Reweighting twisted boundary conditions
Abstract
Imposing twisted boundary conditions on the fermionic fields is a procedure extensively used when evaluating, for example, form factors on the lattice. Twisting is usually performed for one flavour and only in the valence, and this causes a breaking of unitarity. In this work we explore the possibility of restoring unitarity through the reweighting method. We first study some properties of the approach at tree level and then we stochastically evaluate ratios of fermionic determinants for different boundary conditions in order to include them in the gauge averages, avoiding in this way the expensive generation of new configurations for each choice of the twisting angle, $\theta$. As expected the effect of reweighting is negligible in the case of large volumes but it is important when the volumes are small and the twisting angles are large. In particular we find a measurable effect for the plaquette and the pion correlation function in the case of $\theta=\pi/2$ in a volume $16\times 8^3$, and we observe a systematic upward shift in the pion dispersion relation.
 Publication:

arXiv eprints
 Pub Date:
 September 2015
 DOI:
 10.48550/arXiv.1509.04540
 arXiv:
 arXiv:1509.04540
 Bibcode:
 2015arXiv150904540B
 Keywords:

 High Energy Physics  Lattice
 EPrint:
 7 pages, 9 figures, talk presented at the 33rd International Symposium on Lattice Field Theory, 1418 July 2015, Kobe International Conference Center, Kobe, Japan