Imprint of primordial gravitational wave with extremely low frequency on gravitational lens system

Abstract: Primordial gravitational waves with extremely low frequency are expected to origin from inflation in the early Universe. The detection of such kind of gravitational waves is of great significance to verify the inflationary theory and determine the energy scale of inflation. B-mode of polarization of cosmic microwave background shows to be a promising probe of extremely low frequency primordial gravitational wave. In order to find a complementary observational feature induced by primordial gravitational wave with extremely low frequency, we propose an alternative way of detection by investigating the effect of primordial gravitational wave with extremely low frequency on a gravitational lens system with a non-aligned source-deflector-observer configuration. The results show that, with a series of chosen parameters, gravitational lens system with perturbation from extremely low frequency primordial gravitational wave could induce time delay which could deviate from the time delay deduced from theoretical model as much as about one hundred percent, meaning that gravitational lens system with a non-aligned configuration could serve as a potential long-base-line detector of extremely low frequency primordial gravitational wave.