The non-linear Glasma

TL;DR

This paper investigates the non-linear evolution of quantum fluctuations in the Glasma post-collision, revealing how instabilities and non-linear interactions lead to enhanced fluctuation growth and turbulence, with implications for isotropization.

Contribution

It provides a combined analytical and numerical study of non-linear fluctuation dynamics in the Glasma, highlighting the role of instabilities and turbulence in heavy-ion collisions.

Findings

Fluctuations grow significantly due to instabilities and non-linear interactions.

Growth of fluctuations extends beyond the initially unstable momentum band.

Gauge invariant pressure correlations exhibit wave turbulence behavior.

Abstract

We study the evolution of quantum fluctuations in the Glasma created immediately after the collision of heavy nuclei. It is shown how the presence of instabilities leads to an enhancement of non-linear interactions among initially small fluctuations. The non-linear dynamics leads to an enhanced growth of fluctuations in a large momentum region exceeding by far the originally unstable band. We investigate the dependence on the coupling constant at weak coupling using classical statistical lattice simulations for SU(2) gauge theory and show how these non-linearities can be analytically understood within the framework of two-particle irreducible (2PI) effective action techniques. The dependence on the coupling constant is only logarithmic in accordance with analytic expectations. Concerning the isotropization of bulk quantities, our results indicate that the system exhibits an order-one anisotropy on parametrically large time scales. Despite this fact, we find that gauge invariant pressure correlation functions seem to exhibit a power law behavior characteristic for wave turbulence.