Protogalactic Extension of the Parker Bound

Abstract

We extend the Parker bound on the galactic flux $\mathcal{F}$ of magnetic monopoles. By requiring that a small initial seed field must survive the collapse of the protogalaxy, before any regenerative dynamo effects become significant, we develop a stronger bound. The survival and continued growth of an initial galactic seed field $\le 10^{-9}$G demand that $\mathcal{F}\le 5\times 10^{-21}(m/10^{17}GeV){cm}^{-2}{sec}^{-1}{sr}^{-1}$. For a given monopole mass, this bound is four and a half orders of magnitude more stringent than the previous `extended Parker bound', but is more speculative as it depends on assumptions about the behavior of magnetic fields during protogalactic collapse. For monopoles which do not overclose the Universe (${\Omega }_m<1$), the maximum flux allowed is now $8\times 10^{-19}$ cm^{-2} s^{-1} sr^{-1}, a factor of 150 lower than the maximum flux allowed by the extended Parker bound.

Comments: 9 pages, 1 eps figure