July 2002 arXiv papers — page 24

John Singleton, Charles Mielke, William Hayes, John Schlueter

The quasiparticle scattering rates in high-quality crystals of the quasi-two-dimensional superconductor $κ$-(BEDT-TTF)$_2$Cu(NCS)$_2$ ~are studied using the Shubnikov-de Haas effect and MHz penetration-depth experiments. There is strong evidence that the broadening of the Landau-levels is primarily caused by spatial inhomogeneities, indicating a quasiparticl

S. Chen, B. Trauzettel, R. Egger

We propose a Landauer-like theory for nonlinear transport in networks of one-dimensional interacting quantum wires (Luttinger liquids). A concrete example of current experimental focus is given by carbon nanotube Y junctions. Our theory has three basic ingredients that allow to explicitly solve this transport problem: (i) radiative boundary conditions to des

E. Christova, H. Eberl, S. Kraml, W. Majerotto

Supersymmetric loop contributions can lead to different decay rates of H+\to t\bar b and H-\to b\bar t. We calculate the decay rate asymmetry δ^CP = \frac{Γ(H+\to t\bar b)-Γ(H-\to b\bar t)}{{Γ(H+\to t\bar b)+Γ(H-\to b\bar t)} at next-to-leading order in the MSSM with complex parameters. We analyse the parameter dependence of δ^CP with emphasis on the phases

Z. Bajnok, G. Bohm, G. Takacs

An asymptotic theory is developed for general non-integrable boundary quantum field theory in 1+1 dimensions based on the Langrangean description. Reflection matrices are defined to connect asymptotic states and are shown to be related to the Green functions via the boundary reduction formula derived. The definition of the $R$-matrix for integrable theories

Brian P. Dolan, C. Nash

It is shown that the quarks and leptons of the standard model, including a right-handed neutrino, can be obtained by gauging the holonomy groups of complex projective spaces of complex dimensions two and three. The spectrum emerges as chiral zero modes of the Dirac operator coupled to gauge fields and the demonstration involves an index theorem analysis on a

Vincenzo Piazza, Vittorio Pellegrini, Fabio Beltram, Werner Wegscheider

Time-dependent capacitance measurements reveal an unstable phase of electrons in gallium arsenide quantum well that occurs when two Landau levels with opposite spin are brought close to degeneracy by applying a gate voltage. This phase emerges below a critical temperature and displays a peculiar non-equilibrium dynamical evolution. The relaxation dynamics is

Florence Durret, Christophe Adami, Catarina Lobo

We have derived the galaxy luminosity function (GLF) in the cluster of galaxies Abell 496 from a wide field image in the I band. A single Schechter function reproduces quite well the GLF in the 17 <= I_{AB} <= 22 (-19.5 <= M_I <= -14.5) magnitude interval, and the power law index of this function is found to be somewhat steeper in the outer regions than in t

Taichi Itoh, Sang-Jin Sin

We study the classification of D-branes in all compact Lie groups including non-simply-laced ones. We also discuss the global structure of the quantum moduli space of the D-branes. D-branes are classified according to their positions in the maximal torus. We describe rank 2 cases, namely $B_2$, $C_2$, $G_2$, explicitly and construct all the D-branes in $B_r$

Yu. A. Fomin, G. V. Kulikov, M. Yu. Zotov

Bursts of the count rate of extensive air showers (EAS) lead to the appearance of clusters in time series that represent EAS arrival times. We apply methods of nonlinear time series analysis to twenty EAS cluster events found in the data set obtained with the EAS-1000 prototype array. In particular, we use the Grassberger-Procaccia algorithm to compute the c

L. B. Leinson

We use the field theoretical model to perform relativistic calculations of neutrino energy losses caused by the direct Urca processes on nucleons in the degenerate baryon matter. By our analysis, the direct neutron decay in the superdense nuclear matter under beta equilibrium is open only due to the isovector meson fields, which create a large energy gap bet

James Babington, David E. Crooks, Nick Evans

We deform the AdS/CFT Correspondence by the inclusion of a non-supersymmetric scalar mass operator. We discuss the behaviour of the dual 5 dimensional supergravity field then lift the full solution to 10 dimensions. Brane probing the resulting background reveals a potential consistent with the operator we wished to insert.

