Results for "Remi Soummer"

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Apodized Pupil Lyot Coronagraphs for Arbitrary Telescope AperturesDec 09 2004In the context of high dynamic range imaging, this study presents a breakthrough for the understanding of Apodized Pupil Lyot Coronagraphs, making them available for arbitrary aperture shapes. These new solutions find immediate application in current, ... More
New Completeness Methods for Estimating Exoplanet Discoveries by Direct DetectionMar 24 2010We report new methods for evaluating realistic observing programs that search stars for planets by direct imaging, where observations are selected from an optimized star list, and where stars can be observed multiple times. We show how these methods bring ... More
Detection and Characterization of Exoplanets and Disks using Projections on Karhunen-Loeve EigenimagesJul 17 2012We describe a new method to achieve point spread function (PSF) subtractions for high- contrast imaging using Principal Component Analysis (PCA) that is applicable to both point sources or extended objects (disks). Assuming a library of reference PSFs, ... More
Fast computation of Lyot-style coronagraph propagationNov 02 2007We present a new method for numerical propagation through Lyot-style coronagraphs using finite occulting masks. Standard methods for coronagraphic simulations involve Fast Fourier Transforms (FFT) of very large arrays, and computing power is an issue ... More
Shaped pupil design for the Gemini Planet ImagerMay 11 2009The Gemini Planet Imager (GPI) is an instrument designed for the Gemini South telescope to image young Jupiter-mass planets in the infrared. To achieve the high contrast needed for this, it employs an apodized pupil Lyot coronagraph (APLC) to remove most ... More
Speckle Suppression with the Project 1640 Integral Field SpectrographDec 17 2010Project 1640 is a high-contrast imaging instrument recently commissioned at Palomar observatory. A combination of a coronagraph with an integral field spectrograph (IFS), Project 1640 is designed to detect and characterize extrasolar planets, brown dwarfs, ... More
Pushing the Limits of Exoplanet Discovery via Direct Imaging with Deep LearningApr 12 2019Further advances in exoplanet detection and characterisation require sampling a diverse population of extrasolar planets. One technique to detect these distant worlds is through the direct detection of their thermal emission. The so-called direct imaging ... More
On the energetics of stratified turbulent mixing, irreversible thermodynamics, Boussinesq models, and the ocean heat engine controversyMar 11 2009Jul 16 2009A key issue in stratified turbulence theory concerns the nature of the link between D(APE), the dissipation rate of available potential energy APE, and W_{r,turbulent}, the turbulent rate of change of background gravitational potential energy GPE_r, which ... More
Thermodynamic inadmissibility of the incompressible hydrodynamics description of turbulent stratified fluid flows at low Mach numbersNov 19 2007The incompressible Navier-Stokes equations currently represent the primary model for describing stratified turbulent fluid flows at low Mach number. The validity of the incompressible assumption, however, has so far only been rigorously established for ... More
Geometric optics and instability for semi-classical Schrodinger equationsMay 23 2005Oct 27 2005We prove some instability phenomena for semi-classical (linear or) nonlinear Schrodinger equations. For some perturbations of the data, we show that for very small times, we can neglect the Laplacian, and the mechanism is the same as for the corresponding ... More
Perturbed geodesics on the moduli space of flat connections and Yang-Mills theoryJun 28 2010If we consider the moduli space of flat connections of a non trivial principal SO(3)-bundle over a surface, then we can define a map from the set of perturbed closed geodesics, below a given energy level, into families of perturbed Yang-Mills connections ... More
Introduction to Phase Transitions in Random Optimization ProblemsApr 19 2007Notes of the lectures delivered in Les Houches during the Summer School on Complex Systems (July 2006).
Une propriete du groupe a 168 elementsMar 24 2003Let an affine space of dimension n over a field k. To each point correponds a section of the linear group G to the affine group. Generally, every section is like this, excpt in the case card(k)=2 and n=3, where G is the group of cardinality 168.
