Can finite-range correlations hide in the statistics of an extended quantum state? The Schrödinger-Nagasawa transform represents the wave function by positive forward and backward diffusion fields whose product is the Born density. We promote them to branching superprocesses, \(Φ_F\) and \(Φ_B\): diffusion samples stochastic paths, whereas Bohm/Fisher-controlled branching generates genealogies of alternative continuations. With rates evaluated on the prescribed Born density, their means reproduce Schrödinger dynamics exactly. The connected sector exhibits supercritical, critical, and subcritical clustering in confinement and has critical dimension \(d_c=2\) in free space. Stationary eigenmodes remain extended; subcritical clusters acquire the reduced de~Broglie scale. We then let the branching rate respond to the fluctuating product \(Φ_FΦ_B\). In the reciprocal basis, the fields equal a smooth reference \(R\) plus centered fluctuations \(ψ_F,ψ_B\), defining the signed kernel \(C_{\rm FB}(x,y)=\mathbb E_ω[ψ_F(x)ψ_B(y)]\). On the anticorrelated branch, \(ρ_{\rm BSM}(x)=-C_{\rm FB}(x,x)\) is the positive organized connected weight. Stationary matching of this weight to the Born profile is imposed as a closure condition, while off-diagonal decay defines the correlation range. The pair equation splits into collective and relative sectors: spectral cancellation selects the Born collective mode, while suppression of the leading density fluctuation selects the anticorrelated source channel. With relative diffusivity \(D_{\rm eff}\) and positive relaxation rate \(μ_{\rm FB}\), correlations have screening length \(ξ_{\rm FB}=\sqrt{D_{\rm eff}/μ_{\rm FB}}\). Within this reciprocal closure, an extended Born-shaped connected weight and a finite correlation range can coexist in one stochastic kernel.
Can finite-range correlations hide in the statistics of an extended quantum state? The Schrödinger-Nagasawa transform represents the wave function by positive forward and backward diffusion fields whose product is the Born density. We promote them to branching superprocesses, (Φ_F) and (Φ_B): diffusion samples stochastic paths, whereas Bohm/Fisher-controlled branching generates genealogies of alternative continuations. With rates evaluated on the prescribed Born density, their means reproduce Schrödinger dynamics exactly. The connected sector exhibits supercritical, critical, and subcritical clustering in confinement and has critical dimension (d_c=2) in free space. Stationary eigenmodes remain extended; subcritical clusters acquire the reduced de~Broglie scale. We then let the branching rate respond to the fluctuating product (Φ_FΦ_B). In the reciprocal basis, the fields equal a smooth reference (R) plus centered fluctuations (ψ_F,ψ_B), defining the signed kernel (C_{\rm FB}(x,y)=\mathbb E_ω[ψ_F(x)ψ_B(y)]). On the anticorrelated branch, (ρ_{\rm BSM}(x)=-C_{\rm FB}(x,x)) is the positive organized connected weight. Stationary matching of this weight to the Born profile is imposed as a closure condition, while off-diagonal decay defines the correlation range. The pair equation splits into collective and relative sectors: spectral cancellation selects the Born collective mode, while suppression of the leading density fluctuation selects the anticorrelated source channel. With relative diffusivity (D_{\rm eff}) and positive relaxation rate (μ_{\rm FB}), correlations have screening length (ξ_{\rm FB}=\sqrt{D_{\rm eff}/μ_{\rm FB}}). Within this reciprocal closure, an extended Born-shaped connected weight and a finite correlation range can coexist in one stochastic kernel.
Branching stochastic mechanics (BSM) provides a reciprocal branching representation of the Schrödinger--Nagasawa pair. Its centered forward--backward kernel CFB=Eω[ψFψB] resolves an organized connected sector, with weight ρBSM=−CFB(x,x) on the anticorrelated branch.
