooting, Karhunen-Loeve decomposition and Galerkin's projection methodologies. The resulting advantages in estimating parameters have been studied and discussed for chaotic and turbulent dynamics using sma

G. Sardanashvily

We show that any solution of a smooth first order dynamic equation can be made Lyapunov stable at will by the choice of an appropriate time-dependent Riemannian metric.

E Strahov

A combinatorial interpretation is provided for the moments of characteristic polynomials of random unitary matrices. This leads to a rather unexpected consequence of the Keating and Snaith conjecture: the moments of $\midξ(1/2+it)\mid$ turn out to be connected with some increasing subsequences problems (such as the last passage percolation problem).

Andrzej Sitarz

We introduce a family of noncommutative 4-spheres, such that the instanton projector has its first Chern class trivial: $ch_1(e) = B χ+ b ξ$. We construct for them a 4-dimensional cycle and calculate explicitly the Chern-Connes paring for the instanton projector.

Romeo Brunetti, Klaus Fredenhagen, Rainer Verch

A new approach to the model-independent description of quantum field theories will be introduced in the present work. The main feature of this new approach is to incorporate in a local sense the principle of general covariance of general relativity, thus giving rise to the concept of a "locally covariant quantum field theory". Such locally covariant

Mordehai Milgrom

I investigate the properties of forces on bodies in theories governed by the generalized Poisson equation div[mu(abs(grad_phi))grad_phi]=G rho, for the potential phi produced by a distribution of sources rho. This equation describes, inter alia, media with a response coefficient, mu, that depends on the field strength, such as in nonlinear, dielectric, or di

S. S. e Costa

This article simply presents several coordinate systems for 2 and 3-dimensional hyperbolic spaces, describing the general solutions of Helmholtz equation in each one of these systems.

Justin Roberts

Rozansky and Witten proposed in 1996 a family of new three-dimensional topological quantum field theories, indexed by compact (or asymptotically flat) hyperkaehler manifolds. As a byproduct they proved that hyperkaehler manifolds also give rise to Vassiliev weight systems. These may be thought of as invariants of hyperkaehler manifolds, so the theory is of i

Philippe Caldero

We study multiplicative properties of the (quantum) dual canonical basis B* associated to a semi-simple complex Lie group G. We provide a subset D of B* such that the following property holds : if two elements b, b' in B* q-commute and if one of these elements is in D, then the product bb' is in B* up to a power of q, where q the quantum parameter. I

A. Sciarrino

A q-analogue of the embedding chains of the Arima-Iachello model is proposed. The generators of the deformed U(6)-subalgebras are written in terms of the generators of gl_{q}(6), using q-bosons.

Thomas Friedrich, Stefan Ivanov

We compute the scalar curvature of 7-dimensional ${G}_2$-manifolds admitting a connection with totally skew-symmetric torsion. We prove the formula for the general solution of the Killing spinor equation and express the Riemannian scalar curvature of the solution in terms of the dilation function and the NS 3-form field. In dimension n=7 the dilation functio

Nicolas Perrin

Let $\mathbb{Q_3}$ the smooth quadric in P^4 (the 4-dimensional projective space). In this note we completely describe the closure of the open set of vector bundles in ${\bf M}_{\mathbb{Q}_3}(0,2,0)$. This description gives another example where the conditions given in math.AG/0112199 for a sheaf to be limit of vector bundles are necessary and sufficient.

Nicolas Perrin

Let X be a smooth 3-fold and let E be a rank 2 torsion free sheaf. In the first part of this paper, we give some necessary conditions for the sheaf E to be limit of vector bundles. In the second part, we describe an example of this problem. Thanks to the construction of Ellingsrud and Stromme, we describe a familly of rank 2 sheaves on P^3 (the 3-dimensional

Stephen D. Miller

The first nontrivial zeroes of the Riemann $ζ$ function are $\approx 1/2+\pm14.13472i$. We investigate the question of whether or not any other L-function has a higher lowest zero. To do so we try to quantify the notion that the L-function of a ``small'' automorphic representation (i.e. one with small level and archimedean type) does not have small z

Nieto B. Isidro

In [BN] the authors construct a special complex of degree 20 over M, which for an open three dimensional set parametrizes smooth complex surfaces of degree four invariant which are Heisenberg invariant and each member of the family contains 32 lines but only 16 skew lines. The coordinates of the lines however need not be real. For a point l in a Zariski open

