(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

He says "choose the states with standard momentum k to be orthonormal", does he mean for example state with momentum (0,0,0,M1) and with momentum (0,0,0,M2) to be orthogonal or states with the same k^2 to be orthogonal if they have different k?

Also where he calculates in the next page, the "scalar product for [states of] arbitrary momenta" why is k' defined there the "same" as that in formula (2.5.12)? I dont get it...

2. Relevant equations

in the book...

3. The attempt at a solution

if the states of one given k^2 are orthogonal among each other then I dont get why k' as defined in page 66 could have the same square as k (that comes from p)... otherwise I dont get why we expect k' to be of the form of a "standard momentum" according to the way it is defined

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# Weinberg QFT p.65-66

Can you offer guidance or do you also need help?

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