Foundations of Physics最新文献

The worldline of a free electron is revealed by applying Dirac’s velocity operator to its Dirac wave function whose space-time arguments are expressed in a proper time by a Lorentz transformation. This motion can be decomposed into two parts: the electron’s global motion of its inertia (or spin) center and an inherent local periodic motion about this point that produces the electron’s spin and has the zitterbewegung frequency found by Schrödinger in his operator analysis of Dirac’s wave equation. This zitter motion corresponds to the so-called polarization and magnetization currents in Gordon’s decomposition of Dirac’s current. In an inertial “rest”-frame fixed at the inertia center, Dirac’s wave function for a free electron with its spin in a specified direction implies that the zitter motion is a perpetual circular motion about the inertia center in a plane orthogonal to this spin direction with a radius one half of the Compton radius and moving at the speed of light. The electron continuously accelerates about the spin center without any external force because the inertia is effective at the spin center, rather than at its charge center where the electron interacts with the electro-magnetic field. This analysis confirms the nature of zitterbewegung directly from Dirac’s wave equation, agreeing with the conclusions of Barut and Zanghi, Beck, Hestenes, Rivas and Salesi from their classical Dirac particle models of the electron. Furthermore, these five classical models are equivalent and express the same free electron dynamics as Dirac’s equation..

This paper introduces the physics and philosophy of strange metals, which are characterized by unusual electrical and thermal properties that deviate from conventional metallic behaviour. The anomalous strange-metal behaviour discussed here appears in the normal state of a copper-oxide high-temperature superconductor, and it cannot be described using standard condensed-matter physics. Currently, it can only be described through a holographic dual, viz. a four-dimensional black hole in anti-de Sitter spacetime. This paper first introduces the theory of, and specific experiments carried out on, strange metals. Then it discusses a number of philosophical questions that strange metals open up regarding the experimental evidence for holography and its realist interpretation. Strange metals invert the explanatory arrows, in that usual holographic arguments are seen as giving explanations of the bulk quantum-gravity theory from the boundary. By contrast, the aim here is, by using holography, to explain the experimentally discovered and anomalous properties of strange metals.

In this short article, I seek to clarify some of the broader motivations and ambitions guiding my work on electron spin. I respond to Sanchioni (Found. Phys. 55(67), 1–11 2025), who has criticized my recent study of the electron’s anomalous magnetic moment (Sebens Found. Phys. 55(48), 1–28 2025). I argue against viewing quantum field theory instrumentally as merely “an architecture of consistent predictions” and in favor of explaining physical phenomena using descriptions of what is actually out there in nature. I defend the importance of asking how the move from the Dirac equation (with self-interaction) to quantum field theory takes you from a variable to fixed magnetic moment, emphasizing my agreement with Sanchioni that the Dirac equation yields only a flawed model of the electron. I explain that quantum field theory, as it stands, is incomplete, and discuss how we might be able to arrive at a better explanation of the electron’s anomalous magnetic moment.

The Pusey–Barrett–Rudolph (PBR) theorem establishes (psi)-onticity for individual quantum systems, but its standard formulation relies on the Preparation Independence Postulate (PIP). This has led to a prevalent view that rejecting PIP leaves open the possibility of (psi)-epistemic models for individual systems. In this work, we show that this understanding is incomplete: once the PBR theorem establishes (psi)-onticity for composite systems prepared in product states, the (psi)-onticity of the individual subsystems follows directly from the tensor-product structure of quantum mechanics, without invoking PIP or any further auxiliary assumptions. This result removes a key auxiliary assumption from the PBR theorem, closes a persistent loophole for preserving (psi)-epistemic models, and strengthens the conceptual foundations of (psi)-ontology.

