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A conformally coupled massive scalar field in the de Sitter expanding universe with the mass term treated as a perturbation

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JournalClassical and Quantum Gravity
DatePublished - 7 Jul 2009
Issue number13
Volume26
Number of pages14
Pages (from-to)1-14
Original languageEnglish

Abstract

We study conformally coupled massive scalar field theory with the mass term treated as a perturbation in the expanding half of de Sitter spacetime as a toy model for comparing various perturbative formalisms. We point out that the in-out perturbation theory breaks down due to infrared divergences coming from the infinite future. We then clarify the relation between the free-theory vacuum and the true vacuum using the Bogolubov transformation and show that the discrepancy between the free-theory out-vacuum and the true vacuum causes apparent pair creation of free-theory particles and makes the in-out two-point function differ from the true two-point function. We also identify the infinite Bogolubov coefficients as the cause of infrared divergences. We then examine two alternative approaches: the Euclidean and in-in formalisms. We verify that there are no infrared divergences in perturbation theory with the mass term treated as a perturbation in either of these approaches and that the two-point function of the massive scalar field is reproduced correctly by these methods.

    Research areas

  • PARTICLE CREATION, GRAVITON PROPAGATOR, QUANTUM-FIELDS, SPACETIME, STATES

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