Results for "Nicolas Boulanger"

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A note on local BRST cohomology of Yang-Mills type theories with free abelian factorsFeb 10 2018We extend previous work on antifield dependent local BRST cohomology for matter coupled gauge theories of Yang-Mills type to the case of gauge groups that involve free abelian factors. More precisely, we first investigate in a model independent way how ... More
Dual actions for massless, partially-massless and massive gravitons in (A)dSApr 16 2018Jul 12 2018We provide a unified treatment of electric-magnetic duality, at the action level and with manifest Lorentz invariance, for massive, massless as well as partially-massless gravitons propagating in maximally symmetric spacetimes of any dimension n>3. For ... More
Mixed-symmetry multiplets and higher-spin curvaturesJan 11 2015Sep 08 2015We study the higher-derivative equations for gauge potentials of arbitrary mixed-symmetry type obtained by setting to zero the divergences of the corresponding curvature tensors. We show that they propagate the same reducible multiplets as the Maxwell-like ... More
Higher-derivative harmonic oscillators: stability of classical dynamics and adiabatic invariantsNov 16 2018The status of classical stability in higher-derivative systems is still subject to discussions. In this note, we argue that, contrary to general belief, many higher-derivative systems are classically stable. The main tool to see this property are Nekhoroshev's ... More
Mixed symmetry gauge fields in a flat backgroundOct 22 2003Dec 02 2003We present a list of all inequivalent bosonic covariant free particle wave equations in a flat spacetime of arbitrary dimension. The wave functions are assumed to have a finite number of components. We relate these wave equations to equivalent versions ... More
On geometric equations and duality for free higher spinsJan 29 2003We provide a general scheme for dualizing higher-spin gauge fields in arbitrary irreducible representations of GL(D,R). We also give a recipe for constructing Fronsdal-like field equations and Lagrangians for such exotic fields.
An action principle for Vasiliev's four-dimensional higher-spin gravityFeb 10 2011Mar 15 2011We provide Vasiliev's fully nonlinear equations of motion for bosonic gauge fields in four spacetime dimensions with an action principle. We first extend Vasiliev's original system with differential forms in degrees higher than one. We then derive the ... More
Tensor gauge fields in arbitrary representations of GL(D,R): II. Quadratic actionsJun 20 2006Nov 07 2006Quadratic, second-order, non-local actions for tensor gauge fields transforming in arbitrary irreducible representations of the general linear group in D-dimensional Minkowski space are explicitly written in a compact form by making use of Levi-Civita ... More
Gauge invariants and Killing tensors in higher-spin gauge theoriesMay 09 2005Jul 03 2005In free completely symmetric tensor gauge field theories on Minkowski space-time, all gauge invariant functions and Killing tensor fields are computed, both on-shell and off-shell. These problems are addressed in the metric-like formalisms.
A classification of local Weyl invariants in D=8May 25 2004Nov 15 2004Following a purely algebraic procedure, we provide an exhaustive classification of local Weyl-invariant scalar densities in dimension D=8.
