We construct nuclear energy density functionals in terms of
derivatives of densities up to sixth, next-to-next-to-next-to-leading
order (NLO). A phenomenological functional built in this way
conforms to the ideas of the density matrix expansion and is rooted
in the expansions characteristic to effective theories. It builds on
the standard functionals related to the contact and Skyrme forces,
which constitute the zero-order (LO) and second-order (NLO) expansions,
respectively. At N
LO, the full functional with density-independent
coupling constants, and with the isospin degree of freedom taken into
account, contains 376 terms, while the functionals restricted by the Galilean
and gauge symmetries contain 100 and 42 terms, respectively. For
functionals additionally restricted by the spherical, space-inversion, and time-reversal
symmetries, the corresponding numbers of terms are equal to 100, 60,
and 22, respectively.
B.G. Carlsson, J. Dobaczewski, M. Kortelainen
Date: October 6, 2008