Sagnac gyroscopes, GINGERINO, and GINGER

GINGER (Gyroscopes IN GEneral Relativity), based on an array of large dimension ring laser gyroscopes, is aiming at testing on Earth General Relativity effects, like the gravito-electric and gravito-magnetic effects (also known as De Sitter and Lense-Thirring effects) and the Lorentz violation. The sensitivity is a function of the size and of the losses of the ring laser optical cavity. In this kind of measurement long term stability is matter of concern, and underground location is desirable for its natural thermal stability and for being isolated from atmospheric disturbances. Considering the present sensitivity of the RLG prototype GINGERINO, and assuming total losses of 6 ppm, a 40 m perimeter and 1 day of integration time, a sensitivity of the order of frad/s could be achieved. The construction of GINGER is at present under discussion.