Tensor gauge fields in arbitrary representations of GL(D,R) : duality & Poincare lemmaAug 07 2002Sep 30 2003Using a mathematical framework which provides a generalization of the de Rham complex (well-designed for p-form gauge fields), we study the gauge structure and duality properties of theories for free gauge fields transforming in arbitrary irreducible ... More
Consistent deformations of [p,p]-type gauge field theoriesFeb 23 2004Mar 12 2004Using BRST-cohomological techniques, we analyze the consistent deformations of theories describing free tensor gauge fields whose symmetries are represented by Young tableaux made of two columns of equal length p, p>1. Under the assumptions of locality ... More
Anyonic glueballs from an effective-string modelSep 30 2015Relying on an effective-string approach in which glueballs --- bound states of pure Yang-Mills theory --- are modelled by closed strings, we give arguments suggesting that anyonic glueballs, \textit{i.e.} glueballs with arbitrary spin, may exist in $(2+1)$-$\,$dimensional ... More
Massless spin-two field S-dualityDec 11 2002Jan 30 2003We present a review of the homological algebra tools involved in the standard de Rham theory and their subsequent generalizations relevant for the understanding of free massless higher spin gauge structure. M-theory arguments suggest the existence of ... More
A Higgs Mechanism for Gravity. Part II: Higher Spin ConnectionsFeb 22 2006May 09 2006We continue the work of hep-th/0503024 in which gravity is considered as the Goldstone realization of a spontaneously broken diffeomorphism group. We complete the discussion of the coset space Diff(d,R)/SO(1,d-1) formed by the d-dimensional group of analytic ... More
Structure constants of shs$[λ]$: the deformed-oscillator point of viewApr 15 2016Jun 20 2016We derive and spell out the structure constants of the $\mathbb{Z}_2$-graded algebra $\mathfrak{shs}[\lambda]\,$ by using deformed-oscillators techniques in $Aq(2;\nu)\,$, the universal enveloping algebra of the Wigner-deformed Heisenberg algebra in 2 ... More
The unitary representations of the Poincare group in any spacetime dimensionNov 24 2006An extensive group-theoretical treatment of linear relativistic wave equations on Minkowski spacetime of arbitrary dimension D>2 is presented in these lecture notes. To start with, the one-to-one correspondence between linear relativistic wave equations ... More
An Exotic Theory of Massless Spin-Two Fields in Three DimensionsDec 01 2000Mar 23 2001It is a general belief that the only possible way to consistently deform the Pauli-Fierz action, changing also the gauge algebra, is general relativity. Here we show that a different type of deformation exists in three dimensions if one allows for PT ... More
Non-linear parent action and dual gravityJun 17 2008Apr 29 2012We give a reformulation of non-linear Einstein gravity, which contains the dual graviton together with the ordinary metric and a shift gauge field. The metric does not enter through a `kinetic' Einstein-Hilbert term, but via topological couplings, and ... More
Higher-spin algebras and cubic interactions for simple mixed-symmetry fields in AdS spacetimeJul 25 2011Dec 21 2011Nonabelian Fradkin-Vasiliev cubic interactions for dual-graviton-like gauge fields with gravity and themselves are constructed in anti-de Sitter spacetime. The Young diagrams of gauge potentials have shapes of 'tall-hooks', i.e. two columns the second ... More
Gauge fields and infinite chains of dualitiesFeb 27 2015We show that the particle states of Maxwell's theory, in $D$ dimensions, can be represented in an infinite number of ways by using different gauge fields. Using this result we formulate the dynamics in terms of an infinite set of duality relations which ... More
High-dimensional sequence transductionDec 09 2012We investigate the problem of transforming an input sequence into a high-dimensional output sequence in order to transcribe polyphonic audio music into symbolic notation. We introduce a probabilistic model based on a recurrent neural network that is able ... More
Non-abelian cubic vertices for higher-spin fields in anti-de Sitter spaceNov 29 2012Dec 29 2012We use the Fradkin-Vasiliev procedure to construct the full set of non-abelian cubic vertices for totally symmetric higher spin gauge fields in anti-de Sitter space. The number of such vertices is given by a certain tensor-product multiplicity. We discuss ... More
