Renormalization Group Flow, Stability, and Bulk Viscosity in a Large N Thermal QCD Model

TL;DR

This paper explores the UV completion of a large N QCD model by introducing new degrees of freedom, analyzes the stability of the brane configurations, studies the renormalization group flow from IR to UV, and proposes a method to compute bulk viscosity indicating non-conformality.

Contribution

It presents a novel approach to UV completion in large N QCD models using anti-branes and fluxes, and develops a scheme to evaluate bulk viscosity related to non-conformal behavior.

Findings

Stability can be achieved with appropriate world-volume fluxes.

UV degrees of freedom alter the RG flow from IR confining to UV conformal.

A calculational scheme for bulk viscosity signals non-conformality.

Abstract

The ultraviolet completion of a large N QCD model requires introducing new degrees of freedom at certain scale so that the UV behavior may become asymptotically conformal with no Landau poles and no UV divergences of Wilson loops. These UV degrees of freedom are represented by certain anti-branes arranged on the blown-up sphere of a warped resolved conifold in a way that they are separated from the other set of branes that control the IR behavior of the theory. This separation of the branes and the anti-branes creates instability in the theory. Further complications arise from the curvature of the ambient space. We show that, despite these analytical hurdles, stability may still be achieved by switching on appropriate world-volume fluxes on the branes. The UV degrees of freedom, on the other hand, modify the RG flow in the model. We discuss this in details by evaluating the flow from IR confining to UV conformal. Finally we lay down a calculational scheme to study bulk viscosity which, in turn, would signal the inherent non-conformality in this model.