On the Analysis Dependence of DESI Dynamical Dark Energy

We continue scientific scrutiny of the DESI dynamical dark energy (DE) claim by explicitly demonstrating that the result depends on the analysis pipeline. Concretely, we define a likelihood that converts the w0waCDM model back into the (flat) ΛCDM model, which we fit to DESI constraints on the ΛCDM model from DR1 Full-Shape (FS) modeling and BAO. We further incorporate CMB constraints. Throughout, we find that w0 and wa are within 1σ of the ΛCDM model. Our work makes it explicit that, in contrast to DR1 and DR2 BAO, there is no dynamical DE signal in FS modeling, even when combined with BAO and CMB. Moreover, one confirms late-time accelerated expansion today (q0<0) at ≳3.4σ in FS modeling + BAO. On the contrary, DR1 and DR2 BAO fail to confirm q0<0 under similar assumptions. Our analysis highlights the fact that trustable scientific results should be independent of the analysis pipeline.