Chalnoth said:
Not personally, no. But it's a well-known result. However, there is a caveat that I did not mention: the result only applies for a closed FRW universe:
http://www.springerlink.com/content/jg1350836415r215/
That aside, it's largely irrelevant, because it's only a heuristic tool anyway at this level of discussion...
...
... forces energy to not be conserved.
Your reference is to a 1992 paper which is available for a price of $12.50.
==exerpt==
THE ENERGY OF A CLOSED UNIVERSE IN A REFERENCE FRAME
FORMED BY A SET OF FREELY MOVING CLOCKS
N. N. Gorobei and A. S. Luk'yanenko UDC 530.12:517.988.38
The Hamiltonian of a closed universe is found in a reference frame formed by a
set of freely moving clocks. In this physically defined gauge the energy of the
universe is positively defined.
In gravitational theory in the absence of a planar asymptote the Hamiltonian of a closed
universe reduces to a linear combination of couples of the first sort and vanishes on the surface of the couples. This serves as the basis for the assertion found in the literature that
the energy of a closed universe is equal to zero [1]...
==endquote==
This is the sort of thing that bothers me when people talk about the total energy being zero. In 1992 one typically did not consider a constant dark energy density. After 1998 we think of dark energy as over 70 percent. And the amount increases as the volume increases.
As you point out there is no Energy Conservation law for the universe.
It is far from certain that the total energy of our universe is even well-defined. If the spatial volume is infinite the energy might be infinite or simply not defined.
I fail to see how it could be considered as
heuristic to study a spatial finite case with zero cosmological constant. It is too unreal. Too unrelated to the actual universe to serve as a reliable guide, I would think. But that is what these two 1992 authors seem to be doing with their closed FRW case.
Of course I can't be sure without seeing the article that they are assuming the cosmological constant is zero, but that was normal back then. It would help if you could find a paper that proves this result in the case of positive Lambda.
I remain unconvinced for the time being, but thanks for looking. It was interesting to see what you did come up with!
================================
You give a nice summary of the usual justifications for assuming one of the various inflation scenarios. You mention the horizon problem, you mention the scale-independence of the CMB power spectrum (which I think is one of the strongest supports), you didn't mention flatness though you might have. I agree that these are strong arguments, and one hears them recited over and over.
However there are other ways of addressing the horizon problem, for example. The various types of inflation are not the only answers to these puzzles. I believe I have the option to remain unconvinced at this point. It may be a matter of taste, and level of skepticism.
the general idea of inflation is essentially guaranteed to be accurate.
I don't believe that. I like the idea of inflation very much! I don't however consider it guaranteed to be accurate.
Basically, there needs to be an accelerated expansion of space in the distant past for there to be any large-scale correlations on the CMB whatsoever. If there isn't such an accelerated expansion, then the fact that the CMB is nearly uniform is a fundamental impossibility, as different regions of the CMB will not have had enough time to ever be in contact with one another.
No, that is not true. What you say is model dependent. In some models there would not have been enough time, in others there would have been enough time.
So we can be quite certain of an accelerated expansion in the distant past.
Not on that grounds. Inflation is not the only way of addressing the horizon problem---the near temperature-uniformity of the CMB. Therefore we cannot be certain inflation occurred merely because the CMB is nearly the same temperature all over.
Secondly... a nearly constant scaling rate for the fluctuations...
That is what I was referring to earlier when I mentioned the scale-independence of the CMB power spectrum! From my point of view that is pretty impressive. It is much stronger evidence for inflation than the horizon business--the temp uniformity. Temp uniformity too easy to explain by newer mainstream models.
Therefore we can be confident... We don't yet know the mechanism that caused [inflation], but we're working on that.
I'm not sure who "we" is. Are you personally working on "inflaton" mechanisms? Or any other exotic physics that might be responsible for the fine-tuned behavior, the graceful exit, the decay, the re-heating...? I haven't seen much research about possible inflation mechanisms lately. If you know of anything recent, say in the past 2 or 3 years, please let me know---hopefully available at arxiv online.