GR Seminars Fall 2012
The standard seminar time and place is Monday, 1:30pm, Room 4102.
Non-standard times and/or places are indicated in red type.
Tentative speakers are indicated in green type.

DATE	SPEAKER	AFFILIATION	TITLE
Sept. 10	Alejandro Satz	UMD	Renormalization group flow of black hole entropy
Sept. 20 (Thurs, 4pm) MCFP Colloquium	Alberto Nicolis	Columbia U	Effective field theories for fluids and superfluids
Sept. 24 (Joint w/ EPT, 2:15pm)	Gia Dvali	NYU, CERN, LMU, MPI Munich	Geometry as Bose-Einstein  Condensate
Oct. 1	Jeandrew Brink	NITheP,  Stellenbosch University	Thoughts on an A* test of GR
Oct. 9 (Tue, 2pm, 1201) MCFP Colloquium	James Hartle	UCSB	The Quantum State of the Universe
Oct. 15	Charles Misner	UMD	Evanescent Laws: Gravity evades energy conservation and eats entropy on the cosmological scale
Oct. 22-25: JSI Workshop, Annapolis, MD			Workshop webpage
Oct. 29	Jonathan McKinney	UMD	Black Hole Event Horizon Phenomena: Observations Confront Theory
Nov. 8 (Thurs, 4pm, 1201) MCFP Colloquium	Marc Kamionkowski	Johns Hopkins	Covering the bases
Nov. 12	Shahar Hadar	Racah Institute	Ringdown amplitudes in extreme mass ratio inspiral
Nov. 19	Tanja Hinderer	UMD	Tidal effects in the gravitational waveform from neutron star inspirals
Nov. 26	Anil Zenginoglu	Cal Tech	Green functions, caustic echoes, and self-force
Dec. 3	Laura Blecha	UMD Astronomy	Gravitational-wave recoil: Consequences and signatures in the pre-LISA era
Dec. 10	John Friedman	University of Wisconsin–Milwaukee	Binary inspiral with extreme mass ratios

For more information about GRT group seminars contact Ted Jacobson. For information concerning the Elementary Particle Theory group
seminars see the EPT seminar page, the Theoretical Quarks, Hadrons, Nuclei group seminars see the TQHN seminar page, and scheduled
seminars in the UMD Physics Department see the Department calendar. The webpages of the UMD-NASA Goddard Joint Space-Science Institute
and the Maryland Center for Fundamental Physics also hold regular events of interest to the group.

Seminars from previous semesters can be found here: spring 2002, fall 2002, spring 2003, fall 2003, spring 2004, fall 2004, spring 2005,
fall 2005, spring 2006, fall 2006, spring 2007, fall 2007, spring 2008, fall 2008, spring 2009, fall 2009, 2010, spring 2011, fall 2011.

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ABSTRACTS
==================================================
Alejandro Satz, UMD
Renormalization group flow of black hole entropy

It has long been theorized that at least a part of the
Bekenstein-Hawking entropy of black holes is due to the entanglement
entropy of quantum field fluctuations on the black hole background.
The entanglement entropy has a leading order divergence proportional
to the area of the horizon, and it is known that the divergence can be
absorbed in a renormalization of Newton's constant. In this talk
(based on work done with Ted Jacobson) I will generalize and extend
this observation to propose a framework for understanding black hole
entropy in the context of the renormalization group. Introducing a
Wilsonian cutoff scale, we can partition the quantum degrees of
freedom that contribute to the entropy so that effects of the
high-momentum degrees of freedom are encoded in the running of the
gravitational couplings (including G), while low-momentum ones give a
quantum entanglement entropy with an inbuilt UV cutoff. I will discuss
how this scenario is realized free fields and the problems raised by
its extension to interacting fields.

=================================
Alberto Nicolis, Columbia Univeristy
Effective field theories for fluids and superfluids

I will present a novel field theoretical framework that captures the long-distance
and low frequency dynamics of hydrodynamical systems. The approach is that of
effective field theories, whose building blocks are the infrared degrees of freedom
and symmetries. Possible applications include questions in condensed matter physics,
heavy-ion collisions, astrophysics and cosmology, and quantum hydrodynamics.
Moreover, this formulation naturally invites (and answers) new questions in
classical hydrodynamics.

