2020/04/13 by Adriano Testa, Mark B. Wise
Mathematics · Physics and Astronomy · #Anisotropy #Bispectrum #Classical mechanics #Conformal map #Cosmological perturbation theory #Cosmology and Gravitation Theories #Curvature #Galaxies: Formation, Evolution, Phenomena #Geometry #Inflation (cosmology) #Inflaton #Mathematics #Non-Gaussianity #Observable #Perturbation theory (quantum mechanics) #Physics #Quantum electrodynamics #Quantum mechanics #Solar and Space Plasma Dynamics #Spectral density #Theoretical physics #astro-ph.CO #hep-ph
paper · pdf · doi:10.1103/physrevd.102.023533
published as Phys. Rev. D 102, 023533 (2020) · 13 pages, 2 figures
arxiv created 2020/04/13 · openalex publication_date 2020/07/22 · arxiv updated 2020/07/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
In general relativity, predictions for observable quantities can be expressed in a coordinate independent way. Nonetheless it may be inconvenient to do so. Using a particular frame may be the easiest way to connect theoretical predictions to measurable quantities. For the cosmological curvature bispectrum such frame is described by the conformal Fermi coordinates. In single field inflation it was shown that going to this frame cancels the squeezed limit of the density perturbation bispectrum calculated in global coordinates. We explore this issue in quasisingle field inflation when the curvaton mass and the curvaton-inflaton mixing are small. In this case, the contribution to the bispectrum from the coordinate transformation to conformal Fermi coordinates is of the same order as that from the inflaton-curvaton interaction term but does not cancel it.