As far as the universe structural thing goes, I've heard and read about the Klein bottle model , but I've also heard and read good arguments for the "torus" (donut) model. An excellent book I'm reading now makes an argument for an arrangement of membranes assembled into some sort of "bulk" of light and dark matter and energy.
The author, Lisa Randall is a high energy physicist and mathematician at Harvard, and looks enough like Jodie Foster to be her twin. The book is titled, Warped Passages. I'm a little more than halfway through and I'm pretty impressed with her ability to explain very complex things in everyday language. She's at the forefront of those who believe that they will soon be able to unite the force of gravity with the other three basic forces already well known and explained.
It seems that the Large Hadron Collider at CERN which will come on line in a year or two will likely enable further exploration of this subject matter...or as I call it "more and more about less and less". And it seems from what has been discovered over the past ten years or so that the universe at least "appears" to have an inside part and an outside part, as far as our perspectives are concerned. Think of the outside as the past, and the inside as the future.
flow....