English

Plectic structures in p-adic de Rham cohomology

Number Theory 2025-03-07 v3

Abstract

Given a Hilbert modular form for a totally real field FF, and a prime pp split completely in FF, the ff-eigenspace in pp-adic de Rham cohomology of the Hilbert modular variety has a family of partial filtrations and partial Frobenius maps, indexed by the primes of FF above pp. The general plectic conjectures of Nekovar and Scholl suggest a "plectic comparison isomorphism" comparing these structures to etale cohomology. We prove this conjecture in the case [F:Q]=2[F : \mathbf{Q}] = 2 under some mild assumptions; and for general FF we prove a weaker statement which is strong evidence for the conjecture, showing that plectic Hodge filtration has a canonical splitting given by intersecting with simultaneous eigenspaces for the partial Frobenii. (In memory of Jan Nekovar)

Keywords

Cite

@article{arxiv.2211.12078,
  title  = {Plectic structures in p-adic de Rham cohomology},
  author = {David Loeffler and Sarah Livia Zerbes},
  journal= {arXiv preprint arXiv:2211.12078},
  year   = {2025}
}

Comments

Revised version with minor corrections. To appear in Journal of Number Theory

R2 v1 2026-06-28T06:34:06.257Z