The Vector Manifestation and Effective Degrees of Freedom at Chiral Restoration

The role of effective degrees of freedom on the vector and axial-vectorsusceptibilities and the pion velocity at chiral restoration is analyzed. Weconsider two possible scenarios, one in which pions are considered to be theonly low-lying degrees of freedom -- that we shall refer to as "standard" --and the other in which pions, vector mesons and constituent quarks (orquasiquarks in short) are the relevant low-lying degrees of freedom -- that weshall refer to as "vector manifestation (VM)." We show at one-loop order inchiral perturbation theory with hidden local symmetry Lagrangian that while inthe standard scenario, the pion velocity vanishes at the chiral transition, itinstead approaches unity in the VM scenario. If the VM is realized in nature,the chiral phase structure of hadronic matter can be much richer than that inthe standard one and the phase transition will be a smooth crossover: Sharpvector and scalar excitations are expected in the vicinity of the criticalpoint. Some indirect indications that lend support to the VM scenario, and inconsequence to BR scaling, are discussed.Comment: Based on talks given at "Chiral 02," Kyoto, Japan, 7-9 October 2002 and "SCGT02," Nagoya, Japan, 10-13 December 200