BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Markus B. Fröb (U. Leipzig) DTSTART:20250310T100000Z DTEND:20250310T110000Z DTSTAMP:20260423T024824Z UID:NKUA-HEP/35 DESCRIPTION:Title: Modular Hamiltonians\, relative entropy and the entropy-area law in de S itter spacetime\nby Markus B. Fröb (U. Leipzig) as part of NKUA HEP S eminars\n\n\nAbstract\nIn a very general setting\, entropy quantifies the amount of information about a system that an observer has access to. Howev er\, in contrast to quantum mechanics\, in quantum field theory naive meas ures of entropy are divergent. To obtain finite results\, one needs to con sider measures such as relative entropy\, which can be computed from the m odular Hamiltonian using Tomita--Takesaki theory.\n\nIn this talk\, I will explain the connection between the quantum-mechanical expressions for (re lative) entropy\, the modular Hamiltonian and Tomita--Takesaki theory. I t hen present two examples of modular Hamiltonians that were recently derive d: one for conformal fields in diamond regions of conformally flat spaceti mes (including de Sitter)\, and one for fermions of small mass in diamond regions of two-dimensional Minkowski spacetime. I will give results for th e relative entropy between the de Sitter vacuum state and a coherent excit ation thereof in diamonds and wedges\, and show explicitly that the result satisfies the expected properties for a relative entropy. Finally\, I wil l use thermodynamic relations to determine the local temperature that is m easured by an observer\, and consider the backreaction of the coherent exc itation on the geometry to prove an entropy-area law for de Sitter spaceti me.\n\nBased on arXiv:2308.14797\, 2310.12185\, 2311.13990 and 2312.04629. \n LOCATION:https://researchseminars.org/talk/NKUA-HEP/35/ END:VEVENT END:VCALENDAR