Differential fields and Geodesic flows II : Geodesic flows of pseudo-Riemannian algebraic varietiesMar 01 2017We define the notion of a smooth pseudo-Riemannian algebraic variety $(X,g)$ over a field $k$ of characteristic $0$, which is an algebraic analogue of the notion of Riemannian manifold and we study, from a model-theoretic perspective, the algebraic differential ... More
Tensorizing maximal correlationsApr 09 2010Dec 30 2010The maximal (or Hilbertian) correlation coefficient between two random variables X and Y, denoted by \{X:Y\}, is the supremum of the |Corr(f(X),g(Y))| for real measurable functions f, g, where "Corr" denotes Pearson's correlation coefficient. It is a ... More
Nonlinear Schrodinger equations with repulsive harmonic potential and applicationsOct 31 2002Mar 14 2003We study the Cauchy problem for Schrodinger equations with repulsive quadratic potential and power-like nonlinearity. The local problem is well-posed in the same space as that used when a confining harmonic potential is involved. For a defocusing nonlinearity, ... More
A generic framework for the development of geospatial processing pipelines on clustersSep 28 2016The amount of remote sensing data available to applications is constantly growing due to the rise of very-high-resolution sensors and short repeat cycle satellites. Consequently, tackling computational complexity in Earth Observation information extraction ... More
Diffusion, localization and dispersion relations on ``small-world'' latticesMar 23 1999The spectral properties of the Laplacian operator on ``small-world'' lattices, that is mixtures of unidimensional chains and random graphs structures are investigated numerically and analytically. A transfer matrix formalism including a self-consistent ... More
Front-end Electronics for the CALICE/EUDET CalorimetersJan 30 2009The CALICE collaboration is involved in the design of compact calorimeters featuring a high granularity. The technical developments have to overcome various design issues such as the power dissipation, the integration of the front-end electronics inside ... More
APE dissipation is a form of Joule heating. It is irreversible, not reversibleJun 29 2018Available Potential Energy (APE) dissipation plays a central role in the description of mixing in turbulent stratified fluids. The dominant paradigm is that it converts APE into background gravitational potential energy ${\rm GPE}_r$, and that the APE ... More
Inference with Hamiltonian Sequential Monte Carlo SimulatorsDec 19 2018The paper proposes a new Monte-Carlo simulator combining the advantages of Sequential Monte Carlo simulators and Hamiltonian Monte Carlo simulators. The result is a method that is robust to multimodality and complex shapes to use for inference in presence ... More
Cascade of phase shifts for nonlinear Schrodinger equationsFeb 11 2005We consider a semi-classical nonlinear Schrodinger equation. For initial data causing focusing at one point in the linear case, we study a nonlinearity which is super-critical in terms of asymptotic effects near the caustic. We prove the existence of ... More
Optimisation problems and replica symmetry breaking in finite connectivity spin-glassesJul 09 1997Oct 25 1997A formalism capable of handling the first step of hierarchical replica symmetry breaking in finite-connectivity models is introduced. The emerging order parameter is claimed to be a probability distribution over the space of field distributions (or, equivalently ... More
Decomposition into weight * level + jump and application to a new classification of primesNov 06 2007Jan 18 2010In this paper we introduce an Euclidean decomposition of elements a_n of an increasing sequence of natural numbers into weight * level + jump which we use to classify the numbers a_n either by weight or by level. We then show that this decomposition can ... More
Heat flow on the moduli space of flat connections and Yang-Mills theoryAug 02 2010Apr 07 2013It is known that there is a bijection between the perturbed closed geodesics, below a given energy level, on the moduli space of flat connections M and families of perturbed Yang-Mills connections depending on a small parameter. In this paper we study ... More
Stable blow-up dynamic for the parabolic-parabolic Patlak-Keller-Segel modelMar 19 2014We consider the parabolic-parabolic two-dimensional Patlak-Keller-Segel problem. We prove the existence of stable blow-up dynamics in finite time in the radial case. We extend in this article the result of [36] for the parabolic-elliptic case.
