The usual view is that QCD in the limit of a large number of colors (Nc) becomes stringy: high-lying hadrons can be described as flux tubes and thus may be modelled as a hadronic string theory. It is also known that at large Nc, QCD has a deconfinement transition at a temperature Tc. This talk concerns the thermodynamics of the hadronic phase of large Nc QCD above Tc – i.e., a metastable phase. The key issue is to relate this to the hadron string description. The argument exploits the fact that hadrons interact weakly at large Nc; the fact that the effective string theory has a Hagedorn temperature TH also plays an essential role. Using these two inputs it shown that near TH, the energy density and pressure of the hadronic phase of large Nc QCD has the following scaling behavior: E ∼(TH-T)-(D⊥-6)/2 (for D⊥ <6) and P ∼(TH-T)-(D⊥-4)/2 (for D⊥<4) where D⊥ is the effective number of transverse dimensions of the string theory. It is easy to see that when D⊥< 6 the behavior is qualitatively distinct from what is seen in typical statistical models. In principle, such behavior could be observed in lattice studies to verify the stringy nature of the dynamics of large Nc QCD. To do this, lattice studies of the metastable hadronic phase are essential. The practicality of computing D⊥ in lattice simulations at moderately large Nc is discussed.
URL : http://ptp.ipap.jp/link?PTPS/168/285/
DOI : 10.1143/PTPS.168.285