Foundations of Physics最新文献

Beginning with the Everett-DeWitt many-worlds interpretation of quantum mechanics, there have been a series of proposals for how the state vector of a quantum system might split at any instant into orthogonal branches, each of which exhibits approximately classical behavior. In an earlier version of the present work, we proposed a decomposition of a state vector into branches by finding the minimum of a measure of the mean squared quantum complexity of the branches in the branch decomposition. In the present article, we adapt the earlier version to quantum electrodynamics of electrons and protons on a lattice in Minkowski space. The earlier version, however, here is simplified by replacing a definition of complexity which takes the physical vacuum as 0 complexity starting point, with a definition which takes the bare vacuum as starting point. As a consequence of this replacement, the physical vacuum itself is expected to branch yielding branches with energy densities slightly larger than that of the unbranched vacuum. If the vacuum energy renormalization constant is chosen as usual to give 0 energy density to the unbranched vacuum, in an expanding universe vacuum branches will appear to have a combination of dark energy and dark matter densities. The hypothesis that vacuum branching is the origin of the observed dark energy and dark matter densities leads to an estimate of (mathcal {O}(10^{-18} {m}^3)) for the parameter b which enters the complexity measure governing branch formation and sets the boundary between quantum and classical behavior.

The Newton-Wigner states and operator are widely accepted to provide an adequate notion of spatial localization of a particle in quantum field theory on a spacelike hypersurface. Replacing the spacelike with a timelike hypersurface, we construct one-particle states of massive Klein-Gordon theory that are localized on the hypersurface in the temporal as well as two spatial directions. This addresses the longstanding problem of a “time operator" in quantum theory. It is made possible by recent advances in quantization on timelike hypersurfaces and the introduction of evanescent particles. As a first application of time-localized states, we consider the time-of-arrival problem. Our results are in accordance with semiclassical expectations of causal propagation of massless and massive particles. As in the Newton-Wigner case, localization is not perfect, but apparent superluminal propagation is exponentially suppressed.

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 examines the physical meaning of the wave function in Bohmian mechanics (BM), addressing the debate between causal and nomological interpretations. While BM postulates particles with definite trajectories guided by the wave function, the ontological status of the wave function itself remains contested. Critics of the causal interpretation argue that the wave function’s high-dimensionality and lack of back-reaction disqualify it as a physical entity. Proponents of the nomological interpretation, drawing parallels to the classical Hamiltonian, propose that the wave function is a “law-like" entity. However, this view faces challenges, including reliance on speculative quantum gravity frameworks (e.g., the Wheeler-DeWitt equation) and conceptual ambiguities about the nature of “nomological entities". By systematically comparing BM to Hamilton-Jacobi theory, this paper highlights disanalogies between the wave function and the classical action function. These differences—particularly the wave function’s dynamical necessity and irreducibility—support a sui generis interpretation, where the wave function represents a novel ontological category unique to quantum theory. The paper concludes that the wave function’s role in BM resists classical analogies, demanding a metaphysical framework that accommodates its non-local, high-dimensional, and dynamically irreducible nature.

This paper aims to construct an ontology grounded in the interpretation of Relational Quantum Mechanics, which serves as a robust framework for a realist interpretation of quantum mechanics without the need for additional theoretical constructs. Using the notion of relational properties, we formulate Relational Quantum Mechanics’s ontology. Our analysis highlights the ontological significance of Rovelli (Int. J. Theor. Phys., 35, 1637–1678, 1996)’spostulates. Moreover, we apply this ontological perspective to quantum mechanics paradoxes and show that it provides new insights into those paradoxes, underscoring Relational Quantum Mechanics explanatory power.

The polarization,magnetization and conductivity features of a conductor polarizable and magnetizable medium are described by a continuum collection of the antisymmetric tensor fields and a continuum collection of the vector fields in the Minkowski’s space-time. The conservation principle of the energy-momentum four-vector of the total system is provided in a fully canonical approach. The conservation principle of the energy-momentum four-vector of the total system gives the force four-vector on the free external charges moving in the conductor magneto-dielectric medium. The total classical relativistic Cherenkov’s radiation power emerged by a charged particle uniformly moving inside the medium is calculated. The quantum relativistic Cherenkov’s radiation power of a charged particle moving inside a homogeneous conductor magneto-dielectric medium is calculated by two methods. In the first method the motion of the charged particle is described by the relativistic quantum mechanics. The quantum relativistic Cherenkov’s radiation power of the charged particle moving in the medium is calculated in the initial state that the charged particle is in a very sharp normalized distribution in the momentum space and the quantum relativistic fields describing the medium are in the vacuum states. In the second approach the motion of an electron moving in the medium is described by the quantum relativistic Dirac’s field. The quantum relativistic Cherenkov’s radiation power of the electron moving in the medium is computed in the initial state that the quantum relativistic Dirac’s field is contained an electron with a definite spin and a very sharp normalized distribution in the momentum space and the quantum relativistic dynamical fields modeling the medium are in the vacuum states. The two methods of the calculation of the quantum relativistic Cherenkov’s radiation power of the electron moving inside the conductor magneto-dielectric medium are compared.

In this short paper, we propose a new framework for obtaining basic aspects of quantum mechanics that originate from estimating the mean value of the position of a statistical system based on the generalized Bayes estimators. We show that while the first-order estimation leads to a classical system, the second-order estimation produces the time-independent Schrödinger equation. The Born rule describes the probabilistic nature of quantum particles, and Max Born postulated it independently from the Schrödinger equation. We show that under the proposed model, both the Schrödinger equation and the Born rule are captured organically; particularly, we show that the Born rule leads to the Schrödinger equation. Finally, we show how the proposed model deals with the transition from quantum mechanics into classical mechanics when dealing with macroscopic objects without external assumptions.

The electron’s spin magnetic moment is ordinarily described as anomalous in comparison to what one would expect from the Dirac equation. But, what exactly should one expect from the Dirac equation? The standard answer would be the Bohr magneton, which is a simple estimate of the electron’s spin magnetic moment that can be derived from the Dirac equation either by taking the non-relativistic limit to arrive at the Pauli equation or by examining the Gordon decomposition of the electron’s current density. However, these derivations ignore two effects that are central to quantum field theoretic calculations of the electron’s magnetic moment: self-interaction and mass renormalization. Those two effects can and should be incorporated when analyzing the Dirac equation, to better isolate the distinctive improvements of quantum field theory. Either of the two aforementioned derivations can be modified accordingly. Doing so yields a magnetic moment that depends on the electron’s state (even among z-spin up states). This poses a puzzle for future research: How does the move to quantum field theory take you from a state-dependent magnetic moment to a fixed magnetic moment?

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.

It is proposed that measurement devices can be modelled to have an open decoherence dynamics that is faster than any other relevant timescale, which is referred to as the ultradecoherence limit. In this limit, the measurement device always assumes a definite state upto the accuracy set by the fast decoherence timescale. Further, it is shown that the clicking rate of measurement devices can be derived from its underlying parameters, not only for the von Neumann ideal measurement devices but also for photon detectors in equal footing. This study offers a glimpse into the intriguing physics of measurement processes in quantum mechanics, with many aspects open for further investigation.