High-order temperature fluctuations in hot and dense QCD matter from multi-charge holography
We investigate temperature cumulants from second to sixth order across the QCD phase diagram using a lattice-calibrated multi-charge Einstein--Maxwells--dilaton model under heavy-ion charge constraints. Near the model's critical end point at $(μ_B,T)\simeq(547,112)$~MeV, the enhanced heat capacity produces a local suppression of the temperature variance. The higher-order cumulants develop sign reversals on the high-temperature side of the transition, with the onset moving to lower baryon chemical potentials as the order increases. Ratios of different cumulant orders provide a consistency check of the expected mean-field critical behavior. At fixed chemical potentials, their limits on both sides of the critical point agree with the predictions for the critical-isotherm exponent $δ=3$. The freeze-out analysis reveals nonmonotonic collision-energy dependence that need not be accompanied by sign reversals. On a representative trajectory, the variance reaches a local minimum near $\sqrt{s_{NN}}\simeq6$~GeV, with its position and depth depending on the freeze-out path. Temperature cumulants probe the thermal response and its critical scaling, providing information complementary to conserved-charge fluctuations for exploring the QCD phase diagram.