Results for "M. Doleans"

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An introduction to Multitrace Formulations and Associated Domain Decomposition SolversMay 14 2016Multitrace formulations (MTFs) are based on a decomposition of the problem domain into subdomains, and thus domain decomposition solvers are of interest. The fully rigorous mathematical MTF can however be daunting for the non-specialist. We introduce ... More
Stabilised hybrid discontinuous Galerkin methods for the Stokes problem with non-standard boundary conditionsOct 30 2018In several studies it has been observed that, when using stabilised $\mathbb{P}_k^{}\times\mathbb{P}_k^{}$ elements for both velocity and pressure, the error for the pressure is smaller, or even of a higher order in some cases, than the one obtained when ... More
Overlapping Schwarz preconditioners for high order edge finite elements: application to the time-harmonic Maxwell's equationsMay 15 2016Developing high-speed microwave field measurement systems for wireless, medical or engineering industries is a challenging task. These systems generally rely on high frequency (from 1 to 60GHz) electromagnetic wave propagation in waveguides. High order ... More
Parallel preconditioners for high order discretizations arising from full system modeling for brain microwave imagingMay 15 2016Jun 03 2016This paper combines the use of high order finite element methods with parallel preconditioners of domain decomposition type for solving electromagnetic problems arising from brain microwave imaging. The numerical algorithms involved in such complex imaging ... More
Nonlinear Preconditioning: How to use a Nonlinear Schwarz Method to Precondition Newton's MethodMay 14 2016For linear problems, domain decomposition methods can be used directly as iterative solvers, but also as preconditioners for Krylov methods. In practice, Krylov acceleration is almost always used, since the Krylov method finds a much better residual polynomial ... More
A New Domain Decomposition Method for the Compressible Euler EquationsFeb 22 2005In this work we design a new domain decomposition method for the Euler equations in 2 dimensions. The basis is the equivalence via the Smith factorization with a third order scalar equation to whom we can apply an algorithm inspired from the Robin-Robin ... More
Low RF power plasma ignition and detection for in-situ cleaning of 1.3 GHz 9-cell cavitiesFeb 08 2019Superconducting Radio Frequency (SRF) cavities performance preservation is crucial, from vertical test to accelerator operation. Field Emission (FE) is still one of the performance limiting factors to overcome and plasma cleaning has been proven successful ... More
Efficient Design Scheme of Superconducting CavityAug 21 2000For many next-generation high intensity proton accelerator applications including the Spallation Neutron Source (SNS), superconducting (SC) RF provides the technology of choice for the linac. In designing the superconducting cavity, several features, ... More
Optimized Schwarz Methods for Maxwell equationsOct 17 2006Sep 26 2008Over the last two decades, classical Schwarz methods have been extended to systems of hyperbolic partial differential equations, and it was observed that the classical Schwarz method can be convergent even without overlap in certain cases. This is in ... More
New constructions of domain decomposition methods for systems of PDEsFeb 23 2005We propose new domain decomposition methods for systems of partial differential equations in two and three dimensions. The algorithms are derived with the help of the Smith factorization of the operator. This could also be validated by numerical experiments. ... More
Numerical assessment of two-level domain decomposition preconditioners for incompressible Stokes and elasticity equationsJun 29 2017Solving the linear elasticity and Stokes equations by an optimal domain decomposition method derived algebraically involves the use of non standard interface conditions. The one-level domain decomposition preconditioners are based on the solution of local ... More
Can classical Schwarz methods for time-harmonic elastic waves converge?Oct 31 2018We show that applying a classical Schwarz method to the time harmonic Navier equations, which are an important model for linear elasticity, leads in general to a divergent method for low to intermediate frequencies. This is even worse than for Helmholtz ... More
