Recent content by peterprp

Sorry, there is a mistake in the formula. The right-hand side is ## \sum_\vec{k} c^\dagger_{k+q}c_k ##

Hello, I can't understand where this formula ((8.5), Rössler, Solid State Theory, Springer) comes from (see attached file). The label l stands for the electrons positions and c and c dagger are the free electron creation and annihilation operator. This expression is used to write the linear...