Results for "Jean-Philippe Goldman"

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DisMo: A Morphosyntactic, Disfluency and Multi-Word Unit Annotator. An Evaluation on a Corpus of French Spontaneous and Read SpeechFeb 08 2018We present DisMo, a multi-level annotator for spoken language corpora that integrates part-of-speech tagging with basic disfluency detection and annotation, and multi-word unit recognition. DisMo is a hybrid system that uses a combination of lexical resources, ... More
Einstein tori and crooked surfacesFeb 27 2017In hyperbolic space, the angle of intersection and distance classify pairs of totally geodesic hyperplanes. A similar algebraic invariant classifies pairs of hyperplanes in the Einstein universe. In dimension 3, symplectic splittings of a 4-dimensional ... More
Crooked HalfspacesNov 18 2012May 17 2013We develop the Lorentzian geometry of a crooked halfspace in 2+1-dimensional Minkowski space. We calculate the affine, conformal and isometric automorphism groups of a crooked halfspace, and discuss its stratification into orbit types, giving an explicit ... More
Gradient estimates for a degenerate parabolic equation with gradient absorption and applicationsAug 10 2007Qualitative properties of non-negative solutions to a quasilinear degenerate parabolic equation with an absorption term depending solely on the gradient are shown, providing information on the competition between the nonlinear diffusion and the nonlinear ... More
Stick-slip Transition in the Scalar Arching ModelJan 07 1998When some granular material contained into a silo is pushed upwards with a piston, an irregular stick-slip motion of the system of grains is observed. We show how one can adapt the `Scalar Arching Model' -- proposed as a model for giant stress fluctuations ... More
Convex Sobolev inequalities and spectral gapMar 11 2005This note is devoted to the proof of convex Sobolev (or generalized Poincar\'{e}) inequalities which interpolate between spectral gap (or Poincar\'{e}) inequalities and logarithmic Sobolev inequalities. We extend to the whole family of convex Sobolev ... More
Economics need a scientific revolutionOct 29 2008I argue that the current financial crisis highlights the crucial need of a change of mindset in economics and financial engineering, that should move away from dogmatic axioms and focus more on data, orders of magnitudes, and plausible, albeit non rigorous, ... More
An introduction to Dunkl theory and its analytic aspectsNov 24 2016Dunkl theory is a far reaching generalization of Fourier analysis and special function theory related to root systems. During the sixties and seventies, it became gradually clear that radial Fourier analysis on rank one symmetric spaces was closely connected ... More
Monitoring the Extragalactic High Energy SkyJan 21 2019Blazars are jetted active galactic nuclei with a jet pointing close to the line of sight, hence enhancing their intrinsic luminosity and variability. Monitoring these sources is essential in order to catch them flaring and promptly organize follow-up ... More
The Generalization of the Decomposition of Functions by Energy OperatorsAug 15 2012Apr 23 2014This work starts with the introduction of a family of differential energy operators. Energy operators ($Psi_R^+$, $Psi_R^-$) were defined together with a method to decompose the wave equation in a previous work. Here the energy operators are defined following ... More
Conformal geometry of the supercotangent and spinor bundlesApr 09 2010Feb 05 2013We establish, via geometric quantization of the supercotangent bundle sM of (M,g), a correspondence between its conformal geometry and those of the spinor bundle. In particular, the Kosmann Lie derivative of spinors is obtained by quantization of the ... More
Conformally equivariant quantization for spinning particlesAug 20 2012Jan 06 2015This work takes place over a conformally flat spin manifold (M,g). We prove existence and uniqueness of the conformally equivariant quantization valued in spinor differential operators, and provide an explicit formula for it when restricted to first order ... More
The conformal approach to asymptotic analysisAug 11 2015This essay was written as an extended version of a talk given at a conference in Strasbourg on "Riemann, Einstein and geometry", organized by Athanase Papadopoulos in September 2014. Its aim is to present Roger Penrose's approach to asymptotic analysis ... More
On Lars Hörmander's remark on the characteristic Cauchy problemApr 23 2005Sep 19 2005We extend the results of a work by L. H\"ormander in 1990 concerning the resolution of the characteristic Cauchy problem for second order wave equations with regular first order potentials. The geometrical background of this work was a spatially compact ... More
