Structures in the Mirror Universe

Abstract

The idea of the universe with a mirror sector having all particles and forces identical to those in the familiar sector has been proposed in the context of neutrino physics as well as superstring theories. Assuming that all the quark and charged lepton masses in the mirror universe are scaled by a common factor, $ζ$, as is required in one interpretation of the neutrino data, we investigate domains of the parameter $ζ$ where physical conditions are favorable for cooling in the age of the universe that can lead to the formation of compact structures given the initial condition $Ω_B =Ω_{\tilde{B}}$ ($\tilde{B}$ denoting the mirror baryon). In particular we ask whether there is a region in $ζ$-space for which primordial Jeans mass mirror clouds cannot cool in the present age of the universe. We find that for most of the area of interest in the parameter space, atomic hyperfine structure cooling is effective in a time period short compared to the age of the universe but long compared to the free fall time for globular-sized objects expected on the basis of simple Jeans length analysis.