Gravitational, shear and matter waves in Kantowski-Sachs cosmologies

Zoltán Keresztes, Mats Forsberg, Michael Bradley, Peter K.S. Dunsby, László Gergely

Research output: Contribution to journalArticle

5 Citations (Scopus)


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 π /2 and share the same speed of sound.

Original languageEnglish
Article number042
JournalJournal of Cosmology and Astroparticle Physics
Issue number11
Publication statusPublished - Nov 25 2015


  • cosmological perturbation theory
  • gravitational waves / theory

ASJC Scopus subject areas

  • Astronomy and Astrophysics

Fingerprint Dive into the research topics of 'Gravitational, shear and matter waves in Kantowski-Sachs cosmologies'. Together they form a unique fingerprint.

  • Cite this