Tangent spaces on the trianguline variety at companion points

Many results about the geometry of the trianguline variety have been obtained by Breuil-Hellmann- Schraen. Among them, using geometric methods, they have computed a formula for the dimension of the tangent space of the trianguline variety at dominant crystalline generic points, which has a conjectural generalisation to companion (i.e. non -dominant) points. In an earlier work, they proved a weaker form of this formula under the assumption of modularity using arithmetic methods. We prove a generalisation of a result of Bellaiche-Chenevier in p-adic Hodge theory and use it to extend the arithmetic methods of Breuil-Hellmann-Schraen to a wide class of companion points. (c) 2023 Royal Dutch Mathematical Society (KWG). Published by Elsevier B.V. All rights reserved.