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Search Results: 1 - 10 of 27478 matches for " Robert Gayet "
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Coulomb-Volkov approach of ionization by extreme ultraviolet laser pulses in the subfemtosecond regime
Guillaume Duchateau,Eric Cormier,Robert Gayet
Physics , 2002, DOI: 10.1103/PhysRevA.66.023412
Abstract: In conditions where the interaction betweeen an atom and a short high-frequency extreme ultraviolet laser pulse is a perturbation, we show that a simple theoretical approach, based on Coulomb-Volkov-type states, can make reliable predictions for ionization. To avoid any additional approximation, we consider here a standard case : the ionization of hydrogen atoms initially in their ground state. For any field parameter, we show that the method provides accurate energy spectra of ejected electrons, including many above threshold ionization peaks, as long as the two following conditions are simultaneously fulfilled : (i) the photon energy is greater than or equal to the ionization potential ; (ii) the ionization process is not saturated. Thus, ionization of atoms or molecules by the high order harmonic laser pulses which are generated at present may be addressed through this Coulomb-Volkov treatment.
Dilemas éticos en las investigaciones sobre sexualidad y VIH/sida
Cecilia Gayet
Estudios Demográficos y Urbanos , 2011,
Abstract:
Smooth moduli spaces of associative submanifolds
Damien Gayet
Mathematics , 2010,
Abstract: Let $M^7$ be a smooth manifold equipped with a $G_2$-structure $\phi$, and $Y^3$ be an closed compact $\phi$-associative submanifold. In \cite{McL}, R. McLean proved that the moduli space $\bm_{Y,\phi}$ of the $\phi$-associative deformations of $Y$ has vanishing virtual dimension. In this paper, we perturb $\phi$ into a $G_2$-structure $\psi$ in order to ensure the smoothness of $\bm_{Y,\psi}$ near $Y$. If $Y$ is allowed to have a boundary moving in a fixed coassociative submanifold $X$, it was proved in \cite{GaWi} that the moduli space $\bm_{Y,X}$ of the associative deformations of $Y$ with boundary in $X$ has finite virtual dimension. We show here that a generic perturbation of the boundary condition $X$ into $X'$ gives the smoothness of $\bm_{Y,X'}$. In another direction, we use the Bochner technique to prove a vanishing theorem that forces $\bm_Y$ or $\bm_{Y,X}$ to be smooth near $Y$. For every case, some explicit families of examples will be given.
Vanishing theorems for associative submanifolds
Damien Gayet
Mathematics , 2009,
Abstract: Let M^7 a manifold with holonomy in G_2, and Y^3 an associative submanifold with boundary in a coassociative submanifold. In [5], the authors proved that M_{X,Y}, the moduli space of its associative deformations with boundary in the fixed X, has finite virtual dimension. Using Bochner's technique, we give a vanishing theorem that forces M_{X,Y} to be locally smooth.
Hypersurfaces symplectiques réelles et pinceaux de Lefschetz réels
Damien Gayet
Mathematics , 2006,
Abstract: In a compact, symplectic real manifold, i.e supporting an antisymplectic involution, we use Donaldson's construction to build a codimension 2 symplectic submanifold invariant under the action of the involution. If the real part of the manifold is not empty, and if the symplectic form $\om$ is entire, then for all $k$ big enough, we can find a hypersurface Poincar\'e dual of $k[\omega]$ such that its real part has at least $k^{\dim X/4}$ connected components, up to a constant independant of $k$. Finally we extend to our real case Donaldson's construction of Lefschetz pencils.
Rational convexity of lagrangian immersed submanifolds
D. Gayet
Mathematics , 1999,
Abstract: We prove that a compact, immersed, submanifold of C^n, lagrangian for a Kahler form, is rationally convex, generalizing a theorem of Duval and Sibony for embedded submanifolds.
Seiberg-Witten invariants and real curves
Damien Gayet
Mathematics , 2004,
Abstract: On a compact oriented four-manifold with an orientation preserving involution c, we count solutions of Seiberg-Witten equations, which are moreover symmetrical in relation to c, to construct "real" Seiberg-Witten invariants. Using Taubes' results, we prove that on a symplectic almost complex manifold with an antisymplectic and antiholomorphic involution, this invariants are not all trivial, and that the canonical bundle is represented by a real holomorphic curve.
Los matrimonios de los hombres de más de 35 a os: la búsqueda del rejuvenecimiento? Una perspectiva a partir de las diferencias de edades entre cónyuges
Cecilia I. Gayet
Estudios Demográficos y Urbanos , 2002,
Abstract:
Deformations of associative submanifolds with boundary
Damien Gayet,Frederik Witt
Mathematics , 2008, DOI: 10.1016/j.aim.2010.09.014
Abstract: Let $M$ be a topological $G_2$-manifold. We prove that the space of infinitesimal associative deformations of a compact associative submanifold $Y$ with boundary in a coassociative submanifold $X$ is the solution space of an elliptic problem. For a connected boundary $\partial Y$ of genus $g$, the index is given by $\int_{\partial Y}c_1(\nu_X)+1-g$, where $\nu_X$ denotes the orthogonal complement of $T\partial Y$ in $TX_{|\partial Y}$ and $c_1(\nu_X)$ the first Chern class of $\nu_X$ with respect to its natural complex structure. Further, we exhibit explicit examples of non-trivial index.
Rational convexity of non generic immersed lagrangian submanifolds
J. Duval,D. Gayet
Mathematics , 2008,
Abstract: We prove that an immersed lagrangian submanifold in $\C^n$ with quadratic self-tangencies is rationally convex. This generalizes former results for the embedded and the immersed transversal cases.
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