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We study those Lagrangian surfaces in complex Euclidean space which are foliated by circles or by straight lines. The former, which we call cyclic, come in three types, each one being described by means of, respectively, a planar curve, a…

Differential Geometry · Mathematics 2009-09-18 Henri Anciaux , Pascal Romon

The projective linear group \(\pgl(\comp,4)\) acts on cubic surfaces, considered as points of $\mathbb{P}_{\mathbb{C}}^{19}$. We compute the degree of the $15$-dimensional projective variety given by the Zariski closure of the orbit of a…

Algebraic Geometry · Mathematics 2019-10-22 Laura Brustenga i Moncusí , Sascha Timme , Madeleine Weinstein

Edge-to-edge tilings of the sphere by congruent quadrilaterals are completely classified in a series of three papers. This second one applies the powerful tool of trigonometric Diophantine equations to classify the case of…

Combinatorics · Mathematics 2023-06-06 Yixi Liao , Erxiao Wang

In this paper, we study the interplay between tropical and analytic geometry for closed subschemes of toric varieties. Let $K$ be a complete non-Archimedean field, and let $X$ be a closed subscheme of a toric variety over $K$. We define the…

Algebraic Geometry · Mathematics 2017-01-12 Walter Gubler , Joseph Rabinoff , Annette Werner

A Laman graph $G$ is a minimally rigid graph in dimension two, and its realization number is its number of distinct embeddings with fixed generic edge lengths. While conjectured to grow exponentially in the number of vertices of $G$, the…

Combinatorics · Mathematics 2025-11-13 Amelia Bielby , Arushi Chauhan , Cassia Pearce , Yue Ren

We prove a Poincar\'e duality for the Chow rings of smooth fans whose support are tropical linear spaces. As a consequence, we show that cycles and cocycles on tropical manifolds are Poincar\'e dual to each other. This allows us to define…

Algebraic Geometry · Mathematics 2021-04-07 Andreas Gross , Farbod Shokrieh

We construct and study the tropical moduli space \(\mathcal{M}_3^{\mathrm{trop}}\) of degree-$3$ tropical rational maps \(\mathbb{T}\PP^1 \to \mathbb{T}\PP^1\) up to post-composition. Using a combinatorial description in terms of slope…

Algebraic Geometry · Mathematics 2026-05-18 Tony Shaska , Mohammad-Reza Siadat

We propose an algebraic geometric framework to study the expressivity of linear activation neural networks. A particular quantity of neural networks that has been actively studied is the number of linear regions, which gives a…

Machine Learning · Computer Science 2024-10-10 Paul Lezeau , Thomas Walker , Yueqi Cao , Shiv Bhatia , Anthea Monod

We prove that a smooth projective surface of degree $d$ in $\mathbb P^3$ contains at most $d^2(d^2-3d+3)$ lines. We characterize the surfaces containing exactly $d^2(d^2-3d+3)$ lines: these occur only in prime characterize $p$ and, up to…

Algebraic Geometry · Mathematics 2024-06-26 Janet Page , Tim Ryan , Karen E. Smith

Let d be a positive integer. There are several versions of d-gonality for tropical curves, stable d-gonality and divisorial d-gonality, which are both inspired by d-gonality for compact Riemann surfaces. However, that conditions are not…

Algebraic Geometry · Mathematics 2018-10-05 Yuki Kageyama

We classify completely the surfaces of general type whose canonical map is 3-to-1 onto a surface of minimal degree in projective space. These surfaces fall into 5 distinct classes and we give explicit examples belonging to each of these…

Algebraic Geometry · Mathematics 2007-05-23 M. Mendes Lopes , R. Pardini

We study an irreducible component H(X) of the Hilbert scheme Hilb^{2t+2}(X) of a smooth cubic hypersurface X containing two disjoint lines. For cubic threefolds, H(X) is always smooth, as shown in arXiv:2010.11622. We provide a second proof…

Algebraic Geometry · Mathematics 2025-04-22 Yilong Zhang

K3 polytopes appear in complements of tropical quartic surfaces. They are dual to regular unimodular central triangulations of reflexive polytopes in the fourth dilation of the standard tetrahedron. Exploring these combinatorial objects, we…

Algebraic Geometry · Mathematics 2019-07-17 Gabriele Balletti , Marta Panizzut , Bernd Sturmfels

We consider tropical hemispaces, defined as tropically convex sets whose complements are also tropically convex, and tropical semispaces, defined as maximal tropically convex sets not containing a given point. We introduce the concept of…

Metric Geometry · Mathematics 2019-03-26 Ricardo D. Katz , Viorel Nitica , Sergei Sergeev

We define multidimensional tropical series, i.e. piecewise linear functions which are tropical polynomials locally but may contain an infinite number of monomials. Tropical series appeared in the study of the growth of pluriharmonic…

Algebraic Geometry · Mathematics 2025-06-10 Nikita Kalinin

We use floor decompositions of tropical curves to prove that any enumerative problem concerning conics passing through projective-linear subspaces in $\RP^n$ is maximal. That is, there exist generic configurations of real linear spaces such…

Algebraic Geometry · Mathematics 2011-02-10 Erwan Brugallé , Nicolas Puignau

This paper is devoted to the bounding and computation of the dimension of deformation spaces of tropical curves and hypersurfaces. This characteristic is interesting in light of the fact that it often coincides with the dimension of…

Algebraic Geometry · Mathematics 2018-06-06 Boaz Elazar

In this paper we study a construction of algebraic curves from combinatorial data. In the study of algebraic curves through degeneration, graphs usually appear as the dual intersection graph of the central fiber. Properties of such graphs…

Algebraic Geometry · Mathematics 2017-05-03 Takeo Nishinou

Given a tropical variety X and two non-negative integers p and q we define homology group $H_{p,q}(X)$. We show that if X is a smooth tropical variety that can be represented as the tropical limit of a 1-parameter family of complex…

Algebraic Geometry · Mathematics 2020-12-09 Ilia Itenberg , Ludmil Katzarkov , Grigory Mikhalkin , Ilia Zharkov

We study tropical degree bounds, stable tropical intersections, and tropical B\'ezout-type estimates through the geometry of Newton polytopes, mixed subdivisions, and lattice indices. We establish an upper bound for the tropical degree of a…

Algebraic Geometry · Mathematics 2026-05-26 Mounir Nisse