By a finite group cover of G, we will mean an M -definable connected group H with a surjective M -definable map H → G, whose kernel K is finite. The kernel K must lie within the center of H, because the action of H on K by conjugation yields a necessarily-trivial homomorphism from the connected group H to the finite group of automorphisms of K. If πi : Hi → G are finite group covers of G for i ...

The loop homology of a closed orientable manifoldM of dimensionm is the commutative algebra H∗(LM) = H∗+m(LM) equipped with the Chas-Sullivan loop product. Here LM denotes the free loop on M . There is also a homomorphism of graded algebras I from H∗(LM) to the Pontryagin algebra H∗(ΩM). The primary purpose of this paper is to study the loop homology and the homomorphism I, when M is a fibered ...

Let G and H be two groups. For simplicity, we denote by + the group operation in each of these groups. A function f : G → H is called a (group) homomorphism if for every x, y ∈ G it holds that f(x+ y) = f(x) + f(y). One important special case of interest is when H is a finite field and G is a vector space over this field; that is, G = H for some natural number m. In this case, a homomorphism f ...

We show the problem of counting homomorphisms from the fundamental group of a homology 3-sphere M to a finite, non-abelian simple group G is #P-complete, in the case that G is fixed and M is the computational input. Similarly, deciding if there is a non-trivial homomorphism is NP-complete. In both reductions, we can guarantee that every non-trivial homomorphism is a surjection. As a corollary, ...

This paper investigates ways to enlarge the Hamiltonian subgroup Ham of the symplectomorphism group Symp(M) of the symplectic manifold (M,ω) to a group that both intersects every connected component of Symp(M) and characterizes symplectic bundles with fiber M and closed connection form. As a consequence, it is shown that bundles with closed connection form are stable under appropriate small per...

A homomorphism of a hypergroup (H, ◦) is a function f : H → H satisfying f(x ◦ y) ⊆ f(x) ◦ f(y) for all x, y ∈ H. A homomorphism of a hypergroup (H, ◦) is called an epimorphism if f(H) = H. Denote by Hom(H, ◦) and Epi(H, ◦) the set of all homomorphisms and the set of all epimorphisms of a hypergroup (H, ◦), respectively. In this paper, the elements of Hom(Zn, ◦m) and Epi(Zn, ◦m) are characteriz...

Let A be a separable C∗-algebra and let B be a stable C∗-algebra with a strictly positive element. We consider the (semi)group Ext(A,B) (resp. Ext(A,B)) of homotopy classes of asymptotic (resp. of genuine) homomorphisms from A to the corona algebra M(B)/B and the natural map i : Ext(A,B) −→ Ext(A,B). We show that if A is a suspension then Ext(A,B) coincides with E-theory of Connes and Higson an...

Let X be a Riemann surface equipped with a projective structure (i.e., a covering by coordinate charts such that the transition functions are of the form z 7−→ (az + b)/(cz + d)). Let L be a line bundle on X such that L = TX . Let J (L) −→ X denote the jet bundle of order m for the line bundle L. For i ≥ j, there is a natural restriction homomorphism from J (L) onto J (L). We prove that for any...

Let $nin mathbb{N}$. An additive map $h:Ato B$ between algebras $A$ and $B$ is called $n$-Jordan homomorphism if $h(a^n)=(h(a))^n$ for all $ain A$. We show that every $n$-Jordan homomorphism between commutative Banach algebras is a $n$-ring homomorphism when $n < 8$. For these cases, every involutive $n$-Jordan homomorphism between commutative C-algebras is norm continuous.