Solution
= Solution
\b[Covered by the official notes:] explicit field contraction and Lorentz invariance as a tensor scalar (PDF pp. 15–16; handwritten pp. 10–11).<Symmetry and Relativity 2011 Exam Solution Notes>[PDF pp. 15–16; handwritten pp. 10–11: explicit field contraction and Lorentz invariance as a tensor scalar]{ref}