fixing ideas on dark matter and other cosmos stuff

These question and answers are from between Dr. Cheng and myself. Of
course, I'm asking questions and he's answering after the ***. I had
the complete wrong idea about dark matter....oops.

First, if dark matter is attributed to the expansion of the universe
and dark energy is attributed with an accelerating universe via the
cosmological constant, then how are they not directly related?
***Dark matter, just like ordinary matter, is subject to gravitational
attraction, while dark energy, to gravitational REPULSION. In our
universe there are (4%) ordinary matter/energy (called baryonic matter),
(21%) dark matter and (75%) dark energy. So dark matter and dark energy
are NOT, under our present understanding, "directly related".

Second, what are the chances that the expansion is not due to vacuum
energy? Kari said that some have tried pinning expansion to vacuum
energy, but that the vacuum energy is orders of magnitude less than
what is needed to achieve what we observe. However, would this vacuum
energy need to be handled as nonuniform if one considers that space is
warped? Whoever looked into this, how did they handle consideration
of vacuum energy? Does it even change according to the warped-ness of
space? (pardon the layered questions)
*** Cosmological constant is the name of the math term in Einstein's
equation that has the effect of being gravitational repulsive. Its most
probable PHYSICAL interpretation: "it's the energy of the vacuum". But a
straightforward calculation shows that the quantum mechanical vacuum
energy is 120 orders of magnitude too large compared to the observed
amount of dark energy (NOT too small). If it is the cosmological
constant, the warped-ness of spacetime will not bring any nonuniformity
in dark energy.

Third, I read somewhere that there are drag effects of objects
orbiting in space. Could a more fluid-like consideration of space
give rise to the expanding universe (high/low pressure systems
depending on empty/filled space or rotating vortices)?
*** Yes a rotating gravitational source can drag the spacetime around
it. But all this is consistently accounted for in the context of general
relativistic description of the expanding universe.

Lastly, is dark matter thought to exist as a constant amount; if not,
where might it come from?
*** Dark matter is definitely not uniform. In fact the present
understanding of the observed cosmological structure (galaxies, clusters
of galaxies, voids...) is built on the idea that structure formation
started among the dark matter first (from gravitational clumping), then
the baryonic matter falls into the grav. Potential wells formed by dark
matter. The favored idea of the origin is that they are the cosmological
thermal relics (just like the cosmological microwave background
radiation).

slacker

So, I've been thinking a lot lately about various things.
1. How exactly the universe expands.
2. How gravitation works.
3. 4-dimensional cross-product.
4. How to experimentally make sense of critical slowing down.
5. Ion channel desensitization vs. sensory adaptation.
6. Developing apps.
7. Wondering why I don't follow through with any of these ideas...or
at least why I take so long in addressing them.

I'll go through each topic, but perhaps I won't do it all in this
post...that could make for a very long post.

1. I think the current explanation among many astronomers and
cosmologists is that the universe expands because of dark energy and
matter. Dark matter is like gravity, but it works in reverse. What I
don't understand is where this stuff comes from. Can it's effects be
attributed to something else? Take this site's explanation, for
example: http://www.physlink.com/education/askexperts/ae404.cfm
Although, "where" the stuff is has been mapped according to
measurements of a galactic supercluster by Hubble:
http://hubblesite.org/newscenter/archive/releases/2007/01/image/a/
I don't think it yet answers my questions though. I certainly don't
think it proves anything...whether dark matter is real or not. It
seems to strongly suggest that it's out there though. It may still be
just a coincidence of currently known forces; although explaining the
observed effects with what we have in our toolbox doesn't seem to work
well enough. Perhaps that just means we need to expand what we know
instead of creating something new. I don't think it is impossible for
us to create a new tool to explain the cosmos, but in the end realize
it is just a special case of tools we already have.
My loosely assembled, guesswork hypothesis is that if the amount of
dark energy in our universe is not fixed, then it must come from
somewhere. That somewhere might be a higher dimension, but then
anything existing in that higher dimension must be losing that energy.
This would imply a conservation of energy among all dimensions. This
would allow the dark stuff to infiltrate our known dimensions and
possibly give rise to the cosmological constant (but this would only
be to accelerate the universe...whatever that really means). If the
amount of dark energy is actually fixed, then perhaps it is diffusing
as suggested by the recent Hubble map and subsequent measurements may
indicate. BUT if dark energy is really an occurrence of stuff we
already can measure and know about, then one of two things may happen
(although I'm not sure if they'd be mutually exclusive). Either it
comes about from energy associated with vacuum or it comes about
because of gravitational effects on space itself...like fluid effects.

I'll have to finish talking about this later. Have to go to UMSL.

Edit to finish:

I talked with an astronomer student in the lab next to mine, and I asked her about dark matter and energy. I need to be careful with the two terms since they are not linked like typical matter is with energy we deal with everyday. "Light" matter can be related to energy by it's mass with everyone's favorite E=mc^2, where E is the energy of a mass of matter, m, and c is the speed of light in vacuum. Dark matter and energy don't have this sort of relation...direct correlation...as far as anyone knows. Dark matter does give rise to the expansion of the universe as I said above, but dark energy is strictly associated with the cosmological constant that possibly accelerates the universe.................I have trouble with this still. They seem to describe the same action, but apparently there's a big difference that I'm not getting.

I emailed some questions about this stuff to a professor in my department...supposedly he'd know best when it comes to this stuff. Dr. Ta-Pei Cheng, I'm counting on you!