The century of the incomplete revolution: searching for general relativistic quantum field theory

In fundamental physics, the first part of the twentieth century has been characterized by two important steps towards a major conceptual revolution: quantum mechanics and general relativity. Each of these two theories has profoundly modified some key part of our understanding of the physical world. Quantum mechanics has changed what we mean by matter and by causality and general relativity has changed what we mean by “where” and “when”. The last part of the century has then been characterized by the search for a new synthesis: a unitary and comprehensive conceptual framework, capable of replacing the Newtonian framework and embracing the astonishing features of the world that have been revealed by quantum mechanics and by general relativity. Lacking a better expression, we can loosely denote a theoretical framework capable of doing so as a “background independent theory”, or, more accurately, “general relativistic quantum field theory”.