Michael Anshelevich

In this paper we investigate the properties of the free Sheffer systems, which are certain families of martingale polynomials with respect to the free Levy processes. First, we classify such families that consist of orthogonal polynomials; these are the free analogs of the Meixner systems. Next, we show that the fluctuations around free convolution semigroup

Sadayoshi Kojima, Shigeru Mizushima, Ser Peow Tan

The Andreev-Thurston theorem states that for any triangulation of a closed orientable surface Σ_g of genus g which is covered by a simple graph in the universal cover, there exists a unique metric of curvature 1, 0 or -1 on the surface depending on whether g=0, 1 or \ge 2 such that the surface with this metric admits a circle packing with combinatorics given

Vishwambhar Pati

A question of interest in Linear Algebra is whether all n x n complex matrices can be unitarily tridiagonalised. The answer for all n not equal to 4 (affirmative or negative) has been known for a while, whereas the case n=4 seems to have remained open. In this paper, we settle the n=4 case in the affirmative. Some machinery from complex algebraic geometry ne

Alexander B. Konovalov

We study the unit group of the modular group algebra KG, where G is a 2-group of maximal class. We prove that the unit group of KG possesses a section isomorphic to the wreath product of a group of order two with the commutator subgroup of the group G.

Richard P. Stanley

A survey of recent progress in three areas of algebraic combinatorics: (1) the Saturation Conjecture for Littlewood-Richardson coefficients, (2) the n! and (n+1)^{n-1} conjectures, and (3) longest increasing subsequences of permutations.

Anthony Varilly

The orthocentroidal circle of a nonequilateral triangle has diameter GH, joining the centroid to the orthocenter. We show that the incenters of triangles with a given Euler line simply cover the interior of the orthocentroidal circle, and that their Fermat points also lie within this circle.

J. L. F. Barbon, A. Paredes

We study the spectrum of density fluctuations of Fractional Hall Fluids in the context of the noncommutative hidrodynamical model of Susskind. We show that, within the weak-field expansion, the leading correction to the noncommutative Chern--Simons Lagrangian (a Maxwell term in the effective action,) destroys the incompressibility of the Hall fluid due to st

M. Faber, A. N. Ivanov

Correlation functions of fermionic fields described by the massless Thirring model are analysed within the operator formalism developed by Klaiber and the path-integral approach with massless fermions quantized in the chiral symmetric phase. We notice that Klaiber's composite fermion operators possess non-standard properties under parity transformations

Stanley Deser, Andrew Waldron

We examine the causality and degrees of freedom (DoF) problems encountered by charged, gravitating, massive higher spin fields. For spin s=3/2, making the metric dynamical yields improved causality bounds. These involve only the mass, the product eM_P of the charge and Planck mass and the cosmological constant Λ. The bounds are themselves related to a gauge

Ofer Aharony, Micha Berkooz, Eva Silverstein

We exhibit a simple class of exactly marginal "double-trace" deformations of two dimensional CFTs which have AdS_3 duals, in which the deformation is given by a product of left and right-moving U(1) currents. In this special case the deformation on AdS_3 is generated by a local boundary term in three dimensions, which changes the physics also in the

Gabriele Honecker

We present special classes of orientifold models involving supersymmetry breaking via branes at angles. Type II superstring theories are compactified on a two torus times a four-dimensional orbifold. Combining worldsheet parity with a reflection of half of the compact coordinates leads to D6-branes at angles which are mapped onto each other by the orbifold g

I. B. Pestov

It is substantiated that spin is a notion associated with the group of internal symmetry that is tightly connected with the geometrical structure of spacetime. The wave equation for the description of the particles with spin one half is proposed. On this ground it is shown that the spin of electron is exhibited through the quantum number and accordingly the

Ludwik Turko

Symmetry invariant local interaction of a many body system leads to global constraints. We obtain explicit forms of the global macroscopic condition assuring that at the microscopic level the evolution respects the overall symmetry.

