This post is just a rambling stream of consciousness and should provoke thought but not be considered a reliable source of information.

The energy density of dark energy is about four times the energy density of the cosmic microwave background radiation.

In a quantum gravity theory, what would be the average energy density of gravitons in the universe? How would that compare to dark energy?

Numerically, how would Alexander Deur's conception of dark energy as at least partially due to diversion of gravitons excessively towards places where dark matter effects are observed work out?

Does a calculation of the Schwarzschild radius of the universe include dark energy?

The Schwarzschild radius of the universe is slightly smaller than the size of the universe (13.7 billion light years v. 13.8 billion light years). Does that mean that we are inside a black hole? The 0.7% discrepancy is not statistically significant, could they be an exact match. What would that imply?

I considered the notion that dark energy is a soup of energy outside the universe that is gobbled up as it expands. But this doesn't address the pull of gravity from outside the universe that we would feel if that was the case. On the other hand, if the soup of energy outside the universe were spherically symmetric, would we observe it at all?

If gravity is the curvature of space-time, why is a non-vacuum universe almost perfectly flat?

The only baryon number violating and lepton violating interaction in the Standard Model is the sphaleron. But, the energy scale where it should be possible for sphaleron events to take place is ca. 10 TeV. This is a temperature 100,000 times greater than the 100 MeV = 2 trillion degrees kelvin temperature at which quark-gluon plasma would occur (i.e. 2*10^20 K). It corresponds to a conventional cosmology time after the Big Bang time of 10^-14 seconds (considerably after "inflation" but prior to everything else in the standard cosmology). This isn't long enough to reach modern matter-antimatter asymmetry levels in baryons and charged leptons from pure energy and maybe didn't happen at all. Rather than devising ways to reach a pure energy starting point, we have to assume that the starting part was not pure energy.

Also, renormalization of all of the Standard Model constants cannot be ignored at this energy scale, and more importantly, the impact of quantum gravity on the renormalization of the Standard Model constants probably cannot be safely ignored at that energy scale. What direction does including a graviton in the model have on the other Standard Model constant renormalizations? How material is the tweak? Could it lead to gauge unification within the Standard Model?

If the timeline of the Big Bang prior to 10^-12 seconds (where the "quark era" of quark-gluon plasma starts), is unreliable, then maybe this never happens.

Whose frame of reference is being used in the standard cosmology chronology? Everything is moving at relativistic speeds at this point so the time frame of the moving particles is very different from a hypothetical outside observer.

We know that the ratio of particles in the universe is 15 up quarks per 9 down quarks per 1 electron per 10^9 photons. But what about other particles?

We know that there are about 10^80 baryons in the universe, and we know that about 49% of the mass of a proton or neutron comes from gluons (49% comes from the kinetic energy of the quarks and 2% comes from the Higgs field derived mass of the quarks). There are also quite precise gluon density measurements, but I don't know how to convert that to how many gluons at present at any given time in an average proton or neutron. But, with that you could get the number of gluons on the universe at any given time.

We think that there are a much higher number of neutrinos in the universe, but don't know the neutrino-antineutrino ratio, and have only weak support for the lamdaCDM assumption that the number of electron neutrinos is approximately equal to the number of muon neutrinos is approximately equal to the number of tau neutrinos as a result of neutrino oscillation.

We know that in addition to these components that there are a relatively negligible number of top quarks, bottom quarks, charm quarks, strange quarks, W+ bosons, W- bosons, and Z bosons at any given time. This is because all of these particles have very short mean lifetimes and only emerge "on shell" in high energy environments which are relatively rare. But, nonetheless, this isn't zero. My intuition is that the frequency of each depends upon the amount of ordinary matter that it is at the requisite temperature at any given time adjusted by the creation rate and decay rate of these particles.

We have extremely precise figures on all of these factors except the temperature mix of the matter in the universe and actually can do pretty well even with the temperature mix because we have a pretty good census of stars (which are pretty much the only places in the universe hot enough) and we know quite a bit about the temperature of stars.

Given that QGP is almost entirely absent in Nature because the universe hasn't been at 100 MeV temperatures for about 13.8 billion years, it seems likely that while there may be some places hot enough for muon and strange quark formation (and we do see muons in nature), that almost no place is hot enough for top quarks, bottom quarks, charm quarks and tau leptons to be created and that W and Z bosons and Higgs bosons that are on shell should likewise be very rare.

In quantum gravity, we also don't know how many gravitons there are in the universe, on average. This could be appreciable and at least on the same order of magnitude as the CMB.

In quantum gravity, gravitational energy is localized and is a source of gravitons.

I think that mass-energy is conserved in quantum gravity and the cheat that denies this is general relativity is a serious chink in the armor of general relativity as a theory.

I think that it is plausible that the Big Bang never had a density greater than the black hole-neutron star threshold density (about 10^20 g/m^3), and that there are no primordial black holes, hence that there is a maximum density in the universe which may be, or may be a consequence of, an ultraviolet fixed point. What is the mass of the universe?

10^55 grams. What is its volume of the mass of the universe at this density? 10^35 m^3. What is the radius of this volume if it is spherical? About 3*10^12 meters. This is 3*10^9 km and is 0.000317107023 light years (about 167 light minutes) and is 20.0537614 Astronomical Units. This is about 5% larger than the size of a sphere centered in the Sun and extending to the orbit of the planet Uranus. This would be quite different from standard theory however and might screw up Big Bang nucleosynthesis, although it is hard to be clear how. If you cut it to 4% of the mass (removing dark matter and dark energy), this cuts the radius by roughly one-third to about 6.5 AU and about 56 light minutes (about 15% farther than the orbit of Jupiter).

I remain deeply skeptical of cosmological inflation as a theory.

The temperature of the universe is proportionate to 1/t^3 where t is time. The estimated age of the universe is 13.8 +/0.21 billion years. The estimated temperature at ca. 10^-12 to 10^-6 seconds is 100 MeV.

Suppose that there is no dark energy or dark matter, then the Schwartzchild radius is 548 million light years because only about 4% of the mass-energy of the universe in lambda CDM is ordinary matter. So, this would be a black hole from the inception. Are we inside a black hole?

Do black holes have an internal shell structure of density with black hole's interior mass always containing sufficient mass to form a black hole at every radius?

Big Bang nucleosynthesis, which is more precisely confirmed than ever, is a tight constraint on alternatives to the Standard Model of Cosmology and other BSM theories.

The precision with which we know the up and down quarks recently significantly improved and strongly rules out the otherwise attractive zero mass up quark.

We know that the Schwarzschild radius establishes a minimum density to form a black hole. Is it possible that there is another upper boundary threshold of some sort (density, mass, who knows) at which a black hole explodes or leaks? How could that be tested?

How different would the universe be if it had two generations of fermions instead of three? I don't think it would be very different. What kind of mathematical structure or mechanism would require three and exactly three generations of fermions?