Improved null tests of $\Lambda$CDM and FLRW in light of DESI DR2

Understand

The DESI DR2 BAO data, in combination with CMB and different SNIa datasets, exclude the flat $\Lambda$CDM model at more than 2.5$\sigma$ when analyzed through the $w_0w_a$CDM parametrization for evolving dark energy.

• This simple parametrization may not accurately capture the behavior of the entire redshift range at late times, which may introduce bias in the results.
• We use null tests that probe for deviations from flat $\Lambda$CDM at late times, independent of any specific dark energy parametrization.
• We provide several diagnostics for null tests and discuss their advantages and disadvantages.