Cohomology of p-adic period domains

Cohomology of p-adic period domains

🎙 David Hansen 👥 3K 📅 January 23, 2026 ⏱ 61 min 👁 323 📄 original study 🧭 2026-08-16
Available in: English (current) Français

Keywords

p-adic period domainscohomologyDrinfeld spaceadmissible locussmooth representations

Summary

David Hansen presents a general formula for the cohomology of p-adic period domains, a problem open for over 35 years. He begins by introducing the Drinfeld space, a rigid analytic space that is the admissible locus in projective space, and recalls its known cohomology for n=2, computed by Drinfeld. He then defines a family of smooth admissible representations of GL_n(Q_p) indexed by subsets I, which serve as building blocks. The main theorem, joint with Dwenhan, states that the cohomology of the Drinfeld space is isomorphic to a direct sum of these representations with specific shifts. Hansen extends this to general Grassmannians, presenting the admissible locus and a formula for the cohomology in the case of the Grassmannian Gr(2,4), based on work of Rapoport-Zink and a 2005 paper. The talk emphasizes the elementary nature of the formula and its surprising features, suggesting rich phenomenology. The presentation is technical, aimed at experts, and includes a discussion of the historical context and open questions.

161 words

Critical Evaluation

Value of the Information & Strength of the Argument

The talk provides a significant new result in p-adic geometry, offering a general formula for cohomology that was previously unknown. The argumentation is clear and logical, building from known cases to the general theorem. Hansen carefully explains the construction of the relevant representations and the structure of the proof, which relies on stratification and induction. The value is high as it opens new avenues for research and provides explicit computations in a field where such results are rare.

Scientific Rigor, Source Quality, Title Accuracy

The talk is rigorous, with references to foundational works by Drinfeld, Schneider-Stuhler, and Rapoport-Zink. The title accurately reflects the content. The speaker is a recognized expert, and the presentation is consistent with current research. The description provides minimal context, but the talk itself is self-contained for experts. The title is appropriate and does not overstate the content.

150 words

Title / Content Match

The title accurately reflects the content, which focuses on computing the cohomology of p-adic period domains.

Quality & Reliability

8/10

The talk presents original research with a clear theorem and proof sketch, building on established work by Drinfeld and Schneider-Stuhler. The speaker is a recognized expert, and the content is mathematically rigorous, though the presentation is informal and lacks detailed technical verification.

Key Moments

Cited Sources

  • Drinfeld's original work on p-adic period domains — Referenced as the foundational work defining Drinfeld space and its cohomology for n=2.
  • Schneider-Stuhler (1991) on cohomology of Drinfeld space — Referenced as the prior result for general n, proved in 1991.
  • Rapoport-Zink (1996) on admissible loci — Referenced as defining the admissible locus in general Grassmannians.
  • Paper from 2005 on cohomology of Gr(2,4) — Referenced as the only known example for d>1, published in Inventiones.

Concurring Sources

  • Drinfeld's original work — The talk builds on Drinfeld's foundational results, which are consistent with the new formula.
  • Schneider-Stuhler's theorem — The new formula generalizes the known result for Drinfeld space, confirming it.

Contribution & Novelties

The talk presents a new general formula for the cohomology of p-adic period domains, a problem open for decades. The formula is elementary and reveals unexpected patterns, suggesting rich phenomenology. This is a significant advance in non-archimedean geometry.

Pour aller plus loin :

  • Drinfeld space — Provides background on the Drinfeld space and its role in p-adic geometry.
  • Local Langlands correspondence — Connected to the cohomology of the Drinfeld tower, as mentioned in the talk.
  • p-adic Hodge theory — Relevant to the period domains and their cohomology.

87 words

Radar Profile

The radar profile shows high scores in technical level and information quality, with slightly lower scores in quantity and reliability, reflecting the advanced nature of the content and the reliance on established but specialized literature.

Reliability 8/10

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