Relativistic string-based electron correlation methods

Highly-accurate relativistic electronic-structure studies on heavy elements require general and efficient many-body methods. In order to achieve spectroscopic accuracy, the description of in particular dynamic electron correlation is of crucial importance. Modern wavefunction-based electron correlation approaches of high efficiency are typically based on a string representation of many-particle quantities. The focus in this chapter lies on the introduction to a suite of new relativistic electronic-structure methods which treat electron correlation and relativistic effects on the same footing and to a number of concepts of importance for relativistic many-body methods. Several applications to small heavy-element systems are discussed where the presented methods are put to critical tests in direct comparison with other modern approaches of relativistic electronic-structure theory.