On smooth-group actions on reductive groups and spherical buildings
2025PreprintSean Cotner
With an appendix by Sean Cotner, Joshua M. Lansky, and Loren Spice.
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Works
290 results
The stack of spherical Langlands parameters
2024PreprintSean Cotner
With an appendix by Sean Cotner. Per the arXiv v2 comment, the appendix allows the paper's Theorem 2.5 to be generalized.
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Hom schemes for algebraic groups
2023PreprintSean Cotner
Accepted for publication in Algebra & Number Theory.
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Lifting G-Valued Galois Representations when ℓ ≠ p
2024Journal articleSean Cotner
Forum of Mathematics, Sigma
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Morphisms of Character Varieties
2024Journal articleSean Cotner
International Mathematics Research Notices
A corrigendum to this paper is published on the author's homepage.
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Векторное произведение
Aug 5, 2026OtherSergey
Ориентация тройки векторов, определение векторного произведения через длину, перпендикулярность и правую тройку, геометрический смысл (площадь параллелограмма), свойства с доказательствами и полный вывод формулы через определитель.
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90
Базис, координаты и проекция вектора
Aug 5, 2026TheorySergey
Разложение вектора по базису на плоскости и в пространстве, ортонормированный базис и декартова система координат, координаты вектора и линейные операции над ними, проекция вектора на ось, её линейность и проекция на вектор.
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The torsion component of the Picard scheme
Jul 29, 2026OtherBogdan Zavyalov
Every finite flat commutative group scheme over a noetherian local ring is the torsion component of the Picard scheme of a smooth projective scheme with 3-dimensional fibers, built as a quotient of a complete intersection. An application: Hodge numbers that jump in a smooth projective family.
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Fun example: empty colimit does not commute with empty limit
Jul 29, 2026NotesBogdan Zavyalov
Why the definition of a filtered category insists on non-emptiness: the empty colimit fails to commute with the empty limit, and that is the only failure.
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A non-Noetherian local ring with finitely generated maximal ideal
Jul 29, 2026NotesBogdan Zavyalov
A complete local ring with a finitely generated maximal ideal is Noetherian. Drop completeness and it fails: an ultraproduct construction gives a non-Noetherian local ring whose maximal ideal is principal.
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