BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:K. Narayan (Chennai Maths Institute) DTSTART:20230801T190000Z DTEND:20230801T203000Z DTSTAMP:20260423T042508Z UID:UKYhepth/59 DESCRIPTION:Title: de Sitter space\, extremal surfaces and time-entanglement\nby K. Nar ayan (Chennai Maths Institute) as part of Theoretical Physics Seminars (Ke ntucky)\n\nLecture held in CP 303.\n\nAbstract\nI will describe extremal s urfaces in de Sitter space anchored at the future boundary I+. Since such surfaces do not return\, they require extra data or boundary conditions in the past (interior). In entirely Lorentzian de Sitter spacetime\, this le ads to future-past timelike surfaces stretching between I±. Apart from an overall −i factor (relative to spacelike surfaces in AdS) their areas a re real and positive. With a no-boundary type boundary condition\, the top half of these timelike surfaces joins with a spacelike part on the hemisp here giving a complex-valued area. Motivated by these\, we describe two as pects of “time-entanglement” in simple toy models in quantum mechanics . One is based on a future-past thermofield double type state entangling t imelike separated states\, which leads to entirely positive structures. An other is based on the time evolution operator and reduced transition ampli tudes\, which leads to complex-valued entropy. There are close parallels w ith pseudo-entropy which we will clarify.\n LOCATION:https://researchseminars.org/talk/UKYhepth/59/ END:VEVENT END:VCALENDAR