I can't quite place it
Link doesn't work.
sorry, does it work now?
Yeah. I don't know what it is, but it looks like something in relativistic quantum mechanics.
It looks like an altered form of the complex fourier series. BAsed on that i think it deals with energy distribution across frequencies, but beyond that i am not sure. The first line uses dummy indices in a form similar to the notation uses in tensor calculus, so i think chroot may be right.
It's the general solution of the wave equation for a (classical) string with tension [tex]\alpha'[/tex] and length L. Compare Polchinski's String Theory, equation 1.3.22.
well, we were way off.
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