Extension of Finite Mass

In Lecture 22 we saw that S_μ = (u*σ_μu) transforms like a 4-vector. This means that, for arbitrary B_μ, B μ   ( u*   σ μ   u ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429492501/e6a0c676-1f8d-4684-97a0-6bf3353f7ce0/content/eq456.tif"/>