Strong Gravity

This series consists of talks in areas where gravity is the main driver behind interesting or peculiar phenomena, from astrophysics to gravity in higher dimensions.

Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

 

Thursday Mar 17, 2011
Speaker(s): 

The local and global properties of the retarded and Feynman Green functions to the wave equation in curved spacetime are crucial for radiation reaction in the classical theory and for renormalisation in the quantum quantum theory. Building on an insight due to Avramidi, we provide a system of transport equations for determining key fundamental geometrical bitensors determining the local Hadamard singularity structure of these Green’s functions.

Collection/Series: 
Scientific Areas: 

 

Thursday Mar 03, 2011
Speaker(s): 

The upcoming launch of the space-based gravitational wave interferometer detector LISA will yield an unprecedented amount of astrophysical and cosmological science from a variety of gravitational wave sources. Among these, the extreme mass ratio inspirals (EMRIs) of stellar-mass compact objects into supermassive black holes will provide a unique opportunity to test the predictions of General Relativity for strongly gravitating systems since the masses and spins of these sources are expected to be measured with precisions better than about 1 part in 10^4.

Collection/Series: 
Scientific Areas: 

 

Thursday Feb 17, 2011
Speaker(s): 

Assuming exotic matter, several models representing static, spherically symmetric wormhole solutions of Einstein's field equations have been considered in the literature. We examine the dynamical stability of such wormholes in one of the simplest model, in which the matter is described by a massless ghost scalar field, and prove that all solutions are unstable with respect to linear fluctuations and possess precisely one unstable, exponentially in time growing mode.

Collection/Series: 
Scientific Areas: 

 

Friday Feb 04, 2011
Speaker(s): 

The long awaited discovery of the double radio pulsar system, PSR J0737-3039A/B, surpassed most expectations, both theoretical and observational, as a tool to probe general relativity, stellar evolution and pulsar theories. The Double Pulsar provides a unique and the most complete and clean test of theories of gravity in a regime sensitive to possible strong-gravitational self-field effects. All six post-Keplerian parameters have been measured (including the measurement of the relativistic spin precession), some parameters to a precision of 10^{-4}.

Collection/Series: 
Scientific Areas: 

 

Thursday Jan 06, 2011
Speaker(s): 

Inflation is one of the foundational paradigms of our picture of the Universe. Yet distinguishing between the multitude of different inflationary models presents major observational challenges. In this talk, I will discuss a number of inflationary observables, specifically the tilt and running of the primordial power spectrum, compensated isocurvature modes, and non-Gaussianity, and the extent to which they might be constrained by future galaxy surveys and 21 cm experiments.

Collection/Series: 
Scientific Areas: 

 

Thursday Dec 16, 2010
Speaker(s): 

NANOGrav is a consortium of radio astronomers and gravitational wave physicists whose goal is to detect gravitational waves using an array of millisecond pulsars as clocks. Whereas interferometric gravitational wave experiments use lasers to create the long arms of the detector, NANOGrav uses earth-pulsar pairs. The limits that pulsar timing places on the energy density of gravitational waves in the universe are on the brink of limiting models of galaxy formation and have already placed limits on the tension of cosmic strings.

Collection/Series: 
Scientific Areas: 

 

Thursday Dec 02, 2010
Speaker(s): 

There has been a growing interest in electromagnetic counterparts to gravitational wave signals. Of particular interest here, are counterparts to gravitational wave signals from super-massive black hole mergers. We consider a circumbinary disk, hollowed out by torques from the binary, and provide an analytic solution to its response following merger. There are two changes to the potential which occur during the merger process: an axisymmetric mass-energy loss and asymmetric recoil kick given to the resulting super-massive black hole.

Collection/Series: 

 

Thursday Nov 11, 2010
Speaker(s): 

Numerical simulations of binary black holes with spin have revealed some surprising behavior: for antialigned spins in the orbital plane, 1) one sees an up-and-down "bobbing" of the entire orbital plane at the orbital frequency and 2) the merged black hole receives an enormous kick that depends on the phase at merger. Natural questions are: What causes the bobbing? Can the kick be viewed as a post-merger continuation of the bobbing?

Collection/Series: 

 

Thursday Oct 28, 2010
Speaker(s): 

I will present the latest results from the searches for gravitational waves from the coalescence of binary systems of neutron stars and black holes in LIGO and Virgo data. We present results on data from the Fifth Science Run LIGO run S5 from Nov 2005 to Oct 2007, which was joint with Virgo's first Science Run VSR1 from May to Oct 2007. We also show how these methods are being applied in the current LIGO S6/ Virgo VSR2 data-taking run started in July 2009, and recently ended in October 2010.

Collection/Series: 

 

Thursday Oct 14, 2010
Speaker(s): 

I discuss a model for particle acceleration in the current sheet separating the open and closed field line regions, and crossing the
neutral line region, of a pulsar's magnetosphere, which has substantial kinship to the phenomena observed in planetary magnetospheres within the solar system. Possible applications to gamma ray emission from pulsars are also described.

Collection/Series: 

Pages