======================================
Gia Dvali, NYU, CERN, LMU, MPI Munich
Geometry as Bose-Einstein  Condensate

We review some new ideas in black hole physics that  give a microscopic quantum
description of an entity that semi-classically is viewed as a black hole geometry. 
In this description black hole geometry is a Bose-Einstein condensate of gravitons. 
Its  special property is that no-matter how large is a black hole the graviton condensate
is always at the critical point of quantum phase transition. This fact goes against the
usual intuition that macroscopic objects are classical with exponential accuracy. 
This picture indicates  that all the existing mysteries and paradoxes of the black hole physics
are artifacts of semi-classical treatment and are eliminated at the quantum level. 
We discuss both fundamental as well observational consequences of this picture. 
======================================
Jeandrew Brink
Thoughts on an A* test of GR

I review some of the features of the galactic center that
make it a good laboratory for extracting the multipole
structure of the massive central compact object. This
information will allow us to test the tenets that underlie our
understanding of General Relativity. I comment on the time-line to
experimentally measuring the quadrupole moment with existing
and planned observations in the gravitational wave and electromagnetic
spectrum. I conclude with a discussion of the current and needed theoretical
infrastructure required to make a conclusive test. Focusing in
particular, on the importance of strong field resonant effects during
the final stages of the inspiral.

====================================
James Hartle, UCSB
The Quantum State of the Universe

If the universe is a quantum mechanical system then it has a quantum state. 
A theory of that state is a necessary part of any final theory that makes predictions
for the large scale features of the universe that we observe today. This talk will
focus one particular theory of the quantum state --- Hawking's no-boundary
wave function of the universe. We will concentrate summarizing the current
situation of its predictions for such large scale features of the universe as
classical spacetime, inflation, the arrows of time, the CMB spectrum, the
existence of isolated systems, the number of time dimensions, and the topology
of space.

====================================
Jonathan McKinney, UMD
Black Hole Event Horizon Phenomena: Observations Confront Theory

The black holes in M87 and SgrA* have event horizons with the largest angular size
on the sky among all black holes in the Universe.  Such event horizon scales are now
accessible to Earth-wide radio interferometry, so these systems potentially offer the
best chance to probe and even test Einstein's general relativity theory.  I discuss the
latest observations, rough interpretations, theories, and simulations that attempt to
make sense of what goes on near black hole event horizons.

====================================
Marc Kamionkowski,  Johns Hopkins U
Covering the bases

One of the principal aims of cosmology today is to seek subtle correlations in primordial
perturbations, beyond the standard two-point correlation that has been mapped precisely
already, that may hint at new physics beyond that in the simplest single-field slow-roll
models.  I will describe in this talk a new class of such correlations and how they may
be sought with galaxy surveys and in the CMB. I will then turn my attention to a new
formalism, total-angular-momentum (TAM) waves, that my collaborators and I have
recently developed.  In most of the literature, cosmological perturbations are decomposed
into Fourier modes, or plane waves.  However, for calculations that aim to produce
predictions for angular correlations on a spherical sky, a decomposition into TAM
waves provides a far more direct and intuitive route from theory to observations. 
I will describe the formalism and illustrate its utility with a few sample calculations.
====================================
Shahar Hadar
Ringdown amplitudes in extreme mass ratio inspiral

An extreme mass ratio inspiral terminates when the small compact object plunges
into the large black hole (BH) it orbited. Its trajectory, hence also the emitted
gravitational waveform, starts (quite) universally from the innermost stable
circular orbit. Next, the binary merges and the final black hole rings down until
it reaches steady state. In this stage the geometry constitutes an open resonant
cavity for gravitational perturbations, which are described by quasinormal modes
(QNMs). For a plunge into non-rotating BHs, I present (semi-) analytical results
for the QNM ringdown amplitudes and hence the late time waveform, and
successfully compare to amplitudes extracted from numerical waveforms.
For near-extremal Kerr BHs, I present analytical results for the amplitudes,
excited in the highly symmetric near-horizon region. I show part of the computation
can be carried out at exact extremality and carried to near-extremality by diffeomorphism.
====================================
Anil Zenginoglu
Green functions, caustic echoes, and self-force

