The leading -correction to the gravitational low-energy effective action of closed (type II) superstring theory in four-spacetime dimensions defines the Einstein-Grisaru-Zanon gravity action that is applied for a calculation of the leading corrections to the Schwarzschild solution and the Hubble function in the Friedmann-Lemaitre-Robertson-Walker universe, in the first order with respect to the effective string-generated coupling. The solutions found are compared to the corresponding solutions in the Einstein-Bel-Robinson gravity that also modifies the Einstein gravity by the terms quartic in the spacetime curvature. We consider the black hole shadows in the Einstein-Grisaru-Zanon gravity theory and derive the upper bound on the string coupling parameter from the Hawking temperature of a black hole.

中文翻译：

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爱因斯坦-格里萨鲁-扎农引力


四时空维度中闭合（II 型）超弦理论的引力低能有效作用的前导修正定义了爱因斯坦-格里萨鲁-扎农引力作用，该作用应用于计算史瓦西解和Friedmann-Lemaitre-Robertson-Walker 宇宙中的哈勃函数，相对于有效弦生成耦合处于一阶。将找到的解与爱因斯坦-贝尔-罗宾逊引力中的相应解进行比较，爱因斯坦-贝尔-罗宾逊引力也通过时空曲率中的四次项修改了爱因斯坦引力。我们考虑爱因斯坦-格里萨鲁-扎农引力理论中的黑洞阴影，并从黑洞的霍金温度推导出弦耦合参数的上限。