Microwave Tomographic Imaging of Cerebrovascular Accidents by Using High-Performance ComputingJul 09 2016The motivation of this work is the detection of cerebrovascular accidents by microwave tomographic imaging. This requires the solution of an inverse problem relying on a minimization algorithm (for example, gradient-based), where successive iterations ... More
An example of explicit implementation strategy and preconditioning for the high order edge finite elements applied to the time-harmonic Maxwell's equationsNov 14 2017Nov 18 2017In this paper we focus on high order finite element approximations of the electric field combined with suitable preconditioners, to solve the time-harmonic Maxwell's equations in waveguide configurations.The implementation of high order curl-conforming ... More
Explicit implementation strategy of high order edge finite elements and Schwarz preconditioning for the time-harmonic Maxwell's equationsMay 15 2016May 14 2017In this paper we focus on high order finite element approximations of the electric field combined with suitable preconditioners, to solve the time-harmonic Maxwell's equations in waveguide configurations. The implementation of high order curl-conforming ... More
Solution of the time-harmonic Maxwell equations using discontinuous Galerkin methodsOct 17 2006Apr 11 2007We present numerical results concerning the solution of the time-harmonic Maxwell's equations discretized by discontinuous Galerkin methods. In particular, a numerical study of the convergence, which compares different strategies proposed in the literature ... More
A two-level domain-decomposition preconditioner for the time-harmonic Maxwell's equationsMay 23 2017Feb 21 2018The construction of fast iterative solvers for the indefinite time-harmonic Maxwell's system at mid- to high-frequency is a problem of great current interest. Some of the difficulties that arise are similar to those encountered in the case of the mid- ... More
Domain decomposition preconditioning for the high-frequency time-harmonic Maxwell equations with absorptionNov 10 2017Oct 04 2018This paper rigorously analyses preconditioners for the time-harmonic Maxwell equations with absorption, where the PDE is discretised using curl-conforming finite-element methods of fixed, arbitrary order and the preconditioner is constructed using Additive ... More
Two-level preconditioners for the Helmholtz equationMay 23 2017Feb 21 2018In this paper we compare numerically two different coarse space definitions for two-level domain decomposition preconditioners for the Helmholtz equation, both in two and three dimensions. While we solve the pure Helmholtz problem without absorption, ... More
Hybrid discontinuous Galerkin discretisation and domain decomposition preconditioners for the Stokes problemOct 28 2016Aug 18 2017Solving the Stokes equation by an optimal domain decomposition method derived algebraically involves the use of non standard interface conditions whose discretisation is not trivial. For this reason the use of approximation methods such as hybrid discontinuous ... More
Hybrid discontinuous Galerkin discretisation and preconditioning of the Stokes problem with non standard boundary conditionsOct 28 2016Solving the Stokes equation by an optimal domain decomposition method derived algebraically involves the use of non standard interface conditions whose discretisation is not trivial. For this reason the use of approximation methods such as hybrid discontinuous ... More
Domain decomposition preconditioning for the high-frequency time-harmonic Maxwell equations with absorptionNov 10 2017Mar 06 2019This paper rigorously analyses preconditioners for the time-harmonic Maxwell equations with absorption, where the PDE is discretised using curl-conforming finite-element methods of fixed, arbitrary order and the preconditioner is constructed using Additive ... More
Neutralino-Nucleon Scattering RevisitedJul 01 1993We present a detailed discussion of the elastic scattering of a supersymmetric neutralino off a nucleon or nucleus, with emphasis on the spin--independent interaction. We carefully treat QCD effects on the squark exchange contribution. In particular, ... More
