Recent content by Diracmai

The definition of Spectral Function need us to calculate the average value of commutator(retard or advance green function) according to all the occupied states. In the T=0 condition, we only need to compute the average value in the ground state. So, the function is independent of T. However, if...

In the Green Function theory. The Spectrum Function can be related to DOS. However, in the nonzero T condition, we can also define Spectrum Function. In the other hand, in my conception, DOS is the independent quantity which is determined by the system. So, does it mean DOS is actually a...

Ok! Actually, I also take the some viewpoint as you. In addition, I have another question.Generally, when we use Laudau phase transition theory, we always choose T and order parameter as free energy's variables. In this condition, it that means we hold other thermodynamic variable as constant...

At first, we need some state parameters(like P/T/V) to fully describe a system. And the order parameter is also a parameter which could describe the property of the system. However, in the Laudau theory, why it said that order parameter is an external parameter(not a independent variable)? Is...