Homework 7 : Dark Energy and the Early Universe

(due at the start of class on the 10^th December 2002)

1. [5 points] State and briefly explain two pieces of evidence that “dark energy” dominates the universe at the present time.

2. [5 points] Muons have a mass of M=1.9´10^-28 kg. Using the formula given in the class, calculate the threshold temperature for muons.

3. [5 points] It is thought that significant quantities of gravitational radiation were created at the end of the Planck Epoch and the end of the Inflationary Epoch. By considering the redshifting effect of the expanding universe, explain why it would be much easier (but still quite difficult) to detect the gravitational waves resulting from the Inflationary Epoch.

4. [5 points] What is the “relic problem”? Explain how the idea of inflation solves this problem.

5. [5 points] In the normal big-bang model, time itself has a beginning. How does the “chaotic inflation” model get around this conclusion?

6. [5 extra credit points] Do you believe that inflation really occurred? Do you think that the solution to the cosmological “problems” lies elsewhere? Feel free to say what you think… any good attempt at an answer will get full credit!