Topological susceptibility in 2-flavor lattice QCD with fixed topology

Abstract

We determine the topological susceptibility $\ddot{I}{‡}_t$ in the trivial topological sector generated by lattice simulations of two-flavor QCD with overlap Dirac fermion, on a $16^3\times 32$ lattice with lattice spacing $\sim$ 0.12 fm, at six sea quark masses $m_q$ ranging from $m_s/6$ to $m_s$ (where $m_s$ is the physical strange quark mass). The $\ddot{I}{‡}_t$ is extracted from the plateau (at large time separation) of the time-correlation function of the flavor-singlet pseudoscalar meson ($\hat{I}{\cdot }^{\prime }$), which arises from the finite size effect due to fixed topology. In the small $m_q$ regime, our result of $\ddot{I}{‡}_t$ is proportional to $m_q$ as expected from chiral effective theory. Using the formula $\ddot{I}{‡}_t=m_q\hat{I}\pounds /N_f$ by Leutwyler-Smilga, we obtain the chiral condensate in $N_f=2$ QCD as $\hat{I}{\pounds }^{\overline{\mathrm{MS}}}(2GeV)=[252(5)(10)\mathrm{MeV}{]}^3$, in good agreement with our previous result obtained in the $\hat{I}\mu$-regime.

7 pages, 3 figures, talk presented at the 25th International Symposium on Lattice Field Theory, Regensburg, Germany, 30 Jul - 4 Aug 2007