ABSTRACT
The phase transitions of the Lipkin model with particle-particle and particle-hole channels are established, by means of the https://www.w3.org/1998/Math/MathML"> SU ( 2 ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429076619/c00d8d0d-b3a0-431a-a3c2-e044ea15f7a5/content/eq2829.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> coherent states and the catastrophe formalism. It is shown that in different regions of the control parameter space the even and odd spin coherent states describe either the ground or the first excited states.
