Rollercoaster cosmology

(Abridged) Does inflation have to happen all in one go? The answer is a resounding no! All cosmological problems can be solved by sequence of short bursts cosmic acceleration, interrupted epochs decelerated expansion. spectrum perturbations will still match the CMB and LSS if earliest stage last ${\cal O}(50)-{\cal O}(60)$ efolds at least O}(15)$ long. Other stages considerably shorter. But as long they add up expansion between them are shorter also overall less, ensuing cosmology pass muster. presence interruptions resets efold clock each accelerating stage, changes its value pivot point. This change opens theory space, loosening bounds. In particular some models that seem excluded N}=60$ fit very well with N}=30$. Interesting predictions both scalar tensor spectra rapidly modified wavelengths. These features could tested future spectroscopy searches wavelength primordial gravity probes. spatial curvature these larger than largest perturbations, because $\Omega_{\tt k}$ evolves differently $\frac{\delta \rho}{\rho}|_{\tt S}$. Finally, many accelerated expansion, abundance reheating products from previous does not get completely wiped out. implies universe may contain additional populations particles, more rare visible ones, or even black holes, created during late epoch before reheating, which dark matter.