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Marked chain-order polytopes are convex polytopes constructed from a marked poset, which give a discrete family relating a marked order polytope with a marked chain polytope. In this paper, we consider the Gelfand-Tsetlin poset of type A,…

Algebraic Geometry · Mathematics 2021-04-21 Naoki Fujita

We prove that on a Bott-Samelson variety $X$ every movable divisor is nef. This enables us to consider Zariski decompositions of effective divisors, which in turn yields a description of the Mori chamber decomposition of the effective cone.…

Algebraic Geometry · Mathematics 2017-11-27 Georg Merz , David Schmitz , Henrik Seppänen

The Hodge algebra structures on the homogeneous coordinate rings of Grassmann varieties provide semi-toric degenerations of these varieties. In this paper we construct these semi-toric degenerations using quasi-valuations and triangulations…

Algebraic Geometry · Mathematics 2018-04-12 Xin Fang , Peter Littelmann

Tropical geometry and the theory of Newton-Okounkov bodies are two methods which produce toric degenerations of an irreducible complex projective variety. Kaveh-Manon showed that the two are related. We give geometric maps between the…

Algebraic Geometry · Mathematics 2021-07-05 Laura Escobar , Megumi Harada

Assume that the valuation semigroup $\Gamma(\lambda)$ of an arbitrary partial flag variety corresponding to the line bundle $\mathcal L_\lambda$ constructed via a full-rank valuation is finitely generated and saturated. We use Ehrhart…

Algebraic Geometry · Mathematics 2020-11-24 Christian Steinert

We demonstrate how pipe dreams can be applied to the theory of poset polytopes to produce toric degenerations of flag varieties. Specifically, we present such constructions for marked chain-order polytopes of Dynkin types A and C. These…

Algebraic Geometry · Mathematics 2024-03-18 Ievgen Makedonskyi , Igor Makhlin

The Gelfand-Tsetlin and the Feigin-Fourier-Littelmann-Vinberg polytopes for the Grassmannians are defined, from the perspective of representation theory, to parametrize certain bases for highest weight irreducible modules. These polytopes…

Combinatorics · Mathematics 2022-08-10 Oliver Clarke , Akihiro Higashitani , Fatemeh Mohammadi

Matching fields were introduced by Sturmfels and Zelevinsky to study certain Newton polytopes and more recently have been shown to give rise to toric degenerations of various families of varieties. Whenever a matching field gives rise to a…

Combinatorics · Mathematics 2020-10-09 Oliver Clarke , Akihiro Higashitani , Fatemeh Mohammadi

We study the additivity of Newton-Okounkov bodies. Our main result states that on two-dimensional subcones of the ample cone the Newto-Okounkov body associated to an appropriate flag acts additively. We prove this by induction relying on…

Algebraic Geometry · Mathematics 2026-01-23 Robert Wilms

Motivated by the construction of Newton--Okounkov bodies and toric degenerations via cluster algebras in [GHKK18, FO25], we consider a family of Newton--Okounkov polytopes of a complex smooth Fano variety $X$ related by a composition of…

Symplectic Geometry · Mathematics 2025-08-07 Yunhyung Cho , Myungho Kim , Yoosik Kim , Euiyong Park

We present a new approach to construct $T$-equivariant flat toric degenerations of flag varieties and spherical varieties, combining ideas coming from the theory of Newton-Okounkov bodies with ideas originally stemming from PBW-filtrations.…

Algebraic Geometry · Mathematics 2017-10-03 Xin Fang , Ghislain Fourier , Peter Littelmann

Let \Delta be the Okounkov body of a divisor D on a projective variety X. We describe a geometric criterion for \Delta to be a lattice polytope, and show that in this situation X admits a flat degeneration to the corresponding toric…

Algebraic Geometry · Mathematics 2014-02-18 Dave Anderson

Let $G$ be a semisimple algebraic group over $\mathbb{C}$. For a reduced word $\bf i$ of the longest element in the Weyl group of $G$ and a dominant integral weight $\lambda$, one can construct the string polytope $\Delta_{\bf i}(\lambda)$,…

Algebraic Geometry · Mathematics 2020-08-06 Yunhyung Cho , Yoosik Kim , Eunjeong Lee , Kyeong-Dong Park

It is known that the homogeneous coordinate ring of a Grassmannian has a cluster structure, which is induced from the combinatorial structure of a plabic graph. A plabic graph is a certain bipartite graph described on the disk, and there is…

Combinatorics · Mathematics 2022-02-22 Akihiro Higashitani , Yusuke Nakajima

A Newton-Okounkov convex body is a convex body constructed from a projective variety with a valuation on its homogeneous coordinate ring; this is deeply connected with representation theory. For instance, the Littelmann string polytopes and…

Quantum Algebra · Mathematics 2016-03-07 Naoki Fujita , Satoshi Naito

A flag variety is a smooth projective homogeneous variety. In this paper, we study Newton-Okounkov polytopes of the flag variety $Fl(\mathbb{C}^4)$ arising from its cluster structure. More precisely, we present defining inequalities of such…

Algebraic Geometry · Mathematics 2023-10-11 Yunhyung Cho , Naoki Fujita , Akihiro Higashitani , Eunjeong Lee

Anderson proved that the finite generation of the value semigroup $\Gamma_{Y_\bullet}(D)$ in the construction of the Newton-Okounkov body $\Delta_{Y_\bullet}(D)$ induces a toric degeneration of the corresponding variety $X$ to some toric…

Algebraic Geometry · Mathematics 2018-01-15 Georg Merz

We prove a formula for the push-forward class of Bott-Samelson resolutions in the algebraic cobordism ring of the flag bundle. We specialise our formula to connective K-theory providing a geometric interpretation to the double…

Algebraic Geometry · Mathematics 2014-10-29 Thomas Hudson

Generalizing the notion of Newton polytope, we define the Newton-Okounkov body, respectively, for semigroups of integral points, graded algebras, and linear series on varieties. We prove that any semigroup in the lattice Z^n is…

Algebraic Geometry · Mathematics 2012-03-30 Kiumars Kaveh , A. G. Khovanskii

We construct a family of compactifications of the affine cone of the Grassmannian variety of 2-planes. We show that both the tropical variety of the Pl\"ucker ideal and familiar valuations associated to the construction of Newton-Okounkov…

Algebraic Geometry · Mathematics 2019-01-15 Christopher Manon , Jihyeon Jessie Yang