Could our Universe have begun with Negative Lambda?

Understand

In this paper we present an informal description of the Cyclic Inflation scenario which allows our universe to "start" with a negative potential energy, inflate, and then gracefully exit to a positive potential energy universe.

• We discuss how this scenario fares in comparison with the standard inflationary paradigm with respect to the classic cosmological puzzles associated with the horizon, flatness and isotropy of our current universe.
• We also discuss some of the most debilitating problems of cyclic cosmologies, Tolman's entropy problem, and the problem with the overproduction of blackholes.
• We also sketch the calculation of the primordial spectrum in these models and possible observable signatures.