Talk detail

Participant	Tartaglia, Angelo
Institution	Politecnico di Torino - Corso Duca degli Abruzzi 24 - Torino - - Italy

Session	SG1	Accepted		Order	Time
Talk	Oral abstract	Title	GINGER: measuring gravitomagnetic effects by means of light
Co-authors
Abstract	GINGER is a proposal for a new experiment aimed to the detection of the gravito-magnetic Lense-Thirring effect at the surface of the Earth. The technique to be used is based on the behavior of light beams in ring lasers also known as gyrolasers. A three-dimensional set of ringlasers will be mounted on a rigid “monument” and with various orientations in space. The propagation of light in a rotating system is indeed anisotropic; part of the anisotropy is purely kinematical (Sagnac effect), part is due to the gravito-magnetic field of the Earth (gravito-magnetic frame dragging). In a ring laser a light beam travelling counterclockwise is superposed to another beam travelling in the opposite sense. The anisotropy in the propagation leads to standing waves with slightly different frequencies in the two directions; the final effect is a beat frequency proportional to the size of the instrument and its absolute rotation rate in space, including the gravito-magnetic drag. Current laser techniques and the performances of the best existing ring lasers allow at the moment a sensitivity within one order of magnitude of the required accuracy for the detection of gravito-magnetic effects, so that the objective of the proposed measurement is in the range of feasibility and aims to improve the sensitivity of a couple of orders of magnitude with respect to present. The experiment is planned to be built in the Gran Sasso National Laboratories in Italy and is based on an international collaboration among four Italian groups, the Technische Universitaet Muenchen and the Canterbury University in Christchurch (NZ).

Session	SG1	Accepted		Order	Time
Talk	Oral abstract	Title	Relativistic positioning, pulsars and space-time geodesy
Co-authors
Abstract	A fully relativistic method to allow for self-positioning in space-time will be presented. The method is based on the use of at least four independent sources of pulsated electromagnetic signals, whose position in space is given. Good sources can be pulsars and specifically X-ray pulsars; in addition one can consider artificial emitters to be laid down on the surface of celestial bodies of the Solar system. A simple algorithm using linear equations permits the piecewise reconstruction of the space-time trajectory of an observer elaborating on the locally measured time intervals between the arrivals of the pulses from the various sources. The accuracy of the positioning depends both on the quality of the emitters and of the clock carried by the observer. In principle the local structure of space-time can be reconstructed extending geodetic techniques to four dimensions. A simulated example will be presented with four real pulsars and the final issue will be the world-line of a point on the Earth, during three days.