Positronium is the simplest bound state, built of an electron and a positron. Studies of
positronium in vacuum and its decays in medium tell us about quantum electrodynamics …

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 …

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

Discrete symmetries play an important role in particle physics with violation of CP connected
to the matter-antimatter imbalance in the Universe. We report the most precise test of P, T …

We report a new measurement of the n= 2 Lamb shift in Muonium. Our result of 1047.2 (2.3)
stat (1.1) syst MHz comprises an order of magnitude improvement upon the previous best …

We report the results of a new measurement of the positronium 2 S 3 1→ 2 P 3 2 (ν 2)
interval. Using a modified experimental arrangement we have significantly reduced the …

We consider a general relativistic fermion antifermion pair that they interact via an attractive
Coulomb type interparticle interaction potential in the 2+ 1 dimensional spacetime …

We generalize the Unruh-DeWitt detector model to second quantization. We illustrate this
model by applying it to an excited particle in a superposition of relativistic velocities. We …

The Dirac–Coulomb equation with positive-energy projection is solved using explicitly
correlated Gaussian functions. The algorithm and computational procedure aims for a parts …

Precision study of few-electron, high-Z ions is a privileged field for probing high-field, bound-
state quantum electrodynamics (BSQED). However, the accuracy of such tests is plagued by …