Partition Function in One, Two, and Three Spatial Dimensions from Effective Lagrangian Field Theory
Figure 1
Ferromagnet in three spatial dimensions: Feynman diagrams of the low-temperature expansion of the partition function up to three loops . The vertices are numbered according to the piece of the effective Lagrangian they belong to. Vertices from the leading term are depicted by a filled circle. Loops in are suppressed by three powers of momentum.
