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.

==================================================

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.