David Nacin | Searcharxiv

arXiv2012

The Minimal Non-Koszul A(Gamma)

The algebras $A(Γ)$, where $Γ$ is a directed layered graph, were first constructed by I. Gelfand, S. Serconek, V. Retakh and R. Wilson. These algebras are generalizations of the algebras $Q_n$, which are related to factorizations of non-commutative polynomials. It was conjectured that these algebras were Koszul. In 2008, T.Cassidy and B.Shelton found a counterexample to this claim, a non-Koszul $A(Γ)$ corresponding to a graph $Γ$ with 18 edges and 11 vertices. We produce an example of a directed layered graph $Γ$ with 13 edges and 9 vertices which produces a non-Koszul $A(Γ)$. We also show this is the minimal example with this property.

math.QA↗

arXiv2005

The Algebra $K_3$ is Koszul

The algebras $Q_n$ describe the relationship between the roots and coefficients of a non-commutative polynomial. I.Gelfand, S.Gelfand, and V. Retakh have defined quotients of these algebras corresponding to graphs. In this work we find the Hilbert series of the class of algebras corresponding to the graph $K_3$. We also show this algebra is Koszul using the lattice definition.

math.QA↗

arXiv2005

The Algebra $P_n$ is Koszul

The algebras $Q_n$ describe the relationship between the roots and coefficients of a non-commutative polynomial. I.Gelfand, S.Gelfand, and V. Retakh have defined quotients of these algebras corresponding to graphs. In this work we find the Hilbert series of the class of algebras corresponding to the $n$-vertex path, $P_n$. We also show this algebra is Koszul. We do this by first looking at class of quadratic algebras we call Partially Generator Commuting. We then find a sufficient condition for a PGC-Algebra to be Koszul and use this to show a similar class of PGC algebras, which we call ch$P_n$, is Koszul. Then we show it is possible to extend what we did to the algebras $P_n$ although they are not PGC. Finally we examine the Hilbert Series of the algebras $P_n$

math.QA↗