Future Gravitational Wave Detectors Based on Atom InterferometryNov 29 2016We present the perspective of using atom interferometry for gravitational wave (GW) detection in the mHz to about 10 Hz frequency band. We focus on light-pulse atom interferometers which have been subject to intense developments in the last 25 years. ... More
Local available energetics of multicomponent compressible stratified fluidsDec 04 2017Feb 20 2018We extend the local theory of available potential energy (APE) to a general multicomponent compressible stratified fluid, accounting for the effects of diabatic sinks and sources. As for simple compressible fluids, the total potential energy density of ... More
Thermodynamics/dynamics coupling and thermodynamic consistency of Boussinesq and anelastic binary fluids with an arbitrary nonlinear equation of stateNov 23 2010Jun 21 2011This paper shows that the energetics of Boussinesq and anelastic fluids possesses a term that can be identified as the approximation $\delta W_{ba}$ to the compressible work of expansion/contraction $\delta W =-P {\rm d}\upsilon$, where $P$ is the pressure ... More
Understanding mixing efficiency in the oceans: Do the nonlinearities of the equation of state matter?Jun 23 2009Jul 16 2009There exist two central measures of turbulent mixing in turbulent stratified fluids, both caused by molecular diffusion: 1) the dissipation rate D(APE) of available potential energy (APE); 2) the turbulent rate of change Wr,turbulent of background potential ... More
Stochastic Equivariant Cohomologies and Cyclic CohomologyJul 22 2005We give two stochastic diffeologies on the free loop space which allow us to define stochastic equivariant cohomology theories in the Chen-Souriau sense and to establish a link with cyclic cohomology. With the second one, we can establish a stochastic ... More
Some ideas about quantitative convergence of collision models to their mean field limitFeb 04 2009May 06 2009We consider a stochastic $N$-particle model for the spatially homogeneous Boltzmann evolution and prove its convergence to the associated Boltzmann equation when $N\to \infty$. For any time $T>0$ we bound the distance between the empirical measure of ... More
Linear vs. nonlinear effects for nonlinear Schrodinger equations with potentialMay 21 2004We review some recent results on nonlinear Schrodinger equations with potential, with emphasis on the case where the potential is a second order polynomial, for which the interaction between the linear dynamics caused by the potential, and the nonlinear ... More
Global existence results for nonlinear Schrodinger equations with quadratic potentialsMay 11 2004Feb 18 2005We prove that no finite time blow up can occur for nonlinear Schroedinger equations with quadratic potentials, provided that the potential has a sufficiently strong repulsive component. This is not obvious in general, since the energy associated to the ... More
Stochastic Homogenization of Reflected Diffusion ProcessesDec 20 2007Sep 18 2009We investigate a functional limit theorem (homogenization) for Reflected Stochastic Differential Equations on a half-plane with stationary coefficients when it is necessary to analyze both the effective Brownian motion and the effective local time. We ... More
The notion of conservation for residual distribution schemes (or fluctuation splitting schemes), with some applicationsApr 03 2019In this paper, we discuss the notion of discrete conservation for hyperbolic conservation laws. We introduce what we call a fluctuation splitting schemes (or residual distribution, also RDS) and show on several examples how this cal lead to new development. ... More
Low Order Aberrations in Band-Limited Lyot CoronagraphsJul 22 2005We study the way Lyot coronagraphs with unapodized entrance pupils respond to small, low order phase aberrations. This study is applicable to ground-based adaptive optics coronagraphs operating at 90% and higher Strehl ratios, as well as to some space-based ... More
High-contrast Imager for Complex Aperture Telescopes (HiCAT): 6. Software Control Infrastructure and CalibrationMar 07 2019High contrast imaging using coronagraphy is one of the main avenues to enable the search for life on extrasolar Earth analogs. The HiCAT testbed aims to demonstrate coronagraphy and wavefront control for segmented on-axis space telescopes as envisioned ... More