Vadim Borokhov, Anton Kapustin, Xinkai Wu

We study vortex-creating, or monopole, operators in 3d CFTs which are the infrared limit of N=2 and N=4 supersymmetric QEDs in three dimensions. Using large-Nf expansion, we construct monopole operators which are primaries of short representations of the superconformal algebra. Mirror symmetry in three dimensions makes a number of predictions about such oper

R. M. Avagyan, A. A. Saharian, A. H. Yeranyan

The vacuum expectation values of the energy--momentum tensor are investigated for massless scalar fields satisfying Dicichlet or Neumann boundary conditions, and for the electromagnetic field with perfect conductor boundary conditions on two infinite parallel plates moving by uniform proper acceleration through the Fulling--Rindler vacuum. The scalar case is

K. H. Ahn, T. Lookman, A. Saxena, A. R. Bishop

We present an atomic scale theory of lattice distortions using strain related variables and their constraint equations. Our approach connects constrained {\it atomic length} scale variations to {\it continuum} elasticity and describes elasticity at several length scales. We apply the approach to a two-dimensional square lattice with a monatomic basis, and fi

Jens Erler, Mingxing Luo

We present a new QCD sum rule with high sensitivity to the continuum regions of charm and bottom quark pair production. Combining this sum rule with existing ones yields very stable results for the MS-bar quark masses, m_c(m_c) and m_b(m_b). We introduce a phenomenological parametrization of the continuum interpolating smoothly between the pseudoscalar thres

Eric A. Galapon

We raise the possibility of developing a theory of constructing quantum dynamical observables independent from quantization and deriving classical dynamical observables from pure quantum mechanical consideration. We do so by giving a detailed quantum mechanical derivation of the classical time of arrival at arbitrary arrival points for a particle in one dime

L. Tessieri, J. Wilkie

We examine the effects of intra-environmental coupling on decoherence by constructing a low temperature spin--spin-bath model of an atomic impurity in a Debye crystal. The impurity interacts with phonons of the crystal through anti-ferromagnetic spin-spin interactions. The reduced density matrix of the central spin representing the impurity is calculated by

Igor V. Volovich

In modern quantum information theory one deals with an idealized situation when the spacetime dependence of quantum phenomena is neglected. However the transmission and processing of (quantum) information is a physical process in spacetime. Therefore such basic notions in quantum information theory as qubit, channel, composite systems and entangled states sh

Romeo Brunetti, Klaus Fredenhagen

Using a recent construction of observables characterizing the time of occurence of an effect in quantum theory, we present a rigorous derivation of the standard time-energy uncertainty relation. In addition, we prove an uncertainty relation for time measurements only.

Yoon-Ho Kim, Warren P. Grice

The quantum state of the photon pair generated from type-II spontaneous parametric down-conversion pumped by a ultrafast laser pulse exhibits strong decoherence in its polarization entanglement, an effect which can be attributed to the clock effect of the pump pulse or, equivalently, to distinguishing spectral information in the two-photon state. Here, we pr

Wolfgang Orthuber

The function $γ(x)=\frac{1}{\sqrt{1-x^2}}$ plays an important role in mathematical physics, e.g. as factor for relativistic time dilation in case of $x=β$ with $β=\frac{v}{c}$ or $β=\frac{pc}{E}$. Due to former considerations it is reasonable to study the power series expansion of $γ(x)$. Here its relationship to the binomial distribution is shown, especiall

A. Harpaz, N. Soker

The question of what is the source of the energy carried by the radiation is discussed. The case of a hyperbolic motion is analyzed, describing the solutions suggested in the past for the &#34;energy balance paradox&#34;. The solution to the paradox is found in considerind the stress force created in the curved electric field of the accelerated charge, that

M. I. Molina

We consider a macroscopic body propagating in a one-dimensional resistive medium, consisting of an ideal gas at temperature $T$. For a whole family of collisions with varying degree of inelasticity, we find an exact expression for the effective force on the moving body as a function of the body&#39;s speed and the value of the restitution coefficient. At low

A. Perelomova, S. Leble

The general hydro-thermodynamic system of equations in 2+1 dimensions with arbitrary equations of state (Taylor series approximation) is split to eigen modes: Tollmienn-Schlichting (TS) wave and two acoustic ones. A mode definition is realized via local relation equations, extracted from the linearization of the general system over boundary layer flow. Each

A. Esser, R. Redmer, G. Röpke

On the basis of a quantum-statistical approach to the electrical conductivity of nonideal plasmas we derive analytical results in the classical low-density regime, in the degenerate Born limit, and for the contribution of the Debye-Onsager relaxation effect. These explicit results are used to construct an improved interpolation formula of the electrical cond

