Higher order (α/π)2 (Z α)6 logarithmic corrections to the hydrogen Lamb shift are calculated. The results obtained show the two-loop contribution has a very peculiar behavior, and significantly alter the theoretical predictions for low lying S-states. PACS numbers 31.30 Jv, 12.20 Ds, 06.20 Jr, 32.10 Fn Typeset using REVTEX E-mail address: [email protected]

On the analogy with the Lamb shift, we study the vacuum effect that proton’s electric field interacts with virtual particles in the vacuum. We find a possible quantum instability that triggered by an external force, proton’s electric field interacting with virtual particles spontaneously induces a quantum force that back reacts on the proton in the direction of the external trigger force. Such ...

This thesis reports on the implementation of the Fröhlich Hamiltonian in an ultracold atomic mixture. To this end, impurity atoms are immersed into a macroscopic Bose-Einstein condensate (BEC). The impurities are tightly trapped in one direction by a species-selective optical potential. In this scenario their coupling to the excitations (phonons) of the BEC causes energy shifts of their externa...

We calculate hard spin-independent three-loop radiative corrections to energy levels in muonium and positronium which are due with polarization insertions two-photon exchange diagrams. These could be relevant for the new generation of precise $1S\text{\ensuremath{-}}2S$ $2S\text{\ensuremath{-}}2P$ measurements positronium.