Gravitational, shear and matter waves in Kantowski-Sachs cosmologies
2015 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 11, 042Article in journal (Refereed) PublishedText
A general treatment of vorticity-free, perfect fluid perturbations of Kantowski-Sachs models with a positive cosmological constant are considered within the framework of the 1+1+2 covariant decomposition of spacetime. The dynamics is encompassed in six evolution equations for six harmonic coefficients, describing gravito-magnetic, kinematic and matter perturbations, while a set of algebraic expressions determine the rest of the variables. The six equations further decouple into a set of four equations sourced by the perfect fluid, representing forced oscillations and two uncoupled damped oscillator equations. The two gravitational degrees of freedom are represented by pairs of gravito-magnetic perturbations. In contrast with the Friedmann case one of them is coupled to the matter density perturbations, becoming decoupled only in the geometrical optics limit. In this approximation, the even and odd tensorial perturbations of the Weyl tensor evolve as gravitational waves on the anisotropic Kantowski-Sachs background, while the modes describing the shear and the matter density gradient are out of phase dephased by pi/2 and share the same speed of sound.
Place, publisher, year, edition, pages
Institute of Physics (IOP), 2015. no 11, 042
cosmological perturbation theory, gravitational waves / theory
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:umu:diva-113745DOI: 10.1088/1475-7516/2015/11/042ISI: 000365821200043OAI: oai:DiVA.org:umu-113745DiVA: diva2:889881