Kirill A. Kazakov

The problem of non-perturbative description of stationary flames with arbitrary gas expansion is considered. A general method for deriving equations for the flame front position is developed. On the basis of the Thomson circulation theorem an implicit integral of the flow equations is constructed. With the help of this integral the flow structure near the fl

O. Mineev, E. Garber, J. Frank, A. Ivashkin

A photon detector for BNL experiment E949 is described. The detector consists of lead/scintillator ``sandwich&#39;&#39; of 25 layers of 5 mm thick scintillator BC404 and 24 layers of 2 mm lead absorber. Readout is implemented with 30-60 cm long WLS fibers (BCF99-29AA) glued into grooves in the BC404. Average yield was measured with cosmic rays to be about 43

William Bialek

We all are fascinated by the phenomena of intelligent behavior, as generated both by our own brains and by the brains of other animals. As physicists we would like to understand if there are some general principles that govern the structure and dynamics of the neural circuits that underlie these phenomena. At the molecular level there is an extraordinary uni

Madeleine Soyeur, Matthias F. M. Lutz, Bengt Friman

The $π^-p \to e^+e^- n$ and $π^+n \to e^+e^- p$ reaction cross sections are calculated below and in the vicinity of the vector meson ($ρ^0$, $ω$) production threshold. These processes are largely responsible for the emission of $e^+e^-$ pairs in pion-nucleus reactions and contribute to the dilepton spectra observed in relativistic heavy ion collisions. They

X. Qu, M. Aldana, Leo P. Kadanoff

In this work we analyze the stochastic dynamics of the Kauffman model evolving under the influence of noise. By considering the average crossing time between two distinct trajectories, we show that different Kauffman models exhibit a similar kind of behavior, even when the structure of their basins of attraction is quite different. This can be considered as

C. Radhakrishnan

Taking the example of Koretweg--de Vries equation, it is shown that soliton solutions need not always be the consequence of the trade-off between the nonlinear terms and the dispersive term in the nonlinear differential equation. Even the ordinary one dimensional linear partial differential equation can produce a soliton.

Simone Severini

A digraph D is the pattern of a matrix M when D has an arc ij if and only if the ij-th entry of M is nonzero. Study the relationship between unitary matrices and their patterns is motivated by works in quantum chaology and quantum computation. In this note, we prove that if a Cayley digraph is a line digraph then it is the pattern of a unitary matrix. We pro

Gerard Laumon

In 1967, Langlands conjectured a natural correspondence between automorphic representations and Galois representations, over number fields as well as over function fields. In 1983, Drinfeld discovered a geometric analog of the Langlands correspondence in the function field case, which extends the geometric class field theory of Lang and Rosenlicht. The so ca

S. Caenepeel, Bin Zhu

Using approximations, we give several characterizations of separability of bimodules. We also discuss how separability properties can be used to transfer some representation theoretic properties from one ring to another one: contravariant finiteness of the subcategory of (finitely generated) left modules with finite projective dimension, finitistic dimension

Dirk Siersma, Mihai Tibar

We study the topology of polynomial functions by deforming them generically. We explain how the non-conservation of the total ``quantity&#39;&#39; of singularity in the neighbourhood of infinity is related to the variation of topology in certain families of boundary singularities along the hyperplane at infinity.

Tamas Hausel, Michael Thaddeus

The moduli space of stable bundles of rank 2 and degree 1 on a Riemann surface has rational cohomology generated by the so-called universal classes. The work of Baranovsky, King-Newstead, Siebert-Tian and Zagier provided a complete set of relations between these classes, expressed in terms of a recursion in the genus. This paper accomplishes the same thing f

Tamas Hausel, Michael Thaddeus

The moduli space of stable vector bundles on a Riemann surface is smooth when the rank and degree are coprime, and is diffeomorphic to the space of unitary connections of central constant curvature. A classic result of Newstead and Atiyah-Bott asserts that its rational cohomology ring is generated by the universal classes, that is, by the Kunneth components

P. Suranyi, L. C. R. Wijewardhana

In a Randall-Sundrum theory (RS1) 3+1 dimensional black holes and higher dimensional black holes are not the natural continuations of each other. 3+1 dimensional black holes decay into a large number of 4+1 dimensional black holes at a critical mass, $M_{\rm crit}\sim 10^{32}$ TeV. Those black holes themselves may become unstable above another, albeit much s

Christian Beck

We consider deterministic chaotic models of vacuum fluctuations on a small (quantum gravity) scale. As a suitable small-scale dynamics, nonlinear versions of strings, so-called `chaotic strings&#39; are introduced. These can be used to provide the `noise&#39; for second quantization of ordinary strings via the Parisi- Wu approach of stochastic quantization.

