  Dipolar interaction between the magnetic moments of electrons is studied as a
source for electron spin decay in quantum dots or arrays of quantum dots. This
magnetic interaction will govern spin decay, after other sources, such as the
coupling to nuclear spins or spin orbit coupling, have been eliminated by a
suitable sample design. Electron-electron (Coulomb) interactions, important for
magnetic properties, are included. Decomposing the dipolar operator according
to the symmetric group of electron permutations allows one to deduce vanishing
decay channels as a function of electron number and spatial symmetries of the
quantum dot(s). Moreover, we incorporate the possibility of rapid phonon
induced spin conserving transitions which crucially affect the temperature
dependence of spin decay rates. An interesting result is that a sharp increase
of the spin decay rate occurs already at relatively low temperatures.
