The Half-Integer Charged Particles of the Orbifold Models
  In this paper, we consider half-integer charged particles predicted by models of orbifold compactification of the $E_8\times E_8$ heterotic string theory. We find that it is possible for half-integer charged particles to exist in our universe, and the location of half-interger charged particles in a galaxy should be in the centers of the galaxy. By qualitative analysis, we find half-interger charged particles may be helpful in explaining the formation of SMBH at the large redshift and solving the UHECR puzzle. 
C.Y. Sun, D.H. Zhang