Cross-validation

The Well harness

PolymathicAI's The Well is a 15 TB collection of physics simulations across fluid dynamics, plasma, astrophysics, and reaction–diffusion systems. BPR's scaling predictions are checked against it automatically.

Read this first. Most of these checks test spectral exponents that standard physics also predicts (Kolmogorov −5/3, enstrophy −3, and so on). They show that BPR's scaling relations are consistent with known physics, not that BPR is right about particles. They are labelled consistent for that reason. Two are BPR-specific and labelled conjectural.

IDDatasetPredictionPredictedObservedσStatus
PW2.1acoustic_scattering_inclusionsMode entropy H/Hmax > 0.5> 0.500.696passconsistent
PW3.1rayleigh_benardNu ~ Raβ (Class C)0.3070.2870.82consistent
PW4.1active_matterKuramoto transition direction—correctpassconsistent
PW5.1MHD_64E(k) ~ k−5/3−1.667−2.1800.45consistent
PW6.1brusselatorTuring wavelength λT = 2π/kc0.3930.3331.51consistent
PW7.1turbulent_radiative_layer_2D2D enstrophy cascade α = −3−3.000−3.0060.01consistent
PW8.1turbulence_gravity_coolingStratified Fr < 1 cascade−3.0−3.150.30consistent
PW9.1rayleigh_taylor_instabilityStratified buoyancy α = −3−3.000−3.6611.32consistent
PW10.1supernova_explosion_64Post-shock Kolmogorov−1.667−2.12.11consistent
PW11.1turbulent_radiative_layer_3DCooling-steepened spectrum−3.5−3.960.91consistent
PW12.1acoustic_scattering_mazeMode entropy > 0.5> 0.500.870passconsistent
PW13.1shear_flow2D enstrophy k−3−3.0−3.91.85consistent
PW14.1planetsweGeostrophic k−3−3.0−3.51.05consistent
PW15.1helmholtz_staircaseMode spacing CV < 0.3< 0.300.1000.50consistent
PW16.1viscoelastic_instabilityα = −(3 + Wi1/3)−6.68−6.820.27conjectural BPR-specific
PW17.1euler_multi_quadrants_openBCBurgers shock α = −2−2.000−2.9731.95conjectural
PW18.1convective_envelope_rsgCompressible stellar α = −4−4.000−4.0230.05consistent
PW19.1post_neutron_star_mergerCompressible MHD α = −3−3.000−3.0850.17consistent
PW1.1gray_scottExempt. Gray–Scott spots are self-replicating structures, not Turing instabilities: det J = F(F+k) > 0 at the trivial state, so the bifurcation condition is never met.exempt

18 validators pass, 1 exempt. Several observed exponents differ from the predicted ones by well over 10 percent while the quoted σ is small; the σ reflects the fit uncertainty of the observed exponent, not a claim of precision agreement. Source: experiments/the_well_harness.py.

What was learned from it

  • Turing wavelength corrected. The original validator targeted Gray–Scott, which is not Turing-unstable. Switching to the Brusselator gives a genuine test, at 1.5σ.
  • Class B vs Class C. The wrong universality class was initially applied to Rayleigh–Bénard convection. Corrected.
  • Radiative cooling steepens spectra from k−5/3 towards k−3 to k−4, consistent with the simulations.
  • One new formula, α = −(3 + Wi1/3) for viscoelastic turbulence, agrees at 0.27σ and is not in the existing literature. It is a conjecture.