Now showing items 1-20 of 22

• #### Calculating conjugacy classes in Sylow p-subgroups of finite Chevalley groups of rank six and seven ﻿

[OWP-2013-10] (Mathematisches Forschungsinstitut Oberwolfach, 2013-04-10)
Let $G(q)$ be a finite Chevalley group, where $q$ is a power of a good prime $p$, and let $U(q)$ be a Sylow $p$-subgroup of $G(q)$. Then a generalized version of a conjecture of Higman asserts that the number $k(U(q))$ of ...
• #### Cocharacter-closure and spherical buildings ﻿

[OWP-2015-12] (Mathematisches Forschungsinstitut Oberwolfach, 2015-07-29)
Let $k$ be a field, let $G$ be a reductive $k$-group and $V$ an affine $k$-variety on which $G$ acts. In this note we continue our study of the notion of cocharacter-closed $G(k)$-orbits in $V$. In earlier work we used a ...
• #### Cocharacter-Closure and the Rational Hilbert-Mumford Theorem ﻿

[OWP-2014-16] (Mathematisches Forschungsinstitut Oberwolfach, 2014-12-20)
For a field $k$, let $G$ be a reductive $k$-group and $V$ an affine $k$-variety on which $G$ acts. Using the notion of cocharacter-closed $G(k)$-orbits in $V$ , we prove a rational version of the celebrated Hilbert-Mumford ...
• #### Contractive Idempotents on Locally Compact Quantum Groups ﻿

[OWP-2012-19] (Mathematisches Forschungsinstitut Oberwolfach, 2012)
A general form of contractive idempotent functionals on coamenable locally compact quantum groups is obtained, generalising the result of Greenleaf on contractive measures on locally compact groups. The image of a convolution ...
• #### G-complete reducibility in non-connected groups ﻿

[OWP-2013-09] (Mathematisches Forschungsinstitut Oberwolfach, 2013-04-10)
In this paper we present an algorithm for determining whether a subgroup $H$ of a non-connected reductive group $G$ is $G$-completely reducible. The algorithm consists of a series of reductions; at each step, we perform ...
• #### Ghost Algebras of Double Burnside Algebras via Schur Functors ﻿

[OWP-2012-09] (Mathematisches Forschungsinstitut Oberwolfach, 2012-07-03)
For a finite group $G$, we introduce a multiplication on the $\mathbb{Q}$-vector space with basis $\mathscr{S}_{G\times G}$, the set of subgroups of ${G \times G}$. The resulting $\mathbb{Q}$-algebra $\tilde{A}$ can be ...
• #### Invariant Four-forms and Symmetric Pairs ﻿

[OWP-2012-03] (Mathematisches Forschungsinstitut Oberwolfach, 2012-04-24)
We give criteria for real, complex and quaternionic representations to define $s$-representations, focusing on exceptional Lie algebras defined by spin representations. As applications, we obtain the classification of ...
• #### K-Triviality, Oberwolfach randomness, and differentiability ﻿

[OWP-2012-17] (Mathematisches Forschungsinstitut Oberwolfach, 2012-12-21)
We show that a Martin-Lof random set for which the effective version of the Lebesgue density theorem fails computes every $K$-trivial set. Combined with a recent result by Day and Miller, this gives a positive solution to ...
• #### Legendrian rational unknots in lens spaces ﻿

[OWP-2013-06] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
We classify Legendrian rational unknots with tight complements in the lens spaces $L(p,1)$ up to coarse equivalence. As an example of the general case, this classification is also worked out for $L(5, 2)$. The knots are ...
• #### Low rank differential equations for hamiltonian matrix nearness problems ﻿

[OWP-2013-01] (Mathematisches Forschungsinstitut Oberwolfach, 2013-02-08)
For a Hamiltonian matrix with purely imaginary eigenvalues, we aim to determine the nearest Hamiltonian matrix such that so me or all eigenvalues leave the imaginary axis. Conversely, for a Hamiltonian matrix with all ...
• #### Module Categories for Group Algebras over Commutative Rings ﻿

[OWP-2012-12] (Mathematisches Forschungsinstitut Oberwolfach, 2012-10-01)
We develop a suitable version of the stable module category of a finite group $G$ over an arbitrary commutative ring $k$. The purpose of the construction is to produce a compactly generated triangulated category whose ...
• #### Multiple Bernoulli series and volumes of moduli spaces of flat bundles over surfaces ﻿

[OWP-2013-04] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
Using Szenes formula for multiple Bernoulli series, we explain how to compute Witten series associated to classical Lie algebras. Particular instances of these series compute volumes of moduli spaces of flat bundles over ...
• #### Near critical density irregular sampling in bernstein spaces ﻿

[OWP-2013-16] (Mathematisches Forschungsinstitut Oberwolfach, 2013-07-23)
We obtain sharp estimates for the sampling constants in Bernstein spaces when the density of the sampling set is near the critical value.
• #### Noncompact harmonic manifolds ﻿

[OWP-2013-08] (Mathematisches Forschungsinstitut Oberwolfach, 2013-04-10)
The Lichnerowicz conjecture asserts that all harmonic manifolds are either flat or locally symmetric spaces of rank 1. This conjecture has been proved by Z.I. Szab ́o [Sz] for harmonic manifolds with compact universal ...
• #### 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 ...
• #### On the geometry of regular maps from a quasi-projective surface to a curve ﻿

[OWP-2013-03] (Mathematisches Forschungsinstitut Oberwolfach, 2013-03-14)
We explore consequences of the triviality of the monodromy group, using the condition of purity of the mixed Hodge structure on the cohomology of the surface X.
• #### Polynomiality, wall crossings and tropical geometry of rational double hurwitz cycles ﻿

[OWP-2012-13] (Mathematisches Forschungsinstitut Oberwolfach, 2012-12-04)
We study rational double Hurwitz cycles, i.e. loci of marked rational stable curves admitting a map to the projective line with assigned ramification profiles over two fixed branch points. Generalizing the phenomenon ...
• #### Rate of Convergence of the Density Estimation of Regression Residual ﻿

[OWP-2012-08] (Mathematisches Forschungsinstitut Oberwolfach, 2012)
Consider the regression problem with a response variable $Y$ and with a $d$-dimensional feature vector $X$. For the regression function $m(x) = \mathbb{E}\{Y|X = x\}$, this paper investigates methods for estimating the ...
• #### Spatial-Skin Effect for a Spectral Problem with "Slightly Heavy" Concentrated Masses in a Thick Cascade Junction ﻿

[OWP-2012-10] (Mathematisches Forschungsinstitut Oberwolfach, 2012-07-03)
The asymptotic behavior (as $\varepsilon \to 0$) of eigenvalues and eigenfunctions of a boundary- value problem for the Laplace operator in a thick cascade junction with concentrated masses is studied. This cascade junction ...
• #### Strongly Consistent Density Estimation of Regression Redidual ﻿

[OWP-2012-07] (Mathematisches Forschungsinstitut Oberwolfach, 2012)
Consider the regression problem with a response variable $Y$ and with a $d$-dimensional feature vector $X$. For the regression function $m(x) = \mathbb{E}\{Y|X = x\}$, this paper investigates methods for estimating the ...