Preflight 4

Post your response on the course Compass site

Due Friday, March 12, 12noon

Readings

Required

BDF (2011) Annual Review of Nuclear and Particle Science, 61, 47; The Primordial Lithium Problem

A review of the cosmic lithium problem by some crank.

Carroll (2006) Nature Physics 2 653-654; "Dark matter is real"

A short, elegant discussion of the bullet cluster and its implications for dark matter.

Questions

1. Primordial Nucleosynthesis: Concordance and Baryonic Dark Matter

   1. What is a baryon--explain as precisely as you can. Also explain it in nontechnical terms you would use with someone at, say, Kam's. Give an everyday example of baryonic matter.
   2. Explain briefly how observations of the light elements probe the baryonic content of the universe. Which light element is the most sensitive probe of the baryonic density?
   3. Before CMB anisotropies were observed, primordial nucleosynthesis provided the best evidence for non-baryonic dark matter in the universe. BBN still probes dark matter; how does this work?
   
   

2. Primordial Nucleosynthesis: The Lithium Problem

   1. State the primordial lithium (⁷Li) problem as clearly and simply as you can. What role do CMB anisotropies play in the lithium problem.
   2. There are three basic types of solutions to the lithium problem. What are they? For each, explain the assumptions at work, for example, what is assumed to be correct and what incorrect.
   3. What observations/experiments are needed to pin down the solution to the Li problem?
   4. In your view, what is the most promising solution to the Li problem? The least? Why?
   
   

3. Non-Baryonic Dark Matter: Existence and Indirect Evidence

   1. What is a WIMP?
   2. Why would the existence of (and especially the detection of) WIMPs be important for our understanding of particle physics?
   3. Why is it expected that dark matter might have weak-scale interactions (i.e., interactions similar to those of neutrinos)?
   4. How do observations of the bullet cluster, as discussed in the Carroll paper, provide indirect evidence for WIMPs? What alternatives explanations have been offered for the bullet cluster observations?
   
   
4. Other questions or comments?