ICTS

In 1986 A Zamolodchikov derived the remarkable result that in two-dimensional quantum field theories renormalization group flows are irreversible. This has strong consequences for theories of critical phenomena. Although a generalization to higher dimensions was proposed in 1988, it was not until 2011 that a proof was given in four dimensions. Since then other proofs, including in three dimensions, have been given which rely on ideas from quantum information theory. I will try to describe these with a minimum of technical detail.