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Thermodynamics! (Density of States)

  1. Feb 4, 2010 #1
    1. The problem statement, all variables and given/known data
    Consider an isolated system consisting of a large number N of very weakly interacting localized particles of spin 1/2. Each particle has a magnetic moment [tex]\mu[/tex] which can point either parallel or antiparallel to an applied field H. The energy E of the system is then E = -(n1-n2)[tex]\mu[/tex]H, where n1 is the number of spins aligned parallel to H, and n2 is the number of spins aligned antiparallel to H.

    (a) Consider the energy range between E and E+[tex]\delta[/tex]E where [tex]\delta[/tex] is very small compared to E, but is microscopically large so that [tex]\delta[/tex]E>>[tex]\mu[/tex]H What is the total number of states [tex]\Omega[/tex](E) lying in this energy range?

    2. Relevant equations
    I really have no clue.

    3. The attempt at a solution
    I've been sitting with my small study group talking about this for an hour, and we're no closer to a solution than when we started. We've looked at the answer and it reminds us of the classical "drunken sailor" problem. Trust me when I say we've attempted this solution from every angle we can think of.
  2. jcsd
  3. Feb 4, 2010 #2
    How many states are there with a given/fixed energy, say, 0 or mu_H or mu*H or whatever it is?

    After you know that, you'll want to sum up that number for every energy between E and delta E. Since the gap is big enough (delta E >> mu H), you can transform the sum into an integral.
  4. Feb 6, 2010 #3
    Think about the possible number of states that exist between E and delta E. Like your drunken sailor problem, in which different ways could they move? How is that similar to your particles? Could you use a common formula for this situation as you might have used in the drunken sailor?
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