  Gauge symmetries emerge from a redundant description of the effective action
for light degrees of freedom after the decoupling of heavy modes. This
redundant description avoids the use of explicit constraints in configuration
space. For non-linear constraints the gauge symmetries are non-linear. In a
quantum field theory setting the gauge symmetries are local and can describe
Yang-Mills theories or quantum gravity. We formulate gauge invariant fields
that correspond to the non-linear light degrees of freedom. In the context of
functional renormalization gauge symmetries can emerge if the flow generates or
preserves large mass-like terms for the heavy degrees of freedom. They
correspond to a particular form of gauge fixing terms in quantum field
theories.
