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arXiv · 1703.10166

Schwinger-Keldysh Diagrammatics for Primordial Perturbations

Xingang Chen·Yi Wang·Zhong-Zhi Xianyu
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Abstract

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.

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Xingang Chen, Yi Wang, Zhong-Zhi Xianyu. 2017-12-05. Schwinger-Keldysh Diagrammatics for Primordial Perturbations. https://doi.org/10.1088/1475-7516%2F2017%2F12%2F006

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