Science is a process of objectification and the generation of models creates a duality- versus a phenomenological or ontological awareness of being. Phew. Which may be why I find it irresistible when the models themselves take on an almost mystical quality that is tantalizingly suggestive or difficult. I suspect someone like Baudrillard would have regarded this as a fetish- as if the technical jargon of string theorists, or whoever, makes a sort of gizmo that stands in for spirituality. I find the mechanics and language of these theories almost as wondrous as what’s being said with them. Maybe the fetish thing is right and it’s all about the words and numbers. I could just forget about everything else and, say, make big silver words and symbols like h or D-Space and polish them to the point where you can barely see the forms, just everything else reflected in them.
Discover Blog Cosmic Variance has a good piece on a topic I get a kick out of- extra dimensions. It reports on research into the question that a five year old would ask about extra dimensions- “if there are all these extra dimensions, how come we don’t see them?” The Calibau-Yau manifild in string theory, which I’ve posted about before, is a sort of torus that’s too small to see. In electromagnetism, solutions are also provided by wrapping an extra dimension into a circle, that’s too small to see. At this point the question becomes, “why are the dimensions we see so large, and the rest so small?”
The post reports on an academic paper that finds a “multiverse” as part of a possible solution;
Upping the number of dimensions to D, it is possible to find black branes that do exactly this – when you cross an event horizon, you enter a region in which some number of the extra dimensions have become compact. The number of compact dimensions is determined by the symmetry of the event horizon. If the event horizon has (D-4)-dimensional spherical symmetry, then the region inside of the black brane is effectively four dimensional. Further, the 4 dimensional region has a natural “slicing” into space and time, that yields a cosmology. The big-bang in this 4-dimensional cosmology corresponds to the event horizon of the black brane.
These black branes can be embedded in a D-dimensional de Sitter space, which has some very interesting properties itself. Most relevant for us is that energy conservation does not work in de Sitter space, since it has a finite temperature. This means that every once in a while, a fluctuation will occur that produces one of the black brane solutions, and therefore a 4-dimensional universe. This is a mechanism of dynamical compactification.
The devil is now in the details. First off, the brane needs to be charged under the gauge field for there to be one of these interesting solutions. For each value that the charge can take, a slightly different lower-dimensional universe will be produced, and if there are different types of gauge fields, then universes with different numbers of dimensions will be produced as well. There is a “landscape” of many possible lower-dimensional vacua, just like in string theory. Dynamical compactification will be happening all over the place in the D-dimensional de Sitter space, realizing all of these possibilities in different spacetime regions, and yielding what is referred to as a “multiverse.”
The zeroth order question is if any of these universes look like ours. This involves having an early time epoch of inflation and late-time evolution towards a universe dominated by a small cosmological constant. We found that the answer can be yes on both counts for the models we studied.