Phantom dark energy nature of bulk-viscosity universe in modified f(Q)-gravity

This paper deals with an anisotropic, cosmological model in the modified theory of f(Q)-gravity filled with bulk-viscosity fluid. We investigated the modified f(Q)-gravity with quadratic form f(Q) = -alpha Q(2), where Q is the non-metricity scalar and alpha is a positive constant, in Locally-Rotationally Symmetric (LRS) Bianchi type-I space time universe. We have solved the modified Einstein's field equations with bulk-viscosity factor xi(t) = xi H-0 + xi H-1(2) and obtained average scale factor a(t) = k(0)[e(k1t) sech(k(2)t)](3) where k(0) is a constatnt and k(1) = xi(1)(m+2)(2)/108 alpha(2m+1), and k(2) = -(m+2)root xi(1)(m+2)(2)+48 alpha xi(0) (2m+1)/108 alpha(2m+1). We have investigated the model in two cases xi(0) = 0 and xi(1) = 0. We have found the best-fit values of model parameters with observational datasets like Union 2.1 compilation and Joint Light Curve Analysis (JLA) datasets by applying R-2-test formula in curve-fitting. Using these best-fit values of model parameters, we have studied the cosmological parameter like Hubble parameter H and deceleration parameter q, equation of state (EoS) parameter, age of the present universe t(0), etc. We have obtained a transit model (i.e. decelerating to accelerating in current) in the first case xi(0) = 0 and a transit phase model from accelerating to decelerating in the second case xi(1) = 0. We have investigated the EoS parameter omega(v) for bulk-viscosity and obtained the present values as -1.2 < omega(v) < 2.5, which is supported by the observational results. We have also analyzed energy conditions and statefinder parameters and found that our model approaches to LCDM model in the future.