We solve semiclassical Einstein equations in two dimensions with a massive
source and we find a static, thermodynamically stable, quantum black hole
solution in the Hartle-Hawking vacuum state. We then study the black hole
geometry generated by a boundary mass sitting on a non-zero tension 1-brane
embedded in a three-dimensional BTZ black hole. We show that the two geometries
coincide and we extract, using holographic relations, information about the CFT
living on the 1-brane. Finally, we show that the quantum black hole has the
same temperature of the bulk BTZ, as expected from the holographic principle.Comment: 10 pages, 2 figures, RevTex, ``point particle of mass \mu '' changed
with ``massive boundary source'' for better clarity. Action in (50) written
in Z_2 symmetric form. Appendix clarified. Minor corrections and references
added. Version accepted for pubblication in PRD15 (2006