The Universal Deformation of the Witt Ring Scheme
  We determine the universal deformation over reduced base rings of the Witt ring scheme enhanced by a Frobenius lift and Verschiebung. It agrees with a q-deformation earlier introduced by the second author, for which we also give a simpler description. In the appendix we discuss a Witt vector theory for ind-rings which may be of independent interest. 
Christopher Deninger and Young-Tak Oh
math.RA