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Journal Article

Cosmic microwave background from effective field theory


Choudhury,  Sayantan
Quantum Gravity & Unified Theories, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;

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Choudhury, S. (2019). Cosmic microwave background from effective field theory. Universe, 5(6): 155. Retrieved from http://arxiv.org/abs/1712.04766.

Cite as: https://hdl.handle.net/21.11116/0000-0002-4AC9-9
In this work, we study the key role of generic Effective Field Theory (EFT)
framework to quantify the correlation functions in a quasi de Sitter background
for an arbitrary initial choice of the quantum vacuum state. We perform the
computation in unitary gauge in which we apply St$\ddot{u}$ckelberg trick in
lowest dimensional EFT operators which are broken under time diffeomorphism.
Particularly using this non-linear realization of broken time diffeomorphism
and truncating the action by considering the contribution from two derivative
terms in the metric we compute the two point and three point correlations from
scalar perturbations and two point correlation from tensor perturbations to
quantify the quantum fluctuations observed in Cosmic Microwave Background (CMB)
map. We also use equilateral limit and squeezed limit configurations for the
scalar three point correlations in Fourier space. To give future predictions
from EFT setup and to check the consistency of our derived results for
correlations, we use the results obtained from all class of canonical single
field and general single field $P(X,\phi)$ model. This analysis helps us to fix
the coefficients of the relevant operators in EFT in terms of the slow roll
parameters and effective sound speed. Finally, using CMB observation from
Planck we constrain all of these coefficients of EFT operators for single field
slow roll inflationary paradigm.