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

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Jun 6 2019 - 1:00pm
Room #: 405
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Thursday May 16, 2019
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Ground-based gravitational wave observatories have begun to uncover a large number of compact binary coalescences in the universe through gravitational wave signals. I will discuss novel and effective techniques we have developed recently to analyze the publicly available LIGO/Virgo bulk strain data from scratch. Built on simple ideas and easy to implement, those address the questions of template bank construction, signal processing, trigger ranking, and fast parameter estimation.

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Thursday Mar 21, 2019
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The conservation law for the total (orbital plus spin) angular momentum of a Dirac particle in the presence of gravity requires that spacetime is not only curved, but also has a nonzero torsion. The coupling between the spin and torsion in the Einstein–Cartan theory of gravity generates gravitational repulsion at extremely high densities, which prevents a singularity in a black hole and may create there a new, closed, baby universe undergoing one or more nonsingular bounces.

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Thursday Mar 14, 2019

At the event horizon of a black hole, gravity reaches its most extreme behaviour. Studying the dynamics of event horizons is key to understand gravity in is ultra-strong field regime and investigate the most fundamental properties of black holes. Black hole collisions provide a unique scenario to observe event horizons in a highly distorted and violently changing regime, which leads to a vast collection of phenomena that has not yet been detected by Advanced LIGO and Virgo.

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Thursday Mar 07, 2019
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By applying a parabolic-hyperbolic formulation of the constraints and superposing Kerr-Schild black holes, a simple method is introduced to initialize time evolution of binary systems. As the input parameters are essentially the same as those used in the post-Newtonian (PN) setup the proposed method interrelates various physical expressions applied in PN and in fully relativistic formulations. The global ADM charges are also determined by the input parameters, and no use of boundary conditions in the strong field regime is made.

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Thursday Jan 24, 2019
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The source of about half of the heaviest elements in the Universe has been a mystery for a long time. Although the general picture of element formation is well understood, many questions about the nuclear physics processes and particularly the astrophysical details remain to be answered. Here I focus on recent advances in our understanding of the origin of the heaviest and rarest elements in the Universe.

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Thursday Jan 17, 2019
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There is observational evidence that the X-ray continuum source that creates the broad fluorescent emission lines in some Seyfert Galaxies may be compact and located at a few gravitational radii above the black hole. We consider two scenarios for the X-ray emission. The first possibility is that the X-rays may be produced by particles accelerated in an electrostatic gap at the base of a putative jet.

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Thursday Jan 10, 2019
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The detection of gravitational waves from mergers of compact binaries in the first two runs of the Advanced LIGO-Virgo have brought in valuable insights into fundamental physics and astrophysics. The coalescence process sweeping the components through a range of frequencies at highly relativistic velocities, have enabled some of the first tests of general relativity in its highly dynamical and extremely strong field regime. The recent detection of the binary neutron star merger has shed first light on the elusive neutron star equation of state.

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Thursday Dec 13, 2018
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Over the last few years gravitational wave (GW) detections have marked
the beginning of a new era of astrophysical observations. When the
emitters include a compact object like a neutron star, the GW signal
is accompanied by emissions in different bands, e.g. X-rays,
gamma-rays, optical and neutrinos. The interpretation of such
multimessenger signals allows us to gain a deeper understanding of the
interiors of compact objects. One main challenge is to link our
knowledge of nuclear interactions to macroscopic properties of dense

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Thursday Oct 18, 2018
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The unexpected diversity of planetary systems has posed challenges to our classical understanding of planetary formation. For instance, Jupiter sized planets have been detected with short orbital periods of a few days in misaligned orbits with respect to the spin-axis of their host stars. I will first describe the statistical implication of detecting misaligned hot Jupiters and will suggest how dynamical interactions between an outer perturber and the inner planet, can naturally lead to the formation of such misaligned hot Jupiters.

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Thursday Oct 04, 2018
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Conventional equations of state suggest that in complete gravitational collapse a singular state of matter with infinite density could be reached finally to a black hole, the characteristic feature of which is its apparent horizon, where light rays are first trapped. The loss of information to the outside world this implies gives rise to serious difficulties with well-established principles of quantum mechanics and statistical physics.

 

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