Wednesday May 11th 2016 at Geneva – Francesca Vidotto (Radboud University Nijmegen): How classical spacetime emerges in Loop Quantum Gravity

Abstract: “Is space an entity or a net of relations? Is classical spacetime emergent? If it is emergent, what is it emerging from? Is spacetime fundamentally discrete or continuous? Is time an ingredient of the fundamental equations of the world? Is time flowing? These philosophical questions need to find an answer in a concrete realisation of a quantum theory of gravity. I illustrate the basics of Loop Quantum Gravity and the specific answers that each of these (philosophical) questions finds in the context of this (physical) theory. I focus on the notion of spacetime emergence: I argue that classical spacetime emerges from the quanta of spacetime, no differently from the emergence of electromagnetism having photons. This quantum emergence is studied in Loop Quantum Gravity, where there is a notion of classical limit. This limit should not be confused with a thermodynamical limit, that may exist but it is not necessary to recover classical spacetime. These ideas can be illustrated in analogy with the case of electromagnetism.” In terms of technical difficulty, this talk rates 4/5