Nuclear sigma term in the Skyrme model: Pion-nucleus interaction

The nuclear sigma term is calculated including the nuclear matrix element of the derivative of the NN interaction with respect to the quark mass, m(q) partial derivative V-NN/partial derivative m(q). The NN potential is evaluated in the Skyrmion-Skyrmion picture within the quantized product ansatz. The contribution of the NN potential to the nuclear sigma term provides repulsion to the pion-nucleus interaction. The strength of the s-wave pion-nucleus optical potential is estimated including such a contribution. The results are consistent with the analysis of the experimental data.