Estimate of the systematic error in tau decay due to duality violations
  With the help of a physically motivated ansatz, which is fitted to the data, we estimate the size of possible duality violations in hadronic tau decay. The result is that the uncertainty associated with these violations could impact the alpha_s determination from the total decay width at a level which we estimate to be \delta alpha_s(m_tau) \sim 0.003-0.010. Consequently, it cannot be neglected. 
Oscar Cata (Frascati), Maarten Golterman (SFSU) and Santiago Peris   (IFAE/UAB)