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In loop quantum cosmology, the slow-roll inflation is generic, and when the kinetic energy of the scalar field dominates at the bounce, the evolution of the Friedmann-Lemaître-Robertson-Walker universe will go through three distinguishable epochs, bouncing, transition, and finally slow-roll inflation, before the reheating commences. The bouncing dynamics are insensitive of the potential and initial conditions, so that the expansion factor and the scalar field can be described uniquely by a universal solution during this epoch. After about 105 Planck time, the epoch of transition starts and the universe rapidly turns over from the kinetic energy dominated state to the potential energy dominated one, whereby the slow-roll inflationary phase begins. In this paper, we consider the power law plateau potential and study the pre-inflationary cosmology for different sets of initial conditions, so that during the slow-roll inflation epoch enough e-folds will be produced. Considering the generalized reheating and comparing with the recent Planck 2018 data, we are able to constrain the total number of e-folds (NT) from the bounce till today to be consistent with the current observable universe. Depending on the matter driving the reheating (subject to the different dominant equations of states), we report the observationally allowed NT and reheating temperature and find in particular NT≃127, which is significantly different from the one NT≳141 obtained previously without considering the reheating phase.
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Quantum cosmology, eternal inflation, and swampland conjectures
Abstract In light of the recent swampland conjectures, we explore quantum cosmology and eternal inflation beyond the slow roll regime. We consider a model of a closed universe with a scalar field ϕ in the framework of tunneling approach to quantum cosmology. The scalar field potential is assumed to have a maximum at ϕ = 0 and can be approximated in its vicinity as V ( ϕ )≈ 3 H 2 - 1/2 m 2 ϕ 2 . Using the instanton method, we find that for m < 2 H the dominant nucleation channel for the universe is tunneling to a homogeneous, spherical de Sitter space. For larger values of m / H , the most probable tunneling is to an inhomogeneous closed universe with a domain wall wrapped around its equator. We determine the quantum state of the field ϕ in the nucleated universe by solving the Wheeler-DeWitt equation with tunneling boundary conditions. Our results agree with earlier work which assumed a slow-roll regime m ≪ H . We finally show that spherical universes nucleating with m < 2 H undergo stochastic eternal inflation with inflating regions forming a fractal of dimension d > 2. For larger values of m the field ϕ is unstable with respect to formation of domain walls and cannot be described by a perturbative stochastic approach.
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- Award ID(s):
- 2110466
- PAR ID:
- 10462648
- Date Published:
- Journal Name:
- Journal of Cosmology and Astroparticle Physics
- Volume:
- 2023
- Issue:
- 04
- ISSN:
- 1475-7516
- Page Range / eLocation ID:
- 034
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1088/1475-7516/2023/04/034