Here we investigate how this sector forms, localizes, and propagates under Bohm/Fisher feedback. We retain the branching covariance on the prescribed background as the bare noise kernel and truncate the nonlinear interaction to Bohm/Fisher drift vertices. A Martin--Siggia--Rose--Janssen--de Dominicis formulation and a causal two-loop two-particle-irreducible (2PI) closure determine response and correlation functions self-consistently. While the free connected theory exhibits secular growth and ultraviolet accumulation, the dressed theory develops a finite relative screening length. A reduced numerical evolution shows bounded formation of the localized sector, and a self-similar Fisher construction defines a saturated information velocity c⋆.
A Born--Oppenheimer separation connects this internal organization to collective propagation. The instantaneous adiabatic kernel has two pole families at fixed internal momentum: a gapless difference branch and a gapped sum branch. Projecting both inverse response kernels onto the same localized internal profile defines their collective coefficients. If both propagation speeds match c⋆ and the projected gap matches mc⋆2/ℏ, the gapped branch takes the infrared Klein--Gordon form. These matching conditions define a candidate relativistic fixed point whose dynamical realization remains to be tested.
Relaxation to equilibrium of a drifted Brownian motion is quantified by a transition probability density function, whose main (multiplicative) entry is an inferred Feynman-Kac kernel of the Schrödinger semigroup operator. Although seemingly devoid of a natural probabilistic significance (except for its explicit path integral definition), the pertinent kernel relaxes to equilibrium as well. The implicit Feynman-Kac potential V(x), continuous, confining and bounded from below, may take negative values. If positive, V(x) can be interpreted as the killing rate of the decaying diffusion process. In case of relaxing F-K kernels the killing effects are tamed (often overcompensated). The taming inavoidably appears in conjunction with the existence of the negativity subdomains of V(x) in R. If locally V(x)<0, its sign inversion −V(x) can be interpreted as the branching (cloning, alternatively bifurcation) rate in the course of the other wise free random motion. The arising killed diffusion processes with branching, we interpret as the possible path-wise background of tamed (relaxing) Feynman-Kac diffusions. We present acomputer-assisted path-wise arguments, towards a consistency of the killing/branching taming scenario, for a number of nonlinear model systems in one space dimension. Special attention is paid to Feynman-Kac potential shapes in the double well form, where an analytic access to eigenvalues and eigenfunctions is scarce. Throughout the paper the dynamics refers to the positive real time. Since the Newton-type equations of motion for admissible classical trajectories have a Euclidean form (due to the sign inverted force term), we give a brief resume of a couple of their explicit solutions, without recourse to the Euclidean time intuitions, and the instanton lore of related quantum model systems.
A quantum state can be written in phase space, but the resulting object is not generally the probability density of a positive stochastic process on ordinary phase space. We spell this out for Wigner dynamics. If a positive phase-space process is required only to reproduce the Born density after integrating over momentum, the requirement fixes only an integrated current; the local drift and diffusion remain underdetermined. If one instead requires all Weyl-ordered expectation values, the phase-space object is fixed to be the Wigner function. For non-quadratic potentials the Wigner--Moyal generator contains higher-order, signed momentum-transfer terms, so it is not the Fokker--Planck generator of a positive Brownian diffusion. The exact Wigner function must therefore be reconstructed, in a stochastic representation, as a weighted empirical measure \[ \FW(\z,t)=\E_{\Pp}[W_tδ(\z-\z_t)], \qquad \z=(q,p), \] rather than the unweighted density of sampled carrier trajectories. With classical Hamiltonian flow as the carrier, all nonclassical correction beyond classical transport sits in the Moyal residual and can be represented by signed weights or branching events. The same split defines a residual diagnostic that vanishes for quadratic Hamiltonians and measures what classical carrier transport misses in anharmonic dynamics. The formulation also gives a forward--reverse relation for signed Wigner path measures. The ratio of forward and reversed contributions separates into a positive magnitude factor and a sign factor. This sign records the parity of the Wigner interference contribution; it is not a thermodynamic entropy production.
