This paper extends the stochastic electrodynamic framework of Papers 1, 2, and 3 [1–3] to relativistic quantum mechanics, deriving the Dirac equation from the relativistic Coulomb field. The non-relativistic Brownian motion of Paper 1 is generalised to a four-dimensional stochastic process in Minkowski spacetime, parameterised by proper time τ . The relativistic diffusion coefficient isD4D = ℏ/m—exactly twice the non-relativistic value ℏ/2m—arising from the additional contribution of the temporal component of the four-dimensional Wiener process. The covariant zero-point field spectral tensor Sμν(ω) = (ℏω^3/6π^2ϵ0c^3)gμν is derived from the relativistic Coulomb field through the Lorentz-covariant Einstein–Hopf detailed balance and the ergodic theorem, whose applicability to the SED electron-vacuum system is proved in Paper 3 [3]. Relativistic stochastic optimal control gives the Hamilton–Jacobi–Bellman (HJB) equation in four-dimensional configuration space, which yields the Klein–Gordon equation for spin-0 particles through the relativistic Itô correction (ℏ/2m)□. Linearisation of the relativistic Lagrangian −mc√uμuμ via Dirac matrices γμ satisfying {γμ, γν} = 2gμν converts the second-order HJB equation into a first-order equation—the Dirac equation: (iℏγμ∂μ−eγμAμ/c−mc)ψ = 0. The central new result is that spin- 1/2 is not introduced by the linearisation: it is already present in the geometry of the four-dimensional stochastic path. The mass-shell constraint uμuμ = −c^2 forces the relativistic Brownian path to be helical, with radius ℏ/mc and angular frequency 2mc^2/ℏ (Zitterbewegung). The angular momentum of this helix is ℏ/2 (spin- 1/2 ) and the magnetic moment gives g = 2—both following from the Coulomb field without additional assumptions. The linearisation then finds the unique first-order wave equation consistent with this pre-existing helical spin structure. The four-component Dirac spinor encodes four degrees of freedom already determined by the stochastic path: two spin states (helix handedness) and two time directions (particle/antiparticle).
This paper extends the stochastic electrodynamic framework of Papers 1, 2, and 3 [1–3] to relativistic quantum mechanics, deriving the Dirac equation from the relativistic Coulomb field. The non-relativistic Brownian motion of Paper 1 is generalised to a four-dimensional stochastic process in Minkowski spacetime, parameterised by proper time τ . The relativistic diffusion coefficient isD4D = ℏ/m—exactly twice the non-relativistic value ℏ/2m—arising from the additional contribution of the temporal component of the four-dimensional Wiener process. The covariant zero-point field spectral tensor Sμν(ω) = (ℏω^3/6π^2ϵ0c^3)gμν is derived from the relativistic Coulomb field through the Lorentz-covariant Einstein–Hopf detailed balance and the ergodic theorem, whose applicability to the SED electron-vacuum system is proved in Paper 3 [3]. Relativistic stochastic optimal control gives the Hamilton–Jacobi–Bellman (HJB) equation in four-dimensional configuration space, which yields the Klein–Gordon equation for spin-0 particles through the relativistic Itô correction (ℏ/2m)□. Linearisation of the relativistic Lagrangian −mc√uμuμ via Dirac matrices γμ satisfying {γμ, γν} = 2gμν converts the second-order HJB equation into a first-order equation—the Dirac equation: (iℏγμ∂μ−eγμAμ/c−mc)ψ = 0. The central new result is that spin- 1/2 is not introduced by the linearisation: it is already present in the geometry of the four-dimensional stochastic path. The mass-shell constraint uμuμ = −c^2 forces the relativistic Brownian path to be helical, with radius ℏ/mc and angular frequency 2mc^2/ℏ (Zitterbewegung). The angular momentum of this helix is ℏ/2 (spin- 1/2 ) and the magnetic moment gives g = 2—both following from the Coulomb field without additional assumptions. The linearisation then finds the unique first-order wave equation consistent with this pre-existing helical spin structure. The four-component Dirac spinor encodes four degrees of freedom already determined by the stochastic path: two spin states (helix handedness) and two time directions (particle/antiparticle).
