hi there, In this wikipedia article https://en.wikipedia.org/wiki/Electromagnetic_tensor we have the following invariant : FαβFμη εαβμη = 8 E*B However the determinant is the square of this quantity divided by 8, i.e. ( E*B )2 . Now from the definition of the determinant for a 4x4 matrix , we have : MiaMjbMkcMid εijkl = εabcd det(M) [D] Now If I raise the expression 1/8 FαβFμη εαβμη to the power of 2, I would get : 1/8 FαβFμη εαβμη 1/8 FθλFσω εθλσω [E] Now If I compare this expression with equation D above, I see that some indices do not fall into the right place and also in Equation D, we have the expression for the determinant , however in expression E, we see that we have the matrix F multiplied 4 times much like in expression D (or is it rows or columns that get multiplied). We should also bear in mind that the magnetic field is the spatial part of F and that the electric field is the time part : Fi0 = Ei and Fijεijk = Bk How can we reconcile expression E with D then ? or is this an error perhaps ?