宇宙的替代标量场暗区：标量-张量宇宙学框架下的宇宙暴胀、精质和火劫模型
The alternative scalar field dark sector of the Universe: Cosmological inflation, quintessence and ekpyrotic model in the framework of scalar-tensor cosmology
- University of Wrocław（弗罗茨瓦夫大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
论文研究标量-张量宇宙学框架下暗区的标量场描述，涵盖暴胀有效场论、精质暗能量及火劫循环模型，并利用观测诊断和DESI数据探讨暗能量时间演化。
AI中文摘要：
本论文研究宇宙暗区的标量场描述，重点涉及标量-张量宇宙学、暴胀有效场论、精质以及火劫/循环暴胀替代模型。论文首先回顾了标量-张量引力理论，从布兰斯-迪克理论出发，扩展到一般的非最小耦合标量场。特别关注标量场的解释、乔丹与爱因斯坦共形框架之间的关系，以及共形变换在宇宙学中的作用。这为将标量场视为修正物质或额外的引力自由度提供了理论基础。第二部分从有效场论的角度讨论宇宙暴胀。分析了时间平移的自发破缺、绝热扰动的戈德斯通描述、高维算符、辐射修正和普朗克抑制项，并探讨了紫外敏感性和η问题。第三部分致力于精质作为最简单的动力学暗能量模型。讨论了‘追踪’、‘标度’、‘解冻’和‘冻结’行为，以及观测诊断，如状态发现参数、$(\omega_{\phi},\omega'_{\phi})$平面和$Om(z)$诊断。DESI DR2结果被用作考虑超越严格宇宙学常数的时间依赖有效暗能量的动机。最后一部分研究火劫和循环宇宙学。火劫阶段被分析为一种基于超刚性标量场状态方程的平滑机制。讨论了扰动、非高斯性、张量模式、反弹条件、熵产生、测地线不完备性和相位分辨场空间距离界限。
英文摘要：
This dissertation investigates scalar field descriptions of the dark sector (of the Universe), with emphasis on scalar-tensor cosmology, inflationary effective field theory, quintessence, and ekpyrotic/cyclic alternatives to inflation. The thesis first reviews scalar-tensor theories of gravity, starting from Brans-Dicke theory and extending to general non-minimally coupled scalar fields. Particular attention is paid to the interpretation of the scalar field, the relation between the Jordan and Einstein conformal frames, and the role of conformal transformations in cosmology. This provides the theoretical basis for treating scalar fields either as modified matter or as additional gravitational degrees of freedom. The second part discusses cosmological inflation from the viewpoint of effective field theory. The spontaneous breaking of time translations, the Goldstone description of adiabatic perturbations, higher-dimensional operators, radiative corrections and Planck-suppressed terms are analyzed in the context of ultraviolet sensitivity and the eta problem. The third part is devoted to quintessence as the simplest dynamical dark energy model. 'Tracking', 'scaling', 'thawing' and 'freezing' behaviors are discussed, together with observational diagnostics such as the statefinder parameters, the $(ω_ϕ,ω'_ϕ)$ plane and the $Om(z)$ diagnostic. The DESI DR2 results are used as motivation for considering time-dependent effective dark energy beyond a strict cosmological constant. The final part studies ekpyrotic and cyclic cosmologies. The ekpyrotic phase is analyzed as a smoothing mechanism based on an ultra-stiff scalar field equation of state. Perturbations, non-Gaussianity, tensor modes, bounce conditions, entropy production, geodesic incompleteness and phase-resolved field-space distance bounds are discussed.
