Results for "Thomas Teubner"

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Top Quark PhysicsApr 06 1999In this contribution I review the physics of top quarks at a future Linear Collider. Main emphasis is put on the process e+ e- to ttbar close to threshold. Different physical observables, their sensitivity to the basic parameters and their theoretical ... More
Exclusive Top Threshold Matching at Lepton CollidersNov 08 2018The threshold scan at future lepton colliders is the most precise known method to determine the top quark mass (well below 100 MeV), a fundamental parameter of the Standard Model that co-determines the stability properties of the electroweak vacuum. We ... More
Hadronic contributions to the anomalous magnetic moment of the electron and the hyperfine splitting of muoniumAug 21 2012Motivated by recent progress of theory and experiment on the anomalous magnetic moment of the electron, a_e, we update the hadronic contributions to a_e. Using our up-to-date compilation of e^+ e^- \to hadrons data, we find the leading order hadronic ... More
The hadronic vacuum polarisation contributions to the muon $g-2$Feb 17 2018The hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon, $a_{\mu}^{\rm had, VP}$ have been re-evaluated from the combination of $e^+e^-\rightarrow {\rm hadrons}$ cross section data. Focus has been placed on the development ... More
Determination of the strong coupling constant from the CLEO measurement of the total hadronic cross section in $e^+e^-$ annihilation below 10.56 GeVJul 17 2007Using recent CLEO III results for the cross section for $e^+e^- \to {\rm hadrons}$ at seven centre-of-mass energies between 6.964 and 10.538 GeV, we derive a value for the strong coupling constant $\alpha_s(M_Z^2)=0.110_{-0.012}^{-0.010}{}_{-0.011}^{+0.010}$ ... More
The muon $g-2$ and $α(M_Z^2)$: a new data-based analysisFeb 08 2018Jul 13 2018This work presents a complete re-evaluation of the hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon, $a_{\mu}^{\rm had, \, VP}$ and the hadronic contributions to the effective QED coupling at the mass of the $Z$ ... More
Radiative Corrections to the top quark widthJul 28 1993Calculations of radiative corrections to the top quark width are reviewed. QCD effects are discussed for $t-\bar t$ systems produced in $e^+e^-$ annihilation near the energy threshold.}
Multijet events in the k_T-factorisation schemeMay 31 2007Aug 27 2008A Markovian Monte Carlo algorithm for multi-parton production in the high-energy limit is proposed and the matching with unintegrated parton densities is discussed.
The muon $g-2$ and $α(M_Z^2)$: a new data-based analysisFeb 08 2018This work presents a complete re-evaluation of the hadronic vacuum polarisation contributions to the anomalous magnetic moment of the muon, $a_{\mu}^{\rm had, \, VP}$ and the hadronic contributions to the effective QED coupling at the mass of the $Z$ ... More
Theory of Elastic Vector Meson ProductionOct 13 1999The elastic production of vector mesons at HERA is discussed from the theoretical point of view. We briefly review different models, their successes and shortcomings. Main emphasis is put on recent issues in perturbative QCD calculations. Models including ... More
The Muon (g-2) Theory Value: Present and FutureNov 09 2013This White Paper briefly reviews the present status of the muon (g-2) Standard-Model prediction. This value results in a 3 - 4 standard-deviation difference with the experimental result from Brookhaven E821. The present experimental uncertainty is $\pm ... More
The strong coupling from $e^+e^-\to$ hadrons below charmMay 21 2018We use a new compilation of the hadronic $R$-ratio from available data for the process $e^+e^-\to\mbox{hadrons}$ to determine the strong coupling, $\alpha_s$. We make use of all data for the $R$-ratio from threshold to a center-of-mass energy of 2 GeV ... More
The strong coupling from $e^+e^-\to$ hadronsNov 05 2018We use a new compilation of the hadronic $R$-ratio from available data for the process $e^+e^-\to$ hadrons below the charm mass to determine the strong coupling $\alpha_s$, using finite-energy sum rules. Quoting our results at the $\tau$ mass to facilitate ... More
Fully-differential Top-Pair Production at a Lepton Collider: From Threshold to ContinuumDec 06 2017May 02 2018We present an approach to predict exclusive $W^+bW^-\bar{b}$ production at lepton colliders that correctly describes the top-anti-top threshold as well as the continuum region. We incorporate $t\bar{t}$ form factors for the NLL threshold resummation derived ... More
High-Energy Scattering and Diffraction: Theory SummaryJun 20 2000New developments in the theory and phenomenology of high-energy scattering and diffraction that were presented and discussed at DIS2000 are reviewed.
