Sekiguchi-Suwa theory revisited
  We present an account of the construction by S. Sekiguchi and N. Suwa of a cyclic isogeny of affine smooth group schemes unifying the Kummer and Artin-Schreier-Witt isogenies. We complete the construction over an arbitrary base ring. We extend the statements of some results in a form adapted to a further investigation of the models of the group schemes of roots of unity. 
Ariane M\'ezard, Matthieu Romagny and Dajano Tossici
math.NT math.AG