Foundations of Physics最新文献

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.

The concept of presence has been extensively explored in philosophy, yet the notion of particle presence within quantum theory remains under-examined. In this article, we explore particle presence through an analysis of a paradox arising from weak measurements. We show that the classical intuition about particle presence involves an erroneous logical combination of propositions from single-time weak values, leading to inconsistencies that result in the deduction of discontinuous trajectories. Instead, we argue that by treating presence as a property defined across time by measuring sequential weak values, the discontinuity paradox is resolved, providing a coherent, non-classical account of particle presence. We discuss some advantages and drawbacks of this account, and consider applications to other cases of trajectory discontinuity.

I take a pragmatist perspective on quantum theory. This is not a view of the world described by quantum theory. In this view quantum theory itself does not describe the physical world (nor our observations, experiences or opinions of it). Instead, the theory offers reliable advice—on when to expect an event of one kind or another, and on how strongly to expect each possible outcome of that event. The event’s actual outcome is a perspectival fact—a fact relative to a physical context of assessment. Measurement outcomes and quantum states are both perspectival. By noticing that each must be relativized to an appropriate physical context one can resolve the measurement problem and the problem of nonlocal action. But if the outcome of a quantum measurement is not an absolute fact, then why should the statistics of such outcomes give us any objective reason to accept quantum theory? One can describe extensions of the scenario of Wigner’s friend in which a statement expressing the outcome of a quantum measurement would be true relative to one such context but not relative to another. However, physical conditions in our world prevent us from realizing such scenarios. Since the outcome of every actual quantum measurement is certified at what is essentially a single context of assessment, the outcome relative to that context is an objective fact in the only sense that matters for science. We should accept quantum theory because the statistics these outcomes display are just those it leads us to expect.

The crystalline solids admit two models: the one of vibrating atoms and the one of phonons. The model of phonons allows explaining certain properties of crystalline solids that the model of vibrating atoms does not allow. Usually, the model of phonons is assigned a diminished ontological status as quasi-particles. Recently, there has been a proposal to homologate the ontological status of phonons with that of emergent particles, such as photons. In this article, this proposal will be critically examined, and it will be proposed that the model of phonons and the model of vibrating atoms could be considered in ontological parity.

In a recent paper [Carcassi, Oldofredi and Aidala, Found Phys 54, 14 (2024)] it is claimed that the whole Harrigan–Spekkens framework of ontological models is inconsistent with quantum theory. They show this by showing that all pure quantum states in (psi )-ontic models must be orthogonal. In this note, we identify some crucial assumptions that lack physical motivation in their argument to the extent that the main claim is incorrect.