Can a marginally open universe amplify magnetic fields?

TL;DR

This paper critically reevaluates claims that an open universe can significantly amplify primordial magnetic fields, concluding instead that such fields decay similarly to flat universe scenarios, resulting in negligible present-day amplitudes.

Contribution

It provides a rigorous reexamination of magnetic field amplification in open universes, challenging previous claims and demonstrating decay rates comparable to flat universe models.

Findings

Magnetic fields decay similarly in open and flat universes.

Present-day magnetic field strength is extremely small (<10^{-59} G).

Open universe does not significantly amplify primordial magnetic fields.

Abstract

In a series of recent papers, including arXiv:1210.1183, it was claimed that large-scale magnetic fields generated during inflation in a spatially open universe could remain astrophysically significant at the present time since they experienced superadiabatic amplification specific to an open universe. We reexamine this assertion and show that, on the contrary, large-scale magnetic fields in a realistic open universe decay in much the same manner as they would in a spatially flat universe. Consequently, their amplitude today is extremely small (B0 < 10^{-59} G) and is unlikely to be of astrophysical significance.