Constraining $f(T,B,T_G,B_G)$ gravity by dynamical system analysis

The evolutionary behavior of the Universe has been analysed through the dynamical system analysis in $f(T,B,T_G,B_G)$ gravity, where $T$, $B$, $T_G$, and $B_G$ respectively represent torsion, boundary term, teleparallel Gauss-Bonnet term and Gauss-Bonnet boundary term. We use the transformation, $f(T,B,T_G,B_G)=-T+\mathcal{F}(T, B, T_G, B_G)$ in order to obtain the deviation from the Teleparallel Equivalent of General Relativity (TEGR). Two cosmological models pertaining to the functional form of $\mathcal{F}(T, B, T_G, B_G)$ have been studied. The well motivated forms are: (i) $\mathcal{F}(T, B, T_G, B_G) = f_{0} T^{m} B^{n}T_{G}^{k}$ and (ii) $\mathcal{F}(T, B, T_G, B_G)=b_{0} B + g_{0} T_{G}^{k}$. The evolutionary phases of the Universe have been identified through the detailed analysis of the critical points. Further, with the eigenvalues and phase space diagrams, the stability and attractor nature of the accelerating solution have been explored. The evolution plots have been analyzed for the corresponding cosmology and compatibility with the present observed value of standard density parameters have been shown.