Know the Star, Know the Planet. V. Characterization of the Stellar Companion to the Exoplanet Host HD 177830Jul 28 2015Jul 29 2015HD 177830 is an evolved K0IV star with two known exoplanets. In addition to the planetary companions it has a late-type stellar companion discovered with adaptive optics imagery. We observed the binary star system with the PHARO near-IR camera and the ... More
Planetary system, star formation, and black hole science with non-redundant masking on space telescopesApr 08 2009Apr 13 2009Non-redundant masking (NRM) is a high contrast, high resolution technique relevant to future space missions concerned with extrasolar planetary system and star formation, as well as general high angular resolution galactic and extragalactic astronomy. ... More
Orbital Motion of HR 8799 b,c, d using Hubble Space Telescope data from 1998: Constraints on Inclination, Eccentricity and StabilityOct 06 2011HR 8799 is currently the only multiple-planet system that has been detected with direct imaging, with four giant planets orbiting at large separations from this young late A star. Orbital motion provides insight into the stability, and possible formation ... More
High Resolution Infrared Imaging & Spectroscopy of the Z Canis Majoris System During Quiescence & OutburstDec 11 2012We present adaptive optics photometry and spectra in the JHKL-bands along with high spectral resolution K-band spectroscopy for each component of the Z Canis Majoris system. Our high angular resolution photometry of this very young (<1 Myr) binary, comprised ... More
The ExoEarth Yield Landscape for Future Direct Imaging Space TelescopesApr 26 2019The expected yield of potentially Earth-like planets is a useful metric for designing future exoplanet-imaging missions. Recent yield studies of direct-imaging missions have focused primarily on yield methods and trade studies using "toy" models of missions. ... More
Trajectories in phase diagrams, growth processes and computational complexity: how search algorithms solve the 3-Satisfiability problemSep 26 2000Most decision and optimization problems encountered in practice fall into one of two categories with respect to any particular solving method or algorithm: either the problem is solved quickly (easy) or else demands an impractically long computational ... More
Produit de Moyal stochastique sur l'espace de WienerSep 24 2004We propose a stochastic extension of deformation quantization on a Hilbert space. The Moyal product is defined in this context on the space of functionals belonging to all of the Sobolev spaces of the Malliavin calculus.
Stable blow up dynamics for the 1-corotational energy critical harmonic heat flowJun 05 2011We exhibit a stable finite time blow up regime for the 1-corotational energy critical harmonic heat flow from $\Bbb R^2$ into a smooth compact revolution surface of $\Bbb R^3$ which reduces to the semilinear parabolic problem $$\partial_t u -\pa^2_{r} ... More
Cutoff phenomenon for the simple exclusion process on the complete graphOct 23 2010Dec 13 2011We study the time that the simple exclusion process on the complete graph needs to reach equilibrium in terms of total variation distance. For the graph with n vertices and 1<<k<n/2 particles we show that the mixing time is of order (n/2)\log \min(k, ... More
The Entropy of the K-Satisfiability ProblemMar 02 1996The threshold behaviour of the K-Satisfiability problem is studied in the framework of the statistical mechanics of random diluted systems. We find that at the transition the entropy is finite and hence that the transition itself is due to the abrupt ... More
Robust Model Reduction by $L^1$-norm Minimization and Approximation via Dictionaries: Application to Linear and Nonlinear Hyperbolic ProblemsJun 19 2015We propose a novel model reduction approach for the approximation of non linear hyperbolic equations in the scalar and the system cases. The approach relies on an offline computation of a dictionary of solutions together with an online $L^1$-norm minimization ... More
Reconstructing a Random Potential from its Random WalksApr 19 2007The problem of how many trajectories of a random walker in a potential are needed to reconstruct the values of this potential is studied. We show that this problem can be solved by calculating the probability of survival of an abstract random walker in ... More
