title: polyhedra inscribed in quadrics
speakers：jean-marc schlenker, anton thalmaier
time：2020/11/12，21:00-22:00
link：
code：929725
abstract：in 1832, jakob steiner published a book which opened new perspectives on geometry, and in particular on polyhedra. among other questions, he asked: what are the combinatorial types of polyehdra that can be realized in $\rr^3$ with their vertices on a quadric? the question is projectively invariant and, up to projective transformation, there are only three quadrics in $\rr^3$. the question was first answered in the 1990s for polyhedra inscribed in an ellipsoid, using hyperbolic geometry. i will explain this result and how the question can be answered for the other two quadrics using anti-de sitter and half-pipe geometry. (new results are joint work with jeff danciger and sara maloni.)
