根据 DESI DR2 测量结果探讨动态暗物质的宇宙学后果
Cosmological consequences of a dynamical dark matter in the light of DESI DR2 measurements
AI总结：
基于 DESI DR2 测量，探讨动态暗物质宇宙学后果。提出 DDM 模型，研究其对多数据集影响。结果显示该模型对非零晚期 DM EoS 有偏好，与弱引力透镜数据更吻合，优于\(\Lambda\)CDM 但相对 DE 的 CPL 参数化不利。
AI中文摘要：
近期 DESI 结果显示偏好违反零能量条件的早期幻像行为的动态暗能量。本文探索另一种解释，即这种偏好源于非常规暗物质动力学而非动态暗能量。提出一种动态暗物质（DDM）模型，其状态方程（EoS）非零，在过渡标度因子\(a_t\)处平滑插值早期和晚期渐近线，并研究其对包括 CMB、DESI DR2 BAO、SNeIa（PantheonPlus、Union3 和 DESY5）及增长率数据等宇宙学数据集的影响。发现早期 EoS 与零一致，当前值为负，显著性在\(0.42\sigma\)到\(3.02\sigma\)之间，取决于数据集组合。最强偏好来自 CMB、DESI 和 DESY5 的组合，给出当前 EoS 为\(-0.060^{+0.013}_{-0.028}\)，\(a_t = 0.41^{+0.088}_{-0.13}\)（68%置信水平）。当纳入增长率数据且考虑所有三个 SNeIa 汇编时，对非零晚期 DM EoS 的偏好持续，物质密度\(\Omega_m\)相对于\(\Lambda\)CDM 略有升高。该模型还预测\(\sigma_8\)和\(S_8\)低于\(\Lambda\)CDM，与弱引力透镜数据更吻合，而\(H_0\)不变且与局部距离阶梯测量存在张力。DDM 模型优于\(\Lambda\)CDM（对于 Planck+DESI+DESY5，\(\Delta \chi^2_{\rm MAP} = -14.093\)，\(\Delta {\rm DIC} = -7.838\)），但相对于 DE 的 CPL 参数化不利（\(\Delta \chi^2_{\rm MAP} = 6.755\)，\(\Delta {\rm DIC} = 7.966\)）。这种偏好在其他数据集组合中也一致。
英文摘要：
Recent DESI results exhibit preference for a Null Energy Condition violating dynamical dark energy, with early phantom behaviour. We explore an alternative interpretation in which this preference arises from unconventional dark matter dynamics rather than from dynamical dark energy. We propose a dynamical dark matter (DDM) model, with a non-zero equation of state (EoS) that smoothly interpolates between early time and late time asymptotes across a transition scale factor $a_t$, and study its consequences against cosmological datasets including CMB, DESI DR2 BAO, SNeIa (PantheonPlus, Union3, and DESY5) and growth rate data. We find the early time EoS to be consistent with zero, while the present day value is negative at a significance ranging from $0.42σ$ to $3.02σ$ depending on the dataset combination. The strongest preference occurs from the combination of CMB, DESI, and DESY5 giving the present day EoS to be $-0.060^{+0.013}_{-0.028}$ and $a_t = 0.41^{+0.088}_{-0.13}$ at 68\% CL. This preference for a non-zero, late time DM EoS persists when growth rate data are included and across all three SNeIa compilations considered, while the matter density $Ω_m$ mildly shifts to higher values relative to $Λ$CDM. The model also predicts a lower $σ_8$ and $S_8$ than $Λ$CDM, in better agreement with weak-lensing data, while $H_0$ remains unchanged and in tension with local distance-ladder measurements. The DDM model is preferred over $Λ$CDM ($Δχ^2_{\rm MAP} = -14.093$, $Δ{\rm DIC} = -7.838$ for Planck+DESI+DESY5) but disfavored relative to the CPL parameterization of DE ($Δχ^2_{\rm MAP} = 6.755$, $Δ{\rm DIC} = 7.966$). This preference is consistent among other combination of datasets as well.
