November 2008 arXiv papers — page 25

T. Wu, J. J. Ying, G. Wu, R. H. Liu

The temperature dependence of electron spin resonance (ESR) was studied in the oxypnictide superconductors LaFeAsO$_{1-x}$F$_x$ (x = 0.0 and 0.13). In the samples, the ESR signal indicates that the g factor and peak-to-peak linewidth strongly depend on temperature, especially at low temperatures. It indicates a strong coupling picture with existence of local

Kuo-Ying Wang, Dudley E. Shallcross

Modeling is a very important tool for scientific processes, requiring long-term dedication, desire, and continuous reflection. In this work, we discuss several aspects of modeling, and the reasons for doing it. We discuss two major modeling systems that have been built by us over the last 10 years. It is a long and arduous process but the reward of understan

V. F. Kharchenko, A. V. Kharchenko

A rigorous formalism for determining the electric dipole polarizability of a three-hadron bound complex in the case that the system has only one bound (ground) state has been elaborated. On its basis, by applying a model wave function that takes into account specific features of the structure of the lightest hypernucleus and using the known low-energy experi

Rajiv Ranjan, Rajkumar Buyya

This chapter describes Aneka-Federation, a decentralized and distributed system that combines enterprise Clouds, overlay networking, and structured peer-to-peer techniques to create scalable wide-area networking of compute nodes for high-throughput computing. The Aneka-Federation integrates numerous small scale Aneka Enterprise Cloud services and nodes that

Anatoliy A. Pogorui

It is well known that the real and imaginary parts of any holomorphic function are harmonic functions of two variables. In this paper we generalize this property to finite-dimensional commutative algebras. We prove that if some basis of a subspace of a commutative algebra satisfies a polynomial equation then components of a hyperholomorphic function on the s

G. Q. Liu, L. Deng, M. Chavez, E. Bertone

Based on spectrophotometric observations from the Guillermo Haro Observatory (Cananea, Mexico), a study of the spectral properties of the complete sample of 24 blue straggler stars (BSs) in the old Galactic open cluster M67 (NGC 2682) is presented. All spectra, calibrated using spectral standards, were recalibrated by means of photometric magnitudes in the B

Yehui Huang, Yuqin Yao, Yunbo Zeng

Regarded as the integrable generalization of Camassa-Holm (CH) equation, the CH equation with self-consistent sources (CHESCS) is derived. The Lax representation of the CHESCS is presented. The conservation laws for CHESCS are constructed. The peakon solution, N-soliton, N-cuspon, N-positon and N-negaton solutions of CHESCS are obtained by using Darboux tran

P. Garaud, C. Guervilly

The rotation rate of the solar radiative zone is an important diagnostic for angular-momentum transport in the tachocline and below. In this paper we study the contribution of viscous and magnetic stresses to the global angular-momentum balance. By considering a simple linearized toy model, we discuss the effects of field geometry and applied boundary condit

Andrei A. Bulatov, Evgeny S. Skvortsov

The Local Search algorithm (or Hill Climbing, or Iterative Improvement) is one of the simplest heuristics to solve the Satisfiability and Max-Satisfiability problems. It is a part of many satisfiability and max-satisfiability solvers, where it is used to find a good starting point for a more sophisticated heuristics, and to improve a candidate solution. In t

Vilton Pinheiro

We prove that any C^{1+} transformation, possibly with a (non-flat) critical or singular region, admits an invariant probability measure absolutely continuous with respect to any expanding measure whose Jacobian satisfies a mild distortion condition. This is an extension to arbitrary dimension of a famous theorem of Keller for maps of the interval with negat

Sean Timothy Paul

Let X be a smooth, linearly normal n dimensional complex projective variety. Assume that the projective dual of X has codimension one with defining polynomial D(X). In this paper the log of the norm of D(X) is expressed as the restriction to the Bergman metrics of an energy functional on X. We show how, for smooth plane curves, this energy functional reduces

Sean Timothy Paul

In this paper I give new elementary proofs of basic results of Gelfand, Kapranov and Zelevinskywhich express discriminants and resultants in terms of determinants of direct images of Cayley-Koszul complexes of sheaves.

