Foundations of Physics最新文献

Recent results have shown that singularities can be avoided from the general relativistic standpoint in Lorentzian-Euclidean black holes by means of the transition from a Lorentzian to an Euclidean region where time loses its physical meaning and becomes imaginary. This dynamical mechanism, dubbed “atemporality”, prevents the emergence of black hole singularities and the violation of conservation laws. In this paper, the notion of atemporality together with a detailed discussion of its implications is presented from a philosophical perspective. The main result consists in showing that atemporality is naturally related to conservation laws.

We present a comparative study between classical probability and quantum probability from the Bayesian viewpoint, where probability is construed as our rational degree of belief on whether a given statement is true. From this viewpoint, including conditional probability, three issues are discussed: (i) given a measure of the rational degree of belief, does it satisfy the axioms of the probability? (ii) Given the probability satisfying these axioms, is it seen as the measure of the rational degree of belief? (iii) Can the measure of the rational degree of belief be evaluated in terms of the relative frequency of events occurring? Here we show that as with the classical probability, all these issues can be resolved affirmatively in the quantum probability, provided that the relation to the relative frequency is slightly modified from the Laplace law of succession in case of a small number of observations. This implies that the relation between the Bayesian probability and the relative frequency in quantum mechanics is the same as that in the classical probability theory, including conditional probability.

In most day-to-day physics, one is modelling other systems and it is possible to maintain a provisional separation of subject and object, or of investigator and system being investigated. Ultimately, though, we are part of the universe. The fact that we act in the domain that we are representing can make it impossible to stabilize certain facts or features of the world as objects of knowledge. I’ll suggest that this casts light on the sense in which the universe is participatory and use differences in the way that the effects propagate to distinguish the classical and quantum worlds.  

The ultimate extension of Penrose’s Spin Geometry Theorem is given. It is shown how the local geometry of any curved Lorentzian 4-manifold (with (C^2) metric) can be derived in the classical limit using only the observables in the algebraic formulation of abstract Poincaré-invariant elementary quantum mechanical systems. In particular, for any point q of the classical spacetime manifold and curvature tensor there, there exists a composite system built from finitely many Poincaré-invariant elementary quantum mechanical systems and a sequence of its states, defining the classical limit, such that, in this limit, the value of the distance observables in these states tends with asymptotically vanishing uncertainty to lengths of spacelike geodesic segments in a convex normal neighbourhood U of q that determine the components of the curvature tensor at q. Since the curvature at q determines the metric on U up to third order corrections, the metric structure of curved (C^2) Lorentzian 4-manifolds is recovered from (or, alternatively, can be defined by the observables of) abstract Poincaré-invariant quantum mechanical systems.

In a recent reply to my criticisms (Carcassi et al. in Found Phys 55:5, 2025), Carcassi, Oldofredi, and Aidala (COA) admitted that their no-go result for (psi )-ontic models is based on the implicit assumption that all states are equally distinguishable, but insisted that this assumption is a part of the (psi )-ontic models defined by Harrigan and Spekkens, thus maintaining their result’s validity. In this note, I refute their argument again, emphasizing that the ontological models framework (OMF) does not entail this assumption. I clarify the distinction between ontological distinctness and experimental distinguishability, showing that the latter depends on dynamics absent from OMF, and address COA’s broader claims about quantum statistical mechanics and Bohmian mechanics.

I revisit the Wigner (or Weyl–Wigner, WW) representation of the quantum electromagnetic field. I show that, assuming that Fock states are just mathematical concepts devoid of physical reality, WW suggests a realistic interpretation which turns out to be (classical) Maxwell theory with the assumption that there is a random radiation filling space, the vacuum field. I elucidate why, in sharp contrast, non-relativistic quantum mechanics of particles does not admit a realistic interpretation via WW. I interpret experiments involving entangled light beams within WW, in particular optical tests of Bell inequalities. I show that WW provides clues in order to construct local models for those experiments. I give arguments why Bell definition of local realism is not general enough.

Perspectivalism is a natural ingredient of unitary one-world quantum mechanics. After briefly reviewing arguments for this thesis, we argue that a radical version of perspectivalism is able to provide local and relativistically covariant accounts of physical processes, and thus offers a way out of several no-go theorems. According to this radical perspectivalism, different perspectives are independent of each other and remain so even when they make causal contact. This leads to a worldview that is highly counter-intuitive, but does not lead to conflicts with experience. Moreover, locality and compatibility with relativity theory are positive points of radical perspectivalism.

Although the magnitude of the shift in the double-slit interference pattern when two electron beams pass outside a long solenoid has been confirmed in beautiful experiments, the direction of the deflection does not seem to appear in the published literature. It is claimed that careful quantum analysis gives a deflection direction opposite from that given by a classical electrodynamic analysis. Here we give a classical analysis of the interaction, and emphasize that the angle of deflection does not involve Planck’s constant. It is again suggested that a classical lag effect of order (1/c^{2}) forms the basis for the observed shift in the particle interference pattern. The effect is claimed to be the analogue of a nonrelativistic electric effect, and the analogous magnetic and electric forces are given for the two different situations. The magnetic interaction is considered in two different inertial frames where different electromagnetic fields are involved. An optical analogy is also mentioned. Finally, we note that electromagnetic fluctuations might wash out the lag effect for macroscopic solenoids.

Certain considerations from cosmology (Ellis, in: arXiv preprint, 2006. arXiv:astro-ph/0602280; Stud Hist Philos Mod Phys 46:5–23, 2014) and other areas of physics (Sklar, in: PSA Proceedings of the biennial meeting of the philosophy of science association, pp. 551–564, 1990; Frisch, in: Philos Sci 71:696–706, 2004) pose challenges to the traditional distinction between laws and initial conditions, indicating the need for a more nuanced understanding of physical modality. A solution to these challenges is provided by presenting a conceptual framework according to which laws and fundamental lawlike assumptions within a theory’s nomic structure determine what is physically necessary and what is physically contingent from a physical theory’s point of view. Initial conditions are defined within this framework in terms of the possible configurations of a physical system allowed by the laws and other lawlike assumptions of a theory. The proposed deflationary framework of physical modality offers an alternative way of understanding the distinction between laws and initial conditions and allows the question of the modal status of the initial conditions of the Universe to be asked in a meaningful way.

Plane waves of spin angular momentum density in an ideal elastic solid are analyzed using vector and bispinor descriptions. In both classical and quantum physics, spin density is the axial vector field whose curl is equal to twice the incompressible intrinsic momentum density. The second-order vector wave equation assumes that temporal changes of spin density in an ideal elastic solid are attributable to convection, rotation, and torque density. The corresponding first-order wave equation for Dirac bispinors incorporates terms describing wave propagation, convection, rotations of the medium and rotations of wave velocity relative to the medium. The two rotation terms are also operators for rotational kinetic energy and conventional potential energy, respectively. The potential energy corresponds to half the mass term of the free electron Dirac equation. Bispinor plane wave solutions are constructed consistent with the usual dynamical operators of relativistic quantum mechanics. Lagrangian and Hamiltonian densities are also constructed with each term having a clear classical physics interpretation. The intrinsic momentum associated with the Belinfante–Rosenfeld stress tensor is explained. Application to elementary particles is discussed, including classical physics analogues of the Pauli exclusion principle, interaction potentials, fermions, bosons, and antimatter.