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The goal of this paper is to study the link between the topology of the degenerate flag varieties and combinatorics of the Dellac configurations. We define three new classes of algebraic varieties closely related to the degenerate flag…

Combinatorics · Mathematics 2018-08-14 Ange Bigeni , Evgeny Feigin

We study tropicalization of symplectic flag varieties with respect to the Pl\"ucker embedding. We identify a particular maximal prime cone in this tropicalization by explicitly giving its facets. For every interior point of this maximal…

Algebraic Geometry · Mathematics 2024-07-02 George Balla , Xin Fang

We present a review on the recently discovered link between the Lie theory,the theory of quiver Grassmannians, and various degenerations of flag varieties. Our starting point is the induced Poincar\'{e}--Birkhoff--Witt filtration on the…

Representation Theory · Mathematics 2022-01-13 Evgeny Feigin

We construct a family of flat semitoric degenerations for the Hibi variety of every finite distributive lattice. The irreducible components of each degeneration are the toric varieties associated with polytopes forming a regular subdivision…

Algebraic Geometry · Mathematics 2021-12-16 Evgeny Feigin , Igor Makhlin

In this thesis we study toric degenerations of projective varieties. We compare different constructions to understand how and why they are related as s first step towards developing a global framework. In focus are toric degenerations…

Algebraic Geometry · Mathematics 2018-06-07 Lara Bossinger

We show that in type A or C any degenerate flag variety is in fact isomorphic to a Schubert variety in an appropriate partial flag manifold.

Representation Theory · Mathematics 2014-07-17 Giovanni Cerulli Irelli , Martina Lanini

This paper is about the combinatorics of finite point configurations in the tropical projective space or, dually, of arrangements of finitely many tropical hyperplanes. Moreover, arrangements of finitely many tropical halfspaces can be…

Combinatorics · Mathematics 2019-06-21 Michael Joswig , Georg Loho

In this article we investigate the regularity properties of linear degenerations of flag varieties. We classify the linear degenerations of (partial) flag varieties that are smooth. Furthermore, we study the singular locus of irreducible…

Algebraic Geometry · Mathematics 2025-08-01 Sabino Di Trani

In this paper, we give a tropical method for computing Gromov-Witten type invariants of Fano manifolds of special type. This method applies to those Fano manifolds which admit toric degenerations to toric Fano varieties with singularities…

Algebraic Geometry · Mathematics 2010-01-19 Takeo Nishinou

We develop a theory of multi-stage degenerations of toric varieties over finite rank valuation rings, extending the Mumford--Gubler theory in rank one. Such degenerations are constructed from fan-like structures over totally ordered abelian…

Algebraic Geometry · Mathematics 2018-05-16 Tyler Foster , Dhruv Ranganathan

We study finite dimensional approximations to degenerate versions of affine flag varieties using quiver Grassmannians for cyclic quivers. We prove that they admit cellular decompositions parametrized by affine Dellac configurations, and…

Algebraic Geometry · Mathematics 2024-11-08 Alexander Pütz

We describe the effect of Feigin's flat degeneration of the type $\textrm{A}$ flag variety on its Schubert varieties. In particular, we study when they stay irreducible and in several cases we are able to encode reducibility of the…

Representation Theory · Mathematics 2023-02-21 Lara Bossinger , Martina Lanini

In this paper, we study the deformation theory of degenerate algebraic curves on singular varieties which appear as the degenerate limit of families of varieties. For this purpose, we systematically develop a new method to calculate the…

Algebraic Geometry · Mathematics 2017-05-03 Takeo Nishinou

A polytrope is a tropical polyhedron that is also classically convex. We study the tropical combinatorial types of polytropes associated to weighted directed acyclic graphs (DAGs). This family of polytropes arises in algebraic statistics…

Combinatorics · Mathematics 2025-10-16 Carlos Améndola , Kamillo Ferry

A deformation $U$, of a graded $K$-algebra $A$ is said to be of PBW type if $grU$ is $A$. It has been shown for Koszul and $N$-Koszul algebras that the deformation is PBW if and only if the relations of $U$ satisfy a Jacobi type condition.…

Rings and Algebras · Mathematics 2007-05-23 Thomas Cassidy , Brad Shelton

We introduce the PBW degeneration for basic classical Lie superalgebras and construct for all type I, $\mathfrak{osp}(1,2n)$ and exceptional Lie superalgebras new monomial bases. These bases are parametrized by lattice points in convex…

Representation Theory · Mathematics 2022-09-20 Ghislain Fourier , Deniz Kus

We study semi-stable degenerations of toric varieties determined by certain partitions of their moment polytopes. Analyzing their defining equations we prove a property of uniqueness.

Algebraic Geometry · Mathematics 2007-12-21 Marina Marchisio , Vittorio Perduca

We relate properties of weighted flags (or multiflags) of type AD to statistics of the corresponding Weyl groups. For type A, we recover the Mahonian statistics on symmetric groups. Finally, we sketch briefly an easy extension incorporating…

Combinatorics · Mathematics 2018-11-13 Roland Bacher

Recently E. Feigin introduced the $\mathbb G_a^N$-degenerations of semisimple algebraic groups and their associated degenerate flag varieties. It has been shown by Feigin, Finkelberg, and Littelmann that the degenerate flag varieties in…

Algebraic Geometry · Mathematics 2013-08-13 Chuck Hague

We present families of tableaux which interpolate between the classical semi-standard Young tableaux and matching field tableaux. Algebraically, this corresponds to SAGBI bases of Pl\"ucker algebras. We show that each such family of…

Commutative Algebra · Mathematics 2020-09-10 Oliver Clarke , Fatemeh Mohammadi