S. Pailhes, X. Fabreges, L. P. Regnault, L. Pinsard-Godart

By using polarized inelastic neutron scattering measurements, we show that the spin-lattice quantum entanglement in mutliferroics results in hybrid elementary excitations, involving spin and lattice degrees of freedom. These excitations can be considered as multiferroic Godstone modes. We argue that the Dzyaloshinskii-Moriya interaction could be at the origi

A. Altland, V. Gurarie, T. Kriecherbauer, A. Polkovnikov

We consider the behavior of an interacting many particle system under slow external driving -- a many body generalization of the Landau-Zener paradigm. We find that a conspiracy of interactions and driving leads to physics profoundly different from that of the single particle limit: for practically all values of the driving rate the particle distributions in

Florin Ambro

For a toric log variety with standard coefficients, we show that the minimal log discrepancy at a closed invariant point bounds the Cartier index of a neighbourhood.

Maxim Kontsevich, Yan Soibelman

We define new invariants of 3d Calabi-Yau categories endowed with a stability structure. Intuitively, they count the number of semistable objects with fixed class in the K-theory of the category ("number of BPS states with given charge" in physics language). Formally, our motivic DT-invariants are elements of quantum tori over a version of the Grothe

Carlos Pena-Garay, Aldo Serenelli

Standard solar models (SSM) are facing nowadays a new puzzle: the solar composition problem. New determinations of solar metal abundances lead SSM calculations to conflict with helioseismological measurements, showing discrepancies that extend from the convection zone to the solar core and can not be easily assigned to deficiencies in the modelling of the so

Priyotosh Bandyopadhyay

Cascade decays of Supersymmetric (SUSY) particles are likely to be prolific sources of Higgs bosons at the Large Hadron Collider (LHC). In this work, we explore, with the help of detailed simulation, the role of non-universal gaugino masses in the production of the Higgs bosons under SUSY cascades. The analysis is carried out by choosing an appropriate set o

V. Bardek, J. Feinberg, S. Meljanac

The Calogero model bears, in the continuum limit, collective excitations in the form of density waves and solitary modulations of the density of particles. This sector of the spectrum of the model was investigated, mostly within the framework of collective field theory, by several authors, over the past fifteen years or so. In this work we shall concentrate

Jason Maron, Mordecai-Mark Mac Low

Finite-difference simulations of fluid dynamics and magnetohydrodynamics generally require an explicit diffusion operator, either to maintain stability by attenuating grid-scale structure, or to implement physical diffusivities such as viscosity or resistivity. If the goal is stability only, the diffusion must act at the grid scale, but should affect structu

Itzhak Bars, Shih-Hung Chen

2T-gravity in d+2 dimensions predicts 1T General Relativity (GR) in d dimensions, augmented with a local scale symmetry known as the Weyl symmetry in 1T field theory. The emerging GR comes with a number of constraints, particularly on scalar fields and their interactions in 1T field theory. These constraints, detailed in this paper, are footprints of 2T-grav

Danny Bickson

The canonical problem of solving a system of linear equations arises in numerous contexts in information theory, communication theory, and related fields. In this contribution, we develop a solution based upon Gaussian belief propagation (GaBP) that does not involve direct matrix inversion. The iterative nature of our approach allows for a distributed messag

T. Aaltonen

We report on a search for inclusive production of squarks and gluinos in ppbar collisions at sqrt{s}=1.96 TeV, in events with large missing transverse energy and multiple jets of hadrons in the final state. The study uses a CDF Run II data sample corresponding to 2 fb-1 of integrated luminosity. The data are in good agreement with the standard model predicti

Marcy Barge, Beverly Diamond, John Hunton, Lorenzo Sadun

Anderson and Putnam showed that the cohomology of a substitution tiling space may be computed by collaring tiles to obtain a substitution which "forces its border." One can then represent the tiling space as an inverse limit of an inflation and substitution map on a cellular complex formed from the collared tiles; the cohomology of the tiling space is comput

Haris Aziz, Mike Paterson

Weighted voting games are ubiquitous mathematical models which are used in economics, political science, neuroscience, threshold logic, reliability theory and distributed systems. They model situations where agents with variable voting weight vote in favour of or against a decision. A coalition of agents is winning if and only if the sum of weights of the co

