Submitted:
27 September 2026
Posted:
28 September 2026
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Abstract
The first paper of Principles of Artificial Science I proposed a global gauge architecture for Big Knowledge Assembly Dynamics. The present paper develops its first concrete mechanism: knowledge assembly under U(1) symmetry. The theoretical scaffold is quantum electrodynamics (QED), but the purpose is not to identify economic or cognitive systems with physical electromagnetic systems. Rather, QED provides a minimal mathematical structure for a single-charge dynamical system: a one-dimensional Abelian phase symmetry, a gauge potential, a covariant derivative, a field strength, and path-dependent phase transport. Previous work has independently constructed U(1)-type local dynamics in market dynamics and reasoning dynamics, within broader programs of economic dynamics and higher-cognition theory. The present paper does not reconstruct those local theories. It asks a new question: can previously separated U(1)-structured knowledge blocks be assembled through one reusable structural interface? We represent a local knowledge block by and introduce a common U(1) assembly template Each domain is related to this common template by a structural map Knowledge assembly therefore does not require QED, market dynamics, and reasoning dynamics to become identical. It requires designated structural relations to be preserved across domain-specific realizations. We formulate a preliminary criterion of U(1)-assemblability in terms of compatibility with covariant differentiation, curvature, and holonomy.The resulting framework is then applied to four contemporary AI problems: compositional generalization, continual learning and catastrophic forgetting, long-horizon trajectory drift, and cross-domain frame mismatch. In each case, the U(1) model suggests a common principle: knowledge should be transformed without confusing changes of representational frame with changes of structural content. The paper therefore interprets U(1) symmetry not merely as a shared mathematical form across disciplines, but as the first candidate technology for covariant AI knowledge assembly.
Keywords:
artificial science
; big knowledge dynamics
; knowledge assembly
; U(1) symmetry
; QED
; market dynamics
; reasoning dynamics
; covariant derivative
; dynamic phase
; berry phase
; holonomy
; compositional generalization
; continual learning
1. Introduction: The First Concrete Mechanism of Knowledge Assembly
The first paper in this series introduced a global architecture for Big Knowledge Assembly Dynamics. Its central transition was
shared structure → global symmetry → localization → connection → curvature
That framework was deliberately general. It described the geometry within which different mechanisms of knowledge assembly could later be developed.
The present paper begins that development.
Among the gauge structures relevant to the Artificial Standard Model program, U(1) is the simplest. Its importance does not lie merely in mathematical simplicity. It is the natural starting point because several previously developed domain-specific dynamical models already possess a single-charge, Abelian gauge organization.
In economic dynamics, market dynamics was explicitly constructed using quantum electrodynamics as a conceptual and mathematical model: buying and selling intentions carry market charge; moving market charge generates market current; a cognitive field accompanies this flow; and global and local gauge potentials and field strengths are distinguished. The theory explicitly identifies market dynamics and QED as single-charge systems sharing U(1) symmetry.
Reasoning dynamics independently develops an analogous structure. Logical charge acts as the source; moving logical charge generates logical current and a cognitive field; the global level describes a general rational reasoner, whereas the local level introduces individual differences through a position-dependent phase. The theory explicitly moves from constant phase
θ = C
to local phase
θ = θ(x),
and uses this transition to motivate local gauge symmetry.
Higher-cognition theory places reasoning dynamics in a broader cognitive program that integrates reasoning, decision making, and competition, while economic dynamics provides the broader methodological system in which U(1), SU(3), SU(2), and symmetry-breaking mechanisms occupy distinct structural positions.
These previous studies provide the local dynamics.
The new question is no longer:
Can a market or reasoning process be represented by a U(1)-type gauge model?
That question has already been explored.
The present question is:
This changes the problem from interdisciplinary modeling to Artificial Science.
The basic proposal is:
QED, Market Dynamics, Reasoning Dynamics → a shared U(1) knowledge-assembly interface.
The three theories are not identified with one another. Their empirical objects and semantics remain different. What is assembled is the structural machinery that governs charge-like sources, phases, potentials, covariant transport, and field strength.
This paper therefore develops the first mechanism-specific claim of Big Knowledge Dynamics:
Knowledge blocks become composable not by becoming identical, but by preserving a common covariant structure across changing local representations.
