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arXiv 1801.04056hep-thgr-qc
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修正的标量-张量引力理论下的早期宇宙

Early Universe with modified scalar-tensor theory of gravity

Ranajit Mandal, Chandramouli Sarkar, Abhik Kumar Sanyal

摘要:

具有非最小耦合的标量-张量引力理论是解释晚期宇宙演化所需的暗能量的一个相当好的候选者。在这里,我们研究的非常早期阶段的宇宙演化与修改版本的理论,其中包括标量曲率平方项。本研究的一个关键方面是,所考虑的作用的量子动力学一般以半经典近似下的de-Sitter展开而不是幂律结束。这证明了de-Sitter展开下的通货膨胀机制分析是正确的。另一个关键的方面是,在研究引力微扰时,由微扰作用量得到的微扰广义标量场方程,当与背景标量场方程的微扰形式相匹配时,耦合参数与势的关系与经典场方程的解的关系完全相同,假定deSitter展开。研究还表明,量子理论是很好的行为,暴胀参数落在观测范围内,量子微扰分析表明,功率谱没有偏离标准的一个从最小耦合理论。

英文摘要:

Scalar-tensor theory of gravity with non-minimal coupling is a fairly good candidate for dark energy, required to explain late-time cosmic evolution. Here we study the very early stage of evolution of the universe with a modified version of the theory, which includes scalar curvature squared term. One of the key aspects of the present study is that, the quantum dynamics of the action under consideration ends up generically with de-Sitter expansion under semiclassical approximation, rather than power-law. This justifies the analysis of inflationary regime with de-Sitter expansion. The other key aspect is that, while studying gravitational perturbation, the perturbed generalized scalar field equation obtained from the perturbed action, when matched with the perturbed form of the background scalar field equation, relates the coupling parameter and the potential exactly in the same manner as the solution of classical field equations does, assuming de-Sitter expansion. The study also reveals that the quantum theory is well behaved, inflationary parameters fall well within the observational limit and quantum perturbation analysis shows that the power-spectrum does not deviate considerably from the standard one obtained from minimally coupled theory.

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