Unramified Quadrangles of Type E6, E7 and E8
This chapter deals with the case that the building at infinity of the Bruhat-Tits building Ξ is a Moufang quadrangle of type E⁶, E₇, and E₈. It begins with a hypothesis that takes into account a quadratic space of type Eℓ for ℓ = 6, 7 or 8, K which is complete with respect to a discrete valuation, the two residues of Ξ, and the two root group sequences of a Moufang polygon. It then considers the case that Ξ is an unramified quadrangle if the proposition δΨ = 2 holds. It also explains two other propositions: Ξ is a semi-ramified quadrangle if δΛ = 1 and δΨ = 2 holds, and a ramified quadrangle if δΛ = δΨ = 1 holds.
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