Using Bethe's hypothesis, C N Yang exactly solved the one-dimensional (1D) delta-function interacting spin-1/2 Fermi gas with an arbitrary spin-imbalance in 1967. At that time, using a different method, M Gaudin solved the problem of interacting fermions in a spin-balanced case. Later, the 1D delta-function interacting fermion problem was named as the Yang-Gaudin model. It has been in general agreed that a key discovery of C N Yang's work was the cubic matrix equation for the solvability conditions. % This equation was later independently found by R J Baxter for commuting transfer matrices of 2D exactly solvable vertex models. % The equation has since been referred to Yang-Baxter equation, being the master equation to integrability. % The Yang-Baxter equation has been used to solve a wide range of 1D many-body problems in physics, such as 1D Hubbard model,
SU(N) Fermi gases, Kondo impurity problem and strongly correlated electronic systems etc. % In this paper, we will briefly discuss recent developments of the Yang-Gaudin model on several breakthroughs of many-body phenomena, ranging from the universal thermodynamics to the Luttigner liquid, the spin charge separation, the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like pairing state and the quantum criticality. % These developments demonstrate that the Yang-Gaudin model has laid out a profound legacy of the Yang-Baxter equation.
Recently, researchers have proposed the Asymmetric Bethe ansatz method - a theoretical tool that extends the scope of Bethe ansatz-solvable models by "breaking" partial mirror symmetry via the introduction of a fully reflecting boundary. Within this framework, the integrability conditions which were originally put forward by Gaudin have been further generalized. In this work, building on Gaudin's generalized kaleidoscope model, we present a detailed investigation of the relationship between DN symmetry and its integrability. We demonstrate that the mathematical essence of integrability in this class of models is characterized by a newly proposed Kaleidoscope Yang-Baxter Equation. Furthermore, we show that the solvability of a model via the coordinate Bethe ansatz depends not only on the consistency relations satisfied by scattering matrices, but also on the model's boundary conditions and the symmetry of the subspace where solutions are sought. Through finite element method based numerical studies, we further confirm that Bethe ansatz integrability arises in a specific symmetry sector. Finally, by analyzing the algebraic structure of the Kaleidoscope Yang-Baxter Equation, we derive a series of novel quantum algebraic identities within the framework of quantum torus algebra.