Positive particle frequencies in some time-periodic universes |
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Authors: | Philippe Droz-Vincent |
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Institution: | (1) Laboratoire de Physique Théorique, GCR, CNRS URA 769, Université Pierre et Marie Curie, Tour 22-12, boite courrier 142, 4 place Jussieu, 75252 Paris Cedex 05, France |
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Abstract: | We consider the Klein-Gordon equation in FRW-like universes which are periodic in a suitable scale of time. In a remarkable sector of solutions, the Floquet theory of differential equations allows for generalizing the notion of particle frequency. In this sense, the sesquilinear form associated with Gordon's current is positive definite when restricted to the sub-sector of positive frequencies. |
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Keywords: | 81R20 81T20 |
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