# Death of Tullio Regge

Tullio Regge, a theoretical and mathematical physicist who made fundamental contributions to science worldwide, died on October 23, 2014, at the age of 83. A longer obituary can be found at http://sigrav.na.infn.it/tullio-regge.

Regge graduated from Turin, Italy, and received his PhD from Rochester, USA. He was at the Max Planck Institute for Physics where he worked with Werner Heisenberg. Then he was appointed to the chair of Relativity at Turin University. He also was a member of the Institute for Advanced Study, Princeton, USA, and a staff member at CERN. He returned to Italy to Turin University then to Turin Polytecnico.

Regge has worked in and across the two main revolutions in theoretical physics of the last century: general relativity and quantum mechanics.

In quantum mechanics, at the end of the 1950’s Regge proposed a truly innovative theory, using complex angular momenta in scattering theory to describe strong nuclear forces among elementary particles, known as the theory of Regge poles. This led to the model of Veneziano, which in turn promoted the development of String Theory.

In general relativity, in 1961 he proposed a new way to solve Einstein’s equations with his theory of discrete gravity, based on the `discretization’ of spacetime. This theory, known as Regge calculus was the first discrete gauge theory suitable for numerical simulation, and an early relative of lattice gauge theory. He and Ponzano developed a quantum version now known as the Ponzano-Regge model. This was the first of a series of state sum models for quantum gravity known as spin foam models. In mathematics, the model also developed into the Turaev-Viro model, an example of a quantum invariant. While at Princeton, Regge and Wheeler made fundamental contributions to the study of black holes, especially through what is known as the Regge-Wheeler equation.

He also worked on numerous other problems in general relativity, e.g. in quantum constrained systems, in quantum vortices and supergravity, and lower dimensional gravity.

He had many students and collaborators, who gratefully look back to his contributions and keep his memory alive. Italian physics in particular, and world theoretical physics has lost one of its most important characters.