# The molecular field approximation

MFA

$$\hat{A}\hat{B}\approx \hat{A}\langle\hat{B}\rangle+\hat{B}\langle\hat{A}\rangle-\langle\hat{A}\rangle\langle\hat{B}\rangle$$

What this mean physically? What we neglect here?

If I calculate Neel temperature using this method $$T_N^{MFA}$$ and using RPA method $$T_N^{RPA}$$ is there some relation between those temperatures?

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