Gyroscopes IN GEneral Relativity (GINGER) is a proposed experiment with the aim of measuring in a ground laboratory the gravitoelectric and gravitomagnetic effects foreseen by general relativity through an array of ring laser gyroscopes. GINGERINO is a square ring-laser prototype that has been built to investigate the level of noise inside the Gran Sasso underground laboratory. GINGERINO has shown the advantage of the underground location. Now it provides suitable data for geophysics and seismology. Since May 2017, it has continuously acquired data. The analysis of the first 90 days shows that the duty cycle is higher than 95%, and the quantum shot noise limit is of the order of 10(rad/s)/Hz. It is located in a seismically active area, and it recorded part of the central Italy earthquakes. Its high sensitivity in the frequency band of fraction of hertz makes it suitable for seismology studies. The main purpose of the present analysis is to investigate the long-term response of the apparatus. Simple and fast routines to suppress the disturbances coming from the laser have been developed. The Allan deviation of the raw data reaches some 10 after about 10 s of integration time, while the processed data show an improvement of 1 order of magnitude. Disturbances at the daily time scale are present in the processed data, and the expected signal induced by polar motion and solid Earth tides is covered by those disturbances.

The sensitivity to angular rotation of the top class Sagnac gyroscope GINGERINO is carefully investigated with standard statistical means, using 103 days of continuous operation and the available geodesic measurements of the Earth angular rotation rate. All features of the Earth rotation rate are correctly reproduced. The unprecedented sensitivity of fractions of frad/s is attained for long term runs. This excellent sensitivity and stability put Sagnac gyroscopes at the forefront for fundamental physics, in particular for tests of general relativity and Lorentz violation, where the sensitivity plays the key role to provide reliable data for deeper theoretical investigations.

The debate on gravity theories to extend or modify general relativity is very active today because of the issues related to ultraviolet and infrared behavior of Einstein’s theory. In the first case, we have to address the quantum gravity problem. In the latter, dark matter and dark energy, governing the large-scale structure and the cosmological evolution, seem to escape from any final fundamental theory and detection. The state of the art is that, up to now, no final theory, capable of explaining gravitational interaction at any scale, has been formulated. In this perspective, many research efforts are devoted to test theories of gravity by space-based experiments. Here, we propose straightforward tests by the GINGER experiment, which, being Earth based, requires little modeling of external perturbation, allowing a thorough analysis of the systematics, crucial for experiments where sensitivity breakthrough is required. Specifically, we want to show that it is possible to constrain parameters of gravity theories, like scalar–tensor or Horava–Lifshitz gravity, by considering their post-Newtonian limits matched with experimental data. In particular, we use the Lense–Thirring measurements provided by GINGER to find out relations among the parameters of theories and finally compare the results with those provided by LARES and Gravity Probe B satellites.

Ring laser gyroscopes are top sensitivity inertial sensors used in the measurement of angular rotation. It is well known that the response of such remarkable instruments can in principle access the very low frequency band, but the occurrence of nonlinear effects in the laser dynamics imposes severe limitations in terms of sensitivity and stability. We report here general relationships aimed at evaluating corrections able to effectively account for nonlinear laser dynamics. The so-derived corrections are applied to analyse thirty days of continuous operation of the large area ring laser gyroscope GINGERINO leading to duly reconstruct the Sagnac frequency ω s. The analysis shows that the evaluated corrections affect the measurement of the Earth rotation rate Ω ⊕ at the level of 1 part in 1.5 × 10 3. The null shift term ω ns plays a non negligible role. It turns out proportional to the optical losses μ of the ring cavity, which are changing in time at the level of 10% within the considered period of thirty days. The Allan deviation of estimated Ω ⊕ shows a remarkable long term stability, leading to a sensitivity better than 10 −10 rad/s with more than 10 s of integration time, and approaching (8.5 ± 0.5) × 10 −12 rad/s with 4.5 × 10 5 s of integration time.

Measuring in a single location on Earth its angular rotation rate with respect to the celestial frame, with a sensitivity enabling access to the tiny Lense-Thirring effect, is an extremely challenging task. GINGERINO is a large frame ring laser gyroscope, operating as free running and unattended inside the underground laboratory of the Gran Sasso, Italy. The main geodetic signals, i.e., annual and Chandler wobbles, daily polar motion, and length of the day, are recovered from GINGERINO data using standard linear regression methods, demonstrating a sensitivity approaching tens of frad/s, therefore close to the requirements for Earth-based Lense-Thirring and Lorentz violation tests.