I am reading a nice book (Quarks and Leptons, by Halzen and Martin) about particle physics. It states that the general form of the propagator of a virtual particle is:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]

\dfrac{i\sum_{\text{spins}}}{p^2 - m^2}

[/tex]

I see that this is the case for the Dirac propagator:

[tex]

\dfrac{i(\displaystyle{\not}{p} + m)}{p^2 - m^2} = \dfrac{i\sum_{s}u_s(p)\bar{u}_s(p)}{p^2 - m^2}

[/tex]

but how can I prove that always holds?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Virtual particle propagators in QFT

**Physics Forums | Science Articles, Homework Help, Discussion**