Physics 260, Problem Set 7 due: Tuesday, November 15 at Noon Please place your completed problem sets in the “Physics 260” box in the physics department mailroom (Rutherford 103b). You are encouraged to discuss these problems with your colleagues, but you must write up your own solutions; the solutions you hand in should reﬂect your own work and understanding. Late problem sets will be penalized 10% per day late, unless an extension has been obtained from me or a TA before the due date. Reading : Chapter 18 of Bernstein et al. 1. Bernstein et al, Chapter 18, problem 5. 2. Bernstein et al, Chapter 18, problem 12. 3. Bernstein et al, Chapter 18, problem 13. 4. Consider a universe where there are two types of matter: dust and curvature. The density of matter evolves with time as ρ matter ( t ) = ρ0 R ( t )-3 and curvature evolves as ρ curvature =-kR ( t )-2 where ρ0 and k are constants. The Friedman equation is ( ˙ R R ) 2 = 8 πG 3 ( ρ matter + ρ curvature ) Before the discovery of dark energy this was believed to be a very good approximation to
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