  We consider, computationally and experimentally, the scaling properties of
force networks in the systems of circular particles exposed to compression in
two spatial dimensions. The simulations consider polydisperse and monodisperse
particles, both frictional and frictionless, and in experiments we use
monodisperse and bidisperse particles. While for some of the considered systems
we observe consistent scaling exponents describing the behavior of the force
networks, we find that this behavior is it not universal. In particular,
monodisperse frictionless systems that partially crystallize under compression,
show scaling properties that are significantly different compared to the other
considered systems. The findings of non-universality are confirmed by
explicitly computing fractal dimension for the considered systems. The results
of physical experiments are consistent with the results obtained in simulations
of frictional particles.
