BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Tadahiro Miyao (Hokkaido University) DTSTART:20260922T140000Z DTEND:20260922T150000Z DTSTAMP:20260712T200404Z UID:IAMP_seminars/198 DESCRIPTION:Title: From Hubbard to Heisenberg at Half Filling\nby Tadahiro Miyao (Hokkaido University) as part of One world IAMP mathematical physics semin ar\n\n\nAbstract\nThe half-filled repulsive Hubbard model is commonly repl aced\, in the strong-coupling regime\, by an antiferromagnetic Heisenberg model at the superexchange scale (J_0(U)=4t^2/U). This replacement is a s tandard principle in condensed matter physics\, but its justification at t he level of canonical Gibbs states requires more than identifying the lead ing effective Hamiltonian.\n\nIn this talk\, I will present a quantitative Hubbard-to-Heisenberg comparison for thermodynamic quantities. We compar e the canonical pressure densities of the Hubbard model and the correspond ing Heisenberg model on finite tori\, with an error term for the pressure density that is independent of the system size. The proof combines a stro ng-coupling Lie--Schwinger/Schrieffer--Wolff diagonalisation with a defect decomposition controlling sectors with empty or doubly occupied sites. A s consequences\, we obtain staggered-magnetisation comparison in fixed pos itive fields and suppression of charge defects.\n LOCATION:https://researchseminars.org/talk/IAMP_seminars/198/ END:VEVENT END:VCALENDAR