Curvature by cgiovanetti · Pull Request #35 · TonyZhou729/ABCMB

cgiovanetti · 2026-06-15T19:11:10Z

Flagging this as done pending review. Eliminates tabulated bessel functions at a cost of 0.2s with or without lensing. Fully implements curvature.

@TonyZhou729 I'll give it a review first and let you know when it's ready for you.

Three research reports (ABCMB flat-geometry audit, CLASS curvature equations, CLASS hyperspherical/transfer machinery) plus the condensed design doc for the Omega_k implementation. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

…s_l hierarchy factors, curved Einstein constraints and ICs - main.py: omega_k (=Omega_k h^2) default + derived K = -omega_k H100^2; closure omega_Lambda subtracts omega_k; expected_keys updated. - species.py: Curvature(BackgroundFluid) pseudo-fluid (rho ~ a^-2, w=-1/3) makes H/aH_prime automatically curved; curvature_s_l() free-streaming coefficients; CLASS-verbatim (arXiv:1305.3261) s_l factors in the photon T/pol, massless-nu and massive-nu hierarchies; cot_K l_max truncations; s2^2 = 1-3K/k^2 factors in all adiabatic ICs. - perturbations.py: (k^2-3K) Einstein constraints + K h'/2 in eta' (both get_derivatives and make_output_table copies); s2^2 in eta_ini. - background.py: sqrt(1-K rs^2) in the rs ODE; rA_rec = sin_K(chi_rec). - ABCMBTools.py: sin_K/cot_K helpers via entire functions of K chi^2 (series at small argument: smooth through K=0, AD-safe branches). - model_specs.py: Curvature registered in LCDM species; static curvature/omega_k_ref specs; curved k_min for the perturbation grid (closed: sqrt(8K) nu=3 cutoff; open: sqrt(|K|)); |K| in scale2. All value-level changes reduce exactly to the flat equations at K = 0. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

… + curved Limber lensing - spectrum.py: _transfer_sources extracted (shared flat/curved; s_2 factor in the polarization weight, = 1 exactly at K=0); Cl_one_ell consumes prebuilt sources; new _Cl_all_ells_curved generates Phi_l^nu(chi) by the exact dimensionful forward recurrence (seeds Phi_0, Phi_1 in closed form; smooth through K=0) in one chunked, checkpointed lax.scan over ALL integer ells, contracting against the LOS sources at each l — radial functions T0/T1/T2/E per CLASS transfer_radial_function; evanescent region clamped and masked at the same |Phi|~1e-10 threshold as the flat tables (cutoff variable q*S_K(chi), thresholds reused from the tables' lower edges); closed-universe l>=nu termination and open supercurvature q^2<=0 masks. get_Cl: static specs['curvature'] switch (False = existing flat tables). - lensing_Cl: curved-sky Limber (q=(l+1/2)/S_K, sin_K window, 1/(S_K^2 k^3) measure, WKB amplitude (1-K l^2/q^2)^(-1/2)) — reduces exactly to the prior flat integrand at K=0. lensing_power_spectrum: curved Poisson k^3/(k^2-3K)^2 and Omega_k(1+z)^2 in Om(z). - species.py truncations use the dimensionless g = tau*cot_K(tau) factor so the flat path keeps the original floating-point evaluation order. - main.py: pass specs['curvature'] into SpectrumSolver. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>