The Recipe for Universe Formation: Heat and Rotation

After the Big Bang, our universe began to expand and emerge, forming stars, galaxies and planetary systems. Yet the specifics of this formation process have long remained a mystery to scientists. Now, researchers have taken a closer look at how the universe was formed.

Everyone knows that there are transitions between liquid, solid and gaseous phases. Similarly, time and space can undergo a phase transition. Yet can a similar process create a whole expanding universe such as ours? In order to find that out, scientists made a series of calculations and developed a theory about universe creation.

The researchers found that there is indeed a critical temperature at which an empty, flat spacetime turns into an expanding universe with mass. Essentially, the empty spacetime begins to boil and little bubbles form, one of which expands and eventually takes up all of spacetime. Yet in order for this to occur, the universe has to rotate. However, this required rotation can be arbitrarily small.

While this particular phenomenon is possible, though, our own universe does not seem to have come into existence in this way. The phase-transition model does not replace the Big Bang theory.

"Today, cosmologists know a lot about the early universe--we are not challenging the findings," said Daniel Grumiller, one of the researchers, in a news release. "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."

This new theory is actually the next logical step after the so-called "AdS-CFT correspondence." This conjecture describes a peculiar connection between theories of gravity and quantum field theories. In certain limiting cases, statements from quantum field theories can be translated into statements concerning gravitational theories and vice versa. This is particularly surprising since the two don't have much in common at first glance.

In this particular kind of correspondence, the quantum field theory is always described in one fewer dimension than the gravitational theory--something called the "holographic principle." A quantum field theory with two spatial dimensions can describe a physical situation in three spatial dimensions.

It's been suspected for a while that there may be a similar version of the "holographic principle" for flat spacetimes, but until now there hasn't been any models showing this. Last year, though, the researchers established such a model, which led to the current question about phase transitions in quantum field theories.

The new findings reveal that a phase transition between an empty spacetime and an expanding universe is possible. This is particularly surprising, and reveals that scientists are only just beginning to understand these remarkable correspondence relations.

The findings are published in the journal Physical Review Letters.