  Coarse graining techniques offer a promising alternative to large-scale
simulations of complex dynamical systems, as long as the coarse-grained system
is truly representative of the initial one. Here, we investigate how the
dynamical properties of oscillator networks are affected when some nodes are
merged together to form a coarse-grained network. Moreover, we show that there
exists a way of grouping nodes preserving as much as possible some crucial
aspects of the network dynamics. This coarse graining approach provides a
useful method to simplify complex oscillator networks, and more generally any
network whose dynamics involves a Laplacian matrix.
