We report on a study of the finite-temperature QCD transition region for temperatures between 139 and 196 MeV, with a pion mass of 200 MeV and two space-time volumes: $24^3\times 8$ and $32^3\times 8$, where the larger volume varies in linear size between 5.6 fm (at $T=139\mathrm{MeV}$) and 4.0 fm (at $T=195\mathrm{MeV}$). These results are compared with the results of an earlier calculation using the same action and quark masses but a smaller, $16^3\times 8$ volume. The chiral domain wall fermion formulation with a combined Iwasaki and dislocation suppressing determinant ratio gauge action are used. This lattice action accurately reproduces the $SU(2{)}_L\times SU(2{)}_R$ and $U(1{)}_A$ symmetries of the continuum. Results are reported for the chiral condensates, connected and disconnected susceptibilities and the Dirac eigenvalue spectrum. We find a pseudocritical temperature, $T_c$, of approximately 165 MeV consistent with previous results and strong finite-volume dependence below $T_c$. Clear evidence is seen for $U(1{)}_A$ symmetry breaking above $T_c$ which is quantitatively explained by the measured density of near-zero modes in accordance with the dilute instanton gas approximation.

• Received 25 September 2013

DOI:https://doi.org/10.1103/PhysRevD.89.054514