Towards the nonlinear regime in extensions to GR: assessing possible
  options
  Testing General Relativity and exploring possible departures has received
further input with the possibility to do so through gravitational waves emitted
in strongly gravitating/highly dynamical scenarios and also through the
availability of exquisitely sensitive cosmological observations. However, most
extensions suffer from severe pathologies at the mathematical level which have
stymied a thorough exploration of putative theories. With the aid of a model
problem which captures typical pathologies, we explore suggested methods to
control them. We find that the approach that modifies the equations to control
higher-order gradients is both robust and efficient.
