Abstract
In the R+αR2 gravity theory, we show that if freely propagating massless particles have an almost isotropic distribution, then the spacetime is almost Friedmann-Robertson-Walker (frw). This extends the result proved recently in general relativity (α = 0), which is applicable to the microwave background after photon decoupling. The higher-order result is in principle applicable to a massless species that decouples in the early universe, such as a relic graviton background. Any future observations that show small anisotropies in such a background would imply that the geometry of the early universe were almost frw.
Original language | English |
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Pages (from-to) | 1309-1321 |
Number of pages | 13 |
Journal | General Relativity and Gravitation |
Volume | 27 |
Issue number | 12 |
DOIs | |
Publication status | Published - Dec 1995 |