Optimistic limits of colored Jones polynomials and complex volumes of hyperbolic links

The optimistic limit is the mathematical formulation of the classical limit which is a physical method to expect the actual limit by using saddle point method of certain potential function. The original optimistic limit of the Kashaev invariant was formulated by Yokota, and a modified formulation was suggested by the author and others. The modified version was easier to handle and more combinatorial than the original one. On the other hand, it was known that the Kashaev invariant coincides with the evaluation of the colored Jones polynomial at the certain root of unity. The optimistic limit of the colored Jones polynomial was also formulated by the author and others, but it was so complicated and needed many unnatural assumptions. In this article, we suggest a modified optimistic limit of the colored Jones polynomial, following the idea of the modified optimistic limit of the Kashaev invariant, and show that it determines the complex volume of a hyperbolic link. Furthermore, we show that this optimistic limit coincides with the optimistic limit of the Kashaev invariant modulo $4\pi^2$. This new version is easier to handle and more combinatorial than the old version, and has many advantages than the modified optimistic limit of the Kashaev invariant. Because of these advantages, several applications have already appeared and more are in preparation now.