Quantum information processing: The case of vanishing interaction energyOct 27 2002We investigate the rate of operation of quantum "black boxes" ("oracles") and point out the possibility of performing an operation by a quantum "oracle" whose average energy equals zero. This counterintuitive result not only presents a generalization ... More
Self-Organized Topological State with Majorana FermionsJul 08 2013Nov 06 2013Topological phases, quite generally, are difficult to come by. They either occur under rather extreme conditions (e.g. the quantum Hall liquids, which require high sample purity, strong magnetic fields and low temperatures) or demand fine tuning of system ... More
Spin Response of Electrons on the Surface of a Topological InsulatorJan 11 2012The surface of a topological insulator hosts a very special form of a quasi-two dimensional metallic system when it is embedded in a topologically trivial medium like the vacuum. The electronic properties of this unusual 2D metal are distinct in many ... More
Massive Neutrino in Non-commutative Space-timeDec 24 2007Apr 01 2008We consider the noncommutative standard model based on $SU(3)\times SU(2)\times U(1)$. We study the gauge transformation of right handed neutrino and its direct interaction with photon in the noncommutative space-time. We show that the massive Dirac neutrinos, ... More
Infinite order excitonic Bloch equations for asymmetric nanostructuresJul 04 2003We present a new exciton-based formalism for calculating the coherent response of asymmetric semiconductor multiple quantum well structures to ultra-short optical pulses valid to infinite order in the optical field and including the self-generated intraband ... More
Scalar StoponiumAug 18 1993We study the decays of a scalar \stst\ bound state \sigst, where \st\ is the lighter stop eigenstate. If \st\ has no tree--level 2--body decays, the dominant decay modes of \sigst\ are $gg$ or, if $m_h < \mst \ll \mstt$, a pair of light scalar Higgs bosons ... More
A new signal for scalar top bound state productionOct 01 1993We study the production and decay of a scalar \stst\ bound state \sigst\ at hadron supercolliders, where \st\ is the lighter stop eigenstate. If \st\ has no tree--level 2--body decays, the dominant decay modes of \sigst\ are $gg$ or, if $m_h < \mst \ll ... More
Photon Neutrino Scattering in Non-Commutative SpaceNov 04 2005Jan 19 2006We extend the non-commutative standard model based on the minimal $SU(3)\times SU(2)\times U(1)$ gauge group to include the interaction of photon with neutrino. We show that, in the gauge invariant manner, only the right handed neutrino can directly couple ... More
Lorentz Conserving Noncommutative Standard ModelMar 29 2007May 10 2007We consider Lorentz conserving noncommutative field theory to construct the Lorentz conserving noncommutative standard model based on the gauge group $SU(3)\times SU(2)\times U(1)$. We obtain the enveloping algebra-valued of Higgs field up to the second ... More
Shelving and Probe Efficiency in Trapped Ion ExperimentsFeb 24 2014A generalized probe sequence typical of trapped ion experiments using shelving is studied. Detection efficiency is analyzed for finite shelved state lifetimes and using multi-modal count distributions. Multi-modal distributions are more appropriate for ... More
The Neutralino Relic Density in Minimal N=1 SupergravityJul 10 1992We compute the cosmic relic (dark matter) density of the lightest supersymmetric particle (LSP) in the framework of minimal $N=1$ Supergravity models with radiative breaking of the electroweak gauge symmetry. To this end, we re--calculate the cross sections ... More
Quantization and $2π$ Periodicity of the Axion Action in Topological InsulatorsJun 17 2010Nov 10 2010The Lagrangian describing the bulk electromagnetic response of a three-dimensional strong topological insulator contains a topological `axion' term of the form '\theta E dot B'. It is often stated (without proof) that the corresponding action is quantized ... More
Production and Decay of Scalar Stoponium Bound StatesDec 02 1993In this paper we discuss possible signatures for the production of scalar \stst\ (stoponium) bound states \sigst\ at hadron colliders, where \st\ is the lighter scalar top eigenstate. We first study the decay of \sigst; explicit expressions are given ... More
