title: No black-hole theorem in three-dimensional gravity
abstract: A common property of known black-hole solutions in (2+1)-dimensional gravity is that they require a negative cosmological constant. To explain this, it is shown in this Letter that a (2+1)-dimensional gravity theory which satisfies the dominant energy condition forbids the existence of a black hole.
authors.affiliation: Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
authors.initials: D
authors.lastname: Ida