# The relation between spectral function and band structure

I am confused by the wavevector in spectral function A(k,w). How to understand this k for a periodic structure? And how is it related to the k (in first Brillouin Zone) we use in the band structure? If there are multibands, then in band structure for the same k we have several energies. To roughly reproduce spectral function, do I expect several peaks for the same k in A(k,w) or I need to unfold the multibands, and the multi energies for same k in band structure appear at different k in A(k,w)? Thanks!

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