Isocurvature perturbations in multiple inflationary models

Polarski, David; Starobinsky, Alexei A.

doi:10.1103/physrevd.50.6123

Cited by 229 publications

(322 citation statements)

References 22 publications

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“…A common feature of isocurvature perturbations is that they might not survive after the end of inflation [28,29,30]. If during reheating all the scalar fields decay into the same species (photons, neutrinos, cold dark matter and baryons), the only remaining perturbations will be of adiabatic t ype.…”

Section: Initial Conditions In the Radiation Eramentioning

confidence: 99%

Oscillations during inflation and the cosmological density perturbations

2001

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Adiabatic (curvature) perturbations are produced during a period of cosmological inflation that is driven by a single scalar field, the inflaton. On particle physics grounds -though -it is natural to expect that this scalar field is coupled to other scalar degrees of freedom. This gives rise to oscillations between the perturbation of the inflaton field and the perturbations of the other scalar degrees of freedom, similar to the phenomenon of neutrino oscillations. Since the degree of the mixing is governed by the squared mass matrix of the scalar fields, the oscillations can occur even if the energy density of the extra scalar fields is much smaller than the energy density of the inflaton field. The probability of oscillation is resonantly amplified when perturbations cross the horizon and the perturbations in the inflaton field may disappear at horizon crossing giving rise to perturbations in scalar fields other than the inflaton. Adiabatic and isocurvature perturbations are inevitably correlated at the end of inflation and we provide a simple expression for the cross-correlation in terms of the slow-roll parameters.

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Section: Initial Conditions In the Radiation Eramentioning

confidence: 99%

Oscillations during inflation and the cosmological density perturbations

2001

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“…The above expression can be easily integrated (see [23] for details). The expansion rate H is then given by…”

Section: Decoherence In the Modelmentioning

confidence: 99%

“…In this section we illustrate the role of isocurvature perturbations for decoherence in an inflationary model with V (ϕ, χ) = 1 2 m 2 ϕ 2 + 1 2 µ 2 χ 2 , a model which has been studied extensively in [23] (see also [18]). We first present exact numerical results for two cases: a) µ = 1.05m and b) µ = 10m.…”

Section: Decoherence In the Modelmentioning

confidence: 99%

Decoherence from isocurvature perturbations in inflation

Prokopec

Rigopoulos²

2007

J. Cosmol. Astropart. Phys.

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We discuss the possible role of isocurvature perturbations for the quantum decoherence of the curvature perturbation during inflation. We point out that if the inflaton trajectory in field space is curved, the adiabatic mode is generically coupled to the isocurvature mode and thus tracing out the latter can cause the curvature perturbation to decohere. We explicitly investigate this suggestion in a model of inflation with two decoupled massive fields and find that decoherence is effective for a wide range of mass ratios. In particular, we calculate the entanglement entropy for this model and show that it grows after horizon exit, providing a quantitative measure for decoherence.

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“…An essential property of this approach is that this type of transition from a quantum to a classical description of the perturbations, including the complete loss of quantum coherence, does not require any actual consideration of very small interactions between a given mode of perturbations and other degrees of freedom ("environment") in the Universe. Though these interactions do of course exist and do lead to the transformation of an initial pure quantum state into a mixed state, their actual structure is unimportant for observable quantities as far as the exponentially small decaying mode of perturbations may be neglected (note however that it must be taken into account if one wants to calculate the entropy of cosmological perturbations [10]). This is precisely why this transition was called "decoherence without decoherence" in [7].…”

Section: Introductionmentioning

confidence: 99%

Quantum-to-classical transition of cosmological perturbations for non-vacuum initial states

1997

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Transition from quantum to semiclassical behaviour and loss of quantum coherence for inhomogeneous perturbations generated from a non-vacuum initial state in the early Universe is considered in the Heisenberg and the Schrödinger representations, as well as using the Wigner function. We show explicitly that these three approaches lead to the same prediction in the limit of large squeezing (i.e. when the squeezing parameter |r k | → ∞): each two-modes quantum state (k, − k) of these perturbations is equivalent to a classical perturbation that has a stochastic amplitude, obeying a non-gaussian statistics which depends on the initial state, and that belongs to the quasi-isotropic mode (i.e. it possesses a fixed phase). The Wigner function is not everywhere positive for any finite r k , hence its interpretation as a classical distribution function in phase space is impossible without some coarse graining procedure. However, this does not affect the transition to semiclassical behaviour since the Wigner function becomes concentrated near a classical trajectory in phase space when |r k | → ∞ even without coarse graining. Deviations of the statistics of the perturbations in real space from a Gaussian one lie below the cosmic variance level for the N -particles initial states with N = N (|k|) but may be observable for other initial states without statistical isotropy or with correlations between different k modes. As a way to look for this effect, it is proposed to measure 0 the kurtosis of the angular fluctuations of the cosmic microwave background temperature.

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Isocurvature perturbations in multiple inflationary models

Cited by 229 publications

References 22 publications

Oscillations during inflation and the cosmological density perturbations

Oscillations during inflation and the cosmological density perturbations

Decoherence from isocurvature perturbations in inflation

Quantum-to-classical transition of cosmological perturbations for non-vacuum initial states

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