Origin of ultra-light fields during inflation and their suppressed non-Gaussianity
arXiv:1908.06956 · doi:10.1088/1475-7516/2020/10/018
Abstract
We study the structure of multi-field inflation models where the primordial curvature perturbation is able to vigorously interact with an ultra-light isocurvature field -- a massless fluctuation orthogonal to the background inflationary trajectory in field space. We identify a class of inflationary models where ultra-light fields can emerge as a consequence of an underlying "scaling transformation" that rescales the entire system's action and keeps the classical equations of motion invariant. This scaling invariance ensures the existence of an ultra-light fluctuation that freezes after horizon crossing. If the inflationary trajectory is misaligned with respect to the scaling symmetry direction, then the isocurvature field is proportional to this ultra-light field, and becomes massless. In addition, we find that even if the isocurvature field interacts strongly with the curvature perturbation --transferring its own statistics to the curvature perturbation-- it is unable to induce large non-Gaussianity. The reason is simply that the same mechanism ensuring a suppressed mass for the isocurvature field is also responsible for suppressing its self-interactions. As a result, in models with light isocurvature fields the bispectrum is generally expected to be slow-roll suppressed, but with a squeezed limit that differs from Maldacena's consistency relation.
arXiv comment12 pages + 2 pages appendices
References in corpus (40)
- Non-Gaussian features of primordial fluctuations in single field inflationary models
- Adiabatic and entropy perturbations from inflation
- Single field consistency relation for the 3-point function
- The inflationary prediction for primordial non-gaussianity
- Quasi-Single Field Inflation and Non-Gaussianities
- Features of heavy physics in the CMB power spectrum
- Signatures of Supersymmetry from the Early Universe
- Primordial non-gaussianities from multiple-field inflation
- Large non-Gaussianities with Intermediate Shapes from Quasi-Single Field Inflation
- Scalar perturbations during multiple-field slow-roll inflation
- Non-Gaussianity as a Particle Detector
- On the consistency relation of the 3-point function in single field inflation
- Mass hierarchies and non-decoupling in multi-scalar field dynamics
- Large non-Gaussianity in multiple-field inflation
- Conditions for large non-Gaussianity in two-field slow-roll inflation
- Inflation models and observation
- Non-Gaussianity beyond slow roll in multi-field inflation
- A covariant approach to general field space metric in multi-field inflation
- Spectral Running and Non-Gaussianity from Slow-Roll Inflation in Generalised Two--Field Models
- Primordial fluctuations and non-Gaussianities in sidetracked inflation
- A Statistical Approach to Multifield Inflation: Many-field Perturbations Beyond Slow Roll
- Non-Gaussian perturbations in hybrid inflation
- Universality of multi-field -attractors
- A generalized non-Gaussian consistency relation for single field inflation
- Hyper non-Gaussianities in inflation with strongly non-geodesic motion
- Multi-field inflation and cosmological perturbations
- Cumulative effects in inflation with ultra-light entropy modes
- Spontaneous Symmetry Probing
- Non-Gaussianities in N-flation
- Revisiting non-Gaussianity in multifield inflation with curved field space
- Landscape tomography through primordial non-Gaussianity
- Non-Gaussianity from the hybrid potential
- Shift-Symmetric Orbital Inflation: single field or multi-field?
- On Non-Gaussianities in Multi-Field Inflation (N fields): Bi- and Tri-spectra beyond Slow-Roll
- Reconstructing the Inflationary Landscape with Cosmological Data
- Constraints on holographic multi-field inflation and models based on the Hamilton-Jacobi formalism
- Spectral distortion anisotropies from single-field inflation
- General formula for the running of local fNL
- Evolution of non-Gaussianity in multi-scalar field models
- A simple, exact, model of quasi-single field inflation