Primordial fluctuations and non-Gaussianities in sidetracked inflation

Abstract

Heavy scalar fields can undergo an instability during inflation as a result of their kinetic couplings with the inflaton. This is known as the geometrical destabilization of inflation, as it relies on the effect of the negative curvature of the field-space manifold overcoming the stabilizing force of the potential. This instability can drive the system away from its original path in field space into a new inflationary attractor, a scenario that we dub sidetracked inflation. We study this second phase and its observable consequences in several classes of two-field models. We show that cosmological fluctuations exhibit varied behaviours depending on the potential and the field space geometry, and that they can be captured by single-field effective theories with either a modified dispersion relation, a reduced speed of sound, or an imaginary one --- the latter case describing a transient tachyonic growth of the fluctuations. We also numerically calculate the bispectrum with the transport approach, finding large non-Gaussianities of equilateral and orthogonal shapes. In the hyperbolic geometry the potentials of our models present a pole at the boundary of the Poincaré disk and we discuss their relationships with $\alpha$-attractors.

58+10 pages, 18 figures. Minor modifications. Version published in JCAP

References in corpus (23)

• The Standard Model Higgs boson as the inflaton
• The Effective Field Theory of Inflation
• Primordial Non-Gaussianities from Inflation Models
• Nonperturbative Dynamics Of Reheating After Inflation: A Review
• The Unity of Cosmological Attractors
• Generation and Characterization of Large Non-Gaussianities in Single Field Inflation
• The shape of primordial non-Gaussianity and the CMB bispectrum
• Perturbations in generalized multi-field inflation
• Large Field Inflation and Double $\alpha$-Attractors
• Heavy fields, reduced speeds of sound and decoupling during inflation
• Strongly Coupled Perturbations in Two-Field Inflationary Models
• Primordial perturbations from inflation with a hyperbolic field-space
• Effective field theory of weakly coupled inflationary models
• Universality of multi-field $\alpha$-attractors
• Attractor Behaviour in Multifield Inflation
• Inflationary perturbation theory is geometrical optics in phase space
• Numerical evaluation of the bispectrum in multiple field inflation
• Moment transport equations for the primordial curvature perturbation
• Transport equations for the inflationary trispectrum
• Geometrical destabilization, premature end of inflation and Bayesian model selection
• Numerically evaluating the bispectrum in curved field-space - with PyTransport 2.0
• Higher derivatives and power spectrum in effective single field inflation
• On degenerate models of cosmic inflation

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