This paper examines the role of perspectivism in Relational Quantum Mechanics, situating it within the broader landscape of quantum interpretations and the scientific realism debate. We argue that, while interpretations such as QBism embrace strong forms of perspectivism, Relational Quantum Mechanics adopts a “soft” perspectivism, limiting the observer’s role to selecting experimental contexts without compromising its realist framework. We also explore the historical roots of Relational Quantum Mechanics, showing that relational ideas in the works of Bohr and other pioneers similarly avoided strong perspectivist commitments. By analyzing both contemporary and historical perspectives, we argue that Relational Quantum Mechanics offers a minimalist yet robust relational interpretation, distinct from more subjectivist approaches.

This paper considers the prospects for a quantum perspectivism that seeks to reconcile competing approaches to quantum theory as distinct scientific perspectives on quantum reality. In other areas of the philosophy of science, perspectivism holds the promise of a way to embrace pluralism without contradiction—what appear to be competing theories can be accepted because they each provide a distinct “window on the same reality.” The contemporary situation in quantum foundations is arguably a case of underdetermination. If this is so, this brand of perspectivism may offer a resolution.

The transition from unitary, reversible von Neumann-Everett quantum processes to non-unitary, irreversible processes and measurements is explored through infinite tensor products interpreted as nested, chained, or iterated Wigner’s friend scenarios. Infinite tensor products can disrupt unitary equivalence through sectorization and factorization, drawing parallels to concepts from real analysis, recursive mathematics, and statistical physics.

In the histories formulation of quantum theory, sets of coarse-grained histories that are consistent obey the classical probability rules. It has been argued that these sets can describe the quasi-classical behaviour of closed quantum systems, e.g. Omnès (Rev. Mod. Phys. 64(2), 339, 1992) and Hartle (Les Houches1992). Most physical scenarios admit multiple different consistent sets and one can view each of these as a separate context. Using propositions from different consistent sets to make inferences leads to paradoxes such as contrary inferences, first noted by Kent (Phys. Rev. Lett. 78(15), 2874, 1997). In this contribution, we use the consistent histories to describe a quasi-classical and macroscopic system to show that paradoxes involving contextuality persist even in the quasi-classical limit. This is distinctively different from the contextuality of standard quantum theory, where the contextuality paradoxes do not persist in the quasi-classical limit. Specifically, we consider different consistent sets for the arrival time problem of a (quasi-classical) ball in an infinite square well. For this setting, we construct two different consistent sets. We find the probabilities that each consistent set assigns to the simple question of whether the ball ever crossed the middle of the interval. We show that one consistent set concludes with certainty that the ball crossed it while the other consistent set concludes with certainty that it did not. Our results point to the need for constraints on the histories sets, additional to the consistency condition, to recover the correct quasi-classical limit in this formalism and lead to the motto ‘all consistent sets are equal’, but ‘some consistent sets are more equal than others’.

We take causality and uniqueness of events observation as our driving forces. They are embedded in the way we define distinct observers, which then require a finite time to communicate between each other. This inevitably leads to the existence of a maximal transfer-information velocity between arbitrary (not necessarily inertial) reference frames. Inertial reference frames are defined by fixing the geometrical properties of (spatial) distance without any reference to relativity, electromagnetism, or laws of physics in general. For these inertial reference frames, the causality condition fixes the causal group to be the orthochronous inhomogeneous Lorentz group times dilatations. The mathematics we will use are quite basic.

This paper develops a comprehensive framework for the extension of classical and quantum mechanics to fractal settings. We begin by summarizing the classical formulation of Fractal Nambu Mechanics and then introduce its quantization. The Fractal Hamilton-Jacobi Theory is established to describe dynamical systems evolving over fractal time and space, followed by a fractal generalization of the quantum Hamilton-Jacobi framework. We further formulate the Fractal Nambu-Hamilton-Jacobi Theory and propose its quantum counterpart–the Quantum Fractal Nambu-Hamilton-Jacobi Theory. These constructions demonstrate how the structure of Nambu mechanics, when combined with local fractal calculus, can provide new insights into systems with multiple invariants and non-smooth geometric evolution.