  Proxy-SU(3) symmetry is an approximation scheme extending the Elliott SU(3)
algebra of the sd shell to heavier shells. When introduced in 2017, the
approximation had been justified by calculations carried out within the Nilsson
model. Recently our group managed to map the cartesian basis of the Elliott
SU(3) model onto the spherical shell model basis, proving that the proxy-SU(3)
approximation corresponds to the replacement of the intruder orbitals by their
de Shalit-Goldhaber partners, paving the way for using the proxy-SU(3)
approximation in shell model calculations. The connection between the
proxy-SU(3) scheme and the spherical shell model has also been worked out in
the original framework of the Nilsson model, with identical results.
