firstname = "Victor"
lastname = "Tselyaev"
email = "tselyaev@nuclpc1.phys.spbu.ru"
affiliation = "Saint-Petersburg State University"
city = "Saint-Petersburg"
country = "Russia"
passportname = ""
birthday = ""
citizenship = ""
passportnumber = ""
passportissued = ""
passportexpire = ""
workplace = ""
workaddress = ""
visadates = ""
talktitle = "Spurious states and stability condition in the extended RPA theories"
section = "B - Nuclear physics"
talkabstract = "Theoretical description of the properties of the ground and excited states of atomic nuclei within the framework of the modern microscopic approaches leads to the problems of the spurious (ghost) states and of convergence and stability of the model's solutions. In practice, the last problems arise in the calculations using a large model configuration space. The extended RPA (random phase approximation) theories are analyzed here from the point of view of these problems. Two kinds of such theories are considered: the quasiparticle-phonon coupling model within the time-blocking approximation and the second RPA. It is shown that stability is ensured by making use of the subtraction method proposed previously (generalized Thouless theorem). The spurious states are eliminated with the help of a combination of the subtraction method and the projection technique. These results are illustrated by the calculations of the low-lying states in 208-Pb."
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