We study charged black hole solutions in 4-dimensional (4D) Einstein–Gauss–Bonnet–Maxwell theory to the linearized perturbation level. We first compute the shear viscosity to entropy density ratio. We then demonstrate how bulk causal structure analysis imposes an upper bound on the Gauss–Bonnet coupling constant in the AdS space. Causality constrains the value of Gauss–Bonnet coupling constant \(\alpha _{GB}\) to be bounded by \(\alpha _{GB}\le 0\) as \(D\rightarrow 4\).

中文翻译：

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4维爱因斯坦-高斯-帽子-麦克斯韦理论中黑洞的因果关系

我们在4维（4D）Einstein–Gauss–Bonnet–Maxwell理论中研究带电黑洞解到线性化扰动水平。我们首先计算剪切粘度与熵密度之比。然后，我们证明了整体因果结构分析是如何对AdS空间中的高斯-贝奈特耦合常数施加上限的。因果关系将高斯-贝纳特耦合常数\（\ alpha _ {GB} \）的值约束为\（\ alpha _ {GB} \ le 0 \）作为\（D \ rightarrow 4 \）。