Abstract

We revisit the variable \(\Lambda\) theory recently developed by Alexander et al. [1, 2]. We implement it to explain the current expansion of the Universe. The varying \(\Lambda\) theory reduces one degree of freedom. The varying \(\Lambda\) term (cosmological term) follows the energy density of the Universe. We consider such a theory which does not respect self-dual symmetry. The Bianchi identity enforces the \(\Lambda\) term to be a constant for a theory without torsion. However, torsion can incorporate a varying \(\Lambda\) term in the action. We consider a form of the action which has such a varying \(\Lambda\) term, and the presence of only nonrelativistic matter energy density. We fit the luminosity distance according to the model and compare it with that in the \(\Lambda\textrm{{CDM}}\) model and find their close behavior. However, we find a current value of matter energy density \(\rho_{m0}\) larger than the critical energy density. Using the supernova data from Union 2.1 compilation, we further consider a different set of parameters, for which \({\kappa\rho_{m0}}/{3H_{0}^{2}}\) becomes close to unity but, however, greater. For this set of parameters, we find a negative value in the effective equation of state, however, the model has a very different pattern of the Hubble parameter from the standard scenario.

中文翻译：

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重新讨论了不同的$$ \ boldsymbol {\ Lambda} $$理论

摘要

我们回顾一下亚历山大等人最近开发的变量\（\ Lambda \）理论。[1，2]。我们执行它来解释宇宙的当前扩展。变化的\（\ Lambda \）理论减少了一个自由度。变化的\（\ Lambda \）项（宇宙学项）遵循宇宙的能量密度。我们认为这样的理论不尊重自我双重对称。Bianchi身份将\（\ Lambda \）项强制为无扭转理论的常数。但是，扭转可以在动作中包含变化的\（\ Lambda \）项。我们考虑一种动作形式，它具有不同的\（\ Lambda \）项，并且只有非相对论物质能量密度的存在。我们根据模型拟合光度距离，并将其与\（\ Lambda \ textrm {{CDM}} \）模型中的光度距离进行比较，并找到它们的接近行为。但是，我们发现物质能量密度\（\ rho_ {m0} \）的当前值大于临界能量密度。使用来自Union 2.1编译的超新星数据，我们进一步考虑了一组不同的参数，对于这些参数，\（{\ kappa \ rho_ {m0}} / {3H_ {0} ^ {2}} \）变得接近统一，但是，但是，更大。对于这组参数，我们在有效状态方程中找到一个负值，但是，该模型的哈勃参数模式与标准方案的模式非常不同。