The discussion centers on the impact of the cosmological constant on the formation of structures in the universe, exploring both theoretical implications and potential experimental tests. Participants examine how the cosmological constant influences large-scale structure formation and the Integrated Sachs-Wolfe Effect as a means of testing its presence.
Participants generally agree on the influence of the cosmological constant on structure formation and the relevance of the Integrated Sachs-Wolfe Effect, but the discussion includes multiple perspectives on the implications and interpretations of these effects.
Some assumptions regarding the nature of gravitational potentials and their decay over time are present but not fully explored. The discussion does not resolve the extent of the cosmological constant's impact on structure formation.
kimbyd said:Yes. The cosmological constant makes it harder for large gravitationally-bound structures to form. It also causes gravitational potentials for larger systems to decay over time (resulting in the Sachs-Wolfe effect).
The effect is most clearly visible using the Integrated Sachs-Wolfe Effect. With no cosmological constant, there should be no correlation between the hot/cold spots on the CMB and local structure. The ISW Effect, however, creates such a correlation because of the aforementioned decay of gravitational potentials. A photon enters a gravitational well. Then, over the time it takes the photon to traverse the well, the well has decayed a bit, meaning the photon gains more energy entering the well than it loses escaping it. The result is a net blueshift. The reverse happens when the photon travels through a large void.lucas_ said:What experiments (if any) can test the presence of the cosmological constant?