## A transverse gradient expansion for holographic collisions of localized shocks

#### by Dr. Sebastian Waeber

*Technion*

##### at Particles and Fields Seminar

Mon, 05 Feb 2024, 14:00

Sacta-Rashi Building for Physics (54), room 207

#### Abstract

Both the observation of a sizable transverse flow in holographic calculations of localized shock collisions,

and the need to consider transverse energy density fluctuations to explain the large event-by-event

fluctuations of flow observables during heavy ion collision, motivate to study collisions of holographic

projectiles with a realistic granular, transverse structure. On the other hand, in order to solve the problem of

whether the vorticity of the quark gluon plasma can explain the polarization of Lambda-Hyperions emitted during heavy

ion collisions, one also needs to solve collisions of projectiles with realistic aspect ratios to produce

initial data for subsequent hydro-evolutions. Solving holographic collisions of highly Lorentz contracted shocks,

while also taking into account transverse energy density fluctuations is computationally very challenging.

A framework is introduced to substantially simplify the computation of the collision of localized shocks in five

dimensional Anti-de Sitter space. We exploit the large disparity between transverse and longitudinal scales and expand

Einstein equations in transverse gradients. We find that already at first order our results agree well with the exact

solutions, while the approximation offers an order of magnitude improvement regarding run time and memory.

We employ this technique to compute the vorticity and hydrodynamization time of the quark gluon plasma, starting from

initial projectiles which correspond to realistic nuclear models of boosted heavy ions with Lorentz contractions

corresponding to RHIC collisions.

Created on 30-01-2024 by Lublinsky, Michael (lublinm)

Updaded on 30-01-2024 by Lublinsky, Michael (lublinm)