Magnetogenesis in bouncing cosmology

We consider the process of magnetogenesis in the context of nonsingular bounce cosmology. We show that large primordial magnetic fields can be generated during contraction without encountering strong coupling and backreaction issues. The fields may seed large-scale magnetic fields with observationally interesting strengths. This result leads to a theoretical constraint on the relation of the energy scale of the bounce cosmology to the number of effective $e$-foldings of the contracting phase in the case of scale invariance for the power spectrum of primordial magnetic fields. We show that this constraint can be satisfied in a sizable region of the parameter space for the nonsingular bounce cosmology.

Figure 1

Dependence of the upper bound of the magnetic fields $B_0$ on the model parameter $q$ in the bounce model under consideration. Other model parameters have been taken to be the same as those provided in Ref. [81].

Figure 2

The theoretical constraint of the energy scale of the bounce cosmology $|H_e|/M_{\mathrm{pl}}$ along with the model parameter $q$. The green shadow area satisfies the theoretical constraint (43) and hence bounce models within this regime are well behaved. We take the effective $e$-folding number to be $N=10$ as an example.