Set Of Conjugacy Classes Research Articles

On the coadjoint Virasoro action

The set of coadjoint orbits of the Virasoro algebra at level 1 is in bijection with the set of conjugacy classes in a certain open subset SL˜(2,R)+ of the universal cover of SL(2,R). We strengthen this bijection to a Morita equivalence of quasi-symplectic groupoids, integrating the Poisson structure on vir1⁎(S1) and the Cartan-Dirac structure on SL˜(2,R)+, respectively.

Minimal reduction type and the Kazhdan–Lusztig map

We introduce the notion of minimal reduction type of an affine Springer fiber, and use it to define a map from the set of conjugacy classes in the Weyl group to the set of nilpotent orbits. We show that this map is the same as the one defined by Lusztig in Lfromto, (2011) and that the Kazhdan–Lusztig map in Kazhdan and Lusztig, (1998) is a section of our map. This settles several conjectures in the literature. For classical groups, we prove more refined results by introducing and studying the “skeleta” of affine Springer fibers.

On Shalika germs

Let G be (the group of F-points of) a reductive group over a local field F satisfying the assumptions of Debacker (Ann Sci Ecole Norm Sup 35(4):391–422, 2002), sections 2.2, 3.2, 4.3. Let \(G_{{\text {reg}}}\subset G\) be the subset of regular elements. Let \(T\subset G\) be a maximal torus. We write \(T_{{\text {reg}}}=T\cap G_{{\text {reg}}}\). Let dg, dt be Haar measures on G and T. They define an invariant measure Open image in new window on Open image in new window. Let \(\mathcal {H}\) be the space of complex valued locally constant functions on G with compact support. For any \(f\in \mathcal {H}\), \(t\in T_{{\text {reg}}}\), we put \(I_t(f)=\int _{G/T}f(\dot{g}t\dot{g}^{-1})dg/dt\). Let \(\mathcal U\) be the set of conjugacy classes of unipotent elements in G. For any \(\Omega \in \mathcal U\) we fix an invariant measure \(\omega \) on \(\Omega \). It is well known—see, e.g., Rao (Ann Math 96:505-510, 1972)—that for any \(f\in \mathcal {H}\) the integral $$\begin{aligned} I_\Omega (f)=\int _\Omega f\omega \end{aligned}$$ is absolutely convergent. Shalika (Ann Math 95:226–242, 1972) showed that there exist functions \(j_\Omega (t)\), \(\Omega \in \mathcal U\), on \(T\cap G_{{\text {reg}}}\), such that $$\begin{aligned} I_t(f)=\sum _{\Omega \in \mathcal U}j_\Omega (t)I_\Omega (f) \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \quad \qquad \qquad \qquad \qquad \qquad ({\star }) \end{aligned}$$ for any \(f\in \mathcal {H}\), \(t\in T\)near to e, where the notion of near depends on f. For any \(r\ge 0\) we define an open \({\text {Ad}}(G)\)-invariant subset \(G_r\) of G, and a subspace \(\mathcal {H}_r\) of \(\mathcal {H}\), as in Debacker (Ann Sci Ecole Norm Sup 35(4):391–422, 2002). Here I show that for any \(f\in \mathcal {H}_r\) the equality \((\star )\) holds for all \(t\in T_{{\text {reg}}}\cap G_r\).

Homotopical rigidity of polygonal billiards

Consider two k-gons P and Q. We say that the billiard flows in P and Q are homotopically equivalent if the set of conjugacy classes in the fundamental group of P, viewed as a punctured sphere, which contain a periodic billiard orbit agrees with the analogous set for Q. We study this equivalence relationship and compare it to the notions of order equivalence and code equivalence, introduced in [1,2]. In particular we show if P is a rational polygon, and Q is homotopically equivalent to P, then P and Q are similar, or affinely similar if all sides of P are vertical and horizontal.

From conjugacy classes in the Weyl group to unipotent classes

LetGGbe a connected reductive algebraic group over an algebraic closed field. We define a (surjective) map from the set of conjugacy classes in the Weyl group to the set of unipotent classes inGG.

Monomiality of finite groups with some conditions on conjugacy classes

We present some arithmetical-type conditions on the set of conjugacy classes of a finite group that are sufficient for the monomiality of the group, i.e., for the property that all its irreducible complex characters are induced by linear characters of subgroups.

Finite Subgroups in Algebras and Cohomology

We give a cohomological characterization of the set of conjugacy classes of finite subgroups of the projective multiplicative group of a finite dimensional algebra that become conjugate to a given group over some finite separable extension of the base field. We provide two applications.

Accidental parabolics and relatively hyperbolic groups

By constructing, in the relative case, objects analogous to Rips and Sela’s canonical representatives, we prove that the set of conjugacy classes of images by morphisms without accidental parabolic, of a finitely presented group in a relatively hyperbolic group, is finite.

The Commutativity Relation in the Symmetric Semigroup

We compute the cardinality of the centralizer of an injection or surjection provided that the basic set is countable. We prove a formula for the cardinality of the set of conjugacy classes in the infinite symmetric group.

Rings associated with hyperbolic groups

Abstract We define quasiconvexity cone Qcone(τ) over an infinite hyperbolic (in the sense of Gromov) group τ as the set of conjugacy classes of infinite quasiconvex subgroups H⊂τ and show that the abelian group of Qcone(τ)-divisors, i.e. finite sums of points from Qcone(τ) with integer coefficients, can be equipped with a natural structure of commutative associative ring with identity. Euler characteristic can be considered as a rational-valued function on Qcone(τ). This approach gives another point of view on the strengthened form of Hanna Neumann's conjecture on the maximal rank of the intersection of two finitely generated subgroups of the free group on two generators.

On the $I(G)$-adic Topology of the Burnside Ring of Compact Lie Groups

Let G be a compact Lie group and let A(G) denote torn Dieck's Burnside ring [2], [3, 5.5]. As a set, A(G) consists of equivalence classes of compact G-ENR's, and as a module, A(G) is a free abelian group with basis [G/H], where H runs over 0(G) : the set of conjugacy classes (//) such that NH/H is finite. Here (H) denotes the conjugacy class of H in G and NH the normalizer of H. In [3, 5.12] torn Dieck defined homomorphisms between A(G) and A(H); ResH A(G} > A ( H ) IndH : A(H) » A(G) where Res% is rf and IndR is e G R in torn Dieck's notation. Now let e be the trivial subgroup of G. Then Res : A(G) >A(e)=Z (-the ring of integers)