Nonequilibrium thermodynamics of spacetime: The role of gravitational dissipation
Nonequilibrium thermodynamics of spacetime: The role of gravitational dissipation
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DOI：
10.1103/physrevd.81.024016
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发表时间：
2009-09
影响因子：
5
通讯作者：
G. Chirco;S. Liberati
中科院分区：
文献类型：
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作者：
G. Chirco;S. Liberati
在[T. Jacobson，Phys. Rev. Lett. 75，1260（1995）.]结果表明，爱因斯坦方程可以作为平衡时空热力学的局域本构方程导出。最近，在试图将同样的方法扩展到引力的$f（R）$理论的情况下，人们发现，为了充分描述这个理论以及经典的广义相对论（GR），确实需要一个非平衡设置[C]。埃灵河Guedens和T. Jacobson，Phys. Rev. Lett. 96，121301（2006）.]。在这里，详细说明这一点，我们表明，导致非平衡时空热力学的耗散字符实际上是相关的-无论是在GR以及在$f（R）$重力-非局部热通量与纯引力/内部自由度的理论。特别是，在GR的情况下，我们表明，内部熵产生项是相同的所谓的潮汐加热项的Hartle-Hawking。同样，对于f（R）引力的情况下，我们表明，耗散效应可以与推广这一项加上标量贡献，其存在是明确合理的标量张量表示的理论。最后，我们表明，允许的引力自由度可以固定的局部时空因果结构的运动学，通过特定的等效原理制定。从这个意义上说，这种物理描述似乎超越了爱因斯坦的引力理论。
In [T. Jacobson, Phys. Rev. Lett. 75, 1260 (1995).] it was shown that the Einstein equation can be derived as a local constitutive equation for an equilibrium spacetime thermodynamics. More recently, in the attempt to extend the same approach to the case of $f(R)$ theories of gravity, it was found that a nonequilibrium setting is indeed required in order to fully describe both this theory as well as classical general relativity (GR) [C. Eling, R. Guedens, and T. Jacobson, Phys. Rev. Lett. 96, 121301 (2006).]. Here, elaborating on this point, we show that the dissipative character leading to nonequilibrium spacetime thermodynamics is actually related---both in GR as well as in $f(R)$ gravity---to nonlocal heat fluxes associated with the purely gravitational/internal degrees of freedom of the theory. In particular, in the case of GR we show that the internal entropy production term is identical to the so-called tidal heating term of Hartle-Hawking. Similarly, for the case of $f(R)$ gravity, we show that dissipative effects can be associated with the generalization of this term plus a scalar contribution whose presence is clearly justified within the scalar-tensor representation of the theory. Finally, we show that the allowed gravitational degrees of freedom can be fixed by the kinematics of the local spacetime causal structure, through the specific equivalence principle formulation. In this sense, the thermodynamical description seems to go beyond Einstein's theory as an intrinsic property of gravitation.