Effective Field Theory of small r. (arXiv:2003.12755v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Qiu_T/0/1/0/all/0/1">Taotao Qiu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Katsuragawa_T/0/1/0/all/0/1">Taishi Katsuragawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ni_S/0/1/0/all/0/1">Shulei Ni</a>

The recent observations from CMB have imposed a very stringent upper-limit on
the tensor/scalar ratio $r$ of inflation models, which indicates that the
primordial gravitational waves (PGW), even though possible to be detected,
should be very tiny. However, current experiments on PGW is ambitious to detect
such a tiny signal by improving the accuracy to an even higher level. Whatever
their results are, it will give us much information about the early universe,
not only from the astrophysical side but also from the theoretical side, e.g.,
model building. In this paper, we are interested in analyzing what kind of
inflation models can be favored by future observations, using the facility of
the effective field theory (EFT) approach. We show that $r$ can be expressed in
EFT language, and more importantly, by plotting the contours in the parameter
spaces, we indicate how $r$ can be affected by model parameters in various
concrete examples.

The recent observations from CMB have imposed a very stringent upper-limit on
the tensor/scalar ratio $r$ of inflation models, which indicates that the
primordial gravitational waves (PGW), even though possible to be detected,
should be very tiny. However, current experiments on PGW is ambitious to detect
such a tiny signal by improving the accuracy to an even higher level. Whatever
their results are, it will give us much information about the early universe,
not only from the astrophysical side but also from the theoretical side, e.g.,
model building. In this paper, we are interested in analyzing what kind of
inflation models can be favored by future observations, using the facility of
the effective field theory (EFT) approach. We show that $r$ can be expressed in
EFT language, and more importantly, by plotting the contours in the parameter
spaces, we indicate how $r$ can be affected by model parameters in various
concrete examples.

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