Events

Violation of the Third Law of Black Hole Mechanics in Vacuum Gravity

We demonstrate numerically the existence of solutions of five-dimensional vacuum gravity describing the
formation, in finite time, of an extremal rotating black hole from a pre-existing Schwarzschild black hole.
This is the first example of a violation of the third law of black hole mechanics in vacuum gravity and
demonstrates that the third law is false independently of any matter model. We also demonstrate the
existence of solutions describing the formation, in finite time, of an extremal rotating black hole from
vacuum initial data that does not contain a black hole.

Monday, September 28, 2026 11:00 AM

Inperson
BHI Conference Room

Virtual
Zoom

Image: Ana Carvalho

Is LIGO really observing black holes?

The observation of gravitational radiation emitted by black hole mergers is now providing direct experimental evidence of black holes. According to general relativity, the merger remnant emits “ringdown” radiation: a superposition of damped exponentials (“quasinormal modes”) with complex frequencies that depend only on the final black hole’s mass and spin. These spectral lines uniquely identify the black hole, just like the 21 cm line identifies interstellar hydrogen. In the first part of the talk I will discuss recent theoretical and experimental developments in this “black hole spectroscopy” program, including the importance of nonlinear effects and new models of the frequency-domain waveform based on the black hole’s greybody factors. In the second part of the talk I will discuss recent subsolar-mass LIGO-Virgo-KAGRA public alerts. If these events are real, it is tantalizing to conclude that they may be primordial black holes. I will argue that one should first exclude alternative explanations of astrophysical origin, such as the merger of subsolar-mass neutron stars formed in collapsar disks.

Monday, October 5, 2026 11:00 AM

Inperson
G10

Virtual
Zoom

Monday, October 12, 2026

Modeling emission from super-Eddington supermassive black holes

Tidal disruption events (TDEs) light up hidden supermassive black holes and encode information about the
properties of both these black holes and their environments. They also regularly produce super-Eddington
mass return rates, providing a local test of extreme black hole growth. The light curves and spectra of TDEs
show signatures of these super-Eddington feeding rates, including evidence of large outflows, very high
electron densities, and strongly ionizing but obscured emission. Many of these signatures are also seen in
other candidates for super-eddington accretion, including luminous fast blue optical transients, ambiguous
nuclear transients, and little red dots. However, properties of the system such as the origin, mass/energy
budget and black hole mass are often better understood in TDEs. I’ll discuss how we can use theoretical
models to connect the observed light curves and spectra to the actual source emission as well as to the
properties of the gas surrounding the black hole in these transients. More broadly I’ll discuss how we can
combine theoretical models with observations to investigate the black hole mass function, probe emission
from forming and evolving accretion disks, and study the properties of stars on size scales we cannot
observe outside our own galactic nuclei.

Monday, October 19, 2026 11:00 AM

Inperson
G10

Virtual
Zoom

Monday, October 26, 2026 11:00 AM

Inperson
G10

Virtual
Zoom

Monday, November 2, 2026 11:00 AM

Inperson
G10

Virtual
Zoom

Monday, November 2, 2026 11:00 AM

Inperson
G10

Virtual
Zoom

Monday, November 23, 2026 – Monday, November 30, 2026

Monday, December 7, 2026 11:00 AM

Inperson
G10

Virtual
Zoom

Monday, December 14, 2026 11:00 AM

Inperson
G10

Virtual
Zoom

Monday, December 21, 2026 – Monday, January 18, 2027