Generalized field mixing for endpoint criticality with marginal flow: resolving the four-state Potts endpoint in the square-lattice $J_1$--$J_2$ Ising model (opens in new tab)

Identifying the asymptotic criticality of a critical endpoint is challenging, as pseudo-first-order signatures persist over accessible system sizes and mask its underlying critical nature. This ambiguity is amplified at endpoints controlled by a marginally irrelevant scaling field, where logarithmic flow delays the onset of asymptotic scaling. Here we develop a generalized field-mixing framework for endpoint criticality governed by one relevant ...