Uniqueness of $\mathcal{N}=2$ and $3$ pure supergravities in 4DFeb 08 2018Dec 14 2018After proving the impossibility of consistent non-minimal coupling of a real Rarita-Schwinger gauge field to electromagnetism, we re-derive the necessity of introducing the graviton in order to couple a complex Rarita-Schwinger gauge field to electromagnetism, ... More
Stochastic description of geometric phase for polarized waves in random mediaJul 11 2012We present a stochastic description of multiple scattering of polarized waves in the regime of forward scattering. In this regime, if the source is polarized, polarization survives along a few transport mean free paths, making it possible to measure an ... More
Unfolding Mixed-Symmetry Fields in AdS and the BMV Conjecture: I. General FormalismDec 18 2008Apr 23 2009We present some generalities of unfolded on-shell dynamics that are useful in analysing the BMV conjecture for mixed-symmetry fields in constantly curved backgrounds. In particular we classify the Lorentz-covariant Harish-Chandra modules generated from ... More
Flato-Fronsdal theorem for higher-order singletonsOct 28 2014We prove a generalised Flato-Fronsdal theorem for higher-order, scalar and spinor, singletons. In the resulting infinite tower of bulk higher-spin fields, we point out the occurrence of partially-massless fields of all depths. This leads us to conjecture ... More
Strong obstruction of the Berends-Burgers-van Dam spin-3 vertexFeb 01 2010In the eighties, Berends, Burgers and van Dam (BBvD) found a nonabelian cubic vertex for self-interacting massless fields of spin three in flat spacetime. However, they also found that this deformation is inconsistent at higher order for any multiplet ... More
Modeling Temporal Dependencies in High-Dimensional Sequences: Application to Polyphonic Music Generation and TranscriptionJun 27 2012We investigate the problem of modeling symbolic sequences of polyphonic music in a completely general piano-roll representation. We introduce a probabilistic model based on distribution estimators conditioned on a recurrent neural network that is able ... More
On The Uniqueness of Minimal Coupling in Higher-Spin Gauge TheoryMay 19 2008Jun 12 2008We address the uniqueness of the minimal couplings between higher-spin fields and gravity. These couplings are cubic vertices built from gauge non-invariant connections that induce non-abelian deformations of the gauge algebra. We show that Fradkin-Vasiliev's ... More
A note on spin-s dualityJun 03 2003Sep 07 2003Duality is investigated for higher spin ($s \geq 2$), free, massless, bosonic gauge fields. We show how the dual formulations can be derived from a common "parent", first-order action. This goes beyond most of the previous treatments where higher-spin ... More
Spin three gauge theory revisitedAug 07 2005Mar 26 2006We study the problem of consistent interactions for spin-3 gauge fields in flat spacetime of arbitrary dimension n>3. Under the sole assumptions of Poincar\'e and parity invariance, local and perturbative deformation of the free theory, we determine all ... More
Advances in Optimizing Recurrent NetworksDec 04 2012Dec 14 2012After a more than decade-long period of relatively little research activity in the area of recurrent neural networks, several new developments will be reviewed here that have allowed substantial progress both in understanding and in technical solutions ... More
How higher-spin gravity surpasses the spin two barrier: no-go theorems versus yes-go examplesJul 02 2010Jan 23 2012Aiming at non-experts, we explain the key mechanisms of higher-spin extensions of ordinary gravity. We first overview various no-go theorems for low-energy scattering of massless particles in flat spacetime. In doing so we dress a dictionary between the ... More
Unfolding Mixed-Symmetry Fields in AdS and the BMV Conjecture: II. Oscillator RealizationDec 23 2008May 28 2009Following the general formalism presented in arXiv:0812.3615 -- referred to as Paper I -- we derive the unfolded equations of motion for tensor fields of arbitrary shape and mass in constantly curved backgrounds by radial reduction of Skvortsov's equations ... More
