BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Chong Wang (Perimeter Institute) DTSTART:20200518T183000Z DTEND:20200518T193000Z DTSTAMP:20260423T024740Z UID:Kadanoff/3 DESCRIPTION:Title: A theory of deconfined pseudo-criticality\nby Chong Wang (Perimeter I nstitute) as part of Kadanoff seminars\n\n\nAbstract\nIt has been proposed that the deconfined criticality in (2+1)d - the quantum phase transition between a Neel anti-ferromagnet and a valence-bond-solid (VBS) - may actua lly be pseudo-critical\, in the sense that it is a weakly first-order tran sition with a generically long correlation length. The underlying field th eory of the transition would be a slightly complex (non-unitary) fixed poi nt as a result of fixed points annihilation. This proposal was motivated b y existing numerical results from large scale Monte-Carlo simulations as w ell as conformal bootstrap. However\, an actual theory of such complex fix ed point\, incorporating key features of the transition such as the emerge nt SO(5) symmetry\, is so far absent. Here we propose a Wess-Zumino-Witten (WZW) nonlinear sigma model with level k=1\, defined in 2+ϵ dimensions\, with target space S^(3+ϵ) and global symmetry SO(4+ϵ). This gives a for mal interpolation between the deconfined criticality at d=3 and the SU(2)_ 1 WZW theory at d=2 describing the spin-1/2 Heisenberg chain. The theory c an be formally controlled\, at least to leading order\, in terms of the in verse of the WZW level 1/k. We show that at leading order\, there is a fix ed point annihilation at d*≈2.77\, with complex fixed points above this dimension including the physical d=3 case. The pseudo-critical properties such as correlation length\, scaling dimensions and the drifts of scaling dimensions as the system size increases\, calculated crudely to leading or der\, are qualitatively consistent with existing numerics.\n LOCATION:https://researchseminars.org/talk/Kadanoff/3/ END:VEVENT END:VCALENDAR