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arXiv 2204.01255gr-qc
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Cartan $F(R)$引力与等效标量张量理论

Cartan $F(R)$ Gravity and Equivalent Scalar-Tensor Theory

Tomohiro Inagaki, Masahiko Taniguchi

摘要:

研究了$F(R)$引力中的Cartan形式. $F(R)$引力是通过用$R$的函数代替爱因斯坦-希尔伯特作用量中的里奇标量$R$来解释宇宙加速膨胀的理论。众所周知,$F(R)$引力通过保角变换被改写为标量张量理论。Cartan $F(R)$引力是基于Vierbein提出的Riemann-Cartan几何来描述的。在Cartan形式中,Ricci标量$R$被分成两部分,一部分来自Levi-Civita联络,另一部分来自挠率.假设自旋联系独立的物质作用量,我们成功地将Cartan $F(R)$引力作用量改写为Einstein-Hilbert作用量和具有正则动力学项和势项的标量场,而不需要任何保角变换.由此产生的标量-张量理论在应用通常的慢滚场景时很有用。作为一个简单的情况下,我们采用Starobinsky模型和宇宙学微波背景辐射的波动进行评估。

英文摘要:

We investigate the Cartan formalism in $F(R)$ gravity. $F(R)$ gravity has been introduced as a theory to explain cosmological accelerated expansion by replacing the Ricci scalar $R$ in the Einstein-Hilbert action with a function of $R$. As is well-known, $F(R)$ gravity is rewritten as a scalar-tensor theory by using the conformal transformation. Cartan $F(R)$ gravity is described based on the Riemann-Cartan geometry formulated by the vierbein. In the Cartan formalism, the Ricci scalar $R$ is divided into two parts, one derived from the Levi-Civita connection and the other from the torsion. Assuming the spin connection independent matter action, we have successfully rewritten the action of Cartan $F(R)$ gravity into the Einstein-Hilbert action and a scalar field with canonical kinetic and potential terms without any conformal transformations. The resulting scalar-tensor theory is useful in applying the usual slow-roll scenario. As a simple case, we employ the Starobinsky model and evaluate fluctuations in the cosmological microwave background radiation.

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