Infeld–Van der Waerden symbols

The Infeld–Van der Waerden symbols, sometimes called simply Van der Waerden symbols, are an invariant symbol associated to the Lorentz group used in quantum field theory. They are named after Leopold Infeld and Bartel Leendert van der Waerden.

Source: Wikipedia — Infeld–Van der Waerden symbols (CC BY-SA 4.0)