Nonminimal Scalar-curvature Coupling Noncanonical Warm Inflation

Abstract

We investigate a noncanonical warm inflationary model with a nonminimal coupling between the inflaton field and scalar curvature. Within the Jordan frame, we derive the modified background equations and establish the slow-roll conditions through a linear stability analysis. We find that the nonminimal coupling enhances the effective damping and modifies the potential gradient, facilitating slow-roll evolution even for relatively steep potentials. Using the stochastic approach, we derive the Langevin equation for inflaton fluctuations and obtain the primordial scalar and tensor power spectra. Our results show that the scalar spectrum is nearly scale-invariant, while the combined effects of nonminimal coupling, noncanonical dynamics, and thermal dissipation can further suppress the tensor-to-scalar ratio. Moreover, the model can sustain warm inflation even in the weak-dissipation regime and accommodate sub-Planckian field excursions in suitable parameter regions. These findings highlight the potential of this framework as a viable extension of conventional warm inflation.