Gravity’s Rainbow

According to Quantum Mechanics, Zero Point Energy (ZPE) is the lowest possible energy that a quantum mechanical system may have. Unlike in classical mechanics, quantum systems constantly fluctuate in their lowest energy state as described by the Heisenberg uncertainty principle. The same behaviour appears also in Quantum Field Theory and, if one wishes to also apply the quantum world to General Relativity, one should obtain a quantum theory of the gravitational field, better known as Quantum Gravity. Unfortunately, such a theory is still lacking. However, there is no barrier to searching for a possible ZPE candidate, even if it is well known that every ZPE calculation is plagued by divergences. Usually, the divergences are kept under control with the help of a regularisation and renormalisation procedure.