On expansions for the Black-Scholes prices and hedge parametersSep 17 2018Jun 06 2019We derive new formulas for the price of the European call and put options in the Black-Scholes model, under the form of uniformly convergent series generalizing previously known approximations. We also provide precise boundaries for the convergence speed ... More
The endogenous dynamics of markets: price impact and feedback loopsSep 15 2010We review the evidence that the erratic dynamics of markets is to a large extent of endogenous origin, i.e. determined by the trading activity itself and not due to the rational processing of exogenous news. In order to understand why and how prices move, ... More
The (unfortunate) complexity of the economyApr 06 2009This article is a follow-up of a short essay that appeared in Nature 455, 1181 (2008) [arXiv:0810.5306]. It has become increasingly clear that the erratic dynamics of markets is mostly endogenous and not due to the rational processing of exogenous news. ... More
H2+ and HD+: candidates for a molecular clockMar 27 2014We investigate the leading systematic effects in ro-vibrational spectroscopy of the molecular hydrogen ions H2+ and HD+, in order to assess their potential for the realization of optical clocks that would be sensitive to possible variations of the proton-to-electron ... More
Modeling of the multiwavelength emission of M87 with H.E.S.S. observationsSep 15 2007M87 is the first extragalactic source detected in the TeV range that is not a blazar. The large scale jet of M87 is not aligned with the line of sight. Modification of standard emission models of TeV blazars appears necessary to account for the gamma-ray ... More
Solutions a divers problemes de decision dans un groupe hyperboliqueFeb 05 2007We give solutions to several decision problems in word hyperbolic groups
On The Use of Conjugate Teager-Kaiser Energy Operators with Matched FiltersJul 13 2016This work presents the proof of concept of using energy operator theory based on the conjugate Teager-Kaiser energy operators in matched filters for signal detection in multipath fading channels. To do so, we consider signals in the space $\mathcal{S}(\mathbb{R})$ ... More
Invariance homotopique de certains espaces de configurationsJun 30 2004For a smooth manifold A, we consider the ordered configuration space F_k(AxR) of k distinct points in AxR. We obtain an explicit homotopy construction of the configuration space F_k(AxR) and of the (k-2)-fold suspension of F_k(A). Under certain conditions, ... More
On growth-optimal tax rates and the issue of wealth inequalitiesAug 02 2015Aug 25 2015We introduce a highly stylized, yet non trivial model of the economy, with a public and private sector coupled through a wealth tax and a redistribution policy. The model can be fully solved analytically, and allows one to address the question of optimal ... More
Crises and collective socio-economic phenomena: simple models and challengesSep 02 2012Dec 29 2012Financial and economic history is strewn with bubbles and crashes, booms and busts, crises and upheavals of all sorts. Understanding the origin of these events is arguably one of the most important problems in economic theory. In this paper, we review ... More
Elements for a Theory of Financial RisksJun 08 1998Estimating and controlling large risks has become one of the main concern of financial institutions. This requires the development of adequate statistical models and theoretical tools (which go beyond the traditionnal theories based on Gaussian statistics), ... More
Anomalous relaxation in complex systems: from stretched to compressed exponentialsMay 07 2007We attempt to give a bird's eye view of the physical mechanisms leading to anomalous relaxation, and the relation of this phenomenon with anomalous diffusion and transport. Whereas in some cases these two notions are indeed deeply related, this needs ... More
Predictions of Very High Energy gamma-ray fluxes for three Active Galactic NucleiSep 15 2007M87 is the first extragalactic source detected at the TeV that is not a blazar. To account for the recent observations of M87 made by the High Energy Stereoscopic System (H.E.S.S.) telescope array, we developed a new multi-blob synchrotron self-Compton ... More
Multiwavelength modeling of TeV AGN observed by HESSSep 10 2007Sep 12 2007The High Energy Stereoscopic System (H.E.S.S.) experiment, a ground-based gamma-ray Cherenkov telescope array located in Namibia, has now detected many extragalactic objects, which redshifts range from z=0.00183 up to z=0.2, possibly more. With the increasing ... More
Clifford Theorem for real algebraic curvesApr 01 2005We establish for smooth projective real curves the equivalent of the classical Clifford inequality known for complex curves. We also study the cases when equality holds.
