In equation (2.5.47),(adsbygoogle = window.adsbygoogle || []).push({});

I am getting

U(R(\hat p) = e^{+i \phi J_3} e^{+i \theta J_2}

Instead of the "-" signs in the exponential. This makes a phase difference under parity and time reversal of a massless particle.

Is this one of the active rotation vs. passive rotation problem? If so, it is not clear to me.

Oops, I think, the problem may be with (2.4.27)

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

Dismiss Notice

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!

# Help with page 73 of Weinbergs QFT, vol.1

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