The gradient expansion solutions to hydrodynamic equations are found to be divergent in many cases. The application of resurgence theory rescues the divergent series solutions and reproduces hydrodynamic attractors in Bjorken flow[1,2] and Gubser flow[3,4]. In this talk, I will first present my result of Borel-resummed hydrodynamics in a different situation, a viscous fluid system that undergoes Hubble flow at a controlled rate. Then the topic of effective viscosity will also be discussed.
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