To be clear, I came up with this idea today, 02 August 2010, while visualizing certain physics concepts in a non-traditional manner. Namely, the image of space-time as a 2-dimensional fabric, with mass as a third dimensional force that bends and warps it towards the mass. I will explain my imaging and thought process step by step, and state my final idea at the end.
The 2D model has a couple of flaws. 1) Obviously, space alone is three dimensional, and time is a fourth, so we are severely compressing dimensions in the model. 2) It implies an external 'down' direction. So I created a new model in my head. I started with a 3D grid in a cube, something like a a fictional holographic projection. When I place a mass-model (a blank, dark grey sphere) in this cube, the grid lines simply bend towards the object from all directions, bending more sharply the closer they are to the object and the more massive the object. This is a slightly more accurate representation of the space-time distortion caused by mass.
Now, do to a conversation I had earlier in the day, I imagined what effects hypothetical 'negative mass' matter would have, should it actually exist. Zero mass is all flat lines, and positive mass bends ST (Space-Time) towards itself, so negative mass might bend space away from itself.
This would cause the ST grid lines to distort away from the mass object. Two given points in the space-time fabric would move apart from each other. Which is a solid description of Inflation. Which is currently hypothesized to be caused by dark energy.
My idea replaces Dark Energy (and possibly Dark Matter, will go into details in a moment) with the existence of Negative Matter, whose existence, while not directly predicted, is very certainly allowed by relativity, and is an actual requirement for certain mathematical equations describing how wormholes might form or other forms of FTL and/or time travel. It has the same conceptual effect as Dark Energy, and fits with known mathematical physics models. This gives it an appeal of simplicity. However, some one with a heavier math background is going to have to do the number crunching to see if it fits.
How this might also replace Dark Matter: If the galaxies are being pushed apart by space-time around them being expanded by the existence of NM(Negative Matter) in large quantities, then that same NM would also be creating 'hills' around the 'valleys' of the galaxies, making a much steeper climb for any star that might otherwise be able to escape the galaxy's gravity. Thus you no longer need the gravitational effect of Dark Matter. Instead of DM(Dark Matter) holding the galaxies together, NM pushes the galaxies together. Part of the test of this idea would be to see if this can properly account for with regards to the already measured light distortions that have already been measured as part of the search for proof of DM.
This part I believe has already been speculated upon before, but if NM actually exists, it would have a certain amount of 'anti-gravity' effect. Mind you, a pound of NM would (probably) not fly off the earth's surface (at least, not very far) if left unattended, but it would flatten out ST around it a little, making everything else weigh a little bit less in the process. Much math would have to be done to be certain of the probably effects.
The concept is elegant and simple in many ways. And NM would be dark because light would automatically be bent away from it, instead of towards it. It would tend to spread out thinly, pushing away from itself as well as positive matter. And over all, be as hard to detect directly as both DM and DE.
Now to go see if I can poke any holes in this with some research.