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In this paper we present several results on the expected complexity of a convex hull of $n$ points chosen uniformly and independently from a convex shape. (i) We show that the expected number of vertices of the convex hull of $n$ points,…

Computational Geometry · Computer Science 2011-11-24 Sariel Har-Peled

It is well established that a general pair of twisted cubic curves in complex projective space has ten common secant lines. As an initial investigation, we show that the monodromy group of the ten common secant lines over the complex…

We construct explicit examples of cubic surfaces over $\bbQ$ such that the 27 lines are acted upon by the index two subgroup of the maximal possible Galois group. This is the simple group of order $25 920$. Our examples are given in…

Number Theory · Mathematics 2010-07-27 Andreas-Stephan Elsenhans , Jörg Jahnel

We study three families of polyhedral cones whose sections are regular simplices, cubes, and crosspolytopes. We compute solid angles and conic intrinsic volumes of these cones. We show that several quantities appearing in stochastic…

Probability · Mathematics 2021-01-01 Zakhar Kabluchko , Hauke Seidel

The Cayley--Salmon theorem implies the existence of a 27-sheeted covering space specifying lines contained in smooth cubic surfaces over $\mathbb{C}$. In this paper we compute the rational cohomology of the total space of this cover, using…

Algebraic Geometry · Mathematics 2021-01-05 Ronno Das

In this paper, we construct a natural probability measure on the space of real branched coverings from a real projective algebraic curve $(X,c_X)$ to the projective line $(\mathbb{C}\mathbb{P}^1,\textrm{conj})$. We prove that the space of…

Algebraic Geometry · Mathematics 2021-02-17 Michele Ancona

We present a new normal form for cubic surfaces that is well suited for p-adic geometry, as it reveals the intrinsic del Pezzo combinatorics of the 27 trees in the tropicalization. The new normal form is a polynomial with eight terms,…

Algebraic Geometry · Mathematics 2020-10-21 Marta Panizzut , Emre Can Sertöz , Bernd Sturmfels

We first review some topics in the classical computational geometry of lines, in particular the O(n^{3+\epsilon}) bounds for the combinatorial complexity of the set of lines in R^3 interacting with $n$ objects of fixed description…

Metric Geometry · Mathematics 2007-05-23 Frank Sottile , Thorsten Theobald

We consider random lines in $\mathbb{R}^3$ (random with respect to the kinematic measure) and how they intersect $\mathbb{S}^2$. It is known that the entry point and the exit point behave like \textit{independent} uniformly distributed…

Probability · Mathematics 2023-08-07 Dmitriy Bilyk , Alan Chang , Otte Heinävaara , Ryan W. Matzke , Stefan Steinerberger

A polynomial transformation of the real plane $\Bbb R^2$ is a mapping $\Bbb R^2\to\Bbb R^2$ given by two polynomials of two variables. Such a transformation is called quadratic if the degrees of its polynomials are not greater than two. In…

Algebraic Geometry · Mathematics 2015-07-08 Ruslan Sharipov

We study the systole of a random surface, where by a random surface we mean a surface constructed by randomly gluing together an even number of triangles. We study two types of metrics on these surfaces, the first one coming from using…

Differential Geometry · Mathematics 2017-05-17 Bram Petri

In this paper we investigate the distribution of the set of values of a linear map at integer points on a quadratic surface. In particular, it is shown that subject to certain algebraic conditions, this set is equidistributed. This can be…

Number Theory · Mathematics 2016-01-20 Oliver Sargent

In this short note we use the polynomial partitioning lemma to strengthen a recent result of Dvir and Gopi about the number of rich lines in high dimensional Euclidean spaces. Our result shows that if there are sufficiently many rich lines…

Combinatorics · Mathematics 2021-02-16 Marton Hablicsek , Zachary Scherr

The subject of this paper is the study of various families of quartic K3 surfaces which are invariant under a certain $(\mathbb{Z}/2\mathbb{Z})^{4}$ action. In particular, we describe families whose general member contains $8,16,24$ or $32$…

Algebraic Geometry · Mathematics 2017-07-19 Florian Bouyer

It is shown that there exist non-singular cubic surfaces in CP^3 containing 5 twistor lines. This is the maximum number of twistor fibres that a non-singular cubic can contain. Cubic surfaces in CP^3 with 5 twistor lines are classified up…

Differential Geometry · Mathematics 2015-06-23 John Armstrong , Massimiliano Povero , Simon Salamon

The orthogonal projection of a 4-cube onto a uniform random 3-subspace in R^4 is a convex 3-polyhedron P with 14 vertices almost surely. Three numerical characteristics of P -- volume, surface area and mean width -- are studied. These…

Metric Geometry · Mathematics 2012-05-11 Steven R. Finch

We establish a bound of $O(n^2k^{1+\eps})$, for any $\eps>0$, on the combinatorial complexity of the set $\T$ of line transversals of a collection $\P$ of $k$ convex polyhedra in $\reals^3$ with a total of $n$ facets, and present a…

Computational Geometry · Computer Science 2008-07-09 Haim Kaplan , Natan Rubin , Micha Sharir

We show that the probability that a multilinear polynomial $f$ of independent random variables exceeds its mean by $\lambda$ is at most $e^{-\lambda^2 / (R^q Var(f))}$ for sufficiently small $\lambda$, where $R$ is an absolute constant.…

Probability · Mathematics 2012-06-11 Warren Schudy , Maxim Sviridenko

We obtain formulae for the expected number and height distribution of critical points of smooth isotropic Gaussian random fields parameterized on Euclidean space or spheres of arbitrary dimension. The results hold in general in the sense…

Probability · Mathematics 2016-09-20 Dan Cheng , Armin Schwartzman

Let k be a field of characteristic other than 2,3. We prove that there are no geometrically smooth quartic surfaces in IP^3 with more than 64 lines. As a key step, we derive the sharp bound that any line meets at most 20 other lines on a…

Algebraic Geometry · Mathematics 2016-11-14 Slawomir Rams , Matthias Schuett