## Carlos Herdeiro

## Black holes and scalar fields

In the 1970s a set of uniqueness theorems for black holes in vacuum and electro-vacuum were established within general relativity. These theorems motivated the "no-hair conjecture" (Wheeler) stating that the end-point of gravitational collapse should be described by black holes characterized by only mass, electric charge and angular momentum, all of them global quantities with an associated Gauss law. I will discuss a new mechanism that makes possible the existence of stationary solutions in Einstein's gravity minimically coupled to scalar fields, describing black holes with scalar "hair". I will then discuss the implications for the no-hair conjecture.

João G. Rosa

**Fluctuation-dissipation dynamics in the early Universe**

Several open problems in modern cosmology, such as the early period of inflation or the present-day acceleration, can be addressed by postulating the existence of new scalar fields that drive expansion in different periods of the Universe’s evolution. I will explain how the dynamics of these fields is generically modified by interactions with the surrounding thermal plasma and is described by an effective Langevin equation that encodes the related effects of dissipation and thermal fluctuations. Finally, I will illustrate the cosmological impact of these effects in the case of inflationary models and cosmological phase transitions.