May 2003 arXiv papers — page 26

L. F. Wei, Franco Nori

The unavoidable finite time intervals between the sequential operations needed for performing practical quantum computing can degrade the performance of quantum computers. During these delays, unwanted relative dynamical phases are produced due to the free evolution of the superposition wave-function of the qubits. In general, these coherent "errors"

Y. C. Huang

This paper has been withdrawn by the authors because the paper is largely revised and improved.

Pablo Arrighi

There are many falsely intuitive introductions to quantum theory and quantum computation in a handwave. There are also numerous documents which teach those subjects in a mathematically sound manner. To my knowledge this paper is the shortest of the latter category. The aim is to deliver a short yet rigorous and self-contained introduction to Quantum Computat

Jose L. Cereceda

In this paper, a new measure of entanglement for general pure bipartite states of two qutrits is formulated.

Ole Steuernagel

Comment on "Quantum Interferometric Optical Lithography: Exploiting Entanglement to Beat the Diffraction Limit" The effective absorption rates in quantum lithography are very low.

Timo O. Reiss, Navin Khaneja, Steffen J. Glaser

Broadband implementations of time-optimal geodesic pulse elements are introduced for the efficient creation of effective trilinear coupling terms for spin systems consisting of three weakly coupled spins 1/2. Based on these pulse elements, the time-optimal implementation of indirect SWAP operations is demonstrated experimentally. The duration of indirect SWA

Charles D. Hill, Hsi-Sheng Goan

In this paper we apply the canonical decomposition of two qubit unitaries to find pulse schemes to control the proposed Kane quantum computer. We explicitly find pulse sequences for the CNOT, swap, square root of swap and controlled Z rotations. We analyze the speed and fidelity of these gates, both of which compare favorably to existing schemes. The pulse s

Y. C. Huang, Z. X. Liu, X. G. Li

This paper has been withdrawn by the authors because the paper is largely revised and improved, and to appear in Mechanics Research Communications.

Himadri S. Chakraborty, Thomas Niederhausen, Uwe thumm

Using a wave packet propagation approach, we find that the resonant charge transfer process of H^- near a Cu(111) surface is strongly influenced by transient hybrid states. These states originate from an ion-induced confinement parallel to the surface together with the surface-localization character of the metal potential along the surface normal. The lowest

Mihai V. Putz, Nino Russo

In the framework of the density functional theory a new electronegativity formulation via the Feynman-Kleinert path integral formalism in the markovian limit is proposed. The computation of the electronic density follows, in terms of partition function, the same procedure of the Levy constrained-search for the wave function. The obtained electronegativity sc

A. Penaranda, L. Ramirez-Piscina

We perform simulations of planar arrays of superheated superconducting granules (PASS) under an external magnetic field, analyzing transitions undergone by the system when the external field is slowly increased from zero. We observe, for high concentrations, the existence of an interval of external fields for which no transitions are induced. This effect is

Vasyl P. Lukomsky, Ivan S. Gandzha

In the framework of the canonical model of hydrodynamics, where fluid is assumed to be ideal and incompressible, waves are potential, two-dimensional, and symmetric, the authors have recently reported the existence of a new type of gravity waves on deep water besides well studied Stokes waves (Phys. Rev. Lett., 2002, v. 89, 164502). The distinctive feature o

E. Creutz

I will describe some of the events that led to the creation of General Atomic, a research and development organization founded in San Diego in 1956.

J. B. Almeida, V. Lakshminarayanan

Free-space propagation can be described as a shearing of the Wigner distribution function in the spatial coordinate; this shearing is linear in paraxial approximation but assumes a more complex shape for wide-angle propagation. Integration in the frequency domain allows the determination of near-field diffraction, leading to the well known Fresnel diffractio

Johannes Schimpl, Helena M. Petrilli, Peter E. Bloechl

N2 association to the FeMo-cofactor of nitrogenase, including the recently identified central N ligand, has been investigated using first-principles electronic structure calculations. The oxidation state of the resting state of the cofactor and its electronic structure has been identified. A single proton is added to the sulfur bridges following each electro

Andre Gsponer

The only military application in which depleted-uranium (DU) alloys out-perform present-day tungsten alloys is long-rod penetration into a main battle-tank's armor. However, this advantage is only on the order of 10%, and it disappears when the comparison is made in terms of actual lethality of complete anti-tank systems instead of laboratory-type steel

