Title: Relative Property (T) for Nilpotent Subgroups,
Abstract: We show that relative Property (T) for the abelianization of a nilpotent
normal subgroup implies relative Property (T) for the subgroup itself. This and
other results are a consequence of a theorem of independent interest, which
states that if $H$ is a closed subgroup of a locally compact group $G$, and $A$
is a closed subgroup of the center of $H$, such that $A$ is normal in $G$, and
$(G/A, H/A)$ has relative Property (T), then $(G, H^{(1)})$ has relative
Property (T), where $H^{(1)}$ is the closure of the commutator subgroup of $H$.
In fact, the assumption that $A$ is in the center of $H$ can be replaced with
the weaker assumption that $A$ is abelian and every $H$-invariant finite
measure on the unitary dual of $A$ is supported on the set of fixed points.