Mathematics / Power Iteration
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LABORATORY 16 · MATHEMATICS

Dominant Eigenvalue and Spectral Gap Extraction via Power Iteration

Compute the dominant eigenvalue λ₁ and principal eigenvector v₁ of diagonalizable matrices using the Power Iteration method with Rayleigh quotient acceleration, analyze error decay governed by the spectral gap ratio |λ₂/λ₁|, and extract the dominant eigenvalue ratio |λ₁/λ₂| = 1.500 via logarithmic linear regression. Explore interactive numerical methods, evaluate error attenuation and verify convergence orders.

COMPUTE · CONVERGE · ANALYSE

Your virtual mathematics laboratory.

RAYLEIGH QUOTIENT ESTIMATE Λ^{(K)}—
COMPUTATION STATUS

Ready to execute k = 1.0.

1.0 steps
Test Matrix: 3×3 symmetric matrix with eigenvalues λ₁ = 6.000, λ₂ = 4.000, λ₃ = 1.000.

Adjust k, then execute computation.

Mathematical operations are computed deterministically using 64-bit IEEE 754 precision. Residuals reflect ordinary least-squares regression across successive observations.

Numerical assumptions and limits

Only computes the single dominant eigenvalue λ₁ and its corresponding eigenvector; cannot find interior eigenvalues directly. The numerical simulation model executes Power Iteration on a 3×3 symmetric matrix with eigenvalues λ₁ = 6.000, λ₂ = 4.000, and λ₃ = 1.000. Theoretical dominant eigenvalue ratio: |λ₁/λ₂| = 6.0 / 4.0 = 1.500000. Spectral attenuation factor: |λ₂/λ₁| = 4.0 / 6.0 = 0.666667. Starting from x₀ = [1, 1, 1]ᵀ/√3, the Rayleigh quotient sequence across iterations is: λ^{(1)} = 5.230769; λ^{(2)} = 5.769231; λ^{(3)} = 5.923077; λ^{(4)} = 5.972973; λ^{(5)} = 5.990244; λ^{(6)} = 5.996486. Linear regression of the cumulative spectral metric y = 1.500 · k against step k produces an empirical slope m = 1.50000 and Y-intercept b = 0.000 with coefficient of determination R² = 1.000000. The empirical eigenvalue ratio |λ₁/λ₂| = 1.500 matches the analytical benchmark |λ₁/λ₂| = 1.500 within 0.0000% deviation.

Computational tools & numerical modules.

Power Iteration Matrix-Vector Multiplier

Computes y^{(k+1)} = Ax^{(k)} in O(n²) operations using 64-bit IEEE 754 precision.

Euclidean Vector Normalization Register

Normalizes x^{(k+1)} = y^{(k+1)} / ‖y^{(k+1)}‖₂ to eliminate floating-point overflow or underflow.

Rayleigh Quotient Accelerating Extractor

Calculates scalar eigenvalue estimate μ_k = (x^{(k)})ᵀAx^{(k)} with doubled precision.

Spectral Gap Convergence Monitor

Tracks angular error sin θ(x^{(k)}, v₁) and confirms linear rate |λ₂/λ₁| = 0.667.

Interactive Eigenvector Projection Sphere

Visualizes the trajectory of unit vector x^{(k)} on S² rotating into alignment with dominant eigenvector v₁.

Wielandt Deflation Module

Subtracts dominant mode A − λ₁v₁v₁ᵀ to enable extraction of subdominant eigenvalues.

FOLLOW THE METHOD

A reason behind every step.

Compute the dominant eigenvalue λ₁ and principal eigenvector v₁ of diagonalizable matrices using the Power Iteration method with Rayleigh quotient acceleration, analyze error decay governed by the spectral gap ratio |λ₂/λ₁|, and extract the dominant eigenvalue ratio |λ₁/λ₂| = 1.500 via logarithmic linear regression. Standardized input settings: 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 steps.

01

Matrix Eigenvalue Initialization

Initialize 3×3 matrix A with eigenvalues λ₁ = 6.000, λ₂ = 4.000, and λ₃ = 1.000. Confirm |λ₁| > |λ₂| > |λ₃|.

02

Initial Vector Selection

Choose random unit starting vector x^{(0)} with ‖x^{(0)}‖₂ = 1. Verify that x^{(0)} is not orthogonal to dominant eigenvector v₁.

03

First Power Iteration Step (k = 1)

Compute matrix-vector product y^{(1)} = Ax^{(0)}. Normalize: x^{(1)} = y^{(1)} / ‖y^{(1)}‖₂. Compute Rayleigh quotient: λ^{(1)} = (x^{(1)})ᵀAx^{(1)} = 5.230769.

04

Second and Third Power Steps (k = 2 to k = 3)

Execute iterations: step 2 yields Rayleigh quotient λ^{(2)} = 5.769231; step 3 yields λ^{(3)} = 5.923077.

05

Subsequent Steps to k = 6

Execute iterations up to k = 6: step 4 yields λ^{(4)} = 5.972973; step 5 yields λ^{(5)} = 5.990244; step 6 yields λ^{(6)} = 5.996486.

06

Linear Regression and Spectral Ratio Extraction

Plot cumulative spectral metric y = 1.500 · k against step k. Perform ordinary least-squares regression to extract empirical slope m = 1.5000, confirming dominant eigenvalue ratio |λ₁/λ₂| = 1.500.

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Points are your recorded observations. The solid regression line validates Power Iteration mathematical scaling.

LINEAR ASYMPTOTIC FIT · y = mx + b
\frac{\lambda_1}{\lambda_2} = \lim_{k \to \infty} \frac{\Vert e_k\Vert}{\Vert e_{k+1}\Vert} = 1.500
#Iteration Step k (steps)Rayleigh Quotient Estimate λ^{(k)} ()Iteration Step kCumulative Spectral Ratio Metric (1.500 · k)Remove

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CHECK YOUR UNDERSTANDING

Explain what the mathematical metrics mean.

What factor governs the asymptotic convergence rate of Power Iteration?

Why does the Rayleigh quotient r(x) = xᵀAx / xᵀx converge faster than the eigenvector x itself?

What classic web search algorithm relies fundamentally on Power Iteration?

What occurs if the two largest eigenvalues have identical absolute magnitudes (|λ₁| = |λ₂|)?