Armand Coudray
Armand Coudray

ATER, Université de Franche-Comté (Besançon)

Bio

I am currently an ATER (Temporary Research and Teaching Agent) at the University of Franche-Comté, in Besançon (France). I did my PhD under the supervision of Jean-Philippe Nicolas at the University of Western Britanny, in the Atlantic Britanny Mathematic Laboratory (LMBA). My thesis deals with the asymptotic behaviour of zero rest mass fields in radiative spacetimes and can be found here.

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Interests
  • General Relativity, Mathematical Relativity.
  • Asymptotic analysis, Conformal methods, Conformal scattering, Peeling-off property.
  • Wave equation, Maxwell Klein-Gordon field.
  • Radiative spacetime, Vaidya spacetime, Robinson-Trautman spacetime.
Education
  • PhD in Mathematics

    Univeristy of Western Britanny

  • Master 2 in Theoritical Physics

    Aix-MArseille University

  • Master 1 in Fundamental Physics

    Sorbonne University

My Research

My research so far is centred on radiative spacetimes and conformal methods in general relativity. Here are the details.

Geometry of type D radiative spacetimes : I’m interested with the geometry of null congruences in radiative spacetimes and I studied the ingoing radial null geodesics in the Vaidya spacetime. With Jean-Philippe Nicolas, we gave a classification of the integral curves of the ingoing principal directions of the Vaidya metric depending on their limits in the past. In particular we prove that there exists an unique curves that admits a finite limits asymptotically in the past and we proved that this geodesic generates the event horizon of the Vaidya white hole. Then we investigated the behaviour of the horizon in the Vaidya spacetime for a general choice of mass. I proved that it not possible to extend directly these results in a pure radiative type D Robinson-Trautman spacetime.

Asymptotic analysis in Vaidya spacetime for the wave equation : I use the conformal methods developped by Penrose in the 60’s to analyze the aasymptotic behaviour of scalar waves in the Vaidya spacetime. I proved the peeling-off behaviour (that corresponds to the asymptotic regularity) of waves in the Vaidya spacetime, and I constructed the conformal scattering operator for the scalar waves. The scattering operator is proved to be an isomorphism that associates the strace of the rescaled field on the past boundary to its trace on the future boundary.

Recent Publications
(2023). Peeling-off behavior of wave equation in the Vaidya spacetime. Journal of Hyperbolic differential Equations 20, 02.
(2021). Geometry of Vaidya spacetimes. General Relativity and Gravitation 53, 73.