The construction of global Green functions in black hole spacetimes has
been an outstanding problem. I will present its numerical solution, revealing
several universal features of wave propagation around black holes.
Among these features are the trapping of energy at the photon sphere and its
leakage, which lead to a rich phenomenology including intensity amplification
at caustics and a generically four-fold structure of caustic echoes due to
Hilbert transforms. I will also discuss hyperboloidal compactification
which has proven essential for handling the multiple scales involved.
Global approximations to Green functions can be used to calculate the self-force
in extreme mass ratio inspirals.
====================================
Laura Blecha
Gravitational-Wave Recoil: Consequences and Signatures in the Pre-LISA Era

The asymmetric merger of two supermassive black holes (SMBHs) imparts a
gravitational-wave (GW) recoil kick to the merged SMBH. This kick may
displace the SMBH from the galactic center or even eject it entirely. As GWs
from these events will not be directly observed in the near future, we wish to
focus on understanding the electromagnetic signatures of recoil that could be
identified independently of a GW detection. I will describe the results of
hydrodynamic galaxy merger simulations that include GW recoil, focusing
on the observable signatures of recoil, the effects of galactic gas content on
observability, and implications for BH-galaxy co-evolution. Finally, I will
discuss observations and modeling of a recently-discovered recoiling BH
candidate that is the most promising such candidate to date.


====================================
Jonathan McKinney, UMD
Black Hole Event Horizon Phenomena: Observations Confront Theory

The black holes in M87 and SgrA* have event horizons with the largest angular size
on the sky among all black holes in the Universe.  Such event horizon scales are now
accessible to Earth-wide radio interferometry, so these systems potentially offer the
best chance to probe and even test Einstein's general relativity theory.  I discuss the
latest observations, rough interpretations, theories, and simulations that attempt to
make sense of what goes on near black hole event horizons.

====================================
Marc Kamionkowski,  Johns Hopkins U
Covering the bases

One of the principal aims of cosmology today is to seek subtle correlations in primordial
perturbations, beyond the standard two-point correlation that has been mapped precisely
already, that may hint at new physics beyond that in the simplest single-field slow-roll
models.  I will describe in this talk a new class of such correlations and how they may
be sought with galaxy surveys and in the CMB. I will then turn my attention to a new
formalism, total-angular-momentum (TAM) waves, that my collaborators and I have
recently developed.  In most of the literature, cosmological perturbations are decomposed
into Fourier modes, or plane waves.  However, for calculations that aim to produce
predictions for angular correlations on a spherical sky, a decomposition into TAM
waves provides a far more direct and intuitive route from theory to observations. 
I will describe the formalism and illustrate its utility with a few sample calculations.
====================================
Shahar Hadar
Ringdown amplitudes in extreme mass ratio inspiral

An extreme mass ratio inspiral terminates when the small compact object plunges
into the large black hole (BH) it orbited. Its trajectory, hence also the emitted
gravitational waveform, starts (quite) universally from the innermost stable
circular orbit. Next, the binary merges and the final black hole rings down until
it reaches steady state. In this stage the geometry constitutes an open resonant
cavity for gravitational perturbations, which are described by quasinormal modes
(QNMs). For a plunge into non-rotating BHs, I present (semi-) analytical results
for the QNM ringdown amplitudes and hence the late time waveform, and
successfully compare to amplitudes extracted from numerical waveforms.
For near-extremal Kerr BHs, I present analytical results for the amplitudes,
excited in the highly symmetric near-horizon region. I show part of the computation
can be carried out at exact extremality and carried to near-extremality by diffeomorphism.
====================================
John Friedman
Binary inspiral with extreme mass ratios

Gravitational waves from the inspiral of a stellar-size black hole to a
supermassive black hole can be accurately approximated by a point
particle moving in a Kerr background. At first order the ratio of the
masses, one must renormalize the perturbed metric to compute the
deviation of the particle's path from a geodesic of the Kerr geometry.
The talk presents progress on computing the particle's acceleration
("self-force") in a gauge that is constructed from the gauge-invariant
Weyl tensor -- from the solution to the Teukolsky equation. Along the way,
a computation of essentially gauge-invariant quantities allows one
to check the results against post-Newtonian calculations and to compute
currently inaccessible post-Newtonian parameters.