Protecting the Primordial Baryon Asymmetry From Erasure by Sphalerons
  If the baryon asymmetry of the universe was created at the GUT scale, sphalerons together with exotic sources of $(B-L)$-violation could have erased it, unless the latter satisfy stringent bounds. We elaborate on how the small Yukawa coupling of the electron drastically weakens previous estimates of these bounds. 
James M. Cline, Kimmo Kainulainen and Keith A. Olive