It never ceases to amaze me how well standard cosmology theory fits the ever increasing amount of data with precision. The results just released from the Atacama Cosmology Telescope (ACT) confirm that, even on the smallest scales, the predictions of the Lambda CDM universe preceded by an epic of inflation are correct. This study extracts data for L modes of The CMB between 500 and 10,000. (For a discussion on how these L modes refer to large and small scales of the universe see my posts here and here.)I will show three plots and interpret the results.
In the first plot above, we see results for the the power spectrum of the CMB plotted out to L = 3000 for their 148 GHz detector and their 218 GHz detector. As the top panel shows, the second through seventh peaks of the theoretical CMB power spectrum are confirmed with near exactness!
The next plot is also very interesting. Here we see the CMB power spectrum results out to L = 10000. The key is to notice the red versus the green line. The green line shows what the power spectrum should be if the only physics affecting the CMB photons were processes that occurred during and before the photons were emitted. (Called primary processes.) The red line is how the spectrum changes with the further assumption that, after the CMB photons were created, they have been affected by processes in the "foreground" like inverse Compton scattering from free electrons in galaxy clusters, gravitational lensing, etc... (Secondary processes.) This means the matter and other contents of the universe are interacting and affecting the CMB photons precisely as cosmologists have predicted they should.
The last plot shown is related to gravitational lensing. Here, A_L is a parameter that quantifies how much gravitational lensing the CMB photons have experienced since being emitted. A_L = 0 means they have experienced no lensing and A_L = 1 means they have experienced the exact amount of lensing predicted by the standard Lambda CDM cosmology. The red line is the results for when ACT data is combined with WMAP. As one can see, A_L = 1 is heavily favored over A_L = 0, and the lensing of the CMB has been "detected" by 2.8 sigma.
Conclusions: The Lambda CDM model initiated with a brief phase of inflation continues to fit the data with incredible precision. ACT has shown that the standard cosmology theory continues be confirmed down to the smallest scales of the universe. The prediction for the shape of the CMB power spectra arising from both primary and secondary sources fit the data quite well out to L=10000. Now all we need to do is hope some group like Planck finds a detection of B-modes and experimental verification of standard cosmology will be nearly complete.
(Image Credit: Das, S. et al.)
Sudeep Das, Tobias A. Marriage, & et al. (2010). The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave
Background Power Spectrum at 148 and 218 GHz from the 2008 Southern Survey E-Print arXiv: 1009.0847v1
