Effects of quantum instantons on the thermodynamics of theCPN−1model

Jens O. Andersen, Daniël Boer, Harmen J. Warringa
2006 Physical Review D  
Using the 1/N expansion, we study the influence of quantum instantons on the thermodynamics of the CP^(N-1) model in 1+1 dimensions. We do this by calculating the pressure to next-to-leading order in 1/N, without quantum instanton contributions. The fact that the CP^1 model is equivalent to the O(3) nonlinear sigma model, allows for a comparison to the full pressure up to 1/N^2 corrections for N=3. Assuming validity of the 1/N expansion for the CP^1 model makes it possible to argue that the
more » ... sure for intermediate temperatures is dominated by the effects of quantum instantons. A similar conclusion can be drawn for general N values by using the fact that the entropy should always be positive.
doi:10.1103/physrevd.74.045028 fatcat:z7asf3rhovak7kmxtwv5cb6loe