Obstructions to dimensional reduction in hot QCD

TL;DR

This paper investigates the limitations of dimensional reduction in hot QCD, showing that fermion-induced screening lengths can obstruct the applicability of effective long-distance theories at high temperatures relevant for collider experiments.

Contribution

It provides evidence that fermion effects hinder dimensional reduction in hot QCD, potentially up to temperatures of 10 T_c, impacting theoretical modeling of quark-gluon plasma.

Findings

Screening masses in pure gauge theories are well described by dimensionally reduced theories.

Fermions introduce meson-like screening lengths that dominate at certain temperature ranges.

Obstruction to dimensional reduction may persist up to temperatures of 10 T_c or higher.

Abstract

I describe results on screening masses in hot gauge theories. Wilsonian effective long distance theories called dimensionally reduced (DR) theories describe very well the longest screening length in pure gauge theories. In the presence of fermions, meson-like screening lengths dominate the long-distance physics for 3T_c/2 < T < 3 T_c, and thus obstruct perturbative DR. Extrapolation of our results indicates that a form of this obstruction may remain till temperatures of 10 T_c or higher, and therefore affect the entire range of temperature expected to be reached even at the Large Hadron Collider.