32 research outputs found
Ground-state hyperfine structure of H-, Li-, and B-like ions in middle-Z region
The hyperfine splitting of the ground state of H-, Li-, and B-like ions is
investigated in details within the range of nuclear numbers Z = 7-28. The
rigorous QED approach together with the large-scale configuration-interaction
Dirac-Fock-Sturm method are employed for the evaluation of the
interelectronic-interaction contributions of first and higher orders in 1/Z.
The screened QED corrections are evaluated to all orders in (\alpha Z)
utilizing an effective potential approach. The influence of nuclear
magnetization distribution is taken into account within the single-particle
nuclear model. The specific differences between the hyperfine-structure level
shifts of H- and Li-like ions, where the uncertainties associated with the
nuclear structure corrections are significantly reduced, are also calculated.Comment: 22 pages, 11 tables, 2 figure
Floquet-Markov description of the parametrically driven, dissipative harmonic quantum oscillator
Using the parametrically driven harmonic oscillator as a working example, we
study two different Markovian approaches to the quantum dynamics of a
periodically driven system with dissipation. In the simpler approach, the
driving enters the master equation for the reduced density operator only in the
Hamiltonian term. An improved master equation is achieved by treating the
entire driven system within the Floquet formalism and coupling it to the
reservoir as a whole. The different ensuing evolution equations are compared in
various representations, particularly as Fokker-Planck equations for the Wigner
function. On all levels of approximation, these evolution equations retain the
periodicity of the driving, so that their solutions have Floquet form and
represent eigenfunctions of a non-unitary propagator over a single period of
the driving. We discuss asymptotic states in the long-time limit as well as the
conservative and the high-temperature limits. Numerical results obtained within
the different Markov approximations are compared with the exact path-integral
solution. The application of the improved Floquet-Markov scheme becomes
increasingly important when considering stronger driving and lower
temperatures.Comment: 29 pages, 7 figure