Large-scale homogeneity vs. small- scale inhomogeneity: testing ...
Large-scale homogeneity vs. small- scale inhomogeneity: testing ...
Large-scale homogeneity vs. small- scale inhomogeneity: testing ...
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• Cosmological principle: Universe is<br />
homogeneous and isotropic<br />
<strong>Large</strong>-<strong>scale</strong> Cosmic Homogeneity<br />
− Homogeneous: different regions of the<br />
Universe have the same mean density<br />
− Isotropic: looks the same in all<br />
directions<br />
• Allows use of Friedmann-Robertson-<br />
Walker (FRW) spacetime metric<br />
• Need FRW to convert redshifts to<br />
distances, via Friedmann eqn:<br />
2<br />
H<br />
2<br />
H0 = ! Ra"4 + ! Ma "3 + ! ka "2 + ! #<br />
01/18/2013<br />
Morag I. Scrimgeour<br />
Springel et al. (2005)<br />
4