# The 35th International Symposium on Lattice Field Theory

18-24 June 2017
Palacio de Congresos
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# Contribution Parallel

Seminarios 8
Algorithms and Machines

# Fighting topological freezing in the two-dimensional CP$^{N-1}$ model

## Speakers

• Dr. Martin HASENBUSCH

## Content

We perform Monte Carlo simulations of the CP$^{N-1}$ model on the square lattice for $N=10$, $21$, and $41$. Our focus is on the severe slowing down related to instantons. To fight this problem we employ open boundary conditions as proposed by Lüscher and Schaefer for lattice QCD. Furthermore we test the efficiency of parallel tempering of a line defect. Our results for open boundary conditions are consistent with the expectation that topological freezing is avoided, while autocorrelation times are still large. The results obtained with parallel tempering are encouraging.

## Preferred track (if multiple tracks have been selected)

Algorithms and Machines