Chiral Extrapolation of Light Mesons from the Lattice

The $\rho (770)$ meson is the most extensively studied resonance in lattice QCD simulations in two ($N_f=2$) and three ($N_f=2+1$) flavors. We analyze all available phase shifts from $N_f=2$ simulations using unitarized Chiral Perturbation Theory (UCHPT), and allowing not only for the extrapolation in mass but also in flavor, $N_f=2\to N_f=2+1$. The flavor extrapolation requires information from a global fit to $\pi\pi$ and $\pi K$ phase shifts from experiment. In the chiral extrapolations of $N_f=2$ simulations, the $K\bar K$ channel has a significant effect and leads to $\rho(770)$ masses surprisingly close to the experimental one. We also discuss recent results on the chiral extrapolations of $N_f=2+1$ lattice QCD data of the $\rho(770)$ meson and the $\sigma(600)$ that have become available.