The upper bound on the tensor-to-scalar ratio consistent with quantum gravity

• 作者: Lina Wu Qing Gao Yungui Gong Yiding Jia Tianjun Li
• 来源期刊: 理论物理通讯（英文版）
• 年，卷（期）: 2021,（7）
• 所属期刊栏目: GRAVITATIONAL THEORY,ASTROPHYSICS AND COSMOLOGY
• 页码范围: 115-120
• 页数: 6页
• 语种: 英文

摘要

We consider the polynomial inflation with the tensor-to-scalar ratio as large as possible which can be consistent with the quantum gravity(QG)corrections and effective field theory(EFT).To get a minimal field excursion Δφ for enough e-folding number N,the inflaton field traverses an extremely flat part of the scalar potential,which results in the Lyth bound to be violated.We get a CMB signal consistent with Planck data by numerically computing the equation of motion for inflaton φ and using Mukhanov-Sasaki formalism for primordial spectrum.Inflation ends at Hubble slow-roll parameter ∈H1=1 or ?=0.Interestingly,we find an excellent practical bound on the inflaton excursion in the format a+b√r,where a is a tiny real number and b is at the order 1.To be consistent with QG/EFT and suppress the high-dimensional operators,we show that the concrete condition on inflaton excursion is △φ/Mpl＜0.2×√10(≌)0.632.For ns=0.9649,Ne=55,and △φ/MPl＜0.632,we predict that the tensor-to-scalar ratio is smaller than 0.0012 for such polynomial inflation to be consistent with QG/EFT.