Multiplicative Cauchy functional equation in the cone of positive-definite symmetric matrices
Annales Polonici Mathematici 82 (2003), 1-7 MSC: 39B52, 15A15, 39B22. DOI: 10.4064/ap82-1-1
We solve the multiplicative Cauchy equation for real functions of symmetric positive definite matrices under the differentiability restriction. The specialty of the problem lies in the symmetry of the multiplication.