2. Mathematical Scaffold and Prior U(1) Foundations
2.1. QED as a Minimal Structural Scaffold
The gauge group of QED is
U(1) = {eiθ | θ ∈ ℜ}.
For a charged field ψ(x), a local phase transformation takes the form
ψ(x) ↦ eiqθ(x)ψ(x).
The ordinary derivative does not transform covariantly under an arbitrary local phase transformation. One therefore introduces a gauge potential Aμ and defines
With this sign convention, gauge covariance requires the accompanying potential transformation

so that the covariant derivative transforms in the same U(1) representation as the charged field.
The corresponding Abelian field strength is
Unlike a non-Abelian gauge theory,
[Aμ,Aν] = 0.
Thus the essential U(1) scaffold consists of only a few structures:
These relations, rather than the physical identity of electromagnetic entities, are what concern Artificial Science.
2.2. Structural Correspondence Without Ontological Identity
The present proposal does not imply
market charge = electric charge,
nor
logical charge = electric charge.
Instead, QED supplies a structural template.
We distinguish
from
A substantive cross-domain relation therefore requires preservation of specified mathematical relations, not merely similarity in vocabulary.
This distinction is crucial for knowledge assembly. Artificial Science does not need different disciplines to refer to the same objects. It requires them to possess sufficiently compatible structures that one system can be transported into the structural coordinates of another without destroying designated invariants.
2.3. Prior Domain Foundations
2.3.1. Economic Dynamics as the Methodological Frame
The Contents, Methods, and Significance of Economic Dynamics presents economic dynamics as a Standard-Model-inspired theoretical program. It explicitly identifies market dynamics and QED as sharing U(1), sub-economic dynamics and QCD as sharing SU(3), economic externality dynamics and weak-isospin dynamics as sharing SU(2), and ordinary rationality with a symmetry-breaking mechanism.
Of particular importance for the present paper is its description of market dynamics as a single-charge dynamic system, with market charge carried by buying and selling intentions. It also explicitly proposes U(1) symmetry as a morphism connecting market dynamics and QED within a category of single-charge dynamics.
This prior proposal is an important precursor of the present work. The difference is that the current paper shifts from a category of structurally corresponding dynamics to an operational framework for AI knowledge assembly.
2.3.2. Market Dynamics
Market dynamics provides the most fully developed economic U(1) block.
Its source is market charge. Moving market charge produces market current, which is associated with a cognitive field. Gauge-theoretic modeling distinguishes global and local levels, as well as gauge potential and gauge field strength.
The previously developed framework includes:
- market charge;
- market current;
- dynamic phase;
- global/local gauge potential;
- global/local gauge field strength; and
- U(1) gauge transformation.
The present paper treats these as one already constructed local knowledge block rather than reconstructing their economic semantics.
2.3.3. Reasoning Dynamics
Reasoning dynamics provides the principal cognitive U(1) block.
Its source is logical charge:
qL·
Movement of logical charge produces logical current and an associated cognitive field. The global level abstracts away individual differences, whereas the local level treats individual reasoners as distinct local realizations.
At the global level,
ψ ↦ eiθψ,θ = C,
whereas localization yields
ψ(x) ↦ eiθ(x)ψ(x).
The previous theory further identifies different reasoning potentials at the local level with differences in knowledge, training, language capacity, skill, and task preparation.
These properties make reasoning dynamics especially important for Artificial Science because the local coordinate x already has a natural interpretation in terms of heterogeneous cognitive agents.
2.3.4. Higher Cognition
Higher-cognition theory supplies a broader cognitive container. It integrates reasoning, decision making, and competition, and it explicitly describes logical charge, logical flow, cognitive field, and the extension of gauge-based dynamics from cognition to economics.
Its role in the current paper is therefore not to provide a fourth independent U(1) field theory, but to establish that reasoning dynamics belongs to a larger knowledge architecture in which structural transformations can be reused across cognitive domains.
