| ρο/a4 | ρο/a3 | k | Λ | Βig Bang | Big Crunch | Polynomial Expansion | Exponential Expansion |
| x | 0 | ||||||
| x | 0 | >0 | |||||
| x | +1 | ||||||
| x | +1 | ||||||
| x | 0 | <0 | |||||
| x | -1 | ||||||
| x | -1 | >0 | |||||
| x | 0 | ||||||
| x | +1 | >0 | |||||
| x | 0 | <0 |
QuarkDecay said:the Universe of the first row has a ρο/a4
I'm sure it's talking about a radiation-dominated universe, where the density scales as ##1/a^4##.PeterDonis said:What does "has a ##\rho_0 / a^4##" mean?
It's asking what the eventual fate of the universe in question is. Will it expand forever, or will it recollapse? If it expands forever, what will the function ##a(t)## look like? Will it be a polynomial like ##a(t) = t^b##, or will it be exponential like ##a(t) = e^{bt}## (where ##b## is some constant in either case)?QuarkDecay said:The left part of the columns describes the characteristics of the Universe Model, and depending on these, it's supposed to be filled with 1 or 2 "x" on the right part.
For example, the Universe of the first row has a ρο/a4 with flat curvature (k=0). ρο/a3 and Λ are not filled in because they don't exist for this specific model.
I know that for the ρο/a4 (which is the ρr) was bigger during the Big Bang phase. So I suppose that there must be an "x" on the Big Bang column. But I'm not sure about the k=0 after that, and what are the two expansions supposed to mean? Expotential expansion= inflation? Polynomial expansion = the "normal" expansion rate we currently have?
kimbyd said:I'm sure it's talking about a radiation-dominated universe
An FRW cosmological model is a mathematical description of the evolution of the universe based on the Friedmann-Lemaître-Robertson-Walker (FRW) metric. It is a type of cosmological model that is based on the assumption that the universe is homogeneous and isotropic on large scales.
The key differences between different FRW cosmological models lie in the values of the parameters used to describe the universe, such as the matter density, dark energy density, and curvature. These parameters can vary in different models, resulting in different predictions for the evolution of the universe.
FRW cosmological models explain the expansion of the universe through the use of the Friedmann equations, which describe how the scale factor of the universe changes with time. The expansion is driven by the matter and energy content of the universe, as well as the curvature of space.
Yes, FRW cosmological models can be tested and verified through observations of the universe. For example, the cosmic microwave background radiation, the large-scale structure of the universe, and the redshift of distant galaxies can all provide evidence for or against different FRW cosmological models.
Yes, there are some limitations to FRW cosmological models. For instance, they do not take into account the effects of dark matter and dark energy, which are believed to make up a significant portion of the universe. Additionally, they do not explain the initial conditions of the universe or the existence of structures such as galaxies and clusters of galaxies.