Random reals and the relation 171-1171-1171-1

It is consistent that ₁(₁,(:n))² holds in any random extension for n finite and countable.     

On multipliers in the spaces 207-01207-01207-01

. . , . , , , . , . .

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Finally, the author wishes to express his gratefulness to Prof. P. I. Lizorkin for raising the problem and for his attention during the elaboration of the present work.     

Limit periodic Schur algorithms,the case 441-1441-1441-1

We show that if a function bounded in the unit disk gives rise to a limit periodic Schur algorithm with ||=1, d _n ,< then the function can be continued analytically to a meromorphic function in the entire plane except, possibly, for an essential singularity at z=–1. The lpS provides a very good approximation to the function.This research was supported in part by the US National Science Foundation under Grant DMS-9103141.     

On multicyclic operators and the Vasjunin-Nikol'ski206-1206-1206-1discotheca

If A is a bounded linear multicyclic operator acting on a complex Banach spaceX, then thedisc of A is defined by: disc A = sup(R ∈ Cyc A) min{dimR′: R′ ? R, R′ ∈ Cyc A}, where Cyc A denotes the family of all finite dimensional subspacesR ofX such that X = (R+AR+A ² R+?)^?. It is shown that if the set {λ ∈ ?: dim ker (λ-A)^* ≥ n} has nonempty interior (in particular, if A is a Fredholm operator of index -n), then disc A ≥ n+1. This result affirmatively answers a question of V.I. Vasjunin and N.K. Nikol'skiï. In the case whenX is a Hilbert space, it is shown that the set of all operators A such that A is n-multicyclic, but disc A =∞, is dense in the set of all n-multicyclic operators. If M_λ = "multiplication by λ" acting on the disk algebra (and many other spaces of continuous and/or analytic functions), then M_λ is cyclic, but disc M_λ = ∞. However, the analogous result is false if the disk algebra is replaced by the algebra of functions analytic on the disk and smooth on the boundary, or algebras of Lipschitz functions. If T is a multicyclic unicellular operator, then T is cyclic and disc T=1.     

From the 1-2-3 conjecture to the Riemann hypothesis

This survey presents some combinatorial problems with number-theoretic flavor. Our journey starts from a simple graph coloring question, but at some point gets close to dangerous territory of the Riemann Hypothesis. We will mostly focus on open problems, but we will also provide some simple proofs, just for adorning.     

离散Leslie—Gower型捕食与被捕食系统的Neimark—Sacker分岔

本文利用映射的分岔理论讨论了离散Leslie—Gower型捕食与被捕食系统的Neimark—Sacker分岔,并通过数值模拟验证了所得结果的正确性。     

275-01275-01275-01Regularity of the spatial derivatives of the solutions to parabolic systems in divergence form

Sunto Si dimostra che, nelle ipotesi: fⁱ L^2,(Q, ^N), 0<< n+2, i=0,1,..., n, uL^2,(Q,^N)H _–T ^*0,1/2() (Q,^N), D_iuL^2,(Q,^N),i=1,2,...,n, la soluzione v: Q ^N del problema di Cauchy-Dirichlet: ha derivate spaziali D_iv appartenenti a L^2,(Q,^N) e che sussiste la maggiorazione:.

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Lavoro eseguito con contributo finanziario del M.U.R.S.T. e nell'ambito del G.N.A.F.A. del C.N.R.     

On the nonvanishing of the central value of the Rankin-Selberg -functions

We characterize the nonvanishing of the central value of the Rankin-Selberg -functions in terms of periods of Fourier-Jacobi type. This characterization is based on the Langlands philosophy on functoriality and on applications of invariant theory to automorphic representations. The result is the symplectic analog of the Gross-Prasad conjecture.

     

Best-possible one-sided approximations in the classes 688-01688-01688-01by trigonometric polynomials in the metric of L1

The quantities are calculated, where is the best approximation from above of the function f by trigonometric polynomials of order ⩽n—1 in the metric of L₁. Translated from Matematicheskie Zametki, Vol. 22, No. 3, pp. 357–370, September, 1977.     

Boundedness of the first eigenvalue of the -Laplacian

We prove that for any 1$">, any compact manifold of three or more dimensions carries Riemannian metrics of volume one with the first eigenvalue of the -Laplacian arbitrarily large.