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Note on the internal stabilization of stochastic parabolic equations with linearly multiplicative gaussian noise

Viorel Barbu — 2013

ESAIM: Control, Optimisation and Calculus of Variations

The parabolic equations driven by linearly multiplicative Gaussian noise are stabilizable in probability by linear feedback controllers with support in a suitably chosen open subset of the domain. This procedure extends to Navier − Stokes equations with multiplicative noise. The exact controllability is also discussed.

Exact null internal controllability for the heat equation on unbounded convex domains

Viorel Barbu — 2014

ESAIM: Control, Optimisation and Calculus of Variations

The liner parabolic equation y t - 1 2 𝔻 y + F · y = 1 0 u ∂y ∂t − 1 2   Δy + F · ∇ y = 1 x1d4aa; 0 u with Neumann boundary condition on a convex open domain x1d4aa; ⊂ ℝ with smooth boundary is exactly null controllable on each finite interval if 𝒪is an open subset of x1d4aa; which contains a suitable neighbourhood of the recession cone of x1d4aa; . Here, : ℝ → ℝ is a bounded, -continuous function, and  = ∇, where is convex and coercive.

The internal stabilization by noise of the linearized Navier-Stokes equation

Viorel Barbu — 2011

ESAIM: Control, Optimisation and Calculus of Variations

One shows that the linearized Navier-Stokes equation in 𝒪 R d , d 2 , around an unstable equilibrium solution is exponentially stabilizable in probability by an internal noise controller V ( t , ξ ) = i = 1 N V i ( t ) ψ i ( ξ ) β ˙ i ( t ) , ξ 𝒪 , where { β i } i = 1 N are independent Brownian motions in a probability space and { ψ i } i = 1 N is a system of functions on 𝒪 with support in an arbitrary open subset 𝒪 0 𝒪 . The stochastic control input { V i } i = 1 N is found in feedback form. One constructs also a tangential boundary noise controller which exponentially stabilizes in probability the equilibrium...

Feedback stabilization of Navier–Stokes equations

Viorel Barbu — 2003

ESAIM: Control, Optimisation and Calculus of Variations

One proves that the steady-state solutions to Navier–Stokes equations with internal controllers are locally exponentially stabilizable by linear feedback controllers provided by a L Q control problem associated with the linearized equation.

The internal stabilization by noise of the linearized Navier-Stokes equation

Viorel Barbu — 2011

ESAIM: Control, Optimisation and Calculus of Variations

One shows that the linearized Navier-Stokes equation in 𝒪 R d , d 2 , around an unstable equilibrium solution is exponentially stabilizable in probability by an internal noise controller V ( t , ξ ) = i = 1 N V i ( t ) ψ i ( ξ ) β ˙ i ( t ) , ξ 𝒪 , where { β i } i = 1 N are independent Brownian motions in a probability space and { ψ i } i = 1 N is a system of functions on 𝒪 with support in an arbitrary open subset 𝒪 0 𝒪 . The stochastic control input { V i } i = 1 N is found in feedback form. One constructs also a tangential boundary noise controller which exponentially stabilizes in probability the equilibrium solution. ...

Grauert's line bundle convexity, reduction and Riemann domains

Viorel Vâjâitu — 2016

Czechoslovak Mathematical Journal

We consider a convexity notion for complex spaces X with respect to a holomorphic line bundle L over X . This definition has been introduced by Grauert and, when L is analytically trivial, we recover the standard holomorphic convexity. In this circle of ideas, we prove the counterpart of the classical Remmert’s reduction result for holomorphically convex spaces. In the same vein, we show that if H 0 ( X , L ) separates each point of X , then X can be realized as a Riemann domain over the complex projective space...

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