  We study the mechanisms which reduce the proton 1d(3/2)-1d(5/2) spin-orbit
splitting and the neutron 1f(7/2) subshell closure in 42Si. We use various
self-consistent mean field models: non-relativistic Skyrme-Hartree-Fock and
relativistic density-dependent Hartree-Fock. Special attention is devoted to
the influence of a tensor component in the effective interaction. It is found
that the tensor force indeed governs the reduction of the 1d proton spin-orbit
splitting. On the other hand, the reduction of the neutron 1f(7/2) subshell
closure is not clearly related to the tensor force.