Abstract The Dirac equation, central to relativistic quantum mechanics, governs spin- 1 2 particles and their antiparticles, with each spinor component satisfying a Klein–Gordon-type equation—the quantum counterpart of the relativistic mass-shell condition. In our prior work (Yordanov 2024 Sci. Rep. 14 6507), we derived the Dirac equation using stochastic optimal control (SOC) theory by linearizing both the Lagrangian’s kinetic term and the Hamilton–Jacobi–Bellman (HJB) equation, but that earlier linearized derivation did not preserve the relativistic mass-shell condition. Here, we formulate the SOC problem starting from a specified covariant Lagrangian for a single relativistic charged particle in an external electromagnetic field, in which the standard relativistic square-root kinetic term and the minimal electromagnetic coupling are retained in their original form. In addition, the Lagrangian is supplemented by a covariant spin-field coupling term describing the interaction of the particle’s intrinsic spin with the electromagnetic field. Because this spin-field term is matrix-valued, it is incorporated through scalarization so that the HJB problem remains scalar. To retain a scalar HJB formulation, the present construction is restricted to electromagnetic backgrounds for which σ μ ν F μ ν admits a spacetime-independent eigenspinor; the Dirac equation is then obtained in the corresponding fixed spin sector. This yields a relativistically consistent SOC derivation in which the ℏ → 0 limit of the HJB equation recovers the proper-time relativistic Hamilton–Jacobi equation, whose stationary form yields the classical mass-shell condition, while the stationary HJB equation yields the quantum-corrected mass-shell relation. We illustrate the theory with stochastic simulations of the Dirac–Landau problem (electron in a uniform magnetic field): at the analytic optimal drift the average stochastic action attains a local minimum, and the average action components are consistent with the Dirac–Landau values within statistical uncertainty.
We extend the stochastic coherence framework based on the Onsager-Machlup action to Minkowski spacetime. The configuration space R^n is replaced by M4, the scalar phase by a Lorentz rotor R in Spin+(1,3), and the observables by the four-current j^mu and spin tensor S^mu nu, both bilinear in R. We show that the combination of the relativistic stochastic Hamilton-Jacobi equation and the C^infty regularity of the bilinear observables over nodal surfaces forces the orbital winding number around nodal tubes to satisfy alpha = 2k with k a natural number, yielding orbital angular momentum quantized in integer multiples of h-bar: L = k in the non-negative integers. This establishes a strict topological separation between orbital angular momentum (determined by nodal regularity on the base manifold) and intrinsic spin (determined by the fiber group Spin+(1,3)). The variational derivation from the Onsager-Machlup action produces hydrodynamic equations that match the Takabayasi-Hestenes decomposition of the Dirac equation term by term. The derivation is non-circular: the dynamical constraint and the regularity requirement are logically independent. Additionally, we establish that the positivity condition rho >= 0 (inherent to any probability density) requires the internal orientation to be described by rotors in Spin+(1,3) rather than by SO+(1,3), as only the spinorial formulation guarantees a future-directed probability current. Finally, applying the Laidlaw-DeWitt decomposition to the many-body configuration space, we show that the double-cover structure of Spin+(1,3) fixes the exchange character to chi = -1 for spinorial representations, recovering Fermi-Dirac statistics without an independent symmetrization postulate. The framework remains within the domain of the free theory; extensions to curved spacetimes and many-body interactions are left for future work.
This paper derives the Dirac equation as the logically forced relativistic completion of the de Broglie wave dynamics established in prior work of this series. Starting from the logical foundation that yields Lorentz/Poincaré invariance, we promote the non-relativistic framework (continuous spacetime, Fourier duality, local plane-wave structures, and probability conservation via statistical energy flux) to the relativistic regime. We show that the requirements of exact local relativistic plane-wave structures (with phase gradients satisfying the mass-shell condition pμpμ=m2c2), first-order time evolution (needed for clean probability conservation), and full Lorentz covariance together force the introduction of a specific non-commuting algebraic structure and a multi-component wave function. The Dirac equation emerges as the unique linear differential operator of order at most one in the spacetime derivatives that consistently glues these local structures across smooth backgrounds while preserving a conserved four-current with positive-definite time component. This multi-component structure arises naturally as the minimal algebraic consequence of the constraints, without any separate postulate for intrinsic angular momentum. In exact analogy with the emergence of the finite invariant causal speed in special relativity, the Dirac dynamics is revealed not as an ad-hoc linearization of the Klein--Gordon equation, but as the mathematically inevitable description of indivisible particles in continuous relativistic spacetime. The derivation thereby completes the single-particle sector of the series, demonstrating that core structures of relativistic quantum mechanics flow deductively from a small number of deep, nearly tautological commitments.