The Perturbative QCD Potential and the ttbar ThresholdFeb 20 1998We include the full second-order corrections to the static QCD potential in the analysis of the ttbar threshold cross section. There is an unexpectedly large difference between the QCD potential improved by the renormalization-group equation in momentum ... More
Transport properties of heterogeneous materials derived from Gaussian random fields: Bounds and SimulationApr 27 2000We investigate the effective conductivity ($\sigma_e$) of a class of amorphous media defined by the level-cut of a Gaussian random field. The three point solid-solid correlation function is derived and utilised in the evaluation of the Beran-Milton bounds. ... More
Skewed Parton Distributions and F_2^D at beta -> 1Oct 24 2000We show that the diffractive structure function is perturbatively calculable in the domain where the diffractive mass is small but still outside the resonance region. In this domain, which can be characterized by Lambda^2/Q^2 << 1-beta << (Lambda^2/Q^2)^1/2, ... More
Top Quark Pair Production at Threshold: Complete Next-to-next-to-leading Order Relativistic CorrectionsJan 23 1998The complete next-to-next-to-leading order (i.e. $O(v^2)$, $O(v \alpha_s)$ and $O(\alpha_s^2)$) relativistic corrections to the total photon mediated $t\bar t$ production cross section at threshold are presented in the framework of nonrelativistic quantum ... More
Exclusive top production at a Linear Collider at and off the thresholdJan 24 2018We review exclusive top pair production including decays at a future high-energy lepton collider, both in the threshold region and for higher energies. For the continuum process, we take complete QCD next-to-leading order matrix elements for the $2\to ... More
Momentum Distributions in $t\bar t$Apr 27 1993We apply the Green function formalism for $t-\bar t$ production and decay near threshold in a study of the effects due to the momentum dependent width for such a system. We point out that these effects are likely to be much smaller than expected from ... More
The strange and charm quark contributions to the anomalous magnetic moment of the muon from lattice QCDNov 03 2014We describe a new technique (published in Phys. Rev. D89 114501) to determine the contribution to the anomalous magnetic moment of the muon coming from the hadronic vacuum polarisation using lattice QCD. Our method uses Pad\'e approximants to reconstruct ... More
Hadronic contributions to the muon anomalous magnetic moment Workshop. $(g-2)_μ$: Quo vadis? Workshop. Mini proceedingsJul 14 2014Jul 21 2014We present the mini-proceedings of the workshops Hadronic contributions to the muon anomalous magnetic moment: strategies for improvements of the accuracy of the theoretical prediction and $(g-2)_{\mu}$: Quo vadis?, both held in Mainz from April 1$^{\rm ... More
Axial Contributions at the Top ThresholdMar 11 1999We calculate the contributions of the axial current to top quark pair production in e+ e- annihilation at threshold. The QCD dynamics is taken into account by solving the Lippmann-Schwinger equation for the P wave production using the QCD potential up ... More
Top Quark Pair Production close to Threshold: Top Mass, Width and Momentum DistributionApr 27 1999Sep 14 1999The complete NNLO QCD corrections to the total cross section $\sigma(e^+e^- \to Z*,\gamma*\to t\bar t)$ in the kinematic region close to the top-antitop threshold are calculated by solving the corresponding Schroedinger equations exactly in momentum space ... More
Analytic Calculation of Two Loop Corrections to Heavy Quark Pair Production Vertices Induced by Light QuarksJul 28 1997Jul 07 1998Non-singlet ${\cal{O}}(\alpha_s^2)$ corrections from light quarks are calculated analytically for the massive quark-antiquark pair production rates through the vector, axial-vector, scalar and pseudoscalar currents for all energies above the threshold. ... More
Comment on the Average Momentum of Top Quarks in the Threshold RegionNov 07 1993The behavior of the momentum distribution of top quarks in the threshold region is investigated. The qualitative behavior, in particular the dependence of the average momentum on the strong coupling constant can be understood from analytical calculations ... More
Polarization in Top Quark Pair Production near ThresholdNov 25 1994The polarization dependent momentum distributions of top quarks and their decay products are calculated for $t\bar t$ production at future $e^+e^-$ colliders with polarized beams. The Green function formalism is applied to this reaction near energy threshold. ... More
Polarization in Top Quark Production and Decay near ThresholdNov 23 1994Theoretical results are presented for top quarks produced in annihilation of polarized electrons on positrons. Polarization studies for $t\bar t$ pairs near threshold are free from hadronization ambiguities. This is due to the short lifetime of the top ... More