Science with Liquid Mirror Telescopes: Season 1996 of NASA Orbital Debris ObservatoryJun 16 1997We present preliminary results of observations made, during the spring of 1996, with the 3-m liquid mirror telescope of the NASA Orbital Debris Observatory. A 20-arcmin-wide strip of sky was observed at latitude of 32deg56 N using 10 narrow-band filters. ... More
On the orbital stability of Gaussian solitary waves in the log-KdV equationJan 08 2014Aug 06 2014We consider the logarithmic Korteweg-de Vries (log-KdV) equation, which models solitary waves in anharmonic chains with Hertzian interaction forces. By using an approximating sequence of global solutions of the regularized generalized KdV equation in ... More
Splitting methods for the nonlocal Fowler equationSep 15 2011Aug 09 2012We consider a nonlocal scalar conservation law proposed by Andrew C. Fowler to describe the dynamics of dunes, and we develop a numerical procedure based on splitting methods to approximate its solutions. We begin by proving the convergence of the well-known ... More
Some preliminary results on a kinetic scheme that has an Lattice Boltzmann method flavourApr 29 2019In this short paper, we intend to describe one way to construct arbitrarily high order kinetic schemes on regular meshes. The method can be arbitrarily high order in space and time, and run at CFL one. This is a common feature with the Lattice Boltzmann ... More
Focusing at a point with caustic crossing for a class of nonlinear equationsJan 14 2003We consider the asymptotic behavior of solutions to nonlinear partial differential equations in the limit of short wavelength. For initial data which cause focusing at one point, we highlight critical indexes as far as the influence of the nonlinearity ... More
Active Regression by StratificationOct 22 2014We propose a new active learning algorithm for parametric linear regression with random design. We provide finite sample convergence guarantees for general distributions in the misspecified model. This is the first active learner for this setting that ... More
Fast Inference of Interactions in Assemblies of Stochastic Integrate-and-Fire Neurons from Spike RecordingsFeb 25 2011We present two Bayesian procedures to infer the interactions and external currents in an assembly of stochastic integrate-and-fire neurons from the recording of their spiking activity. The first procedure is based on the exact calculation of the most ... More
Theoretical study of collective modes in DNA at ambient temperatureNov 02 1999The instantaneous normal modes corresponding to base pair vibrations (radial modes) and twist angle fluctuations (angular modes) of a DNA molecule model at ambient temperature are theoretically investigated. Due to thermal disorder, normal modes are not ... More
Statistical Mechanics of Torque Induced Denaturation of DNAApr 20 1999Sep 24 1999A unifying theory of the denaturation transition of DNA, driven by temperature T or induced by an external mechanical torque Gamma is presented. Our model couples the hydrogen-bond opening and the untwisting of the helicoidal molecular structure. We show ... More
Circuits in random graphs: from local trees to global loopsJul 09 2004We compute the number of circuits and of loops with multiple crossings in random regular graphs. We discuss the importance of this issue for the validity of the cavity approach. On the one side we obtain analytic results for the infinite volume limit ... More
Relaxation and Metastability in the RandomWalkSAT search procedureJan 15 2003Jan 29 2003An analysis of the average properties of a local search resolution procedure for the satisfaction of random Boolean constraints is presented. Depending on the ratio alpha of constraints per variable, resolution takes a time T_res growing linearly (T_res ... More
Innovation rather than improvement: a solvable high-dimensional model highlights the limitations of scalar fitnessAug 17 2017Dec 12 2017Much of our understanding of ecological and evolutionary mechanisms derives from analysis of low-dimensional models: with few interacting species, or few axes defining "fitness". It is not always clear to what extent the intuition derived from low-dimensional ... More
On the role of quadratic oscillations in nonlinear Schroedinger equations II. The $L^2$-critical caseApr 09 2004Sep 06 2004We consider a nonlinear semi-classical Schroedinger equation for which quadratic oscillations lead to focusing at one point, described by a nonlinear scattering operator. The relevance of the nonlinearity was discussed by R. Carles, C. Fermanian-Kammerer ... More
