SL(2,ℝ) (Thurston)

Shear flow, geodesic divergence, rotation-shear coupling
symmetrydim 37 metrics

What It Measures

The character of 2x2 matrix dynamics — whether the accumulated transformation rotates, shears, or stretches.

Converts each byte triple to an SL(2,R) matrix via the KAK decomposition: a rotation, a hyperbolic boost, and a second rotation. These three parameters span all three conjugacy classes of 2x2 matrices with determinant 1. The geometry classifies each matrix by its trace: elliptic (|trace| < 2, rotation-dominated), parabolic (|trace| = 2, shear), or hyperbolic (|trace| > 2, exponential stretch). A running product of matrices accumulates the signal's overall dynamical character.

Metrics

hyperbolic_fraction

Fraction of matrices with |trace| > 2. L-System Dragon, pulse-width modulation, and Morse code all score 1.0 (every matrix is hyperbolic — their binary structure pushes the boost parameter to extreme values). Earthquake P-wave scores 0.014 (almost entirely elliptic — the smooth waveform creates small boosts). This separates signals with discontinuous jumps (hyperbolic) from smooth oscillations (elliptic).

lyapunov_exponent

Average rate of exponential growth in the running matrix product, computed over blocks of 50 matrices. Rainfall (1.98) and Collatz gap lengths (1.96) score highest — their bursty or irregular dynamics create matrices whose product grows rapidly. Earthquake P-wave (0.020) is the lowest non-degenerate value: its smooth oscillation produces near-identity matrices that barely grow. This is a genuine Lyapunov exponent of the matrix cocycle, not an ad-hoc estimate.

mean_trace

Average trace of all matrices. L-System Dragon, Morse code, and Rule 110 all score 7.52 (far into the hyperbolic regime). DNA sequences score around -2.6 (elliptic regime with negative trace — the base pair frequencies create matrices with trace near the elliptic boundary). Logistic period-3 scores -2.77 (deepest into the negative-trace elliptic region). The sign of mean_trace separates two flavors of rotational dynamics: positive trace means the rotations partially cancel; negative means they compound.

parabolic_fraction

Fraction of matrices near the elliptic/hyperbolic boundary (|trace²-4| <= 0.2). Ambient microseism (0.40) and bearing inner fault (0.39) score highest — their narrowband oscillations produce matrices that hover near the boundary. This is the rarest conjugacy class: most data is either clearly elliptic or clearly hyperbolic, with few matrices landing in the thin parabolic strip. High parabolic fraction signals a critical or transitional dynamical regime.

mean_spectral_radius

Average spectral radius (largest singular value) of the individual SL(2,R) matrices. Pulse-Width Mod, Morse Code, and Square Wave all hit 7.39 (maximum — binary jumps create large boosts). BTC Returns (1.02) is near the identity matrix. This separates signals that create "gentle" matrices (smooth oscillations, radius near 1) from those that create "violent" matrices (binary jumps, radius >> 1).

trace_autocorrelation

Lag-1 autocorrelation of the matrix trace sequence. Logistic period-2 (1.0) and fBm Persistent (1.0) score highest. Fibonacci Word scores 0.0 (traces change unpredictably). Trace autocorrelation captures persistence in the conjugacy class — does the signal stay in the elliptic/hyperbolic regime, or does it switch rapidly?

lyapunov_std

Standard deviation of the block-wise Lyapunov exponent estimates. BTC Close (0.61) and Van der Pol (0.59) score highest — their Lyapunov exponents vary dramatically across blocks, indicating intermittent dynamics. Constants and logistic period-2 score 0.0 (perfectly uniform growth rate). High std with moderate mean Lyapunov indicates alternating laminar and turbulent phases.

Atlas Rankings

cocycle_growth_burstiness
SourceOriginValue
Critical Transition (Fold)iterated-maps0.7121
Takagi Functionspecial-functions0.7111
Spectral Form Factorrandom-matrix-quantum0.6941
···
Logistic r=3.2 (Period-2)iterated-maps0.0000
Logistic r=3.83 (Period-3 Window)iterated-maps0.0000
Logistic r=3.74 (Period-5 Window)iterated-maps0.0000
cocycle_growth_rate
SourceOriginValue
Aubry-André Criticalrandom-matrix-quantum1.9883
Rainfall (ORD Hourly)atmospheric1.9817
Mian-Chowlanumber-theory1.9815
···
Logistic r=3.2 (Period-2)iterated-maps0.0000
Stable Noisestochastic-process0.0079
Student-t Noisestochastic-process0.0147
hyperbolic_fraction
SourceOriginValue
Periodic Wordsymbolic-dynamics1.0000
Gap-Word β-Shiftsymbolic-dynamics1.0000
Fibonacci Wordsymbolic-dynamics1.0000
···
MFPT Inner Unloadedmachine-vibration0.0064
Stable Noisestochastic-process0.0065
Intermittency Type-IIIiterated-maps0.0071
mean_spectral_radius
SourceOriginValue
Pell Wordsymbolic-dynamics7.3891
Penrose Substitutionsymbolic-dynamics7.3891
Golden-Mean β-Shiftsymbolic-dynamics7.3891
···
MFPT Inner Unloadedmachine-vibration1.0055
Intermittency Type-IIIiterated-maps1.0125
Intermittency Type-IIiterated-maps1.0172
mean_trace
SourceOriginValue
Thue-Morsesymbolic-dynamics7.5244
Collatz Cycle Wordnumber-theory7.5244
Fibonacci Wordsymbolic-dynamics7.5244
···
Logistic r=3.83 (Period-3 Window)iterated-maps-5.1102
Euler Totient Rationumber-theory-1.9706
Random Telegraphstochastic-process-1.9317
parabolic_fraction
SourceOriginValue
Stable Noisestochastic-process0.9148
Student-t Noisestochastic-process0.7484
Intermittency Type-IIiterated-maps0.7010
···
Thue-Morsesymbolic-dynamics0.0000
Periodic Wordsymbolic-dynamics0.0000
Gap-Word β-Shiftsymbolic-dynamics0.0000
trace_autocorrelation
SourceOriginValue
Takagi Functionspecial-functions0.9998
OTOC Growthrandom-matrix-quantum0.9998
Spectral Form Factorrandom-matrix-quantum0.9993
···
Thue-Morsesymbolic-dynamics0.0000
Fibonacci Wordsymbolic-dynamics0.0000
Collatz Cycle Wordnumber-theory0.0000

When It Lights Up

SL(2,R) is the most algebraically rich Thurston geometry in the framework. Its conjugacy class decomposition (elliptic/parabolic/hyperbolic) provides a three-way classification that no other metric replicates. In the symmetry view, hyperbolic_fraction is the primary separator: it cleanly divides binary/symbolic sources (fraction near 1.0) from smooth continuous signals (fraction near 0). The lyapunov_exponent adds a growth-rate axis, and mean_trace adds a polarity axis. Together they place each source in a 3D space where binary chaos, smooth oscillation, and critical behavior occupy distinct regions.

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