Physics of Galaxy Cluster Outskirts
High-resolution spectral imaging observations of the SZ effects promise to provide a vastly broaden view of structure and evolution of galaxy clusters, by enabling unique measurements of thermodynamic and kinematic properties of the cluster gas via thermal and kinematic SZ effects. One of the new frontiers includes the exploration of the extremely low-density regions in the outskirts of galaxy clusters and its connection to the Cosmic Web, where X-ray observations would require exceptionally long integration times. Modern hydrodynamical simulations make robust testable predictions about their properties. However, recent X-ray and microwave observations revealed tensions with the theoretical predictions. Resolving these puzzles will likely require improved understanding of the cluster gas physics. In this talk, I will discuss recent advances in our understanding of the physics of galaxy cluster outskirts, with highlights on emerging problems and challenges and implications for cluster cosmology in the era of multi-wavelength cluster surveys.