TQFT at work for IR-renormalons, resurgence and Lefschetz decomposition

Abstract

We investigate the implications of coupling a topological quantum field theory (TQFT) to Yang-Mills theory with $SU(N)$ gauge group in the context of the IR-renormalon problem. Coupling a TQFT to QFT does not change the local dynamics and perturbation theory, but it does change the bundle topology. Crucially, the configurations with integer topological charge but fractional action contribute to the path integral of the original theory. In the semi-classical regime, these are critical points at infinity, called neutral bions, and since ${\rm Arg}(g^2)=0$ is a Stokes line, their Lefschetz thimbles are two-fold ambiguous. Therein, the ambiguity in the gluon condensate is sourced by the neutral bions. The Fourier decomposition of multi-branched observables at strong coupling is compatible with the saddle decomposition at weak coupling. TQFT coupling and non-renormalization of $\theta$ angle impose constraints and helps to identify IR-renormalon. In certain IR-CFTs, we prove irrelevance of bions, and absence of IR-renormalons.