On interpretation of fluctuations of conserved charges at high T

Fluctuations of conserved charges calculated on the lattice which can be measured experimentally, are well reproduced by a hadron resonanse gas model at temperatures below Tch ~ 155 T ch ∼ 155 MeV and radically deviate from the hadron resonance gas predictions above the chiral restoration crossover. This behaviour is typically interpreted as an indication of deconfinement in the quark-gluon plasma regime. We present an argument that this interpretation may be too simple. The argument is based on the scaling of quantities with the number of colors: demonstration of deconfinement and QGP requires observable that is sensitive to ~ Nc² ∼ N c 2 gluons while the conserved charges are sensitive only to quarks and above Tch T ch scale as Nc¹ N c 1 . The latter scaling is consistent with the existence of an intermediate regime characterized by restored chiral symmetry and by approximate chiral spin symmetry which is a symmetry of confining interaction. In this regime the energy density, pressure and entropy density scale as Nc¹ N c 1 . In the large Nc N c limit this regime might become a distinct phase separated from the hadron gas and from QGP by phase transitions. A natural observable that associates with deconfinement and is directly sensitive to deconfined Nc²-1 N c 2 - 1 gluons is the Polyakov loop; in the Nc=3 N c = 3 world it remains very close to 0 at temperatures well above chiral crossover, reaches the value ~ 0.5 ∼ 0.5 around ~ 3Tch ∼ 3 T ch and the value close to 1 at temperatures ~ 1 ∼ 1 GeV.