Revisiting the Israel junction conditions in Einstein-Cartan gravity

Revisiting wormhole energy conditions in Riemann-Cartan spacetimes and under Weyl transformations

We show that the violation of the null energy condition by matter, required by traversable wormholes, can be removed in spacetimes with torsion. In addition, we show that this violation can also be removed in the conformal frame obtained by a Weyl transformation. This comes about because both conformally transformed wormholes and wormholes in spacetimes with torsion become sustained thanks to a combination of 'normal' matter, that satisfies the null energy condition, and an induced 'geometric' energy-momentum tensor that is able to greatly violate the null energy condition.

重新审视存在挠率时3-brane上的有效爱因斯坦方程

Revisiting effective Einstein equations on a 3-brane in the presence of torsion

本文重新审视了5维Riemann-Cartan bulk时空中3-brane上的有效爱因斯坦方程，提出了一般形式的连接条件，并据此推导出Z2对称brane上的标准形式方程，突出了与已有研究的差异。

Braneworld Remarks in Riemann-Cartan Manifolds

We analyze the projected effective Einstein equation in a 4-dimensional arbitrary manifold embedded in a 5-dimensional Riemann-Cartan manifold. The Israel-Darmois matching conditions are investigated, in the context where the torsion discontinuity is orthogonal to the brane. Unexpectedly, the presence of torsion terms in the connection does not modify such conditions whatsoever, despite of the modification in the extrinsic curvature and in the connection. Then, by imposing the Z_2-symmetry, the Einstein equation obtained via Gauss-Codazzi formalism is extended, in order to now encompass the to…

Revisiting the Darmois and Lichnerowicz junction conditions

What have become known as the "Darmois" and "Lichnerowicz" junction conditions are often stated to be equivalent, "essentially" equivalent, in a "sense" equivalent, and so on. One even sees not infrequent reference to the "Darmois-Lichnerowicz" conditions. Whereas the equivalence of these conditions is manifest in Gaussian-normal coordinates, a fact that has been known for close to a century, this equivalence does not extend to a loose definition of "admissible" coordinates (coordinates in which the metric and its first order derivatives are continuous). We show this here by way of a simple, b…

扭转局域旋转对称II类时空中连接面的协变分布方法

A Covariant Distributional Approach for Junctions in Torsional Locally Rotationally Symmetric Class II Spacetimes

该研究提出一种坐标无关的协变分布框架，用于研究扭转局域旋转对称II类时空中的连接面，推导了拼接流形可微性条件，规避了依赖坐标的Israel-Darmois框架的缺陷。

Possible Generalizations within Braneworld Scenarios: Torsion fields

In this Chapter we introduce the aspects in which torsion can influence the formalism of braneworld scenarios in general, and also how it is possible to measure such kind of effects, namely, for instance, the blackstring transverse area corrections and variation of quasar luminosity due to those corrections. We analyze the projected effective Einstein equation in a 4-dimensional arbitrary manifold embedded in a 5-dimensional Riemann-Cartan manifold. The Israel-Darmois matching conditions are investigated, in the context where the torsion discontinuity is orthogonal to the brane. Unexpectedly, …