Let G be a locally compact,
noncompact group and π a weakly continuous, uniformly bounded representation of
G on a Hilbert space H. Suppose there exists a non-zero ξ in H such that the
function x →⟨π(x)ξ,ξ⟩ vanishes at infinity, Then π is not algebraically irreducible
when lifted to a representation of L1(G). This implies that the left regular
representation of L1(G), for G noncompact, contains no algebraically irreducible
subrepresentations.