Timeline for Dark energy and neutrinos
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 20, 2022 at 19:16 | comment | added | Andrew | @qatch These notes might help: astro.princeton.edu/~gk/A403/state.pdf | |
| Dec 20, 2022 at 18:13 | comment | added | qatch | I am more familiar with the classical EOS, so may be that is a misleading analogy: for an ideal gas p = nRT/V holds. So if you double the volume you get half the pressure – in an isolated system. You can double the volume by doubling n as well. So having a source of particles, such as fusion for neutrinos, could -in theory- contribute to a change in volume. | |
| Dec 18, 2022 at 12:31 | comment | added | Andrew | @qatch I'm not sure what you mean. You can calculate the equation of state for a relativistic gas of particles and you find $p=\frac{1}{3}\rho$. | |
| Dec 18, 2022 at 10:44 | comment | added | qatch | w will give me something to think about. However, the equation of state does not take into account possible source terms, does it? Could it change the game? | |
| Dec 18, 2022 at 10:33 | vote | accept | qatch | ||
| Dec 18, 2022 at 2:19 | comment | added | Andrew | @DaveTheWave Essentially it follows from the symmetry of FRW spacetimes (homogeneity and isotropy) that the stress energy tensor has the form $T^{i}_{\ \ j} = {\rm diag}(-\rho, p, p, p)$, so there's only really one relationship needed in the equation of state. You can also calculate the stress energy explicitly for special cases, like pressureless dust, the Maxwell stress-energy tensor for the electromagnetic field, or for the cosmological constant, and $\rho=wp$ falls out naturally in those cases. | |
| Dec 17, 2022 at 23:36 | comment | added | user353451 | Andrew said: we assume that the relationship between density ρ and pressure p is given by an equation of state of the form p=wρ .Why is this assumed? | |
| Dec 17, 2022 at 20:12 | comment | added | niels nielsen | excellent! thanks for this explanation, I had not seen it before. -NN | |
| Dec 17, 2022 at 17:24 | history | answered | Andrew | CC BY-SA 4.0 |