1988/01/20 by V. Subrahmanyam, V Subrahmanyam, Mustansir Barma +1 · 1 citation
Physics and Astronomy · #Physics of Superconductivity and Magnetism #Quantum chaos and dynamical systems #Quantum many-body systems
paper · doi:10.1088/0022-3719/21/2/002
crossref issued 1988/01/20 · crossref published 1988/01/20 · crossref published-print 1988/01/20 · openalex publication_date 1988/01/20 · crossref published-online 2000/11/21 · crossref created 2002/07/26 · crossref deposited 2020/04/10 · openalex created_date 2025/10/10 · crossref indexed 2026/07/31 · openalex updated_date 2026/07/31
It is pointed out that homogeneously mixed-valent and excitonic insulator phases proposed earlier for the Falicov-Kimball model break a local symmetry of the Hamiltonian. An Elitzur-type proof on the impossibility of spontaneously breaking a local symmetry is given to show that such phases are not possible at nonzero temperature. At zero temperature, the possibility of breaking a local symmetry is demonstrated in a related model, but it is argued that such symmetry breaking does not occur in the Falicov-Kimball model.