Challenges to the standard cosmological model in recent cosmological observations

宇宙学的标准模型，ΛCDM，已被证明是非常有效的描述我们的宇宙的动力学。它假定爱因斯坦场方程中存在一个基本常数Λ，它表现为一个均匀分布的、随时间恒定的真空能量密度，主导着我们宇宙当前的能量收支，虽然宇宙常数在唯象水平上工作得很好，但它也是一些重要理论难题的起源，如旧的宇宙常数或符合问题。此外，在过去的几年里，我们所掌握的技术设施的惊人改进已经允许检测到ΛCDM内部的一些紧张关系。它们会影响哈勃参数H 0和σ8，即8 h^{−1} Mpc尺度下质量涨落的均方根。累积起来，与ΛCDM的张力超过了3σ水平：这对标准宇宙学来说是一个巨大的挑战。几年后，紧张局势可能得到解决，或导致我们的理解取得突破。这迫使我们考虑新的理论景观。这个项目包括探索这种景观的唯象可行性，主要是那些涉及动力学真空和暗能量模型，这些模型已经在以前的研究中被证明能够放松一些上述紧张局势。该分析将包括对大质量中微子及其与动态暗能量成分的潜在简并性的研究，以及我们宇宙的暴胀阶段和当前加速阶段之间的可能联系。Gómez-Valent获得了两年的博士后奖学金。他是最早指出张力与和谐宇宙学的综合效应的人之一，并在分析几个互补的宇宙学数据集方面有很强的专业知识。我已经和他一起发表了一篇论文，因此我相信他是成功完成这个项目的合适人选。

The standard model of cosmology, the ΛCDM, has proven to be extremely effective in describing the dynamics of our universe. It assumes the presence of a fundamentalconstant in Einstein’s field equations, Λ , behaving as a uniformly-distributed and constant-in-time vacuum energy density, which dominates the current energy budget of our cosmos.Although the cosmological constant works quite well at the phenomenological level, it is also the origin of some important theoretical conundrums, as the old cosmological constant or the coincidence problems. Moreover, in the last years, the amazing improvement of the technological facilities at our disposal have allowed to detect some tensions within the ΛCDM. They affect e.g. the Hubble parameter H0 and σ8 , i.e. the root mean square of mass fluctuations at scales of 8 h^{−1} Mpc. Cumulatively, the tension with ΛCDM is at more than 3σ level: this represents therefore a great challenge to standard cosmology. In a few years, the tensions could be resolved or lead to a breakthrough in our understanding. This forces us to consider new theoretical landscapes.This project consists in exploring the phenomenological viability of such landscapes,mainly those involving dynamical vacuum and dark energy models which have already proven in previous investigations to be capable of loosening some of the aforesaid tensions. The analysis will include a study of massive neutrinos and their potential degeneracy with the dynamical dark energy components, together with the possible connection between the inflationary and the current speeding-up phases of our universe.This project is meant to support A. Gómez-Valent with a post-doc fellowship for two years.He has been one of the first to point out the combined effect of the tensions with the concordance cosmology and has a strong know-how in analyzing several complementary cosmological datasets. I already published a paper with him and I am therefore confident he is the right person to carry this project to successful completion.