W. R. Gibbs

There has been a discrepancy between values of the pion-nucleon sigma term extracted by two different methods for many years. Analysis of recent high precision pion-nucleon data has widened the gap between the two determinations. It is argued that the two extractions correspond to different quantities and that the difference between them can be understood an

M. Bender, H. Flocard, P. -H. Heenen

We investigate the coexistence of spherical, deformed and superdeformed states at low spin in S32, Ar36, Ar38 and Ca40. The microscopic states are constructed by configuration mixing of BCS states projected on good particle number and angular momentum. The BCS states are themselves obtained from Hartree-Fock BCS calculations using the Skyrme interaction SLy6

Ben-Hao Sa, Xu Cai, an Tai, Zhong-Qi Wang

We present simulation results of net charge fluctuation in $Au+Au$ collisions at $\sqrt{s_{nn}}$=130 GeV from a dynamic model, JPCIAE. The calculations are done for the quark-gluon phase before hadronization, the pion gas, the resonance pion gas from $ρ$ and $ω$ decays and so on. The simulations of the charge fluctuation show that the discrepancy exists betw

Wang Qi, Sergey Yu. Kun, Tian Wendong, Li Songlin

We have tested recent suggestion of anomalous sensitivity in highly excited quantum many-body systems. Two independent measurements of cross sections for the 19F+93Nb strongly dissipative heavy-ion collisions have been performed at incident energies from 102 to 108 MeV in steps of 250 keV.In the two measurements we used different, independently prepared, 93N

Huaping Lu, Shihong Wang, Xiaowen Li, Guoning Tang

Two-dimensional one-way coupled map lattices are used for cryptograph where multiple space units produce chaotic outputs in parallel. One of the outputs plays the role of driving for synchronization of the decryption system while the others perform the function of information encoding. With this separation of functions the receiver can establish a self-check

C. L. Pando L

We have studied the discrete nonlinear Schroedinger equation (DNLSE) with on-site defects and periodic boundary conditions. When the array dynamics becomes chaotic, the otherwise quasiperiodic amplitude correlations between the oscillators are destroyed. However, we show that synchronization of symbolic information of suitable amplitude signals is possible i

A. Zenchuk, E. Goldobin

We investigate analytically a long Josephson 0-$π$-junction with several 0 and $π$ facets which are comparable to the Josephson penetration length $λ_J$. Such junctions can be fabricated exploiting (a) the d-wave order parameter symmetry of cuprate superconductors; (b) the spacial oscillations of the order parameter in superconductor-insulator-ferromagnet-su

Haken Ciftci, Richard L. Hall, Qutaibeh D. Katatbeh

We study the discrete spectrum of the Hamiltonian H = -Delta + V(r) for the Coulomb plus power-law potential V(r)=-1/r+ beta sgn(q)r^q, where beta > 0, q > -2 and q \ne 0. We show by envelope theory that the discrete eigenvalues E_{n\ell} of H may be approximated by the semiclassical expression E_{n\ell}(q) \approx min_{r>0}\{1/r^2-1/(mu r)+ sgn(q) beta(nu r

J. Dimock

We study scalar quantum field theory on a compact manifold. The free theory is defined in terms of functional integrals. For positive mass it is shown to have the Markov property in the sense of Nelson. This property is used to establish a reflection positivity result when the manifold has a reflection symmetry. In dimension d=2 we use the Markov property to

Oliver Johnson, Yuri Suhov

This paper considers the problem of data compression for dependent quantum systems. It is the second in a series under the same title. As in the previous paper, we are interested in Lempel--Ziv encoding for quantum Gibbs ensembles. Here, we consider the canonical ideal lattice Bose- and Fermi-ensembles. We prove that as in the case of the grand canonical ens

J. A. Sethian

We review some recent work in fast, efficient and accurate methods to compute viscosity solutions and non-viscosity solutions to static Hamilton-Jacobi equations which arise in optimal control, anisotropic front propagation, and multiple arrivals in wave propagation. For viscosity solutions, the class of algorithms are known as ``Ordered Upwind Methods'&