Parton Model in Lorentz Invariant Non-Commutative SpaceMay 26 2004Aug 22 2004We consider the Lorentz invariant non-commutative QED and complete the Feynman rules for the theory up to the order $\theta^2$. In the Lorentz invariant version of the non-commutative QED the particles with fractional charges can be also considered. We ... More
Electromagnetic Response of Weyl SemimetalsMar 22 2013Jun 27 2013It has been suggested recently, based on subtle field-theoretical considerations, that the electromagnetic response of Weyl semimetals and the closely related Weyl insulators can be characterized by an axion term E.B with space and time dependent axion ... More
The Charm Quark Contribution to the Proton Structure FunctionOct 14 2006Dec 27 2006The charm quark structure function $F^c_2$ and the longitudinal structure function $F_l^p$ are directly sensitive to the gluon content of proton and therefore are crucial in understanding of proton structure function, in particular at low momentum transfer ... More
The decay of singlet scalar dark matter to unparticle and photonMay 06 2008We consider the unparticle physics introduced by Georgi and show that if the standard model is extended to include a singlet scalar as a dark matter candidate, there is a channel which leads to its decay to photon and unparticle. We calculate the decay ... More
An Estimate of Referent of Noun Phrases in Japanese SentencesDec 13 1999In machine translation and man-machine dialogue, it is important to clarify referents of noun phrases. We present a method for determining the referents of noun phrases in Japanese sentences by using the referential properties, modifiers, and possessors ... More
On the canonically invariant calculation of Maslov indicesMay 30 2003Jun 18 2003After a short review of various ways to calculate the Maslov index appearing in semiclassical Gutzwiller type trace formulae, we discuss a coordinate-independent and canonically invariant formulation recently proposed by A Sugita (2000, 2001). We give ... More
Viscosity in cosmological simulations of clusters of galaxiesDec 06 2005The physics of the intracluster medium, in particular the values for the thermal conductivity and the viscosity are largely unknown and subject to an ongoing debate. Here, we study the effect of viscosity on the thermal state of the intracluster medium ... More
Evolution of the Internal Dynamics of Galaxy ClustersOct 16 2000We consider a sample of 51 distant galaxy clusters at 0.15<z<0.9 (<z> about 0.3), each cluster having at least 10 galaxies with available redshift in the literature. We select member galaxies, analyze the velocity dispersion profiles, and evaluate in ... More
Higher-order QCD corrections to supersymmetric particle production and decay at the LHCJan 27 2015Feb 23 2015We review recent results on higher-order calculations to squark and gluino production and decay at the LHC, as obtained within the Collaborative Research Centre / Transregio 9 "Computational Particle Physics". In particular, we discuss inclusive cross ... More
Supersymmetry and Future CollidersJul 28 1999In this talk, I review precision SUSY study at LHC and TeV scale e+e- linear colliders (LC). We discuss the study of the 3 body decay of the second lightest neutralino \chi^0_2--> \chi^0_1 ll or the 2 body decay \chi^0_2-->\tilde{l}l at LHC. In the former ... More
Two-loop mixing of dimension-five flavor-changing operatorsSep 30 1994Oct 17 1994We calculate the two-loop QCD mixing of the dimension-five flavor-changing operators that arise in the Standard Model after integrating out the $W$, $Z$ and Higgs bosons and the top-quark, i.e.~the mixing among gluonic and photonic magnetic moment operators. ... More
The Vector Meson Mass in Chiral Effective Field TheoryMay 01 2014A brief overview of Quantum Chromodynamics (QCD) as a non-Abelian gauge field theory, including symmetries and formalism of interest, will precede a focused discussion on the use of an Effective Field Theory (EFT) as a low energy perturbative expansion ... More
How much can supergravity teach us about microscopic features of BPS black holes?Dec 20 2000We review recent results in the study of regular four dimensional BPS black holes in toroidally compactified type II (or M) theory. We discuss the generating solution for this kind of black holes, its microscopic description(s), and compute the corresponding ... More