We can therefore distinguish the functions of the four prior works:
The present paper adds a fifth level:
3. The U(1) Knowledge-Assembly Interface
3.1. Unified Data Structure for Single-Charge Knowledge Blocks
Let a local single-charge knowledge block be represented as
Here ψi is the local knowledge state; qi is the domain-specific charge-like source; θi is its local dynamical phase; Ai is its gauge potential or knowledge connection in the local representation; Fi is the corresponding field strength or assembly curvature; and Ji is the relevant current or sourced dynamical flow.
For the three central blocks,
KQED,KM,KR,
the empirical meanings differ.
Yet all three may instantiate the same abstract arrangement:
The purpose of abstraction is not to erase semantics. It is precisely the opposite: each domain retains its semantics while exposing the part of its mathematical organization that can be transported.
We therefore define a shared structural template:
Here U(1) is the symmetry group; ρ is its representation on the fiber; L→M is the designated line-bundle-like structural carrier; D is a covariant derivative (connection); F is its curvature; and Hol denotes closed-loop holonomy. The bundle language is used only on the specified shared structural subspace, not as an ontological claim about the source domains.
This is the U(1) Knowledge-Assembly Interface.
3.2. Structural Mapping Rather than Direct Identification
For each domain define
The role of ᵢ is to extract the designated U(1) structure from a domain-specific knowledge block.
Thus QED, market dynamics, and reasoning dynamics do not map directly into one another:
KM≢KQED,
KR≢KQED,
and
KM≢KR.
Instead,
Likewise,
This apparently small change is conceptually important.
It replaces the claim
Market dynamics resembles QED.
with the stronger but more disciplined claim:
QED and market dynamics each admit a mapping into a common U(1) structural interface whose preserved relations can be explicitly specified.
The same applies to reasoning.
Knowledge assembly therefore takes the form
A knowledge structure is first lifted from its local semantic realization into a shared structural space and is then re-grounded in another domain.
We call this
This is the first concrete assembly operation of Artificial Science.
3.3. Preservation Conditions and U(1)-Assemblability
The existence of a mapping alone is insufficient. Almost anything can be mapped to anything if no preservation condition is imposed.
A meaningful structural map should therefore preserve designated structural relations.
At minimum, the following should be examined.
For these geometric conditions, let fi: Mi → M denote the base-space map on the designated shared subspace, and let Φi be a U(1)-equivariant bundle/state map covering fi. This distinguishes the semantic lift from the geometric data needed to compare connections, curvature, and holonomy.
First, the group action:
Φi(ρi(g)Ψi) = ρ(g)Φi(Ψi).
Second, covariant differentiation:
Third, curvature:
on the designated shared subspace.
Fourth, closed-loop transport:
for every closed loop C in the designated shared subspace, up to the equivalence relation appropriate to the representation.
These requirements lead to a preliminary definition.
Definition 1. U(1)-Assemblability
Two single-charge knowledge blocks Kᵢ and Kⱼ are U(1)-assemblable relative to a specified structural subspace if there exist compatible base maps and U(1)-equivariant bundle/state maps satisfying the preservation conditions below.
Φi:Ki → Ω1,Φj:Kj → Ω1
that preserve the designated U(1) group action and are compatible with the required covariant transport relations.
A stronger form additionally requires preservation of curvature and holonomy.
This definition deliberately includes the phrase “relative to a specified structural subspace.” We do not assume that the entire semantic content of two disciplines is gauge-equivalent.
That restriction is essential.
4. Phase Transport, Berry-Type Phase, and Abelian Holonomy
The local models already contain dynamical phase.
The present paper asks what happens when these phases are assembled.
Within a local U(1) block,
When knowledge is transported along a path C, the Abelian parallel-transport factor is
Because U(1) is Abelian, no path-ordering operator is required.
For a closed loop,
The result is a phase holonomy.
For an open path, the transport factor is gauge-covariant and depends on endpoint frames. For a closed loop in an Abelian U(1) model, the holonomy phase is gauge invariant. Moreover, local flatness F = 0 need not force globally trivial holonomy when the relevant base region is not simply connected.
A conceptual cross-disciplinary loop may be written:
The question is whether the transported structural state returns identically to its initial condition.
If
U(C) = 1,
the closed assembly path has trivial U(1) holonomy.
If
U(C) ≠ 1,
the state retains a residual phase.
This residual phase can encode a form of knowledge path memory.