Emmanuel Giroux

On décrit ici des relations entre la géométrie globale des variétés de contact closes et celle de certaines variétés symplectiques, à savoir les variétés de Stein compactes. L'origine de ces relations est l'existence de livres ouverts adaptés aux structures de contact. We discuss relations between the global geometry of closed contact manifolds and t

D. Shklyarov, G. Zhang

We introduce and study, in the framework of a theory of quantum Cartan domains, a q-analogue of the Berezin transform on the unit ball. We construct q-analogues of weighted Bergman spaces, Toeplitz operators and covariant symbol calculus. In studying the analytical properties of the Berezin transform we introduce also the q-analogue of the SU(n,1)-invariant

Marcus Hutter

Walley's Imprecise Dirichlet Model (IDM) for categorical data overcomes several fundamental problems which other approaches to uncertainty suffer from. Yet, to be useful in practice, one needs efficient ways for computing the imprecise=robust sets or intervals. The main objective of this work is to derive exact, conservative, and approximate, robust and

Mohamed saidi

In this paper we prove that complete families of smooth and projective curves, of genusg>2, in characteristic p>0, with a constant geometric fundamental group, are isotrivial.

Mohammad T. Dibaei, Siamak Yassemi

In the derived category of the category of modules over a commutative Noetherian ring $R$, we define, for an ideal $\fa$ of $R$, two different types of cohomological dimensions of a complex $X$ in a certain subcategory of the derived category, namely $\cd(\fa, X)=\sup\{\cd(\fa, \H_{\ell}(X))-\ell|\ell\in\Bbb Z\}$ and $-\inf{\mathbf R}\G_{\fa}(X)$, where $\cd

Phung Ho Hai, Nguyen Huy Hung

We propose a new method to investigate the dimension of the space of integrals on a Hopf algebra $H$ and other properties of $H$-comodules.

Nguyen Phuong Dung, Phung Ho Hai

Hecke symmetries generalize the usual tensor symmetry of vector spaces $v\otimes w\arrow w\otimes v$ as well as the symmetry of vector superspaces. To a Hecke symmetry $R$ there associates a quadratic algebra which can be interpreted as the function algebra upon a certain quantum space. This paper investigates the Poincare series of this quadratic algebra. W

Phung Ho Hai

A quantum group of type A is defined as a Hopf algebra associated to a Hecke symmetry. We show the homology of a Koszul complex associated to the Hecke symmetry is one dimensional and determines a group-like element in the Hopf algebra. This group-like element can be interpreted as a homological determinant as suggested by Yu. Manin.

Salih Celik

Differential geometry of the quantum Lie superalgebra of the extended quantum superplane and its Z$_2$-graded Hopf algebra structure is obtained. Its Z$_2$-graded dual Hopf algebra is also given.

T. Gannon

As is well-known, nonunitary RCFTs are distinguished from unitary ones in a number of ways, two of which are that the vacuum 0 doesn't have minimal conformal weight, and that the vacuum column of the modular S matrix isn't positive. However there is another primary field, call it o, which has minimal weight and has positive S column. We find that oft

Horatiu Nastase

D4-D8 and D3-D7 systems are studied and a possible holographic dual of large N QCD (SU(N) gauge fields and fundamental quarks) is sought. A candidate system is found, for which however no explicit solution is available. Susy is broken by having a $D7-\bar{D7}$ condensing to a D5. The mechanism for supersymmetry breaking is then used to try to construct a Sta

Alex Buchel, James T. Liu

We discuss the thermodynamics of the N=2*, SU(N) gauge theory at large 't Hooft coupling. The tool we use is the non-extremal deformation of the supergravity solution of Pilch and Warner (PW) [hep-th/0004063], dual to N=4, SU(N) gauge theory softly broken to N=2. We construct the exact non-extremal solution in five-dimensional gauged supergravity and fur

Falk Bruckmann, Daniel Nogradi, Pierre van Baal

We use the fermion zero-modes in the background of multi-caloron solutions with non-trivial holonomy as a probe for constituent monopoles. We find in general indication for an extended structure. However, for well separated constituents these become point-like. We analyse this in detail for the SU(2) charge 2 case, where one is able to solve the relevant Nah