Hoffman’s conscious-agent formalism defines agents by Markov kernels on finite sets, anda programme has sought to obtain quantum mechanics—complex amplitudes, Hilbert space,unitary evolution and the Born rule—as outputs of that stochastic substrate. Papers I–III ofthis series closed the passive-readout, witness-inequality and Born-rule-inversion routes. Herewe examine the Eulerian control principles on the continuous-time nearest-neighbour jumprelative of the programme’s N -cycle substrate, with the phase S posited as an agent-carriedvariable and the rates depending on the population density, and ask which of them are exactlythe lattice Schrödinger pair at finite lattice spacing a. (i) No member with a kinetic termquadratic in the rates is exact, for any N , wherever its stationary drift exists (a degree count);by Legendre duality, (ii) no globally optimising member, with any cost, over an S-independentadmissible rate set, is exact on the whole configuration space, because the reduced Hamiltonianof a minimiser (maximiser) is convex (concave) in the phases while the lattice Schrödingerenergy is neither; (iii) an optimising member with bothprates free nevertheless exists—the2 —whose minimiser isconvex bond cost cQ (J) = ℏJ arcsin(J/Jmax ) + ℏJmax 1 − J 2 /Jmaxexactly the lattice Schrödinger pair, density dependence included, on the open winding-zerosector where every real bond phase satisfies |∆x | < πℏ/2, and which fails on the outer half ofthe zone, nodes included, and on every configuration with nonzero winding; with an activitycost selecting the symmetric part of the rates, that optimiser is the Bell–Vink process; (iv)exact stationary-point members exist beyond that sector, Bell–Vink among them, determinedup to the split of each bond energy and a uniform circulating current, with the branchselection as the rate law. The cost cQ is the entropic (Schrödinger-bridge) bond cost with thenoise scale continued to imaginary values, cE |Jmax →iJmax = −i cQ on principal branches, aformal correspondence. As a diagnostic, the fixed-noise Nelson–Yasue member with κ = +1carries the Euclidean sign of the quantum potential, κQ = −κ; the κ = −1 (Guerra–Morato)member is exact in the continuum and, where its stationary drift exists, departs from thelattice target at O(a2 ). Nelson’s law of motion, imposed on the fixed-total-rate kinematicswithin the rate bound |bx | ≤ 2νa for odd N , has the real-time sign, is exact for plane wavesand pure-potential configurations, and departs at O(a2 ) generically, with an exact vanishingfamily and in-regime counterexamples at N = 5, 7. A programme-status section recordsthat the substrate, read as a one-time operational probabilistic theory, lies in the classicalbranch of the Hardy and Chiribella–D’Ariano–Perinotti reconstructions, and corrects onestatement of Paper III (Barandes’ precondition is met by every finite-alphabet process; thesentence was true but empty). These are bounded no-go theorems for the reading constructedhere; no claim is made about quantum mechanics emerging from stochastic dynamics ingeneral. All machine results are exact-arithmetic and rerun bit-identically. The Round-1lattice results and the reconstruction-axiom checks were preregistered with blind priors; thetheorems added in revision were prompted by review and are machine-checked by successorverifiers, not preregistered.
