Measurement, Decoherence, and Negotiated Reality: The Foundations of Quantum Mechanics in the Planck Core Framework

This paper resolves the measurement problem and the problem of intersubjectivity—two foundational puzzles of quantum mechanics—within the Planck Core Framework, without requiring any additional postulates beyond the three axioms of the framework. I prove that measurement is not a mysterious non-unitary "collapse" of the wavefunction, but a unitary process of entanglement establishment between subsystems of the quantum bit network. The apparent collapse arises from the observer's limited access to the full entanglement structure: what we perceive as a definite measurement outcome is simply our location within a specific entanglement branch. The Born rule is derived, not postulated—the probability of an outcome is proportional to the number of entanglement threads in the corresponding branch. The Wigner's friend paradox is resolved by proving that different observers may occupy different branches, but their descriptions converge when they exchange information via entanglement. I further introduce the concept of the "information eye"—a hypothetical direct entanglement sensor—and prove that any macroscopic biological organism operating at biological temperatures will inevitably perceive a decohered, classicalised representation of reality, not the underlying quantum information network itself. The classical appearance of the macroscopic world is thus derived as a contingent consequence of thermodynamic constraints on biological evolution, not a fundamental feature of reality. This work completes the derivation of quantum mechanics from the Planck Core Framework, establishing that no special measurement postulate is required.