Abstract

Let the matrix operator L = D∂xx + q (x) A0, with D = diag (1, ν), ν ≠ 1, q ∈ L∞ (0, π), and A0 is a Jordan block of order 1. We analyze the boundary null controllability for the system yt − Ly = 0. When [see formula in PDF] and q is constant, q = 1 for instance, there exists a family of root vectors of [see formula in PDF] forming a Riesz basis of L2(0,π;ℝ2). Moreover F. Ammar Khodja et al. [J. Funct. Anal. 267 (2014) 2077–2151] shows the existence of a minimal time of control depending on condensation of eigenvalues of [see formula in PDF], that is to say the existence of T0 (ν) such that the system is null controllable at time T > T0 (ν) and not null controllable at time T < T0 (ν). In the same paper, the authors prove that for all τ ∈ [0, + ∞], there exists ν ∈] 0, + ∞ [ such that T0 (ν) = τ. When q depends on x, the property of Riesz basis is no more guaranteed. This leads to a new phenomena: simultaneous condensation of eigenvalues and eigenfunctions. This condensation affects the time of null controllability.

Highlights

  • Introduction and main resultsThis paper deals with the controllability of two coupled one-dimensional parabolic equations, with different diffusion coefficients, where the control is exerted at one boundary point

  • The authors used the method of moments of Fattorini-Russell to give a necessary and sufficient condition of null controllability at any time T > 0 for system (1.5)

  • We study the null controllability properties of system (1.5) to the case where D = Id and

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Summary

Introduction and main results

This paper deals with the controllability of two coupled one-dimensional parabolic equations, with different diffusion coefficients, where the control is exerted at one boundary point. This result was generalized by [1] to the case n ≥ 2, m ≥ 1 In these two papers, the authors used the method of moments of Fattorini-Russell to give a necessary and sufficient condition of null controllability at any time T > 0 for system (1.5). The authors used the method of moments of Fattorini-Russell to give a necessary and sufficient condition of null controllability at any time T > 0 for system (1.5) In both cases, the sequence of eigenvalues Λ = {Λk}k≥1 ⊂ R+. Λ = {Λk}k≥1 which does eigenfunctions is complete not but satisfy the it is not a Rgaiepszcobnadsiisti(osneeaPpproepa.ri2n.g4)info(r1s.o4m) heo√wνev∈/erQt∗+heansedquqe∈ncLe∞o(f0a,sπs)oc.iAatseda consequence, we will see that a minimal time of control T0 ∈ [0, +∞], depends simultaneously of condensation of eigenvalues and associated eigenfunctions of (L∗, D(L∗)) To this end, we will use the block methods moment developed by A.

Introduce
Some preliminary results Let us consider the vectorial operator
Positive null controllability result
The negative null controllability result
20 Let us recall that with
Some preliminary results
Approximate controllability

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