Statistical Physics and Light-Front Quantization

TL;DR

This paper develops a finite-temperature light-front quantum field theory framework, connecting it to parton distributions and thermodynamics, with applications to quantum chromodynamics and heavy ion collisions.

Contribution

It introduces a comprehensive light-front finite-temperature formalism, including a new density matrix and thermodynamic calculations, advancing the understanding of relativistic statistical systems.

Findings

Established a general form of the statistical operator compatible with Poincare symmetry.

Connected light-front densities to experimentally measured parton distributions.

Demonstrated thermodynamic calculations using discretized light-cone quantization at high chemical potential.

Abstract

Light-front quantization has important advantages for describing relativistic statistical systems, particularly systems for which boost invariance is essential, such as the fireball created in a heavy ion collisions. In this paper we develop light-front field theory at finite temperature and density with special attention to quantum chromodynamics. We construct the most general form of the statistical operator allowed by the Poincare algebra and show that there are no zero-mode related problems when describing phase transitions. We then demonstrate a direct connection between densities in light-front thermal field theory and the parton distributions measured in hard scattering experiments. Our approach thus generalizes the concept of a parton distribution to finite temperature. In light-front quantization, the gauge-invariant Green's functions of a quark in a medium can be defined in terms of just 2-component spinors and have a much simpler spinor structure than the equal-time fermion propagator. From the Green's function, we introduce the new concept of a light-front density matrix, whose matrix elements are related to forward and to off-diagonal parton distributions. Furthermore, we explain how thermodynamic quantities can be calculated in discretized light-cone quantization, which is applicable at high chemical potential and is not plagued by the fermion-doubling problem.