The discussion centers on the nature of the cosmological constant and its potential variability in relation to spacetime dynamics. Participants argue that the cosmological constant is treated as a constant due to the lack of evidence supporting its variability, making it the simplest model consistent with current data. The concept of "dark energy" is introduced as a framework for models that allow for changes over time, but these models often revert to a constant when compared with observational data. Ultimately, the consensus is that while dynamic models can be constructed, they do not provide additional predictive power based on existing evidence.
PREREQUISITESAstronomers, physicists, and cosmologists interested in the fundamental nature of the universe, particularly those exploring the implications of the cosmological constant and dark energy on cosmic evolution.
Because a constant is the simplest model, and we have no evidence that it's not constant, so we use the simplest model that's consistent with the evidence.mad mathematician said:
I wonder how difficult it would be to to write down a model where it changes with time.PeterDonis said:
We usually call it "dark energy" when it's not assumed to be perfectly constant.mad mathematician said:
It's straightforward to write down the model; indeed doing that is an exercise in some advanced GR textbooks. The usual way is to use a scalar field.mad mathematician said: