  Convective cores are the hydrogen reservoirs of main sequence stars that are
more massive than around 1.2 solar masses. The characteristics of the cores
have a strong impact on the evolution and structure of the star. However, such
results rely on stellar evolution codes, in which simplistic assumptions are
often made on the physics in the core. Indeed, mixing is commonly considered to
be instantaneous and the most basic nuclear networks assume beryllium at its
equilibrium abundance. Those assumptions lead to significant differences in the
central composition of the elements for which the timescale to reach nuclear
equilibrium is lower than the convective timescale. In this work, we show that
those discrepancies impact the nuclear energy production and, therefore, the
size of convective cores in models computed with overshoot. We find that cores
computed with instantaneous mixing are up to 30% bigger than those computed
with diffusive mixing. Similar differences are found when using basic nuclear
networks. Additionally, we observed an extension of the duration of the main
sequence due to those core size differences. We then investigated the impact of
those structural differences on the seismic modeling of solar-like oscillators.
Modeling two stars observed by Kepler, we find that the overshoot parameter of
the best models computed with a basic nuclear network is significantly lower,
compared to models computed with a full nuclear network. This work is a
necessary step in improving the modeling of convective cores, which is key to
determining accurate ages in the framework of future space missions such as
Plato.
