arXiv 2102.084382021-02-16gr-qcastro-ph.CO

加速膨胀作为引力的表现：当暗能量属于左边时

Accelerated expansion as manifestation of gravity: when Dark Energy belongs to the left

Leonardo Giani

备注：: PhD thesis, comments are welcome

摘要：

为了解释宇宙晚期的加速膨胀，我们必须求助于某种形式的暗能量。在宇宙学的标准模型中，后者被解释为宇宙学常数$Λ$。然而，由于一些原因，宇宙学常数并不完全令人满意。在这篇论文中，我们研究了几何性质的暗能量模型，因此也是引力理论的一种表现形式。在论文的第一部分，我们将回顾$Λ$ CDM模型，并给出了一个简短的分类景观的替代暗能量候选人的基础上洛夫洛克定理。论文的第二部分是介绍我们在暗能量方面的主要结果。首先，我们将报告我们关于涉及微分算子$\Box^{-1}R$的引力非定域修正的研究，重点是一个特定的模型，以及在宇宙演化的后期，这个和类似的理论所共有的共同行为。然后，我们介绍了一种新的类修改的引力理论的基础上的反曲率张量$A^{μν}$（逆的Ricci张量），并评估其作为暗能量的来源的能力。最后，我们将讨论我们在强引力透镜竞赛中预言的一类漂移效应，它既可以用来研究宇宙的有效状态方程，又可以用来约束对等效原理的违反。

英文摘要：

In order to explain the Late-times accelerated expansion of the Universe we must appeal to some form of Dark Energy. In the standard model of cosmology, the latter is interpreted as a Cosmological Constant $Λ$. However, for a number of reasons, a Cosmological Constant is not completely satisfactory. In this thesis we study Dark Energy models of geometrical nature, and thus a manifestation of the underlying gravitational theory. In the first part of the thesis we will review the $Λ$CDM model and give a brief classification of the landscape of alternative Dark Energy candidates based on the Lovelock theorem. The second part of the thesis is instead devoted to the presentation of our main results on the topic of Dark Energy. To begin with, we will report our studies about nonlocal modifications of gravity involving the differential operator $\Box^{-1}R$, with emphasis on a specific model and on the common behavior shared by this and similar theories in the late stages of the evolution of the Universe. Then we introduce a novel class of modified gravity theories based on the anticurvature tensor $A^{μν}$ (the inverse of the Ricci tensor), and assess their capability as source of Dark Energy. Finally, we will discuss a type of drift effects which we predicted in the contest of Strong Gravitational Lensing, which could be employed both to study the effective equation of state of the Universe and to constrain violations of the Equivalence Principle.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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英文摘要：

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