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We prove the sharp bound of at most 64 lines on complex projective quartic surfaces (resp. affine quartics) that are not ruled by lines. We study configurations of lines on certain non-K3 surfaces of degree four and give various examples of…

Algebraic Geometry · Mathematics 2017-05-23 Víctor González-Alonso , Sławomir Rams

We combine classical Vinberg's algorithms with the lattice-theoretic/arithmetic approach from arXiv:1706.05734 [math.AG] to give a method of classifying large line configurations on complex quasi-polarized K3-surfaces. We apply our method…

Algebraic Geometry · Mathematics 2025-05-19 Alex Degtyarev , Sławomir Rams

We show that there cannot be more than 64 lines on a quartic surface admitting isolated rational double points over an algebraically closed field of characteristic $p \neq 2,\,3$, thus extending Segre--Rams--Sch\"utt theorem. Our proof…

Algebraic Geometry · Mathematics 2022-03-15 Davide Cesare Veniani

We estimate the number of lines on a non-K3 quartic surface. Such a surface with only isolated double point(s) contains at most twenty lines; this bound is attained by a unique configuration of lines and by a surface with a certain limited…

Algebraic Geometry · Mathematics 2025-07-01 Alex Degtyarev , Sławomir Rams

We investigate the number of straight lines contained in a K3 quartic surface \(X\) defined over an algebraically closed field of characteristic 3. We prove that if \(X\) contains 112 lines, then \(X\) is projectively equivalent to the…

Algebraic Geometry · Mathematics 2024-04-09 Davide Cesare Veniani

We show that the maximal number of (real) lines in a (real) nonsingular spatial quartic surface is 64 (respectively, 56). We also give a complete projective classification of all quartics containing more than 52 lines: all such quartics are…

Algebraic Geometry · Mathematics 2017-06-20 Alex Degtyarev , Ilia Itenberg , Ali Sinan Sertöz

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

For each integer $D\ge3$, we give a sharp bound on the number of lines contained in a smooth complex $2D$-polarized $K3$-surface in $\mathbb{P}^{D+1}$. In the two most interesting cases of sextics in $\mathbb{P}^4$ and octics in…

Algebraic Geometry · Mathematics 2019-09-13 Alex Degtyarev

We prove that a K3 quartic surface defined over a field of characteristic 2 can contain at most 68 lines. If it contains 68 lines, then it is projectively equivalent to a member of a 1-dimensional family found by Rams and Sch\"utt.

Algebraic Geometry · Mathematics 2022-03-15 Davide Cesare Veniani

We show that the number of lines contained in a supersingular quartic surface is 40 or at most 32, if the characteristic of the field equals 2, and it is 112, 58, or at most 52, if the characteristic equals 3. If the quartic is not…

Algebraic Geometry · Mathematics 2024-03-05 Alex Degtyarev

Over a field k of characteristic 3, we prove that there are no smooth quartic surfaces S in IP^3 with more than 112 lines. Moreover, the surface with 112 lines is projectively equivalent over k-bar to the Fermat quartic. As a key…

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

This paper deals with surfaces with many lines. It is well-known that a cubic contains 27 of them and that the maximal number for a quartic is 64. In higher degree the question remains open. Here we study classical and new constructions of…

Algebraic Geometry · Mathematics 2007-05-23 Samuel Boissiere , Alessandra Sarti

We give a defining equation of a complex smooth quartic surface containing 56 lines, and investigate its reductions to positive characteristics. This surface is isomorphic to the complex Fermat quartic surface, which contains only 48 lines.…

Algebraic Geometry · Mathematics 2016-09-06 Ichiro Shimada , Tetsuji Shioda

We advance our understanding of the configurations of low degree smooth rational curves on (quasi-)polarized complex K3-surfaces. We apply our efficient approach to classify the configurations of at least 36 lines on K3-sextics with at…

Algebraic Geometry · Mathematics 2025-12-10 Alex Degtyarev , Sławomir Rams

Given d in IN, we prove that all smooth K3 surfaces (over any field of characteristic p other than 2,3) of degree greater than 84d^2 contain at most 24 rational curves of degree at most d. In the exceptional characteristics, the same bounds…

Algebraic Geometry · Mathematics 2022-03-07 Sławomir Rams , Matthias Schütt

We show that the classical Fermat quartic has exactly three smooth spatial models. As a generalization, we give a classification of smooth spatial (as well as some other) models of singular $K3$-surfaces of small discriminant. As a…

Algebraic Geometry · Mathematics 2019-09-13 Alex Degtyarev

Let K be a field of characteristic 2. We give a geometric proof that there are no smooth quartic surfaces in IP^3 with more than 64 lines (predating work of Degtyarev which improves this bound to 60). We also exhibit a smooth quartic…

Algebraic Geometry · Mathematics 2019-11-13 Slawomir Rams , Matthias Schütt

We introduce certain rational functions on a smooth projective surface X in IP^3 which facilitate counting the lines on X. We apply this to smooth quintics in characteristic zero to prove that they contain no more than 127 lines, and that…

Algebraic Geometry · Mathematics 2022-03-10 Sławomir Rams , Matthias Schütt

We find upper bounds, sharp in most cases, on the number of real hyperplane sections of real smooth polarized $K3$-surfaces that split into lines. Most bounds coincide with their complex counterparts.

Algebraic Geometry · Mathematics 2025-12-09 Alex Degtyarev

We prove that the maximal number of conics in a smooth sextic $K3$-surface $X\subset\mathbb{P}^4$ is 285, whereas the maximal number of real conics in a real sextic is 261. In both extremal configurations, all conics are irreducible.

Algebraic Geometry · Mathematics 2024-03-05 Alex Degtyarev
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