Silvia Vaula&#39;

We construct with a geometric procedure the supersymmetry transformation laws and Lagrangian for all the ``variant&#39;&#39; D=11 and D=10 Type IIA supergravities. We identify into our classification the D=11 and D=10 Type IIA ``variant&#39;&#39; theories first introduced by Hull performing T-duality transformation on both spacelike and timelike circles. We

P. A. Horváthy

Vortex dynamics in a thin superfluid ${}^4$He film as well as in a type II superconductor is described by the classical counterpart of the model advocated by Peierls, and used for deriving the ground states of the Fractional Quantum Hall Effect. The model has non-commuting coordinates, and is obtained by reduction from a particle associated with the ``exotic

Edward Witten

The GUT-based approach to physics has been attractive since it was first put forward close to thirty years ago; it has been enriched by new ideas, notably supersymmetry and strings; and there are real hints that it is on the right track, notably from measurements of the weak mixing angle and neutrino masses. In this article (based on my Heinrich Hertz lectur

Michael S. Chanowitz

Because of two 3 sigma anomalies, the Standard Model (SM) fit of the precision electroweak data has a poor confidence level, CL= 0.010. Since both anomalies involve challenging systematic issues, it might appear that the SM could still be valid if the anomalies resulted from underestimated systematic error. Indeed the CL of the global fit could then increase

Andreas S. Kronfeld, Paul B. Mackenzie, James N. Simone, Shoji Hashimoto

Short description of our calculation of the form factor needed to determine CKM element |V_{cb}| from the exclusive decay B -> D^*lν. For full details, see hep-ph/0110253. Also, here we recommend distribution for CKM fits.

Gudrun Hiller

I discuss the theoretical and empirical status of $b \to s γ$, $b \to s \ell^+ \ell^-$ decays, as well as their future prospects. I emphasize those observables in rare $b$-decays which can potentially establish new physics and distinguish between extensions of the Standard Model. I briefly review current models of electroweak symmetry breaking, all of which

Oliver Schroeder, Hugo Reinhardt

In Yang-Mills theories, variational calculations of the Rayleigh-Ritz type face the problem that on the one hand, calculability puts severe constraints on the space of test wave functionals; on the other hand, the test wave functionals have to be gauge invariant. The conflict between the two requirements can be resolved by introducing a projector. In this pa

P. Kroll

The basic theoretical ideas of the handbag factorization and its application to wide-angle scattering reactions are reviewed. With regard to the present experimental program carried out at JLab, wide-angle Compton scattering is discussed in some detail.

M. E. Carrington, Hou Defu, R. Kobes

We present a simple set of rules for obtaining the imaginary part of a self energy diagram at finite temperature in terms of diagrams that correspond to physical scattering amplitudes.

Rishikesh Vaidya

The patterns of R violation resulting from imposition of a gauged U(1) horizontal symmetry, on the minimal supersymmetric standard model are systematically analyzed. We concentrate on a class of models with integer U(1) charges chosen to reproduce the quark masses and mixings as well as charged lepton masses exactly or approximately. The U(1) charges are fur

L. Herrera, J. Martin, J. Ospino

It is shown that unlike the perfect fluid case, anisotropic fluids (principal stresses unequal) may be geodesic, without this implying the vanishing of (spatial) pressure gradients. Then the condition of vanishing four acceleration is integrated in non-comoving coordinates. The resulting models are necessarily dynamic, and the mass function is expressed in t

S. M. Kozyrev

We have studied the properties of the static, spherically symmetric solution of Jordan, Brans-Dicke theory. An exact interior solution for standard space-time line element in the Schwarzschild form is obtained.

