Gravitational collisions and the quark-gluon plasma

TL;DR

This thesis investigates the thermalization process in heavy-ion collisions using AdS/CFT duality, revealing universal behaviors in shock wave interactions and matching experimental data from LHC collisions.

Contribution

It introduces a detailed numerical framework for studying shock wave collisions and plasma relaxation at strong coupling, highlighting universal features and providing computational tools.

Findings

Shock waves pass through each other in a transparent regime.

Plasma relaxation is insensitive to shock profiles at high energies.

Good agreement with LHC collision data.

Abstract

This thesis addresses the thermalisation of heavy-ion collisions within the context of the AdS/CFT duality. The first part clarifies the numerical set-up and studies the relaxation of far-from-equilibrium modes in homogeneous systems. Less trivially we then study colliding shock waves and uncover a transparent regime where the strongly coupled shocks initially pass right through each other. Furthermore, in this regime the later plasma relaxation is insensitive to the longitudinal profile of the shock, implying in particular a universal rapidity shape at strong coupling and high collision energies. Lastly, we study radial expansion in a boost-invariant set-up, allowing us to find good agreement with head-on collisions performed at the LHC accelerator. As a secondary goal of this thesis, a special effort is made to clearly expose numerical computations by providing commented Mathematica notebooks for most calculations presented. Furthermore, we provide interpolating functions of the geometries computed, which can be of use in other projects.