In the quant paper “SWAP AND CAP/FLOORS WITH FIXING IN ARREARS OR PAYMENT DELAY”, section 4 (Ibor-with-Delay), first paragraph reads
for caps, p(x) = (x - K)^x with K the strike.
I think you mean to use plus sign to indicate positive payoff for cap; that is,
for caps, p(x) = (x - K)^+ with K the strike.
I am reading the online version at http://developers.opengamma.com/quantitative-research/In-Arrears-and-Payment-Delay-Swaps-and-Caps-OpenGamma.pdf