專題演講 Seminar

Title

Quantum pion liquid

Speaker

Marc Winstel (Goethe University Frankfurt)

Abstract

In the intermediate density region of the QCD phase diagram, there have been conjectures about different phenomena involving spatial modulations of the chiral order parameter. The most prominent one in the discussion is the so-called inhomogeneous chiral phase, where the chiral condensate spontaneously breaks translational invariance in addition to chiral symmetry. A recent Functional Renormalization group study finds a so-called Moat regime in the vicinity of the critical point, where mesonic dispersion relations favor non-vanishing momenta. This regime is understood as a precursor for an inhomogeneous phase, but, in general, favors all phenomena related to spatial inhomogeneities in mesonic correlation functions.

In this talk, I am going to discuss a scenario recently termed 'quantum pion liquid', which is a regime with oscillating, exponentially suppressed spatial correlation functions of mesonic fields. I present results, where this regime is observed in two-different low-energy effective models with different field content and different methodologies. In the first part of the talk a scalar O(N) model, which is tuned to classically feature an inhomogeneous phase, is studied using lattice field theory in order to investigate the effect of bosonic quantum fluctuations on the inhomogeneous condensate. First results indicate that the inhomogeneous condensate is indeed disordered through bosonic quantum fluctuations. Instead, a quantum pion liquid behavior is obtained in the two-point correlation functions. A mechanism for the disordering as well as possible alternative regimes are discussed.

In the second part of the talk, I am going to study 2+1-dimensional four-fermion and Yukawa models in the mean-field approximation. Using a stability analysis based on homogeneous ground states, strong evidence for the absence of inhomogeneous chiral condensates in this model is presented. By accessing the inverse of the mesonic two-point correlation functions in the mean-field approach, a quantum pion liquid with oscillating, but exponentially suppressed two-point correlation functions is observed at non-vanishing chemical potential. The existence of this regime aligns with expectations based on symmetry arguments, that are also applicable to QCD at non-vanishing baryon density. The phase diagram of the model at non-vanishing temperature and chemical potential is presented.

Language

演講語言 (Language): in English

Hosted by

楊廸倫 助研究員
Yang, Di-Lun / Assistant Research Fellow