LAUSR

Abstract In this work we revisit constraints on K-inflation with DBI kinetic term and power-law kinetic term from reheating. For DBI kinetic term we choose monomial potentials, V ∝ φn with n = 2/3 , 1 , 2 and 4, and natural inflaton potential, and for power-law kinetic term we choose quadratic, quartic and exponential potentials. The phase of reheating can be parameterized in terms of reheating temperature Tre, number of e-folds during reheating Nre and effective equation of state during reheating wre. These parameters can be related to the spectral index ns and other inflationary parameters depending on the choice of inflaton kinetic term and potential. By demanding that wre should have a finite range and Tre should be above electroweak scale, one can obtain the bounds on ns that can provide bounds on tensor-to-scalar ratio r. We find, for K-inflation with DBI kinetic term and quadratic and quartic potentials, that the upper bound on r for physically plausible value of 0 ≤ wre ≤ 0.25 is slightly larger than the Planck-2018 and BICEP2/Keck array bound, and for n = 2/3 and 1, the reheating equation of state should be less than 0 to satisfy Planck-2018 joint constraints on ns and r. However, natural inflation with DBI kinetic term is compatible with Planck-2018 bounds on r and joint constraints on ns and r for physically plausible range 0 ≤ wre ≤ 0.25. The quadratic and quartic potential with power-law kinetic term are also compatible with Planck-2018 joint constraints on ns and r for 0 ≤ wre ≤ 1. However, for exponential potential with power-law kinetic term, the equation of state during reheating wre should be greater than 1 for r − ns predictions to lie within 68%C.L. of joint constraints on ns and r from Planck-2018 observations.