P. Di Vecchia, A. Liccardo, R. Marotta, F. Pezzella

We compute the annulus diagram corresponding to the interaction of a fractional D3 brane with a gauge field on its world-volume and a stack of N fractional D3 branes on the orbifolds C^2 /Z_2 and C^3/Z_2 x Z_2. We show that its logarithmic divergence can be equivalently understood as due either to massless open string states circulating in the loop or to mas

G. Arutyunov, S. Penati, A. Santambrogio, E. Sokatchev

We study the large N degeneracy in the structure of the four-point amplitudes of 1/2-BPS operators of arbitrary weight k in perturbative N=4 SYM theory. At one loop (order g^2) this degeneracy manifests itself in a smaller number of independent conformal invariant functions describing the amplitude, compared to AdS_5 supergravity results. To study this pheno

Frederic Leblond, Amanda W. Peet

Recently, a singularity theorem for full SD-brane spacetimes was given in hep-th/0305055. We comment on the relation between this and previous work as well as provide a more geometric formulation interpreted as a no-go theorem. We then point out that some setups of physical interest escape the theorem: cosmological applications, half-SDp-branes and decaying

P. A. Horvathy

The acceleration-dependent system with noncommuting coordinates, proposed by Lukierski, Stichel and Zakrzewski [Ann. Phys. 260, 224 (1997)] is derived as the non-relativistic limit of Mathisson's classical electron [Acta Physica Polonica 6, 218 (1937)], further discussed by Weyssenhoff and Raabe [Acta Physica Polonica 9, 7 (1947)]. The two-parameter cent

B. Z. Kopeliovich, J. Raufeisen

These lectures present an overview of the current status of the QCD based phenomenology for open and hidden heavy flavor production at high energies. A unified description based on the light-cone color-dipole approach is employed in all cases. A good agreement with available data is achieved without fitting to the data to be explained, and nontrivial predict

D. L. Adams

DIAL will enable users to analyze very large, event-based datasets using an application that is natural to the data format. Both the dataset and the processing may be distributed over a farm, a site (collection of farms) or a grid (collection of sites). Here we describe the goals of the project, the current design and implementation, and plans for future dev

G. C. Branco, J. -M. Gerard, R. Gonzalez Felipe, B. M. Nobre

The possibility of achieving a gauge coupling grand unification by increasing the QCD degrees of freedom at higher energies is investigated. When confronted with precision low-energy data, the generic weak-mixing angle relation sin^2(theta_W) = N/2(N+1) requires N=7 colors at the GUT scale M_U ~ 10^17 GeV. With the exclusive addition of light Higgs doublets

S. M. Barr, I. Dorsner

An approach is suggested for modeling quark and lepton masses and mixing in the context of grand unified theories that explains the curious fact that m_u ~ m_d even though m_t >> m_b. The structure of the quark mass matrices is such as to allow a non-Peccei-Quinn solution of the Strong CP Problem.

T. L. Trueman

Recent polarized proton experiments at Brookhaven National Laboratory are used as a basis for a model of the energy dependence of the analyzing power of proton-carbon elastic scattering. In addition to their practical value for polarimetry, the results of this analysis give constraints on the size of the Pomeron spin-flip coupling as well as information on t

Kui-Yong Liu, Zhi-Guo He, Kuang-Ta Chao

We study the production of $J/ψ+c\bar{c}$ in $e^+e^-$ annihilation through two virtual photons. The cross section is estimated to be 23 fb at $\sqrt{s}=10.6$ GeV, which is smaller by a factor of six than the calculated cross section for the same process but through one virtual photon. As a result, while the annihilation into two photons may be important for

Abdou Abdel-Rehim, Deirdre Black, Amir Fariborz, Salah Nasri

We first review how the simple K-matrix unitarized linear SU(2) sigma model can explain the experimental data in the scalar pi pi scattering channel of QCD up to about 800 MeV. Since it is just a scaled version of the minimal electroweak Higgs sector, which is often treated with the same unitarization method, we interpret the result as support for this appro

Malgorzata Worek

We show how the transverse tau tau spin correlations can be used to measure the parity of the Higgs boson and hence to distinguish a CP-even H boson from CP-odd A in the future high energy accelerator experiments. We investigate the subsequent decays of the tau into pi nu and rho nu. The prospects for the measurement of the Higgs boson parity with a mass of