Upsilon photoproduction at HERA compared to estimates of perturbative QCDJan 26 1999We estimate the cross section for gamma p -> Upsilon p by two independent methods. First, by studying the corrections to the naive leading-order QCD formula and, second, by using parton-hadron duality. The estimates are in good agreement with each other ... More
The QCD description of diffractive rho meson electroproductionSep 24 1996We critically review the QCD predictions for the cross sections sigma_L and sigma_T for diffractive rho meson electroproduction in longitudinally and transversely polarised states in the HERA energy region. We show that both perturbative and non-perturbative ... More
Extracting alpha_s from Electron-Positron Annihilation around 10 GeVSep 19 1996Jun 11 1997The total cross section for electron-positron annihilation into hadrons is calculated in the region just below the B meson threshold. QCD corrections up to third order, quark mass effects, initial state radiation, the running of alpha_QED and the tails ... More
Radiation of Light Fermions in Heavy Fermion ProductionMay 09 1995The rate for the production of a pair of massive fermions in $e^+ e^-$ annihilation plus real or virtual radiation of a pair of massless fermions is calculated analytically. The contributions for real and virtual radiation are displayed separately. The ... More
An Inflationary Fixed Point Operator in XQueryNov 21 2007We introduce a controlled form of recursion in XQuery, inflationary fixed points, familiar in the context of relational databases. This imposes restrictions on the expressible types of recursion, but we show that inflationary fixed points nevertheless ... More
Improved predictions for g-2 of the muon and α_{\rm QED}(M_Z^2)Nov 08 2006Apr 20 2007We update the Standard Model predictions of the anomalous magnetic moment of the muon, a_\mu = (g-2)/2, and the value of the QED coupling at the Z-boson mass, incorporating the new e^+e^- \to \pi\pi data obtained by CMD-2 and KLOE, as well as the corrected ... More
The SM prediction of g-2 of the muonSep 17 2002Sep 20 2002We calculate (g-2)/2 of the muon, by improving the determination of the hadronic vacuum polarisation contribution, a_mu^{had,LO}, and its uncertainties. The different e+e- data sets for each exclusive (and the inclusive) channel are combined in order ... More
Hadron Radiation in Tau Production and the Leptonic Z Boson Decay RateJul 07 1995Secondary radiation of hadrons from a tau pair produced in electron positron collisions may constitute an important obstacle for precision measurements of the production cross section and of branching ratios. The rate for real and virtual radiation is ... More
Radiation of Heavy QuarksJul 20 1994The rate for the production of massive fermions radiated off a pair of massless fermions is calculated analytically. Combined with the analytic calculation of the corresponding virtual contribution one obtains the order $\alpha^2$ correction to the cross ... More
Radiation of Light Fermions in Heavy Fermion ProductionNov 22 1995Nov 23 1995Recent analytic calculations on the rate for the production of a pair of massive fermions in $e^+ e^-$ annihilation plus real or virtual radiation of a pair of massless fermions are discussed. The contributions for real and virtual radiation are displayed ... More
Hadron Radiation in Leptonic $Z$ DecaysJan 19 1994Apr 08 1994The rate for the final state radiation of hadrons in leptonic $Z$ decays is evaluated, using as input experimental data for $\sigma (e^+e^-\to hadrons)$ in the low energy region. Configurations with a lepton pair of large and a hadronic state of low invariant ... More
Small x gluon from exclusive J/psi productionSep 27 2007Exclusive J/psi production, gamma* p -> J/psi p, offers a unique opportunity to determine the gluon density of the proton in the small x domain. We use the available HERA data to determine the gluon distribution in the region 10^{-4} <~ x <~ 10^{-2} and ... More
On the boundedness of an iteration involving points on the hypersphereJan 11 2010Oct 05 2010For a finite set of points $X$ on the unit hypersphere in $\mathbb{R}^d$ we consider the iteration $u_{i+1}=u_i+\chi_i$, where $\chi_i$ is the point of $X$ farthest from $u_i$. Restricting to the case where the origin is contained in the convex hull of ... More
Causes and Explanations in the Structural-Model Approach: Tractable CasesDec 12 2012In this paper, we continue our research on the algorithmic aspects of Halpern and Pearl's causes and explanations in the structural-model approach. To this end, we present new characterizations of weak causes for certain classes of causal models, which ... More
Dynamic Conjunctive QueriesApr 05 2017The article investigates classes of queries maintainable by conjunctive queries (CQs) and their extensions and restrictions in the dynamic complexity framework of Patnaik and Immerman. Starting from the basic language of quantifier-free conjunctions of ... More
Nef reduction and anticanonical bundlesOct 31 2003We investigate the structure of smooth projective 3-folds X with -K_X nef and K_X^3=0.
