- Simon Catterall (Syracuse)
- Juven Wang (CMSA, Harvard)
- Yi-Zhuang You (UCSD)
- David Tong (DAMTP, Cambridge)
The most common mechanism for generating fermion masses arises when scalar fields acquire vacuum expectation values in theories with Yukawa interactions. Such a mechanism is necessarily associated with the spontaneous breaking of symmetries. However, recent work in both the condensed matter and high-energy physics communities has shown that this is not the only possibility — in certain theories, fermions can acquire masses without breaking chiral symmetries. Examples of such symmetric mass generation can be found in gapped boundary states of topological superconductors and observations of massive symmetric phases in staggered lattice fermions. The key constraint that allows such a mechanism to operate is the cancellation of all ‘t Hooft anomalies, both perturbative local and non-perturbative global anomalies in the theory. In the context of lattice gauge theories, this has led to renewed hope that it should be possible to construct classes of anomaly-free chiral lattice fermion theories using mirror models. There is also a growing interest in understanding the nature of the gap-opening transition and the unique signature that characterizes the symmetric gapped phase. Other possible applications and future directions of symmetric mass generation include supersymmetric or non supersymmetric duality, the flavor hierarchy problem, the strong CP problem, and applications to gapping the Fermi surfaces in strongly correlated electron systems.