We consider soft graviton scattering for a theory where Einstein's gravity is minimally coupled to a scalar field in the presence of a cosmological constant, i.e. in a background de Sitter space. Employing a perturbative expansion in a small cosmological constant, we compute leading, subleading and sub-subleading corrections to Weinberg's soft graviton amplitude for the tree-level scatterings in the static patch of de Sitter space. We observe similar universal features of the soft graviton amplitude as found in [JHEP10(2023)055] for the soft photons.
de Sitter corrections to supertranslation Ward identity and soft graviton theorem
School of Physics, The University of Electronic Science and Technology of China（电子科技大学物理学院）；Indian Institute of Information Technology Allahabad (IIITA)（安拉阿巴德信息技术学院）
We exploit a recent computation of one graviton loop corrections to the self-mass [1] to quantum-correct the field equation for a massless, conformally coupled scalar on a de Sitter background. With the obvious choice for the finite part of the $R^2 ϕ^2$ counterterm, we find that neither plane wave mode functions nor the response to a point source acquires large infrared logarithms. However, we do find a decaying logarithmic correction to the mode function and a short distance logarithmic running of the potential in addition to the power-law effect inherited from flat space.
Soft Gravitons Screen Couplings in de Sitter Space
de Sitter空间量子涨落的标度不变性导致引力子传播子中出现de Sitter对称性破缺的红外辐射。我们研究了软引力子对宇宙视界内物质场局部动力学的物理效应。我们证明了在标量场和狄拉克场论中，红外谱不破坏洛伦兹不变性。在这两种情况下，超前的红外辐射都可以被与时间相关的波函数重整化因子吸收。在具有$λϕ^4$和Yukawa相互作用的相互作用场论中，我们发现耦合变得与时间有关，具有确定的标度指数。我们认为，耦合的相对标度指数是规范不变的和物理的，因为我们可以使用耦合的演化作为一个物理时间。
Evanescent gravitons in Warped Anti-de Sitter space
除了黑洞外，关于Warped-Anti de Sitter（WAdS）空间的三维有质量引力相空间包含随时间指数衰减的解。它们描述了倏逝引力子的结构，虽然由有效质量不为零的波动方程控制，但不携带净引力能。在拓扑大质量引力的情况下，已经发现了这种解的明确例子;在这里，我们将它们推广到更一般的无幽灵的大质量形变，不同之处在于，由于高阶项的存在，衰减率得到了校正。
We consider a model of Bose-Einstein condensate of weakly interacting off-shell gravitons in the regime that is far from the quantum critical point. Working in static spherically symmetric setup, recent study has demonstrated that the effective spacetime geometry of this condensate is a gravastar. In this paper we make three generalizations: introducing a composite of two sets of off-shell gravitons with different wavelength to enable richer geometries for the interior and exterior spacetimes, working in $f({\mathcal R})$ gravity, and extending the calculations to higher dimensions. We find th…
In this work we present a systematic study of AdS$_{d+1}$ loop amplitudes for gluons and gravitons using momentum space techniques. Inspired by the recent progress in tree level computation, we construct a differential operator that can act on a scalar factor in order to generate gluon and graviton loop integrands: this systematizes the computation for any given loop level Witten diagram. We then give a general prescription in this formalism, and discuss it for bubble, triangle, and box diagrams.
We define a perturbative S-matrix in a local patch of de Sitter background in the limit when the curvature length scale ($\ell$) is large and study the 'soft' behavior of the scalar QED amplitudes in de Sitter spacetime in generic dimensions. We obtain the leading and subleading perturbative corrections to flat space soft photon theorems in the large $\ell$ limit, and comment on the universality of these corrections. We compare our results with the electromagnetic memory tails obtained earlier in $d=4$ using classical radiation analysis.
We compute the leading order non-Gaussianity, i.e., the bispectrum, of the tensor perturbation in the general $α$-vacuum on de Sitter space in general relativity. In addition to the well-known Bunch-Davies (BD) vacuum, there exits an infinite number of de Sitter invariant vacua represented by a real parameter $α$ and a phase $ϕ$, with $α=0$ being the BD vacuum. They are called $α$-vacua. In the standard slow-roll inflation, as de Sitter invariance no longer applies, the $α$-vacua lose its relevance in the rigorous sense. Nevertheless, if we assume that the parameter $α$ is only weakly dependen…
