Optical Conductivity in the Cuprates from Unparticle*

The optical conductivity of optimally doped cuprates above the superconducting dome exhibits a universal power law of the form, $\omega^{-\frac{2}{3}}$. Unparticles, scale-invariant matter with an algebraic propagator, is a candidate to explain this phenomenon. We explore the possibility of using unparticle to produce such power law behavior. We apply unparticle-gauge couplings and linear response theory at finite temperature to calculate the optical conductivity. We find that simply expanding a four-point correlation function using Wick's theorem is not sufficient to obtain the power law. We investigate the role played by non-Wick processes in determining the power law