Recombination epoch

When comparing these results with observations it should be kept in mind that the line strengths in some cases are sensitive to, for example, the density distribution of the ejecta. This is especially true for the Na I, Mg I], and [Si I] lines, for which the ionization is dominated by photoionization by diffuse UV emission, mainly from O I recombination lines. This is sensitive to both the density and to resonance line blocking in the UV. At epochs less than -450 days the density in the core can be so high that forbidden lines like the [O I] and [Si I] lines are optically thick, resulting in P-Cygni type absorptions also for these lines. 

WMAP also found a TE (temperature-polarization) cross-correlation. At small angles the TE amplitude was perfectly consistent with the standard picture of the recombination era. But there was also a large angle TE signal that gave an estimate for the electron scattering optical depth since reionization r = 0.17 0.04. Based on this the epoch of reionization was 200 million years after the Big Bang. 

Finally we must deal with perturbations not to pressureless matter but to baryons and photons. At early times, the universe is radiation dominated, and pr = p/3 for radiation. Before the epoch of recombination, the same Thomson scattering processes that keep the baryons ionized also keep the radiation tightly-coupled to the ions. The nuclei have pressure pb = (5kT/dmp)p [Pg.182]

Pitch-scale modification is performed by recombining the frames on epochs which are set at... 

Pitch-scale modification is performed 1 recombining the frames on epochs that are set at different distances apart from the analysis epochs, as shown in Figure 14.3. All other things being equal, if we take for example a section of speech with an average pitch of 100 Hz, the epochs will lie 10 ms apart. From these epochs we perform the analysis and separate the speech into the pitch-synchronous frames. We can now create a new set of epochs that are closer together, say 9 ms apart. If we now recombine the frames by the overlap-add method, we find that we have created a signal that now has a pitch of 1.0/0.009 = 111 Hz. Conversely, if we create a synthetic set of epochs that... 

Since during its evolution beyond the horizon, any dynamical change in the fluctuation spectra was causally forbidden, the fluctuating gravitational field experienced by the recombining hydrogen atoms was directly related to the fluctuation spectra of the inflationary epoch, determined by the quantum fluctuations of the field(s) of that era. This observation leads promptly to the conclusion that the spectra should be very close to the ZeTdovich-Harrison spectra. Detailed features of the power spectra seem to effectively rule out some of the concurrent inflationary models. 

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