Universal Extra Dimensions on Real Projective Plane
  We propose a six dimensional Universal Extra Dimensions (UED) model
compactified on a real projective plane $RP^2$, a two-sphere with its antipodal
points being identified. We utilize the Randjbar-Daemi-Salam-Strathdee
spontaneous sphere compactification with a monopole configuration of an extra
$U(1)_X$ gauge field that leads to a spontaneous radius stabilization. Unlike
the sphere and the so-called $S^2/Z_2$ compactifications, the massless $U(1)_X$
gauge boson is safely projected out. We show how a compactification on a
non-orientable manifold results in a chiral four dimensional gauge theory by
utilizing 6D chiral gauge and Yukawa interactions. The resultant Kaluza-Klein
mass spectra are distinct from the ordinary UED models compactified on torus.
We briefly comment on the anomaly cancellation and also on a possible dark
matter candidate in our model.
