2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/77477For a theory $T$ in $L, T_σ$ is the theory of the models of $T$ with an automorphism $σ$. If $T$ is an unstable model complete theory without the independence property, then $T_σ$ has no model companion. If $T$ is an unstable model complete theory and $T_σ$ has the amalgamation property, then $T_σ$ has no model companion. If $T$ is model complete and has the fcp, then $T_σ$ has no model completion.Logictext