I can't get the first OPE in Polchinski's String Theory book. It is
:∂Xμ(z)∂Xμ(z)::∂′Xν(z′)∂′Xν(z′):=:∂Xμ(z)∂Xμ(z)∂′Xν(z′)∂′Xν(z′):
−4⋅α′2(∂∂′ln|z−z′|2):∂Xμ(z)∂′Xμ(z′):+2⋅ημμ(−α′2∂∂′ln|z−z′|2)2
∼Dα′22(z−z′)4−2α′(z−z′)2:∂′Xμ(z′)∂′Xμ(z′):−2α′z−z′:∂′2Xμ(z′)∂′Xμ(z′):
I can see how the first equality comes about from Eq. (2.2.9) and Polchinski's hint. However, I don't know how to get part of the asymptotic. Thanks to Prahar I got the first term. I definitely don't know how to get the other terms. I'm not really sure how to make use of his hint to Taylor expand. So if you want to just give a hint, that's fine, just please don't tell me to Taylor expand ;)
Any help would be greatly appreciated.
This post imported from StackExchange Physics at 2015-02-01 13:24 (UTC), posted by SE-user 0celo7