Vacua in locally de Sitter cosmologies, and how to distinguish them
arXiv:2304.10395 · doi:10.1103/PhysRevD.109.025007
Abstract
(1+1)-dimensional locally de Sitter Friedmann-Robertson-Walker cosmologies with compact spatial sections allow cosh, sinh and exponential evolution laws, each with a freely-specifiable spatial circumference parameter, and the value of this parameter has an invariant geometric meaning for the cosh and sinh evolution laws. We identify geometrically preferred states for a quantised massive scalar field on these cosmologies, some singled out by adiabatic criteria in the distant past, with an ambiguity remaining due to a massive zero mode, and others induced from the Euclidean vacuum on standard (1+1)-dimensional de Sitter space by a quotient construction. We show that a comoving quantum observer, modelled as an Unruh-DeWitt detector, can distinguish these states from the Euclidean vacuum on standard de Sitter space. Numerical plots are given in selected parameter regimes. We also evaluate the field's stress-energy tensor expectation value for those states that are induced from the Euclidean vacuum by a quotient construction.
arXiv comment33 pages, 3 figures. v2: presentational clarifications, expanded title
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