Dilatons in hidden local symmetry for hadrons in dense matter

With the explicit breaking of scale invariance by the trace anomaly of QCD rephrased in terms of spontaneous breaking, low-energy strong interaction dynamics of dense and/or hot matter can be effectively captured by – in addition to the Nambu–Goldstone bosons and the vector mesons – two dilaton fields, the “soft” field that is locked to chiral symmetry and the “hard” field which remains unaffected by chiral symmetry. The scale anomaly in which the soft component intervenes can be shown to vanish at the chiral transition, while that of the hard component remains broken throughout the QCD sector. We argue for a remarkable role of the “homogeneous Wess–Zumino term” of the form ωμBμ on the structure of a single baryon as well as dense baryonic matter. The emerging structure of the dense hadronic matter so obtained suggests a chiral symmetry restored but (quark-)confined phase at high density and a possible remedy to the defect found in the structure of holographic dense matter described in string theory.