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Paper IPM / P / 14630  


Abstract:  
Inspired by thermodynamical dissipative phenomena, we consider constant bulk viscosity for dark fluid in a spatially flat twocomponent Universe. Our viscous dark energy model represents Phantom crossing avoiding BigRip singularity. We propose a nonminimal derivative coupling scalar field with zero potential to describe viscous dark energy model. In this approach, coupling constant (κ) is related to viscosity coefficient (γ) and energy density of dark energy at the present time (Ω_{DE}^{0}). This coupling is bounded as κ ∈ [−1/9H_{0}^{2}(1−Ω_{DE}^{0}), 0] and for γ = 0 leads to κ = 0. To perform robust analysis, we implement recent observational data sets including Joint Lightcurve Analysis (JLA) for SNIa, Gamma Ray Bursts (GRBs) for most luminous astrophysical objects at high redshifts, Baryon Acoustic Oscillations (BAO) from different surveys, Hubble parameter from HST project, Planck data for CMB power spectrum and CMB Lensing. Joint analysis of JLA+GRBs+BAO+HST shows that Ω_{DE}^{0}=0.700^{+0.021}_{−0.023} , γ = 0.1406^{+0.0064}_{−0.0065} and H_{0}=69.1^{+3.5}_{−2.8} at 1σ confidence interval. Planck TT observation provides γ = 0.32^{+0.31}_{−0.26} at 68% confidence limit for viscosity coefficient. Tension in Hubble parameter is alleviated in this model. Cosmographic distance ratio indicates that current observed data prefer to increase bulk viscosity. Finally, the competition between Phantom and Quintessence behavior of viscous dark energy model can accommodate cosmological old objects reported as a sign of age crisis in ΛCDM model.
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