  The unconstrained reduced action corresponding to the dynamics of scalar
fluctuations about the Friedmann-Robertson-Walker (FRW) background is derived
using Dirac's method of description of singular Lagrangian systems. The results
are applied to so-called negative mode problem in description of tunneling
transitions with gravity. With our special choice of physical variable, the
kinetic term of the reduced action has a conventional signature for a wide
class of models. In this representation, the existence of a negative mode
justifying the false vacuum decay picture turns out to be manifest. We also
explain how the present result becomes consistent with the previously proved
``no negative mode (supercritical supercurvature mode) theorem''.
