Field theoretical approach to spin models

We developed a systematic non-perturbative method base on Dyson-Schwinger theory and the derivable theory for Ising model at broken phase. Based on these methods, we obtain critical temperature and spin spin correlation beyond mean field theory. The spectrum of Green function obtained from our methods become gapless at critical point, so the susceptibility become divergent at T-c. The critical temperature of Ising model obtained from this method is fairly good in comparison with other non-cluster methods. It is straightforward to extend this method to more complicate spin models for example with continue symmetry.

Automated summary

The systematic non-perturbative method developed based on Dyson-Schwinger theory and the derivable theory for Ising model at broken phase allows for obtaining critical temperature and spin spin correlation beyond mean field theory. The gapless spectrum of Green function obtained from this method at critical point results in divergent susceptibility at T-c. The critical temperature of Ising model obtained from this method is fairly good compared to other non-cluster methods and can be extended to more complex spin models with continuous symmetry.