On bound states of Dirac particles in gravitational fieldsOct 18 2006We investigate the quantum motion of a neutral Dirac particle bouncing on a mirror in curved spacetime. We consider different geometries: Rindler, Kasner-Taub and Schwarzschild, and show how to solve the Dirac equation by using geometrical methods. We ... More
A note about a pure spin-connection formulation of General Relativity and spin-2 duality in (A)dSDec 30 2015We investigate the problem of finding a pure spin-connection formulation of General Relativity with non-vanishing cosmological constant. We first revisit the problem at the linearised level and find that the pure spin-connection, quadratic Lagrangian, ... More
Three-dimensional fractional-spin gravityDec 19 2013Feb 10 2014Using Wigner-deformed Heisenberg oscillators, we construct 3D Chern--Simons models consisting of fractional-spin fields coupled to higher-spin gravity and internal non-abelian gauge fields. The gauge algebras consist of Lorentz-tensorial Blencowe-Vasiliev ... More
Consistent deformations of dual formulations of linearized gravity: A no-go resultOct 29 2002Feb 10 2003The consistent, local, smooth deformations of the dual formulation of linearized gravity involving a tensor field in the exotic representation of the Lorentz group with Young symmetry type (D-3,1) (one column of length D-3 and one column of length 1) ... More
4D Higher Spin Gravity with Dynamical Two-Form as a Frobenius--Chern--Simons Gauge TheoryMay 19 2015Mar 25 2016We provide an off-shell formulation of four-dimensional higher spin gravity based on a covariant Hamiltonian action on an open nine-dimensional Poisson manifold whose boundary consists of the direct product of spacetime and a noncommutative twistor space ... More
Parity violating vertices for spin-3 gauge fieldsSep 15 2005Mar 23 2006The problem of constructing consistent parity-violating interactions for spin-3 gauge fields is considered in Minkowski space. Under the assumptions of locality, Poincar\'e invariance and parity non-invariance, we classify all the nontrivial perturbative ... More
No Self-Interaction for Two-Column Massless FieldsJul 13 2004We investigate the problem of introducing consistent self-couplings in free theories for mixed tensor gauge fields whose symmetry properties are characterized by Young diagrams made of two columns of arbitrary (but different) lengths. We prove that, in ... More
A minimal BV action for Vasiliev's four-dimensional higher spin gravityMay 15 2012Feb 14 2013The action principle for Vasiliev's four-dimensional higher-spin gravity proposed recently by two of the authors, is converted into a minimal BV master action using the AKSZ procedure, which amounts to replacing the classical differential forms by vectorial ... More
Gravitational and gauge couplings in Chern-Simons fractional spin gravityApr 16 2015Mar 01 2016We provide a necessary and sufficient condition for the consistency of the supertrace, through the existence of a certain ground state projector. We build this projector and check its properties to the first two orders in the number operator and to all ... More
A Higher-Spin Chern-Simons Theory of AnyonsNov 18 2013We propose Chern-Simons models of fractional-spin fields interacting with ordinary tensorial higher-spin fields and internal color gauge fields. For integer and half-integer values of the fractional spins, the model reduces to finite sets of fields modulo ... More
Uniqueness of $\mathcal{N}=2$ and $3$ pure supergravities in 4DFeb 08 2018After proving the impossibility of consistent non-minimal coupling of a real Rarita-Schwinger gauge field to electromagnetism, we re-derive the necessity of introducing the graviton in order to couple a complex Rarita-Schwinger gauge field to electromagnetism, ... More
A classification of global conformal invariantsSep 14 2018We provide the full classification, in arbitrary even and odd dimensions, of global conformal invariants, i.e., scalar densities in the spacetime metric and its derivatives that are invariant, possibly up to a total derivative, under local Weyl rescalings ... More
Inconsistency of interacting, multi-graviton theoriesJul 27 2000Oct 05 2000We investigate, in any spacetime dimension >=3, the problem of consistent couplings for a finite collection of massless, spin-2 fields described, in the free limit, by a sum of Pauli-Fierz actions. We show that there is no consistent (ghost-free) coupling, ... More
