What Are the New States of Matter at Exceedingly High Density and Temperature?
Until the universe was a few microseconds old, it was hot enough that quarks and gluons were free particles, part of hot primordial plasma. A little later, it had cooled enough to condense into baryons, where they have been imprisoned by the strong nuclear force (QCD) ever since. This QCD phase transition may have left its signature in a gravitational wave signal; LISA will begin a search for such a signal. Quark-gluon plasma may also play a role in the interiors of neutron stars, and x-ray observations of them could shed light on its behavior. Meanwhile, nuclear physicists using the Relativistic Heavy Ion Collider at Brookhaven National Laboratory are colliding high energy beams of gold nuclei to see if they can form brief samples of quark-gluon plasma. An upgrade of the RHIC facility is one of the mid-term items in our Facilities Outlook. How Were the Elements from Iron to Uranium Made? Nuclei of the lightest elements were formed within the first few seconds of the universe, but heav
