O(m alpha^7 ln(alpha)^2) corrections to positronium energy levels

We present a calculation of the O(m alpha^7 ln(alpha)^2) corrections to positronium energy levels. The result is used to estimate the current uncertainty in theoretical predictions of the positronium spectrum.Comment: revtex, 12 pages, result correcte

Delbruck scattering and the g-factor of a bound electron

The leading contribution of the light-by-light scattering effects to g-factor of a bound electron is derived. The corresponding amplitude is expressed in terms of low-energy Delbruck scattering of a virtual photon. The result reads Delta g = (7/216) alpha (Z alpha)^5

Top quark production at threshold with O(alpha_s^2) accuracy

We calculate the next-to-next-to-leading order correction to the cross section for top quark pair production in e+e- annihilation in the threshold region, resumming all O [ (alpha_s/beta)^n (alpha_s^2, beta^2, alpha_s beta) ] terms of perturbation series. We find that the magnitude of the NNLO correction is comparable to the size of the NLO corrections.Comment: 15 pages, Latex, one figure, some misprints correcte

Virtual annihilation contribution to orthopositronium decay rate

Order alpha^2 contribution to the orthopositronium decay rate due to one-photon virtual annihilation is found to be delta Gamma = (alpha/pi)^2 (pi^2 ln(alpha) - 0.8622(9))Gamma_LO.Comment: 2 pages, no figure

Ionization Potential of the Helium Atom

Ground state ionization potential of the He^4 atom is evaluated to be 5 945 204 221 (42) MHz. Along with lower order contributions, this result includes all effects of the relative orders alpha^4, alpha^3*m_e/m_alpha and alpha^5*ln^2(alpha).Comment: 4 page

O(alpha^3 ln alpha) corrections to muonium and positronium hyperfine splitting

We compute O(alpha^3 ln alpha) relative corrections to the ground state hyperfine splitting of a QED two body bound state with different masses of constituents. The general result is then applied to muonium and positronium. In particular, a new value of the muon to electron mass ratio is derived from the muonium ground state hyperfine splitting.Comment: 4 pages, revte

Quantum Electrodynamics of the Helium Atom

Using singlet S states of the helium atom as an example, I describe precise calculation of energy levels in few-electron atoms. In particular, a complete set of effective operators is derived which generates O(m*alpha^6) relativistic and radiative corrections to the Schr"odinger energy. Average values of these operators can be calculated using a variational Schr"odinger wave function.Comment: 23 pages, revte