What if Planck's Universe isn't flat?

Philip Bull, Marc Kamionkowski

(Submitted on 6 Feb 2013)

Inflationary theory predicts that the observable Universe should be very close to flat, with a spatial-curvature parameter |Omega_K| < 10^-4. The WMAP satellite currently constrains |Omega_K| < 0.01, and the Planck satellite will be sensitive to values near 10^-3. Suppose that Planck were to find Omega_K to be non-zero at this level. Would this necessarily be a serious problem for inflation? We argue that an apparent departure from flatness could be due either to a local (wavelength comparable to the observable horizon) inhomogeneity, or a truly superhorizon departure from flatness. If there is a local inhomogeneity, then secondary CMB anisotropies distort the CMB frequency spectrum at a level potentially detectable by a next-generation experiment. We discuss how these spectral distortions would complement constraints on the Grishchuk-Zel'dovich effect from the CMB power spectrum at large angular scales in discovering the source of the departure from flatness.

Comments:	5 pages, 3 figures
Subjects:	Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
Cite as:	arXiv:1302.1617 [astro-ph.CO]
	(or arXiv:1302.1617v1 [astro-ph.CO] for this version)

Submission history

From: Philip Bull [view email]
[v1] Wed, 6 Feb 2013 23:44:30 GMT (195kb,D)

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Source...arXiv:1302.1617v1 [astro-ph.CO]