标题： 标量-张量引力的共形类 显示英文标题

标题： Conformal classes of Brans-Dicke gravity

摘要： 基于无量纲引力耦合常数的行为，对引力的Brans-Dicke理论进行了分类。 注意到当前文献中关于标量-张量引力理论可以表述的两个不同的共形框架：Jordan框架和Einstein框架，哪一个才是物理的，这种讨论在大多数情况下可能是没有意义的，因为这两个框架可能属于同一个共形类。 还注意到，带有普通物质非最小耦合的Brans-Dicke引力的Jordan框架表述，即仅仅是广义相对论的Jordan框架表述，具有尺度不变性，这与带有最小耦合物质的Brans-Dicke引力的Jordan框架表示（Brans-Dicke理论的原始表述）的情况不同，在后者中，非零质量普通物质的存在会破坏理论的尺度不变性。 显示英文摘要

摘要： A classification of Brans-Dicke theories of gravitation, based on the behaviour of the dimensionless gravitational coupling constant, is given. It is noted that the discussion takes place in the current literature, about which of the two distinguished conformal frames in which scalar-tensor theories of gravity can be formulated: the Jordan frame and the Einstein frame, is the physical one, may, in most cases, be meaningless for both frames may belong to the same conformal class. It is also noted that the Jordan frame formulation of Brans-Dicke gravity with ordinary matter nonminimally coupled, that is shown to be just the Jordan frame formulation of general relativity, is scale-invariant, unlike the situation with the Jordan frame representation of Brans-Dicke gravity with matter minimally coupled (the original formulation of Brans-Dicke theory), where the presence of nonzero mass ordinary matter breaks the scale-invariance of the theory.