Bulk viscous matter and the cosmic acceleration of the universe in $f(Q,T)$ gravity

Understand

We have studied bulk viscosity in the modified $f(Q, T)$ gravity theory formalism, where $Q$ represents the non-metricity and $T$ denotes the trace of energy-momentum tensor within a flat Friedmann-Lema\^{i}tre-Robertson-Walker metric (FLRW).

• Here, we have explicitly considered the effective equation of state, which includes a bulk viscosity term, and obtained the exact solutions by assuming a specific form of $f(Q, T)=\alpha Q+\beta T$, where $\alpha$ and $\beta$ are constants.
• Furthermore, we have found constraints on the model parameters with some external datasets, such as the revised Hubble datasets consisting of 57 data points, Baryon acoustic oscillations (BAO) datasets, and the newly published Pantheon samples with 1048 points to obtain the best fitting values of the model parameters.
• The obtained model is found to be in good agreement with observations.