On the origin of the BAOtr-DESI tension

On the origin of the BAOtr-DESI tension
Ioannis Pantos, Leandros Perivolaropoulos
arXiv:2604.11106v2 Announce Type: replace
Abstract: The fiducial-independent angular/transverse BAO dataset, obtained from two-point angular correlation functions in thin redshift shells (hereafter BAOtr), systematically prefers smaller comoving distance ratios $D_{rm M}/r_{rm d}$ than the DESI DR2 three-dimensional BAO measurements at $z lesssim 0.65$, driving dataset-dependent CPL dark-energy inferences and conflicting conclusions about the Hubble tension. We investigate whether this disagreement can be attributed to the $Lambda$CDM fiducial assumed in the 3D BAO pipeline, or resolved within the CPL parametrisation. We show that the published 3D BAO distances are fiducial-independent by construction, with residual effects at $lesssim 0.3%$ — negligible against the 10–18% BAOtr uncertainties. We then scan the CPL parameter space with $Omega_m$ and $H_0$ jointly determined at each $(w_0, w_a)$ by the Planck $theta_*$ constraint and optimisation against the DESI data. Two complementary tests are performed: a direct comparison of each DESI-optimized model with the BAOtr data, and an $alpha$-interpolation test that anchors the prediction to the DESI measurements. Both reveal an inescapable trade-off: models that fit DESI well ($chi^2_{rm DESI} lesssim 5$) yield $chi^2_{rm BAOtr} gtrsim 42$, while reducing the BAOtr tension to $chi^2_{rm BAOtr} sim 37$ requires $chi^2_{rm DESI} gtrsim 8$. No CMB-consistent CPL model fits both datasets simultaneously. The direct comparison at $z = 0.510$ — where BAOtr and DESI disagree by $3.7sigma$ (data-versus-data) — sets an irreducible tension floor that no smooth modification of $D_{rm M}(z)$ can remove. These conclusions are robust across analysis methods, extrapolation schemes, and substitution of SDSS for DESI. The remaining explanations are observational systematics — most plausibly in the BAOtr measurements — or new physics beyond CPL.arXiv:2604.11106v2 Announce Type: replace
Abstract: The fiducial-independent angular/transverse BAO dataset, obtained from two-point angular correlation functions in thin redshift shells (hereafter BAOtr), systematically prefers smaller comoving distance ratios $D_{rm M}/r_{rm d}$ than the DESI DR2 three-dimensional BAO measurements at $z lesssim 0.65$, driving dataset-dependent CPL dark-energy inferences and conflicting conclusions about the Hubble tension. We investigate whether this disagreement can be attributed to the $Lambda$CDM fiducial assumed in the 3D BAO pipeline, or resolved within the CPL parametrisation. We show that the published 3D BAO distances are fiducial-independent by construction, with residual effects at $lesssim 0.3%$ — negligible against the 10–18% BAOtr uncertainties. We then scan the CPL parameter space with $Omega_m$ and $H_0$ jointly determined at each $(w_0, w_a)$ by the Planck $theta_*$ constraint and optimisation against the DESI data. Two complementary tests are performed: a direct comparison of each DESI-optimized model with the BAOtr data, and an $alpha$-interpolation test that anchors the prediction to the DESI measurements. Both reveal an inescapable trade-off: models that fit DESI well ($chi^2_{rm DESI} lesssim 5$) yield $chi^2_{rm BAOtr} gtrsim 42$, while reducing the BAOtr tension to $chi^2_{rm BAOtr} sim 37$ requires $chi^2_{rm DESI} gtrsim 8$. No CMB-consistent CPL model fits both datasets simultaneously. The direct comparison at $z = 0.510$ — where BAOtr and DESI disagree by $3.7sigma$ (data-versus-data) — sets an irreducible tension floor that no smooth modification of $D_{rm M}(z)$ can remove. These conclusions are robust across analysis methods, extrapolation schemes, and substitution of SDSS for DESI. The remaining explanations are observational systematics — most plausibly in the BAOtr measurements — or new physics beyond CPL.