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Physics Colloquium: Paul Sorensen

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October 7, 2019 | 4:00 pm - 5:00 pm

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Title: Before Nuclei: Experimenting With Hot Nuclear Matter

Abstract: The overarching goal of colliding nuclei at relativistic energies is to understand the nature of the matter that existed a few microseconds after the Big Bang, when temperatures were too high for hadrons to emerge as relevant degrees of freedom. The challenge is to deposit enough energy into a small enough region that certain periods of the collision evolution can be treated thermodynamically and described as a new form of matter: a quark-gluon plasma (QGP). As described by Art Poskanzer, one of the founders of the field, the hope rested on the idea that “when a system gets complicated enough, sometimes it becomes simple again.” This challenging endeavor holds great promise: of the several phases and phase transitions that occurred in the early universe, only the QGP-hadron phase transition has any chance of being directly recreated in the laboratory. The electro-weak phase transition, would require energy densities roughly 8 to 9 orders of magnitude larger than those needed to create the QGP. Thus while it’s possible to leverage the already very high densities of nuclei to reach energy densities commensurate with the QGP phase through heavy-ion collisions, it’s not clear if humans will ever have the ability to reach energy densities comparable with any of the earlier stages of the universe’s evolution. As such, this may be a unique era in the study of the phases of the early universe: an era when an investigated phase is actually recreated in a laboratory setting. Since it’s likely that the physics of the other phases will have to be inferred from indirect observations, it’s especially important to study the surprising emergent phenomena of the one phase we can explore through direct observation. I will present a status report on these explorations.



October 7, 2019

4:00 pm - 5:00 pm
Event Categories:
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301 Riddick Hall
2401 Stinson Dr.
Raleigh, NC