Each isometric complex structure on a 2ℓ-dimensional euclidean space E
corresponds to an identification of the Clifford algebra of E with the
canonical anticommutation relation algebra for ℓ ( fermionic) degrees of
freedom. The simple spinors in the terminology of E.~Cartan or the pure spinors
in the one of C. Chevalley are the associated vacua. The corresponding states
are the Fock states (i.e. pure free states), therefore, none of the above
terminologies is very good.Comment: 10