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Second quantization

What is the physical interpretation of the operator a_\alpha and what is the effect of a_\alpha on a given state |\alpha_1\alpha_2\dots\alpha_n\rangle_{\mathrm{AS}} ? Consider the following matrix element \begin{equation} \langle\alpha_1\alpha_2 \dots \alpha_n|a_\alpha|\alpha_1'\alpha_2' \dots \alpha_m'\rangle \tag{11} \end{equation} where both sides are antisymmetric. We distinguish between two cases. The first (1) is when \alpha \in \{\alpha_i\} . Using the Pauli principle of Eq. (6) it follows \begin{equation} \langle\alpha_1\alpha_2 \dots \alpha_n|a_\alpha = 0 \tag{12} \end{equation} The second (2) case is when \alpha \notin \{\alpha_i\} . It follows that an hermitian conjugation \begin{equation} \langle \alpha_1\alpha_2 \dots \alpha_n|a_\alpha = \langle\alpha\alpha_1\alpha_2 \dots \alpha_n| \tag{13} \end{equation}