The neutron star on your table-top

How do you probe the inside of a neutron star? These are so dense that a teaspoon of matter weighs more than all of the earth's population put together! Well, even on NASA's budget, we can't travel to a star just yet. But we can study ultra-cold atoms, which behave just like neutrons when cooled with lasers to a billion times colder than room temperature. This has left theorists out in the cold. How can one understand matter when the interactions between the particles are infinitely strong?

Swinburne University theorists Xiaji Liu, Peter Drummond and Hui Hu have developed a new path to solve this problem. Their novel approach uses exact solutions to the quantum theory of three bodies interacting very strongly. The results help explain the physics which holds inside a neutron star - or for ultra-cold atoms. They may also help to understand new superconductors, which could help to conserve energy here on earth. Importantly, these predictions can be tested in a physics laboratory.

The results, just published in physics' most prestigious journal, overturn previous ideas. The SUT theory, called a virial expansion, is in agreement with experiment. Previous results were not in agreement. See the graph below. The new SUT theory is in black, and shows how energy changes with increasing temperature (or entropy), as compared to the experimental measurements (vertical bars). The old theory, in orange, doesn't agree with experiment.

These are the very first measurements. They require a high vacuum, incredibly low temperatures, and obviously have large errors. Clearly the experimentalists will burn more midnight oil to improve the accuracy of their measurements, and give the new SUT theory a thorough workout. After all - we still don't have a starship!

For more details, see:

Virial Expansion for a Strongly Correlated Fermi Gas

Xia-Ji Liu, Hui Hu, and Peter D. Drummond

Phys. Rev. Lett. 102, 160401 (2009)