[Paper Review] Colliding shockwaves and hydrodynamics in extreme conditions

Paul M. Chesler|arXiv (Cornell University)|Jun 7, 2015

Solar and Space Plasma Dynamics3 citations

TL;DR

Using numerical holography, this study models proton-nucleus collisions by simulating the collision of a planar energy sheet with a localized energy distribution, finding that the resulting debris forms a lump with transverse size $ R \sim 1/T_{\text{m eff}} $ and exhibits strong gradients and flow. Despite these extreme conditions, the post-collision dynamics are well-described by viscous hydrodynamics, supporting the use of hydrodynamic models for proton-nucleus collision debris.

ABSTRACT

Using numerical holography, we study the collision of a planar sheet of energy with a bounded localized distribution of energy. The collision, which mimics proton-nucleus collisions, produces a localized lump of debris with transverse size $R \sim 1/T_{ m eff}$ with $T_{ m eff}$ the effective temperature, and has large gradients and large transverse flow. Nevertheless, the post-collision evolution is well-described by viscous hydrodynamics. Our results bolster the notion that debris produced in proton-nucleus collisions may be modeled using hydrodynamics.

Motivation & Objective

• To investigate whether hydrodynamics can describe extreme, non-equilibrium conditions produced in proton-nucleus collisions.
• To model the collision of a planar energy sheet with a localized energy distribution as a proxy for proton-nucleus scattering.
• To determine whether viscous hydrodynamics accurately captures the post-collision evolution under large gradients and transverse flow.
• To assess the validity of hydrodynamic descriptions in systems with effective temperatures and localized energy distributions.

Proposed method

• Numerical holography is employed to simulate the collision of a planar energy sheet with a bounded, localized energy distribution in a strongly coupled plasma.
• The simulation tracks the evolution of energy density and flow after the collision, focusing on the formation of a localized debris region.
• The effective temperature $ T_{\text{m eff}} $ is used to characterize the scale of the resulting debris, with transverse size $ R \sim 1/T_{\text{m eff}} $.
• Viscous hydrodynamics is applied to model the post-collision evolution, comparing predictions with the holographic results.
• The analysis focuses on the presence of large gradients and transverse flow in the debris, testing hydrodynamic applicability.

Experimental results

Research questions

• RQ1 Can viscous hydrodynamics describe the post-collision evolution of debris formed in a planar energy sheet collision with a localized source?
• RQ2 What is the transverse size of the debris formed in such collisions, and how does it scale with the effective temperature?
• RQ3 How do large gradients and strong transverse flow affect the validity of hydrodynamic descriptions?
• RQ4 To what extent does the holographic simulation support the use of hydrodynamics in modeling proton-nucleus collision debris?

Key findings

• The debris formed after the collision has a transverse size $ R \sim 1/T_{\text{m eff}} $, indicating a direct scaling between spatial extent and effective temperature.
• Despite large gradients and significant transverse flow, the post-collision evolution remains well-described by viscous hydrodynamics.
• The results support the applicability of hydrodynamic models to describe the dynamics of debris in proton-nucleus collisions.
• Numerical holography confirms that hydrodynamic behavior emerges even in highly non-equilibrium, extreme conditions with strong collective flow.