This article reviews recent developments in tests of fundamental physics using atoms and
molecules, including the subjects of parity violation, searches for permanent electric dipole …

Positronium (Ps) is an exotic hydrogenic atom composed of an electron bound to a positron
via the Coulomb force. Being composed of two low-mass leptons, positronium is, for all …

Einstein's general theory of relativity from 1915 1 remains the most successful description of
gravitation. From the 1919 solar eclipse 2 to the observation of gravitational waves 3, the …

Charged lepton system symmetry under combined charge, parity, and time-reversal
transformation (CPT) remains scarcely tested. Despite stringent quantum-electrodynamic …

The photon—the quantum excitation of the electromagnetic field—is massless but carries
momentum. A photon can therefore exert a force on an object upon collision. Slowing the …

In 1928, Dirac published an equation that combined quantum mechanics and special
relativity. Negative-energy solutions to this equation, rather than being unphysical as initially …

The field of experimental positronium physics has advanced significantly in the last few
decades, with new areas of research driven by the development of techniques for trapping …

Antihydrogen atoms with K or sub-K temperature are a powerful tool to precisely probe the
validity of fundamental physics laws and the design of highly sensitive experiments needs …

Abstract The Facility for Antiproton and Ion Research (FAIR) will be the accelerator-based
flagship research facility in many basic sciences and their applications in Europe for the …

The observation of hyperfine structure in atomic hydrogen by Rabi and co-workers,, and the
measurement of the zero-field ground-state splitting at the level of seven parts in 1013 are …