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Register a new userEvidence for Scale-Scale Correlations in the Cosmic Microwave Background Radiation
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Jesus Pando
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We perform a discrete wavelet analysis of the COBE-DMR 4yr sky maps and find a significant scale-scale correlation on angular scales from about 11 to 22 degrees, only in the DMR face centered on the North Galactic Pole. This non-Gaussian signature does not arise either from the known foregrounds or the correlated noise maps, nor is it consistent with upper limits on the residual systematic errors in the DMR maps. Either the scale-scale correlations are caused by an unknown foreground contaminate or systematic errors on angular scales as large as 22 degrees, or the standard inflation plus cold dark matter paradigm is ruled out at the $> 99%$ confidence level.
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Observations from the first flight of the Medium Scale Anisotropy Measurement (MSAM) are analyzed to place limits on Gaussian fluctuations in the Cosmic Microwave Background Radiation (CMBR). This instrument chops a 30arcmin beam in a 3 position pattern with a throw of $pm40arcmin$; the resulting data is analyzed in statistically independent single and double difference datasets. We observe in four spectral channels at 5.6, 9.0, 16.5, and 22.5~icm, allowing the separation of interstellar dust emission from CMBR fluctuations. The dust component is correlated with the IRAS 100~micron map. The CMBR component has two regions where the signature of an unresolved source is seen. Rejecting these two source regions, we obtain a detection of fluctuations which match CMBR in our spectral bands of $0.6 times 10^{-5} < Delta T/T < 2.2 times 10^{-5}$ (90% CL interval) for total rms Gaussian fluctuations with correlation angle 0fdg5, using the single difference demodulation. For the double difference demodulation, the result is $1.1 times 10^{-5} < Delta T/T < 3.1 times 10^{-5}$ (90% CL interval) at a correlation angle of 0fdg3.
The second flight of the Medium Scale Anisotropy Measurement (MSAM1-94) observed the same field as the first flight (MSAM1-92) to confirm our earlier measurement of cosmic microwave background radiation (CMBR) anisotropy. This instrument chops a 30arcmin beam in a 3 position pattern with a throw of $pm40arcmin$, and simultaneously measures single and double differenced sky signals. We observe in four spectral channels centered at 5.6, 9.0, 16.5, and 22.5~icm, providing sensitivity to the peak of the CMBR and to thermal emission from interstellar dust. The dust component correlates well with the IRAS 100~micron map. The CMBR observations in our double difference channel correlate well with the earlier observations, but the single difference channel shows some discrepancies. We obtain a detection of fluctuations in the MSAM1-94 dataset that match CMBR in our spectral bands of $Delta T/T = 1.9^{+1.3}_{-0.7}times 10^{-5}$ (90% confidence interval, including calibration uncertainty) for total rms Gaussian fluctuations with correlation angle 0fdg3, using the double difference demodulation.
In this note we investigate the effects of perturbations in a dark energy component with a constant equation of state on large scale cosmic microwave background anisotropies. The inclusion of perturbations increases the large scale power. We investigate more speculative dark energy models with w<-1 and find the opposite behaviour. Overall the inclusion of perturbations in the dark energy component increases the degeneracies. We generalise the parameterization of the dark energy fluctuations to allow for an arbitrary const ant sound speeds and show how constraints from cosmic microwave background experiments change if this is included. Combining cosmic microwave background with large scale structure, Hubble parameter and Supernovae observations we obtain w=-1.02+-0.16 (1 sigma) as a constraint on the equation of state, which is almost independent of the sound speed chosen. With the presented analysis we find no significant constraint on the constant speed of sound of the dark energy component.
We discuss the signature of the scale of short distance physics in the Cosmic Microwave Background. In addition to effects which depend on the ratio of Hubble scale H during inflation to the energy scale M of the short distance physics, there can be effects which depend on $dot{phi}^2/M^4$ where $phi$ is the {it classical background} of the inflaton field. Therefore, the imprints of short distance physics on the spectrum of Cosmic Microwave Background anisotropies generically involve a {it double expansion}. We present some examples of a single scalar field with higher order kinetic terms coupled to Einstein gravity, and illustrate that the effects of short distance physics on the Cosmic Microwave Background can be substantial even for H << M, and generically involve corrections that are not simply powers of H/M. The size of such effects can depend on the short distance scale non-analytically even though the action is local.
Cosmic string networks generate cosmological perturbations actively throughout the history of the universe. Thus, the string sourced anisotropy of the cosmic microwave background is not affected by Silk damping as much as the anisotropy seeded by inflation. The spectrum of perturbations generated by strings does not match the observed CMB spectrum on large angular scales (l<1000) and is bounded to contribute no more than 10% of the total power on those scales. However, when this bound is marginally saturated, the anisotropy created by cosmic strings on small angular scales l>2000 will dominate over that created by the primary inflationary perturbations. This range of angular scales in the CMB is presently being measured by a number of experiments; their results will test this prediction of cosmic string networks soon.
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