25 citations · 51 across the 10 of their papers we have counts for
10 papers
On cubic surfaces with a rational line
Andreas-Stephan Elsenhans, Jörg Jahnel
We report on our project to construct non-singular cubic surfaces over with a rational line. Our method is to start with degree 4 Del Pezzo surfaces in diagonal form. For th…
On the quasi group of a cubic surface over a finite field
Andreas-Stephan Elsenhans, Jörg Jahnel
We construct nontrivial homomorphisms from the quasi group of some cubic surfaces over $\bbF_{\!p}$ into a group. We show experimentally that the homomorphisms constructed are the…
On the Brauer-Manin obstruction for cubic surfaces
Andreas-Stephan Elsenhans, Jörg Jahnel
We describe a method to compute the Brauer-Manin obstruction for smooth cubic surfaces over such that $\Br(S)/\Br(\bbQ)$ is of order two or four. This covers the vast majori…
Determinantal quartics and the computation of the Picard group
Andreas-Stephan Elsenhans, Jörg Jahnel
We test the methods for computing the Picard group of a surface in a situation of high rank. The examples chosen are resolutions of quartics in $\bP^3$ having 14 singularities…
When is the (co)sine of a rational angle equal to a rational number?
Jörg Jahnel
If the cosine of a rational multiple of is a rational number then it is an integral multiple of . For this fact, we give a proof accessible to an interested school stu…
More cubic surfaces violating the Hasse principle
Jörg Jahnel
We generalize L.J. Mordell's construction of cubic surfaces for which the Hasse principle fails.