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05 / Symmetry & loops

Change the frame.
Follow what survives.

Four finite explorers connect local transport, retained structure, singlet-loop energy and geometric phase. Inspect the assumptions behind each calculation.

Finite mathematical models; physical matching remains separate

Local frames and loop transport

Change the local frames while retaining the loop observable. The transformation law alone does not select a physical gauge group or coupling.

Local frames and a non-Abelian loop

Change two physical link angles and four locally chosen frames. Matrix entries can change while the trace of the closed loop stays fixed.

All angles are radians; matrices, traces and probabilities are dimensionless.

Choose the model inputs

Loop trace 0.490691. Frame-change trace error 0.

Normalized loop trace
0.490691
Trace after frame changes
0.490691
Trace difference
0
Matrix covariance error
2.01e-16
An oriented four-link loopFollow nodes 0, 1, 2, 3, then 0. The order in the matrix product is reversed because operators act on the rightmost state first.0123U₁₀ = exp(i a σₓ)U₂₁ =exp(i b σᵧ)U₃₂ = U₁₀†U₀₃ = U₂₁†0 → 1 → 2 → 3 → 0Products act right to left
The arrows mark transport direction. Local frame choices conjugate the full loop at its base point.
Three different loop readouts
ReadoutValueDefinition
Wilson cost0.5093091 − Re Tr W/2
Interferometer dark-port probability0.2546545(1 − Re Tr W/2)/2
Forced singlet-return probability0.2407776|Tr W/2|²

The first-link matrix changes by Frobenius norm 0.8381477. At W = −I the interferometer dark port has probability one while the forced-return probability is also one: these are distinct readouts.

Inspect the loop and a changed link
Loop matrix entries: W and W′
EntryOriginal complex valueTransformed complex value
1, 10.49069 + 0.47984i0.49069 + 0.47984i
1, 2-0.40416 + 0.60467i-0.72718 − 0.013385i
2, 10.40416 + 0.60467i0.72718 − 0.013385i
2, 20.49069 − 0.47984i0.49069 − 0.47984i
First link: U₁₀ and U′₁₀
EntryOriginal complex valueTransformed complex value
1, 10.76484 + 0i0.82438 − 0.45036i
1, 20 + 0.64422i-0.16439 + 0.30092i
2, 10 + 0.64422i0.16439 + 0.30092i
2, 20.76484 + 0i0.82438 + 0.45036i
Equations and conventions used
U′yx = gyUyxgx−1; W = U03U32U21U10; W′ = g0Wg0−1.
Re Tr W / 2 = 1 − 2 sin²a sin²b.

An exact four-link SU(2) example. Local frame changes relabel the same loop. Its energy and physical dynamics are not determined by this kinematic calculation.

Downloads include the chosen inputs, units and model scope. Values use standard floating-point arithmetic. Read the source and its version notes.

Try this investigationVary the frame angles without changing the physical link configuration. Check which displayed quantities remain invariant.

Which structure is retained?

Compare the group that preserves the selected metric, blocks and volume structure. Additional retained tensors impose additional restrictions.

Retained structure and the gauge group

Choose exactly which tensors are retained, inspect the stabilizer dimension, and test the global quotient condition for a representation.

Group dimensions and q = 6Y are integers. κ₃ and κ₂ are illustrative responses in a common chosen unit.

Choose the model inputs

S(U(3) × U(2)), dimension 12. Product-volume quotient residue 0.

Selected stabilizer
S(U(3) × U(2))
Real Lie-group dimension
12
Tr Q² for the product-volume case
30
12κ₃ + 18κ₂ (chosen response unit)
30

The separate blocks and a parallel product-volume tensor are retained exactly.

Retained tensors and their stabilizers
Retained choiceGroupDimensionSelected
combinedU(5)25
blocksU(3) × U(2)13
productS(U(3) × U(2))12Yes
separateSU(3) × SU(2)11

Global representation test

For S(U(3) × U(2)), q + 2t₃ + 3t₂ = 6, with residue 0 modulo 6. This representation descends through the stated ℤ₆ quotient.

