Spin of a quickly moving electron

[Adam Lewis]

Suppose an electron crosses worldlines with me such our relative velocities $v$ are a substantial fraction of that of light. Say the electron's spin is in some state $\mid\psi\rangle$; for example the doublet state. I would like to know, or read references that describe how to calculate, what state I see in my frame. Thank you.

 

[jfy4]

You are looking for the Lorentz Boosts in QFT for a Dirac Spinor.

This is a pretty standard item to learn during the laborious process of learning QFT. It's actually one of the first things your learn. Some normal QFT books that treat this are: Peskin is standard, and I know it's in Magiorre too.