Abstract
AbstractThis 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.
Highlights
An ordinary liquid can be considered a derived, ‘effective’ entity, as it is composed of molecules
As we have noted, they raise the possibility that there is a transition, as it were, from an ‘earlier’ quantum state, which in general lacks any correspondence to a classical emergent state, to a ‘later’ classical cosmology well described by relativistic spacetime
We have seen that just such a phenomenon is at least possible in cosmological models based on string theory and Loop Quantum Gravity (LQG)
Summary
An ordinary liquid can be considered a derived, ‘effective’ entity, as it is composed of molecules. Relativistic spacetime must to some extent be a derived, effective entity, and not all fundamental states need correspond to full classical spacetime: some might not have an effective spacetime description. Spacetime might be composed of something non-spatiotemporal, QG may permit a ‘transition’ from a non-spatiotemporal to a spatiotemporal phase, an event maybe to be identified with the big bang, with ‘earlier’ non-spatiotemporal states of the universe. As the scare quotes indicate, it does not make obvious literal sense to talk of a ‘transition’ from the non-temporal to the temporal, since transition is a temporal notion.
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