Do hyperbolic harmonics exist?

[gerald V]

TL;DR

Do functions comparable to the spherical harmonics exist in case of sign changes in the algebra?

With the algebra so(3) are associated the spherical harmonics. I would assume that comparably with the algebra so(2,1) are associated functions that can be addressed as hyperbolic harmonics. But I nowhere found any reference to them. Do they exist and if so, where can they be found?

Thank you very much in advance.

 

[DrDu]

https://projecteuclid.org/journals/...of-non-compact-groups-in-a/cmp/1103840513.pdf