标题： 广义相对论时间不对称扩展中的宇宙学 显示英文标题

标题： Cosmology in time asymmetric extensions of general relativity

摘要： 我们研究了由时间不对称广义相对论扩展所支配的宇宙的宇宙学行为，这是一种基于在哈密顿框架中添加新的时间不对称项的新修改引力理论，这种方式保证了约束代数和局域物理保持不变。 然而，在宇宙学尺度上，这些新项可能产生显著影响，能够改变早期和晚期的宇宙演化，并且涉及的修正函数的选择自由使得该场景能够产生大量宇宙学行为。 对于基本的修正假设，我们进行了详细的动态分析，提取出稳定的晚期解。 除此之外，我们发现宇宙可以形成暗能量主导且加速膨胀的解，即使没有显式的宇宙常数，其中暗能量可以表现为类似 quintessence（ quintessence 类似）、phantom（幽灵类）或者有效宇宙常数的行为。 此外，它也可能导致物质主导、大撕裂或者经历从物质主导到暗能量主导的序列。 另外，在闭合曲率的情况下，宇宙可能会经历宇宙反弹或转变，甚至表现出循环行为。 最后，这些场景可以轻松满足观测和现象学要求。 因此，时间不对称宇宙学可以成为描述宇宙的良好候选理论。 显示英文摘要

摘要： We investigate the cosmological behavior in a universe governed by time asymmetric extensions of general relativity, which is a novel modified gravity based on the addition of new, time-asymmetric, terms on the Hamiltonian framework, in a way that the algebra of constraints and local physics remain unchanged. Nevertheless, at cosmological scales these new terms can have significant effects that can alter the universe evolution, both at early and late times, and the freedom in the choice of the involved modification function makes the scenario able to produce a huge class of cosmological behaviors. For basic ansatzes of modification, we perform a detailed dynamical analysis, extracting the stable late-time solutions. Amongst others, we find that the universe can result in dark-energy dominated, accelerating solutions, even in the absence of an explicit cosmological constant, in which the dark energy can be quintessence-like, phantom-like, or behave as an effective cosmological constant. Moreover, it can result to matter-domination, or to a Big Rip, or experience the sequence from matter to dark energy domination. Additionally, in the case of closed curvature, the universe may experience a cosmological bounce or turnaround, or even cyclic behavior. Finally, these scenarios can easily satisfy the observational and phenomenological requirements. Hence, time asymmetric cosmology can be a good candidate for the description of the universe.