Clockwork axions in cosmology. Is chromonatural inflation chrononatural?

Abstract

Abstract Many cosmological models rely on large couplings of axions to gauge fields. Examples include theories of magnetogenesis, inflation on a steep potential, chiral gravitational waves, and chromonatural inflation. Such theories require a mismatch between the axion field range and the mass scale appearing in the a F F ˜ $$ aF\tilde{F} $$ coupling. This mismatch suggests an underlying monodromy, with the axion winding around its fundamental period a large number of times. We investigate the extent to which this integer can be explained as a product of smaller integers in a UV completion: in the parlance of our times, can the theory be “clockworked”? We argue that a clockwork construction producing a potential μ 4 cos a j F a $$ {\mu}^4 \cos \left(\frac{a}{j{F}_a}\right) $$ for an axion of fundamental period F a will obey the constraint μ < F a . For a some applications, including chromonatural inflation with sub-Planckian field range, this constraint obstructs a clockwork UV completion. Alternative routes to a large coupling include fields of large charge (an approach limited by strong coupling) or kinetic mixing (requiring a lighter axion). Our results suggest that completions of axion cosmologies that explain the large parameter in the theory potentially alter the phenomenological predictions of the model.

Keywords

• Anomalies in Field and String Theories
• Cosmology of Theories beyond the SM