  A conformally invariant model of two interacting massless particles in
Minkowski space was proposed by Casalbuoni and Gomis [1]. We generalize this
model to the case of de Sitter space from the perspective of geodesic distance,
in such a way that the resulting, generalized action reduces to the original
action in a limit that de Sitter radius goes to infinity. We analyze the
Hamiltonian formulation in accordance with Dirac's prescription for constrained
Hamiltonian systems and carry out its subsequent canonical quantization in
coordinate representation following DeWitt. As the result, we derive a
fourth-order differential wave equation for bilocal fields that, in the
infinite radius limit, reproduces one obtained in the original model for
Minkowski space case.