Product-volume quotient diagnostic
QuantityValue
q = 6Y1
Color triality t₃1
Weak parity t₂1
q + 2t₃ + 3t₂ modulo 60
Kernel action on this representation1 + 0i

The center generator Q is fixed by the stated embedding. Its trace weights give the displayed linear combination of two supplied block responses. A physical identification still requires action normalization, matter conventions, scale matching and any quantum corrections.

Equations and conventions used
(A,B,z) ↦ (z−2A, z³B); kernel generated by (e2πi/3I₃, −I₂, eiπ/3).
A representation descends through ℤ₆ iff q + 2t₃ + 3t₂ ≡ 0 (mod 6).
Q = diag(−2I₃,3I₂); Tr Q² = 30; κcentral = 12κ₃ + 18κ₂.

The rank-three and rank-two carriers are supplied inputs here. Their source-level reconstruction requires the assumptions in the articles. The response sliders do not determine measured gauge couplings.

Downloads include the chosen inputs, units and model scope. Values use standard floating-point arithmetic. Read the source and its version notes.

Try this investigationChange one retained-structure choice and explain the change in the permitted group before interpreting it physically.

An explicit finite energy response

Compare the exact finite singlet-loop energy with its stated approximation. Hopping and penalty scales are inputs to this model.

Exact singlet-loop response

Compare the exact energy shift of the declared finite singlet model with its leading weak-hopping loop term. Change the carrier rank, hopping and holonomy.

The singlet penalty Δ is the energy unit. Hopping is t/Δ; displayed energies and gaps are divided by Δ. Angles are radians.

Choose the model inputs

Exact energy shift 0.001072956 Δ; finite-model gap 0.6784925 Δ.

Exact E(W) − E(I), in Δ
0.00107295645
Leading loop term, in Δ
0.00136030346
Exact excitation gap, in Δ
0.678492492
Uniform finite-model bound, in Δ
0.08333333

SU(3): diag(exp(iθ),exp(−iθ),1). The selected eigenangles are 1.2, -1.2, 0 radians. The second SU(3) angle is inactive for this selection.

Exact and leading singlet-loop responseThe solid curve is the exact finite-model result; the dashed curve is the leading weak-hopping expression. The angle family and hopping are held as stated.Energy change / Δ000.001140.7850.002281.570.003422.360.004573.14Holonomy angle θ / radians
Exact energy change / Δ Leading loop term / Δ. The solid curve is the exact finite-model result; the dashed curve is the leading weak-hopping expression. The angle family and hopping are held as stated.
Selected finite-model quantities
QuantityValue
Ground energy E(W)/Δ-0.07849249223
Identity ground energy E(I)/Δ-0.07956544869
Root z/Δ1.078492492
Secular residual6.66e-16
Real trace Re Tr W1.72471551
Imaginary trace Im Tr W0
Loop cost m − Re Tr W1.275284
Exact Hessian κ̂ₘ/Δ0.0008392853737
Weak-hopping κloop/Δ0.001066666667
Absolute approximation error / Δ0.0002873470028

For W = exp(iX) close to identity, the convention is E(W) − E(I) = ½κ̂ₘ Tr X² + O(X⁴). Along the balanced slice, Tr X² = 2θ². The exact Hessian is positive when hopping is nonzero; it vanishes at t = 0.

