Fundamental indeterminacy of spacetime

Project Information

FIndS

Grant agreement ID: 101109486

DOI

10.3030/101109486

Project closed

EC signature date 2 May 2023

Start date 1 June 2023

End date 31 May 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 173 847,36

Coordinated by

LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN
Germany

Periodic Reporting for period 1 - FIndS (Fundamental indeterminacy of spacetime)

Reporting period: 2023-06-01 to 2025-05-31

Summary of the context and overall objectives of the project

We currently lack a truly fundamental theory of nature that provides a quantum description of space and time (i.e. a theory of quantum gravity (QG)), and that would explain the early times of the universe and the physics of black holes. An important conceptual obstacle currently stands in the way of the development of QG: influential research programmes attempting to find a theory of QG yield theories in which spacetime is emergent, rather than fundamental. Such approaches, called emergent spacetime theories (ESTs), raise critical philosophical challenges. Indeed, the way we conceptualise and experiment the world is embedded in notions of space and time. As a result, the very possibility of considering major approaches of QG as descriptions of the fundamental physical world, beyond their mere mathematical content, is non-trivial. The project seeks to address that challenge by providing a clear, intelligible interpretation of what it means for spacetime to be emergent in ESTs.

The first objective of this project is to spell out, in a standard scientific realist context, the notion of spacetime indeterminacy in ESTs and its impact on the way spacetime emergence is to be understood. The second objective is to shift from standard scientific realism to perspectival realism in order to take seriously the presence of distinct agents’ perspectives within the account of spacetime emergence. The third objective is to demonstrate the philosophical virtues of the resulting account.

Overall, this project is expected to provide a unified solution to the current conceptual problems of ESTs. This is expected to benefit the (philosophy of) physics’ community working in QG by providing them with a novel conceptual grasp of spacetime emergence.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Research Activities: The projects’ objectives were pursued by bibliographical and analytical work of the researcher. Training in quantum gravity has been performed in parallel, namely upon attending an LMU course (‘Introduction to quantum gravity’ by Daniele Oriti). The research outcomes were in the form of 1 published academic work in the peer-reviewed British Journal for Philosophy of Science, 2 published academic work in edited books, and 1 paper in its final stage of preparation to be submitted to a peer-reviewed journal.

Networking was developed and scientific exchanges took place via short academic visits in the Netherlands and in Switzerland, and via online seminars bringing together European and non-European researchers. New international collaborations were developed with research groups in Switzerland and Portugal.

Teaching-related activities: The researcher proposed a seminar for young researchers in the philosophy of quantum physics, and will be teaching a philosophy module at the bachelor level (teaching mission scheduled for 2024-2025 and delayed to the winter semester 2025-2026).

Dissemination of the research: The research’s outcomes were presented at 5 international (peer-reviewed) conferences in Greece, Serbia, Austria, Portugal and England. Further dissemination took place in 4 invited seminars in Munich and other European and non-European research groups (the Netherlands, Switzerland and Australia).

Various academic services have been provided: Organisation of the Philosophy of Physics Reading Group, LMU Munich, 2024-2025. Election as a Council Member of the Society for the Metaphysics of Science (2025). Service in the administrative committee of the Société de Philosophie des Sciences (2021-2024; 2024-2027). This includes a representative role during the RDIPS 2024, 19-20/09/2024 Lyon (France), and a Vice-president role for the "Jeunes chercheurs et jeunes chercheuses" prize 2025.Participation as a speaker to the “Curiosity meets know-how - Exchange of experience for female scientists”, 6/10/2023, Ludwig-Maximilians-Universität München (Organised by the Federal Ministry of Education and research - Germany).

Organisation of the post-MSCA fellowship era: To ensure the further development of the project beyond the MSCA fellowship, training has been followed on the acquisition and management of third-party research funding. A follow-up research project has been developed, to be submitted for future funding.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Letertre, L. (2025). ‘Temporal nonlocality from indefinite causal orders’, the British Journal for the Philosophy of Science, https://doi.org/10.1086/734907. This paper shows how Adlam's principle of temporal locality can be violated within a model-dependent protocol involving indefinite causal orders interpreted in terms of retrocausal influences. It also discusses the theoretical and philosophical distinctions between standard entanglement of quantum positions on the one hand and indefiniteness of spacetime on the other hand. This is of importance to bridge interpretations across quantum physics, an issue relevant to the third objective of the project.

Letertre, L. (forthcoming). ‘Non-Humean laws of nature without spacetime’. In ‘Metaphysics of laws’, S. Psillos, S. Ioannidis, V. Seifert (Eds.), Routledge Studies in Philosophy of Science Series, forthcoming at the end of 2025. This paper explores how laws of nature can be understood in the face of a non-fundamental spacetime, and defends a recent account in terms of global constraints, with implications on the general ontological picture of the physical world. This work paves the way for the first objective of the project, and defended the hypothesis of spacetime indeterminacy against common objections.

Letertre, L. (final stage of preparation, and to be presented in an international conference in September 2025). ‘Spacetime emergence as a case of metaphysical indeterminacy’. This paper straightforwardly implements both the first and third objectives of the project. The defended thesis is that spacetime in ESTs is affected by quantum metaphysical indeterminacy, of which two possible interpretations yield distinct accounts of spacetime emergence.

Note: A review paper has been edited during the mission (Letertre L., (forthcoming in 2025), ‘Introduction à la métaphysique de la mécanique quantique’. In “Sciences & métaphysiques. Regards croisés”, Philippe Huneman and François Papale (Ed.), Editions Matériologiques). It aims at introducing the metaphysics of quantum mechanics to a broader (possibly non-expert) French-speaking audience.

Future research: The second objective of the project will be pursued beyond the MSCA fellowship.

Spacetime emergence - Illustration generated with the assistance of OpenAI's DALL·E