Mukhanov-Sasaki equation in a manifestly gauge-invariant linearized cosmological perturbation theory with dust reference fields

• DOI: 10.1103/physrevd.102.023524
• Publication Date: 2020-07-14T18:43:41Z
• Authors: Kristina Giesel; Laura Herold; Bao-Fei Li; Parampreet Singh
• Keywords: Friedmann–Lemaître–Robertson–Walker metric; Cosmological perturbation theory

The aim of this article is to understand the role dust reference fields, often also called clocks, on cosmological perturbations around a flat FLRW universe. We derive Mukhanov-Sasaki (MS) equation for Brown-Kuchar (BK) and Gaussian models, which both consider four fields as fields. reduced phase space Dirac observables, that gauge-invariant part theory, constructed by means an observable map applied all elementary variables coupled system, consisting gravity, massive scalar field degrees freedom. evolution these observables governed so physical Hamiltonian can be derived once set are chosen differs each model. First, well corresponding equations motion full general relativity. Then from this, version background contain fingerprint Afterwards we study linear metric using scalar-vector-tensor decomposition MS variable in formalism expressed terms observables. involves additional contributions understood back reactions These were absent if energy momentum density their vanishing. nature correction suggest BK contribute differently. Using numerical simulations behavior during inflation.