Dipartimento di Matematica, Sapienza Università di Roma, Sala di Consiglio
Giovedì 9 Febbraio 2023, ore 16:00
*Speaker:* Daniel Ueltschi, University of Warwick
*Title*: Quantum spin chains, loop representations, dimerisation
*Abstract:* In contrast to their classical counterparts, one-dimensional
quantum spin systems are interesting, they have intriguing behaviour, and
they are difficult to study. I will describe a family of systems with
nearest-neighbour interactions and O(n) symmetry. Its ground state phase
diagram is expected to have a rich structure. For large spins it is
possible to prove the occurrence of dimerisation in an open domain. The
proof involves a loop representation and the method of cluster expansions.
This is joint work with Jakob Bjornberg, Peter Muhlbacher, and Bruno
Nachtergaele.