Links for 2012-03-31

The search for ways to unify and understand physical phenomena goes back to Kaluza and Klein, who in the 1920s tried to combine electromagnetism with gravity by adding a fourth spatial dimension to the usual three (plus time). More recent theoretical work has suggested that a theory of everything may need 11 spacetime dimensions. Boada et al. are suggesting an experimental strategy for investigating how matter behaves in extra dimensions. Their idea is to encode a fourth spatial dimension in an internal degree of freedom offered by atoms trapped in an optical lattice, and do it in such a way as to exactly reproduce the physics described by a 4D Hamiltonian. The authors show two ways of observing such effects: one is to look for single-particle effects, such as rates of decay of excited states as a function of dimensionality; another is to search for many-body effects such as insulator-to-superfluid transitions that depend on the number of dimensions.

Experimental work on cold, trapped metastable noble gases is reviewed. The aspects which distinguish work with these atoms from the large body of work on cold, trapped atoms in general is emphasized. These aspects include detection techniques and collision processes unique to metastable atoms. Several experiments exploiting these unique features in fields including atom optics and statistical physics are described. Precision measurements on these atoms including fine structure splittings, isotope shifts, and atomic lifetimes are also discussed.

Recent progress and future prospects of matter-wave interferometry with complex organic molecules and inorganic clusters are reviewed. Three variants of a near-field interference effect, based on diffraction by material nanostructures, at optical phase gratings, and at ionizing laser fields are considered. The theoretical concepts underlying these experiments and the experimental challenges are discussed. This includes optimizing interferometer designs as well as understanding the role of decoherence. The high sensitivity of matter-wave interference experiments to external perturbations is demonstrated to be useful for accurately measuring internal properties of delocalized nanoparticles. The prospects for probing the quantum superposition principle are investigated in the limit of high particle mass and complexity.