December 11, 2013
What’s The Recipe For A Universe?: Apply Heat And Stir
John P. Millis, PhD for redOrbit.com - Your Universe Online
For several decades now the leading model for the origin and evolution of the known Universe is a concept known as the Big Bang. Nearly 15 billion years ago, quantum fluctuations of the infinite vacuum of space-time caused the emergence of a rapidly expanding Universe, ultimately filled with matter and radiation.But what initially caused the fluctuation? According to quantum mechanics, it is a natural result of the probabilistic nature of quantum systems. However, new research from a team of scientists from the Vienna University of Technology, Harvard, MIT and the University of Edinburgh, claim that perhaps a phase transition is the key.
Usually, the term phase transition brings to mind the conversion of water to ice or steam. It seems, however, that the very fabric of space-time can undergo such transitions. While this in itself is not new – Steven Hawking’s work from 1983 found phase transitions in empty space could lead to the creation of black holes – the revelation came when the team found that at a certain critical temperature otherwise empty space “starts to boil, little bubbles form, one of which expands and eventually takes up all of space-time,” explains Daniel Grumiller from the Vienna University of Technology.
Apparently, all it takes is just the right amount of heat and the presence of rotation. In other words: apply heat and stir. While Grumiller and his team are not necessarily looking to completely replace the Big Bang theory, they are interested in knowing how such a phase transition could play a role in the evolution of the Universe. Reports Grumiller, “Today, cosmologists know a lot about the early universe – we are not challenging their findings. But we are interested in the question, which phase transitions are possible for time and space and how the mathematical structure of spacetime can be described.”
The underlying theory behind this new phase transition model is a strange correlation between statements of quantum field theory and gravitational theory. These two ideas are, quite literally, worlds apart in their formulations, yet a distinct correspondence persists. To make it work, the particular property of gravity can be expressed quantum mechanically by describing the geometry in one fewer spatial dimension than it would have gravitationally – a procedure known as the holographic principle.
Practically, this means describing the gravitational system in some sort of exotic geometry, instead of the usual flat space-time model we are used to. While the principle is not necessarily excluded from operation in such geometries, it had never been demonstrated to translate properly.
This new work, finally bridges that gap, and uses a flat geometry, and within that system examines phase transitions. Initially, the team was skeptical. As Grumiller explains, “At first, this was a mystery for us. This would mean a phase transition between an empty space-time and an expanding universe. To us, this sounded extremely implausible.”
Of course, as it turns out, this is exactly what the team found. But there is still considerable work to do. “We are only beginning to understand these remarkable correspondence relations.”