An interaction system has a finite set of agents that interact pairwise, depending on the current state of the system. Symmetric decomposition of the matrix of interaction coefficients yields the representation of states by self-adjoint matrices and hence a spectral representation. As a result,...

Introduction -- Set functions, capacities and games -- The core and the selectope of games -- Integrals -- Decision under risk and uncertainty -- Decisions with multiple criteria -- Dempster-Shafer and possibility theory.