Introduction to Partial Differential Equations

Undergraduate exercise sessions for the ETH Zurich course on first and second order PDEs, covering the method of characteristics and the Laplace, heat, and wave equations.

Instructor: Prof. Dr. Mikaela Iacobelli

Term: Fall

Location: ETH Zurich, Department of Mathematics

I was a teaching assistant responsible for holding weekly exercise sessions. The course is instructed by Prof. Dr. Mikaela Iacobelli.

Content

The course provides a general overview of first and second order PDEs, with a focus on the solution of quasilinear first order PDEs with the method of characteristics, and on the study of three fundamental types of second order partial differential equations: the Laplace equation, the heat equation, and the wave equation.

My role

I taught and led a class of 40 engineering students weekly throughout the semester. I also designed weekly exercise sheets and corrected student submissions.

Schedule

Week Date Topic Materials
1 30.09.2022 Introduction and classification of PDEs

Order, linearity, quasilinearity, homogeneity, examples, and associated conditions to obtain a unique solution.

2 07.10.2022 First order equations and the method of characteristics

Quasilinear equations, the method of characteristics, and worked examples.

3 14.10.2022 Existence and uniqueness for the characteristics method

Further examples of the characteristics method and the existence and uniqueness theorem.

4 21.10.2022 Conservation laws and shock waves

Conservation laws, formation of shocks, and weak solutions.

5 28.10.2022 Shock waves and classification of second order PDEs

The Rankine-Hugoniot and entropy conditions; classification of second order linear PDEs.

6 04.11.2022 The one-dimensional wave equation

Canonical form and general solution. The Cauchy problem and d’Alembert’s formula.

7 11.11.2022 Non-homogeneous wave equation and separation of variables

Domain of dependence. The non-homogeneous one-dimensional wave equation. Nonhomogeneous d’Alembert formula. Separation of variables.

8 18.11.2022 Separation of variables for heat and wave equations

Homogeneous problems; Dirichlet and Neumann boundary conditions.

9 25.11.2022 Non-homogeneous equations, resonance, and the energy method

Separation of variables for non-homogeneous equations. Resonance. The energy method for the wave and heat equations and uniqueness of solutions.

10 02.12.2022 Elliptic equations and maximum principles

The weak maximum principle. The mean value principle. The strong maximum principle.

11 09.12.2022 Applications of the maximum principle

Uniqueness via the maximum principle. The maximum principle for the heat equation. Separation of variables for elliptic problems.

12 16.12.2022 Separation of variables in rectangles and circular domains

Dirichlet and Neumann compatibility conditions. The Laplace equation in circular domains.

13 23.12.2022 Laplace equation on annulus and sectors

The Laplace equation in circular domains continued: annulus and sectors.