J. Schneider, A. Boccaletti, A. Aylward, P. Baudoz

The physical characterization of exoplanets will require to take spectra at several orbital positions. For that purpose, a direct imaging capability is necessary. Direct imaging requires an efficient stellar suppression mechanism, associated with an ultrasmooth telescope. We show that before future large space missions (interferometer, 4-8 m class coronograp

Mikhail Belolipetsky, Tsachik Gelander, Alex Lubotzky, Aner Shalev

We give estimates on the number $AL_H(x)$ of arithmetic lattices $Γ$ of covolume at most $x$ in a simple Lie group $H$. In particular, we obtain a first concrete estimate on the number of arithmetic 3-manifolds of volume at most $x$. Our main result is for the classical case $H=PSL(2,R)$ where we compute the limit of $\log AL_H(x) / x\log x$ when $x\to\infty

J. Baudon, M. Hamamda, J. Grucker, F. Perales

We consider the extension of optical meta-materials to matter waves. We show that the generic property of pulsed comoving magnetic fields allows us to fashion the wave-number dependence of the atomic phase shift. It can be used to produce a transient negative group velocity of an atomic wave packet, which results into a negative refraction of the matter wave

Pierluigi Contucci, Cristian Giardina, Claudio Giberti

We study the properties of fluctuation for the free energies and internal energies of two spin glass systems that differ for having some set of interactions flipped. We show that their difference has a variance that grows like the volume of the flipped region. Using a new interpolation method, which extends to the entire circle the standard interpolation tec

Peter Collas, David Klein

Examples of axially symmetric solutions to Einstein's field equations are given that exhibit anomalous "negative frame dragging" in the sense that zero angular momentum test particles acquire angular velocities in the opposite direction of rotation from the source of the metric.

J. Bland-Hawthorn

We present evidence that the accretion of warm gas onto the Galaxy today is at least as important as cold gas accretion. For more than a decade, the source of the bright H-alpha emission (up to 750 mR) along the Magellanic Stream has remained a mystery. We present a hydrodynamical model that explains the known properties of the H-alpha emission and provides

Agnieszka Sierpowska-Bartosik, Diego F. Torres

LS I +61 303 has been recently detected as a periodic gamma-ray source by the Major Atmospheric Imaging Cerenkov (MAGIC) telescope. A distinctive orbital correlation of the $γ$-ray emission was found. This work shows that the range of uncertainties yet at hand in the orbital elements of the binary system LSI as well as in the possible assumptions on the stel

Yu Nakayama, Shinsei Ryu, Makoto Sakaguchi, Kentaroh Yoshida

We investigate non-relativistic limits of the N=3 Chern-Simons matter system in 1+2 dimensions. The relativistic theory can generate several inequivalent super Schodinger invariant theories, depending on the degrees of freedom we choose to retain in the non-relativistic limit. The maximally supersymmetric Schrodinger invariant theory is obtained by keeping a

Takayuki Miyadera, Hideki Imai

We discuss the Bennett-Brassard 1984 (BB84) quantum key distribution protocol in the light of quantum algorithmic information. While Shannon's information theory needs a probability to define a notion of information, algorithmic information theory does not need it and can assign a notion of information to an individual object. The program length necessar

IceCube Collaboration

Contributions of the IceCube Collaboration to the 3rd International Workshop on Acoustic and Radio EeV Neutrino detection Activities (ARENA 2008). The conference was held at Roma University "Sapienza," June 25-27, 2008, in Rome, Italy. This is an html index of the IceCube Collaboration contributions, with clickable links to the individual papers.

Yael S. Elmatad, David Chandler, Juan P. Garrahan

The variation with respect to temperature T of transport properties of 58 fragile structural glass forming liquids (68 data sets in total) are analyzed and shown to exhibit a remarkable degree of universality. In particular, super-Arrhenius behaviors of all super-cooled liquids appear to collapse to one parabola for which there is no singular behavior at any

Heinz Siedentop

The ground state energy of the Mueller functional of large (neutral) atoms of atomic number Z agrees with the quantum mechanical ground state energy up to order o(Z to the 5/3). ----- Die Grundzustandsenergie des Muellerfunktionals von grossen (neutralen) Atomen der Ordnungszahl Z stimmt mit der quantenmechanischen Grundzustandsenergie bis zur Ordnung o(Z ho

V. E. Guiseppe

Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The Majorana Collaboration proposes to assemble an array of HPGe detectors to search for neutrinoless double-beta decay in Ge-76. Our proposed method uses the well-established

