Abstract
Inflationary magnetogenesis has long been assumed to be the most promising mechanism for producing large-scale magnetic fields in our universe. However, generically, such models are plagued with either backreaction or strong coupling problems within the standard framework. This paper has shown that the reheating phase can play a crucial role in alleviating those problems along with CMB. Assuming the electrical conductivity to be negligible during the entire period of reheating, the classic Faraday electromagnetic induction changes the magnetic field's dynamics drastically. Our detailed analysis reveals that this physical phenomenon not only converts a large class of magnetogenesis model observationally viable without any theoretical problem but also can uniquely fix the perturbative average inflaton equation of state, $\omega_{\phi} = (p+2)/(p+2)$ during reheating given a specific value of the large scale magnetic field. This observation hints the inflaton to assume the potential of form $V(\phi) \sim \phi^p$ near its minimum with $p \gtrsim 3.5$ if one considers the limit of the present-day strength of the large scale magnetic field to be $\mathcal{P}_{B0}^{\frac{1}{2}} \gtrsim 10^{-18}$ G. Our analysis opens up a new avenue towards constraining the inflationary and magnetogenesis model together via reheating.
Highlights
Reheating is one of the most important early phases of our universe
While probing the reheating phase through those observables, we further show how the observables can, in turn, constrain the magnetogenesis model itself
The primary motivation of our present study will be to see in detail how the problems can be resolved partially by the reheating phase for various inflationary models and simultaneously provide constraints on the reheating. Taking into account both the cosmic microwave background (CMB) anisotropic constraints on the inflationary power spectrum and the present value of the large scale magnetic field, our analysis reveals an important connection among the reheating parameters ðTre; wreÞ, magnetogensis models and inflationary scalar spectral index ðnsÞ
Summary
Reheating is one of the most important early phases of our universe. It essentially links the standard thermal universe with its prethermal phase, namely the inflationary universe, through a complicated nonlinear process. From the cosmic microwave background (CMB) anisotropy [1], one can estimate the baryon content of the universe, which agrees extremely well with the theoretical prediction of big bang nucleosynthesis (BBN) [5,6,7,8]. With the successful standard big bang model, we have a very good understanding over a large timescale of the universe from the present (redshift z 1⁄4 0) to BBN stage ðz ∼ 109Þ at an energy scale ∼Oð1Þ MeV. The tiny fluctuation of CMB anisotropy can be successfully linked
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