Cosmological Acceleration through Transition to Constant Scalar Curvature

Parker, Leonard; Komp, William; Vanzella, Daniel A. T.

doi:10.1086/374265

Cited by 25 publications

(24 citation statements)

References 58 publications

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“…This paper is not the first to investigate the possibility that vacuum fluctuations of matter fields may be responsible for dark energy and here we make a cursory overview of these earlier works. Apart from our earlier papers [12,14], in which we investigated the late-time one-loop quantum backreaction from one-loop inflationary fluctuations of massless and minimally and nonminimally coupled scalars, and of gravitons, probably the closest to our work are the papers of Ringeval, Suyama, Takahashi, Yamaguchi and Yokoyama [17], of Aoki and Iso [18], results of which we discussed in the previous paragraph, and of Parker and Raval [19][20][21][22][23], and of Parker and Vanzella [45,46]. Refs.…”

Section: Minimally Coupled Limitmentioning

confidence: 99%

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Late-time quantum backreaction of a very light nonminimally coupled scalar

2016

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We investigate the backreaction of the quantum fluctuations of a very light (m H today ) nonminimally coupled spectator scalar field on the expansion dynamics of the Universe. The one-loop expectation value of the energy momentum tensor of these fluctuations, as a measure of the backreaction, is computed throughout the expansion history from the early inflationary universe until the onset of recent acceleration today. We show that, when the nonminimal coupling ξ to Ricci curvature is negative (ξ c = 1/6 corresponding to conformal coupling), the quantum backreaction grows exponentially during inflation, such that it can grow large enough rather quickly (within a few hundred e-foldings) to survive until late time and constitute a contribution of the cosmological constant type of the right magnitude to appreciably alter the expansion dynamics. The unique feature of this model is in that, under rather generic assumptions, inflation provides natural explanation for the initial conditions needed to explain the late-time accelerated expansion of the Universe, making it a particularly attractive model of dark energy.

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Section: Minimally Coupled Limitmentioning

confidence: 99%

“…Now it is straightforward to match the two solutions (45) and (46), which are just the continuity conditions for the mode function and its derivative,…”

Section: B Sudden Transition Approximationmentioning

confidence: 99%

Late-time quantum backreaction of a very light nonminimally coupled scalar

2016

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“…In fact, if quantum effects in curved space-time are considered [47], in general one finds curvature corrections that are necessary to account for the renormalizability of matter fields in such backgrounds. These corrections are known to be quadratic in the Ricci and Riemann tensors at high energies, but other types of R−dependent corrections may arise in the infrared, thus having a relevant impact on the late-time cosmic expansion [48,49]. This fact has also motivated recent studies of hybrid scenarios in which the EinsteinHilbert Lagrangian is supplemented with f (R) corrections of the Palatini type [50,51,52,53,54,55,56].…”

Section: Introductionmentioning

confidence: 99%

Born-Infeldf(R)gravity

2014

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Motivated by the properties of matter quantum fields in curved spacetimes, we work out a gravity theory that combines the Born-Infeld gravity Lagrangian with an f (R) piece. To avoid ghost-like instabilities, the theory is formulated within the Palatini approach. This construction provides more freedom to address a number of important questions such as the dynamics of the early universe and the cosmic accelerated expansion, among others. In particular, we consider the effect that adding an f (R) = aR 2 term has on the early-time cosmology. We find that bouncing solutions are robust against these modifications of the Lagrangian whereas the solutions with loitering behavior of the original Born-Infeld theory are very sensitive to the R 2 term. In fact, these solutions are modified in such a way that a plateau in the H 2 function may arise yielding a period of (approximately) de Sitter inflationary expansion. This inflationary behavior may be found even in a radiation dominated universe.

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“…The VCDM model gives a satisfactory fit to the observed CMBR power spectrum and SNe-Ia data [17]. It may also lead to the observed suppression of the CMBR power spectrum at very low values of l [18].…”

Section: Introductionmentioning

confidence: 99%

Acceleration of the universe, vacuum metamorphosis, and the large-time asymptotic form of the heat kernel

Parker

Vanzella

2004

Phys. Rev. D

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We investigate the possibility that the late acceleration observed in the rate of expansion of the Universe is due to vacuum quantum effects arising in curved spacetime. The theoretical basis of the vacuum cold dark matter ͑VCDM͒, or vacuum metamorphosis, cosmological model of Parker and Raval is reexamined and improved. We show, by means of a manifestly nonperturbative approach, how the infrared behavior of the propagator ͑related to the large-time asymptotic form of the heat kernel͒ of a free scalar field in curved spacetime leads to nonperturbative terms in the effective action similar to those appearing in the earlier version of the VCDM model. The asymptotic form that we adopt for the propagator or heat kernel at large proper time s is motivated by, and consistent with, particular cases where the heat kernel has been calculated exactly, namely in de Sitter spacetime, in the Einstein static universe, and in the linearly expanding spatially flat Friedmann-Robertson-Walker ͑FRW͒ universe. This large-s asymptotic form generalizes somewhat the one suggested by the Gaussian approximation and the R-summed form of the propagator that earlier served as a theoretical basis for the VCDM model. The vacuum expectation value for the energy-momentum tensor of the free scalar field, obtained through variation of the effective action, exhibits a resonance effect when the scalar curvature R of the spacetime reaches a particular value related to the mass of the field. Modeling our Universe by an FRW spacetime filled with classical matter and radiation, we show that the back reaction caused by this resonance drives the Universe through a transition to an accelerating expansion phase, very much in the same way as originally proposed by Parker and Raval. Our analysis includes higher derivatives that were neglected in the earlier analysis, and takes into account the possible runaway solutions that can follow from these higher-derivative terms. We find that the runaway solutions do not occur if the universe was described by the usual classical FRW solution prior to the growth of vacuum energy density and negative pressure ͑i.e., vacuum metamorphosis͒ that causes the transition to an accelerating expansion of the universe in this theory.

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Cosmological Acceleration through Transition to Constant Scalar Curvature

Cited by 25 publications

References 58 publications

Late-time quantum backreaction of a very light nonminimally coupled scalar

Late-time quantum backreaction of a very light nonminimally coupled scalar

Born-Infeldf(R)gravity

Acceleration of the universe, vacuum metamorphosis, and the large-time asymptotic form of the heat kernel

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