Important features of space and time are taken to be missing in quantum gravity, allegedly requiring an explanation of the emergence of spacetime from non-spatio-temporal theories. In this paper, we argue that the explanatory gap between general relativity and nonspatio-temporal quantum gravity theories might significantly be reduced with two moves. First, we point out that spacetime is already partially missing in the context of general relativity when understood from a dynamical perspective. Second, we argue that most approaches to quantum gravity already start with an in-built distinction between structures to which the asymmetry between space and time can be traced back.
A ''duality'' is a formal mapping between the spaces of solutions of two empirically equivalent theories. In recent times, dualities have been found to be pervasive in string theory and quantum field theory. Naïvely interpreted, duality-related theories appear to make very different ontological claims about the world-differing in, for example, spacetime structure, fundamental ontology, and mereological structure. In light of this, duality-related theories raise questions familiar from discussions of underdetermination in the philosophy of science: in the presence of dual theories, what is one to say about the ontology of the world? In this paper, we undertake a comprehensive and nontechnical survey of the landscape of possible ontological interpretations of duality-related theories. We provide a significantly enriched and clarified taxonomy of options-several of which are novel to the literature. INTRODUCTIONContemporary physics is built upon two central-and prima facie incompatible-frameworks: the theory of general relativity, on the one hand, and the standard model of particle physics-a certain quantum field theory-on the other.Although these two frameworks are strikingly effective at describing the actual world in their relevant domains (viz., macroscopic, astrophysical, and cosmological scales for general relativity, and atomic, subatomic, and molecular scales for the standard model), they rest upon very different assumptions. For example, one central feature of general relativity is that spacetime is rendered dynamical (i.e., it is not a fixed background, but rather ''curves'' in response to its matter content); by contrast, spacetime remains a fixed background in the standard model of particle physics.This notwithstanding, various fields of physics-such as the study of the early universe or of black holes-lie at the intersection of the domains of these two theories and thereby call for a quantum theory of gravity. 1 Constructing such a theory capable of overcoming the tensions between general relativity and the standard model is an ongoing matter of profound difficulty; at present, there exist several candidate options which remain the subject of active research (cf. Huggett & Wüthrich, 2013 for a philosophical overview of such options.)According to the naïve ontological picture presented by string theory-arguably the most popular extant research programme in quantum gravity-reality is constituted by one-dimensional strings, as well as by other higher dimensional entities called ''branes.'' Moreover, reality is not made up of four spacetime dimensions (three spatial
Spacetime functionalism is the view that spacetime is a functional structure implemented by a more fundamental ontology. Lam and Wüthrich have recently argued that spacetime functionalism helps to solve the epistemological problem of empirical coherence in quantum gravity and suggested that it also (dis)solves the hard problem of spacetime, namely the problem of offering a picture consistent with the emergence of spacetime from a non-spatio-temporal structure. First, I will deny that spacetime functionalism solves the hard problem by showing that it comes in various species, each entailing a different attitude towards, or answer to, the hard problem. Second, I will argue that the existence of an explanatory gap, which grounds the hard problem, has not been correctly taken into account in the literature.
‘Space does not exist fundamentally: it emerges from a more fundamental non-spatial structure.’ This intriguing claim appears in various research programs in contemporary physics. Philosophers of physics tend to believe that this claim entails either that spacetime does not exist, or that it is derivatively real. In this article, I introduce and defend a third metaphysical interpretation of the claim: reductionism about space. I argue that, as a result, there is no need to subscribe to fundamentality, layers of reality and emergence in order to analyse the constitution of space by non-spatial entities. It follows that space constitution, if borne out, does not provide empirical evidence in favour of a stratified, Aristotelian in spirit, metaphysics. The view will be described in relation to two particular research programs in contemporary physics: wave function realism and loop quantum gravity.
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