Harry B. Hunt, Lenore R. Mullin, Daniel J. Rosenkrantz, James E. Raynolds

We describe a methodology for designing efficient parallel and distributed scientific software. This methodology utilizes sequences of mechanizable algebra--based optimizing transformations. In this study, we apply our methodology to the FFT, starting from a high--level algebraic algorithm description. Abstract multiprocessor plans are developed and refined

Barry F. Madore, Wendy L. Freedman, Jane Rigby, S. E. Persson

We present revised and improved mid-infrared Period-Luminosity (PL) relations for Large Magellanic Cloud (LMC) Cepheids based on double-epoch data of 70 Cepheids observed by Spitzer at 3.6, 4.5, 5.8 and 8.0um. The observed scatter at all wavelengths is found to decrease from +/-0.17 mag to +/-0.14 mag, which is fully consistent with the prediction that the t

A. E. Allahverdyan, D. B. Saakian

We study adaptive control of classical ergodic Hamiltonian systems, where the controlling parameter varies slowly in time and is influenced by system's state (feedback). An effective adiabatic description is obtained for slow variables of the system. A general limit on the feedback induced negative entropy production is uncovered. It relates the quickest

Victor Chulaevsky, Yuri Suhov

This paper is a follow-up of our recent papers \cite{CS08} and \cite{CS09} covering the two-particle Anderson model. Here we establish the phenomenon of Anderson localisation for a quantum $N$-particle system on a lattice $\Z^d$ with short-range interaction and in presence of an IID external potential with sufficiently regular marginal cumulative distributio

Armen E. Allahverdyan, Karen Hovhannisyan

We discuss restrictions imposed by quantum mechanics on the process of matrix elements transfer from the one system to another. This is relevant for various processes of partial state transfer (quantum communication, indirect measurement, polarization transfer, {\it etc}). Given two systems A and B with initial density operators $λ$ and $r$, respectively, we

Diederik Aerts, Sylvia Pulmannova

A 'state property system' is the mathematical structure which models an arbitrary physical system by means of its set of states, its set of properties, and a relation of 'actuality of a certain property for a certain state'. We work out a new axiomatization for standard quantum mechanics, starting with the basic notion of state property syste

Sergey Loyka, Francois Gagnon

An analytical technique for the outage and BER analysis of the nx2 V-BLAST algorithm with the optimal ordering has been presented in [1], including closed-form exact expressions for average BER and outage probabilities, and simple high-SNR approximations. The analysis in [1] is based on the following essential approximations: 1. The SNR was defined in terms

Hernando Quevedo, Alberto Sanchez

We study the properties of the space of thermodynamic equilibrium states of the Bañados-Teitelboim-Zanelli (BTZ) black hole in (2+1)-gravity. We use the formalism of geometrothermodynamics to introduce in the space of equilibrium states a $2-$dimensional thermodynamic metric whose curvature is non-vanishing, indicating the presence of thermodynamic interacti

A. S. Sefat, D. J. Singh, R. Jin, M. A. McGuire

We report synthesis and single crystal measurements of magnetic, transport and thermal properties of single crystalline BaCo$_2$As$_2$ as well as first principles calculations of the electronic structure and magnetic behavior. These results show that BaCo$_2$As$_2$ is a highly renormalized paramagnet in proximity to a quantum critical point, presumably of fe

Szu-yu Sophie Chen

We consider natural conformal invariants arising from the Gauss-Bonnet formulas on manifolds with boundary, and study conformal deformation problems associated to them. The key technique we used is to derive boundary C^2 estimates directly from C^0 estimates for fully nonlinear equations. The main result has appeared in the author's thesis.

H. Landsman, L. Ruckman, G. S. Varner

The excellent radio frequency transparency of cold polar ice, combined with the coherent Cherenkov emission produced by neutrino-induced showers when viewed at wavelengths longer than a few centimeters, has spurred considerable interest in a large-scale radio-wave neutrino detector array. The AURA (Askaryan Under-ice Radio Array) experimental effort, within

Fionn Murtagh

The history of data analysis that is addressed here is underpinned by two themes, -- those of tabular data analysis, and the analysis of collected heterogeneous data. "Exploratory data analysis" is taken as the heuristic approach that begins with data and information and seeks underlying explanation for what is observed or measured. I also cover some

Aurel Meyer, Zinovy Reichstein

We use a recent theorem of N. A. Karpenko and A. S. Merkurjev to settle several questions in the theory of essential dimension.

