Universitäts-Sternwarte München

Fakultät für Physik der Ludwig-Maximilians-Universität


Gravitational dynamics
Summer semester 2020

Tutorials overview

This class will require you to write small computer programs to solve physical problems. This will be done incrementally in small steps, so if you only have little programming experience to date you will have the opportunity to pick this up. (Like all important skills, this will require some effort and lots of experimentation from your side.) But keep in mind that programming is not the main aspect of these tutorials — understanding physics is.

Each of the tutorials will involve a general discussion about the goals of the current exercise set and the related physical and numerical issues. You are expected to participate in, and prepare for, these discussions. The tutorials will also give you the opportunity to discuss particular programming aspects. Do not be afraid to ask questions, out of a mistaken belief that this will make you appear stupid in front of your peers (who are often less knowledgeable than they would like you to believe).

You will work on the exercises at home and discuss your results in the tutorials. Keep in mind that the later exercises build upon the earlier ones, so you will need to keep your programs up to date. We will provide some example code fragments for each tutorial, which you can use as basis for your own programs if you are stuck.

You will need

  • a C/C++ or Fortran compiler (e.g., gcc or gfortran),
  • a text editor (such as emacs or vim),
  • a program to produce graphs (for example, gnuplot).


Due to the ongoing Corona crisis it is unlikely that we will be able to conduct regular exams in this semester. For this reason, your grade in this course will be based on a written Hausarbeit to be handed in at the end of the semester (deadline 2020-08-10). The general rules for this Hausarbeit are as follows:

  • For each tutorial from T1 through T11, provide a brief summary outlining the physical background of that tutorial’s subject, your solution(s) to the problems posed, and a few plots showing the results of your computations plus a short discussion interpreting your results. (Usually, one or two plots will be sufficient, but sometimes more may be required — this is for you to judge. More does not mean better. Try to make your plots display the information you want to convey as concisely as possible. This is a skill you must learn, and the quality of your plots will affect your grade.)
  • For one tutorial of your choice from T4 through T11, provide an extended analysis of an aspect of the subject of your own design that goes well beyond the general questions we pose as part of the tutorial content. Don’t choose a topic based on whether you think it will be easy, but rather choose one that appeals to your curiosity and allows for experimentation. Try to surprise us with some deeper insight into the physics involved.

The general discussions we will have during the tutorials should give you a good idea of what is expected in such a scientific report.

Tutorial session times

Monday, 16:00–18:00, Online via Zoom (meeting ID see tutorial T0).

Tutorial schedule

Tutorial numberContentDate

T0Introduction to the shell and gnuplot 2020-05-04
T1Units and acceleration; first program 2020-05-11
T2Gravitational forces; vectors and loops 2020-05-18
T3Euler integrator 2020-05-25
T4Euler and other integrators 2020-06-08
T5Kepler fitting 2020-06-15
T6Multiple (test) particles and extended potentials 2020-06-22
T7General 3-body problem (ejection, softening) 2020-06-29
T8Lagrange points (restricted 3-body problem) 2020-07-06
T9General N-body problem (free-fall collapse) 2020-07-13
T10Dynamical friction 2020-07-20
T11Colliding galaxies 2020-07-27
T12Visualization of galaxies in cosmological simulations2020-08-03

Letzte Änderung 30. Juli 2020 23:20 durch Webmaster (webmaster@usm.uni-muenchen.de)