Revisiting the evidence for dynamical dark energy: from DES-SN5Y to DES-Dovekie

Abstract Recent analyses combining DESI DR2 BAO measurements with CMB and supernova data have suggested a preference for dynamical dark energy, particularly when using the DES-SN5Y and DES-SN5Y $$(z&gt;0.1)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>z</mml:mi> <mml:mo>&gt;</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> supernova samples. With the revision of this dataset into the DES-Dovekie compilation, it is important to reassess the robustness of this result. In this work, we analyze a broad class of dark energy parametrizations, including w CDM, $$w_0w_a$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>w</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:msub> <mml:mi>w</mml:mi> <mml:mi>a</mml:mi> </mml:msub> </mml:mrow> </mml:math> CDM, BA, JBP, Efstathiou, and GEDE models, using DESI DR2 BAO, a compressed CMB likelihood, and supernova data. We find that the DES-SN5Y dataset consistently yields a stronger preference for deviations from $$\Lambda $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Λ</mml:mi> </mml:math> CDM compared to DES-Dovekie. In particular, redshift-dependent parametrizations favor the region $$w_0 &gt; -1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>w</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:mo>&gt;</mml:mo> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> and $$w_a &lt; 0$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>w</mml:mi> <mml:mi>a</mml:mi> </mml:msub> <mml:mo>&lt;</mml:mo> <mml:mn>0</mml:mn> </mml:mrow> </mml:math> , corresponding to a Quintom-B–type evolution with phantom crossing. This behavior is observed across multiple models, indicating that it is not specific to a single parametrization. We find that the DES-SN5Y $$(z&gt;0.1)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>z</mml:mi> <mml:mo>&gt;</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> sample also preserves the same qualitative behavior, although the deviations from the $$\Lambda $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Λ</mml:mi> </mml:math> CDM limit become significantly weaker compared to the full DES-SN5Y sample. However, when DES-Dovekie is used, the statistical preference for dynamical dark energy is significantly reduced. The improvement over $$\Lambda $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>Λ</mml:mi> </mml:math> CDM drops to below the $$1\sigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>1</mml:mn> <mml:mi>σ</mml:mi> </mml:mrow> </mml:math> level for most models, and the Bayesian evidence weakens from moderate to weak or inconclusive. Similarly, for the DES-SN5Y $$(z&gt;0.1)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>z</mml:mi> <mml:mo>&gt;</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> sample, the preference for dynamical dark energy becomes intermediate between the DES-SN5Y and DES-Dovekie cases, with mostly weak or inconclusive evidence. Overall, the DES-Dovekie and DES-SN5Y $$(z&gt;0.1)$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>z</mml:mi> <mml:mo>&gt;</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> datasets weaken the preference for dynamical dark energy compared to the full DES-SN5Y dataset.

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