Abstract
Primordial magnetic field generated in the inflationary era can act as a viable source for the present day intergalactic magnetic field of sufficient strength. We present a fundamental origin for such a primordial generation of the magnetic field, namely through anomaly cancellation of U(1) gauge field in quantum electrodynamics in the context of hilltop inflation. We have analysed at length the power spectrum of the magnetic field, thus generated, which turns out to be helical in nature. We have also found that magnetic power spectrum has significant scale-dependence giving rise to a non-trivial magnetic spectral index, a key feature of this model. Interestingly, there exists a large parameter space, where magnetic field of significant strength can be produced.
Highlights
Introduction and MotivationCitation: Chakraborty, S.; Pal, S.; SenGupta, S
The most promising origin of such a magnetic field is primordial in nature
We have proposed a new model which inhibits a term in addition to the Maxwell’s action, which originates naturally from anomaly cancellation of the U (1) gauge theory. This additional piece in the electromagnetic Lagrangian is absolutely essential to maintain gauge invariance of the electromagnetic Lagrangian at the quantum level. Classically this term is sufficient to warrant that conformal invariance is kept intact while helical modes are generated in a hilltop inflationary scenario
Summary
We provide a completely new viewpoint to the inflationary magnetogenesis scenario, where we need not have to invoke any ad-hoc coupling between the scalar field and Maxwell’s action by hand, rather starting from a fundamental theory we have been able to demonstrate the possibility to arrive at a viable scenario. Enough, as it will turn out, the model has the potential to predict non-trivial features for the primordial magnetic field in general, which using future measurements can either reinforce the model or possibly rule it out.
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