2017/03/31 by Xingang Chen, Yi Wang, Zhong-Zhi Xianyu · 2 citations
Physics and Astronomy · #hep-th #astro-ph.CO #hep-ph
paper · pdf · doi:10.1088/1475-7516/2017/12/006
published as JCAP 1712 (2017) 006 · 40 pages. JCAP published version
arxiv created 2017/12/05 · arxiv updated 2017/12/06
We present a systematic introduction to the diagrammatic method for practical calculations in inflationary cosmology, based on Schwinger-Keldysh path integral formalism. We show in particular that the diagrammatic rules can be derived directly from a classical Lagrangian even in the presence of derivative couplings. Furthermore, we use quasi-single-field inflation as an example to show how this formalism, combined with the trick of mixed propagator, can significantly simplify the calculation of some in-in correlation functions. The resulting bispectrum includes the lighter scalar case (m<3H/2) that has been previously studied, and the heavier scalar case (m>3H/2) that has not been explicitly computed for this model. The latter provides a concrete example of quantum primordial standard clocks, in which the clock signals can be observably large.