W. Chen, Tingxiu Zhong

Civan and Sliepcevich [1, 2] suggested that special matrix solver should be developed to further reduce the computing effort in applying the differential quadrature (DQ) method for the Poisson and convection-diffusion equations. Therefore, the purpose of the present communication is to introduce and apply the Lyapunov formulation which can be solved much mor

W Chen, Weixing He, Tingxiu Zhong

Recently, Bert, Wang and Striz [1, 2] applied the differential quadrature (DQ) and harmonic differential quadrature (HDQ) methods to analyze static and dynamic behaviors of anisotropic plates. Their studies showed that the methods were conceptually simple and computationally efficient in comparison to other numerical techniques. Based on some recent work by

W Chen, Xinwei Wang, Yongxi Yu

This paper shows that the weighting coefficient matrices of the differential quadrature method (DQM) are centrosymmetric or skew-centrosymmetric if the grid spacings are symmetric irrespective of whether they are equal or unequal. A new skew centrosymmetric matrix is also discussed. The application of the properties of centrosymmetric and skew centrosymmetri

Pedro Cabalar

In this work we present additional results related to the property of strong equivalence of logic programs. This property asserts that two programs share the same set of stable models, even under the addition of new rules. As shown in a recent work by Lifschitz, Pearce and Valverde, strong equivalence can be simply reduced to equivalence in the logic of Here

Henry Prakken

The purpose of this paper is to address some criticisms recently raised by John Horty in two articles against the validity of two commonly accepted defeasible reasoning patterns, viz. reinstatement and floating conclusions. I shall argue that Horty&#39;s counterexamples, although they significantly raise our understanding of these reasoning patterns, do not

Kamal Jain, Mohammad Mahdian, Evangelos Markakis, Amin Saberi

In this paper, we will formalize the method of dual fitting and the idea of factor-revealing LP. This combination is used to design and analyze two greedy algorithms for the metric uncapacitated facility location problem. Their approximation factors are 1.861 and 1.61, with running times of O(mlog m) and O(n^3), respectively, where n is the total number of v

M. S. Reis, J. P. Araujo, V. S. Amaral, E. K. Lenzi

We analyzed the magnetic behavior of a S-spin system within framework of the Tsallis nonextensive statistics, employing the normalized approach. Unusual properties on magnetization, entropy and susceptibility emerge, as a consequence of nonextensivity. We further show that the nonextensive approach can be relevant to the field of manganites, materials which

Kedar Damle, David A. Huse

The low-energy properties of a system at a critical point may have additional symmetries not present in the microscopic Hamiltonian. This letter presents the theory of a class of multicritical points that provide an interesting example of this in the phase diagrams of random antiferromagnetic spin chains. One case provides an analytic theory of the quantum c

Dirk K. Morr, Nikolaos A. Stavropoulos

We study quantum interference of electronic waves that are scattered by multiple non-magnetic impurities in a d_x2-y2-wave superconductor. We show that the number of resonance states in the density-of-states (DOS), as well as their frequency and spatial dependence change significantly as the distance between the impurities or their orientation relative to th

F. Ancilotto, D. G. Austing, M. Barranco, R. Mayol K. Muraki

We present experimental results for the ground state electrochemical potentials of a few electron semiconductor artificial molecule made by vertically coupling two quantum dots, in the intermediate coupling regime, in perpendicular and parallel magnetic fields up to 5 T. We perform a quantitative analysis based on local-spin density functional theory. The ag

Michael Bretz

An intriguing heuristic model of development, decline, and change conceived by Bernard J.F. Lonergan (BL) in the late 1940&#39;s was laid out in a manner now recognizable as representing an early model of complexity. This report is a first effort toward eventually translating that qualitative vision, designated Emergent Probability, into a viable network com

S. O. Hong, Y. S. Kwon, M. H. Jung

We present experimental results of electrical resistivity, Hall coefficient, magnetic susceptibility, and specific heat for single crystals of Ce-based intervalent compound CeNiSi$_2$. The results show similar behaviors observed in Yb-based intervalent compounds and support recent thoery of the Anderson lattice, in which the Fermi-liquid coherence is gloval

M. H. Jung, A. Alsmadi, H. C. Kim, Yunkyu Bang

We report the discovery of pressure-induced superconductivity in a semimetallic magnetic material CeTe$_{1.82}$. The superconducting transition temperature $T_{SC}$ = 2.7 K (well below the magnetic ordering temperatures) under pressure ($>$ 2 kbar) is remarkably high, considering the relatively low carrier density due to a charge-density-wave transition asso

N. Lacevic, F. W. Starr, T. B. Schroder, V. N. Novikov

We present a calculation of a fourth-order, time-dependent density correlation function that measures higher-order spatiotemporall correlations of the density of a liquid. From molecular dynamics simulations of a glass-forming Lennard-Jones liquid, we find that the characteristic length scale of this function has a maximum as a function of time which increas

