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We study subvarieties of the flag variety called Hessenberg varieties, defined by certain linear conditions. These subvarieties arise naturally in applications including geometric representation theory, number theory, and numerical…

Algebraic Geometry · Mathematics 2007-05-23 Julianna S. Tymoczko

We study geometric and topological properties of Hessenberg varieties of codimension one in the type A flag variety. Our main results: (1) give a formula for the Poincar\'e polynomial, (2) characterize when these varieties are irreducible,…

Algebraic Geometry · Mathematics 2026-04-22 Laura Escobar , Martha Precup , John Shareshian

After proving that every Schubert variety in the full flag variety of a complex reductive group $G$ is a general Hessenberg variety, we show that not all such Schubert varieties are adjoint Hessenberg varieties. In fact, in types A and C,…

Algebraic Geometry · Mathematics 2021-07-19 Laura Escobar , Martha Precup , John Shareshian

Regular nilpotent Hessenberg varieties form an important family of subvarieties of the flag variety, which are often singular and sometimes not normal varieties. Like Schubert varieties, they contain distinguished points called permutation…

Algebraic Geometry · Mathematics 2022-12-29 Hiraku Abe , Erik Insko

Regular semisimple Hessenberg varieties are a family of subvarieties of the flag variety that arise in number theory, numerical analysis, representation theory, algebraic geometry, and combinatorics. We give a "Giambelli formula" expressing…

Algebraic Geometry · Mathematics 2011-08-31 Dave Anderson , Julianna Tymoczko

In this paper we consider certain closed subvarieties of the flag variety, known as Hessenberg varieties. We give a connectedness criterion for semisimple Hessenberg varieties generalizing a criterion given by Anderson and Tymoczko. We show…

Algebraic Geometry · Mathematics 2013-10-17 Martha Precup

We study a collection of Hessenberg varieties in the type A flag variety associated to a nonzero semisimple matrix whose conjugacy class has minimal dimension. We prove each such minimal semisimple Hessenberg variety is a union Richardson…

Algebraic Geometry · Mathematics 2024-12-13 Rebecca Goldin , Martha Precup

This paper studies the geometry and combinatorics of three interrelated varieties: Springer fibers, Steinberg varieties, and parabolic Hessenberg varieties. We prove that each parabolic Hessenberg variety is the pullback of a Steinberg…

Algebraic Geometry · Mathematics 2020-02-11 Martha Precup , Julianna Tymoczko

Hessenberg varieties are a family of subvarieties of the flag variety, including the Springer fibers, the Peterson variety, and the entire flag variety itself. The seminal example arises from a problem in numerical analysis and consists for…

Algebraic Geometry · Mathematics 2007-05-23 Julianna S. Tymoczko

Hessenberg varieties $\mathcal{H}(X,H)$ form a class of subvarieties of the flag variety $G/B$, parameterized by an operator $X$ and certain subspaces $H$ of the Lie algebra of $G$. We identify several families of Hessenberg varieties in…

Algebraic Geometry · Mathematics 2023-01-25 Rebecca Goldin , Julianna Tymoczko

This paper investigates the geometry of regular Hessenberg varieties associated with the minimal indecomposable Hessenberg space in the flag variety of a complex reductive group. These varieties form a flat family of irreducible…

Algebraic Geometry · Mathematics 2024-11-27 Erik Insko , Martha Precup , Alexander Woo

Hessenberg varieties are subvarieties of the flag variety parametrized by a linear operator $X$ and a nondecreasing function $h$. The family of Hessenberg varieties for regular $X$ is particularly important: they are used in quantum…

Algebraic Geometry · Mathematics 2021-04-27 Erik Insko , Julianna Tymoczko , Alexander Woo

Flag varieties are well-known algebraic varieties with many important geometric, combinatorial, and representation theoretic properties. A Hessenberg variety is a subvariety of a flag variety identified by two parameters: an element $X$ of…

Algebraic Geometry · Mathematics 2017-10-17 Elizabeth Drellich

Regular nilpotent Hessenberg varieties form a family of subvarieties of the flag variety arising in the study of quantum cohomology, geometric representation theory, and numerical analysis. In this paper we construct a paving by affines of…

Algebraic Geometry · Mathematics 2007-06-13 Julianna S. Tymoczko

In this paper, we study the geometry of various Hessenberg varieties in type A, as well as families thereof, with the additional goal of laying the groundwork for future computations of Newton-Okounkov bodies of Hessenberg varieties. Our…

Algebraic Geometry · Mathematics 2021-02-04 Hiraku Abe , Lauren DeDieu , Federico Galetto , Megumi Harada

Although regular semisimple Hessenberg varieties are smooth and irreducible, semisimple Hessenberg varieties are not necessarily smooth in general. In this paper we determine the irreducible components of semisimple Hessenberg varieties…

Algebraic Geometry · Mathematics 2017-09-19 Erik Insko , Martha Precup

Hessenberg varieties are a family of subvarieties of full flag varieties. This family contains well-known varieties such as Springer fibers, Peterson varieties, and permutohedral varieties. It was introduced by De Mari-Procesi-Shayman in…

Algebraic Geometry · Mathematics 2025-11-18 Tatsuya Horiguchi , Mikiya Masuda , Takashi Sato , Haozhi Zeng

Our concern in this paper is the dimension and inclusion relations of Schubert varieties in twisted partial affine flag varieties. In the end we apply our results to some local models of certain Schubert varieties.

Algebraic Geometry · Mathematics 2010-11-25 Timo Richarz

We generalize the classification of isomorphism classes of Schubert varieties in complete flag varieties G/B to a class of partial flag varieties G/P. In particular, we classify all Schubert varieties in G/P where P is a minimal parabolic…

Combinatorics · Mathematics 2025-11-25 Yanjun Chen

This article explores the relationship between Hessenberg varieties associated with semisimple operators with two eigenvalues and orbit closures of a spherical subgroup of the general linear group. We establish the specific conditions under…

Algebraic Geometry · Mathematics 2023-09-13 Mahir Bilen Can , Martha Precup , John Shareshian , Özlem Uğurlu
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