  These are intended to be review notes on emergent symmetries, i.e.,
symmetries which manifest themselves in specific sectors of energy in many
systems. The emphasis is on the physical aspects rather than computation
methods. We include some background material and go through more recent
problems in field theory, statistical mechanics and condensed matter. These
problems illustrate how some important symmetries, such as Lorentz invariance
and supersymmetry, usually believed to be fundamental, can arise naturally in
low-energy regimes of systems involving a large number of degrees of freedom.
The aim is to discuss how these examples could help us to face other complex
and fundamental problems.
