Condensed Matter Physics of QCD

Understanding QCD in extreme conditions requires linking usually disparate strands of theoretical physics, including particle and nuclear physics, cosmology, astrophysics and condensed matter physics. Krishna Rajagopal and Frank Wilczek study the properties of the cold dense quark matter that may lie at the centers of neutron stars. This stuff is the QCD analogue of a superconductor. However, if probed with ordinary light it looks like a transparent insulator and not like an electric conductor, as previously assumed. The properties of sufficiently dense quark matter have now been understood from first principles, but many interesting questions remain to be answered at lower densities. Progress requires coupled advances in theory, astrophysical observation, and experiments on analogue systems made of ultracold fermionic atoms. Robert Jaffe and Edward Farhi did the first work on quark matter in astrophysics. This work makes contact with research in Xray astronomy, condensed matter theory and ultracold cold atoms carried out elsewhere in our department.

Krishna Rajagopal also does research on hot quark matter, of the sort that filled the universe shortly after the big bang and that is created in current experiments at the Relativistic Heavy Ion Collider. He has analyzed the critical point in the QCD phase diagram and has proposed signatures for its experimental detection. Gunther Roland is leading the experimental search for the critical point, and he and his MIT colleagues on the PHOBOS experiment are leading the study of even hotter quark matter.

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