A gauge invariant prescription to avoid $\gamma$-crossing instability in
  Galileon bounce
  We revisit the evolutions of scalar perturbations in a non-singular Galileon
bounce. It is known that the second order differential equation governing the
perturbations is numerically unstable at a point called $\gamma$-crossing. This
instability is usually circumvented using certain gauge choices. We show that
the perturbations can be evolved across this point by solving the first order
differential equations governing suitable gauge invariant quantities without
any instabilities. We demonstrate this method in a matter bounce scenario
described by the Galileon action.
