A Classical Manifestation of the Pauli Exclusion Principle

The occupied and unoccupied fermionic BPS quantum states of a type-IIA string stretched between a D6-brane and an orthogonal D2-brane are described in M-theory by two particular holomorphic curves embedded in a Kaluza–Klein monopole. The absence of multiply-occupied fermionic states — the Pauli exclusion principle — is manifested in Mtheory by the absence of any other holomorphic curves satisfying the necessary boundary conditions. Stable, non-BPS states with multiple strings joining the D6-brane and D2brane are described M-theoretically by non-holomorphic curves.