Redeeming Bad Theories
Itamar Yaakov
TL;DR
We address the problem of describing IR fixed points of 3d $\mathcal{N}=4$ gauge theories at zero Chern-Simons level in the presence of a 'bad' monopole spectrum, proposing a Seiberg-like dual where the interacting sector is dual to a $U(N_f-N_c)$ theory with $N_f$ flavors and a decoupled free hypermultiplet sector consisting of $2N_c-N_f$ hypermultiplets. The authors test the proposal with global-symmetry matching, moduli-space structure, and a regularized squashed-$S^3$ partition function computed via localization and hyperbolic gamma integrals, showing partition-function equality under analytic continuation of IR R-charges. They further develop a controlled procedure to integrate out flavors in the matrix model, demonstrating vacuum matching between original and dual theories and interpreting an ambiguous prefactor as the decoupled free sector. These results provide a practical handle on IR observables such as entanglement entropy and supersymmetric Wilson loops in bad theories, and pave the way for broader checks and generalizations of 3d Seiberg-like dualities.
Abstract
We give a Seiberg-like dual description of the interacting superconformal infrared fixed point of $\mathcal{N}=4$ gauge theory in three dimensions with vanishing Chern Simons level and $N_c\le N_f<2N_c$ fundamental flavors. These theories are known as "bad" theories due to the existence of unitarity violating monopole operators. We show that, in a dual description, all such operators are realized by free fields and the remainder theory is the Seiberg-like dual previously identified using the type IIB brane construction.
