This is useful information, thanks!
To be sure: after electroweak symmetry breaking, particle mass is (or is considered?) constant in the evolving universe. Correct?
It seems it has to be like that, for baryon density is (considered?) proportional to a^-3.
My understanding is that particle...
Full spacetime symmetry by the perfect cosmological principle implies a universe in stationary state, where all global features, including physical units, are intrinsically constant. The standard cosmological principle does not provide time translation symmetry, so does not guarantee general...
Yes, that’s what I gathered, the physical frame simply being the (observational) frame where observables are measured using rods and clocks. This seems evident. Though, a complication arises in remote observation in standard cosmology. Given the cosmological principle, in constant time slices...
Well the Einstein frame is. But indeed, this forum is on GR, so you’re right. Please forget the references, since not important to the question. I still like to know what physical frame means in the context of GR. The statement that the Einstein frame is physical, or not, supposes a definition...
The term “physical frame” is likely best known of the (long) debat on whether the Einstein or Jordan frame is the physical frame. So I gave two references in that context. But so far I have not found a definition of what exactly makes a frame a “physical frame”. Therefore my question.
So far I...
I do not have such a reference. But https://arxiv.org/abs/1407.6874 is about equivalence of the Jordan and Einstein frames in FLRW context, and takes the position that since dimensionfull quantities depend on (potentially varying) physical units, only dimensionless quantities are “really...
My question is about the precise definition of what is being referred to as “physical frame”, in particular in the context of cosmology. Is it simply the observational frame in which physical units are held constant? Is the FLRW frame physical? A good reference would also be helpful. Thanks for...
The point I try to raise is not whether Λ or K are part of the fluid equation. These densities represent energy, indeed of geometrical origin rather than being a matter fluid, although they can be represented as fluid components with EoS. But, as I already mentioned, I understand these energy...
De Sitter spacetime can be open, flat or closed, i.e., of negative, zero or positive Gaussian curvature K, and Friedmann equation
H2 = HΛ2 - Ka-2 ∝ρΛ + ρk
In general ρ ∝ a-3(1+wρ)
Curvature energy is represented by the density ρk ∝a-2, therefore wk = -1/3
Ok, maybe the question is wrong and I am just misunderstanding this. Retry:
There is no matter energy in de Sitter (empty), but still there is energy (cosmological constant w=-1 and curvature energy w=-1/3). Correct?
Then, as I understood, this energy is gravitational energy, therefore is...
Hi,
Gravitational energy in de Sitter has equation of state w=-1 (cosmological constant) and w=-1/3 (curvature energy in open or closed de Sitter). Is this just gravitational radiation, and how does this accord with the equation of state of photon radiation w=1/3?
Does this mean that densities...
Perhaps the original question was confusing. It did not mention spatial slices, though. The question is purely about which statement is right: A) observation shows that the Universe is homogeneous on the large scale, or B) Observation shows inhomogeneity due to expansion. The first statement I...
I understand the difference between light cone and constant time slices. The latter are considered homogeneous by the cosmological principle. Looks fair. The constant time slices are spacelike however, so one can not observe anything within the slice. One can observe on the light cone, which I...