Black matter

This course describes the theoretical and observational foundations of the so-called cosmological dark matter problem. The latter manifests itself through gravitational effects at different astrophysical scales, from the scale of galaxies to cosmological scales (the observable universe as a whole). It constitutes about 85% of the total matter in the universe, and it is excluded that it is composed of the elementary particles characterizing the known ordinary matter. The course will focus on potential solutions to this problem connecting the infinitely small (elementary particles) to the infinitely large (large scale universe).

The objectives are (1) to awaken the students to a modern and major problem of fundamental physics in a cosmological context, (2) to transmit to them an advanced theoretical corpus allowing them to have a solid basis of understanding of this problem, (3) to teach them to make use of several fundamental concepts coming from several disciplines to deal with a problem which is interdisciplinary in nature (classical mechanics, statistics, fluids, thermodynamics, quantum field theory, general relativity, etc.).

Prerequisites*:

Differential and integral calculus, differential equations, classical mechanics, statistical mechanics, fluid mechanics, thermodynamics, special relativity.

Recommended Prerequisites:

Particle physics, elements of general relativity and cosmology (homogeneous universe).

Final exam: Written exam (3 hours).

This course describes the theoretical and observational foundations of the so-called cosmological dark matter problem. The latter manifests itself through gravitational effects at different astrophysical scales, from the scale of galaxies to cosmological scales (the observable universe as a whole). It constitutes about 85% of the total matter in the universe, and it is excluded that it is composed of the elementary particles characterizing the known ordinary matter. Despite its mysterious origin, its properties are nevertheless fundamental to understand the formation of galaxies.

The course will detail the gravitational signatures of dark matter at different astrophysical scales, and will explore a scenario in which it would find its origin in exotic particles thermally produced in the primordial universe: thermal production, chemical and kinetic decoupling in the primordial universe, direct and indirect searches, and discussion of alternative scenarios, will be the main points addressed. The aim is to connect the infinitely small to the infinitely large in a very concrete way. The course will thus give an overview of the state of the art by confronting relatively recent theoretical developments and observational constraints, reporting on a research topic that is still exploratory and that calls for extremely varied physics notions. The course will be given at the blackboard (or in videoconference if necessary), where many calculations will be detailed, without slides.