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We show that a pseudoeffective R-divisor has numerical dimension 0 if it is numerically trivial on a subvariety with ample normal bundle. This implies that the cycle class of a curve with ample normal bundle is big, giving an affirmative…

Algebraic Geometry · Mathematics 2013-12-05 John Christian Ottem

We prove an asymptotic formula for the number of ${\rm SL}_3({\mathbb Z})$-equivalence classes of integral ternary cubic forms having bounded invariants. We use this result to show that the average size of the 3-Selmer group of all elliptic…

Number Theory · Mathematics 2013-12-25 Manjul Bhargava , Arul Shankar

Our purpose in this paper is to construct new examples of twisted Brill Noether loci on curves of genus g greater than 2 with negative expected dimension. We begin by completing the proof of Butler's conjecture for coherent systems of…

Algebraic Geometry · Mathematics 2026-04-21 L. Brambila-Paz , P. E. Newstead

Let (S,H) be a polarized K3 surface. We define Brill-Noether filtration on moduli spaces of vector bundles on S. Assume that (c_1(E),H) > 0 for a sheaf E in the moduli space. We give a formula for the expected dimension of the Brill-Noether…

Algebraic Geometry · Mathematics 2007-05-23 Maxim Leyenson

In spaces of nonpositive curvature the existence of isometrically embedded flat (hyper)planes is often granted by apparently weaker conditions on large scales. We show that some such results remain valid for metric spaces with non-unique…

Metric Geometry · Mathematics 2016-03-15 Dominic Descombes , Urs Lang

Let X be a ruled surface over a nonsingular curve C of genus $g\geq0$. Let $M_H:=M_{X,H}(2;c_1,c_2)$ be the moduli space of H-stable rank 2 vector bundles E on X with fixed Chern classes $c_i:=c_i(E)$ for $i=1,2$. The main goal of this…

Algebraic Geometry · Mathematics 2024-01-23 L. Costa , I. Macías Tarrío

We extend the structure theory of Burago--Gromov--Perelman for Alexandrov spaces with curvature bounded below, to the setting of Busemann spaces with non-negative curvature. We prove that any finite-dimensional Busemann space with…

Metric Geometry · Mathematics 2026-04-20 Bang-Xian Han , Liming Yin

This paper establishes the conjecture that a non-singular projective hypersurface of dimension $r$, which is not equal to a linear space, contains $O(B^{r+\epsilon})$ rational points of height at most $B$, for any choice of $\epsilon>0$.…

Number Theory · Mathematics 2007-05-23 T. D. Browning , D. R. Heath-Brown

In this short note, I point out that results of Ballico and Kool--Shende--Thomas together imply that on $K3$, Enriques, and Abelian surfaces, if $L$ is a very ample and $(2p_a(L)-2g-1)$-spanned line bundle, then the equigeneric Severi…

Algebraic Geometry · Mathematics 2019-09-23 Thomas Dedieu

An orthogonality space is a set equipped with a symmetric and irreflexive binary relation. We consider orthogonality spaces with the additional property that any collection of mutually orthogonal elements gives rise to the structure of a…

Rings and Algebras · Mathematics 2020-03-19 Jan Paseka , Thomas Vetterlein

The Birch and Swinnerton-Dyer conjecture states that the rank of the Mordell-Weil group of an elliptic curve E equals the order of vanishing at the central point of the associated L-function L(s,E). Previous investigations have focused on…

Number Theory · Mathematics 2010-09-15 John Goes , Steven J Miller

By the theorem of Mantel $[5]$ it is known that a graph with $n$ vertices and $\lfloor \frac{n^{2}}{4} \rfloor+1$ edges must contain a triangle. A theorem of Erd\H{o}s gives a strengthening: there are not only one, but at least…

Combinatorics · Mathematics 2020-03-11 Chuanqi Xiao , Gyula O. H. Katona

We introduce a variant of global generation for coherent sheaves on abelian varieties which, under certain circumstances, implies ampleness. This extends a criterion of Debarre asserting that a continuously globally generated coherent sheaf…

Algebraic Geometry · Mathematics 2023-02-15 Giuseppe Pareschi

We develop a Morse-Lusternik-Schnirelmann theory for the distance between two points of a smoothly embedded circle in a complete Riemannian manifold. This theory suggests very naturally a definition of width that generalises the classical…

Differential Geometry · Mathematics 2025-03-27 Lucas Ambrozio , Rafael Montezuma , Roney Santos

The symplectic Brill--Noether locus ${\mathcal S}_{2n, K}^k$ associated to a curve $C$ parametrises stable rank $2n$ bundles over $C$ with at least $k$ sections and which carry a nondegenerate skewsymmetric bilinear form with values in the…

Algebraic Geometry · Mathematics 2020-05-01 Ali Bajravani , George H. Hitching

We prove relations among the classes of certain divisors on the moduli spaces of curves with marked points, generalizing the Brill-Noether Ray Theorem of Eisenbud and Harris.

Algebraic Geometry · Mathematics 2016-09-07 Adam Logan

We prove that for every bipartite graph $H$ and positive integer $s$, the class of $K_{s,s}$-subgraph-free graphs excluding $H$ as a pivot-minor has bounded average degree. Our proof relies on the announced binary matroid structure theorem…

Combinatorics · Mathematics 2026-03-24 Rutger Campbell , James Davies , Robert Hickingbotham

For a line bundle L on a smooth surface S, it is now known that the degree of the Severi variety of cogenus-d curves is given by a universal polynomial in the Chern classes of L and S if L is d-very ample. For S rational, we relax the…

Algebraic Geometry · Mathematics 2013-02-08 Steven L. Kleiman , Vivek V. Shende , with an appendix by Ilya Tyomkin

Inspired by a width invariant on permutations defined by Guillemot and Marx, Bonnet, Kim, Thomass\'e, and Watrigant introduced the twin-width of graphs, which is a parameter describing its structural complexity. This invariant has been…

Logic in Computer Science · Computer Science 2024-08-07 Édouard Bonnet , Jaroslav Nešetřil , Patrice Ossona de Mendez , Sebastian Siebertz , Stéphan Thomassé

Block and Weinberger show that an arithmetic manifold can be endowed with a positive scalar curvature metric if and only if its $\rationals$-rank exceeds 2. We show in this article that these metrics are never in the same coarse class as…

Differential Geometry · Mathematics 2007-05-23 Stanley S. Chang