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arXiv 2005.04234hep-thastro-ph.COgr-qchep-ph
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宇宙学的自举:从对称性和因式分解旋转关联函数

The Cosmological Bootstrap: Spinning Correlators from Symmetries and Factorization

Daniel Baumann, Carlos Duaso Pueyo, Austin Joyce, Hayden Lee, Guilherme L. Pimentel

摘要:

我们将宇宙学的自举方法推广到包含自旋的无质量粒子的关联函数。在德西特空间中,这些关联函数同时受到对称性和局部性的约束。特别是,德西特等距在时空的未来边界上成为共形对称,这反映在边界关联函数必须满足的一组沃德恒等式中。我们解决这些沃德恒等式的作用与重量移动运营商的标量种子解决方案。利用这种移重方法,我们导出了无质量自旋1和自旋2场与共形耦合标量的三点和四点关联函数。由树级交换产生的四点函数在特定的运动构形中是奇异的,并且这些奇异性的系数满足一定的因式分解性质。我们表明,在许多情况下,这些分解限制关联函数的结构唯一的,而不必解决的共形沃德恒等式。无质量自旋粒子的定域性附加约束表现为边界上的流守恒。我们发现,四点函数只满足当前守恒,如果s,t,和u-通道是相互关联的,导致非平凡的约束之间的耦合的保守电流和其他运营商的理论。对于自旋为1的电流,这意味着电荷守恒,而自旋为2的电流,我们恢复从纯粹的边界的角度来看,等效原理。对于多个自旋为1的场,我们恢复了Yang-Mills理论的结构。最后,我们将我们的方法应用于慢卷暴胀,并导出了一些唯象相关的标量张量三点函数。

英文摘要:

We extend the cosmological bootstrap to correlators involving massless particles with spin. In de Sitter space, these correlators are constrained both by symmetries and by locality. In particular, the de Sitter isometries become conformal symmetries on the future boundary of the spacetime, which are reflected in a set of Ward identities that the boundary correlators must satisfy. We solve these Ward identities by acting with weight-shifting operators on scalar seed solutions. Using this weight-shifting approach, we derive three- and four-point correlators of massless spin-1 and spin-2 fields with conformally coupled scalars. Four-point functions arising from tree-level exchange are singular in particular kinematic configurations, and the coefficients of these singularities satisfy certain factorization properties. We show that in many cases these factorization limits fix the structure of the correlators uniquely, without having to solve the conformal Ward identities. The additional constraint of locality for massless spinning particles manifests itself as current conservation on the boundary. We find that the four-point functions only satisfy current conservation if the s, t, and u-channels are related to each other, leading to nontrivial constraints on the couplings between the conserved currents and other operators in the theory. For spin-1 currents this implies charge conservation, while for spin-2 currents we recover the equivalence principle from a purely boundary perspective. For multiple spin-1 fields, we recover the structure of Yang-Mills theory. Finally, we apply our methods to slow-roll inflation and derive a few phenomenologically relevant scalar-tensor three-point functions.

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