Higher-Loop Calculations of the Ultraviolet to Infrared Evolution of a Vectorial Gauge Theory in the Limit $N_c \to \infty$, $N_f \to \infty$ with $N_f/N_c$ Fixed

Understand

We consider an asymptotically free vectorial SU($N_c$) gauge theory with $N_f$ fermions in the fundamental representation and analyze higher-loop contributions to the evolution of the theory from the ultraviolet to the infrared in the limit where $N_c \to \infty$ and $N_f \to \infty$ with $r=N_f/N_c$ a fixed, finite constant.

• We focus on the case where the $n$-loop beta function has an infrared zero, at $\xi=\xi_{IR,n\ell}$, where $\xi=\alpha N_c$.
• We give results on $\xi_{IR,n\ell}$, the anomalous dimension of the fermion bilinear evaluated at $\xi_{IR,n\ell}$, denoted $\gamma_{IR,n\ell}$, and certain structural properties of the beta function, $\beta_\xi$.
• The approach to this limit is investigated, and it is shown that the leading correction terms are strongly suppressed, by the factor $1/N_c^2$.