Soon-Tae Hong, Yong-Wan Kim, Young-Jai Park, K. D. Rothe

Following the symplectic approach we show how to embed the Abelian Proca model into a first-class system by extending the configuration space to include an additional pair of scalar fields, and compare it with the improved Dirac scheme. We obtain in this way the desired Wess-Zumino and gauge fixing terms of BRST invariant Lagrangian. Furthermore, the integra

P. Fonseca, A. Zamolodchikov

We study the analytic properties of the scaling function associated with the 2D Ising model free energy in the critical domain $T \to T_c$, $H \to 0$. The analysis is based on numerical data obtained through the Truncated Free Fermion Space Approach. We determine the discontinuities across the Yang-Lee and Langer branch cuts. We confirm the standard analytic

M. Porrati

We show that standard Einstein gravity coupled to a free conformal field theory (CFT) in Anti de Sitter space can undergo a Higgs phenomenon whereby the graviton acquires a nonzero mass (and three extra polarizations). We show that the essential ingredients of this mechanism are the discreteness of the energy spectrum in AdS space, and unusual boundary condi

Joseph C. Varilly

We give an introductory survey to the use of Hopf algebras in several problems of noncommutative geometry. The main example, the Hopf algebra of rooted trees, is a graded, connected Hopf algebra arising from a universal construction. We show its relation to the algebra of transverse differential operators introduced by Connes and Moscovici in order to comput

Ian Blokland, Andrzej Czarnecki, Kirill Melnikov

Elaborating on a previous letter, we use a new approach to compute energy levels of a non-relativistic bound-state of two constituents, with masses m and M, by systematic expansions - one in powers of m/M and another in powers of (1-m/M). Technical aspects of the calculations are described in detail. Theoretical predictions are given for O(alpha(Z*alpha)^5)

A. C. Melissinos

We discuss a numerical relation between the cosmological constant and the vacuum energy arising from the Casimir effect in extra dimensions

Andrzej Czarnecki, Kirill Melnikov

We compute O(alpha_s^2) QCD corrections to the lepton invariant mass spectrum in the decay b --> u l nu_l, relevant for the determination of the CKM matrix element |V_{ub}|. Our method can also be used to evaluate moments of the lepton energy distribution with an O(alpha_s^2) accuracy. The abelian part of our result gives the neutrino invariant mass spectrum

D. V. Anchishkin, A. M. Gavrilik, S. Y. Panitkin

Within recently proposed approach aimed to effectively describe the observed non-Bose type behavior of the intercept \lambda of two-particle correlation function C(p,K) of identical pions or kaons detected in heavy-ion collisions, the q-deformed oscillators and q-Bose gas picture are employed. For the intercept \lambda, connected with deformation parameter q

H. Y. Cheng, Y. -Y. Keum, K. -C. Yang

We discuss the angular distribution analysis of $B\to J/ψK^{*}$ decays and a way to resolve discrete ambiguites in the determination of the unitary triangle $ϕ_1(=β)$. We study the status of factorization hypothesis in the color-suppressed B meson decays: $B\to J/ψK^{(*)}$ within the general factorization approach and QCD-factorization method.

C. Carimalo, A. Schiller, V. G. Serbo

Inelastic QED processes, the cross sections of which do not drop with increasing energy, play an important role at high-energy colliders. Such reactions have the form of two-jet processes with the exchange of a virtual photon in the t-channel. We consider them in the region of small scattering angles $m/E \lesssim θ\ll 1$, which yields the dominant contribut

Johan Bijnens, Elisabetta Pallante, Joaquim Prades

We comment on the recent calculations of the pion pole part of the light-by-light contribution to the muon anomalous magnetic moment and we point out where the analysis in our previous work was mistaken.

A. Ringwald

X-ray free electron lasers (FELs) have been proposed to be constructed both at SLAC in the form of the so-called Linac Coherent Light Source as well as at DESY, where the so-called XFEL laboratory is part of the design of the electron-positron linear collider TESLA. In addition to the immediate applications in condensed matter physics, chemistry, material sc

E. E. Kolomeitsev, P. Filip

Production of $ϕ(1020), Λ^*(1520)$ and $\bar{K^*}(892)$ resonances at the final stage of a heavy-ion collision is considered. It is shown that original momentum distributions and abundance of resonances formed during the process of heavy ion collision may differ significantly from their measured spectra and yields. Reconstruction probability of resonances de

Rene Bellwied

An overview is presented of the results of the STAR experiment from the analysis of Au+Au collisions at $\sqrt{s_{_{NN}}} = 130$ GeV acquired during the first year of RHIC operation. The transverse momentum distribution of negative hadrons has been studied out to 6 GeV/$c$ in central Au+Au collisions and elliptic flow measurements out to 4.5 GeV/$c$ in non-c

A. V. Nesterenko, I. L. Solovtsov

The properties of the new analytic running coupling are investigated at the higher loop levels. The expression for this invariant charge, independent of the normalization point, is obtained by invoking the asymptotic freedom condition. It is shown that at any loop level the relevant $β$ function has the universal behaviors at small and large values of the in

Joaquim Prades

The present Standard Model prediction for muon g-2 is reviewed. Emphasis is put in discussing the main hadronic uncertainties at present.