Ramesh Anishetty, Santosh Kumar Kudtarkar

A systematic method of analysing Bethe-Salpeter equation using spectral representation for the relativistic bound state wave function is given. This has been explicitly applied in the context of perturbative QCD with string tension in the $1 \over N$ expansion. We show that there are only a few stable bound state mesons due to the small "threshold mass&#

Ramesh Anishetty, Santosh Kumar Kudtarkar

General properties of the light and heavy quark propagators have been investigated in the context of string tension interaction. Confinement, chiral symmetry breaking, spectral properties of the propagator are analytically studied and numerically validated. We show that the propagator is analytic in the infrared region even for massless quarks with a non zer

Kenichi Naito, Makoto Oka, Makoto Takizawa, Toru Umekawa

Effects of the U_A(1) breaking interaction on the low-lying nonet scalar mesons are studied using the extended Nambu-Jona-Lasinio model. The strength of the U_A(1) breaking interaction is determined by the electromagnetic decays of the eta meson. We find that the U_A(1) breaking interaction gives rise to about 150 MeV mass difference between the sigma and a_

V. Barger, James P. Kneller, Hye-Sung Lee, Danny Marfatia

We place constraints on the number of relativistic degrees of freedom and on the baryon asymmetry at the epoch of Big Bang Nucleosynthesis (BBN) and at recombination, using cosmic background radiation (CBR) data from the Wilkinson Microwave Anisotropy Probe (WMAP), complemented by the Hubble Space Telescope (HST) Key Project measurement of the Hubble constan

CDF Collaboration

We present the results of a search for pair production of scalar top quarks in an R-parity violating supersymmetry scenario in 106 pb-1 of ppbar collisions at $\sqrt{s} = 1.8$ TeV collected by the Collider Detector at Fermilab. In this mode each scalar top quark decays into a tau lepton and a b quark. We search for events with two tau's, one decaying lep

H. Boutaleb-Joutei, A. M. Elgasmi

Some shortcomings in regard to our lack of conceptual understanding of string theory are displayed and prescription to untangle them is proposed. String theory should be a fundamental dynamics of four dimensional symmetric space-times. Properties of the two dimensional equivalent action are studied, in the hydrodynamic approximation. In the pressureless regi

Myeongju Chae, Piotr T. Chrusciel

We study the behavior near the singularity t=0 of Gowdy metrics. We prove existence of an open dense set of boundary points near which the solution is smoothly "asymptotically velocity term dominated" (AVTD). We show that the set of AVTD solutions satisfying a uniformity condition is open in the set of all solutions. We analyse in detail the asymptot

G. S. Atwal, N. W. Ashcroft

Spin correlations in an interacting electron liquid are studied in the high-frequency limit and in both two and three dimensions. The third-moment sum rule is evaluated and used to derive exact limiting forms (at both long- and short-wavelengths) for the spin-antisymmetric local-field factor, $\lim_{ω\to \infty}G_-({\bf q, ω})$. In two dimensions $\lim_{ω\to

Bo Soderberg

We investigate in some detail a recently suggested general class of ensembles of sparse undirected random graphs based on a hidden stub-coloring, with or without the restriction to nondegenerate graphs. The calculability of local and global structural properties of graphs from the resulting ensembles is demonstrated. Cluster size statistics are derived with

R. Gonczarek, M. Krzyzosiak

It is proven that there exist some universal relations between the energy gap and the differences of the thermodynamic potential, entropy, specific heat and critical magnetic field for many two- and three-dimensional models of superconductivity with spin-singlet Cooper pairs forming \textit{s} or \textit{d} or \textit{g} etc. states. The obtained formulae ma

P. Nikolic, T. Senthil

This paper is concerned with physics of the low energy singlet excitations found to exist below the spin gap in numerical studies of the Kagome lattice quantum Heisenberg antiferromagnet. Insight into the nature of these excitations is obtained by exploiting an approximate mapping to a fully frustrated transverse field Ising model on the dual dice lattice. T

Sergey V. Buldyrev, H. Eugene Stanley

We study a three-dimensional system of particles interacting via spherically-symmetric pair potentials consisting of several discontinuous steps. We show that at certain values of the parameters desribing the potential, the system has three first-order phase transitions between fluids of different densities ending in three critical points.

