The symmetry energy and other open questions concerning effective functionals

The nuclear structure community is striving to determine a nuclear energy functional which is as universal and as accurate as possible. When a functional is determined by fitting free parameters, the constraints on these parameters coming from excited states (like the well-known giant resonances) are not, as a rule, imposed. This work shows that at least three constraints could be imposed on Skyrme functionals, by explaining the physical background and discussing their relevance.