两个视界的故事

A tale of two theories of gravity in asymptotically Anti-de Sitter spacetime

We consider two BF formulations of the theory of gravity with a negative cosmological constant, of Plebanski and of MacDowell-Mansouri. Both give the standard Einstein equations in the bulk but differ in expressions of edge charges. We compute the asymptotic charges explicitly in both theories for AdS-Schwarzschild, AdS-Kerr, and AdS-Taub--NUT solutions. We find that while in the case of the Plebanski theory the charges are divergent, they are finite for MacDowell-Mansouri theory. Furthermore, we show that in the case of the arbitrary asymptotically AdS spacetimes, MacDowell--Mansouri asymptot…

两个中心的故事

The tale of two centres

我们研究运动的领域中的两个固定的中心所描述的家庭的爱因斯坦-爱因斯坦-麦克斯韦理论。随着激子耦合的变化，观察到规则和混沌运动之间的过渡。

A tale of two dyons

We present a one-parameter family of stationary, asymptotically flat solutions of the Einstein-Maxwell equations with only a mild singularity, which are endowed with mass, angular momentum, a dipole magnetic moment and a quadrupole electric moment. We briefly analyze the structure of this solution, which we interpret as a system of two extreme co-rotating black holes with equal masses and electric charges, and opposite magnetic and gravimagnetic charges, held apart by an electrically charged, magnetized string which also acts as a Dirac-Misner string.

两个鞍点的故事

A Tale of Two Saddles

本文在JT引力与物质耦合的生成泛函计算中发现了一个新的壳上副本虫洞鞍点，证明其作用量低于不连通鞍点，并通过引入一步副本对称性破缺的LM式构造刻画其贡献，同时表明量子修正可能进一步稳定该鞍点。

Generalized Uncertainty Principle, Black Holes, and White Dwarfs: A Tale of Two Infinities

It is often argued that quantum gravitational correction to the Heisenberg's uncertainty principle leads to, among other things, a black hole remnant with finite temperature. However, such a generalized uncertainty principle also seemingly removes the Chandrasekhar limit, i.e., it permits white dwarfs to be arbitrarily large, which is at odds with astrophysical observations. We show that this problem can be resolved if the parameter in the generalized uncertainty principle is negative. We also discuss the Planck scale physics of such a model.

A Tale of Two Actions: A Variational Principle for Two-Dimensional Causal Sets

In this paper we will explore two different proposals for the action for causal sets: the Benincasa-Dowker action and a modified version of the chain action. We propose a variational principle for two-dimensional causal sets and use it for both actions to determine which causal sets at least on average satisfy a discrete version of the Einstein equation. Specifically, we test this method on causal sets embedded in 2d Minkowski, de Sitter, and anti-de Sitter spacetimes and compare these results to the most prominent nonmanifoldlike causal sets, Kleitman-Rothschild causal sets.

全息热关联函数：关于富克斯型ODE与积分围道的故事

Holographic thermal correlators: A tale of Fuchsian ODEs and integration contours

本文利用grSK几何分析全息场论中守恒流的实时热关联函数，通过研究AdS黑洞背景下的富克斯型线性化波动方程，论证了该几何在处理表观奇点时的必要性，并指出黑洞scrambling物理与能量传输的联系适用范围有限。

Loop quantum cosmology of k=1 FRW: A tale of two bounces

We consider the k=1 Friedman-Robertson-Walker (FRW) model within loop quantum cosmology, paying special attention to the existence of an ambiguity in the quantization process. In spatially non-flat anisotropic models such as Bianchi II and IX, the standard method of defining the curvature through closed holonomies is not admissible. Instead, one has to implement the quantum constraints by approximating the connection via open holonomies. In the case of flat k=0 FRW and Bianchi I models, these two quantization methods coincide, but in the case of the closed $k$=1 FRW model they might yield diff…

两个变化常数的宇宙学故事

A Cosmological Tale of Two Varying Constants

我们制定了一个简单的广义相对论的扩展，其中包括时空变化的牛顿引力“常数”，$G$，和精细结构“常数”，$α$，这概括了布朗-迪克理论和我们的理论变化$α.$我们确定弗里德曼宇宙在这个理论中的行为。在辐射和尘埃占主导地位的时代，$αG$接近一个恒定值，$α$的变化率等于$G$的变化率的大小。宇宙的膨胀动力学由PDMATHAMM的变化所支配，但PDMATHAMM的变化对$α.$的时间变化有显著的影响。PDMATHAMM的时间变化被空间曲率或精粹场的膨胀所支配，就像没有$G$变化的情况一样。

Bianchi宇宙学：两种倾斜流体的故事

Bianchi Cosmologies: A Tale of Two Tilted fluids

我们用动力系统方法研究了含有两个倾斜$γ$ -律完美流体的Bianchi VI型$_0$宇宙学模型.完整的状态空间是11维的，但单调函数的存在大大简化了分析。我们限制注意一个特定的，物理上有趣的，不变的子空间，并找到所有的平衡点，是未来稳定的完整的11维状态空间，因此，这些是本地吸引子，并作为后期的渐近线倾斜VI型$_0$模型包含两个倾斜的流体的开放集。我们发现，如果其中一种流体的状态方程参数$γ<6/5$，最僵硬的流体将在后期的动态无关紧要。对于值$γ=6/5$，存在2维分叉集，并且如果两种流体的刚度都大于$γ=6/5$，则两种流体将渐近地具有极端倾斜。我们调查的情况下，其中一个流体是非常倾斜的细节。我们还考虑了一个刚性流体（$γ=2$）接近初始奇异性的情况下，并发现在一般的Bianchi模型与$γ<2$发生的混沌行为被抑制。