A Theoretical Synthesis
Gravity as Feedback, Spacetime as Equilibrium
"Gravity is not fundamental, but rather the unique feedback mechanism required to preserve energy conservation in a system subject to continuous weak measurement."
This document synthesizes the Bath Framework for emergent gravity. Recent theoretical stress-testing has refined the model's prediction:
The framework does not reproduce standard General Relativity, but rather Unimodular Gravity.
This is a theoretical advantage: it naturally decouples the massive vacuum energy of the Bath from the emergent geometry, solving the cosmological constant problem without fine-tuning.
The ontology and operational equivalence of the Bath.
The universe is permeated by a "Bath": a large-N, Lorentz-invariant Quantum Field Theory in its vacuum state.
The coupling is operationally equivalent to a continuous weak measurement of the system's shape.
Empirically, the universe does not undergo runaway heating. Therefore, the open-system dynamics must include a "Drift" or "Feedback" Hamiltonian that cancels the measurement-induced heating.
The unique feedback law consistent with no-signaling and statistical conservation is a long-range attractive interaction.
Gravity is not chosen — it is forced by consistency requirements.
The coupling strength emerges from microscopic parameters:
The weakness of gravity is linked to the large size of the Bath.
To recover a 1/r Newtonian potential from this feedback, the Bath's retarded TT correlator must possess a massless pole (1/k²) in the infrared.
The mechanism: mass suppresses vacuum fluctuations, generating a force even though coupling is purely radiative.
The most significant update to the framework.
Standard General Relativity requires the exchange propagator to couple to both:
Shear term
Trace term
A rigorous derivation proves that a Bath coupled only to TTT cannot generate the trace term necessary for full GR.
While temporal components (T00) are recovered via current conservation, the scalar trace (T) remains decoupled.
Unimodular Gravity: A theory invariant only under volume-preserving diffeomorphisms.
This apparent limitation resolves a fatal flaw in emergent gravity approaches:
The vacuum energy of the Bath would act as a massive Cosmological Constant, curving the universe into a singularity.
Vacuum energy (pure trace: Tμν ∝ ημν) decouples completely from equations of motion.
The framework is falsifiable through two distinct channels.
The model predicts a specific TT-decoherence functional.
Distinct from standard environmental noise or Penrose/Diósi collapse models.
Because the theory is Unimodular:
The −½T² coupling becomes dynamically relevant in extreme conditions.
The corpus presents a self-consistent derivation of gravity as the hydrodynamics of a "Shape Measurement" Bath.
"Spacetime is not fundamental; it is the equilibrium state of a system minimizing information leakage to its environment."
Can this framework be tested in the laboratory?