Fat Inflatons, Large Turns and the $\eta$-problem

Abstract

It is commonly believed that a successful period of inflation driven by a single or several scalar fields requires a specific hierarchy of masses given by $M_{inf}\ll H\ll M_{heavy}$, where $M_{inf}$ can correspond to several or a single light field and $M_{heavy}$ corresponds to any heavy field that might be integrated out if it satisfies suitable conditions. This is at the heart of the so called $\eta$-problem in inflation, since large contributions to the masses of the inflatons might spoil the slow-roll conditions required for inflation. We show that, while this is an unavoidable conclusion in single field inflation, in multifield inflation, heavy fields as defined above, may be fully responsible for a successful period of what we call fat slow-roll inflation. Moreover we show that in this scenario, the turning rate of the inflationary trajectory, $\Omega /H$, is larger than one. Thus, the $\eta$-problem is evaded with large turns in fat inflation. Depending on the perturbations' mass spectra, cosmological predictions will differ either slightly or largely with respect to those of the single field case. We illustrate this scenario in a concrete example in Type IIB string flux compactifications, where a probe D5-brane moving along the angular and radial directions in a warped throat drives fat D5-brane natural inflation. An instantaneous superplanckian decay constant can be defined, consistent with our low energy approximations, thanks to the strong warping of the geometry. We compute the cosmological observables, which differ from the single field case. We also discuss fat inflation in the context of recently proposed swampland de Sitter conjectures.

arXiv comment41 pages, 13 figures. Minor typos fixed, references added, appendix A expanded. To appear in JCAP

References in corpus (41)

• Non-Gaussian features of primordial fluctuations in single field inflationary models
• Hierarchies from Fluxes in String Compactifications
• The String Landscape, Black Holes and Gravity as the Weakest Force
• On the Geometry of the String Landscape and the Swampland
• Cosmology and Fundamental Physics with the Euclid Satellite
• A General Analytic Formula for the Spectral Index of the Density Perturbations produced during Inflation
• Distance and de Sitter Conjectures on the Swampland
• Adiabatic and entropy perturbations from inflation
• Bounds on Slow Roll and the de Sitter Swampland
• Features of heavy physics in the CMB power spectrum
• Racetrack Inflation
• Scalar perturbations during multiple-field slow-roll inflation
• Perturbations in generalized multi-field inflation
• The string swampland constraints require multi-field inflation
• D3-brane Potentials from Fluxes in AdS/CFT
• CLASS: The Cosmology Large Angular Scale Surveyor
• On the importance of heavy fields during inflation
• Heavy fields, reduced speeds of sound and decoupling during inflation
• Primordial Bispectrum from Multifield Inflation with Nonminimal Couplings
• Geometrical Destabilization of Inflation
• Hyperinflation
• 3-branes on resolved conifold
• Constraints on modular inflation in supergravity and string theory
• Equilateral non-Gaussianity from heavy fields
• Gauge/Gravity Duality and Warped Resolved Conifold
• Primordial fluctuations and non-Gaussianities in sidetracked inflation
• Mirror Symmetries for Brane Configurations and Branes at Singularities
• Warping the Weak Gravity Conjecture
• Scaling attractors in multi-field inflation
• Inflation from Wrapped Branes
• The rapid-turn inflationary attractor
• Angular inflation in multi-field $\alpha$-attractors
• Hyperinflation generalised: from its attractor mechanism to its tension with the `swampland conjectures'
• Sound Speed of Primordial Fluctuations in Supergravity Inflation
• Cosmic inflation in a landscape of heavy-fields
• D-brane Potentials in the Warped Resolved Conifold and Natural Inflation
• On the viability of m**2 phi**2 and natural inflation
• Spiral Inflation
• The Strong Multifield Slowroll Condition and Spiral Inflation
• Post-inflationary Scalar Tensor Cosmology and Inflationary Parameters
• Prospects for Primordial Gravitational Waves in String Inflation

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• On the inflationary massive field with a curved field manifold
• Attractors, Bifurcations and Curvature in Multi-field Inflation
• On Primordial Black Holes from Rapid Turns in Two-field Models
• Sharp turns in axion monodromy: primordial black holes and gravitational waves
• The Multi-Field, Rapid-Turn Inflationary Solution
• On chromonatural inflation in string theory
• Non-Gaussianities in models of inflation with large and negative entropic masses
• Dynamical consistency conditions for rapid turn inflation
• (Slow-)Twisting inflationary attractors
• Non-Gaussianity in rapid-turn multi-field inflation
• On the Consistency of Rapid-Turn Inflation
• Hitchhiker's Guide to the Swampland: The Cosmologist's Handbook to the string-theoretical Swampland Programme
• Generalised conditions for rapid-turn inflation
• Loops in inflation with strongly non-geodesic motion
• Escape from the swamp with spectator
• The UV Sensitivity of Axion Monodromy Inflation
• Rapid-turn inflation in supergravity is rare and tachyonic
• Primordial gravitational waves from excited states
• Consistency Condition for Slow-roll and Rapid-turn Inflation