Net-baryon number fluctuations across the chiral phase transition at finite density in strong-coupling lattice QCD

We investigate the net-baryon number fluctuations across the chiral phase transition at finite density in the strong-coupling and chiral limits. Mesonic field fluctuations are taken into account by using the auxiliary field Monte Carlo method. We find that the higher-order cumulant ratios, Sσ and kappa σ ^2, show oscillatory behavior around the phase boundary at μ /Tgtrsim 0.2, and there exists a region where the higher-order cumulant ratios are negative. The negative region of kappa σ ^2 is found to shrink with increasing lattice size. This behavior agrees with the expectations from the scaling analysis.