4.1. Berry-Type Phase and Abelian Holonomy
The preceding phase should not automatically be identified with a Berry phase.
A Berry-type geometric phase requires a normalized parameterized state family, a parameter space, and the associated Berry connection. It should not be identified with the preceding knowledge-gauge holonomy unless a specific line-bundle identification or pullback map is established.
Let
|Ψ(λ)⟩
be a normalized family over a parameter space. The Berry connection and closed-loop geometric phase are then
𝒜B = i⟨Ψ|dΨ⟩.
For a closed path,
γB=∮𝒜B.
This permits three conceptually distinct phase structures:
and
The first records local dynamical evolution.
The second records geometric memory associated with movement through a parameterized state family.
The third records the residual gauge transformation after closed-loop parallel transport.
Under appropriate model conditions these structures may be related, but they should not be identified without establishing the relevant bundle, state-family, and pullback maps. The Berry phase is defined modulo 2π under a smooth phase-gauge change of the normalized state family.
This distinction was already anticipated in the general gauge framework of Artificial Science I (1); the present paper provides its first Abelian implementation.
5. Contemporary AI Problems Under U(1) Assembly
The value of a knowledge-assembly theory should not depend solely on its mathematical elegance. It should also provide new ways to formulate concrete AI problems.
The U(1) framework suggests a common diagnosis of several contemporary problems:
Four issues are particularly relevant.
5.1. Compositional Generalization
LLMs can often manipulate familiar components but remain imperfect at systematically recombining them under new structural constraints. A 2025 ACL study introduced Ordered CommonGen to test both composition and instruction-sensitive ordering across 36 LLMs; even the strongest instruction-following model in that study achieved only about 75% ordered coverage.
From the perspective of Big Knowledge Dynamics, this suggests a distinction between
and
A model may possess A, B, and C individually while failing to preserve the intended structural relation when they are recombined.
The U(1) response is not that every compositional task is literally Abelian. Rather, U(1) provides the minimal example of a shared interface under which local components can change representation while maintaining a preserved transformation rule.
Thus:
The latter is the concern of knowledge assembly.
5.2. Continual Learning and Catastrophic Forgetting
Continual learning must balance plasticity with preservation. Recent work continues to identify catastrophic forgetting and efficient transfer between old and new tasks as central problems, including approaches that route new inputs through reusable adapters rather than repeatedly overwriting a single undifferentiated parameter system.
Big Knowledge Dynamics reformulates this problem as:
and
Suppose an old knowledge state is
Ψold,
and new experience induces
Ψold → Ψnew.
Ordinary parameter change alone does not tell us whether a deep structural invariant has been preserved.
The gauge formulation instead asks whether the update is covariant:
A future implementation could distinguish legitimate local adaptation from destructive change of shared structure.
In this sense, catastrophic forgetting may sometimes be viewed not merely as loss of stored information, but as failure to preserve selected invariants during local updating.
This is a hypothesis to be tested, not an established explanation of catastrophic forgetting.
5.3. Long-Horizon Trajectory Drift
As AI systems operate for longer periods, evaluation of individual actions becomes increasingly insufficient. OpenAI reported in 2026 that internal testing of long-running models revealed failures not captured by earlier evaluations and motivated trajectory-level monitoring rather than examination of isolated actions.
This shift from state evaluation to trajectory evaluation is closely aligned with the path language of Big Knowledge Dynamics.
Two trajectories can share the same apparent initial and terminal task,
C1,C2:xA → xB,
while producing different internal transformations:
Thus:
For a U(1) system, the difference may appear as accumulated phase.
For later non-Abelian systems, it can become a matrix-valued order effect.
The important conceptual move is that long-horizon degradation can be studied not only as error accumulated at individual steps but also as trajectory-dependent structural drift.
This gives Yang’s non-integrable phase factor and holonomy a concrete Artificial Science role.
5.4. Cross-Domain Transfer and Frame Mismatch
Cross-domain transfer creates a different difficulty.
Suppose a model has learned a valid structure in domain i, but domain j represents the same underlying relation differently.
An ordinary difference operator may interpret
Ψj − Ψi
as a change in knowledge content.
But part of the difference may be due only to a change of local frame.
