无真空能量的热引力宇宙加速检验
Testing cosmic acceleration from thermogravity without vacuum energy
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中文总结 AI 辅助
本文首次在背景层检验热引力理论，发现普适能量不守恒模型被超新星和BAO数据强烈否定，而仅暗物质不守恒的$\xi\mathrm{CDM}$模型虽拟合更优，但会增大声学视界并加剧$H_0$张力。
中文摘要 AI 辅助
我们首次在背景层面对一种热引力理论进行观测检验，该理论中爱因斯坦方程被截断为无迹版本，宇宙学常数$\Lambda$不参与引力作用，且受控的能量守恒破坏阻碍了将$\Lambda$作为积分常数重新引入的通常做法。因此，我们设定$\Lambda=0$，并探究晚期加速是否可仅由能量不守恒产生，且相对于平坦$\Lambda\mathrm{CDM}$模型不引入额外背景参数。我们将一种最小普适实现与仅暗物质参与不守恒的模型进行对比。在结合超新星和重子声学振荡（BAO）距离数据时，普适模型被强烈否定，加入DESI BAO数据后拟合劣化程度相对于$\Lambda\mathrm{CDM}$达到$\Delta\chi^2\simeq 51$，因为物质产生将$H(z)$的中间红移归一化过于紧密地绑定于当前加速。然而，这一结论应谨慎解读，因为普适不守恒会修改观测字典本身。相反，将不守恒限制于暗物质时，重子和光子可观测量的背景层不受影响，因此可进行自洽分析。由此得到的$\xi\mathrm{CDM}$模型可视为$\Lambda\mathrm{CDM}$的单参数扩展，在所考虑的背景数据集组合中相对于$\Lambda\mathrm{CDM}$提供改进的拟合，改进幅度达$\Delta\chi^2=-4.85$，最大贝叶斯偏好为$\ln\mathcal{B}=2.77$。然而，当使用大爆炸核合成（BBN）或宇宙微波背景（CMB）信息校准BAO标尺时，降低的有效早期暗物质密度增大了声学视界，并将$H_0$推向更低值，从而加剧而非缓解与距离阶梯校准的张力。
英文摘要
We present a first background-level observational test of a thermogravity theory in which the Einstein equations are clipped to a trace-free version, the cosmological constant $Λ$ does not gravitate, and controlled violations of energy conservation obstruct the usual reinstatement of $Λ$ as an integration constant. We therefore set $Λ=0$ and ask whether late-time acceleration can instead be generated solely by energy non-conservation, with no extra background parameter relative to flat $Λ\mathrm{CDM}$. We contrast a minimal universal implementation with a model in which only CDM partakes in non-conservation. The universal model is strongly disfavored when combining Supernovae and BAO distances, with the inclusion of DESI BAO worsening the fit by $Δχ^2\simeq 51$ relative to $Λ\mathrm{CDM}$, because matter creation ties the intermediate-redshift normalization of $H(z)$ too rigidly to the present acceleration. This conclusion, however, should be interpreted with caution, since universal non-conservation would modify the observational dictionary itself. By contrast, restricting non-conservation to CDM leaves baryonic and photon observables unaffected at the background level and therefore allows a self-contained analysis. The resulting $ξ\mathrm{CDM}$ model, which can be thought of as a one parameter extension of $Λ\mathrm{CDM}$, provides an improved fit relative to $Λ\mathrm{CDM}$ for the background dataset combinations considered, with improvements reaching $Δχ^2=-4.85$ and a maximum Bayesian preference of $\ln\mathcal{B}=2.77$. However, when the BAO ruler is calibrated using BBN or CMB information, the reduced effective early-time CDM density increases the sound horizon and drives $H_0$ towards lower values, thereby increasing rather than alleviating the tension with the distance-ladder calibration.
发表机构
- University of Sheffield（谢菲尔德大学）
- Imperial College London（帝国理工学院）
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