For each finite-dimensional, simple, complex Lie algebra
and each root of
unity (with some
mild restriction on the order) one can define the Witten–Reshetikhin–Turaev (WRT) quantum
invariant
of
oriented
–manifolds
. We construct an
invariant
of
integralhomology spheres ,
with values in
,
the cyclotomic completion of the polynomial ring
, such that the
evaluation of
at each root of unity gives the WRT quantum invariant of
at that root of unity. This result generalizes the case
proved by Habiro. It
follows that
unifies all the
quantum invariants of
associated with
and represents the quantum invariants as a kind of “analytic
function” defined on the set of roots of unity. For example,
for all roots of unity are determined by a “Taylor expansion” at any
root of unity, and also by the values at infinitely many roots of unity
of prime power orders. It follows that WRT quantum invariants
for all roots
of unity are determined by the Ohtsuki series, which can be regarded as the Taylor expansion
at
, and hence
by the Lê–Murakami–Ohtsuki invariant. Another consequence is that the WRT quantum
invariants
are algebraic integers. The construction of the invariant
is
done on the level of quantum group, and does not involve any finite-dimensional
representation, unlike the definition of the WRT quantum invariant. Thus, our
construction gives a unified, “representation-free” definition of the quantum invariants
of integral homology spheres.
Keywords
quantum invariants, integral homology spheres, quantized
enveloping algebras, ring of analytic functions on roots of
unity