Casimir force between $\delta-\delta^{\prime}$ mirrors transparent at   high frequencies
  We investigate, in the context of a real massless scalar field in $1+1$ dimensions, models of partially reflecting mirrors simulated by Dirac $\delta-\delta^{\prime}$ point interactions. In the literature, these models do not exhibit full transparency at high frequencies. In order to provide a more realistic feature for these models, we propose a modified $\delta-\delta^{\prime}$ point interaction that enables full transparency in the limit of high frequencies. Taking this modified $\delta-\delta^{\prime}$ model into account, we investigate the Casimir force, comparing our results with those found in the literature. 
Alessandra N. Braga, Jeferson Danilo L. Silva, and Danilo T. Alves
quant-ph hep-th