Mimetic DBI Inflation in Confrontation with Planck2018 data
Kourosh Nozari, Narges Rashidi

TL;DR
This paper investigates mimetic gravity with a DBI-like scalar field, analyzing its compatibility with Planck2018 data, and finds that certain parameter ranges and constant sound speeds yield models consistent with observational constraints.
Contribution
It introduces and tests the viability of Mimetic DBI inflation models against Planck2018 data, highlighting conditions for stability and observational consistency.
Findings
Mimetic DBI models can be free of ghost and gradient instabilities.
Models with constant sound speed are consistent with Planck2018 data for specific parameters.
Varying sound speed models are generally ruled out by combined observational data.
Abstract
We study mimetic gravity in the presence of a DBI-like term which is a non-canonical setup of the scalar field's derivatives. We consider two general cases with varying and constant sound speeds and construct the potentials for both the DBI and Mimetic DBI models. By considering the power-law scale factor as , we seek for the observational viability of these models. We show that, the Mimetic DBI model in some ranges of the parameters space is free of ghost and gradient instabilities. By studying and behavior in confrontation with Planck2018 data, we find some constraints on the model's parameters. We show that for the case with varying sound speed, although power-law DBI inflation is not consistent with Planck2018 TT, TE, EE+low E+lensing data, but the Mimetic DBI inflation is consistent with Planck2018 TT, TE, EE+low E+lensing data at 95…
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