We briefly review the manifold incarnations and facets of the notion that gravity, in certain regards, can be re-conceived as the product of two gauge theories. We begin with a short history of the relationship between gauge and gravity theories in the context of “\(\hbox {gravity} = \hbox {gauge} \times \hbox {gauge}\)”. This is followed by modern approaches to gauge/gravity scattering amplitude relations, focussing on the Bern–Carrasco–Johansson colour-kinematic duality and double-copy construction of gravitational amplitudes from gauge amplitudes. This includes a partial characterisation of what gravity theories admit a gauge theory squared origin. We then consider classical and off-shell perspectives on “\(\hbox {gravity} =\hbox {gauge} \times \hbox {gauge}\)”. First we review field theoretic approaches to understanding the colour-kinematic duality and the double-copy prescription, including kinematic algebras and colour-kinematic duality and double-copy manifesting Lagrangians. We then consider classical double-copy-like methods for constructing gravitational solutions from gauge theory solutions. To close, we consider a purely field theoretic take on “\(\hbox {gravity} =\hbox {gauge} \times \hbox {gauge}\)”. This framework centres on a convolutive product of gauge theories, at the level of spacetime fields themselves, that yields gravitational theories.

我们简要回顾了这一概念的多种体现和方面，即在某些方面，引力可以被重新构想为两种规范理论的产物。我们首先在“ \(\hbox {gravity} = \hbox {gauge} \times \hbox {gauge}\) ”的背景下简要介绍规范和引力理论之间的关系。接下来是规范/重力散射振幅关系的现代方法，重点是伯尔尼-卡拉斯科-约翰逊颜色运动二元性和来自规范振幅的重力振幅的双重复制构造。这包括重力理论承认规范理论平方原点的部分特征。然后我们考虑“ \(\hbox {gravity} =\hbox {gauge} \times \hbox {gauge}\) ”的经典和离壳视角。首先，我们回顾了理解颜色运动对偶性和双拷贝处方的场论方法，包括运动代数和颜色运动对偶性以及双拷贝表现拉格朗日量。然后，我们考虑经典的类似双拷贝的方法，用于从规范理论解构建引力解。最后，我们考虑“ \(\hbox {gravity} =\hbox {gauge} \times \hbox {gauge}\) ”的纯场论。这个框架以规范理论的卷积产物为中心，在时空场本身的层面上，产生了引力理论。