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?
The cosmological constant, denoted by the Greek letter Λ (lambda), is a term in Einstein's theory of general relativity that represents the energy density of empty space. It is often used to explain the observed accelerated expansion of the universe. In terms of structure formation, the cosmological constant plays a role in determining the overall geometry and expansion rate of the universe, which can affect the formation and evolution of galaxies and other large-scale structures.
The cosmological constant affects structure formation in two main ways. First, it influences the overall expansion rate of the universe, which in turn affects the growth of structures. A higher cosmological constant leads to a faster expansion rate, which can suppress the growth of structures. Second, the cosmological constant also affects the curvature of the universe, which can influence the distribution and clustering of matter. A positive cosmological constant leads to a flat universe, while a negative cosmological constant can result in a negatively curved universe.
The cosmological constant is often associated with dark energy, which is the term used to describe the mysterious force driving the accelerated expansion of the universe. In fact, the cosmological constant is one possible explanation for dark energy, as it represents a constant energy density that could be causing the expansion. However, there are other theories and models that attempt to explain dark energy, and the exact nature of this phenomenon is still not fully understood.
According to the standard model of cosmology, the value of the cosmological constant is considered to be a fundamental constant that does not change over time. However, there are some theories and models that suggest the value of the cosmological constant may vary over time or in different regions of the universe. This is still an area of active research and debate among scientists.
The value of the cosmological constant has a significant impact on the ultimate fate of the universe. If the value is positive, it will continue to drive the accelerated expansion of the universe, eventually leading to a "heat death" scenario where all matter and energy are evenly dispersed and the universe reaches a state of maximum entropy. If the value is negative, the expansion of the universe may eventually slow down and reverse, leading to a "big crunch" where the universe collapses in on itself. The exact fate of the universe depends on the value of the cosmological constant and other factors such as the amount of dark matter and dark energy present.