I Cosmological constant and structure formation

[Ranku]

TL;DR Summary

Hoe much is structure formation in the universe affected by the presence of cosmological constant?

How much impact does the presence of the cosmological constant have on the formation of structures in the universe? On a larger scale, is there less structure formation because of the presence of the cosmological constant?

 

[kimbyd]

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).

 

[lucas_]

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).

What experiments (if any) can test the presence of the cosmological constant?

 

[kimbyd]

What experiments (if any) can test the presence of the cosmological constant?

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.

The ISW effect has been observed to a reasonably-high degree of accuracy, as the predicted correlation does indeed exist.