A note on Masuoka's theorem for semisimple irreducible Hopf algebras

摘要

Masuoka proved (Proc Am Math Soc 137(6):1925-1932, 2009) that a finite-dimensional irreducible Hopf algebra H in positive characteristic is semisimple if and only if it is commutative semisimple if and only if the Hopf subalgebra generated by all primitives is semisimple. In this note, we give another proof of this result by using Hochschild cohomology of coalgebras.