Dark Matter (Lecture & Seminar 2025)

When: Tuesday 08:15 – 09:45, Summer Semester 2025

Where: Room 2.28.2.011, University of Potsdam, Golm

Who: Dr. Marcel S. Pawlowski

Slides and literature (password protected): AIP Cloud

Description

The course will provide an introduction to the topic of Dark Matter, its background, and current debates around its nature. It will start with a historical overview of how the concept of dark matter was developed. This will be followed by summaries of different lines of observational evidence pointing to its existence, ranging from the dynamics of galaxies, over clusters of galaxies, to cosmological scales. We will then discuss what dark matter might be, ranging from early baryonic dark matter candidates and why they were ruled out, to non-baryonic particle dark matter candidates. In addition, the successes and problems of an alternative approach of modifying the laws of gravity in the low-acceleration regime will be presented. After a discussion of ongoing direct and indirect detection experiments for dark matter, we will spend the rest of the course on the current ‘standard’ model of cosmology Lambda Cold Dark Matter (LCDM), ranging from its implementation on cosmological simulations, possible other detection avenues revealed by simulation predictions, and finally problems on small scales, and possible solution to these.

Set-up of the course

Since the topic of Dark Matter  is one of active scientific research, and its nature is an as-yet unsolved question, the focus of the course will not only be on merely disseminating. Instead, its aim is to provide an understanding of the process of scientific research, provide a glimpse at ongoing scientific debates, and an introduction of the current status of research. 

The course will consist to equal parts of a lecture component introducing concepts, methods, and results, as well as a more interactive component in which the students are asked to contribute. For this, we will have open discussions on the topics introduced in the lecture. In addition, each student will have to present and (co-)lead one such session. This could either be a typical seminar talk of ~20-30 min presenting a classic paper in the field (see below for an incomplete list), or the preparation of a discussion session with the class consisting of a brief (~10 min) introduction followed by leading a debate on a question related to dark matter. For the former, up to two students can team up, while for the latter, two-three students can team up (but will need to moderate or present opposing views during the discussion). The seminar talks will be scheduled in the first ~half of the semester, the discussions in the second half.

Requirements for passing

To successfully pass the course, the students will be required to 

• attend most lectures and presentations,
• actively contribute to discussions by asking questions or offering answers, and 
• present a talk or lead a discussion in one session.

There will be no grades and no exercise classes in this course.

Learning Outcomes

At the end of this course, you should be able to

• explain the different lines of evidence for a missing mass problem / for dark matter
• summarize different dark matter candidates
• explain why which candidates are viable and others not
• discuss the main pros and cons of the alternative modified gravity approach MOND
• Talk about different avenues by which the existence of dark matter could be verified experimentally or observationally
• Introduce the LCDM model, the basics of cosmological simulations, and current open issues such as some small-scale problems.

Some Possible Topics for Talks or Discussion Sessions

Talk topics:

• Analogies: Discovery of Neptune vs. non-discovery of Vulcan
• Classical papers, e.g.:
  • Zwicky, F., “Die Rotverschiebung von extragalaktischen Nebeln”, Helvetica Physica Acta, vol. 6, pp. 110–127, 1933. (English translation) 
  • Freeman, K. C., “On the Disks of Spiral and S0 Galaxies”, The Astrophysical Journal, vol. 160, p. 811, 1970. doi:10.1086/150474.
  • Rubin, V. C. and Ford, W. K., “Rotation of the Andromeda Nebula from a Spectroscopic Survey of Emission Regions”, The Astrophysical Journal, vol. 159, p. 379, 1970. doi:10.1086/150317.
  • Ostriker, J. P., Peebles, P. J. E., and Yahil, A., “The Size and Mass of Galaxies, and the Mass of the Universe”, The Astrophysical Journal, vol. 193, p. L1, 1974. doi:10.1086/181617.
  • Einasto, J., Kaasik, A., and Saar, E., “Dynamic evidence on massive coronas of galaxies”, Nature, vol. 250, no. 5464, pp. 309–310, 1974. doi:10.1038/250309a0.
  • Clowe, D. et al., "A Direct Empirical Proof of the Existence of Dark Matter" ApJ, 648, L1091. doi:0.1086/508162
• "Small-scale problems" of cosmology (pick one):
  • Missing Satellites
  • Core-Cusp
  • Too-Big-To-Fail
  • Planes of Satellite Galaxies.

Discussion topics:

• Dark Matter and Philosophy of Science: Karl Popper vs. Thomas Kuhn
• Verifying Dark Matter: (How) can we (best) find evidence for dark substructures?
• Dark Matter vs. Modified Gravity
• Small-scale problems of ΛCDM: Alternative Dark Matter or Baryonic Solutions?
• A galaxy without dark matter as proof of dark matter’s existence?

List of sessions

• 8.4.2025:
  LECTURE TOPIC: Introduction
• 15.4.2025: cancelled (Marcel traveling)
• 22.4.2025:
  LECTURE TOPIC: A historical perspective: How Dark Matter came to matter
  + planning of student-led discussions / seminars
• 29.4.2025:
  LECTURE TOPIC: Galaxies and their Dynamics
• 6.5.2025: alternative lecturer Mariana Julio (Marcel traveling, Sonneberg)
  LECTURE TOPIC: Dark Matter in Dwarf Galaxies and Scaling Relations
• 13.5.2025:
  LECTURE TOPIC: Galaxy Clusters + Mass From Gravitational Lensing
  + TALK on TBD by TBD
• 20.5.2025:
  LECTURE TOPIC: Early Universe and Structure, Cosmological Scales, CMB, BBN
  + TALK on TBD by TBD
• 21.5.2025:
  LECTURE TOPIC: DM Candidates, Particle DM and Detection Experiments
  + DEBATE on TBD by TBD
• 3.6.2025: cancelled (Marcel and team traveling, Pittsburgh)
• 10.6.2025: cancelled (Pfingstwoche according to PULS?)
• 17.6.2025:
  LECTURE TOPIC: Modified Gravity as a Dark Matter Alternative
  + DEBATE on TBD by TBD
• 24.06.2025: alternative lecturer Jamie Kanehisa (Marcel -> Science & Fiction Berlin)
  LECTURE TOPIC: Testing LCDM on small scales with cosmological simulations
• 1.7.2025:
  LECTURE TOPIC: ΛCDM and Dark Matter Halos
  + TALK on TBD by TBD
  8.7.2025:
  LECTURE TOPIC: Small-Scale problems of ΛCDM and possible solutions
  + DEBATE on TBD by TBD
• 15.7.2025: possibly cancelled or alternative lecturer? (TBD Marcel traveling, Roman at STScI)
  Summary / Buffer
  + TALK on TBD by TBD