**3 December 2020***Mathematical and Theoretical Physics Seminar*

Location: **Jacobs University Bremen - Online **

When: 3.12.2020, 13:00 CET

**Speaker:** Betti Hartmann (USP, Brazil & Uni Oldenburg & Jacobs University Bremen)**Title:** Scalar field stars and black holes with scalar hair

Abstract: With direct gravitational wave detections as well as the first

picture of the shadow of a black hole, there exists now complementary

observational evidence that black holes - a priori a theoretical

prediction of the best theory of gravity that we have to this day,

General Relativity - do, indeed, (seem to) exist in the universe. These

recent observations show that the corresponding black holes can be

extremely well matched to the Kerr solution, a vacuum solution of the

Einstein equation that describes a black hole determined only by its

mass and angular momentum. Observable black holes hence seem to be very

simple objects that carry no additional structure ("hair"). However,

models appearing in theories that try to explain e.g. the nature of dark

energy or the inflationary epoch in the primordial universe as well as

recent studies within the gauge/gravity duality contain black hole

solutions that often carry hair. Moreover, stars made out of scalar

fields - so-called "boson stars" - provide viable alternatives to

supermassive black holes.

In this talk, I will discuss boson stars and black holes that carry

non-trivial scalar hair, respectively. I will motivate the models

discussed and explain their applications.

More details can be found here.