Barbara V. Jacak

Lawrence Berkeley National Laboratory


Primary Section: 13, Physics
Membership Type: Member (elected 2009)

Research Interests

I am a nuclear physicist, but my research lies on the boundary between nuclear and particle physics. Using beams of nuclei accelerated to nearly the speed of light, I study what happens to matter when the temperature is raised to 4 trillion degrees. Under such conditions, which occurred in the early universe about a microsecond after the Big Bang, protons and neutrons melt into a plasma of their constituent quarks and gluons. Astoundingly, at temperatures near the phase transition, the plasma behaves as a liquid rather than a gas. Experiments, including my own, indicate that the plasma is extremely opaque, its constituents are strongly coupled, and the liquid flows nearly freely, i.e. with a vanishingly small viscosity to entropy ratio. Its behavior is remarkably similar to that of other strongly coupled systems. Several observed features can be described in the limit of infinitely strong coupling with calculations from string theory, which also describe ultracold gases of atoms. We are currently studying the properties of this novel liquid. Measurements of energy and momentum transport, as well as how the strong interaction is screened within the plasma, should help reveal the relevant degrees of freedom in its interior.

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