Indecomposable Uq ( sln ) modules for q h = − 1 and BRS intertwiners

A class of indecomposable representations of Uq(s`n) is considered for q an even root of unity (qh = −1 ) exhibiting a similar structure as (height h ) indecomposable lowest weight Kac-Moody modules associated with a chiral conformal field theory. In particular, Uq(s`n) counterparts of the Bernard-Felder BRS operators are constructed for n = 2, 3 . For n = 2 a pair of dual d2(h) = h dimensional Uq(s`2) modules gives rise to a 2h dimensional indecomposable representation including those studied earlier in the context of tensor product expansions of irreducible representations. For n = 3 the interplay between the Poincaré-Birkhoff-Witt and (Lusztig) canonical bases is exploited in the study of d3(h) = h(h+1)(2h+1) 6 dimensional indecomposable modules and of the corresponding intertwiners. ∗E-mail: [email protected] †E-mail: [email protected] ‡E-mail: [email protected] §Permanent address