Diederik Aerts

The role of operational quantum mechanics, quantum axiomatics and quantum structures in general is presented as a contribution to a compendium on quantum physics, its history and philosophy.

B. R. Conrad, W. G. Cullen, B. C. Riddick, E. D. Williams

Ultra-thin oxide (UTO) films were grown on Si(111) in ultrahigh vacuum at room temperature and characterized by scanning tunneling microscopy. The ultra-thin oxide films were then used as substrates for room temperature growth of pentacene. The apparent height of the first layer is 1.57 +/- 0.05 nm, indicating standing up pentacene grains in the thin-film ph

Paolo Aluffi, Matilde Marcolli

We give a general procedure to construct algebro-geometric Feynman rules, that is, characters of the Connes-Kreimer Hopf algebra of Feynman graphs that factor through a Grothendieck ring of immersed conical varieties, via the class of the complement of the affine graph hypersurface. In particular, this maps to the usual Grothendieck ring of varieties, defini

Jer-Shing Huang, Thorsten Feichtner, Paolo Biagioni, Bert Hecht

An experimentally realizable prototype nanophotonic circuit consisting of a receiving and an emitting nano antenna connected by a two-wire optical transmission line is studied using finite-difference time- and frequency-domain simulations. To optimize the coupling between nanophotonic circuit elements we apply impedance matching concepts in analogy to radio

Mats Persson

A simple expression for the conductance steps in the inelastic electron tunneling from spin excitations in a single magnetic atom adsorbed on a non-magnetic metal surfaces is derived. The inelastic coupling between the tunneling electron and the spin is via the exchange coupling and is treated in an impulsive approximation using the Tersoff-Hamann approximat

S. F. Timashev, Yu. S. Polyakov, R. M. Yulmetyev, S. A. Demin

The flicker-noise spectroscopy (FNS) approach is used to determine the dynamic characteristics of neuromagnetic responses by analyzing the magnetoencephalographic (MEG) signals recorded as the response of a group of control human subjects and a patient with photosensitive epilepsy (PSE) to equiluminant flickering stimuli of different color combinations. Para

Adam J. Burgasser

Brown dwarfs are natural clocks, cooling and dimming over time due to insufficient core fusion. They are also numerous and present in nearly all Galactic environments, making them potentially useful chronometers for a variety of Galactic studies. For this potential to be realized, however, precise and accurate ages for individual sources are required, a pros

A. Hosford, S. G. Ryan, A. E. Garcia Perez, J. E. Norris

The discovery of the Spite plateau in the abundances of 7Li for metal-poor stars led to the determination of an observationally deduced primordial lithium abundance. However, after the success of the Wilkinson Microwave Anisotropy Probe (WMAP) in determining the baryon density, OmegaBh^2, there was a discrepancy between observationally determined and theoret

Hiroyuki Nakaoka

Past studies of the Brauer group of a scheme tells us the importance of the interrelationship among Brauer groups of its finite étale coverings. In this paper, we consider these groups simultaneously, and construct an integrated object "Brauer-Mackey functor". We realize this as a {\it cohomological Mackey functor} on the Galois category of finite ét

S. M. A. Gama, G. Smirnov

We prove an existence and uniqueness of solution for the Cauchy problem of the simplest nonlinear short-wave equation, $u_{tx}=u-3u^{2}$, with periodic boundary condition.

Vincenzo Savona

We present an overview of the advances in the physics of polaritons in semiconductor microcavities, starting from their first discovery in 1992. After summarizing the research during the early years, when the basic optical properties were investigated, we describe the important results related to the phenomenon of parametric polariton scattering, highlightin

Luc Museur, Jean Pierre Petitet, Jean Pierre Michel, Wladimir Marine

We report on picosecond UV-laser processing of hexagonal boron nitride (hBN) at moderately high pressures above 500 bar. The main effect is specific to the ambient gas and laser pulse duration in the ablation regime: when samples are irradiated by 5 ps or 0.45 ps laser pulses in nitrogen gas environment, multiple nucleation of a new crystalline product - BN

Said Mesloub, Abdelouahab Mansour

A hyperbolic problem wich combines a classical(Dirichlet) and a non-local contraint is considered.The existence and uniqueness of strong solutions are proved,we use a functionnal analysis method based on a priori estimate and on the density of the range of the operator generated by the considered problem.

