Periodic cosmic evolution in Hybrid and Logarithmic Teleparallel Gravity

Abstract

In this work, we investigate a cosmological model within modified teleparallel gravity using two functional forms of $f(T)$: a hybrid model $f(T)=e^{\gamma T}T^{\sigma}$ and a logarithmic model, in the context of a periodic cosmic evolution driven by an oscillating deceleration parameter $q(t)=m\cos(kt)-1$. This approach describes a cyclic Universe with successive transitions between decelerating and accelerating phases. By constraining the model with observational values $m \simeq 0.48$ and $H_0 = 69.2\,\text{km}\,\text{s}^{-1}\,\text{Mpc}^{-1}$, we recover the present accelerated expansion with $q_0 \approx -0.52$, while larger values $m \geq 1$ lead to strongly oscillatory regimes including super-acceleration. For the hybrid model ($\gamma = 0.1$, $\sigma = -0.5$), the energy density remains positive, while the pressure oscillates. The equation of state evolves dynamically, crossing both quintessence and phantom regimes. In contrast, the logarithmic model stabilizes the dynamics, regularizes divergences, and yields smoother evolution, with the equation of state mainly remaining in the quintessence regime. The analysis of energy conditions shows that the violation of the SEC supports accelerated expansion, while the partial validity of NEC and DEC ensures physical consistency. Overall, this framework provides a flexible alternative to the standard $\Lambda$CDM model, allowing a unified description of different phases of cosmic expansion.