Diffractive electroproduction of rho meson excitationsJan 24 1997We use perturbative QCD and parton-hadron duality to estimate the cross sections for the diffractive electroproduction of rhoprime(1-) and rho(3-) resonances which occur in the 1.3-1.8 GeV mass interval. We present the cross sections and the ratios sigma_L/sigma_T ... More
Predictions for g-2 of the muon and alpha_QED(M_Z^2)Dec 18 2003Apr 28 2004We calculate (g-2) of the muon and the QED coupling alpha(M_Z^2), by improving the determination of the hadronic vacuum polarization contributions and their uncertainties. We include the recently re-analysed CMD-2 data on e^+e^- -> pi^+ pi^-. We carefully ... More
Q^2 dependence of diffractive vector meson electroproductionDec 31 1999We give a general formula for the cross section for diffractive vector meson electroproduction, gamma^* p -> Vp. We first calculate diffractive qqbar production, and then use parton-hadron duality by projecting out the J^P = 1^- state in the appropriate ... More
Spectral Correlations in the Crossover Transition from a Superposition of Harmonic Oscillators to the Gaussian Unitary EnsembleJul 20 1998We compute the spectral correlation functions for the transition from a harmonic oscillator towards the Gaussian Unitary Ensemble (GUE). We use a variant of the supersymmetry method to obtain analytical results in a fast and elegant way. In contrast to ... More
Thermodynamic formalism for transport coefficients with an application to the shear modulus and shear viscosityDec 07 2016We discuss Onsager's thermodynamic formalism for transport coefficients and apply it to the calculation of the shear modulus and shear viscosity of a monodisperse system of repulsive particles. We focus on the concept of extensive "distance" and intensive ... More
On the quantifier-free dynamic complexity of ReachabilityJun 13 2013Jan 28 2015The dynamic complexity of the reachability query is studied in the dynamic complexity framework of Patnaik and Immerman, restricted to quantifier-free update formulas. It is shown that, with this restriction, the reachability query cannot be dynamically ... More
Sélection de la structure d'un perceptron multicouches pour la réduction dun modèle de simulation d'une scierieDec 05 2008Simulation is often used to evaluate the relevance of a Directing Program of Production (PDP) or to evaluate its impact on detailed sc\'enarii of scheduling. Within this framework, we propose to reduce the complexity of a model of simulation by exploiting ... More
Infinite reduced words and the Tits boundary of a Coxeter groupJan 05 2013Sep 18 2014Let (W,S) be a finite rank Coxeter system with W infinite. We prove that the limit weak order on the blocks of infinite reduced words of W is encoded by the topology of the Tits boundary of the Davis complex X of W. We consider many special cases, including ... More
An optimization principle for the computation of MHD equilibria in the solar coronaDec 21 2006AIMS: We develop an optimization principle for computing stationary MHD equilibria. METHODS: Our code for the self-consistent computation of the coronal magnetic fields and the coronal plasma uses non-force-free MHD equilibria. Previous versions of the ... More
Probabilistic Reasoning about Actions in Nonmonotonic Causal TheoriesOct 19 2012We present the language {m P}{cal C}+ for probabilistic reasoning about actions, which is a generalization of the action language {cal C}+ that allows to deal with probabilistic as well as nondeterministic effects of actions. We define a formal semantics ... More
Two-Variable Logic with Two Order RelationsOct 07 2011Mar 03 2012It is shown that the finite satisfiability problem for two-variable logic over structures with one total preorder relation, its induced successor relation, one linear order relation and some further unary relations is EXPSPACE-complete. Actually, EXPSPACE-completeness ... More
Elagage d'un perceptron multicouches : utilisation de l'analyse de la variance de la sensibilité des paramètresDec 04 2008The stucture determination of a neural network for the modelisation of a system remain the core of the problem. Within this framework, we propose a pruning algorithm of the network based on the use of the analysis of the sensitivity of the variance of ... More
How deals with discrete data for the reduction of simulation models using neural networkJun 10 2009Simulation is useful for the evaluation of a Master Production/distribution Schedule (MPS). Also, the goal of this paper is the study of the design of a simulation model by reducing its complexity. According to theory of constraints, we want to build ... More
