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We present a projectively invariant description of planar linear 3-webs. For a non-hexagonal 3-web, we introduce family of projective torsion-free Cartan connections, the web leaves being geodesics for each member of the family, and give a…

Differential Geometry · Mathematics 2019-03-05 Sergey I. Agafonov

In 1951, Ankeny, Artin, and Chowla published a brief note containing four congruence relations involving the class number of $\mathbb{Q}(\sqrt{d})$ for positive squarefree integers $d\equiv 1 \bmod{4}$. Many of the ideas present in their…

Number Theory · Mathematics 2024-11-12 Nic Fellini

It is conjectured that the dual variety of every smooth nonlinear subvariety of dimension $> \frac{2N}{3}$ in projective $N$-space is a hypersurface, an expectation known as the duality defect conjecture. This would follow from the truth of…

Algebraic Geometry · Mathematics 2020-07-01 Grayson Jorgenson

In this paper, we provide an $O(n \mathrm{polylog} n)$ bound on the expected complexity of the randomly weighted Voronoi diagram of a set of $n$ sites in the plane, where the sites can be either points, interior-disjoint convex sets, or…

Computational Geometry · Computer Science 2015-03-23 Sariel Har-Peled , Benjamin Raichel

Two recent papers by Kawarabayashi, Thomas and Wollan, "A New Proof of the Flat Wall Theorem" (arXiv:1207.6927) and "Quickly Excluding a Non-Planar Graph" (arXiv:2010.12397) provide major improvements over Robertson and Seymour's original…

Combinatorics · Mathematics 2023-04-07 Dan Arnon

After Chern's conjecture on the discreteness of the constant scalar curvatures of compact minimal submanifolds $M^n$ in unit spheres $\mathbb{S}^{n+q}$, Z. Q. Lu proposed a conjecture regarding the second gap, based on his ingenious…

Differential Geometry · Mathematics 2026-01-13 Weiran Ding , Jianquan Ge , Fagui Li , Xize Yang

We prove a certain 'fat hyperplane section' Weak Lefschetz-type theorem for etale cohomology of non-projective varieties, similar to a result of Goresky and MacPherson (over complex numbers). This statement easily yields certain (vast)…

Algebraic Geometry · Mathematics 2015-02-03 Mikhail V. Bondarko

We develop a holonomy reduction procedure for general Cartan geometries. We show that, given a reduction of holonomy, the underlying manifold naturally decomposes into a disjoint union of initial submanifolds. Each such submanifold…

Differential Geometry · Mathematics 2014-05-08 Andreas Cap , A. Rod Gover , Matthias Hammerl

Introducing the deformation theory of holomorphic Cartan geometries, we compute infinitesimal automorphisms and infinitesimal deformations. We also prove the existence of a semi-universal deformation of a holomorphic Cartan geometry.

Differential Geometry · Mathematics 2020-04-01 Indranil Biswas , Sorin Dumitrescu , Georg Schumacher

In the representation theory of reductive $p$-adic groups $G$, the issue of reducibility of induced representations is an issue of great intricacy. It is our contention, expressed as a conjecture in [3], that there exists a simple geometric…

Representation Theory · Mathematics 2010-08-05 Anne-Marie Aubert , Paul Baum , Roger Plymen

In this note we give a version of Hao Huang's proof of the sensitivity conjecture, shedding some light on the origin of the magical matrix $A$ in that proof. For the history of the subject and the importance of this conjecture to the study…

Combinatorics · Mathematics 2019-07-29 Roman Karasev

In this note, we discuss recently discovered counterexamples to Mordell's Pellian Equation Conjecture and the Ankeny-Artin-Chowla-Conjecture. We provide a verification of the counterexample to Mordell's Pellian Equation Conjecture that can…

Number Theory · Mathematics 2025-04-30 Andreas Reinhart

We prove a conjecture by Ruzsa from 2006 on a discrete version of the Brunn-Minkowski inequality, stating that for any $A,B\subset\mathbb{Z}^k$ and $\epsilon>0$ with $B$ not contained in $n_{k,\epsilon}$ parallel hyperplanes we have…

Combinatorics · Mathematics 2023-06-26 Peter van Hintum , Peter Keevash , Marius Tiba

We prove a sharp continuum Beck-type theorem for hyperplanes. Our work is inspired by foundational work of Beck on the discrete problem, as well as refinements due to Do and Lund. The inductive proof uses recent breakthrough results in…

Classical Analysis and ODEs · Mathematics 2025-10-14 Paige Bright , Alexander Ortiz , Dmitrii Zakharov

We present a short proof of Klartag's central limit theorem for convex bodies, using only the most classical facts about log-concave functions. An appendix is included where we give the proof that thin shell implies CLT. The paper is…

Probability · Mathematics 2019-07-22 Daniel J. Fresen

In the theory of digraphs, the study of cycles is a subject of great importance and has given birth to a number of deep questions such as the Behzad-Chartrand-Wall conjecture (1970) and its generalization, the Caccetta-H\"{a}ggkvist…

Combinatorics · Mathematics 2016-10-21 Muhammad A. Khan

In 2010, Brasselet, Sch\"urmann and Yokura conjectured an equality of characteristic classes of singular varieties between the Goresky-MacPherson $L$-class $L_*(X)$ and the Hirzebruch homology class $T_{1*}(X)$ for a compact complex…

Algebraic Geometry · Mathematics 2024-03-20 J. Fernández de Bobadilla , I. Pallarés

In 1989, D. Happel pointed out for a possible connection between the global dimension of a finite-dimensional algebra and its Hochschild cohomology: is it true that the vanishing of Hochschild cohomology higher groups is sufficient to…

K-Theory and Homology · Mathematics 2023-09-18 Guilherme da Costa Cruz

The double ramification (DR) cycle associated to a line bundle on a family of curves detects where the line bundle becomes fibrewise-trivial. The Hodge-DR Conjecture proposes a formula for powers of the first Chern class of a natural line…

Algebraic Geometry · Mathematics 2025-10-23 Alessandro Chiodo , David Holmes

We investigate a stronger formulation of Webb's conjecture on the contractibilty of the orbit space of the p-subgroup complexes in terms of finite topological spaces. The original conjecture, which was first proved by Symonds and, more…

Group Theory · Mathematics 2018-05-25 Kevin Ivan Piterman