摘要

With the extended logarithmic flow equations and some extended Vertex operators in generalized Hirota bilinear equations, extended bigraded Toda hierarchy (EBTH) was proved to govern the Gromov-Witten theory of orbiford c(NM) in literature. The generating function of these Gromov-Witten invariants is one special solution of the EBTH. In this article, the multifold Darboux transformations and their determinant representations of the EBTH are given with two different gauge transformation operators. The two Darboux transformations in different directions are used to generate new solutions from known solutions which include soliton solutions of (N,N)-EBTH, i.e. the EBTH when N = M. From the generation of new solutions, we can find the big difference between the EBTH and the extended Toda hierarchy (ETH). Also, we plotted the soliton graphs of the (N,N)-EBTH from which some approximation analysis is given. From the analysis on velocities of soliton solutions, the difference between the extended flows and other flows are shown. The two different Darboux transformations constructed by us might be useful in Gromov-Witten theory of orbiford c(NM).