Volume 26, 2020
|Number of page(s)||50|
|Published online||13 January 2020|
The cost of controlling strongly degenerate parabolic equations*
Dipartimento di Matematica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica,
2 Institut de Mathématiques de Toulouse; UMR 5219, Université de Toulouse; CNRS UPS IMT 31062 Toulouse Cedex 9, France.
** Corresponding author: firstname.lastname@example.org
Accepted: 18 January 2018
We consider the typical one-dimensional strongly degenerate parabolic operator Pu = ut − (xαux)x with 0 < x < ℓ and α ∈ (0, 2), controlled either by a boundary control acting at x = ℓ, or by a locally distributed control. Our main goal is to study the dependence of the so-called controllability cost needed to drive an initial condition to rest with respect to the degeneracy parameter α. We prove that the control cost blows up with an explicit exponential rate, as eC/((2−α)2T), when α → 2− and/or T → 0+. Our analysis builds on earlier results and methods (based on functional analysis and complex analysis techniques) developed by several authors such as Fattorini-Russel, Seidman, Güichal, Tenenbaum-Tucsnak and Lissy for the classical heat equation. In particular, we use the moment method and related constructions of suitable biorthogonal families, as well as new fine properties of the Bessel functions Jν of large order ν (obtained by ordinary differential equations techniques).
Mathematics Subject Classification: 35K65 / 33C10 / 93B05 / 93B60 / 35P10 / 34B08
Key words: Degenerate parabolic equations / null controllability / moment problem / Bessel functions
© EDP Sciences, SMAI 2020
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