On expansions for the Black-Scholes prices and hedge parametersSep 17 2018Mar 19 2019We derive new formulas for the price of the European call and put options in the Black-Scholes model, under the form of uniformly convergent series generalizing previously known approximations. We also provide precise boundaries for the convergence speed ... More
Centralisateurs dans un groupe cristallographique 2-dimensionnelFeb 17 2007Nous explicitons les centralisateurs dans un sous-groupe discret cocompact d'isometrie du plan euclidien ----- We make explicit the centralizers of a discrete cocompact subgroup of isometries of the Euclidean plane.
Groupe a classes de conjugaisons infinies : quelques exemplesDec 21 2005We consider the group property of being icc. We give several examples of icc groups and study its stability under usual algebraic constructions.
Sur la conjecture des fibres de SeifertMar 09 2007Nous rappelons l'historique de la demonstration de la conjecture des fibres de Seifert, ainsi que ses motivations et ses diverses generalisations. ----- We recall the history of the proof of the Seibert fiber space conjecture, as well as its motivations ... More
Higher Symmetries of the Laplacian via QuantizationJul 28 2011Feb 12 2014We develop a new approach, based on quantization methods, to study higher symmetries of invariant differential operators. We focus here on conformally invariant powers of the Laplacian over a conformally flat manifold and recover results of Eastwood, ... More
Configuration spaces of an embedding torus and cubical spacesMar 21 2006For a smooth manifold M obtained as an embedding torus, A U Cx[-1,1], we consider the ordered configuration space F_k(M) of k distinct points in M. We show that there is a homotopical cubical resolution of F_k(M) defined from the configuration spaces ... More
Rigidity of diagonally embedded triangle groupsJun 07 2019We show local rigidity of hyperbolic triangle groups generated by reflections in pairs of $n$-dimensional subspaces of $R^{2n}$ obtained by composition of the geometric representation in $PGL(2, R)$ with the diagonal embeddings into $PGL(2n, R)$ and $PSp^\pm(2n, ... More
Glassy dynamics: mean-field `landscape' pictures versus growing length scale scenariiAug 27 2004This is a short review on the compatibility between (a) mean-field, mode-coupling theories of the glass transition, where potential energy landscape ideas are natural, and (b) the necessity of describing the slowing down of glassy materials in terms of ... More
Aging in glassy systems: new experiments, simple models, and open questionsOct 25 1999Dec 18 2000We review the most striking experimental results on aging in a variety of disordered systems, which reveal similar features but also important differences. We argue that a generic model that reproduce many of these features is that of {\it pinned defects} ... More
Semi-algebraic geometry with rational continuous functionsMar 14 2016Oct 11 2016Let X be an affine real algebraic set . We investigate on the theory of algebraically constructible functions on X and the description of the semi-algebraic subsets of X when we replace the polynomial functions on X by some rational continuous functions ... More
Resonances in two-electron atoms below the critical chargeJul 29 2015The critical nuclear charge Zc required for a heliumlike atom to have at least one bound state was recently determined with high accuracy from variational calculations. Analysis of the wave functions further suggested that the bound state changes smoothly ... More
New Observables in Inclusive Production of QuarkoniaMar 21 2019After an introduction motivating the study of quarkonium production, we review the recent developments in the phenomenology of quarkonium production in inclusive scatterings of hadrons and leptons. We naturally address data and predictions relevant for ... More
Fixed points of automorphisms of real algebraic curvesSep 28 2006We bound the number of fixed points of an automorphism of a real curve in terms of the genus and the number of connected components of the real part of the curve. Using this bound, we derive some consequences concerning the maximum order of an automorphism ... More
On stable norm in word hyperbolic groupsMar 09 2007This work is concerned with the stable norm in word hyperbolic groups as defined by Gromov. We give a short elementary proof of one of its basic property, that is existence of a computable uniform non null lower bound for stable norm in a word hyperbolic ... More
Centre, commutativite et conjugaison dans un graphe de groupeOct 28 2005We give characterizations of the center, of conjugated and of commuting elements in a fundamental group of a graph of group. We deduce various results : on the one hand we give a sufficient condition for the center, the centralizers, and the root structures ... More
Conjugacy problem in groups of non-oriented geometrizable 3-manifoldsDec 21 2005We have proved in [Topology, 45 1 (2006)] that fundamental groups of oriented geometrizable 3-manifolds have a solvable conjugacy problem. We now consider the case of groups of non-oriented geometrizable 3-manifolds in order to conclude that fundamental ... More
Power-laws in economy and finance: some ideas from physicsAug 07 2000We discuss several models in order to shed light on the origin of power-law distributions and power-law correlations in financial time series. From an empirical point of view, the exponents describing the tails of the price increments distribution and ... More
Very special divisors on 4-gonal real algebraic curvesApr 05 2013Given a real curve, we study special linear systems called "very special" for which the dimension does not satisfy a Clifford type inequality. We classify all these very special linear systems when the gonality of the curve is small.
