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SUMMARY:Time Dependent Flux Backgrounds in type IIB supergravity
DTSTART:20260416T123000Z
DTEND:20260416T133000Z
DTSTAMP:20260416T182200Z
UID:indico-event-1798@indico.dfa.unipd.it
DESCRIPTION:Speakers: Ahmed Rakin Kamal (Masaryk University)\n\nWe analyti
 cally construct families of type IIB supergravity backgrounds in ten dimen
 sions in which the four-dimensional metric is time dependent\, while the s
 ix-dimensional internal space is an arbitrary compact Calabi-Yau manifold 
 (with no restriction on holonomy) up to an overall time-dependent scale fa
 ctor. Our solutions include cases with all fluxes (three-form and self-dua
 l five-form) switched on\, as well as cases with subsets of these fluxes\,
  together with a time-dependent axiodilaton in most cases. These construct
 ions require no local sources. We show that the associated energy-momentum
  tensors (both 10D and the resulting 4D effective) satisfy the null\, weak
 \, strong\, and dominant energy conditions. In our explicit constructions\
 , the Ricci scalar of the four-dimensional Einstein frame metric is negati
 ve\; such backgrounds may find applications to anisotropic or FLRW cosmolo
 gies in the early universe. We also revisit the Maldacena--Nuñez no-go an
 alysis\, incorporating new elements that appear in our constructions\, nam
 ely an overall noncompact spacetime-dependent scale factor multiplying the
  internal metric\, and field strengths with components partially covering 
 the noncompact directions. We argue that\, with these generalizations\, a 
 four-dimensional Einstein-frame metric with positive Ricci scalar cannot b
 e ruled out by such an analysis.\n\nhttps://indico.dfa.unipd.it/event/1798
 /
LOCATION:P2A (Dipartimento di Fisica e Astronomia - Edificio Paolotti)
URL:https://indico.dfa.unipd.it/event/1798/
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