The Universe didn’t start off with a big bang, but a big whimper. Or so say four physicists from the University of Melbourne and RMIT. They compare the beginning of the Universe with that of freezing of water, indicating that the Universe underwent a rapid phase transition. Before you think this is the next big theory, all set to replace the Big Bang as the new standard cosmological theory, hold on!
Crystallizing out the Universe
Lead researcher of the group, James Quach, says that the early Universe can be compared with a liquid – something which has no particular shape or form. This liquid froze, “crystallizing” into three spatial and one temporal (time) dimension. In a slightly more technical language, consider a crystal lattice forming as a result of some parameter – say temperature – varying from high to low. As the temperature lowers, the lower energy states of the crystal become more and more important. Quach and his group say that these low energy states form the spatial degrees of freedom of the Universe. They herald in a new theory called ‘quantum graphity’.
The stimulus behind the theory proposal is very simple: dissatisfaction. Physicists are unsure as to how the bang in the Big Bang happened. More precisely, the structure of space-time thought to exist at the time of the Big Bang requires a modern theory of quantum gravity. Basically, Einstein’s equations of general relativity and quantum mechanics cannot be reconciled and this creates the problem. Right now, we have no satisfactory theory of quantum gravity.
Do away with it, says the group. Imagine the Universe as a group of dynamical space-time blocks, like small crystalline blocks floating around in a liquid. As the temperature cools, the blocks coalesce and this gives rise to a bigger crystal, simulating the freezing out of space-time from an existing soup.
But what about anisotropy and the visible structure in the Universe? Here is where the water-freezing analogy comes in most handy. When water freezes into ice, cracks develop on the surface. Quach and team describe these cracks as some visible structure. Problem is that they aren’t sure what scale to look at and this scale varies all the way from the microscopic to the ultra macroscopic.
All of this sounds fine and dandy, except that this new model must explain or, better predict, the data seen by the various cosmological experiments. Right now, the group doesn’t seem to have the right scale in mind. More problems arise from asking the question where did the soup that crystallized come from?
The work appears in Physical Review D here: http://arxiv.org/abs/1203.5367