Cosmology

Course goals

Course aim:
Discuss the evidence for an expanding universe, Hubble’s law and the concept of a
cosmological redshift. Discuss the ideas of large-scale homogeneity and isotropy, and the
composition of the universe.
2. Explain the equivalence principle and write down the metric for open, closed and flat
(FLRW) universes. Write down Friedmann, fluid and acceleration equations. Use them to
predict the evolution of the universe in the presence of some perfect fluid.
3. Discuss the most important observations that establish the existence and the properties
of dark matter and dark energy and how they are modeled from the theoretical
perspective.
4. Explain the evidence in favor of primordial inflation, the process of nucleosynthesis and
the reach of our laws of physics.
5. Explain the classification of galaxies through their different properties. Distinguish
between elliptical and spirals and be able to fit our own Milky Way into this classification.
6. Have a basic understanding of how stellar population composition and evolutionary
processes determine the observed properties of galaxies.
7. Describe the scaling relations of galaxies, including those that relate to the supermassive
black holes at their centers.

Content

The course is divided in two parts. The first part of the course starts with a historical introduction
to the building of the cosmological model. It is followed by the introduction of key concepts in
Einstein’s theory of relativity, which then allows for the introduction of the Friedman-Lemaitre-
Robertson-Walker cosmological model for an expanding universe. Several observational probes
of cosmology will be introduced, such as the cosmic microwave background, supernovae and the
large-scale structure. From these, we will learn about the presence and nature of dark energy
and dark matter. We will conclude the first part with a description of the earliest moments of the
Universe and the building of a complete timeline for its history.

The second part of the course focuses on extragalactic astrophysics. The goal is to overcome the
assumption of galaxies as single points and understand the origin of their diversity. This diversity
presents some structure, which is quantified in so-called “scaling relations” for different galaxy
types. We will learn that some of these relations can be used for cosmological studies, thereby
connecting to the first part of the course. We will also discuss how they connect to the
supermassive black holes at the centers of galaxies. Finally, we will peek into the stellar
population composition of galaxies and some of the key evolutionary processes and understand
how they lead to observed colors and estimates of galactic distances.