Kecoglu, IbrahimBerker, A. Nihat2024-06-232024-06-23202300378-43711873-2119https://doi.org/10.1016/j.physa.2023.129248https://hdl.handle.net/20.500.12469/5798Kecoglu, Ibrahim/0000-0002-2141-8401; Berker, A/0000-0002-5172-2172The global phase diagrams of the Ashkin-Teller model are calculated in d = 2 and 3 by renormalization-group theory that is exact on the hierarchical lattice and approximate on the recently improved Migdal-Kadanoff procedure. Three different ordered phases occur in the dimensionally distinct phase diagrams that reflect three-fold order-parameter permutation symmetry, a closed symmetry line, and a quasi-disorder line. First- and second-order phase boundaries are obtained. In d = 2, second-order phase transitions meeting at a bifurcation point are seen. In d = 3, first- and second-order phase transitions are separated by tricritical and critical endpoints.eninfo:eu-repo/semantics/closedAccessFirst and second-order phase transitionsBifurcation, tricritical, critical-end pointsExact renormalization-group solutionHierarchical lattices in d=2 and 3Ashkin-Teller spin modelArticle630WOS:00109929200000110.1016/j.physa.2023.1292482-s2.0-85173582720Q2Q2