P. Zenczykowski

It is proved that symmetry structure of the parity-viol. (p.v.) amplitudes of weak radiative hyperon decays in the VMD approach, and the violation of Hara's theorem in particular, are also obtained when direct coupling e_q \bar{q}γ_μq A^μ of photon to quarks is used in place of VMD. Thus, violation of Hara's theorem in VMD-based models does not resul

Valeriya Gadiyak, Xiangdong Ji, Chulwoo Jung

Using an approach free from momentum extrapolation, we calculate the nucleon magnetic moment and the fraction of the nucleon spin carried by the quark angular momentum in the quenched lattice QCD approximation. Quarks with three values of lattice masses, 210, 124 and 80 MeV, are formulated on the lattice using the standard Wilson approach. At every mass, 100

Steven Gottlieb

The cost of dynamical quark simulations with improved staggered quarks is estimated based on current and planned running by the MILC collaboration. I find that a few 10s of Teraflop years should be sufficient to calculate down to a lattice spacing of 0.045 fm.

Steven Gottlieb

Recently, we have benchmarked and tuned the MILC code on a number of architectures including Intel Itanium and Pentium IV (PIV), dual-CPU Athlon, and the latest Compaq Alpha nodes. Results will be presented for many of these, and we shall discuss some simple code changes that can result in a very dramatic speedup of the KS conjugate gradient on processors wi

Wolfhard Janke, Ralph Kenna

The two-dimensional Ising model with Brascamp-Kunz boundary conditions has a partition function more amenable to analysis than its counterpart on a torus. This fact is exploited to exactly determine the full finite-size scaling behaviour of the Fisher zeroes of the model. Moreover, exact results are also determined for the scaling of the specific heat at cri

A. Duncan, S. Pernice, J. Yoo

Chiral perturbation theory gives direct and unambiguous predictions for the form of various two-point hadronic correlators at low momentum in terms of a finite set of couplings in a chiral Lagrangian. In this paper we study the feasibility of extracting the couplings in the chiral Lagrangian (through 1-loop order) by fitting two-point correlators computed in

K. N. Anagnostopoulos, W. Bietenholz, J. Nishimura

We study the question whether matrix models obtained in the zero volume limit of 4d Yang-Mills theories can describe large N QCD strings. The matrix model we use is a variant of the Eguchi-Kawai model in terms of Hermitian matrices, but without any twists or quenching. This model was originally proposed as a toy model of the IIB matrix model. In contrast to

S. Bilson-Thompson, F. D. R. Bonnet, D. B. Leinweber, A. G. Williams

The dynamics of instantons and anti-instantons in lattice QCD can be studied by analysing the action and topological charge of configurations as they approach a self-dual or anti-self-dual state, i.e. a state in which S/S_0=|Q|. We use cooling to reveal the semi-classical structure of the configurations we study. Improved actions which eliminate discretizati

B. Joo, I. Horvath, K. F. Liu

We develop an implementation for a recently proposed Noisy Monte Carlo approach to the simulation of lattice QCD with dynamical fermions by incorporating the full fermion determinant directly. Our algorithm uses a quenched gauge field update with a shifted gauge coupling to minimize fluctuations in the trace log of the Wilson Dirac matrix. The details of tun

Wolfhard Janke, Ralph Kenna

We report on a new method to extract thermodynamic properties from the density of partition function zeroes on finite lattices. This allows direct determination of the order and strength of phase transitions numerically. Furthermore, it enables efficient distinguishing between first- and second-order transitions, elucidates crossover between them and illumin

Aleph, CDF, Delphi, L3

Combined results on b-hadron lifetimes, b-hadron production rates, B^0_d - \bar{B^0_d} and B^0_S - \bar{B^0_s} oscillations, the decay width difference between the mass eigenstates of the B^0_s - \bar{B^0_s} system, the average number of c and \bar{c} quarks in b-hadron decays, and searches for CP violation in the B^0_d - \bar{B-0_d} system are presented. Th

T. E. Browder

We review recent progress at the two $e^+ e^-$ B factories. The first measurement of CP violation and the prospects for measuring all the angles of the unitarity triangle are discussed.