The covariant derivative is designed precisely for this distinction:
This suggests the following hypothesis:
Some apparent cross-domain transfer failures may arise not from missing knowledge but from uncorrected representational-frame changes.
The corresponding AI problem is therefore not simply translation between representations.
It is:
If these can be separated, knowledge learned in one domain may become reusable in another without forcing both domains into an identical representational system.
5.5. Unified Interpretation of the Four AI Problems
The four issues can now be placed within one structure:
| AI problem | BKD interpretation | U(1)mechanism |
| Compositional generalization | components exist but lack a stable structural interface | shared invariant template |
| Catastrophic forgetting | local update damages previously preserved structure | covariant updating |
| Long-horizon drift | transported state depends on trajectory | phase accumulation and holonomy |
| Cross-domain transfer failure | frame change is confused with content change | connection and covariant derivative |
These correspondences should be understood as research hypotheses, not as claims that the listed AI problems have already been solved by gauge models.
Their value is that four apparently different engineering problems can be reformulated using one structural vocabulary:
This is the first indication that Big Knowledge Dynamics may function not only as an interdisciplinary theoretical synthesis but also as a design language for AI systems.
6. Structural Reuse and Semantic Re-Grounding
6.1. Structural Reuse and Training Efficiency
The central engineering hypothesis of this series is that AI systems need not relearn structurally equivalent relations independently in every domain.
If
and
then learning an invariant relation in the shared structural space may reduce the amount of relearning required when the system encounters a new local realization.
The proposed transition is:
This could be tested through measurable quantities such as sample efficiency, transfer speed, parameter reuse, cross-domain accuracy, forgetting rate, and representation stability.
The hypothesis is not that structural reuse automatically increases efficiency.
A gain should occur only when the identified shared structure is genuine and when the cost of mapping into and out of the shared interface is lower than the cost of independently relearning the corresponding relation.
Thus one may write schematically:
Cassembly = Clift + Cshared + Creground.
Structural reuse is advantageous only when
This provides a direct empirical criterion for future AI experiments.
6.2. Structural Lift and Semantic Re-Grounding
Mathematical structure alone is insufficient for knowledge assembly.
Suppose market dynamics and reasoning dynamics both admit U(1)-type organization. It does not follow that market charge and logical charge have the same meaning.
Therefore the full assembly process contains two complementary operations:
and
The structural lift maps a local knowledge block into the shared interface:
The semantic re-grounding maps the transferable structural relation into another local domain:
where Γj is a domain-specific semantic re-grounding map defined on the relevant image of the shared interface. No global inverse of Φj is assumed.
Thus knowledge assembly may be written schematically as
This structure protects the theory from a common error of interdisciplinary analogy.
The transferable object is not the entire domain.
The transferable object is the designated invariant structure.
The target domain must then re-establish its own semantics.
Hence:
This principle will become even more important in the later SU(3) and SU(2) papers, where internal structure is richer and noncommutativity makes direct analogy still more dangerous.
7. The Abelian Limit and Transition to Non-Abelian Assembly
The U(1) model represents the simplest case of knowledge assembly.
Its simplicity comes from commutativity:
[Aμ,Aν] = 0.
Consequently, field strength contains no gauge-potential commutator term:
Fμν = ∂μAν − ∂νAμ.
This makes U(1) the natural first laboratory for testing structural lift, covariant comparison, phase transport, Berry-type memory, Abelian holonomy, and cross-domain re-grounding.
But precisely because it is Abelian, U(1) cannot represent the full complexity of knowledge assembly.
When two knowledge transformations do not commute,
TATB ≠ TBTA,
a scalar phase is insufficient.
The internal transformation itself becomes order-dependent.
That is the point at which Big Knowledge Dynamics must leave the Abelian regime.
8. Discussion: From U(1) Transport to Non-Abelian Assembly
This paper began from four previous bodies of work and changed their role.
Economic dynamics supplied a general Standard-Model organization.
Market dynamics supplied an economic single-charge U(1) system.
Reasoning dynamics supplied a cognitive single-charge U(1) system.
Higher-cognition theory situated reasoning dynamics within a broader cognitive architecture.
The present paper does not add another independent local dynamics.
