Fitting f ( Q , T ) gravity models with a Λ CDM limit using H ( z ) and Pantheon data

We proposed five $f(Q,T)$ models, which are an extension of symmetric teleparallel gravity, where $Q$ is the non-metricity and $T$ is the trace of the stress–energy tensor. By taking specific values of their parameters, these models have a $\Lambda$CDM limit. Using cosmic chronometers and supernovae Ia data, we found that our models are consistent with $\Lambda$CDM at a 95% confidence level. To see whether one of these models can challenge $\Lambda$CDM at a background perspective, we computed the Bayesian evidence for them and $\Lambda$CDM. According to it, the concordance model is preferred over four of them, showing a weak preference against $f(Q,T)=-Q/G_N+bT$ and $f(Q,T)=-(Q+2\Lambda )/G_N+bT$, a substantial preference against $f(Q,T)=-(Q+2H_0^{2}c{(Q/\left(6H_0^2\right))}^{n+1})/G_N+bT$, and a strong preference against $f(Q,T)=-(Q+2H_0^{2}c{(Q/\left(6H_0^2\right))}^{n+1}+2\Lambda )/G_N+bT$. Interestingly, a model including a $T^2$ dependence ($f(Q,T)=-(Q+2\Lambda )/G_N-\left({\left(16\pi \right)}^2{G}_{N}b\right)/\left(120H_0^2\right)T^2$) showed a substantial preference against $\Lambda$CDM. Therefore, we encourage further analyses of this model to test its viability outside the background perspective.