T. E. Browder

I describe the recent measurement of the CP violating parameter $\sin 2 ϕ_1 =(0.99\pm 0.14\pm 0.05)$ from the Belle experiment at KEK.

Julio C. Fabris

Fundamental theories, like strings, supergravity, Kaluza-Klein, lead after dimensional reduction and a suitable choice of field configurations, to an effective action in four dimensions where gravity is coupled non-mininally to one scalar field, and minimally to another scalar field. These scalar fields couple non-trivially between themselves. A radiation fi

Yvonne Choquet-Bruhat, Vincent Moncrief

We prove that spacetimes satisfying the vacuum Einstein equations on a manifold of the form $Σ\times U(1)\times R$ where $Σ$ is a compact surface of genus $G>1$ and where the Cauchy data is invariant with respect to U(1) and sufficiently small exist for an infinite proper time in the expanding direction.

J. Mark Heinzle, Roland Steinbauer

This work is devoted to a mathematical analysis of the distributional Schwarzschild geometry. The Schwarzschild solution is extended to include the singularity; the energy momentum tensor becomes a delta-distribution supported at r=0. Using generalized distributional geometry in the sense of Colombeau's (special) construction the nonlinearities are treat

I. B. Pestov

In this work, the experiment is discussed on the verification of the principle of universality of gravitational interactions and some related problems of gravity theory and physics of elementary particles. The meaning of this proposal lies in the fact that the self-consistency of General Relativity, as it turns out, presuppose the existence of the nongravita

A. B. Dzyubenko

A novel unitary transformation of the Hamiltonian that allows one to partially separate the center-of-mass motion for charged electron-hole systems in a magnetic field is presented. The two-mode squeezed oscillator states that appear at the intermediate stage of the transformation are used for constructing a trial wave function of a two-dimensional (2D) char

Igor Zutic

There is a renewed interest to study spin-polarized transport and spin dynamics in various electronic materials. The motivation to examine the spin degrees of freedom (mostly in electrons, but also in holes and nuclei) comes from various sources: ranging from novel applications which are either not feasible or ineffective with conventional electronics, to us

M. A. Kayali, N. A. Sinitsyn

In this article we study the formation of the two modes Bose-Einstein condensate and the correlation between them. We show that beyond the mean field approximation the dissociation of a molecular condensate due to the chemical potential curve crossing leads to the formation of two modes condensate. We also show that these two modes are correlated in a two mo

A. Vecchione, D. Zola, G. Carapella, M. Gombos

Low frequency transport measurements are performed on GdSr$_2$RuCu$_2$O$_8$ pellets. The observed current-voltage curves are qualitatively explained in the framework of a simple phenomenological model accounting for coexistence of ferromagnetism and superconductivity in the sample. A Curie temperature $T_{cM}$=133 K and a superconducting critical temperature

L. Leuzzi, F. Ritort

In this paper we consider an exactly solvable model which displays glassy behavior at zero temperature due to entropic barriers. The new ingredient of the model is the existence of different energy scales or modes associated to different relaxational time-scales. Low-temperature relaxation takes place by partial equilibration of successive lower energy modes

S. Jung, S. Kim, B. Kahng

We introduce a deterministic model for scale-free networks, whose degree distribution follows a power-law with the exponent $γ$. At each time step, each vertex generates its offsprings, whose number is proportional to the degree of that vertex with proportionality constant m-1 (m>1). We consider the two cases: first, each offspring is connected to its parent

G. Misguich, C. Lhuillier, M. Mambrini, P. Sindzingre

In the first part of this paper, the extension of the Lieb-Schultz-Mattis theorem to dimensions larger than one is discussed. A counter example to the original formulation of Lieb-Schultz-Mattis and Affleck is exhibited and a more precise statement is formulated. The degeneracy of the ground-state in symmetry breaking phases with long-range order is analyzed

