Discrete confocal quadrics and incircular nets

YMSC Topology Seminar

Organizers：

陈伟彦、高鸿灏、黄意、林剑锋、邱宇、孙巍峰

Speaker：

Alexander Bobenko (TU Berlin)

Time：

Mon., 13:30-14:30, May 25, 2026

Venue：

B627, Shuangqing Complex Building A

Online：

Zoom meeting ID: 405 416 0815

Password: 111111

Title：

Discrete confocal quadrics and incircular nets

Abstract:

We propose a geometric discretisation of confocal quadrics that are described by an integrable system. These correspond to triply orthogonal coordinate systems, also known as elliptic coordinates. We also demonstrate that special discrete confocal conics lead to incircular nets. The latter are comprised of line congruences that build elementary quadrilaterals with inscribed circles. This is an elementary talk with many pictures and incidence theorems in projective, hyperbolic, and Laguerre geometries.