Transport coefficients and nonextensive statistics

We discuss the basic transport phenomena in gases and plasmas obeying the $q$-nonextensive velocity distribution (power-law). Analytical expressions for the thermal conductivity ($K_q$) and viscosity ($\eta_q$) are derived by solving the Boltzmann equation in the relaxation-time approximation. The available experimental results to the ratio {$K_q$}/$\eta_q$ constrains the $q$-parameter on the interval $0.74 \leq q \leq 1$. In the extensive limiting case, the standard transport coefficients based on the local Gaussian distribution are recovered, and due to a surprising cancellation, the electric conductivity of a neutral plasma is not modified.