Let G be a finite simple group and k an algebraically closed field of prime characteristic dividing the order G. We show that for all 2-cocycles α ∈ Z2(G;k×), first Hochschild cohomology twisted algebra HH1(kαG) is nonzero.

We prove that the first reduced cohomology with values in a mixing Lp-representation, 1 < p < ∞, vanishes for a class of amenable groups including amenable Lie groups. In particular this solves for this class of amenable groups a conjecture of Gromov saying that every finitely generated amenable group has no first reduced lp-cohomology. As a byproduct, we prove a conjecture by Pansu. Namely, th...

We study the stability of singular points for smooth Poisson structures as well as general Lie algebroids. We give sufficient conditions for stability lying on the first (not necessarily linear) approximation of the given Poisson structure or Lie algebroid at a singular point. The main tools used here are the classical Lichnerowicz-Poisson cohomology and the deformation cohomology for Lie algeb...

We describe a method for computing presentations of cohomology rings of small finite p-groups. The description differs from other accounts in the literature in two main respects. First, we suggest some techniques for improving the efficiency of the obvious linear algebra approach to computing projective resolutions over a group algebra. Second, we use an implementation of the multiplicative str...

On a symplectic manifold M , the quantum product defines a complex, one parameter family of flat connections called the A-model or Dubrovin connections. Let ~ denote the parameter. Associated to them is the quantum D module D/I over the Heisenberg algebra of first order differential operators on a complex torus. An element of I gives a relation in the quantum cohomology of M by taking the limit...

A large chunk of the intersection theory of the moduli stacks of n-marked, genus 0 stable maps to a specified target variety X is encoded by the quantum cohomology ring of X. In particular, one can use the associativity of the ring structure to calculate Gromov-Witten invariants and, thus, in favorable circumstances, to calculate the number of rational curves in X passing through an appropriate...

Large-structure tools like toposes and derived categories in cohomology never go far from arithmetic in practice, yet existing formalizations are stronger than ZFC. We formalize the practical insight by grounding the entire toolkit of EGA and SGA at the level of finite order arithmetic. Grothendieck pre-empted many set theoretic issues in cohomology by positing a universe: “a set ‘large enough’...

In the cohomology ring of an extraspecial p-group, the subring generated by Chern classes and transfers is studied. This subring is strictly larger than the Chern subring, but still not the whole cohomology ring, even modulo nilradical. A formula is obtained relating Chern classes to transfers. Introduction Methods to determine the cohomology ring of a finite group almost always presuppose that...