G. Tiana, M. H. Jensen, K. Sneppen

A feedback mechanism that involves the proteins p53 and mdm2, induces cell death as a controled response to severe DNA damage. A minimal model for this mechanism demonstrates that the respone may be dynamic and connected with the time needed to translate the mdm2 protein. The response takes place if the dissociation constant k between p53 and mdm2 varies fro

J. Sadowski, R. Mathieu, P. Svedlindh, J. Kanski

We have observed a paramagnetic-to-ferromagnetic phase transition in short period InGaMnAs/InGaAs superlattices. The thicknesses of magnetic InGaMnAs layers in the structures studied was chosen to be 4 or 8 molecular layers (12 Åor 24 Å). The nonmagnetic InGaAs spacer layers are 12 Åthick. The In content of InGaMnAs and InGaAs layers was chosen in such a way

Alexander N. Gorban, Iliya V. Karlin

In this paper, we review the construction of low-dimensional manifolds of reduced description for equations of chemical kinetics from the standpoint of the method of invariant manifold (MIM). MIM is based on a formulation of the condition of invariance as an equation, and its solution by Newton iterations. A review of existing alternative methods is extended

R. Beck, A. Kohen, G. Leibovitch, H. Castro

We have studied the evolution of the Zero-Bias Conductance Peak (ZBCP) splitting under applied magnetic fields in tunneling experiments on Y1Ba2Cu3O7-x(YBCO), and particular its hysteresis. We have been able to distinguish between two possible contributions to the splitting. One of them is connected to Meissner screening currents whose variation in increasin

G. Ballabio, G. Profeta, S. de Gironcoli, S. Scandolo

Distortions of the $\sqrt3\times\sqrt3$ Sn/Ge(111) and Sn/Si(111) surfaces are shown to reflect a disproportionation of an integer pseudocharge, $Q$, related to the surface band occupancy. A novel understanding of the $(3\times3)$-1U (``1 up, 2 down&#39;&#39;) and 2U (``2 up, 1 down&#39;&#39;) distortions of Sn/Ge(111) is obtained by a theoretical study of t

Bosiljka Tadic, G. J. Rodgers

We introduce a model of information packet transport on networks in which the packets are posted by a given rate and move in parallel according to a local search algorithm. By performing a number of simulations we investigate the major kinetic properties of the transport as a function of the network geometry, the packet input rate and the buffer size. We fin

Danuta Makowiec

Large and stable indices of the world wide stock markets such as NYSE and SP 500 together with NASDAQ -- the index representing markets of new trends, and WIG -- the index of the local stock market of Eastern Europe, are considered. Due to the relation between artificial insymmetrised patterns (AIP) and time series, stationary and temporary properties of sto

Matthias A. Hein

We discuss the temperature, frequency, and power-dependent surface resistance of the boride superconductor MgB2 in relation to possible applications for passive microwave devices. The data available in the literature are compared with results for polycrystalline Nb3Sn and epitaxial YBa2Cu3O7-x, which are representative of the classical and cuprate supercondu

R. Vollmer, A. Faißt, C. Pfleiderer, H. v. Löhneysen

We report the magnetic field dependence of the low temperature specific heat of single crystals of the first Pr-based heavy fermion superconductor PrOs$_4$Sb$_{12}$. The low temperature specific heat and the magnetic phase diagram inferred from specific heat, resistivity and magnetisation provide compelling evidence of a doublet ground state and hence superc

S. X. Dou, S. Soltanian, J. Horvat, X. L. Wang

Doping of MgB2 by nano-SiC and its potential for improvement of flux pinning was studied for MgB2-x(SiC)x/2 with x = 0, 0.2 and 0.3 and a 10wt% nano-SiC doped MgB2 samples. Co-substitution of B by Si and C counterbalanced the effects of single-element doping, decreasing Tc by only 1.5K, introducing pinning centres effective at high fields and temperatures an

P. J. Burke

We develop an rf circuit model for single walled carbon nanotubes for both dc and capacitively contacted geometries. By modeling the nanotube as a nano-transmission line with distributed kinetic and magnetic inductance as well as distributed quantum and electrostatic capacitance, we calculate the complex, frequency dependent impedance for a variety of measur

