No Arabic abstract
Let $Lambda$ be the set of partitions of length $geq 0$. We introduce an $mathbb{N}$-graded algebra $mathbb{A}_q^d(Lambda)$ associated to $Lambda$, which can be viewed as a quantization of the algebra of partitions defined by Reineke. The multiplication of $mathbb{A}^d_q(Lambda)$ has some kind of quasi-commutativity, and the associativity comes from combinatorial properties of certain polynomials appeared in the quantized cohomological Hall algebra $mathcal{H}^d_q$ of the $d$-loop quiver. It turns out that $mathbb{A}^d_q(Lambda)$ is isomorphic to $mathcal{H}^d_q$, thus can be viewed as a combinatorial realization for $mathcal{H}^d_q$.
We show that the generic Hall algebra of nilpotent representations of an oriented cycle specialised at $q=0$ is isomorphic to the generic extension monoid in the sense of Reineke. This continues the work of Reineke.
In this note we give a version of Hao Huangs proof of the sensitivity conjecture, shedding some light on the origin of the magical matrix $A$ in that proof. For the history of the subject and the importance of this conjecture to the study of boolean functions, we refer to the original paper. Here we only state the main result: Consider the boolean cube $Q_n={0,1}^n$ as a graph, whose edges connect pairs of vertices differing in one coordinate. Then any its induced subgraph on greater than $2^{n-1}$ (the half) vertices has degree of some vertex at least $sqrt{n}$.
The canonical bases of cluster algebras of finite types and rank 2 are given explicitly in cite{CK2005} and cite{SZ} respectively. In this paper, we will deduce $mathbb{Z}$-bases for cluster algebras for affine types $widetilde{A}_{n,n},widetilde{D}$ and $widetilde{E}$. Moreover, we give an inductive formula for computing the multiplication between two generalized cluster variables associated to objects in a tube.
We show that the $imath$Hall algebra of the Jordan quiver is a polynomial ring in infinitely many generators and obtain transition relations among several generating sets. We establish a ring isomorphism from this $imath$Hall algebra to the ring of symmetric functions in two parameters $t, theta$, which maps the $imath$Hall basis to a class of (modified) inhomogeneous Hall-Littlewood ($imath$HL) functions. The (modified) $imath$HL functions admit a formulation via raising and lowering operators. We formulate and prove Pieri rules for (modified) $imath$HL functions. The modified $imath$HL functions specialize at $theta=0$ to the modified HL functions; they specialize at $theta=1$ to the deformed universal characters of type C, which further specialize at $(t=0, theta =1)$ to the universal characters of type C.
We introduce a Hopf algebra structure of subword complexes, including both finite and infinite types. We present an explicit cancellation free formula for the antipode using acyclic orientations of certain graphs, and show that this Hopf algebra induces a natural non-trivial sub-Hopf algebra on $c$-clusters in the theory of cluster algebras.