BHI Colloquium, April 10 | Delilah Gates "Polarization Whorls from High-Spin Black Holes" | Nevin Weinberg "Nonlinear tides in coalescing neutron stars"


Tuesday, April 10, 2018, 1:30pm


BHI Conference Room (211) 20 Garden Street, Cambridge

Delilah Gates

Harvard Physics

"Polarization Whorls from High-Spin Black Holes "


We consider electromagnetic emissions from the near-horizon region of a high-spin black hole. Assuming the source polarization respects the spacetime symmetries, we analytically compute the polarization profile measured by a distant observer. The universal constraints we obtain are a new example of critical behavior in astronomy that could be observed at the Event Horizon Telescope.

Nevin Weinberg
Massachusetts Institute of Technology

"Nonlinear tides in coalescing neutron stars"


With the first detection of a binary neutron star merger by LIGO and Virgo, the impact of tides on the gravitational wave signal is already beginning to place interesting constraints on the neutron star equation of state. Most analyses assume that the tide can be treated as a linear perturbation to the star until very late in the inspiral. I will show, however, that the linear approximation is invalid even at relatively early stages of the inspiral and that nonlinear fluid effects become important around the time the binary enters LIGO's bandpass (around 30 Hz). Although the precise influence of nonlinear and superfluid tidal effects are not yet well constrained, I will show that they may significantly modify the gravitational wave and electromagnetic signals.