m at h . D G ] 1 4 Fe b 20 06 Variations on A . Kneser ’ s theorem

2 3 Fe b 20 06 Variations on the Tait – Kneser theorem

At every point, a smooth plane curve can be approximated, to second order, by a circle; this circle is called osculating. One may think of the osculating circle as passing through three infinitesimally close points of the curve. A vertex of the curve is a point at which the osculating circle hyper-osculates: it approximates the curve to third order. Equivalently, a vertex is a critical point of...

ar X iv : s ub m it / 06 54 18 7 [ m at h . SG ] 1 4 Fe b 20 13 A natural Gromov - Witten

We prove that the Gromov-Witten moduli space of a compact symplectic manifold carries a unique virtual fundamental class that satisfies certain naturality conditions. The theorem also applies to moduli spaces of relative J-holomorphic maps. The virtual fundamental class is constructed using only Gromov-type perturbations; it is based on introducing stabilizing divisors and systematically applyi...

ar X iv : m at h / 06 02 37 1 v 1 [ m at h . A G ] 1 7 Fe b 20 06 Braid Monodromy of Hypersurface Singularities

ar X iv : h ep - l at / 0 60 20 18 v 1 1 4 Fe b 20 06 Efficient Cluster Algorithm for CP ( N − 1 ) Models

Despite several attempts, no efficient cluster algorithm has been constructed for CP (N − 1) models in the standard Wilson formulation of lattice field theory. In fact, there is a no-go theorem that prevents the construction of an efficient Wolff-type embedding algorithm. In this paper, we construct an efficient cluster algorithm for ferromagnetic SU (N)-symmetric quantum spin systems. Such sys...

ar X iv : m at h / 06 05 27 6 v 4 [ m at h . D S ] 1 6 Ju n 20 06 SUPERRIGIDITY , WEYL GROUPS , AND ACTIONS ON THE CIRCLE

We propose a new approach to superrigidity phenomena and implement it for lattice representations and measurable cocycles with Homeo+(S ) as the target group. We are motivated by Ghys’ theorem stating that any representation ̺ : Γ → Homeo+(S ) of an irreducible lattice Γ in a semi-simple real Lie group G of higher rank, either has a finite orbit or, up to a semi-conjugacy, extends to G which act...