The big-bang theory: construction, evolution and statusJun 20 2016Over the past century, rooted in the theory of general relativity, cosmology has developed a very successful physical model of the universe: the {\em big-bang model}. Its construction followed different stages to incorporate nuclear processes, the understanding ... More
Recent advances about the uniqueness of the slowly oscillating periodic solutions of Wright's equationSep 22 2009Sep 24 2009An old conjecture in delay equations states that Wright's equation \[ y'(t)= - \alpha y(t-1) [ 1+y(t)], \alpha \in \mathbb{R} \] has a unique slowly oscillating periodic solution (SOPS) for every parameter value $\alpha>\pi/2$. We reformulate this conjecture ... More
On the regularity of solutions of one dimensional variational obstacle problemsJun 13 2016Sep 03 2016We study the regularity of solutions of one dimensional variational obstacle problems in $W^{1,1}$ when the Lagrangian is locally H\"older continuous and globally elliptic. In the spirit of the work of Sychev ([Syc89, Syc91, Syc92]), a direct method is ... More
An elementary proof of the positivity of the intertwining operator in one--dimensional trigonometric dunkl theoryNov 21 2016This note is devoted to the intertwining operator in the one--dimensional trigonometric Dunkl setting. We obtain a simple integral expression of this operator and deduce its positivity.
On expansions for the Black-Scholes prices and hedge parametersSep 17 2018Dec 10 2018We derive new formulas for the price of the European call and put options in the Black-Scholes model, under the form of uniformly convergent series generalizing previously known approximations. We also provide precise boundaries for the convergence speed ... More
Split extensions of group with infinite conjugacy classesMar 25 2007We characterize the group property of being with infinite conjugacy classes (or icc, i.e. in which all conjugacy classes beside 1 are infinite) for split extensions of groups.
Copula-based Hierarchical Aggregation of Correlated Risks. The behaviour of the diversification benefit in Gaussian and Lognormal TreesNov 04 2011Nov 10 2011The benefits of diversifying risks are difficult to estimate quantitatively because of the uncertainties in the dependence structure between the risks. Also, the modelling of multidimensional dependencies is a non-trivial task. This paper focuses on one ... More
Conformally Equivariant Quantization - a Complete ClassificationFeb 20 2011Apr 15 2012Conformally equivariant quantization is a peculiar map between symbols of real weight $\delta$ and differential operators acting on tensor densities, whose real weights are designed by $\lambda$ and $\lambda+\delta$. The existence and uniqueness of such ... More
Equivariant quantization of spin systemsSep 12 2010We investigate the geometric and conformally equivariant quantizations of the supercotangent bundle of a pseudo-Riemannian manifold $(M,g)$, which is a model for the phase space of a classical spin particle. This is a short review of our previous works. ... More
Conformal scattering on the Schwarzschild metricDec 04 2013Oct 17 2015We show that existing decay results for scalar fields on the Schwarzschild metric are sufficient to obtain a conformal scattering theory. Then we re-interpret this as an analytic scattering theory defined in terms of wave operators, with an explicit comparison ... More
A series representation for the Black-Scholes formulaOct 03 2017Oct 27 2017We prove and test an efficient series representation for the European Black-Scholes call, which generalizes and refines previously known approximations, and works in every market configuration.
