David Gay (University of Georgia) will speak in the topology seminar at 3:30pm, Thursday 20th November, in MSCS 422. TITLE: Trisections: Heegaard splittings for 4-manifolds ABSTRACT: This reports on joint work with Rob Kirby. We show that every smooth, closed, oriented 4-manifold splits (uniquely up to stabilization) into 3 nice pieces in precise analogy with the way every smooth, closed, oriented 3-manifold is split (uniquely up to stabilization) by a Heegaard splitting into 2 nice pieces. This talk will give definitions and examples to highlight the striking parallels between the 3- and 4-dimensional theories, and also to present several natural open questions.