New Unfolded Higher Spin Systems in $AdS_3$Dec 28 2014Jan 29 2016We investigate the unfolded formulation of bosonic Lorentz tensor fields of arbitrary spin in $AdS_3$ containing a parity breaking mass parameter. They include deformations of the linearisations of the Prokushkin--Vasiliev higher spin theory around its ... More
Filtering from Observations on Stiefel ManifoldsSep 25 2014This paper considers the problem of optimal filtering for partially observed signals taking values on the rotation group. More precisely, one or more components are considered not to be available in the measurement of the attitude of a 3D rigid body. ... More
Consistent deformations of free massive field theories in the Stueckelberg formulationJun 12 2018Jul 11 2018Cohomological techniques within the Batalin-Vilkovisky (BV) extension of the Becchi-Rouet-Stora-Tyutin (BRST) formalism have proved invaluable for classifying consistent deformations of gauge theories. In this work we investigate the application of this ... More
On the uniqueness of higher-spin symmetries in AdS and CFTMay 22 2013Oct 08 2013We study the uniqueness of higher-spin algebras which are at the core of higher-spin theories in AdS and of CFTs with exact higher-spin symmetry, i.e. conserved tensors of rank greater than two. The Jacobi identity for the gauge algebra is the simplest ... More
An Action for Matter Coupled Higher Spin Gravity in Three DimensionsDec 07 2015Jan 20 2016We propose a covariant Hamiltonian action for the Prokushkin and Vasiliev's matter coupled higher spin gravity in three dimensions. The action is formulated on ${\cal X}_4 \times {\cal Z}_2$ where ${\cal X}_4$ is an open manifold whose boundary contains ... More
Higher Spin Interactions in Four Dimensions: Vasiliev vs. FronsdalAug 17 2015Dec 12 2015We consider four-dimensional Higher-Spin Theory at the first nontrivial order corresponding to the cubic action. All Higher-Spin interaction vertices are explicitly obtained from Vasiliev's equations. In particular, we obtain the vertices that are not ... More
Observation of a non-adiabatic geometric phase for elastic wavesMar 23 2011Feb 02 2012We report the experimental observation of a geometric phase for elastic waves in a waveguide with helical shape. The setup reproduces the experiment by Tomita and Chiao [A. Tomita, R.Y. Chiao, Phys. Rev. Lett. 57 (1986) 937-940, 2471] that showed first ... More
Frobenius-Chern-Simons gauge theoryJul 04 2016Given a set of differential forms on an odd-dimensional noncommutative manifold valued in an internal associative algebra H, we show that the most general cubic covariant Hamiltonian action, without mass terms, is controlled by an Z_2-graded associative ... More
Gravitational cubic interactions for a simple mixed-symmetry gauge field in AdS and flat backgroundsJul 10 2011Aug 03 2011Cubic interactions between the simplest mixed-symmetry gauge field and gravity are constructed in anti-de Sitter (AdS) and flat backgrounds. Nonabelian cubic interactions are obtained in AdS following various perturbative methods including the Fradkin-Vasiliev ... More
No consistent cross-interactions for a collection of massless spin-2 fieldsSep 14 2000We report a no-go theorem excluding consistent cross-couplings for a collection of massless, spin-2 fields described, in the free limit, by the sum of Pauli-Fierz actions (one for each field). We show that, in spacetime dimensions >2, there is no consistent ... More
On Killing tensors and cubic vertices in higher-spin gauge theoriesFeb 09 2006The problem of determining all consistent non-Abelian local interactions is reviewed in flat space-time. The antifield-BRST formulation of the free theory is an efficient tool to address this problem. Firstly, it allows to compute all on-shell local Killing ... More
2D sigma models and differential Poisson algebrasMar 19 2015We construct a two-dimensional topological sigma model whose target space is endowed with a Poisson algebra for differential forms. The model consists of an equal number of bosonic and fermionic fields of worldsheet form degrees zero and one. The action ... More
Are Cosmological Gas Accretion Streams Multiphase and Turbulent?Sep 14 2016Simulations of cosmological filamentary accretion streams into galactic halos reveal that such flows are warm at T$\sim$10$^4$K, laminar, and provide high gas accretion efficiency onto galaxies. We present a phenomenological scenario which suggests that ... More