Gluon sivers and experimental considerations for TMDsDec 14 2012The study and characterisation of transverse-momentum-dependent distribution functions (TMDs) is a major goal of the Electron-Ion Collider (EIC) physics programme. The study of gluon TMDs poses a greater challenge than for quark TMDs in DIS measurements, ... More
Strong-Field QED and High Power LasersNov 22 2011This contribution presents an overview of fundamental QED processes in the presence of an external field produced by an ultra-intense laser. The discussion focusses on the basic intensity effects on vacuum polarisation and the prospects for their observation. ... More
Predictions of Physical Observables from Minimal Neutrino StructuresJul 31 2003We find all possible seesaw textures which can describe in a natural way the currently observed neutrino oscillation pattern in terms of a minimum number of parameters. Natural here means due only to the relative smallness (vanishing) of some parameters ... More
Charged lepton flavor violation and the origin of neutrino massesDec 18 2013The neutrino oscillations imply that charged lepton flavor violation (CLFV) processes do exist. Even if the associated rates are in general expected very suppressed, it turns out that this is not always necessarily the case. In the framework of the three ... More
Leptogenesis at the TeV scaleNov 08 2001Apr 16 2002We present a general description of the problems encountered when attempting to build a simple model of leptogenesis and hence of baryogenesis at an energy scale as low as 1-10 TeV. We consider three possible lepton asymmetry enhancement mechanisms in ... More
The exact packing measure of Lévy treesAug 01 2010We study fine properties of L\'evy trees that are random compact metric spaces introduced by Le Gall and Le Jan in 1998 as the genealogy of continuous state branching processes. L\'evy trees are the scaling limits of Galton-Watson trees and they generalize ... More
Packing and Hausdorff measures of stable treesJan 29 2010In this paper we discuss Hausdorff and packing measures of random continuous trees called stable trees. Stable trees form a specific class of L\'evy trees (introduced by Le Gall and Le Jan in 1998) that contains Aldous's continuum random tree (1991) which ... More
Mittag-Leffler functions and complete monotonicityDec 16 2013Dec 17 2013We consider two operations on the Mittag-Leffler function which cancel the exponential term in the expansion at infinity, and generate a completely monotonic function. The first one is the action of a certain differential-difference operator, and leads ... More
Comparing Fréchet and positive stable lawsOct 07 2013Jan 27 2014Let ${\bf L}$ be the unit exponential random variable and ${\bf Z}_\alpha$ the standard positive $\alpha$-stable random variable. We prove that $\{(1-\alpha) \alpha^{\gamma_\alpha} {\bf Z}_\alpha^{-\gamma_\alpha}, 0< \alpha <1\}$ is decreasing for the ... More
Total positivity of a Cauchy kernelMay 06 2013We study the total positivity of the kernel $1/(x^2 + 2 \cos(\pi\a)xy +y^2).$ The case of infinite order is characterized by an application of Schoenberg's theorem. We then give necessary conditions for the cases of any given finite order with the help ... More
Some issues concerning the proton charge radius puzzleJul 20 2012Oct 24 2012An explanation of the difference of the charge radius of the proton as determined from the Lamb shift in electronic hydrogen and from elastic electron scattering off the proton on the one side and the recent high precision determination with muonic hydrogen ... More
Calculation of the Electroelastic Green's Function of the Hexagonal Infinite MediumMar 10 2015The electroelastic 4 $\times$ 4 Green's function of a piezoelectric hexagonal (transversely isotropic) infinitely extended medium is calculated explicitly in closed compact form (eqs. (73) ff. and (88) ff., respectively) by using residue calculation. ... More
Taking back control of HPC file systems with Robinhood Policy EngineMay 06 2015Today, the largest Lustre file systems store billions of entries. On such systems, classic tools based on namespace scanning become unusable. Operations such as managing file lifetime, scheduling data copies, and generating overall filesystem statistics ... More
Orbits of curves under the Johnson kernelAug 23 2011Apr 07 2014This paper has two main goals. First, we give a complete, explicit, and computable solution to the problem of when two simple closed curves on a surface are equivalent under the Johnson kernel. Second, we show that the Johnson filtration and the Johnson ... More
