  We study the collective behavior of Majorana modes in the vortex state of
chiral $p$-wave superconductors. Away from the isolated vortex limit, the
zero-energy Majorana states communicate with each other on a vortex lattice,
and form a coherent band structure with non-trivial topological character. We
revealed that the topological nature of Majorana bands changes sensitively via
quantum phase transitions in the two-dimensional (2D) systems, as sweeping
magnetic field or Fermi energy. Through the dimensional reduction, we showed
the existence of generic superconducting Weyl phase in a low magnetic field
region of quasi-2D-chiral superconductors.