Regular BPS black holes: macroscopic and microscopic description of the generating solutionFeb 23 2000Jun 06 2000In this paper we construct the BPS black hole generating solution of toroidally compactified string (and M) theory, giving for it both the macroscopic and microscopic description. Choosing a proper U-duality gauge the latter will be given by a bound state ... More
Comment on ``A Comparison Between Broad Histogram and Multicanonical Methods''Nov 30 2000Jan 08 2001A recent paper by A. R. Lima, P. M. C. de Oliveira, and T. J. P. Penna [cond-mat/0002176; J. Stat. Phys. 99:691 (2000)], seems to contain at least two mistakes which deserve comment, one concerning the numerical data, the other being of a conceptual kind. ... More
Geometry of the Grosse-Wulkenhaar ModelFeb 19 2009Feb 22 2010We define a two-dimensional noncommutative space as a limit of finite-matrix spaces which have space-time dimension three. We show that on such space the Grosse-Wulkenhaar (renormalizable) action has natural interpretation as the action for the scalar ... More
QCD Coupling Constant at Finite TemperatureMay 02 1996We work out the method for evaluating the QCD coupling constant at finite temperature ($T$) by making use of the finite $T$ renormalization group equation up to the one-loop order on the basis of the background field method with the imaginary time formalism. ... More
Direct evidence for a characteristic dynamic lengthscale in the intermediate phase of glassesJul 23 2010AC conductivity spectra of xAgI-(1-x)AgPO$_3$ fast ion conducting glasses spanning the flexible, intermediate (isostatically rigid) and stressed rigid phases are analyzed. The rescaled frequency dependent spectra are mapped into time-dependent mean square ... More
Andreev reflection at QGP/CFL interfaceJan 23 2002Apr 12 2002In this letter we address the question of the phenomena of Andreev reflection between the cold quark-gluon plasma phase and CFL color superconductor. We show that there are two different types of reflections connected to the structure of the CFL phase. ... More
Multi-particle correlations of an oscillating scattererNov 16 2005Using multi-particle distribution functions we calculate the correlations produced by a periodically driven scatterer in a system of noninteracting electrons at zero temperature. The multi-particle correlations due to a quantum exchange effect are expressed ... More
Quantum pumping: Coherent Rings versus Open ConductorsJul 28 2003We examine adiabatic quantum pumping generated by an oscillating scatterer embedded in a one-dimensional ballistic ring and compare it with pumping caused by the same scatterer connected to external reservoirs. The pumped current for an open conductor, ... More
The helium abundances in HgMn and normal starsJul 26 2004The parameter-free model of diffusion in the atmospheres of HgMn stars (Michaud 1986; Michaud et al 1979) predicts that helium should sink below the He II ionization zone in order that diffusion of other elements may take place, and that all HgMn stars ... More
The universal effective potential for three-dimensional massive scalar field theory from the Monte Carlo study of the Ising modelJan 29 1994We study the low-energy effective action $S_{eff}[\varphi]$ for the one-component real scalar field theory in three Euclidean dimensions in the symmetric phase, concentrating on its static part --- effective potential $V_{eff}(\varphi)$. It characterizes ... More
Ultra-high Energy Predictions of Proton-Air Cross Sections from Accelerator Data: an UpdateSep 13 2011At $\sqrt s = 57\pm 7$ TeV, the Pierre Auger Observatory (PAO) collaboration has recently measured the proton-air inelastic production cross section $\sigma_{\rm p-air}$. Assuming a helium contamination of 25%, they subtracted 30 mb from their measured ... More
Ultra-high Energy Predictions of proton-air Cross Sections from Accelerator DataMay 21 2007We predict $\sigma_{p{-}\rm air}^{\rm prod}$, the proton--air inelastic production cross section, at $pp$ center-of-mass energies $2\le\sqrt s \le 100000$ TeV, using high energy predictions from a saturated Froissart bound parameterization of accelerator ... More
