A form factor approach to finite temperature correlation functions in c=1 CFT

The excitation spectrum of specific conformal field theories (CFT) with central charge $c=1$ can be described in terms of quasi-particles with charges $Q=-p,+1$ and fractional statistics properties. Using the language of Jack polynomials, we compute form factors of the charge density operator in these CFTs. We study a form factor expansion for the finite temperature density-density correlation function, and find that it shows a quick convergence to the exact result. The low-temperature behavior is recovered from a form factor with $p+1$ particles, while the high-temperature limit is recovered from states containing no more than 3 particles.