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arXiv 1704.03372gr-qchep-th
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引力畴壁与$G$的动力学

Gravitational domain walls and the dynamics of $G$

Claudio Bunster, Andrés Gomberoff

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8 pages, 2 figures
发表信息：
Phys. Rev. D 96, 025013 (2017)
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摘要：

从基本粒子物理学的观点来看，引力常量$G$非常小。这导致了一个问题，即它是否可以从最初的与微观单位相称的值衰减到现在的值。本文提出了导致这种衰减的机制。它基于这样的假设，即$G$在被一种新的畴壁（即“G-壁”）隔开的宇宙区域内可能取不同的值。这个想法是通过引入规范势$A_{μνρ}$及其共轭$D$来实现的，它决定了$G$的值作为积分常数而不是基本常数。当通过$G$ -墙时，$G$的值跳跃。这个过程扩展了以前对宇宙学常数的研究，但推广远不是简单的：（1）从两侧看，$G$壁的内禀几何是不一样的，因为黑洞热力学第二定律规定，$G$的跳跃必须引起长度尺度的不连续。(ii)$G$中的衰减步长的大小由函数$G(D)$控制，可以选择该函数，以便朝着渐近线$G=0$减小$G$的值，而无需微调。结果表明：（1）将$G$作为动力学变量处理，并与$G$ -壁和物质耦合的引力场的动力学，可从给出的作用原理得出。(ii)撞击在$G$壁上的粒子可能被折射或反射。(iii)当在两个粒子之间插入$G$ -壁时，两个粒子之间的各种力发生变化。(iv)$G$ -壁可以通过隧道效应和热效应成核。半经典概率进行了评估。(v)~如果作用量原理构造正确，当黑洞吸收G壁而改变引力常量时，黑洞的熵会增加。

英文摘要：

From the point of view of elementary particle physics the gravitational constant $G$ is extraordinarily small. This has led to ask whether it could have decayed to its present value from an initial one commensurate with microscopical units. A mechanism that leads to such a decay is proposed herein. It is based on assuming that $G$ may take different values within regions of the universe separated by a novel kind of domain wall, a "G-wall". The idea is implemented by introducing a gauge potential $A_{μνρ}$, and its conjugate $D$, which determines the value of $G$ as an integration constant rather than a fundamental constant. The value of $G$ jumps when one goes through a $G$-wall. The procedure extends one previously developed for the cosmological constant, but the generalization is far from straightforward: (i) The intrinsic geometry of a $G$-wall is not the same as seen from its two sides, because the second law of black hole thermodynamics mandates that the jump in $G$ must cause a discontinuity in the scale of length. (ii) The size of the decay step in $G$ is controlled by a function $G(D)$ which may be chosen so as to diminish the value of $G$ towards the asymptote $G=0$, without fine tuning. It is shown that: (i) The dynamics of the gravitational field with $G$ treated as a dynamical variable, coupled to $G$-walls and matter, follows from an action principle, which is given. (ii) A particle that impinges on a $G$-wall may be refracted or reflected. (iii) The various forces between two particles change when a $G$-wall is inserted in between them. (iv) $G$-walls may be nucleated trough tunneling and thermal effects. The semiclassical probabilities are evaluated. (v)~If the action principle is constructed properly, the entropy of a black hole increases when the value of the gravitational constant is changed through the absorption of a G-wall by the hole.

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