arXiv subjects

Sacha C. Blumen

Publications and source records attributed to Sacha C. Blumen.

4 recordsLinked to original sources

arXiv2009

On the $U_{q}(osp(1|2n))$ and $U_{-q}(so(2n+1))$ Uncoloured Quantum Link Invariants

Let $L$ be a link and $Φ^{A}_{L}(q)$ its link invariant associated with the vector representation of the quantum (super)algebra $U_{q}(A)$. Let $F_{L}(r,s)$ be the Kauffman link invariant for $L$ associated with the Birman--Wenzl--Murakami algebra $BWM_{f}(r,s)$ for complex parameters $r$ and $s$ and a sufficiently large rank $f$. For an arbitrary link $L$, we show that $Φ^{osp(1|2n)}_{L}(q) = F_{L}(-q^{2n},q)$ and $Φ^{so(2n+1)}_{L}(-q) = F_{L}(q^{2n},-q)$ for each positive integer $n$ and all sufficiently large $f$, and that $Φ^{osp(1|2n)}_{L}(q)$ and $Φ^{so(2n+1)}_{L}(-q)$ are identical up to a substitution of variables. For at least one class of links $F_{L}(-r,-s) = F_{L}(r,s)$ implying $Φ^{osp(1|2n)}_{L}(q) = Φ^{so(2n+1)}_{L}(-q)$ for these links.

math.QA↗

arXiv2006

The Birman-Wenzl-Murakami algebra, Hecke algebra and representations of U_{q}(osp(1|2n))

A representation of the Birman-Wenzl-Murakami algebra BW_{t}(-q^{2n},q) exists in the centraliser algebra End_{U_q(osp(1|2n))}(V^{\otimes t}), where V is the fundamental (2n+1)-dimensional irreducible U_{q}(osp(1|2n))-module. This representation is defined using permuted R-matrices acting on V^{\otimes t}. A complete set of projections onto and intertwiners between irreducible U_{q}(osp(1|2n))-summands of V^{\otimes t} exists via this representation, proving that End_{U_q(osp(1|2n))}V^{\otimes t}) is generated by the set of permuting R-matrices acting on V^{\otimes t}. We also show that a representation of the the Iwahori-Hecke algebra H_{t}(-q) of type A_{t-1} exists in the centraliser algebra End_{U_q(osp(1|2))}[(V^{+}_{1/2})^{\otimes t}], where V^{+}_{1/2} is a two-dimensional irreducible representation of U_{q}(osp(1|2)).

math.QA↗

arXiv2006

Quantum Superalgebras at Roots of Unity and Topological Invariants of Three-manifolds

The general method of Reshetikhin and Turaev is followed to develop topological invariants of closed, connected, orientable 3-manifolds from a new class of algebras called pseudo-modular Hopf algebras. Pseudo-modular Hopf algebras are a class of Z_2-graded ribbon Hopf algebras that generalise the concept of a modular Hopf algebra. The quantum superalgebra U_q(osp(1|2n)) over C is considered with q a primitive N^th root of unity for all integers N >= 3. For such a q, a certain left ideal I of U_q(osp(1|2n)) is also a two-sided Hopf ideal, and the quotient algebra U_q^(N)(osp(1|2n)) = U_q(osp(1|2n)) / I is a Z_2-graded ribbon Hopf algebra. For all n and all N >= 3, a finite collection of finite dimensional representations of U_q^(N)(osp(1|2n)) is defined. Each such representation of U_q^(N)(osp(1|2n)) is labelled by an integral dominant weight belonging to the truncated dominant Weyl chamber. Properties of these representations are considered: the quantum superdimension of each representation is calculated, each representation is shown to be self-dual, and more importantly, the decomposition of the tensor product of an arbitrary number of such representations is obtained for even N. It is proved that the quotient algebra U_q^(N)(osp(1|2n)), together with the set of finite dimensional representations discussed above, form a pseudo-modular Hopf algebra when N >= 6 is twice an odd number. Using this pseudo-modular Hopf algebra, we construct a topological invariant of 3-manifolds. This invariant is shown to be different to the topological invariants of 3-manifolds arising from quantum so(2n+1) at roots of unity.

math.QA↗

arXiv2005

Two generalisations of the Binomial theorem

We prove two generalisations of the Binomial theorem that are also generalisations of the q-binomial theorem. These generalisations arise from the commutation relations satisfied by the components of the co-multiplications of non-simple root vectors in the quantum superalgebra U_{q}(osp(1|2n)).

math.QA↗