  Background: Average energies of nuclear collective modes may be efficiently
and accurately computed using a non-relativistic constrained approach without
reliance on a random phase approximation (RPA). Purpose: To extend the
constrained approach to the relativistic domain and to establish its impact on
the calibration of energy density functionals. Methods: Relativistic RPA
calculations are compared against the predictions of the corresponding
constrained approach using two accurately calibrated energy density
functionals. Results: We find excellent agreement-at the 2% level or
better-between the predictions of the relativistic RPA and the corresponding
constrained approach for magic (or semi-magic) nuclei ranging from 16O to
208Pb. Conclusions: An efficient and accurate method is proposed for
incorporating nuclear collective excitations into the calibration of future
energy density functionals.
