• Summary
• Reading List
• Problem Set
• Answers

Week 12 - Cosmology III [11] [13]

Summary

I have attached homework due Friday. Becasue of the extension of the last set, I made this set only two problems.

Also attached: Peebles and Yu (1970). Even I was not yet a physicist when this was written. The paper talks about clumping on different mass scales, but it is now looked at as the first paper to sort out what the source of anisotropy of the CMB is. Read it for Thursday morning.

I'd like to offer advice on the sorts of questions you should be thinking about as you read. The detailed ones are great: what are the units of Figure 3? What is a chemical potential?... but also ask some broader ones. I have in mind

What is the main result?

For example, the main result of the Mather paper is that the universe was in good thermal equilibrium when it was hot enough to make e+ e- pairs.

Why did this happen when it did, not before or after?

What did this result allow to happen next? ie Who needed this?

I am reminded of an essay I read by Louis Alvarez, inventor of the bubble chamber. He said when he learned something new he asked himself five questions.

1. Do I believe this?
2. How do I know it?
3. Does it contradict anything else I believe?
4. What does it imply?
5. Do I believe this?

I can not promise that you will all win Nobel prizes if you ask those sorts of questions, but I'll take credit if you do!

Reading List

• ``Primeval Adiabatic Perturbation in an Expanding Universe''
  [ ADS, PDF ]
  REF: Peebles, P. J. E., Yu, J. T. 1970, Astrophys. J., 162, 815-+ .

Problem Set

Problem 1 -