Spin-2 twisted duality in (A)dSJul 12 2018Nov 21 2018Starting from the dual Lagrangians recently obtained for (partially) massless spin-2 fields in the Stueckelberg formulation, we write the equations of motion for (partially) massless gravitons in (A)dS in the form of twisted-duality relations. In both ... More
Action principles for higher and fractional spin gravitiesMar 14 2016Mar 25 2016We review various off-shell formulations for interacting higher-spin systems in dimensions 3 and 4. Associated with higher-spin systems in spacetime dimension 4 is a Chern-Simons action for a superconnection taking its values in a direct product of an ... More
Deformations of vector-scalar modelsDec 21 2017Feb 24 2018Abelian vector fields non-minimally coupled to uncharged scalar fields arise in many contexts. We investigate here through algebraic methods their consistent deformations ("gaugings"), i.e., the deformations that preserve the number (but not necessarily ... More
A Hybrid Recurrent Neural Network For Music TranscriptionNov 06 2014We investigate the problem of incorporating higher-level symbolic score-like information into Automatic Music Transcription (AMT) systems to improve their performance. We use recurrent neural networks (RNNs) and their variants as music language models ... More
Dark soliton past a finite-size obstacleJan 04 2005Sep 05 2005We consider the collision of a dark soliton with an obstacle in a quasi-one-dimensional Bose condensate. We show that in many respects the soliton behaves as an effective classical particle of mass twice the mass of a bare particle, evolving in an effective ... More
Clusters of proteins in bio-membranes: insights into the roles of interaction potential shapes and of protein diversityJun 07 2011It has recently been proposed that proteins embedded in lipidic bio-membranes can spontaneously self-organize into stable small clusters, or membrane nano-domains, due to the competition between short-range attractive and longer-range repulsive forces ... More
Partial list of bipartite Bell inequalities with four binary settingsNov 21 2007Jan 30 2008We give a partial list of 26 tight Bell inequalities for the case where Alice and Bob choose among four two-outcome measurements. All tight Bell inequalities with less settings are reviewed as well. For each inequality we compute numerically the maximal ... More
Entangled photons for competitive multi-armed bandit problem: achievement of maximum social reward, equality, and deception preventionApr 12 2018The competitive multi-armed bandit (CMAB) problem is related to social issues such as maximizing total social benefits while preserving equality among individuals by overcoming conflicts between individual decisions, which could seriously decrease social ... More
Toric generalized Kähler structuresSep 22 2015Sep 25 2015Given a compact symplectic toric manifold $(M,\omega, \mathbb{T})$, we identify a class $DGK_{\omega}^{\mathbb{T}}(M)$ of $\mathbb{T}$-invariant generalized K\"ahler structures for which a generalisation the Abreu-Guillemin theory of toric K\"ahler metrics ... More
Anderson localization of elementary excitations in a one dimensional Bose-Einstein condensateFeb 27 2006Aug 01 2006We study the elementary excitations of a transversely confined Bose-Einstein condensate in presence of a weak axial random potential. We determine the localization length (i) in the hydrodynamical low energy regime, for a domain of linear densities ranging ... More
Many-body Green's function GW and Bethe-Salpeter study of the optical excitations in a paradigmatic model dipeptideSep 03 2013We study within the many-body Green's function GW and Bethe-Salpeter formalisms the excitation energies of a paradigmatic model dipeptide, focusing on the four lowest-lying local and charge-transfer excitations. Our GW calculations are performed at the ... More
Arithmeticity vs. non-linearity for irreducible latticesJul 06 2004We establish an arithmeticity vs. non-linearity alternative for irreducible lattices in suitable product groups, such as for instance products of topologically simple groups. This applies notably to a (large class of) Kac-Moody groups. The alternative ... More
Equivariant measurable liftingsDec 05 2013May 16 2014We discuss equivariance for linear liftings of measurable functions. Existence is established when a transformation group acts amenably, as e.g. the Moebius group of the projective line. Since the general proof is very simple but not explicit, we also ... More
