Coherence and Sakharov oscillations in the microwave sky
19968 pages
Part of Microwave background anisotropies. Proceedings, 31st Rencontres de Moriond, 16th Moriond Astrophysics Meeting, Les Arcs, France, March 16-23, 1996, 263-270
Contribution to:
- Published: 1997
e-Print:
- astro-ph/9612015 [astro-ph]
Report number:
- IMPERIAL-TP-96-97-8
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Abstract:
I discuss the origin of the "Sakharov oscillations" (or "secondary Doppler peaks") in standard angular power spectra of the Cosmic Microwave Background anisotropies calculated for inflationary models. I argue that these oscillations appear because perturbations from inflation have a set of properties which makes them "passive perturbations". All passive perturbations undergo a period of linear "squeezing" resulting in a dramatic degree of (classical) phase coherence of pressure waves in the photon-baryon fluid. This phase coherence eventually is reflected in oscillatory features in the angular power spectrum of the temperature anisotropies observed today. Perturbations from cosmic defects are "active perturbations" which have sharply contrasting properties. Active perturbations are highly non-linear and the degree of phase coherence in a given model reflects the interplay between competing effects. A large class of active models have non-oscillatory angular power spectra, and only an extremely exotic class has the same degree of coherence as is found in all passive models. I discuss the significance of the search for these oscillations (which transcends the testing of any given model) and take a critical look at the degree to which the question of coherence has been treated so far in the literature.References(15)
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