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An alternative to the effective field theory approach to treat ghosts inhigher derivative theories is to attempt to integrate them out via theEuclidean path integral formalism. It has been suggested that this method couldprovide a consistent framework within which we might tolerate the ghost degreesof freedom that plague, among other theories, the higher derivative gravitymodels that have been proposed to explain cosmic acceleration. We consider theextension of this idea to treating a class of terms with order six derivatives,and find that for a general term the Euclidean path integral approach works inthe most trivial background, Minkowski. Moreover we see that even in de Sitterbackground, despite some difficulties, it is possible to define a probabilitydistribution for tensorial perturbations of the metric.

Tackling Higher Derivative Ghosts with the Euclidean Path Integral