Asymptotic Behavior of Solutions to the Extension Problem for the Fractional Laplacian on Noncompact Symmetric Spaces

This work deals with the extension problem for the fractional Laplacian on Riemannian symmetric spaces \(G/K\) of noncompact type and of general rank, which gives rise to a family of convolution operators, including the Poisson operator. More precisely, motivated by Euclidean results for the Poisson semigroup, we study the long-time asymptotic behavior of solutions to the extension problem for \(L^1\) initial data. In the case of the Laplace-Beltrami operator, we show that if the initial data is bi-K-invariant, then the solution to the extension problem behaves asymptotically as the mass times the fundamental solution, but this convergence may break down in the non bi-K-invariant case.