String Connection?

The possibility of a connection between string theory and RHIC collisions is unexpected and exhilarating,” Dr. Orbach said. “String theory seeks to unify the two great intellectual achievements of twentieth-century physics, general relativity and quantum mechanics, and it may well have a profound impact on the physics of the twenty-first century.”

In this narrow class of theories, the hot plasma in the 4D theory corresponds to a black hole in the 10D equivalent description, which matches very well with Stephen Hawking's prediction that black holes have temperature. Moreover, there is a direct relationship between vibrations in the plasma, such as sound waves, and vibrations of the black-hole horizon. For example, when an object is dropped into the black hole in 10D, the equivalent picture in 4D is a hot, expanding region that dissolves into a plasma. Using this equivalence, various theorists, including the present author, have deduced that if such plasmas were real, they would be almost perfect liquids.

Since Maldacena's conjecture does not apply to QCD, however, the viscosity of the real quark-gluon plasma cannot be computed via string theory. This makes the RHIC announcement that the viscosity of its plasma is comparable to the values one finds from string-theory calculations even more surprising. If this is true, the quark-gluon plasma created at RHIC could be the most perfect fluid in nature. This in itself is an interesting fact, but it could also indicate that string theory has some relation to real QCD. However, we first need more quantitative evidence from RHIC, such as an upper bound on the viscosity.

Blackholes at RHIC


A statement from RHIC theoretical nuclear physicist Dmitri Kharzeev:

Alice

The existence of such a phase and its properties are key issues in QCD for the understanding of confinement and of chiral-symmetry restoration. For this purpose, we intend to carry out a comprehensive study of the hadrons, electrons, muons and photons produced in the collision of heavy nuclei. Alice will also study proton-proton collisions both as a comparison with lead-lead collisions in physics areas where Alice is competitive with other LHC experiments