Super-Planckian axions from near-conformality

We present a novel framework for obtaining large hierarchies in axion decay constants as well as trans-Planckian field excursions, with no need for tuning or a large number of fields. We consider a model with two or more conformal field theories with a common cutoff, which are linked by a gauged diagonal symmetry. This construction is dual to the geometry of a warped space with two or more throats glued at a common brane. Besides allowing for calculability, the dual picture makes it possible to interpret the hierarchy of decay constants entirely in terms of the geometry. Our setup can be applied to any framework which requires large field excursions or multiple hierarchies of decay constants, such as natural inflation or ultralight axions.

Figure 1

Schematic drawing of the two-throat construction. The coordinates $z_1$ and $z_2$ grow from the UV brane to the ${\mathrm{IR}}_1$ and ${\mathrm{IR}}_2$ branes, respectively. The wave-functions of the fields $A_{5,1}$ and $A_{5,2}$ are represented by dashed lines.