Cosmology and particles in the early universe

Physics, Second Cycle
1 year
first or second
slovenian, english

Prof. Dr. Borut Bajc, Assist. Prof. Dr. Miha Nemevšek

Hours per week – 1. or 2. semester:
Content (Syllabus outline)

Homogenous and isotropic universe: redshift and Hubble’s law, the age of the universe, mass density, baryons and dark matter, the cosmological principle and FRWL space-time.

Expanding universe and thermal production: Friedman's equation, time evolution of the universe, big bang cosmology, temperature and number densities of particles, equilibrium thermodynamics.

Beyond equillibrium: Boltzmann equations for annihilation, nucleosynthesis, cosmic microwave background, foton decoupling and recombination, discovery of CMB, neutrino cosmology, N_eff and CMB fluctuations.

Dark matter: candidates for dark matter, longevity, production in the early universe, thermal freeze-out, freeze-in, conservation of entropy and its dilution with decays of long-lived particles.

Phase transitions: false vacuum decay, Euclidean action and bounce solutions, thin wall bubbles, stability of the universe in the SM, basics of finite temperature field theory, restoration of symmetries, electroweak baryogenesis, domain walls, cosmic strings, magnetic monopoles, Kibble's mechanism and Parker's bound.

Baryogenesis: baryon asymmetry, the basic idea and Sakharov's conditions, erasure of existing asymmetries, lepton number asymmetry, sphalerons and leptogenesis.

Axions: the strong CP problem, Peccei-Quinn symmetry and the Weinberg-Wilczek axion, axions and stars, hidden axions, axionic dark matter, production modes in the early universe.

Inflation and accelerated expansion: cosmological constant, initial conditions, flatness, homogeneity and magnetic monopoles. Model(s) of inflation, gravitational waves and scalar perturbations.


The early universe, Edward Kolb, Michael Turner, Frontiers in Physics, Westview Press (1994).
Modern Cosmology, Scott Dodelson, Academic Press; 1st ed.(2003).
Steven Weinberg, Cosmology, Oxford University Press; 1st edition (2008).
Viatcheslav Mukhanov, Physical Foundations of Cosmology, Cambridge University Press; 1st edition (2005).

Ta-Pei Cheng, Relativity, Gravitation and Cosmology: A Basic Introduction, Oxford University Press; 2nd ed. (2010).
Erick Weinberg, Classical Solutions in Quantum Field Theory: Solitons and Instantons in High Energy Physics, Cambridge University Press; 1st edition (2012).

Objectives and competences

Objectives. Students are acquainted with the basics of theory of physical processes in the early universe. They learn basic principles of cosmology, thermodynamics, energy content and creation of elementary particles, dark matter and light nuclei.

Competences. Understanding of thermal processes, cross-sections and high-temperature potentials.

Intended learning outcomes

Knowledge and understanding. Theoretical basics of gravitation and cosmology, thermodynamical processes in the early universe, behaviour of elementary particles and searches for new processes.

Application. Acquired knowledge will prepare

the students for research work and enable them to solve problems in a wider field of modern physics of elementary particles, physics of neutrinos, nucleosynthesis and baryogenesis.

Reflection. Musing on the theoretical approach and consistency of relativistic quantum models and their testability.

Transferable skills. Methodology and technical skills are useful in broad physics fields of particle physics and cosmology, complementary to the knowledge of astrophysics, nuclear physics and thermodynamics.

Learning and teaching methods

Lectures, exercises, seminar, homeworks and consultations.


seminar or instead colloqia or instead written exam (50%)
grading: 1-5 (fail), 6-10 (pass) (according to the Statute of UL)
oral exam (50%)

Lecturer's references

Prof. dr. Borut Bajc in doc. dr. Miha Nemevšek

B. Bajc, S. Lavignac and T. Mede, ``Resurrecting the minimal renormalizable supersymmetric SU(5) model,'' JHEP 1601 (2016) 044.

K. S. Babu, B. Bajc and V. Susič, A minimal supersymmetric E_6 unified theory,'' JHEP 1505 (2015) 108. M. Nemevšek, G. Senjanović in Y. Zhang,Warm Dark Matter in Low Scale Left-Right Theory,'' JCAP 1207 (2012) 006.
T. A. Chowdhury, M. Nemevšek, G. Senjanović and Y. Zhang, Dark Matter as the Trigger of Strong Electroweak Phase Transition,'' JCAP 1202 (2012) 029. A. Melfo, M. Nemevšek, F. Nesti, G. Senjanović and Y. Zhang,Inert Doublet Dark Matter and Mirror/Extra Families after Xenon100,'' Phys. Rev. D 84 (2011) 034009.