Collapse Without an Observer: Quantum Measurement as Field Gradient Localization

The quantum measurement problem has resisted resolution for nearly a century. Quantum mechanics describes particles as waves — diffuse probability distributions spread across space. Measurement appears to collapse this distribution instantaneously to a single definite location. What causes the collapse? Standard quantum mechanics provides no answer. The wavefunction evolves deterministically under the Schrödinger equation until measurement, at which point it collapses probabilistically. The transition between these two behaviors has no physical mechanism in the standard formulation. This paper proposes a physical mechanism, presented here in corrected form. Within the Field Intrinsic Gravity Induced Density (FIGID) framework, a particle is a diffuse field condensation — a region of elevated field density spread over some volume. Measurement is a two-stage physical process. In the first stage, a which-path probe couples to the condensation asymmetrically: the probe's own field ends in a distinguishably different configuration depending on which path the particle took. This coupling entangles the probe with the condensation and redistributes the particle's phase structure into the joint particle–probe field. Interference disappears from the particle's own state not because the condensation localized, but because its coherence now resides in the combined configuration. In the second stage, the condensation localizes — at final registration, when it enters the steep gradient environment of a macroscopic detector and condenses to a definite position with probability proportional to its local field density. This is wavefunction collapse, and it requires no observer. The revision from Version 1 is specific and is documented in the Version Note below. The earlier claim that a which-path detector's mass-sourced gradient forces localization at the slit is withdrawn. The quantum eraser demonstrates that coherence survives the which-path interaction — it is redistributed, not destroyed — which is impossible if localization occurred at the slit. The corrected mechanism, developed in full mathematical form in the companion paper Coherence Is a Field Configuration, replaces gradient strength with coupling asymmetry as the decoherence variable and defers localization to registration.