Session B4: Invited Session: Numerical Relativity Beyond Astrophysics

Higher dimensional gravity and black holes

Gravity in higher dimensions exhibits new, and perhaps unexpected, phenomena when confronting with intuition gained in 4 dimensions. Its understanding however is of key importance due to its role in trans-Planckian and gauge-gravity dualities in scenarios involving black holes. In this talk we present an overview of efforts to achieve this understanding in strongly gravitating scenarios through numerical efforts. In particular we discuss some relevant examples, immediate challenges and opportunities for near future endeavors.   

Dynamical Hawking radiation and holographic thermalization

Holography provides a powerful tool to study non-equilibrium dynamics in strongly coupled quantum field theories, mapping challenging D dimensional quantum dynamics on to semi-classical gravity in D+1 dimensions. One interesting quantum field theory process to study is the creation and thermalization of a D = 4 strongly coupled quark-gluon plasma. Heavy ion collisions at RHIC and the LHC suggest that quark-gluon plasma can be created and thermalize in a time as short as 1 fm/c, the time it takes for light to traverse the diameter of a proton. Understanding the dynamics responsible for such rapid thermalization is a challenge using traditional perturbative field theory. Via holography, the creation of a quark-gluon plasma maps into the process of gravitational collapse and black brane formation. The thermalization of the quark-gluon plasma maps into the relaxation of the black brane geometry and thermalization of its Hawking radiation. I will describe new techniques for studying holographic thermalization and present results for thermalization times and mechanisms.   

High-speed black hole collisions with application to trans-Planckian particle scattering

We review the present status of modeling high-energy collisions of black holes in the context of TeV gravity scenarios, i.e. extensions of the standard model that involve extra dimensions and thus predict a reduction of the fundamental Planck scale to levels closer to the electroweak scale. Particle collisions above the TeV range, such as those performed at the LHC or occurring in cosmic-ray interactions with the earth's atmosphere, offer the exciting opportunity to probe these extra-dimensional models. As gravity becomes the dominant interaction, the relevant particle collisions, should be well described by point-particle collisions or their general relativistic analog, high-energy collisions of black holes. Furthermore, modeling in the framework of classical general relativity should provide a good description of these events assuming that the collision energies exceed the fundamental Planck scale by a sufficient amount. With this motivation in mind, we discuss the simulation of black-hole collisions in the framework of D-dimensional general relativity. Specifically, we summarize our current understanding of the loss of energy and momentum in the form of gravitational waves in these collisions which impacts the analysis of experimental data. We also compare numerical with analytic predictions and discuss the validity of the assumption that internal structure of the particles becomes irrelevant for the modeling.