Tuesday, September 7, 2010

Standard Cosmology Theory Is Confirmed By ACT For Smallest Scales In The Universe.

ResearchBlogging.orgIt 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


  1. So when are you guys going to give us our inch long theory of everything? =:) Actually, will the theory of everything replace the standard model? Or just make it more concise and less messy?

  2. Stan, I think it is still unknown whether a "theory of everything" will be an inch long or whether it will be huge. (Here's to hoping it is!) As you know, the standard model is actually long and messy as it is and perhaps the idea that the theory that best explains the universe is less messy is just a pie in the sky dream.

    I think the only thing we can hope for sure is that we will be able to extend the standard model in a way that makes good sense and will account for new data while making verified predictions.

    For example, supersymmetry extends the standard model in a straight forward way, fits all the data we could ever dream of :) (like it's extension string theory) and so once we can find a ways to falsify it we should be in business if it can pass such tests.

    Is supersymmetry less messy? Well, in principle at high energies it is, but at low energies where all symmetries are broken the thing is very messy indeed. Unfortunately, beautiful theories become ugly when we have to get them to fit nature.

  3. JS,

    Did you take a day off or wasted three days messing around with this article?

  4. Anonymous,

    I read this article last night so I almost made it a full 3 days off. :) (After watching Boise St. beat Virginia Tech.)

  5. JS,

    Good for you! Be one with where you are.

    Also, one does not learn of God by reading others' writings and interpretations, especially controlling interpretations. Explore on your own. Follow Your Bliss! per Campbell, and many others.

    Instead of using your knowledge to justify the nonsense of eons past, experience the Universe and write about it. There is a grace in that. The rest is arrogance. Hawking did is to write about what he thought, gracefully. It is God's problem how to deal with Hawking, not yours. That's all.

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