Superrigidity for irreducible lattices and geometric splittingApr 12 2005We prove general superrigidity results for actions of irreducible lattices on CAT(0) spaces; first, in terms of the ideal boundary, and then for the intrinsic geometry (including for infinite-dimensional spaces). In particular, one obtains a new and self-contained ... More
Some Historical Aspects of Error Calculus by Dirichlet FormsJan 12 2014We discuss the main stages of development of the error calculation since the beginning of XIX-th century by insisting on what prefigures the use of Dirichlet forms and emphasizing the mathematical properties that make the use of Dirichlet forms more relevant ... More
Improving Monte Carlo simulations by Dirichlet formsJan 27 2013Equipping the probability space with a local Dirichlet form with square field operator \Gamma and generator A allows to improve Monte Carlo simulations of expectations and densities as soon as we are able to simulate a random variable X together with ... More
Graphes parfaits : structure et algorithmesAug 31 2013This work is the PhD thesis of Nicolas Trotignon, written in 2004 under the supervision of Fr\'ed\'eric Maffray. It is motivated by the desire for a better understanding of perfect graphs. The proof of the Claude Berge's perfect graph conjecture in 2002 ... More
Nonsmooth differential geometry - An approach tailored for spaces with Ricci curvature bounded from belowJul 03 2014We discuss in which sense general metric measure spaces possess a first order differential structure. Building on this, we then see that on spaces with Ricci curvature bounded from below a second order calculus can be developed, permitting to define Hessian, ... More
On torsion torsionfree triplesJan 03 2008We study torsion torsionfree(=TTF) triples in abelian and triangulated categories. (Notice that TTF triples in a triangulated category are essentially in bijection with recollement data for this triangulated category.) In particular, we complete Jans' ... More
Fragmentation cross-sections and model uncertainties in Cosmic Ray propagation physicsOct 30 2015Abundances and energy spectra of cosmic ray nuclei are being measured with high accuracy by the AMS experiment. These observations can provide tight constraints to the propagation models of galactic cosmic rays. In the view of the release of these data, ... More
Examination of uncertainties in nuclear data for cosmic ray physics with the AMS experimentSep 18 2015Oct 24 2015High-energy Li-Be-B nuclei in cosmic rays are being measured with unprecedent accuracy by the AMS experiment. These data bring valuable information to the cosmic ray propagation physics. In particular, combined measurements of B/C and Be/B ratios may ... More
Finiteness of entropy for the homogeneous Boltzmann equation with measure initial conditionMar 01 2012Mar 16 2015We consider the $3D$ spatially homogeneous Boltzmann equation for (true) hard and moderately soft potentials. We assume that the initial condition is a probability measure with finite energy and is not a Dirac mass. For hard potentials, we prove that ... More
svcR: An R Package for Support Vector Clustering improved with Geometric Hashing applied to Lexical Pattern DiscoveryApr 23 2015We present a new R package which takes a numerical matrix format as data input, and computes clusters using a support vector clustering method (SVC). We have implemented an original 2D-grid labeling approach to speed up cluster extraction. In this sense, ... More
Multitype Contact Process with Frozen statesJan 26 2004We study a generalization of the two colors multitype contact process intended to mimic an example of interspecific competition called allelopathy.
Théorèmes de de Finetti, limites de champ moyen et condensation de Bose-EinsteinSep 03 2014Feb 13 2015These lecture notes treat the mean-field approximation for equilibrium states of N body systems in classical and quantum statistical mechanics. A general strategy to justify effective models based on assumptions of statistical independence of the particles ... More
Sur la modélisation de l'interaction entre polarons et cristaux quantiquesJun 02 2013This text is a summary (in french) of recent works in collaboration with Mathieu Lewin, on the modelling of polarons in quantum crystals.
