- Article
20 Pages
We develop a self-contained variational calculus for the coordination of synchronised agents. An agent is modelled as an overdamped (Onsager–Machlup) dynamical system on a five-dimensional manifold
whose coordinates are an internal Kuramoto order parameter R, a phase variance , and three S-entropy coordinates
. Crucially, and in contrast to a preliminary version of this work, every construct used here—the S-entropy coordinates, the partition potential, and the governing Lagrangian—is derived within the paper from three stated axioms (bounded phase space, categorical exclusion, finite resolution); the manuscript depends on no external or unpublished result. We prove (i) a triple-equivalence identity establishing the S-entropy coordinates from maximum-entropy counting; (ii) the explicit Euler–Lagrange equations of the agent action, given in full rather than asserted; (iii) the Kuramoto synchronisation bifurcation, with the corrected critical coupling
(for a Gaussian frequency law,
), replacing an erroneous coefficient in the preliminary version; (iv) a formal, analogy-free definition of partition extinction and an observable-commutation theorem that separates functional from ontological indistinguishability; and (v) a coordination calculus for ensembles. We are explicit that the five coordination bands on R are operational classification cut-offs, not phase transitions: the only genuine transition in the model is the Kuramoto bifurcation. Rather than the self-referential numerical checks of the preliminary version, we report nine external experiments against public data (atomic shell structure, the Kuramoto onset by direct simulation, the Wiedemann–Franz constant across eleven metals, sleep-EEG order parameters from PhysioNet, enzyme kinetics, antidepressant meta-analysis, superconductor transport, and representation-disjoint classifiers on a benchmark dataset). Two of these external tests forced corrections to the theory and are reported as such. We are deliberately narrow about applicability: the S-entropy coordinates measure the shape of an agent’s state distribution, not the content or ecological salience of its information; the model is stochastic (Langevin) but single-scale and on a fixed manifold, so it does not represent the multiscale fluctuation and metastability of real biological collectives; and we exhibit a concrete interpretable Lagrangian and a real-data ensemble instance rather than claim to capture any such collective in full. A Scope and Limitations section delimits the defensible claims.
Int. J. Topol.
19 September 2026


![Single-Agent State Manifold and Partition Potential. (A) Synchronisation potential
V
sync
(
R
;
K
)
=
(
K
c
−
K
)
R
2
/
2
+
K
R
4
/
4
on the linear y-axis versus the internal Kuramoto order parameter
R
∈
[
0
,
1
]
on the linear x-axis, for three coupling regimes: subcritical (
K
=
0.5
<
K
c
=
1
, steel blue, single minimum at
R
=
0
), critical (
K
=
K
c
, seagreen, quartic flat bottom), and supercritical (
K
=
3
>
K
c
, crimson, double-well with stable minimum at
R
*
=
1
−
K
c
/
K
≈
0.816
). The pitchfork bifurcation at
K
=
K
c
is the only genuine phase transition in the model. Empirical content of Theorem 4 (Synchronisation bifurcation). (B) Variance-floor term
V
var
(
σ
2
;
T
,
K
)
=
k
B
T
σ
2
+
k
B
T
/
(
K
σ
2
)
of the partition potential (Definition 5) on the linear y-axis versus phase variance
σ
2
on the linear x-axis, for three coupling strengths
K
∈
{
1
,
2
,
4
}
. Each curve has a unique minimum at
σ
min
2
=
1
/
K
(vertical dashed lines). Higher coupling K produces a lower variance floor. (C) Variance floor scaling figure on log-log axes:
σ
min
2
versus K, six measurement points (steel blue), with theoretical line
σ
min
2
=
k
B
T
/
K
(crimson). Slope is exactly
−
1
on log-log axes, confirming the analytical prediction. Experiment E05 reports relative error
1.11
×
10
−
16
. (D) Three-dimensional surface of the partition potential
Φ
(
R
,
σ
2
)
=
V
sync
+
V
var
+
V
SF
+
V
ent
over
(
R
,
σ
2
)
∈
[
0.05
,
0.95
]
×
[
0.1
,
1.5
]
,
25
×
25
grid, viridis colourmap, fixed
K
=
2
,
K
c
=
0.5
, S-entropy
S
=
(
0.5
,
0.5
,
0.5
)
. The global minimum lies at
(
R
*
,
σ
min
2
)
=
(
0.866
,
0.707
)
(the coherent regime); the surface rises sharply at low
σ
2
(variance-floor barrier) and at
R
=
0
(turbulent saddle).](https://mdpi-res.com/cdn-cgi/image/width=470%2Cheight=317/https://mdpi-res.com/ijt/ijt-03-00021/article_deploy/html/images/ijt-03-00021-g001-550.jpg)