Physics (Internal)

Observing the Dimensionality of our Parent Vacuum

This event is part of the HET Seminar Series.

Abstract:
It seems generic to have vacua with lower dimensionality than ours. We consider
the possibility that the observable universe originated in a transition from
one of these vacua. Such a universe has anisotropic spatial curvature. This may
be directly observable through its late-time effects on the CMB if the last
period of slow-roll inflation was not too long. These affect the entire sky,
leading to correlations which persist up to the highest CMB multipoles, thus
allowing a conclusive detection above cosmic variance. Further, this
anisotropic curvature causes different dimensions to expand at different rates.
This leads to other potentially observable signals including a quadrupolar
anisotropy in the CMB which limits the size of the curvature. Conversely, if
isotropic curvature is observed it may be evidence that our parent vacuum was
at least 3+1 dimensional. Such signals could reveal our history of
decompactification, providing evidence for the existence of vastly different
vacua.