Existence of positive radial solution for Neumann problem on the Heisenberg group

The existence of at least one positive radial solution of the Neumann problem − Δ H n u + R ( ξ ) u = a ( | ξ | H n ) | u | p − 2 u − b ( | ξ | H n ) | u | q − 2 u , is proved on the Heisenberg group H n , via the variational principle, where a ( | ξ | H n ) , b ( | ξ | H n ) are nonnegative radial functions and R ( ξ ) satisfies suitable conditions.