Fall 2009 ASTR596/496NPA Fields

Preflight 3

Post Response on the course Compass site Due Friday, Oct. 2, noon

Reading:

Cyburt, Fields, & Olive 2003, Phys. Lett. B 567, 227 (astro-ph/0207583)
An actual research paper, by undisputed experts in the field (ahem). Don't worry so much about the statistical details here; the thing to get out of this is the basic discussion of where things stand in light of WMAP.

Recommended

For additional background on BBN, I strongly recommend you to take a look at

Boyd, Chapter 9
A good overview of cosmology in general, and big bang nucleosynthesis in particular.
Kolb & Turner, Chapter 4.
A very nice discussion of the basic physics, close to the one presented in class. However, the observational situation, and the strategies used to connect observations with theory, has changed considerably in the decade since this chapter was written.
Fields & Sarkar, Big-Bang Nucleosynthesis
This Mini-Review for the Particle Data Group; short and sweet, but a little dense, particularly if you are not armed with a particle physics background.

Questions

The questions are really meant to help guide your thinking as you read. You may find it helpful to look at the questions first and bear them in mind as you read.

  1. BBN Theory

    1. What assumptions are made in the usual ("standard") BBN calculation? All of these are at some level testable; which of these assumptions strikes you as the least secure and thus most important to test? Optional: How might you go about testing this assumption in the context of the BBN calculation?
    2. Explain how each of the four fundamental forces plays a key role in BBN.

  2. Alternative Universes
    Discuss how the universe would be different today if the proton and neutron masses were interchanged, that is, if mp > mn. For definiteness, let this be the only perturbation to the physics we know today: any other particle properties, masses, quantum numbers are the same. Be sure to mention the impact of this mass swap for BBN, for example, would there be a change in the amount of 4He produced, and if so, would there be more or less?

  3. Battle of the Baryons
    Precision CMB data have become available in recent years, with the release of WMAP data marking a major milestone. These data have already revolutionized cosmology, and will continue to do so. The impact of this for BBN is discussed in the brilliant paper by Cyburt, Fields, and Olive (see above). As noted above, don't get bogged down by the statistical detail, but read it to find out:

    1. How does a CMB-BBN comparison test cosmology? How does this comparison stand in light of WMAP? What are the main successes, outstanding problems?
    2. How has the CMB changed our approach to BBN? (What were things like before, how are things different now?)

  4. What material did you find difficult, confusing, or unclear? What material would you like to know more about?

  5. Other questions or comments?

Brian D. Fields
Last modified: Wed Sep 30 13:43:45 CDT 2009