论文标题
超越（回到）palatini二次重力和通货膨胀
Beyond (and back to) Palatini quadratic gravity and inflation
论文作者
论文摘要
我们研究嵌入Palatini $ f（r）$重力的单场慢速通货膨胀，其中$ f（r）$的增长速度快于$ r^2 $。出人意料的是，该理论的一致性要求约旦框架的反气势从下方不受限制。更令人惊讶的是，这对应于从下方界定的爱因斯坦框架充气电势。我们证明，对于所有此类palatini $ f（r）$，存在一个通用强耦合极限，对应于二次$ f（r）$，线性术语错误的符号和乔丹框架中的宇宙常数。在这样的限制下，张量比$ r $ $ r $不取决于原始的输注量潜力，而标量频谱索引$ n_s $确实如此。不幸的是，该系统是从缓慢滚动方案中定义不明的。一种可能的方法是升级到$ f（r，x）$型号，并使用$ x $ jordan框架流动性术语升级。这种修改本质上使通货膨胀预测不受影响。
We study single-field slow-roll inflation embedded in Palatini $F(R)$ gravity where $F(R)$ grows faster than $R^2$. Surprisingly, the consistency of the theory requires the Jordan frame inflaton potential to be unbounded from below. Even more surprisingly, this corresponds to an Einstein frame inflaton potential bounded from below and positive definite. We prove that for all such Palatini $F(R)$'s, there exists a universal strong coupling limit corresponding to a quadratic $F(R)$ with the wrong sign for the linear term and a cosmological constant in the Jordan frame. In such a limit, the tensor-to-scalar ratio $r$ does not depend on the original inflaton potential, while the scalar spectral index $n_s$ does. Unfortunately, the system is ill-defined out of the slow-roll regime. A possible way out is to upgrade to a $F(R,X)$ model, with $X$ the Jordan frame inflaton kinetic term. Such a modification essentially leaves the inflationary predictions unaffected.
