A 3D shape with all straight edges and flat faces is a polyhedron. Other 3D shapes with least one curved surface are not polyhedra. A 3D shape with regular polygonal faces, meeting at equal angles, is ...
The ε perturbation around the Migdal transformation proposed by Martinelli and Parisi has been computed up to second order for the Ising model in two dimensions on a triangular lattice. Perturbation ...