A. Gozar, G. Blumberg, P. B. Littlewood, B. S. Dennis

Raman measurements in the 1.5 - 20 cm-1 energy range were performed on single crystals of Sr_{14-x}Ca_xCu_{24}O_{41}. A quasielastic scattering peak (QEP) which softens with cooling is observed in the polarization parallel to the ladder direction for samples with x = 0, 8 and 12. The QEP is a Raman fingerprint of pinned collective density wave excitations sc

V. Dupuis, E. Vincent, M. Alba, J. Hammann

We have studied the slow dynamics of the ferromagnetic phases of the re-entrant CdCr_{2x}In_{2-2x}S_4 system for 0.85<x<=1 by means of low frequency ac susceptibility and magnetization measurements. Experimental procedures widely used in the investigation of the out-of-equilibrium dynamics of spin glasses (such as the x=0.85 compound) have been applied to se

J. Viana Lopes, J. M. B. Lopes dos Santos, Yu. G. Pogorelov

We revisit the theory of magnetoresistance for a system of nanoscopic magnetic granules in metallic matrix. Using a simple model for the spin dependent perturbation potential of the granules, we solve Boltzmann equation for the spin dependent components of the non equilibrium electronic distribution function. For typical values of the geometric parameters in

Yasushi Suto

Density profiles of cosmological virialized systems, or dark halos, have recently attracted much attention. I first present a brief historical review of numerical simulations to quantify the halo density profiles. Then I describe the latest results on the universal density profile and their observational confrontation. Finally I discuss a clustering model of

R. Beck, V. Shoutenkov, M. Ehle, J . I. Harnett

The total and polarized radio continuum emission of 20 barred galaxies was observed with the Very Large Array (VLA) at 3, 6, 18 and 22 cm and with the Australia Telescope Compact Array (ATCA) at 6 cm and 13 cm. Maps at 30 arcsec angular resolution are presented here. Polarized emission (and therefore a large-scale regular magnetic field) was detected in 17 g

C. Trundle, P. L. Dufton, D. J. Lennon, S. J. Smartt

Absolute and differential chemical abundances are presented for the largest group of massive stars in M31 studied to date. These results were derived from intermediate resolution spectra of seven B-type supergiants, lying within four OB associations covering a galactocentric distance of 5 - 12 kpc. The results are mainly based on an LTE analysis, and we addi

David Branch

Identifying the progenitors of Type Ib and Type Ic supernovae requires knowing, among other things, whether SNe Ib eject hydrogen, and whether SNe Ic eject helium, and perhaps even hydrogen. Recently it has become clear that some SNe Ib do eject hydrogen, and it may be that all SNe Ib do. Two arguments that have been made in the past that SNe Ic eject helium

G. Chartas, W. N. Brandt, S. C. Gallagher, G. P. Garmire

We report the discovery of X-ray broad absorption lines (BALs) from the BALQSO APM 08279+5255 originating from material moving at relativistic velocities with respect to the central source. The large flux magnification by a factor of ~ 100 provided by the gravitational lens effect combined with the large redshift (z = 3.91) of the quasar have facilitated the

Michael Feast

The galactic kinematics of Mira variables derived from radial velocities, Hipparcos proper motions and an infrared period-luminosity relation are reviewed. Local Miras in the 145-200day period range show a large asymmetric drift and a high net outward motion in the Galaxy. Interpretations of this phenomenon are considered and (following Feast and Whitelock 2

V. S. Geroyannis

We study numerically the so-called ``turn-over scenario&#39;&#39; for rotating magnetic white dwarfs and neutron stars. According to this scenario, the magnetic symmetry axis of the model inclines at a gradually increasing angle (the so-called ``turn-over angle&#39;&#39;) relative to the invariant angular momentum axis. Consequently, the model becomes ``perp

S. Dreizler, T. Rauch, P. Hauschildt, S. L. Schuh

Recently, 46 low-luminosity object transits were reported from the Optical Gravitational Lensing Experiment. Our follow-up spectroscopy of the 16 most promising candidates provides a spectral classification of the primary. Together with the radius ratio from the transit measurements, we derived the radii of the low-luminosity companions. This allows to exami

A. Cimatti, L. Pozzetti, M. Mignoli, E. Daddi

We present the redshift distribution of a complete sample of 480 galaxies with Ks<20 distributed over two independent fields covering a total area of 52 arcmin^2. The redshift completeness is 87% and 98% respectively with spectroscopic and high-quality and tested photometric redshifts. The redshift distribution of field galaxies has a median redshift z_{med}