Scaling limits for symmetric Ito-Levy processes in random mediumDec 19 2008Dec 26 2008We are concerned with scaling limits of the solutions to stochastic differential equations with stationary coefficients driven by Poisson random measures and Brownian motions. We state an annealed convergence theorem, in which the limit exhibits a diffusive ... More
A Krylov Stability-Corrected Coordinate-Stretching Method to Simulate Wave Propagation in Unbounded DomainsFeb 02 2012Apr 13 2012The Krylov subspace projection approach is a well-established tool for the reduced order modeling of dynamical systems in the time domain. In this paper, we address the main issues obstructing the application of this powerful approach to the time-domain ... More
From inherent structures to pure states: some simple remarks and examplesDec 03 1999Feb 16 2000The notions of pure states and inherent structures, i.e. stable configurations against 1-spin flip are discussed. We explain why these different concepts accidentally coincide in mean-field models with infinite connectivity and present an exactly solvable ... More
Learning and generalization theories of large committee--machinesJan 25 1996The study of the distribution of volumes associated to the internal representations of learning examples allows us to derive the critical learning capacity ($\alpha_c=\frac{16}{\pi} \sqrt{\ln K}$) of large committee machines, to verify the stability of ... More
On the stability of critical chemotactic aggregationSep 12 2012We consider the two dimensional parabolic-elliptic Patlak-Keller-Segel model of chemotactic aggregation for radially symmetric initial data. We show the existence of a stable mechanism of singularity formation and obtain a complete description of the ... More
Quantized slow blow up dynamics for the corotational energy critical harmonic heat flowJan 09 2013We consider the energy critical harmonic heat flow from $\Bbb R^2$ into a smooth compact revolution surface of $\Bbb R^3$. For initial data with corotational symmetry, the evolution reduces to the semilinear radially symmetric parabolic problem $$\partial_t ... More
Analysis of the computational complexity of solving random satisfiability problems using branch and bound search algorithmsDec 11 2000The computational complexity of solving random 3-Satisfiability (3-SAT) problems is investigated. 3-SAT is a representative example of hard computational tasks; it consists in knowing whether a set of alpha N randomly drawn logical constraints involving ... More
Washing out of the 0-pi transition in Josephson junctionsJul 21 2014We consider a Josephson junction formed by a quantum dot connected to two bulk superconductors in presence of Coulomb interaction and coupling to both an electromagnetic environment and a finite density of electronic quasi-particles. In the limit of large ... More
The effect of mechanical stirring on buoyancy-driven circulationsJun 23 2009The theoretical analysis of the energetics of mechanically-stirred horizontal convection for a Boussinesq fluid yields the formula: G(APE) = \gamma_{mixing} G(KE) + (1+\gamma_{mixing}) W_{r,laminar} where G(APE) and G(KE) are the work rate done by the ... More
On the local view of atmospheric available potential energyNov 23 2017The possibility of constructing Lorenz's concept of available potential energy (APE) from a local principle has been known for some time, but has received very little attention so far. Yet, the local APE framework offers the advantage of providing a positive ... More
The expansion of polynomial invariants for $2$-decompositions of generalized graphsAug 23 2016The $2$-decomposition for ribbon graphs was introduced in [Annals of Combinatorics 15 (2011), pp 675-706]. We extend this result to half-edged ribbon graphs and to rank $D$-weakly colored graphs [SIGMA 12 (2016), 030], generalizing therefore the $2$-sums ... More
Tricritical Points in Random Combinatorics: the (2+p)-SAT caseOct 01 1998The (2+p)-Satisfiability (SAT) problem interpolates between different classes of complexity theory and is believed to be of basic interest in understanding the onset of typical case complexity in random combinatorics. In this paper, a tricritical point ... More
