The dynamical behavior of physical processes is usually modeled via differential equations. But if the states of the physical system are in some ways constrained, like for example by conservation laws or position constraints, then the mathematical model also contains algebraic equations to describe these constraints. Such systems, consisting of both differential and algebraic equations, are called differential-algebraic systems.
In this talk, we introduce linear differential-algebraic equations, both with constant and variable coefficients. In particular, we will present their canonical forms, and we will discuss what do they imply about the existence, uniqueness and smoothness of solutions.