Alberto Rosso, Thierry Giamarchi

We study the X-ray diffraction spectrum produced by a collectively pinned charge density wave (CDW), for which one can expect a Bragg glass phase. The spectrum consists of two asymmetric divergent peaks. We compute the shape of the peaks, and discuss the experimental consequences.

J. F. Weisz, F. Claro

We study two correlated electrons in a nearest neighbour tight- binding chain, with both on site and nearest neighbour interaction. Both the cases of parallel and antiparallel spins are considered. In addition to the free electron band for two electrons, there are correlated bands with positive or negative energy, depending on wheather the interaction parame

Han Pu, Weiping Zhang, Pierre Meystre

We investigate theoretically the four-wave mixing of optical and matter waves resulting from the scattering of a short light pulse off an atomic Bose-Einstein condensate, as recently demonstrated by D. Schneble {\em et al.} [ Science {\bf 300}, 475 (2003)]. We show that atomic ``pair production'' from the condensate results in the generation of both

S. Sharma, J. K. Dewhurst, C. Ambrosch-Draxl

We report first-principles calculations of the frequency dependent linear and second-order optical properties of the two probable extended-solid phases of CO$_2$--V, i.e. $I\bar42d$ and $P2_12_12_1$. Compared to the parent $Cmca$ phase the linear optical susceptibility of both phases is much smaller. We find that $I\bar42d$ and $P2_12_12_1$ differ substantia

M. R. Evans, T. Hanney

We study a zero-range process with two species of interacting particles. We show that the steady state assumes a simple factorised form, provided the dynamics satisfy certain conditions, which we derive. The steady state exhibits a new mechanism of condensation transition wherein one species induces the condensation of the other. We study this mechanism for

Pedro A. Pury, Manuel O. Caceres

The multifractal characterization of the distribution over disorder of the mean first-passage time in a finite chain is revisited. Both, absorbing-absorbing and reflecting-absorbing boundaries are considered. Two models of dichotomic disorder are compared and our analysis clarifies the origin of the multifractality. The phenomenon is only present when the di

L. I. Deych, M. V. Erementchouk, A. A. Lisyansky, Alexey Yamilov

We numerically study the distribution function of the conductance (transmission) in the one-dimensional tight-binding Anderson and periodic-on-average superlattice models in the region of fluctuation states where single parameter scaling is not valid. We show that the scaling properties of the distribution function depend upon the relation between the system

Antonio Coniglio, Annalisa Fierro, Mario Nicodemi

We discuss recent developments in the formulation of a Statistical Mechanics approach to non thermal systems, such as granular media. We review a few important numerical results on the assessment of Edwards' theory and, in particular, we apply these ideas to study a mean field model of a hard sphere binary mixture under gravity, which can be fully analyt

Wei-Guo Yin, W. N. Mei

We calculate the angular resolved photoemission spectra (ARPES) of a spin-1/2 Heisenberg antiferromagnet as a function of magnetic fields using both the exact diagonalization method and self-consistent Born approximation. Below the saturation field $B_C$, strong scattering between spin waves and a hole, created by photoemission of an electron, significantly

M. A. Avila, S. L. Bud'ko, P. C. Canfield

We have grown RFe2Ge2 single crystals for R = Y and ten members of the lanthanide series (Pr, Nd, Sm, Gd-Tm, Lu) using Sn flux as the solvent. The method yields clean, high quality crystal plates as evidenced by residual resistivities and RRR values in the range of 3-12 uOhm cm and 20-90 respectively. The crystals are also virtually free of magnetic impuriti

N. S. Skantzos, D. Saad, Y. Kabashima

We analyze the security and reliability of a recently proposed class of public-key cryptosystems against attacks by unauthorized parties who have acquired partial knowledge of one or more of the private key components and/or of the plaintext. Phase diagrams are presented, showing critical partial knowledge levels required for unauthorized decryption

Freddy Bouchet

The relaxation towards equilibrium of systems with long range interactions is not yet fully understood. As a step towards such a comprehension, we propose the study of the dynamical equilibrium fluctuations in a model system with long range interaction. We compute analytically, from the microscopic dynamics, the autocorrelation function of the order paramete

