BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Miguel Montero (Harvard U.) DTSTART:20200618T140000Z DTEND:20200618T150000Z DTSTAMP:20260423T024806Z UID:HEPTUW/2 DESCRIPTION:Title: N othing is certain in string compactifications\nby Miguel Montero (Harv ard U.) as part of HEP seminars TU Wien (Vienna)\n\n\nAbstract\nA bubble o f nothing is a spacetime instability where a compact dimension collapses. After nucleation\, it expands at the speed of light\, leaving "nothing" be hind. There are a couple of robust mechanisms that can prevent the existen ce of a bubble: Either it is not energetically favourable to produce them \, or there is a topological obstruction to their existence. The latter is often the case with SUSY-preserving boundary conditions. I will explain how to understand the topological obstruction in detail using bordism\, wh ich will show that it is very generically absent even for a SUSY-compatibl e spin structure. As a proof of principle\, we construct and embed in stri ng theory an explicit bubble of nothing for a T3 with completely periodic (SUSY-compatible) spin structure. There is a dynamical obstruction due to a positive energy theorem which is circumvented by higher-derivative cor rections. Our model can be embedded in string theory. Our techniques can be used to construct a plethora of bubbles of nothing for spaces of intere st like CY6's\, G2 manifolds\, or Sasaki-Einstein manifolds. We will expla in how to study and circumvent the topological and dynamical obstruction i n these cases. Avoiding the dynamical obstruction means avoiding a modifie d energy condition which might be related to the Weak Gravity Conjecture. Our results lend support to the conjecture that any \nnon-supersymmetric vacuum of quantum gravity is ultimately unstable.\n LOCATION:https://researchseminars.org/talk/HEPTUW/2/ END:VEVENT END:VCALENDAR