Jon Loveday

The Sloan Digital Sky Survey (SDSS) is making a multi-colour, three dimensional map of the nearby Universe. The survey is in two parts. The first part is imaging one quarter of the sky in five colours from the near ultraviolet to the near infrared. In this imaging survey we expect to detect around 50 million galaxies to a magnitude limit g ~ 23. The second p

J. M. Paredes, M. Ribo, E. Ros, J. Marti

The microquasar nature of LS5039 was revealed by May 1999 VLBA+VLA observations showing a two-sided jet at milliarcsecond scales. Here we present follow-up interferometric observations carried out with the EVN and MERLIN at 5 GHz in March 2000. The obtained maps with both the EVN and MERLIN show a two-sided jet with a similar position angle to the previous V

P. A. Price, S. R. Kulkarni, B. P. Schmidt, T. J. Galama

GRB 010921 was the first HETE-2 GRB to be localized via its afterglow emission. The low-redshift of the host galaxy, z=0.451, prompted us to undertake intensive multi-color observations with the Hubble Space Telescope with the goal of searching for an underlying supernova component. We do not detect any coincident supernova to a limit 1.34 mag fainter than S

Manuel Peimbert, Antonio Peimbert

The determination of the heavy element abundances from giant extragalactic H II regions is based on collisionally excited lines. We argue that in the presence of temperature variations the abundances determined are lower limits to the real heavy element abundances. To determine the real abundances it is necessary to take into account the temperature variatio

Wayne H. Baumgartner, Donald J. Horner, Richard F. Mushotzky

We present the abundances of the intermediate elements obtained by performing a stacked analysis of all the galaxy clusters in the archive of the X-ray telescope ASCA. We give the abundances of Fe, Si, S, and Ni as a function of cluster temperature from 1--10 keV, and place strong upper limits on the abundances of Ca and Ar. We show that the abundances of th

Yousaf Butt, Diego Torres, Gustavo Romero, Josep M. Paredes

The unidentified EGRET source 3EG J1828+0142, located at (l,b) ~ (31.9,5.8) (Hartman et al. 1999), is particularly enigmatic since it displays very high variability over timescales of months (Torres et al. 2000, Tompkins 1999) yet no blazar has been found within the 95% confidence contour of the gamma-ray location error-box (Punsly et al 2000). It also has a

M. Yu. Zotov, G. V. Kulikov, Yu. A. Fomin

We apply certain methods of nonlinear time series analysis to the extensive air shower clusters found earlier in the data set obtained with the EAS-1000 Prototype array. In particular, we use the Grassberger-Procaccia algorithm to compute the correlation dimension of samples in the vicinity of the clusters. The validity of the results is checked by surrogate

Sergei M. Ananyan, Brian D. Serot, John Dirk Walecka

Weak-interaction currents are studied in a recently proposed effective field theory of the nuclear many-body problem. The Lorentz-invariant effective field theory contains nucleons, pions, isoscalar scalar ($σ$) and vector ($ω$) fields, and isovector vector ($ρ$) fields. The theory exhibits a nonlinear realization of $SU(2)_L \times SU(2)_R$ chiral symmetry

M. Paternostro, M. S. Kim, G. M. Palma

The problems related to the management of large quantum registers could be handled in the context of distributed quantum computation: unitary non-local transformations among spatially separated local processors are realized performing local unitary transformations and exchanging classical communication. In this paper, we propose a scheme for the implementati

C. N. Leung, Yvonne Y. Y. Wong

If the small and large coupling behavior of a physical system can be computed perturbatively and expressed respectively as power series in a coupling parameter $g$ and $1/g$, a Padé approximant embracing the two series can interpolate between these two limits and provide an accurate estimate of the system&#39;s behavior in the generally intractable intermedi

Nakwoo Kim, Jeong-Hyuck Park

We study the superalgebra of the M-theory on a fully supersymmetric pp-wave. We identify the algebra as the special unitary Lie superalgebra, su(2|4;2,0) or su(2|4;2,4), and analyze its root structure. We discuss the typical and atypical representations deriving the typicality condition explicitly in terms of the energy and other four quantum numbers. We cla

A. Rebhan, P. van Nieuwenhuizen, R. Wimmer

We show that the anomalous contribution to the central charge of the 1+1-dimensional N=1 supersymmetric kink that is required for BPS saturation at the quantum level can be linked to an analogous term in the extra momentum operator of a 2+1-dimensional kink domain wall with spontaneous parity violation and chiral domain wall fermions. In the quantization of