Winning the Nobel Prize would cap most physicists’ careers. For 2017 winner Rainer Weiss, the prize might not even have been the biggest moment of his year.

The 85-year-old professor emeritus at MIT shared the Nobel Prize for Physics for conceiving and shepherding a set of observatories that allowed scientists to prove Einstein’s assertion about gravitational waves: accelerating objects send ripples cascading through the universe at light speed. The invisible waves are so faint that even the most powerful distort space-time by less than the width of...

"Exact Gravitational Wave Signatures from Colliding Extreme Black Holes"

Abstract:

The low-energy dynamics of any system admitting a continuum of static configurations is approximated by slow motion in moduli (configuration) space. In the talk I will describe how this moduli space approximation can be utilized to study collisions of two maximally charged Reissner–Nordstrom black holes of arbitrary masses, and to compute analytically the gravitational...

This talk is devoted to Berryphases that appear in the context of asymptotic symmetries in general relativity. These phases arise when a coherent state is acted upon by symmetry transformations that trace a...

The causal structure of spacetimes containing fully evaporated black holes is considered from the perspective of Lorentzian geometry. The starting point is provided by theorems, due to Kodama, Geroch and Wald, that derive non-global hyperbolicity from a set of premises relating two partial Cauchy surfaces that, respectively, are thought of as lying before and after the evaporation. Here, we consider the...

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...

Title: Not quite a black hole: from quadratic gravity to gravitational wave echoes

Abstract:

Astrophysical black hole candidates might be horizonless ultracompact objects. Of particular interest is the plausible fundamental connection with quantum gravity. The puzzle is...

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...

Abstract: I will discuss some recent work on the problem of motion in general relativity, done in collaboration with Bob Geroch (Chicago). I will introduce a sense in which a collection of bodies -- including the solutions to some hyperbolic system -- could be said to "track" a curve, and then discuss some of the consequences of this idea. See arXiv:1707.04222 [gr-qc] for details.

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.

Title: Modeling the Supermassive Black Hole and Host Galaxy Connection Over Cosmic Time

Abstract: Stellar and gas dynamics lead us to believe that a supermassive black hole (SMBH) lurks at the center of every massive galaxy. Their masses correlate with host...

The Black Hole Initiative hosts weekly colloquia every Tuesday from 1:30-2:30pm. The talks are held in the Black Hole Initiative Conference Room (220) at 20 Garden Street.