Noah Bittermann, Sebastian Garcia-Saenz, Kurt Hinterbichler, Rachel A. Rosen

We find and classify the simplest ${\cal N}=2$ SUSY multiplets on AdS$_4$ which contain partially massless fields. We do this by studying representations of the ${\cal N}=2$, $d=3$ superconformal algebra of the boundary, including new shortening conditions that arise in the non-unitary regime. Unlike the ${\cal N}=1$ case, the simplest ${\cal N}=2$ multiplet containing a partially massless spin-2 is short, containing several exotic fields. More generally, we argue that ${\cal N}=2$ supersymmetry allows for short multiplets that contain partially massless spin-$s$ particles of depth $t=s-2$.

Özenç Güngör, Glenn D. Starkman

We present a model for a classical, non-singular bouncing cosmology without violation of the null energy condition (NEC). The field content is General Relativity plus a real scalar field with a canonical kinetic terms and only renormalizable, polynomial type self-interaction for the scalar field in the Jordan frame. The universe begins vacuum-energy dominated and contracting at $t=-\infty$. We consider a closed universe with a positive spatial curvature, which is responsible for the universe bouncing without any NEC violation. An $R\phi^2$ coupling between the Ricci scalar and the scalar field drives the scalar from the initial false vacuum to the true vacuum during the bounce. The model is sub-Planckian throughout its evolution and every dimensionful parameter is below the effective field theory scale $M_P$, so we expect no ghost-type or tachyonic instabilities. This model solves the horizon problem and extends co-moving particle geodesics to past infinity, resulting in a geodesically complete universe without singularities. We solve the Friedman equations and the scalar field equation of motion numerically, and analytically under certain approximations.