<P> At high densities but relatively low temperatures, quarks are theorized to form a quark liquid whose nature is presently unknown . It forms a distinct color - flavor locked (CFL) phase at even higher densities . This phase is superconductive for color charge . These phases may occur in neutron stars but they are presently theoretical . </P> <P> Color - glass condensate is a type of matter theorized to exist in atomic nuclei traveling near the speed of light . According to Einstein's theory of relativity, a high - energy nucleus appears length contracted, or compressed, along its direction of motion . As a result, the gluons inside the nucleus appear to a stationary observer as a "gluonic wall" traveling near the speed of light . At very high energies, the density of the gluons in this wall is seen to increase greatly . Unlike the quark--gluon plasma produced in the collision of such walls, the color - glass condensate describes the walls themselves, and is an intrinsic property of the particles that can only be observed under high - energy conditions such as those at RHIC and possibly at the Large Hadron Collider as well . </P> <P> The gravitational singularity predicted by general relativity to exist at the center of a black hole is not a phase of matter; it is not a material object at all (although the mass - energy of matter contributed to its creation) but rather a property of spacetime at a location . It could be argued, of course, that all particles are properties of spacetime at a location, leaving a half - note of controversy on the subject . </P> <P> A supersolid is a spatially ordered material (that is, a solid or crystal) with superfluid properties . Similar to a superfluid, a supersolid is able to move without friction but retains a rigid shape . Although a supersolid is a solid, it exhibits so many characteristic properties different from other solids that many argue it is another state of matter . </P>

Materials can be classified as solids liquids or gases