Challenges to the standard cosmological model in recent cosmological observations

宇宙学的标准模型，Λ清洁发展机制，已被证明在描述我们宇宙的动力学方面非常有效。它假定爱因斯坦的场方程组中存在一个基本常数Λ，它表现为一个均匀分布的、时间恒定的真空能量密度，它控制着我们宇宙当前的能量收支。尽管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，比如旧的宇宙常数或符合问题。此外，在过去的几年里，我们掌握的技术设施的惊人改进使我们能够发现Λ清洁发展机制内部的一些紧张局势。它们影响例如哈勃参数H0和σ8，即8h^{−1}Mpc尺度下质量起伏的均方根。总体而言，与Λ清洁发展机制的紧张程度超过3σ：因此，这对标准宇宙学来说是一个巨大的挑战。几年后，紧张局势可能会得到解决，或者导致我们在理解上取得突破。这迫使我们考虑新的理论景观。这个项目包括探索这些景观的现象学可行性，主要是那些涉及动态真空和暗能量模型的景观，这些模型在以前的调查中已经被证明能够缓解一些上述紧张局势。分析将包括研究大质量中微子及其与动态暗能量分量的潜在简并，以及膨胀和我们宇宙当前加速阶段之间的可能联系。该项目旨在支持A.Gómez-Valent两年的博士后奖学金。他是第一个指出紧张与和谐宇宙学的综合影响的人之一，并在分析几个互补的宇宙学数据集方面拥有很强的专业知识。我已经与他发表了一篇论文，因此我相信他是成功完成这一项目的合适人选。

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.