# Probing spectral properties of the QGP with real-time lattice simulations

## TL;DR

This paper introduces a novel method combining linear response theory and classical-statistical lattice simulations to extract spectral functions of non-Abelian gauge theories in high-occupancy regimes, bridging non-equilibrium and thermal properties.

## Contribution

It presents a new approach to measure spectral functions in non-Abelian gauge theories using real-time lattice simulations applicable far from equilibrium.

## Key findings

- Spectral functions can be connected to HTL formalism.
- Method allows extraction of quasiparticle lifetimes.
- Potential to measure transport coefficients and study early heavy-ion collision stages.

## Abstract

We present a new method to obtain spectral properties of a non-Abelian gauge theory in the region where occupation numbers are high. The method to measure the (single-particle) spectral function is based on linear response theory and classical-statistical lattice simulations. Although we apply it to a system far from equilibrium in a self-similar regime, the extracted spectral function can be understood within the hard thermal loop (HTL) formalism and can thus be connected to thermal equilibrium at high temperatures. This allows us to obtain quantities like the lifetime of quasiparticles that are beyond the leading order and difficult to compute within HTL. The approach has the potential to measure transport coefficients, to study the earliest stages of heavy-ion collisions in a controlled way and it can be employed beyond the range of validity of HTL.