 
      
  
 An autonomous continuous-time
  linear dynamical system is a matrix $A
  \in \R ^{n \times  n}$.
 It models the behavior of a
  signal $x: \R  \to \R ^n$
  by
  
A signal $x$ satisfying Equation~\eqref{defining} is called a solution or a trajectory. For $t \in \R $, $x(t) \in \R ^n$ is called the state and $\R ^n$ is called the state space. $n$ is called the state dimension.