Abstract
The axion causes two serious cosmological problems, domain wall and isocurvature perturbation problems. Linde pointed that the isocurvature perturbations are suppressed when the Peccei-Quinn (PQ) scalar field takes a large value $\sim M_{\text{pl}}$ (Planck scale) during inflation. In this case, however, the PQ field with large amplitude starts to oscillate after inflation and large fluctuations of the PQ field are produced through parametric resonance, which leads to the formation of domain walls. We consider a supersymmetric axion model and examine whether domain walls are formed by using lattice simulation. It is found that the domain wall problem does not appear in the SUSY axion model when the initial value of the PQ field is less than $10^{3}\times v$ where $v$ is the PQ symmetry breaking scale.
Highlights
The axion [1,2] is a scalar particle which results from the Peccei-Quinn (PQ) mechanism [3,4], the most attractive solution to the strong CP problem [5]
Domain walls are formed because the axion potential has N discrete minima (N ∈ Z is the QCD anomaly factor depending on the axion model), and the initial values of the axion field are spatially random
We have investigated the isocurvature and domain wall problems in the SUSY axion model
Summary
The axion [1,2] is a scalar particle which results from the Peccei-Quinn (PQ) mechanism [3,4], the most attractive solution to the strong CP problem [5]. Linde pointed out that these two problems are solved simultaneously when the PQ field Φ takes a large expectation value jΦij ∼ Mpl during inflation [20] In this case, the axion misalignment fluctuations are suppressed as δθa δa jΦij=N. [28], it was shown that the scalar field corresponding to the flat direction starts to oscillate by SUSY breaking mass terms and that it causes parametric resonance after inflation, which may lead to domain wall formation. We perform the lattice simulations for the case that the initial value of the PQ field is larger than v at most by a factor 103 and find that the axion fluctuations generated by parametric resonance are not large enough to produce domain walls.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have