'Gravastar' uses both GR and QM. The model is not simple. In my model, the universe has no beginning. It always exists as we now observe it, as a 'system of huge masses of atoms/molecules'. During expansion, the internal energies of these huge masses change into their speeds and during contraction, the speeds change into internal energies. The system always tries to attain normal internal energy and normal speed. But the thermodynamic changes lead it to the extremes and the system remains pulsating. The model is thus very simple. Not only that, in my model there are only three arbitrary physical constants, the mass, radius and speed of the fundamental particle of matter. Other physical constants including the mass of electrons/neutrons, can be derived from these three, and so my model is the simplest model possible.