Laura's solution is here (as a .GIF image):

http://camoo.freeshell.org/20.15.gifHowever, it seems to me (on a casual reading) that it contains several major errors.

In particular,

is supposed to be antisymmetric, so the statement:

Quote:

is nonzero only if

c is the

index

is incorrect. Furthermore the equation:

manifestly makes no sense, as there are two free indices on the left, and none (or one, if

d is unsummed) on the right. Finally:

Quote:

and

is also wrong, since the two right hand sides are equal, but

.

I have posted my solution as Exercise [20.15]b; hopefully that is error-free!