Inverted Hypersphere Cosmology (IHC) posits that the universe is the real projective four-space RP4 = S4/Z2, derived from a single non-preferential axiom with zero free parameters. This topology has three immediate consequences for singularity physics. First, the Hartle-Hawking no-boundary condition follows directly from the axiom rather than being imposed as an extra postulate: the pre-geometric vacuum selects compact boundaryless Euclidean 4-geometries, so no initial singular boundary exists. Second, the antipodal identification on S4 is precisely CPT symmetry on de Sitter spacetime; every black hole at position x is therefore CPT-paired with a white hole at its antipodal partner -x, approximately 14 Gpc distant. The singularity at x is identified with its CPT image, becoming a traversable junction: geodesics extend through it with total affine parameter delta-lambda = 2. 24M (finite), while the Kretschmann scalar K = 48M2/r6 still diverges. Third, the non-trivial fundamental group pi1 (RP4) = Z2 prevents a global Cauchy surface, rendering the Penrose singularity theorem inapplicable in its standard form. Information is conserved nonlocally through the antipodal pairing on timescale t ~ pi*RS/c ~ 44 Gyr. Two observational tests are presented. Against the Planck 2018 low-l CMB spectrum, the IHC Hartle-Hawking infrared cutoff at kₘin = H0/c reduces the quadrupole tension from -4. 77 sigma (LCDM) to -0. 69 sigma, with delta-chi2 = 26. 6 over l = 2-3. An MCMC fit over l = 2-29 independently recovers the RP4-corrected cutoff scale 2H0/c at 0. 02 sigma from the posterior median, with Hamimeche-Lewis delta-ln-L = +2. 71 against LCDM. The Z2 projection (even-l bosonic modes only) is confirmed at the sub-0. 1 sigma level. Against GWTC-4. 0 (44 confident binary black hole events from O1-O4a), IHC predicts local dynamics identical to general relativity (gammaPPN = 1), achieving chi2/n = 0. 110 with the Hawking area theorem satisfied in all 44 events with 29-36% margin. The joint Bayes factor across independent datasets is ln B = +11. 07 (odds 64, 216: 1, decisive evidence on the Jeffreys scale).
Peacock et al. (Thu,) studied this question.