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arXiv 1602.01078hep-thastro-ph.COgr-qc
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非局部引力的共形对称性和非线性扩张

Conformal symmetry and nonlinear extensions of nonlocal gravity

Giulia Cusin, Stefano Foffa, Michele Maggiore, Michele Mancarella

备注：
27 pages, 4 figures
发表信息：
Phys. Rev. D 93, 083008 (2016)
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摘要：

本文研究了非定域$R\,\Box^{-2}R$引力理论的两个非线性推广。我们扩展这个理论在两个不同的方式建议共形对称性，要么取代$\Box^{-2}$与$(-\Box + R/6)^{-2}$，这是运营商进入的作用为一个共形耦合标量场，或取代$\Box^{-2}$与潘尼兹算子的逆，这是一个四阶导数运营商，进入的有效作用引起的共形异常。我们表明，前一个修改给出了一个有趣的和可行的宇宙学模型，与暗能量状态方程今天$w_{\rm DE}\simeq -1.01$，非常密切地模仿$Λ$ CDM和渐近演化成德西特解决方案。基于Paneitz算子的模型似乎被与观测值的比较所排除。我们还回顾了一些问题的因果关系的非局部理论，我们指出，这些非局部模型可以修改，以便很好地插入之间的Starobinski膨胀在原始宇宙和加速膨胀在最近的时代。

英文摘要：

We study two nonlinear extensions of the nonlocal $R\,\Box^{-2}R$ gravity theory. We extend this theory in two different ways suggested by conformal symmetry, either replacing $\Box^{-2}$ with $(-\Box + R/6)^{-2}$, which is the operator that enters the action for a conformally-coupled scalar field, or replacing $\Box^{-2}$ with the inverse of the Paneitz operator, which is a four-derivative operator that enters in the effective action induced by the conformal anomaly. We show that the former modification gives an interesting and viable cosmological model, with a dark energy equation of state today $w_{\rm DE}\simeq -1.01$, which very closely mimics $Λ$CDM and evolves asymptotically into a de Sitter solution. The model based on the Paneitz operator seems instead excluded by the comparison with observations. We also review some issues about the causality of nonlocal theories, and we point out that these nonlocal models can be modified so to nicely interpolate between Starobinski inflation in the primordial universe and accelerated expansion in the recent epoch.

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