Andrei M. Bykov, Yury A. Uvarov, Donald C. Ellison

Non-thermal X-ray emission in some supernova remnants originates from synchrotron radiation of ultra-relativistic particles in turbulent magnetic fields. We address the effect of a random magnetic field on synchrotron emission images and spectra. A random magnetic field is simulated to construct synchrotron emission maps of a source with a steady distributio

Andreas Seifahrt, Sven Thorwirth, Henrik Beuther, Silvia Leurini

We combine multifrequency observations from the millimeter to near infrared wavelengths that demonstrate the spatial distributions of H2, CO, and NH3 emission, which are all manifestations of various shocks driven by outflows of deeply embedded sources in NGC6334I. In addition to the well-known northeast-southwest outflow we detect at least one more outflow

P. J. Baker, S. R. Giblin, F. L. Pratt, R. H. Liu

We report heat capacity measurements of the pnictide materials SmFeAsO$_{1-x}$F$_x$, NdFeAsO, LaFeAsO$_{1-x}$F$_x$ and LiFeAs. For SmFeAsO$_{1-x}$F$_x$, with x close to 0.1, we use 3 He measurements to demonstrate a transfer of entropy from the peak at TN to a previously unidentified ~2 K feature which grows with increasing doping. Our results on the Sm samp

M. C. Guclu

At LHC energies the Lorentz factor will be 3400 for the Pb + Pb collisions and the electromagnetic interactions will play important roles. Cross sections for the electromagnetic particle productions are very large and can not be ignored for the lifetimes of the beams and background. In this article, we are going to study some of the electromagnetic processes

Hiroshi Shinaoka, Masatoshi Imada

We study the Anderson-Hubbard model in the Hartree-Fock approximation and the exact diagonalization under the coexistence of short-range interaction and diagonal disorder. We show that there exist unconventional soft gaps, where the single-particle (SP) density of states (DOS) $A$ follows a scaling in energy $E$ as $A(E)\propto \exp[-(-γ\log |E-E_F|)^d]$ irr

Andre Sopczak, Khaled Bekhouche, Chris Damerell, Tim Greenshaw

Charge Coupled Devices (CCDs) have been successfully used in several high energy physics experiments over the past two decades. Their high spatial resolution and thin sensitive layers make them an excellent tool for studying short-lived particles. The Linear Collider Flavour Identification (LCFI) collaboration is developing Column-Parallel CCDs (CPCCDs) for

Sergey P. Kuznetsov

A system of two coupled non-autonomous oscillators is considered. Dynamics of complex amplitudes is governed by differential equations with periodic piecewise continuous dependence of the coefficients on time. The Poincaré map is derived explicitly. With exclusion of the overall phase, on which the evolution of other variables does not depend, the Poincaré m

Antoni Szczurek

I discuss mechanisms of exclusive production of mesons at high energies. Some illustrative examples for the FNAL Tevatron and CERN LHC as well as for lower energies are shown.

Marin Treselj, Andreas Seifahrt, Klaus-Werner Hodapp, Ana Bedalov

We present the first results of a large imaging survey to identify wide brown dwarf companions to stars within 10 pc. We have performed a deep (H-band limit ~ 19.0 mag), wide field (up to 16x16 arcmin) astrometric imaging campaign in two epochs around more than 230 nearby stars. Preliminary results show that the wide low-mass companion fraction is far lower

Andreas Seifahrt, Ansgar Reiners, Aleks Scholz, Gibor Basri

We present first results from a multi-object spectroscopy campaign in IC2602, the Hyades, the Pleiades, and the Coma cluster using VLT/FLAMES. We analysed the data for radial velocity, rotational velocity, and H-alpha activity. Here, we highlight three aspects of this study in the context of rotational braking and the rotation-activity relationship among low

