In scalar-tensor gravity, the prototype alternative to general relativity hinted at by string theories, black holes do not obey the Jebsen-Birkhoff theorem. Non-isolated black holes can be highly dynamical and the teleological concept of event horizon is replaced by the apparent or trapping horizon. Dynamical solutions describing inhomogeneities embedded in a cosmological "background" and the phenomenology of their apparent horizons, which often appear and vanish in pairs, will be described. Isolated black holes, in contrast, are the same as in general relativity.

Place: Physics Dept. Meeting Room, 2th floor, IST