2012/10/24 by Atsushi Naruko, Naruko, Atsushi, Yu-ichi Takamizu +3 · 3 citations
Decision Sciences · Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Phenomenology (hep-ph) #High Energy Physics - Theory (hep-th) #Scientific Computing and Data Management
paper · pdf · doi:10.48550/arxiv.1210.6525
openalex publication_date 2012/10/24 · openalex created_date 2019/12/26 · openalex updated_date 2026/07/28
We develop a theory of nonlinear cosmological perturbations on superhorizon scales for a multi-component scalar field with a general kinetic term and a general form of the potential in the context of inflationary cosmology. We employ the ADM formalism and the spatial gradient expansion approach, characterised by O(ε2), where ε=1/(HL) is a small parameter representing the ratio of the Hubble radius to the characteristic length scale L of perturbations. We provide a formalism to obtain the solution in the multi-field case. This formalism can be applied to the superhorizon evolution of a primordial non-Gaussianity beyond the so-called δN formalism which is equivalent to O(ε0) of the gradient expansion. In doing so, we also derive fully nonlinear gauge transformation rules valid through O(ε2). These fully nonlinear gauge transformation rules can be used to derive the solution in a desired gauge from the one in a gauge where computations are much simpler. As a demonstration, we consider an analytically solvable model and construct the solution explicitly.