A collective phase in resource competition in a highly diverse ecosystemSep 05 2016Organisms shape their own environment, which in turn affects their survival. This feedback becomes especially important for communities containing a large number of species; however, few existing approaches allow studying this regime, except in simulations. ... More
When sound slows down bubblesJan 21 2010Apr 06 2010We present experimental evidence that a bubble moving in a fluid in which a well-chosen acoustic noise is superimposed can be significantly slowed down for moderate acoustic pressures. Through mean velocity measurements, we show that a condition for this ... More
Heuristic average-case analysis of the backtrack resolution of random 3-Satisfiability instancesJan 14 2004An analysis of the average-case complexity of solving random 3-Satisfiability (SAT) instances with backtrack algorithms is presented. We first interpret previous rigorous works in a unifying framework based on the statistical physics notions of dynamical ... More
Dictionary Identification - Sparse Matrix-Factorisation via $\ell_1$-MinimisationApr 30 2009Mar 01 2010This article treats the problem of learning a dictionary providing sparse representations for a given signal class, via $\ell_1$-minimisation. The problem can also be seen as factorising a $\ddim \times \nsig$ matrix $Y=(y_1 >... y_\nsig), y_n\in \R^\ddim$ ... More
Toward Optimal Stratification for Stratified Monte-Carlo IntegrationMar 12 2013We consider the problem of adaptive stratified sampling for Monte Carlo integration of a noisy function, given a finite budget n of noisy evaluations to the function. We tackle in this paper the problem of adapting to the function at the same time the ... More
Semiclassical Nonlinear Schrodinger equations with potential and focusing initial dataDec 19 2002Jul 03 2003We study the asymptotic behaviour of solutions to semi-classical nonlinear Schrodinger equations with a potential, for concentrating and oscillating initial data, when the nonlinearity is repulsive and the potential is a polynomial of degree at most two. ... More
On a Nonlinear Partial Integro-Differential EquationNov 19 2009Consistently fitting vanilla option surfaces is an important issue when it comes to modelling in finance. Local volatility models introduced by Dupire in 1994 are widely used to price and manage the risks of structured products. However, the inconsistencies ... More
Polynomial Invariants for Arbitrary Rank $D$ Weakly-Colored Stranded GraphsApr 27 2015Mar 23 2016Polynomials on stranded graphs are higher dimensional generalization of Tutte and Bollob\'as-Riordan polynomials [Math. Ann. 323 (2002), 81-96]. Here, we deepen the analysis of the polynomial invariant defined on rank 3 weakly-colored stranded graphs ... More
Elliptic Yang-Mills Flow TheoryMar 06 2013Dec 05 2013We lay the foundations of a Morse homology on the space of connections on a principal $G$-bundle over a compact manifold $Y$, based on a newly defined gauge-invariant functional $\mathcal J$. While the critical points of $\mathcal J$ correspond to Yang-Mills ... More
Focusing of Spherical Nonlinear Pulses in ${\mathbb R}^{1+3}$, III. Sub and Supercritical casesDec 20 2002We study the validity of geometric optics in $L^\infty$ for nonlinear wave equations in three space dimensions whose solutions, pulse like, focus at a point. If the amplitude of the initial data is subcritical, then no nonlinear effect occurs at leading ... More
Phase-Retrieval-Based Wavefront Metrology for High Contrast CoronagraphyMar 05 2019We discuss the use of parametric phase-diverse phase retrieval as an in-situ high-fidelity wavefront measurement method to characterize and optimize the transmitted wavefront of a high-contrast coronagraphic instrument. We apply our method to correct ... More
Discovery of a low-mass companion inside the debris ring surrounding the F5V star HD206893Dec 01 2016Dec 06 2016Uncovering the ingredients and the architecture of planetary systems is a very active field of research that has fuelled many new theories on giant planet formation, migration, composition, and interaction with the circumstellar environment. We aim at ... More
The Kappa Andromedae System: New Constraints on the Companion Mass, System Age & Further MultiplicitySep 13 2013Kappa Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55 AU was recently announced. In this work, we present the first spectrum of the companion, "kappa And B," using the Project 1640 high-contrast imaging platform. ... More