Microscopic calculation of the 3He(alpha,gamma)7Be and 3H(alpha,gamma)7Li capture cross sections using realistic interactionsNov 12 2010Jan 25 2011The radiative capture cross sections for the 3He(alpha,gamma)7Be and 3H(alpha,gamma)7Li reactions are calculated in the fully microscopic fermionic molecular dynamics approach using a realistic effective interaction that reproduces the nucleon-nucleon ... More
Sources of false positives and false negatives in the STATCHECK algorithm: Reply to Nuijten et al. (2016)Oct 04 2016Nov 16 2016STATCHECK is an R algorithm designed to scan papers automatically for inconsistencies between test statistics and their associated p values (Nuijten et al., 2016). The goal of this comment is to point out an important and well-documented flaw in this ... More
Congruences for Convolutions of Hilbert Modular FormsJan 20 2012Let $\f$ be a primitive, cuspidal Hilbert modular form of parallel weight. We investigate the Rankin convolution $L$-values $L(\f,\g,s)$, where $\g$ is a theta-lift modular form corresponding to a finite-order character. We prove weak forms of Kato's ... More
Phase diagrams of 2D and 3D disordered Bose gases in the local density approximationOct 03 2012We study the superfluid transitions in bidimensional (2D) and tridimensional (3D) disordered and interacting Bose gases. We work in the limit of long-range correlated disorder such that it can be treated in the local density approximation. We present ... More
Contrasting influence of charged impurities on transport and gain in terahertz quantum cascade lasersOct 29 2015Transport and gain properties of a resonant-phonon terahertz quantum cascade laser are calculated using nonequilibrium Green's functions. Impurity scattering is shown to be responsible for contrasting nonlinear effects in the transport and the gain properties. ... More
Higher rank lattices cannot act on hyperbolic spacesJul 07 2016We prove that any action of a higher rank lattice on a Gromov-hyperbolic space is elementary. More precisely, it is either elliptic or parabolic. This is a large generalization of the fact that any action of a higher rank lattice on a tree has a fixed ... More
Constructive discrepancy minimization for convex setsApr 01 2014Apr 12 2016A classical theorem of Spencer shows that any set system with n sets and n elements admits a coloring of discrepancy O(n^1/2). Recent exciting work of Bansal, Lovett and Meka shows that such colorings can be found in polynomial time. In fact, the Lovett-Meka ... More
Laminations géodésiques platesNov 29 2013Sep 11 2014Since their introduction by Thurston, geodesic laminations on hyperbolic surfaces occur in many contexts. In this paper, we propose a generalization of geodesic laminations on locally CAT(0), complete, geodesic metric spaces, whose boundary at infinity ... More
Sampling and reconstructing signals from a union of linear subspacesNov 18 2009Dec 02 2009In this note we study the problem of sampling and reconstructing signals which are assumed to lie on or close to one of several subspaces of a Hilbert space. Importantly, we here consider a very general setting in which we allow infinitely many subspaces ... More
Algebraic moment closure for population dynamics on discrete structuresMay 15 2014Moment closure on general discrete structures often requires one of the following: (i) an absence of short closed loops (zero clustering); (ii) existence of a spatial scale; (iii) ad hoc assumptions. Algebraic methods are presented to avoid the use of ... More
The topology of positive scalar curvatureMay 16 2014Jun 25 2014In this survey article, given a smooth closed manifold M we study the space of Riemannian metrics of positive scalar curvature on M. A long-standing question is: when is this space non-empty (i.e. when does M admit a metric of positive scalar curvature)? ... More
Loop groups and string topologyFeb 26 2008Survey article on loop groups and their representations, following a course of three lectures held at the summer school "algebraic groups" at the Georg-August-Universitaet zu Goettingen, June 27--July 13, 2005. We discuss loop groups, their central extensions, ... More
Geometry of branes on supergroupsSep 02 2008In this note we analyze the geometry of maximally symmetric boundary conditions in Lie supergroup Wess-Zumino-Novikov-Witten models. We find that generically the worldvolume of a brane is a twisted superconjugacy class, very much like in the Lie group ... More
AA Dor - An Eclipsing sdOB - Brown Dwarf BinaryNov 25 2003AA Dor is an eclipsing, close, post common-envelope binary consisting of a sdOB primary star and an unseen secondary with an extraordinary small mass - formally a brown dwarf. The brown dwarf may have been a former planet which survived a common envelope ... More
