Title
"Absence of Phase Transitions in 2D O(N) Spin Model, --Analysis of the Renormalization Group Flow--"
Keiichi Ito (Setsunan University)
Abstract
The 2D O(N) Spin model with large N is investigated by block spin transformation by integrating out fluctuation fields which are decomposed into parallel ones with the block spins and the ones orthogonal to the block spins. The latters are almost free massive Gaussian and enable us to apply perturbative calculations since one can show that the fluctuations obey the N^{-1} expansion (this is central limit theorem applied to the fluctuations). The domain walls are subtle to define and prohibit our perturbative calculations but they have high energies. Thus the flow reaches beta=0 after many iterations.
