This is the equation for the luminosity of gravitational waves from a pair of rotating bodies, with quadrupole tensor Q.
Can anyone explain the meaning of the angled bracket notation here? I know that it usually denotes the inner product, but that usually looks like $<a,b>$.
I found a paper which describes the same thing in this way: 
But that doesn't really help me.
I know almost nothing about tensor mathematics... I just need to compute the summation given in the first equation, given the tensor Q. If someone could explain how, that would be very helpful.
Thanks!
It's Dirac or Bra-ket notation.
https://en.m.wikipedia.org/wiki/Bra%E2%80%93ket_notation