## 30 September 2007

### Einstein notation for common vector operators

I keep getting tripped up by Einstein summation convention when combined with common vector operators like grad, div, and curl. So I put together a cheatsheet:

Please let me know if you find it useful, or if you find any mistakes.

I posted the cheatsheet using Scribd following some hints from Peter Chen. Within the $\LaTeX$ I finally found a way to show Page n of m. I also found I could use Mathematica's Signature command to doublecheck the two identities

Sum[Signature[{i,j,k}] d[i] d[j] f e[k], {i, 1,3}, {j,1,3}, {k,1,3}]
Sum[Signature[{i,j,k}] d[i] d[j] f[k], {i,1,3}, {j,1,3}, {k,1,3}]