Michele Casula, Sandro Sorella

We introduce a simple generalization of the well known geminal wavefunction already applied in Quantum Chemistry to atoms and small molecules. The main feature of the proposed wavefunction is the presence of the antisymmetric geminal part together with a Jastrow factor. Both the geminal and the Jastrow play a crucial role in determining the remarkable accura

M. Eisterer, M. Zehetmayer, H. W. Weber

The influence of anisotropy on the transport current in MgB$_2$ polycrystalline bulk samples and wires is discussed. A model for the critical current density is proposed, which is based on anisotropic London theory, grain boundary pinning and percolation theory. The calculated currents agree convincingly with experimental data and the fit parameters, especia

E. Abad, A. Provata, G. Nicolis

We study the effect of fractal initial conditions in closed reactive systems in the cases of both mobile and immobile reactants. For the reaction $A+A\to A$, in the absence of diffusion, the mean number of particles $A$ is shown to decay exponentially to a steady state which depends on the details of the initial conditions. The nature of this dependence is d

M. Ricco, G. Fumera, T. Shiroka, O. Ligabue

A singular evolution toward an insulating phase, shown by 23Na and 13C NMR, has been observed in the superconducting fullerides (NH3)xNaK2C60 for x>1. Unlike most common cases, this insulating phase is non magnetic and 13C spin lattice relaxation shows the presence of a spin gap. These two features suggest that a charge disproportion from C60^(3-) to C60^(2-

T. Domanski

Using the equation of motion technique for Green's functions we derive the exact solution of the boson fermion model in the atomic limit. Both (fermion and boson) subsystems are characterised by the effective three level excitation spectra. We compute the spectral weights of these states and analyse them in detail with respect to all possible parameters.

V. M. Loktev, V. Turkowski

The superconducting properties of the 2D fermion system with local and different types of the indirect boson-exchange attractions in the cases of s-wave and d-wave pairing are reviewed and analysed at T=0. In particular, the possibility of the crossover from the Bose-Einstein condensation regime to the BCS-like superconductivity with the carrier density and

V. M. Loktev, V. Turkowski

The superconducting properties of a layered system are analyzed for the cases of zero- and non-zero angular momentum of the pairs. The effective thermodynamic potential for the quasi-2D XY-model for the gradients of the phase of the order parameter is derived from the microscopic superconducting Hamiltonian. The dependence of the superconducting critical tem

S. K. Yip

We show that, for a quantum point contact between two superconductors of different gap magnitudes, Andreev bound states do not exist for certain phase differences and gap ratios. Continuum states may dominate the transport, and the supercurrent noise is qualitatively different from the case of equal gaps.

A. S. Moskvin, E. V. Zenkov

We examine the effects of electron inhomogeneity on IR optical conductivity of cuprates. Nanoscopic electron inhomogeneity is believed to be inherent property of doped cuprates throughout the phase diagram beginning from electron-hole droplets in insulating parent system and ending by a topological phase separation in electron-hole bose liquid (EHBL) phase.

L. B. Kong, L. Yan, K. B. Chong, C. Y. Tan

LaAlO3-Ba0.5Sr0.5TiO3 (LAO-BST) thin films, with different LAO contents, were deposited on Pt/Ti/SiO2/Si and (100) LaAlO3 substrate, via a pulsed laser deposition (PLD). Phase composition and microstructure of the LAO-BST thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The LAO-BST thin films were solid solutio

Masahide Sato, Makio Uwaha, Tomonori Mori, Yukio Hirose

By taking account of the alternation of structural parameters, we study bunching of impermeable steps induced by drift of adatoms on a vicinal face of Si(001). With the alternation of diffusion coefficient, the step bunching occurs irrespective of the direction of the drift if the step distance is large. Like the bunching of permeable steps, the type of larg

E. Ben-Naim, P. L. Krapivsky

We study a class of growth processes in which clusters evolve via exchange of particles. We show that depending on the rate of exchange there are three possibilities: I) Growth: Clusters grow indefinitely; II) Gelation: All mass is transformed into an infinite gel in a finite time; and III) Instant Gelation. In regimes I and II, the cluster size distribution

