EPJB Colloquium - Fulfillment of sum-rules and Goldstone modes in many body theories

Schematic representation of the two body mean field

This EPJ B Colloquium article explores applications of the Self-Consistent Random Phase Approximation (SCRPA) approach to Fermi systems with a continuously broken symmetry. Correlations beyond those considered by standard Random Phase Approximation (RPA) are summed up, thereby correcting for the quasi-boson approximation in standard RPA.

Desirable properties of standard RPA, such as fulfilment of the energy-weighted sum rule and the appearance of Goldstone (zero) modes, are preserved. The authors show theoretically as well as numerically, for a model case, that SCRPA maintains all the properties of standard RPA for practically all instances of spontaneously-broken symmetries. A simpler approximate form of SCRPA, the so-called renormalised RPA, also exhibits these properties. The SCRPA equations are first outlined as an eigenvalue problem, and then it is shown how an equivalent many-body Green’s function approach can be formulated.

We found this possibility of publication very well suited to our needs, the editors were always available with a very efficient follow-up of our demands. All the documents guaranteeing the peer reviewing and the authorizations of publication are clear. The only drawback is the visible contradiction between the author instructions for the word versions and the website for testing the PDF version, but even there the editors help us very quickly and efficiently.

Jean-Marc Bordy, CEA Saclay, France
Co-Editor EPJ Web of Conferences vol. 124, 2016

ISSN: 2100-014X (Electronic Edition)

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