Session X06: Isaacson Award Session: Challenges in Gravitational Wave Research

Live

Meeting the technical challenges of building sensitive broadband gravitational wave detectors like LIGO and Virgo extends to searching their data as deeply as possible, finding weak signals buried under instrumental noise. Today this task employs big resources, both human and computational. Peter Kafka and Kip Thorne first raised awareness of the possibilities and necessity of this effort in the 1970s and `80s. I will survey how the foundations of today's methods were laid during the late `80s and early `90s, with coordinated discussions among both the interferometry groups and the bar detector groups at the time. This led to the first joint interferometric data run, the so-called `100 hour run' of the Glasgow and Munich prototypes. I will then focus in on the most difficult data challenge of all, the search for gravitational wave pulsars. LIGO's upper limits so far have revealed how surprisingly smooth neutron stars are, despite their having a semi-solid crust. As search sensitivities improve, the first positive detection will give us exciting and fundamental new insights into the exotic physics of neutron stars.   

Live

The era of gravitational wave astronomy will not only shed new light on the astrophysics of black hole and neutron star binaries, but also promises unique probes of fundamental physics. I will discuss some exciting ways that multimessenger observations of black holes and neutron stars can be used to look for new types of matter that are inaccessible to terrestrial labs. The phenomenon of superradiance enables a rotating black hole to grow an oscillating cloud of ultralight bosons, spinning down in the process. Gravitational waves from such a source would be a distinct signature of axions or dark photons. With its high densities and gravitational compactness, a neutron star can become a collection site for dark matter, eventually forming a tiny black hole at its center that devours the star from the inside. I will discuss recent theoretical work to model such sources and understand the rich, strong-field dynamics involved.   

Live

I'll pick up after the early history presented by Schutz. By the mid-90s, the foundations for gravitational wave data analysis had been established, but many of the methods had never been tried on actual instrumental data. I'll discuss how these methods were tested and further developed on data from the LIGO 40m prototype, starting with a group of Kip Thorne's students and postdocs, and morphing into systems still being used today. I will then talk about one of the most beautiful and exciting possibilities, which Rai Weiss has always championed: the detection of a cosmological background of stochastic gravitational waves. In the same way as the electromagnetic cosmic background radiation gives us a clear picture of the universe when it was a few hundred thousand years old, the gravitational wave stochastic background (when detected!) will give us insight into the behaviour of the universe both at current times and at very early times.