We derive the Dirac equation from three postulates concerning the internal complex structure of time: (P1) physical time comprises two orthogonal components, past-fixed (pf) and future-pending (fp); (P2) pf ⊥ fp; and (P3) |T|² = pf² + fp² = 1. These postulates entail that temporal evolution is a first-order phase rotation e^{iθ} (yielding the Schrödinger equation) and that spatial extension of the conservation law gives E² = m²c⁴ + c²p² (yielding the Minkowski metric). The first-order requirement and the causality constraint (both derived from the same postulates) jointly exclude the square-root Hamiltonian on grounds of non-locality, leaving matrix linearisation as the unique path. The resulting Clifford algebra {γ^μ, γ^ν} = 2g^{μν} encodes the Minkowski metric already derived from the postulates, completing a self-consistent chain from temporal ontology to the Dirac equation. The four-component spinor is interpreted as the direct product of the pf–fp doublet (2 components) and the two directions of phase rotation (particle/antiparticle), providing a physical origin for spin-1/2 and its 4π periodicity (Möbius structure). Charge conjugation C, parity P, and time reversal T are reformulated as phase-rotation reversal, spatial phase-gradient reversal, and phase-angle reversal, respectively; CPT invariance is proved as a direct consequence of |T|² = 1. Connections to prior quantum-circuit experiments — in which entanglement was found to be a necessary condition for the linear accumulation of measurement-induced irreversibility — are discussed in the context of the Dirac spinor’s inter-sector coupling. complex time; Dirac equation; Clifford algebra; spinor structure; CPT invariance; Minkowski metric; quantum–relativity unification; temporal ontology; measurement irreversibility
Quantum mechanics is defined here as the theoretical framework crystallised at the fifth Solvay Conference of 1927, comprising five postulates: the wavefunction, the canonical commutation relation [x, p] = iℏ, the Born rule, the Schrödinger equation, and the transition probability rule. We present a complete derivation of all five Solvay postulates from purely classical foundations, starting from the directly observable Coulomb field of the electron. The single empirical input is ℏ—measured from pre-Solvay experiments (Planck 1900–1911, Einstein 1905, Casimir 1948/Lamoreaux 1997) without quantum mechanical interpretation, in the same way G was measured by Cavendish (1798) without general relativity. By Einstein’s photoelectric theory (1905) generalized to all electromagnetic fields, the Coulomb field energy is carried in electromagnetic quanta, each carrying both electric and magnetic fields with energy density ϵ0E^2. Lorentz invariance uniquely determines the ZPF spectral energy density u(ω) ∝ ω^3 (Boyer 1969, 1975). The Casimir force measurement gives the total ZPF energy per mode B = ℏ; classical E/B equipartition from Maxwell’s equations gives the electric energy per mode ℏω/2. The central original contribution is the physical justification of the Compton frequency cutoff ωc = mc^2/ℏ: an electron cannot emit an electromagnetic quantum with energy exceeding mc^2, because the residual electron would require negative mass, never observed in nature. By equating two independent expressions for the momentum variance of the ZPF-driven harmonic oscillator—one from the Abraham–Lorentz equation, one from Nelson’s osmotic velocity formula—D = ℏ/2m is derived without any quantum assumption. The ZPF-driven motion is then proved to be Brownian motion in the precise sense of Wiener (1923): all four Wiener conditions are verified from the properties of the ZPF established in Sections 3–4. This answers the question Nelson (1966) explicitly left open: “We do not attempt to give a physical explanation of why the electron should undergo Brownian motion.” The physical explanation is that the electron cannot escape its own Coulomb field. By Itô’s stochastic calculus and Nelson’s theorem, this gives the Schrödinger equation as an effective description valid for timescales Δt ≫ ℏ/mc^2. The transformation ψ = √ρe^(iS/ℏ) linearises the nonlinear Fokker–Planck equation, explaining why superposition holds. All five Solvay postulates emerge as consequences of classical physics plus the single measured constant ℏ. No Solvay postulate is assumed anywhere.
This paper extends the stochastic electrodynamic framework of Paper 1 [3] to multiparticle systems, providing a physical derivation of quantum entanglement. When a highenergy gamma ray creates an electron-positron pair, both particles emerge from the same spacetime point and share a common electromagnetic quantum field. We propose that the electromagnetic vacuum retains a cross-correlation component S(12)E (x1, x2, ω) in their joint electromagnetic quantum field, arising from the common creation event. The spatial dependence of this cross-correlation—a sinc(ωr12/c) factor—is derived from the known two-point vacuum correlation function of the electromagnetic field, not postulated. This cross-correlation is identified as the physical carrier of quantum entanglement. The two particles undergo correlated Brownian motion in six-dimensional configuration space, each with diffusion coefficient D = ℏ/2m derived in [3]. Nelson’s stochastic mechanics in configuration space gives the two-particle Schrödinger equation. The foundational ergodicity assumption underlying Papers 1 and 2—that the coupled electron-vacuum system admits a unique stationary ergodic measure—is proved in the companion Paper 3 [5] via the Caldeira–Leggett model and the Ford–Kac–Mazur theorem. The EPR paradox is resolved: the instantaneous correlation upon measurement is a consequence of conditional probability applied to a joint stochastic process, not a physical signal. Bell inequality violations are derived explicitly: the cross-correlation is nonlocal in configuration space, bypassing Bell’s locality assumption while satisfying the no-signalling theorem. Decoherence arises naturally as disruption of S(12)E by environmental electromagnetic noise. Fermi and Bose statistics emerge as boundary conditions on the joint stochastic process in configuration space.