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A. Cooray (Caltech)
We have now clearly detected prominent wiggles in the angular power spectrum of cosmic microwave background temperature fluctuations resulting through acoustic oscillations in the photon-baryon plasma at early times. The oscillations in baryons are frozen in at the time of decoupling from photons and are expected to be present in the power spectrum of matter fluctuations today. Compared to CMB peaks, due to small baryon to cold dark matter density fractions of order 10% to 15% in currently flavored cosmologies, the oscillations in the matter power spectrum have amplitudes which are significantly smaller with amplitudes less than 10%. The oscillations are also present just above the scale at which non-linear gravitational evolution effects at low redshifts modify the linear power spectrum. The small amplitude and the non-linear effects provide a challenge for the detection of baryon oscillations.
We discuss various observational possibilities of baryon oscillations in the matter power spectrum and suggest that surveys sensitive to galaxy groups at redshifts around one may be better than surveys at low redshifts involving galaxies. We discuss cosmological and astrophysical uses of the baryon oscillation detections and possibilities to extract cosmological parameters from such observations . The proposed Dark Energy Explorer Telescope, a wide-field imaging mission to map a quarter of the sky at X-ray wavelengths, may provide an opportunity to study baryon oscillations in the matter power spectrum through both three-dimensional and two-dimensional clustering information.
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