Prix de thèse 2015


Benjamin MARTIN

Benjamin Martin prepared his PhD thesis in Nantes in Computer Science after a Bachelor in Mathematics at the University of Nantes and a Master Degree in Computer Science at the University of Nantes too. The thesis directed and co-directed by Laurent Granvilliers, Alexandre Goldsztejn, Christophe Jermann is titled « Rigorous Algorithms for non-linear biobjective optimization ». The thesis deals with the interval based rigorous algorithm, i.e. with guaranteed results, to solve biobjective problems. The candidate proposes a certified continuation method that tracks locally a connected manifold of optimal solutions, which supplements other techniques from the literature. The proposed method  adapts finely to the shape of manifolds and deals with singularities resulting from inequality constraints in biobjective problems. Moreover, the candidate develops an interval Branch & Bound (B&B) algorithm that globally computes a verified enclosure of the optimal solutions. This method integrates constraint propagation techniques, noticeably exploiting bounds on the objectives, in order to enhance the solving process. The jury particularly appreciated the fact that the thesis presents both strong theoretical and applied results.



Samuel Vaiter did is PhD thesis in Mathematics at the Univerity Paris Dauphine under the direction of Gabriel Peyré. He studied Computer Science and Mathematics at the ENS Lyon (Bachelor) and ENS Cachan (Master) respectively. The thesis is titled « Low Complexity Regularization of Inverse Problems ». This thesis is concerned with recovery guarantees and sensitivity analysis of variational regularization for noisy linear inverse problems. This is cast as a convex optimization problem by combining a data fidelity and a regularizing functional promoting solutions conforming to some notion of low complexity related to their non-smoothness points. This thesis makes a very nice contribution to the field of linear inverse problems, convex geometry and analysis. The candidate has provided a unified framework for analyzing the robustness (vis a vis noise) and sensitivity of solutions to the inverse problem. The results are sharp enough to recover some of the known results for special instances. At the same time, the framework is general enough to accommodate most regularizers used in practice. The jury particularly appreciated the fact that Samuel Vaiter was able to put under a single umbrella a series of techniques and results for treating a variety of problems.


Le jury 2015 est présidé par Roberto Wolfler (Paris Nord LIPN)  :

  • Frédéric BONNANS, Jean-Baptiste HIRIART-URRUTY et Marc QUINCAMPOIX pour la SMAI 
  • Luce BROTCORNE, Jean-Charles BILLAUT et Arnaud RENAUD pour la ROADEF
  • Michel DE LARA, Laurent DUMAS et Roberto WOLFLER pour le PGMO