Notation for contractions with gamma matrices
In the study of Dirac fields in quantum field theory, Richard Feynman invented the convenient Feynman slash notation (less commonly known as the Dirac slash notation[1]). If A is a covariant vector (i.e., a 1-form),
![{\displaystyle {A\!\!\!/}\ {\stackrel {\mathrm {def} }{=}}\ \gamma ^{0}A_{0}+\gamma ^{1}A_{1}+\gamma ^{2}A_{2}+\gamma ^{3}A_{3}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/b19d66f2f5a1184d2f03bf4793c0541b9a738818)
where γ are the gamma matrices. Using the Einstein summation notation, the expression is simply
.