Linked Cluster Expansions on non-trivial topologies

Linked cluster expansions provide a useful tool both for analytical and numerical investigations of lattice field theories. The expansion parameters in the interaction strength fields at neighboured lattice sites are coupled. They result into convergent series for free energies, correlation functions and susceptibilities. The expansions have been generalized to field theories at finite temperature and to a finite volume. Detailed information on critical behaviour can be extracted from the high order behaviour of the susceptibility series. We outline some of the steps by which the 20th order is achieved. (orig.)