I used to follow his work more closely than I do now, but might prove relevant:
http://casa.colorado.edu/~ajsh/schww.html
Also Gabriel LaFreniere has put together a strictly scientific model of the universe based solely on electrons:
http://www.glafreniere.com/matter.htm that would require negative mass to bind molecules together.
I think the negative mass would "exist" beyond the planck horizon and be the cause for expansion as well.