The Mad Era: A Possible New Resolution to the Horizon, Flatness, and   Monopole Problems
  A cosmology with a dynamical Planck mass $m_{pl}$ is shown to solve the horizon and monopole problems (and possibly flatness) if there is an early MAD (modified aging) era where the universe becomes older than in the standard model as a result of a large $m_{pl}$: the causality condition is $m_{pl}(T_c)/ m_{pl}(T_o) \gta T_c/T_o$ ($T_c$ is some high temperature while $T_o = 2.74K$.) Unlike inflation, there is no period of vacuum domination nor any entropy violation. We study: a) bare scalar theories of gravity, b) self-interacting models, and c) bare theories with a phase transition in the matter sector. 
Katherine Freese and Janna J Levin