  Higher Derivative (HD) Field Theories can be transformed into second order
equivalent theories with a direct particle interpretation. In a simple model
involving abelian gauge symmetries we examine the fate of the possible gauge
fixings throughout this process. This example is a useful test bed for HD
theories of gravity and provides a nice intuitive interpretation of the "third
ghost" occurring there and in HD gauge theories when a HD gauge fixing is
adopted.

High Energy Physics - Theory