Can you explain what this notation is: p^\mu = m u^\mu
What's the backslash, is that m times u or μ, is that exponentiation, which are vectors and which are scalars?
What's the backslash, is that m times u or μ, is that exponentiation, which are vectors and which are scalars?
mu is being used as an index (mu=0,1,2,3) on the components of the vectors p and u, m is a scalar representing rest mass.
This notation can be naturally extended to tensor products of vectors in the tangential and co-tangential spaces to the base manifold that is spacetime (simply called "tensors" by physicists): https://en.wikipedia.org/wiki/Einstein_notation