# Explain why the entropy is non-nul

1. Jan 23, 2015

### romeo31415

1. The problem statement, all variables and given/known data
Bonjour,

Given the hamiltonian

Show that

3. The attempt at a solution

I cannot explain why S=0

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Last edited: Jan 23, 2015
2. Jan 25, 2015

### MisterX

One thing you may be able do for is use the exact solution for the partition function $Z$ of the Ising chain.
$S = \partial_T k_B T \ln Z$

In other situations like this one may be able to start by using $S = k_B \ln \Omega(T, H)$, where $\Omega(T, H)$ is the number of states corresponding to T and H.

Last edited: Jan 25, 2015