  Torsion semi-stable representations can be constructed and studied using
Breuil modules. In this paper, we define the notion of pylonet and prove that
some categories of Breuil modules naturally define pylonets. As a consequence,
we are able to define full subcategories of Breuil's categories with very nice
properties (in particular, they are abelian). In a second part of this work, we
try to make very explicit some abstract constructions coming from the general
theory of pylonets (developped earlier in the paper). These explicitations
should be very useful to make computations with torsion semi-stable Galois
representations.

Number Theory