Andreas Seifahrt, Christiane Helling, Adam J. Burgasser, Katelyn N. Allers

Observational facilities allow now the detection of optical and IR spectra of young M- and L-dwarfs. This enables empirical comparisons with old M- and L- dwarfs, and detailed studies in comparison with synthetic spectra. While classical stellar atmosphere physics seems perfectly appropriate for old M-dwarfs, more physical and chemical processes, cloud forma

Ye-Chuan Xu, Bang-Gui Liu

We propose a natural two-speed model for the phase dynamics of Si(111) 7$\times$7 phase transition to high temperature unreconstructed phase. We formulate the phase dynamics by using phase-field method and adaptive mesh refinement. Our simulated results show that a 7$\times$7 island decays with its shape kept unchanged, and its area decay rate is shown to be

D. F. Papadopoulos, Z. A. Anastassi, T. E. Simos

A new Runge-Kutta-Nyström method, with phase-lag of order infinity, for the integration of second-order periodic initial-value problems is developed in this paper. The new method is based on the Dormand and Prince Runge-Kutta-Nyström method of algebraic order four\cite{pa}. Numerical illustrations indicate that the new method is much more efficient than the

N. G. Tselios, Z. A. Anastassi, T. E. Simos

In this paper we present two new methods based on an implicit Runge-Kutta method Gauss which is of algebraic order fourth and has two stages: the first one has zero dispersion and the second one has zero dispersion and zero dissipation. The efficiency of these methods is measured while integrating the radial Schrödinger equation and other well known initial

D. S. Vlachos, Z. A. Anastassi, T. E. Simos

In this work we introduce a new family of 14-steps linear multistep methods for the integration of the Schrödinger equation. The new methods are phase fitted but they are designed in order to improve the frequency tolerance. This is achieved by eliminating the first derivatives of the phase lag function at the fitted frequency forcing the phase lag function

Maciej Ulas

In this paper we give solutions of certain diophantine equations related to triangular and tetrahedral numbers and propose several problems connected with these numbers. The material of this paper was presented in part at the 11th International Workshop for Young Mathematicians - NUMBER THEORY, Kraków, 14th-20th september 2008.

D. S. Vlachos, Z. A. Anastassi, T. E. Simos

In this work we introduce a new family of twelve-step linear multistep methods for the integration of the Schrödinger equation. The new methods are constructed by adopting a new methodology which improves the phase lag characteristics by vanishing both the phase lag function and its first derivatives at a specific frequency. This results in decreasing the se

William J. Martin, Hajime Tanaka

Association schemes were originally introduced by Bose and his co-workers in the design of statistical experiments. Since that point of inception, the concept has proved useful in the study of group actions, in algebraic graph theory, in algebraic coding theory, and in areas as far afield as knot theory and numerical integration. This branch of the theory, v

Peter Collas, David Klein

We prove a theorem that gives an easily verifiable necessary and sufficient condition for a reference frame with fixed spacelike coordinates to be nonrotating in the sense of Walker. Applications are discussed.

Z. A. Anastassi, D. S. Vlachos, T. E. Simos

In the present paper we introduce a new methodology for the construction of numerical methods for the approximate solution of the one-dimensional Schrödinger equation. The new methodology is based on the requirement of vanishing the phase-lag and its derivatives. The efficiency of the new methodology is proved via error analysis and numerical applications.

G. A. Panopoulos, Z. A. Anastassi, T. E. Simos

In this paper we present two optimized eight-step symmetric implicit methods with phase-lag order ten and infinite (phase-fitted). The methods are constructed to solve numerically the radial time-independent Schrödinger equation with the use of the Woods-Saxon potential. They can also be used to integrate related IVPs with oscillating solutions such as orbit

Z. A. Anastassi, D. S. Vlachos, T. E. Simos

We construct a family of two new optimized explicit Runge-Kutta methods with zero phase-lag and derivatives for the numerical solution of the time-independent radial Schrödinger equation and related ordinary differential equations with oscillating solutions. The numerical results show the superiority of the new technique of nullifying both the phase-lag and

Peter Collas, David Klein

We exhibit timelike geodesic paths for a metric, introduced by Bonnor [11] and considered also by Steadman [13], and show that coordinate time runs backward along a portion of these geodesics.

