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ternaus / quest-qmc

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t = 0 simluation gives wrong energy values. #8

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
At t = 0, problem becomes one-site and can be solved analytically.

Hamiltonian becomes:
H = U (n_up - 0.5) * (n_down - 0.5) - mu (n_up + n_down)

where n_up and n_down are numbers 0 or 1.

Let's consider the case mu = 0, U = -4. This gives 4 energy states.

E1 = U / 4 = -1
E2 = -U /4 = 1
E3 = -U / 4 = 1
E4 = U / 4 = -1

So at low temperature (big beta) total energy should go to -1, but instead in 
the simulation it goes to -2.

Similar business with non zero mu. Picture attached.

Original issue reported on code.google.com by iglovi...@gmail.com on 6 Nov 2013 at 7:46

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GoogleCodeExporter commented 9 years ago 
Total energy in the QUEST output is defined in some strange manner. Explanation 
is given in the https://code.google.com/p/quest-qmc/wiki/Output

Original comment by iglovi...@gmail.com on 7 Nov 2013 at 10:44