Cosmological consequences of a principle of finite amplitudes

Abstract

Over 30 years ago, Barrow & Tipler proposed the principle according to which the action integrated over the entire 4-manifold describing the universe should be finite. Here we explore the cosmological consequences of a related criterion, namely that semi-classical transition amplitudes from the early universe up to current field values should be well defined. On a classical level, our criterion is weaker than the Barrow-Tipler principle, but it has the advantage of being sensitive to quantum effects. We find significant consequences for early universe models, in particular: eternal inflation and strictly cyclic universes are ruled out. Within general relativity, the first phase of evolution cannot be inflationary, and it can be ekpyrotic only if the scalar field potential is trustworthy over an infinite field range. Quadratic gravity eliminates all non-accelerating backgrounds near a putative big bang (thus imposing favourable initial conditions for inflation), while the expected infinite series of higher-curvature quantum corrections eliminates Lorentzian big bang spacetimes altogether. The scenarios that work best with the principle of finite amplitudes are the no-boundary proposal, which gives finite amplitudes in all dynamical theories that we have studied, and string-inspired loitering phases. We also comment on the relationship of our proposal to the swampland conjectures.

50 pages, 3 figures, 1 table. Matches the published version

References in corpus (38)

• On the Geometry of the String Landscape and the Swampland
• Eternal inflation and its implications
• New Ekpyrotic Cosmology
• Galilean Genesis: an alternative to inflation
• Generating Ekpyrotic Curvature Perturbations Before the Big Bang
• The Classical Universes of the No-Boundary Quantum State
• Inflationary schism after Planck2013
• A new kind of cyclic universe
• A Matter Bounce By Means of Ghost Condensation
• On the evolution of universes in quadratic theories of gravity
• No Rescue for the No Boundary Proposal
• The Real No-Boundary Wave Function in Lorentzian Quantum Cosmology
• Subluminal Galilean Genesis
• Metastability in Quadratic Gravity
• The Matter Bounce Alternative to Inflationary Cosmology
• The No-Boundary Proposal as a Path Integral with Robin Boundary Conditions
• A Safe Beginning for the Universe?
• Dark Energy and the Return of the Phoenix Universe
• Generalized Galilean Genesis
• Light propagation in a homogeneous and anisotropic universe
• Emergent Universe and Genesis from the DHOST Cosmology
• String Cosmology backgrounds from Classical String Geometry
• Classical Inflationary and Ekpyrotic Universes in the No-Boundary Wavefunction
• ${\alpha }^{\prime }$-Cosmology: solutions and stability analysis
• New non-perturbative de Sitter vacua in ${\alpha }^{\prime }$-complete cosmology
• Lessons for quantum cosmology from anti-de Sitter black holes
• Toward evading the strong coupling problem in Horndeski genesis
• On the Creation of the Universe via Ekpyrotic Instantons
• Novel higher-curvature variations of $R^2$ inflation
• Finite Action Principle Revisited
• Horndeski genesis: consistency of classical theory
• Scale-invariant perturbations from NEC violation: A new variant of Galilean Genesis
• A Quantum Complete Prelude to Inflation
• Topological Gravity as the Early Phase of Our Universe
• The Shape of Bouncing Universes
• No-boundary solutions are robust to quantum gravity corrections
• Theories with limited extrinsic curvature and a nonsingular anisotropic universe
• de Sitter Complementarity, TCC, and the Swampland

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• Review of the No-Boundary Wave Function
• Finiteness and the Swampland
• Scalar and Tensor Perturbations in DHOST Bounce Cosmology
• Quantum improved charged black holes
• Asymptotic Safety: Swampland or Wonderland?
• Uses of Complex Metrics in Cosmology
• Action principle selection of regular black holes
• General String Cosmologies at Order ${\alpha }^{\prime }{}^3$
• Microphysical manifestations of viscosity and consequences for anisotropies in the very early universe
• WKB Approaches to Restore Time in Quantum Cosmology: Predictions and Shortcomings
• Quantum Circuit Complexity of Primordial Perturbations
• Cosmology at the top of the ${\alpha }^{\prime }$ tower
• On the initial singularity and extendibility of flat quasi-de Sitter spacetimes
• Finite Action Principle and Horava-Lifshitz Gravity: early universe, black holes and wormholes
• Suppression of spacetime singularities in quantum gravity
• Past extendibility and initial singularity in Friedmann-Lemaître-Robertson-Walker and Bianchi I spacetimes
• A small Universe
• Allowable Complex Scalars from Kaluza-Klein Compactifications and Metric Rescalings
• Revisiting the no-boundary proposal with a scalar field
• How to Create Universes with Internal Flux
• Hitchhiker's Guide to the Swampland: The Cosmologist's Handbook to the string-theoretical Swampland Programme
• Conformal Cores of Quantum Black Holes in Quadratic Gravity
• Delicate curvature bounces in the no-boundary wave function and in the late universe
• Singularity and differentiability at the origin of static and spherically symmetric black holes
• Finite Action Principle and wormholes