Uniform bounds

Mục đích của luận văn là trình bày lại kết quả của P. H. Quý trong bài báo "On the uniform bound of the index of reducibility of parameter ideals of a module whose polynomial type is at most one". Kết quả khẳng định nếu M là R-môđun hữu hạn sinh sao cho p(M) ≤ 1 thì irM(q M) bị chặn trên với mọi iđêan tham số q của M.

40p capheviahe26 02-02-2021 51 4   Download

We prove that Cayley graphs of SL2 (Fp ) are expanders with respect to the projection of any fixed elements in SL(2, Z) generating a non-elementary subgroup, and with respect to generators chosen at random in SL2 (Fp ). 1. Introduction Expanders are highly-connected sparse graphs widely used in computer science, in areas ranging from parallel computation to complexity theory and cryptography; recently they also have found some remarkable applications in pure mathematics; see [5],[10], [15], [20], [21] and references therein. ...

19p dontetvui 17-01-2013 51 7   Download

We prove that in every finitely generated profinite group, every subgroup of finite index is open; this implies that the topology on such groups is determined by the algebraic structure. This is deduced from the main result about finite groups: let w be a ‘locally finite’ group word and d ∈ N. Then there exists f = f (w, d) such that in every d-generator finite group G, every element of the verbal subgroup w(G) is equal to a product of f w-values.

69p noel_noel 17-01-2013 50 8   Download

We find a sharp combinatorial bound for the metric entropy of sets in Rn and general classes of functions. This solves two basic combinatorial conjectures on the empirical processes. 1. A class of functions satisfies the uniform Central Limit Theorem if the square root of its combinatorial dimension is integrable. 2. The uniform entropy is equivalent to the combinatorial dimension under minimal regularity. Our method also constructs a nicely bounded coordinate section of a symmetric convex body in Rn . ...

47p noel_noel 17-01-2013 60 11   Download

It is shown that the bilinear Hilbert transforms Hα,β (f, g)(x) = p.v. R f (x − αt)g(x − βt) dt t map Lp1 (R) × Lp2 (R) → Lp (R) uniformly in the real parameters α, β when 2

46p tuanloccuoi 04-01-2013 39 7   Download

We present an analysis of bounded-energy low-tension maps between 2-spheres. By deriving sharp estimates for the ratio of length scales on which bubbles of opposite orientation develop, we show that we can establish a ‘quantization estimate’ which constrains the energy of the map to lie near to a discrete energy spectrum. One application is to the asymptotics of the harmonic map flow; we find uniform exponential convergence in time, in the case under consideration.

71p tuanloccuoi 04-01-2013 83 8   Download

Given a bounded valence, bushy tree T , we prove that any cobounded quasi-action of a group G on T is quasiconjugate to an action of G on another bounded valence, bushy tree T . This theorem has many applications: quasi-isometric rigidity for fundamental groups of finite, bushy graphs of coarse PD(n) groups for each fixed n; a generalization to actions on Cantor sets of Sullivan’s theorem about uniformly quasiconformal actions on the 2-sphere; and a characterization of locally compact topological groups which contain a virtually free group as a cocompact lattice. ...

51p tuanloccuoi 04-01-2013 53 7   Download

For each k ∈ Z, we construct a uniformly contractible metric on Euclidean space which is not mod k hypereuclidean. We also construct a pair of uniformly contractible Riemannian metrics on Rn , n ≥ 11, so that the resulting manifolds Z and Z are bounded homotopy equivalent by a homotopy equivalence which is not boundedly close to a homeomorphism. We show that for these lf spaces the C ∗ -algebra assembly map K∗ (Z) → K∗ (C ∗ (Z)) from locally finite K-homology to the K-theory of the bounded propagation algebra is not a monomorphism ...

21p tuanloccuoi 04-01-2013 40 7   Download