Gribov Confinement and Chiral Perturbation Theory
  I discuss the chiral dynamics of Gribov's theory of confinement. At a critical coupling $\alpha_s^c$ the light quark vacuum undergoes a series of phase transitions which should be taken into account in the application of chiral perturbation theory. The Gribov theory offers a simple explanation of the value of the pion nucleon sigma term without need to invoke a large strange quark component in the nucleon. 
S. D. Bass