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2205.11543

On Bayesian Mechanics: A Physics of and by Beliefs

Maxwell J. D. Ramstead, Dalton A. R. Sakthivadivel, Conor Heins, Magnus Koudahl, Beren Millidge, Lancelot Da Costa, Brennan Klein, Karl J. Friston

incompletemedium confidence
Category
Not specified
Journal tier
Specialist/Solid
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper correctly asserts the Gibbs form p(x) ∝ e^{-λ J(x)} and the parallel-transport differential relation dp = −λ p dJ (equivalently ∂x log p = −λ ∂x J), and sketches a gauge-theoretic interpretation of constrained maximum entropy (see eqs. (6–9) and (10), and the claims “p(x)=e^{−λJ(x)}” and “maximum of entropy is parallel transport” ). However, the derivation omits the normalization constraint multiplier α and subsequently makes the imprecise claim that the “−1” term can be absorbed into λ (footnote 17), which mixes a constant with the multiplier of J(x) and obscures the necessary normalizing constant Z(λ) ( ). The candidate solution provides the standard, complete variational treatment with both constraints, the partition function, and the conditions for existence/uniqueness of λ, and derives the same dp = −λ p dJ relation rigorously. Hence, the model’s solution is correct and technically complete, while the paper’s argument is sound in essence but technically incomplete.

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The paper offers a cogent and timely bridge between constrained maximum entropy and gauge-theoretic notions of covariance and parallel transport, aligning well with current interest in the FEP/CMEP duality. The core mathematical statements (Gibbs form and parallel-transport ODE) are essentially correct, but the derivation is informal in places: the normalization constraint multiplier is omitted, the constant term in the Euler–Lagrange condition is handled imprecisely, and standard existence/uniqueness conditions are not stated. These are straightforward to fix and do not affect the main claims.