The Bethe-Salpeter equation (BSE) approach is a theoretical spectroscopy technique that considers screened electron-hole Coulomb interaction, to accurately describe the process of optical absorption. 
In principle, the screening between the e-h pair is dynamical, i.e. frequency dependent. 
In practice, dynamics is often neglected, due to the large computational cost and because week dynamics in typical semiconductors with small exciton-binding energies, compared to plasmon frequencies. 
For materials with large exciton-binding energy, such as low-dimensional systems, dynamical screening can be important. 
We incorporated dynamical screening into the BSE approach and quantify the importance of dynamics of electronic screening from first principles. 
We study the optical absorption of linear oligoacene crystals and show that the exciton binding energy is on the order of 1 eV, leads to dynamical correction on the order of 0.15 eV, an order larger than that in crystalline semiconductors. 
We also show that Including this effect improves agreement with experimental results for the exciton binding energies.