Event-by-Event Fluctuations in Particle Multiplicities and Transverse Energy Produced in 158.A GeV Pb+Pb collisionsAug 31 2001Mar 20 2002Event-by-event fluctuations in the multiplicities of charged particles and photons, and the total transverse energy in 158$\cdot A$ GeV Pb+Pb collisions are studied for a wide range of centralities. For narrow centrality bins the multiplicity and transverse ... More
Transverse mass distributions of neutral pions from $^{208}$Pb-induced reactions at 158$\cdot A$ GeVAug 03 2001Dec 20 2001Results on transverse mass spectra of neutral pions measured at central rapidity are presented for impact parameter selected 158$\cdot A$ GeV Pb + Pb, and Pb + Nb collisions. The distributions cover the range $0.5 \mathrm{GeV}/c^{2} \le m_{T} - m_{0} ... More
The clustering properties of the first galaxiesNov 17 2009Jun 01 2010We study the clustering properties of the first galaxies formed in the Universe. We find that, due to chemical enrichment of the inter-stellar medium by isolated Population III stars formed in mini-halos at redshift z>30, the (chronologically) first galaxies ... More
Dust absorption along the line of sight for high-redshift objectsJul 10 2006We estimate the optical depth distribution of dust present in absorption systems along the line of sight of high redshift galaxies and the resulting reddening. We characterize the probability distribution of the transmission to a given redshift and the ... More
Neutral gas density in Damped Lyman Alpha systemsJun 28 2006We estimate the intrinsic neutral gas density in Damped Lyman Alpha systems ($\Omega_{HI}^{(DLA)}$) in the redshift range $ 2.2 \lesssim z \lesssim 5$ from the DLA SDSS DR_3 sample of optically selected quasars. We take into account self-consistently ... More
The very first Pop III stars and their relation to bright z~6 quasarsOct 04 2007We discuss the link between dark matter halos hosting the first PopIII stars formed at redshift z > 40 and the rare, massive, halos that are generally considered to host bright z~6 quasars. We show that within the typical volume occupied by one bright ... More
A New Approach to the Internal Calibration of Reverberation Mapping SpectraSep 13 2016We present a new procedure for the internal (night-to-night) calibration of time series spectra, with specific applications to optical AGN reverberation mapping data. The traditional calibration technique assumes that the narrow [OIII]$\lambda$5007 emission ... More
Two-photon annihilation of singlet cold dark matters due to noncommutative space-timeOct 01 2012Detecting the cosmic rays, in particular gamma-ray, coming from the dark matter annihilation or decay is an indirect way to survey the nature of the dark matter. In the commutative space-time, the annihilation of the dark matter candidates (WIMPs) to ... More
Riemann-Hilbert approach to multi-time processes; the Airy and the Pearcey caseApr 26 2011We prove that matrix Fredholm determinants related to multi-time processes can be expressed in terms of determinants of integrable kernels \`a la Its-Izergin-Korepin-Slavnov (IIKS) and hence related to suitable Riemann-Hilbert problems, thus extending ... More
The transition between the gap probabilities from the Pearcey to the Airy process; a Riemann-Hilbert approachMay 21 2010Mar 31 2011We consider the gap probability for the Pearcey and Airy processes; we set up a Riemann--Hilbert approach (different from the standard one) whereby the asymptotic analysis for large gap/large time of the Pearcey process is shown to factorize into two ... More
Quark Droplets in the NJL Mean FieldJul 20 1998We study the conditions for the existence of stable quark matter in the Nambu--Jona-Lasinio mean field at zero temperature and discuss its interpretation.
Paracontrolled quasilinear SPDEsOct 25 2016We introduce a non-linear paracontrolled calculus and use it to renormalise a class of singular SPDEs including certain quasilinear variants of the periodic two dimensional parabolic Anderson model.
Fractional Supersymmetry as a Superposition of Ordinary SupersymmetrySep 05 2005It is shown how to derive fractional supersymmetric quantum mechanics of order k as a superposition of k-1 copies of ordinary supersymmetric quantum mechanics.