Values across the displayed angle family
Energy shift and gap across the loop family
θ / radExact shift / ΔLeading shift / ΔGap / Δ
0000.6795654
0.31415930.000082170530.00010441280.6794833
0.62831850.00032081370.00040743040.6792446
0.94247780.00069302870.00087939150.6788724
1.2566370.0011629520.0014740970.6784025
1.5707960.0016850510.0021333330.6778804
1.8849560.0022084030.002792570.677357
2.1991150.0026816070.0033872750.6768838
2.5132740.0030578780.0038592360.6765076
2.8274330.0032998020.0041622540.6762656
3.1415930.0033832260.0042666670.6761822
Equations and conventions used
λak = 2t cos[(θa + 2πk)/4], k = 0,1,2,3.
(Δ/4m) Σa,k(z − λak)−1 = 1; E = Δ − z; gap = z − λ* ≥ Δ/(4m).
E(W) − E(I) ≈ [2t⁴/(mΔ³)] [m − Re Tr W].

A finite model with a unique ground state for the stated ranks and penalty. Its finite-dimensional excitation gap is not the four-dimensional Yang–Mills mass gap. At rank three, choose the balanced slice or the full diagonal two-angle family diag(exp(iθ),exp(iφ),exp(−i(θ+φ))). At rank two, the family selector and φ do not enter the SU(2) calculation.

Downloads include the chosen inputs, units and model scope. Values use standard floating-point arithmetic. Read the source and its version notes.

Try this investigationVary the penalty-to-hopping ratio. Identify the regime in which the leading loop approximation tracks the exact calculation.

Finite projection and geometric phase

Follow a specified projector path and inspect the survival probability and accumulated phase. A finite sequence and its continuum limit are distinct calculations.

Finite projections and geometric phase

Follow a rank-one state around a latitude by successive orthogonal projections. Compare the retained probability and phase with the continuous parallel-transport limit.

Angles are radians. N is the number of numerical projection steps around the loop; it does not count the six inner generative levels.

Choose the model inputs

Survival probability 0.6291609; phase error 0.01528674 radians.

Survival probability
0.62916094
Finite phase modulo 2π / rad
-1.55550959
Continuous phase −2πb / rad
-1.57079633
Phase error modulo 2π / rad
0.0152867382

The per-step overlap is 0.98097 − 0.095671i. The accumulated phase before reduction modulo 2π is -1.55550959 radians.

Retention through a loop of finite projectionsThe retained probability tends to one as the same smooth loop is sampled more finely.Survival probability020.2533.50.5650.7596.51128Number of numerical projection steps N
Survival probability. The retained probability tends to one as the same smooth loop is sampled more finely.
Finite projection sequence and continuous comparison
NSurvival probabilityFinite phase / rad (mod 2π)Phase error / rad
20.0625-1.22e-161.57079633
40.152587891-1.287002220.283794109
70.344568015-1.487567710.083228618
80.394243265-1.507836090.0629602406
160.62916094-1.555509590.0152867382
320.793413021-1.567002240.0037940821
640.890768214-1.569849520.000946806729
1280.943809283-1.570559730.000236594747

The columns expose two different convergence scales: probability loss is generally order 1/N, while the phase error for this symmetric latitude sampling is order 1/N² away from singular overlaps. Seven samples here are a numerical choice; the temporal model’s sevenfold structure is discussed separately.

Equations and conventions used
ψ(φ) = (√(1 − b), √b eiφ), b = sin²(θ/2).
⟨ψ(φ + 2π/N)|ψ(φ)⟩ = 1 − b + b e−2πi/N.
Psurvive = [1 − 4b(1 − b)sin²(π/N)]ᴺ; γN = −N arg(1 − b + b e2πi/N); γ∞ = −2πb.

A prescribed family of rank-one projectors and a specified postselected sequence. The survival probability is part of the model, and a zero overlap leaves the phase undefined. This example supplies no spacetime dynamics.

Downloads include the chosen inputs, units and model scope. Values use standard floating-point arithmetic. Read the source and its version notes.

Try this investigationIncrease the number of projections and compare both phase and survival. Record the path and the sequence length with the result.

Continue into the advanced models

These workspaces are entry points to the broader gauge research section. Reproduce a baseline before changing its assumptions.

THE QUESTIONS BEHIND THE CALCULATION

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