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Production of thermal photons in viscous fluid dynamics with temperature-dependent shear viscosity

We compute the spectrum of thermal photons created in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV, taking into account dissipative corrections in production processes corresponding to the quark--gluon plasma and hadronic phases. To describe the evolution of the fireball we use a viscous fluid dynamic model with different parametrizations for the temperature--dependence of $η/s$. We find that the spectrum significantly depends on the values of $η/s$ in the QGP phase, and is almost insensitive to the values in the hadronic phase. We also compare the influence of the temperature--dependence of $η/s$ on the spectrum of thermal photons to that of using different equations of state in the fluid dynamic simulations, finding that both effects are of the same order of magnitude.