Two-Photon Laser Spectroscopy of Transition Ions in Crystals: Inter- Configurational TransitionsNov 18 1998Symmetry adaptation techniques are applied to the determination of the intensity of two-photon absorption transitions, between Stark levels of configurations with opposite parities, for transition ions in finite symmetry environments. The equivalence ... More
Symmetry Adaptation and Two-Photon Spectroscopy of Ions in Molecular or Solid-State Finite SymmetryNov 18 1998Finite symmetry adaptation techniques are applied to the determination of the intensity strength of two-photon transitions for ions with one partly-filled shell nl in crystalline environments of symmetry G. We treat the case of intra- configurational ... More
Statistical Mechanics of $qp$-Bosons in $D$ DimensionsDec 06 1995Jan 02 1996This paper is concerned with statistical properties of a gas of $qp$-bosons without interaction. Some thermodynamical functions for such a system in $D$ dimensions are derived. Bose-Einstein condensation is discussed in terms of the parameters $q$ and ... More
171Yb+ System Stability, 5D3/2 Hyperfine State Detection Efficiency and F=2 LifetimeOct 09 2013A data acquisition system is described that is designed to stabilize cooling and probe rates to maximize detection sensitivity and minimize possible systematic errors due to correlations between drifting experimental conditions and varying drive parameters. ... More
From the microcosm of the atomic nuclei to the macrocosm of the starsJun 08 2007A necessary condition for the reliable modelling of the structure or evolution of the stars and of their concomitant nucleosynthesis is the availability of good quality nuclear data in a very wide area of the chart of nuclides. This short review presents ... More
Bound States and Instabilities of VorticesMar 28 1995We examine the spectrum of small perturbations around global and local (gauge) abelian vortices, using simple numerical matrix techniques. The results are of interest for both cosmic strings and for their condensed matter analogues, superfluid and superconducting ... More
Coincidence of Universe age in $Λ$CDM and Milne cosmologiesMay 08 2006Nov 09 2006The age of the Universe in the $\Lambda$CDM cosmology with $\Omega_{matter}=0.26$ and $\Omega_{\Lambda}=0.74$ is the same as in the Milne cosmology which correspods to an almost empty universe. In both cases it is a reciprocal Hubble constant, $1/H_0$, ... More
A non-perturbative treatment of the generalized Su-Schreiffer-Heeger Hamiltonian on a dimerOct 11 2000Starting from the Hamiltonian for a dimer which includes all the electronic and electron-phonon terms consistent with a non-degenerate orbital, by a sequence of displacement and squeezing transformation we obtain an effective polaronic Hamiltonian. The ... More
A Study of Cyg OB2: Pointing the Way Towards Finding Our Galaxy's Super Star ClustersJul 30 2003New optical MK classification spectra have been obtained for 14 OB star candidates identified by Comeron et al. (2002) and presumed to be possible members of the Cyg OB2 cluster. All 14 candidate OB stars observed are indeed early-type stars, strongly ... More
Invariant construction of solutions to Einstein's field equations - LRS perfect fluids IIAug 24 1998The properties of LRS class II perfect fluid space-times are analyzed using the description of geometries in terms of the Riemann tensor and a finite number of its covariant derivatives. In this manner it is straightforward to obtain the plane and hyperbolic ... More
Large $\pt$ Hadroproduction of Heavy QuarksNov 10 1993The production of heavy quarks at large $\pt$ ($\pt\gg m$) in hadronic collisions is considered. The analysis is carried out in the framework of perturbative fragmentation functions, thereby allowing a resummation at the NLO level of final state large ... More
A remark on sphaleron erasure of baryon asymmetryNov 24 1999Jan 20 2000We complete an existing result for how the baryon asymmetry left over after a period of full thermal equilibrium depends on different lepton asymmetries.