A model for ripple instabilities in granular mediaJan 28 1998We extend the model of surface granular flow proposed in \cite{bcre} to account for the effect of an external `wind', which acts as to dislodge particles from the static bed, such that a stationary state of flowing grains is reached. We discuss in detail ... More
Dynamics of granular avalanches caused by local perturbationsJul 13 2004Surface flow of granular material is investigated within a continuum approach in two dimensions. The dynamics is described by a non-linear coupling between the two `states' of the granular material: a mobile layer and a static bed. Following previous ... More
Exact Solutions of a Model for Granular AvalanchesAug 11 1999We present exact solutions of the non-linear {\sc bcre} model for granular avalanches without diffusion. We assume a generic sandpile profile consisting of two regions of constant but different slope. Our solution is constructed in terms of characteristic ... More
A novel code generation methodology for block diagram modeler and simulators Scicos and VSSOct 08 2015Block operations during simulation in Scicos and VSS environments can naturally be described as Nsp functions. But the direct use of Nsp functions for simulation leads to poor performance since the Nsp language is interpreted, not compiled. The methodology ... More
Wave and Klein-Gordon equations on hyperbolic spacesApr 01 2011Jul 06 2013We consider the Klein--Gordon equation associated with the Laplace--Beltrami operator $\Delta$ on real hyperbolic spaces of dimension $n\!\ge\!2$; as $\Delta$ has a spectral gap, the wave equation is a particular case of our study. After a careful kernel ... More
Inflationary models inducing non-Gaussian metric fluctuationsSep 17 2002We construct explicit models of multi-field inflation in which the primordial metric fluctuations do not necessarily obey Gaussian statistics. These models are realizations of mechanisms in which non-Gaussianity is first generated by a light scalar field ... More
Lensing at cosmological scales: a test of higher dimensional gravityDec 01 2000Recent developments in gravitational lensing astronomy have paved the way to genuine mappings of the gravitational potential at cosmological scales. We stress that comparing these data with traditional large scale structure surveys will provide us with ... More
A nested factor model for non-linear dependences in stock returnsSep 12 2013The aim of our work is to propose a natural framework to account for all the empirically known properties of the multivariate distribution of stock returns. We define and study a "nested factor model", where the linear factors part is standard, but where ... More
Experts' earning forecasts: bias, herding and gossamer informationOct 04 2004We study the statistics of earning forecasts of US, EU, UK and JP stocks during the period 1987-2004. We confirm, on this large data set, that financial analysts are on average over-optimistic and show a pronounced herding behavior. These effects are ... More
Comment on `Symmetrical Temperature-Chaos effect with Positive and Negative Temperature Shifts in a Spin Glass'Sep 06 2002Comment on the paper P. E. Jonsson, H. Yoshino, and P. Nordblad, Phys. Rev. Lett. 89, 097201 (2002), also cond-mat/0203444.
Renormalization Group Approach To Error-Correcting CodesJun 26 2001We explain an algorithm that approximately but efficiently assesses particular parity-check error-correcting codes of large, but finite, blocklength. This algorithm is based on the ``renormalization-group'' approach from physics: the idea is to continually ... More
Option pricing and hedging with minimum local expected shortfallAug 27 2003We propose a versatile Monte-Carlo method for pricing and hedging options when the market is incomplete, for an arbitrary risk criterion (chosen here to be the expected shortfall), for a large class of stochastic processes, and in the presence of transaction ... More
The Reconstruction of Science PhylogenyApr 21 2009Jul 17 2010We are facing a real challenge when coping with the continuous acceleration of scientific production and the increasingly changing nature of science. In this article, we extend the classical framework of co-word analysis to the study of scientific landscape ... More
Why three-body physics do not solve the proton radius puzzleMay 03 2012May 24 2012The possible involvement of weakly bound three-body systems in the muonic hydrogen spectroscopy experiment [1], which could resolve the current discrepancy between determinations of the proton radius, is investigated. Using variational calculations with ... More
