# Past Events

- 2018 Sep 041:30pm to 2:30pmBHI conference Room: 20 Garden Street, Cambridge (Lunch will be served at 1:00 pm)Director of the BHI, Avi Loeb will have an informal talk with members of the BHI community on new research and current ideas.
- 2018 May 09
# Rainer Weiss to speak at BHI Conference Banquet May 9, 2018

6:00pm## Location:

Sheraton Commander HotelWinning 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 a human...

Read more about Rainer Weiss to speak at BHI Conference Banquet May 9, 2018 - 2018 May 01
# Yurij Baryshev: "Feynman's field-theoretical approach to gravitation" | Shahar Hadar: "Exact Gravitational Wave Signatures from Colliding Extreme Black Holes" | Max Riegler: "Warped Black Holes in Lower Spin Gravity"

1:30pm to 2:30pm## Location:

BHI Conference Room (211) 20 Garden Street, Cambridge__Shahar Hadar__Max Planck Institute for Gravitational Physics

"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 radiation generated...

Read more about Yurij Baryshev: "Feynman's field-theoretical approach to gravitation" | Shahar Hadar: "Exact Gravitational Wave Signatures from Colliding Extreme Black Holes" | Max Riegler: "Warped Black Holes in Lower Spin Gravity" - 2018 Apr 24
# BHI Colloquium, April 24 | "Black Hole Entropy from Soft Hair" Malcolm Perry | "Berry Phases of Boundary Gravitons" Blagoje Oblak | Lydia Bieri "Gravitational Wave Memory"

1:30pm to 2:30pm## Location:

BHI Conference Room (211) 20 Garden Street, CambridgeBlafoje Oblak

ETH Zurich

Abstract:

This talk is devoted to Berry phases 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 closed path in...

Read more about BHI Colloquium, April 24 | "Black Hole Entropy from Soft Hair" Malcolm Perry | "Berry Phases of Boundary Gravitons" Blagoje Oblak | Lydia Bieri "Gravitational Wave Memory" - 2018 Apr 17
# BHI Colloquium, April 17 "Casual properties of evaporating Black Holes," Martin LeSourd

1:30pm## Location:

20 Garden Street, BHI conference room"Casual Properties of evaporating Black Holes"

Martin LeSourd, Oxford University

__Abstract__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 Geroch-Wald...

Read more about BHI Colloquium, April 17 "Casual properties of evaporating Black Holes," Martin LeSourd - 2018 Apr 10
# BHI Colloquium, April 10 | Delilah Gates "Polarization Whorls from High-Spin Black Holes" | Nevin Weinberg "Nonlinear tides in coalescing neutron stars"

1:30pm## Location:

BHI Conference Room (211) 20 Garden Street, CambridgeDelilah Gates

Harvard Physics

"Polarization Whorls from High-Spin Black Holes "

__Abstract__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 Horizon Telescope....

Read more about BHI Colloquium, April 10 | Delilah Gates "Polarization Whorls from High-Spin Black Holes" | Nevin Weinberg "Nonlinear tides in coalescing neutron stars" - 2018 Apr 03
# BHI Colloquium, April 3 I "Not quite a black hole: from quadratic gravity to gravitational wave echoes," Jing Ren and "A Galaxy-Scale Fountain of Cold Molecular Gas Pumped by a Black Hole," Grant Tremblay

1:30pm## Location:

BHI Conference Room (211) 20 Garden Street, CambridgeJing Ren

University of Toronto

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

Read more about BHI Colloquium, April 3 I "Not quite a black hole: from quadratic gravity to gravitational wave echoes," Jing Ren and "A Galaxy-Scale Fountain of Cold Molecular Gas Pumped by a Black Hole," Grant Tremblay - 2018 Mar 27
# BHI Colloquium, March 27 | "On the distinguishability of black hole microstates," Andrea Puhm | "Discovery and Opportunity in the X-ray Time Domain," Daryl Haggard

1:30pm## Location:

BHI Conference Room (211) 20 Garden Street, CambridgeAndrea Puhm

CNRS researcher, CPHT, Ecole

Polytechnique, Black Hole Initiative Visiting ScholarTitle: 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...

Read more about BHI Colloquium, March 27 | "On the distinguishability of black hole microstates," Andrea Puhm | "Discovery and Opportunity in the X-ray Time Domain," Daryl Haggard - 2018 Mar 20
# BHI Colloquium, March 20 | "The Motion of Bodies in Spacetime," Jim Weatherall | "Some Philosophers Look at Black Holes" Laura Ruetsche | Gordon Belot

1:30pm to 2:30pm## Location:

BHI Conference Room (211) 20 Garden Street, CambridgeJim Weatherhall

University of California, Irvine

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.

Laura Ruetsche

University of MichiganGordon Belot

Read more about BHI Colloquium, March 20 | "The Motion of Bodies in Spacetime," Jim Weatherall | "Some Philosophers Look at Black Holes" Laura Ruetsche | Gordon Belot

University of Michigan... - 2018 Mar 06
# BHI Colloquium, March 6 | "Coherent Stacking of Multiple Gravitational Wave Events," Frans Pretorius | "Neutron Stars and Stellar Mergers as a Laboratory for Dense QCD Matter," Aleksi Vuorinen

1:30pm to 2:30pm## Location:

BHI Conference Room (211) 20 Garden Street, CambridgeFrans Pretorius

Princeton UniversityAbstract:

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 PhysicsAbstract:

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.