Symmetry group analysis is a powerful tool in the study of differential equations, in particular for determining invariance properties, constructing special solutions or deriving conservation laws in systems of physical interest. The theory of algebras of generalized functions (in the sense of Colombeau) efficiently deals with linear and nonlinear partial differential equations which involve singularities, with applications in such diverse fields as mathematical physics (general relativity, nonsmooth mechanics), nonlinear distributional geometry or global analysis. Fractional calculus extends...