标题： 半对称度规引力：简要概述 显示英文标题

标题： Semi-Symmetric Metric Gravity: A Brief Overview

摘要： 我们综述了半对称度规引力（SSMG）理论，这是一种基于Friedmann和Schouten于1924年提出的连接的标准广义相对论的几何扩展。 半对称连接是一种广义的Levi-Civita连接，允许存在一种简单的扭转形式，该形式用扭转矢量来描述。 爱因斯坦场方程被假定具有与标准广义相对论相同的形式，因此将借助半对称连接构造的爱因斯坦张量与能量-动量张量相关联。 在场方程中包含扭转贡献具有引人入胜的宇宙学意义，尤其是在宇宙的晚期演化过程中。 这些效应可能在高能条件下占主导地位，因此SSMG有可能解决广义相对论和宇宙学中的未解问题，如初始奇点、暴胀或$^7$李问题（大爆炸核合成问题）。 场方程中扭转的显式存在导致能量-动量张量的非守恒，这可以在开放系统的不可逆热力学中解释为描述粒子产生过程。 我们还详细回顾了该理论的宇宙学应用，并通过与多个观测数据集的比较来约束模型参数，对几种模型进行了统计检验。 显示英文摘要

摘要： We present a review of the Semi-Symmetric Metric Gravity (SSMG) theory, representing a geometric extension of standard general relativity, based on a connection introduced by Friedmann and Schouten in 1924. The semi-symmetric connection is a connection that generalizes the Levi-Civita one, by allowing for the presence of a simple form of the torsion, described in terms of a torsion vector. The Einstein field equations are postulated to have the same form as in standard general relativity, thus relating the Einstein tensor constructed with the help of the semi-symmetric connection, with the energy-momentum tensor. The inclusion of the torsion contributions in the field equations has intriguing cosmological implications, particularly during the late-time evolution of the Universe. Presumably, these effects also dominate under high-energy conditions, and thus SSMG could potentially address unresolved issues in General Relativity and cosmology, such as the initial singularity, inflation, or the $^7$Li problem of the Big-Bang Nucleosynthesis. The explicit presence of torsion in the field equations leads to the non-conservation of the energy-momentum tensor, which can be interpreted within the irreversible thermodynamics of open systems, as describing particle creation processes. We also review in detail the cosmological applications of the theory, and investigate the statistical tests for several models, by constraining the model parameters via comparison with several observational datasets.