Using perturbation theory in the Euclidean (imaginary time) formalism as well
as the non-perturbative Fujikawa method, we verify that the chiral anomaly
equation remains unaffected in the presence of nonzero chemical potential,
μ. We extend our considerations to fermions with exact chiral symmetry on
the lattice and discuss the consequences for the recent Bloch-Wettig proposal
for the Dirac operator at finite chemical potential. We propose a new simpler
method of incorporating μ and compare it with the Bloch-Wettig idea.Comment: 12 pages, 3 figures,some typos corrected, a better proof for the \mu
independence of anomaly is given in section IIB, v4: the published versio