Termine

Based on Ballmann´s lecture notes on the Blaschke Conjecture

Abstract

Based on Ballmann´s lecture notes on the Blaschke Conjecture

In this talk we dive into the world of point-line geometries related to spherical buildings of type F4. These turn out to be parapolar spaces of rank 3 with some extra properties. They differ from the other exceptional spherical buildings by the fact that they are not determined by only a field, but one also needs a quadratic alternative division algebra over this field. This makes them a bit harder to tackle and therefore they are omitted by several authors. After a short introduction, we will discuss some analogs of recent results about other exceptional spherical buildings. In particular, we will discuss subgeometries, domestic collineations and kangaroos

Extreme black holes possess event horizons at zero temperature, referred to as degenerate Killing horizons. These horizons are exclusively delineated by a specific limiting procedure, defining a near-horizon geometry or, more broadly, a quasi-Einstein equation which governs their properties. Solutions to this equation manifest as triples (M, g, X), where M represents a closed manifold (the horizon), g denotes a Riemannian metric, and X is a 1-form. The talk will be a overview of these concepts and relevant results which characterize solutions to the quasi-Einstein equation. This is joint work with Eric Bahuaud, Hari Kunduri, and Eric Woolgar.