During the Fall 2019 Semester, a weekly seminar will be held on General Relativity. The seminar will take place at on Friday’s at 10:30am in Science Center 530.
The schedule will be updated below.
|2/7/2020||Lan-Hsuan Huang (University of Connecticut)||Title: Improvability of the dominant energy scalar and Bartnik’s stationary conjecture
Abstract: In this talk, we will introduce the concept of improvabilty of the dominant energy scalar and discuss strong consequences of non-improvability. We employ new, large families of deformations of the modified Einstein constraint operator and show that, generically, their adjoint linearizations are either injective, or else one can prove that kernel elements satisfy a “null-vector equation”. Combined with a conformal argument, we make significant progress toward Bartnik’s stationary conjecture. More specifically, we prove that a Bartnik minimizing initial data set can be developed into a spacetime that both satisfies the dominant energy condition and carries a global Killing field. We also show that this spacetime is vacuum near spatial infinity. This talk is based on the joint work with Dan Lee.
|2/14/2020||Yuewen Chen (CMSA)||Title: Solutions of Jang’s Equation Inside Black Holes
Abstract: Jang’s equation is a degenerate elliptic differential equation which plays an important role in the positive mass theorem. In this talk, we describe a high order WENO (Weighted Essentially Non-Oscillatory) scheme for the Jang’s equation. Some special solutions will be shown, such as those possessing spherical symmetry and axial symmetry.
|2/21/2020||Alex Lupsasca (Harvard)||Title: The Kerr Photon Ring
Abstract: The Event Horizon Telescope image of the supermassive black hole in the galaxy M87 is dominated by a bright, unresolved ring. General relativity predicts that embedded within this image lies a thin “photon ring,” which is itself composed of an infinite sequence of self-similar subrings. Each subring is a lensed image of the main emission, indexed by the number of photon orbits executed around the black hole. I will review recent theoretical advances in our understanding of lensing by Kerr black holes, based on arXiv:1907.04329, 1910.12873, and 1910.12881. In particular, I will describe the critical parameters γ, δ, and τ that respectively control the demagnification, rotation, and time delay of successive lensed images of a source. These observable parameters encode universal effects of general relativity, which are independent of the details of the emitting matter and also produce strong, universal signatures on long interferometric baselines. These signatures offer the possibility of precise measurements of black hole mass and spin, as well as tests of general relativity, using only a sparse interferometric array such as a future extension of the EHT to space.
|2/28/2020||Po-Ning Chen (University of California, Riverside)||TBA|
|3/13/2020||Hsin-Yu Chen (BHI)||TBA|
|3/20/2020||Dan Lee (Queens College, CUNY)||TBA|
|4/10/2020||Sven Hirsch (Duke University)||TBA|
|4/17/2020||Christina Sormani (Lehman College, CUNY)||TBA|
|4/24/2020||Daniel Stern (University of Toronto)||TBA|
Information about last year’s seminar can be found here.