"Detuned" f(R) gravity and dark energy
"Detuned" f(R) gravity and dark energy
复制标题
DOI：
10.1103/physrevd.77.124024
复制
发表时间：
2008-03
影响因子：
5
通讯作者：
N. Deruelle;M. Sasaki;Y. Sendouda
中科院分区：
文献类型：
--
作者：
N. Deruelle;M. Sasaki;Y. Sendouda
在由f(R)拉格朗日引出的引力理论中，物质通常被认为是与度规最小耦合的，因此定义了一个‘’Jordan框架‘’。然而，由于场方程是四阶的，所以引力在标准引力子之上有一个额外的自由度，这从它在共形相关的爱因斯坦框架中的等价描述中可见一斑。我们在作用力中显式地引入了这个额外的标量自由度，并将其耦合到物质上，因此原始度规不再定义Jordan框架。这种“失谐”使f(R)引力进入了更广泛的标量-张量理论。我们认为，跟踪背景物质密度的类似变色龙的失谐可能提供了纯粹的引力模型，该模型解释了目前宇宙的加速度，并避开了局部重力约束。
In gravity theories derived from a f(R) Lagrangian, matter is usually supposed to be minimally coupled to the metric, which hence defines a ''Jordan frame.'' However, since the field equations are fourth order, gravity possesses an extra degree of freedom on top of the standard graviton, as is manifest from its equivalent description in the conformally related, Einstein, frame. We introduce explicitly this extra scalar degree of freedom in the action and couple it to matter, so that the original metric no longer defines a Jordan frame. This ''detuning'' puts f(R) gravity into a wider class of scalar--tensor theories. We argue that a ''chameleon-like'' detuning tracing the background matter density may provide purely gravitational models which account for the present acceleration of the universe and evade local gravity constraints.