[PHYSICS BUG][MEDIUM] dist() accepts w₀, wₐ but silently uses hardcoded ΛCDM formula

[JasperSeehofer]

File: master_thesis_code/physical_relations.py:72

dist() accepts w_0 and w_a parameters but passes them to lambda_cdm_analytic_distance(), which ignores them. The hypergeometric formula used there is the exact analytic result only for flat ΛCDM (w₀ = −1, wₐ = 0):

179888\int_0^z \frac{dz'}{E(z')} = \frac{(1+z)\sqrt{1+\Omega_m(1+z)^3/\Omega_\Lambda}}{\sqrt{\Omega_\Lambda+\Omega_m(1+z)^3}},{}2F_1!\left(\tfrac{1}{3},\tfrac{1}{2};\tfrac{4}{3};-\frac{\Omega_m(1+z)^3}{\Omega\Lambda}\right) - \ldots179888

No warning is raised when non-fiducial w₀, wₐ are supplied. hubble_function() already implements the correct general CPL formula but is not used in the distance integral.

Fix options:

• (a) Remove w_0, w_a arguments from dist() and document the ΛCDM assumption explicitly.
• (b) Fall back to numerical integration via hubble_function() when w_0 != -1 or w_a != 0.

Reference: Hogg (1999), arXiv:astro-ph/9905116, Eq. (14–16).

Physics Change Protocol required.