A. V. Rodina, A. Yu. Alekseev, Al. L. Efros, M. Rosen

We have derived general boundary conditions (BC) for the multiband envelope functions (which do not contain spurious solutions) in semiconductor heterostructures with abrupt heterointerfaces. These BC require the conservation of the probability flux density normal to the interface and guarantee that the multiband Hamiltonian be self--adjoint. The BC are ener

B. Kahng, Y. Park, H. Jeong

We consider a stochastic model for directed scale-free networks following power-laws in the degree distributions in both incoming and outgoing directions. In our model, the number of vertices grow geometrically with time with growth rate p. At each time step, (i) each newly introduced vertex is connected to a constant number of already existing vertices with

T. Jarlborg

Effects of coupling between phonon distortions and stripe-like spin waves in the CuO plane of HgBa$_2$CuO$_4$ are studied by band calculations. Local exchange enhancements depend sensitively on the local structure around Cu sites. Interactions where spin waves have twice as long wave length as phonon waves can lead to a 'dip' in the density of states

Silvia Martins, Jurgen Stilck

We study two models of ringlike polyions which are two-dimensional versions of simple models for colloidal particles (model A) and for rodlike segments of DNA (model B), both in solution with counterions. The counterions may condensate on Z sites of the polyions, and we suppose the number of condensed counterions on each polyion n to be fixed. The exact free

J. Houdayer, M. Mueller

We investigate the phase behaviour of random copolymers melts via large scale Monte Carlo simulations. We observe macrophase separation into A and B--rich phases as predicted by mean field theory only for systems with a very large correlation lambda of blocks along the polymer chains, far away from the Lifshitz point. For smaller values of lambda, we find th

L. Viverit

We show that in dilute boson-fermion mixtures with fermions in two internal states, even when the bare fermion-fermion interaction is repulsive, the exchange of density fluctuations of the Bose condensate may lead to an effective fermion-fermion attraction, and thus to a Cooper instability in the s-wave channel. We give an analytical method to derive the ass

S. Manalo, U. Klein

Paramagnetic pair breaking is believed to be of increasing importance in many layered superconducting materials such as cuprates and organic compounds. Recently, strong evidence for a phase transition to the Fulde-Ferrell-Larkin-Ovchinnikov(FFLO) state has been obtained for the first time. We present a new theory of competing spin and orbital pair breaking i

Marcin Mierzejewski, Maciej M. Maska

We investigate the upper critical field in a stripe--phase and in the presence of a phenomenological pseudogap. Our results indicate that the formation of stripes affects the Landau orbits and results in an enhancement of $H_{c2}$. On the other hand, phenomenologically introduced pseudogap leads to a reduction of the upper critical field. This effect is of p

A. B. Zorin

An all-superconductor charge qubit enabling a radio-frequency readout of its quantum state is described. The core element of the setup is a superconducting loop which includes the single-Cooper-pair (Bloch) transistor. This circuit has two functions: First, it operates as a charge qubit with magnetic control of Josephson coupling and electrostatic control of

B. B. Jin, N. Klein, W. N. Kang, Hyeong-Jin Kim

We have measured the temperature dependence of the microwave surface impedance Zs = Rs + iΩμ_0 \Lamda of two c-axis oriented MgB2 films at a frequency Ω/(2π) of 17.9 GHz employing a dielectric (sapphire) resonator technique. The temperature dependence of the magnetic field penetration depth \Lamda can be well fitted from 5 K close to Tc by the standard BCS i

Samar Chattopadhyay, Arunava Chakrabarti

The existence of cycles of the matrix maps in Fibonacci class of lattices is well established. We show that such cycles are intimately connected with the presence of interesting positional correlations among the constituent `atoms' in a one dimensional quasiperiodic lattice. We particularly address the transfer model of the classic golden mean Fibonacci

M. K. Chattopadhyay, S. B. Roy, Sujeet Chaudhary

Solid solution between nonmagnetic narrow gap semiconductor FeSi and diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with long-range helical magnetic ordering, for a wide range of intermediate concentration. We report various interesting magnetic properties of these alloys, including low temperature re-entrant spin-glass like behaviour

W. Sakikawa, O. Narikiyo

The distribution of the fractal dimension of the two-dimensional Ising model at the critical temperature measured by the Monte-Carlo simulation is discussed. At small spatio-temporal scales it exhibits a multifractal behavior and is well fitted by a non-Gaussian distribution derived from the Rényi or Tsallis entropy.