Autoregressive Time Series Forecasting of Computational DemandNov 14 2007We study the predictive power of autoregressive moving average models when forecasting demand in two shared computational networks, PlanetLab and Tycoon. Demand in these networks is very volatile, and predictive techniques to plan usage in advance can ... More
Alexander varieties and largeness of finitely presented groupsMay 01 2012Let X be a finite CW complex. We show that the fundamental group of X is large if and only if there is a finite cover Y of X and a sequence of finite abelian covers \{Y_N\} of Y which satisfy b_1(Y_N)\geq N. We give some applications of this result to ... More
Isotopy invariants for closed braids and almost closed braids via loops in stratified spacesJun 19 2006Let $\phi : S^1\times D^2\to S^1$ be the natural projection. An oriented knot $K\hookrightarrow V = S^1\times D^2$ is called an almost closed braid if the restriction of $\phi$ to K has exactly two (non-degenerate) critical points (and K is a closed braid ... More
Gauge fields and interactions in matrix string theorySep 03 1997Sep 18 1997It is shown that all possible N sheeted coverings of the cylinder are contained in type IIA matrix string theory as non-trivial gauge field configurations. Using these gauge field configurations as backgrounds the large $N$ limit is shown to lead to the ... More
The D0-brane metric in N = 2 sigma modelsJun 30 2000Aug 07 2000We investigate the physical metric seen by a D0-brane probe in the background geometry of an N=2 sigma model. The metric is evaluated by calculating the Zamolodchikov metric for the disc two point function of the boundary operators corresponding to the ... More
Collective and chaotic motion in self-bound many-body systemsMay 06 1999Feb 28 2000We investigate the interplay of collective and chaotic motion in a classical self-bound N-body system with two-body interactions. This system displays a hierarchy of three well separated time scales that govern the onset of chaos, damping of collective ... More
Gravity in Two Spacetime DimensionsNov 27 2000In this habilitation thesis we provide an introduction to gravitational models in two spacetime dimensions. Focus is put on exactly solvable models. We begin by introducing and motivating different possible gravitational actions, including those of generalized ... More
All Symmetries of Non-Einsteinian Gravity in $d =2$Jul 01 1992Nov 24 1992The covariant form of the field equations for two--dimensional $R^2$--gravity with torsion as well as its Hamiltonian formulation are shown to suggest the choice of the light--cone gauge. Further a one--to--one correspondence between the Hamiltonian gauge ... More
Partial and complete linearization of PDEs based on conservation lawsJan 17 2005A method based on infinite parameter conservation laws is described to factor linear differential operators out of nonlinear partial differential equations (PDEs) or out of differential consequences of nonlinear PDEs. This includes a complete linearization ... More
New Tests of NRQCD from Quarkonia Within JetsJan 21 2016I review the current status of quarkonium production theory based on the non-relativistic QCD factorization formalism (NRQCD). While this theory describes much of the world's data on J/\psi and \Upsilon production, there are still outstanding problems, ... More
Charm production asymmetries from heavy-quark recombinationJun 19 2003Charm asymmetries in fixed-target hadroproduction experiments are sensitive to power corrections to the QCD factorization theorem for heavy quark production. A power correction called heavy-quark recombination has recently been proposed to explain these ... More
Scale Setting in Top Quark DecaysFeb 27 1996Jun 03 1996We compute the $O(\beta_0 \alpha_s^2)$ QCD corrections to the Standard Model decay $t\rightarrow W^+ b$ as well as the non standard decay $t\rightarrow H^+ b$. We then use our results to compute the BLM scale for these decays, and study the dependence ... More
Generalised canonical basic sets for Ariki-Koike algebrasMar 23 2013Jan 22 2014Let H be a non semi-simple Ariki-Koike algebra. According to [18] and [14], there is a generalisation of Lusztig's a-function which induces a natural order (parametrised by a tuple m) on Specht modules. In some cases, Geck and Jacon have proved that this ... More
Cytoskeleton and Cell MotilityMay 12 2011The present article is an invited contribution to the Encyclopedia of Complexity and System Science, Robert A. Meyers Ed., Springer New York (2009). It is a review of the biophysical mechanisms that underly cell motility. It mainly focuses on the eukaryotic ... More