  We study the isospin mass differences of singly heavy baryons, based on a
pion mean-field approach. We consider both the electromagnetic interactions and
the hadronic contributions that arise from the mass difference of the up and
down quarks. The relevant parameters have been already fixed by the baryon
octet. In addition, we introduce the strong hyperfine interactions between the
light quarks inside a chiral soliton and the Coulomb interactions between the
chiral soliton and a heavy quark. The numerical results are in good agreement
with the experimental data. In particular, the results for the neutral mass
relations, which contain only the electromagnetic contributions, are in
remarkable agreement with the data, which implies that the pion mean field
approach provides a good description of the singly heavy baryons.
