Cosmological density fluctuations in stochastic gravity: Formalism and linear analysis

Yuko Urakawa, Keiichi Maeda

    Research output: Contribution to journalArticle

    8 Citations (Scopus)

    Abstract

    We study primordial perturbations generated from quantum fluctuations of an inflaton based on the formalism of stochastic gravity. Integrating out the degree of freedom of the inflaton field, we analyze the time evolution of the correlation function of the curvature perturbation at tree level and compare it with the prediction made by the gauge-invariant linear perturbation theory. We find that our result coincides with that of the gauge-invariant perturbation theory if the e-folding from the horizon-crossing time is smaller than some critical value (∼| slow-roll parameter |-1), which is the case for the scales of the observed cosmological structures. However, in the limit of the superhorizon scale, we find a discrepancy in the curvature perturbation, which suggests that we should include the longitudinal part of the gravitational field in the quantization of a scalar field even in stochastic gravity.

    Original languageEnglish
    Article number024013
    JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
    Volume77
    Issue number2
    DOIs
    Publication statusPublished - 2008 Jan 9

    Fingerprint

    Gravity
    Fluctuations
    gravitation
    formalism
    Perturbation
    perturbation
    Perturbation Theory
    Gauge
    perturbation theory
    Curvature
    curvature
    Invariant Theory
    Quantum Fluctuations
    Gravitational Field
    Folding
    folding
    gravitational fields
    Scalar Field
    horizon
    Discrepancy

    ASJC Scopus subject areas

    • Physics and Astronomy(all)
    • Nuclear and High Energy Physics
    • Mathematical Physics

    Cite this

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    abstract = "We study primordial perturbations generated from quantum fluctuations of an inflaton based on the formalism of stochastic gravity. Integrating out the degree of freedom of the inflaton field, we analyze the time evolution of the correlation function of the curvature perturbation at tree level and compare it with the prediction made by the gauge-invariant linear perturbation theory. We find that our result coincides with that of the gauge-invariant perturbation theory if the e-folding from the horizon-crossing time is smaller than some critical value (∼| slow-roll parameter |-1), which is the case for the scales of the observed cosmological structures. However, in the limit of the superhorizon scale, we find a discrepancy in the curvature perturbation, which suggests that we should include the longitudinal part of the gravitational field in the quantization of a scalar field even in stochastic gravity.",
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