Spin fluctuation effects in the normal state of Hubbard systems

We obtain and discuss the self-energy and the renormalized electronic structure of the normal state in strongly correlated electron systems within the pseudogap regime. The considered effective potentials are found from spin fluctuations within a Hubbard single band model. We find that the self-energy tends to violate the Luttinger theorem as the bandwidths are narrowed and also as the Hubbard U increases. This is an indication that a new fundamental state should be used to describe the system under these conditions. We have used an antiferromagnetic fundamental state and found that in this case the new self-energy does satisfy the Luttinger theorem.