The new formalism of the relativistic gauge-invariant perturbation theory (RMBPT-ODF) with optimized Dirac-Fock approximation and a generalized energy approach is applied to study energy, radiation, spectroscopic characteristics group heavy atomic systems, in particular, levels transition probabilities oscillator strengths transitions 4f7(8S)6s2 8S7/2 4f7(8S)6s6p 8P5/2,7.2,9.2, 4f7(8S)6s7p 8P5/...

It is shown how to adapt the non-perturbative coupled cluster method of many-body theory so that it may be successfully applied to Hamiltonian lattice SU (N) gauge theories. The procedure involves first writing the wavefunctions for the vacuum and excited states in terms of linked clusters of gauge invariant excitations of the strong coupling vacuum. The fundamental approximation scheme then co...

Hamiltonian light-front quantum field theory constitutes a framework for the non-perturbative solution of invariant masses and correlated parton amplitudes of self-bound systems. By choosing light-front gauge and adopting a basis function representation, we obtain a large, sparse, Hamiltonian matrix for mass eigenstates of gauge theories that is solvable by adapting the ab initio no-core method...

This report covers developments in the theory and application of many-body perturbation theory to molecular systems during the period June 2003 through to May 2005. It thus continues three earlier reviews in this series which, in turn, built on my report, written about twenty-five years ago, for a previous Specialist Periodical Reports series published in 1981. Applications of many-body perturb...

We give a summary of recent progress in the field of electronic structure calculations for materials with strong electronic Coulomb correlations. The discussion focuses on developments beyond the by now well established combination of density functional and dynamical mean field theory dubbed “LDA+DMFT”. It is organized around the description of dynamical screening effects in the solid. Indeed, ...

The carrier-density dependence of the photoemission spectrum of the Holstein many-polaron model is studied using cluster perturbation theory combined with an improved cluster diagonalization by Chebychev expansion.

A procedure is given for calculating transition amplitudes that are equal in the length and velocity forms for transitions in atoms with one valence electron within the framework of relativistic many-body perturbation theory starting from the Dirac-Hartree-Fock approximation. This procedure is applied to obtain formindependent secondand third-order dipole matrix elements for the principal trans...

Stark-induced amplitudes for the 6P1/2 − 7P1/2 transition in Tl I are calculated using the relativistic SD approximation in which single and double excitations of Dirac-Hartree-Fock levels are summed to all orders in perturbation theory. Our SD values αS = 368 a 3 0 and |βS |= 298 a 3 0 are in good agreement with the measurements αS=377(8) a 3 0 and βS = 313(8) a 3 0 by D. DeMille, D. Budker, a...