Ralf Gehrke, Karsten Reuter

We present a systematic performance analysis of first-principles basin-hopping (BH) runs, with the target to identify all low-energy isomers of small Si and Cu clusters described within density-functional theory. As representative and widely employed move classes we focus on single-particle and collective moves, in which one or all atoms in the cluster at on

Kuo-Ying Wang

The outbreaks of the severe acute respiratory syndrome (SARS) epidemic in 2003 resulted in unprecedented impacts on people's daily life. One of the most significant impacts to people is the risk of contacting SARS while engaging daily routine activity. In this work we use data from daily underground ridership in Taipei and daily reported SARS cases in Ta

Jiun-Haw Chu, James G. Analytis, Chris Kucharczyk, Ian R. Fisher

Systematic measurements of the resistivity, heat capacity, susceptibility and Hall coefficient are presented for single crystal samples of the electron-doped superconductor Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. These data delineate an $x-T$ phase diagram in which the single magnetic/structural phase transition that is observed for undoped BaFe$_2$As$_2$ at 134 K a

Meheboob Alam, Priyanka Shukla, Stefan Luding

The linear stability analysis of an uniform shear flow of granular materials is revisited using several cases of a Navier-Stokes'-level constitutive model in which we incorporate the global equation of states for pressure and thermal conductivity (which are accurate up-to the maximum packing density $ν_{m}$) and the shear viscosity is allowed to diverge

Ashish Goel, Michael Kapralov, Sanjeev Khanna

In this paper we further investigate the well-studied problem of finding a perfect matching in a regular bipartite graph. The first non-trivial algorithm, with running time $O(mn)$, dates back to König's work in 1916 (here $m=nd$ is the number of edges in the graph, $2n$ is the number of vertices, and $d$ is the degree of each node). The currently most e

Li-Fang Zhu, Bang-Gui Liu

A ternary ferrimagnetic half-metal, constructed through substituting 25% Fe for Mn in zincblende semiconductor MnTe, is predicted in terms of accurate first-principles calculations. It has a large half-metallic (HM) gap of 0.54eV and its ferrimagnetic order is very stable against other magnetic fluctuations. The HM ferrimagnetism is formed because the comple

Zhihao Ma, Sen Zhu

Quantum effects play an important role in quantum measurement theory. The set of all quantum effects can be organized into an algebraical structure called effect algebra. In this paper, we study various topologies on the Hilbert space effect algebra and the projection lattice effect algebra.

Eric R. Hudson

We propose a new method for the production of ultracold molecular ions. This method utilizes sympathetic cooling due to the strong collisions between appropriately chosen molecular ions and laser-cooled neutral atoms to realize ultracold, internal ground-state molecular ions. In contrast to other experiments producing cold molecular ions, our proposed method

Cheng-Liang Jiao, Li Xue, Wei-Min Gu, Ju-Fu Lu

We show that there exists a maximal possible accretion rate, beyond which global slim disk solutions cannot be constructed because in the vertical direction the gravitational force would be unable to balance the pressure force to gather the accreted matter. The principle for this restriction is the same as that for the Eddington luminosity and the correspond

Matthew Kahle

An old theorem of Alexander Soifer's is the following: Given five points in a triangle of unit area, there must exist some three of them which form a triangle of area 1/4 or less. It is easy to check that this is not true if "five" is replaced by "four", but can the theorem be improved in any other way? We discuss in this article two diff

Eric Steinbring, Jean-Charles Cuillandre, Eugene Magnier

Nighttime sky transparency statistics on Mauna Kea are reported based on data from the Canada-France-Hawaii Telescope SkyProbe monitor. We focus on the period beginning with the start of MegaCam wide-field optical imager operations in 2003, and continuing for almost three years. Skies were clear enough to observe on 76% of those nights; attenuations were les

Dean M. Townsley, Boris T. Gaensicke

We review the most decisive currently available measurements of the surface effective temperatures, Teff, of white dwarf (WD) primaries in cataclysmic variables (CVs) during accretion quiescence, and use these as a diagnostic for their time averaged accretion rate, <Mdot>. Using time-dependent calculations of the WD envelope, we investigate the sensitivity o

Andrew D. Box

In the Minimal Supersymmetric Standard Model (MSSM), there are numerous sources of flavour-violation in addition to the usual Kobayashi-Maskawa mixing matrix of the Standard Model. We reexamine the renormalisation group equations (RGEs) with a view to investigating flavour effects in a supersymmetric theory with an arbitrary flavour structure at some high sc