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A variety X with an action of a finite group G is said to be G-unirational if there is a G-equivariant dominant rational map V -> X where V is a faithful linear representation of G. This generalizes the usual notion of unirationality. We…

Algebraic Geometry · Mathematics 2016-10-04 Alexander Duncan

Here we investigate the birational geometry of projective varieties of arbitrary dimension having defective higher secant varieties. We apply the classical tool of tangential projections and we determine natural conditions for uniruledness,…

Algebraic Geometry · Mathematics 2007-05-23 Edoardo Ballico , Claudio Fontanari

We consider linear systems on toric varieties of any dimension, with invariant base points, giving a characterization of special linear systems. We then make a new conjecture for linear systems on rational surfaces.

Algebraic Geometry · Mathematics 2007-05-23 Antonio Laface , Luca Ugaglia

This paper introduces a new structure of commutative semiring, generalizing the tropical semiring, and having an arithmetic that modifies the standard tropical operations, i.e. summation and maximum. Although our framework is combinatorial,…

Algebraic Geometry · Mathematics 2010-08-02 Zur Izhakian

We extend tropicalization and tropical compactification of subvarieties of algebraic tori to subvarieties of spherical homogeneous spaces. Given a tropical compactification of a subvariety, we show that the support of the colored fan of the…

Algebraic Geometry · Mathematics 2020-08-31 Jenia Tevelev , Tassos Vogiannou

We study the combinatorial properties of a tropical hyperplane arrangement. We define tropical oriented matroids, and prove that they share many of the properties of ordinary oriented matroids. We show that a tropical oriented matroid…

Combinatorics · Mathematics 2007-06-25 Federico Ardila , Mike Develin

In this paper, the concept of toric difference varieties is defined and four equivalent descriptions for toric difference varieties are presented in terms of difference rational parametrization, difference coordinate rings, toric difference…

Symbolic Computation · Computer Science 2016-04-08 Xiao-Shan Gao , Zhang Huang , Jie Wang , Chun-Ming Yuan

An arrangement of finitely many tropical hyperplanes in the tropical torus leads to a notion of `type' data for points, with the underlying unlabeled arrangement giving rise to `coarse type'. It is shown that the decomposition of the…

Combinatorics · Mathematics 2013-01-21 Anton Dochtermann , Michael Joswig , Raman Sanyal

Let U be an open subset of a unirational variety (or more generally of a separably rationally connected variety). We prove that there is rational curve C in U such that the fundamental group of C surjects onto the fundamental group of U.…

Algebraic Geometry · Mathematics 2007-05-23 János Kollár

This paper supplements [17], showing that categorically the layered theory is the same as the theory of ordered monoids (e.g. the max-plus algebra) used in tropical mathematics. A layered theory is developed in the context of categories,…

Rings and Algebras · Mathematics 2012-07-17 Zur Izhakian , Manfred Knebusch , Louis Rowen

In this paper we study tropicalization of Grassmannian and linear varieties. In particular, we study the tropical linear spaces cor- responding to the phylogenetic trees. We prove that corresponding to each subtree of the phylogenetic tree…

Combinatorics · Mathematics 2014-05-01 Ambedkar Dukkipati , Aritra Sen

The homogeneous spectrum of a multigraded finitely generated algebra (in the sense of Brenner-Schr\"oer) always admits an embedding into a toric variety that is not necessarily separated, a so-called toric prevariety. In order to have a…

Algebraic Geometry · Mathematics 2021-07-08 Alex Küronya , Pedro Souza , Martin Ulirsch

The goal of this paper is to introduce a construction of a vector bundle on a tropical variety. When the base is a tropical toric variety these tropicalize toric vector bundles, and are described by the data of a valuated matroid and some…

Algebraic Geometry · Mathematics 2024-05-07 Bivas Khan , Diane Maclagan

We explicitly describe the tropicalization of a cluster variety of finite type C, realizing it as the space of axially symmetric phylogenetic trees. We also find all occurring sign patterns of coordinates, for both the cluster variety and…

Algebraic Geometry · Mathematics 2026-05-08 Igor Makhlin

A smooth variety is called uniformly rational if every point admits a Zariski open neighborhood isomorphic to a Zariski open subset of the affine space. In this note we show that every smooth and rational affine variety endowed with an…

Algebraic Geometry · Mathematics 2017-01-23 Alvaro Liendo , Charlie Petitjean

Generalizing supertropical algebras, we present a "layered" structure, "sorted" by a semiring which permits varying ghost layers, and indicate how it is more amenable than the "standard" supertropical construction in factorizations of…

Commutative Algebra · Mathematics 2011-08-16 Zur Izhakian , Manfred Knebusch , Louis Rowen

We study the multi-height distribution of rational points of smooth, projective and split toric varieties over $\mathbf{Q}$ using the lift of the number of points to universal torsors.

Number Theory · Mathematics 2026-03-16 Nicolas Bongiorno

In this paper we explain four viewpoints on the local tropicalization of formal subgerms of toric germs, which is a local analog of the global tropicalization of subvarieties of algebraic tori. We start by illustrating some of those…

Algebraic Geometry · Mathematics 2025-02-18 Patrick Popescu-Pampu , Dmitry Stepanov

We study the tropicalizations of Severi varieties, which we call tropical Severi varieties. In this paper, we give a partial answer to the following question, ``describe the tropical Severi varieties explicitly.'' We obtain a description of…

Algebraic Geometry · Mathematics 2018-06-20 Jihyeon Jessie Yang

The classical Poincar\'e formula relates the rational homology classes of tautological cycles on a Jacobian to powers of the class of Riemann theta divisor. We prove a tropical analogue of this formula. Along the way, we prove several…

Algebraic Geometry · Mathematics 2023-05-03 Andreas Gross , Farbod Shokrieh