Speaker
Description
When treated as a Quantum Field Theory, General Relativity cannot describe gravity at all energy scales due to the non-renormalizability of the Hilbert-Einstein action. As a consequence, ongoing efforts aim to construct modified actions that improve renormalizability. This way, it might be possible to develop a Quantum Gravity Theory that can make reliable predictions at arbitrarily high energies. One of such modifications involves adding higher derivative terms to the Hilbert-Einstein action. However, these higher-derivative terms also introduce ghost states — which are degrees of freedom with negative energy — that need to be "cured". In this presentation, we will discuss the main problems of a higher derivative theory with a toy model: the Pais-Uhlenbeck oscillator, a scalar higher derivative field theory. We will show how this higher derivative field can be consistently decomposed in two canonical Klein-Gordon fields —standard and ghost— and how the Green's function construction remains consistent from a path integral perspective.