SPACE seminar: Clelia Gambardella - "The impact of θ-angle on the QCD strange and isospin phase diagram"
Aula 4
San Marcellino
Speaker: Clelia Gambardella (Scuola Superiore Meridionale)
Abstract: Quantum Chromodynamics is one of the pillars of the Standard Model of particle physics; nevertheless, several aspects of its dynamics remain poorly understood, particularly in the strongly coupled regime.
A significant example is provided by the topological sector of the theory, governed by the θ-angle and directly connected to the long-standing open Strong CP problem, with deep theoretical and phenomenological implications.
At the same time, understanding QCD at finite density is of great interest, both as a theoretical laboratory for nonperturbative dynamics and for its relevance to extreme environments, such as the interior of neutron stars.
In this talk, I will explore the impact of the θ-angle on the QCD phase diagram at nonzero isospin and strangeness chemical potentials for three light flavours.
I will begin by introducing the Chiral Lagrangian at finite density and by analysing the associated symmetry-breaking patterns, outlining the resulting phase structure.
I will then discuss the phase boundaries and the nature of the corresponding phase transitions, as well as the physical spectrum in the different phases.
Particular emphasis will be placed on the region around θ = π, where I will examine whether Dashen’s phenomenon occurs in the various phases.
Finally, I will present evidence for a novel parity-preserving superfluid phase.
The talk is based on JHEP 07(2025) 252, arXiv 2501.04261, in collaboration with J. Bersini, A. D’Alise and F. Sannino.
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