Cosmology

For thousands of years, astronomy was restricted to what we could see with our eyes. But visible light makes up only a tiny fraction of a spectrum emitted by celestial objects.

We now know that light is not the universe’s sole means to reveal the mysteries of the heavens. Until recently, we simply lacked the windows through which to view these aspects of our universe.

Over the last few decades, astronomers have revolutionized our windows on the universe with telescopes of unprecedented sensitivity to light beyond what we can see with our eyes.

Observatories now allow us to see ghostly particles called neutrinos, and ripples in the fabric of space itself - called gravitational waves.

In his Perimeter Public Lecture on April 3, 2019, Chad Hanna will describe how these new windows have changed our view of the cosmos and explore what new wonders may be unveiled in the decades to come.

Hanna is an associate professor at Pennsylvania State University. His research focuses on studying the universe with gravitational waves using the Laser Interferometer Gravitational-Wave Observatory (LIGO).

Hanna and his research group work to enable multi-messenger astronomy through gravitational wave observations of merging neutron stars and black holes. Prior to joining Penn State, he was a senior postdoctoral researcher at Perimeter Institute.

I'll discuss recent work on finding time-dependent solutions of a black hole interacting with a scalar field. I'll discuss two distinct cases where the back-reaction of the scalar can be found. First, in the case that the scalar is slowly rolling (such as in inflation) the scalar field can be found in terms of super-advanced time coordinate, regular on both horizons. The scalar back-reacts on the geometry, with the black hole accreting and growing more or less as expected. The second case I'll describe briefly is scalar hair in modified gravity - giving a scalar-dressed rotating black hole that is finite on both horizons.