Directional Tests of the Cosmic Distance Duality Relation using Pantheon+ and BAO
Pushty Shrimankar, Gopal Kashyap

TL;DR
This paper tests the isotropy of the cosmic distance duality relation using supernova and BAO data, employing Gaussian Processes and dipole modeling, finding no significant anisotropy.
Contribution
It introduces a model-independent, dipole-based anisotropy test for the CDDR using Gaussian Process reconstruction, accounting for survey effects.
Findings
The dipole amplitude is consistent with isotropy.
No evidence for intrinsic anisotropy in the CDDR.
95% upper bound on anisotropy amplitude is 0.025.
Abstract
We present a model-independent test of anisotropy in the cosmic distance duality relation (CDDR), , using the Pantheon+ type Ia supernova sample and baryon acoustic oscillation (BAO) data. The angular diameter distance is reconstructed via Gaussian Processes, enabling an estimate of without assuming a background cosmology. We also allow for a possible isotropic evolution, parameterized as , and find a redshift-dependent deviation whose significance depends on the assumed supernova calibration. Anisotropy is modeled through a dipole modulation and constrained using a full covariance-based likelihood. To assess statistical significance, we construct null realizations that preserve both the redshift distribution and the survey selection function. We find that the observed dipole amplitude is consistent with isotropic…
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