journal articles

The problem of recovering information from the interior of a black hole is crucial to any resolution of the information loss paradox. In this article, we critically evaluate the program of holographic interior reconstruction within the AdS/CFT correspondence, explaining the conceptual underpinnings and implicit assumptions behind the recovery of black hole interior information, in the face of the apparent impossibility of doing so due to the AMPSS paradox. We also show how the implicit assumptions behind holographic interior reconstruction are the same as those underpinning an apparently unrelated popular resolution of the firewall paradox. By doing so, we highlight how holographic interior reconstruction fits within a larger conceptual strategy for attacking the problem of describing black holes in Quantum Gravity.

We consider the observables describing spatiotemporal properties in the context of two of the most popular approaches to quantum gravity (QG), namely String Theory and Loop QG. In both approaches these observables are described by non-commuting operators. In analogy with recent arguments put forward in the context of non-relativistic quantum mechanics [see Calosi and Mariani (Philos. Compass 16(4):e12731, 2021) for a review], we suggest that the physical quantities corresponding to those observables may be interpreted as ontologically indeterminate—i.e., indeterminate in a way that is non-epistemic and semantic-independent. This working hypothesis has not received enough attention in the current debate on QG, and yet it may prove explanatory useful in several respects. First, it provides a clear background for understanding how some features of QG are ontologically continuous to features of quantum mechanics. Second, it sets the stage for asking new interesting questions about QG, for instance concerning the status of the so-called Eigenstate-Eigenvalue link. Third, it indirectly shows how the debate on ontological indeterminacy may extend well beyond the non-relativistic case, contrary to what seems to be assumed. Fourth, and perhaps more importantly, it provides a promising alternative to the received view on QG [Wüthrich et al. (Philosophy Beyond Spacetime: Implications from Quantum Gravity, Oxford University Press, Oxford, 2021)] according to which spacetime is not fundamental. On the view we shall suggest, spacetime may be indeterminate and yet fundamental.

Reichenbach’s importance to the development of modern philosophy can hardly be overstated. However, many themes and arguments originally developed by Reichenbach are either overlooked or not properly credited to him. In this article, we discuss an important but often forgotten argument of Reichenbach against the Kantian notion of synthetic a priori. We first give a detailed historical reconstruction of the argument and discuss the mild conventionalism that Reichenbach developed following this argument. Then, we recast this argument in the modern language of General Relativity. We show that this argument is still relevant for a modern attempt at articulating the notion of synthetic a priori: Friedman’s relativised synthetic a priori.

This paper presents a philosophical analysis of the structure of black holes, focusing on the event horizon and its fundamental status. While black holes have been at the centre of countless paradoxes arising from the attempt to merge quantum mechanics and general relativity, recent experimental discoveries have emphasised their importance as objects for the development of Quantum Gravity. In particular, the statistical mechanical underpinning of black hole thermodynamics has been a central research topic. The Quantum Membrane Paradigm, proposed by Wallace (Stud Hist Philos Sci Part B 66:103-117, 2019), posits a real membrane made of black hole microstates at the black hole horizon to provide a statistical mechanical understanding of black hole thermodynamics from an exterior observer’s point of view. However, we argue that the Quantum Membrane Paradigm is limited to low-energy Quantum Gravity and needs to be modified to avoid reference to geometric notions, such as the event horizon, which presumably do not make sense in the non-spatiotemporal context of full Quantum Gravity. Our proposal relies on the central dogma of black hole physics. It considers recent developments, such as replica wormholes and entanglement wedge reconstruction, to provide a new framework for understanding the nature of black hole horizons in full Quantum Gravity.

Supersymmetry is a conjectured symmetry that relates standard model’s bosons and fermions. The spin-statistics theorem, which states that a particle’s statistics depends on its spin, is a crucial component of quantum field theory’s analysis of matter. Prima facie, supersymmetry creates problems for the theoretical structure underpinned by the spin-statistics theorem. Since supersymmetry relates bosons and fermions, the distinction between particles obeying Bose–Einstein or Fermi–Dirac statistics seems to collapse since, ultimately, they are part of a single supermultiplet, that is, the actual degree of freedom of supersymmetric quantum field theory. This article aims to evaluate the status of the spin statistics theorem within supersymmetric quantum field theories and which strategies one can implement to make sense of this state of affairs. In particular, we argue that there are two main options in the face of the conflict between Wigner’s theorem and the spin-statistics theorem: either we abandon the validity of the spin-statistics theorem and adopt an invariant superfield ontology, or we abandon Wigner’s theorem and uphold spin-statistics theorem, at the price, however, of introducing a significant redundancy in our ontological. Moreover, we explore how these two options relate to important philosophical debates, such as the nature of superspace and spacetime ontologies, and the debates between motivationalists and interpretationalist regarding physical symmetry. 

Quantum Theory and Humeanism have long been thought to be incompatible due to the irreducibility of the correlations involved in entangled states. In this paper, we reconstruct the tension between Humeanism and entanglement via the concept of causal structure, and provide a philosophical introduction to the ER=EPR conjecture. With these tools, we then show how the concept of causal structure and the ER=EPR conjecture allow us to resolve the conflict between Humeanism and entanglement.

We discuss Manchak (2009a)'s result that there are locally (but not globally) isometric universes observationally indistinguishable from our own. This theorem makes the epistemic predicament of modern cosmology particularly problematic and the prospects of ever gaining knowledge of the global structure of the universe rather unlikely in the context of general relativity. We argue however that this conclusion is too quick; indeed, Manchak's theorem deploys spacetimes which are not physically reasonable, since they have features which are not the product of any physical process. This ultimately rests on the fact that local isometry between two spacetimes is not sufficient to guarantee that they are both physically reasonable. We propose an additional condition to properly define when a spacetime is physically reasonable, and we show that Manchak's spacetimes do not satisfy this further demand.