C. Lämmerzahl

Tests of Lorentz invariance using hydrogen molecules

We discuss the consequences of Lorentz violation (as expressed within the Lorentz-violating extension of the standard model) for the hydrogen molecule, which represents a generic model of a molecular binding. Lorentz-violating shifts of electronic, vibrational and rotational energy levels, and of the internuclear distance are calculated. This offers the possibility of obtaining improved bounds on Lorentz invariance by experiments using molecules.

RUBIDIUM BOSE–EINSTEIN CONDENSATE UNDER MICROGRAVITY

Weightlessness promises to substantially extend the science of quantum gases toward presently inaccessible regimes of low temperatures, macroscopic dimensions of coherent matter waves, and enhanced duration of unperturbed evolution. With the long-term goal of studying cold quantum gases on a space platform, we currently focus on the implementation of an 87Rb Bose–Einstein condensate (BEC) experiment under microgravity conditions at the ZARM drop tower in Bremen (Germany). Special challenges in the construction of the experimental setup are posed by a low volume of the drop capsule (< 1 m3) as well as critical vibrations during capsule release and peak decelerations of up to 50 g during recapture at the bottom of the tower. All mechanical and electronic components have thus been designed with stringent demands on miniaturization, mechanical stability and reliability. Additionally, the system provides extensive remote control capabilities as it is not manually accessible in the tower two hours before and during the drop. We present the robust system and show results from first tests at the drop tower.

ATOMIC QUANTUM SENSORS IN SPACE

In this article we present actual projects concerning high resolution measurements developed for future space missions based on ultracold atoms at the Institut fur Quantenoptik (IQ) of the University of Hannover. This work involves the realization of a Bose–Einstein condensate in a microgravitational environment and of an inertial atomic quantum sensor.

The Space-Time Asymmetry Research (STAR) program

Space-Time Asymmetry Research (STAR) is a proposed satellite mission that aims for significantly improved tests of fundamental space-time symmetry and the foundations of special and general relativity. In the current concept, STAR comprises a series of three subsequent missions with increasingly advanced instruments performing clock to clock comparisons. While the first STAR missions will perform Kennedy-Thorndike (KT) and Michelson-Morley (MM) experiments, later missions will focus on fundamental gravitational physics by precision measurement of gravitational redshift, time dilation and Local Position Invariance (LPI). Compared to previous experimental accuracy, STAR aims for an improvement of at least two orders of magnitude. The STAR1 mission will measure the constancy of the speed of light to one part in 10-17 and derive the Kennedy Thorndike coefficient of the Mansouri-Sexl test theory to 7 × 10-10. The KT experiment will be performed by comparison of an atomic or molecular frequency reference with a length reference (highly stable cavity made e.g. from ultra low expansion (ULE) glass ceramics) during flight around Earth with an orbital velocity of 7 km/s. The corresponding sensitivity to a boost dependent violation of Lorentz invariance as modeled by the KT term in the Mansouri-Sexl test theory or a Lorentz violating extension of the standard model (SME) will be significantly enhanced as compared to Earth-based experiments. The space environment will enhance the measurement precision such that an overall improvement by a factor of 400 over current Earth bound experiments is expected. The STAR1 philosophy is to realize a fast, small - and therefore cheap - mission with a high scientific output, also providing the instrument technology and the spacecraft for the subsequent STAR missions, which plan to use different optical frequency standards. The 180 kg small satellite will be attitude, vibration and temperature controlled. The power consumption of the whole spacecraft will be less than 185 W. The launch of STAR1 is foreseen for 2015, the follow-on missions will be flown with an overlap with the previous mission by two to three years. Each mission has a maximum duration of 5 years (from mission set up to data acquisition) which permits students to experience the full mission lifecycle. Education and training of undergraduate and graduate students is a specific mission goal.

mSTAR: Testing Lorentz invariance in a low Earth orbit with high performance optical frequency standards

fundamental physics test, Kennedy-Thorndike, clocks, ultra-stable cavities, iodine spectroscopy, space instrumentation