On a two-parameter generalization of Hecke algebras and the XY chain in a magnetic field
Paul Martin
The structure and representation theory of a two-parameter generalization of Hecke algebras, denoted HL(q,η), which plays an important role in the construction of the L-site XY chain in a magnetic field is investigated. In particular, the structure of the XY chain representation of the algebra, on C2⊗L, and hence the structure of the centralizer algebra EndHL(q,η)(C2⊗L) for the XY chain representation, is analyzed. It is proved that the full algebra never reduces to the ordinary (one-parameter) Hecke algebra HL(q) in any specialization of the parameters, but contains the Hecke algebra as a quotient in a certain specialization of one of the parameters. This corrects an earlier claim of Hinrichsen and Rittenberg [Phys. Lett. B 275, 350 (1992)]. Bounds are established on the generic dimension of the centralizer algebra 4 ≤ dim(EndHL(q,η)(C⊗L2)) ≤ 8 (the upper bound is realized in every known case). Hence, it is argued that the structure of the centralizer algebra is independent of L, which is consistent with a result of Hinrichsen and Rittenberg, but that it is isomorphic to two commuting copies (rather than one copy) of the Pauli matrices. This contrasts sharply with the dimension of EndHL(q)(C⊗L2), which grows without bound as L increases.
Journal of Mathematical Physics•Nov 1, 1992•2 citations