Real-time Holography: Anomalous Transport and Non-Hermitian systems

In this thesis we investigate the real-time evolution of strongly coupled systems using holographic techniques. In particular, we study the anomalous transport in strongly coupled plasmas, such as the quark-gluon plasma, and the dynamics of non-hermitian PT -symmetric systems. 

First we study the out-of-equilibrium chiral magnetic effect (CME). We consider the back-reaction of the magnetic field on the geometry and monitor the pressure and the chiral magnetic current. We also match the parameters of our model to QCD parameters and draw conclusions that may be relevant to the realisation of the chiral magnetic effect in heavy ion collisions. In particular, we find an equilibration time of about ∼ 0.35 fm/c in the presence of the chiral anomaly for plasma temperatures of the order of T ∼ 300 − 400M eV. We also discuss the interplay between the build-up time of the CME and the short lifetime of the magnetic field. 

The CME is further studied in a generalised setup that includes topological charge dissipation. In holography, this is done by giving the bulk gauge field a mass. We study the cases where axial charge is initially present in the plasma and where axial charge is initially generated. We refine the QCD matching and find that the CME signal at the LHC can be comparable to the signal at RHIC, provided that there is at least three times as much axial charge in the plasma. 

Finally, we study the evolution of non-Hermitian PT symmetric holographic field theories when the couplings are varied with time. The notion of non-Hermitian PT -symmetric quantum theory has recently been generalised to gauge/gravity duality. We show that a non-unitary time evolution in the dual quantum theory corresponds to a violation of the Null Energy Condition (NEC) in the bulk of the asymptotically AdS spacetime. We find that varying the non-Hermitian coupling causes the horizon of a bulk AdS black hole to shrink. Finally, we perform finite-time excursions into the PT-broken regime, where unstable solutions were previously found at finite temperature, in search of new equilibrium solutions.