An all-order discontinuity at the electroweak phase transitionJul 27 1999Aug 27 1999We define a non-local gauge-invariant Green's function which can distinguish between the symmetric (confinement) and broken (Higgs) phases of the hot SU(2)xU(1) electroweak theory to all orders in the perturbative expansion. It is related to the coupling ... More
Why are dense planetary rings only found between 8 and 20 AU?Feb 26 2015Mar 13 2015The recent discovery of dense rings around the Centaur Chariklo (and possibly Chiron) reveals that complete dense planetary rings are not only found around Saturn and Uranus, but also around small bodies orbiting in the vicinity of those giant planets. ... More
The global properties of all variety of AGNDec 13 2004Active Galactic Nuclei (AGN) have been a challenging field of research for the past six decades. Nevertheless, many questions still remain unanswered today, regardless of the tremendous theoretical and technological advances. In this brief review I propose ... More
Insights into the High Temperature Superconducting Cuprates from Resonant Inelastic X-ray ScatteringFeb 21 2014Apr 04 2014Recent improvements in instrumentation have established resonant inelastic x-ray scattering (RIXS) as a valuable new probe of the magnetic excitations in the cuprates. This article introduces RIXS, focusing on the Cu $L_3$ resonance, and reviews recent ... More
Higgs Production by Gluon initiated Weak Boson FusionSep 17 2007The gluon-gluon induced terms for Higgs production through weak-boson fusion are calculated. They form a finite and gauge-invariant subset of the NNLO corrections in the strong coupling constant. This is also the lowest order with sizeable t-channel colour ... More
Vafa-Witten theorem and Lee-Yang singularitiesApr 16 2002Dec 18 2009We prove the analyticity of the finite volume QCD partition function for complex values of the theta-vacuum parameter. The absence of singularities different from Lee-Yang zeros only permits ^ cusp singularities in the vacuum energy density and never ... More
Quasicrystal approximants with novel compositions and structuresFeb 13 2004We identify several new quasicrystal approximants in alloy systems in which quasicrystals have not been previously reported. Some occur in alloys with large size contrast between the constituent elements, either containing small Boron atoms, or large ... More
First-principles prediction of a decagonal quasicrystal containing boronMay 14 2004We interpret experimentally known B-Mg-Ru crystals as quasicrystal approximants. These approximant structures imply a deterministic decoration of tiles by atoms that can be extended quasiperiodically. Experimentally observed structural disorder corresponds ... More
Non-Abelian Stokes Theorem for Wilson Loops Associated with General Gauge GroupsJul 09 1999Dec 08 1999A formula constituting the non-Abelian Stokes theorem for general semi-simple compact gauge groups is presented. The formula involves a path integral over a group space and is applicable to Wilson loop variables irrespective of the topology of loops. ... More
Gravitational double layersFeb 05 2014Feb 20 2014I analyze the properties of thin shells through which the scalar curvature R is discontinuous in gravity theories with R + R^2 Lagrangian on the bulk. These shells/domain walls are of a new kind because they possess, in addition to the standard energy-momentum ... More
Remarks on the stability operator for MOTSNov 26 2012Small deformations of marginally outer trapped surfaces (MOTS) are studied by using the stability operator introduced by Andersson-Mars-Simon. Novel formulae for the principal eigenvalue are presented. A characterization of the many marginally outer trapped ... More
Classification of spacelike surfaces in spacetimeMar 22 2007A classification of 2-dimensional surfaces imbedded in spacetime is presented, according to the algebraic properties of their shape tensor. The classification has five levels, and provides among other things a refinement of the concepts of trapped, umbilical ... More
A singularity theorem based on spatial averagesOct 26 2006May 06 2007Inspired by Raychaudhuri's work, and using the equation named after him as a basic ingredient, a new singularity theorem is proved. Open non-rotating everywhere expanding universes with non-vanishing spatial average of the matter variables are severely ... More
Volume modulus inflation and a low scale of SUSY breakingFeb 07 2008Jul 08 2008The relation between the Hubble constant and the scale of supersymmetry breaking is investigated in models of inflation dominated by a string modulus. Usually in this kind of models the gravitino mass is of the same order of magnitude as the Hubble constant ... More