标题： 粘性时空流体和高曲率引力 显示英文标题

标题： Viscous Spacetime Fluid and Higher Curvature Gravity

摘要： 本文重新考虑了爱因斯坦场方程作为时空热力学系统的状态方程。 我们认为，一种一致的解释使我们能够将表示时空流体体积粘度的标量曲率和宇宙常数项进行识别。 由于在这一解释中，爱因斯坦方程本身对应于近平衡状态，因此不需要引入$f(R)$引力来处理非平衡热力学。 提出了一个逻辑上一致的推广，以包括由于黎曼曲率引起的所谓“潮汐力”的影响。 推导出一种更高曲率引力的状态方程，并讨论了其物理解释。 显示英文摘要

摘要： The Einstein field equation as an equation of state of a thermodynamical system of spacetime is reconsidered in the present Letter. We argue that a consistent interpretation leads us to identify scalar curvature and cosmological constant terms representing the bulk viscosity of the spacetime fluid. Since Einstein equation itself corresponds to a near-equilibrium state in this interpretation invoking $f(R)$ gravity for nonequilibrium thermodynamics is not required. A logically consistent generalization to include the effect of so called 'tidal forces' due to the Riemann curvature is presented. A new equation of state for higher curvature gravity is derived and its physical interpretation is discussed.