  Let $\mathscr{C}$ be an additive category with an involution $\ast$. Suppose
that $\varphi : X \rightarrow X$ is a morphism with kernel $\kappa : K
\rightarrow X$ in $\mathscr{C}$, then $\varphi$ is core invertible if and only
if $\varphi$ has a cokernel $\lambda: X \rightarrow L$ and both $\kappa\lambda$
and $\varphi^{\ast}\varphi^3+\kappa^{\ast}\kappa$ are invertible. In this case,
we give the representation of the core inverse of $\varphi$. We also give the
corresponding result about dual core inverse.
