  The origin of the matter-antimatter asymmetry of the universe remains one of
the outstanding questions yet to be answered by modern cosmology and also one
of only a handful of problems where the need of a larger number of degrees of
freedom than those contained in the standard model (SM) is better illustrated.
An appealing scenario for the generation of baryon number is the electroweak
phase transition that took place when the temperature of the universe was about
100 GeV. Though in the minimal version of the SM, and without considering the
interaction of the SM particles with additional degrees of freedom, this
scenario has been ruled out given the current bounds for the Higgs mass, this
still remains an open possibility in supersymmetric extensions of the SM. In
recent years it has also been realized that large scale magnetic fields could
be of primordial origin. A natural question is what effect, if any, these
fields could have played during the electroweak phase transition in connection
to the generation of baryon number. Prior to the electroweak symmetry breaking,
the magnetic modes able to propagate for large distances belonged to the U(1)
group of hypercharge and hence receive the name of hypermagnetic fields. In
this contribution, we summarize recent work aimed to explore the effects that
these fields could have introduced during a first order electroweak phase
transition. In particular, we show how these fields induce a CP asymmetric
scattering of fermions off the true vacuum bubbles nucleated during the phase
transition. The segregated axial charge acts as a seed for the generation of
baryon number. We conclude by mentioning possible research venues to further
explore the effects of large scale magnetic fields for the generation of the
baryon asymmetry.
