Generalized Global Symmetries of $T[M]$ Theories. I

TL;DR

This paper develops a framework for understanding symmetries, anomalies, and operator spectra in lower-dimensional theories derived from 6d theories compactified on manifolds, emphasizing higher-group symmetries and polarization concepts.

Contribution

It introduces the notion of polarization on manifolds and explores higher-group symmetries in $T[M_d]$ theories, extending the understanding of symmetry structures in compactified theories.

Findings

Higher-group symmetries like 2-group and 3-group are prevalent in $T[M_d]$ theories.

Polarization on $M_d$ determines the spectrum of operators in the reduced theories.

Analysis of 't Hooft anomalies in 5d Chern-Simons matter theories reveals implications for IR physics.

Abstract

We study reductions of 6d theories on a $d$-dimensional manifold $M_d$, focusing on the interplay between symmetries, anomalies, and dynamics of the resulting $(6-d)$-dimensional theory $T[M_d]$. We refine and generalize the notion of "polarization" to "polarization on $M_d$," which serves to fix the spectrum of local and extended operators in $T[M_d]$. Another important feature of theories $T[M_d]$ is that they often possess higher-group symmetries, such as 2-group and 3-group symmetries. We study the origin of such symmetries as well as physical implications including symmetry breaking and symmetry enhancement in the renormalization group flow. To better probe the IR physics, we also investigate the 't Hooft anomaly of 5d Chern-Simons matter theories. The present paper focuses on developing the general framework as well as the special case of $d=0$ and 1, while an upcoming paper will discuss the case of $d=2$, $3$ and $4$.