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48 views

Significance of Landau's Roton concept

Is Roton a fundamental concept or there is more basic description of it in terms of other quasi particles?
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2answers
1k views

How to get an imaginary self energy?

The Lehman representation of the frequency-dependent single particle Green's function is $$G(k,\omega) = \sum_n \frac{|c_k|^2}{\omega - E_n + i\eta}$$ where $n$ enumerates all the eigenstates of the ...