Islands in FRW Cosmologies
Ricardo Esp\'indola, Bahman Najian, and Dora Nikolakopoulou

TL;DR
This paper investigates the existence of island regions in Friedmann-Robertson-Walker cosmologies with radiation, cosmological constant, and curvature, finding that negative cosmological constant is crucial for island formation.
Contribution
It identifies conditions under which island regions can exist in FRW cosmologies, highlighting the role of negative cosmological constant and providing analytic and numerical results.
Findings
In closed universes, the entire Cauchy slice forms an island.
Finite-sized island regions appear at turnaround times for certain parameters.
Negative cosmological constant is essential for the existence of islands.
Abstract
We search for candidate island regions in FRW cosmologies supported by radiation, cosmological constant , and non-zero spatial curvature. The radiation is assumed to be in a thermal state. We apply the necessary conditions introduced in [arXiv:2008.01022]. Both for the open and closed universes with , the Friedmann equation admits recollapsing solutions with a time-symmetric slice. In the case of closed universes, there is always an island that is the whole Cauchy slice. However, for , we also find another finite-sized candidate island region, in the middle of the spacetime, at the turnaround time. In the case of the open universes, we only find a candidate island region for , that appears at the turnaround time. It starts from a finite value of the radial coordinate and extends to infinity. Looking at both open and closed universes, we conclude…
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Taxonomy
TopicsCosmology and Gravitation Theories · Black Holes and Theoretical Physics · Noncommutative and Quantum Gravity Theories
