Published online by Cambridge University Press: 01 January 2022
This article examines two cosmological models of quantum gravity (from string theory and loop quantum gravity) to investigate the foundational and conceptual issues arising from quantum treatments of the big bang. While the classical singularity is erased, the quantum evolution that replaces it may not correspond to classical spacetime: it may instead be a nonspatiotemporal region that somehow transitions to a spatiotemporal state. The different kinds of transition involved are partially characterized, the concept of a physical transition without time is investigated, and the problem of empirical incoherence for regions without spacetime is discussed.
We thank Baptiste Le Bihan, Tushar Menon, Daniele Oriti, and James Read for comments and discussions, as well as audiences at the PSA in Atlanta, the annual meeting of the British Society for the Philosophy of Science in Edinburgh, a workshop at the University of Rome 3, and at the Scuola Internazionale Superiore di Studi Avanzati (SISSA) in Trieste. This work was performed under a collaborative agreement between the University of Illinois at Chicago and the University of Geneva and made possible by grant 56314 from the John Templeton Foundation. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the John Templeton Foundation.