Three dimensional Yukawa models and CFTs at strong and weak couplings

TL;DR

This paper analyzes three-dimensional Yukawa models at finite temperature, revealing their non-conformal behavior at intermediate couplings and providing entropy density ratios that connect to supersymmetric and scalar models.

Contribution

It offers a mean field analysis of Yukawa models across all couplings, connecting their thermodynamic properties to supersymmetric and scalar theories, and clarifies their conformal behavior limitations.

Findings

Entropy density ratio decreases from Stefan-Boltzmann limit to 31/35 at strong coupling.

Yukawa models do not remain conformal at all couplings, only at weak and strong limits.

Fermionic mass vanishes at all couplings, unlike in the WZ model.

Abstract

The massless three dimensional Gross-Neveu-Yukawa (GNY) and Nambu--Jona-Lasinio--Yukawa (NJLY) models at finite temperatures are analyzed within the mean field framework considering all coupling values. When the number of Dirac fermions is taken to be $N_f=1/4$ (GNY) and $N_f=1/2$ (NJLY) these models relate to the supersymmetric Wess-Zumino (WZ) theory with cubic superpotential and one superfield. In this case the results show that the strong-weak entropy density ratio decreases from the Stefan-Boltzmann value, in the weak limit, to $s/s_{free}=31/35$ at strong couplings. This value agrees with the one recently obtained by applying the large-$N$ approximation to the supersymmetric $O(N)$ WZ model with quartic superpotential and $N$ superfields. When $N_f=0$ one obtains $s/s_{free}=4/5$ recovering, as expected, the ratio predicted in the context of the $O(N)$ scalar model. However, contrary to the $O(N)$ WZ model the simple Yukawa models analyzed here do not behave as CFTs for all couplings since the conformal measure exactly vanishes only at the extreme weak and strong limits although the speed of sound indicates that the deviation, at intermediate couplings, appears to be rather small. By comparing the thermal masses behavior in each case one can trace this difference as being a consequence that in the GNY/NJLY case the fermionic mass vanishes for all couplings while within the $O(N)$ WZ it only vanishes at the weak and strong limits. On the other hand, the Yukawa bosonic dimensionless masses display a more universal behavior decreasing from $2 \ln [(1+\sqrt{5})/2]$, at infinite coupling, to zero (at vanishing coupling).