Marco Forgione

This paper argues that the epistemic role of large-scale cosmological simulations is subject to two coupled feedback structures: an external loop (simulations shaping survey pipelines and survey products constraining simulations) and an internal loop (validation outcomes feeding back into parameter and submodel choices across the simulation’s layers). These loops make validation operate less as an isolated model-to-world check and more as a constrained assessment of the adequacy of coupled simulation-pipeline systems; they also raise the risk of anomaly absorption and challenge strict modularity.

The paper discusses the use of robustness analysis in the context of the Hubble tension —the discrepancy between local and global measurements of the expansion rate of the universe. I argue that existing philosophical accounts of robustness are effective for assessing stability within a single measurement pipeline (intra-model robustness), but are limited when comparing across distinct pipelines (inter-model robustness). The paper introduces the concept of ‘bridges’ —shared inferential components between different measurement strategies— as crucial for making inter-model robustness informative. A case study involving the Tip of the Red Giant Branch (TRGB) method illustrates how shared calibration steps can localize disagreements, while the broader Hubble tension remains unresolved due to a lack of such bridges between local and global methods.

Many approaches to quantum gravity—the theory that should account for quantum and gravitational phenomena under the same theoretical umbrella—seem to point at some form of spacetime emergence, i.e., the fact that spacetime is not a fundamental entity of our physical world. This tenet has sparked many philosophical discussions: from the so-called ‘empirical incoherence problem’ to different accounts of emergence and mechanisms thereof. In this contribution, I focus on the partial order relation of causal set theory and argue that causation can be characterized as an a-temporal constraint over the kinematic space defined by the theory. The relation constrains the growth of a new element/event with respect to the other elements/events of a given set. Therefrom, the flow of time emerges from the collection of the possible growths of the given set, where each possibility is characterized by a classical probability assigned by the dynamics of the theory.

This book offers a clear account of timelessness together with the discussion of temporality in fundamental physics and cosmology. The multi-disciplinary approach to the problem of time and timelessness shows the remarkable difference between pre-relativistic debates and current developments. This book thoroughly discusses notions of timelessness and time emerging in the most recent literature on Quantum Gravity, String Theory and Cosmology. The contributions explore, among many aspects, the historical-philosophical roots of the notions of temporality and atemporality, the role of mathematics in defining time and temporality with respect to both order relations and causality, approaches to quantum gravity and cosmology that make use of quantum fluids and condensate to approximate space–time in general relativity, time and timelessness in black holes and the problem of cosmological time in bouncing cosmologies. The novelty of this volume lies in the interaction among scientists, philosophers, and historians in exploring the nature of time and timelessness and the origin of these concepts. The book represents a valuable toolkit for researchers and graduate students in physics, cosmology, philosophy and the history of those fields.

I will argue that the development of Feynman diagrams came from the physicist’s capacity of visualizing phenomena and that such visualization-skill contributed to the forming of a narrative explanation in the sense of Wise ( 2011 ) and Morgan ( 2001 ). The second part of the paper explores the extent to which Feynman diagrams can be considered as weak representations of quantum phenomena. I will review some of the most common arguments in support of the instrumentalist view and I will suggest that a form of weak representation that does not imply ontological commitment can be applied to the diagrams. Such a form of weak representation will be characterized as non-denotative, intentional, and as conveying a physical interpretation through narrative explanations.

The paper explores the application of robustness analysis to the Hubble tension —the discrepancy between measurements of the Hubble constant from the cosmic distance ladder and the early universe. I argue that, depending on how robustness analysis is defined and applied, one might conclude that the tension stems either from unaccounted systematics or from new physics. Ultimately, I suggest that caution and a more refined robustness analysis are needed when comparing results from large-scale experiments and scientific collaborations in cosmology.

With the present paper I maintain that the group field theory (GFT) approach to quantum gravity can help us clarify and distinguish the problems of spacetime emergence from the questions about the nature of the quanta of space. I will show that the mechanism of phase transition suggests a form of indifference between scales (or phases) and that such an indifference allows us to black-box questions about the nature of the ontology of the fundamental levels of the theory. I consider the GFT approach to quantum gravity which derives spacetime as an emergent property from abstract non-geometrical tetrahedra through a processes of phase transition. Because the physical interpretation of the tetrahedra is problematic in view of their (non)-spatiotemporal nature, I will apply the considerations about phase transitions to GFT and conclude that the fundamental ontology of the theory and the mechanism of spacetime emergence can and should be treated separately.

The paper considers the absorber theory of radiation by (Wheeler and Feynman 1945) and (Wheeler and Feynman 1949) and advances the idea that the theory is grounded on the philosophical intuition of overall processes. Such intuition consists of having to consider advanced and retarded radiation as well as the interaction between absorbers and emitter. I discuss the discrepancy between microdynamic time-symmetry and the asymmetry of the experimental evidences. In doing so, I consider (Price, 1991)'s reformulation of the theory and argue that it overlooks the philosophical intuition. I then compare the overall process idea with some accounts of holism and ultimately suggest that it also played an important role in Feynman's later works.

This paper argues that the path integral formulation of quantum mechanics suggests a form of holism for which the whole (total ensemble of paths) has properties that are not strongly reducible to the properties of the parts (the single trajectories). Feynman’s sum over histories calculates the probability amplitude of a particle moving within a boundary by summing over all the possible trajectories that the particle can undertake. These trajectories and their individual probability amplitudes are thus necessary in calculating the total amplitude. However, not all possible trajectories are differentiable, thus suggesting that they are not physical possibilities, but only mathematical entities. It follows that if the possible differentiable trajectories are taken to be part of the physical system, they are not sufficient to calculate the total probability amplitude. The conclusion is that the total ensemble is weakly non-supervenient upon the physically possible trajectories.