Vahe' Petrosian

The aim of this paper is to describe new statistical methods for determination of the correlations among and distributions of physical parameters from a multivariate data with general and arbitrary truncations and selection biases. These methods, developed in collaboration with B. Efron of Department of Statistics at Stanford, can be used for analysis of com

Li-Xin Li

In this Letter we use a simple model to demonstrate the observational signatures of the magnetic connection between a black hole and a disk: (1) With the magnetic connection more energy is dissipated in and radiated away from regions close to the center of the disk; (2) The magnetic connection can produce a very steep emissivity compared to the standard accr

S. Wachter, D. W. Hoard, C. D. Bailyn, S. Corbel

We report long-term simultaneous optical and (RXTE) X-ray observations of the soft X-ray transient and low mass X-ray binary X1608-52 spanning from 1999 to 2001. In addition to the usual X-ray outburst and quiescent states, X1608-52 also exhibits an extended low intensity state during which the optical counterpart, QX Nor, is found to be about two magnitudes

Feng Yuan, Sera Markoff, Heino Falcke

The recent {\em Chandra} observation of the radio source at the center of our Galaxy, Sgr A$^*$, puts new constraints on its theoretical models. The spectrum is very soft, and the source is rapidly variable. We consider different models to explain the observations. We find that the features of the x-ray spectrum can be marginally explained with an advection-

C. E. Jones, Shantanu Basu

We decipher intrinsic three-dimensional shape distributions of molecular clouds, cloud cores, Bok globules, and condensations using recently compiled catalogues of observed axis ratios for these objects mapped in carbon monoxide, ammonia, through optical selection, or in continuum dust emission. We apply statistical techniques to compare assumed intrinsic ax

M. A. P. Torres, P. J. Callanan, M. R. Garcia, J. E. McClintock

We present spectroscopic observations of the X-ray transient XTE J1118+480 acquired during different epochs following the 2000 March outburst. We find that the emission line profiles show variations in their double-peak structure on time scales longer than the 4.1 hr orbital period. We suggest that these changes are due to a tidally driven precessing disk. D

E. Lastennet, T. Lejeune, E. Oblak, P. Westera

The BaseL Stellar Library (BaSeL) is a library of synthetic spectra which has already been used in various astrophysical applications (stellar clusters studies, characterization and choice of the COROT potential targets, eclipsing binaries,...). This library could provide useful indications to 1) choose the best photometric system for the GAIA strategy by ev

M. Castellanos, A. I. Diaz, G. Tenorio-Tagle

A thorough analysis of well studied giant HII regions on galactic discs for which we know the ionizing stellar population, the gas metallicity and the Wolf-Rayet population, leads to photoionization models which can only match all observed line intensity ratios ([OIII], [OII], [NII], [SII] and [SIII] with respect to the intensity of H$β$), as well as the H$β

J. Delabrouille, J. Kaplan

We describe the Planck HFI design and expected performances for measuring CMB polarisation.

Anthony Challinor, Floor van Leeuwen

We investigate the impact of peculiar velocity effects due to the motion of the solar system relative to the microwave background (CMB) on high resolution CMB experiments. It is well known that on the largest angular scales the combined effects of Doppler shifts and aberration are important; the lowest Legendre multipoles of total intensity receive power fro

Sandro S. e Costa, R. Opher

We present new mathematical alternatives for explaining rotation curves of spiral galaxies in the MOND context. For given total masses, it is shown that various mathematical alternatives to MOND, while predicting flat rotation curves for large galactic radii, predict curves with different peculiar features for smaller radii. They are thus testable against ob

D. Grupe

This paper will give a short description of a `cookbook' for the XMM-Newton data reduction software XMMSAS. This `cookbook' has been developed at the Max-Planck-Institut für extraterrestrische Physik (MPE), Garching. The task of this `cookbook' is to describe the necessary XMMSAS tasks and show examples to make it easy for new users of the XMMSAS

H. J. Rocha-Pinto, B. V. Castilho, W. J. Maciel

We have investigated a group of stars known to have low chromospheric ages, but high kinematical ages. Isochrone, chemical and lithium ages are estimated for them. The majority of stars in this group show lithium abundances much smaller than expected for their chromospheric ages, which is interpreted as an indication of their old age. Radial velocity measure