Foundations of Physics最新文献

Recent no-go theorems on interpretations of quantum theory featuring an assumption of ‘Absoluteness of Observed Events’ (AOE) are shown to have an unexpectedly strong corollary: one cannot reject AOE and at the same time assume that the ‘observed events’ in question can all be (i) single-valued and (ii) embedded within a single background space-time common to all observers. Consequently, interpretations that reject AOE appear incompatible with a ‘block universe’ view of space-time.

A first-principles derivation of deformed quantum mechanics is presented for the (alpha ')-corrected heterotic string. Upon compactification, the leading corrections induces a quartic momentum correction term to a scalar dispersion relation. This modification is precisely equivalent to a deformed canonical commutator whose single deformation parameter is set by the Calabi-Yau volume, internal curvature, and background fluxes, thereby establishing a finite minimal length. Positivity of the four-derivative coupling confines the Lee-Wick ghost to scales far above the higher-derivative cutoff, whose value and thus the threshold for stringy corrections is fixed by the same geometric data. Moreover, these inputs can amplify the deformation, pushing the minimal length well beyond the string scale. Earlier proposals based on generalized-uncertainty-principle deformations suggested, on purely phenomenological grounds, that quantum-gravity effects might emerge at such elevated scales; the present analysis provides the first rigorous string-theoretic foundation for that scenario. Finally, unlike standard phenomenological models, the deformation derived here depends on the probe mass, yielding significant implications for important physical problems such as species-sensitive black-hole bounds.

In this work, we show that the quantum mechanical notions of density operator, positive operator-valued measure (POVM), and the Born rule, are all simultaneously encoded in the categorical notion of a natural transformation of functors. In particular, we show that given a fixed quantum system A, there exists an explicit bijection from the set of density operators on the associated Hilbert space (mathcal {H}_A) to the set of natural transformations between the canonical measurement and probability functors associated with the system A, which formalize the way in which quantum effects (i.e., POVM elements) and their associated probabilities are additive with respect to a coarse-graining of measurements.

By removing a fractal from time-rolled Minkowski spacetime, we construct an extendible spacetime without closed timelike curves whose every extension contains closed timelike curves. This settles a question posed by Geroch.

This paper argues that von Neumann entropy plays two conceptually distinct roles in quantum theory. When applied to global mixed states, it expresses the quantum analogue of the informational entropy. But when applied to reduced states of entangled systems, it measures objective physical correlations. We propose that this second usage realizes a new informational kind, which we call relational information. Unlike information in communication theory, it reflects structural interdependence between systems, not probability about a certain outcome. We further suggest that this informational kind has ontological significance: relational information is a physically instantiated feature of entangled systems, and not merely an agent-relative concept.

Collapse theories provide one of the main approaches to the quantum measurement problem. Roderich Tumulka’s collapse theory (GRWf) has attracted interest because it offers a relativistic collapse theory. GRWf utilises an ontology of flashes to accommodate EPR-Bell type non-local influences within a relativistic theory, an idea suggested by John Bell. Tim Maudlin raises a concern with Tumulka’s flash ontology, arguing that it is too sparse to convincingly account for certain microscopic phenomena. This paper proposes a modification to GRWf that addresses the problem of sparseness, whilst retaining a relativistic treatment of quantum non-locality. The proposal, referred to as the space-time normalisation interpretation (STN), combines the GRWf flash ontology with a statistical interpretation of the wavefunction. The statistical structure of the interpretation is presented as a Hawkes process, consisting of flashes and an intensity function governing their occurrence. For a single-particle system, the square modulus of a renormalised wavefunction serves as the intensity function of the Hawkes process.

We introduce a minimal, mathematically controlled modification of the classical action principle that embeds a small, divergence-free field (f_mu (x)) into the Euler–Lagrange equations primarily through modifications in electrodynamics. This modification preserves locality, causality, and charge conservation while generating controlled, small deviations from standard classical trajectories, providing a unified, quantitative framework for mild classical indeterminism. The field (f_mu) is Lorentz-covariant and characterized by a physically motivated spectral density, ensuring consistency across particle, scalar, and gauge systems. To leading order, we derive corrected forces, compute ensemble-averaged trajectory shifts, and identify spectral signatures accessible to high-precision experiments such as Penning traps and cathode beams. With ultraviolet-regularized spectra, the predicted deviations lie within current experimental sensitivity, establishing a direct bridge between foundational theory and empirical testability.

I argue for an approach to the Foundations of Physics that puts the question in the title center stage, rather than asking “what is the case in the world?”. This approach, algorithmic idealism, attempts to give a mathematically rigorous in-principle-answer to this question both in the usual empirical regime of physics and in some more exotic regimes within cosmology, philosophy, and science fiction (but soon perhaps real) technology. I begin by arguing that quantum theory, in its actual practice and in some interpretations, should be understood as telling an agent what they should expect to observe next (rather than what is the case), and that the difficulty of answering this former question from the usual “external” perspective is at the heart of persistent enigmas such as the Boltzmann brain problem, extended Wigner’s friend scenarios, Parfit’s teletransportation paradox, or our understanding of the simulation hypothesis. Algorithmic idealism is a conceptual framework, based on two postulates that admit several possible mathematical formalizations, cast in the language of algorithmic information theory. Here I give a non-technical description of this view and show how it dissolves the aforementioned enigmas: for example, it claims that you should never bet on being a Boltzmann brain regardless of how many there are, that shutting down computer simulations does not generally terminate its inhabitants, and it predicts the apparent embedding into an objective external world as an approximate description.