Valery L. Pokrovsky, Hongduo Wei

We study the shift of the the superconducting transition temperature $T_c$ in ferromagnetic-superconducting bi-layers and in a superconducting film supplied a square array of ferromagnetic dots. We find that the transition temperature in these two cases change presumably in opposite direction and that its change is not too small. We extend these results to m

Qiang-Hua Wang, Z. D. Wang

Motivated by recent discoveries of novel superconductors such as Na$_x$CoO$_2\cdot y$H$_2$O and Sr$_2$RuO$_4$, we analysize features of quasi-particle scattering due to impurities and interfaces for possible gapful $d_{x^2-y^2}+id_{xy}$ and $p_x+ip_y$ Cooper pairing. A bound state appears near a local impurity, and a band of bound states form near an interfa

Yoichi Ando, A. N. Lavrov, Seiki Komiya

Detailed behavior of the magnetoresistance (MR) is studied in lightly doped antiferromagnetic La_{1.99}Sr_{0.01}CuO_{4}, where, thanks to the weak ferromagnetic moment due to spin canting, the antiferromagnetic (AF) domain structure can be manipulated by the magnetic field. The MR behavior demonstrates that CuO_2 planes indeed contain anti-phase AF domain bo

M. V. Simkin, V. P. Roychowdhury

Recently we discovered (cond-mat/0212043) that the majority of scientific citations are copied from the lists of references used in other papers. Here we show that a model, in which a scientist picks three random papers, cites them,and also copies a quarter of their references accounts quantitatively for empirically observed citation distribution. Simple mat

D. Villani, R. M. Ghigliazza, R. Carmona

We extract the frequency content of a noisy signal by use of Discrete Fourier Transform. Our analysis overcomes the limitations imposed by incommensurate lattices. After computing the deterministic component, we show the relevance of the method in removing spurious autocorrelations from the signal residuals. Results are presented for a temperature time serie

L. Velazquez, R. Sospedra, J. C. Castro, F. Guzman

We study the N-dependence of the thermodynamical variables and the dynamical behavior of the well-known Hamiltonian Mean Field model. Microcanonical analysis revealed a thermodynamic limit which defers from the a priory traditional assumption of the N-dependence of the coupling constant g as 1/N: to tend N?infinity keeping constant E/N^3 and g/N, prescriptio

Rosalba Perna, Re'em Sari, Dale Frail

The two leading interpretations of achromatic breaks that are observed in the light curves of GRBs afterglow are (i) the manifestation of the edge of a jet, which has a roughly uniform energy profile and a sharp edge and (ii) a line of sight effect in jets with a variable energy profile. The first scenario requires the inner engine to produce a jet with a di

G. Wallerstein, G. Gonzalez, M. D. Shetrone

Radial velocities were measured for 5 potential post-AGB stars, two in the globular cluster NGC 1851 and three in the dSph galaxy Ursa Minor. All five potential PAGB stars were found to be radial velocity non-members.

Paul A. Crowther

We discuss the various post-main sequence phases of massive stars, focusing on Wolf-Rayet stars, Luminous Blue Variables, plus connections with other early-type and late-type supergiants. End states for massive stars are also investigated, emphasising connections between Supernovae originating from core-collapse massive stars and Gamma Ray Bursts.

Paul A Crowther

We discuss the determination of fundamental parameters of `normal' hot, massive OB-type stars, namely temperatures, luminosities, masses, gravities and surface abundances. We also present methods used to derive properties of stellar winds -- mass-loss rates and wind velocities from early-type stars.

Adam J. Burgasser, J. Davy Kirkpatrick, James Liebert, Adam Burrows

We present 6300--10100 Å spectra for a sample of 13 T dwarfs observed using LRIS mounted on the Keck I 10m Telescope. A variety of features are identified and analyzed, including pressure-broadened K I and Na I doublets; narrow Cs I and Rb I lines; weak CaH, CrH, and FeH bands; strong H$_2$O absorption; and a possible weak CH$_4$ band. H$α$ emission is detec

John F. C. Wardle, Daniel C. Homan

We discuss the production of circular polarization in compact radio sources both by the intrinsic mechanism and by Faraday conversion. We pay particular attention to the magnetic field structure, considering partially ordered fiel ds and Laing sheets, and distinguishing between uniform and unidirectional fields. (The latter can be constrained b y flux conser