Recorded 27 October 2021. Mihalis Dafermos of Princeton University presents "Strong Cosmic Censorship versus Λ" at IPAM's Workshop II: Mathematical and Numerical Aspects of Gravitation. Abstract: The strong cosmic censorship conjecture is a fundamental open problem in classical general relativity, first put forth by Roger Penrose in the early 70s. This is essentially the question of whether general relativity is a deterministic theory. Perhaps the most exciting arena where the validity of the conjecture is challenged is the interior of rotating black holes, and there has been a lot of work in the past 50 years in identifying mechanisms ensuring that at least some formulation of the conjecture be true. It turns out that when a nonzero cosmological constant ? is added to the Einstein equations, these underlying mechanisms change in an unexpected way, and the validity of the conjecture depends on a detailed understanding of subtle aspects of black hole scattering theory, surprisingly involving, in the case of negative ?, some number theory. Does strong cosmic censorship survive the challenge of non-zero ?? This talk will try to address this Question! Learn more online at: https://www.ipam.ucla.edu/programs/workshops/workshop-ii-mathematical-and-numerical-aspects-of-gravitation/?tab=schedule