Now showing items 1235-1254 of 1701

• On commuting varieties of nilradicals of borel subalgebras of reductive lie algebras ﻿

[OWP-2012-14] (Mathematisches Forschungsinstitut Oberwolfach, 2012-12-04)
Let $G$ be a connected reductive algebraic group defined over an algebraically closed field $\mathbb{k}$ of characteristic zero. We consider the commuting variety $\mathcal{C}(\mathfrak{u})$ of the nilradical $\mathfrak{u}$ ...
• On Concentrators and Related Approximation Constants ﻿

[OWP-2013-14] (Mathematisches Forschungsinstitut Oberwolfach, 2013-06-10)
Pippenger ([Pip77]) showed the existence of (6m, 4m, 3m, 6)-concentrator for each positive integer m using a probabilistic method. We generalize his approach and prove existence of (6m, 4m, 3m, 5.05)-concentrator (which ...
• On conjugacy of MASAs and the outer automorphism group of the Cuntz algebra ﻿

[OWP-2013-21] (Mathematisches Forschungsinstitut Oberwolfach, 2013-10-29)
We investigate the structure of the outer automorphism group of the Cuntz algebra and the closely related problem of conjugacy of MASAa in $\mathcal{O}_n$. In particular, we exhibit an uncountable family of MASAs, conjugate ...
• On densities of lattice arrangements intersecting every i-dimensional affine subspace ﻿

[OWP-2016-08] (Mathematisches Forschungsinstitut Oberwolfach, 2016-05-10)
In 1978, Makai Jr. established a remarkable connection between the volume-product of a convex body, its maximal lattice packing density and the minimal density of a lattice arrangement of its polar body intersecting every ...
• On Generalizations of Kac-Moody Groups ﻿

[OWP-2010-06] (Mathematisches Forschungsinstitut Oberwolfach, 2010-03-10)
In [7] we define a Curtis-Tits group as a certain generalization of a Kac-Moody group. We distinguish between orientable and non-orientable Curtis-Tits groups and identify all orientable Curtis-Tits groups as Kac-Moody ...
• On Local Combinatorial Formulas for Chern Classes of Triangulated Circle Bundle ﻿

[OWP-2016-16] (Mathematisches Forschungsinstitut Oberwolfach, 2016-08-17)
Principal circle bundle over a PL polyhedron can be triangulated and thus obtains combinatorics. The triangulation is assembled from triangulated circle bundles over simplices. To every triangulated circle bundle over a ...
• On Logic, Choices and Games ﻿

[SNAP-2019-009-EN] (Mathematisches Forschungsinstitut Oberwolfach, 2019-09-04)
Can we always mathematically formalise our taste and preferences? We discuss how this has been done historically in the field of game theory, and how recent ideas from logic and computer science have brought an interesting ...
• On periodic solutions and global dynamics in a periodic differential delay equation ﻿

[OWP-2014-08] (Mathematisches Forschungsinstitut Oberwolfach, 2014-05-13)
• On the containment problem ﻿

[SNAP-2016-003-EN] (Mathematisches Forschungsinstitut Oberwolfach, 2016)
Mathematicians routinely speak two languages: the language of geometry and the language of algebra. When translating between these languages, curves and lines become sets of polynomials called “ideals”. Often there are ...
• On the Derived Category of Grassmannians in Arbitrary Characteristic ﻿

[OWP-2013-24] (Mathematisches Forschungsinstitut Oberwolfach, 2013-12-09)
In this paper we consider Grassmannians in arbitrary characteristic. Generalizing Kapranov's well-known characteristic-zero results we construct dual exceptional collections on them (which are however not strong) as well ...