Speaker:
　　 Dr. Federico Urban
Affiliation：
　  University of British Columbia, Canada
Time: 
　  2:00PM，November 30th (Monday)
Location:
　  Middle conf. room, 3rd floor
Abstract：
　  The origin of the observed dark energy could be explained entirely within the standard model, with no new field required.  I will show how the low-energy sector of the chiral QCD Lagrangian, once embedded in a spacetime with non-trivial topology, gives rise to a cosmological vacuum energy density which can be can be presented entirely in terms of QCD parameters and the Hubble constant.  The QCD Veneziano ghost (responsible for the solution of the axial U(1) problem) plays a crucial role in the computation of the vacuum energy, because the ghost's properties at very large but finite distances slightly differ from their infinite volume Minkowski values.  After a review of the mechanism in a non-expanding universe I will describe our attempts to understand the dynamics of the ghost field in a FLRW universe, and mention several possible ways (primarily cosmological) for this proposal to be tested.