The dilaton solves three stubborn problems with axion cosmology at once

Standard QCD axion cosmology runs into three distinct technical obstacles: the axion field must be non-periodic, the effective theory must hold well above the inflationary scale, and a small explicit symmetry-breaking term is needed to collapse dangerous domain walls before they dominate the universe. Karananas and Shaposhnikov show that the dilaton — the pseudo-Nambu-Goldstone boson of spontaneously broken approximate scale invariance — satisfies all three requirements within a single coherent framework. The result reframes the dilaton not merely as a gravitational curiosity but as a natural host for axion physics, potentially connecting dark matter to the origin of mass scales in nature.