(from email invite)

To kick off journal club for the year, I will be presenting something on false vacuum decay. Imagine that there are two vacuum states of a scalar field which permiates the universe. This can be represented by constructing a potential for the scalar field with two local minima, where one minimum is lower than the other. Now, one defines a boundary condition for the universe: at some point in the distant past (older than the age of the universe in the big bang picture) the region of space that our universe now occupies was in the higher energy vacuum state (false vacuum). Since the scalar field is a quantum field, there is some probability that a region of space will tunnel to the true vacuum. To obey energy conservation, this region must be a bubble of a minimum radius (depends on the potential chosen, but that radius would be on the order of kilometers). Once the bubble is formed, it will expand until eventually the false vacuum region is replaced by a true vacuum region. The exciting part happens when you include gravity (the zero point energy of the scalar field acts as a cosmological constant) in this picture. The region inside the bubble looks like our universe - undergoing accelerated expansion which started at some finite time in the past. So, the "Big Bang" could have been the formation of a true vacuum region. This scenario has spawned a number of cosmologies, and I will talk about a few.

- Current Mood: hopeful

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csnspoonless