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29 mars 2017: 1 événement

  • Séminaires SPOC

    Mercredi 29 mars 10:30-11:30 - Julian Rasch - Munster University

    Bias-Reduction in Variational Regularization

    Résumé : Variational methods suffer from inevitable bias. The simplest example
    is l^1 -regularization, which leads to sparse solutions, but however affects
    the quantitative peak values. We present a two-step method to reduce
    bias. After solving the standard variational problem, the key idea is to
    add a consecutive debiasing step minimizing the data fidelity on an appro-
    priate space, the so-called model subspace. Here, these spaces are defined
    by Bregman distances or infimal convolutions thereof, using the subgra-
    dient appearing in the optimality condition of the variational method. In
    particular, they lead to a decomposition of the overall bias into two parts,
    model and method bias, of which we shall tackle the latter. We provide
    numerous examples and experiments to illustrate both the performance
    and the statistical behavior of the method.

    En savoir plus : Séminaires SPOC

29 mars 2017: 1 événement

  • Séminaires Math-Physique

    Mercredi 29 mars 16:15-17:15 - Alexei Iantchenko

    Séminaire Math-Phys : Quasi-normal modes for Dirac fields in black holes

    Résumé : The quasi-normal modes are the scattering resonances for incoming waves
    by black holes. I will consider the properties of the resonances for the
    Dirac waves in non-rotating and slowly rotating black holes : asymptotic
    distribution and resonance expansions

    Lieu : Salle A318

    En savoir plus : Séminaires Math-Physique