High accuracy results for the energy levels of the molecular ions H2+, D2+ and HD+, up to J=2Jan 19 2007We present a nonrelativistic calculation of the rotation-vibration levels of the molecular ions H2+, D2+ and HD+, relying on the diagonalization of the exact three-body Hamiltonian. The J=2 levels are obtained with a very high accuracy of 10^{-14} a.u. ... More
Analytical matrix elements of the Uehling potential in three-body systems, and applications to exotic moleculesNov 30 2012Dec 28 2012Exact analytical expressions for the matrix elements of the Uehling potential in a basis of explicitly correlated exponential wave functions are presented. The obtained formulas are then used to compute with an improved accuracy the vacuum polarization ... More
Statistical models for company growthOct 22 2002Nov 19 2002We study Sutton's `microcanonical' model for the internal organisation of firms, that leads to non trivial scaling properties for the statistics of growth rates. We show that the growth rates are asymptotically Gaussian in this model, at variance with ... More
Non-standard baryon-dark matter interactionsJun 03 2009After summarizing the respective merits of the Cold Dark Matter (CDM) and Modified Newtonian Dynamics (MOND) paradigms in various stellar systems, we investigate the possibility that a non-standard interaction between baryonic and dark matter could reproduce ... More
Virtual screening with support vector machines and structure kernelsAug 01 2007Support vector machines and kernel methods have recently gained considerable attention in chemoinformatics. They offer generally good performance for problems of supervised classification or regression, and provide a flexible and computationally efficient ... More
Time-dependent Bragg diffraction bymultilayer gratingsNov 25 2015The time-dependent Bragg diffraction by multilayer gratings working by reflection or by transmission is investigated. The study is performed by generalizing the time-dependent coupled-wave theory previously developed for one-dimensional photonic crystal ... More
Expérimentation d'une ressource pour une situation de recherche et de preuve entre pairsMar 23 2012This paper is about an experiment with the goal of testing a primary teacher's resource. This is the next part of a research presented at EMF2009. This resource must help a teacher to practice a research and proof activity between peers with her pupils ... More
Conductance statistics in small GaAs:Si wires at low temperatures. I. Theoretical analysis: truncated quantum fluctuations in insulating wiresApr 16 1993We analyse in detail Mott's variable range hopping in one dimension, expanding on earlier work by Raikh and Ruzin. We show that the large conductance fluctuations in disordered insulators result from a subtle interplay between purely quantum phenomena ... More
Will a Large Economy Be Stable?Jan 28 2019We study networks of firms with Leontief production functions. Relying on results from Random Matrix Theory, we argue that such networks generically become unstable when their size increases, or when the heterogeneity in productivities/connectivities ... More
A covariance kernel for proteinsOct 16 2003We propose a new kernel for biological sequences which borrows ideas and techniques from information theory and data compression. This kernel can be used in combination with any kernel method, in particular Support Vector Machines for protein classification. ... More
Bandwidth smearing in optical interferometry: Analytic model of the transition to the double fringe packetJul 09 2012Bandwidth smearing is a chromatic aberration due to the finite frequency bandwidth. In long-baseline optical interferometry terms, it is when the angular extension of the source is greater than the coherence length of the interferogram. As a consequence, ... More
The extrasolar planet atmosphere and exosphere: Emission and transmission spectroscopyDec 10 2008We have entered the phase of extrasolar planets characterization, probing their atmospheres for molecules, constraining their horizontal and vertical temperature profiles and estimating the contribution of clouds and hazes. We report here a short review ... More
Length in the Cremona groupMar 15 2018Feb 13 2019The Cremona group is the group of birational transformations of the plane. A birational transformation for which there exists a pencil of lines which is sent onto another pencil of lines is called a Jonqui\`eres transformation. By the famous Noether-Castelnuovo ... More
Eigenvector dynamics: theory and some applicationsAug 22 2011We propose a general framework to study the stability of the subspace spanned by $P$ consecutive eigenvectors of a generic symmetric matrix ${\bf H}_0$, when a small perturbation is added. This problem is relevant in various contexts, including quantum ... More
