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Free keywords:
High Energy Physics - Theory, hep-th,Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO,General Relativity and Quantum Cosmology, gr-qc
Abstract:
The no-boundary proposal provides a compelling theory for the initial
conditions of our universe. We study the implications of such initial
conditions for ekpyrotic and cyclic cosmologies. These cosmologies allow for
the existence of a new type of "ekpyrotic instanton", which describes the
creation of a universe in the ekpyrotic contraction phase. Remarkably, we find
that the ekpyrotic attractor can explain how the universe became classical. In
a cyclic context, in addition to the ekpyrotic instantons there exist de
Sitter-like instantons describing the emergence of the universe in the dark
energy phase. Our results show that typically the ekpyrotic instantons yield a
higher probability. In fact, in a potential energy landscape allowing both
inflationary and cyclic cosmologies, the no-boundary proposal implies that the
probability for ekpyrotic and cyclic initial conditions is vastly higher than
that for inflationary ones.
