To indicate the difference with matrices in regular space, it is conventional to indicate indices of regular-space vectors and matrices with Roman letters (like vi for the ith ...To indicate the difference with matrices in regular space, it is conventional to indicate indices of regular-space vectors and matrices with Roman letters (like vi for the ith component of vector v, and Aij for the ith row, jth column of matrix A), and those of Minkowski-space vectors and matrices with Greek letters - so we write xμ for the μth component of the four-vector ¯x, where μ can be 0, 1, 2,…
