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We study the closure of the graph of the birational map from a projective space to a Grassmannian. We provide explicit description of the graph closure and compute the fibers of the natural projection to the Grassmannian. We construct…

Algebraic Geometry · Mathematics 2024-03-18 Evgeny Feigin , with an appendix in collaboration with Wojciech Samotij

We conceptualize in the paper the linear degenerate symplectic flag varieties as symmetric degenerations within the framework of type $A$ equioriented quivers. First, in the larger context of symmetric degenerations, we give a…

Representation Theory · Mathematics 2024-05-07 Magdalena Boos , Giovanni Cerulli Irelli , Xin Fang , Ghislain Fourier

PBW degenerations are a particularly nice family of flat degenerations of type A flag varieties. We show that the cohomology of any PBW degeneration of the flag variety surjects onto the cohomology of the original flag variety, and that…

Representation Theory · Mathematics 2017-10-31 Martina Lanini , Elisabetta Strickland

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 define a set of PBW-semistandard tableaux that is in a weight preserving bijection with the set of monomials corresponding to integral points in the Feigin-Fourier-Littelmann-Vinberg polytope for highest weight modules of the symplectic…

Representation Theory · Mathematics 2022-04-04 George Balla

Following the historical track in pursuing $T$-equivariant flat toric degenerations of flag varieties and spherical varieties, we explain how powerful tools in algebraic geometry and representation theory, such as canonical bases,…

Algebraic Geometry · Mathematics 2016-09-06 Xin Fang , Ghislain Fourier , Peter Littelmann

We study toric degenerations arising from Gr\"obner degenerations or the tropicalization of partial flag varieties. We produce a new family of toric degenerations of partial flag varieties whose combinatorics are governed by matching fields…

Algebraic Geometry · Mathematics 2023-10-12 Oliver Clarke , Fatemeh Mohammadi , Francesca Zaffalon

We study algebraic, combinatorial and geometric aspects of weighted PBW-type degenerations of (partial) flag varieties in type $A$. These degenerations are labeled by degree functions lying in an explicitly defined polyhedral cone, which…

Representation Theory · Mathematics 2020-02-28 Xin Fang , Evgeny Feigin , Ghislain Fourier , Igor Makhlin

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

Motivated by bases of representations compatible with the PBW filtration for basic Lie superalgebras by Kus and Fourier, we generalise the construction of degenerations of flag varieties via favourable modules to the super setup. In the…

Algebraic Geometry · Mathematics 2026-05-07 Ibrahim Ahmad

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

The two best studied toric degenerations of the flag variety are those given by the Gelfand--Tsetlin and FFLV polytopes. Each of them degenerates further into a particular monomial variety which raises the problem of describing the…

Algebraic Geometry · Mathematics 2024-02-28 Evgeny Feigin , Igor Makhlin

In recent years PBW degenerations of Demazure modules and Schubert varieties were defined and studied in several papers. Various interesting properties (such as these PBW degenerations embedding naturally into the corresponding degenerate…

Representation Theory · Mathematics 2019-11-28 Igor Makhlin

We continue, generalize and expand our study of linear degenerations of flag varieties from [G. Cerulli Irelli, X. Fang, E. Feigin, G. Fourier, M. Reineke, Math. Z. 287 (2017), no. 1-2, 615-654]. We realize partial flag varieties as quiver…

Algebraic Geometry · Mathematics 2019-02-01 Giovanni Cerulli Irelli , Xin Fang , Evgeny Feigin , Ghislain Fourier , Markus Reineke

Our main goal is to show that the Gelfand--Tsetlin toric degeneration of the type A flag variety can be obtained within a degenerate representation-theoretic framework similar to the theory of PBW degenerations. In fact, we provide such…

Representation Theory · Mathematics 2020-10-07 Igor Makhlin

We show that the moduli space of stable n-pointed rational curves can be flatly degenerated to a projective toric variety. We arrive at this by showing that the Chow quotients of the Grassmannians admit toric degenerations, which in turn,…

Algebraic Geometry · Mathematics 2007-05-23 Yi Hu

Toric geometry provides a bridge between algebraic geometry and combinatorics of fans and polytopes. For each polarized toric variety (X,L) we have associated a polytope P. In this thesis we use this correspondence to study birational…

Algebraic Geometry · Mathematics 2016-11-26 Edilaine Ervilha Nobili

We show that a weight variety, which is a quotient of a flag variety by the maximal torus, admits a flat degeneration to a toric variety. In particular, we show that the moduli spaces of spatial polygons degenerate to polarized toric…

Algebraic Geometry · Mathematics 2007-05-23 Philip Foth , Yi Hu

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

We study geometric and combinatorial properties of the degenerate flag varieties of type A. These varieties are acted upon by the automorphism group of a certain representation of a type A quiver, containing a maximal torus T. Using the…

Algebraic Geometry · Mathematics 2012-11-16 Giovanni Cerulli Irelli , Evgeny Feigin , Markus Reineke
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