Excited-state quantum phase transitions in the anharmonic Lipkin-Meshkov-Glick model: Static aspects Gamito, J. Arias, J. M. Pérez Fernández, P. Pérez Bernal, Francisco The basic Lipkin-Meshkov-Glick model displays a second-order ground-state quantum phase transition and an excited-state quantum phase transition (ESQPT). The inclusion of an anharmonic term in the Hamiltonian implies a second ESQPT of a different nature. We characterize this ESQPT using the mean field limit of the model. The alternative ESQPT, associated with the changes in the boundary of the finite Hilbert space of the system, can be properly described using the order parameter of the ground-state quantum phase transition, the energy gap between adjacent states, the participation ratio, and the quantum fidelity susceptibility. 2022-12-16T10:05:46Z 2022-12-16T10:05:46Z 2022-10-17 journal article Gamito, J... [et al.]. Excited-state quantum phase transitions in the anharmonic Lipkin-Meshkov-Glick model: Static aspects. PHYSICAL REVIEW E 106, 044125 (2022). DOI: [10.1103/PhysRevE.106.044125] https://hdl.handle.net/10481/78499 10.1103/PhysRevE.106.044125 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional American Physical Society