A new two-step renormalization procedure is proposed. In the first step, the effects of high-energy states are considered in the conventional (Feynman) perturbation theory. In the second step, the coupling to many-body states is eliminated by a similarity transformation. The resultant effective Hamiltonian contains only interactions which do not change particle number. It is subject to numerica...

Based on potential–energy curves that were derived from ab initio calculations within the framework of many-body perturbation theory, mixed quantum–classical simulations have been performed to understand the dynamics of the photodesorption process of iodine from KI(100). Dissipation and recoil processes were included by adding a surface oscillator to the ab initio potentials. Using this approac...

We construct an equation-of-state for nuclear matter based on the chiral Lagrangian. The relevant scales are discussed and an effective chiral power expansion scheme, which is constructed to work around the nuclear saturation density, is presented. A realistic equation-of-state is obtained by adjusting one free parameter, when the leading and subleading terms in the expansion are included. The ...

An efficient model describing the He-atom scattering process is presented. The He–surface interaction potential is calculated from first principles by exploiting second-order Rayleigh–Schrödinger many-body perturbation theory and fitted by using a variety of pairwise interaction potentials. The attractive part of the fitted analytical form has been upscaled to compensate the underestimation of ...

The long-range quadrupole-quadrupole R−5 and leading dispersion R−6 interactions between all pairs of excited Hg 6s6p P0, P1, P2, and P1 atoms are determined. The quadrupole moments are calculated using the ab initio relativistic configuration-interaction method coupled with many-body perturbation theory. The van der Waals coefficients are approximated using previously calculated static polariz...

We calculate the low-lying spectra of heavy tin isotopes from A = 120 to A = 130 using the 2s1d0g7/20h11/2 shell to define the model space. An effective interaction has been derived using 132Sn as closed core employing perturbative many-body techniques. We start from a nucleon–nucleon potential derived from modern meson exchange models. This potential is in turn renormalized for the given mediu...

We show that the existence of algebraic forms of quantum, exactly-solvable, completely-integrable A−B−C−D and G2, F4, E6,7,8 Olshanetsky-Perelomov Hamiltonians allow to develop the algebraic perturbation theory, where corrections are computed by pure linear algebra means. A Lie-algebraic classification of such perturbations is given. In particular, this scheme admits an explicit study of anharm...

Extensive calculations of the electric-dipole matrix elements in alkali-metal atoms are conducted using the relativistic all-order method. This approach is a linearized version of the coupled-cluster method, which sums infinite sets of many-body perturbation theory terms. All allowed transitions between the lowest ns, np1/2, np3/2 states and a large number of excited states are considered in th...

Energies, transition probabilities, and lifetimes are calculated for 3d states in Ca-like ions with nuclear charges Z ranging from 22 to 100. Relativistic many-body perturbation theory ~MBPT!, including the Breit interaction, is used to evaluate retarded M1 and E2 matrix elements. The calculations start from a 1s2s2p3s3p Dirac-Fock potential. First-order perturbation theory is used to obtain in...

We construct an equation-of-state for nuclear matter based on the chiral Lagrangian. The relevant scales are discussed and an effective chiral power expansion scheme, which is constructed to work around the nuclear saturation density, is presented. A realistic equation-of-state is obtained by adjusting one free parameter, when the leading and subleading terms in the expansion are included. The ...