Theoretical Particle Physics in the Early Universe

This lecture focuses on topics of the early universe from a theoretical (astro)particle perspective with crosslinks to cosmology and collider physics. After a short review of the history of our universe, we will start our journey with puzzles the Big Bang provides for us and learn how inflation can solve them. We will get to know selected particle physics models that could accommodate such an inflationary epoch. In order to explain our own existence some mechanism had to create the observable baryon asymmetry. We will get to know different concepts to explain this observation (e.g. leptogenesis and baryogenesis) and introduce famous models of particle physics that could provide such a mechanism. We will discuss their phenomenology and testability. Naturally, we will also touch neutrino physics at this point and learn about sterile neutrinos. This will bring us also to another important topic of astroparticle physics, namely dark matter. We will discuss different mechanisms (e.g. freeze-out vs freeze-in) and candidates (e.g. WIMPS, FIMPS, axions, asymmetric dark matter). We will review theoretical calculations and discuss crucial effects that are important for a precise determination of the relic density. Moreover, we will learn about the complementarity of e.g. collider physics.

After successful completion of the module the students are familiar with the main open questions of astroparticle physics and possible theoretical concepts to solve those (e.g. inflation, leptogenesis, baryogenesis, sterile neutrinos, dark matter). This course will prepare students with the necessary background to carry out supervised research in this field and bridge to current research.

Quantum Field Theory 1 and / or Relativity, Particles and Fields.

As much as possible, all topics will be presented at the blackboard with step-by-step derivations. An interactive learning environment is welcome, students are encouraged to ask questions and initiate discussions during the lectures. Selected topics will be more deeply discussed during the weekly exercise sessions.

Blackboard

weekly exercises

The lecture will not strictly follow one textbook, but will refer for specific topics to the relevant chapters in the corresponding books.

Kolb, Turner: The Early Universe

Dodelson: Modern Cosmology

Mukhanov: Physical Foundations of Cosmology

Valle: Neutrinos in High Energy and Astroparticle Physics

Liddle: Cosmological Inflation and Large-Scale Structure

White: A Pedagogical Introduction to Electroweak Baryogenesis

There will be an oral exam of 30 minutes duration. Therein the achievement of the competencies given in section learning outcome is tested exemplarily at least to the given cognition level using calculation problems and comprehension questions.

For example an assignment in the exam might be:

• What motivates inflation?
• What is the slow roll approximation?
• Explain the Boltzmann equation for leptogenesis and the implications of washout.
• Compare the mechanisms of freeze-out and freeze-in.