New Framework for Axion Kinetic Misalignment in Cosmic Inflation

Recent research by Hyun Min Lee and colleagues presents a framework utilizing the Peccei-Quinn (PQ) symmetry to address the initial conditions for axion kinetic misalignment during cosmic inflation. The paper, titled "Inflation models with Peccei-Quinn symmetry and axion kinetic misalignment" (arXiv:2408.17013), introduces a complex scalar field and an additional Higgs doublet that are coupled to gravity, alongside three right-handed neutrinos for the seesaw mechanism. This approach aims to resolve the strong CP problem through the QCD potential for axions, which are hypothetical particles proposed to explain dark matter.

The authors propose that by assuming explicit violation of the PQ symmetry in the scalar potential due to quantum gravity effects, a significant initial velocity for the axion can be achieved at the end of inflation. This is crucial as it helps avoid the so-called axion quality problem, which concerns the stability of axion mass over time. The study outlines how inflation is driven by the radial distance in the scalar field space, leading to successful inflationary predictions and establishing the initial axion velocity.

Furthermore, the research discusses the dynamics following inflation, indicating that a sufficiently high reheating temperature can be achieved primarily through Higgs-portal couplings to the PQ field. This finding is significant as it maintains consistency with the axion kinetic misalignment and ensures stability for the Higgs fields during inflation, while also preventing the restoration of PQ symmetry post-reheating.

The implications of this work extend to the understanding of dark matter and the early universe, potentially influencing future research in cosmology and particle physics.