Sensitive gravity-gradiometry with atom interferometry: progress towards an improved determination of the gravitational constant

We here present a high sensitivity gravity-gradiometer based on atom interferometry. In our apparatus, two clouds of laser-cooled rubidium atoms are launched in fountain configuration and interrogated by a Raman interferometry sequence to probe the gradient of gravity field. We recently implemented a high-flux atomic source and a newly designed Raman lasers system in the instrument set-up. We discuss the applications towards a precise determination of the Newtonian gravitational constant G. The long-term stability of the instrument and the signal-to-noise ratio demonstrated here open interesting perspectives for pushing the measurement precision below the 100 ppm level

5D gravity and the discrepant G measurements

It is shown that 5D Kaluza-Klein theory stabilized by an external bulk scalar field may solve the discrepant laboratory G measurements. This is achieved by an effective coupling between gravitation and the geomagnetic field. Experimental considerations are also addressed.Comment: 13 pages, to be published in: Proceedings of the 18th Course of the School on Cosmology and Gravitation: The gravitational Constant. Generalized gravitational theories and experiments (30 April-10 May 2003, Erice). Ed. by G. T. Gillies, V. N. Melnikov and V. de Sabbata, (Kluwer), 13pp. (in print) (2003

The Uncertainty in Newton's Constant and Precision Predictions of the Primordial Helium Abundance

The current uncertainty in Newton's constant, G_N, is of the order of 0.15%. For values of the baryon to photon ratio consistent with both cosmic microwave background observations and the primordial deuterium abundance, this uncertainty in G_N corresponds to an uncertainty in the primordial 4He mass fraction, Y_P, of +-1.3 x 10^{-4}. This uncertainty in Y_P is comparable to the effect from the current uncertainty in the neutron lifetime, which is often treated as the dominant uncertainty in calculations of Y_P. Recent measurements of G_N seem to be converging within a smaller range; a reduction in the estimated error on G_N by a factor of 10 would essentially eliminate it as a source of uncertainty in the calculation of the primordial 4He abundance.Comment: 3 pages, no figures, fixed typos, to appear in Phys. Rev.

Validity of general mental ability for the prediction of job performance and training success in Germany: A meta-analysis

Hülsheger UR, Maier GW, Stumpp T. Validity of general mental ability for the prediction of job performance and training success in Germany: A meta-analysis. International Journal of Selection and Assessment. 2007;15(1):3-18.A meta-analysis into the operational validity of general mental ability (GMA) measures in Germany is presented. The meta-analysis addresses the question whether findings of US and European meta-analyses are generalizable to Germany given the differences in the education systems of these countries. The high level of differentiation in the German educational system is expected to enhance the homogeneity of applicant pools resulting in a low level of variability in predictor scores which reduces the observed GMA performance relationships. Our analysis is based on 54 independent German articles and unpublished reports. Results indicated an operational validity of rho = .467 for training success (k = 90; N = 11,969) and rho = .534 for job performance (k = 9; N = 746). Moderator analyses showed that job complexity and the year of publication are relevant moderator variables, with lower job complexity levels and older studies being associated with higher operational validities. Findings suggest that overall German operational validities are comparable with findings in the United States or other European countries. However, for training success operational GMA validities are slightly lower in Germany compared with US or European meta-analyses

The nuclear liquid-gas phase transition: Present status and future perspectives

More than two decades ago, the van der Waals behavior of the nucleon -nucleon force inspired the idea of a liquid-gas phase transition in nuclear matter. Heavy-ion reactions at relativistic energies offer the unique possibility for studying this phase transition in a finite, hadronic system. A general overview of this subject is given emphasizing the most recent results on nuclear calorimetry. (orig.)Available from TIB Hannover: RO 801(96-31) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman