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

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