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Heisenberg algebra and a graphical calculus

Mikhail Khovanov (2014)

Fundamenta Mathematicae

A new calculus of planar diagrams involving diagrammatics for biadjoint functors and degenerate affine Hecke algebras is introduced. The calculus leads to an additive monoidal category whose Grothendieck ring contains an integral form of the Heisenberg algebra in infinitely many variables. We construct bases of the vector spaces of morphisms between products of generating objects in this category.

Modular representations of finite groups with trivial restriction to Sylow subgroups

Paul Balmer (2013)

Journal of the European Mathematical Society

Let k be a field of characteristic p . Let G be a finite group of order divisible by p and P a p -Sylow subgroup of G . We describe the kernel of the restriction homomorphism T ( G ) T ( P ) , for T ( ) the group of endotrivial representations. Our description involves functions G k × that we call weak P -homomorphisms. These are generalizations to possibly non-normal P G of the classical homomorphisms G / P k × appearing in the normal case.

On the exponent of the cokernel of the forget-control map on K₀-groups

Francis X. Connolly, Stratos Prassidis (2002)

Fundamenta Mathematicae

For groups that satisfy the Isomorphism Conjecture in lower K-theory, we show that the cokernel of the forget-control K₀-groups is composed by the NK₀-groups of the finite subgroups. Using this information, we can calculate the exponent of each element in the cokernel in terms of the torsion of the group.

Quasigroup automorphisms and symmetric group characters

Brent Kerby, Jonathan D. H. Smith (2010)

Commentationes Mathematicae Universitatis Carolinae

The automorphisms of a quasigroup or Latin square are permutations of the set of entries of the square, and thus belong to conjugacy classes in symmetric groups. These conjugacy classes may be recognized as being annihilated by symmetric group class functions that belong to a λ -ideal of the special λ -ring of symmetric group class functions.

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