The giant vortex state for a Bose-Einstein condensate in a rotating anharmonic trap : extreme rotation regimesSep 10 2008Dec 01 2009We study the fast rotation limit for a Bose-Einstein condensate in a quadratic plus quartic confining potential within the framework of the two dimensional Gross-Pitaevskii energy functional. As the rotation speed tends to infinity with a proper scaling ... More
Effective mass of free neutrons in neutron star crustDec 11 2005The inner layers of a neutron star crust, composed of a Coulomb lattice of neutron rich nuclear clusters immersed in a sea of ``free'' superfluid neutrons, are closely analogous to periodic condensed matter systems such as electronic, photonic or phononic ... More
Scalar Extension of Abelian and Tannakian CategoriesJun 02 2008We introduce and develop the notion of scalar extension for abelian categories. Given a field extension F'/F, to every F-linear abelian category A satisfying a suitable finiteness condition we associate an F'-linear abelian category A' and an exact F-linear ... More
On the equivalence between standard and sequentially ordered hidden Markov modelsJan 30 2012Chopin (2007) introduced a sequentially ordered hidden Markov model, for which states are ordered according to their order of appearance, and claimed that such a model is a re-parametrisation of a standard Markov model. This note gives a formal proof ... More
Real-time update of multi-fractal analysis on dynamic time series using incremental discrete wavelet transformsNov 21 2005An algorithm is presented to update the multi-fractal spectrum of a time series in constant time when new data arrives. The discrete wavelet transform (DWT) of the time series is first updated for the new data value. This is done optimally in terms of ... More
Euler obstruction and Lipschitz-Killing curvaturesMay 23 2014Applying a local Gauss-Bonnet formula for closed subanalytic sets to the complex analytic case, we obtain characterizations of the Euler obstruction of a complex analytic germ in terms of the Lipschitz-Killing curvatures and the Chern forms of its regular ... More
The GRB followup Euro-US Consortium: results from the ESO telescopesJan 15 2002In October 1997, the Italian and Dutch GRB teams started a collaboration on ESO optical follow-up of rapidly and accurately localized GRBs. Subsequently, starting April 1, 2000, this collaboration was extended to astronomers from other countries, who ... More
GoSam 2.0: Automated one loop calculations within and beyond the Standard ModelOct 13 2014We present GoSam 2.0, a fully automated framework for the generation and evaluation of one loop amplitudes in multi leg processes. The new version offers numerous improvements both on generational aspects as well as on the reduction side. This leads to ... More
Pascal, Fermat et la géométrie du hasardSep 11 2013Ce m\'emoire r\'ealis\'e \`a l'IUFM de Cr\'eteil en 1998 sous la direction d'Evelyne Barbin \'etudie l'histoire du d\'ebut du calcul des probabilit\'es. Sources: correspondance entre Pascal et Fermat, et Trait\'e du triangle arithm\'etique de Pascal. ... More
Lepton Photon 2001 Concluding RemarksJan 16 2002Jan 21 2002Important new results have been presented at this conference. The direct violation of CP in $K^{0}\to \pi+\pi$ has been firmly established in two independent experiments, NA48 at CERN and KTeV at Fermilab. Both Babar at SLAC and Belle at KeK have determined ... More
Simulation and approximation of Levy-driven stochastic differential equationsJan 20 2009We consider the problem of the simulation of Levy-driven stochastic differential equations. It is generally impossible to simulate the increments of a Levy-process. Thus in addition to an Euler scheme, we have to simulate approximately these increments. ... More
Traveling the Silk Road: A measurement analysis of a large anonymous online marketplaceJul 31 2012Nov 28 2012We perform a comprehensive measurement analysis of Silk Road, an anonymous, international online marketplace that operates as a Tor hidden service and uses Bitcoin as its exchange currency. We gather and analyze data over eight months between the end ... More
Remarks on the spectrum of the Dirac operatorJun 03 2003We describe a new family of examples of hypersurfaces in the sphere satisfying the limiting-case in C. B\"ar's extrinsic upper bound for the smallest eigenvalue of the Dirac operator.