Dual pairs in the Pin-group and duality for the corresponding spinorial representation

In this paper, we give a complete picture of Howe correspondence for the setting (O(E,b),Pin(E,b),Π), where O(E,b) is an orthogonal group (real or complex), Pin(E,b) is the two-fold Pin-covering of O(E,b), and Π is the spinorial representation of Pin(E,b). More precisely, for a dual pair (G,G′) in O(E,b), we determine explicitly the nature of its preimages (G̃,G′~) in Pin(E,b), and prove that apart from some exceptions, (G̃,G′~) is always a dual pair in Pin(E,b); then we establish the Howe correspondence for Π with respect to (G̃,G′~).