Exploring Intermediate and Natural Inflation under a Nonminimal Derivative Coupling: The John-George Framework

Ferdinand Mavoa, Mohamed C Sow, Hoavo Hova, Moussiliou G Ganiou, Cheikh S Touré, and Antonin D Kanfon
2026-05-14 7 views 0 downloads

 

Intermediate and natural inflation are investigated within a nonminimal derivative coupling scalar field model, namely the John–George framework. The derivative coupling introduces enhanced gravitational friction, modifying inflaton dynamics and enabling sustained accelerated expansion even for sub-Planckian parameter values. The field equations and slowroll parameters are derived in a flat Friedmann–Lemaître–Robertson–Walker spacetime. For intermediate inflation, the effective potential is reconstructed assuming a power-law scalar field evolution, while a periodic potential with a decay constant, ? describes the natural inflation. Numerical analysis of inflationary observables yields ?? = 0.96397 and ? = 0.0019 for intermediate inflation, and ?? = 0.961176 and ? = 0.00651 for natural inflation at ? = 60efolds. These predictions are in excellent agreement with Planck and BICEP/Keck constraints. The enhanced friction mechanism slows the inflaton evolution and suppresses the tensor-toscalar ratio, bringing the model well within observational bounds. Parameter analysis indicates that ? ? 0.5–1 and ? ? 0.5 provide optimal agreement with data. The John–George framework, therefore, constitutes a viable and competitive alternative to standard inflationary scenarios.

 

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