Cosmological networks
  Networks often represent systems that do not have a long history of studies
in traditional fields of physics, albeit there are some notable exceptions such
as energy landscapes and quantum gravity. Here we consider networks that
naturally arise in cosmology. Nodes in these networks are stationary observers
uniformly distributed in an expanding open FLRW universe with any scale factor,
and two observers are connected if one can causally influence the other. We
show that these networks are growing Lorentz-invariant graphs with power-law
distributions of node degrees. These networks encode maximum information about
the observable universe available to a given observer.
