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Journal of the Australian Mathematical Society

Coordinate and momentum representations in quantum mechanics

Derek F. Lawden

Published May 1, 1968• 2 citations
Publisher

Abstract

On the basis of physical principles having a very general nature, A. Landé [1] has demonstrated that the mathematical structure of quantum mechanics can be derived without having recourse to the introduction of special assumptions of an ad hoc type (such as commutation rules governing canonical observables) which are not immediately suggested by our knowledge of the physical world, but which have simply originated as rules which mathematical physicists have discovered by past experience to yield conclusions in conformity with experiment.

DOI
10.1017/s1446788700005358

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On the basis of physical principles having a very general nature, A. Landé [1] has demonstrated that the mathematical structure of quantum mechanics can be derived without having recourse to the introduction of special assumptions of an ad hoc type (such as commutation rules governing canonical observables) which are not immediately suggested by our knowledge of the physical world, but which have simply originated as rules which mathematical physicists have discovered by past experience to yield conclusions in conformity with experiment.
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The framework of classical physics includes the well-established Helmholtz wave equation, which accurately describes the propagation, interference, and diffraction behaviors of steady-state time-harmonic waves such as acoustic and electromagnetic waves at the macroscopic level. Verified by centuries of experiments, it is a universally recognized deterministic formula in fundamental physics. However, traditional physics has long operated within fixed boundaries: academia has always matched the Helmholtz equation with one-dimensional real scalar coordinates, applying it only to macroscopic matter wave fields, and never attempting to use it to describe the microscopic quantum world or the underlying ontology of the universe. Meanwhile, Heisenberg’s matrix mechanics, starting from the microscopic mathematical properties, derived the uncertainty principle based on the non-commutation relations of matrices, directly proving that microscopic mechanical quantities cannot be completely represented by real scalars. The microscopic universe is inherently adapted to matrix-dimensional structures, which is the fundamental cause of the proliferation of paradoxes in quantum mechanics under the real-coordinate framework.Addressing these dual shortcomings of the existing physical system, this paper presents original research: it fully retains the differential operators, wave constraints, and steady-state solution rules of the classical Helmholtz equation, introduces no new physical constants or artificial ad-hoc assumptions, and only replaces the real-space coordinates X and Y within the equation with second-order two-dimensional linear matrix coordinates, independently constructing a theoretical system of two-dimensional linear two-dimensional waves adapted to the microscopic ontology of the universe. It must be clearly defined: classical physics only has real-coordinate Helmholtz waves, used to explain macroscopic waves; the Helmholtz wave model based on two-dimensional linear matrix coordinates is an exclusive original theory of this paper, forming a dedicated new classical system to describe the true microscopic ontology of the universe.Drawing on rigorously verified traditional mathematical and physical tools such as the classical Helmholtz wave principle, Heisenberg’s matrix mechanics, the uncertainty principle, the linear projection theorem, and the principle of wave field superposition, this paper systematically elaborates the mathematical structure, dimensional characteristics, and evolutionary laws of two-dimensional linear two-dimensional waves, and reveals the ultimate physical nature of quantum observation collapse: all material entities in the microscopic world are two-dimensional linear two-dimensional Helmholtz waves, while the human macroscopic perceptual world and detection devices can only carry one-dimensional real information. The essence of the observation process is not the random collapse of the wavefunction as defined by quantum mechanics, but rather the observation system actively extracting one degree of freedom from the two-dimensional matrix wave, with the remaining single dimension completing dimensionality-reduction projection and mapping into the one-dimensional real physical space, ultimately forming the observational illusion of localized particles.This original theory can explain the two core experimental puzzles that have plagued quantum physics for a century without contradictions or ad-hoc patches: First, when observing the interference pattern throughout the double-slit experiment, this observation mode collects the steady-state information of the global superposition of two-dimensional waves without performing dimensional extraction, and thus does not trigger collapse; Second, when a single photon enters the human eye’s retina or a single-point detector completes fixed-point detection, the observation system imposes localized boundary conditions to force the extraction of the wave field dimension, realizing the "screen projection" imaging of two-dimensional waves onto one-dimensional reality, which macroscopically manifests as wavefunction collapse. This study breaks down the barriers between macroscopic classical waves and microscopic quantum phenomena, providing a unified explanation for microscopic phenomena such as wave-particle duality and quantum observation collapse with an original classical model, and offering a new underlying perspective for the grand unification research in fundamental physics.
Since this book is closely connected to quantum mechanics, these introductory words will briefly and informally recall some postulates of this theory. Interested readers are urged to consult traditional books on quantum mechanics to complement the discussion ahead and for descriptions of experimental evidence that give rise to the postulates. In physics there are several “equivalent formulations” of quantum mechanics, and a catalogue of the most important appears in [StyO2]. The discussion here is restricted to the nonrelativistic case.
The objective of this work is to investigate whether the position--momentum duality can be reformulated, without ad hoc hypotheses and without circular reasoning, as a direct consequence of the spectral structure of bilocal unitary propagation. We start from the architecture already established in the Action--Phase program: the physical phase is given by ϕ=S/ℏ\phi=S/\hbarϕ=S/ℏ; self-adjoint structural operators organize the dynamics on a discrete lattice; such operators admit interpretation as unitary filters via Cayley realization; and the discrete unitary evolution can be written exactly as propagation by a bilocal kernel W(x,y)W(x,y)W(x,y). The central question is to determine under what hypotheses this bilocal kernel can be represented as a function of a self-adjoint structural operator, W^=f(H^),H^=H^†, \hat W=f(\hat H), \qquad \hat H=\hat H^\dagger, W^=f(H^),H^=H^†, and how this structure implies the existence of an intrinsic spectral basis in which the propagation becomes diagonal. It is shown, step by step, that the spectral decomposition of H^\hat HH^ induces a corresponding decomposition of the kernel, W(x,y)=∑nf(λn) ϕn(x)ϕn∗(y), W(x,y)=\sum_n f(\lambda_n)\,\phi_n(x)\phi_n^*(y), W(x,y)=∑n​f(λn​)ϕn​(x)ϕn∗​(y), so that the unitary evolution begins to act multiplicatively on the spectral modes, Ψ~n(t+Δt)=f(λn)Ψ~n(t), \widetilde\Psi_n(t+\Delta t)=f(\lambda_n)\widetilde\Psi_n(t), Ψn​(t+Δt)=f(λn​)Ψn​(t), without the introduction of additional structures. In the homogeneous case, it is demonstrated that the eigenfunctions of the structural operator are discrete Fourier modes and that the continuous spectral parameter coincides with the usual wavenumber. In this regime, the spectral representation exactly reproduces the momentum sector of standard quantum mechanics. Outside this case, ``momentum'' is reinterpreted more generally as the spectral coordinate of the operator generating the propagation. The result of this stage is, therefore, conceptually precise: the position--momentum duality does not need to be postulated as an ontological duplication, but emerges as a duality between the nodal basis and the spectral basis of the same structural operator that governs the unitary propagation. The work does not intend, at this stage, to completely reconstruct the theory of canonical observables, nor to definitively resolve multiparticle systems or formulate a general covariant theory. Its role is to establish the minimum layer in which the spectral structure of propagation provides the mathematical origin of position--momentum duality, opening a controlled continuation program for these problems.