Magnetic Susceptibility of the QCD Vacuumat a Finite Quarkchemical Potential
Abstract
We investigate the QCD magnetic susceptibility chi at the finite quarkchemical potential (mu>0) and at zero temperature (T=0) to explore the pattern of the magnetic phase transition of the QCD vacuum. For this purpose, we employ the nonlocal chiral quark model derived from the instanton vacuum in the presence of the chemical potential in the chiral limit. Focusing on the NambuGoldstone phase, we find that the magnetic susceptibility remains almost stable to mu~200 MeV, and falls down drastically until the the quarkchemical potential reaches the critical point mu_c~320 MeV. Then, the strength of the chi is reduced to be about a half of that at mu=0, and the firstorder magnetic phase transition takes place, corresponding to the chiral restoration. From these observations, we conclude that the response of the QCD vacuum becomes weak and unstable to the external electromagnetic field near the critical point, in comparison to that for vacuum. It is also shown that the breakdown of Lorentz invariance for the magnetic susceptibility, caused by the finite chemical potential, turns out to be small.
 Publication:

Journal of Korean Physical Society
 Pub Date:
 August 2009
 DOI:
 10.3938/jkps.55.429
 arXiv:
 arXiv:0804.0056
 Bibcode:
 2009JKPS...55..429N
 Keywords:

 High Energy Physics  Phenomenology
 EPrint:
 12 pages, 2 figures