  We study a Majorana zero-energy state bound to a hedgehog-like point defect
in a topological superconductor described by a Bogoliubov-de Gennes (BdG)-Dirac
type effective Hamiltonian. We first give an explicit wave function of a
Majorana state by solving the BdG equation directly, from which an analytical
index can be obtained. Next, by calculating the corresponding topological
index, we show a precise equivalence between both indices to confirm the index
theorem. Finally, we apply this observation to reexamine the role of another
topological invariant, i.e., the Chern number associated with the Berry
curvature proposed in the study of protected zero modes along the lines of
topological classification of insulators and superconductors. We show that the
Chern number is equivalent to the topological index, implying that it indeed
reflects the number of zero-energy states. Our theoretical model belongs to the
BDI class from the viewpoint of symmetry, whereas the spatial dimension of the
system is left arbitrary throughout the paper.