The Schrödinger equation and the Born rule constitute two of the most successful structures in quantum mechanics. The former governs the continuous evolution of the wave function, while the latter connects its squared amplitude to the statistical distribution of experimental outcomes. Yet these two structures operate at different descriptive levels: the Schrödinger state is continuous, spatially extended, and phase-sensitive, whereas individual experiments terminate in localized physical events. This paper develops a theoretical framework for reconstructing the physical relation between these two levels. Rather than proceeding only in the conventional direction from Schrödinger dynamics to Born probabilities, we introduce an inverse explanatory strategy: from Born back to Schrödinger. Born statistics are treated as an empirical constraint from which the physical role of the wave function is reconsidered. We propose that, for the single-particle regime examined here, the wave function may be interpreted functionally as a dynamical propagation structure rather than as the localized particle itself. Its amplitude, phase, conserved current, gauge-covariant propagation momentum, and associated velocity field jointly define a structured family of possible motions. This interpretation leads to three separations: propagation from localization, propagation from physical population, and arrival from detector registration. A physical preparation generates a source measure (\mu_0^{\rm phys}); Schrödinger dynamics generates a propagation map (\Phi_\Psi); and microscopic detector dynamics is represented by a response map (\mathcal R_D). The Born problem can then be formulated as the closure condition RD[(ΦΨ)∗μ0phys]=?μBorn,D. This relation is not claimed here as a derived law, but as the central dynamical problem that a physical reconstruction of quantum probability must solve without inserting the Born measure at either boundary. The paper synthesizes six preceding studies on wave-packet localization, Born's scattering interpretation, the emergence of probability, the physical meaning of the wave function, source-to-detector transport, and unified propagation dynamics. It places the resulting framework in dialogue with Madelung and Hamilton–Jacobi formulations, Bohmian mechanics, decoherence, Quantum Darwinism, structural and symmetry-based derivations of the Born rule, Everettian approaches, objective-collapse theories, and detector models. The resulting proposal is best understood as a propagation-first theoretical reconstruction program: Schrödinger dynamics organizes possible propagation, while Born statistics constrain how that propagation becomes physically realized. Keywords: Schrödinger equation; Born rule; wave function; quantum foundations; propagation structure; quantum probability; quantum trajectories; source-to-detector transport; detector response; wave–particle duality; Bohmian mechanics; quantum measurement
The Born rule provides the empirically successful statistical connection between the Schrödinger wave function and the outcomes of quantum experiments. Yet two logically distinct questions are often compressed into this rule: what the wave function describes during propagation, and why repeated localized particle events exhibit the statistics associated with its squared amplitude. In an earlier analysis, we proposed a deliberately restricted interpretation of the single-particle Schrödinger wave function as a complex-amplitude representation of the spatial--directional structure of quantum propagation. The present paper advances that proposal by one dynamical step. We begin not from an abstract probability distribution, but from the operational structure of electron-scattering experiments. Irrespective of the detailed electron-generation mechanism, a completed preparation procedure produces an actual electron flux crossing a source-exit surface. We therefore introduce a \textbf{preparation boundary} Σ0, and define N0 as the actual number of electrons crossing Σ0 during a specified time interval. A second surface, ΣD, represents an idealized detection boundary. For a Schrödinger state Ψ(r,t), the exact continuity structure definesρΨ=∣Ψ∣2,jΨ=mℏIm(Ψ∗∇Ψ),and, wherever ρΨ=0,vΨ=ρΨjΨ. We investigate the trajectory hypothesis that a localized electron configuration crossing Σ0 at (X0,t0) evolves according todtdX=vΨ(X,t).This generates a boundary-to-boundary flow mapΦΨ:(X0,t0)⟶(XD,tD). An ensemble of actual source crossings therefore defines a physical source measure μ0, while the corresponding distribution of detector crossings is the push-forwardμD=(ΦΨ)∗μ0. The Born problem can then be reformulated sharply: under what physical conditions does the source-generated measure μ0, transported by the Schrödinger flow, produce the standard Born distribution at ΣD? The trajectory law and the equivariance of ∣Ψ∣2 are closely related to established de Broglie--Bohm theory, and the connection between quantum flux and asymptotic surface crossings is rigorously developed in the flux-across-surfaces literature. We do not claim these mathematical structures as new. The contribution of the present work is instead to reconstruct the quantum-statistical problem from the complete experimental chainpreparation→source crossing→Schro¨dinger flow→trajectory→detection crossing→statistics,and thereby isolate a distinct \textbf{source-measure problem}. If Born statistics are to be dynamically accounted for rather than imposed at the outset, the remaining question is not only how ∣Ψ∣2 is transported, but why the microscopic preparation process produces the particular source ensemble whose boundary transport yields Born statistics. The present paper does not claim to solve that final problem. It formulates it as a concrete boundary-transport problem that can be addressed analytically, numerically, and ultimately through explicit models of electron preparation.