  We evolve stellar models to study the rotational profiles of the
pre-explosion cores of single massive stars that are progenitors of core
collapse supernovae (CCSNe), and find large rotational shear above the iron
core that might play an important role in the jet feedback explosion mechanism
by amplifying magnetic fields before and after collapse. Initial masses of 15
Mo and 30 Mo and various values of the initial rotation velocity are
considered, as well as a reduced mass-loss rate along the evolution and the
effect of core-envelope coupling through magnetic fields. We find that the
rotation profiles just before core collapse differ between models, but share
the following properties. (1) There are narrow zones of very large rotational
shear adjacent to convective zones. (2) The rotation rate of the inner core is
slower than required to form a Keplerian accretion disk. (3) The outer part of
the core and the envelope have non-negligible specific angular momentum
compared to the last stable orbit around a black hole (BH). Our results suggest
the feasibility of magnetic field amplification which might aid a jet-driven
explosion leaving behind a neutron star. Alternatively, if the inner core fails
in exploding the star, an accretion disk from the outer parts of the core might
form and lead to a jet-driven CCSN which leaves behind a BH.
