Physics Colloquium with Florian Kühnel

Abstract: What is the nature of dark matter? This unknown part of the Universe's
content is to the best of our current understanding about five times as
abundant as ordinary matter. Despite decades of intense research, its
characteristics still remain mysterious. Yet, it is essential for
explaining the structure in our Universe. The usual assumption is that
the dark matter comprises weakly-interacting particles. No evidence for
these has been found so far.

I will discuss another well-motivated dark matter candidate: black holes
produced in the early Universe, so-called primordial black holes. These
could have seeded any of the observed black holes, such as the
supermassive black holes in galactic centres and those detected through
gravitational waves (2017 & 2020 Nobel Prizes in Physics, respectively).
Furthermore, these macroscopic objects are natural dark matter
candidates as — a priori — they would not require new particles or
interactions; the very same mechanism which generates cosmic structure
may also generate black holes. To date, there are already numerous hints
for the existence of these fascinating objects, which I will touch upon
in this colloquium.