AdS$_3$/AdS$_2$ degression of Fronsdal fields

We analyze the Kaluza-Klein type procedure in AdS$_3$ space called the dimensional degression. The topological theory of the Fronsdal field in AdS$_3$ is reformulated in terms of the fields propagating in AdS$_2$. We find that the Fronsdal field in AdS$_3$ leads to finitely many Kaluza-Klein modes. Namely, the obtained spectrum is the massive Klein-Gordon and Proca fields in AdS$_2$. The result is derived by using the specific mode expansion, the gauge fixing, and 2-dimensional Schouten identities.