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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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
2024ZeitschriftenartikelSean Cotner
Forum of Mathematics, Sigma
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Morphisms of Character Varieties
2024ZeitschriftenartikelSean Cotner
International Mathematics Research Notices
A corrigendum to this paper is published on the author's homepage.
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Векторное произведение
5. Aug. 2026SonstigesSergey
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
5. Aug. 2026TheorieSergey
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
29. Juli 2026SonstigesBogdan 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
29. Juli 2026NotizenBogdan 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
29. Juli 2026NotizenBogdan 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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