Apodized Pupil Lyot Coronagraphs for Arbitrary Apertures. IV. Reduced Inner Working Angle and Increased Robustness to Low-Order AberrationsDec 08 2014The Apodized Pupil Lyot Coronagraph (APLC) is a diffraction suppression system installed in the recently deployed instruments Palomar/P1640, Gemini/GPI, and VLT/SPHERE to allow direct imaging and spectroscopy of circumstellar environments. Using a prolate ... More
Introduction to stellar coronagraphyMar 26 2007Oct 06 2008This paper gives a simple and original presentation of various coronagraphs inherited from the Lyot coronagraph. We first present the Lyot and Roddier phase mask coronagraphs and study their properties as a function of the focal mask size. We show that ... More
Obstructed Telescopes vs Unobstructed Telescopes for Wide Field Survey - A Quantitative AnalysisMar 12 2014Telescopes with unobstructed pupil are known to deliver clean point spread function (PSF) to their focal plane, in contrast to traditional telescopes with obstructed pupil. Recent progress in the manufacturing aspheric surfaces and mounting accuracy favors ... More
A Method for Visuo-Spatial Classification of Freehand Shapes Freely SketchedMay 07 2013We present the principle and the main steps of a new method for the visuo-spatial analysis of geometrical sketches recorded online. Visuo-spatial analysis is a necessary step for multi-level analysis. Multi-level analysis simultaneously allows classification, ... More
Electrical-modelling, design and simulation of cumulative radiation effects in semiconductor pixels detectors: prospects and limitsOct 28 2014Nov 19 2014Silicon detectors have gained in popularity since silicon became a widely used micro/nanoelectronic semiconductor material. Silicon detectors are used in particle physics as well as imaging for pixel based detecting systems. Over the past twenty years ... More
The dynamics of proving uncolourability of large random graphs I. Symmetric Colouring HeuristicApr 28 2003We study the dynamics of a backtracking procedure capable of proving uncolourability of graphs, and calculate its average running time T for sparse random graphs, as a function of the average degree c and the number of vertices N. The analysis is carried ... More
Assessment of algorithms for computing moist available potential energyDec 06 2017Atmospheric moist available potential energy (MAPE) has been traditionally defined as the potential energy of a moist atmosphere relative to that of the adiabatically sorted reference state defining a global potential energy minimum. Finding such a reference ... More
Magnetic Field dragging in accretion discsDec 22 2011Accretion discs are composed of ionized gas in motion around a central object. Sometimes, the disc is the source of powerful bipolar jets along its rotation axis. Theoretical models invoke the existence of a bipolar magnetic field crossing the disc and ... More
Temporal Evolution of Coronagraphic Dynamic Range, and Constraints on Companions to VegaSep 12 2006The major obstacle to the direct detection of companions to nearby stars is the overwhelming brightness of the host star. Current instruments employing the combination of adaptive optics (AO) and coronagraphy can typically detect objects within 2'' of ... More
The First H-band Spectrum of the Massive Gas Giant Planet beta Pictoris b with the Gemini Planet ImagerJul 16 2014Using the recently installed Gemini Planet Imager (GPI), we have taken the first H-band spectrum of the planetary companion to the nearby young star beta Pictoris. GPI is designed to image and provide low-resolution spectra of Jupiter sized, self-luminous ... More
Comparison of optical observational capabilities for the coming decades: ground versus spaceSep 24 2009Ground-based adaptive optics (AO) in the infrared has made exceptional advances in approaching space-like image quality at higher collecting area. Optical-wavelength applications are now also growing in scope. We therefore provide here a comparison of ... More
Speckle Suppression Through Dual Imaging Polarimetry, and a Ground-Based Image of the HR 4796A Circumstellar DiskJun 16 2009Jun 25 2009We demonstrate the versatility of a dual imaging polarimeter working in tandem with a Lyot coronagraph and Adaptive Optics to suppress the highly static speckle noise pattern--the greatest hindrance to ground-based direct imaging of planets and disks ... More