PhD Thesis Presentation: Selected Topics in Relativistic Astrophysics and Gravity

PhD Thesis Presentation

Cadidate: Ryan Westernacher-Schneider

Abstract

Part IA: We present numerical measurements of relativistic scaling relations in (2 + 1)- dimensional conformal fluid turbulence, which perform favourably over their non-relativistic versions. As seen with incompressible turbulence in past studies, we find that the energy spectrum exhibits k^{−2} scaling rather than the Kolmogorov/Kraichnan expectation of k^{−5/3}.

Part IB: We compute the fractal dimension D of a turbulent anti-deSitter black brane reconstructed from boundary fluid data using the fluid-gravity duality. Our value of D = 2.584(1) is consistent with the upper bound D ≤ 3, resolving a recent claim that D = 3+1/3. We describe how to covariantly define the fractal dimension of spatial sections of the horizon, and we speculate on assigning a ‘bootstrapped’ value to the entire horizon.

Part II: We report progress implementing a fluid code with post-Newtonian (PN) gravity in spherical symmetry. The PN formalism couples a fluid, its self-gravity, and a black hole via elliptic equations. This eliminates radiative modes, allowing larger time steps, which is helpful for studying systems with very long time scales, eg. tidal disruption events.

Part III: Asteroseismology of rotating core-collapse supernovae is possible with a multimessenger strategy. We show an l = 2, m = 0, n > 2, f = 280 Hz mode of the core is responsible for emission in gravitational waves and neutrinos. The angular harmonics of the neutrino emission is consistent with the mode energy around the neutrinospheres, where r ∼ 70 km. Thus, neutrinos carry information about the mode in the outer region of the core, whereas gravitational waves probe the deep inner core below r = 30 km.

Examination Committee:

• Dr. Robert Wickham, Chair
• Dr. Eric Poisson, Advisor
• Dr. Luis Lehner, Co-Advisor
• Dr. Huan Yang, Advisory Committee Member
• Dr. Joshua Faber, External Examiner