# What is the meaning of $\not{p}$ in physics?

I am reading Srednicki's QFT book in physics. On page 286, the formula $(45.16)$ has a notation $\not{p}$. What is the meaning of $\not{p}$ in physics? Thank you very much.

This is Feynman slash notation, viz. $\not{v}=\gamma^\mu v_\mu$ for any four-vector $v_\mu$ (in this case four-momentum).
It's called the Feynman slash, and it's shorthand for $\gamma^\mu p_\mu$, where $\gamma^\mu$ are the Dirac gamma matrices.