Closed-time-path functional formalism in curved spacetime: Application to cosmological back-reaction problems

Calzetta, Esteban; Hu, B. L.

doi:10.1103/physrevd.35.495

Cited by 500 publications

(571 citation statements)

References 24 publications

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“…We consider correlation functions with (external) momenta much smaller than the Hubble scale H in the quantum theory, using the Closed Time Path (CTP) formalism (also known as in-in formalism, see e.g. [29,30]), as is also done by Weinberg in [31,32]. Furthermore we formulate a classical theory with statistical fluctuations, in such a way that correlation functions in this theory can easily be compared with those in the quantum theory.…”

Section: Introductionmentioning

confidence: 99%

Classical approximation to quantum cosmological correlations

Meulen¹,

Smit²

2007

J. Cosmol. Astropart. Phys.

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Abstract:We investigate up to which order quantum effects can be neglected in calculating cosmological correlation functions after horizon exit. As a toy model, we study φ 3 theory on a de Sitter background for a massless minimally coupled scalar field φ. We find that for tree level and one loop contributions in the quantum theory, a good classical approximation can be constructed, but for higher loop corrections this is in general not expected to be possible. The reason is that loop corrections get non-negligible contributions from loop momenta with magnitude up to the Hubble scale H, at which scale classical physics is not expected to be a good approximation to the quantum theory. An explicit calculation of the one loop correction to the two point function, supports the argument that contributions from loop momenta of scale H are not negligible. Generalization of the arguments for the toy model to derivative interactions and the curvature perturbation leads to the conclusion that the leading orders of non-Gaussian effects generated after horizon exit, can be approximated quite well by classical methods. Furthermore we compare with a theorem by Weinberg. We find that growing loop corrections after horizon exit are not excluded, even in single field inflation.

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Section: Introductionmentioning

confidence: 99%

Classical approximation to quantum cosmological correlations

Meulen¹,

Smit²

2007

J. Cosmol. Astropart. Phys.

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“…For this purpose we should use the in-in or the closed time-path formalisms in which the time contour starting from the infinite past must run to the infinite future without fixing the final condition and come back to the infinite past again in calculating the generating functional [12]. This method has been applied to various cosmological problems by a number of authors [13,14,15]. The generating functional in the present model is given by…”

Section: Model and Equation Of Motionmentioning

confidence: 99%

“…From now on we refer to m φ as the renormalized mass, and assume that M < m φ . Then one can neglect S k (ω) in (14) to yield the solution…”

Section: Model and Equation Of Motionmentioning

confidence: 99%

Can oscillating scalar fields decay into particles with a large thermal mass?

Yokoyama

2006

Physics Letters B

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We calculate the dissipation rate of a coherently oscillating scalar field in a thermal environment using nonequilibrium quantum field theory and apply it to the reheating stage after cosmic inflation. It is shown that the rate is nonvanishing even when particles coupled to the oscillating inflaton field have a larger thermal mass than it, and therefore the cosmic temperature can be much higher than inflaton's mass even in the absence of preheating. Its cosmological implications are also discussed.

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“…In addition to that, the Schwinger-Keldysh formalism [60][61][62] will be used for calculating the non-Abelian contributions.…”

Section: Jcap11(2009)028mentioning

confidence: 99%

Anisotropic trispectrum of curvature perturbations induced by primordial non-Abelian vector fields

Bartolo¹,

Dimastrogiovanni²,

Matarrese³

et al. 2009

J. Cosmol. Astropart. Phys.

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Motivated by the interest in models of the early universe where statistical isotropy is broken and can be revealed in cosmological observations, we consider an SU (2) theory of gauge interactions in a single scalar field inflationary scenario. We calculate the trispectrum of curvature perturbations, as a natural follow up to a previous paper of ours, where we studied the bispectrum in the same kind of models. The choice of a non-Abelian set-up turns out to be very convenient: on one hand, gauge boson self-interactions can be very interesting being responsible for extra non-trivial terms (naturally absent in the Abelian case) appearing in the cosmological correlation functions; on the other hand, its results can be easily reduced to the U (1) case. As expected from the presence of the vector bosons, preferred spatial directions arise and the trispectrum reveals anisotropic signatures. We evaluate its amplitude τ N L , which receives contributions both from scalar and vector fields, and verify that, in a large subset of its parameter space, the latter contributions can be larger than the former. We carry out a shape analysis of the trispectrum; in particular we discuss, with some examples, how the anisotropy parameters appearing in the analytic expression of the trispectrum can modulate its profile and we show that the amplitude of the anisotropic part of the trispectrum can be of the same order of magnitude as the isotropic part.

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Closed-time-path functional formalism in curved spacetime: Application to cosmological back-reaction problems

Cited by 500 publications

References 24 publications

Classical approximation to quantum cosmological correlations

Classical approximation to quantum cosmological correlations

Can oscillating scalar fields decay into particles with a large thermal mass?

Anisotropic trispectrum of curvature perturbations induced by primordial non-Abelian vector fields

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