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Séminaire de Théorie Algorithmique des Nombres

Admissibility of filtered $(\varphi,N)$-modules

Léo Poyeton

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le 06 décembre 2022 à 10:00

Filtered (φ,N)(\varphi,N)-modules over a pp-adic field KK are semi-linear objects which are easy to define and can be implemented on a computer. The modules Dst(V)D_{st}(V) defined by pp-adic Hodge theory, where VV is a pp-adic representation of the absolute Galois group of KK, provide examples of filtered (varphi,N)(varphi,N)-modules. When VV is nice enough (semi-stable), the data of Dst(V)D_{st}(V) is sufficient to recover VV. A necessary and sufficient condition for a filtered (φ,N)(\varphi,N)-module DD to be written as Dst(V)D_{st}(V) for some semi-stable representation VV is the condition of "admissibility" which imposes conditions on the way the different structures of the (varphi,N)(varphi,N)-module interact with each other. In a joint work with Xavier Caruso, we try to provide an algorithm which takes a filtered (φ,N)(\varphi,N)-module as an input and outputs whether it is admissible or not. I will explain how we can implement filtered (φ,N)(\varphi,N)-modules on a computer and why this question is well posed. I will then present an algorithm which answers the question if the (φ,N)(\varphi,N)-module is nice enough and explain the difficulties we are facing both in this nice case and in the general case.