Volume LIII develops the holographic and quantum‑informational formulation of the R-layer Mode Theory (RLMT), establishing a framework in which cosmological spacetime and its perturbations emerge from layered modular dynamics. Building on the holographic principle, double holography, and the interplay between quantum gravity and quantum information, this volume introduces the R-layer holographic program: a non‑perturbative, coarse‑grained description in which modular Hamiltonians, entanglement wedges, and causal structure are encoded in a hierarchy of R-layers. At the microscopic level, the theory assumes that the fundamental degrees of freedom reside on a lower-dimensional quantum system coupled to an auxiliary bath, analogous to brane-world and double-holographic constructions. Bulk geometry is reconstructed from information-theoretic quantities such as entanglement entropy, relative entropy, and modular flow. We formulate a set of R-layer consistency conditions that relate boundary modular flow, emergent bulk causal structure, and the stability of semiclassical cosmological backgrounds. In appropriate limits, a generalized Ryu–Takayanagi relation for the R-layer entanglement functional yields effective Einstein equations with cosmological matter sources, while deviations encode controlled violations of locality and standard energy conditions. The framework is extended to cosmological perturbation theory by embedding the R-layer into a perturbed FLRW universe. Gauge‑invariant perturbation variables are constructed, and modified evolution equations for scalar, vector, and tensor modes are derived. These equations contain R-layer correction terms arising from non‑equilibrium modular flows, finite entanglement depth, and imperfect encoding of bulk locality. We analyze observational consequences, including modifications to the matter power spectrum, CMB anisotropies, and gravitational-wave propagation. Volume LIII thus provides the holographic and quantum‑informational foundation of RLMT, offering a unified language that connects modular flow, emergent geometry, and cosmological dynamics. It establishes a testable framework for probing the quantum structure of spacetime through cosmological observables.
Tsuyoshi Tohi (Wed,) studied this question.