Emergence of FLRW Cosmology from Discrete Horizon Layering

This paper shows that a spatially flat FLRW cosmology can emerge directly from the discrete growth of a Schwarzschild black-hole horizon, without invoking bulk Einstein equations or assuming any stress-energy content in the interior. In the external Schwarzschild frame, each Planck-scale incorporation event increases the mass by a fixed increment and correspondingly enlarges the horizon by 2 Planck lengths. Although the growth occurs in discrete steps, the information capacity of successive layers increases with the horizon area, so each new layer contributes an increasingly fine element to an information-weighted radial coordinate. Interpreting this layered structure as encoding causal depth produces a continuous comoving radius and a smooth, isotropic spatial geometry. The resulting interior metric is the spatially flat FLRW line element, and an expansion law H(t) ≈ 1/t follows kinematically from the assumed horizon-growth prescription. The derivation is microstructure-agnostic within a broad class of models satisfying spherical symmetry, the area–information relation, and null-synchronized horizon updates. In this way, coasting cosmologies acquire a horizon-based, holographically inspired effective description, with FLRW dynamics generated from the outside as the continuum limit of a layered causal architecture on a growing black-hole horizon.