Five-Dimensional Kaluza-Klein Cosmology in f (R, T) Gravity Theory with Dark Energy

Abstract

We study a five-dimensional Kaluza-Klein cosmology in f (R, T) = λ (R + T) gravity with a time-dependent effective cosmological constant. Exact solutions are obtained for the Hubble parameter, deceleration parameter, pressure, energy density, and Λ (t) under an exponential volumetric expansion. Numerical analysis shows sustained accelerated expansion with the deceleration parameter remaining negative throughout cosmic evolution and confirms WEC, DEC, and NEC, while SEC is violated. Comparisons with CMB and supernova constraints demonstrate observational consistency and highlight a viable mechanism for time-dependent dark energy.