From Newton's equations to the Schrödinger equation: domain walls as the quantization condition
Can particles at definite positions in real space, obeying Newton's equations under an ordinary interaction force, have a coarse-grained description that is the Schrödinger equation? We present a medium of companion particles on a line under a force of exactly that kind: each companion pays for the mismatch of the signed inverse gaps to its two neighbors. A binary polarity carried by each companion makes stationary states with nodes dynamically stable and supplies the quantization condition. Finite chains relax into the stationary densities of the box and the harmonic oscillator and develop double-slit fringes. In the smooth limit the Schrödinger equation emerges, with $ψ$ carrying two real fields rather than being fundamental.