Position--Momentum Duality as Spectral Diagonalization of Bilocal Propagation A Continuation of the Action--Phase Program
Jonatan P. camargo
Abstract
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 \(\phi=S/\hbar\); 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 \(W(x,y)\). The central question is to determine under what hypotheses this bilocal kernel can be represented as a function of a self-adjoint structural operator, \[ \hat W=f(\hat H), \qquad \hat H=\hat H^\dagger, \] 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 \(\hat H\) induces a corresponding decomposition of the kernel, \[ W(x,y)=\sum_n f(\lambda_n)\,\phi_n(x)\phi_n^*(y), \] so that the unitary evolution begins to act multiplicatively on the spectral modes, \[ \widetilde\Psi_n(t+\Delta t)=f(\lambda_n)\widetilde\Psi_n(t), \] 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.