Monday, 17 February, 2025, 16:45 h, HIT H 42

Anna Hasenfratz
(University of Colorado Boulder)

Symmetric Mass Generation: A New Paradigm

Abstract:
Symmetric Mass Generation (SMG) is a new non-perturbative mechanism for giving mass to fermions without breaking chiral symmetries. The mass arises not from a pairing of elementary fermions as it would arise in a classical Lagrangian but as a consequence of the presence of a non-trivial vacuum state consisting of a symmetric multi-fermion condensate.
A necessary condition for a theory to possess an SMG phase is that all 't Hooft anomalies (both continuous and discrete) of the theory must vanish. In four dimensions this condition is satisfied if the system has multiples of eight massless Dirac flavors. The simplest systems that can exhibit SMG are SU(2) gauge with 4 and SU(3) gauge with 8 massless Dirac flavors. In this talk I will show that both systems indeed exhibit a strongly coupled SMG phase. Perhaps even more interesting is that both systems appear to lie at the opening of the conformal window with a renormalization group beta function that just touches zero.
Since SMG is a new and unusual phenomenon, I plan to give a gentle introduction to SMG. I will not spend much time to discuss details of the numerical analysis but will explain the conclusions in general terms.

Host: Peter Stoffer (UZH)