Lorentz breaking Effective Field Theory and observational tests

Analogue models of gravity have provided an experimentally realizable test field for our ideas on quantum field theory in curved spacetimes but they have also inspired the investigation of possible departures from exact Lorentz invariance at microscopic scales. In this role they have joined, and sometime anticipated, several quantum gravity models characterized by Lorentz breaking phenomenology. A crucial difference between these speculations and other ones associated to quantum gravity scenarios, is the possibility to carry out observational and experimental tests which have nowadays led to a broad range of constraints on departures from Lorentz invariance. We shall review here the effective field theory approach to Lorentz breaking in the matter sector, present the constraints provided by the available observations and finally discuss the implications of the persisting uncertainty on the composition of the ultra high energy cosmic rays for the constraints on the higher order, analogue gravity inspired, Lorentz violations.Comment: 47 pages, 4 figures. Lecture Notes for the IX SIGRAV School on "Analogue Gravity", Como (Italy), May 2011. V.3. Typo corrected, references adde

Germanium gamma-ray spectrometer PGS for the MARS-96 mission

The Precision Gamma-ray Spectrometer (PGS) on the Russian MARS-96 spacecraft is designed to measure 0.1--8 MeV gamma rays in order to determine the elemental composition of the Martian surface, to study solar flares, and to determine energy spectra and times of arrival of gamma-ray bursts. The PGS instrument contains two high-purity, n-type germanium crystals, each similar to the one used on the Mars Observer mission. Each crystal is contained in a titanium can with Helicoflex cryogenic metal seals. An annealing capability allows repair of radiation damage. The detectors are cooled via nitrogen heat pipes attached to a passive radiator mounted on the back side of a solar panel. The radiators are designed to keep the Ge detectors below 100 K during the interplanetary flight. The electronics include first-stage electronics mounted on each crystal can and 4096-channel pulse height analyzers. Two parallel channels of electronics are provided and can be cross-switched by telecommands. In November 1995 integration of the flight detectors with flight electronics and testing of the complete system cooled by the passive radiator were successfully completed. The energy resolution degrades to about 3 keV in the flight configuration. Warming the radiators indicated that for the worst case when the radiator views Mars at the equator the maximum temperature of the detectors will be limited by the diode action of the heat pipes to 118 K. Extensive calibrations with radioactive sources are in progress. The authors conclude that they have an improved design for planetary and gamma-ray burst studies and the PGS instrument is ready for launch in November 1996