The algebra associated

In a classic paper, Gerstenhaber showed that first order deformations of an associative k-algebra a are controlled by the second Hochschild cohomology group of a. More generally, any n-parameter first order deformation of a gives, due to commutativity of the cup-product on Hochschild cohomology, a graded algebra morphism Sym• (kn ) → Ext2•bimod (a, a). We prove that any extension aof the n-parameter first order deformation of a to an infinite order formal deformation provides a canonical ‘lift’ of the graded algebra morphism above to a dg-algebra morphism Sym• (kn ) → RHom• ...

17p noel_noel 17-01-2013 54 4   Download

We define and study an algebra Ψ∞ (M0 ) of pseudodifferential opera1,0,V tors canonically associated to a noncompact, Riemannian manifold M0 whose geometry at infinity is described by a Lie algebra of vector fields V on a compactification M of M0 to a compact manifold with corners. We show that the basic properties of the usual algebra of pseudodifferential operators on a compact manifold extend to Ψ∞ (M0 ).

32p noel_noel 17-01-2013 40 6   Download

The interplay between geometry and topology on complex algebraic varieties is a classical theme that goes back to Lefschetz [L] and Zariski [Z] and is always present on the scene; see for instance the work by Libgober [Li]. In this paper we study complements of hypersurfaces, with special attention to the case of hyperplane arrangements as discussed in Orlik-Terao’s book [OT1]. Theorem 1 expresses the degree of the gradient map associated to any homogeneous polynomial h as the number of n-cells that have to be added to a generic hyperplane section D(h) ∩ H to obtain the complement in...

36p tuanloccuoi 04-01-2013 228 8   Download

Tuyển tập các báo cáo nghiên cứu khoa học ngành toán học tạp chí Journal of Operator Theory đề tài: Các nhóm máy lẻ của C *- đại số kết hợp với phép quay phi lý...

4p matuot_266 26-08-2011 71 5   Download