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## Homework Statement

Simplify/Evaluate these expressions involving the Kronecker delta, using Einstein's summation convention:

a)[tex]\delta_{qr}[/tex][tex]\delta_{rp}[/tex][tex]\delta_{pq}[/tex]

b)[tex]\delta_{pp}[/tex][tex]\delta_{qr}[/tex][tex]\delta_{rq}[/tex]

## Homework Equations

[tex]\delta_{ij}[/tex]=0 when i =/= j

[tex]\delta_{ij}[/tex]=1 when i = j

## The Attempt at a Solution

a)[tex]\delta_{qr}[/tex][tex]\delta_{rp}[/tex][tex]\delta_{pq}[/tex]

=[tex]\delta_{qp}[/tex][tex]\delta_{pq}[/tex]

=[tex]\delta_{qq}[/tex] = 3 (summation over repeated q)

b)[tex]\delta_{pp}[/tex][tex]\delta_{qr}[/tex][tex]\delta_{rq}[/tex]

=[tex]\delta_{pp}[/tex][tex]\delta_{qq}[/tex]

=(3)(3)

=9

[Am I actually able to evaluate the [tex]\delta_{qr}[/tex][tex]\delta_{rq}[/tex] part before the [tex]\delta_{pp}[/tex] part, I mean you can't do that with matrices... :S]

Thank you