De Sitter Invariance and a Possible Mechanism of Gravity
  It is believed that gravity will be explained in the framework of the existing quantum theory when one succeeds in eliminating divergencies at large momenta or small distances (although the phenomenon of gravity has been observed only at nonrelativistic momenta and large distances). We consider a quantum-mechanical description of systems of two free particles in de Sitter invariant quantum theory (i.e. the paper contains nothing but the two-body de Sitter kinematics). In our pure algebraic approach the cosmological constant problem does not arise. It is shown that a system can be simultaneously quasiclassical in relative momentum and energy only if the cosmological constant is not anomalously small. We explicitly construct the relative distance operator. The corresponding eigenvectors differ from standard ones at both, large and small momenta. At large momenta they ensure fast convergence of quasiclassical wave functions. There also exists an anomalously large (but finite) contribution from small momenta, which is a consequence of the fact that the cosmological constant is finite. We argue that gravity might be a manifestation of this contribution. 
Felix Lev