Charged 4D Einstein-Gauss-Bonnet-AdS black holes: Shadow, energy emission, deflection angle and heat engine

Recently, there has been a surge of interest in the 4D Einstein-Gauss-Bonnet (4D EGB) gravity theory which bypasses the Lovelock theorem and avoids Ostrogradsky's instability. Such a novel theory has non-trivial dynamics and presents several predictions for cosmology and black hole physics. Motivated by recent astrophysical observations and the importance of anti-de Sitter spacetime (AdS), we investigate shadow geometrical shapes and deflection angle of light from the charged AdS black holes in 4D EGB gravity theory. We explore the shadow behaviors and photon sphere around such black holes, and inspect the effect of different parameters on them. Then, we present a study regarding the energy emission rate of such black holes and analyze the significant role of the Gauss-Bonnet (GB) coupling constant in the radiation process. Then, we perform a discussion of holographic heat engines of charged 4D EGB-AdS black holes by obtaining the efficiency of a rectangular engine cycle. Finally, by comparing heat engine efficiency with the Carnot efficiency, we indicate that the ratio eta/eta c is always less than one which is consistent with the thermodynamic second law. (C) 2020 The Author(s). Published by Elsevier B.V.