  Symmetry energy coefficients of asymmetric nuclear matter are investigated as
the inverse of nuclear matter polarizabilities with two different approaches.
Firstly a general calculation shows they may depend on the neutron-proton
asymmetry itself. The choice of particular prescriptions for the density
fluctuations lead to certain isospin (n-p asymmetry) dependences of the
polarizabilities. Secondly, with Skyrme type interactions, the static limit of
the dynamical polarizability is investigated corresponding to the inverse
symmetry energy coefficient which assumes different values at different
asymmetries (and densities and temperatures). The symmetry energy coefficient
(in the isovector channel) is found to increase as n-p asymmetries increase.
The spin symmetry energy coefficient is also briefly investigated.