Eigenvector dynamics: general theory and some applicationsMar 28 2012Jul 16 2012We propose a general framework to study the stability of the subspace spanned by $P$ consecutive eigenvectors of a generic symmetric matrix ${\bf H}_0$, when a small perturbation is added. This problem is relevant in various contexts, including quantum ... More
Eigenvector dynamics under free additionJan 21 2013Jan 06 2015We investigate the evolution of a given eigenvector of a symmetric (deterministic or random) matrix under the addition of a matrix in the Gaussian orthogonal ensemble. We quantify the overlap between this single vector with the eigenvectors of the initial ... More
Quantifier Elimination and Rectilinearisation Theorem for Generalised Quasianalytic AlgebrasMar 15 2013Mar 23 2013An algebra of germs of real functions is generalised quasianalytic if to each element of the algebra we can associate, injectively, a power series with nonnegative real exponents. We prove a quantifier elimination and a rectilinearisation result for generalised ... More
Bounds for entries of $γ$-vectors of flag homology spheresDec 04 2016Apr 04 2017We present some enumerative and structural results for flag homology spheres. For a flag homology sphere $\Delta$, we show that its $\gamma$-vector $\gamma^\Delta=(1,\gamma_1,\gamma_2,\ldots)$ satisfies: \begin{align*} \gamma_j=0,\text{ for all } j>\gamma_1, ... More
A method to rigorously enclose eigendecompositions of interval matricesDec 21 2011In this paper, a rigorous computational method to enclose eigendecompositions of complex interval matrices is proposed. Each eigenpair $x=(\lambda,v)$ is found by solving a nonlinear equation of the form $f(x)=0$ via a contraction argument. The set-up ... More
A Characterization of Semisimple Plane Polynomial AutomorphismsApr 14 2008Apr 24 2008It is well-known that an element of the linear group ${\rm GL}_n(\C)$ is semisimple if and only if its conjugacy class is Zariski closed. The aim of this paper is to show that the same result holds for the group of complex plane polynomial automorphisms. ... More
A Perron theorem for matrices with negative entries and applications to Coxeter groupsNov 16 2015Handelman (J. Operator Theory, 1981) proved that if the spectral radius of a matrix $A$ is a simple root of the characteristic polynomial and is strictly greater than the modulus of any other root, then $A$ is conjugate to a matrix $Z$ some power of which ... More
The effect of classical noise on a quantum two-level systemMay 07 2008We consider a quantum two-level system perturbed by classical noise. The noise is implemented as a stationary diffusion process in the off-diagonal matrix elements of the Hamiltonian, representing a transverse magnetic field. We determine the invariant ... More
Determinants over graded-commutative algebras, a categorical viewpointMar 28 2014We generalize linear superalgebra to higher gradings and commutation factors, given by arbitrary abelian groups and bicharacters. Our central tool is an extension, to monoidal categories of modules, of the Nekludova-Scheunert faithful functor between ... More
Search for high-energy gamma-ray emission from galaxies of the Local Group with Fermi/LATOct 18 2011Normal galaxies begin to arise from the shadows at high energies, as can be seen with the discovery of high-energy gamma-ray emission from the Andromeda galaxy (M 31) by the Fermi /LAT collaboration. We present a study on the search for high-energy emission ... More
Trend followers lose more often than they gainAug 16 2005We solve exactly a simple model of trend following strategy, and obtain the analytical shape of the profit per trade distribution. This distribution is non trivial and has an option like, asymmetric structure. The degree of asymmetry depends continuously ... More
Worse fluctuation method for fast Value-at-Risk estimatesSep 16 1999We show how one can actually take advantage of the strongly non-Gaussian nature of the fluctuations of financial assets to simplify the calculation of the Value-at-Risk of complex non linear portfolios. The resulting equations are not hard to solve numerically, ... More
Conservation Laws for Cosmological PerurbationsApr 21 1998We briefly recall the problem of defining conserved quantities such as energy in general relativity, and the solution by introducing a symmetric background. We apply the general formalism to perturbed Robertson-Walker spacetimes with de Sitter geometry ... More
Quantum theory of the Generalised Uncertainty Principle and the existence of a Minimal LengthFeb 01 2016We extend significantly previous works on the Hilbert space representations of the Generalized Uncertainty Principle (GUP) in 3+1 dimensions of the form $[X_i,P_j] = i F_{ij}$ where $ F_{ij} = f(P^2) \delta_{ij} + g(P^2) P_i P_j $ for any functions $f$. ... More