Instead, it performs the first explicit act of Artificial Science knowledge assembly:
The central mathematical object is
The central operation is
And the central methodological requirement is
This framework also gives a common interpretation to several contemporary AI issues. Compositional generalization concerns whether components can be recombined under preserved structural constraints. Continual learning asks how local change can occur without destroying previously learned invariants. Long-horizon behavior raises the problem of trajectory-dependent transformation. Cross-domain transfer requires distinguishing representation change from content change.
These are not four independent issues from the viewpoint of Big Knowledge Dynamics.
They share one underlying problem:
For a single-charge system, U(1) provides the minimal mathematical answer.
But knowledge systems are not always single-component.
Many forms of knowledge contain multiple interacting internal dimensions. Their transformations may be noncommutative, and the order of assembly may itself alter the result.
Thus the next stage is not simply “a larger U(1).”
It is a qualitative transition:
The next paper therefore turns to three-charge knowledge systems and SU(3) symmetry.
9. Conclusions
The present paper develops U(1) symmetry as the first concrete knowledge-assembly mechanism of Artificial Science.
The argument can be summarized as follows:
The crucial transition is from structural correspondence to structural operation.
Previous work showed that several domains can be modeled by related U(1)-type structures.
Artificial Science asks what can be done with that fact.
The answer proposed here is:
The deeper implication for artificial intelligence is equally simple:
References
- Baez, J. C.; Muniain, J. P. Gauge Fields, Knots and Gravity; World Scientific, 1994. [Google Scholar]
- Berry, M. V. Quantal phase factors accompanying adiabatic changes. Proc. R. Soc. Lond. A 1984, 392, 45–57. [Google Scholar] [CrossRef]
- Bonnet, D.; et al. Bayesian continual learning and forgetting in neural networks. Nat. Commun. 2025, 16, 9614. [Google Scholar] [CrossRef] [PubMed]
- Julian, J.; Koh, Y. S.; Bifet, A. Building adaptive knowledge bases for evolving continual learning models. npj Artif. Intell. 2025, 1, 26. [Google Scholar] [CrossRef]
- Nakahara, M. Geometry, Topology and Physics, 2nd ed.; Institute of Physics Publishing, 2003. [Google Scholar]
- OpenAI. Saf. Alignment An. Era Long.-Horiz. Model. 2026. [CrossRef]
- Peskin, M. E.; Schroeder, D. V. An Introduction to Quantum Field Theory; Addison-Wesley, 1995. [Google Scholar]
- Sakai, Y.; Kamigaito, H.; Watanabe, T. Revisiting compositional generalization capability of large language models considering instruction following ability. Proc. ACL 2025, 2025, 31219–31238. [Google Scholar] [CrossRef]
- Simon, B. Holonomy, the quantum adiabatic theorem, and Berry’s phase. Phys. Rev. Lett. 1983, 51, 2167–2170. [Google Scholar] [CrossRef]
- Yang, C. N. Integral formalism for gauge fields. Phys. Rev. Lett. 1974, 33, 445–447. [Google Scholar] [CrossRef]
- Yang, C. N.; Mills, R. L. Conservation of isotopic spin and isotopic gauge invariance. Phys. Rev. 1954, 96, 191–195. [Google Scholar] [CrossRef]
- Yang, Y. Principles of Market Dynamics: Economic Dynamics and Standard Model (II); Preprints, 2024. [Google Scholar] [CrossRef]
- Yang, Y. Principles of Reasoning Dynamics; Preprints, 2024. [Google Scholar] [CrossRef]
- Yang, Y. The Contents, Methods, and Significance of the Economic Dynamics: The Economic Dynamics and the Standard Model (I); Preprints, 2024. [Google Scholar] [CrossRef]
- Yang, Y. The Topics, Methods, and Significance of a Higher Cognition Theory; Preprints, 2024. [Google Scholar] [CrossRef]
- Yang, Y. Gauge Symmetry Struct. Big Knowl. Assem. Dyn. Princ. Artif. Sci. I (1) Preprint manuscript. 2026. [CrossRef]
- Zee, A. Quantum Field Theory in a Nutshell, 2nd ed.; Princeton University Press, 2010. [Google Scholar]
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