Reconstruction of dark energy using DESI DR2
Xue Zhang, Yuansheng Xu, Yu Sang
Abstract
Abstract Using a model-independent Gaussian process (GP) method to reconstruct the dimensionless luminosity distance D and its derivatives, we derive the evolution of the dimensionless Hubble parameter E , the deceleration parameter q , and the state parameter w of dark energy. We utilize the PantheonPlus, SH0ES, and Gamma Ray Burst (GRB) data to derive the dimensionless luminosity distance D . Additionally, we employ observational H ( z ) data (OHD) and baryon acoustic oscillations (BAO) from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) to obtain the first derivative of the dimensionless luminosity distance <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>D</mml:mi> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> </mml:math> . To obtain the reconstructed D and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>D</mml:mi> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> </mml:math> , we utilize the fiducial value from each dataset, with particular emphasis on the varying H 0 . According to the reconstruction results obtained from PantheonPlus+SH0ES+GRB+OHD and PantheonPlus+SH0ES+GRB+OHD+DESI data, we find that E is consistent with the predictions of the ΛCDM model at a 2 σ confidence level within the redshift range of z < 2. However, the reconstruction results for q exhibit deviations from the ΛCDM model in the range of z < 0.3. Furthermore, we observe that the mean value of w exhibits evolving behavior, transiting from w < −1 to w > −1 around <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">wt</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.46</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.120</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.235</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . Combining data from DESI DR2 can slightly enhance the accuracy of our constraints.