Figure 1

Space-time diagram (sketch) showing the evolution of fixed comoving scales. The vertical axis is time, the horizontal axis is physical distance. The Hagedorn phase ends at the time $t_R$ and is followed by the radiation-dominated phase of standard cosmology. The blue curve represents the Hubble radius $H^{-1}$ which is cosmological during the quasistatic Hagedorn phase, shrinks abruptly to a microphysical scale at $t_R$ and then increases linearly in time for $t>t_R$. Fixed comoving scales (labeled by $k_1$ and $k_2$) which are currently probed in cosmological observations have wavelengths which are smaller than the Hubble radius during the Hagedorn phase. They exit the radius at times $t_i(k)$ just prior to $t_R$, and propagate with a wavelength larger than the Hubble radius until they reenter the Hubble radius at times $t_f(k)$.Reuse & Permissions