Andrea Puhm CNRS researcher, CPHT, Ecole Polytechnique, Black Hole Initiative Visiting Scholar
Title: On the distinguishability of black hole microstates
Abstract: A challenging question in the context of the information paradox is how to distinguish black hole microstates without having access to the entire spacetime. In the context of holography, one can ask how one can distinguish microstates of a black hole in anti-de Sitter space by measurements performed in the dual conformal field theory. I will discuss one...
Abstract: Within the next few years we can anticipate that the LIGO/Virgo detectors will have observed many tens or even hundreds of binary compact object merger events. One avenue to extract more information from this catalog is to stack the signals from a subset of events that are expected to share a common feature, enhancing the effective signal-to-noise ratio that the feature can be measured with. Thanks to the uniqueness properties of black holes in Einstein gravity, binary black hole mergers are ideal targets for stacking, allowing for stringent tests of dynamical, strong-field gravity, or detecting deviations from the predictions of general relativity.
I will describe an initial study exploring the utility of stacking to detect higher-order quasi-normal ringdown modes post-merger.
Though binary neutron star systems do not share such a uniqueness property, there may nevertheless be aspects of merger signals that could be enhanced using stacking. I will discuss one such example that would seek to detect a post-merger signal from the subclass of events where a hypermassive remnant forms.
Aleksi Vuorinen Helsinki Institute of Physics
Abstract: Outside the interiors of black holes, neutron stars contain the densest forms of matter in our present-day Universe. This makes them a unique laboratory for strong interaction physics, as novel phases of QCD matter may be present in their extremely dense cores, or produced at the high temperatures reached in stellar mergers. In my talk, I will concentrate on the quantitative constraints that various types of neutron star observations, including the gravitational wave signatures of their mergers, have recently set for the properties of dense nuclear and quark matter. In particular, I will demonstrate that the Equation of State of cold and dense QCD matter is significantly constrained by the known existence of two-solar-mass stars and by the recent LIGO constraint on the tidal deformabilities of the two stars involved in the gravitational wave observation GW170817.
Abstract: I will present a model for stellar mass black hole binary (BHB) mergers accelerated by an active galactic nucleus (AGN) accretion disk. This model predicted the existence of 'overweight' stellar mass BHB mergers, detectable by LIGO (McKernan, Ford, et al. 2014). In more recent work, we find the rate of BHB merger by this channel can span the range 1e-4-1e4 Gpc^-3 yr^-1, depending on a variety of poorly constrained astrophysical parameters. Thus, with LIGO's measured rates (12-213 Gpc^-3 yr^-1), we can already constrain some aspects of AGN physics. I will also present the predicted mass and spin spectrum of BH produced via this channel. Notably, retrograde spin BH, evolving in a gas disk play a key role in the shape of the spin distribution among AGN-produced BHB mergers. Finally, I will discuss how this channel can be constrained by LIGO observations and other future theoretical and observational work.
Erin Kara University of Maryland
Abstract: Accreting supermassive black holes can produce more electromagnetic and kinetic luminosities than the combined stellar luminosity of an entire galaxy. Most of the power output from an Active Galactic Nucleus is released close to the black hole, and therefore studying the inner accretion flow--at the intersection of inflow and outflow--is essential for understanding how black holes grow and how they affect their surrounding environments. In this talk, I will present a new way of probing these environments, through X-ray reverberation mapping, which allows us to map the gas falling on to black holes and measure the effects of strongly curved spacetime close to the event horizon.